VintageBigBlue.org

 

Re: Ovision warranty - reply from Ovision


Aug 13, 2008

 


----------------------------

#38855 Aug 13, 2008

I have emailed Franck about this, but I am curious what others think.

The Ovision web site states, "The machining accuracy is three times

better than the current 'High precision ' Losmandy brass worms, or

previous steel versions." and elsewhere, "The tracking warranty is + /

- 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

for the HP worm, so I am having difficulty resolving the "three times

better" statement. Am I missing something here?



Frank Barrett

celestialwonders.com



----------------------------

#38885 Aug 14, 2008

I don't get it either. I am not aware of any Losmandy advertised P.E.

guarantee--did I miss something? regards Greg N

--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> I have emailed Franck about this, but I am curious what others think.

> The Ovision web site states, "The machining accuracy is three times

> better than the current 'High precision ' Losmandy brass worms, or

> previous steel versions." and elsewhere, "The tracking warranty is + /

> - 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

> Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

> for the HP worm, so I am having difficulty resolving the "three times

> better" statement. Am I missing something here?

>

> Frank Barrett

> celestialwonders.com

>



----------------------------

#38887 Aug 14, 2008

Greg,

No, it may just be me. I know the Titan advertises +/- 5 arc secs,

but I am not sure if that is the same worm as the HP worm. The HP

worm came out at the same time as the Titan, so I may or may not be

making a valid assumption here. I do know my HP worm is within that

tolerance. It is also clear that those of you who have the Ovision

worm are getting better (some much better) performance than the

warranty. I may be splitting hairs, but if the Ovision is only

helping me by getting rid of the 76 sec error I am wondering what the

value proposition is over the MWB? I too have the form filled out,

just waiting for one more nudge...



Frank Barrett

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> I don't get it either. I am not aware of any Losmandy advertised P.E.

> guarantee--did I miss something? regards Greg N

>

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > I have emailed Franck about this, but I am curious what others think.

> > The Ovision web site states, "The machining accuracy is three times

> > better than the current 'High precision ' Losmandy brass worms, or

> > previous steel versions." and elsewhere, "The tracking warranty is + /

> > - 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

> > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

> > for the HP worm, so I am having difficulty resolving the "three times

> > better" statement. Am I missing something here?

> >

> > Frank Barrett

> > celestialwonders.com

> >

>



----------------------------

#38888 Aug 14, 2008

Greg,



Another way to look at it: If Franck is warranting 10 arc sec or

better and also claiming three times better than Losmandy, does that

imply that Losmandy is in the neighborhood of 30 arc sec? Clearly

that is ridiculous, so again, I am wondering what I am missing.



Frank Barrett

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> I don't get it either. I am not aware of any Losmandy advertised P.E.

> guarantee--did I miss something? regards Greg N

>

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > I have emailed Franck about this, but I am curious what others think.

> > The Ovision web site states, "The machining accuracy is three times

> > better than the current 'High precision ' Losmandy brass worms, or

> > previous steel versions." and elsewhere, "The tracking warranty is + /

> > - 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

> > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

> > for the HP worm, so I am having difficulty resolving the "three times

> > better" statement. Am I missing something here?

> >

> > Frank Barrett

> > celestialwonders.com

> >

>



----------------------------

#38889 Aug 14, 2008

Well SOMEBODY should try the MWB so it might as well be you! My

thinking is the G11 is 15 arc seconds peak to peak and the Ovision

brings you in at about a 1/3 or better than that but because of either

language or conservatism the language barrier on the web site does not

reflect what we wish it would say plainly and clearly.



I don't know if Franck would actually ship a 10 arc second peak to

peak worm at this point. It doesn't seem to me to be in his interest.



You can certainly say: I would like to see the worm certification

before it ships. He sent me mine before he shipped. I don't know if

he does that always. But if he sends you the certification values and

it's 9 arc seconds peak to peak then you would, I imagine, be tempted

to say: well, no thank you.



We had a post here yesterday from someone who was getting 6 arc

seconds peak to peak with a very smooth, easily guided curve. (I asked

about that since the chart looked tighter than 6 arc seconds, didn't

see a reply.)



Clearly the peak to peak is not the ONLY criterion of performance

because we saw in Floyd's case he has those little spikey things which

is what Ovision is really trying to eliminate. And AP's Mach1 was

certified at 7 arc seconds peak to peak without PEC turned on. But

Ovision's should be a guidable peak to peak worm cycle with no weird

random jumps from the bearings and bearing blocks. I think that's

what people are paying for. You should be able to get the equivalent

or damned close of AP Mach1 PE and guide-ability for Losmandy price +

$500. If you don't get that, then it's fair to say you're going to be

disappointed. And based on my conversation with him at NEAF I think

Franck understands that underlying issue is whether one can get AP

level performance out of a Losmandy mount. That, in a sense, is what

the game is here.



So to my way of thinking, let's just say that if you get an Ovision

you should be expecting to meet or beat the AP Mach 1 standard, which

is a reasonable goal that we've now seen demonstrated I think in three

cases, maybe four. We've also seen Franck take a unit back without

problems and send another one (which is causing the delay that keeps

us from having four cases).



As for what the GUARANTEE is, since I don't make it, I can't say. The

issue is a little bit dicey because there is the potential of a clumsy

user boogering the threads. He might find it upsetting to get

boogered threads back and have to refund since he has certified the

units before shipping them out and knows they weren't boogered when

they left.



I think that part of the concern here is what is the character of the

person you're dealing with wayyy out there in France. On this score I

can say that after spent half an hour yacking with him at NEAF I

decided this was not a Burgess Optics of castles in the sky and long

delays in execution. I was holding a well machined part in my hand

and looking at it carefully. These parts were already being sold in

France. I'm less inhibited about things French. I've lived there and

speak French. My judgment of Franck's character was that it was good

and I sent the money and got a good product back faster than I thought

it would happen. Other people have since done so too. He's got

people who depend on him to operate expensive equipment in remote

parts of the world. All in all, the character issue holds together in

a way that indicates someone who loves his work and takes his

responsibilities seriously. I think you'll get a part that you won't

want to send back, if you do send it back and haven't boogered it I

expect that will work out OK too, but I'm not part of the business

circuit here. (I'm not volunteering to get dumped on if things don't

work out because I'm not getting cut in on the profits when they do.)



But my sense of the character issue, which goes to the heart of

whether you think you can recover your funds for a bad unit, I think

Franck is "good people."





On the technicals: we don't know the value proposition vs. the MWB

because neither unit group members who have operated it in the cold,

and we don't have data. The MWB is being put out by a guy who is

smart and able to pull off a project; he has indicated he wants to do

a run and will probably let it go after that (I can't imagine there's

a career to be made in aftermarket Lsomandy worms). Ovision is an

on-going astronomy business which has an interest in selling good

mounts because it sells a full panoply of astronomical equipment.

This is Ovision's second worm design. You can say that's bad because

they didn't get it right first time round or that's good in the sense

that the company is actively pursuing this issue and the track record

bodes well for a future commitment over time. Ovision certifies the

worm and provides precision bearings and machines its own worm which

it puts into its own block. MWB requires you put in your own innards.

For most people that means the Losmandy brass worm plus Losmandy

bearings or upgrade bearings. To me MWB and Ovision look price

equivalent taking everything into consideration. It may be that both

cure the 76 second problem and that Ovision smooths out some

additional squiggles which only people imaging at f/15 care about. I

can't answer that.



If you're imaging with an 80mm f/6 there might not be any value in

EITHER option.



Between me and you guys, if I DID have many thousands invested in

imaging equipment and cared deeply about this issue I would buy BOTH

the MWB -AND- the Ovision and test them for myself. I would plan on

keeping one and selling the other, or swapping the one I liked less

into the Dec axis. The only reason I'm not jumping on the MWB is that

I don't even own a DSLR. You all did catch that Franck is ordering a

pair of MWBs? Prospective Ovision customers should be glad to see

that. That shows curiosity and dedication to the subject matter and a

"commitment over time."





regards

Greg N



























--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> Greg,

> No, it may just be me. I know the Titan advertises +/- 5 arc secs,

> but I am not sure if that is the same worm as the HP worm. The HP

> worm came out at the same time as the Titan, so I may or may not be

> making a valid assumption here. I do know my HP worm is within that

> tolerance. It is also clear that those of you who have the Ovision

> worm are getting better (some much better) performance than the

> warranty. I may be splitting hairs, but if the Ovision is only

> helping me by getting rid of the 76 sec error I am wondering what the

> value proposition is over the MWB? I too have the form filled out,

> just waiting for one more nudge...

>

> Frank Barrett

> celestialwonders.com

>







----------------------------

#38891 Aug 14, 2008

OK here's the French text:





Les vis sans fin que nous proposons dans ce kit ne sont pas des vis

Losmandy. Elles sont fabriqu.es tout comme le carter et d'autres

pi.ces selon notre cahier des charges par une entreprise sp.cialis.e.

Elles b.n.ficient d'une pr.cision de r.alisation trois fois sup.rieure

aux vis Losmandy de s.rie actuelles d.nomm.es "High precision Worm",

tant pour les versions acier que laiton.



Here's my translation.



The worm that we offer in this kit is not the Losmandy worm. It, as

well as the single block and other parts, are part of the

specifications in our contract with a specialized [machining] company.

Our worms are machined to tolerances three times superior to the

current Losmandy "High precision worms", whether steel or brass.



I recall reading that the Ovision machining is good to .0005mm. So

he's saying that Losmandy tolerances are around .0015mm.



So the 3x business seems to come from references to machining

tolerances. This would not automatically translate to a 3x improvement

in PE.



Now I have to see if I can find the comments about PE results.



regards

Greg N











--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> Greg,

> No, it may just be me. I know the Titan advertises +/- 5 arc secs,

> but I am not sure if that is the same worm as the HP worm. The HP

> worm came out at the same time as the Titan, so I may or may not be

> making a valid assumption here. I do know my HP worm is within that

> tolerance. It is also clear that those of you who have the Ovision

> worm are getting better (some much better) performance than the

> warranty. I may be splitting hairs, but if the Ovision is only

> helping me by getting rid of the 76 sec error I am wondering what the

> value proposition is over the MWB? I too have the form filled out,

> just waiting for one more nudge...

>

> Frank Barrett

> celestialwonders.com

>

> --- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@> wrote:

> >

> > I don't get it either. I am not aware of any Losmandy advertised P.E.

> > guarantee--did I miss something? regards Greg N

> >

> > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

wrote:

> > >

> > > I have emailed Franck about this, but I am curious what others

think.

> > > The Ovision web site states, "The machining accuracy is three times

> > > better than the current 'High precision ' Losmandy brass worms, or

> > > previous steel versions." and elsewhere, "The tracking warranty

is + /

> > > - 5 arc seconds for the G11 mount ( total of 10" peak to peak

)...".

> > > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds

as well

> > > for the HP worm, so I am having difficulty resolving the "three

times

> > > better" statement. Am I missing something here?

> > >

> > > Frank Barrett

> > > celestialwonders.com

> > >

> >

>



----------------------------

#38892 Aug 14, 2008

But you're right:





La pr.cision garantie est au maximum de + / - 5 secondes d'arc soit 10

secondes d'arc cr.te . cr.te sur un tour de vis tangente de la monture

pour les montures G11 et + / - 10 secondes d'arc soit 20 secondes

d'arc cr.te . cr.te pour les montures GM8. Tout ceci sans bien s.r

utiliser de syst.me de correction d'erreur p.riodique.



This part of the guarnatee is for a "maximum +/- 5 arc seconds or 10

arc seconds peak to peak." And double that, 20 arc seconds p to p,

for the g8.



This guarantee contrasts with teh actual delivered units which have

been +/- 3 arc seconds or 6 arc seconds peak to peak or better. Mine

was measured at 3.5 arc seconds peak to peak. That's because I don't

image. The world always gives the good stuff to the people that don't

need it.



You would think he'd tighten up the guarantee but who knows. There

might be some seriously messed up G11 worm wheels out there and maybe

that's something he can't control. Or maybe when they wrote the text

they went conservative.



We've had people here say they would rather have a PE of 10 or even 15

arc seconds and be able to guide it out without having quick spikes,

so that's where the PE spec and the machining spec of 5/10,000th of a

mm have to be brought together and considered. I interpret them to

mean: "we'll give you good to damned good PE, with no spikes." Not:

"We'll give you better PE than any other arrangement, but you'll have

spikes."



regards

Greg N









--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> Greg,

> No, it may just be me. I know the Titan advertises +/- 5 arc secs,

> but I am not sure if that is the same worm as the HP worm. The HP

> worm came out at the same time as the Titan, so I may or may not be

> making a valid assumption here. I do know my HP worm is within that

> tolerance. It is also clear that those of you who have the Ovision

> worm are getting better (some much better) performance than the

> warranty. I may be splitting hairs, but if the Ovision is only

> helping me by getting rid of the 76 sec error I am wondering what the

> value proposition is over the MWB? I too have the form filled out,

> just waiting for one more nudge...

>

> Frank Barrett

> celestialwonders.com

>

> --- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@> wrote:

> >

> > I don't get it either. I am not aware of any Losmandy advertised P.E.

> > guarantee--did I miss something? regards Greg N

> >

> > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

wrote:

> > >

> > > I have emailed Franck about this, but I am curious what others

think.

> > > The Ovision web site states, "The machining accuracy is three times

> > > better than the current 'High precision ' Losmandy brass worms, or

> > > previous steel versions." and elsewhere, "The tracking warranty

is + /

> > > - 5 arc seconds for the G11 mount ( total of 10" peak to peak

)...".

> > > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds

as well

> > > for the HP worm, so I am having difficulty resolving the "three

times

> > > better" statement. Am I missing something here?

> > >

> > > Frank Barrett

> > > celestialwonders.com

> > >

> >

>







----------------------------

#38894 Aug 14, 2008

Greg,



It's always the same picture: when it comes to guarantee something (an

bear the consequence of it), people become cautious.



Normally, the Ovision worm assembly should perform much better than

+/- 10" peak to peak (for the G-11. On a statistical base...



Regards



Claudio

---------------

--- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> But you're right:

>

>

> La pr.cision garantie est au maximum de + / - 5 secondes d'arc soit 10

> secondes d'arc cr.te . cr.te sur un tour de vis tangente de la monture

> pour les montures G11 et + / - 10 secondes d'arc soit 20 secondes

> d'arc cr.te . cr.te pour les montures GM8. Tout ceci sans bien s.r

> utiliser de syst.me de correction d'erreur p.riodique.

>

> This part of the guarnatee is for a "maximum +/- 5 arc seconds or 10

> arc seconds peak to peak." And double that, 20 arc seconds p to p,

> for the g8.

>

> This guarantee contrasts with teh actual delivered units which have

> been +/- 3 arc seconds or 6 arc seconds peak to peak or better. Mine

> was measured at 3.5 arc seconds peak to peak. That's because I don't

> image. The world always gives the good stuff to the people that don't

> need it.

>

> You would think he'd tighten up the guarantee but who knows. There

> might be some seriously messed up G11 worm wheels out there and maybe

> that's something he can't control. Or maybe when they wrote the text

> they went conservative.

>

> We've had people here say they would rather have a PE of 10 or even 15

> arc seconds and be able to guide it out without having quick spikes,

> so that's where the PE spec and the machining spec of 5/10,000th of a

> mm have to be brought together and considered. I interpret them to

> mean: "we'll give you good to damned good PE, with no spikes." Not:

> "We'll give you better PE than any other arrangement, but you'll have

> spikes."

>

> regards

> Greg N

>

>

>

>

>

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > Greg,

> > No, it may just be me. I know the Titan advertises +/- 5 arc secs,

> > but I am not sure if that is the same worm as the HP worm. The HP

> > worm came out at the same time as the Titan, so I may or may not be

> > making a valid assumption here. I do know my HP worm is within that

> > tolerance. It is also clear that those of you who have the Ovision

> > worm are getting better (some much better) performance than the

> > warranty. I may be splitting hairs, but if the Ovision is only

> > helping me by getting rid of the 76 sec error I am wondering what the

> > value proposition is over the MWB? I too have the form filled out,

> > just waiting for one more nudge...

> >

> > Frank Barrett

> > celestialwonders.com

> >

> > --- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@> wrote:

> > >

> > > I don't get it either. I am not aware of any Losmandy

advertised P.E.

> > > guarantee--did I miss something? regards Greg N

> > >

> > > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

> wrote:

> > > >

> > > > I have emailed Franck about this, but I am curious what others

> think.

> > > > The Ovision web site states, "The machining accuracy is three

times

> > > > better than the current 'High precision ' Losmandy brass worms, or

> > > > previous steel versions." and elsewhere, "The tracking warranty

> is + /

> > > > - 5 arc seconds for the G11 mount ( total of 10" peak to peak

> )...".

> > > > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds

> as well

> > > > for the HP worm, so I am having difficulty resolving the "three

> times

> > > > better" statement. Am I missing something here?

> > > >

> > > > Frank Barrett

> > > > celestialwonders.com

> > > >

> > >

> >

>



----------------------------

#38896 Aug 14, 2008

I think you're right, there is a tendency to be cautious. The fact is

something like a guarantee bears on the character of the dealer and

what he's trying to do. Ovision is clearly not your normal

astronomical supply company. It is deeply involved in pushing the

envelope on equipment: they were selling G11s equipped with Skysensors

back in the day when Gemini was not available. They have an

aftermarket modification that pushes the Dec head forward so it won't

hit the mount at all. These guys have been tinkering for quite some

time.



They also did a test of a 9.25 some time ago for French magazine where

the 9.25 came out pretty poor and they took it into their shop and

tweaked it to be considerably better. All this was duly reported in

the review.



I don't know of any U.S. retail astronomy outfit that is "so deep"

into the products that it will actually sell that kind of aftermarket

retrofit. The most hands-on company I know is Company Seven and all

they do is evaluate stuff before they ship it.



regards

Greg N





--- In Losmandy_users@yahoogroups.com, "schinazic"

claudio.schinazi@...> wrote: >

> Greg,

>

> It's always the same picture: when it comes to guarantee something (an

> bear the consequence of it), people become cautious.

>

> Normally, the Ovision worm assembly should perform much better than

> +/- 10" peak to peak (for the G-11. On a statistical base...

>

> Regards

>

> Claudio

>







----------------------------

#38897 Aug 14, 2008

Greg,



Bingo! That's the ticket! I knew I had to be misinterpreting

something because it just didn't pass the common sense test. The

nudge is given, I will be placing an order today. Actually, 10 arc

sec PE (which is the *worst* case for the G11 per the warranty) is not

too bad if the errors are smooth and can be handled with PEC or guided

out. With the milling tolerances you are noting I am beginning to

understand why the tracking charts I've seen are so smooth. Amplitude

means nothing, smoothness and periodicity are everything. Greg,

thanks for straightening me out, this time g>, I appreciate it. I am

too embarrassed to say how much I have invested in my imaging setup,

but I will say that the $500 price tag for this upgrade is minuscule

in comparison and will make all the world of difference when imaging

with the 10" LX200R at 2540mm focal length. I will take the risk and

jump on board!



Frank Barrett

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> OK here's the French text:

>

>

> Les vis sans fin que nous proposons dans ce kit ne sont pas des vis

> Losmandy. Elles sont fabriqu.es tout comme le carter et d'autres

> pi.ces selon notre cahier des charges par une entreprise sp.cialis.e.

> Elles b.n.ficient d'une pr.cision de r.alisation trois fois sup.rieure

> aux vis Losmandy de s.rie actuelles d.nomm.es "High precision Worm",

> tant pour les versions acier que laiton.

>

> Here's my translation.

>

> The worm that we offer in this kit is not the Losmandy worm. It, as

> well as the single block and other parts, are part of the

> specifications in our contract with a specialized [machining] company.

> Our worms are machined to tolerances three times superior to the

> current Losmandy "High precision worms", whether steel or brass.

>

> I recall reading that the Ovision machining is good to .0005mm. So

> he's saying that Losmandy tolerances are around .0015mm.

>

> So the 3x business seems to come from references to machining

> tolerances. This would not automatically translate to a 3x improvement

> in PE.

>

> Now I have to see if I can find the comments about PE results.

>

> regards

> Greg N

>

>

>

>

>

>

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > Greg,

> > No, it may just be me. I know the Titan advertises +/- 5 arc secs,

> > but I am not sure if that is the same worm as the HP worm. The HP

> > worm came out at the same time as the Titan, so I may or may not be

> > making a valid assumption here. I do know my HP worm is within that

> > tolerance. It is also clear that those of you who have the Ovision

> > worm are getting better (some much better) performance than the

> > warranty. I may be splitting hairs, but if the Ovision is only

> > helping me by getting rid of the 76 sec error I am wondering what the

> > value proposition is over the MWB? I too have the form filled out,

> > just waiting for one more nudge...

> >

> > Frank Barrett

> > celestialwonders.com

> >

> > --- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@> wrote:

> > >

> > > I don't get it either. I am not aware of any Losmandy

advertised P.E.

> > > guarantee--did I miss something? regards Greg N

> > >

> > > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

> wrote:

> > > >

> > > > I have emailed Franck about this, but I am curious what others

> think.

> > > > The Ovision web site states, "The machining accuracy is three

times

> > > > better than the current 'High precision ' Losmandy brass worms, or

> > > > previous steel versions." and elsewhere, "The tracking warranty

> is + /

> > > > - 5 arc seconds for the G11 mount ( total of 10" peak to peak

> )...".

> > > > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds

> as well

> > > > for the HP worm, so I am having difficulty resolving the "three

> times

> > > > better" statement. Am I missing something here?

> > > >

> > > > Frank Barrett

> > > > celestialwonders.com

> > > >

> > >

> >

>



----------------------------

#38900 Aug 14, 2008

I figured it was time to jump in and talk about my experience with the

G11 before and after the Ovision upgrade.



I purchased my G11 back in 1999 and after a few nights of adjustment

the imaging results were acceptable. But every 3 or 4 frames would be

ruined by random tracking errors. This always caused me to look at

other alternatives to the G11.



Then life took over and I didn't do much imaging for about 3 years.

When I got back into imaging and found out that Losmandy was now

offering a new high precision worm I thought that this might cure some

of my random tracking errors. But I was not 100% convinced so I held

off buying the new worm until 6 months ago.



I bought 2 worms and figured the best of the two would end-up driving

the ra. When they arrived I tested them both. These worms were harder

to guide then my original 1999 steel ra worm with a much steeper P.E.

curve. I guessed that these worms might have been made at the same

time because they were bought together.



After investing $100 and ending up with a bad taste in my mouth I

replaced the "high precision" worm with my original steel one and went

back to accepting some bad frames.



Then at NEAF I heard about the Ovision worm assembly and hoped that

this would work as advertised. About 4 weeks ago I sent in my order

and figured that if this worm did not work out at least it had a warranty.



Let me say that Ovision could teach a few other companies how to

treat their customers my first email to them was replied to within 10

min. The worm was ready when he said it would be and before it was

shipped he sent me test data.



When the worm arrived I installed it on my mount with mixed feelings

remembering back to the other "high precision" worms that I tried. But

I was not prepared for the results that this worm gave me.



This worm had a much lower uncorrected P.E. much lower than my 1999

steel non high precision worm. Gone were the sudden jumps in ra that

caused my auto guider to go nuts. Also for the first time my auto

guider was making very few guide corrections something I was not used

to with this mount.



To say I was pleased is an understatement.



After training the mounts P.E.C and misaligning my polar alignment I

took a few test shots. The P.E. was hard distinguish from my local

seeing again something I have never seen this mount do.



Then I decided to take the Ovision worm out and retest all the other

worms so they would all be tested under the same conditions. The

results were still the same my 1999 steel worm beat out the "high

precision" worms from Losmandy. But the Ovision worm made the most

night and day difference. All the worms except for the Ovision were

tested with the same worm blocks and I tried as hard as possible to

maintain the same alignment in relation to the worm gear with all the

worms I tested.



Chuck



--- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> OK here's the French text:

>

>

> Les vis sans fin que nous proposons dans ce kit ne sont pas des vis

> Losmandy. Elles sont fabriqu.es tout comme le carter et d'autres

> pi.ces selon notre cahier des charges par une entreprise sp.cialis.e.

> Elles b.n.ficient d'une pr.cision de r.alisation trois fois sup.rieure

> aux vis Losmandy de s.rie actuelles d.nomm.es "High precision Worm",

> tant pour les versions acier que laiton.

>

> Here's my translation.

>

> The worm that we offer in this kit is not the Losmandy worm. It, as

> well as the single block and other parts, are part of the

> specifications in our contract with a specialized [machining] company.

> Our worms are machined to tolerances three times superior to the

> current Losmandy "High precision worms", whether steel or brass.

>

> I recall reading that the Ovision machining is good to .0005mm. So

> he's saying that Losmandy tolerances are around .0015mm.

>

> So the 3x business seems to come from references to machining

> tolerances. This would not automatically translate to a 3x improvement

> in PE.

>

> Now I have to see if I can find the comments about PE results.

>

> regards

> Greg N

>

>

>

>

>

>

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > Greg,

> > No, it may just be me. I know the Titan advertises +/- 5 arc secs,

> > but I am not sure if that is the same worm as the HP worm. The HP

> > worm came out at the same time as the Titan, so I may or may not be

> > making a valid assumption here. I do know my HP worm is within that

> > tolerance. It is also clear that those of you who have the Ovision

> > worm are getting better (some much better) performance than the

> > warranty. I may be splitting hairs, but if the Ovision is only

> > helping me by getting rid of the 76 sec error I am wondering what the

> > value proposition is over the MWB? I too have the form filled out,

> > just waiting for one more nudge...

> >

> > Frank Barrett

> > celestialwonders.com

> >

> > --- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@> wrote:

> > >

> > > I don't get it either. I am not aware of any Losmandy

advertised P.E.

> > > guarantee--did I miss something? regards Greg N

> > >

> > > --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@>

> wrote:

> > > >

> > > > I have emailed Franck about this, but I am curious what others

> think.

> > > > The Ovision web site states, "The machining accuracy is three

times

> > > > better than the current 'High precision ' Losmandy brass worms, or

> > > > previous steel versions." and elsewhere, "The tracking warranty

> is + /

> > > > - 5 arc seconds for the G11 mount ( total of 10" peak to peak

> )...".

> > > > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds

> as well

> > > > for the HP worm, so I am having difficulty resolving the "three

> times

> > > > better" statement. Am I missing something here?

> > > >

> > > > Frank Barrett

> > > > celestialwonders.com

> > > >

> > >

> >

>







----------------------------

#38901 Aug 14, 2008

Well you hang out on the AP group they still like to trash-talk

Losmandies. Can't blame 'em, though. A lot of folks tried Losmandy

mounts and moved on because of the PE problem. This is the first real

breakthrough we've had after years of discussing the problem. By "we"

I mean those of us who don't know how to re-engineer the worm assembly

as Rainer did some time ago.



Is your mount a Gemini version or a stepper version?



Did you quantify the P.E.?



regards

Greg N



--- In Losmandy_users@yahoogroups.com, "goalt00" goalt@...> wrote:

>

>

> I figured it was time to jump in and talk about my experience with the

> G11 before and after the Ovision upgrade.

>

> I purchased my G11 back in 1999 and after a few nights of adjustment

> the imaging results were acceptable. But every 3 or 4 frames would be

> ruined by random tracking errors. This always caused me to look at

> other alternatives to the G11.

>

> Then life took over and I didn't do much imaging for about 3 years.

> When I got back into imaging and found out that Losmandy was now

> offering a new high precision worm I thought that this might cure some

> of my random tracking errors. But I was not 100% convinced so I held

> off buying the new worm until 6 months ago.

>

> I bought 2 worms and figured the best of the two would end-up driving

> the ra. When they arrived I tested them both. These worms were harder

> to guide then my original 1999 steel ra worm with a much steeper P.E.

> curve. I guessed that these worms might have been made at the same

> time because they were bought together.

>

> After investing $100 and ending up with a bad taste in my mouth I

> replaced the "high precision" worm with my original steel one and went

> back to accepting some bad frames.

>

> Then at NEAF I heard about the Ovision worm assembly and hoped that

> this would work as advertised. About 4 weeks ago I sent in my order

> and figured that if this worm did not work out at least it had a

warranty.

>

> Let me say that Ovision could teach a few other companies how to

> treat their customers my first email to them was replied to within 10

> min. The worm was ready when he said it would be and before it was

> shipped he sent me test data.

>

> When the worm arrived I installed it on my mount with mixed feelings

> remembering back to the other "high precision" worms that I tried. But

> I was not prepared for the results that this worm gave me.

>

> This worm had a much lower uncorrected P.E. much lower than my 1999

> steel non high precision worm. Gone were the sudden jumps in ra that

> caused my auto guider to go nuts. Also for the first time my auto

> guider was making very few guide corrections something I was not used

> to with this mount.

>

> To say I was pleased is an understatement.

>

> After training the mounts P.E.C and misaligning my polar alignment I

> took a few test shots. The P.E. was hard distinguish from my local

> seeing again something I have never seen this mount do.

>

> Then I decided to take the Ovision worm out and retest all the other

> worms so they would all be tested under the same conditions. The

> results were still the same my 1999 steel worm beat out the "high

> precision" worms from Losmandy. But the Ovision worm made the most

> night and day difference. All the worms except for the Ovision were

> tested with the same worm blocks and I tried as hard as possible to

> maintain the same alignment in relation to the worm gear with all the

> worms I tested.

>

> Chuck

>

>



----------------------------

#38903 Aug 14, 2008

As far as I know (I did some search three years ago),only a few mount

manufacturers publish PE specifications, Astro Physics and Takahashi if I

remember correctly. Their mounts are more expensive than Losmandy and were

not readily available in 2005.







I think that the consensus is that the source of tracking errors (sometimes

not with the worm rotation period) are caused by the worm assembly - glad to

find out here that there are now alternatives available. As I mentioned

before, I have been lucky with my Dec (mechanically identical) worm

assembly, my PE (with compensation for drift) is below 10 arcsecs peak to

peak, the values advertised (in 2005) for the Takahashi mounts, if memory

serves me well.







I am now measuring systematically variation of the tracking error along the

24 hour worm gear. It appears that while the 'periodic' errors remain about

the same, the drift changes. Obviously, the large worm gear is not perfect

either. Roy Gralak wrote me how to compensate for a drift in PemPro.

Unfortunately, based on limited number of observations, the drift varies

along the worm gear in a relatively short period of time (10 - 30 minutes).

I think the only solution is guiding.







Some G11 users achieved great results, some of us are not so lucky (or

competent, no offense to anyone). That's, of course, the challenge and fun

of this hobby.







LN







-----Original Message-----

From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com]

On Behalf Of gnowellsct

Sent: Thursday, August 14, 2008 7:12 AM

To: Losmandy_users@yahoogroups.com

Subject: [Losmandy_users] Re: Ovision warranty







I don't get it either. I am not aware of any Losmandy advertised P.E.

guarantee--did I miss something? regards Greg N



--- In Losmandy_users@ mailto:Losmandy_users%40yahoogroups.com>

yahoogroups.com, "Frank Barrett" frankb@...> wrote: >

> I have emailed Franck about this, but I am curious what others think.

> The Ovision web site states, "The machining accuracy is three times

> better than the current 'High precision ' Losmandy brass worms, or

> previous steel versions." and elsewhere, "The tracking warranty is + /

> - 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

> Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

> for the HP worm, so I am having difficulty resolving the "three times

> better" statement. Am I missing something here?

>

> Frank Barrett

> celestialwon celestialwonders.com> ders.com

>











[Non-text portions of this message have been removed]







----------------------------

#38909 Aug 14, 2008

www.losmandy.com/hgm-titan.html



sixth bullet: Tracking: +/- 5 arc sec. or better.



Frank Barrett

celestialwonders.com



--- In Losmandy_users@yahoogroups.com, "Ladislav Nemec" nemecl@...>

wrote: >

> As far as I know (I did some search three years ago),only a few mount

> manufacturers publish PE specifications, Astro Physics and Takahashi

if I > remember correctly. Their mounts are more expensive than Losmandy

and were > not readily available in 2005.

>

>

>

> I think that the consensus is that the source of tracking errors

(sometimes > not with the worm rotation period) are caused by the worm assembly -

glad to > find out here that there are now alternatives available. As I mentioned

> before, I have been lucky with my Dec (mechanically identical) worm

> assembly, my PE (with compensation for drift) is below 10 arcsecs

peak to > peak, the values advertised (in 2005) for the Takahashi mounts, if

memory > serves me well.

>

>

>

> I am now measuring systematically variation of the tracking error

along the > 24 hour worm gear. It appears that while the 'periodic' errors

remain about > the same, the drift changes. Obviously, the large worm gear is not

perfect > either. Roy Gralak wrote me how to compensate for a drift in PemPro.

> Unfortunately, based on limited number of observations, the drift varies

> along the worm gear in a relatively short period of time (10 - 30

minutes). > I think the only solution is guiding.

>

>

>

> Some G11 users achieved great results, some of us are not so lucky (or

> competent, no offense to anyone). That's, of course, the challenge

and fun > of this hobby.

>

>

>

> LN

>

>

>

> -----Original Message-----

> From: Losmandy_users@yahoogroups.com

[mailto:Losmandy_users@yahoogroups.com] > On Behalf Of gnowellsct

> Sent: Thursday, August 14, 2008 7:12 AM

> To: Losmandy_users@yahoogroups.com

> Subject: [Losmandy_users] Re: Ovision warranty

>

>

>

> I don't get it either. I am not aware of any Losmandy advertised P.E.

> guarantee--did I miss something? regards Greg N

>

> --- In Losmandy_users@ mailto:Losmandy_users%40yahoogroups.com>

> yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > I have emailed Franck about this, but I am curious what others think.

> > The Ovision web site states, "The machining accuracy is three times

> > better than the current 'High precision ' Losmandy brass worms, or

> > previous steel versions." and elsewhere, "The tracking warranty is + /

> > - 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

> > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

> > for the HP worm, so I am having difficulty resolving the "three times

> > better" statement. Am I missing something here?

> >

> > Frank Barrett

> > celestialwon celestialwonders.com> ders.com

> >

>

>

>

>

>

> [Non-text portions of this message have been removed]

>



----------------------------

#38915 Aug 15, 2008

Well, I do not have Titan and I was referring to the situation in 2005. It

appears that similar claim is made for the Ovision worm assembly for G11.

OK, I should not have written about stuff 3 years ago.



LN







-----Original Message-----

From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com]

On Behalf Of Frank Barrett

Sent: Thursday, August 14, 2008 6:26 PM

To: Losmandy_users@yahoogroups.com

Subject: [Losmandy_users] Re: Ovision warranty







www.losmandy www.losmandy.com/hgm-titan.html>

.com/hgm-titan.html



sixth bullet: Tracking: +/- 5 arc sec. or better.



Frank Barrett

celestialwon celestialwonders.com> ders.com



--- In Losmandy_users@ mailto:Losmandy_users%40yahoogroups.com>

yahoogroups.com, "Ladislav Nemec" nemecl@...>

wrote: >

> As far as I know (I did some search three years ago),only a few mount

> manufacturers publish PE specifications, Astro Physics and Takahashi

if I > remember correctly. Their mounts are more expensive than Losmandy

and were > not readily available in 2005.

>

>

>

> I think that the consensus is that the source of tracking errors

(sometimes > not with the worm rotation period) are caused by the worm assembly -

glad to > find out here that there are now alternatives available. As I mentioned

> before, I have been lucky with my Dec (mechanically identical) worm

> assembly, my PE (with compensation for drift) is below 10 arcsecs

peak to > peak, the values advertised (in 2005) for the Takahashi mounts, if

memory > serves me well.

>

>

>

> I am now measuring systematically variation of the tracking error

along the > 24 hour worm gear. It appears that while the 'periodic' errors

remain about > the same, the drift changes. Obviously, the large worm gear is not

perfect > either. Roy Gralak wrote me how to compensate for a drift in PemPro.

> Unfortunately, based on limited number of observations, the drift varies

> along the worm gear in a relatively short period of time (10 - 30

minutes). > I think the only solution is guiding.

>

>

>

> Some G11 users achieved great results, some of us are not so lucky (or

> competent, no offense to anyone). That's, of course, the challenge

and fun > of this hobby.

>

>

>

> LN

>

>

>

> -----Original Message-----

> From: Losmandy_users@ mailto:Losmandy_users%40yahoogroups.com>

yahoogroups.com

[mailto:Losmandy_users@ mailto:Losmandy_users%40yahoogroups.com>

yahoogroups.com] > On Behalf Of gnowellsct

> Sent: Thursday, August 14, 2008 7:12 AM

> To: Losmandy_users@ mailto:Losmandy_users%40yahoogroups.com>

yahoogroups.com > Subject: [Losmandy_users] Re: Ovision warranty

>

>

>

> I don't get it either. I am not aware of any Losmandy advertised P.E.

> guarantee--did I miss something? regards Greg N

>

> --- In Losmandy_users@ mailto:Losmandy_users%40yahoogroups.com>

> yahoogroups.com, "Frank Barrett" frankb@> wrote:

> >

> > I have emailed Franck about this, but I am curious what others think.

> > The Ovision web site states, "The machining accuracy is three times

> > better than the current 'High precision ' Losmandy brass worms, or

> > previous steel versions." and elsewhere, "The tracking warranty is + /

> > - 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

> > Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

> > for the HP worm, so I am having difficulty resolving the "three times

> > better" statement. Am I missing something here?

> >

> > Frank Barrett

> > celestialwon celestialwon celestialwonders.com>

ders.com> ders.com > >

>

>

>

>

>

> [Non-text portions of this message have been removed]

>











[Non-text portions of this message have been removed]







----------------------------

#38919 Aug 15, 2008

Ladislav



I have a hunch that you have hit another deficiency in the G11 that I have

been looking at off and on for a while now. A much longer periodic error in

the tracking of the order of about 30-45 minutes*. This became obvious on my

mount when I once let PEMPro run for a 'considerable' time. The drift in RA

that showed on the PEMPro capture graph slowed, stopped, then reversed!



I started doing some calculations (using my bearing fundamental frequency

calculation spreadsheet which can be found towards the bottom of this page

www.wilmslowastro.com/software/software.htm>) around the RA shaft

needle bearings and one of the pass frequencies came out about right.



My initial conclusion is that my RA shaft has been machined slightly

undersized** - something I have seen other people report - and this is

causing the shaft to 'climb up' and then 'drop over' the rollers in the

needle bearings. I think the only fix will be to buy a new RA shaft.



Regards

Mark



* Just from memory, I do not have the documents with me at the moment to

check.

** Iirc the spec for the needle bearings on the shaft dimension is quite

tight, of the order of 0.0005"





2008/8/14 Ladislav Nemec nemecl@...>

> As far as I know (I did some search three years ago),only a few mount

> manufacturers publish PE specifications, Astro Physics and Takahashi if I

> remember correctly. Their mounts are more expensive than Losmandy and were

> not readily available in 2005.

>

> I think that the consensus is that the source of tracking errors (sometimes

> not with the worm rotation period) are caused by the worm assembly - glad

> to

> find out here that there are now alternatives available. As I mentioned

> before, I have been lucky with my Dec (mechanically identical) worm

> assembly, my PE (with compensation for drift) is below 10 arcsecs peak to

> peak, the values advertised (in 2005) for the Takahashi mounts, if memory

> serves me well.

>

> I am now measuring systematically variation of the tracking error along the

> 24 hour worm gear. It appears that while the 'periodic' errors remain about

> the same, the drift changes. Obviously, the large worm gear is not perfect

> either. Roy Gralak wrote me how to compensate for a drift in PemPro.

> Unfortunately, based on limited number of observations, the drift varies

> along the worm gear in a relatively short period of time (10 - 30 minutes).

> I think the only solution is guiding.

>

> Some G11 users achieved great results, some of us are not so lucky (or

> competent, no offense to anyone). That's, of course, the challenge and fun

> of this hobby.

>

> LN

>





[Non-text portions of this message have been removed]



----------------------------

#38924 Aug 15, 2008

Mark,



Yes! I didn't see this post until after I replied to your earlier

post, but this seems to describe the very low frequency drift I see in

my 40+ minute PE curve. Do you think that is what I am seeing? Do

you think this is serious enough to warrant fixing? It seems to me it

can be easily guided out, no?



Frank Barrett

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "Mark Crossley" public@...> wrote:

>

> Ladislav

>

> I have a hunch that you have hit another deficiency in the G11 that

I have

> been looking at off and on for a while now. A much longer periodic

error in

> the tracking of the order of about 30-45 minutes*. This became

obvious on my

> mount when I once let PEMPro run for a 'considerable' time. The

drift in RA

> that showed on the PEMPro capture graph slowed, stopped, then reversed!

>

> I started doing some calculations (using my bearing fundamental

frequency

> calculation spreadsheet which can be found towards the bottom of

this page

> www.wilmslowastro.com/software/software.htm>) around the RA shaft

> needle bearings and one of the pass frequencies came out about right.

>

> My initial conclusion is that my RA shaft has been machined slightly

> undersized** - something I have seen other people report - and this is

> causing the shaft to 'climb up' and then 'drop over' the rollers in the

> needle bearings. I think the only fix will be to buy a new RA shaft.

>

> Regards

> Mark

>

> * Just from memory, I do not have the documents with me at the moment to

> check.

> ** Iirc the spec for the needle bearings on the shaft dimension is quite

> tight, of the order of 0.0005"

>

>

> 2008/8/14 Ladislav Nemec nemecl@...>

>

> > As far as I know (I did some search three years ago),only a few

mount

> > manufacturers publish PE specifications, Astro Physics and

Takahashi if I

> > remember correctly. Their mounts are more expensive than Losmandy

and were

> > not readily available in 2005.

> >

> > I think that the consensus is that the source of tracking errors

(sometimes

> > not with the worm rotation period) are caused by the worm assembly

- glad

> > to

> > find out here that there are now alternatives available. As I

mentioned

> > before, I have been lucky with my Dec (mechanically identical) worm

> > assembly, my PE (with compensation for drift) is below 10 arcsecs

peak to

> > peak, the values advertised (in 2005) for the Takahashi mounts, if

memory

> > serves me well.

> >

> > I am now measuring systematically variation of the tracking error

along the

> > 24 hour worm gear. It appears that while the 'periodic' errors

remain about

> > the same, the drift changes. Obviously, the large worm gear is not

perfect

> > either. Roy Gralak wrote me how to compensate for a drift in PemPro.

> > Unfortunately, based on limited number of observations, the drift

varies

> > along the worm gear in a relatively short period of time (10 - 30

minutes).

> > I think the only solution is guiding.

> >

> > Some G11 users achieved great results, some of us are not so lucky (or

> > competent, no offense to anyone). That's, of course, the challenge

and fun

> > of this hobby.

> >

> > LN

> >

>

>

> [Non-text portions of this message have been removed]

>







----------------------------

#38926 Aug 15, 2008

Hi Mark,



Another possibility is that the RA worm-gear is out of round or has

some systematic errors, perhaps introduced by the cutting equipment

that itself has a periodic error of 30-40 minutes.



Did you try to move the gear to a different spot and see if the same

error repeats? You can simply slew to make RA rotate, say 180 degrees,

and then start there as the new CWD position.



If the shaft size is the problem, I've found that a third shaft

bearing may actually help. It adds a third support point to the shaft.

If it's not perfectly in-line with the other two bearings (very

likelyl!) it will exert some pressure on the the RA shaft and keep it

from moving around. At least that's what it did in mine. I spent some

time trying to line up all three bearings, but in the end, left things

so that the shaft goes in and comes out only with some effort. This

doesn't seem to affect tracking for me, as my PE is under 4 arcseconds

peak-to-peak :) But I'm sure the shaft doesn't move around (up, down,

or sideways) on its own.



One more possibility is simple atmospheric refraction. Slow moving air

masses can often introduce an apparent drift in the tracking rate, and

can even reverse the direction of the drift when it passes by.



As Frank pointed out, this should be very easy to guide out, so I'm

not sure the fix warrants a major surgery :-)



Regards,



-Paul



--- In Losmandy_users@yahoogroups.com, "Mark Crossley" public@...>

wrote: >

> My initial conclusion is that my RA shaft has been machined slightly

> undersized** - something I have seen other people report - and this

is > causing the shaft to 'climb up' and then 'drop over' the rollers in

the > needle bearings. I think the only fix will be to buy a new RA shaft.



----------------------------

#38932 Aug 15, 2008

Paul



The shaft is definitely undersized. I measured it with some digital

callipers, and with the RA clutch loose it it possible to physically see the

movement in the Dec assembly.



The drift I am not too concerned about, it is slow and guiding easily

removes it. However what is more concerning is that I believe it also

introduces sudden 'jumps' in the movement. I haven't finished looking into

this but I think this happens as the shaft looses support from the top

bearing, the clutch holds the dec assembly in position, but then the clutch

slips and the RA shaft drops back against the needle bearings.



I quite often 'hear' this sudden movement as a 'crack' sound as I slew

heavier scopes around the sky. At first I thought it was my SCT moving in

it's bolts on the Losmandy rail. But it happened with my C9.25 and now

(louder!) with C14, I don't really notice it with the 4" Apo, I'm guessing

the clutch can hold that weight. I also have the occasional image spoilt by

a 'jump' too.



I hadn't posted anything about this before as I wanted to investigate it in

more depth before pontificating, but Ladislav's post prompted me to post

something. I haven't looked into this for maybe 6 months or more - so you

can see the priority I am giving it :) Moving to a different part of the

worm wheel would be one thing to test, but the way I play with my mount

means I frequently run on differnet worm wheel sections.



One thing I have tried is switching back to the standard Nylon clutches in

an attempt to allow the RA shaft to slip constantly to the 'bottom' (or at

least more smoothly) It does seem to have reduced the audible 'cracks'.



I did think about the third bearing option, but as all bearings slip to some

degree, I wondered if they would end up self algining themselves over time.

My last thoughts were to bit the bullet and order a new RA shaft from Scott.

My concern being that the QA at Losmandy doesn't seem to be very high and

the chances of getting another undersized shaft seem high - where bearings

run directly against a shaft without an inner race I think the shaft should

be precision ground to size rather than machined.



And don't get me started on the disk between the RA and Dec assemblies. It

looks great but dimensionally it is truely awful - no wonder my

orthagonality isn't good.



Regards

Mark





2008/8/15 Paul K pkane2001@...>

> Hi Mark,

>

> Another possibility is that the RA worm-gear is out of round or has

> some systematic errors, perhaps introduced by the cutting equipment

> that itself has a periodic error of 30-40 minutes.

>

> Did you try to move the gear to a different spot and see if the same

> error repeats? You can simply slew to make RA rotate, say 180 degrees,

> and then start there as the new CWD position.

>

> If the shaft size is the problem, I've found that a third shaft

> bearing may actually help. It adds a third support point to the shaft.

> If it's not perfectly in-line with the other two bearings (very

> likelyl!) it will exert some pressure on the the RA shaft and keep it

> from moving around. At least that's what it did in mine. I spent some

> time trying to line up all three bearings, but in the end, left things

> so that the shaft goes in and comes out only with some effort. This

> doesn't seem to affect tracking for me, as my PE is under 4 arcseconds

> peak-to-peak :) But I'm sure the shaft doesn't move around (up, down,

> or sideways) on its own.

>

> One more possibility is simple atmospheric refraction. Slow moving air

> masses can often introduce an apparent drift in the tracking rate, and

> can even reverse the direction of the drift when it passes by.

>

> As Frank pointed out, this should be very easy to guide out, so I'm

> not sure the fix warrants a major surgery :-)

>

> Regards,

>

> -Paul

>





[Non-text portions of this message have been removed]







----------------------------

#38934 Aug 15, 2008

Paul,



When I discovered my shafts were undersized I had them chrome plated and centerless ground to

1.2495". I also did the third bearing mod but instead of adding a third bearing I replaced the

original with one that was 1.25" long. Since I now have PemPro2, when the mount is put back together

I'll take some PE measurements. I had never taken any of the mount, but then I wasn't using it for

imaging at that time either.



Don

----- Original Message -----

From: "Paul K" pkane2001@...>

To: Losmandy_users@yahoogroups.com>

Sent: Friday, August 15, 2008 8:27 AM

Subject: [Losmandy_users] Re: Low frequency errors - Was: Ovision warranty





> Hi Mark,

>

> Another possibility is that the RA worm-gear is out of round or has

> some systematic errors, perhaps introduced by the cutting equipment

> that itself has a periodic error of 30-40 minutes.

>

> Did you try to move the gear to a different spot and see if the same

> error repeats? You can simply slew to make RA rotate, say 180 degrees,

> and then start there as the new CWD position.

>

> If the shaft size is the problem, I've found that a third shaft

> bearing may actually help. It adds a third support point to the shaft.

> If it's not perfectly in-line with the other two bearings (very

> likelyl!) it will exert some pressure on the the RA shaft and keep it

> from moving around. At least that's what it did in mine. I spent some

> time trying to line up all three bearings, but in the end, left things

> so that the shaft goes in and comes out only with some effort. This

> doesn't seem to affect tracking for me, as my PE is under 4 arcseconds

> peak-to-peak :) But I'm sure the shaft doesn't move around (up, down,

> or sideways) on its own.

>

> One more possibility is simple atmospheric refraction. Slow moving air

> masses can often introduce an apparent drift in the tracking rate, and

> can even reverse the direction of the drift when it passes by.

>

> As Frank pointed out, this should be very easy to guide out, so I'm

> not sure the fix warrants a major surgery :-)

>

> Regards,

>

> -Paul



----------------------------

#38935 Aug 15, 2008

Hi Don,



Chrome plating sounds like the real solution to the undersized shaft

problem! Did you experience any problems with the shaft before, or

did you just find that it was undersized?



Regards,



-Paul



--- In Losmandy_users@yahoogroups.com, "Don D'Egidio" djd521@...>

wrote: >

> Paul,

>

> When I discovered my shafts were undersized I had them chrome

plated and centerless ground to > 1.2495". I also did the third bearing mod but instead of adding a

third bearing I replaced the > original with one that was 1.25" long. Since I now have PemPro2,

when the mount is put back together > I'll take some PE measurements. I had never taken any of the

mount, but then I wasn't using it for > imaging at that time either.

>

> Don

>



----------------------------

#38936 Aug 15, 2008

Paul,



Both were undersized at 1.247". You could feel the side to side movement even when the clutches were

tight.



Don

----- Original Message -----

From: "Paul K" pkane2001@...>

To: Losmandy_users@yahoogroups.com>

Sent: Friday, August 15, 2008 11:01 AM

Subject: [Losmandy_users] Re: Low frequency errors - Was: Ovision warranty





> Hi Don,

>

> Chrome plating sounds like the real solution to the undersized shaft

> problem! Did you experience any problems with the shaft before, or

> did you just find that it was undersized?

>

> Regards,

>

> -Paul

>

> --- In Losmandy_users@yahoogroups.com, "Don D'Egidio" djd521@...>

> wrote:

>>

>> Paul,

>>

>> When I discovered my shafts were undersized I had them chrome

> plated and centerless ground to

>> 1.2495". I also did the third bearing mod but instead of adding a

> third bearing I replaced the

>> original with one that was 1.25" long. Since I now have PemPro2,

> when the mount is put back together

>> I'll take some PE measurements. I had never taken any of the

> mount, but then I wasn't using it for

>> imaging at that time either.

>>

>> Don

>>

>

>

>

---------------

>

> Yahoo! Groups Links

>

>

>

>



----------------------------

#38971 Aug 15, 2008

I strongly believe so although I need more data to document it. Will look

closely at your link. The advantage of this slow variation of the drift is

that it can be fairly efficiently guided out if there is no flexing between

the guidescope and the main OTA. I experimented with on off-axis (cheap

Meade) beam splitter but, so far, have not been able to make it work. I

would be satisfied with consistently good 3 minute exposures at FOV slightly

over 30 arcmins. So far, it sometimes works, sometimes it does not work.







One can settle with, say 70% of good such images rejecting the rest. We get

what we paid for. On the AP forum people are signing odes on their mounts

that seem to do everything and then some. Too old and poor to buy one.







Thanks, LN







-----Original Message-----

From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com]

On Behalf Of Mark Crossley

Sent: Friday, August 15, 2008 1:53 AM

To: Losmandy_users@yahoogroups.com

Subject: [Losmandy_users] Low frequency errors - Was: Ovision warranty







Ladislav



I have a hunch that you have hit another deficiency in the G11 that I have

been looking at off and on for a while now. A much longer periodic error in

the tracking of the order of about 30-45 minutes*. This became obvious on my

mount when I once let PEMPro run for a 'considerable' time. The drift in RA

that showed on the PEMPro capture graph slowed, stopped, then reversed!



I started doing some calculations (using my bearing fundamental frequency

calculation spreadsheet which can be found towards the bottom of this page

www.wilmslow www.wilmslowastro.com/software/software.htm>

astro.com/software/software.htm>) around the RA shaft

needle bearings and one of the pass frequencies came out about right.



My initial conclusion is that my RA shaft has been machined slightly

undersized** - something I have seen other people report - and this is

causing the shaft to 'climb up' and then 'drop over' the rollers in the

needle bearings. I think the only fix will be to buy a new RA shaft.



Regards

Mark



* Just from memory, I do not have the documents with me at the moment to

check.

** Iirc the spec for the needle bearings on the shaft dimension is quite

tight, of the order of 0.0005"



2008/8/14 Ladislav Nemec nemecl@earthlink. mailto:nemecl%40earthlink.net>

net>

> As far as I know (I did some search three years ago),only a few mount

> manufacturers publish PE specifications, Astro Physics and Takahashi if I

> remember correctly. Their mounts are more expensive than Losmandy and were

> not readily available in 2005.

>

> I think that the consensus is that the source of tracking errors

(sometimes > not with the worm rotation period) are caused by the worm assembly - glad

> to

> find out here that there are now alternatives available. As I mentioned

> before, I have been lucky with my Dec (mechanically identical) worm

> assembly, my PE (with compensation for drift) is below 10 arcsecs peak to

> peak, the values advertised (in 2005) for the Takahashi mounts, if memory

> serves me well.

>

> I am now measuring systematically variation of the tracking error along

the > 24 hour worm gear. It appears that while the 'periodic' errors remain

about > the same, the drift changes. Obviously, the large worm gear is not perfect

> either. Roy Gralak wrote me how to compensate for a drift in PemPro.

> Unfortunately, based on limited number of observations, the drift varies

> along the worm gear in a relatively short period of time (10 - 30

minutes). > I think the only solution is guiding.

>

> Some G11 users achieved great results, some of us are not so lucky (or

> competent, no offense to anyone). That's, of course, the challenge and fun

> of this hobby.

>

> LN

>



[Non-text portions of this message have been removed]











[Non-text portions of this message have been removed]







----------------------------

#39000 Aug 16, 2008

I received the following reply from Gilles Cohen at Ovision. I hope I

am not breaching protocol by posting this here, but I think it maybe

helpful to others in the decision process. BTW, I, like Greg am in no

way affiliated with Ovision.



Start of quote:



Hello,



our own worms have always been warrantied to 10" PP, even before we

introduce the NS design.

This is achieved for several reasons:



- our machining accuracy is 3 times better than Losmandy's worms (even

if they are now called HP worms).

- we have total control on the main factors than make the worm

accurate :

the shape of the teeth (clean and right cutting angle) , and roundness

of the worm. So we are always below 10", I would say 10" is the worst

we get.



We know Scott very well and have discussed the worm design several

times. He doesn't advertise on accuracy. He only gives an accuracy

machining level which is 2/10 000 of an inch.

With this accurracy, if the roundness and teeth cut match positively (

25% chance) you will obtain a 10" PP.

If they match negatively ( 25% chance I mean the opposite way) you

could get a 30" PP result. The other 50% is a worm between 10 and 30" PP.



Our worms have a very clean cut, and are mounted in the housing: this

cancels the 1/3 period. Because the bearings are also perfectly

square, you will also get less high frequency events in your PE cycle.



End of quote.



This also shows there is life at Ovision, but I have not yet received

confirmation on my order. Perhaps they are working through the email

backlog.



Frank Barrett

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:

>

> I have emailed Franck about this, but I am curious what others think.

> The Ovision web site states, "The machining accuracy is three times

> better than the current 'High precision ' Losmandy brass worms, or

> previous steel versions." and elsewhere, "The tracking warranty is + /

> - 5 arc seconds for the G11 mount ( total of 10" peak to peak )...".

> Now if I am not mistaken Losmandy advertises +/- 5 arc seconds as well

> for the HP worm, so I am having difficulty resolving the "three times

> better" statement. Am I missing something here?

>

> Frank Barrett

> celestialwonders.com

>



----------------------------

#39001 Aug 16, 2008

Well it's not inconceivable with the discussion on this group and the

Astromart review that they've had say thirty orders. From their

perspective that would be a "flood." It's not much gross in terms of

running a business though. Just part of what you need to get by. But

they also sell lots of other stuff.



They apparently have a view of the Losmandy HP worm that indicates

it's not very HP. This is consistent with a post we just got from

someone else. I don't know what to make of it. Seems like the brass

has been better for most folks. But maybe that's it, it's only better

for three out of four.



It's interesting to see, and perhaps a bit sad to note, that even

without the Value Added Tax their prices run about 2x higher than the

U.S. for U.S. mounts. I've seen complaints from other European

members, not just French.



regards

Greg N

--- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@...> wrote:



>

> This also shows there is life at Ovision, but I have not yet received

> confirmation on my order. Perhaps they are working through the email

> backlog.

>

> Frank Barrett

> celestialwonders.com

>



----------------------------

#39004 Aug 16, 2008

I think what was said about the worms and the tolerances is probably

true. I do know that with any tolerance there will be variance and so

a percentage will be on the high and low side of this tolerance. Whe

you realize just how little an arcsec is and what it takes to make

this variation, then any slight change in the CNC rig will cause an

arcsec or two.



My thought has always been that the first few pieces that come off of

the CNC machine, right after it was calibrated at a specific

temperature, will be the best. The ones made at the end of the run

will likely be the worst.



If you go to a machine shop that has a "High End" CDN machine, you

will be shocked at what it cost to have a worm made. $50 for a worm is

not exactly expensive, it is quite cheap. I think you would have to

have ordered quite a few to get it anywhere near that price.



So, Ovision's worm that seems to cost $125+ is more along the lines of

the cost for a part made with very close tolerances. If they are

quoting correctly, .0002" fir the Losmandy would be .0000666" for the

Ovision! Now that would be like a part made for NASA for the Space

Shuttle or even greater! This is amazing quality control!



Floyd

--- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> Well it's not inconceivable with the discussion on this group and the

> Astromart review that they've had say thirty orders. From their

> perspective that would be a "flood." It's not much gross in terms of

> running a business though. Just part of what you need to get by. But

> they also sell lots of other stuff.

>

> They apparently have a view of the Losmandy HP worm that indicates

> it's not very HP. This is consistent with a post we just got from

> someone else. I don't know what to make of it. Seems like the brass

> has been better for most folks. But maybe that's it, it's only better

> for three out of four.

>

> It's interesting to see, and perhaps a bit sad to note, that even

> without the Value Added Tax their prices run about 2x higher than the

> U.S. for U.S. mounts. I've seen complaints from other European

> members, not just French.

>

> regards

> Greg N

>

> --- In Losmandy_users@yahoogroups.com, "Frank Barrett" frankb@> wrote:

>

> >

> > This also shows there is life at Ovision, but I have not yet received

> > confirmation on my order. Perhaps they are working through the email

> > backlog.

> >

> > Frank Barrett

> > celestialwonders.com

> >

>







----------------------------

#39013 Aug 16, 2008

I think it's pretty damned good and I wouldn't be surprised to learn

sometime that Ovision is making worms for other mount makers but I

don't know enough about the industry.



Although I'm jumping threads I meant to add that I really liked the

photo of your viewing site. Were I there, I would not be taking a

pad, but it looks like a nice place to catch photons.



regards

Greg N



--- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@...> wrote:

>

> I think what was said about the worms and the tolerances is probably

> true. I do know that with any tolerance there will be variance and so

> a percentage will be on the high and low side of this tolerance. Whe

> you realize just how little an arcsec is and what it takes to make

> this variation, then any slight change in the CNC rig will cause an

> arcsec or two.

>

> My thought has always been that the first few pieces that come off of

> the CNC machine, right after it was calibrated at a specific

> temperature, will be the best. The ones made at the end of the run

> will likely be the worst.

>

> If you go to a machine shop that has a "High End" CDN machine, you

> will be shocked at what it cost to have a worm made. $50 for a worm is

> not exactly expensive, it is quite cheap. I think you would have to

> have ordered quite a few to get it anywhere near that price.

>

> So, Ovision's worm that seems to cost $125+ is more along the lines of

> the cost for a part made with very close tolerances. If they are

> quoting correctly, .0002" fir the Losmandy would be .0000666" for the

> Ovision! Now that would be like a part made for NASA for the Space

> Shuttle or even greater! This is amazing quality control!

>

> Floyd

>



----------------------------

#39016 Aug 16, 2008

Hi Greg,

There is a bit of room there that is just open area, no concrete. You

can always come as my guest and take a grassy spot!

Floyd --- In Losmandy_users@yahoogroups.com, "gnowellsct" tim71pos@...> wrote:

>

> I think it's pretty damned good and I wouldn't be surprised to learn

> sometime that Ovision is making worms for other mount makers but I

> don't know enough about the industry.

>

> Although I'm jumping threads I meant to add that I really liked the

> photo of your viewing site. Were I there, I would not be taking a

> pad, but it looks like a nice place to catch photons.

>

> regards

> Greg N

>

>

> --- In Losmandy_users@yahoogroups.com, "Floyd Blue" fblue@> wrote:

> >

> > I think what was said about the worms and the tolerances is probably

> > true. I do know that with any tolerance there will be variance and so

> > a percentage will be on the high and low side of this tolerance. Whe

> > you realize just how little an arcsec is and what it takes to make

> > this variation, then any slight change in the CNC rig will cause an

> > arcsec or two.

> >

> > My thought has always been that the first few pieces that come off of

> > the CNC machine, right after it was calibrated at a specific

> > temperature, will be the best. The ones made at the end of the run

> > will likely be the worst.

> >

> > If you go to a machine shop that has a "High End" CDN machine, you

> > will be shocked at what it cost to have a worm made. $50 for a worm is

> > not exactly expensive, it is quite cheap. I think you would have to

> > have ordered quite a few to get it anywhere near that price.

> >

> > So, Ovision's worm that seems to cost $125+ is more along the lines of

> > the cost for a part made with very close tolerances. If they are

> > quoting correctly, .0002" fir the Losmandy would be .0000666" for the

> > Ovision! Now that would be like a part made for NASA for the Space

> > Shuttle or even greater! This is amazing quality control!

> >

> > Floyd

> >

>



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