VintageBigBlue.org

 

Re: PE .....................was: G11 or Not


May 26, 2006

 


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

#29937 May 26, 2006

Hi,

> arcsecond tracking errors? Especially when the fix sometimes involves

> drilling holes into certain parts of the mount!!!

>



I found this statement interesting.



. Where do I have to drill holes in order to adjust a standard G11

mount ?



regards Rainer



PS Please fellow members in this group do not get mad at me but I think

I found out what the letters PE mean



Paranoia Expected :-))))



Are we not expecting too much from a mount that costs US 2,500.00 ?

(without Gemini GoTO and US $ 3,500.00 with Gemini GoTo)



The average PE in this case "Periodic Error" of these mounts is about

+5" arcseconds maybe up to +-10" arcseconds. With a little bit of

tuning you can get it quitestable and repeatable.



Anyhow, as many say, for visual it is irrelevant and when we do imaging

we know that we have to autoguide. . So What ? or better said . Where

is the problem ?



We have seen in many postings of graphs that the worm of the Losmandy

mounts do deliver nice periodic curves without big jumps.



Are we not in the situation that we are chasing already the seeing ?



again regards Rainer



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

#29946 May 26, 2006

Rainer,

From my point of view I find your statement interesting :) since I

have seen your beautifully machined replacement for the entire

worm/motor assembly!!!



In my case I had to drill out the worm bearing block to remove the

ball bearings, then I had to ream out the inside of the blocks. I

also had to dremel material off the cylindrical plug on one of the

bearing blocks to get the Oldham coupler alignment perfect since I

was lead to believe by Scott L. (I phoned him by the way ;) and

others in this group that the source of my problems was coupler

alignment. BTW from all the data I collected I now believe that bad

coupler alignment only contributes to "noise".



PS I agree with explanation of PE, and of course we are expecting too

much, but when you cant afford and AP900 etc isnt that all we can

do !?!



Regards

Eric

--- In Losmandy_users@yahoogroups.com, "Rainer" rsbfoto@...> wrote:

>

> Hi,

>

> > arcsecond tracking errors? Especially when the fix sometimes

involves

> > drilling holes into certain parts of the mount!!!

> >

>

> I found this statement interesting.

>

> . Where do I have to drill holes in order to adjust a standard G11

> mount ?

>

> regards Rainer

>

> PS Please fellow members in this group do not get mad at me but I

think

> I found out what the letters PE mean

>

> Paranoia Expected :-))))

>

> Are we not expecting too much from a mount that costs US 2,500.00 ?

> (without Gemini GoTO and US $ 3,500.00 with Gemini GoTo)

>

> The average PE in this case "Periodic Error" of these mounts is

about

> +5" arcseconds maybe up to +-10" arcseconds. With a little bit of

> tuning you can get it quitestable and repeatable.

>

> Anyhow, as many say, for visual it is irrelevant and when we do

imaging

> we know that we have to autoguide. . So What ? or better said .

Where

> is the problem ?

>

> We have seen in many postings of graphs that the worm of the

Losmandy

> mounts do deliver nice periodic curves without big jumps.

>

> Are we not in the situation that we are chasing already the seeing ?

>

> again regards Rainer

>



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

#29950 May 26, 2006

Hi Rainer,



You raise a couple of excellent points. For my money (already

spent!), the G-11 is about the best mount I could possibly choose

without going all the way to the $10,000 range. Takahashi produces

mounts in a similar price range, which are probably smoother, but I

haven't researched them that carefully. Still the uncorrected PE is

about in the same range as a properly adjusted G-11.



For me, what makes the difference is that I feel quite comfortable

stripping down my G-11 and reassembling it, whereas with a Tak mount

I would be a fair bit more worried. Also, Scott Losmandy answers his

phone when I call :) and is very helpful and supportive.



In a few years I may sell my G-11 and buy something like a Paramount

ME but that is a ways off and the G-11 is working just dandy. I've

had what seems like a fairly extreme case of the bearing-induced

error, and even still I am very happy with the mount, and have been

able to learn its ins and outs fast enough to keep well ahead of my

imaging skills.



Your other excellent point is chasing seeing. A while back I was

guiding with short exposures, but I get the same or better results

with a decent polar alignment and 5+ second guide exposures. So long

as the mount's periodic error (whether bearing-induced or worm-

induced) stays around or below 1 arc second per 10 second period, I

am happy.



A smooth curve seems way more important than the magnitude of error

over a 4 minute period.



Wayne







--- In Losmandy_users@yahoogroups.com, "Rainer" rsbfoto@...> wrote:

>

> Hi,

>

> > arcsecond tracking errors? Especially when the fix sometimes

involves

> > drilling holes into certain parts of the mount!!!

> >

>

> I found this statement interesting.

>

> . Where do I have to drill holes in order to adjust a standard G11

> mount ?

>

> regards Rainer

>

> PS Please fellow members in this group do not get mad at me but I

think

> I found out what the letters PE mean

>

> Paranoia Expected :-))))

>

> Are we not expecting too much from a mount that costs US 2,500.00 ?

> (without Gemini GoTO and US $ 3,500.00 with Gemini GoTo)

>

> The average PE in this case "Periodic Error" of these mounts is

about

> +5" arcseconds maybe up to +-10" arcseconds. With a little bit of

> tuning you can get it quitestable and repeatable.

>

> Anyhow, as many say, for visual it is irrelevant and when we do

imaging

> we know that we have to autoguide. . So What ? or better said .

Where

> is the problem ?

>

> We have seen in many postings of graphs that the worm of the

Losmandy

> mounts do deliver nice periodic curves without big jumps.

>

> Are we not in the situation that we are chasing already the seeing ?

>

> again regards Rainer

>







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