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RE: [Losmandy_users] Pointing issues


Nov 14, 2001

 


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#6728 Nov 14, 2001

Hi Folks

attached are some graphs of my G-11 doing a telescope pointing map thru a

TV101 @f11 with an st7e.



The scatter diagram shows my dilema.....the RA pointing is right on and the

DEc is the one causing the RMS value to be so hi.

The other 2 graphs are this 50 star observations map in the DEC and in the

RA which reinforces this predicament.



Anyone care to take a shot at what might be the cause?



its got me and the folks at Software Bisque stumped



thanks



Clear skies...good eyes



JImmy



www.frenchriverobservatory.com





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Get your FREE download of MSN Explorer at explorer.msn.com/intl.asp



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

#6729 Nov 14, 2001

Hi Folks

attached are some graphs of my G-11 doing a telescope pointing map thru a

TV101 @f11 with an st7e.



The scatter diagram shows my dilema.....the RA pointing is right on and the

DEc is the one causing the RMS value to be so hi.

The other 2 graphs are this 50 star observations map in the DEC and in the

RA which reinforces this predicament.



Anyone care to take a shot at what might be the cause?



its got me and the folks at Software Bisque stumped



thanks









Clear skies...good eyes



JImmy



www.frenchriverobservatory.com





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

Get your FREE download of MSN Explorer at explorer.msn.com/intl.asp



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

#6730 Nov 14, 2001

Mr Thibert:



1. My commendations on your data collection and prsentation. You may

be interested to know that when I took statistics we were told that

small sample size theory will let you get away with thirty

observations--in case you want to save yourself some time.



2. You didn't indicate what you're pointing WITH. It could be Gemini,

dscs, or the analog setting circles.



3. It looks to me that there must be some kind of slippage in the Dec

that is mechanical in nature. I never graphed the weird results I got

when my dsc's were incorrectly gapped, but basically, since the

friction is all wrong, it goes wrong one way as you go in one

direction and aother way when you go in the other direction. If you

graphed that, that would be error around a mean. I have to believe

that even if you are using Gemini that there is something in the dec

assembly that is screwy.



4. If it were dscs, I would suggest first off that you check the

gapping. Since you are reputed on this group as a capable and smart

individual, I doubt that's the problem, we've discussed gapping ad

infinitum ad nauseam. The next step would be to switch the mechanical

components of one axis into the other to see if the source of the

error changes. I don't know how you would do that on a gemini but it

might be possible. Since I've never seen or touched a Gemini I can't

offer an opinion. It certainly is possible with dscs. If you are

using analog circles it may be that you are unaware that the vernier

markings (on those scopes pre spring 2001 that had two sets) are not

180 degrees apart and as you flip to read the vernier on the other

side you are unware of the shift occurring.



My general thought is that until you begin to switch and watch, you're

not going to isolate the problem. Consider:



1. Make Gemini perform 360 turn in one direction (centering on a

physical object like a distant tree to make sure) and then another, do

it for the Dec axis. Do it many times, perhaps with stops in each

direction, to see how Dec readout changes during the exercsie and

whether it's the same reading at each stop. (you use high power,

center on a tree, on a doorbell across the street, etc, that gets you

within an arc minute or two of where you were for the first

measurement)



2. Now switch the wires between RA and Dec input and repeat hte 360

test in each direction.



Hopefully this exercise will show the Dec error in action. When you

switch the wires, if the error continues, it means there is probably

some kind of encoder/mesh issue with the Dec axis. If the error seems

to shift to the RA axis (you can't do 360 degree turns, but yo can do

180) then the problem is probably in the "brain" or computer. I don't

know whether Gemini asks you to set default tics like a dsc computer

but if these are set wrong they would also give a wide range of

variance around a mean.



My general comment is that you have wide variance around the same mean

as in your well-functioning RA and I believe this indicates a hardware

problem. It might need to make the trip to the Losmandy hospital in

LA. If I am right, we also have an explanation as to why software

types would be stumped.

good luck

Greg Nowell



--- In Losmandy_users@y..., "James A. Thibert" thibertj@h...> wrote:

> Hi Folks

> attached are some graphs of my G-11 doing a telescope pointing map

thru a

> TV101 @f11 with an st7e.

>

> The scatter diagram shows my dilema.....the RA pointing is right on

and the

> DEc is the one causing the RMS value to be so hi.

> The other 2 graphs are this 50 star observations map in the DEC and

in the

> RA which reinforces this predicament.

>

> Anyone care to take a shot at what might be the cause?

>

> its got me and the folks at Software Bisque stumped

>

> thanks

>

> Clear skies...good eyes

>

> JImmy

>

> www.frenchriverobservatory.com

>

>

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

> Get your FREE download of MSN Explorer at

explorer.msn.com/intl.asp







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

#6741 Nov 15, 2001

Hi Greg



thanks for the suggestions.



I am using the Gemini.The DSC's are not connected.However,you make a good

point about their possible contribution to a mechanical error.

I had already taken the DSC off the RA axis (and the clutch knob with the

handles) because it was getting in the way and catching the CCD cables).

I noticed an improvement in RA but attributed it to some other mods made at

the time.



Using T-point (or Gemini for that matter)allows one to ignore the DSC and

turn them off so the encoder tics don't come into play (the optical shaft

encoders of Gemini are fixed)



You may be right though in the mechanical suggestions and I will check the

DEC dsc tonight.It could be that while the gap is set ok and that it was

running well when I was using the DSC's, that there is error induced from

the teeth or meshing of the encoder gear and the DSC gear.

The DEC errors data has been analysed on several occasions by Software

Bisque and while I have been concentrating on RA,all the graphs have had

this DEC propensity.



They call it "non-repeatable errors"



The key to these programs being that they can mathematically account for a

consistant offset (like out-of-round gears,PEC,polar alignment offset etc)

but the math can't accomodate an error that occurs sporadically throughout

the axis.



That would tend to support the mechanical theory and the easiest thing to do

is remove the DSC hardware altogether.



The next trick would be the 360 tests you suggest.



thanks...I'll let you know how it works out



Clear skies...good eyes



JImmy



www.frenchriverobservatory.com







----Original Message Follows----





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

Get your FREE download of MSN Explorer at explorer.msn.com/intl.asp



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#60325 Nov 11, 2017

Have had my G11 for about 2 years and have had pointing problems since about first 8 months in. Have had paddle and control box rehabbed twice and now both are undergoing a full reworking. I'm sure Losmandy will rehab my units appropriately but my questions are not about the fixes. I would like advice from the group on what to look for in pointing problems and what might go into correcting them. I understand it's a complex system but is there a check list of possible problems that I can look to addressing if my system encounters further issues. I have researched the web as much as I can and read the info on the Gemini 2 site but would like some guidance from the members on this as I have this feeling I'm not doing all I can to correct the problems. I have a TAK130 sitting on the G11 mount and tripod and all are in excellent operating order. Thanks, Doc



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#60326 Nov 12, 2017

Hi Doc,

I find it valuable to do these steps if my pointing goes haywire...

I am using a Gemini 1, not a Gemini 2.. They differ in hardware, but I'm not aware of any difference between the two in software algorithms...

So try these steps to diagnose what's going on.

(I use Gemini.net to more easily get to internal pointing model values.. You get that and basic ASCOM software from the ASCOM website.)

1. Using the Gemink.net Advanced window, download the internal parameters ("Read from Gemini".) Write down the existing pointing model parameter values.. I think there are about 9 of these, and they are explained in the Gemini manual.. .Later, you will. compare the values to those of a good model...

2. Store the existing pointing model in a file, and name that file "Nov 12 2017 bad pointing" or something like that...

3. In Gemini.net, on the Advanced window,. uncheck the tick box "Synch performs additional Align ". Also inchecjk the box "PC sends to Gemini on connect" to make sure your PC, that may have bad values in its default file, does not send those to the handset.

4. Exit Gemini.net (software disconnect the Gemini from the PC...the cable can still be there.)

5. From the handset, perform a Cold Boot.. This sets all internal model values to zero.

6. Reconnect Gemini to the PC.. Use Gemini.net to Read the Mount values.. Ensure they are all zero still.. Also look at the Latitude, Longitude, Elevation, UTC date and time.. (There is a tickbox for having Gemini.net send the correct PC known date and time to the Gemini when it connects.. I do use that. ).

7. Start a sky chart on the PC that links to Gemini.net.. For that, I use both Stellarium-scope. (from Dragon-Welch computing website I think is www.dragonwelchcomputing.com) and the sky chart itself Stellarium from. Stellarium.org.. .You run Stellarium first to set its location to your site, then Save configuration, then exit.. Second, start Stellarium-scope, then select mount Gemini.net, then start Stellarium (a button on Stellarium-scope can do that).. Your Stellarium should show "scope" pointed at Polaris, if you are in positive latitude.. (You can minimize the Stellarium-scope window...just don't kill the program as it nicely links Stellarium and the Gemini.net together.. )

8. From the handset,. use Align Telescope to go to a bright star in its list.. Sometimes, this initial point is accurate, and sometimes, for unknown reason, it will be way off...

(I never know if this is due to old Daylight savings time change dates internal to the Gemini1 code, or why this happens... but it does even for a cold boot..

It's the weirdest thing because the mount correctly knows CWD...and time and location...how can it be so far far off in 1st star point?! )

9. When you have centered your first Alignment star, complete handset alignment pressing the buttons that requires..

10. Look at the Model parameters using Gemini.net.. .They will all still be zero.. What changed?. The settings for RA and DEC offset encoder counts...

11. Look at the skychart.. It should show the "scope" right atop the star you aligned to.

12. Back to Gemini.net, advanced page.. Now check the tick box for "Synch performs additional Align".. That allows the Sky chart software to not only Synch the existing (all zero) model, but allows Gemini to calculate new parameter values.. .

13. Back to the Sky chart.. Use your mouse to select a new star... (important!:) on the same side of the meridian as the first star.. (Press the spacebar to center and track that star on Stellarium.. .) That means keep the 2nd ( and 3rd ) stars East of the meridian if the 1st star was East.. Or stars 2 and 3 must be West if the first star was West.. Use the (Control-1 in Stellarium) issue a goto from the sky chart to move the scope, then center the star on your scope with your handset.. Then on the sky chart do a Synch (Control-3 from Stellarium). Do that again for a 3rd star also same side of meridian as 1st star.

11. Now use Gemini.net "advanced" page,. Read from Gemini, and look at the model pointing parameters again.. You should see a few non-zero values.. You can save that data in a file with some name..."Model with 3 stars Nov 12 2017" etc.

12. Now use the sky chart to pick 3 stars on the opposite side of meridian.. Synch (and "Synch performs additional Align" is checked in Gemini.net) and Align to those from the sky chart.. .Download and look at the parameter list and see more values change...

14. At this point,. I stop and save the model as full model for the. date.. .Your system should accurately point to new objects around the sky.. I also Un-check the box "Synch performs additional Align " because I don't want added star's data to somehow mess up the calculations (which are a black- box to me)...

15.. Now examine the model values.. .How do your original "bad" model values compare?Let us know what you find.....

I hope all these steps get you to a good and repeatable solution, and more enjoyment of your system.

-Michael Herman.







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#60327 Nov 12, 2017

typo: "gemink.net" is wrong...gemini.net is correct...sorry for that!

Michael.



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#60328 Nov 12, 2017

AH HA! All my ���problems���will disappear if I just use ���gemink.net��� ! Must be some super secret decoderring version! ��***typo: "gemink.net"is wrong...gemini.net is correct...sorry forthat! ��

Michael��



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#60329 Nov 12, 2017

HI Derek,

I try my best...but since I've repeated that list a few times this year...yes...it's time to make a PDF and just point to that.. I can add screen shots too... another benefit...

I rely wish I had access to the source code so I could remedy or at least understand the causes of these strange pointing errors.. But...it is locked up.. Gemini2 code might be open but...I don't have one!

Michael.



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#60330 Nov 12, 2017

Gemini2 code might be open but...I don't have one!



Neither Gemini 1 or 2 source code is .open.. Gemini.NET is.



Regards,



-Paul



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#60331 Nov 12, 2017

Fortunately you know someone who does.. ��When it gets more into the dumping rainseason maybe it will magically appear on your porch.. ��Ya just never know.. ��:-)) ��Derek ��

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

Sent: Sunday, November 12, 201711:57 AM

To: Losmandy_users@yahoogroups.com

Subject: RE: [Losmandy_users]Pointing issues

���� HI Derek, ��

I try my best...but since I've repeated that list a few times thisyear...yes...it's time to make a PDF and just point to that.�� I can addscreen shots too... another benefit.����

��

I rely wish I had access to the source code so I could remedy or atleast understand the causes of these strange pointing errors.�� But...it islocked up.�� Gemini2 code might be open but...I don't have one!

��

Michael��

��

��



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#60332 Nov 12, 2017

Figured as much.. ��Derek ��

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

Sent: Sunday, November 12, 201712:14 PM

To: Losmandy_users@yahoogroups.com

Subject: RE: [Losmandy_users]Pointing issues

���� >Gemini2 code might be open but...I don't have one!



Neither Gemini 1 or 2 source code is ���open���. Gemini.NET is.



Regards,



-Paul

�� Virus-free.www.avg.com



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#60333 Nov 12, 2017

Paul,

I understand and the openness of Gemini.net is of great value.. .Your authorship and maintenance and improvements of that are also a fabulous benefit.

The Orion Atlas/Synta EQ6 group has a PC interface program called EQMOD that is so good, people sell off their hand controllers completely and just use that.. .In their EQMOD pointing model method, they do model cone error and some other parameters, but as importantly, they triangulate in the region between known "align" stars, so each portion of the sky can have a unique "pointing model" for its part of the sky. (actually each star ).. Then any other object is just interpolated.. Extrapolation is used outside "align" points but that is a less certain region.. You add align stars across the sky as the need arises for new targets, which you just interpolate position...

The Atlas mount itself is not as rigid a platform as the G11, or maybe not even as solid as the GM8.. The tripod is weak, the mount head is inadequately coupled to the tripod, the AZ and elevation adjustments are weak.. PE is worse.. But still the Atlas GoTos are rarely if ever far from their target.. There is just a conceptual difference in how the sky and mount and scope are modeled between the EQMOD and the Gemini.

So...my question is:. Do you think there could be a way to do that multiple star triangulation and interpolation, using the Gemini model system.. That is, keep all the Gemini parameters zero, yet get its encoder tick positions, and then map the GoTo sky chart location to the Gemini through a PC program like EQMOD is doing?

Anyway...not a short term project for sure...

Best,Michael..



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#60336 Nov 12, 2017

Do you think there could be a way to do that multiple star triangulation and interpolation, using the Gemini��> model system.��



Michael, yes, of course, you could do the same with Gemini.NET with some coding. Alternatively, you could easily create an ASCOM hub that would be independent of Gemini and Gemini.NET. Original T-Point works this way, although it's not free. Existing Gemini implementation of the pointing model has the benefit that it works without a PC, which none of the other PC-based software can claim.

I had an idea about 4-5 years ago to implement a very simple pointing corrector as part of Gemini.NET, but after a few attempts, I found that my chosen method (using only three stars) wasn't accurate enough, so I gave up :)



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#60337 Nov 12, 2017

Thanks, Paul.

I agree that the best approach is understanding how to best use Gemini, as it does work well.



If my list of steps work for Doc (PuzzleWuzzle), then his problem is solved on the practical level...

Let's see what Doc reports as progress,.. or remaining trouble.







Best,Michael



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#60340 Nov 12, 2017

��Food for thought.. If Gemini is unique in modeling withouta PC, why would the answer be to modify Gemini.net / ASCOM?? ��Visual Observers who setup each time arean after thought to Gemini 2.. I continue to wish I had not acquired thismount.. And no.. I am not an idiot, and I will figure it out or I will beat itto death with a large sledgehammer.. ��I have never made it to the 3rdstar and seldom to the second.. And I am staring at The Summer Triangle!! ��There.. I said it.. ��Derek







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#60341 Nov 13, 2017

If Gemini is unique in modeling without a PC, why would the��> answer be to modify Gemini.net / ASCOM??



Primarily because this can be done without involving the author of Gemini, Rene Goerlich.�� Only he can make changes to Gemini internals.��

Anybody with some coding skills can create an ASCOM hub, or contribute some source code into Gemini.NET source tree.

Regards,

�� -Paul



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#60349 Nov 14, 2017

Derek,When as frustrated as you seem to be, post your location.�� Perhaps someone nearby can stop by and give you a hand.�� Many folks are pleased with their G11 and G2.�� No reason to suffer alone.�� Get local help.Dave...



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#60369 Nov 15, 2017

Hi Derek,��I.m a relative rookie in that I.ve only had my mount for about 10 months, but I.ve learned things with that have really with astro photography. First, make sure the safety limits at set specially for your gear. Believe it or not this really affects pointing without ever reaching those limits. Second, because I am using SGP with plate solving, I cold start the mount and don.t do any alignment. This solved all of my pointing in astrophotography.

Rob��

Sent from my iPhone

On Nov 14, 2017, at 5:50 PM, 'Derek C Breit' breit_ideas@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:



��Hello, Dave spoken in my best HALvoice> ��I am slowly working on it. Obviouslysince so many love their mounts, it has to be me and I continue to have little .AHHA. moments and pick up a little tidbit of info every time out.. I dohave local help. I just haven.t utilized yet.. Rest assured that I willif it doesn.t all .come together. in the next few attempts.. ��I am pretty much shut down for the rainyseason, though I will setup if work and weather cooperate.. If I am stillfrustrated in April, then we will have trouble.. ��:-)) ��DerekMorgan Hill, CA��

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

Sent: Tuesday, November 14, 20172:02 PM

To: Losmandy_users@yahoogroups.com

Subject: RE: [Losmandy_users]Pointing issues

���� Derek,When as frustrated as you seem to be, post your location.�� Perhapssomeone nearby can stop by and give you a hand.�� Many folks are pleasedwith their G11 and G2.�� No reason to suffer alone.�� Get local help.

Dave...



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#60370 Nov 15, 2017

.make sure the safety limits at set specially for your gear. Believe it or not this really affects pointing without ever reaching those limits.. ��Are you sure about that? I haven.t experienced that, though the gemini settings have to match the mount �� ��.I am using SGP with plate solving. ��100% agree on this one. Alignment was such a headache and then fine tuning the targets. SGP and plate solving are a god send. That and polemaster have turned a chore into a pleasure �� ��Thanks ��Brian �� ��Brian ValenteBrianvalentephotography.com

��From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com] Sent: Wednesday, November 15, 2017 12:58 PMTo: Losmandy_users@yahoogroups.comSubject: Re: [Losmandy_users] Pointing issues



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#60371 Nov 15, 2017

Yes, I.m very sure. I was having problems with pointing, especially around the meridian where Gemini was trying to keep from doing a meridian flip so it would try to use safety limits to point east with a west flip, if that make sense.These problems went away as well as some others when I adjusted safety limits to my gear to, which were not nearly as liberal as the presets for the mount.

Rob



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#60372 Nov 15, 2017

So you are using limits to ���trick��� the mount into doing (or not doing) meridian flips, is that correct? ��Thanks ��Brian �� ��Brian ValenteBrianvalentephotography.com

��From: Losmandy_users@yahoogroups.com [mailto:Losmandy_users@yahoogroups.com] Sent: Wednesday, November 15, 2017 1:42 PMTo: losmandy_users@yahoogroups.com; losmandy_users@yahoogroups.comSubject: Re: [Losmandy_users] Pointing issues



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