The following files have been uploaded to
the Files area of the [email protected] group.
By: Edward Plumer <eplumer@...>
Description:
Spreadsheet to compute compatible settings between Gemini-II and NINA v1.11 to do a meridian flip.
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Re: Meridian Flips and NINA
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Re: Meridian Flips and NINA
LOL, a tale of two Pauls , I was asking Paul Kanevsky if he knew anything about the Gemini-ASCOM support for "CanSetPierSide" and was asking Paul Borland if he would post his parameters .... Sorry about that confusion
--
Edward
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Re: Very odd polar align issue
Thanks Brian,
I am planning to re-run this all step by step hopefully tonight. I am not doing any Gemini PEC, I just enabled the PPEC algorithm in PHD2 - I thought that was the recommended one to pick. Maybe I should have just used the default?
Some of the guide calibrations failed because for an unknown reason my wifi router is not reliable when I use it outside and I have a replacement coming today. So sometimes calibration would fail with a timed out command to the mount, which is causing some noise in the logs.
The GA definitely indicates poor PA which was surprising since I've been using Sharpcap for a while now and getting (what I thought) were good results.
I'll snap some pics of the rig later today. It's a pretty small payload (60mm refractor & small guide cam). I only have two cables coming off the mount (12VDC and a USB3.0 cable)?
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Re: Meridian Flips and NINA
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The mount does random gotos during meridian flip, and in this case it moved the DEC axis 90 degrees from where it was supposed to point.?
90 degrees?is a little too specific?for a random goto bug. That sounds more like a settings issue
On Mon, Jun 28, 2021 at 9:49 AM "Guilherme V¨ºnere < venere@...> wrote: Hi Jim
I haven't tried yet, but I can try tonight. Yesterday after my failed test I went back to 1.10 HF3 and restored my config which worked before. This morning when i went outside to check on the scope, it was again pointing?to the North?horizon like this:
This happened after the flip was done, while NINA was attempting to do the Plate Solve. It happened before, and I think it's related to a bug I reported here a few days ago, which seems to be caused by Gemini firmware. The mount does random gotos during meridian flip, and in this case it moved the DEC axis 90 degrees from where it was supposed to point. So while the flip worked, I still lost half of my session :(
Guilherme
On Mon, Jun 28, 2021 at 9:15 AM Jim Waters < jimwaters@...> wrote: Peter, Guilherme
Have either?of you tried Edward's or my settings?
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Jim W
Phoenix, AZ. USA
Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes
-- Brian?
Brian Valente portfolio
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Re: Very odd polar align issue
Based on this data, i'd say your polar alignment is off by quite a bit, and the GA also indicates this
looking at your guidelogs, i think you are trying to do too many things at one time (PPEC algorithm, etc.) - I think the baseline guiding is really the best place for you right now
i'm also wondering about your scope balance, snags, etc. can you send a couple pics of your setup?
are you doing any sort of PEC?
Thanks Brian,
Here is a logfile. Some of the data is during guiding, and some from guiding assistant
-- Brian?
Brian Valente portfolio
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Re: Meridian Flips and NINA
Hi Jim
I haven't tried yet, but I can try tonight. Yesterday after my failed test I went back to 1.10 HF3 and restored my config which worked before. This morning when i went outside to check on the scope, it was again pointing?to the North?horizon like this:
This happened after the flip was done, while NINA was attempting to do the Plate Solve. It happened before, and I think it's related to a bug I reported here a few days ago, which seems to be caused by Gemini firmware. The mount does random gotos during meridian flip, and in this case it moved the DEC axis 90 degrees from where it was supposed to point. So while the flip worked, I still lost half of my session :(
Guilherme
On Mon, Jun 28, 2021 at 9:15 AM Jim Waters < jimwaters@...> wrote: Peter, Guilherme
Have either?of you tried Edward's or my settings?
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Jim W
Phoenix, AZ. USA
Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes
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Re: Very odd polar align issue
Thanks Brian,
Here is a logfile. Some of the data is during guiding, and some from guiding assistant
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Re: Very odd polar align issue
>>>
I did some guiding, and I was around 1.0 total RMS and surprisingly DEC was really low (around 0.5) and my understanding of a bad PA is that it would likely show in DEC more than RA.
not necessarily - it would show as corrections primarily (or only) in one direction. if you can upload some guidelogs we can tell pretty quickly. PA is important, but I think the need for highly precise PA is a bit overrated. Guiding is ideal for removing larger periods or drift. it's critical only if you are doing unguided
Thank you both. Great info Michael, I'll definitely be checking all these areas
Brian: I did go through that document but I also tried a lot of other things so my PHD logfiles are not clean. I will need to redo this
I did some guiding, and I was around 1.0 total RMS and surprisingly DEC was really low (around 0.5) and my understanding of a bad PA is that it would likely show in DEC more than RA.
At some point I may need to look at my guiding equipment. I have 6.45 arc seconds/pixel on the guider as I got a small setup to keep the weight down for the skyguider
I also tried a couple of test subs and I was able to get 5 and 10 min subs with reasonable FWHM and eccentricity (although not hugely better than 180s with my Skyguider, but much longer subs)
I'm sure it is something silly I am doing and not anything wrong with the mount
I'm also going to do the Sharpcap PA twice, with different rotation directions - I am suspecting something was off here but I dont know what as I have been using it for a year on the star tracker
I'll be able to try it tonight or tomorrow and report back
Thanks so much for all the help
-- Brian?
Brian Valente portfolio
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Re: Very odd polar align issue
Thank you both. Great info Michael, I'll definitely be checking all these areas
Brian: I did go through that document but I also tried a lot of other things so my PHD logfiles are not clean. I will need to redo this
I did some guiding, and I was around 1.0 total RMS and surprisingly DEC was really low (around 0.5) and my understanding of a bad PA is that it would likely show in DEC more than RA.
At some point I may need to look at my guiding equipment. I have 6.45 arc seconds/pixel on the guider as I got a small setup to keep the weight down for the skyguider
I also tried a couple of test subs and I was able to get 5 and 10 min subs with reasonable FWHM and eccentricity (although not hugely better than 180s with my Skyguider, but much longer subs)
I'm sure it is something silly I am doing and not anything wrong with the mount
I'm also going to do the Sharpcap PA twice, with different rotation directions - I am suspecting something was off here but I dont know what as I have been using it for a year on the star tracker
I'll be able to try it tonight or tomorrow and report back
Thanks so much for all the help
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Re: Meridian Flips and NINA
Peter, Guilherme
Have either?of you tried Edward's or my settings?
------------------------
Jim W
Phoenix, AZ. USA
Losmandy GM811G, NINA 1.11, ASI2600MC Pro, Sky-Watcher Scopes
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
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I estimate the weight of the gear will be around 65 - 70lbs.
the spec of the G11 is 60lbs imaging, 75lbs visual
Michael,
Thanks for this info. I assume the grease is for the worm? Your rig looks quite heavy. How much weight are you sporting? I have a 12" truss Newtonian that I want to mount in the fall. It seems from looking at your setup my G11 should be able to handle it? I estimate the weight of the gear will be around 65 - 70lbs.
I'll defiantly give the loose hanging weight a go. One thing to note, with the worm blocks removed you have very free rotation so easy to get a precise balance.?
Thanks for all the support guys,
??
Peter
-- Brian?
Brian Valente portfolio
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Michael,
Thanks for this info. I assume the grease is for the worm? Your rig looks quite heavy. How much weight are you sporting? I have a 12" truss Newtonian that I want to mount in the fall. It seems from looking at your setup my G11 should be able to handle it? I estimate the weight of the gear will be around 65 - 70lbs.
I'll defiantly give the loose hanging weight a go. One thing to note, with the worm blocks removed you have very free rotation so easy to get a precise balance.?
Thanks for all the support guys,
??
Peter
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Vishal,
I also recommend going for the G11 with your 130mm refractor.? I originally purchased a GM811G to carry a small 85mm refractor, then bought a G11 dec when I upsized to a 130mm refractor.
I found dec backlash easier to control with the larger worm wheel on the G11 dec axis.? The longer saddle clamp on the G11 is also nice to use with when mounting longer scopes.
I can feel the weight difference between the two if I'm carrying either mount in one arm (the 811 is definitely "easier"), although I can't think of a time when this has mattered.
Thanks,
Dwight
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Peter...
You have revealed a clue to your RA drive issues: your 240 sec error (worm fundamental period) depends on which side of the meridian you are targeting.
Try this:
1. Fully balance your RA by testing the motor (total Gemini) current with the counterweight bar horizontal.? Adjust your DEC balance first, then balance your RA to get to minimum total Gemini power current.
2. Wrap a length of flexible cord, such as clothesline, around the RA axis do that the cord hangs off the? East side of the RA.? This direction minimizes ring gear chatter.
3. Tie a one or two pound weight to the cord, so that when the RA rotates during imaging, the weight does not bump the tripod or other part of the mount.
That torque from the hanging weight will provide a constant torque to the RA worm and ring gear and always "preload" the contact surface.? In this way the contact region will not flip over as you image through the meridian.?
Then take your PE data on both sides of meridian, and see what your results look like.? I'll hope your flippin' problem is eliminated.
Here is how this appears on my G11T.??
I suggest use of the CRC Brake and Caliper grease to minimize worm to ring gear "chatter" that was observed by me and others....if you put the wrapped cord hanging off the West side by mistake.? This particular grease has 3 lubricants: MolyD, Graphite, and Teflon in a heavy very wide temp range (-30C to +200C?) anticorrosion grease.? It eliminated chatter observed using other greases like Super lube.??
Best of luck,
Michael
Alan,
I will try a rigid one piece coupler. My RA has the OPW. I've found it's possible to feel it the gearbox is aligned or not with the coupler by rotating worm with your fingers. The nice thing about the Mclennan gearboxes is they have a metal plate.??I have removed the motor cover as is is really cosmetic, so will then be able to use a hex head screw to tighten down the motor box more sensitively to hopefully get a good alignment. My planned testing on this issue is as follows.
1. Install a new worm undamaged by the use of the Oldham coupler set screws. Use a dial caliper to measure any wobble in the worm for a baseline measurement.
2. Install the gearbox using two different clamp style couplers from Ruland. I have already posted the part number of one and will get the part number for a rigid coupler if there is one with the correct O.D. Repeat the dial measurement.
3. Run an imaging session and get new FFT data.
The reason for these tests is mostly to better understand to magnitude of errors caused by different elements in the drive chain. I've already demonstrated how much better the FFT looks with the 125:1 gearbox in terms of higher frequency components. I'll be testing the 50:1 and 80:1 gearboxes in near future too.?
Currently, there is an 80s and a 240s error as show early in the FFT plot I posted. These have a corrected magnitude of 0.35 arcsec using the hysteresis PHD2 algorithm. I've not found the Predictive PEC algorithm works. These numbers change depending on which site of the meridian I'm on. Usually, after the flip the 240s goes away completely, but since my current project is the Cygnes Wall no flip has been needed so the error is a problem for the resolution I'm at.
Peter
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Re: Yet another DIY spring loaded worm - ultra minimalist approach
Hi Greg -
I'd love to see a few images of what you've done to? the mount.?
If I understand your description, you're basically just using the
small rubber bands as some flexible shim material to keep the worm
meshed?? That certainly is minimalist. Have you run into any
issues where the pressure is causing extra load on the motors due
to worm friction?? I'm interested to hear how it works out for you
during imaging.
Good luck, and please keep us posted,
-Tony
On 6/27/2021 1:56 PM, Greg wrote:
toggle quoted message
Show quoted text
I have a quite old G11 (18yrs) with a brass RA and steel DEC worm
which I got for $100 w/o weights or controller. With a complete
clean/lube and Gemini-II w/new motors- I've used it for about a
year now with very good AP results at 1000mm fl considering its
age (.5-1" guiding on calm nights with good seeing).
That is with the exception for the need to adjust the seasonal
temperature sensitive worm block positions and the nightly pause
to add one or two 12oz magnetic weights when going
over-the-meridian (with the associated backlash / bouncing).
After reading the latest attempts to solve or mitigate the issues
with the legacy worm design w/o the wait or expense of buying the
Losmandy upgrades, I decided to play with some ideas. While I do
3D modelling and printing, but don't have a machine shop, I am
trying a super minimalist approach.?
I added? ~ 1/2" long, 1/4" wide, 1/16" thick piece of rubber band
inside the post hole for the outside RA and DEC worm blocks. The
DEC band is centered at 90¡ã off the axis of the worm to push the
worm directly toward the ring gear and the RA is centered at 45¡ã
to push toward both?the ring gear and back against the worm axis
(keeping pressure between the ring gear teeth and the worm). The
cushioned blocks are now slightly off snug tight and the other
blocks are just snug, which gives the blocks some ability to move
without being loose. I will need to keep an eye on them working
their way loose, but the mount seems to be behaving at least as
good as it was before, with visibly improved DEC backlash.
I will update this thread when I get more data on the mount's
guiding behavior. While I don't expect to not need to use the
weights, I am hopeful the sensitivity to temperature and
over-the-meridian and backlash /bouncing is improved.
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
Alan,
I will try a rigid one piece coupler. My RA has the OPW. I've found it's possible to feel it the gearbox is aligned or not with the coupler by rotating worm with your fingers. The nice thing about the Mclennan gearboxes is they have a metal plate.??I have removed the motor cover as is is really cosmetic, so will then be able to use a hex head screw to tighten down the motor box more sensitively to hopefully get a good alignment. My planned testing on this issue is as follows.
1. Install a new worm undamaged by the use of the Oldham coupler set screws. Use a dial caliper to measure any wobble in the worm for a baseline measurement.
2. Install the gearbox using two different clamp style couplers from Ruland. I have already posted the part number of one and will get the part number for a rigid coupler if there is one with the correct O.D. Repeat the dial measurement.
3. Run an imaging session and get new FFT data.
The reason for these tests is mostly to better understand to magnitude of errors caused by different elements in the drive chain. I've already demonstrated how much better the FFT looks with the 125:1 gearbox in terms of higher frequency components. I'll be testing the 50:1 and 80:1 gearboxes in near future too.?
Currently, there is an 80s and a 240s error as show early in the FFT plot I posted. These have a corrected magnitude of 0.35 arcsec using the hysteresis PHD2 algorithm. I've not found the Predictive PEC algorithm works. These numbers change depending on which site of the meridian I'm on. Usually, after the flip the 240s goes away completely, but since my current project is the Cygnes Wall no flip has been needed so the error is a problem for the resolution I'm at.
Peter
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Re: Meridian Flips and NINA
On Mon, Jun 28, 2021 at 12:00 AM, "Guilherme V¨ºnere wrote:
?
The flip *did not occur*. NINA stopped after the second exposure, showing the flip interface, but said the flip was done already without the mount actually moving. Gemini was tracking fine and stopped just for a second while the supposed?flip happened
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Hi Guilherme You have described perfectly the experience I now have. It used to work with 1.10 HF3 version, then stopped with 1.11 as I recall and certainly with the nightly builds. Good luck with your test of the HF3 version. This problem needs to be run to ground,. I do not want to have to give up using NINA. Peter
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Re: Changing the servo motor encoders from 256 to 512 or 1024. Any reason not to do this?
I'm just saying, that from a theoretical perspective, a one-piece coupler maintains a kind of symmetry where it's indifferent to whatever the shaft angle is, and thus it will rotate at a constant speed.? This is as opposed to the oldham coupler where the center plastic piece slides back and forth, and thus the "gear ratio" changes a little bit for different orientations.? Remember those Shimano Biopace elliptical chainrings?
Another nice thing about the ruland type couplings is that if the colinear alignment is off, it will be rather obvious since it won't fit.
With that being said, Michael is right that there are many different causes for the 240s error.? Maybe try purposely mis-aligning the oldham coupler and see if the problem gets worse.
I forgot what system you have, but is there some way to pre-align the worm and gear shafts before putting on the coupler?
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Edward Plumer
Michael Herman