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ES Losmandy G11 RA Backlash

Sunil Bhaskar Bhaskaran All Messages By This Member #69462 Hi, ? ? ? I own a ES Losmandy G11 Pmc8 variant of the Gemini2 system and I seem to have some serious RA backlash issues. I tried to get help in the ES Pmc8 forum but I was told to approach the Losmandy group. The mount is around 3 years old and I recently lubricated it using Super Lube. Guiding seems to be all over the place and most of my subs are getting discarded by SGP. The mount worked fine when it was in US but now after relocating to India(shipped via freight), it seems to have developed some serious backlash issues. I managed to fix the DEC backlash to some extend but the RA seems to be a whole different story. Appreciate any help you guys can provide. The autoguider is qhy5ll on a 200mm finder. Attaching the phd2 log. Please let me know if anyother details are needed from my end. Sunil?
Mark Christensen All Messages By This Member #69463 Sunil, First reaction is that RA backlash should never matter when guiding: The scope should be slightly heavy eastward and the guide rate should be less than 100%. That way the RA never reverses and hence backlash is a complete non-issue. To debug the problem I suggest you turn off dither along with any other "feature" - when diagnosing problems the simpler the configuration the better. It may be the fact that you have dither turned on for both axes that is causing RA backlash to show up. Second reaction is, have you tried readjusting the RA worm? That needs to be done with the motor removed while rotating the worm by hand so you can see and feel what is going on. The worm wheel (large gear attached to the axis) needs to go through the full rotation so that you don't bind on the (unknown) high spot on the gear. Third reaction is, I hope for your sake than when you shipped it the clutches were loose! Best Wishes, Mark Christensen
Brian Valente Member Profile All Messages By This Member #69464 Hi Sunil >>>First reaction is that RA backlash should never matter when guiding: The scope should be slightly heavy eastward and the guide rate should be less than 100%. That way the RA never reverses and hence backlash is a complete non-issue. Mark is spot on here, RA backlash is a non-issue in guiding unless somehow you managed to get your guidespeed above 1x (which I don't think is possible) To diagnose further we'd need to see your guidelogs, and preferably a baseline guiding as defined in these steps: toggle quoted message Show quoted text On Sat, Dec 26, 2020 at 7:09 AM Mark Christensen <mjcw500@...> wrote: Sunil, First reaction is that RA backlash should never matter when guiding: The scope should be slightly heavy eastward and the guide rate should be less than 100%. That way the RA never reverses and hence backlash is a complete non-issue. To debug the problem I suggest you turn off dither along with any other "feature" - when diagnosing problems the simpler the configuration the better. It may be the fact that you have dither turned on for both axes that is causing RA backlash to show up. Second reaction is, have you tried readjusting the RA worm? That needs to be done with the motor removed while rotating the worm by hand so you can see and feel what is going on. The worm wheel (large gear attached to the axis) needs to go through the full rotation so that you don't bind on the (unknown) high spot on the gear. Third reaction is, I hope for your sake than when you shipped it the clutches were loose! Best Wishes, Mark Christensen -- Brian? Brian Valente portfolio
Brian Valente Member Profile All Messages By This Member #69465 oop sorry i see it here in the op let me look at it toggle quoted message Show quoted text On Sat, Dec 26, 2020 at 5:16 AM Sunil Bhaskar Bhaskaran <cyclops12321@...> wrote: Hi, ? ? ? I own a ES Losmandy G11 Pmc8 variant of the Gemini2 system and I seem to have some serious RA backlash issues. I tried to get help in the ES Pmc8 forum but I was told to approach the Losmandy group. The mount is around 3 years old and I recently lubricated it using Super Lube. Guiding seems to be all over the place and most of my subs are getting discarded by SGP. The mount worked fine when it was in US but now after relocating to India(shipped via freight), it seems to have developed some serious backlash issues. I managed to fix the DEC backlash to some extend but the RA seems to be a whole different story. Appreciate any help you guys can provide. The autoguider is qhy5ll on a 200mm finder. Attaching the phd2 log. Please let me know if anyother details are needed from my end. Sunil? -- Brian? Brian Valente portfolio
Brian Valente Member Profile All Messages By This Member #69466 HI Sunil Here's my observations from your guidelog looking at your two longest runs 1. your settings are not very optimized for your conditions and equipment. your min move on RA is too high, it's at 1" and you are guiding at 0.82" so i'd say for that min moves your guiding is where i would expect it. Run guiding assistant and/or set that value lower 2. your seeing looked less good in the second long run (segment 11), i think your exposure time should be longer to even that out - maybe 2.5-3 seconds 3.? you should enable dec backlash compensation in PHD which will clean up your DEC guiding. a guiding assistant run should make a recommendation there, but if not i would start with 800ms with a max of 2500ms and let it adjust itself 4. after tightening up min mov in RA (and DEC too), if you still need better guiding results you can try predictive PEC algorithm for RA. i'd set the period to 239.9 and disable auto adjust period.? that should be a good start toggle quoted message Show quoted text On Sat, Dec 26, 2020 at 5:16 AM Sunil Bhaskar Bhaskaran <cyclops12321@...> wrote: Hi, ? ? ? I own a ES Losmandy G11 Pmc8 variant of the Gemini2 system and I seem to have some serious RA backlash issues. I tried to get help in the ES Pmc8 forum but I was told to approach the Losmandy group. The mount is around 3 years old and I recently lubricated it using Super Lube. Guiding seems to be all over the place and most of my subs are getting discarded by SGP. The mount worked fine when it was in US but now after relocating to India(shipped via freight), it seems to have developed some serious backlash issues. I managed to fix the DEC backlash to some extend but the RA seems to be a whole different story. Appreciate any help you guys can provide. The autoguider is qhy5ll on a 200mm finder. Attaching the phd2 log. Please let me know if anyother details are needed from my end. Sunil? -- Brian? Brian Valente portfolio
Sunil Bhaskar Bhaskaran All Messages By This Member #69467 Mark, ? ? ? ? ? ?Appreciate the responses. The truth is I have been battling this issue for the past 8 months when I couldn't use the mount at all. Before that it functioned well. Not this bad. To answer you questions :? 1)RA Backlash : I apologize for the wrong methodology . I was referring to the worm wheel an the worm block wiggle. No matter how much I tighten, there seems to be movement when I wiggle the counter weight shaft. There is no DEC play but there is severe RA play. 2) I have tried adjusting but these seem to be very different from the traditional G11 worm blocks. No offence but the Gemini 2 ones look way better and sturdier than the one I have. The worm cover is just that - a cover. I I have seen videos from the Losmandy channel in youtube but the motor assembly is very different. While Gem2 is servo mine is stepper.WHen I tried to remove it, something was preventing it from coming off. Do I need to loosen the couplings which connect the motor to the worm mesh? 3) The mount worked fine for a while. But being in a humid and ununsed state took its toll I guess. The lube inside had solidified and I had to relube everything except the worm wheel.
Sunil Bhaskar Bhaskaran All Messages By This Member #69468 Brian, ? ? ? ? ? ? ?All the values entered in the toolbar(except the Hysterisis) was recommeded by phd2. The one thing I gotta mention is that the weather here is a bit hazy so I was taking longer duration guide pulses (2s - 3s) I believe.I have enabled backlash compensation and ran guiding assistant. I am attaching calibration and guiding assistant info as well.
Tom & Barbara Coverdale All Messages By This Member #69469 Mark, ?Your comment on Sunil having is clutches unlocked to transport got me?to thinking. I transport my G-8 into the Mojave Desert for?Bortle 1/2 imaging and never do anything to the clutches. Am I risking damage to my drive trains or anything?else by not releasing the clutches? The entire mount is a foam and?plastic box latched tightly shut. Thanks Tom? --- mjcw500@... wrote: From: "Mark Christensen" <mjcw500@...> To: [email protected] Subject: Re: [Losmandy_users_io] ES Losmandy G11 RA Backlash Date: Sat, 26 Dec 2020 07:08:53 -0800 Sunil, First reaction is that RA backlash should never matter when guiding: The scope should be slightly heavy eastward and the guide rate should be less than 100%. That way the RA never reverses and hence backlash is a complete non-issue. To debug the problem I suggest you turn off dither along with any other "feature" - when diagnosing problems the simpler the configuration the better. It may be the fact that you have dither turned on for both axes that is causing RA backlash to show up. Second reaction is, have you tried readjusting the RA worm? That needs to be done with the motor removed while rotating the worm by hand so you can see and feel what is going on. The worm wheel (large gear attached to the axis) needs to go through the full rotation so that you don't bind on the (unknown) high spot on the gear. Third reaction is, I hope for your sake than when you shipped it the clutches were loose! Best Wishes, Mark Christensen
Brian Valente Member Profile All Messages By This Member #69470 Hi Sunil Ah - i did not see a guiding assistant run there Screen captures aren't useful for analysis, if you can upload the log that included the GA run that would be great. Are you sure the log you previously uploaded was after this? The exposure time i saw was 1 second. Based on your previous log you uploaded, RA was performing under what you set for min move and there was no backlash compensation applied, so all the things I mentioned are still valid recommendations. also I would say your guidespeed is too low at 0.4x - you want to be at least 0.5x or higher Guiding Assistant is sometimes just a guideline, and in your case if you are looking for guiding better than what it recommended, you will need to tweak those settings toggle quoted message Show quoted text On Sat, Dec 26, 2020 at 11:24 AM Sunil Bhaskar Bhaskaran <cyclops12321@...> wrote: Brian, ? ? ? ? ? ? ?All the values entered in the toolbar(except the Hysterisis) was recommeded by phd2. The one thing I gotta mention is that the weather here is a bit hazy so I was taking longer duration guide pulses (2s - 3s) I believe.I have enabled backlash compensation and ran guiding assistant. I am attaching calibration and guiding assistant info as well. -- Brian? Brian Valente portfolio
Sunil Bhaskar Bhaskaran All Messages By This Member #69471 Brian, ? ? ? ? ? ? ? ? ? I wanted to share the screen so that you can have a better idea as to why I had chosen the numbers for guiding :D. I am attaching the phd2 log during which I ran the guide assistant. As for the guide speed the phd2 wizard automatically chose this value. I had good success with .4x speed but will try out .5 tonight and compare results. One small change was observed by me today morning - even after almost eliminating DEC play the mount seems to have? developed significant DEC play now. Is it possible that weather caused some compression or something? It did get chilly yesterday. I had just to change my exposures in phd2 from 2 to 3 and vice versa as the moonlight or something was really blowing up my stars. Only reducing the duration managed to help me atleast guide the mount little bit. ? Sunil ?
Brian Valente Member Profile All Messages By This Member #69472 hmm I don't see the calibration prior to the GA run, but it looks to me like you may have had an orthagonality?problem there Towards the end of the log the long guiding runs look pretty good, you're only .05 pixels difference between the axis. I think RA needs to be more responsive, so a faster guiderate 0.5 or higher would probably do it toggle quoted message Show quoted text On Sat, Dec 26, 2020 at 7:47 PM Sunil Bhaskar Bhaskaran <cyclops12321@...> wrote: Brian, ? ? ? ? ? ? ? ? ? I wanted to share the screen so that you can have a better idea as to why I had chosen the numbers for guiding :D. I am attaching the phd2 log during which I ran the guide assistant. As for the guide speed the phd2 wizard automatically chose this value. I had good success with .4x speed but will try out .5 tonight and compare results. One small change was observed by me today morning - even after almost eliminating DEC play the mount seems to have? developed significant DEC play now. Is it possible that weather caused some compression or something? It did get chilly yesterday. I had just to change my exposures in phd2 from 2 to 3 and vice versa as the moonlight or something was really blowing up my stars. Only reducing the duration managed to help me atleast guide the mount little bit. ? Sunil ? -- Brian? Brian Valente portfolio
Mark Christensen All Messages By This Member #69473 Persons Coverdale, By locking the clutches (including when person-handling the mount in and out of the boxes) you are taking an unnecessary risk of damaging the AL worm. I once saw a cheaper (poor quality cast gears) mount shred a section of its worm wheel (aka ring gear in some quarters) when the user hefted it with the counterweight attach. An extreme case but an extreme result. You may get lucky on any give trek and you may not. Why take the risk in the future? Mark C.
Tom & Barbara Coverdale All Messages By This Member #69474 Mark. Thanks so much. In my ignorance I have maintain the clutches fairy tight to help with unloading and setting up. I had no idea I could damage the Mount. Thanks again and I’ll keep them very loose from now on. ?Tom --- mjcw500@... wrote: From: "Mark Christensen" <mjcw500@...> To: [email protected] Subject: Re: [Losmandy_users_io] ES Losmandy G11 RA Backlash Date: Sun, 27 Dec 2020 18:21:57 -0800 Persons Coverdale, By locking the clutches (including when person-handling the mount in and out of the boxes) you are taking an unnecessary risk of damaging the AL worm. I once saw a cheaper (poor quality cast gears) mount shred a section of its worm wheel (aka ring gear in some quarters) when the user hefted it with the counterweight attach. An extreme case but an extreme result. You may get lucky on any give trek and you may not. Why take the risk in the future? Mark C.
Sunil Bhaskar Bhaskaran All Messages By This Member #69573 Brian, ? ? ? ? ? ?Apologies for the delay in responding. I did a few more tests and adjusted the wormgear and all to see if there were any improvements. Sadly, I didn't notice much. I am attaching additional guide logs with mount speeds changed from .4 to .5. Calibration was performed after the speed change was implemented. ALso just to be sure I installed The PEMPRO and ran it thrice. The first was taken without any adjustments to the worm. The second graph is when I noticed binding/grinding in the DEC & RA and thus loosened them a bit.? NOTE : For the first two graphs, PEMPRo determined my Image scale was around 6 arc/sec and guiding rate was 1 but in reality the scale is 2.02 arc/sec and guide rate was .4. Thus I performed the operation a third time with adjusted values and got better results. Incase you are unable to see the PEMPRO results here is a condensed version :? Run 1 ) Peak to Peak : 30.26 Arc/secs , RMS : 10.99 Arc/secs Run 2 ) Peak to Peak : 35.79 Arc/secs , RMS : 11.56 Arc/secs Run 3) Peak to Peak :? 12.03 Arc/secs, RMS : 3.85 Arc/secs Unfortunately, the PMC-8 is a closed system so I cannot input these values into my mount to improve my PE. Guiding is the only way to rectify this. But is this in anyway explaining the issue I am facing with my mount? Attaching phd2 guidelog and the PEC results Sunil

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