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On Wed, May 28, 2025 at 07:55 AM, <dkfcpalfd@...> wrote:

I had considered DEC backlash as having negative impact.? However, the symptoms of the problem..... all of a sudden appearing...... when I go along with countless plate solves inside 10 pixels on both axes, then all of a sudden, the error on both axes goes much larger, and stays that way for weeks, until the firmware is re-flashed, then it's instantly back to less than 10 pixel error...... made me think there may be some issue going on besides backlash.

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Well, thanks for your help.? I think if more people had the problem, it may be easier to diagnose.

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I also explored the idea of static electricity in my dome somehow corrupting the firmware.... who knows.

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Overall, I'm happy with the upgrade, so I'll just continue on.

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I had considered DEC backlash as having negative impact.? However, the symptoms of the problem..... all of a sudden appearing...... when I go along with countless plate solves inside 10 pixels on both axes, then all of a sudden, the error on both axes goes much larger, and stays that way for weeks, until the firmware is re-flashed, then it's instantly back to less than 10 pixel error...... made me think there may be some issue going on besides backlash.

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Well, thanks for your help.? I think if more people had the problem, it may be easier to diagnose.

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I also explored the idea of static electricity in my dome somehow corrupting the firmware.... who knows.

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Overall, I'm happy with the upgrade, so I'll just continue on.

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Thanks.

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Dan

The mount does have large DEC backlash, and I assumed that backlash was the reason for the DEC error being larger.? However, Sunday night, I did some plate solving, and I saw DEC go as close as 1.8 pixels of error.? The solving finally finished at 5 and 7 pixels of error for RA/DEC.? I have spent plenty of time trying to adjust out DEC backlash, and have it operating the best I can.? I know for a fact, that the Titan mount is known to have huge backlash, as one of the authors of PHD2 told me that on the phone.? The Guiding Assistant does show a large backlash.

Thanks for the information, Dan. Backlash could still be the cause of this, since backlash only plays a role when switching direction of the DEC motor. Depending on how the initial or successive plate-solve/re-center operations go, you may or may not be switching DEC direction, which may result in a large backlash... or not :)

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I also have a Titan mount, and backlash is something that's not that hard to adjust out. You need a little baclkash, but a very large amount is counter-productive. Don't know if PHD2 authors actually know anything about the Titan, but having operated one for years, I can tell you that backlash can be reduced to an arbitrarily small amount. You just need to make very small adjustments using the wing-head screws to push the worm into the gear. I usually have the worm adjusted with some?

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Can't imagine how MS update could affect such a complex process as plate solving/recentering. Usually it's really obvious when MS breaks something -- things just stop working altogether :)

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It sounds like there's enough sag/slop somewhere in your system that causes the large error. If the mount guides well, I can't imagine why re-centering after a plate solve would not bring the mount to the correct position within a few arcseconds of the desired position. Double-check you plate solution settings, maybe there's something there you can adjust. With the large focal length of your system, I have to assume there are not that many stars in the FOV to make plate solves precise and predictable.?

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Thanks for your response, Paul.? Let me try to address all your questions:

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I have an Edge 14 SCT on the mount, with the 0.7X reducer.? I have a QHY 600 mono imager, taking visible light through an ONAG.? I typically run plate solving through the luminescent filter, which is an Antlia.? ? I'm solving with ASTAP through SGP.? Normally the first plate match may have a pretty good amount of error, but successive plate matches get successively closer.? I have the solver set to do up to 7 plate matches.? Normally it would stop in 2 to 4 plate matches, and that would be pixel error of less than 15 on both axes (when the mount has recently been flashed).

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When I said the 30 and 250 pixels, it could never get better than that.? It would start large, and successively go smaller, but really couldn't get closer than 30 and 250.

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The mount does have large DEC backlash, and I assumed that backlash was the reason for the DEC error being larger.? However, Sunday night, I did some plate solving, and I saw DEC go as close as 1.8 pixels of error.? The solving finally finished at 5 and 7 pixels of error for RA/DEC.? I have spent plenty of time trying to adjust out DEC backlash, and have it operating the best I can.? I know for a fact, that the Titan mount is known to have huge backlash, as one of the authors of PHD2 told me that on the phone.? The Guiding Assistant does show a large backlash.

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I used to do modeling with the mount, but don't do much of that anymore.? I sometimes go to a bright star, center it, and do a modeling/alignment..... that's about it.

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No possibility for mirror flop:? I have the SMFS focuser, and the primary is locked down.? I don't think there's focuser sag with the SMFS.? Meridian flips did not cause this.... those are rare for me to do.... I'll do a 2 to 3 hour session per night, and plan it so a flip is not needed.

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TVC is at the default setting.... don't recall... that's either 0 or 5.? I tried increasing that setting for my autoguiding one time, and the guiding went terrible, so I leave it at the default setting.

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My question is how could the plate solving all of a sudden get very accurate when I flash the mount with L6.XX, without that being the result of the flashing?? So.... for 2 out of 2 prior flashings, the solving after several weeks reverted back to the more inaccurate state, and that would happen all of a sudden.... I try to solve, and it gets no better than the 30/250.? It stays that way for weeks, until I flash again, and the solving then goes very accurate.

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It just makes me wonder if MS Updates have somehow corrupted Gemini, or there's something else going on.

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Thanks.

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Dan

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Hi Dan,

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When you see the plate solving went great, and then got worse, are you referring to the initial centering of the object is within 10 pixels at first, then goes to more like 250 pixels in DEC off center? Hard to imagine that anything in L6.x could cause this.

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This sounds like it could be that some DEC backlash worm-gear adjustment may be needed. Do you have TVC set to 0? What does your PHD2 backlash calibration look like?

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Do you do meridian flips, and can you tell if the larger centering error occurs just on one side of the meridian?

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Do you build a pointing model before doing plate solves? If so, how many stars, and are you building it on both side of the meridian?

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What is your optical train? Refractor? Reflector? Any chance of mirror flop or possibly some focuser sag?

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Regards,

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?-Paul

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On Tue, May 27, 2025 at 07:42 PM, <dkfcpalfd@...> wrote:

I am running a Losmandy Titan mount, and quite a few months ago I upgraded from Gemini 2 L5 to L6.02.? I flashed my encoder ports with the PIC kit, and installed the latest Gemini ASCOM driver, and updated the ASCOM platform.? After installing L6.02, I ran PEMPro and uploaded a new PEC curve, and re-calibrated PHD2.

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My guiding got excellent.... somewhere around a 20 to 30% reduction in guiding error.? My plate solving got incredibly accurate for me.... easily within 10 pixels per axis.? I also noticed my PHD2 guiding calibrations improved... most all of the step plots were on the axes; whereas, they weren't before.??

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However, after a week or two, the guiding stayed good, but the plate solving got inaccurate again.... I couldn't get closer than 30 pixels for RA, and 250 pixels for DEC.? It stayed that way for weeks.

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I finally re-flashed L6.02 (later discovered I could have done an HGM Reset).? The plate solving went extremely accurate again, immediately.... less than 10 pixels per axis.? But, after a few weeks, the plate solving went south again.... back to no better than 30 pixels RA, and 250 pixels DEC.? The guiding still stayed great.

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So, now, this past Friday, I flashed the mount with L6.12.? The plate solving went great again.... less than 10 pixels per axis, and the guiding was great.? So..... that's 3 out of 3 flashing events where the result was the plate solving got great.

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I got the release notes from the Losmandy website for the various versions.... L6.02 to L6.12.? I did not see any notes regarding my situation, but I did notice one of the release notes for one of the versions post L6.02 was not very specific, it said, "Many Gemini fixes...."

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I'm running WIN 10 on my PC, and connect to mount via Ethernet.? I'm wondering if Microsoft Updates could have somehow corrupted L6.02?? I'm keeping my fingers crossed that some improvements were made and L6.12 hangs in there for me.

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I look forward to hearing from others on this issue.

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Regards,

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Dan

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On Mon, May 26, 2025 at 07:12 PM, Russ wrote:

Seeing this message on the HC tonight. I assume this battery is on the Gemini II Mainboard (as opposed to the HC)?

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First clear night in 2 weeks and when I tried to slew to various targets, couldn't get anything even remotely near it. Also noticed the HC date is from 2022 and time completely wrong. I reentered time and date and hit the Set Button (also powered on/off the HC) but when powered back on, time/date wrong. Tried setting it via PC Interface (which shows correct) but with the error message on the HC, tomorrow I am just going to open up the Gemini 2 Main Panel and see what battery is there.

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If your Gemini 2 was purchased used do a visual inspection on the battery type to confirm what is in the battery holder before ordering or buying new batteries for the first time.? Gemini 2 controllers have been around long enough and some have had the battery holder replaced with a higher capacity battery holder.??

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If you buy a spare at the same time you buy a fresh battery you'll never get caught out with a dead one in the field and no replacement in hand.

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Battery has not enough voltage for ARM to retain date or time. ?So when you reboot…..it’s all lost. ?Battery is in MU. ? it’s a CR2354 or CR2450.

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Batteries need replacing every year more or less (mostly more). ?Life of the battery is dependent on a few things, usage and average ambient temp. ?

The more you use your Gemini the more the battery will last. ?Stored away units are a classic with dead batteries. Best replace before use. ? Cold ambient lowers battery life as well. YMMV ….some batteries last longer …some shorter. ?All user dependent !

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cheers

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Brendan

Yes. Just take off the four cover screws on the G2 control box to find the battery. It is a CR2450, 3V coin battery as in attached pic.??

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John

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Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user

Seeing this message on the HC tonight. I assume this battery is on the Gemini II Mainboard (as opposed to the HC)?

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First clear night in 2 weeks and when I tried to slew to various targets, couldn't get anything even remotely near it. Also noticed the HC date is from 2022 and time completely wrong. I reentered time and date and hit the Set Button (also powered on/off the HC) but when powered back on, time/date wrong. Tried setting it via PC Interface (which shows correct) but with the error message on the HC, tomorrow I am just going to open up the Gemini 2 Main Panel and see what battery is there.

One last interesting point is with the PHD2 slew command in the Callibration assistant. I ran it several times and found that the CA slew command would go to the celestial equator but the following nudge north to take out backlash would cause a meridian flip. The cause was that I initiated the slew when the mount was at CWD park position and the PHD team suggested I move to a known star before initiating the slew - that fixed it and I had tried adjusting my mount limits and varied the degrees off the equator to no effect.

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I thought this may be a random situation but tried it over several nights and it had the same effect. The PHD2 team said they were changing their code to set a greater degree off the equator

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FYI,

Ken

On Sun, May 25, 2025 at 01:47 PM, Paul Kanevsky wrote:

Did you calibrate and capture the new curve using PEMPro near the celestial equator and not near the pole?

Yes

When you measure the curve using PEMPro, you should make sure that PEC playback is turned off on Gemini. If it's left on during PEMPro PE capture, you're recording a correction for an already 'corrected' curve instead of the actual periodic error of the worm.

Yes I made sure

Try turning off PPEC in PHD2 if you have it on, and make sure to recalibrate the guider before attempting to guide. And at this point, make sure that PEC is turned on in Gemini.

I changed to Hysteresis for the calibration

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I ended up clearing PEC last night and did another PemPro run. I again had to invert the curve and it was successful. After that I did PHD2 calibration and I now don't have any of the PHD2 worm cycle blips I had for some reason last time.

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It all looks good now but one thing I noticed was that my PA does go out even as the mount is just covered until the next session. Once I get my permanent pier in place some of this may be a little easier to lock down. One thing that helped was unguided PHD2 session logs to indicate worm gear PE issues and Dec drift with bad PA.

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Thanks again,

Ken

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PS - looking forward to Rene's PEC developments and Ray's PemPRO updates to support those changes.

Hi Ken,

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Did you calibrate and capture the new curve using PEMPro near the celestial equator and not near the pole?

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When you measure the curve using PEMPro, you should make sure that PEC playback is turned off on Gemini. If it's left on during PEMPro PE capture, you're recording a correction for an already 'corrected' curve instead of the actual periodic error of the worm.

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Try turning off PPEC in PHD2 if you have it on, and make sure to recalibrate the guider before attempting to guide. And at this point, make sure that PEC is turned on in Gemini.

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Any updates on GEMPro version of PEMPro would need to come from Ray, I don't have any new information to share.

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Regards,

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? -Paul

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On Sat, May 24, 2025 at 07:07 PM, Oberon510 wrote:

Anyone in the UK have one of these they are looking to part company with?

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Thanks, David

On Sun, May 11, 2025 at 07:16 PM, Paul Kanevsky wrote:

There is something wrong with the worm or your measurement, despite PEC being able to correct for it. That large peak is very unusual, and well exceeds any other periodic error I've seen from Losmandy mounts. At the very least, I'd try to clean, regrease, and adjust the worm/gear mesh, but also, possibly swap the DEC and RA worms to see if you get a better result with another worm.

I did the clean/regrease and worm adjustment (2 times and it came good). The new PEC was good from a clear night and the inverted curve appeared to fix the 4 minute movements BUT when running PHD2 the 4 minute wanders came back but not as bad. Is it required that you clear all PEC when sending the inverted curve from PemPRO after starting with the non-inverted curve? My thought was that it would write over the previous curve but now I am wondering.

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Thanks,

Ken

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PS - any news on the next PEC development.

Thanks, Tom.

Thanks, Brendan. I'll try your suggestions and will search through the forum for more info.

Check the setscrew on the belt pulleys. Check both. They can come loose..?

More inserting circles. Best to do a search of the forum posts like this explain them better

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I’ve never used them, yes shame on me. ?

Also forum search for 492 drive issues. ?Info is available from year 2000’ish onwards. ? Most Topics have been covered dozens of times. ?Not fobbing you off it’s just sometimes easier to search. ?

But if you need more info post away

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cheers

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Brendan

Swap Ra motor drive plug to DEC and visa versa?

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Since they are the same you need to probably give some DEC commands to see if it moves. ? But since DEC is now Ra it should.?

The motors have gears inside ….sounds like a stripped gear. ?You can take them off and then run them on the bench to make it easier. ?Remember to mark which is Ra and DEC so you can follow your actions?

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From memory setting circles have a friction grub screw somewhere. ?Which allow you to move it to local Sidereal Ra setting for that date. It’s probably stuck to mount, not to axes. ? I’m not really sure. ?I was waiting for someone more knowledgable than me on these matters to post.?

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Brendan