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Hello,
I bought an RA extension and 12" pier extension for my g11.? The goal was to improve meridian flips with my 130mm refractor. I checked all the screws in both components and they are tight.??
Guuding was good before the extensions .3 to .7 I. Both RA and DEC.? Now, DEC is still good, right now it's 0.4 but RA is 1.5, 1.8, 2.2 or more.? Last light after the flip it improved.? Tonight I moved the CW to make it east heavy.? That did not really help.? I have tried adjusting the aggression but that doesn't make much difference (I use an ASIAIR).? Again, the problems started with the new RA and pier extensions.? I hate to lose the first clear nights in two months so any suggestions are appreciated.? ?
Tom
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Hi Tom, hard to tell what’s changed in your setup, but I’d at least check the balance in Dec and RA and make sure the additional hardware hasn’t affected the worm/gear mesh.
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Regards,
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? -Paul
On Tue, Jan 28, 2025 at 12:49 AM, <Tjkallenbach@...> wrote:
Hello,
I bought an RA extension and 12" pier extension for my g11.? The goal was to improve meridian flips with my 130mm refractor. I checked all the screws in both components and they are tight.??
Guuding was good before the extensions .3 to .7 I. Both RA and DEC.? Now, DEC is still good, right now it's 0.4 but RA is 1.5, 1.8, 2.2 or more.? Last light after the flip it improved.? Tonight I moved the CW to make it east heavy.? That did not really help.? I have tried adjusting the aggression but that doesn't make much difference (I use an ASIAIR).? Again, the problems started with the new RA and pier extensions.? I hate to lose the first clear nights in two months so any suggestions are appreciated.? ?
Tom
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After making any mod like this you should do a new polar alignment, a new PEC curve (if you do that), and a new guiding steps calibration. Also make sure you are still balanced and redo carefully. The extensions themselves should not cause an issue.? Also be careful to not to judge guiding from one night's results as seeing could have a big impact.
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Regards.
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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
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John and Paul,
Thank you for the replies.? Apparently I don't have notifications enabled so I just saw your messages.
My balance is good and I do a new polar alignment and calibration every night because it only takes a few minutes.? This problem has been happening for several months now, but we have had clouds for two months so I hasn't been a big deal.? Two months ago, I tightened all the screws and waited for a clear night to try it out.??
I thought about taking both extensions off and trying it again but that seems like a lot of work.? I am using one , 21 lb (I think it is) CW located about halfway up the shaft.? I think I tried using the 7 lb and 21 lb closer to the mount to reduce the moment but as I recall, they were too heavy even close to the mount.?
In the past I balanced the scope without regard for it being east-heavy.? Last night I adjusted the CW slightly so that it would be east-heavy.? No difference.? The DEC runs around .3-.7 by the RA is all over the place.? Sometimes it will be very good, then all of a sudden it spikes above the x-axis.? Then it spikes below the x-axis.? Dithering used to take very little time but now it takes a long time to return to stable guiding.??
Paul, how would the worm gear have been affected?? What should I check?
Tom
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Tom, how does the autoguider calibration look compared to before? Does it take RA and/or DEC more time to reverse direction? If dithering takes a lot longer now, I start suspecting increased backlash (due to worm/gear mesh being too loose) or, alternatively, some stiction which is the result of a tight worm mesh.
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If you run a calibration, and then record some autoguiding logs, it may help to post them here for others to take a look. It may show when and why some of the large RA jumps appear.
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Regards,
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? -Paul
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On Tue, Jan 28, 2025 at 05:26 PM, Thomas Kallenbach wrote:
John and Paul,
Thank you for the replies.? Apparently I don't have notifications enabled so I just saw your messages.
My balance is good and I do a new polar alignment and calibration every night because it only takes a few minutes.? This problem has been happening for several months now, but we have had clouds for two months so I hasn't been a big deal.? Two months ago, I tightened all the screws and waited for a clear night to try it out.??
I thought about taking both extensions off and trying it again but that seems like a lot of work.? I am using one , 21 lb (I think it is) CW located about halfway up the shaft.? I think I tried using the 7 lb and 21 lb closer to the mount to reduce the moment but as I recall, they were too heavy even close to the mount.?
In the past I balanced the scope without regard for it being east-heavy.? Last night I adjusted the CW slightly so that it would be east-heavy.? No difference.? The DEC runs around .3-.7 by the RA is all over the place.? Sometimes it will be very good, then all of a sudden it spikes above the x-axis.? Then it spikes below the x-axis.? Dithering used to take very little time but now it takes a long time to return to stable guiding.??
Paul, how would the worm gear have been affected?? What should I check?
Tom
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Paul,
I took a couple of screen shots of what is happening tonight.
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On Tue, Jan 28, 2025 at 10:38 PM, Thomas Kallenbach wrote:
Paul,
I took a couple of screen shots of what is happening tonight.
Tom, i do see the jumps, but it's hard to see when or why they happen from a screen shot. Can you capture some autoguider logs (text) showing the position error, and corrections? Don't know if you can get that from ASIAir.
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This is after the meridian flip.?
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Hi Tom,
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How an ASI Air records the guiding data and how it could be used to diagnose RA errors is not something I am familiar with. However, if you can do some guiding with PHD2, that would provide some useful information. You can view the night's guide data with PEMPro Log Viewer , PHD2 Log Viewer or PECPrep to view the period of the errors and what mount components may be involved - worm, gearbox, etc. Addition of your extensions is most likely not the cause of poorer RA performance. But you may have jarred something else, and the worm tension may need to be reset. Analysis of guide logs can narrow this down to the mechanical component. Are you able to use PHD2?
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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
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John,
I have not used PHD2.? I've only used the asi air.? I don't know if the air produces a detailed log.
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On Wed, Jan 29, 2025 at 12:40 AM, Thomas Kallenbach wrote:
I have not used PHD2.? I've only used the asi air.? I don't know if the air produces a detailed log.
Hi Tom,
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You will need to connect a laptop to your mount to run PHD2. The guide logs then appear in the Documents folder, which is what is needed. The apps I mentioned will only work with PHD2 files as far as I know. But PEMPro Log Viewer and PECPrep already know the typical errors associated with a Losmandy mount - 239s for the worm period, 76s for the bearings, 32s for the gearbox, etc. So, they will tell you the magnitude of these errors and which is contributing the most. How to dig this info out of an ASI Air, perhaps someone else will jump in with the technique. Most likely you jostled something in the drivetrain when you reassembled the mount. You may need to reseat the worm gear or potentially compress the worm blocks a little bit.?
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But if you mount is guiding better on one side of the meridian than the other, you may want to go more east heavy with scope in RA so it will take up the backlash a bit more. This would mean sliding your counterweights up the shaft a little bit.
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Good luck,
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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
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I'm sorry to hear of these problems.? So your guiding problems started after the installation of new parts and the issue has been going on for months and so far nothing you have done since has changed the basic error rate??
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In the months since the mount upgrades have you changed your phone or O/S version, updated the ASIAIR app and ASIAIR hardware firmware, updated the Gemini 2 firmware or HC firmware?? Have you changed where the ASIAIR and Gemini 2 get power and is the ZWO ASI camera on its own 12V 5A power supply???
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The usual wosdom is that after changing out parts then having a new problem pop up is that you broke it by changing something.? Go back to the beginning and put it back to the way it was and retest.? I suggest uninstalling the RA extension first as it is the only moving part you repllaced assuming the pier is installed correctly and the fasteners are torqued down.? What brand of RA extension did you buy??
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Thomas,
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After the merdian flip the DEC and RA behaviors were consistent, about 0.5 arc sec. That is what you'd expect - seeing limited performance. People pay thousands more than you did to get that with absolute encoders and other things.
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But, before the meridian flip the RA was three times worse than the DEC. Notice also, that because the RA was much worse the max scale change from +- 8 arc sec before the flip to +-2 arc sec after,
making the DEC look much smoother pre-flip. But the DEC error value displayed was virtually the same before and after the flip, while the RA was much better after the flip.
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The post-flip performance is very good. But, because the data is only for a brief sample of time... It is possible that, by coincidence, the post flip captures were on a different part of the worm cycle. So, if you can, try to get the ASI Air to display 8 minutes of data, or take multiple, consecutive screen captures over 8 minutes with some overlap so you can see the full pattern. Do this with the scope on each side of the pier.
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The reason for eight minutes is that four minutes is the worm period of the G11, so by capturing 8 minutes (at least) of error data you can see multiple worm cycles.
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If that is too tedious then, go the PhD2 route and inspect the logs as suggested. But do so over two full worm cycles at the minimum; eight minutes or more. Your choice.
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If it turns out that the pre- and post-flip behavior shown in these four graphs (postings 83492 and 83493) is replicated across multiple worm cycles then the problem has something to do with cable drag, mechanics of how the mount is connected to your pier, or something that is orientation dependent (balance, whatever), not the mount and drive itself.
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Hope you get plenty of clear weather to work on this.
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Mark Christensen
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One last point: Make sure the scope is pointed at least 30 degrees above the horizon in both orientations (pointing east, pointing west). That will take out any effects of refraction.
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Mark C
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Thanks for all the advice.? I really appreciate it.? The asiair does provide a PHD2 guide log.? I am completely unfamiliar with it.? It is a text file with a lot of text.? I will attach it.? Please let me know if this is what is needed.? And don't worry about telling me I am an idiot...I'm used to it, my wife does it all the time.
Tom
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Thanks, Tom. You can use PHD log viewer to review the results of this log.?
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> ?Last night I adjusted the CW slightly so that it would be east-heavy.?
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When you say you adjusted it, what did you do? The weight needs to be re-adjusted after flipping to the other side of the mount to make sure the east side remains the heavier one. I'd just add a 2-3lb weight (a magnet?) to the CW on one side, and move it to the OTA side on the other.?
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It does appear that the error is significantly higher in RA on the west side of the mount, compared to the east. This is from the west side:
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And this is from the east. RA is better, although there are still occasional random spikes, though fewer and not as large:
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The large spike error doesn't repeat with the worm cycle, so is not caused by the worm (largest periodic error component seems to be at 2x worm cycle, magnitude of 1.4 arcsecs, so nothing major:
Regards,
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? -Paul
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On Wed, Jan 29, 2025 at 01:20 PM, Thomas Kallenbach wrote:
Thanks for all the advice.? I really appreciate it.? The asiair does provide a PHD2 guide log.? I am completely unfamiliar with it.? It is a text file with a lot of text.? I will attach it.? Please let me know if this is what is needed.? And don't worry about telling me I am an idiot...I'm used to it, my wife does it all the time.
Tom
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Paul,
I moved the CW after the flip to keep the east bias.? I did not do that last night, I did it the night before.? I have the log but the guiding was just as bad.? What do you think I should look into next?
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On Wed, Jan 29, 2025 at 06:19 PM, Thomas Kallenbach wrote:
Paul,
I moved the CW after the flip to keep the east bias.? I did not do that last night, I did it the night before.? I have the log but the guiding was just as bad.? What do you think I should look into next?
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I'd try to collect a few worm-cycles of autoguider data with actual corrections disabled -- just tracking on a star. Do this from both sides of the mount, and we can then see if the issue is mechanical or software/configuration related.
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It is also possible that, as was suggested previously, you wind up on different parts of the worm-gear when pointing from east or west sides, and if the gear is slightly eccentric, one side may cause a tighter worm mesh than the other. To check, move the scope 90 degrees in RA from CWD position (should be roughly at the meridian). Then, loosen the clutches and move the mount back to CWD manually, not using the motors. Turn off and cold start Gemini. This will shift the worm-gear by 90 degrees relative to where it was with your previous tries. Then, try guiding (or collecting unguided log data) from both sides, as before. See if things change because of the different position of the worm gear.
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Once you've done all of the things suggested already, the next step would be to see why or how the RA extension is causing this. You may need to loosen everything up, make sure nothing is askew, everything lines up properly. Reassemble carefully, don't overtighten. If that doesn't help, I would try to find out if the RAExt is actually what's causing it by removing it and testing again without.?
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Regards,
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? -Paul
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Hi Tom,
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I looked at your guide log with PEMPro Log Viewer and I see this log has multiple runs one after the other. So I am not sure which you consider having the problem and which are good. Attached is a screen shot of the very last one. Here we can see you have the typical 240s worm error which is not terrible (Y-axis in Arc-Sec). But you also have some 120s error, which is multiple of 240, and 32 secs which is the gear box. But all these values are changing from run to run suggesting you made mechanical changes between them. If you download this app from Ray Gralak's website, you can also open the log file and scroll through the runs. You may need to convert it to a Notepad text file first to open.?
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When we see these errors, we can sometimes correct them very well by creating a PEC curve using PEMPro (free for 60 days, not like the always free Log Viewer) and upload to the Gemini 2 unit. The upload curve should mostly correct for the common periodic errors and let your guide program correct for the seeing effects. In PHD2 we also use the PPEC corrective algorithm which can be used to correct for the largest magnitude error by setting the appropriate period in seconds. If you wish to proceed with PEMPro there is an instruction file on how to use with Losmandy mounts:
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I think these are the latest correct instructions. We still have no explanation why your mount changed from better to worse, so this may still involve some worm adjustments. There are a number of good videos on this subject on the Losmandy YouTube channel.
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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
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Paul Kanevsky
Chip Louie
