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What's wrong with this mount? Help please .
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Hello,
below is a screenshot of phd I did last night. Every night tracking looks the same. I do polar alignment with polemaster, mount is perfectly balanced in RA and DEC, do a calibration where I should do, than run a guiding assistant and look at this. My old cheap celestron mount tracks better than this. My setup weights nothing. I use a SW 0,8 kg counterweight. Every frame has got bad stars. Seb |
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Looking at that graph... it seems like you have acceptable or even good guiding in DEC (other than the parts where you are dithering, which is expected). The big issue I see is in RA. Even there, for the most part you have good guiding, then "something" happens and you're seeing PHD2 trying to correct. It is impossible for PHD2 to correct these type of one time events. Some things to look would be looseness in the clutches, perhaps combined with cable drag. The other thing I noticed was that you have a guiding capture time of 4 seconds; you may want to reduce that a bit to 2 or 2.5 seconds, so that whatever corrections PHD2 sends are implemented quicker, and a motion of the star is detected a bit quicker - this is probably a secondary issue with diagnosing what's causing the? jumps in RA being the primary.
Providing a photo of your set up and more details might also be helpful. The mechanics of the mount are only one part of getting good guiding! |
开云体育Hi! Where in the sky was the star? Where was the mount pointed? I've had some odd behavior lately trying to image a variable star very close to zenit, with the mount far to the east of pier. Trying to diagnose that a bit - so was thinking if your case maybe was similar? Good guiding at some parts of the sky, and then other things happens in other directions? Best, Magnus
Den 2020-05-13 kl. 18:19, skrev Arun
Hegde:
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Hi Seb there's really no way to tell with just a screen shot, there are way too many variables in there I suggest you do a baseline guiding, as outlined in this guide:? that eliminates the easiest problems when it comes to? and then if you still have issues, the PHD forums are probably a better place to share the baseline guiding and get feedback (i'm a regular over there so I will look at it there as well) if we determine there's something going on with the mount, we can take it from there, but i already see there are a number of PHD settings that would contribute to less than ideal guiding On Wed, May 13, 2020 at 1:11 AM Sebastian Kotulski <sebkotulski@...> wrote: Hello, --
Brian? Brian Valente portfolio |
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Hello Friends,
I have a very light setup: TS 50/330 with flattener and Canon 1100D side by side with ASI min guider scope and ASI 120MM. It weights nothing. I have a shortened counterweight bar and a SW 0,8 kg counterweight. My mount is GM8 with Gemini 2 with high precision worm and hight torque motors. As I said before, a did a polar alignment with a polemaster and sharpcap. Guiding assistant showed PA error 0,7. Before making a phd calibration I removed any dec backlash pressing north for a few seconds. After that I did a calibration close to a meridain and equator crossing on the east side. My balance was biased towards the counterweight. 4 or 2 sec guiding capture time didnt make any difference. RA axis was going smooth and sudenly hills and mountains. I dont have any backlash. In fact I think that my worm and worm gear are to tight, and maybe thats an issue.I have just stripped the RA axis and try to clean it and regrease with superlube. Below is a picture of my Celestron CG5 mount tracking with the same scope on it. You can compare. |
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Sebastion:
Perhaps a couple of suggestions you can try: Have you done anything with periodic error correction? If you don't have PEMPro you can download it and use it free for like a month. More than enough time to analyze your PE and send a correction curve to the mount. Try increasing your correction pulses from 2500 to 3200. Multiple pulses show not enough movement is occurring. Try increasing your RA aggression to 75 or 80 and your Hysteresis to 20. Increasing the latter often smooths the corrections into shorter but larger pulses, learning from past behavior. Cut exposures from 4 to 1 to 2 seconds so corrections are made more often. Also try turning off the dithering until you try a few adjustments.? Click on the brain to make sure you are using the right focal length, etc. Sometimes I have forgotten this when changing rigs. Also a new darks library is needed if you changed guiding cams. Hope some of the above help. Perhaps you have already tried a few or all of these. Good luck! John |
开云体育Hi Sebastian ? Lots of info coming your way. ? Just to add to John’s comments. Default RA is 70 and Hys 10.? Your RA Osc is very low and PHD manual suggest 0.30 to 0.35. To increase RA Osc they say increase RA Agg and or decease Hys. ? So I would suggest you first increase Agg to 70 and leave Hys at 10. Then try more Agg of 75 or 80. After that decide on increasing or deceasing Hys. Try to get a better RA Osc number. ? Cheers Richard ? From: [email protected] <[email protected]>
On Behalf Of John Kmetz via groups.io
Sent: Thursday, 14 May 2020 9:32 AM To: [email protected] Subject: Re: [Losmandy_users_io] What's wrong with this mount? Help please . ? Sebastion: |
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Sebastian,
I've never (in decades) used Hys. In my opinion it is an nice idea that probably isn't needed in most cases and just confuses people since the two (Agg and Hys) usually fight each other - Aggressiveness wants to make changes immediately, while Hysteresis says "wait a minute". Instead, set Hysteresis to zero and Aggressiveness to 45 to 50 (actually 0.45 and 0.50). With zero Hys, of course, any Aggresiveness (aka Feedback in systems engineering - why do astronomers have to create a new term?) above 50% can result in oscillations. I feel the same way about PEC - it probably causes more trouble/confusion than it is worth for most people. Heresy, of course, to many. But then I usually use the original PhD just because it is simpler - the fewer features active at any time the simpler it is to get to the root of a 'problem'. 25 years in aerospace software and systems made me very conservative. So I agree with John - turn off dithering until you debug the rest of the hardware/software. By the way, you don't want the mount perfectly balanced. You want it slightly heavy east and of course, a guide rate if 100% or (ideally) less. I usually run at 50% given my skies. As others remarked, you DEC looks fine, a testimony to your good polar alignment. Mark |
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Arun Hegde
I'm not the OP, but I did have a question here that I am hoping some others that have posted here who have more experience than I do can clarify. When I look at Sebastian's graph - what I see is that the RA excursion leads the corrections that PHD2 applies - that is, the excursion does not seem to be caused by a PHD2 guide command, rather, it is an outside excursion that PHD2 is trying to correct. And after the excursion is corrected, the guiding in RA is fine again. Am I reading this wrong? Just trying to understand as I am trying to improve my own guiding. It does make sense to me that excessive aggressiveness can cause oscillations, as perhaps happened with the second excursion, but it does seem to me that something triggered both large excursions as there seem to be other smaller excursions that PHD2 was able to correct without issue.
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Hi Sebastian This is really not the way to go about this.? I don't recommend tweaking the mount..? As I mentioned before, without looking at the logs a lot of suggestions are just shooting in the dark. your guiding can be improved but there's no way to know how to do that without seeing the detials let me again *highly* recommend that you perform a baseline guiding as outlined below, and report back here (or to the PHD forums) with your results On Fri, May 15, 2020 at 8:44 AM Sebastian Kotulski <sebkotulski@...> wrote: Thank you all for your support. I will take into account your suggestions. I am a little disappointed that I have to tweak this mount. I have had higher expectations. If the weather is good, I will try again this weekend and let you know. --
Brian? Brian Valente portfolio |
开云体育What is it doing (or not doing)?
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I have a GM811G with spring loaded worm. I've found that increasing RA aggression is key to keeping the RA in check. I'd experiment with that value and see if it improves things. I've found that I can go above 100% for best results. My last try it was something like %135. I'd also recommend not making the RA clutch too tight. Make it just tight enough to prevent it from slipping in any position the mount may be in. The clutch screw puts pressure on a bearing, and I imagine that it could cause stiction if too tight.?
Jamie |
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i recommend avoiding rings if at all possible. They really aren't the most stable option and can introduce flexure On Wed, May 20, 2020 at 12:22 PM Sebastian Kotulski <sebkotulski@...> wrote: I would like to mount a guider on top of the main scope, but still have not found the proper rings. --
Brian? Brian Valente portfolio |
开云体育That depends on the rings. ?These rings are rock solid and a huge improvement in stability: ??On May 20, 2020, at 3:28 PM, Brian Valente <bvalente@...> wrote:
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Timothy Campbell
Jamie Amendolagine
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