Deal with right ascension (RA) Backlash! part 4 (5)
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- Опубліковано 13 січ 2020
- In this video I'll show the basic concept of east heavy balancing to counter backlash in RA on an equatorial mount.
I'll use the old school method of finger meshing to explain things. Cause animations are so 2019!
Featuring: Balti
Edit:
What I didn't mention was that if guiding with a rate of LESS than 1 sidereal (15°/sec), we will never really experience backlash in RA. This is since we'll never actually stop the mount, but only slowing the mount down in the tracking motion. - Наука та технологія
Creativity drives simple solutions! Great job!
Glad it makes sense! Cheers!
A big thank you from Seattle! This concept finally makes sense to me :-).
Thanks! Great to hear!
Now I know why I should have the OTA east heavy if imaging east of the meridian. Thank you for the easy explanation. The Dec backlash is a much bigger problem!
Hi Dan! Cheers and great to hear it helped!
If the backlash is very big, you might want to look into the gear meshing first.
Otherwise, the DEC might actually be treated a bit similar (if you can stand a slight polar miss-alignment).
Set you equipment up as normal, do a polar alignment and star alignment.
Start phd2 or similar and check the polar alignment using drift alignment tool, or do the guiding assistant. Sometimes I just start the guiding for a bit and check which way the DEC drift is heading off to.
One you know which way your drifting, say south for instance, you can balance with this in mind just as you do with the east-bias balancing in RA. Try to only adjust the OTA, or move weights already on the DEC location. Don’t add new weight to the system, or you’ll have to rebalance RA as well.
South drift (north corrections): balance south heavy.
North drift (south corrections): balance north heavy.
With the miss-polar alignment there is now a small, constant drift in one direction. Just like we have a constant drift in RA due to the star tracking, we now have, a much smaller, but still constant drift in DEC. The weight assist might help us from backlash when guiding.
You might want to try how big miss-alignment you need/want if you’re trying this. It might be that whatever small polar error you have is enough depending on the method you're using for polar alignment.
This weight bias will, just as the east balancing, have to be changed after meridian flip.
Also, adding an error to the system to improve another is a balance game. Keep it as small as you can, and also make the weight bias as small as you can to get the result you want.
Trial and error ...
Good luck, and may the dark side be with you ;)
@@astroboden I have an EQR-6 Pro. I think most of the moving parts are belt driven (cue being the very quiet mount tracking as opposed to me CGX-L mount). I had very good guiding with it and everything then went to he11...so I don't know if my tinkering with the initial settings caused the problems or not. It is in my observatory permanently mounted so it is not subject to as much disturbance as would a potable set up be...I also see that belt driven systems may not require the adjustments in RA (CW heavy or OTA heavy) or deliberate errors in the altitude of the mount to offset declination backlash. Since that is my problem if I cannot correct it through settings changes then this could offer me a solution. My problem is that in calibration the South movement is very small hence the Declination backlash.
Ah, the EQR-6 was one of the competitors to the CGX when I was buying it. I have regretted that choice a few times the past year. I finally think I was starting to get it under my thumb before the summer. Haven’t had a chance to use it since.
Anyway, the worm gear backlash will always be there, but the belt drive with reduce the rest of the system backlash I suppose.
RA also rarely shows backlash because one is mostly guiding in < 1 sidereal. So, you’re only slowing down, or just stopping the tracking. Never changing direction.
What kind of adjustments can you do on the EQR-6 and is it only declination backlash that’s the issue?
Sorry, but did I understand the issue correctly that you have too small calibration steps south that the backlash consumes all of it?
Did you play with the auto-guide rate adjustment in the mount?
@@astroboden I sent SW support the log/bug files and they are replacing the mount! Something has gone wrong with it. The persistent problem has made me an expert (almost!) in PhD2 guiding and the related but it is looking like an electronic or circuit board related issue. It is not my first time that I have had an EQR-6 Pro mount go bad on me. Beginning to feel jinxed! They do have a good reputation and similarly this one used to work like a dream until about a month ago it went bad (forced calibration invariably showed very little south movement) If you are interested I could send you the bug log files as well...just an exercise in exorcising our curiosities...
Ah, result! Hope the exercise might stay on the image processing from now on then ;)
Other peoples experience is valuable! Got a small EQM-35. Hope it dosen't go crazy, but one can never get enough log files... haha. I'll take it if you're sharing :)
Hi, thanks for a great video! Is that some kind of hybrid Ramones T shirt you have there? :)
I am a complete EQ mount novice so please excuse what seem like stupid questions. I understand the concept of avoiding RA backlash as the mount tracks objects east to west across the sky andc for the need to make the mount east side heavy, thanks to your great video!
What I don't understand though is this (btw, I am a visual only astronomer, no photography) - I like to switch my targets between east and west regularly when observing. So, if I'm looking at M104 in the east and then decide to switch to M82 in the west, do I have to do a manual meridian flip and do I have to rebalance my mount everytime I cross the meridian with my telescope? I don't have the mount yet, I'm just reasearching the subject at the moment. Up unil now I have had alt az mounts only. Thanks for any help! Keep up the great work. I have subscribed.
Hi mate! Thanks for watching! Glad you like it. Looking back at these videos I get the impression I should be a bit more… lucid.
Anyway! Is it the Mustasch hoody your thinking about? Gothenburg band “Mustasch” in that case. Heavily recommend ;)
The other one is 2112 - the restaurant in Gothenburg owned by members of “In flames”, another awesome “Gothenburg death-metal”. If you haven’t had a listen, you’re in for a treat ;)
Back to the subject of astronomical stuff. First, if you’re into visual astronomy I would not give the whole bias-balancing too much thought. Just balance pretty evenly (I wouldn’t go to town on it) and enjoy the view! The backlash is mostly going to give you a hard time if you’re into long exposure photography and auto-guiding.
But, if you were to join the good/dark side, astrophotography that is ;-) you are correct. You would be rebalancing after a meridian flip. If your gear is suffering backlash that is. Try without fancy fixes until you know you have anything to fix.
The eq-mounts shine when it comes to astrophotography mainly since you don’t get field rotation. A good alt-az mount might be more suitable for visual?
Did that help? Anyway, nice of you to drop by! Welcome back anytime!
May the dark side be with you!
Love ur dog ❤️
I'll pass on the nice comment! He'll be assisting me more ahead ;)