Celestron AVX guide logs - Forums

Topic starter

Sep 16, 2018

Hi All

Im battling with an 11s oscilation on my AVX mount. can anyone who has an AVX and is happy, post me a guide log so that i can benchmark performance and examine my oscilation in context.

Thanks in advance.

Uwe Deutermann

Sep 18, 2018

Hi Kamil!

Unfortunately I cannot help you since I experience the same problem (in RA). Hence I would be as well very interested how to get rid of it. I need to guide with very low frequency (0.5 to 1 second) to compensate, otherwise my stars would be always oblong. But this brings of course seeing into the game, causing that the images are not sharp enough.

Uwe

Kamil

Topic starter

Sep 18, 2018

exacty the same problem. ive logged a warranty ticket with Celestron already.
i have found 2 examples of AVX guide log on the internet that do not show this 11s oscilation.

but obviously happy people dont post their logs to show problems.
a lot of the logs i found shows the 11s oscilation, but most of them are 1/5 the size of mine.

Kamil

Topic starter

Sep 22, 2018

i have logged a ticket with the Agent in South Africa.
providing all measurement details and a description of the issue.

my mount is with them, now I wait for a response.

Rusty

May 19, 2019

I just ran across your post from last year about your AVX and guiding issues. What I have found if to use the drift align tool in PHD2. With that I have been able to go from 180 sec subs maximum to 10 min if I want. I will normally run 5 minute subs. Dec will run between 0.03 and 0.07, while the RA usually runs 0.08 to 0.16. Very seldom will I let PHD2 adjust in both directions. It get crazy, so I usually I set it to run north just a tad in the drift align tool, and that allows me to set if for south adjustments only . This works for me very well.
I've tried to copy and paste last nights text guide log, with no luck. Send me an email at rgskip2@gmail.com and I'll send it to you. Last night was a full moon and I live in the middle of town, So seeing is an issue.

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AwesomeAstro

May 19, 2019

I've found that you can't reasonably expect anything below, say, 0.8" composite RMS on this mount with a telescope as fickle as the 8se (my scope; it appears you have the edge 8HD which is comparable). However, I managed to get my guiding below 1" (sometimes over the course of hours) by:

1) Imaging in the north, away from the celestial equator (I can get as low as 1.2" in the south on a great night, but no better)
2) Tweaking the mechanical backlash of the spur gears and slight adjustments to the worm with its casing's hex bolts
3) Loosening the axes to allow more free motion
4) Setting very diligent PEC on the RA axis using the hand controller and averaging together many runs with Celestron's PECtool (NOT pempro, which never gave me the right amplitude of PE despite everything else on that program being very impressive, which unfortunately made it not workable for me).
5) Oddly enough, by choosing 0.2s exposures on my guide camera in PhD2 and issuing very aggressive corrections (it will ping-pong around more of course, but usually within a fairly tight amplitude). Of course, with bad seeing nights, this sometimes has to be adjusted longer, and on very bad seeing nights (like last night), I had to go to 3 seconds, which is not ideal. I started using exposures around 1-3s like I was told by all the posts, but I achieved incredible results with very short 0.2s exposures on good seeing nights.

I just realized this post is not recent. Shoot. I'll keep this here for information, though. Shoot me a PM, you or anyone else, if you want any sources or results from me.

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Rusty

May 19, 2019

I agree on the .08 RMS. the best I have done is .09 and that only momentarily. I have also changed the ball bearing on the RA axis to a tapered Timken style bearing . See kink below. It smoothed thing out a lot. Adjusted the backlash on the gears etc.

I normally use 1.5 sec to 2 sec guide scope images. I might try faster as you suggested to see.

I suppose all this should be put into perspective. These mounts are mass produced and cost under $1,000, yet we expect them to be perfect, while we will buy a new truck at $ 45,000. Then we put new wheels, maybe a bed cover, tint the windows etc. Anyway hobby or show. :-)

http://rocketsparrow.blogspot.com/2017/01/how-i-made-better-celestron-avx.html

AwesomeAstro

May 19, 2019

Yup, 0.8 arcseconds was under great seeing in the optimal part of the sky (north around 60 degrees in elevation, for me). I do regularly get hours of guiding under 1 arcsecond in this location in the sky, which is pretty great for this mount! I don't take very long subs, however (I'll try 3 minutes on my next targets).

The real issue is consistency and how much accuracy is needed. I think I got a great image of M104 with tracking around 1.3" RMS. It's all about what you can get away with.

I now regularly use 0.2s guide camera exposures with great success, unless the seeing is awful.

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