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CEM70 Untracked / Tracked performance

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#1 aarshad81

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Posted 19 October 2021 - 11:40 AM

Hi there, was wondering what kind of performance you are getting from your CEM70. I have a AT115EDT 644/805mm focal length depending on reducer/flattner, noticing untracked I only tried till 60 seconds, i had some drift going to 120seconds

 

I will soon have some better data including tracked numbers



#2 alphatripleplus

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Posted 19 October 2021 - 11:59 AM

Do you know how accurate your polar alignment is, as that can contribute to drift in both axes?



#3 bobzeq25

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Posted 19 October 2021 - 01:20 PM

I presume you mean guided/unguided.

 

I fail to see why people don't want to guide.  The periodic error of your mount is about 8 arc seconds, peak to peak (and it will not be reduced with good polar alignment).  Even mediocre guiding will reduce that to below 1 arc second rms.

 

Why would you want to throw away that improvement?  You worry about _much_ smaller things.  You might as well have gotten a less expensive scope, the quality of the AT115EDT is being wasted.

 

If your skies are dark, 60 second subs are too short.

 

If you really insist on unguided, you need a better mount, and it needs to be on a fixed pier.  Something like a 10Micron in an observatory.  <smile>


Edited by bobzeq25, 19 October 2021 - 01:22 PM.

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#4 Tony Bonanno

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Posted 19 October 2021 - 01:50 PM

I have the same scope (AT 115 EDT) on my CEM70 set up for imaging.

 

I tried unguided with good polar alignment, just once for kicks.  With 30 sec subs, it was fine.  60 sec subs, I noticed a little distortion in stars, possibly could be better if I'm more careful with setup, balance, PA, etc. 

 

But generally I always use guiding.  With guiding enabled, no complaints at all.  Even with 5 min subs, stars are pretty good.  Typically, I just use 120 second subs.  Guiding is the way to go for sure.


Edited by Tony Bonanno, 19 October 2021 - 01:57 PM.


#5 aarshad81

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Posted 19 October 2021 - 02:46 PM

O for sure i am going the route of guiding, but was just wandering what to expect from a mount like this. Since i got the mount it started raining/cloudy for the  next week and half lol

 

I only had a short window to try some stuff out and just used it unguided. 


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#6 aarshad81

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Posted 19 October 2021 - 02:47 PM

I have the same scope (AT 115 EDT) on my CEM70 set up for imaging.

 

I tried unguided with good polar alignment, just once for kicks.  With 30 sec subs, it was fine.  60 sec subs, I noticed a little distortion in stars, possibly could be better if I'm more careful with setup, balance, PA, etc. 

 

But generally I always use guiding.  With guiding enabled, no complaints at all.  Even with 5 min subs, stars are pretty good.  Typically, I just use 120 second subs.  Guiding is the way to go for sure.

Thanks cool ! 


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