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Upgrading mount... iOptron CEM120

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103 replies to this topic

#101 amoncayo

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Posted 02 October 2019 - 02:40 PM

Five minute guided subs at 2.5 meters of focal length with 55 pounds on the mount. Not the improvement in eccentricity as the nigth work on. I attribute this to cool down of the mirror and stabilization of the atmosphere. I'm now 90 percent convinced that my copy of this mount works for that much weight and focal length. 

 

Rgrds-Ross

Ross,

 

Can you share the fit files for image 34 and for either image 37 or 53? You can post those on the CEM user forum too, since here the file size limit is too small to allow looking at detail.

 

Al



#102 rgsalinger

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Posted 02 October 2019 - 06:03 PM

The camera is a fragment using the ASI071C-  a one shot color camera - so the output may look a little strange to you as they have not been de-bayered.  This is not the absolute corner but it's not the center either. The Planewave has an utterly flat field (it's actually amazing) so it usually doesn't matter (tilted cameras aside) where you take a fragment. 

 

Capture.JPG

 

I moved the imaging system from my Paramount (thanks to my helper) without dismounting the imaging system. The results compare to what I saw on the Paramount. I was pretty amazed when after doing nothing the results changed. The seeing went off as the Jetstream moved in a bit later. 

 

https://www.dropbox....age 23.fit?dl=0 is a link to another one (CCD Image23.fit) which you can peruse. That one has NGC6946 in the middle. 

 

Someday my QHY will return from China and I'll put that back on with an improved adapter spacer and we'll see if this issue (for me) can be closed out. 

 

Rgrds-Ross

 



#103 amoncayo

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Posted 02 October 2019 - 06:07 PM


https://www.dropbox....age 23.fit?dl=0 is a link to another one (CCD Image23.fit) which you can peruse. That one has NGC6946 in the middle. 


Rgrds-Ross

Thanks Ross.

 

I was hoping to see just "how much" elongation was visible in #34, since that was >0.5 eccentricity, relative to the good ones taken later. I'm assuming your guiding only became better as the night progressed? (Or maybe I missed that from your post..?)

 

Al



#104 rgsalinger

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Posted 02 October 2019 - 06:28 PM

No, actually the guiding got worse as the night wore on! By 4AM my subs were close to 3 arc seconds in my second system 10 feet away from the CEM120EC2 

 

I think that what happened was that the mirror finally reached equilibrium and that the seeing improved between 7PM and 9PM. My imaging partner (who is vastly better at this than I am) never images at our location until about 2 hours after sunset. His advice to me when I was initially disappointed was to "wait" which proved to be correct. Once the temp stopped dropping I was surprised at the resultant change in image quality.

 

Nevertheless, I'm still thinking that there's something going on with the encoders, I'm just in a sweet spot of some kind. I'm very curious to see what happens when the big camera comes back. 

 

I also use a 25" F8 RC scope from time to time. We actually use an air conditioner to cool that scope just before/after sunset or we get oblong stars sometimes all night. That scope is a truss design and we still needed fans to keep the airflow laminar where the truss ends and there is a short tube. It never occurred to me that the PW needed some extra cool down as it's been in New Mexico at 8000 feet for a long time where the thin air cools causes faster cooling and less tube current. (Or at least that's my latest crackpot theory.)

 

Rgrds-Ross


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