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C11 Edge hd focal issue

Cassegrain
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#1 cken1

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Posted 31 July 2021 - 09:29 PM

Hi there,
I have just put my cpc1100 Edge on the Wedge to try to learn AP.
Based on 146.5mm back focul, I use 0.7x Reducer+Baader clicklock+Atik OAG+Zwo filter drawer+spacer+zwo 128mc pro to get perfect 146.5mm.
Also, I put CW rail under OTA, make good balance.
My questions are
1. It's really hard to focus on the targets. I use Celestron focus motor, it almost runs out to the end of infinity side. And then I could get the focus or tiny donut rings sometimes. It looks like there is not enough focus travel to reach.
2. Even it balanced perfectly,(IMO though), I still can not get the accurate goto.
3. Because the short gap between the long image rig And double folks base, how can I prevent the camera to hit the base?

Is there anything I did wrong?
Any suggestion would be appreciated!

Thanks,
Jack

#2 cken1

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Posted 31 July 2021 - 09:35 PM

Try to post a photo

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  • Screenshot_20210801_123205.jpg


#3 cken1

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Posted 31 July 2021 - 09:36 PM

One more photo

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  • Screenshot_20210801_123344.jpg


#4 Endymion

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Posted 05 August 2021 - 02:11 AM

Hi Jack,

 

On item 1, this thread may be helpful.   https://www.cloudyni...e/#entry7314214

 

The net is that some C11 EDGEHD + 0.7x focal reducer don't come to focus.  The problem appears to be that the focus stop set in the C11 is off in some scopes so that it can't quite get to focus with the reducer.   Even with a working case, the focus of the C11 needs to be near the end of travel in one direction with the reducer.  

 

On item 2, it may be mirror flop causing the issue with gotos.  You didn't say how far off the gotos were but mirror flop can definitely move the goto off center for the target.

 

 

Regards,

John



#5 Linwood

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Posted 05 August 2021 - 09:29 AM

I have an edge and focal reducer ... 

 

Are you sure you measured the 146 from the end of the focal reducer?   i.e. the flat end after the threads, to the sensor plane in the camera (probably +1mm for filter affect). 

 

I had not heard of issues with the focal reducer, but mine does focus in a different focuser position with and without, which I do not quite understand (if the backfocus distance is in fact identical shouldn't the focus position also be?).  But just take the focal reducer off -- the backfocus is supposed to be the same, so remove one variable, and see if you can get focus with just the imaging train without the FR. 

 

I do not even use my focal reducer, I probably need to adjust back focus, but when I add the focal reducer the corner stars go into streaks while the center are perfect (rather classic backfocus behavior) and at the moment I have no mechanism to adjust.  But still puzzled why without the corners are fine.  But I had no trouble obtaining focus in both cases.  I just went back to the last time I tried it.

 

Focus position at 2000mm was 30055

Focus position at 2800mm was 21388

 

I don't know what the max actually is, but yes, there was a big difference without and with. 



#6 Endymion

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Posted 05 August 2021 - 10:14 PM

Here's how the focusing works with and without the focal reducer on my C11 EDGEHD.   (This is after I had the C11 replaced due to being unable to come to focus.)
 
C11FocusRange

 

 

 

John


Edited by Endymion, 06 August 2021 - 06:58 PM.


#7 Linwood

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Posted 06 August 2021 - 08:32 AM

Image not viewable.



#8 cken1

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Posted 06 August 2021 - 05:48 PM

<p>Thanks John and Linwood!</p>
<p>I am sure that the 146 measurement is correct with or without reducer.</p>
<p>I found my focus position can only reach 29000 to the furthest position. I used a wrench to give the motor another turn gently, and run calibration again. Now it can focused at the near end.</p>

#9 Endymion

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Posted 06 August 2021 - 06:58 PM

Fixed the image problem in previous post.

 

John



#10 cken1

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Posted 08 August 2021 - 08:36 AM

Thanks for updating the photos.
From the photos, I can see it almost same as my one.

#11 FlankerOneTwo

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Posted 09 August 2021 - 03:31 PM

Hi,

 

Note that the distance from the OAG prism to the guide sensor must be the same as the distance to the imaging sensor, otherwise you will not be able to focus both simultaneously. It looks like from your pic that the OAG-imaging distance is quite a bit longer than the OAG-guide distance. You may need to move some of those spacers to the front of the OAG




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