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Focal reducer for Meade ACF 12" - help needed

catadioptric Meade reflector
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#101 kzar

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Posted 24 August 2021 - 02:33 AM

Thank you Ken ! I will give a try tonight provided the weather allows it :)

 

Regardless, it's amazing to see how far your camera is from the rear cell of your Meade lol.gif . By the way, we both have the same focuser. 



#102 Oberon510

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Posted 24 August 2021 - 03:31 PM

Yes it is a long way back and here are my calculations:-

 

AP27TVPH has a back focus of 175mm with 57mm from back lens to the back thread so I have (175-57) 118mm to use from the back thread - have a look at my previous photo which shows the measurement from the back thread of the 27TVPH to the sensor on the camera.

 

My ASI1071MC has a back focus of 17.5mm (Sensor to thread) so the length of my filter wheel and spacers are roughly 100.5mm (118-17.5)

 

In summary my setup is longer because of the 118 to 85 focal length difference between our FRs.

 

Too many calculations for any sane person - good luck with your configuration.



#103 kzar

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Posted 24 August 2021 - 11:56 PM

Agree on your statement "too many calculations fro any sane person...." lol.gif

 

Once the weather clears up, I will see if I can get something out of my configuration. 

 

Out of curiosity : which model of Meade do you have (F8 ? F10). 



#104 Oberon510

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Posted 25 August 2021 - 12:22 AM

10” F8 LX850 OTA



#105 kzar

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Posted 25 August 2021 - 12:42 AM

So we have same models (different size but same optics). 

I will try to update the thread as soon as possible.

Wish you a good week.



#106 kzar

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Posted 31 August 2021 - 02:28 AM

There we go ! I had yesterday an opportunity to test the TS CCDT47 focal reducer on my Meade 14".

 

Please note that since I am still waiting for some adapters to install my OAG, the below raw shots have been taken unguided.

 

First pic is a 80" raw on M57. Stars seem okay for me even though I could improve their shape a bit. 

Attached Thumbnails

  • Capture d’écran 2021-08-31   09.13.14.png

Edited by kzar, 31 August 2021 - 02:53 AM.


#107 kzar

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Posted 31 August 2021 - 02:32 AM

.... and the other one on M13 - 120 unguided. 

 

Generally speaking, I am satisfied with this focal reducer. 

 

Looking forward to having your feedbacks.

 

Regards,

Aygen

 

 

Attached Thumbnails

  • Capture d’écran 2021-08-31   09.15.09.png


#108 Oberon510

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Posted 31 August 2021 - 09:04 AM

Hi Aygen,

 

They look good but will leave it to the experts to comment further. I am not sure how your atmospheric conditions are this season but here we seem to have constant distortion even when we have clear skies. That makes crisp exposures near impossible - maybe winter will be better when El Nino and La Nina subside too. (something you would not have to worry about)

 

One thing that stands out is the magnification of the exposures - mine seem to be larger by more than the FR differences  - 0.67x vs 0.75x (27TVPH). The further your focal distance from the FR the less the magnification - you may want to double check the focal distance you have with the spacers.

 

Ken



#109 kzar

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Posted 31 August 2021 - 09:17 AM

Hi Ken,

 

Thank you. Looking forward to having other views, since I am by far not an expert...wink.gif

 

Regarding your second sentence, do you think there might be an issue with my setup (back focus, etc.) ? When I compare the two above sub-frames with FOV simulations, they seem to correspond. For example, see below M13 FOV simulation that corresponds to my setup (from telescopius.com simulation)

 

As for the atmospheric conditions, it's bee age that we don't have clears skies here in Switzerland - difficult to say frown.gif

 

Aygen

Attached Thumbnails

  • Capture d’écran 2021-08-31   16.13.37.png

Edited by kzar, 31 August 2021 - 09:18 AM.


#110 Oberon510

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Posted 31 August 2021 - 09:34 AM

With regard to the back focus question, I just did a quick comparison of my M13 photo and yours and mine appeared to be more magnified - maybe it is just my quick look or maybe I need to check my focal distance shocked.gif

 

The stars look round at the edges of the photo so the FR appears to be doing a good job.

 

Good luck with the setup - seems you are now "Good to Go"


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#111 carolinaskies

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Posted 31 August 2021 - 07:05 PM

There we go ! I had yesterday an opportunity to test the TS CCDT47 focal reducer on my Meade 14".

 

Please note that since I am still waiting for some adapters to install my OAG, the below raw shots have been taken unguided.

 

First pic is a 80" raw on M57. Stars seem okay for me even though I could improve their shape a bit. 

Can you give the info on the camera as well as backspacing you have set.  I note the CCDT47 suggests 85.  Also, between M57 and M13 did you check focus, which was taken first and how far apart in time?

On the M57 I'm seeing what looks like a touch of Coma or camera tilt perhaps though M13 looks very nice so wondering if you adjusted anything between the shots or if maybe the image train sagged a bit between the shots since M57 is opposite side of the meridian?    



#112 kzar

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Posted 31 August 2021 - 08:13 PM

The cameras is my OSC ASI 2600 MC pro and 85 mm of backspacing was used, as suggested.

I first started with M13 and then slew to M57. When doing that I forgot to lock the mirror and I had to refocus. I did a quick refocus without “really caring” as I just wanted to see how the image would look like. As for the time interval, I would say 20 minutes apart.

If the weather allows it, I will capture M13 (or another target) by end of this week and will share the result just to see whether the CCDT47 meets the expectations:)

#113 carolinaskies

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Posted 31 August 2021 - 08:41 PM

The cameras is my OSC ASI 2600 MC pro and 85 mm of backspacing was used, as suggested.

I first started with M13 and then slew to M57. When doing that I forgot to lock the mirror and I had to refocus. I did a quick refocus without “really caring” as I just wanted to see how the image would look like. As for the time interval, I would say 20 minutes apart.

If the weather allows it, I will capture M13 (or another target) by end of this week and will share the result just to see whether the CCDT47 meets the expectations:)

That shift and refocus likely accounts for the disparity of images.  




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