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ASI678MC and f/4 w/ Televue 2.5x

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#1 Jsterner91

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Posted 26 November 2022 - 12:49 PM

I just purchased an ASI678MC to do some planetary photography. My two scopes are a Meade SN8 f/4 which is 812mm FL. And a 12" Meade Lightbridge. Can this camera be effectively used with a Dob? And should I be using the 2.5x Televue Powermate I have or get a 5x? Any guidance is appreciated

Edited by Jsterner91, 26 November 2022 - 12:51 PM.


#2 RedLionNJ

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Posted 26 November 2022 - 01:03 PM

We have a FAQ, which will explain in more detail these answers your own questions.

 

Since you have 2 micron pixels, you should be aiming at approximately f/10. Focal length is irrelevant, it's focal ratio which matters.

 

So the 2.5x Powermate would be just fine with the f/4 scope.  The f/5 Lightbridge would also be ok with the 2.5x Powermate, although a 2x barlow would be closer to ideal under most conditions.

 

I'm not sure why you would be considering a 5x. That would not be helpful under any of your circumstances.



#3 AndrewXnn

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Posted 26 November 2022 - 03:09 PM

2um pixels and 812mm focal length equates to 0.51 arc sec/pixel.

 

Less than 1 arc sec/pixel means oversampling.

Stars will tend to be bloated and it may be difficult to track properly.

 

Ideally, one wants between 1 to 2 arc sec/pixel.

To obtain that, you'd need an effective focal length between 206 to 412 mm.



#4 Borodog

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Posted 26 November 2022 - 03:17 PM

2um pixels and 812mm focal length equates to 0.51 arc sec/pixel.

Less than 1 arc sec/pixel means oversampling.
Stars will tend to be bloated and it may be difficult to track properly.

Ideally, one wants between 1 to 2 arc sec/pixel.
To obtain that, you'd need an effective focal length between 206 to 412 mm.


This is all incorrect for planetary imaging.

2.5X will be great with that camera and those scopes.

You want to be at a focal ratio of about 5 times the pixel size in microns. 2.5x4 = 10 = 5x2.


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