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What does a ZWO ADC do to focal length?

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#1 Thomas Ashcraft

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Posted 20 February 2017 - 11:12 AM

What does a ZWO ADC do to focal length? Does it act like a barlow? Thanks in advance. Tom



#2 wargrafix

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Posted 20 February 2017 - 11:18 AM

It acts like an extender. The images look a little bigger



#3 martinl

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Posted 20 February 2017 - 12:39 PM

In itself the ADC shouldn't change the focal length. However, it does use ~30mm backfocus so with a moving mirror telescope like an SCT it would extend the total focal length slightly (maybe 100mm?). Also, if you put a Barlow before the ADC, as recommended, the extra distance between the Barlow and the sensor would result in greater magnification. About an extra 0.6x with a shorty Barlow like the Celestron Ultima or Orion Shorty Plus. 



#4 RedLionNJ

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Posted 20 February 2017 - 07:39 PM

Precisely what martini said - 100% correct.



#5 jragsdale

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Posted 23 February 2017 - 04:18 PM

Would this effect a Powermate just the same?



#6 RedLionNJ

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Posted 23 February 2017 - 07:10 PM

Would this effect a Powermate just the same?

Powermates work a little differently in that the image size does not necessarily increase with added distance between the rear surface and the sensor:

 

see http://www.televue.c...werIncrease.jpg for the specific Powermate you have in mind.

 

For those concerned about any perceived need to put the Barlow *before* the ADC - I'm not sure this isn't a fallacy. You can even just screw a "nosepiece Barlow" (e.g. the business end of a Meade #140) into the end of the camera nosepiece, affording a reasonably low magnification (e.g 1.6x).




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