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Televue NP101is backfocus spec

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#1 Donnie D

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Posted 14 August 2020 - 11:30 PM

Does anyone know what the Backfocus is on the Televue NP101is?  I have read the manual for the NP101is , plus other reading, and I have derived at some numbers for back focus. I am not sure my values are correct.

 

Thank you kindly

 

Donald


Edited by Donnie D, 15 August 2020 - 01:02 AM.


#2 rgsalinger

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Posted 15 August 2020 - 01:14 AM

There is no "backfocus spec" for the is series of scopes. Just focus it as you would any other refractor. If you are using a focal reducer or a flattener that's another matter but otherwise there is no "sweet spot". 

Rgrds-Ross



#3 Donnie D

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Posted 15 August 2020 - 01:25 AM

Thank you Ross, I was wondering about that.

 

I found out so far that if you use a reducer/flattener then the reducer/flattener will have  an optimum 55mm back focus. (Distance from flange surface to film or CCD plane). If you use a CCD, be sure the spacing between flange and CCD is 56mm +/-2mm for best results


Edited by Donnie D, 15 August 2020 - 01:26 AM.



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