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Backfocus for RC8 and CCDTV67 0.67 reducer

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#1 lowry_pt

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Posted 21 February 2020 - 12:04 AM

the infamous question.....

 

I have read on so much my brain hurts.

 

IF you have an image of your set up even better.  plan is asi 294. with ( and without the zwo OAG  (16.5mm)

 

I have read 80. I have read 55. and everywhere in between.

 

My friends rc8. we plan to set up at 80mm.  take an image. check edegs. add/remove spacers untill we like it.  then figure out the degress of FOV. with website and caluate the FL. I figured out the formula.  basically 749.66 divided by the FoV in degrees.  

 

and then input that for his guiding etc..

 

  other ideas?

Thank you



#2 bobzeq25

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Posted 21 February 2020 - 12:43 AM

https://astroimages....-my-system.html

 

He talks about backfocus for that reducer, in detail.  I think you would find the whole page a good read.

 

Madratter is an excellent imager, he's on Cloudy Nights, and I'm sure a PM to him with questions will be thoughtfully answered.


Edited by bobzeq25, 21 February 2020 - 12:49 AM.


#3 lowry_pt

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Posted 21 February 2020 - 01:38 AM

https://astroimages....-my-system.html

 

He talks about backfocus for that reducer, in detail.  I think you would find the whole page a good read.

 

Madratter is an excellent imager, he's on Cloudy Nights, and I'm sure a PM to him with questions will be thoughtfully answered.

thank you so much. I did read and was completely appreciative of the blog.  WOW...  I will strive for 67mm.  form teh rear flange. ( i assume. from the camera size edge of the reducer is what is meant?  some people include the 16.3 mm ( or what ever it is).  I know the rec is 85mm for .67. but I have read on more than one occasion we need to get him to 0.73-.75 ish. and thank you again.    i will assume 67. to the edge fo the reducer?

 

Dawn




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