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DSLR Beginner ATM CCD Imaging Dob
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#1 mgx

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Posted 22 April 2021 - 01:56 PM

I am building a little 8" F6 truss Dob. Currently I have it configured for very little in-focus and a 2.5" of back focus.

All my 1.25" and 2" eyepieces I can bring into focus, but now I want to photograph what I am looking at.

The only 1/2 decent pics I have gotten so far is mounting my cell phone over an eyepiece. I have a Nikon D5500,

ZWO CCD, Teleskop Service 2" flip mirror system & off axis guider, a couple ZWO filter wheels, 2x, 5x 1.25" barlows

and a 1.6x 2" barlow.

 

I cannot figure out A focal or prime focus, with or without barlows when using the DSLR or CDD.

I wish I could find some folks with Dob's that use DSLR's or CCD's to photograph and how they are setup.

 

I still have the option to give myself more in-focus if needed.

 

Thanks in advance,

 

Matt

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#2 Tapio

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Posted 22 April 2021 - 02:16 PM

I guess you need to move primary mirror forward for prime focus imaging.
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#3 rblackadar

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Posted 22 April 2021 - 02:33 PM

Agree with Tapio's response.

 

I get a little confused with in-focus and back-focus terminology, but if I understand you correctly, you currently reach eyepiece focus with the focuser racked almost all the way in. This is going to be a problem for the cameras, because you need to rack in even further with them, so that the sensor of the camera is positioned at the same point the field stop of the eyepiece was when the latter was in focus. EP field stops are usually at or close to the shoulder (top of the nosepiece) but camera sensors are recessed deeply -- almost 2" in the case of the DSLR.

 

Any of your Barlows will help the situation, but you still will need to rack in a bit with them.


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#4 mgx

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Posted 22 April 2021 - 02:38 PM

Yes, all eyepieces are almost all the way racked in, because somehow I was thinking I needed more back focus.

I was very proud I had so much on all my lenses. It is a fun thing to try to get all eyepieces, for viewing solar system and deep sky

and be able to just use prime focus DSLR/CCD. I am glad I have a 3" draw length tube. I need one clear nigh, with a sliver of moon,

Mars, Saturn and Jupiter over head, not freezing with clear skies to try to figure this out I think.



#5 spereira

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Posted 22 April 2021 - 04:00 PM

Moving to Lunar Observing & Imaging.

 

smp




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