SC-2 Focus question (s)

Discussion in 'Guiding and Adaptive Optics - StarChaser and AO' started by Galaxyhunter, Feb 18, 2021.

  1. Galaxyhunter

    Galaxyhunter Cyanogen Customer

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    Finally I had a couple hours of half way clear skies, so I started to try to setup the SC-2 & SCT-7 combo before adding the AO-8. On the SC-2, I preliminarily set the pick off mirror all the way in towards the center. I looked at my ST10 & seen the the pick off mirror is set to the edge of the main chip. I also set the guide chip all the way in towards the center, so that I knew that I could only move it one direction.

    I first focused the camera w/ a Bahtinov mask w/o any problems. I moved the scope to put the star on the guide chip. When I moved the guide chip to focus, It started getting worse. Also, about 30% of the Bahtinov mask is getting cut off.

    So my main question is: Does the pick off mirror placement have much of an effect on the ability of reaching focus? It appears that I need more "In" travel but I started out at the MAX in travel. So that I don't waste night after night chasing this, are there any hints that anybody can give to put me in the ballpark?

    Guide chip image attached.
     

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    Galaxyhunter, Feb 18, 2021
    #1
  2. Doug

    Doug Staff Member

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    Yes the mirror position affects focus - by the same distance that the mirror is moved.

    We recently made available the optional ACC13 spacer, which increases the distance between then camera and StarChaser by 0.2". This provides for more flexibility in the mirror position since it will focus with the mirror in any position. Since you ordered before it was made available, we'd be willing to send you one at no charge. Would you like us to do that?
     
    Doug, Feb 19, 2021
    #2
  3. Galaxyhunter

    Galaxyhunter Cyanogen Customer

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    Doug, I'm more then willing to buy this spacer. Is this something I can get directly from your company, or do I have to get this through a dealer?
    Thank you Sir.
     
    Galaxyhunter, Feb 19, 2021
    #3
  4. Galaxyhunter

    Galaxyhunter Cyanogen Customer

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    Doug, Colin sent me a link for this part. From the pic, It looks like I already have this part. I mounted it between the SC-2 & the focus tube. I'll have to get out to the Observatory & bring the camera in & investigate it.
    Thanks, Carl
     
    Galaxyhunter, Feb 19, 2021
    #4
  5. Doug

    Doug Staff Member

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    Yes, put that between the StarChaser and the STC. That will let you focus with the mirror in any position.

    Don't use the threaded holes. This is a multi-purpose adapter and those holes are for a different application. Just put the mounting screws through the bigger holes into the STC.
     
    Doug, Feb 19, 2021
    #5
  6. Galaxyhunter

    Galaxyhunter Cyanogen Customer

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    After looking at the camera, it appears that I do not have the spacer. Will order it soon.
     

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    Galaxyhunter, Feb 19, 2021
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  7. Colin Haig

    Colin Haig Staff Member

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    Good taking to you on the phone.
    I'm pretty sure the thicker piece that you have near the front needs to go between the face the filter wheel and back of guider.
    The thinner plate that holds the nose goes directly on the front of the SC-2.
    When you add the AO-8, put it in between the SC-2 and the nose plate.
     
    Colin Haig, Feb 19, 2021
    #7
  8. Galaxyhunter

    Galaxyhunter Cyanogen Customer

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    Okay, reconfigured. Does this look correct?
     

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    Galaxyhunter, Feb 19, 2021
    #8
  9. Doug

    Doug Staff Member

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    Almost! Flip it over so the protrusion goes into the StarChaser.
     
    Doug, Feb 19, 2021
    #9
  10. Colin Haig

    Colin Haig Staff Member

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    You shouldn't be able to see the screw threads in a gap.
     
    Colin Haig, Feb 19, 2021
    #10
  11. Galaxyhunter

    Galaxyhunter Cyanogen Customer

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    I'm struggling with this. I turned the adaptor over and testing it shows that the guider was a lot closer to focus. I then turned it back to look like the pic. Not there yet. I moved the pick off mirror outwards roughly 1/8". Almost there. I think I'm going to make my own adaptor.


    My next question. How is the SC2 chip sensitivity compared to the guide chip from the ST series cameras? On the ST cameras I have ( ST10xx and ST2000xx ), I loved the fact that if I binned 3x3, I could set the AO8 to 10 Hz and guide off a 12th mag star. If I went to 5 Hz, I could use a 14th mag star. I'm kind of hoping for the same thing.
     
    Galaxyhunter, Mar 1, 2021
    #11

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