Resolved Focusing STF-8300

Discussion in 'STF Series' started by Marcus, Jul 6, 2019.

  1. Marcus

    Marcus Standard User

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    Hello.

    I'm trying to rough focus the 8300 on my SCT 11" with Reducer Corrector. I am using spacers to give me the required 105mm.

    When I tried to rough focus and even a few Grabs I constantly get an elongated image. When I rotate the camera, the elongation also moves.

    Attached is the test photo.

    Appreciate any ideas or help.

    Thank you.
     

    Attached Files:

  2. Colin Haig

    Colin Haig Staff Member

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    Hi Marcus, thanks for reaching out.

    There's a few things I can suggest, and maybe some others users here will chime in as well.
    Next time, upload a FITS image from CCDOPS or MaxIm - we can tell a lot more about what is going on if we have the full header data

    Can we get some more details, and maybe a photo of your equipment setup?
    e.g. specifics
    -telescope optical parameters (11" f/10 ?)
    - model - eg is it a Celestron C11-A or Edge HD 11 ?
    - What brand of focal reducer/corrector and what are its specifications e.g. f/6.3 reducer or Edge 1100 0.7x reducer ?
    - focuser, rotator (if you have one),
    - is there a filter wheel? was the image taken through a filter?
    - how is the camera attached - eg confirm there is no diagonal in place
    - what is the mount? eg Astro-Physics Mach 1, Celestron AVX, Software Bisque Paramount MYT ?
    - permanently mounted on a pier, or on a tripod ?
    - is this a new scope?
    - is this a new camera?

    Some tips:
    - The image is not focused. The dark circle in the centre of the ovals is the shadow of the Secondary Mirror on the telescope. So you need to refine the focus.
    - Remove the reducer and try again. If the stars turn into nice round donuts or nice tight circular stars, you have a problem with the focal reducer eg it is defective, an element is loose/tilted/incorrectly assembled, poor quality
    - If you have a diagonal in the mix, remove it (I'm pretty sure you don't but it can contribute to this kind of problem).
    - Have you collimated the telescope ? Most SCTs have 3-6 adjustable screws on the secondary mirror. Start by collimating the scope with a high magnification eyepiece directly into the back of the scope (with appropriate spacers), and no diagonal. Then replace the eyepiece with the CCD camera. Tweak the collimation. Then add in the reducer, and the stars should just be tighter and good to the edges of the field.
    - do you have a good polar alignment ? how long an exposure was this? eg. if you did a 5 to 10 minute exposure, are the stars trailed?

    When you say you rotate the camera and the elongation moves, can you explain that a bit ? e.g. do the ovals stay in the same orientation of the camera rows?

    Hopefully some other users will chime in on your issue.
     
  3. Marcus

    Marcus Standard User

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    Thank you for such a detail reply. Greatly appreciated.


    -telescope optical parameters (11" f/10 ?)

    11” f/10

    - model - eg is it a Celestron C11-A or Edge HD 11 ?

    (Standard Celestron CGX Equatorial 1100 SCT)

    - What brand of focal reducer/corrector and what are its specifications e.g. f/6.3 reducer or Edge 1100 0.7x reducer ?

    (Celestron f/6.3)

    - focuser, rotator (if you have one),

    (No)

    - is there a filter wheel? was the image taken through a filter?

    (No filter)

    - how is the camera attached - eg confirm there is no diagonal in place

    (Reducer then SCT T adapter then Spacer rings then camera)

    - what is the mount? eg Astro-Physics Mach 1, Celestron AVX, Software Bisque Paramount MYT ?

    (CGX Equatorial)

    - permanently mounted on a pier, or on a tripod ?

    (Tripod)

    - is this a new scope?

    (New and been using since Feb)

    - is this a new camera?

    (Been using an Atik Infinity camera for a few months without any problems)


    Yes need to refine focusing but concerned with the oval image.

    When I rotated the camera (by loosening and then retightening the T adapter) the whole elongated image moves in the same orientation as the camera. Leads me to think it’s in the camera.

    Will try some of your suggestions tomorrow night (weather permitting).

    Again many thanks

    Marcus Rodrigues
    Tasmania
     
    Last edited: Jul 6, 2019
  4. Marcus

    Marcus Standard User

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    FITS File
     

    Attached Files:

  5. Doug

    Doug Staff Member

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    Wow, that's an unusual-looking image. There are also horizontal bands, which I suspect is related.

    First steps:

    1. Download the latest version of SBIG Driver Checker (available on our web site on the STF-8300 product page). Don't use the Update button in your current Driver Checker because we have made updates at times to the checker itself.
    2. Install and run the driver checker.
    3. Update your drivers
    4. Then use the driver checker to update the camera firmware.
    5. Make sure you have the very latest version of CCDOPS installed - also available on our web site.
    6. Try again.
    Also, what is the serial number of this camera?
     
  6. Marcus

    Marcus Standard User

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    Will do.

    Serial number is 83F190202

    Also just checked and Frimware is an older version v2.62. Will update to v2.64 and re try in a few nights time.

    Also is it possible to switch off the fan through software?

    Again many thanks

    Note: able to update to ver 2.63 but cannot get it to 2.64. Have powered down and retried a few times. Will stop here. Have reloaded everything else.

    Marcus
     
    Last edited: Jul 6, 2019
  7. Marcus

    Marcus Standard User

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    Hi Doug.

    Ok, checked collimation. Using eyepiece with and without reducer. Collimation is fine.

    When trying to focus the camera, with and without the reducer, when out of focus, the image is perfectly aligned. That is small black circle in the middle of the the bright circle.

    As soon as I get very close to fine focus, the image then elongates! Over focusing returns the standing image of a black circle in the middle again.

    Earlier when reloading software and firmware, as mentioned in previous email, upgraded firmware to 2.63 but tried again to get to 2.64. It loads but then it waits with the uploading bar full but nothing 10 mins.

    Did Re start to check but still 2.63. Was originally 2.62. All other drivers are fine.

    Not sure if this is a problem.

    Marcus
     
  8. Doug

    Doug Staff Member

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    I’ve asked @Tim to investigate. Maybe he can remote in and have a look.
     
  9. Marcus

    Marcus Standard User

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    Thanks. Have added two more FITs for reference.
     

    Attached Files:

  10. Colin Haig

    Colin Haig Staff Member

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    There is something totally strange showing up in your image "Rough Focus with Reducer.FIT".
    Take a look at the attached - you'll see what I'm getting at.

    There is something growing out of the optical path at the right side - and all I did to find it was screen stretch your image. No evidence of it in the No Reducer.
    Looks to me like you have a bad focal reducer OR you didnt do final collimation with the camera, and its tilted off axis.
    Can you give us a photo of your setup? Am wondering if the nose of the camera is tilted relative to the optical axis when the reducer is in place.

    You should have been able to screw in the reducer and get the same donut shape, but smaller.
    e.g. take an image without the reducer like you did, get the big perfect donut. Screw in the reducer, take an image, get a smaller donut.

    I suggest you try focusing WITHOUT the reducer, and see if you get nice tight stars.

    Other tips:
    When you get close on focusing, don't bin 3x3, bin 1x1.

    What are you using for a light source?
     

    Attached Files:

  11. Marcus

    Marcus Standard User

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    Colin, thank you for your help. Discovered that the problem is with the spacers.

    When I tried it without the reducer, perfect tight stars. With the reducer but without the spacers (to give the 105mm required) again perfect.

    Seems that when I used the Atik infinity with the same setup (slightly less spacers), the camera being much lighter that the 8300, did not show any off axis distortion.

    With more experience I could have saved you all the effort.

    Again many thanks.

    Getting great shots. So much more resolution and sensitivity that the infinity.

    Marcus
     
  12. Colin Haig

    Colin Haig Staff Member

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    Glad to hear it worked out. We'd love to see a few of your fine images when you get a bit of practice in!
     

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