TheSky X autodark issue suspected

Discussion in 'Legacy Models (ST, STL, etc.)' started by Colin Haig, Nov 20, 2020.

  1. Colin Haig

    Colin Haig Staff Member

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    Hi @Jim Bradburn
    Let's discuss your issues here instead of emailing.
    Thanks
    Colin and the Diffraction support team
     
  2. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    I use SkyX Pro by Software Bisque to operate my 16 year old SBIG 1001E camera. I use CCDStack2 to process the images, including the creation of color images. Lately my color images are coming out looking like the attached image. My clear B&W images are fine. Anyone have any ideas?
    Thank you, Jim
     

    Attached Files:

  3. Doug

    Doug Staff Member

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    Since you say your raw images are correct, our equipment did its job correctly.

    We can't really comment on the performance of third party software. I think you need to take this over to CCDStack technical support.

    If you think there's a problem with the camera's raw images, then we'd need to see your raw FITS data.
     
  4. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    I believe these to be raw images taken through all four filters individually. I am not sure I said anything about these raw images.
    Jim
     

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  5. Doug

    Doug Staff Member

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    You said "my clear B&W images are fine". I thought you meant your raw frames. I guess you meant luminance?

    These images have a lot of hot pixels, which are making colored specks when you put together the color image. That's where that mess is coming from.

    The first step is to subtract matching dark frames to reduce the hot pixels. Then you need to align and stack more frames to get cleaner raw images. Then color combine.

    Here's a color stack of your four images:

    hothothot.jpg

    I didn't have dark frames to subtract, but I suppressed the hot pixels by using MaxIm DL's Kernel Filter / Hot Pixel filter. Here's the result:

    Hot Pixels Removed.jpg
     
  6. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    Hello Doug
    I am new to this forum and recently asked to use it rather than communicating through email with Colin.
    So the back story is that I was getting black round spots in a pattern offset from the brightest stars. (image below taken with blue filter) This was most noticeable with color filter images but probably on the luminance as well. Colin suggested it might be a problem with AutoDark, so I took colored filtered images without AutoDark. These showed no dark spots, but produced the bad color images I sent to you.
    Thank you for your patience.
    Jim
     

    Attached Files:

  7. Doug

    Doug Staff Member

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    Okay, now things are making more sense.

    Yes it appears that your auto-dark wasn't dark. It had stars in it.

    There are two probable causes:
    1. The camera didn't close its shutter properly
    2. The software didn't tell the camera to close its shutter
    #2 can be checked by using some other software. Try CCDOPS.

    I'd also suggest doing a stress test on the camera. Take it off the telescope and set it where you can see the shutter. Set it to take a series of short exposures. Observe the shutter and make sure it is actuating on each exposure.

    If the shutter is sticking then contact bill@sbig.com; he can probably help you out.

    If CCDOPS works but your regular acquisition program doesn't, I'd talk to the software vendor.
     
  8. Colin Haig

    Colin Haig Staff Member

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    @Doug we've already determined the shutter is not behaving and that it needs to go to @Bill for repair. We've got an image where the corner is light and the rest of the image is dark, so the shutter didnt fully open or close.
     
  9. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    Colin and Doug
    Bill and I did repair ( actually recalibrated and relocated) the shutter and it is working properly now, after adjustment, according to Bill. There are no more images with the shutter showing. However, if I use auto-dark with a filter, especially colored ones, I get the black star dots.
    I will take a few dark field exposures and see if anything appears. If stars show up, and I read you right, you're saying this is likely a Software Bisque problem in their SkyX Pro camera add-on which is what controls the camera. I can almost hear their reaction, but I will try. I hope I don't end up in a Bob Dylan song:" back in the middle with you"!
    Got a few days of clouds, so it may be a while.
    Jim
     
  10. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    I did six dark images; first three with luminance; one each red, green blue. All 180 seconds at -15C.
    Jim
     

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  11. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    OPPS, not Bob Dylan but two guys from Scotland who are stuck in the middle with you!
     
  12. Colin Haig

    Colin Haig Staff Member

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    Jim, a dark is a dark is a dark, no such thing as a filtered dark (Luminance Dark, Red Dark, Blue Dark, Green Dark). Because the sensor is covered, they're all darks.
    Same for bias frames.
    Only light frames and flat fields have a colour associated with them - as the photons pass through a filter on the way to the sensor.

    Somehow you've managed to create funny FITS Header keys specifying these colour groupings.
    So weird things happening. See the result of summing these colourful darks.
    colourful_darks.png
     
  13. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    Hi Colin
    I understand that completely, but the issue remains of dark spots offsetting star images, most notable on images taken with colored filters. You all suggested there was something wrong with auto dark, so I decided to check to see if anything showed up taking a dark....nothing as expected. So what is causing the dark spots? If it's not auto dark and it's not the shutter, what is it?
    Jim
     
  14. Colin Haig

    Colin Haig Staff Member

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    Let me try to explain:
    I have no evidence that since your shutter got fixed that you now have the problem.
    What I have is dark frames that are incorrectly flagged in the FITS headers, so stacking programs may have issues with them.
    I don't have any new light frames that are produced since you had the shutter fixed.
    Follow?
     
  15. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    And if the shutter is not closing during auto dark, then I should just see another un-calibrated image.
     
  16. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    Will respond but we have a storm coming in now so it won't be for a couple of days. Hopefully the fixed shutter, thanks to Bill. will eliminate the black spot problem as well. The images I sent to Doug where without dark calibration which showed no spots but were terrible images as he rightly noted.
    The six images I took as darks are all stored as .fit images. Since they are darks at a certain exposure and temperature, I created a new calibration library folder but I have no intension of ever stacking them. I may use them to do calibration if I can't use auto dark.
     
  17. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    Hi Colin
    I took images last night despite bright moon and high humidity. Every image was without the offset black spots except images taken through a HII filter. Attached are a two good (luminance and green) and the one bad (HII). None of the images has been run through any manipulating software. I must say I was congratulating you most heartily until this last HII image showed up. Any thoughts?
    Jim
     

    Attached Files:

  18. Colin Haig

    Colin Haig Staff Member

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    Is HII = Hydrogen Beta or did you mean Hydrogen Alpha ?
    Or maybe you meant Sulphur II ?
    I think you've got a naming problem unless you have an exotic filter.

    To me, 9114, looks simply underexposed.
    The core of the galaxy is at about 333 ADU, vs the luminance (which lets all the visible light in) has a core at about 18500 ADU.
    If HII is a narrowband filter, eg Halpha or SI deep in the reds, keep in mind M74 doesnt have a whole ton of those wavelengths it except scattered around the edges in small clumps.
     
  19. Jim Bradburn

    Jim Bradburn Cyanogen Customer

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    Yes, my bad. HII is Ha. I would normally never use on this object, mostly used on nebulae with SII and OIII. I just selected several filters to see if the black spots showed up. They did on this particular image. I am able to make them disappear with some processing. Maybe it's not an issue but would love to know what's causing them. That image was exposed 3 minutes.
     
  20. Colin Haig

    Colin Haig Staff Member

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    Sorry, am not seeing the "black spots".
     

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