stacking question

Discussion in 'Image Capture' started by Ernie, May 10, 2016.

  1. Ernie

    Ernie Cyanogen Customer

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    Just bought the Maxim DL software and have a question about stacking. I am using the SBIG ST-8300 c
    camera and want to take planet photos. As the shutter speed only goes down to 1/10 of a second everything is overexposed and I need to adjust the brightness. Is the proper procedure to do this before the stack is taken or can I (or should I) do it for the entire stack at once after they are taken or do it for the single stacked photo?

    Ernie
     
  2. Colin Haig

    Colin Haig Staff Member

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    Ernie, here's a few ideas for you.

    Use an aperture mask on the front of your scope. Basically, make a cover for the scope that has perhaps a 2" diameter circle cut in it, to reduce the light gathering of the scope. Bristol board / card stock should do just fine. This will prevent over-exposure. If you have a Schmidt Cassegrain or other scope with central obstruction, offset the hole to one side of the secondary.

    You might also be able to use a barlow to increase the image size on the chip, and this will also dim the image down.

    Get the original images as good as you can, before stacking. Check that the camera isn't saturated.

    People who do a lot of planetary imaging tend to use long focal lengths and high shutter speeds, and even grab videos and then pick out individual frames of good seeing. A lot of people are using webcam / usb high speed video cameras to take planetary images. eg 1/60 second and faster.

    Have fun and good luck.
     
  3. Ernie

    Ernie Cyanogen Customer

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    Ok thanks. In order to stack do I have to take pictures one at a time or can I shoot a series continuously?

    Ernie
     
  4. Colin Haig

    Colin Haig Staff Member

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    Hi Ernie,
    Stacking is an activity you do after acquiring your images. With planets, some like Jupiter rotate so fast, that you are seeing a different face of Jupiter in a matter of minutes - so you would want to take your images close together.

    In the Camera Control window, there are three options - Single, Continuous, Autosave. Continuous is great for focusing, it will grab a picture, download it, and show it to you, and repeat. Autosave can do smart things with the images, you'll want to read up on that one.
    One thing you might want to do is go into the Options and select Auto Save All Exposures. Also, turn on Auto-Subfolder. Next, Set Image Save Path and
    make a directory (I use documents\ccd\2016-05-12 so I know when I shot the images, and keeps them tidy).

    So, if you use Continuous (with Auto Save All Exposures), it will grab lots of images. and maybe one or two will be super sharp due to changes in the seeing.

    Just remember that if you've turned on Auto Save All Exposures it will eat up disk space like crazy.
    So, what I do is I use Focus, Continuous without Auto Save All Exposures (turned off), until I start getting semi decent stuff. An example is attached below.
    Then I move to the next step, which is getting decent exposures, so I'd turn on ASAE and shoot continuous. Alternatively, you could just shoot singles. What I sometimes do is watch through another scope for when seeing is steady and no clouds, before starting/stopping images.

    My recommendation would be to practice getting your exposures right and focused, before you move on to Stacking.

    I've attached a cropped sample image of Jupiter that I took about 5 years ago (with a DSLR, not a CCD, but it was a 2 second exposure, so doable with CCD). Its fuzzy, has blue and orange tinges at the edges, and its nothing like the "Hubble shots" that Damien Peach and Grant Blair produce. To get this, I had to shoot quite a few, and then pick through about 40 images to find the best one. Once you get to a level where you are imaging better than this, then its time to move on to processing, in my opinion.
     

    Attached Files:

  5. Ernie

    Ernie Cyanogen Customer

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    Got it but how do I autosave all exposures. On the camera control menu expose tab the choices are single, continuous OR autosave. How can I do both continuous and autosave? Am I missing something?

    Thanks,

    Ernie
     
  6. Colin Haig

    Colin Haig Staff Member

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    Yes, you are missing one of the most amazingly handy little menus. There is a black arrow triangle that has the options. Throughout the MaxIm app, there are a few places with those handy black arrow.
    See the screen shot below. In it, I've selected some of the common things you'll want turned on. Included in that is the Auto Save everything ;-)
     

    Attached Files:

  7. Ernie

    Ernie Cyanogen Customer

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    very helpful, thank you. If I have any success I will send you a picture!

    Thanks,

    Ernie
     

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