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  1. #1
    FractalChemist's Avatar
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    Default (M37) What am I doing wrong?



    So, here's the story: the telescope is a Meade LX90 and the camera is a SBIG ST-8XME. My dad and I were using a DSLR to take pictures, when he randomly says, "we should try the astrophotography camera I have". Yes, he had a several thousand dollar camera he didn't mention.

    Long story short, this is the image. It's a 30 second exposure of M37 and it looks terrible. Can anyone help me figure out what's wrong and how to fix it?
    Attached Images Attached Images

  2. #2
    Dublin sky watch's Avatar
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    The focus is a little off and its quite noisy. What settings had you got at the time of the image? If you can furnish some more details about the shot, would be a big help. I use only dslr myself, so not sure how you might fix it. Bur defo the focus needs to be looked at. Is it done manually or with soft ware?
    Last edited by Dublin sky watch; 04-26-2010 at 06:15 AM.
    Declan.
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  3. #3
    FractalChemist's Avatar
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    Quote Originally Posted by Dublin sky watch View Post
    The focus is a little off and its quite noisy. What settings had you got at the time of the image? If you can furnish some more details about the shot, would be a big help. I use only dslr myself, so not sure how you might fix it. Bur defo the focus needs to be looked at. Is it done manually or with soft ware?
    The focus was done manually. I know next to nothing about the settings. The CCD camera is very different from the DSLR I'm used to using. It's all done on a laptop connected to the camera. The focus is done via the telescope (manually). It was just a test shot to see if we set it up right, but it's reeeeeally noisy as you pointed out. We took a 100 second exposure, but we didn't align the telescope properly so it wasn't tracking, but it too was quite noisy.

    Comment on anything you feel you can.

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    Dublin sky watch's Avatar
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    I use the in house camera for my darks..but I am not familiar enough as to what to do with ccd cameras to reduce noise. One advantage of ccd I thought was that it reduced the noise because of cooling on board. Am sure some one will be along to help you out with this.Sorry I cant help.
    Declan.
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    Quote Originally Posted by FractalChemist View Post
    So, here's the story: the telescope is a Meade LX90 and the camera is a SBIG ST-8XME. My dad and I were using a DSLR to take pictures, when he randomly says, "we should try the astrophotography camera I have". Yes, he had a several thousand dollar camera he didn't mention.

    Long story short, this is the image. It's a 30 second exposure of M37 and it looks terrible. Can anyone help me figure out what's wrong and how to fix it?
    AP is hard - don't be too rough on yourself, it's a start and will only get better. The trick is to tell yourself that your hobby is the process, not the result.

    A couple of suggestions, things that are easy to do and will give big improvements:

    - Focus. Focus is really hard, but a simple tool will make it a bit easier: google Hartmann Mask and make one. Just cut 3 holes out of a piece of thin cardboard and make a thin cardboard "belt" to allow you to pop it on the end of your dew shield. You can make one with duct tape and a cereal box in about 5 minutes - it does not have to be precise or pretty. Then you focus by taking test exposures until the triple stars are reduced to single points.

    - Calibration: this image needs dark frames and flat frames. Darks are easy, just take images with your lens cap on, same exposure time as your live exposures. Take several. Flats require a bit more work, but you can get good ones by just imaging the flat sky before dark. Aim for an exposure that gives your image an average luminosity about a third to a half of maximum. Then you get your imaging software to calibrate with the darks and flats (technically it will subtract the darks and divide by the flats,) and you will see a large improvement. Flats will reduce the "gradient" you are getting (where the image is brighter in the centre) and will also greatly reduce the dust and moisture speckles.

    Good luck
    Richard
    C9.25,AT8RC,SV105,SV80,Pronto,TV60
    on: ParamountMX,G11,GM8,DM6,HalfHitch,M4
    Ottawa, Canada

  6. #6
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    Ottup, thanks for the suggestions. I'll definitely give them a try. I'm going to pour back over the manual again, as we're getting yet another 3 day storm.

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    I recently checked out from the Austin Public Library a copy of Stefan Seip's Digital Astrophotography, A Guide to Capturing the Cosmos. Chapter 5 covers CCD Camera Imaging (40 pages with many photos). The author goes into a lot of detail about Taking Photos (ccd camera setup) and Processing Images (how to use the software to filter out noise, do dark balance, etc.). If your library is part of World Cat sharing, you can probably pick up a copy through interlibrary loan. If not, the book is available on Amazon for $20.
    Good luck and imaging!

 

 

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