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  1. #1
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    Default Astrophotography of Star Fields



    Ok, after a few hours over the past few weeks (with mosquitoes biting my legs, and a field of view the size of a blowhole) I have managed to figure out:


    1. manual focusing (distance of focus to obtain pretty sharp stars) - I did this by focusing at the moon, and using a permanent marker I drew a line along where I should be focusing. If you don't want to look like a Newb (like me ), you can remove it with isopropanol (which removes anything "permanent").
    2. Noise on my DSLR Pentax K100D sucks big time. Its like the 4th of July but in Australia... Makes me want to
    3. I need to buy a serial to usb cable to automate (or at least make exposures a lot easier than using bulb setting, and holding down the button for dear life over 30 seconds or so.
    4. Also managed to get pretty good alignment (off by a bit, but still able to take 30 second - 1 minute shots without a big shift)
    5. Note: unguided, no drift alignment and not the best polar alignment...

    Here are some shots that I did not stack (still learning how - those softwares are really not made for users and usability in mind), but I did process with Noise ninja in Photoshop. Also adjusted the levels to make the sky black (I was shooting right under a half moon) so I am cheating for now....but here are some of my initial star creations:



    Photo details:


    Camera maker
    PENTAX Corporation
    Camera model
    PENTAX K100D Super
    ISO
    800
    Exposure correction
    ---
    Width
    3008 pixels
    Height
    2000 pixels
    Megapixels
    6.02
    Channel depth
    8 bits
    Quality
    JPEG
    Sharpness
    Normal
    Contrast
    Normal
    Saturation
    Normal
    Exposure time
    22.1 sec
    Light source
    ---
    Date-time created
    2009:01:20 04:38:18
    Date modified
    2009:01:20 04:38:18
    Software
    K100D Super Ver 1.00






    Camera maker
    PENTAX Corporation
    Camera model
    PENTAX K100D Super
    ISO
    800
    Exposure correction
    ---
    Width
    1000 pixels
    Height
    665 pixels
    Megapixels
    0.66
    Channel depth
    8 bits
    Quality
    JPEG
    Sharpness
    Normal
    Contrast
    Normal
    Saturation
    Normal
    Exposure time
    19.1 sec
    Light source
    ---
    Date-time created
    2009:01:20 04:31:10
    Date modified
    2009:01:20 04:31:10
    Software
    K100D Super Ver 1.00

    Tried stacking of the first star field at top (with 7 light frames from 10-58 seconds and 2 dark) finally but got this... :
    Name: Gus OTAs: ED 100 PRO refractor, Orion ST80 (not the CF), 8" Dob stuck in Canada Mounts:HEQ5PRO Synscan mount, Manfrotto Tripod CAMS: Guidecam Philips SPC900 webcams (4), Canon unmodded-450D DSLR

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  2. #2
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    Default

    Only need one dark frame. but add a bias frame. Try to get more light frames 7 not really enough

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  4. #3
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    Default

    Quote Originally Posted by heatmizer View Post
    Only need one dark frame. but add a bias frame. Try to get more light frames 7 not really enough
    I respectfully disagree. If you are getting a large amount of random thermal noise, then multiple dark frames will average them out. That way you subtract the noise floor, leaving just the random element for Noise Ninja (or whatever) to do what it does best. You can never have enough light frames.

    If you are going to stack and/or use dark frames, you want to be shooting in RAW so that you get linear data.
    Your camera can do 30 sec exposures without your finger on the button, so I'd start with that. Use the timer so it locks the mirror up too and don't forget to turn off the IS. Does the camera allow you to turn off it's own dark subtraction ? If not, then there's no point in doing dark frames.

    Do a few dark frames at each ISO setting and have a look at the result. You'll soon see the maximum ISO that's worth using as it will suddenly get very noisy. Use the one before that.

    Steve.
    "Oh no! Not another !@#$% hobby" - The wife.

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  6. #4
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    Default

    Ok thanks heat I will add a bias frame. Also thanks Steve will try to adjust ISO settings as you mention
    Name: Gus OTAs: ED 100 PRO refractor, Orion ST80 (not the CF), 8" Dob stuck in Canada Mounts:HEQ5PRO Synscan mount, Manfrotto Tripod CAMS: Guidecam Philips SPC900 webcams (4), Canon unmodded-450D DSLR

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  7. #5
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    Default

    Aputure Timer Remote available on ebay and work well-have one

    or usb serial cable plus remote shutter release can be made up cheaply and free program called DSLR shutter works well and can be controlled by the computer

    also look up Jim Solomons cookbook for digital astrophotography on the net will help

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    Default

    Thanks Trevor,
    im currently using a handheld remote control, but its not programmable (and I have to hold it the whole time). Also my tracking could be a lot better and I think I could use DSLR shutter but I am happy with my results so far in terms of focusing. I just want to see more stars/some gas and dust like your beautiful shots.
    Name: Gus OTAs: ED 100 PRO refractor, Orion ST80 (not the CF), 8" Dob stuck in Canada Mounts:HEQ5PRO Synscan mount, Manfrotto Tripod CAMS: Guidecam Philips SPC900 webcams (4), Canon unmodded-450D DSLR

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  10. #7
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    Default

    I had a k100d and suggest shooting at ISO400 as they have a noisy CCD chip. Canon use a CMOS chip that don't heat up as much.

    With the k100d you can do all that SteveB mentioned above ie: turn off in camera noise reduction. I used mine at ISO800 but they do produce noisy images so suggest the lower rating on warmer nights however ISO800 ok during winter.

    Take 10 darks, 10 flats, 10 bias, and 30 X 30 second subs.

    A correctly polar aligned HEQ5 will easily track unguided for 30 second exposures.

    The attached image which isn't that good in fact was taken using a Pentax

    Camera: Pentax K100D
    Mount: Skywatcher EQ6
    Scope: Stellarvue 80ED
    Configuration: Prime Focus
    EFL: 570mm
    EFR: F7
    Exposures: 40X45s, 30X2min, 2X5min @ 24C
    Total Exposure: 100min
    Date: 30/11/08 9:00 PM WST
    Location: Kelmscott, Western Australia
    Acquisition: Aputure Remote
    Focus: By eye
    Guiding: Orion Starshot Autoguider
    Attached Images Attached Images

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    Default

    Pretty neat trevor. Really nice picture. With all the AP posts lately my interest on AP is growing every day.
    Joel

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