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Stargazing Help with DSLR Astrophotos

  1. Feb 18, 2017 #1

    QuantumPion

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    Hi, I've been trying to take some deep sky images with my DSLR. However, my pictures tend to get washed out and overexposed after more than just a couple seconds. Is there something I can do to fix this, or is this just an issue with ambient city light? I'm already using a lens hood, and viewfinder cap, and it's a moonless night. I am using a 50mm f1.8 lens.

    IMG_1101.jpg
    IMG_1102.jpg
    image hosting api
     
  2. jcsd
  3. Feb 18, 2017 #2

    Chronos

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    Have you tried adjusting the ISO setting? Having it set too high is a common cause of poor contrast.
     
  4. Feb 18, 2017 #3

    russ_watters

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    What is "a few seconds"? But yes, that looks like a symptom of skyglow. Using the "levels" function in photoshop, you can clip the low end. It is a standard technique.
     
  5. Feb 19, 2017 #4

    davenn

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    very easily fixed in PS or lightroom ... lightroom has a nice feature called de-haze that darkens the backgrounds very well
    let me see if I can find an example from my own collection

    Dave
     
    Last edited: Feb 19, 2017
  6. Feb 19, 2017 #5

    davenn

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    OK here's a real fast comparison and edit of a pic of mine in lightroom The object is the LMC ( Large Magellanic Cloud).

    first pic is the jpg out of the camera
    second pic is the RAW file edited and a jpg conversion done
    you can see the huge difference in colour, and detail

    2015_05_08_3682sm.jpg


    2015_05_08_3682-2sm.jpg


    Note I used the term "RAW File" .... I don't know what camera you are using, hopefully it has a RAW imaging mode
    if you are not using it, USE IT !! I cannot stress this enough. Editing jpg files is very self defeating because of the huge
    amount of image compression done to generate the file ... lots of data is lost.


    Dave
     
  7. Feb 19, 2017 #6

    QuantumPion

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    I don't have photoshop but I guess that is the only way around it! I'm using a Canon T5i. ISO was 800 or 1600 I believe. Exposure was 2 seconds for first picture and 3 seconds for second IIRC.
     
  8. Feb 19, 2017 #7

    davenn

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    OK what about lightroom ?
    These days you can get a photoshop and lightroom package for around US$10 - 12 / month subscription really good value
    I had to look up a T5i ( that model naming style is mainly only used in the USA) ..... ahhh, the EOS 700D ... It's one of the 3 Canon cameras I have :smile:
    Also have the 5D MKIII and the 6D.
    The 700D I did surgery on and removed a couple of the filters to make it a better astro camera ... more sensitive at the red end of the spectrum

    you didn't respond to my comments on the use of RAW files ??
    I hope my pic's helped you to show you how to overcome city light skyglow ?

    Dave
     
    Last edited: Feb 19, 2017
  9. Feb 19, 2017 #8

    QuantumPion

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    Yes thanks for the help. Next time I will get RAW's instead of JPEG's so that if I eventually get photoshop or lightroom I can mess around with them. Are there any free/open source tools that can do the required editing? Also, would image stacking multiple ~2 second exposure shots be worthwhile to try?
     
  10. Feb 19, 2017 #9

    davenn

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    there is GIMP -- free, I don't know if it has all the features that LR and PS have, but, from what I understand, it has many of them
    I don't know if it is easier or harder to use

    yes, that is always good ... it wont stop the sky glow, but will give more detail on the starfield

    I have to assume you were shooting those images from a suburban area ... being that the trees were also well lit
    find a spot out of your town/city where the ambient light and the sky glow level is low

    for image stacking a commonly used and free program is DSS ( Deep Sky Stacker) use DSS only for the stacking
    the processing is still done in your other fav editing program. DSS can do processing, but isn't as good as say LR or PS


    Dave
     
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