1. Reminder: Please use our affiliate links for holiday shopping!

Post processing for wide field astrophotography

Discussion in 'Astrophotography' started by tg9413, May 25, 2015.

  1. tg9413

    tg9413 Mu-43 Regular

    76
    Mar 12, 2014
    Hi all,
    Seeing all the wonderful works being done on this forum, I am trying to find some more detail tutorial on how to process the raw file I took for wide-field milky way shots. My set up is a GX7 with oly 12mm, shots taking at 20s, 800 iso, and f2.4. I've also try to bring up the iso to 1600 and f2.0 to get the maximum light I could before star trail suggest by some of the online tips using the expose to the right method to counter the light pollution problem in major city.
    The picture does turn out all blown up. But some how without mentioning the detail, those tutorial seems to be able to salvage the picture by bringing down the exposure and some tweaks and bring out the milky way in the shot.
    I am wondering if is the area I am living in is really too bright or there is something I did wrong in the post process. No matter how I play with lightroom I couldn't bring out the milky way in the shot.
    Oh I am living in bay area, California. It is pretty intense for light pollution, but some of those tutorial were able to pulled it off somewhere near LA or Singapore, so I figure I can't be too far off in term of light pollution.

    One last question, any one know any tutorial for deepsky stacker?

    Thank you very for the help in advance.

    P.S
    Here is a raw file I took, if anyone would take a look, it would be great! :D thank you~

    https://www.dropbox.com/s/2a4ahgc66co778n/_1170440.RW2?dl=0
     
  2. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    There looks to be way too much light pollution to get a decent picture, with that sort of background level the only way I can think of would be a light pollution filter of some kind however they're generally pretty expensive. The way the filters work is they cut out specific wavelengths of light commonly emitted by street lights (sodium vapour lamps for example have a very strong spectral line resulting in the orange glow in the sky).

    Google images for "light pollution filter" for various examples of their use.


    Deepsky stacker had a pretty good wiki however it appears to have died. I can't really help with it's use as I've forgotten much of how to use it... I only used it for timelapses where the priority wasn't quality but speed (batch processing an entire night to produce a frame for video per ~1 minute of real time).
     
  3. wjiang

    wjiang Mu-43 Hall of Famer

    Agreed on the light pollution. I think I see some traces of the milky way towards the bottom of the frame but it's almost complete buried in the glow. At similar exposure settings, I'd be getting the sky squashed in the bottom 1/3 of the histogram. You really need to drive a bit further out (higher is also preferable as it gives a greater chance of being above lit up haze). Make sure you're not under any local artificial lights and that the moon is not up. The milky way should also be facing away from the city if possible, also the higher up in the sky it is the less light pollution it has to go through. The real test is, can you see the milky way with your eyes once adjusted to the darkness? If not, then the camera probably won't work much better.
     
  4. Machi

    Machi Mu-43 Veteran

    208
    May 23, 2015
    Milky Way is clearly visible in your photo after some quick processing so you can definitely try to make some Milky Way images even at your location.
    But there is also lots of noise in the image after processing so I recommend you stacking more images (at least 10) to improve SNR (signal to noise ratio), calibrate all images (dark frame/flat frame) and you must work in at least 16bit depth, 32bit is better. I don't use DeepSkyTracker (I'm using ImageJ) but the help file is here and here is nice info about calibration.
    milkyway.jpg
     
  5. tg9413

    tg9413 Mu-43 Regular

    76
    Mar 12, 2014
    Thank you all for the help. I will try to drive out 2hours down south once the sky clears a bit. Been a weird year, usually there is no cloud at night at all during this time of the year in Bay area, but this year... man would be lucky to get a cloudless night, let alone that have to happen on a good moon phase :/ I do have some image taken with f/2, 10s, 800iso each in time lapse , maybe I will try to stack those and see if I can get anything out at the mean time.