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Astrophotography from Portsmouth, UK.

Discussion in 'Astrophotography' started by Levster, Feb 4, 2015.

  1. Levster

    Levster Mu-43 Top Veteran

    I'm very slowly getting to grips with post processing images so thought I'd start a thread based on what can be achieved from the centre of a small city. These first shots are of Orion:

    Autosave-Edit-Edit-2.jpg by -the-levster-

    orion.jpg by -the-levster-

    Orion-2 copy 2.jpg by -the-levster-

    Orion-2 copy 2-Edit.jpg by -the-levster-

    These were all taken with my Tamron 14-150mm on my EM-10 and tracked using a Polarie Vixen.

    Both shots involved stacking around 30 minutes worth of 30 second exposures, which were stacked in DSS and then tweaked in Photoshop using the Astronomy Tools Action Set http://www.prodigitalsoftware.com/Astronomy_Tools_For_Full_Version.html
     
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  2. Petrochemist

    Petrochemist Mu-43 Top Veteran

    651
    Mar 21, 2013
    N Essex, UK
    Mike
    Very impressive!
    Even in rural Norfolk (where the skies are much clearer than home) I've not managed to get anything near this quality. I really must get to grips with stacking...

    Your shots of the orion nebula are a lot less red than I'm used to seeing. Is that down to your processing or the others using filters to enhance it?
     
  3. Levster

    Levster Mu-43 Top Veteran

    I don't really know! It's either because the red shift is removed when dealing with the light pollution or people add artificial colour during post processing.
     
  4. PMCC

    PMCC Mu-43 Regular

    132
    Feb 18, 2013
    Just IMHO the NR is a bit heavy handed.
     
  5. Levster

    Levster Mu-43 Top Veteran

    I suffer really bad haloes after I've stacked everything and have to resort to quite heavy NR to minimise this. Here are some examples with no NR down to heavy NR:

    Orion-ISO1600-Edit.jpg by -the-levster-
    Orion-ISO1600-Edit-Edit.jpg by -the-levster-
    Orion-ISO1600-Edit-Edit-Edit.jpg by -the-levster-

    I'd love to hear advice on how to minimise the halos without resorting to heavy PP. I'm going to try a technique to create dark frames that include vignette and noise pollution gradients next time.
     
  6. MadMarco

    MadMarco Mu-43 Veteran

    298
    Oct 30, 2014
    Guildford, England
    That's a really odd ringing effect, I'm guessing that you aren't processing with Dark, Flat and Bias frames? If you aren't then I really recommend that you give this a try (Dark frames make a huge difference to the processing).

    In the official DSS guides, they say that you are supposed to create Dark frames at the same time as you create the original images. I can never be bothered to do this every time, so I have a library of darks, flats and bias for most situations. To shoot the darks; put the lens cover on the camera, put the camera in a dark cupboard or outside at night and set time-lapse to shoot 30 shots at the same settings (shutter speed and ISO) as you shot your light frames. There is a section in the FAQ that explains everything quite nicely:

    http://deepskystacker.free.fr/english/faq.htm#lightdarkflatoffset

    In order of importance, here are a few tips:

    1) Shoot RAW, don't bother with JPG
    2) Create Dark frames as a minimum (Bias and Flats are icing on the cake)
    3) Do some adjustments to the image in DSS, the manipulation in there is very effective (Align RGB spikes, Saturation to 13%, adjust Midtone)
    4) If you do any adjustments in Photoshop or other applications, don't set the background to black. The sky isn't black, it's grey and setting it black makes the pictures look over processed.

    Let me know if this helps any.
     
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  7. Levster

    Levster Mu-43 Top Veteran

    I always shoot with lights, darks and bias frames. I shoot at either ISO400, 800 or 1600 and over the past month I have created a set of darks and bias sets for each one (I figure 5C is 5C on any night! I will make some more when it starts warming up). I think the issue is that I'm shooting at around 45 degrees to the horizon over a City, so I get strong light pollution to the bottom, left and right and OK visibly to the top, which should create a single light pollution vignette effect. I also track so each frame probably has a slightly different noise pollution pattern, which when stacked looks a bit crazy!
     
  8. MadMarco

    MadMarco Mu-43 Veteran

    298
    Oct 30, 2014
    Guildford, England
    Hi Levster,

    I've done quite a lot of multiple exposure astrophotography with both my telescope and a couple of different camera/lens combinations and I've not seen this ringing effect before. I live in the middle of Guildford so light pollution can be quite a problem for me; fortunately they have been replacing the street lights with ones that emit less light into the sky, although it's still far from ideal...

    To help deal with the light pollution, you could try a didymium filter. They certainly help with sodium light pollution to some extent and also help with the colour balance, I've got a 72mm one of these and then use reducers so it will fit with any of my lenses. I even use it on my telescope with some expertly applied blu-tack to hold it in place!

    http://www.hoyafilter.com/hoya/products/coloredfilters/redenhancerintensifier/

    I did a test to satisfy myself that I hadn't just wasted my money on the filter. This is a single 20 second exposure @ISO800 taken with the 12-40@12mm on my E-M10, I've done exactly the same processing on both files. Not exactly a slam-dunk, but you can certainly see that the ratio of good to bad light has increased and the effect is compounded as you stack more images.

    PC140211_PS. PC140212_PS.

    I also tend to expose to the right (slightly overexpose) relative to what you would want to see when showing the final image, then bring the values back during post processing. If you over expose by one or two stops and see how that works out for you. Can you post one of your raw files to take a look at?

    Once question, are you putting the RAW images straight into DSS or are you converting to TIFF first? I always go straight from RAW into DSS.

    You could also be suffering from bad "seeing" conditions, this makes the light pollution have a much greater negative effect. For me, the differences between a good night and a bad night are considerable. It looks like a clear night, but in reality there are a lot of very thin high level clouds that will ruin your evenings work. Check out this website for an idea of what the seeing conditions are going to be like:

    https://www.meteoblue.com/en/great-britain/weather-guildford/seeing
     
    Last edited: Feb 17, 2015
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  9. tradesmith45

    tradesmith45 Mu-43 All-Pro

    Dec 13, 2012
    Oregon
    Nice work & you certainly get the E for effort!

    I've done some night sky photography including stacking & stitched panos. Based on this I suspect MadMarco is right, the halos are caused by bad seeing - haze/thin clouds - along w/ light pollution & stacking. Shot a full moon pano in Monument Valley this spring. Had pretty visible haze during the day because the Oak Creek Canyon forest fire had just started. The combo of haze, NR artifacts in post & then stitching produced visible banding in my first panos much like what you are getting.

    Lots of work & experimenting in post helped me to reduce but not eliminate the banding. Alas, I think good seeing is the only complete solution. But those conditions will be rare in an urban environment.

    There is a small not too expensive device you can get - forget what its called - that will read your seeing conditions when pointed at the sky. That could help you choose the better conditions for your in town astro work.

    Keep up the good work!
     
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  10. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Jason
    i know they make sky pollution filters for Eyepieces. I use a Baader Moon and Sky Glow filter and a Baader UHC-S filter with my telescope. Not sure if they make any screw on lens filters. Astronomik I think makes some FF type filters, but not sure how well they'd work for mirrorless.
     
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  11. Levster

    Levster Mu-43 Top Veteran

    I have uploaded a RAW (DNG) from yesterday here:

    https://www.dropbox.com/sh/m7hhe7ewomul6bj/AADl3n711YPzvC05owFkhzoOa?dl=0

    I also created a median filtered image of the above:

    Median.jpg by -the-levster-

    The halo can be seen above as well.
     
  12. MadMarco

    MadMarco Mu-43 Veteran

    298
    Oct 30, 2014
    Guildford, England
    Interesting that you have this as a DNG, are you converting the ORF files prior to processing in DSS? I always put the ORF straight into DSS without converting, I found that this gives much better results.

    When I open your DNG file it has a very strong blue cast.
     
  13. MadMarco

    MadMarco Mu-43 Veteran

    298
    Oct 30, 2014
    Guildford, England
    After a quick dabble processing in PhotoShot:

    O2040025-25a.

    There's definitely good colour information in the image, i just needs teasing out.
     
    Last edited: Feb 17, 2015
  14. tradesmith45

    tradesmith45 Mu-43 All-Pro

    Dec 13, 2012
    Oregon
    FWIW, during a discussion of using m43 cameras for night sky photography, subject of the best NR software came up. Many report that most PP software does a poor job w/ development of long exposure, high ISO .ORF files especially the default presets in Adobe products.

    Since I'm on the mac, can't/haven't used DSS so have no idea how well it does as a RAW developer.

    But I did do a comparison of several NR options. The best of the bunch is DXO Prime now in v10.2 & a close second is OV3. But in both cases, the best NR results come from using these as your RAW developer. Yes. one purpose of stacking is increasing signal to noise & that's usually best done with stacking as the 1st step in your PP workflow.

    Perhaps though when you have poor seeing + light pollution, doing NR, black point, highlight recovery & other corrections before stacking might yield better results. That's how a got the most reduction in banding with my Monument V. pano.

    I've tried both workflows for MW shots but my experiments have been using the M.Z12mm & mine has slight decentering so stacking failed w/ more than about 6 images. So I have no helpful comparisons to show you. But you might give this a try Levester.
     
  15. Levster

    Levster Mu-43 Top Veteran

    I'm not sure why I import as DNG! I will try without next time. What white balance setting do you normally use?
     
  16. Levster

    Levster Mu-43 Top Veteran

    Do you use Photoshop to process your images? What do you fix first? I tend to correct for the light pollution colour first but then that may remove colour from the nebula as well.
     
  17. MadMarco

    MadMarco Mu-43 Veteran

    298
    Oct 30, 2014
    Guildford, England
    I think that the conversion to DNG is where the damage is being done, the really bad blue cast is typical of a RAW converter that isn't processing the images "correctly".

    First thing is to makes sure that you are using the latest version of DSS with updated RAW support:
    http://deepskystacker.free.fr/download/DeepSkyStacker334.rar

    My basic workflow in DSS would then be:
    1) Load Lights, Darks, Flats, Bias straight into DSS as ORF files
    2) Stack using the recommended settings
    3) After stacking, align the RGB spikes by sliding the 2 left most spikes to the right so everything lines up (This does your white balance)
    4) Adjust saturation, 13%-15% usually works OK
    5) Adjust Luminance so the curve is just to the left of the spike as it is rising by altering the second mid-tone slider
    6) Play with the luminance sliders until you get the best detail without a background that is too light or blow highlights
    7) Save image as TIFF

    My Photoshop workflow is:
    1) Load TIFF
    2) Immediately save as a different file name so I have the original to go back to
    3) Image - Adjustments - Levels - Choose Gray point - OK
    4) Image - Adjustments - Levels - Move left slider until it is just before the spike, move the right slider until it is just before the spike - OK
    5) Repeat 3&4 (it's better to do small multiple passes than big lumps)
    6) Image - Adjustments - Levels - Choose Black point, move the black output level to somewhere around 20 (black sky isn't black)

    I also have a workflow that helps with light pollution, but that's quite complicated and will require a proper write-up. I did start writing my DSS workflow in a document with pictures, when it's finished I'll start a new thread as a general purpose guide to astrophotography.
     
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  18. tradesmith45

    tradesmith45 Mu-43 All-Pro

    Dec 13, 2012
    Oregon
    I really look forward to seeing that Marco. I'll have to figure out how to translate from DSS to Nebulosity on the Mac.

    Thanks for your comments here.
     
  19. PMCC

    PMCC Mu-43 Regular

    132
    Feb 18, 2013
    I have a very different workflow. I use IRIS for stacking. Before stacking I develop the RAW with Silkypix, doing CA correction and highlight recovery. Then I import the image into PhotoShop and mainly use curves to bring out the gas.
     
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  20. Levster

    Levster Mu-43 Top Veteran

    This was my efforts from last night:

    post-dss-flats-ps-2.jpg by -the-levster-

    If you squint you can almost make out the Horse Head Nebula! For this one I used 50 x 60 sec at ISO 3200 using my Tamron 14-150mm at full extension. I used 20 bias frames and instead of darks (I will capture some darks tonight at ISO 3200 and redo the stack) I shot at the same space of sky with a double layer of white plastic bag over the lens. My theory here was to use these as Flats so that I not only capture the lens vignette but also capture the light pollution gradient. I then stacked my 50 lights, 20 bias and 20 "flats" and pretty much followed MadMarco's guides. After I tweaked a little bit using some PS actions. The shot looks a bit noisy to me but I was worried about smudging out the nebula.

    The original autosave tif is available here if anyone else fancies a go:

    https://www.dropbox.com/s/c3yj52em1pxb7oe/Autosave001.tif?dl=0

    And after tweaking in DSS:

    https://www.dropbox.com/s/o8fzql7udvr1131/post-dss-flats.TIF?dl=0
     
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