Editing astrophotography

As a follow on from yesterdays first dip into astrophotography I went and did some proper processing this evening…

Astrophotography introduces a whole different level of complexity when it comes to capturing images and processing them… there are more technical aspects to it and new terms to learn… so… started off with using the 10 best light frames and the 7 dark frames I captured last night… I didn’t do any flat or bias frames as this was purely an exercise to get a feel for the whole thing…

Light frames are the actual pictures… typically long exposures for which you need to use a tracking mount of some kind to prevent star trails

This is one of the light frames I used in unedited form…
Editing astrophotography

Dark frames are exactly as they sound… you take dark frames under the same exposure conditions and are designed to help identify the natural noise of the sensor which will be subtracted from the final image… you can create a dark frame by simply fitting the lens cap on… use the same ISO as light frames…

Here is a section of the dark frame zoomed in showing the noise…

Flat frames are a normal exposure but same ISO as light frames but are taken in a way to expose areas of vignetting and marks along the optics… typically even lighting through a white translucent medium (t-shirts are popular)…again the images are used to subtract from the final image…

Bias frames are used to remove the sensor readout signal from the light frames… bias frames should be taken at same ISO as light frames with the cap on but at the fastest shutter speed of your camera…

The amount of frames you need to take seems to be up for debate… have read all sorts of differing view points (as is the way of the interwebs) on what is the best approach but mostly it seems to be as many light frames as you feel you can get away with as this will improve the signal to noise ratio of the final image… the minimum seems to be around 20 with 30 to 50 frames being the average… in some cases upward of 100 light frames are suggested!… along with 10-20 of each dark, flat and bias…

I used the 10 usable light and 7 dark in the end but that still took best part of an hours worth of imaging to achieve (mostly due to fighting my inexperience and the cloud cover)…

First thing I did was add profile corrections and set the white balance to be the same across all the images as stupidly I had left it on Auto White Balance and the images weren’t all the same… then exported them as TIF’s so I could use them in Deep Sky Stacker…

Images were brought into Deep Sky Stacker and processed…

This creates a file called Autosave.tif which in my case had a rather nasty green cast from the iffy white balance… I opened the file in Photoshop first to get rid of the colour cast…

Then imported back to Lightroom to continue the editing… most people use Photoshop exclusively but I am still not comfortable with it… as it was I could do most of the initial editing in Lightroom and tweak the rest in Photoshop after which is my normal workflow for normal photography…

It looks like it worked out ok 🙂
Editing astrophotography

Very very happy with the result considering the single image edit…
diting astrophotography

Just to remind you all that I did this using the camera equipment I already have… A Canon APS-C camera body (7D2) and the same 100-400L lens I use for the motorsport pictures I take at Castle Combe… the only ‘specialist’ bits of kit I had was a Sky Watcher Star Adventurer tracking mount but these are pretty cheap to buy in the grand scheme of things and the SkyTech CLS filter as I live in a Bortal Class 5 light polluted area…

Inspiration for giving me the confidence in trying this comes from Trevor of Astrobackyard… astrophotography and particularly long exposures like this seemed the realm of expensive telescopes with unwieldy tracking mounts in very dark places… this didn’t really appeal especially as it would require me to travel halfway across the UK the find somewhere assuming the weather held out…

Trevor does most of his imaging from his ‘back yard’… the images he produces made me realise I stood a chance of doing this at home with my current camera kit… This image was taken from the parking area round the side of my house…

Check Trevors website, youtube page and Facebook pages out… he is a nice guy 🙂

Astro Backyard on YouTube (well worth going to first)
Astro Backyard web site
Astro Backyard on Facebook

Looking forward to some more clear nights to do some more… 😀

The final image is available to purchase from the astrophotograpy gallery here

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