Widefield deep sky with a DSLR

[andyc (Andy)]

These images are a progression of attempts to take astrophotos with an EOS 60D and an iOptron Skytracker:

The Lagoon and Trifid image is perhaps the first deep sky photo that I'm really happy with. It is 10x 2 minute exposures of the Lagoon and Trifid Nebulas from my southern Sydney backyard, taken with an EOS 60D on an iOptron Skytracker. Focal length is 250mm, f/8, ISO 1600, stacked in DeepSkyStacker, and processed in Photoshop CS2. These were the best 10 frames from 15 taken, and the lens is the stock EF-S 55-250mm zoom. I'm now able to get reasonable stars with the 250mm zoom, mainly thanks to stopping the aperture down a few stops to eliminate aberrations (I should thank Jerry Lodriguss' website for that tip and good hints on focusing a DSLR with the live view window). The Skytracker is excellent and easy to use, not producing significant trailing even at 3-5 minute exposures, so I can cut the aperture and up the exposure time.

The Rho Ophiuchi image is 10x 2 minute exposures with the 60D and EF 100mm macro at f/5, ISO 1250. Not really enough data under suburban skies, but a pleasure to begin seeing some of the structures round Antares. Pretty grainy in the dark areas.

The Eta Carina/Running Chicken region was a stack of 11x 90-second exposures (16.5 minutes total), ISO 2000, f/2.8 at 100mm focal length. I took it the week before the first two photos - much poorer star shapes from having the aperture fully open, but it was taken from a darker location in the Royal National Park before moonrise last week. Nice to (just) catch a dim hint of the little nebulae Gum 39 & Gum 41 near the Running Chicken.

Any hints or tips from others using the Skytracker and a DSLR would be much appreciated, and criticisms are welcome! I have no darks or flats in these images (I flattened the RAWs in Digital Photo Professional), that's another step on the learning curve. One question would be colour balance - on my monitor the colours are OK, but on my phone, the nebulae come out quite magenta - what do you see? Is it in the processing or just my phone?

[raymo]

Yes, definitely lots of magenta. What does the DSS histogram look
like? you can easily remove that colour cast in DSS before moving on to
PS. Nice shots, by the way.
raymo

[andyc (Andy)]

Hi raymo, thanks for the comment, and yes, you're right! There was loads of red/magenta - I looked at the colour balance of background pixels in Photoshop and saw they were frequently unbalanced towards red. I've tried adding a colour balance layer into the photoshop images for each one, hopefully it's helped. Next time I run through the DSS process, I'll look to do exactly as you suggest to remove it early.