Lens Test

[Mickoid (Michael)]

Went out last night to the Melbourne fringe and tested this Sigma 30mm f 1.4 lens. It's not the Art series lens so the quality isn't as good and at f 1.4, it's virtually useless for astrophotography. I stopped down to f 4 to help eliminate the coma, still no good, f 5.6 still had coma, f 8 and there was signs of improvement. I left it there and shot 16 x 2 min subs @ 1600iso with the modded Canon 550d mounted on a Nano Tracker. I think f 11 would have eliminated the coma but stretching the exposure to 4 mins on the Nano Tracker to compensate, was out of the question. Consequently, the test established that I won't be using this lens for astrophotography.

[xelasnave]

You give up too quick.
It's a worthy capture for a start and really you should be able to make slight coma a non issue with StarTools and a small crop...mind you I only see photos generally on a phone...but we'll done I say.
Addition via edit..I looked again it looks great double or treble the exposure time. I spent twenty fours hours stacking 200 24 meg with 3x drizzle to have it crash at the very last moment..but I hope to have a couple when I get some Sun to charge the batteries.
Alex

[xelasnave]

I would also suggest you may get away with higher ISO if your camera has it. I have been experimenting with crazy high ISO 25600 but mainly 3200 and 6400 and each time am getting better with noise reduction...anyways should have some soon to show.
Also a lower fl may be acceptable with StarTools dithering and a crop...and not everyone who looks at them blows them up and goes straight to the corners...and I do think a 3x drizzle fixes stars a bit.
Alex

[JA]

You have some lovely colour there Mick and I agree with Alex to not give up too soon, especially since it may be possible to salvage some of that coma/saggital coma flare (and its attendant minor chromatic abberation) with lens corrections in Adobe Camera Raw or Lightroom etc... I'm not sure if that's part of your processing, but it may help.

In any event looked at as a whole image on screen, rather than pixel peeping, it has some lovely colour and detail.

Best
JA

[Mickoid (Michael)]

Thanks for the encouragement and advice guys. One of the main issues with the 550d is that I find going over 1600 iso on this sensor, colours wash out and I have to saturate in post-processing. This introduces a whole lot of false colour and increased noise.

Because I don't have a permanent location to set up for imaging, my time out in the field needs to be productive. Sure, the picture looks pleasing enough but having to stop down and increase my exposure time means I'm reducing the amount of subs I can take in a session. I'd much rather have a lens that operates well and transmits enough signal at f 4 than having to increase exposure to achieve enough signal at f 8.

Your comments are valid and may work with your camera but I know the capabilities of mine and the solution in this case is to try another lens. A first world problem and I won't be losing sleep over it. Correction - I do lose sleep because of this hobby!

[xelasnave]

You are right and given that context buy another camera and lens to boot as your ability nor your sleep should be limited by your equipment.
Alex

[Mickoid (Michael)]

Nice one Alex, now I've just got to convince my wife that purchasing new photographic equipment will be beneficial for my health!