aperture settings for widefield

[Shelster1973]

Am going to be worrking in a nice dark skies area thsi weekend and not having the opportunity to take my full scope set-up am going to try my hand at some widefield stuff (will be unguided non trracking too, just set-up on tripod and away we go)

Camera wise have a Nikon D7100 and have a nifty 50 I can use as well as a Sigma 10 - 20mm lens.

Was wondering what is the best aperture to set these to for taking images?  Control wise will be a mixture of using the cable release I have and also am taking my laptop with me, so can contrrol through BackYardNikon for some shots longer than 30 secs if I want to (circular trails anyone.......)

Cheers

[Ruud]

I looked here: http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/218-nikkor-ai-s-50mm-f18-review--lab-test-report?start=1

Based on what I see there, I would take a few test shots at f/2.8. The MFT50 data suggest that at  f/1.8, the edges might turn out soft.

Good luck with the project. You'll have to rely on a bit of trial and error, but it's one big experiment anyway.

[Shelster1973]

Cheers Ruud.

was unsure as to go whether wide open for smaller exposure times or big f number, but suppose dof does not really matter when you are imaging infinity

[GarethA]

I would go for one stop down from wide open - so f2.8 - wide open you're likely to get quite bad coma (or at least i did with the v similar canon lens).

I saw a great deneb/sadr/pelican/noth american neb image the other day that someone had done by stacking multiple short exposure/high iso shots using this lens on a static tripod.

I have a sigma 10-20 too and it's good for "landscape astrophotography" - at 10mm you can get away with longer exposures and I had no issues using it wide open - very nice lens.

[jgs001]

I don't know the Nikon lenses, but the Canon 50mm's need to be stopped down to around f/4 - f/4.5. the f/1.4 doesn't have Coma issues at f/3.5 but suffers from red CA in the middle of the image.

[Shelster1973]

Was more inclined to try the 10-20 more at the 10 end.

Another quick question. .....where I will be has some rather good architecture that was thinking of giving a quick blip of flash to highlight but was wondering whether to do the blip at start or end of the exposure......

[jgs001]

Given the completely static nature of the subject, I don't think it really matters whether you light it at the beginning, middle or end. Try both I guess and see  if there's any difference, and if so, which you prefer the look of.

[Psychobilly]

I'd probably do a separate exposure for any ground based objects you want in the final image and then combine them in the PP...

Peter...