Quote:
Originally Posted by luka
You should try stepping up the f-number of the lens. Of course this means less light and longer exposure times...
Is 3.5 the minimum for this lens at 18mm?
At the low(est) f-setting you usually get coma - trailing of the stars in the corners towards the centre. You can see it in the bottom left and top right corners.
|
I believe f/3.5 is the lowest for that lens. I am thinking of buying the Nikon 50mm f/1.8D, which I see you have. For terrestrial photography the Nikon VR 18-200mm f/3.5-5.6G lens is a great all rounder.
I based the exposure time on the formula:
t = 1000/FL (near the pole) and t = 700/FL ( near the celestial equator),
so roughly 700/28 = 25
but did not want to go as long as that just in case. Now that I see the results I could probably try again but at the smaller aperture and longer exposure.
Thanks for the tip on coma. I have read about it but until I experience something for myself I just don't get it.
otherwise the image looks reasonably sharp.
I did have a go a few nights back from my (very light-polluted) backyard at f5.6 and perhaps saw a tiny bit of coma (now I know what to look for) so I could probably go back to that setting and crop.
thanks for the helpful reply, luka.
cheers,
DJDD