Many thanks, dudes.
Quote:
Originally Posted by dugnsuz
Another Cracker Bill - Beautiful.
I've got to get me one them 50mm f1.8 Canon lenses!!!
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Yes, the 50mm f1.8 EF II is basically compulsory for me on a budget. At only $139 for a new one you just have to buy it...
Bang per buck it is very, very good. Focus it at infinity during the day then carefully mark the focus point with an indelible pen. At night you will always then be able to get close to focus. Tip: a blob of blutac on the focus ring is so convenient to hold (lock) your focus once you get it! - and the blutac creates a nice drag (friction) for fine focusing.
Quote:
Originally Posted by dugnsuz
Is f6.3 the 'maximum' f stop on this lens?
Do you image at f6.3 due to abberations at lower f stops?
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The f stop goes all the way to f22 however I haven't experimented with anything lower than f6.3. I think beyond f7.1 we'd start to get diminishing returns.
I stop it down to eliminate field curvature ("coma") from the edges of the frame. At f/1.8 the stars are not round and you get significant aberrations. At f/2.8 it is much better. At f/4 it is very good, and at f6.3 I think the stars, even out at the very edge of the frame, are pretty sharp.
I started imaging with this lens at around f4 and found that f6.3 is just that bit sharper that it justifies the sacrifice of a longer exposure. At 50mm focal length a 2 minute or even a 4 minute unguided exposure will track very well - even on my mount (LXD-75).