I've bought my self a nifty fifty based on some of your recent posts using it. I look forward to getting something as nice as this.
One issue I'm having is achieving accurate focus. I'm using it on my 350d only because I'm using it while the 5d is running on the scope. Although I'm not getting the best of the f1.8 because it's APS-c, it's what I have to work with. The problem I find it that I wind the focus all the way out and although the stars look nice in it, it's more of an accident than intended because I run out of adjustment. Is this common and is there anything I can do to help the situation or is it the nature of the beast on that particular body ?
Hi Ryan, You're up against it with the 350D not having "Live View". IF you
want to persevere with widefield it might be a good idea to sell the 350D
body[$100-125] on ebay, and get an 1100D body[$150-200] on ebay.
Higher max ISO, Live View, bigger LCD screen, and not as noisy.
In case you didn't already know, the focusing ring on all DSLRs goes beyond infinity, so you go to the end and then come back a little. For AP the focus has to be absolutely spot on; achieving this through the viewfinder is almost impossible except by luck. Your best chance is to focus using the brightest star available [Sirius and Canopus are both up at the moment], and then swing to your target. You can also use the moon if it is somewhere in the sky at the time. Some people even stuff around focusing to the best of their ability and then take a short exposure, check the focus, make a small adjustment if necessary, and repeat until they get it right--tedious to say the least, especially as the focus will change with ambient temperature changes, so you have to go through the rigmarole all over again.
You can use a Bahtinov mask with large lenses and telescopes, but I'm not sure if one would work with small lenses; somebody will almost certainly know the answer to that. As far as I recall there is no problem with APS-C lenses coming to focus when fitted to a full frame model.
raymo
Funnily enough I was just taking to my step dad and he's got a 600d that he's thinking about trading up that has live view. The ONLY reason I'm using the 350d at the moment is because it's what I have and my 5d full frame is busy lol. At the moment I'm only dipping my toes into wide field and honestly it's to fill in time while my scope is busy working and Brian cox hasn't got anything fresh on YouTube lol
Something I do with focusing and live view is to prefocus somewhere else in the sky to get it sharp before pointing to my target. Star only I'm talking about here. Live view isn't precisely "live" either, there is a slight lag between when you adjust focus and when you notice it on the screen. So take it slow, focus on a bright star and let go so it settles then adjust a tiny bit one way or the other, again slow and let it settle each time. Do this while watching the live view screen and carefully look for stars appearing or disappearing on the screen. these are just at the edge of magnitude the screen can display. As you move slightly out of focus they become slightly diffuse (out of focus) and vanish from the screen, but when you get the focus spot on perfect they suddenly appear on the screen. That's when you have focus spot on. Be careful with zoom lenses, especially heavy ones as the weight of the glass on some can slowly "wind in" the lens, losing zoom/focus as you tilt upwards. Also dont forget to try stopping down the aperture from say f1.8 to f4 to help sharpen up the stars too. lenses are never sharpest wide open.
My tips re focus place some blue tack on the lens body and the focus ring so it does not move ...its so easy to bump it and you just dint notice and you think your focus was not grest when it may have just moved...also as mentioned be happy with the lens not zoomed all the way out.
And make a small dew cover so as to stop stray light reaching the lens.
I make mine out of stuff from Spotlight that looks like wet suit material..join with contact adhesive takes no time at all.
Alex
