Yes, the flaws in your thinking have to do with sky fog and coma. I
would guess the 1.4 would cause excessive fogging from background
skylight in short order due to the speed. I would also guess that the
1.4 wide open probably has horrible coma. Stars have such a small
angular diameter that they really don't form an image in the
conventional sense. They are tough customers when you try to take their
pictures. If your lens has coma they will show it. And coma is one of
those abberations that grows worse with the angle away from the optical
axis and speed of the lens. Fast, wide angle lens? Ugly, ugly star
photos unless you've got a Maksutov or Schmidt corrector which are
specifically designed to handle coma. There may be more but that's all
I can think of at the moment.
Chuck Norcutt
Moose wrote:
> Geilfuss Charles wrote:
>> Greetings All,
>>
>> I was thumbing through a back-issue of Sky & Telescope when
>> an ad caught my eye. It was from a maker of specialty CCD cameras for
>> astrophotography. That sure looks like an OM Zuiko 50/3.5 macro sitting
>> on their camera. I went to their website and sure enough that's what it
>> is. Seen here:
>>
>> http://www.fli-cam.com/images/Product%20Images/ProLine%20and%20CFW-2-7.jpg
>
> Gary's tests are all at 1:40. In them, the late 50/1.4 lenses reach A
> ratings at f.2.8, while the 50/3.5s are two stops slower for the same
> performance. I don't know what testing at infinity would do, but in
> theory, it should tip towards the 50/1.4.
>
> Since the name of the game in wide field sky photography is light
> gathering ability, I would think the 50/1.4 a better choice. Two stops
> means 1/4 the exposure time. If it turns out to be three stops at
> infinity, that's 1/8 the needed exposure time
>
> The astrophoto experts here may see some flaw in my thinking.
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|
