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Re: [APML] Exposure Question
Brian, those are great! I especially like the Cygnus shot. Well, I stand
baffled but it remains that you should consider doubling your exposures
if you stop down one stop to f/5.6.
Stuart
Brian Larmay wrote:
>Hi Stuart...yes ..as others are amazed also.
>This is at one of my darker locations using a 10 min exposure @ f/4 of
>cygnus.
>It seems to me that for some reason I do capture alot of what is out there
>with these exposure times
>Heres cyg @ 10 mins: http://www.astrobri.com/cygnus.htm and Cassiopeia @ 12
>at yet a darker location: http://www.astrobri.com/cassiopeia.htm
>
>Skyfog does not let me go any longer then this.
>
>I do not comprehend how others can or need to go longer then this unless
>they stop down incredibly.
>
>Brian
>
>
>
>
>My Photography
>Homepage: www.astrobri.com
>
>Geographic Longitude= 88W
>Geographic Latitude= 43N
>Corrected Magnetic Latitude= 53
>
>----- Original Message -----
>From: "Stuart Heggie" <stuart.j.heggie@sympatico.ca>
>To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
>Sent: Saturday, September 20, 2003 4:53 PM
>Subject: Re: [APML] Exposure Question
>
>
>
>
>>Brian, I am amazed you can shoot at f/4 on E200 for only 7 minutes and
>>see anything on the film/slide. I shoot 40 min on Supra 400 at f/4 and
>>my math says you should go 80 min on E200. That said, for every full
>>stop you go down, you double the exposure time and for every factor of 2
>>you change film speed you change the exposure by the same factor (in the
>>opposite direction e.g. half the film speed requires double the exposure
>>time to be even).
>>
>>All this of course ignores reciprocity failure which is a function of
>>the specific film (each layer in the film having its own curve), the
>>outside temp, the sky fog limit and probably the optics of the
>>lens/scope. Some folks subscribe to the argument that a 16mm at 2.8 is
>>different than say a 50mm at 2.8 but I think this is suspicious (mind
>>you the source of this view is pretty expert so I am "agnostic" in this
>>matter).
>>
>>Short answer: if you shoot 7 min now on E200 at f/4 you should shoot 14
>>min on E200 at f/5.6 but that is ignoring the paragraphs above. I cannot
>>imagine that exposures that short are going to get you much.
>>
>>Stuart
>>
>>Brian Larmay wrote:
>>
>>
>>
>>>Hi all,
>>>
>>>Ive been slipping on everything concerning astrophoto since spring and
>>>
>>>
>will
>
>
>>>finally be getting out tonight for some long overdue practice.
>>>My question is concerning exposure time...I always stop my lens to f/4
>>>
>>>
>with
>
>
>>>exposure times of 7 mins, but this time I want to stop down to f/5.6 ...
>>>what would the correct exposure time be then?
>>>Whats the formula?
>>>Will this sharpen my images noticably vs @ f/4?
>>>Will this reduce Vignette and help me to create mosaics alot easier?
>>>
>>>All exposures are made using Kodak E200 tonight.
>>>
>>>Ty,
>>>Brin
>>>
>>>My Photography
>>>Homepage: www.astrobri.com
>>>
>>>Geographic Longitude= 88W
>>>Geographic Latitude= 43N
>>>Corrected Magnetic Latitude= 53
>>>
>>>_______________________________________________
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>>>http://seds.org/mailman/listinfo/astro-photo
>>>
>>>
>>>
>>>
>>>
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