Hi Gary and Charlie,
Hong Kong is cloud covered in the evening for the past weeks, I had only a
glimpse of Comet Neat.
If you want to photograph the Venus transition, the first thing come to my
mind is image scale. The sun's image can be estimated by the following
expression:
Image size of sun on film = focal length / 110
If you are using a 500 mm lens, the sun will be about 4.5 mm on the
film. On the transit day, Venus ' apparent size is about 1/30 of the Sun;
so it is about 0.15 mm on the film. This may be a bit too small, I would
suggest using a longer focal length e.g. by using tele-plus lens. To fill
a 135 film with the sun, you need a focal length of about 2000 mm.
If you intend to use the exposure meter, try spot metering and bracket from
+1EV to +3 EV (or more). It is a good idea to experiment before hand as
suggested by Carlos. If you start in the early morning, exposure will
decrease (shorter exposure) as the Sun rises higher.
I have not used the Thousand Oak solar film but I have used their glass
solar filter. For me, the correct exposure when the Sun is overhead is
f/10, 1/2000 seconds on ISO100 negative film.
I strongly recommend you to try out your set up at least once before the
"Big Day", as a slight overexposure may wash out the tiny Venus black
dot. There are at least two large groups of sunspots on the Sun right now
and they can serve as an indication of correct exposure. Without the
sunspots, it is difficult to tell whether the exposure is correct.
C. H. Yeung
from Hong Kong
At 03:28 AM 16/05/2004 +0200, you wrote:
>Date: Fri, 14 May 2004 18:48:24 -0700 (PDT)
>From: Gary Edwards <zuikowarriors@xxxxxxxxx>
>Subject: [OM] Comet was Re: Transit of Venus/Exposure
>
>Speaking of astrophotography, has anyone had any luck shooting the comet
>currently visible in the western sky? Don't remember the name. Here in
>light-polluted Arlington it is only visible through binoculars or more and
>looks like a fuzzy star.
>
>Gary Edwards
>
>Geilfuss Charles <Charles.Geilfuss@xxxxxxxxxxxxxxxxx> wrote:
>Greetings All,
>I have a question that is directed toward those on the List with
>astrophotography experience. I plan to photograph the early morning (East
>coast USA) solar transit of Venus that will occur on June 8th. I have
>obtained two squares of Thousand Oak solar filter material (ND 5) that I
>will fashion in such a way as to fit on the business end of my longest
>lenses (300/500 both are 72mm) as well as my friend's 8" Meade telescope. I
>will use a digital camera on the Meade (have an adaptor that will fit) as
>well as the OM with slide film. My question is how best to meter with the
>OM? I've read elsewhere to spot meter adjacent to the sun but I wonder if it
>would not be better to meter manually and use some variation of the Sunny 16
>rule. Thanks.
>
>Charlie
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