Stars are so small and so distant that they are nothing but mathematical
points which can not be magnified. Star images do not respond to focal
length and focal ratio in the same way that extended objects do. The
only thing they respond to is the size of the aperture. The bigger the
better unless the lens performs poorly wide open. But if you're just
shooting star trails the images will be blurred anyhow so shoot wide
open and cut the exposure time.
Chuck Norcutt
Komtanoo Pinpimai wrote:
> I don't know much of the theorem, it seems to me that the more f the
> more sharp in the long distance, so everytime I shoot view, I try to
> increase the f as much as my hand can handle the shutter speed. The
> star is really has a great distance, so I had an envision I should
> maximize the f for shooting stars. Could you explain why it will be
> extreme ?
>
> thanks.
>
> On 11/7/05, Richard Lovison <rlovison@xxxxxxxxx> wrote:
>
>>Hi Komtanoo,
>>
>>Why are you shooting at f16? Even if you're including trees or buildings in
>>your image, it seems a bit extreme. If you are shooting just the sky, use
>>the lens wide open or 1 stop down otherwise you're just forcing a needless
>>longer exposure.
>>
>>If you are near to an electrical outlet, a portable blow hair dryer will
>>help with the dew. Here's a link for instructions on building a dew zapper
>>or heating element as mentioned in earlier posts:
>>
>>http://www.astro.uwo.ca/~rasc/HEATER.pdf
>>
>>Richard
>>
>>On 11/7/05, Komtanoo Pinpimai <romerun@xxxxxxxxx> wrote:
>>
>>>
>>>Well, I'm using OM-1n, 50mm lens, and a remote control wire, asa 800
>>>negative film, that's all. I adjusted focus to inf, asa to 100,
>>>aperture to 16, and shutter to B mode. I'd tried to do it many times
>>>with my stupid compact(It can delay its shutter up to 2 mins, but I
>>>found out later that 2 mins will never catch a star so I bought OM,
>>>but faced the dew problem instead).
>>>
>>>
>>>
>>
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>
>
>
> --
> do you know why MAC is no as fast as PC ?
> It's because the company doesn't focus only on
> computers or electronic equipments.They also
> sell burgers and fry.
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