Exposure for star trails, with 1/3 moon

[Daniel_Buck]

I'm going camping next weekend in Joshua Tree, and I figure this might be a good time to try a few shots with star trails. Looking at a lunar callendar, it looks like the moon will be roughly 1/3 lit.

I've never attempted any exposures longer than about 30 seconds. I'm guessing that with reciprocity, if I just leave the shutter open for a few hours at f8, I'll get something of what I want. Will this make the ground to bright though, with about 1/3 moon?

Film I'll be bringing is Tri-x 320, and Provia 100f, shooting 4x5 with both of them, and 8x10 with Tri-x.

Any suggestions for aperture and shutter length for each of these films? I'll have more than one camera with me, and I'll be there for more than one night, so I don't mind leaving one camera in use for some long shutter speeds, 3 hours or so. I won't be staying up all night, so I don't think I'll be able to do a 6 or 8 hour shutter.

[Greg Lockrey]

The moon will burn you out at f/8 for 8 hours. I don't have the number handy but A. Adams has the candle power (f/stop-time-film speed combo) in his book "The Negative" for the exposure of the moon. Here is a web page that may be helpful: http://home.earthlink.net/~kitathome...ra.htm#LVScale

[Mark Sampson]

take a look at a site called "The Nocturnes". Lots of info and cool photos too.

[Donald Miller]

This is an alternative to what you are wanting to accomplish...there is a gallery of ten exposures...select bar is in the upper window.

http://www.tawbaware.com/maxlyons/cg....jpg&gallery=8

[Daniel_Buck]

as far as focusing goes, since I'll have a few cameras with me, I'll probably take one camera, focus it while it's still light out, and then set it aside until it's dark enough to open my shutter.

The moon will burn you out at f/8 for 8 hours. I don't have the number handy but A. Adams has the candle power (f/stop-time-film speed combo) in his book "The Negative" for the exposure of the moon. Here is a web page that may be helpful: http://home.earthlink.net/~kitathome...ra.htm#LVScale

Thanks Greg, at a quick glance I was confused as to how to use the calculations there, I'll look at it again more thoroughly later today after work and see if I can follow it better. Thanks for the link!

take a look at a site called "The Nocturnes". Lots of info and cool photos too.

I'll look it up, thanks!

This is an alternative to what you are wanting to accomplish...there is a gallery of ten exposures...select bar is in the upper window.

http://www.tawbaware.com/maxlyons/cg....jpg&gallery=8

Donald, yes I've done this method with my digital a few times, it seems to work good, and keeps the noise levels down nicely! I don't think I'd want to do anything like this with film though.

[Zach In Israel]

1 Point away from the moon.

For star trails reciprocity should not matter, really. The thing is each spot on the film will be illuminated for a few seconds before the star drifts off to the side. On the other hand the reciprocity should keep sky fog down. You may want a vac back to hold the film flat, but give it a try

To focus find a bright star and focus on that. Remember all stars are at infinity and are point sources. So F# is not as important as raw aperture.

One thing you might try is this, open the lens up all the way, expose for 2-3 seconds, close down a fstop or two and leave for an hour. You will then get a bight star pattern at the start of your exposure.


check out the film forum on cloudy nights:
http://www.cloudynights.com/ubbthrea...t/0/Board/Film

[Zach In Israel]

1 Point away from the moon.

For star trails reciprocity should not matter, really. The thing is each spot on the film will be illuminated for a few seconds before the star drifts off to the side. On the other hand the reciprocity should keep sky fog down. You may want a vac back to hold the film flat, but give it a try

To focus find a bright star and focus on that. Remember all stars are at infinity and are point sources. So F# is not as important as raw aperture.

One thing you might try is this, open the lens up all the way, expose for 2-3 seconds, close down a fstop or two and leave for an hour. You will then get a bight star pattern at the start of your exposure.


check out the film forum on cloudy nights:
http://www.cloudynights.com/ubbthrea...t/0/Board/Film

[Zach In Israel]

1 Point away from the moon.

For star trails reciprocity should not matter, really. The thing is each spot on the film will be illuminated for a few seconds before the star drifts off to the side. On the other hand the reciprocity should keep sky fog down. You may want a vac back to hold the film flat, but give it a try

To focus find a bright star and focus on that. Remember all stars are at infinity and are point sources. So F# is not as important as raw aperture.

One thing you might try is this, open the lens up all the way, expose for 2-3 seconds, close down a fstop or two and leave for an hour. You will then get a bight star pattern at the start of your exposure.


check out the film forum on cloudy nights:
http://www.cloudynights.com/ubbthrea...t/0/Board/Film

[Daniel_Buck]

Thanks Zach! My exposure consern was mostly for the ground, being lit by the moon.

I'm assuming that the wider open my aperture is, the more stars that will actually show up? And the more I close down the aperture, only the brighter stars will show?

[Vaughn]

Daniel -- you will find that the sharpness of the stars will be affected by the f/stop...that is, using the middle f/stops will give you sharp narrow star tracks. Wide open or closed all the way down, the stars and tracks will be wider and not as sharp. Both scenerios assume that the stars are in focus. So you have some control there over their appearence.

It makes sense to me that the wider the aperture, the more stars that will show up.

Vaughn