Help me compose a complex night pic

[blakejd]

So I have a shot in mind that is both photographically technical and... well just technical aspects to it so I'm looking for a little help before I undertake it. I've added a pic below to help explain what I'm going for.
The basic gist of the pic is as follows. I want to shoot the pic at night with the peak noticeable and the path of stars (long exposure) arching across the peak. In the foreground much like the white rock in the pic below is a natural rock arch which I want to highlight. Its located in a canyon not far out of town so there will be some ambient light. First off I've never done a long exposure of stars but I'm assuming you go with a tripod and low ISO (any practice suggestions are welcome). Two aspects I'm a bit unsure of are 1. should I use some sort of flash to highlight the arch (it will be about 100meters away) at the beginning or end of the exposure and 2. I want to shoot it with a bit of snow on the peak and I'm afraid it may overexpose the peak with the long exposure if there is too much light from stars, moon etc. Any suggested reading on the subject would be appreciated. A last complication is that I will have to rappel at night and sit suspended with some kind of rig for the tripod while doing this so I'm not going to be terribly comfy so I can't sit all night trying to get this shot right. This is a bit over my head in the photography aspect so I'm sure gaps in my post are evident. Thanks.

 

[musicaleCA]

Yes, you need to shoot with the lowest ISO possible. And for this kind of exposure, we're talking uber-stable (the camera will need to be absolutely rock solid) and uber-long exposure. You need to be comfy with judging the correct exposure time. As long as you keep it to one stop increments it's not difficult. At 30s, to get one more stop, multiply by two, and you get 1min. To get one more stop, 2min. Then 4min. Then 8min. And so on.

My suggestion is to do a few shots with shorter exposure times to find the correct exposure settings first, either by bumping up the ISO, opening the aperture, or both. Once you have those settings, you can work from there, first getting to the lowest ISO possible and adjusting the exposure time accordingly, then stopping-down the aperture to get an even longer exposure time. And at the last, slapping on an ND filter if you want an even longer exposure time. To really get the stars arcing in the sky, you're going to have to wait at least for the better part of a hour though, and even then, it's not guaranteed.

Use a full battery, and bring one or two spares. Long exposures absolutely eat battery life. Better yet, have a battery grip (omg, I just suggested a battery grip). Even better yet, use low ISO film for the longest exposure. Then you don't have to waste battery power.

To judge whether or not you should fill-in the ridge with flash, you'll need to look at your test exposures. If it needs to be filled-in, then you should mess around with shorter exposures and fill it in with flash (just set it to manual, point, and press the pilot button). Vary the number of times you flash each area and the flash power. This may take a few exposures to get right, so be patient. Once you've figured it out, the same rule will apply to the flash as you increase the exposure time on the camera. For each extra stop of light, multiply the number of times you flash each area by two.

Hope that helps. One last, absolutely important thing to bring: Patience. Lots of it.

Oh, and a flashlight. I've forgotten one while running to get some exposures at sunset, and damn was it ever hard to get what I wanted in pitch black. Couldn't read the rangefinder; had to do it all by memory. >.<

 

[blakejd]

Thanks for the great reply. Hopefully the shot will come out well. one other question for anyone who may know. Does anyone know of a good place online to get information on stars and their movement in the night sky? I'm guessing that this changes throughout the year and will effect the character of the shot.