Shooting the Milky Way

[Codger]

Hello, Everyone:  I'd like to tap into the collective experience of the forum for some insights into photographing the Milky Way.  I'll be working with a film MF-67, using Provia (either 100 or 400 speed) slide film, and a sturdy tripod, of course.  My position with be one of the high ridges in Colorado, elevation between 12-14,000 feet.  I know depth of field isn't an issue, but avoiding star movement is, so I expect to work with either f-5.6 or f-8.  I'm not expecting to include any silhouetted or light-painted objects in the shot: I just want the edge to edge sweep of the thousands of visible stars.  I'm wondering how to do the exposure: too long and there will be elongations of the star spots; too short and I'll miss some of the sensitivity I need to record the lesser lights.  Advice?     Thanks,  Codger

[bill t.]

Put the camera on an equatorial mount so it can track the stars for however long you require.  Without it, you will need to keep your exposures down to something like 30 seconds with a medium-angle lens, longer with a wide angle and shorter with a telephoto.  You would probably need to be near wide open with ISO 400.

There some very cheap and compact telescopes and telescope mounts out there now with motorized axes.  A lot of people are using them for motion control timelapse shots.  I'm sure something could be easily modified to carry your camera.  The forums at timescapes.org could be helpful.

[Steve Lefkovits]

Codger you'll have good results using a polar aligned equatorial mount whose rotation counters the rotation of the earth.  I've done this occasionally using an Astrotrac TT-320X from http://astrotrac.com/ and it's worked out pretty well once I leveled the tripod and aligned the mount with Polaris.

Below is a composite image I made.  If you ignore the foreground silhouette, the Milky Way image is a 3 minute exposure using the Astrotrac mount to keep the stars in the same relative position as the earth turns.  I believe it was at ISO 1600 at F/2.0.



Steve

[bill t.]

Steve, thanks for the Astrotrac link.  I think we used to call the homebrew versions of those things "tangent arms," they never actually worked out very well.  But that looks pretty competent.

I've got an old equatorial mount with a 15 pound counterweight and a huge battery pack and a heavy tripod.  That kit has done a terrific job of making me not want to do landscapes with stars.

But with your superb Milky Way shot in mind and a lightweight tracking device, I'm rarin' to go again!  That beautiful summer Milky Way is approaching optimum position right now (in the northern hemisphere).

The night sky can be simply breathtaking from a dark location, and digital has finally brought us to a point where it that be well represented in photography.

[Steve Lefkovits]

Bill - The Astrotrac is a delight because it's small enough and light enough to come along on a business trip or a camping adventure.  It's rigid, accurate and can track for almost two hours per run.  I've made decent images with lenses up to 400 mm and three minutes with it.  The biggest challenge for me is leveling the tripod so that I don't compound the periodic error of the device.  Highly recommended and very lightweight.  It's been a great introduction to astrophotography for me.