Star trails with slow (LF) lens?

[John Kasaian]

I'd like to give it a shot. I've had good success in the past with 35mm and a F2.8 lens with TMY in the past but my fastest LF lenses are F-6.3(Ektar)and F/5 (Petzval) and my film will be Ilford HP-5+
Any thoughts or suggestions?

[Vaughn]

The issue might be how you wish the star tracks to appear. If you want them crisp and as narrow as possible, then you will need to close down a few stops to get the sharpest image.

Shooting wide open will widen the star tracks a little and one needs to be careful to have the standards and lens perfectly aligned.

[Corran]

I get the best results using f/8, on Provia usually. I still have a stash of T64 though that I prefer for the tungsten color balance. If using Provia, I usually shoot it with an 80B filter, opened up a stop.

1-2 hours minimum.

Example, on T64, using a 58mm XL. Compressed scan, sorry:

http://2.bp.blogspot.com/-Htgob1cZsYA/UowLqMco2dI/AAAAAAAAETo/cr5DaTDpofs/s640/cedar+(37).jpg

I love doing startrails but I haven't in a long time. Very few places near here to do it at, and little to no time (plus weather has been unfavorable!).

[Corran]

Oh, and don't use 400 speed film. Reciprocity kicks in and at the long exposures for these kinds of shots, pretty much any modern 100-speed T-grain film will be "more" sensitive to light than a 400-speed film.

Acros would be the best choice for a b&w film. TMX will work too but with a bit less sensitivity.

Realistically, the fastest aperture you can use is best. When I shot this last image my 75mm f/4.5 Biogon was in the shop getting a CLA. It would've been a better choice (and easier to focus).

[John Kasaian]

Oh, and don't use 400 speed film. Reciprocity kicks in and at the long exposures for these kinds of shots, pretty much any modern 100-speed T-grain film will be "more" sensitive to light than a 400-speed film.

Acros would be the best choice for a b&w film. TMX will work too but with a bit less sensitivity.

Realistically, the fastest aperture you can use is best. When I shot this last image my 75mm f/4.5 Biogon was in the shop getting a CLA. It would've been a better choice (and easier to focus).
How about Delta?:confused:

[Jim Jones]

Years ago my best star trail was for 10 or 11 hours at f/6.3 on Tech Pan.

[David Lobato]

It's easier than you think. Between f4.5 to f8 will work with film ISO 100 - 400. A wider aperture catches dimmer stars. More important is keeping the camera absolutely steady, and avoiding unwanted man made light sources. Find a small bit of landscape to include in the photo. Include the North Star for a central point of rotation. Moonless nights are usually better. For a fascinating photo, set the aperture to f8, and open the shutter for 6-8 hours from beginning of darkness to before the first faint dawn light. Don't forget to set the alarm clock and let the sun begin to rise like I have done. And condensation on the lens can happen. Check it every 30 minutes to an hour during the exposure.

[Corran]

How about Delta?:confused:

I think Delta has worse reciprocity than most T-grain emulsions. It should still work but slightly worse?


Years ago my best star trail was for 10 or 11 hours at f/6.3 on Tech Pan.

Neat, I'd like to see that!

[Vaughn]

Years ago my best star trail was for 10 or 11 hours at f/6.3 on Tech Pan.

Did something similar on TMax100 (4x5) in the bottom of the Grand Canyon. But I fell asleep and did not wake up in time.

[prendt]

Guys, since stars are pinpoint light source it is the real aperture dimension that is important not the f number. Nobody of you saw discussions of this point in the past of this forum? Check the archive.

[appletree]

I follow this guy on instagram (https://instagram.com/valleyofdyingstars/). Shoots LF and a ton of night shots/star trails.
I have been very inspired to go out and shoot some star trails. Never had though, and hardly know the ins and outs of my 4x5 Chamonix yet.

[mijosc]

Does anybody have any suggestions to deal with condensation on the lens? I tried a star trail with my Hasselblad a few years ago, but the lens fogged up. I had planned on trying again with my large format in Glacier National Park or the Grand Tetons this summer.

I had thought about rubber banding a hand warmer to the lens to keep it above the dew point. Do you think that would work? Do those last long enough for a 4-6 hour exposure?

[John Layton]

To help prevent fogging...perhaps throw a couple of silica-gel dry packs into the camera then re-mount the lens, then mount a small, battery operated fan (one that does not vibrate) on a boom arm - and point this at the front of the lens? Have never tried either of these - but just a thought!

[Jac@stafford.net]

Does anybody have any suggestions to deal with condensation on the lens?

This might seem counter-intuitive but my 8x10 sky camera (http://www.digoliardi.net/skc/skc1.jpg) lens had an optional heated filter: a few thin wires through the glass to a 22.5V source, but a lower (18V) voltage worked. Contact www.surplusshed.com. Ask them if they still have Metrogon filters.
.

[Corran]

Guys, since stars are pinpoint light source it is the real aperture dimension that is important not the f number. Nobody of you saw discussions of this point in the past of this forum? Check the archive.

Perhaps more specifics and links to relevant discussions or search terms would be more helpful, rather than snarky comments.

I am 100% certain that the "real" aperture (f/number) is quite important, assuming you want to shoot with a foreground.

[prendt]

Go ahead, serve it out.

[Jim Jones]

[QUOTE=mijosc;1243723]Does anybody have any suggestions to deal with condensation on the lens? . . . [QUOTE]

I made a large lens hood from a rectangular tin can and mounted a resistor inside it beneath the lens. I don't remember the amount of energy the resistor dissipated, but it was perhaps a few watts. A homemade example for a telescope is shown at http://www.skyandtelescope.com/astronomy-equipment/diy-dew-heater/. Since star trail photographs can be more effective with wide angle lenses, most designs intended for telescopes aren't so useful on cameras. You might find more information by googling for heated dew shield, but most links are for commercial units for telescopes.

[Jac@stafford.net]

I made a large lens hood from a rectangular tin can and mounted a resistor inside it beneath the lens. I don't remember the amount of energy the resistor dissipated, but it was perhaps a few watts. A homemade example for a telescope is shown at http://www.skyandtelescope.com/astronomy-equipment/diy-dew-heater/

That is a terrific tip! Thank you.
.

[David Lobato]

Raising the object (lens in this discussion) temperature only a few degrees is enough to prevent condensation. Hence, hand warmers may work fine. A few watts of thermal heat is probably sufficient. Don't overheat the lens and thermally stress its parts with too much electrical power. It's been a long time since Thermodynamics class but there is also the heat flux out of the lens to account for when figuring the energy necessary during the night exposure. For a 5-6 figure cost telescope the thermodynamic calculations are worth it.

[Drew Bedo]

Ummm . . . .What about a portable hair dryer? A few short shots of a low-heat or no-heat setting during the exposure might do the trick. Although in-elegant,tis could be an effective solution if not deeply commuted to doing extensive star-trail imaging.

Alternatively: the Astro-photography world offers battery powered heat wraps and extended dew hoods. Perhaps something purposed designed and off-the-shelf could be adapted to LF photography.

[Liquid Artist]

Does anybody have any suggestions to deal with condensation on the lens? I tried a star trail with my Hasselblad a few years ago, but the lens fogged up.
A couple of years ago I saw some fellow with a Large Telescope who basically wrapped Plumbing Heat Tape around the barrel.
If I remember correctly he powered it with a couple of A cell batteries, and claimed it lasted all night

[tgtaylor]

http://www.telescope.com/Accessories/Dew-Control/Orion-Dew-Zapper-Pro-4-Channel-Prevention-System/pc/-1/c/3/sc/44/e/22.uts The zapper will keep the dew off the lens all night. Choose the correct band for your lens.

An alternative to the above, google dew shields for camera lens. They won't work as good as the above but will last longer than nothing at all. I use a dew shield and a zapper on my 10" SCT. The shield blocks any extraneous light and the zapper keeps gthe dew off.

Thomas