MattKing
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I truly believe you need to reverse that sentiment.
How about: "experience from past failures, plus a little bit of guess work".
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How about: "experience from past failures, plus a little bit of guess work".
Andrew O'Neill
Moderator
If it's clear air ( which doesn't happen always over at the coast.. there's often a lot of moisture in the air ) it is amazingly dark if you head up to those hills North of Jenner ( Meyer's Grade and North of there ) and even more into Mendocino North of Gualala. Almost like being up in the mountains. But we have lots of places with good dark skies.. I can see the milky way easily most nights from my yard and I'm not too far from you. I'm sure if you head anywhere West of Petaluma you'd get to pretty good dark skies soon. I can't remember if I posted it here, but I made a several-hour pinhole image of a lunar eclipse onto instant film.. got a trail through the sky that turned a bit orange and then thinned and mostly disappeared during the eclipse, but it was nothing very special.
@Adrian Bacon
Something that just occurred to me -- you could probably make pinhole sky images if you had a sky tracking mount. Not sure how it would be an improvement over a lens, though. Maybe if you were going to do 8x10 wide angle on a tracker that barely handles a lightweight SLR -- a pinhole camera can be really light compared to big chunks of glass and wood, composite or metal frames and heavy bellows...
Something that just occurred to me -- you could probably make pinhole sky images if you had a sky tracking mount. Not sure how it would be an improvement over a lens, though. Maybe if you were going to do 8x10 wide angle on a tracker that barely handles a lightweight SLR -- a pinhole camera can be really light compared to big chunks of glass and wood, composite or metal frames and heavy bellows...
I doubt it would work within reasonable time, a pinhole just makes a star into a larger fuzzy blob (i.e. spreads out the little amount of light over a larger area), so excombined with the small aperture, one would need just need a much much longer exposure to get said blob to register on film, compared to a lens.
While this is true, it's worth remembering that the reason you can see trails in an untracked long exposure is that the star images record in less than a minute -- I've seen them on FP-3000B prints at around f/8 and 1/15. Trails are made mainly because they're so much easier to see in the print than tiny white dots that can be mistaken for dust shadows.
With a tracked pinhole star image, you'd get pinholes of size roughly determined by brightness -- the brighter the star, the further from the center of its spot it will record. If we were just now starting to measure this kind of thing, this might actually be a practical way to get the magnitudes of a whole bunch of stars with a single exposure.
OP
OP
Just a thought, if you want to give it a try.
For 35mm, ,, we have done this numerous times in the past, you don't have to use a full roll. Shoot as much as the roll as you want, then advance the film as normal, but do not expose.
In the dark open the back of the camera, and cut the roll in half, ... a finger width or more from the film roll cassette feeding edge. This will leave a small portion of the film to be properly cut and then taped to an old leader later.
Remove the exposed film take up reel from the camera, and process normally.
Reusing the cut roll of film.
In the daylight, overlap the lead from the film cassette carefully over an old leader, by aligning the film sprocket holes directly over the other, and then cut the film between between the sprocket holes. Then tape the two halves together, by butting the two edges together . Thin black electrical tape has worked for me, but be sure not to tape over the sprocket holes.
Insert the taped lead into the take up real, and and film cassette back into the camera. Before closing the back, gentle advance film until its flat, then close the back.
Advance the film one shot or two to clear the exposed area of the film.
Note: as you begin shooting, be sure your film counter is advancing, by stating how many shots have been taken. If the tape has not done its job, then of course the film will not advance, and the count will not change.
I've always just cut a new leader on the film left in the cassette when I took a partial roll of 35mm. Wastes a couple frames, but far easier than trying to get another leader spliced on straight.
I live on the east side of Petaluma, and man... nights that are actually clear, it’s incredible what you can see. Unfortunately, we’re still close enough to the ocean that we either usually have cloud cover, or we’re fogged in.
maybe. I might buy a bigger pinhole diaphragm to try out. The one I have is sized to provide reasonable sharpness at 4x5 negative sizes. If I’m trying to record star trails, I actually care less about sharpness and more about actually registering an exposure on the film before the star moves too much.
Now I'm thinking I should build a barn-door tracker and set up with a pinhole on one of my plate cameras and give it a try.
Barndoor tracker, for those not familiar, is the simplest possible sky tracking mount: two boards joined with a hinge, hinge pointed at the celestial pole, and a length of threaded rod butted on one board and threaded into a blind nut in the other. Solder or weld a butterfly nut to the t-rod, calculate the trigonometry required, and manually turn the rod at the right rate (a convenient size will give half a turn ever thirty seconds) to move the camera mounted on the board at the sky rate.
In simplest form, they're good for twenty minutes or so with a fairly wide angle lens, but there are slightly more complex versions with only a few more parts that can hold a pretty accurate track for a couple hours, even with 3-4x magnification over "normal" focal length.
Barndoor tracker, for those not familiar, is the simplest possible sky tracking mount: two boards joined with a hinge, hinge pointed at the celestial pole, and a length of threaded rod butted on one board and threaded into a blind nut in the other. Solder or weld a butterfly nut to the t-rod, calculate the trigonometry required, and manually turn the rod at the right rate (a convenient size will give half a turn ever thirty seconds) to move the camera mounted on the board at the sky rate.
In simplest form, they're good for twenty minutes or so with a fairly wide angle lens, but there are slightly more complex versions with only a few more parts that can hold a pretty accurate track for a couple hours, even with 3-4x magnification over "normal" focal length.
So my current pinhole is 0.4mm and is ~95-100mm from the sheet of film giving me ~f/240-f/250. I suppose I could blow it out to 0.8 or even 1mm and have roughly a quarter the exposure time. Much larger than 1mm though would likely start to be too big for any kind of real definition. I’d have to do some math to figure what f number would be best if I had a good starting point exposure with a lens based setup.
I'd be more inclined (if possible) to shorten your projection distance -- keep the 0.4mm aperture, but widen the angle to 30-40 mm (which would give something like 6-10x the light intensity). Smaller, brighter star images, more of them, so you'll be able to see them better. Assuming your camera isn't a fixed size box, of course. A tracked photo at 40mm on 4x5 would be spectacular, if you get anything (if you can track for an hour with a film like Acros II you might even see brighter nebulae like the Lagoon or Trifid, or M31 and one or two other brighter galaxies).
You guys should check out the Cloudy Nights forums. They have a section devoted to film astrophotography, lots of useful info there.
if I want to change the projection, I’ll have to build another camera. Cutting it down to 40-50mm at 0.4mm is the same as keeping 100mm and going to 0.8mm, both end up at f/125 or so, basically an extra 2 stops of light. I typically just meter for f/256 during the day with my current setup. 0.8mm would basically mean f/128.
second thing is I don’t have a tracker.
Hence my "if not a fixed box." My sheet film pinhole equipment is split between a former electron microscope camera body with pinhole in shutter and 4x5 Graflok mount (two projection distance choices due to a snap-in extension box), and a 1927 Zeiss-Ikon Ideal plate camera with pinhole shutter; on the latter, I can lock the front standard at any distance between about 40 mm and 200+ -- with a constant 0.5 mm pinhole, that runs f/80 to f/400+, give or take. It's f/270 if locked on the 135 mm infinity stop and no focus extension applied.
With a fixed dimension box, it's much simpler to change the pinhole for this purpose...
With a fixed dimension box, it's much simpler to change the pinhole for this purpose...
I have an old toyo field camera with a broken graflock back that I could retrofit to be a pinhole. I’d need to build a new back for it so I could mount a film holder, then tape a pinhole to the lens plate. The bellows and everything else on it are still good.
Sounds like a bunch of work. Probably simpler to build a simple sky tracker.
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