|
Kent, Steve, Scott, Thanks for your informative postings. Kent -- yes the elongation I referred is indeed the "radial appearing" areas visible in the lower right of the larger image. I've been considering a dry air purge, but am reluctant to drill into the camera body for fear of depositing metal filings into some mechanism. (I'm also not real keen to reduce the resale value of the Pentax 67 body. As I sit here, it occurs to me that if I pick up Hutech's vacuum back, I can add another fitting for dry air purge, though this may require higher flow rate than a dry air inlet elsewhere on the body.) Second, I will certainly try push processing the next set of images from this setup. The Sky-90 working at f/4.5 gives good depth on E-200 exposures ranging from 30-60min. But the Traveler at f/6 could definitely use push processing for one hour exposures. I'm very enthused at how well the Traveler's field flattener fills the 67 frame. No vignetting correction on this image! Steve - In your experience, does the Hutech vacuum back help insure accurate focus throughout the film plane (not talking creep here). If vacuum backs are important for astrophotography, how come not for terrestrial. I would think that people that shoot landscapes for extreme enlargement have as challenging a sharpness problem as we do. (Granted, stars make small errors obvious, but I would think that the most demanding terrestrial photography would require vacuum backs as well. Scott - you say you use "the dry air purge system that many on this list are using" Can you give me a pointer to that system (or the elements that comprise it)? I realize that a canister of silca gel and an aquarium pump may do the trick, but if there are some special components you're thinking of, please let me know. (Also, I've never had problems with 35mm film, so even the worst of my imaging environments is not as bad as you've seen I guess.) I image from three areas in Oregon: 1) Larch Mountain -- near the west end of the Columbia river gorge. This is within an hour travel from my home, but can suffer from excessive moisture and air traffic. I use this site very rarely. 2) A snow park on the east side of Mt. Hood. This is where the image I pointed to was taken from. Good dark skies, elevation roughly 5k ft., and the beautiful mountain just to the west (http://www.cse.ogi.edu/~tleen/astro/HoodTwilight.html). Moisture is rarely a problem, although my recollection is that it was on the evening I took the image in question. 3) Central Oregon desert. My favorite for darkness, dryness, and stunning desert scenery. I've had extremely limited imaging opportunity this year (3 evenings). Most weekends near a new moon were clouded out. (This includes a trip to Sunglow Ranch in February that yielded almost no imaging hours!) Hopefully next year will be better. Otherwise I'll have to move or take up a different hobby (photographing the clouds?). Thanks again. Todd
-- Todd K. Leen, Professor Dept. of Computer Science and Engineering OGI School of Science & Engineering Oregon Health & Sciences University 20000 N.W. Walker Road Beaverton, OR 97006 Phone (503) 748-1160 FAX (503) 748-1548 CELL (503) 332-5897 tleen@cse.ogi.edu www.cse.ogi.edu/~tleen |
_______________________________________________ Astro-Photo mailing list Astro-Photo@seds.org http://seds.org/mailman/listinfo/astro-photo
