On 29 May 2012 14:32, John Celio <neo.venator.com+p...@gmail.com> wrote: > I want to try photographing the transit of Venus across the sun on > June 5th, but I've never tried shooting the sun before. Any of you > guys have tips you can share? Is there a special filter I should use, > or would a polarizer or ND filter be sufficient? I'm planning on using > my K 500mm f4.5, so I'll probably need to special order a large enough > filter, and I'll need to do that soon. > > Thanks, > John > > P.S.: Hey Aussie PDMLers, I loved your country! Just got home last > Friday. I hope I get to go back to Australia soon, especially to see > the outback and more of Tasmania.
John, ND filters aren't enough (unless you stack a bunch of them). I've bought a solar filter from these guys for my own plan to photograph the transit: http://stores.ebay.com/Seymour-Solar-Filters It was listed as "Solar - Sun Filter Sheets 9"X12" for Telescopes, Finder" and cost me $17. It lets through 0.001% of the light reaching it. I received it earlier this week but haven't had time to fashion a filter from the sheet. I plan to make a filter for my Tokina 400m f/5.6 and another for my Sigma CAT 600mm f/8. Filters for Solar observing/photography MUST ALWAYS BE ON THE FRONT-MOST ELEMENT. The situation is so dangerous that for larger reflecting telescopes (wider than 8") the "filter" is actually just a hole in the telescope lid (with solar filter material covering the hole, of course) because otherwise the concentrated and focused rays of the Sun (even heavily filtered) could damage the secondary mirror. In a standard lens, placing the filter in the rear filter tray would probably damage said filter after a few minutes of observing the Sun. Now for fun stuff: How long does your lens have to be? If using an APS-C camera, I'd recommend 1000mm. The Sun's angular diameter is ~31.5 arcmin (arc minutes) and it "moves" across the sky at a rate of ~15 arcmin/min. A 1000mm lens will give you a 1.3 degree (78 arcmin) horizontal FoV, so enough to fit ~2.5 Suns. If you orientate your camera such that the Sun moves horizontally across your frame, you should have the entire solar disc in your frame for ~3 mins (assuming you're not using a motorised mount). If you're using a motorised mount, then use a 1600mm lens and have the Sun practically fill your frame (vertically). As you're using a 500mm lens, I would suggest adding at least a 1.4x teleconverter, or ideally a good 2x TC. Venus is going to be ~58 arcsec in diameter, so some 32.5 times smaller than the Sun. Using a 1000mm lens on a K-5 you get 1.05 pixels/arcsec, so the size of Venus on your photograph will be ~60 pixels. I recommend this site for practically all information regarding the transit, including your local times of visibility: http://www.transitofvenus.org If you have an observatory or astronomy club near by, check to see if they're organising an event for the occasion. If they are I'd recommend going to take a look through a powerful telescope, even if you take your gear along and also take photos. Cheers, —M. \/\/o/\/\ --> http://WorldOfMiserere.com http://EnticingTheLight.com A Quest for Photographic Enlightenment -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
