Exposing for the sun (transit of Venus)
In case you hadn't heard yet, there's a transit of Venus next Wednesday with perfect viewing from the Australia/New Zealand kind of longitudes. There was one 8 years ago but the next isn't for more than a century.
The proper way to take a photo of it is with something called Baader AstroSolar Film, a very dense (3.8D or 5D, i.e. 12 or 16 stops) attenuating foil with little to no flare. However it's sold-out everywhere now so I was hoping to fake something up with an R72 (about 8-12 stops depending on red-sensitivity of the film). Glass filters like that have too much flare to be able to render good sun-surface detail but it should allow me to get an image of Venus; if you have the real thing you should be able to get all the texture, sunspots and coronal detail, etc, if you have a long-enough lens.
Can anyone tell me what EV the sun is in a direct exposure? I think it's going to be up near 30 or so, but having a number would be a good start as I'd like to do some test-exposures on Pan-F tomorrow...
I gather (from looking at a few sunspot photos) that the Baader film gives about f/8 1/500 ISO100 depending on conditions, but I don't know if that's the 3.8D or the 5D. If it's the 5D (16.6 stops), that puts the sun at about EV32.
Has any one here successfully photographed the sun and have exposure guidance?
Second problem: my longest lens is now only 240mm, so I think I get a 2.2mm image. Not going to be much detail in there!