They Didn't Ask Me (dr_phil_physics) wrote,
They Didn't Ask Me
dr_phil_physics

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The Transit of Venus

Half-Assed Shooting

As mentioned earlier, my intention was to try to shoot Tuesday June 5th's transit at sunset with the new-to-me 200-600mm f9.5 AIS Nikkor (DW). Now I'm not an idiot. I've taught astronomy courses and have done a little dabbling with telescopes. So I'm not planning to take a high magnification lens and just aim it at the sun and look through the viewfinder. It's not good for the eye(s) and it can be bad for the lens, too, if it heats up too much from being saturated with sunlight. Hence the "shoot the transit at sunset" part.

True story -- once during the various Summer Youth Programs and Summer Institutes at Michigan Tech, I had a bunch of students out at the AMJOCH Observatory built by Physics professor Dave Chimino, and we were looking at sunspots with the Questar telescope outside, while Dave Lucas was running the Celestron in the dome. The Questars are very nice little machines -- my father always wanted one -- and it had a lovely solar filter. Alas, there's a little spring loaded lever which flips a mirror so that the eyepiece looks down to another mirror and becomes an under-the-tube built-in spotting scope. And if that lever, which was loose on the telescope, flips while viewing the sun, you get spotting scope sunlight right smack in the eye. Talk about photo shock eye blink reflex! Ouch! Definitely a design flaw. We put a black plastic film can over the spotting scope port to keep that from happening again.

Anyway, in addition to the UV filter already on the big lens, I'd also acquired a pair of Series IX reflective-type neutral density filters for the big lens. I'll get a proper solar filter at some point, but when I thought about it, I was unable to get the one I wanted in the size I needed in time. Plus the ND filters have some usefulness of their own. Now your typical ND filters are like ND4 and ND8 -- they cut the light by 1/4 (two f-stops) and 1/8 (three f-stops). And they're black absorption filters. But by getting the reflective style, it cuts down both the visible and IR light. And I could get them in stronger sizes. So I got an ND 0.9 (ND8) and ND 1.50 (ND32, five f-stops), sized to fit in the HN-10 lens hood. Which, as I mentioned before, could also work with some other lenses on my bucket lens list. Cheap and frugal doesn't not negate efficient and practical. (thrifty-grin)

Here's the thing. The Nikon D1X plus 200-600mm lens is big and heavy. My tripod isn't the best and I was going to be shooting from the back deck -- not only did I not want to leave it unattended, it's not exactly vibration free either. Now I knew from some shots I've seen taken with other supertelephotos that I could shoot right at the sun at sunset at between 1/1000th and 1/10,000th of a second, so that should help with the unsteadiness. The 200-600 is NOT an ED lens -- Extra Low Dispersion glass -- which means that it has a hard infinity focus stop, i.e. the glass doesn't change with temperature. So my plan was to line things up, set the lens at infinity and 600mm, and not try to focus through the dim f9.5 plus ND32 viewfinder.

Alas, the results were not quite a good as I hoped. This is where those little LCD displays on the back of cameras make things look like you're getting a better picture than you really are. (grin)

Now, one of the issues that comes up is "where is Venus going to be"? This is not so simple, because many telescopes give you inverted images AND transits of Venus come in pairs, and this pair were going to give transit lines on opposite sides of the sun. As near as I could figure out with my prelab of sites, I was expecting Venus in the upper right quadrant. This is vindicated by two images I caught on the web:


Transit data for Tucson AZ -- the image would be rotated clockwise slightly for West Michigan.


From Mlive.com, this shot was from the roof of one of the Grand Rapids downtown parking garages, where the local astronomers had one of their viewing sites. This was from around 7-8pm EDT, about an hour or two before my shoot.


From the Sky & Telescope website, Brian Arnold of Brookfield WI at 6:15pm local (7:15pm EDT), Nikon D90 with a 70-200mm lens @ 200mm, with a Thousand Oaks Solar filter. Two hours before my shoot. (Click on photo for original site.)

The sun was glaringly bright for quite a long time. I had the lens mounted, but sitting inside for an hour. Even at 8:30pm, the sun was too bright to mess with. Finally, right around 9pm, the low angle and cloud layer cut it back enough to try and I quickly assembled things.


Looking at several photographs, I think that the blob by the arrow is Venus and not an artifact. (Click on photo for larger.)


Another shot. (Click on photo for larger.)

Not great by any means, and the images are certainly not telling me anything useful about the quality of the 200-600 lens. But by gosh I had fun -- and that's what matters. (big-sunny-grin)

Dr. Phil
Tags: allendale, photos, super telephoto, transit of venus, weather, west michigan
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