Annular Eclipse May 20,2012

[erno james]

Greetings everyone. I have the opportunity to shoot an annular eclipse later this month. I'm looking for advice on how to best shoot this rare event. I am thinking about renting a 1.4 or even 2 extender for this. Basically, I need to know if the gear I have below will be adequate to get a decent capture. Using advanced theoretical mathematics, I figure I can get a reach of 448 mm using the 1.4 extender and 640 mm with the 2.0 extender.

Gear:
7D
70-200 IS
tripod
B+W ND110 (10 stop filter)
various LEE GNDs

Much obliged for your expertise! Erno (image taken from Google Images)

[Kayaker72]

Erno,

Are you heading North to the Chico area? I am going to be in Monterey, but am trying to figure out how to head north....

BTW, we are thinking along the same lines...here is the thread I posted:

http://community.the-digital-picture...ead.php?t=6015

[erno james]

still up in the air, but i think i may drive out to Bidwell Park. I need to find a tree or something to put in the foreground. sun will be about 2 "handwidths' from the horizon, so not even sure how to do this. I'll be using Live View only on my 7D for this. worse case scenario is a fry my sensor, so will have to upgrade to a 5DM3.

[Kayaker72]

I had the exact same thought.

[Dr Croubie]

FWIW, I filled my APS-C sensor (maybe 90% of sensor height) with the supermoon the other week, using 1000mm f/14 (250 f/3.5 x2 x2).
Don't go too overboard with length, with that tight a framing the moon moved out of shot in about 30 seconds. (It was kinda freaky, watching it move on 5x live-view that quickly).

I know the sun's probably smaller than a supermoon, but 800mm or so is probably long enough for an aps-c (1200mm FF or so?) if you want to get a nice border around it like that palm-tree shot, 200mm x2 = 400mm and a bit of cropping on a 7D should be just nice.

[Kayaker72]

Enro,

There is a thread on this over at CR. They mention Baader filter paper. I just picked some up from http://www.astro-physics.com/. There also seem to be several filters made from the material for telescopes. I found some "astrozap" filters here: http://www.optcorp.com/productList.aspx that seem to be from the same material.

Maybe you have a local photography/telescope store that has some of this material.

Good luck,
Brant

[conropl]

If you know anyone that is a welder, you could use welding glass for your filter.

[Kayaker72]

Thanks Pat. I have seen that you need Shade No. 14 for solar viewing. I've been looking, but haven't yet found what the basis is for the shade numbers. I actually have ordered some shade number 12 from mcmaster.com, but had trouble finding shade number 14. Most welding glass out there seems to be shade #5-8. So, be careful if using welding glass.

For comparison, the Baader filter/film for photography is rated at ND 3.8 (12 2/3 stops). But when I talked to the people at astro-physics they really emphasized that was for photography only and if there was any chance of me looking through the viewfinder, to use the filter/film rated "visual" which is ND 5.0, so 16 2/3 stops.

I am a complete novice about this, so I am being conservative. But it also seems to be about more than just number of stops and that you have to be very careful about blocking non-visible light, both IR and UV.

[conropl]

Brant:
I agree... you do have to be careful when looking at the sun. The last time there was a solar eclipes, we watched at work using the glass that we use to look at 3000 deg F molten metal and 5000 deg F molten zerconia. I always thought it was welding glass, but maybe not. I will check to see where they get it from and what the spec is.

[conropl]

...Most welding glass out there seems to be shade #5-8. So, be careful if using welding glass.

I am a complete novice about this, so I am being conservative. But it also seems to be about more than just number of stops and that you have to be very careful about blocking non-visible light, both IR and UV.

See link below. Welding glass in shades of 10-15. I am not an expert,but it sounds like welding glass in the range you are looking for is avaialble.
http://www.phillips-safety.com/store...hp?cPath=41_68

I saw what was called welding safety glasses that were shades of 5-8, but I do not think those would ever be considered good enough for arc welding.