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-   -   Shooting the upcoming eclipse - Aug 21 2017. A rough guide. (http://www.photobanter.com/showthread.php?t=130371)

PeterN[_6_] May 18th 17 04:43 AM

Shooting the upcoming eclipse - Aug 21 2017. A rough guide.
 
On 5/17/2017 9:57 PM, RichA wrote:
This total solar eclipse's path is right across the U.S., very rare.

For solar filtration (since only insane people look directly at the sun, or shoot it with an unfiltered lens), you can get filters (metallized glass) or filter material (metallized mylar) from companies like: Baader, Seymour Solar, Thousand Oaks Optical and camera stores like B&H, Adorama and telescope companies like Orion (Calif) or Astronomics. Both types come with a ring that slips over the end of the lens or telescope end. Or, the mylar sheeting can be bought without a frame and simply adhered in place. Just don't let it slip-off the end of the lens.

http://www.astronomy.com/2017eclipse

Your six choices for filtering a

-Metallized glass in a frame to fit your lens, (Thousand Oaks, Seymour Solar)or some of the camera/telescope companies. More expensive, around $50 and up.
-Metallized mylar or "solar film." Cheaper, you can get a sheet to make a filter for $15.00 and up. Good optical quality.
-A solar diagonal (right angle viewer) for your telescope. Only works on refractor (lens telescopes, do NOT use them on mirrored scopes) and is expensive $300 and up. Provides the best images. Lunt sells them as well as Baader.
-A dedicated solar telescope from Meade or Lunt. These provides selective-frequency views of the sun (hydrogen alpha, show the flares coming off the surface
-Cheap solar "sunglasses" designed with the mylar material to filter-out solar radiation so it's safe to see. Beware of ordering this stuff off unknown sources on Ebay, like China. No guarantee what they sell works or is safe to use. Make sure the film is a name brand, like
-Projecting an image thought a REFRACTOR telescope onto a white screen made of cardboard or other white material. This is a cheap way to do it, but it can destroyed any telescope eyepiece that has internally-cemented lenses, you have to use and old style telescope eyepiece like a Huygens or Ramsden that just use single element optics. If the material is smooth, like a foamcore board, it produces a surprisingly good image which can be shot freehand.

Focal lengths:
Roughly, the sun will fill a 35mm frame top to bottom using a 2000mm lens. Which means 1500mm on an APS and 1000mm on a m4/3rds. Or you can use a shorter lens but the sun won't fill the frame. You can also filter a wide angle camera lens and do a sequential shot which will produce multiple images tracing a path as the sun moves in the sky.
However, if you want to shoot totality (Moon completely covers the sun), where the sun is blacked out and the much wider (up to 3 degrees wide) solar corona (halo) is visible, you need a lens with about 400mm focal length. Shooting the corona is difficult, can only be done at totality and only with an unfiltered lens, which is dangerous for the viewer and the camera. Also some EVF's on mirrorless cameras will be ruined by exposing them to the bare, unfiltered sun, anything with an OLED EVF.

Do not bother trying to shoot freehand, use a tripod. Exposure times vary hugely from partial eclipse phase to full, so get the filter and practice on the sun before the eclipse to get the hang of shooting it. Since only the sun is visible and everything around it is black (filter is like a super-strong ND) you can roughly point the camera by looking at the ground and orientating it on the tripod until the camera's shadow on the ground is minimized. With a telescope, you can filter (make sure you do it! or you could wreck it or burn you self) the telescope's wider-angle "finder scope" so you can more easily site the sun.

A driven astronomical mount (which tracks the sun as it moves) is superior to a camera tripod, but not essential. Shoot lots of images. Seeing conditions vary wildly during daytime so one second you get a sharp, steady image, the next, it can be slightly blurry, depending on the size of the lens front element(impacted by heat waves and atmospheric density changes the larger it is).


Thanks for the reminder.


--
PeterN


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