Sky and Telescope - August 2017 - 16

Eclipse Photography

p DIY FILTER HOLDER One key to successfully capturing rapid-fire
events at the beginning and end of totality is the ability to quickly and
easily remove and replace a solar filter without disturbing the aim of your
photo setup. Cardboard, masking tape, a little hot-melt glue, and black
spray paint were all the author needed to make this simple slide-out
holder for his Baader AstroSolar filter material.

* If your camera has a ﬂash, turn it off. Except for very speciﬁc photo setups where extra light is needed to illuminate
the foreground, a ﬂash offers no advantage for eclipse photography and will almost certainly annoy others around you.
* You should also disable any auto-ISO setting your camera
may have. Auto ISO is designed to boost a camera's sensitivity in low-light situations - but at the expense of increasing
the digital noise in images. While an eclipse scene might be
dark overall, tricking your camera to use a high ISO setting,

the detail you're generally trying to capture, including the
corona, is bright enough to record well with a lower (and thus
low-noise) ISO setting. For most cameras this falls between
ISO 50 and 400.
* If your camera can save images in RAW format, use it.
Capturing images is only half of the story when it comes
to creating an eclipse masterpiece. The other half is image
processing, and the best results always come from processing
RAW-format images.
* My last generality involves the focal length of lenses. In this
article, as well as other material you might encounter, most
lenses are stated has having an equivalent focal length.
The issue is that many modern cameras use an APS sensor that's smaller than a standard 35-mm frame, essentially
cropping and enlarging the view by 1.5×. This is known as
the crop factor. If your camera has an APS-format sensor,
you need to do the math to determine the real focal length of
the lens you want to use to achieve a given ﬁeld of view. For
example, a 200-mm lens on an APS-equipped camera has a
ﬁeld of view equivalent to that of a 300-mm lens on a fullframe 35-mm camera (200 × 1.5 = 300).

Close-Up Photos
Photographs of the partial eclipse, Baily's Beads, the diamond
ring, and the chromosphere don't need to cover a ﬁeld of view
much larger than the ½° diameter of the Sun's disk. As such,
focal lengths up to 2,000 mm are reasonable. On the other
hand, anything shorter than about 400 mm will sacriﬁce

200 mm 135 mm

400 mm 270 mm

500 mm 330 mm

1,000 mm 670 mm

1,500 mm 1,000 mm

2,000 mm 1,350 mm

p CHOICE OF LENS To capture coronal detail, you'll need a telephoto lens with a focal length of at least 300 to 400 mm. This comparison shows
what some typical lenses will show during totality. Note: The blue values are for cameras equipped with APS (cropped-frame) sensors.

A U G U S T 2 0 1 7 * SK Y & TELESCOPE

BOT TO M: FRED ESPEN A K (6)

Lens Focal Length vs. Field of View

Sky and Telescope - August 2017

Table of Contents for the Digital Edition of Sky and Telescope - August 2017