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Solar disc size at various focal lengths
Copyright ©2007 Gabriel Ditu
How to photograph a solar eclipse



 bullet Safety Issues

The Sun can be viewed safely with the naked eye only during the total phase of the solar eclipse. Even when 99% of the Sun's surface is covered, the remaining crescent cannot be viewed safely. Remember: Galileo Galilei lost his sight due to solar observation.

Safe devices to observe the Sun:
  • Projection of a pinhole on a white surface placed more than half a meter away
  • Filters dedicated for solar obsevation - astronomical shops

 bullet Equipment

To phograph a solar eclipse you need to use a (D)SLR camera attached to a telephoto lens or to a telescope. For a decent size of the solar disc you need to use a focal length between 500mm to 2000mm. To get an idea of how the image will look using different focal lengths look at the pictures on the film strip attached.

See also my Astrophotography Calculator

Focal Length
Field of View
Size of Sun
28mm
46o x 65o
0.25mm
35mm
38o x 54o
0.3mm
50mm
27o x 40o
0.45mm
70mm
19o x 29o
0.6mm
105mm
13o x 19o
0.95mm
135mm
10o x 15o
1.2mm
200mm
7o x 10o
1.8mm
400mm
3.4o x 5.1o
3.7mm
500mm
2.7o x 4.1o
4.6mm
1000mm
1.4o x 2.1o
9.2mm
1500mm
0.9o x 1.4o
13.8mm
2000mm
0.7o x 1.0o
18.4mm


 bullet Calculating Exposures

Best way to determine the correct exposures for partial phases of the eclipse is by trial and error. Make a research to find out the angle of the Sun in the sky because the exposure depends on how close the Sun is to the horizon, since the intensity of the Sun diminshes with the increased atmospheric path length (less than about 20deg from the horizon).

Use the following table as rough guide to calculate the exposure:


Solar Eclipse Exposure Guide (after Fred Espenak)
ISO   fNumber
25 1.4 2 2.8 4 5.6 8 11 16 22
50 2 2.8 4 5.6 8 11 16 22 32
100 2.8 4 5.6 8 11 16 22 32 44
200 4 5.6 8 11 16 22 32 44 64
400 5.6 8 11 16 22 32 44 64 88
800 8 11 16 22 32 44 64 88 128
1600 11 16 22 32 44 64 88 128 176
 
Subject Q Shutter Speed
Solar Eclipse                    
Partial-4ND 11 - - - 1/4000 1/2000 1/1000 1/500 1/250 1/125
Partial-5ND 8 1/4000 1/2000 1/1000 1/500 1/250 1/125 1/60 1/30 1/15
Baiy's Beads 11 - - - 1/4000 1/2000 1/1000 1/500 1/250 1/125
Chromosphere 10 - - 1/4000 1/2000 1/1000 1/500 1/250 1/125 1/60
Prominences 9 - 1/4000 1/2000 1/1000 1/500 1/250 1/125 1/60 1/30
Diamond Ring 5 1/500 1/250 1/125 1/60 1/30 1/15 1/8 1/4 1/2
Corona-0.1 Rs 7 1/2000 1/1000 1/500 1/250 1/125 1/60 1/30 1/15 1/8
Corona-0.2 Rs 5 1/500 1/250 1/125 1/60 1/30 1/15 1/8 1/4 1/2
Corona-0.5 Rs 3 1/125 1/60 1/30 1/15 1/8 1/4 1/2 1sec 2sec
Corona-1.0 Rs 1 1/30 1/15 1/8 1/4 1/2 1sec 2sec 4sec 8sec
Corona-2.0 Rs 0 1/15 1/8 1/4 1/2 1sec 2sec 4sec 8sec 15sec
Corona-4.0 Rs -1 1/8 1/4 1/2 1sec 2sec 4sec 8sec 15sec 30sec
Corona-8.0 Rs -3 1/2 1sec 2sec 4sec 8sec 15sec 30sec 1min 2min


 Exposure formula: t = f2/(I*2Q)
where:  t=exposure time (seconds)
f=f/Number or focal ratio
I=ISO speed (film speed)
Q=brightness exponent

 Abbreviations: ND = Neutral Density filter; Rs = Solar Radii


See also my Astrophotography Calculator


 bullet Essential Accessories

Other essential items needed for a solar eclipse include:
  • A sturdy tripod with a head capable to allow taking a picture under any angle.
  • A cable release
  • Torch
  • Spare batteries (to be installed on eclipse day)
  • A shade cover for the camera
  • A timer, watch, GPS or laptop

 bullet References

Fred Espenak - Mr Eclipse
Eclipse-Chasers.com
NASA - Eclipse Home Page
©Copyright 2017 Gabriel Ditu