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
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 |
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
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
References
Fred Espenak - Mr Eclipse
Eclipse-Chasers.com
NASA - Eclipse Home Page
|
