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ASTRONOMICAL ADVENTURES

Eclipse Tours and More


UPCOMING

2017

OREGON
RIVER
CRUISE

USA Total Solar Eclipse
(2017 Aug. 12)
Details Here!


USA
TOTAL SOLAR
ECLIPSE

USA Total Solar Eclipse
(2017 Aug. 21)
Details Here!


Also See 2017
PREHISTORIC ENGLAND TOUR



PAST TOURS

Indonesia Total Solar Eclipse

Indonesia Solar Eclipse
Makassar Strait
[2016 Mar. 9]


Australia Total Solar Eclipse

Australia Solar Eclipse
Queensland, Kangaroo Isl.
and Adelaide
[2012 November]


Norway Northern Lights Cruise
to Above Arctic Circle
[2010 March 10–21]

China Total Solar Eclipse
2009 China Total
Solar Eclipse

[2009 July]




EXAMPLES
OF OTHER
PAST TOURS

(Links available for some but some links may not work correctly)

Caribbean Cruise Eclipse
[1998 Feb]
African Eclipse Safari
[2001 Jun]
Australia Outback
Solar Eclipse

[2002 Dec]
Transit of Venus
Italy, Athens & Crete

[2004 June]
Hybrid Solar Eclipse
Tahiti Cruise

[2005 April]
Astronomy, Archaeology
& Geology of Arizona

[2005 September]
Egypt Treasures &
Solar Eclipse

[2006 March]
China &
Solar Eclipse

[2009 July/Aug]
RELATIVE IMAGE SIZE OF SUN

Photographing the eclipsed Sun involves (1) image size, (2) exposure time and
(3) exposure times for no blurring without a clock drive. Here we consider Item #1.


WARNING: Do not observe or photograph the Sun out of eclipse or in partial eclipse without safe solar filters. (No filter needed for totally eclipsed Sun). See Eye Safety

The image size of the Sun when photographed depends on the focal length of your camera (or telescope) focal length. Longer focal lengths produce larger images. Typical focal lengths (say 50 to 100 mm) produce very small images compared to the picture frame. For example, the actual image size of the Sun for a 50 mm lens is 0.45 mm. Since a 35 mm frame is about 36 mm wide, the Sun's image would be about 13% of the width.

Small images may be acceptable if the photographer wants multiple images of the Sun in the same frame. However, producing images that show some detail requires much longer focal length.

An Approximate Formula to Compute Sun's Image Size

Image Size (mm) = Focal Length (mm) / 107

The following figure shows the relative size of the Sun's image of a totally eclipsed Sun (with a hypothetical corona) compared to the frame of a 35 mm camera for a range of focal lengths.

(For actual diameters in mm see the table on Exposure Times for No Trailing.)

Focal lengths are given both for full-frame 35 mm cameras and digital cameras that use
a reduced sensor typically about 60-70% of a 35 mm frame width.



Lens Focal Length vs. Image Size for Eclipse Photography
(Click image for larger size)

Figure from F. Espenak & J. Anderson, March 2008
Total Eclipse of 2009 July 22, NASA/TP—2008—214169, Fig. 24.

Focal Length vs. Image Size

Therefore, the same lens produces an image that fills up more of the frame in cameras with a reduced sensor. This effectively makes a 35mm lens on a reduced sensor camera effectively equal to about 1.5x the lens focal length. (See box below.)

Many digital cameras today use an image sensor that is smaller than a full-frame 35 mm camera. Most of these smaller sensors (including Canon, Nikon and Sony) have Advanced Photo System, Type-C sensors (APS-C). For example a Canon EOS 50D sensor is 14.9mm x 22.3mm compared to a 24mm x36mm full-frame. This requires multiplying the focal length of a lens on such a camera by an appropriate lens factor to obtain the equivalent focal length on a full-frame 35 mm camera. Usually the factor is 1.5x though Canon cameras have lens factors of 1.6x. Other digital cameras (e.g., Olympus) use Four Thirds type sensors (13.0mm x 17.3mm) requiring a 2x lens factor.



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