On Wed, 22 Jul 2009 20:00:47 +0530, "mianileng"
wrote:


"David J Taylor"

wrote in message
om...
mianileng wrote:
[]
Here's the very first shot, taken about 10 minutes after the
moment of maximum eclipse:
http://s48.photobucket.com/albums/f2...-22Jul09_1.jpg

Congratulations! And on not burning out the sensor or shutter!
G

Oh yeah. The thought crossed my mind once or twice. But I was so
busy twirling dials to compensate for the constantly changing
light that I didn't stay focussed (no pun intended) on that side
of the matter for long.


You'd be surprised just how long you can focus the full intensity of the
sun on a camera's sensor, with even a wide-angle lens let alone telephoto
focal-lengths, before it will burn a spot in it. The dyes in the Bayer
filter going first, long before any damage to the sensor itself.

Do some calculations on radiation intensity and the heat-sink capabilities
of the sensor's matrix. These calculations were done many years ago in the
sci.astro.amateur newsgroup. Perhaps you could search for that discussion
using Google's "group" search. From vague memory, you will grow bored of
trying to focus on the sun long before it will do any damage (approx. 6
mins. if I recall). This is, of course, when the image of the sun is
focused on the sensor itself, and in such a tight image that it comes from
a wide-angle lens at widest apertures. Telephoto affords many more minutes
of focusing and composing time due to the enlarged image of the solar-disk
spreading its radiation over a wider area. The focal-plane shutters of SLR
design cameras are much more prone to damage than leaf-shutter (P&S)
cameras because the leaf-shutter is in a mid-distance optical path, not at
the point of focus.

That's a fairly nice image of a partial-eclipse, btw. I recall one total
solar-eclipse that I went to photograph in N. America back in the 1970's.
The slight bit of overcast greatly added to the event. It acted as a
rear-projection screen so we could see the diffraction bands pass through
the sky as rainbow bands of colors rapidly washing the full sky from
horizon to horizon. Further adding to the effects witnessed.. Amongst other
effects that the overcast revealed that "clear sky" observers would never
get to enjoy. Like the onrush of the sunset colors against the inverted
sky. (Total-eclipse chaser will know what I mean by an "inverted sky". It's
actually quite freaky, no matter how much you know in advance of what is
going on.) I never wish for perfectly "clear skies" when chasing down a
solar-eclipse now. I learned my lesson from those happenstance
overcast-skies and wouldn't trade that same experience for the world.