"Further Info" wrote in message
...
On Wed, 22 Jul 2009 20:00:47 +0530, "mianileng"

wrote:


"David J Taylor"

wrote in message
. com...
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.


During those moments when I did think about the effect of the
sun's image on the sensor, especially when I removed the filter,
I felt that, since the image on the monitor was not bright enough
to cause flare, it was probably not intense enough to damage the
sensor.

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.


You've confirmed something that's been in my mind after the
event. It was frustrating not to be able to see the progress and
the peak of the eclipse, but I too felt that the clouds made the
photos more interesting.

One observer team, though, was even less fortunate than we were.
The state's Science Promotion Department and the local astronomy
club led the team of more than a hundred individuals to a hill
top that they thought would be a good observation point. The
thick fog that enveloped most of the town lasted much longer at
their location than it did at ours. They never caught even a
glimpse of the whole thing. One local newspaper printed a photo
of the team because they didn't have a single photo of the
eclipse itself.