Re: Starfields from "bulb" and RAW?

In article <1i5ipqs.1jnslj51eb81moN%usenet@xxxxxxxxxx>, usenet@xxxxxxxxxx
says...

NightGuy <nightguy67@xxxxxxxxxxxxxxxx> wrote:

Good day, and thanks in advance for all help.

Can someone either confirm or refute an asumption that a digital camera
(7MP and 8MP) can capture starlight in a widefield shot using the camera's
"bulb" shutter setting and RAW image format?

Assume the camera is tripod mounted, and the camera's timer is used to
avoid vibration of pressing the shutter release.

Utilizing this method, I was able to get some decent shots of a moon/Venus
conjunction using an old 3MP camera. While stars (and even their colors)
were visible on the LCD viewscreen during attempted widefield starfield
shots, stars would not appear in a maximum 4-second exposure JPG image.

So, I'd like to know if higher mega-pixel resolution along with longer
exposures and uncompressed imaging would achieve the desired ends.

The truth of the matter is that if you go longer than about 4 seconds,
you'll end up with star trails. Whether this is what you're looking for
or not is something you don't specify. You can, for instance, stack a
number of 4-second exposures to get a whole star trail exposure, with
some obvious caveats (multiplied noise floor, gaps in star trails
representing the moments between exposures).

Bulb mode makes this easier to accomplish, since you have an arbitrarily
long exposure. Shooting RAW gives you wider lattitude and the
opportunity for a sharper image. Image resolution doesn't have that much
to do with it, though of course the more pixels the better. :-)

Some hints: <http://www.astropix.com/HTML/I_ASTROP/TRIPOD/TRIPOD2.HTM>

If you want the stars without their trails, you'll have to come up with
a rig that compensates for the movement of the earth relative to the
stars.

--
http://www.xoverboard.com/cartoons/2007/070416_argument.html

Thanks Paul; and thank you to everyone else who replied, and thanks for the
sample images. There was good advice and information to read through.

I have been an amateur astronomer since the early '90s, but I spend most of my
time observing and have done little astrophotography. When I do take the time,
I use my old Pentax SLR either piggybacked or through the scope.

The matter really is this: Although it still works wonderfully for that "Kodak
moment", I've been planning on upgrading from my *old* Kodak 6340 P&S. Since I
don't have as much time for photography as I would like at the moment, I can't
justify to myself getting a DSLR just yet. So, I have been considering getting
the Olympus SP-550UZ (and now the SP-560UZ is in the mix), the Fujifilm FinePix
S8000fd, or the Panasonic FZ18. Most of my photography would be in daylight or
indoors, and relying on the high 18x zoom at times, but there would be the
occassional time when I would want to shoot some celestial events or wide angle
starfields without having to lug out all sorts of gear. (Opinions on the
cameras are welcome also!)

So, basically, the initial question was if more megapixels, uncompressed RAW
imaging, and lengthier shutter times using a "bulb" setting was essential,
useful, or moot in regards to capturing star images. Correct me if I'm getting
the message wrong, but it seems RAW and "bulb" -could- be useful, but not
necessary. Just boost the ISO, go longer than 4 seconds, and possibly stack
images.

(Example of unmodified 4x zoom 3.1MP Moon/Venus conjuction taken with the 6340:
http://home.att.net/~nightguy67/photos/astro/moon_venus_full.jpg
The maximum 4-second exposure on the 6340 allows stars to barely be detected)

Thanks again to all.


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