Film or Digital Camera

Bottom line:

Film can be very frustrating.. even for those who have considerable
experience working with it.

Simple widefield shots are easy, a 35mm camera with a 50mm lens pointed in just
about any direction on about any type of a mount will produce some amazing
results.

Dedicated astro-CCDs require a learning curve, usually a bit of $$$, and
various other gear (laptops etc)

In my experience the learning curve for a dedicated astro camera is less than
with a digital camera if you want to take photos of DSOs. Not stacking or
processing required and because of the sensitivity of the camera. Focusing is
easier because you can view the real image directly on the screen. Focusing a
consumer digital camera is tricky because one must focus both the camera and
the telescope.

Your aunt Matilda's digital camera (the one she brought to the family
picnic) can provide surprisingly good astro-images with relatively little
effort.

For photos of the planets, when used in conjunction with a telescope, a
consumer camera can provide some nice photos, but it ain't all that easy, good
photos of Jupiter and Saturn seem to require a great deal of processing. And
most Aunt Matilda cameras do not allow the operator to have total control of
the brightness so getting the exposures correct can be difficult.

And taking photos of DSOs is not easy. There are many fine images produced with
some of the more sophisticated consumer cameras but it does require significant
effort.


Finally, if something is too much work, too epen$sive, or just too darned
frustrating, what do you think the chances are that you will enjoy it?!? )


It is my somewhat limited experience that for photos of the bright planets,
consumer level digital cameras are very nice. But past this level, when
tracking and longer exposures are required, film and dedicated CCD cameras are
actually easier to use.

The cost of a cooled SAC-8 camera is not too different from that of a consumer
camera which allows the operator to control the focus, the shutter speed (bulb
exposures needed here) and aperture. The advantages of the sensitivity of the
cooled CCD camera are significant here and really quite amazing. PLus most are
16 bit which means there is a great deal more dynamic range than is possible
with the 3 8 bit channels of a color digital camera.

Jon

"Chris L Peterson" wrote in message
...
On Sun, 27 Jul 2003 21:48:04 +0100, "Roger Hamlett"
wrote:

... Even with an 'uncooled'
chip, you can massively reduce the noise, by taking a series of 'dark
frames', combining these (median combine), and subtracting this from an
image of the same duration.

Sorry if I'm being pedantic, but this is often stated and entirely
incorrect.
Noise can never be reduced, even a tiny bit, by subtraction. There are two
primary systemic noise sources, dark current noise and readout noise. The
first
is reduced by lowering the chip temperature, the second is fixed. The
effects of
readout noise can be reduced by reducing the number of images that are
stacked,
and by increasing the length of individual exposures. Subtracting a dark
frame
merely removes a bias level, leaving behind exactly the noise that was
already
there. This can be done with film, also, although the non-linear response
of
film makes it a bit trickier.

There is also statistical noise caused by the uneven rate that photons are
collected. This is minimized only by collecting more photons.
Fair comment.
It is stated, because the commonest things that people see, and refer to as
'noise', when imaging, are the slow increase in signal level from thermal
sources in the camera (comprising a time 'sum', of the thermal noise), and
the bias. Both of these are reduced by subtraction. However the random
variation in these levels remain present, but the visual effect is far less
noticeable. :-)

Best Wishes

Fair enough... but the same shots are also easy with digital cameras... and
no waiting to to see if they came out okay (or while airplanes zip through
the images or clouds move start in during the l-o-o-o-n-g wait). Here's a
single 5-minute digicam shot:

Very few Digicams will handle 5 minute exposures. The Canon D60 is certainly
not the ordinary consumer camera.

But my guess is that a cooled camera would require a much shorter exposure time
than the Cannon.

My
intervention in this thread was merely to point out to the original poster
that he may already have all that's needed to start having a lot of
astro-imaging fun and success!

I think my point is that few people have a Digital SLR hanging around that is
of the level of the D60, about $1300 for just the body,

My guess is that if someone has a camera laying around that is capable of doing
serious astrophotography, it is much more likely that it is an old SLR like a
Minolta SRT-101 or a Pentax or some such thing that might be found at a garage
sale for $25 or so....

The typical consumer digital camera has severe limitations when it comes to
photographing DSOs and the like.

jon

Having read most of this thread, I feel I must stop lurking and put my own
expertise to use! Beware of stacking images from small CCD's, such as those
used in web cams. Artefacts, caused by transconductance between the cells on
these small substrates, can be a real problem. They are NOT noise, but are
associated with small charge build up on adjacent cells. Thus the problem
occurs with low contrast (or signal) images. These appear as extended nebulae,
or sharper boundaries on low contrast parts of the image. Normally, this
problem does not occur, as the signal is too small to make an appearance!
However, stacking a large number of frames will make this low level signal
appear. I must say, they do look like the real thing, but they are NOT in
response to photons hitting the CCD. Thus you see images that have apparently
picked up more nebulosity than the space telescope! The same sort of problem
can also occur by over-processing the image using PSP or other paint packages.

Geoff (Electronics engineer turned teacher)