Questions, Telescope, Digital camera

HI All, My name is Mark Flo and I live in the Los Angeles area.

For a long time I have been thinking about a telescope. LA has bad light
problems but I like driving to the desert with binoculars for comet and
meteor shows.

Also I have been thinking about a Telescope. This brings up about 250
questions of which I will post only a few. (grin)

Is there a telescope below $500 that you can attach a digital camera to, and
is there digital camera that is good at this kind of exposure below $500?
Can you take LONG exposures with a digital camera?

Will the MARS rovers find the lost B-17 I saw in the enquirer? (ops off
subject sorry)

I know this can get very in-depth, this is just backyard watching .

"Mark" wrote in message
...
HI All, My name is Mark Flo and I live in the Los Angeles area.

For a long time I have been thinking about a telescope. LA has bad light
problems but I like driving to the desert with binoculars for comet and
meteor shows.

Also I have been thinking about a Telescope. This brings up about 250
questions of which I will post only a few. (grin)

Is there a telescope below $500 that you can attach a digital camera to,
and
is there digital camera that is good at this kind of exposure below $500?
Can you take LONG exposures with a digital camera?

You can attach a digital camera to almost anything and get some results
doing so. It depends on what you expect and what you are taking pictures of
that determines if the telescope is passable. As an example, you could take
digital pictures of the moon with almost any telescope (even a cheap
department store scope) and any digital camera (even an inexpensive web
cam). However, if you want to take pictures of deep space objects
(galaxies, nebula & planetary nebs), you will need to spend a bit more on a
telescope and much more on a digital camera. Regarding the length of
exposure with a digital cam: Yes you can take long exposures, but you can
not do this with the inexpensive point and shoot cameras. The least
expensive camera that I know of is the Canon digital rebal at just about
$1,000. Sorry to give you the bad news.

Al



Will the MARS rovers find the lost B-17 I saw in the enquirer? (ops off
subject sorry)

No, the B-17 is on Venus.:-)



I know this can get very in-depth, this is just backyard watching .

"Al" wrote in message
...

*snip*

exposure with a digital cam: Yes you can take long exposures, but you can
not do this with the inexpensive point and shoot cameras. The least
expensive camera that I know of is the Canon digital rebal at just about
$1,000. Sorry to give you the bad news.

I have a friend who has had very good luck with a Nikon Coolpix 5400, which
retails more in the $500 range but does allow for exposure timing up to 10
minutes.

Do CCDs used in digital cameras exhibit reciprocity failure, as do
many silver-based photographic films?
Regards to all, Alan.

On Mon, 24 Nov 2003 22:28:05 GMT, "Alan R. Betz" wrote:

Do CCDs used in digital cameras exhibit reciprocity failure, as do
many silver-based photographic films?
Regards to all, Alan.

No, nor do CMOS detectors. This is one factor in the much higher sensitivity of
electronic detectors over film.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

"Alan R. Betz" wrote in message
...
Do CCDs used in digital cameras exhibit reciprocity failure, as do
many silver-based photographic films?

No.

Also, newer films have far less reciprocity failure than older ones. Elite
Chrome 100 and 200, for instance, are much better than the old
"Spectroscopic" emulsions that were made for observatories.

Even the newest and best films have reciprocity issues. While this
isn't an issue generally for normal daytime short exposures..it
becomes problematical for exposures longer than a few seconds. CCD
(especially the non antiblooming types) are directly lineal...twice
the exposure time yields twice the photons captured. This is one of
to big advantages of CCD...the other is that while film is only about
10% efficient at capturing photons...CCDs are close to 95% efficient.
Big disadvantage of CCD is that they are expensive...especially in big
chip sizes approaching the 1" x 1 1/2" dimension of a 35mm image.
That is quickly changing with competition and new chip development.

The other big issue with long exposure CCD imaging is the noise
generated by the electronics themselves. Longer exposure are made
possible by cooled chips and this is most commonly provided by a
Peltier cooler...sort of an electronic refrigerator. The need for that
contributes to a lot of the cost of an astronomy specific CCD camera.
But this issue will go away some time in the future. I am a
professional photographer who still mostly uses film in my
business...but not in astrophotography. Within the near future film
will mostly go the way of 8 track tapes and records for most
people...pro or amateur.

Bob Berta


"Alan R. Betz" wrote in message ...
Do CCDs used in digital cameras exhibit reciprocity failure, as do
many silver-based photographic films?
Regards to all, Alan.

(Robert Berta) wrote in message . com...
Even the newest and best films have reciprocity issues. While this
isn't an issue generally for normal daytime short exposures..it
becomes problematical for exposures longer than a few seconds. CCD
(especially the non antiblooming types) are directly lineal...twice
the exposure time yields twice the photons captured. This is one of
to big advantages of CCD...the other is that while film is only about
10% efficient at capturing photons...CCDs are close to 95% efficient.

I don't think that film is that efficient. If I do remember right the
efficency of the best TP hypered film is equivalent to a 5% QE. As for
the CCD efficiency only the very high end back illuminated CCD can
(maybe) reach such a value. Normally the CCD efficiency is in the
range 40% to 60% (it drops quite a lot with short wavelengths) with
peaks approacing 80%.

Big disadvantage of CCD is that they are expensive...especially in big
chip sizes approaching the 1" x 1 1/2" dimension of a 35mm image.
That is quickly changing with competition and new chip development.

The other big issue with long exposure CCD imaging is the noise
generated by the electronics themselves. Longer exposure are made
possible by cooled chips and this is most commonly provided by a
Peltier cooler...sort of an electronic refrigerator. The need for that
contributes to a lot of the cost of an astronomy specific CCD camera.

It doesn't. The cost of the cooling system is rather low compared with
that of the mechanics and the electronics.

Andrea T.

"andrea tasselli" wrote in message
om...
(Robert Berta) wrote in message
. com...
Even the newest and best films have reciprocity issues. While this
isn't an issue generally for normal daytime short exposures..it
becomes problematical for exposures longer than a few seconds. CCD
(especially the non antiblooming types) are directly lineal...twice
the exposure time yields twice the photons captured. This is one of
to big advantages of CCD...the other is that while film is only about
10% efficient at capturing photons...CCDs are close to 95% efficient.

I don't think that film is that efficient. If I do remember right the
efficency of the best TP hypered film is equivalent to a 5% QE. As for
the CCD efficiency only the very high end back illuminated CCD can
(maybe) reach such a value. Normally the CCD efficiency is in the
range 40% to 60% (it drops quite a lot with short wavelengths) with
peaks approacing 80%.
I'd suspect that 'film', when quoted in this context, probably includes
black and white observatory plates, using refrigeration, and hypering. The
highest figure I have ever seen quoted, was an equivalent of about 8% Qe for
these.
Some technologies on CCD's, that may well have other problems (visual
artefacts), do push normal CCD's up a little (microlenses). So chips like
the KAF0402E, manage a 'peak' of about 85%, and values over 50%, for the
majority of the visual spectrum. Realistically the overall improvement is in
the same ratio as quoted, it is just that both figures being given are
pretty much the 'absolute max' figures for the technologies, rather than
figures that are likely to be achieved. :-)

Big disadvantage of CCD is that they are expensive...especially in big
chip sizes approaching the 1" x 1 1/2" dimension of a 35mm image.
That is quickly changing with competition and new chip development.
Unfortunately this change is slowing, as CMOS technology is becoming the
'favoured' mass production sensor. Astronomy is such a small part of the
market, and the slightly higher noise, and reduced sensitivity, doesn't
really affect normal camera applications. CCD prices, are showing signs of
rising a little at the moment (as are LCD screens).

The other big issue with long exposure CCD imaging is the noise
generated by the electronics themselves. Longer exposure are made
possible by cooled chips and this is most commonly provided by a
Peltier cooler...sort of an electronic refrigerator. The need for that
contributes to a lot of the cost of an astronomy specific CCD camera.

It doesn't. The cost of the cooling system is rather low compared with
that of the mechanics and the electronics.
Very true. The same technology, ships as 'electric fridges' for
cars/caravans, and in this application the units are costing peanuts.

Best Wishes