Digital SLRs

Is there an easy way to tell if a digital SLR allows access to the raw
CCD data so that one can do digital noise reduction and false color image
stacking ?

In terms of $/pixel the devices made for astrophotography just don't seem
competetive with digital SLRs. Or is the problem the color CCDs in the
cameras as opposed to monochrome CCDs ?

Tom Rauschenbach wrote:

Is there an easy way to tell if a digital SLR allows access to the raw
CCD data so that one can do digital noise reduction and false color image
stacking ?

Yes, read the specifications. But you needn't bother, they all do. As
do many mid-range cameras. The name varies, but it generally has
'raw'/RAW in the name.

In terms of $/pixel the devices made for astrophotography just don't seem
competetive with digital SLRs.

Economies of scale.

Or is the problem the color CCDs in the
cameras as opposed to monochrome CCDs ?

What problem?


Tim
--
Shares are your votes in a pigologocracy.

On Thu, 13 Oct 2005 21:40:53 -0400, Tom Rauschenbach
wrote:

Is there an easy way to tell if a digital SLR allows access to the raw
CCD data so that one can do digital noise reduction and false color image
stacking ?

Not really. Quite a few cameras these days are able to save in a
proprietary raw mode, but in many cases you may still be dependent on
their own or third party software to extract the image, and it may not
really be raw data.


In terms of $/pixel the devices made for astrophotography just don't seem
competetive with digital SLRs. Or is the problem the color CCDs in the
cameras as opposed to monochrome CCDs ?

Well, DSLRs are sold in very high volume compared with astrocameras,
which makes them comparatively inexpensive. But they are also much less
capable. High quality astroimages require very low noise cameras,
something only possible by active cooling. Also, color sensors are not
capable of high end results (and no DSLR has a monochrome sensor). High
quality color images are made by combining image made through filters
with very carefully controlled passbands designed specifically to
capture common narrow band emissions. Also, processing color images from
one-shot color cameras is much more difficult than processing color
images made through separate filters.

That said, some DSLRs produce results that are not too bad, and with
their low prices offer a reasonably inexpensive entry into astroimaging.
But the quality of their images is still a long ways from reaching what
cooled astrocameras are capable of. Imagers who become serious about
their hobby will quickly outgrow a DSLR.

_________________________________________________

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

Chris L Peterson writes:

That said, some DSLRs produce results that are not too bad, and with
their low prices offer a reasonably inexpensive entry into astroimaging.
But the quality of their images is still a long ways from reaching what
cooled astrocameras are capable of. Imagers who become serious about
their hobby will quickly outgrow a DSLR.

Along that line, does anyone here have any experience or opinions on
the Canon EOS 20Da? It claims to be a 20D with some extra tweaks
for astrophotography (and US$900 higher price tag).

I ran into the reference to it while looking at the B&H site to see
what it was asking for a new DSLR. It may have been reviewed by one
of the astronomy magazines but if so I don't recall having seen it.

To see the full description of the camera go to the B&H site
http://www.bhphoto.com -- search "Digital photography", "SLR digital
cameras", select Canon, and then search the page for "astro". There
is only one entry on this page for the 20Da.

No, I'm not planning to buy a 20Da; I'm comfortable with my SBIG
camera for astrophotography.

Joe Morris

On Fri, 14 Oct 2005 02:55:12 +0100, Tim Auton wrote:

Tom Rauschenbach wrote:

Is there an easy way to tell if a digital SLR allows access to the raw
CCD data so that one can do digital noise reduction and false color image
stacking ?

Yes, read the specifications. But you needn't bother, they all do. As
do many mid-range cameras. The name varies, but it generally has
'raw'/RAW in the name.

In terms of $/pixel the devices made for astrophotography just don't seem
competetive with digital SLRs.

Economies of scale.

Or is the problem the color CCDs in the
cameras as opposed to monochrome CCDs ?

What problem?


Sorry, that's a fair question. It seems to me that if a 1/4 mega pixel
CCD imager for astrophotography sells for $400 US and a 2.1 mega pixel
DSLR can be had for $500 US there must be a serious downside to the DSLR.

On Sat, 15 Oct 2005 23:12:24 -0400, Tom Rauschenbach
wrote:

Sorry, that's a fair question. It seems to me that if a 1/4 mega pixel
CCD imager for astrophotography sells for $400 US and a 2.1 mega pixel
DSLR can be had for $500 US there must be a serious downside to the DSLR.

One flaw in this thinking is the assumption that more pixels is a good
thing. With astroimaging, that isn't necessarily the case. Big megapixel
sensors are very desirable for wide field imaging, but are of no use at
all for DSO imagers- those interested in typical galaxies, clusters,
planetary nebulas, etc. For such objects 1/4 to 1 megapixel sensors are
ideal; there is no value at all in having more.

There are two major problems with DSLRs for astroimaging: they are high
noise, and they are color.

_________________________________________________

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