Pentax k1x0D long exposures (astro photography)

It is yet quite hard to find at least several expert reviews on one of
the 2 new Pentax DSLRs, so behavior at high ISO and long exposure i.e.
5-10-15+ minutes is to me so far unknown.
Is it better or worse than the Nikon's D50/D70 or one of the *ist
series camera?
Is it "improvable" by any means?
(I am not discussing the Canon CMOS DSLR's on this issue, everyone
interested knows they are the best for this kind of work)
The Nikon's workaround for not having the dark frame extracted is, tho'
efficient, quite barbaric IMHO.
If I know well, the D80 has the possibility to disable this dark frame
extraction feature. Also, from what I've read in the K100D's manual,
there is also possible to disable Noise Reduction. If I know wrong,
please correct me. How much improvement does that bring, if any?
The low price on these cameras, together with the overall kit lens
optics, construction and handling quality makes my wish gland drool.

"mirceaar" wrote in message
ups.com...
It is yet quite hard to find at least several expert reviews on one of
the 2 new Pentax DSLRs, so behavior at high ISO and long exposure i.e.
5-10-15+ minutes is to me so far unknown.
Is it better or worse than the Nikon's D50/D70 or one of the *ist
series camera?
Is it "improvable" by any means?
(I am not discussing the Canon CMOS DSLR's on this issue, everyone
interested knows they are the best for this kind of work)
The Nikon's workaround for not having the dark frame extracted is, tho'
efficient, quite barbaric IMHO.
If I know well, the D80 has the possibility to disable this dark frame
extraction feature. Also, from what I've read in the K100D's manual,
there is also possible to disable Noise Reduction. If I know wrong,
please correct me. How much improvement does that bring, if any?
The low price on these cameras, together with the overall kit lens
optics, construction and handling quality makes my wish gland drool.


I have only done a few ten minute exposures but on my DS (and it should be
similar) the DFS works quite well. I did some testing in a dark room and had
some flare particularly at the edges that was dealt with apparently quite
nicely by the DFS. Probably fairly similar to the Nikons with DFS.

mirceaar wrote:
It is yet quite hard to find at least several expert reviews on one of
the 2 new Pentax DSLRs, so behavior at high ISO and long exposure i.e.
5-10-15+ minutes is to me so far unknown.

High ISO is useless in any DSLR for astrowork. As for reports
unfortunately I know of no one.

Is it better or worse than the Nikon's D50/D70 or one of the *ist
series camera?

I bet they're better than the *ist (far too noisy) and probably with
more noise than the D50.

Is it "improvable" by any means?
(I am not discussing the Canon CMOS DSLR's on this issue, everyone
interested knows they are the best for this kind of work)

They're not, except maybe the Da.

The Nikon's workaround for not having the dark frame extracted is, tho'
efficient, quite barbaric IMHO.

Is not about the dark frame but rather about median filtering. Besides,
it can be automated.

If I know well, the D80 has the possibility to disable this dark frame
extraction feature. Also, from what I've read in the K100D's manual,
there is also possible to disable Noise Reduction. If I know wrong,
please correct me. How much improvement does that bring, if any?

Difficult to say without knowing exactly what it is supposed to do and
what effectively does, isn't it?

The low price on these cameras, together with the overall kit lens
optics, construction and handling quality makes my wish gland drool.

If you're happy with QE at best 2x of high end film than yeah,
otherwise yawn..

Andrea T.

Note followup.

" wrote in
oups.com:

Of noise and such in digital cameras for astrophotography:

mirceaar wrote:
(I am not discussing the Canon CMOS DSLR's on this issue, everyone
interested knows they are the best for this kind of work)

They're not, except maybe the Da.

Would you care to elaborate on that? I expect to make that decision in
the medium term. I have a certain amount of Nikon glass and no Canon
anything. If a Nikon D-80 lets me get reasonably close to a Digital
Rebel XT I will be a happy camper.

The Nikon's workaround for not having the dark frame extracted is,
tho' efficient, quite barbaric IMHO.

Is not about the dark frame but rather about median filtering.
Besides, it can be automated.

How is it automated? A pointer to some information would be fine.

If I know well, the D80 has the possibility to disable this dark
frame extraction feature.

Question for mirceaar:
May I ask where you got that information? It would be of considerable
interest to me to be able to follow-up on it.

- Shankar

Shankar Bhattacharyya wrote:
Note followup.

" wrote in
oups.com:

Of noise and such in digital cameras for astrophotography:

mirceaar wrote:
(I am not discussing the Canon CMOS DSLR's on this issue, everyone
interested knows they are the best for this kind of work)

They're not, except maybe the Da.

Would you care to elaborate on that? I expect to make that decision in
the medium term. I have a certain amount of Nikon glass and no Canon
anything. If a Nikon D-80 lets me get reasonably close to a Digital
Rebel XT I will be a happy camper.

I don't know much first-hand on the D80 but from what I've read is
probably slightly worse than a D50 re astrophoto (less sensitivity and
somewhat less dynamic range). This said it is a better general use DSRL
camera than the D50 but not by miles. Back to the original question;
from the test I've done the D50 yields very low thermal noise (compared
to other DSLRs) and a very small amount of amplificator glow.
Sensitivity is quite high in the 600nm range. As a sample, I've
reached at least magnitude 14.2 in a 5min20s shot taken in my
semi-urban backyard using a 200mm f/4 lens.A 3x4min shot in the early
morning hours (not to far from dawn) has shown no less than 14 nebulae
in the Orion Belt region (including B33) using a 105mmf/2.5 lens.


The Nikon's workaround for not having the dark frame extracted is,
tho' efficient, quite barbaric IMHO.

Is not about the dark frame but rather about median filtering.
Besides, it can be automated.

How is it automated? A pointer to some information would be fine.

see - http://www.sfu.ca/~dmunro/DSLRnotes.html

Regards

Andrea T.

Originally Posted by mirceaar

It is yet quite hard to find at least several expert reviews on one of
the 2 new Pentax DSLRs, so behavior at high ISO and long exposure i.e.
5-10-15+ minutes is to me so far unknown.
Is it better or worse than the Nikon's D50/D70 or one of the *ist
series camera? ....snip......

You might be better to pose your query on specialist astro DSLR groups like Yahoo Groups. Canon and Nikon DSLR seem to dominate astro work so there's more feedback although I seen some nice Pentax deepsky images [somewhere]. Regarding lenses for astro work it's better to work with fixed focal length lenses and avoid complex zooms which are always a compremise in both full aperture and image quality mindful that stars are the most critical object a lens can image!

I use my old fixed focal length M42/ Pentax screw lenses with an EOS-M42 adaptor for my Canon 300D. This is no disadvantage as in preferred manual mode all the auto gizmos like zooms, autofocus etc are pointless. In fact autofocus for astro is a pest and most such lenses will focus manually beyond infinity - how useful is that on dim starlight!


Nytecam 51N 0.1W
www.astroman.fsnet.co.uk