Pentax *istDS and Astro-photography

I've bought myself a Pentax DLSR and want to turn to astrophotography.
Has anyone out there used this camera for astrophotography ?

I know that Canon make a 'programmable timer' that allows multiple and long
'B' exposures.

Is there anyting similar for the Pentax digital cameras ? (I know the
pin-out of the 2.5mm Jack, I am considering making some sort of timer -
unless anyone has already done it.)

What's the longest 'B' exposure that can be made before the picture is
overrun with elctronic noise ?

Any thoughts, or help ?


Glosgas

Hi Glogas,

Glosgas wrote:
I've bought myself a Pentax DLSR and want to turn to astrophotography.
Has anyone out there used this camera for astrophotography ?

I know that Canon make a 'programmable timer' that allows multiple and long
'B' exposures.

Is there anyting similar for the Pentax digital cameras ? (I know the
pin-out of the 2.5mm Jack, I am considering making some sort of timer -
unless anyone has already done it.)

What's the longest 'B' exposure that can be made before the picture is
overrun with elctronic noise ?

Any thoughts, or help ?


Glosgas

Did the CD that came with the *istDS include "Pentax Remote Assistant"
software? It can be downloaded from the Pentax USA site:
http://www.pentaximaging.com/custome...tware?softId=1
Scroll a long way down the page to find the Pentax Remote Assistant
software. There are versions for both Windows and Mac. This software
allows the *istD camera to be controlled from a laptop via the supplied
USB cable, including interval and timer modes. Maybe it works also with
the *istDS.

Like other DSLRs, the detector in the Pentax *istDS is not cooled. This
means that noise accumulates with exposure time, at a fairly fast rate.
The warmer it is, the more thermal electrons there are to fill the CCD's
electron well. The higher the ISO setting, the more amplification there
is of this thermal noise, so using high ISO settings in a DSLR is of
limited use in astrophotography (but can help for photographing
aurorae). At the ISO 200 setting, you might be able to go for more than
30 seconds on a good night before the noise is really bad. However, it
is probably better to take multiple 15 second exposures and stack them,
rather than taking a single 60 or 90 second exposure.

I'm not sure if the *istDS has the mirror lock-up function (the *istD
has it). If not, it's advisable to use a hat-trick for multi-second
exposures with a telescope or long telephoto lens. Vibration from the
shutter lasts a fraction of a second and will affect the start of an
exposure, especially with long focal lengths.

Another tip: if you plan to use a telescope instead of a lens, then set
up the camera with all necessary adapters indoors in a clean place (no
airborn dust or dirt) and cap it. This will minimize the time the camera
body is open when you're outside, and reduce the likelihood that the
detector will need cleaning. The detectors in DSLRs seem to be dust
magnets, and will probably attract insects too, if left open for long. I
can only manage a couple of careful lens changes before some small mild
blur-spots appear in the picture and I feel compelled to clean the
detector. Attaching a DSLR to optics which are open to the air (such as
a newtonian) almost guarantees that you'll have dust on the detector
afterwards. It's one of the advantages remaining to film - just wind to
the next frame and you have a fresh clean detector.

Best Regards,
John.

John,

I'm aware of the 'Remote Assistant' software, I donwnloaded it as soon as I
found out about it. Unfortuanately it only works with the *istD camera
(Penatx know this). I've been trying to find software to do the same with
the *istDS.

Thanks for your input.

Steve.
(Glosgas)

"John Shakespeare" wrote in message
...
Hi Glogas,

Glosgas wrote:
I've bought myself a Pentax DLSR and want to turn to astrophotography.
Has anyone out there used this camera for astrophotography ?

I know that Canon make a 'programmable timer' that allows multiple and
long
'B' exposures.

Is there anyting similar for the Pentax digital cameras ? (I know the
pin-out of the 2.5mm Jack, I am considering making some sort of timer -
unless anyone has already done it.)

What's the longest 'B' exposure that can be made before the picture is
overrun with elctronic noise ?

Any thoughts, or help ?


Glosgas

Did the CD that came with the *istDS include "Pentax Remote Assistant"
software? It can be downloaded from the Pentax USA site:
http://www.pentaximaging.com/custome...tware?softId=1
Scroll a long way down the page to find the Pentax Remote Assistant
software. There are versions for both Windows and Mac. This software
allows the *istD camera to be controlled from a laptop via the supplied
USB cable, including interval and timer modes. Maybe it works also with
the *istDS.

Like other DSLRs, the detector in the Pentax *istDS is not cooled. This
means that noise accumulates with exposure time, at a fairly fast rate.
The warmer it is, the more thermal electrons there are to fill the CCD's
electron well. The higher the ISO setting, the more amplification there is
of this thermal noise, so using high ISO settings in a DSLR is of limited
use in astrophotography (but can help for photographing aurorae). At the
ISO 200 setting, you might be able to go for more than 30 seconds on a
good night before the noise is really bad. However, it is probably better
to take multiple 15 second exposures and stack them, rather than taking a
single 60 or 90 second exposure.

I'm not sure if the *istDS has the mirror lock-up function (the *istD has
it). If not, it's advisable to use a hat-trick for multi-second exposures
with a telescope or long telephoto lens. Vibration from the shutter lasts
a fraction of a second and will affect the start of an exposure,
especially with long focal lengths.

Another tip: if you plan to use a telescope instead of a lens, then set up
the camera with all necessary adapters indoors in a clean place (no
airborn dust or dirt) and cap it. This will minimize the time the camera
body is open when you're outside, and reduce the likelihood that the
detector will need cleaning. The detectors in DSLRs seem to be dust
magnets, and will probably attract insects too, if left open for long. I
can only manage a couple of careful lens changes before some small mild
blur-spots appear in the picture and I feel compelled to clean the
detector. Attaching a DSLR to optics which are open to the air (such as a
newtonian) almost guarantees that you'll have dust on the detector
afterwards. It's one of the advantages remaining to film - just wind to
the next frame and you have a fresh clean detector.

Best Regards,
John.

This may not answer all your questions but here is a collection of fine
astrophotos taken in Finland by Janne Kald:

http://www.kolumbus.fi/jkald/index.htm

Many ds-objects have been taken with 240 sec (4 min) - 300 sec (5 min)
exposure time. See eg, M11 on front page.

Jorma Mantyla
Kangasala
Finland

Glosgas wrote:
: John,

: I'm aware of the 'Remote Assistant' software, I donwnloaded it as soon as I
: found out about it. Unfortuanately it only works with the *istD camera
: (Penatx know this). I've been trying to find software to do the same with
: the *istDS.

: Thanks for your input.

: Steve.
: (Glosgas)

: "John Shakespeare" wrote in message
: ...
: Hi Glogas,
:
: Glosgas wrote:
: I've bought myself a Pentax DLSR and want to turn to astrophotography.
: Has anyone out there used this camera for astrophotography ?
:
: I know that Canon make a 'programmable timer' that allows multiple and
: long
: 'B' exposures.
:
: Is there anyting similar for the Pentax digital cameras ? (I know the
: pin-out of the 2.5mm Jack, I am considering making some sort of timer -
: unless anyone has already done it.)
:
: What's the longest 'B' exposure that can be made before the picture is
: overrun with elctronic noise ?
:
: Any thoughts, or help ?
:
:
: Glosgas
: