Re: Pentax *istDS and Astro-photography

Hi Glosgas,

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 ?

Did the CD that came with the *istDS include "Pentax Remote Assistant" software? It can be downloaded from the Pentax USA site, and allows the camera to be controlled from a laptop via USB, including interval and timer modes.
http://www.pentaximaging.com/customer_care/show_software?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 page is for the *istD, but maybe it works also with the *istDS.

Like other DSLRs, the detector in the Pentax *istDS is not cooled. This means that noise accumulates linearly with 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 helps for aurorae). At the ISO 200 setting, you should be able to go for at least 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.

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. Attaching a DSLR to optics which are open to the air (such as a newtonian) almost guarantees that you'll have to clean 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.
.

Relevant Pages

  • Re: Pentax *istDS and Astro-photography
    ... I know that Canon make a 'programmable timer' that allows multiple and long ... This software allows the *istD camera to be controlled from a laptop via the supplied USB cable, ... This means that noise accumulates with exposure time, ... This will minimize the time the camera body is open when you're outside, and reduce the likelihood that the detector will need cleaning. ...
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