Pentax *ist, how to keep the shutter open for bulk mode ?

Hi,

I just bought a Pentax *ist and I would like to do photos with long exposition time (1 or 2 hours, for astronomical purpose).

Since, I don't want to stay 1 hours with my finger on the shutter release button, I bought a remote control.... but finally it is the same problem, to take a picture of one hour, you need to press the button one hour (which is different from some other SLR).

So, I would like to know if the Timer Switch 115 for MZ-S is compatible with the *ist ?

Thanks,

Lateral thinking: how about buying a low cost second hand manual camera body for the astronomical work? The MX, for example, allows the shutter to be locked open for as long as you like and without any battery expenditure. Electronic cameras use up power to keep the shutter open, and 8 hours on B is as much as you might expect from a new set. Any maual body can be equally well locked open with a locking cable release. If you are going to be taking large numbers of astronomical pictures this route might cost less than the toll of replacement batteries.

Does this mean that the optional remote control with the *ist D in bulb mode can be held open for some time? I'd like to be able to hold the shutter open with it for any particular amount of time, ultimately while using the 2 second delay for the mirror lock up.

Dan,

The original thread mentioned the *ist, not the *istD. I presume the *ist uses the CS205 shutter release. The CS205 can lock the shutter open. Here is a link about the pin outs for the CS205 (if you are electronically minded):
https://www.pentaxuser.com/forum/ftopic266.html

However, if you intend doing long exposures on the *istD, there are other issues that need to be considered, and even other methods you can use. If you do a very long exposure the semiconductor noise will be present in the image. You can correct this by doing dark frame subtraction (taking an image of the lens cap, preferably for the same exposure time) and subtracting this from the real image. Another technique is to take several shots and combine them.

The *istD has built in noise removal, which can be disabled. Which approach is best for very long exposures can only be found out with trial and error. However, there are plenty of resources on the web about digital astro photography.

Matt

Thanks for the tips about noise removal.

(after looking in the manual I answered my own question partly too...)
Yes, the remote control can control the bulb.

However, I get the impression that *ist D mirror lockup won't work with the remote (?)

Finally, to keep the shutter open for long time on my *ist, I made a simple cable release (similar to the Pentax CS-205 but cheaper). I found how to do it from:
http://www.hobbymaker.narod.ru/English/Articles/cable_sw_eng.htm

It works perfect!

Glad you have it sorted out Jerome!

I had started a thread on the CS205 and its pinouts way back in November (as soon as I managed to get one):
https://www.pentaxuser.com/forum/ftopic266.html

I know others have benefitted already. But thanks for the link you gave - just adds some extra info

Matt