Hi All, I'm starting a project that will allow me to do long exposure images with a webam, anywhere from 1fps to 0.1fps (1 to 10second exposure or longer).  

I have a modified philips SPC900NC webcam, that will allow me to do long exposures via a 4066 IC and a serial port.  my aim is to use processing to trigger the serial exposure and then use processing to grab the correct 'new' frame from the webcam.

Unfortunately my plan came unstuck when I went looking through the source for the video library, as FPS/frameRate appear to integer based Coupled wiht the fact that 'frameRate' doesn't currently work.

I saw that there are quite a few other video libraries, which have some interesting features that I might be able to use, does anyone know of a library that allows you to do sub 1fps exposures?

Yes, I've sucessfully done that mod without issue and have used it to get some decent astrophotos of some very nice Nebula, object tracking at a few trillion miles or so is a wonderful thing

I should explain a little more about the purpose of what I am trying to do, I am part of a project that is providing free and open source astronomy related software/hardware based around the arduino platform,  We are currently working on a motorised eletronic focuser controller, which is controlled via the ASCOM standard drivers for hooking astronomy kit together using a PC or it will work completely standalone.

So that's where we're at, the logical extension to being able to focus electronically is to have the computer do it for you, there is already software that's out there that will do this, I would like to provide this functionality in our software for free.

I use a program called PHD-Guiding to run the camera in long exposure mode, all it does is look at the same spot of sky and keep a single star in exactly the same position (camera and software have control over the mounts motors) but just grabbing a frame isn't quite as simple as you'd think though, there are timing issues where the long exposure frame  is grabbed, grab the wrong one and you get a blank frame.

Standard capture software doesn't deal with frame rates <5fps, so the framerate controls exposed in the processing video library aren't adequate for the job, only deals with integer values

I'd like to be able to set an arbtrary length 'exposure' and then 'tweak' the frame grab timing until I get what I want.

I'm trying to figure out how its done in the phd guiding software, they've either exposed extra 'things' through the software + hardware hack or there is something else, it should be noted that its quite possible to dump the cameras registers, change and re-upload them to the camera with software available.

I think he might do something like this in the software, hold the serial pin high to stop the camera from emptying the sensor, expose as long as needed, drop the serial pin low, timed grab for the data.

My other issue with the SPC900NC in processing is that I can't actually get it to activate at a decent resolution, always comes up as 176x144 (CIF).

OK, so your issue with the grabbing is that you get blank frames A quick solution (that I've used before) is to have a look at every frame you get, grab a bunch of pixels - some random ones or perhaps a line down the middle - add up the total RGB, compare the total with a threshold value and just ignore frames where the the total is below the threshold. This may not work as well for you since you're looking at a black sky, but still worth a shot.

What exactly is the point of doing it with a hardware hack rather than just stacking up frames in software A better dynamic range Or is there something else

Another fun thing to do with long exposure is light painting à la Pablo Picasso http://bit.ly/3Ym22O - my guess, which may be wrong, is that you can find more people here eager to help on that.

Also check out this thread http://processing.org/discourse/yabb2/num_1243385017.html and http://glowdoodle.com