Jump to content


Finally, long exposure mod actually working.


Recommended Posts

Hi all, I finally found something suitably cheap to rehouse my philips spc900nc webcam, which in turn meant I didn't have any excuses left for not re-doing my long exposure mod :D I found some nice, cheap, small and light food containers in tesco that give plenty of room inside for the webcams circuit boards and the lx mod but not to big to be cumbersome around a telescope.

The first time I did the mod I'd had about 10mins worth of soldering experience, wihch showed, I did the 'dead bug' method which involves bending the pins on a chip (IC) shorting them together and adding a couple of resistors, then 5 wires deal with all of the long exposure stuff.

This time around I had some copper backed proto board and a bit more soldering skill, so I made a nice little circuit board with the chip on it and did some sensible wiring :help: With everything soldered nicely, I checked for shorts, usb and LX cables were routed into the box nicely and the switch in place, everything fitting nicely into the container. I'd pre-made the hole for the 1.25" webcam nosepiece which when screwed into the webcam pulled everything up nice and tight so I didn't need to worry about fixing the webcam circuit boards to anything inside the box. There's enough space on the outside of the box to fit a reasonable sized fan for cooling at a later date too :lol: Time to test everything was working.

I plugged just the webcam in to start off with and started amcap, to make sure it still worked in its own right, everything ok so far :laugh: Next up plug in the long exposure lead to the serial port (I'd already made an adapter to turn it from the original mods parallel to serial) started wxastrocapture, set the lx com port, connected to the camera, set the frame rate to 5fps, exposure to 1/25, gain to 20 (to get low ight levels, as working long exposure mod should give higher light levels if working correctly) checked webcam was working properly in non-long exposure mode, all fine, set exposure length to 5seconds, selected long exposure and bingo nice bright image :D

I'm so pleased I finally got this working properly, should help quite a bit with autoguiding, I didn't have too many issues getting guide stars without the mod but being able to grab a little bit more light can't hurt, I might even try imaging with it through the WO 66 as I have a trust wb5400 that I can use for guiding while the spc is imaging

Link to comment
Share on other sites

No chance to test the webcam on stars yet, so in the meantime I've added a 40mm 12v DC fan, its 1.32w so its drawing 110ma, I've got it hooked up to its own 2400mah 12v supply so it should run for a good couple of sessions before needing a recharge. I wouldn't mind attempting the amp off mod, not sure how the circuit goes though, does anyone have any experience doing this mod?

Link to comment
Share on other sites

Thanks mate, Do you remember me saying I wasn't sure it was working properly, PHD and its frame grab delay was a piggin red herring fella :D If this works well enough I should get more chance of actually hitting a guidestar without moving the scope after its slew which would be nice.

It's definitely working though, hot pixels and all, got to remember to do darks before I start, I wouldn't want to be guiding on a hot pixel for a couple of hours....

Link to comment
Share on other sites

Nice work Reggie. It gives a great deal of satisfaction to build your own stuff. I did a Dew strip Controller, but I used a Velleman Kit which simplified things somewhat. I know if I do anymore I will need an Illuminated Magnifier Jobbie. My eyes are in need of help. :D

Ron. :help:

Link to comment
Share on other sites

I found the velleman kits to be overpriced for what they are but they do come with full instructions making it easier as you say. I'm a real novice at electronics but I pick things up reasonably quickly, so I started by doing the long exposure mod on my spc900nc needless to say it never worked properly for my first go, at around the same time I built myself a pwm servo controller for an electric focuser for my 6SE I built using a servo given to me by a mate a few months ago. All of the circuits I've used so far are incredibly simple and cost under £10 to make. I've used google for all of them, the servo focuser was adapted from an idea where a guy posted a simple focuser w/speed control for the 6SE, I used the servo but instead of ripping its guts out I used the onboard circuit + a pwm circuit using a 555 timer IC (google it, there are tons of circuits you can build with them!!) to give me pwm control of the servo so I can adjust speed and direction. The servo is modified for continuous rotation as well. The dew heater uses a similar circuit to the focuser controller, so that was very easy to build.

I'm going to get myself an 'arduino' project board soon, so I can provide PC control of the focuser and temperature control of the dew heater.

The beauty of these project boards is they are easily programmable, they are USB, they have multiple analog/digital inputs and outputs and they are dirt cheap at about £20. with a single board you could start with just the focus controller, then add in the automatic heater + sensors, program an intervalometer and connect up to a dslr, add in long exposure on/off switch for webcam etc. etc. all you need to do is add the 'modular' circuit to the existing design and write the code for it.

there is also a slew of add on boards for the arduino boards, so you can add lcds, sd card slots, ethernet, bluetooth, gps etc. units to it for more and more functionality.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.