Canon PowerShot A560 for ARHAB
- Some of you may have seen a notice on either the GPSL or ANSR e-mail list regarding using the CHDK software to program several models of the Canon PowerShot series. After doing a bit of reading on the site (http://chdk.wikia.com) I decided to start trolling eBay for the appropriate models and finally hit on an A560 for about $85 plus shipping.
The A560 is a 7.1 Mpixel camera. I just got it yesterday and tried it out. The pictures are not quite as good as my 6 Mp Canon digital SLR, probably due to smaller and inferior lenses. However, it's much better than any point-and-shoot models I've tried to date (Aiptek and Concord models, Canon Powershot A300). The camera is much smaller and lighter than expected - it is roughly the size of the Elph but with a bump on the right side for a handhold/space for second AA battery. It does have an optical zoom, and the lens is at near full extension (~1.5") for the wide-angle setting. This can complicate mounting. It does have a DC input jack roughly the size of most modern cell phone charge jacks which takes 3.15V in. That may be handy for putting the batteries in a warmer place in the payload and increasing their size (unknown yet if a set of NiMH or lithium batteries will work for the entire flight).
The CHDK software will let you script camera commands with incredible detail, simulating practically any menu option or button press you can do interactively. You can also control ISO settings, focus, zoom, exposure, etc. There are several scripts available for taking images at intervals, and the scripting language is an easy-to-understand form of BASIC.
There is even the ability to do motion detection which is fast enough to detect the leader stroke of a lightning flash and open the shutter in time to capture the main stroke(s) a few hundred milliseconds later.
Since you do not have to modify the camera in any way (removing the software from the memory card returns the camera to normal operation), this means you can use the camera for other than ARHAB purposes. I plan to use it for creating time-lapse movies and taking lightning pictures if it's fast enough (some models can't quite go fast enough for that).
I should have this camera ready to go for our first NSTAR flight on March 29th at the Severe Weather Symposium in Lincoln. I'll also post further updates as I get experience using and making scripts.
If you choose to get a camera, check the CHDK site to make sure the particular model is supported. I believe the A560 is the earliest/cheapest model supported. Expect to pay at least $80 for this model, maybe into the $125 range for the A6xx models. Plenty of them, including new-in-box ones, can be found on eBay at any one time.
73 de Mark N9XTN