Hello everyone! I'm Leonardo from Argentina.
You might remember me long ago posting a modded Canon A60 for astrophotography, wich I removed the IR filter, lenses and fooled the E18 error. And also, found strings of "Raw" stuff on its firmware. Because of a loosen bolt, the camera is dead now
You can see some stuff on my webpage (updating...) about the A60:
http://www.astrosanjusto.net63.net/taller/a60focoprimario/index.htmhttp://www.astrosanjusto.net63.net/taller/canona60ir/index.htmHowever, I acquired a Canon A530 and finally could break the silly 15 secs barrier, thanks to CHDK...
On this camera, I made some way-hardcore moddings on the hardware to use it with the telescope, and I wanted to share the idea with you guys. These are:
**Removed the lenses for prime focus
**Removed the IR filter to fully catch the red 656nm spectrum (found on emission nebulas)
**Fooled the Lens Error by using a switch and blocking an optoisolator
**Made an Amp-off circuit to control the CCD voltage during the exposure. This is to avoid the CCD glow at the corners of the image.
**Made an auto-shot switch, a controlable oscilator thar activates the shot button, so there's no need to touch it when mounted on the telescope. Simply activating a switch, the camera will start to make the exposures.
**Peltier cooling to reduce hot pixels and slightly increasing the sensitivity.
The camera is now much more sensitive to the faint fuzzies without the lenses. I've removed the lens system, and replaced with resistors the shutter (and something else I don't remember now), so the camera won't notice.
Then I added a switch to an optoisolator (and blocked another) to trick the camera that the lenses are in place (else, you got the Lens Error).
Thanks to CHDK that disables the built-in dark frame substraction, when making long exposures I was able to see the big CCD glow the camera makes. What is CCD glow? It's an electroluminiscence coming from the very CCD. You can see it at the corners of the image, like a reddish-pink glow. The more exposure you use, the more glow you got. It spoils the dinamic range of the image, and for astrophotography it's not something good. To reduce this glow, one must use a circuit called "Amp-off". It reduces the CCD voltage during the exposure, and restores it before the exposure ends (else you got a black image, or some white lines). Since for CCD webcams there was already an amp off circuit (made by Martin Burry), I started thinking "Why not?". I had to investigate the CCD of the camera. It turned to be a Panasonic MN39620. Sadly, the datasheet was very dissapointing, so I took the tester and started to find with the camera ON, the highest voltage on the CCD wires... A wire with around 13V was found, so I though it was the voltage wire. Then, I made a modification on Martin Burri's amp off circuit and implemented it on the CCD. It worked great! I control the amp off with the PC.
Then made an auto-shot switch, it's an oscilator and a transistor connected to the shot button on the camera. When the oscilator is ON, it's like if somebody is constantly pushing and releasing the button. I made it to automate the imaging process with the telescope, besides this way there's no need to touch the camera, and you avoid vibrations on the telescope thin way...
Finally added peltier cooling to the CCD, with a cold finger made with a piece of aluminium 2mm. It reduces the hot pixels and slightly increases the sensitivity (roughly 7 - 10%). It cannot be cooled much, since the CCD gets full of dew.
I still don't have images likely to make a tutorial of the mod, but since the camera is glued and working, I don't really want to mess with it again.
Here, I attach some images of the mod, and some deep sky images made with the camera on a rural zone in Buenos Aires (San Antonio de Areco). The images were made last week. The telescope is a Hokenn (Synta) reflector 114/500 parabolic mirror, on a EQ3 (CG-4) mount.
Here are some deepsky images:
Globular cluster Omega Centauri (NGC 5139):
http://www.astrosanjusto.net63.net/astrofotos/cumulosg/NGC%205139/NGC%205139%2012%20cuadros%2030s%20procesado.htmGlobular cluster M4:
http://www.astrosanjusto.net63.net/astrofotos/cumulosg/M4/M4%2014%20cuadros%2040s%20procesado.htmM8 nebula:
http://www.astrosanjusto.net63.net/astrofotos/nebulosas/M8/M8%2013%20cuadros%2045s%20procesado.htmSombrero Galaxy M104:
http://www.astrosanjusto.net63.net/astrofotos/galaxias/M104/M104%2020%20cuadros%2030s%20procesado.htmSouthern Pinweel Galaxy, M83:
http://www.astrosanjusto.net63.net/astrofotos/galaxias/M83/M83%207%20cuadros%2060s%20procesado.htmGalaxy NGC 4945:
http://www.astrosanjusto.net63.net/astrofotos/galaxias/NGC%204945/NGC%204945%2021%20cuadros%2045s%20procesado.htmHere are some images of the camera:
