Hardcore modding on a A530, thanks to CHDK!

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Hardcore modding on a A530, thanks to CHDK!
« on: 02 / April / 2009, 00:25:19 »
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:

However, 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):

Globular cluster M4:

M8 nebula:

Sombrero Galaxy M104:

Southern Pinweel Galaxy, M83:

Galaxy NGC 4945:

Here are some images of the camera:

Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #1 on: 02 / April / 2009, 00:27:31 »
Some more images... The dark frames are 65 secs @ ISO 800
« Last Edit: 02 / April / 2009, 00:38:44 by Leonardo Miguel Delgado »

Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #2 on: 02 / April / 2009, 00:31:27 »
And finally the peltier cooling. There's a GIF showing the differences. Sorry to make it long!

I really want to thank the CHDK group, because else all this work would be meaningless.

So, now CHDK soft shoots to the sky :)


Leonardo from Argentina.


Offline PhyrePhoX

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Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #3 on: 02 / April / 2009, 01:29:05 »
wow thats what i call a hardcore hardware mod :D
very nice.


Offline fbonomi

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Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #4 on: 02 / April / 2009, 04:56:33 »

the cooling part, in particular, gives excellent results..

now, send it back asking for a repair under warranty :-)

« Last Edit: 02 / April / 2009, 04:59:04 by fbonomi »

Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #5 on: 02 / April / 2009, 06:43:29 »
Good work !
Lens assemblies often have more than two feedback sensors.
Does the A530 only have two ?
If so, are they measuring zoom position and lens movement ?
Having removed the lens, how did you discover which opto-interrupter needed blocking and which one needed an override switch ?

Did you have to override at a certain point in the power-up ?

Do you think the peltier cooling was worth the effort ?


Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #6 on: 02 / April / 2009, 09:59:48 »
Thanks, it was fun to leave the camera like this....

David, in fact this camera has three optoisolators. One is for the focus lens mechanism, didn't messed with it, I just broke the focus lens and left everything else. If something wrong is here, you get, I believe, the E92 error.

The other opto tells the camera if the lenses are retracted aka "In place". If the camera accidentally was turned off the wrong way, this opto will send the signal to the camera, the camera retractes the lens until the opto is blocked. As you know, the opto has a LED and a photodiode. I cutted the tracks of the LED, and added a switch to the photodiode. When the camera is off, the switch must be off. When the camera turns on, inmediately (in less than two seconds) you must turn on the switch, else you get the Lens Error.

The other opto is next to the CCD, here I attach an image. Inside the orange circle, there's the optoisolator and a little piece of paper blocking it. This opto is related to the optics, but since it has been like a year I did this mod, now I don't remember what this opto does. :lol . What I can tell you, is that it is always blocked.


EDIT: got a question! Someone told me CHDK supports 100 seconds exposures. Is it true, or it works for some cameras only? The 64 seconds limit is because of the hardware?
« Last Edit: 02 / April / 2009, 10:05:19 by Leonardo Miguel Delgado »


Offline PhyrePhoX

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Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #7 on: 02 / April / 2009, 12:58:01 »
64 seconds was and is the only supported open shutter duration. it is not neccesarily a hardware limit, maybe the buffer cant be filled any longer, we dont really know.

Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #8 on: 02 / April / 2009, 14:12:46 »
How's that?

As far as I know, the amp glow should be the limiting factor on the long exposures. In my case, it is gone.  :D

It's really weird...


Offline whoever

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Re: Hardcore modding on a A530, thanks to CHDK!
« Reply #9 on: 02 / April / 2009, 14:58:28 »
Although it may be different in the recent models, the problem as it was perceived way back was this: You could set any shutter duration you wanted, but after the magic 64s the mechanical shutter just closed. I don't recall anybody investigating this to any further detail -- probably because too long exposures with "non-modded" CCD are pretty useless anyway. What stops you from taking several consecutive exposures, say 60 s each, and then summing them up?


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