hi guys,
SAC imaging ccd cameras have caught my attention but i don't have the experience to know which is good for me.
here's the URL to see them : http://www.sac-imaging.com/main.html
and can anione tell me how is Peltier cooled better than air cooled for CCD cameras.
one last thing, could u guys give me your comments on the SAC7 and SAC4 series?
thanks man
some advice on these ccd cameras please?
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tanguan2001
- Posts: 146
- Joined: Fri Oct 10, 2003 10:06 pm
- Location: Braddell
- Contact:
Hi shoelevy,
The main thing to realise about the SAC cameras is that they are modified webcams. So expect to struggle quite a bit! Having said that quite a lot can be done with them. See my website for more details including a frame showing the images from Raw to finished .
http://www.angelfire.com/space2/tgtan/p ... _part1.htm
Pros:
1. Relatively cheap - but being eclipsed by DSLRs
2. Lots of experience and techniques + software available on the web
3. video mode allows selected stacking of many frames avoiding moments of bad seeing
4. Low and repeatable dark current - subtraction of darks is repeatable - even without cooling
5. One shot colour - no need for filters
6. Sensitive to IR, so can be used for IR imaging
7. SAC7 will do long exposure
Cons:
1. Not very sensitive - however I have imaged down to mag 19 - but needs long imaging sessions
2. Small chip - FOV only 9' x 12' on my 8" f/5, so would be even smaller on an f/10 SCT
3. Suffers from banding - I've managed to fix this somewhat in post processing - see my site
4. Small pixels, so again not so sensitive and lower FOV, and no possibility to bin to increase sensitivity
5. Colour balance is very suspect - needs to be adjusted by eye in post-processing
6. Biggest con - only 8 bits, as compared to 16 bits output from conventional astro CCD's. Stacking improves the image depth, but does limit the the S/N ratio particularly in light polluted skies
The Peltier cooling is to reduce CCD noise, but although I have a SAC7B with it, it's not used because in our climate and my open Newtonian, it causes condensation. The SAC4 cannot do long exposure. The SAC8 is a LOT more sensitive, but I have no experience of it.
By the way, I'm considering getting a Canon D300 SLR which has a bigger chip (6 Mpix) and looks like higher sensitivity. Also the output in RAW mode is 12 bits - so my SAC7B may be on the market sometime soon!
Good luck,
TG
The main thing to realise about the SAC cameras is that they are modified webcams. So expect to struggle quite a bit! Having said that quite a lot can be done with them. See my website for more details including a frame showing the images from Raw to finished .
http://www.angelfire.com/space2/tgtan/p ... _part1.htm
Pros:
1. Relatively cheap - but being eclipsed by DSLRs
2. Lots of experience and techniques + software available on the web
3. video mode allows selected stacking of many frames avoiding moments of bad seeing
4. Low and repeatable dark current - subtraction of darks is repeatable - even without cooling
5. One shot colour - no need for filters
6. Sensitive to IR, so can be used for IR imaging
7. SAC7 will do long exposure
Cons:
1. Not very sensitive - however I have imaged down to mag 19 - but needs long imaging sessions
2. Small chip - FOV only 9' x 12' on my 8" f/5, so would be even smaller on an f/10 SCT
3. Suffers from banding - I've managed to fix this somewhat in post processing - see my site
4. Small pixels, so again not so sensitive and lower FOV, and no possibility to bin to increase sensitivity
5. Colour balance is very suspect - needs to be adjusted by eye in post-processing
6. Biggest con - only 8 bits, as compared to 16 bits output from conventional astro CCD's. Stacking improves the image depth, but does limit the the S/N ratio particularly in light polluted skies
The Peltier cooling is to reduce CCD noise, but although I have a SAC7B with it, it's not used because in our climate and my open Newtonian, it causes condensation. The SAC4 cannot do long exposure. The SAC8 is a LOT more sensitive, but I have no experience of it.
By the way, I'm considering getting a Canon D300 SLR which has a bigger chip (6 Mpix) and looks like higher sensitivity. Also the output in RAW mode is 12 bits - so my SAC7B may be on the market sometime soon!
Good luck,
TG
Hi Shoelevy,
You might want to check out these modified webcams from http://www.atik-instruments.com/ as well. They appear comparable to SAC and are cheaper. The malaysian dealer quotes prices way more expensive than the european ones. It might be cheaper to get from europe and import. Try http://www.perseu.pt/.
What I know about peltier vs air-cooled cameras is that air-cooled is like a fan while peltier is like an air-con. A peltier cooled camera can achieve temperatures up to 30deg below ambient temperature while an air-cooled cam just blows ambient air over the ccd chip. Both are attempts to keep the CCD chip cool to reduce noise. But as the experiences of Tanguan show, a peltier cooled cam might only end up introducing condensation in our high humidity environment. You might just want to go for an air-cooled after all if that is the case.
Clearskies,
Chris
You might want to check out these modified webcams from http://www.atik-instruments.com/ as well. They appear comparable to SAC and are cheaper. The malaysian dealer quotes prices way more expensive than the european ones. It might be cheaper to get from europe and import. Try http://www.perseu.pt/.
What I know about peltier vs air-cooled cameras is that air-cooled is like a fan while peltier is like an air-con. A peltier cooled camera can achieve temperatures up to 30deg below ambient temperature while an air-cooled cam just blows ambient air over the ccd chip. Both are attempts to keep the CCD chip cool to reduce noise. But as the experiences of Tanguan show, a peltier cooled cam might only end up introducing condensation in our high humidity environment. You might just want to go for an air-cooled after all if that is the case.
Clearskies,
Chris
"The universe is composed mainly of hydrogen and ignorance." Not exactly...shoelevy wrote:i this is the case does it mean if a filter takes 20 mins to expose then i need a total of 1 hours to a a complete true colour image of the target?Kamikazer wrote:not really...
need three different exposure with r, g, b filter...then combine them during processing...
the ccd has different sensitivity to different wavelengths...so you might need to expose certain colour longer to achieve a balanced image...
from what i know, most, if not all, ccd or cmos are least sensitive to red so you would need to expose red longer...as for blue and green, i'm not sure...
K.L. Lee