camera sensitivity

[russesmnt]

Hello

I'm new to the group and have purchased a 383L OSC camera.  I wanted to upgrade from my DSLR which is a modified Canon XSi.  I purchased the camera last year and have not been able to use it much this past year due to mount problems and having been gone for work.   I now have the time and am able to get back in to astorphotography.

My issue is that my Canon XSi is far more sensitive then my 383.  I know this cant be right and teh reason I went to CCD to get better sensitivity.  I just cant figure out what is wrong.  I use Imageplus 5.5 for camera control and am shooting through a 10" orion astrograph with coma corrector.  I have been trying relitivly bright subjects like M42, M45 and NGC 1499.  The 10 minute subs on my CCD are about equal to a 2 minute sub on my XSi.  I'm pretty sure this is the oposite of what it should be.

I was hoping that someone might have some thoughts on what I am doing wrong.  Any advise is welcome.  Thanks

Rusty

[Konihlav]

Hi Rusty, first of all, my personal thoughts:
- you probably (my point) selected the worst ever OSC ccd camera possible (there are many better choices)
- you won't get higher sensitivity with color CCD camera then with DSLR camera (the sensitivity is not the key parameter, not the key thing)
- what you get (the only advantage of color cooled CCD over color non-cooled DSLR) is the noise-control. Biggest problem of DSLR is to match dark frames with correct temperature to the light frames. On non-cooled DSLR it's the major problem. With cooled CCD you resolve this issue with dark current and other source of noise in general... but you won't get better sensitivity, you only get less noise (result is similar).

back to the problem:
- the major difference is in the A/D conversion. With DSLR you select some ISO value. With CCD you are fixed to some settings made by manufacturer for highest possible dynamic range. Therefore, it's like you use DSLR with ISO value 50 or 25 :-) and that's why the result with 2min subs (or constant subs) looks (especially on the display) much better on DSLR then with CCD
- but, do not worry, the data are there, you only need to dig them out (stretch). Key point is to calibrate the image and correctly stretch the resulting IEEE float FITs when converting into 16bit TIFFs...

Pavel

[russesmnt]

Pavel

Thanks for the education I sure wish I had know this earlier.   I will work on some images more and see if I can find the data you spoke of.  Thanks again for the response.

Rusty

[Lex]

Hi Rusty,

perhaps post one of your pictures or give us a link in order to see what's happening with your pictures...

best

[clouds2nite]

Hi pavel,

Why do you classify the 383L OSC "as the worst OSC ccd camera"? This is a pretty negative statement, needing some explanation. You dont like the colour of the camera or have you a more significant problem with it?

Regards,

John

[Konihlav]

Hi John,

in the last 5 years I tried almost every telescope, couple of mounts, many many CCD cameras, every day studied, every clear night went out to do something...

I had in my hands more over 20 various cameras and I simply don't like KAF-8300. Especially Atik-383L is FAR from being so good like every Atik with SONY chip. I love all SONY cameras made by Atik - there Atik rulez! but in Kodak world Atik is one of the worse... that's my findings.

You can read some stuff on my blog page:
http://blog.astrofotky.cz/pavelpech/

and color? that's terrible. I also had SONY color, but I also did not like it even though it was far superior to color KAF-8300. If you want to hear some recommendation from my side then listen - get as big CCD surface as you can or, if you dare about image scale, resolution, faint detail, but do not care about big FOV then get Atik with SONY chip :-) that's where I ended after all my research.

[clouds2nite]

Hi Pavel,

I have three cameras atik383L+C, Canon 60Da and a modified D (peltier cooled to -40C and with Hap Griffen's Filter mods) on a GSO 200mm RC ota. The senditivity and colour of the 383 is inferior to the 2 Canon DSLRs , the 60Da is convenient to use but the Modified 40D has the superior image but the peltier cooling is very heavy. The 383 requires twice the exposure time 600s per frame comparred with the DSLRs (ISO 1600) 300s for a similar image.  The 383 needs a shorter OTA to get sufficient light to the pixles. 80mmED at f5.6 compared to the 200mm RC at F8.

My preference is the 40D in my observotory at home and the 60Da in the field. My sky is often cloudy and  Mono images using filter wheel takes too much time so I want to use a ONC CCd or a DSLR. I do however like the Atik 383L+  C and will use it for wide field imaging.

Regards, John