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Old 23-07-2007, 06:47 PM
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Dietmar
anatomic astronomer

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comparsion monochromatic vs OSC CCD - which one to pick?

hi DSI friends,

what is really the better one...?

one shot color ccd or monochromatic CCD.

I wondered and I wanted to find out, if the difference in resolution power and color quality is really so big, as so many guys claimed it would be.

well - the result is really surprising for me!!!

I have developed 2 images of the whale: the one on the top has been taken with the SXV H16 monochromatic CCD
the one below with SXV M25C. it is a pseudoluminance image drawn out of the color image by using the channel mixer in B/W.

http://stargazer.christelhager.info/...16-vs-m25c.jpg

here is a comparsion of color-power.

1 LRGB in a perfect night
and a combination of L and color coming from OSC taken with M25C in a night with a little worse transparency.

http://www.stargazer-observatory.com...gb-vs-losc.jpg

processing technique was exactly the same (Photoshop algorhythm).

in my eyes - there is a difference and a advantage of mono-CCD- but it is very small. definitely not that big as so many said it would be. I think this is the point.

I think there are some essential considerations to be done before picking a CCD:

- weather-stability/reliability of individual location of the observatory:

in my case, most of the time we have overcast nights, and when they are clear, seeing is usually around 5/10
only a couple of nights provide us with a better seeing.

therefore a monochromatic CCD will not be able to play out its advantages in luminance power - no good seeing no difference.

- time consumption of image acquisition procedure:

living in aplace where there are more clear and steady night skies than one person could ever use (chile, new mexico, australia(?)) you sure can automatized acquire the data relying on the fact, that next night will provide you with good conditions.
in my place here - I cannot trust the weather at all.
one clear night might be followed by 1 month clouds...

in summer (northern hemisphere) it would take you many nights to complete an object in LRGB, since there is only some 3 or 4 hours time per night.

- effort/result relation:

I think the relation between thse 2 parameters is much better in a OSC CCD.
definitely.

so for all those who have lots of perfect nights I`d say go for LRGB.
for all those (like me) who have some 15 or 20 nights a year with average seeing qualities it might be better to go for OSC CCDs.

- prize.
OSC makes every single frame count - for both. luminance and color.
for monochromatic you still would need a filterwheel and a even more stable focuser to prevent any differential bending. the mount would also have to be more stable. all that results in more costs.

hope this helps all the guys who are still looking for a CCD.
at least it was very exciting to see that the resolution power of a mono is not so much better.



PS: here is the final result of the whale:
http://www.stargazer-observatory.com/4631.html

an M63
http://www.stargazer-observatory.com/m63.html

Last edited by Dietmar; 23-07-2007 at 06:58 PM. Reason: additional data
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Old 23-07-2007, 08:28 PM
Dennis
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A very interesting review with many thoughtful comments that will prove very helpful to anyone facing this decision. I guess Australia could be characterised as "living in a place where there are more clear and steady night skies than one person could ever use" to some extent, making the decision a little more difficult than for European imagers, although I suspect inland Spain would have some fabulous nights too.

Cheers

Dennis
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Old 23-07-2007, 08:41 PM
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ballaratdragons (Ken)
The 'DRAGON MAN'

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Interesting comparison. But I think the colour chip does a better job in your images. The tiny background Galaxies stand out clearer too.
Sounds wierd coz Mono chips are supposed to be better!

Oh, by the way, stunning images
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Old 04-08-2007, 08:08 AM
gbeal
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Hi Diets,
I wish you had this available when I was procrastinating about the next CCD.
I ended up with an ST2000XCM, as you know, and since getting it have wondered if it was the right decision. I love it, imaging is indeed a one shot affair. While I miss the "real" Ha imaging, as an all round imager it is hard to fault.
Gary
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Old 17-08-2007, 10:33 PM
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Dietmar
anatomic astronomer

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thanks Dennis, Ken and Gary.

Gary - Bernhard Hubl works with st2000 for a long time. perhaps he has some interesing tips for you...?
http://hubble.heim.at/

Ken, the reason why the color chiop does a great job is cos the s/n ratio is so wonderful! h16 has a nice kodak chip - but the signal kind of drowns in the nnoise - it needs more data to stand out.
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Old 17-08-2007, 11:32 PM
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ballaratdragons (Ken)
The 'DRAGON MAN'

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Quote:
Originally Posted by Dietmar View Post
thanks Dennis, Ken and Gary.

Gary - Bernhard Hubl works with st2000 for a long time. perhaps he has some interesing tips for you...?
http://hubble.heim.at/
Wow, that's a great site!!!
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