DSLR VS Meade Colour imager II

[kimo]

Hi,
DSLR vs. Meade colour Imager ii. After read some notes from other websites, I realised that DSLR pickup much pollution then astronomical CCD does. Anyone have experience on Meade colour imager ii? How do you compare with DSLR, especially for Singapore sky?
Thank you
Kimo

[orly_andico]

An astronomical CCD does not magically pull less light pollution.

It's exactly the same.

However, a very aggressive light pollution filter (or a narrowband Ha filter) would cut the light pollution very well. It would also cut the available light a lot - hence you would need a much, much longer exposure.

DSLR's cannot do 10-minute exposures, too much noise. This is where an astronomical CCD would work well, because they are cooled.

[cloud_cover]

An astronomical CCD does not magically pull less light pollution.

It's exactly the same.

However, a very aggressive light pollution filter (or a narrowband Ha filter) would cut the light pollution very well. It would also cut the available light a lot - hence you would need a much, much longer exposure.

Agreed. Where a DSLR pulls in more light pollution is when you compare them to Mono CCDs doing narrowband imaging - in that case the very aggressive narrowband filter (often 13/7/3nm passband) cuts out most if not all the light pollution. As Orly said, because now so little light is coming in, the exposure needs to be much longer.

Another possible issue is that DSLR chips tend to work at much higher ISO Equivalents compared to astro CCDs (since the noise is far less an issue in normal daytime shots) hence a similar exposed shot tends to be brighter, therefore showing more of the light pollution (and also more of the target)

DSLR's cannot do 10-minute exposures, too much noise. This is where an astronomical CCD would work well, because they are cooled.

[/quote]

Well, yes and no. You can cool a DSLR (see my thread on effects of cooling on DSLR) and that very drastically reduces the noise in long exposure shots. However, a stock DSLR would really struggle with 10 mins exposures, not that there is a need for such long exposures, since narrowband imaging is not optimal in a DSLR.
As a note: the Meade DSI2 C is NOT A COOLED camera. It does have a very sensitive chip, similar to the Starlight Express Lodestar Guider but because you're opting for the color version the sensitivity is decreased due to the bayer matrix (that makes it color).
There is an aftermarket cooler for the DSI 2 which you may be interested in. Or you can bolt a TEC unit to the rear fins

[orly_andico]

Long exposures really are asking for it...

10 minutes is pretty hard. Your technique needs to be really good to get consistent round 10 minute exposures. Mine isn't, so I have egg stars.