Re: Astro CCDs still dragging their pixel feet
- From: AFM@xxxxxxxxxxxxxxxxxxx
- Date: 12 Apr 2005 18:38:33 -0700
RichA wrote:
> Compared to consumer digital cameras, astro CCD cams
> are still WAY behind when it comes to the number of
> pixels. The latest one is the Meade DSI Pro, an "improvement"
> on the still new DSI, that boasts "4x" the resolution
> of the DSI. Here is the spec;
> Specifications
> CCD Sensor: High Sensitvity Sony® ExView HAD? Monochrome CCD
Sensor
> Pixels: 510 x 492 pixels (250,000 pixels)
>
> That's about 1/160th the count of the average 4 megapixel entry-level
> consumer digicam. In fact, the colour HAD sensor is used in consumer
> video cams because they can't process 30fps (video) if the pixel
count
> is much over 1 million.
>
> Meade mentions that it's capable of exposures of over 1 hour, but
> they intend it to be used to make very short exposures then combine
> them for the finished result because an hour on a non-cooled digital
> camera would be a disaster. They do offer an RGB filter set with it
> for true colour reproduction.
>
> But I can't help wondering when a company will offer a 4 megapixel or
> larger CCD or CMOS-based astro cam with cooling for a price far below
> that of the SBIG and other high priced cameras now on the market.
> When they can sell a consumer camera with 4 megapixels for $200, how
> expensive can the CCD/CMOS element possibly be, even in small
> quantities??
> -Rich
SAC imaging (http://www.sac-imaging.com/) their newest camera seems to
be what you are looking for.
Consumer cameras don't make good astro cameras because don't need
to pay as much attention to things like noise, contrast and efficiency
given that they are used in what we astronomers would consider well-lit
conditions. As you shrink the pixels you need to sacrifice these. It is
quite reasonable to make a large CCD sensor but you should remember the
price of a chip is based almost exclusively on how much silicon it
uses.
Simply adapting a consumer digital camera is possible, and if properly
cooled could produce some respectable images, but is wont be in
anywhere near the same league as SBIG, FLI, or Apogee.
As for the Mead DSI line, I think they provide a good entry for
potential imagers who don't know if they want to jump into a $3000
purchase. The choice not to install a TEC was because the cooling
system would cost more than camera itself and require an external power
supply. Either that or meade is looking to patent convective cooling.
Ian Anderson
www.customopticalsystems.com
.
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