Celestron Fastar - pros and cons

On Sat, 13 Oct 2007 09:10:50 -0700, wrote:

If your goal is to obtain lots of crappy wide field images in a hurry,
then by all means shoot with an F2 focal ratio. If the idea is to
optimize the perameters of each item, i.e. the scope the camera, the
resolution, sig/noise, etc., then tying pixel size to F-ratio will
result in the best performance.

An f/2 system with poor optics will produce "crappy" images. But
undersampled images are not inherently poor. There is no significant
relationship at all between focal ratio and signal-to-noise for properly
exposed images. If you want optimal resolution, you match the focal
length of the telescope to the pixel size of the camera. But as noted,
resolution isn't the only possible goal when imaging. There are plenty
of cases where FOV may be more important.


Remember this: shooting an image at F10 with a 1k x 1k CCD with 24
micron pixels will give you the exact same result (resolution, sig/
noise AND field of view) as shooting that same image at F2.5 with a 1k
x 1k 6 micron pixel CCD.

That's fine if you have the luxury of owning these two cameras. But most
people only have one camera to work with, and will use it in different
configurations for different imaging goals.

With a single camera, I oversample for lunar/planetary images, slightly
undersample for aesthetic deep-sky images, and significantly undersample
for most of my photometry and astrometry work. I wouldn't consider any
of my images (or underlying data) to be "crappy".

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Thu, 11 Oct 2007 23:05:30 +0100, nytecam[_1_]
wrote, in part:

I tested and reviewed the 8" Fastar at
http://home.freeuk.net/m.gavin/fastar.htm

I believe it was from your site that I heard about the ones from
Starizona - but they now appear discontinued too.

John Savard
http://www.quadibloc.com/index.html

On Oct 14, 8:00 pm, (John Savard)
wrote:
On Thu, 11 Oct 2007 23:05:30 +0100, nytecam[_1_]
wrote, in part:

I tested and reviewed the 8" Fastar at
http://home.freeuk.net/m.gavin/fastar.htm

I believe it was from your site that I heard about the ones from
Starizona - but they now appear discontinued too.

John Savardhttp://www.quadibloc.com/index.html

Not AFAIK:

http://starizona.com/acb/hyperstar/specs.aspx

RMOLLISE wrote:
On Oct 14, 8:00 pm, (John Savard)
wrote:

I believe it was from your site that I heard about the ones from
Starizona - but they now appear discontinued too.

Not AFAIK:

http://starizona.com/acb/hyperstar/specs.aspx

Glad to hear it: I couldn't find it when navigating from the *front
page* of their site, it wasn't listed under accessories.

John Savard