"Richard Crisp" wrote in message . com...
I used the same 3nm FWHM Cust Sci filter for both images.

The C14/Dream Machine (IMG10124S) camera was exposed for 20 minutes x 3
exposures.

the AP155/ST10XME was exposed for 15 minutes x 6 exposures.

Unfortunately I blew it: I should have exposed the AP155/ST10XME at 1x1
binning, but used 2x2 binning instead.

If I had done the 1x1 binning, then the plate scales would have been pretty
close: C14/DM: 1.12 arc-sec/pixel versus AP155/ST10: 1.29 arc-sec/pixel.

But using the 2x2 binning on the AP155/ST10XME gave me 2.59 arc-sec/pixel
instead :-(

The AP155 system was operating at f/7 while the C14 was operating at f/12.46

From an exposure perspective, the 2x2 binning used for the ST10 gave me a 4x
speedup, so equivalent exposures at 1x1 binning would have been one hour
sub-exposures for the same exposure depth.

Here's the comparison, flawed as it is:

http://www.rdcrisp.darkhorizons.org/...55edf_page.htm

I will check, I may have some other data better for comparing. Still I think
the comparison is interesting. One thing that surprised me is that the stars
are a bit tighter with the C14. Although the larger aperture favors tighter
stars, I think the figuring of the optics for the C14 is not up to the same
level as the AP155. Still both did credible jobs.

Richard

The C14 shows better resolution, more detail in most areas. The contrast
of the AP155 shot seems "pushed." I noticed less tonal details in the
cloud and the "grain" is more noticeable in the AP155 shot. But
display good detail.
-Rich