"JJK" wrote in message
...
I'd expect a thermally equilibrated C-14 to go deeper than an AP155,
everything else being equal.
I think a more interesting comparison would be between an AP 10" f/14.6
Mak-Cass and the C-14.
I'd love to have the 10" AP to use for the comparison!
Were the images taken on the same day and time (i.e., was the seeing the
same)?
Unfortunately no
Are the two cameras matched in quantum efficiency at the wavelength in
question?
They aren't matched very well anywhere. The KAF3200ME in the ST10XME has
lower QE pretty much across the board.
It also has 6.8 x 6.8 micron pixels versus 24x24 micron pixels.
About the only thing that is matched is the plate scale is similar in the
Thor's image. The plate scale of the c14/img1024s is 1.12 arc-sec/pixel
while for the AP155/st10xme, it is 1.29 arc-sec/pixel.
Were the images processed the same way (there are halo artifacts in the
C14
image)?
processed very similarly. The image saturated in the C14 (the brighter
stars). Saturated images that have been deconvolved usually show rings
around the stars.
I hope to make a more scientific comparison of the cameras in the future by
swapping cameras into the same scope on the same night etc. Just need clear
skies to do so.
Someone had told me that for extended objects like nebulae, that the f/ratio
was the determining factor in exposure time. That apparently is not all of
it.
Richard
"Richard Crisp" wrote:
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