I was trying M13 on your recommendation but I’ve not had any success. I picked
the 240 second exposures in order to get the histogram to peak up in the 1/4 to
1/3 range. But that’s evidently the noise not the data that’s spiking there.
Shorter test images don’t show the cluster at all.
I've had “much” better success on the Crescent nebula. At least there my stars
are coming out decently. I can almost convince myself that there’s a faint
trace of the nebulosity in the stacked version but it’s so close to the noise
level that I haven’t figured out how to separate it from the background noise.
If it’s not all in my imagination!
I'm not really into doubles or open clusters. Planets are interesting but
that’s a whole different ballgame. I have 100 images of Saturn waiting to be
stacked once I figure out Registax or Autostakkert!2. Whichever one takes a
pile of individual images.
I’ve been looking at the ZWO ASI178MM and ASI1600MM. If I was primarily
interested in planetary subjects, I’d go with the ASI178 with it’s narrower
FoV. But I’m seriously considering going with the ASI1600 with its bigger
pixels and wider FoV. Although the nearly $600 difference in price makes it a
hard choice. And I don’t want to get into the habit of thinking every
astrophotography problem can be solved with an expensive new piece of equipment!
But now that the monsoon is settling in, it may have solved my Canon’s heat
issue: it’ll be the cooler fall before the skies clear again to worry about
imaging and SNR! :-)
Mike McDonald
mikemac@xxxxxxxxxxx
On Jul 8, 2018, at 3:26 PM, James Yoder <az.jyoder@xxxxxxxxx> wrote:
Second, you will need to examine your histogram, that should determine your
optimal exposure time . I think (someone correct me if I'm wrong) will
show you the sum of your signal, dark noise, and light pollution. Your
peak should ideally be about 1/3 to 1/2 on the X axis.
Finally, consider what you are imaging, as you know the S/N ratio is
important, so if thier isn't much you can do about the Noise with your
current finances, look for objects with high signals (IE Surface
Brightness)... Globulars(M13), some bright Nebula (M8), even some
Planetaries foot the bill (M57) if your tracking is good. There is also
always open clusters, and even binary systems that are great candidates.
That all being said, I finally decided top purchase a cooled camera myself
about 6 weeks ago. I ordered the QHY128C that has been on back order
forever!
http://www.qhyccd.com/QHY128.html A pricey solution, but should help
address the temperature issues in the summer here (if I get it before
summer is over).
James
