ngc 7662: crown of red on the blue snowball
Posted 14 February 2013 - 12:37 AM
in addition to an opposing pair of red fliers
the nebula appears to have a red "crown" (per Sun Kwok's Cosmic Butterflies)
8" LX200R, SX AO, SX H9, .6"/px
astrodon 5nm OIII, 3nm NII
oiii 30x5 min
nii 23x5 min, 16x20 min
Los Alamitos, CA Bortle White skies
here's my RGB version from 8/19/06
apologies for different orientation
at a bit of a loss to explain the red around the core
in the RGB. perhaps Ha.
looks like i'll have to try this one with more filters next year
edit: NII long sbus were 20 minutes, not 29
Posted 14 February 2013 - 06:10 AM
Posted 14 February 2013 - 09:51 AM
Posted 14 February 2013 - 10:15 AM
Posted 14 February 2013 - 02:45 PM
for this one i just did a simple "balanced NOO" (NII = red, OIII = green and blue) for the star field (nebula was all teal). used a slight stretch to lighten the background stars, to match the red stars brought out below.
That's great Bill! A lot of NII in there. How did you map the colors/blend in the narrowband data?
did a separate narrow band balance pass to bring out the red fliers. don't remember the multiple, but i think it was 4-8x to the NII red channel. this of course turned all the stars red except the saturated central star, hence the first step above. this was a purist linear stretch as i was concentrating on the bright core. followed by a few rounds of RL deconvolution.
Posted 14 February 2013 - 02:54 PM
sorry for the typo, longer subs were 20 minutes.
Very nice. As a novice to all this, but starting to image larger narrow band targets... have not done well with this tiny object. How come you are using 5' subs and not all longer? I see you also have some 29' ones. Theory?
several reasons for short subs:
1. the NII signal is very weak (see response to derek above)
so in order to pick it up i had to go with much longer exposures, and stretch the red data more in order to bring out the red in the color picture (this is a hallmark of narrow band processing). conversely the central OIII signal is quite strong (this is a bright PN!)
since the NII data was relatively weak, due to inherently low signal, not much point to going deeper with OIII as my intent was to portray the two color channels together.
this nebula does have a faint outer OIII shell, so it's not crazy to go with longer exposures too. one of the difficulties with small bright planetaries like this is that this will generate massive diffraction spikes if you have a scope with a spider (reason i don't). and can make for blooms. even my NABG chip will give artifacts (not quite blooms) if you really saturate it. can be processed out in part, but it's a pain.
Posted 15 February 2013 - 02:29 AM
Posted 15 February 2013 - 03:51 PM
one more with this one
and then time for a new filter
Posted 15 February 2013 - 11:32 PM
Posted 16 February 2013 - 02:50 PM
Posted 16 February 2013 - 07:27 PM
nexstar 8 GPS at ~f10, SX-AO, IDAS LPR, H9C
10x60 sec 8/19/06 los alamitos, CA
Posted 16 February 2013 - 07:41 PM