CN FORUMS ARCHIVE Telescope Reviews: On M27 in bicolor

first bicolor hence the essay title for the ensuing rant.

FS102, SX-AO @.3 sec exposures, CS 9.5 nm HA filter/Baader 8.5 nm OIII filter, SX H9
HA: 10/9/07 17x5 min HFD 4.4 on altair, OIII 10/18/07 14x5 min HFD 3.9 on altair
calibrated, combined color balance, ddp, HP filter in maxim.
then to PS...saturation boost, selective sharpening to the apple core, light stretch and smooting, final combine

tried two different ways of creating RGB from bicolor
HA OIII OIII, and HA HA/OIII OIII (combining ha and oiii 50/50 in green).
the first give nice deep reds and great color at the wedge and outer HA area
while the latter showed nicer contrast at the central HA areas.
i wound up combining the two, leaning more towards the first:
used the first as color and second as luminance
then blended that first in at about 50% in darken mode.
then brought the star color of the second in at about 70%

here are the intermediate steps which i found interesting:
HA OIII OIII:

HA HA/OIII OIII:

here's a polished version of the second:

lastly, here's my RGB image from last year
http://whwastro.homestead.com/files/m27-combined.jpg

anto did a great job showing a variety of ways to combine the data last year:
http://tinyurl.com/2sfwgc
i suppose everyone has to go over it when they first try it. to some this is old hat. others are just starting it like me, so here are my observations:

bicolor techinques HA OIII OIII vs HA HA/OIII OIII
note, m27 is a great object to try this with as there's a g0 (almost g2?) star in the field for color balance.

HA HA/OIII OIII
pros:
-better star color balance?
-emphasizes HA/OIII contrast in areas of high OIII signal, eg, center of apple core
-boosts dim HA areas
cons:
-undersaturated, red stars a bit yellow/orange
-deep reds turn to orange
-misses color contrast in low OIII areas (eg, the wedge, HA periphery)
how to compensate for shortcomings:
-increase saturation
-use the difference between HA and OIII as a mask to further increase saturation
(returning the contrast of the wedge)
-apply the HA OIII OIII version using the HUE or color combine technique in PS
to bring nebula colors to more traditional appearance.

HA OIII OIII
pros:
planetary nebula color comes closer to my RGB image.
great color contrast with deep red in the wedge,i.e., areas with high HA and low OIII.
boosts dim OIII areas
cons:
red stars too red, slightly oversaturated
HA signal in center is overwhelmed by bright OIII signal
and detail/contrast is lost as everything goes to white
(could be corrected with less aggressive stretch).
nebula too green?
how to compensate for shortcomings:
-color blur stars
-layer mask to increase center saturation or
-selective sharpening of red channel in bright center portion or
-less agressive stretch in bright center portion.

i guess all you know this, but visually it's never occured to me that most of the fine detail is red. i've used an oiii filter for m 27 many times, but never tried it with a red. anyone know if a red filter brings out the detail. probably need darker skies than mine to see:(

--------------------
-bill w

nexstar 8 GPS
canon 300D, Toucam Pro II
SXV-H9C, H9, SX Lodestar autoguider, SX-AO, DMK 51
FS 102 (OLV), FS60 CSV, 8" LX200R, Lunt 60/50 double stacked PT B1200, Losmandy G 11, ASA DDM60
http://astro.whwiii.net/
image processing monitor calibrated to just differentiate darkest boxes: