I adjust the Blue and Green for this. How much depends on the air mass
that I'm looking through. In this case the blue was divided by 1.41
while the green was divided by 1.32. Red was left alone. This resulted
in the brightest part of the biggest bubble having an adjusted blue ADU
count of 1423, which was 510 above background. Red had an ADU count of
962, which was 45 above background. That's way more difference than can
be accounted for by the response curve. It just didn't register much at
all in red. Green was way down as well which would seem to say little
OIII. I couldn't find much in the way of images on the net that were in
color and went as deep as mine. Only one I found had the bubbles in
"true" color by some amateur and it too was blue. Some Hubble shots
exist but they are all narrow band. Might be possible to get a true
color from that data, I didn't try.

I want to try it in Ha to see if they show up there but it's now out of
my small window of opportunity until next cycle. Or I cut down the
Polaris tree. It keeps so much snow off the observatory I don't want to
do that but may have to. With other trees cut it is growing rapidly and
I see I lost 5 degrees around the pole in just one summer. Last winter
I could get to 72 degrees north. Now it is 67 this winter at the
meridian. Not a good trend! Those branches are 90 feet up so a bit
difficult to trim! Tallest cherry picker in the area only goes to 65 feet.

Rick


Richard Crisp wrote:

cool image Rick

i think you are right about the HII bubbles but the reason they wind up blue
is because of the QE response of your camera being skewed in favor of blue

there's goiing to be Hbeta there too and may well be some [OIII] there too,
so that may skew the color a bit considering your QE at Halpha is pretty low
with the KAI11K sensor

I added two QE plots to this posting: one is for the KAI11002 and the other
is from the KAF3200

the Full Frame KAF series have a completely different red response than the
interline KAI series


"Rick Johnson" wrote in message
...

This is a member of the M81 group. A very faint member. Even at 80
minutes this was a rather noisy image. I needed more color and had been
waiting to get it but the skies had other ideas. It is now into my
Polaris tree. At its declination I can get it only well east of the
meridian when it clears the east side of the tree. At about 3 hours
from the meridian it enters the tree and stays there the rest of the
year. So I have a short window on this one. Maybe next year. I had
figured the bright blue arcs were HII bubbles, apparently not as they
were quite weak in red light and strong in blue. Not sure what to make
of that. Must be bubbles of hot new stars rather than gas clouds. Next
time maybe some H alpha data is in order.

14" LX200R @ f/10, L=8x10' RGB=2x10' binned 3x3, STL-11000XM, Paramount ME

Rick
--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".





--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".