ASTRO: V Aquila

V Aquila is a rather famous carbon star. I've often seen it visually as
redder than more famous carbon stars. Though these stars are variable
and their color changes through the cycle. It is a double star with a
separation of 0.2" so don't expect to see it visually. Since the red
color is so strong I assume the companion is much fainter than the
carbon star. I can't find an estimate of the companion's brightness.
Much about the star seems to vary with the source. I find even the same
source saying its distance is ~400 parsecs and that its distance is
~1200 light-years when 400 parsecs would be about 1300 light-years. I
don't trust either. It's B-V value varies as well but that may be due
to where in the cycle it is measured. I've seen it red as a stop light
and more orange than red. I have no idea where in the cycle it was when
I caught it on September 12, 2010 UT.

Trying to capture its color as seen visually is difficult. Monitors are
so limited that if it is red enough at the core it is way too dim
compared to the background stars. If you brighten it red is already
saturated so all that does is bring up green and blue turning it orange
then yellow. I compromised leaving it dimmer compared to background
stars than it really is. The color ratios are close to the RGB ratios.

The image is rather a composite. Background stars were 5 one minute
images while RGB data was 9 one minute images. Even then the L went
fainter with less noise than the color data. So I processed it as LRGB
rather than RGB as I planned. V Aquila however saturated in red light
so fast I was limited to 5 second exposures for it. I used 24 5 second
exposures in each color to make a RGB image of the star which was then
matted in over the LRGB version which was so saturated it was bright
yellow-white.

If you've never taken a look at this star, not far from M11 it is still
up there for a while.

14" LX200R @ f/10, see text for exposure, STL-11000XM, Paramount ME

Rick
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Third character is a zero rather than a capital "Oh".