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Old May 7th 13, 08:05 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: PN ABELL 70

ABELL 70/PK 38-25.1/PN G038.1-25.4 is a planetary nebula in southeastern
Aquila. The distance to it is rather vague. One paper (URL below)
cites two values, 2500 and 5000 parsecs and rejects the closer as
creating too many problems with their analysis of the nebula. For the
parsec impaired that would be about 16,000 light years.

Visually it is quite interesting with a galaxy as a hat. Most say it
resembles a diamond ring. Most images of this one show the center dark
but I show blue nearly to the core. Might be how their images were
stretched. In any case it is not often you see two unrelated deep sky
objects on top of each other like this. The galaxy is LEDA 187663 with
a redshift light travel time distance of 253 million light-years. That
puts it nearly 16,000 times further than an object that is possibly
16,000 light-years away. Another oddity!

The central star of the nebula is a double star. And a rare type of
binary known as a barium star. They seem to only exist in planetary
nebula and only a very few of those. Another reason this is an atypical
planetary nebula. You can read all about this at
http://arxiv.org/pdf/1109.1519v1.pdf .

This one is low in my sky where I need exceptional seeing which didn't
happen the night I took this. Another problem is that it lies right on
the geostationary satellite belt as seen from my latitude. The result
was a zillion satellite trails through the image, most just above the
nebula though two normal satellites flew through the field as well. OK
not a zillion, just 37 in 100 minutes time. I think that's a record for
me but I haven't been keeping track. There were two asteroids as well
but they were lost in processing out the satellites. Also the sky was
unusually bright this night which prevented me from going very deep.
This is why I chose this relatively bright object as one that could cut
though my strong air glow. It also was a very humid night further
reducing transparency according to my notes. Another I need to revisit
under better conditions. I probably should have picked on some star
cluster instead. I didn't know how bad it was until I processed the
data. But I dread the thought of processing out all those satellite
trails. Due to it being low I have to take it half on one side and half
on the other side of the meridian so will catch exactly the same
geostationary satellites every time!

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Prefix is correct. Domain is arvig dot net

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