Monday, February 15, 2016

sirius b!

I fixed the Astroscan today and was able to improve the collimation a little bit.  I used a laser collimator when putting the front glass plate back, and used pieces of tape as shims on one side of the housing rim where the glass plate needed to be lifted.  I tried it out during twilight and it seemed fine.  No harm done, luckily; the mirror had a couple of marks on it but should not make a difference in the view.

After dark I went out with the 8-inch and tried a few carbon stars, keeping an eye on the seeing, which was pretty good from about 9:30pm to about 10:00pm.  I started to get airy disks while looking at X and T Cancri.  I had seen the E & F in the Trapezium previously.  I went to Rigel and checked it for separation and did a fine focus.  Then to Sirius; I focused again on the 9th magnitude stars which precede it, to remember the dimness, then let the scintillating mess pass through.  Actually it was pretty stable in the center.  But my spider diffraction spikes where nearly W-E...  Several passes and nothing.  Then again and this time a small disk formed as I looked, riding on top of the diffraction spike, at the correct separation.  Tried again and it wasn't there... then it was.  I could hold it about 30% of the time.

So I will call it a success.  This in the 8-inch (really 7.5-inch since I have the outer 1/4-inch of the primary masked off to deal with a turned down edge), f7.25, at 368x (8mm with 2x barlow).

Some bands of cloud started sweeping through.  I looked at the quarter / waxing moon awhile at 368x and orange filter--some heaving from the atmospheric seeing but really nice sharp view along the terminator.  Then looking east I noticed a bright light below Leo -- Jupiter.  I swung the scope over for a look.  A bit mushy, and no Galilean moon events.  The sky was still variable; and tomorrow's a work day, so I packed it in.

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