Friday 8/11/19

Friday night. Feel free to use it as required if you add it to the blog.

After looking in on Rhys, Rachael & Jonny as they shut down the big
dome, I went to see and speak to Peter in the small dome. He was
observing the Moon with some prep work for his talk on Tuesday. We
discussed observing the "Pup" companion star to Sirius. Peter said that
he would think that Rigel and its companion star would be a similar
proposition and a dry run for Sirius. I took this on-board and would use
this later in my session.

I began observing Double Stars at 11:30pm in earnest. The temperature
began dropping rapidly. As it was due east, I located Lambda Orionis, a
close double, and took measures in Position Angle (PA) and Separation
(SEP) with the 12mm Astrometric Reticle giving a magnification of 592x.
Then onto Rigel.

With just a 26mm lens in the 14" sct yielding a magnification of 137x,
the 6th magnitude companion is easily split with a wide gap between the
primary and secondary stars. Measuring the PA & SEP, I found that the
SEP agrees with the official published measure of 9 arc secs, this looks
good for Sirius' companion star as the official separation is 11 arc
secs between the two stars, but Sirius is much, much brighter. While I
waited for Sirius to get to the highest point in the sky, I observed the
components of Omicron Eridanus.

This is a show-piece triple star system with the B & C stars being a
White Dwarf and Red Dwarf respectively. This would make a fantastic
image to photograph. Looking at it with again a 26mm lens and 20mm lens,
the yellow primary star contrasts wonderfully the two faint dwarfs. The
White dwarf is mag 9 and the Red Dwarf is mag 11 against the mag 4 for
Omicron itself. Taking measures in PA & SEP of the primary and both
dwarf stars with my 12mm astrometric reticle, I find that my results
agree with the Official published measures.

At 03:05am I steered the scope to Sirius. The star is over-powering in
the eyepiece even at 137x. The diffraction spikes spread-out in every
direction. Upping the magnification with a 20mm lens at 177x, again the
blazing star is very very bright. I spent over an hour searching for the
companion star with no luck. I did see what I thought was a spec but I
couldn't be sure. The companion at magnitude 8 is positioned at 70
degrees in PA, which is almost due east from north as seen through the
eyepiece. Will keep looking during the winter months.

Mizar AB was the next Double to be measured and duly completed.

At 6am I finished with an observation and measures of Gamma Leo. As the
sky turned from black to dark blue, I completed my measures of this
close double. I must say that these two golden yellow stars look
marvellous against a blue sky!

Fantastic night of observing, very cold but I had a few breaks for tea
and biscuits. I found that the padlock to the dome door had frozen so
needed my cigarette-lighter to unfreeze it. The car was frozen solid and
required several minutes of the engine running with heaters on full
blast before leaving at 7:30am. So home to bed!