Friday, September 28, 2001

Doubles under a full moon

Friday night at Houge Park was an amazing experience for anyone there with a telescope set up. Even before dark, crowds were beginning to gather, and I could tell something was up. By dark hundreds of interested school kids, mostly 3rd and 6th graders, and their families were amassed.

Once I looked up and saw lines 30 people deep at my telescope and Kevin Schuerman's. Ours were the "big guns" that night, mine a 14.5" f/5.6 Dob, Kevin's a 13.1" f/4.5 Dob. Kevin had thought he'd have the biggest scope there, with so much moon out. Sorry Kevin ;-) Lines at the scopes lasted a few hours, then things settled down.

I began by showing Albiero, but soon realized that my ladder was not tall enough to allow the younger children to reach the eyepiece. For a while I would watch parents strain to lift their children skyward, up on a ladder. I soon concluded there had to be another good double to show that would not entail such risk.

I pointed the scope at Eta Cass. This was much better. As each person looked at the double I would ask them quietly to describe the colors. Since we had a discussion on this mailing list about color perception I was interested in a wide sample of opinions. Amazing what a divergent reply one can get. I do believe that experience tends to be an equalizer, since the replies I heard ranged from yellow and tan to white and orange, white and white (amazing!), red and gray, even white and silver!

Later I began pointing the scope at M22, M13, M31 and other bright deep sky objects. The results were quite good. I attribute it to aperture. I also attempted to show a few people NGC404, which was clearly visible just off Beta Andromeda if you knew where to look. Transparency must have been very good.

I had come to Houge Park Friday night with a list of double stars to observe. Little did I expect an invasion. My list waited until the next night.

Saturday about sunset I rushed out to unpack the 14.5" from the back of my truck and set it up in the back yard. It was nearly a full moon, close enough anyway. But I figured it should still be possible to split some doubles. Someone had mentioned on TAC's mailing list the "astronomy forecast" was favorable, and soon after dark I was collimating. After an hour's cool down, I found the star images were still pretty fuzzy, and this was not going to be a great night for pinpoint stars.

However, the list I had was not tight doubles, but the Saguaro Astronomy Club's Best Multiple Stars. So long as there was sufficient separation, I still could observe.

I began with Beta Cepheus. This is Alphirk, the northeastern star in the "box" that defines the main body of the constellation. The primary is very bright white at mag 3.8 with a yellow or rose colored companion west of and close to the primary, significantly dimmer at mag 7.8.

I moved next to Struve 2816, which had been a topic of conversation on TAC during recent discussions on star colors. This is easy to locate along the southern boundary of Cepheus' constellation lines. Find Alderamin, Alpha Cep sitting between the bottom stars of Cepheus' box. Move south and outside the box past Mu Cephei to this triple star. The primary component is visible naked eye in dark skies, at mag 5.7, is bright yellow/white. Two companions shine at mag 8, one 7" NE, the other 2" WSW. This is a nice triple.

I mentioned Mu Cephei. While it is not a double, the sheer richness of color in this star is amazing. If you want to see pure gold in a star, this is a great example.

Just west of the center of the box that makes up the southern part of the constellation Cepheus is the star Xi Cephei. I saw this as a bright white primary with a dimmer yellowish-red companion almost 2" W. The seeing was not good enough to split the third component apart from the secondary, just 1" to its E. I'll try splitting this one again tonight.

Next on my list of colored doubles was Delta Cephei, which I immediately felt was an Albiero clone. The double sits in an area rich in open clusters, I recall visiting many times over the years. The star sits at the northwestern apex of a triangle of bright naked eye stars, at the southwestern corner of the box of Cepheus. Even with the large moon they were visible, at mags 3, 4 and 5. Delta's primary shines at mag 4 and is a nice gold/white color, not quite as rich gold as Albiero. The companion is very blue and sits a wide 42" south.

Struve 2486 is comprised of a pair of twin yellow/white stars off the eastern wing of Cygnus. When looking at MegaStar, this star appears a triple, although again I only saw a double in the soft seeing last night. I had to work a bit to locate this double, matching star patterns on my Tirion Sky Atlas 2000. The approximate location is reached by starting at Gamma Cygni and drawing a line to Delta Cygni. Continue not quite the same distance past Delta. One odd finding was to see the Saguaro list showing a 2 magnitude difference, mag 6.6 and 8.6, but I found the components to be of nearly equal magnitude.

I moved next to Beta Cygni... Albiero. No kidding, this is easily the most magnificent double in the northern sky for color. Albiero is simply stunning. It is even more impressive after sampling other notable doubles. The richness of color is awesome.

I finished the night working hard to locate h1470, approximately between Gamma and Eta Cygni. I star hopped using Tirion's Sky Atlas 2000. A good landmark to start from was a notable chain of stars running NNW/SSE for about one degree just east of the constellation line. It was easily worth the effort. Other than Albiero, which even in all its beauty is rather pedestrian since it is so popular, h1470 is the winner of last night's observing session. It is like Albiero, but the yellow component is a ruddy yellow/red... so rich it was outstanding by itself. Add to that a secondary component so blue that it borders on purple, and you have absolute jewels of stellar evolution. It is a wide pair, almost 30" between the components. The dimmer star lies N of the primary. This is one to add to an observing list!

I'm hoping the steadiness will be better tonight. The scope is still set up, the moon is bigger, and there are many more doubles on the list.

Doubles under a full moon can be fun.

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