After a week of waiting in vain for the odious and opaque offal in the atmosphere to go away, I decided not to wait any longer. I trotted out my 9" Intes Mak in my backyard near Sacramento to split double stars, if nothing else.
Smoke break:
The junk in the sky looked to me like it had two components: Smoke and water vapor. The smoke was low, yellowish/brownish, and it thinned out and essentially disappeared after 20-30 degrees of elevation. The water vapor appeared to be whitish and uniform. The white stuff does not look like, nor act like locally generated smoke -- it might have been smoke, but it didn't look like any smoke I had ever seen. The smoke from agricultural burning is low, and yellowish, and moves through in waves. The smoke from forest fires is higher, 'clumpy' and darker. Maybe it was smoke from Borneo.
Back to astro:
I also had just acquired an adjustable-height observing chair, and I wanted to see how it performed. I had never sat while observing before, and it was amazing and wonderful to sit in comfort while gazing at objects in the sky. Sitting, plus tracking with an equatorial mount made for the most relaxed and comfortable observing session I've ever had.
I started with M3, which looked uncharacteristically dull in the murky miasma. I then did some bright galaxy hunting, in spite of the sorry conditions, but I gave up after bagging only 4.
I felt challenged by Jay Freeman's report on April 19 of his split of Zeta Bootis.
Jay Freeman wrote on April 19:
> Zeta is closing -- _Sky_Catalog_2000.0_ indicates a present separation > only a bit above 0.8 arc seconds, which is beginning to be demanding > for a six-inch aperture.
'Beginning'? This made me laugh out loud, because the Dawes criterion is 4.56"/D (inches), which, for a 6" objective, yields 0.76 arc seconds.
After Jay's report, I looked at it with my f/5.6 10" dob, and though it appeared elongated, I was not able to split it at 190x, which is the highest I can go without using my barlow, which degrades the image.
I wanted to try with the Intes 9". I felt that the .8" separation should be well within range of both scopes (which are 0.46 and 0.51 arc seconds for the 10" and 9", respectively), and I was disappointed with the performance of the 10". The problem is either the optics or the lack of fine collimation (or both).
I wondered if the story was going to be the same with the 9".
It wasn't.
When I first looked at it at 119x, it looked elongated. In the Mak, this is (at the moment) the lowest power I have available. After looking at it for a while (seated in a relaxed and comfortable fashion), I effortlessly boosted the magnification up to 413x. I hoped and expected to see two pinpoints of light, just like other double stars with wider separations. Wrong.
At first what I saw looked like an elongated oval with stripes running through it parallel to the short direction of the oval. As I continued looking at it (seated in a relaxed and comfortable fashion), I came to realize that these were diffraction rings, and I could see the airy disks of the two components, and the first diffraction rings of each component were just touching. It reminded me of two eyes looking through glasses. I felt like they could have been even closer, and I would have been able to split them.
I went on to split a few more less challenging stars, and then started looking for some globular clusters in Ophiuchus. I couldn't find them, but I thought they should be pretty easy. I was puzzled, because it looked to my naked eye like the sky was improving. Sure enough, dew was covering the meniscus, so I packed it in.
--------------------------------------------------------------------- Date: Apr 28/29, 1998 11pm-2am PDT (0600-0900 Apr 29 UTC) Location: Backyard near Sacramento, California 121W 16', 38N 44' Instrument: Intes MK-91 9" f/13.6 Maksutov-Cassegrain Oculars: 26, 17, 10, 7.5mm Sirius Ploessls Seeing: 8/10 fairly steady, moments of very steady Transparency: 6/10 no clouds, but lousy transparency Limiting mag: ~4 - 4.5 (high uniform whitish haze (moisture?) + smoke?)