High Moon

by David Kingsley

Kevin wrote:

...I finally had to stop looking as I was running out of superlatives.

A near-religious experience.

Exactly my experience observing last night near PaloAlto. I set up my 14.5 inch Starmaster in the backyard around sundown on Saturday and checked Mars about 11 pm. Views were OK but not particularly steady. I checked back from time to time, going back and forth between the house as it got later and later.

Although Mars is never getting very high in the sky for us this opposition, September is one of the months when the moon is particularly high around third quarter. When I checked in around 2 am, the moon had risen to at least 60 degrees above the horizon. The views were spectacular that high up. Absolutely wonderful detail at the terminator, including dramatic shadows and structure visible around my favorite " skipping stones" craters (the Messier pair, situated near the terminator last night). When panning over the rest of the moons surface around 2:30 am, I noticed that several craterlets were visible in the otherwise smooth surface of Plato. These craters are a frequently used test of steadiness and resolution, and i have previously had fun seeing how many of the small craters I could track down in a smaller scope. On a particularly good night with my 7 inch Oak classic back in October of 2000, I had been able to count and confirm 11 craters on the floor of Plato (see: http://www.observers.org/reports/2000.10.14.4.html).

Last night, I settled in for my first every detailed count count with the 14.5 inch Starmaster. With the tracking motors on, it was easy to crank up the magnification to around 600x, get comfortable in a chair, and start sketching (eyepieces used: 3x Televue barlow with 9 mm Nager or 8 mm Vixen 8-24 mm zoom). The biggest craterlets were obvious and could be held at all times in the steady seeing. Lots of other ones began to show up as I looked more carefully, and would snap clearly into view for seconds at a time at the limits of resolution. I sketched the locations of a total of 20 different craterlets over the course of about an hour. I did not have any picture or map with me at the eyepiece, so this morning I compared by sketch to the detailed pictures available from NASA's archive of Luner Orbiter satellite photographs see: http://www.lpi.usra.edu/research/lunar_orbiter/images/img/iv_127_h3.jpg), and to a high resolution stacked image of Plato made by Steve Keene and featured on Jim Ferreira 's video astronomy web site (see http://www.fortunecity.com/victorian/canterbury/222/astrovid.htm). All 20 of the spots I diagramed last night corresponds to a crater visible in the high resolution photos. In addition, I found an excellent correlation between the diameter of the craterlets as seen in the photos, and how easy the individual craters had been to see in the eyepiece. The 14.5 inch Starmaster not only showed more total craterlets than I had seen with the 7 inch before, it also showed much more detail and structure in the overall view. The seven or eight largest craters all looked like obvious craters with the 14.5 inch scope, not just small white spots against Plato's dark floor.

The resolution that was visible in Plato last night was typical of the highly detailed views available all over the moon's surface. I wasn't planning on a particularly late observing session, but the views were so steady it I couldn't tear away from the eyepiece. After great views of the moon, and trapezium, and Saturn, it was 6 am before I finally crawled into bed, happy that I had bothered to set up the big scope, and dreaming about what Mars would look like if we could see it as high as last night's moon.