#83 Small Telescope Adventures: Part 6

The Olcott Project:  Adventures with a 2" Telescope--Night 7

Tonight's lunar observation (October 22nd) was aided by still air and mild temperatures.  Our 50 mm refractor is proving to be a wonderful instrument with which to study the lunar surface once again, something we haven't done much of in many years.  We observed our 25th object with Space Eye tonight, a minor milestone.  This marks our second lunar observation, with eight more allowed in our initial project of sixty objects.  We are hoping to eventually include several planets, too.

Object #25:  Sinus Iridum

We used Plate VII from the Field Guide, studying a very attractive and conspicuous area in and around Sinus Iridum, also called "Bay of Rainbows."  The Bay is 242 miles x 157 miles, and has a flat floor that sits about 2,000' lower than adjoining Mare Imbrium.  The curving mountain range ringing the north end are the Jura Mtns., rising to 18,200'.  They were spectacular tonight.  While some of the Bay was still in deep shadow, the mountain tops were brightly lit beyond and into the terminator.  We studied the area at 60x and 75x (without a filter), noting many other involved features (see sketch, below).  This area was lit spectacularly tonight, repaying careful study, and was easily the finest sight on the moon!  The moon was exactly ten days old.

Each curving end of the Juras has a name.  Cape Laplace, on the eastern end, rises to 7900', while Cape Heraclides, on the opposite side of the Bay, rises to 5500'.  The craters Bianchini, Helicon, and Leverrier all require a 2" glass to see clearly.  Their diameters are 23 miles, 15 miles, and 12 miles, respectively.  The adjoining Straight Range/ Montes Recti rises to 5500'.

 Deb's sketch of the Sinus Iridum area.  60x, 2" refractor.  10-day old moon.

Here is what Olcott says about the Sinus Iridum area:  "Capes Heraclides and La Place are at the eastern and western extremities respectively of the Sinus Iridum or "Bay of Rainbows."  They are 135 miles apart.  The former is 4,000' high [now 5500'], and its shadow forms the silhouette of the "moon maiden," best viewed when the moon is 11 days old."

 We also explored the Carpathian Mountains, a complex area near the terminator tonight, and just north of Copernicus.  The crater Tobias Mayer, at the eastern edge of the mountains, is 9300' deep and looked like a circular black pit!  This would also make a good area for detailed observations around the 10-day phase.

Mapman Mike

#82 Small Telescope Adventures: Part 5

The Olcott Project:  Adventures with a 2" Telescope--Night 6

Welcome back Space Eye fans!  The night of October 18th was a classic one, cold, dry and very clear.  However, I used my entire observing time hunting galaxies in Pegasus with the 12".  Despite a low 6-day old moon, I began picking off faint galaxies just after 9:30 pm.  I had a lovely tree blocking my view of the moon, which didn't set until 10:45 pm.  

The night of the 19th was clear but hazy.  However, it was actually warm out.  Deb and I undertook our first lunar observation (7-day moon) with our new 50 mm refractor.  As usual, Space Eye did not disappoint.  Small refractors usually excel at lunar observing, and our scope proved quite amazing.  Due to rather windy conditions we limited ourselves to 30x and 60x, using only the 20 mm and 10 mm Plossls that came with the kit.  They were more than adequate for the job at hand.

We worked off of Olcott's Moon Chart V, selecting two craters to focus on.  We spent about 30 minutes observing them, and Deb even did a little sketch (see below).  Here are my observing notes, followed by Olcott's comments:

Objects #24a and 24b:  Two lunar craters, Albategnius and Hipparchus:  Moon Plate V from the Field Book of the Skies:  These two craters are very conspicuous at first quarter moon, and lie at the very center and along the terminator.  We observed them at 30x and 60x.  The interior of Alba was completely in dark shadow, except for the tip of its central peak, along with one other summit closer to the rim towards the terminator.  Hipparchus was 90% lit.  Since they were both stacked one on top of the other right at the terminator, it is easy to tell that Alba is a deep crater and Hipparchus is not.  Several smaller craters could be seen inside Hipparchus.  Halley, a smaller crater between the two main ones, was prominent, as was Horrocks, at the opposite tip of Hipparchus.  Halley is 22 miles across, while Horrocks is 18 miles in diameter.  Alba is 82 miles (not 65, as mistakenly reported by Olcott in the Field Book), and Hipparchus is 91 miles.  Upon observing them it is easily apparent that they are similarly sized.  The same can be said of Halley and Horrocks, which require at least a 2" scope to be clearly seen.  They were clearly seen.  Other details could be viewed inside Hipparchus, and the rim of Alba was wonderfully distorted and ravaged.

Deb's sketch of an area of the 7-day old moon, observing at 60x with Space Eye.

Here is what Olcott says:  "About the center of the moon, just west of the terminator, lie Albategnius, 65 miles across, and north of it Hipparchus, 90 miles in diameter.  The latter exhibits signs of deterioration and is presumably older than Albategnius, which is very deep and comparatively perfect."

 Olcott discusses several other lunar sights located on Chart V, but we will save them for another first quarter moon session.  As we are coming up towards full moon, we hope to grab another lunar session or two soon.  Please stay tuned!
Mapman Mike