April 22, 2021
Three Are Better Than One
Originally published September 3, 2011
images by George Tarsoudis, Greece
Having finally repaired my mount I was able to observe with my telescopes for the first time in many months. An object that attracted my attention on Thursday and Friday nights was Janssen. George's right-most image reminds me of Thursday's observation (although with opposite lighting) with a large mound visible in the middle of Janssen. Telescopically, this looked like a doming of the floor, adding another complexity to this strange concatenation of craters. But George's higher Sun middle image shows that the elevation is due to a mass of ejecta from Nectaris/Fabricius and perhaps a remnant of the central peak. So external forces rather than internal ones made this topography. But doming would be an attractive idea for doming and splitting of stretched crust could account for the existence the Janssen's big curved rille. I must admit that I did not see the rille while observing. The clock drive wasn't working, nor was the manual right accession slow motion control. I observed with an Intes 6" f/12 Mak that has excellent optics, and experienced first light with a new Astro-Tech 6" f/9 Ritchey-Chrétien. At low powers the RC provided images as stunning as the Mak, and they were quite good at 100X, but the view was softer at higher magnifications. The Astro-Tech is a beautiful, well made instrument with excellent focuser, but its large secondary - it is an astrograph - probably slightly degrades visual imaging. At $299 this is an amazing buy and I am glad to have one.
August 15, 16, & 18, 2011. Newtonian 10 inch @f/6.3 + Unibrain Fire-i 785 camera + 3X barlow + filter Red; Registax.
Rükl plate 67
George's lunar website
Yesterday's LPOD: West of the Usual Action
Tomorrow's LPOD: Rilled Dome