Contains:  Solar system body or event
Sinus Iridum to Plato, 


            Bob Gillette

Sinus Iridum to Plato

Acquisition type: Lucky imaging
Sinus Iridum to Plato, 


            Bob Gillette

Sinus Iridum to Plato

Acquisition type: Lucky imaging

Imaging telescopes or lenses: Santel MK-91 Mak-Cass 230 mm f/13

Imaging cameras: FLIR/Point Grey Grasshopper 2 GigE

Mounts: Astro-Physics AP 900 GTO

Guiding telescopes or lenses: Hutech Borg 60mm

Guiding cameras: ORION StarShoot AutoGuider

Software: Adobe Photoshop CS4  ·  Topaz Denoise AI  ·  Registax 6  ·  Maxim DL5  ·  Software Bisque TheSky6  ·  FireCapture  ·  AS!2

Filters: Baader IR 685

Accessory: Spike-a Bahtinov Mask  ·  Technical Innovations RoboFocus

Date: Jan. 25, 2021

Time: 22:00

Focal length: 3000

Seeing: 3

Transparency: 4

Resolution: 1422x1060

Locations: Roughacre Observatory, Ossipee, NH, United States

Data source: Backyard


Conditions on the night of 25 January seemed marginal, but I’ve long wanted to capture this lunarscape. Seeing and transparency were mediocre, wisps of cloud whipped past the moon, but nature gave me a 10-minute window.

The scene centers on Sinus Iridum – the fancifully named Bay of Rainbows – an asteroid impact crater 236 km across, half drowned in a sea of basalt at the edge of Mare Imbrium. Out in the lava sea, Montes Recti, the Straight Range, points toward the Montes Teneriffe, named for one of the Canary Islands, the peaks of a range submerged in lava just below the iconic crater Plato with its distinctive triangular landslide. Unfortunately, a great system of wrinkle ridges spanning the opening of Iridum doesn’t show in this illumination.

At upper center left are the battered remains of the very old crater J. Herschel, 134 km across, named for John Herschel, son of the better known William Herschel (memorialized elsewhere in the smaller crater Herschel.)

A distinguished astronomer himself, John Herschel further catalogued the northern and southern skies, named four moons of Uranus, studied color blindness, grasped the chemical power of ultraviolet light, invented the blueprint, made a discovery crucial to the chemistry of photography (sodium thiosulphate, the “fixer” that dissolved silver iodide, thus preserving an image on a glass plate and later film) and not incidentally coined the term “photography.”

He and his wife Margaret famously documented the flora of South Africa. Herschel was a friend and inspiration to Charles Darwin, who visited them in South Africa in 1836 on the voyage of the Beagle. Fittingly, Darwin and Herschel lie entombed alongside each other at Westminster Abbey.

Such are the wandering paths of lunar imaging. Best 1,600 of 13,200 frames at 22 FPS.

My thanks to the good folks at AAPOD2 -- Amateur Astronomy Picture of the Day 2 -- for featuring this image on 12 April 21.