Hypatia Sunrise Ray sketch

[Talitha]

Summer's not a good time for lunar observing because of the lack of darkness, but there's usually enough contrast on the terminator to work with. Here's a rough sketch from last night.. the Sun was just setting in the west as it was completed.

A bit NW of Theophilus there's a cute little leaf-shaped crater named Hypatia which has a breach in the eastern wall. As the terminator slowly creeps westward during the Moon's waxing crescent phase, sunlight enters the breach and flows onto the floor, creating what's known as a 'sunrise ray'.

[jgs001]

Superb sketch Carol.

[Dave Smith]

That is a lovely sketch Carol. The Sunrise Ray was also captured by the Consolidated Lunar atlas plate E5. I will attach a crop of it. How long does the phenomenon last?

[Baskii]

It took me a while to figure out where the "sunrise ray" was but now I see what you mean! A very nice effect, and a very nice sketch. How long does the "ray" persist for? Even given the long lunar day I wouldn't have thought it would take too long for the "ray" to cross the crater?

[Talitha]

Thanks! The sunrise rays eventually melt into the rest of the illumination on the crater floor as sunlight slowly pours over the rim. Depending on libration and the individual crater, this can happen rather quickly or slowly... generally within a few hours.

There can be multiple rays when the crater rim has multiple breaches, too. I've attached a really lousy image of some Plato rays from a few years ago (now you know why I sketch them ).

[Cloudwatcher]

Super sketch,Carol. :salute: Illustrates the effect you mention really well I think.

Not what I think of as a 'rough' sketch,indeed if it were one of mine if would be described as a detailed drawing.

Strangely enough I did a sketch of the Moon last night,as seen through binoculars and that really is rough.

Course,I blame the bad visibility,faulty focuser on the binoculars,light pollution,poor quality paper a smudgy rubber, blunt pencil and the subject kept moving!!

Cheers

CW

[Talitha]

Thanks CW! You forgot to mention the roughest thing about your sketch.. it's really difficult to do the full disc. I've only done it once and will never do it again.

Kudos!! :notworthy: