Tag moon

Annular solar eclipse: We’re outside the circle

Photonstopper
Partial eclipse of the sun, dawn, June 10, 2021. Photo by James Guilford.

UPDATE: Rainy skies are expected in Northeast Ohio on eclipse day so here are some places where you can view the event online:

On Saturday, October 14, 2023, there will be plenty of buzz about the annular solar eclipse taking place. The eclipse will happen, blue sky or cloudy, dimming the day’s midday light. Here in Medina, Ohio we won’t, however, be seeing the real attraction, the so-called “Ring of Fire”. We will, however, experience a partial eclipse of the sun; about 35 percent of the sun will be obscured by Moon, making Sun a crescent.

Begins:Sat, Oct 14, 2023 at 11:48 am
Maximum:Sat, Oct 14, 2023 at 1:08 pm 0.462 Magnitude
Ends:Sat, Oct 14, 2023 at 2:29 pm
Duration:2 hours, 41 minutes
Eclipse timings for Medina, Ohio as provided by TimeAndDate.com


What’s an annular eclipse, then? Well, “annular” means ring-shaped, not “annual” as in once a year. The ring, or annulus, we’re talking about here is created by our Moon passing between we Earthbound viewers and Sun covering most, but not all of the solar disk. At its peak, an annular eclipse leaves brilliant ring of sunlight visible, shining around the edges of Moon — the ring of fire. The better-known total solar eclipse occurs when Moon covers all of the solar disk, allowing viewers to see the beautiful haze of Sun’s corona streaming around the dark circle where Moon superimposes Sun.

Solar eclipses take place in three basic varieties: partial, annular, and total and what happens on each occasion is dependent upon the positions of Sun, Moon, and viewer. Why won’t anyone see a total solar eclipse this Saturday? In short, it’s because Moon’s orbit is elliptical, not circular. On an elliptical path Moon will appear larger or smaller from Earth, depending upon Moon’s position on its orbit. We’re fortunate that Moon can so perfectly cover Sun when it’s a bit nearer us, producing glorious total eclipses. But when Moon is a bit farther out for an eclipse and appears smaller, it can’t quite cover all of Sun and that’s when annular eclipses happen.


Coverage graphic courtesy Michael Zeiler, GreatAmericanEclipse.com

Moon is near enough to Earth that parallax influences what viewers experience. At the center line of an annular or total eclipse, the full effect of the event may be enjoyed. Stray off that center line (path of annularity, or path of totality) and a partial eclipse is seen. It’s like someone hiding a few steps behind a tree. If the tree is directly in the line of sight of the viewer, the person is hidden. Take a step to one side, however, and the hidden person begins to be revealed. Parallax.

Viewing: Neither those out west nor we here in Ohio can safely view the annular or partial eclipse phases safely without proper gear. ISO-Certified viewers are the gold standard so long as they are undamaged. Eclipse viewing glasses are available from many sources though it’s probably too late to order them in before this weekend’s event. Maybe think about buying some soon for next year’s total eclipse! There is a mix of opinion regarding #14 welder’s glass — they’re probably alright to use if you have them but be careful — welder’s glass comes in different shades and lighter shades may not provide adequate protection!

Do Not Use: Sunglasses of any sort, photographic negatives, Compact Discs, shiny plastic wrapping, etc. for viewing the sun. If you view the brilliant solar disk improperly, damage to your eyes can result and be instantaneous and permanent. If you happen to have solar eclipse glasses from previous events, those would be great to use but examine them first! Hold the glasses close to a bright light source and look for pinholes, scratches, or other damage; if you can see light spots coming through the lenses throw the glasses away!

Happy, and safe, eclipse viewing to you!

Trials were trying

Photonstopper
Crater Tycho is featured here, its web of light-colored ejecta radiating in all directions. Celestron C11 telescope with ZWO ASI 294MC Pro camera.

Taking advantage of what seem to be rare clear skies, last night (September 1, 2023) I ran first light trials on the Celestron C11 I was given, in combination with my ZWO ASI color astronomy camera. The telescope, with its decent aperture and long focal length, may become the primary observatory instrument. The results were largely disappointing with no good deep sky results, terrible results from Saturn, and not-so-good images of Jupiter. Even Earth’s Moon, usually an easy target, was barely in focus. It didn’t occur to me to use my Bahtinov mask focus aid — my gear is spread across two buildings and three or four locations! Once built, the observatory should help with organization. I hope to try again this coming week when mild, clear nights are forecast and I hope it is only a matter of technique and not an optical issue.

On the positive side, polar alignment was excellent as was goto control alignment so telescope sky tracking was very good during my efforts — until something caused an unexpected reboot of the telescope controller. I don’t know if dew short circuited a connector or if the connector pulled loose from the handbox but it was disconcerting!

The images shown here are simply interesting to look at, though not the quality I’d normally want to show. The first is youngish Crater Tycho showing off its extensive web of ejecta rays. The second picture includes several lunar “seas” including the “C” shaped Sea of Crisis. Two craters are seen near the left edge of the circle; the lower of those craters is named Picard. No, Star Trekkers, not THAT Picard. Still, a fun fact.

Several lunar seas are shown in this image with the Sea of Crisis, the C-shaped feature, on the right. Within the Sea of Crisis are seen two small dots and the lower of the two is Crater Picard. Celestron C11 telecope with ZWO ASI 294MC Pro camera.