SE Newsletter March 1999

"Diamond Ring" Effect

The light actually came from a very short and thin crescent," said Dr. Russell. "We astronomers were at fault in failing to emphasize more strongly that the spectator should use his naked eye for seeing the eclipse at totality and a second or so before and after." "The dwarfed crescent formed the appearance of a globe or drop of light on the retina of the observer. The eye enlarged and rounded it. The effect is like that of looking at an arc light. Actually the light comes from a very small point, but the eye exaggerates it into a ball of light.

This was spontaneously called "the diamond ring" by numbers of observers in New York, and this term, hitherto unknown by astronomers, was apparently fixed forever as as a technical term in the literature of the subject by Saturday night.

"It is a beautiful and perfect description of the effect," said Dr. Russell.

The "diamond ring effect" is a phenomenon which is most often viewed/seen with the naked eye. In comparison, "Baily's beads" are usually seen through a telescope.

"Baily's beads" only last several seconds (from the center line).

In contrast, the "diamond ring effect" can last as much as a minute outside of totality if conditions are just right. In any case, it is very common to see the "diamond ring effect" during the entire 10 to 20 seconds before and after totality. The effect occurs as soon as the sky is dark enough to discern the solar corona. The "diamond" itself may be formed by a thin crescent, a series of short crescent segments and/or beads, or by the last remaining "Baily's bead". It matters not whether the diamond is formed by a single or multiple crescents/beads: it is so incredibly bright that it appears as one single point along the Sun's limb as far as naked eye viewers are concerned.

I suppose I should point out that some care should be exercised in observing both "Baily's beads" and the "diamond ring effect" since serious eye dammage is possible if you stare at the Sun. Nevertheless, I have safely witnessed these effects with the naked eye and through the camera viewfinder of telescopes at over a dozen eclipses with no ill effects.

The key here is to take short glimpses for a second or so at a time and to have enough sense not to lock your eyes on the spectacle and stare.

I'd welcome other's comments on the subject of "Baily's beads" vs. the "diamond ring effect", and the observation of them. Fred Espenak

From: Bob Morris morris@sce.carleton.ca To: SOLARECLIPSES@AULA.COM Subject: Re: [SE] "Baily's beads" vs. the "diamond ring effect" Date: Friday, February 26, 1999 11:29 PM

Does anyone know who the Dr. Russell was who was quoted in the Globe and Mail re the 1925 eclipse?

BTW, the Globe I believe picked up a report from New York. I just have not seen the original report. The New York Times does say that the "diamond ring" (unnamed before the eclipse) was not a phenomenon they were told to look for!

Why? My guess that people before had been ultra cautious and not used naked eye when the sun was not totally covered.

I totally agree with Fred: You can look at the whole sun for 10 sec and only suffer a bad afterimage.

All reports say that eye damage comes from someone "hypnotically" fixating on the crescent sun for, say, 10 min before or after totality.

Looking at the diamond ring before totality with the naked eye ruins night vision.

However, based upon looking at the diamond ring after totality at Aruba, I can say (a) its dynamics, and visual dynamic range make it more spectacular than the cornona (that doesn't mean I won't look at the corona which although can (some say) be seen to change slightly during totality (b) I have no hesitation in advising anyone that observing the diamond ring with the naked eye for ten sec after totality is not only totaly safe but mandatory for full enjoyment of the eclipse.

Yes it requires the discipline to look away after ten sec, but the event itself tells you when to look away.

Is there any research that says observing the naked sun for 10 sec can harm the retina? I'm sure all of us have looked at the sun for perhaps 5-10 sec during our life. Comments? Bob Morris

From: Bob Morris morris@sce.carleton.ca To: SOLARECLIPSES@AULA.COM Subject: Re: [SE] "Baily's beads" vs. the "diamond ring effect" Date: Saturday, February 27, 1999 2:18 AM

Is it not possible that the reason the diamond ring was such a prominent sight at the 1925 eclipse was that the north edge of the shadow split Manhattan in two -- with people on one block getting totality and the next block up not.

This was reported in Mitchell I believe. And a map in the NYT supports it.

Surely someone literally on the very edge of the shadow would get a very prolonged diamind ring?

In an eclipse where one has to travel one would not seat themselves on the edge of the shadow. However, in New York City in 1925 there would be hundreds of thousands of people who could not travel and who thus saw the eclipse from just within or just without the shadow's edge.

And given the number of newspapers in New York, some of these people would have been interviewed.

So, if my suggestion is correct you have a large pool of people who see a prolonged diamond ring. Among these, you have some % who observed with the naked eye.

Even a small % of a large number yields many people who saw a long diamond ring with the naked eye, and a big target pool for reporters.

Just (I hope) an educated supposition!

But according to the front page of the NYT, the diamond ring was the big hit -- for them -- of the eclipse.

And according to the report in Toronto's Globe (which had big reports because the eclipse went through Toronto) the term "diamond ring" became an instant hit in New York!

I presume the Globe got their info from a wire service out of New York. Certainly, in 1925, New York newspapers could not get to Toronto in time for the next day's Star to have an excerpted report -- which it did!

Interesting note: Superman was invented by Canadian Joe Shuster and American Jerry Siegel. In the first Superman comic, the Daily Planet was the Daily Star, named after the Toronto Star! (It got changed fast!)

Superman could have got New York papers to Toronto in time. -) Bob Morris

BTW: the 1925 eclipse completely engulfed Toronto. Trouble was, the clouds rolled in about an hour before eclipse time.

From: M. Jahan Miri jahan@sultan.iasbs.ac.ir To: SOLARECLIPSES@AULA.COM Subject: Re: [SE] "Baily's beads" vs. the "diamond ring effect" Date: Saturday, February 27, 1999 6:41 AM

On Fri, 26 Feb 1999, FRED ESPENAK wrote:

> The beads are formed by direct rays of sunlight which reach us through deep lunar valleys just

As asked before, looking at your (Fred Espenak's) images from 1995 TSE, I noticed the Beads (and the Diamond) have an elliptical and symmetrical shape w.r.t. the "solar limb"?!

The projection of an openning between the solar limb and a valley (or the limb, in case of Diamond) of the Moon would be instead more like a "half"-ellipse (or a crescent). And the solar limb would "not pass through its center", while it seems to do so in the pictures.

Particularly, in the case of the Diamond, it buldges outward of the solar limb even more than inwards. Is it due to scattering? in the Earth's atmospher? How, and why it result in the above effects?

Where one could find a physical description of the effect? Thanks. Best regards, Jahan