Large partial solar eclipse March 20 (1 Viewer)

. Projecting the Sun is quite easy using a small hand mirror with a mask giving a clear mirror of, say, 3 to 5 mm. So don't be put off by the comments of using an astronomical star diagonal.

The refinement using an astronomical star diagonal is complicated by the fact that the mirror is recessed in its housing.
Sometimes the back plate of the star diagonal has 3 or 4 screws. you can take the back plate off and then usually you can just use the mirror which is stuck to the back plate. The problem here is that inevitably you will get fingerprints on the front surface mirror. These fingerprints may be difficult to remove and may etch into the surface of the mirror.
but an astronomer can probably position a star diagonal with the barrel removed so that good projection is achieved.

On March 20 the Sun is 1922 arc seconds across. This is a little over 32 arc minutes and a little over 0.5°.

The diameter of the image of the sun on a screen or a white wall is 1/107th the projection distance. This is for a theoretical infinitesimally small mirror.
At a 5 m projection distance such an image would be 46.6 mm across. Using a real 3 mm mirror this, I think, gives an image 49.6 mm across. So the sun's image is 5 cm across as mentioned previously.

British summertime comes in on March 29, so I presume that Europe also has wintertime on March 20. So daylight saving time does not complicate matters regarding time.

. At about 1400 UTC today using a safely filtered telescope I saw a pair of medium-size sunspots to the right of the centre disc of the Sun through heavy cloud. I don't know if there were any smaller sunspots as the cloud was persistent and quite thick.

At about 1410 UTC today the cloud was a bit less thick, with sometimes about half of the sun's disc being cloud free.
I projected the sun's image onto the white kitchen wall using a very good quality 10×25 Docter binocular.
The two round very nice images of the Sun were bright. With a distance of about 30 cm between the eyepieces and the wall, the images of the Sun were about 3 cm across. Because of the persistent cloud I could not achieve critical focus. However, the clouds drifting across the disc were very nice to watch. I think that I should have been able to see the two medium-size sunspots, which might just be visible to the protected unaided eyes, but the cloud was too thick.
The limb of the Sun was slightly coloured. Maybe chromatic aberration and maybe because I didn't achieve perfect focus. Visually, the quality of the image with this binocular is very good normally.
It does help to have sunspots, as they are great aid to focusing.

One problem I did have was that it is difficult to keep the binocular very steady hand holding and looking at the images on the wall. But it is certainly good enough to have excellent views of a partial solar eclipse, where the changing size of the Crescent Sun would be seen very well.

After many days of cloud I have not been able to see the sun in a clear sky.

. Regarding the last post 22.

At 1504 UTC today, with a fairly clear sky, which was not transparent but rather milky, I had another go projecting the sun's image onto the wall and onto white card.

By increasing the projection distance to about 40 cm and with the two images of the Sun about 4 cm across, I could just see the 2 sunspots, which are fairly close together. They are equally large with an approximate penumbral size of 25 arc seconds each.
However, if I had not known that the sunspots were there it would have been difficult to notice them with a handheld 10×25 binocular. Had the binocular been mounted on a tripod I think that the two sunspots would have been seen fairly certainly.
The image is still quite bright at a 40 cm projection distance with 4 cm images of the Sun.

The sunspots are probably about 0.5mm across with a 40 cm projection distance and 4 centimetre images of the Sun. I was probably viewing them from about 50 cm.

I am happy to use a good quality 10×25 binocular for short periods of projection, but I would not feel confident using a high quality 10×42 binocular for fear of the Sun's heat damaging the eyepieces, particularly any cemented pairs of elements.

I just received accurate values for the diameter of the Sun and Moon.

March 20 09 30:00 UTC

Sun diameter equals 32' 07.40''

Moon diameter equals 33' 22.56''

Therefore, the Moon/Sun size ratio is approximately 1.05.

In other words the Moon's apparent size is 5% bigger than the Sun's apparent size.

The Moon's apparent size varies quite a bit, the Sun less so.
It is of course necessary for the Moon to be apparently bigger than the Sun to cause a total eclipse when they are properly lined up. Otherwise you get an annular eclipse.

. This morning I received the March edition of Sky at Night Magazine.
There is a free solar specs with a protective wrapper included with the magazine.
I presume that the magazine will be in the shops soon. They state that if the free solar specs are not included you should ask the newsagent for the free solar specs.

The classic test in visual light for the correct density of a solar filter is that one can just see the tungsten filament of a 60 W clear tungsten bulb. Unfortunately nowadays these are not usually found although I have some. I just tested the free solar specs and I can just see the centre of a pearl 60 W tungsten bulb either the round classic type or the candle bulb.
One can still get, so called, rough service 60 W tungsten bulbs, but these are pearl.

There are full instructions in the magazine regarding observation of the partial eclipse.

Included are instructions regarding colander projection and also pinhole projection.
I did not mention these before, because people have received permanent eye damage from looking through pinholes.
You must never look through a pinhole at the Sun.
You must never look through the holes in a colander at the Sun.
However, using a colander to project the Sun on a light surface, you will see multiple images of the Crescent Sun during the partial eclipse. This can be viewed by a group of people. You will only be able to see the Crescent and not smaller details such as sunspots as the resolution is not high.
The same applies to mirror projection, where large groups of people can see the partially eclipsed Crescent Sun, but again the detail is not good enough to see sunspots. However, you can follow the progress of the moon across the Sun very easily with these methods.

With my binocular projection method, I use this indoors, such as the kitchen yesterday.
There are real advantages in viewing the projected Sun indoors. You are inside a camera obscura, although it is only partially dark. I.e. darker than outside. If anybody has ever seen the projected sun inside a real camera obscura, you will never forget the observation.

In the sky at night Magazine, it shows binocular projection outside.
For this, they are showing a 10×50 binocular probably.
They have constructed a shade for the front of the binocular, as this is completely necessary to see the projected image of the Sun outside. The problem then is that it is more difficult to find the Sun as you cannot easily reduce the shadow of the binocular to a minimum in order to find the images.
Although I said I use a 10×25 binocular, this is from indoors.

If you are outdoors you can use a small binocular but at a short projection distance.
For use outdoors a cheap 10×50 Bresser, Meade or Celestron Porroprism binocular costing about £20 or £25 or a similar offering from Aldi or Lidl may cost only £15.
You can mount these on a tripod, and take the risk of damaging the eyepieces or any internal plastic, which might melt. However, as the eyepieces are probably three element, with only one cemented pair, you may be lucky and they may survive intact. But for the price one should consider them throwaway binoculars for this purpose. It doesn't really matter if they are collimated or not as you will still get an image. The magazine recommends that you cap one barrel, and this may be necessary to stop the images overlapping with this larger aperture binocular.

Binastro said:

. This morning I received the March edition of Sky at Night Magazine.
There is a free solar specs with a protective wrapper included with the magazine.

Click to expand...

Hi Binastro!

Nice info! As another poster mentioned, this thread should be a sticky.

I just got three pairs of Baader Planetarium solar eyeglasses. I think they will do the job! :t: We will only get 90% eclipse here in Kirkenes, but it should be awesome regardless (weather permitting of course!)

Beautiful weather today: saw Jupiter and three moons, Mars and Venus! :t:

. Hi HighNorth,
You obviously have eyes in the back of your head, but where are the third set of eyes .

Just joking, the eclipse shades are obviously to share with others.

I have projected eclipse images through my telescope onto a large white piece of cardboard for people to watch in the field across from the house. I explained that they shouldn't look directly at the sun even while it's covered by the moon (could get one of Bailey's Beads in their eye!), but some couldn't resist and took a quick glance at totality. Even noted astronomer/journalist and amateur astronomy enthusiast Timothy Ferris fell victim to this irresistible spectacle, which he wrote about in his book, Seeing in the Dark. He looked at the eclipse during totality and didn't get away from the EP fast enough as the sun peered out from behind the moon. He burned a spot on his retina and saw a red spot in the eye for awhile.

You don't have to be an amateur astronomer for this to happen, it also happened to me while watching birds. I was following some swallows chasing bugs over the field in the late afternoon. They zigzag so quickly, they're hard to follow, and as I was quickly panning, I "ran into" the sun. I immediately closed my eyes as soon as I realized this, but it was too late, the sun burned a spot in my left eyeball (it's also the eye I have a cataract in, perhaps by no coincidence). I saw a round red spot afterimage for a few months. I visited the eye doctor, and he said some gel had sloughed off the back of my eye, but was only partially torn so I was seeing the shadow of that gel.

So looking at the sun through a telescope or binoculars can be harmful, and when you're following birds in the sky with a low hanging sun, you need to be extra careful. Glancing at the sun naked eye for a second won't harm you, because you can't look long enough before its brightness forces you to look away, otherwise, we'd all be blind. But during an eclipse, people get a false sense of security that they can watch the sun because it's darkened, but they run the risk of damaging their vision if the sun emerges before they can look away.

When I lived on the "Mean Streets" of New Jersey, home to Joe Piscopo, Kevin Spacey, Alan Alda, Derek Jeter, and "the Boss," the son of a local pet shop was told not to look at the sun because there was going to be an eclipse so he walked around that day with his chin buried in his chest. Ironically, he ran into a stop sign and got a nice sized bump on his head.

I also had a friend named Marlene who refused to look at Comet Hale-Bopp through a telescope because she thought it would burn her eye out, and I couldn't convince her otherwise.

Brock

. Hi Brock,
. One second with unaided eyes is too long, and can do permanent damage in the worst cases.
One 10th of a second is about a sensible limit with the unaided eyes. And even this should be avoided and only occur by accident.

With optical aid, such as a binocular or a telescope there is no safe limit. You simply must not look at the Sun with optical aid. If you happen to catch the sun using optical aid and don't get permanent eye damage, it is pure luck. You may simply have been panning fast enough to save your eyes from damage.

It is when one deliberately stares at the Sun directly with the unaided eyes that real trouble follows.

With a telescope, permanent damage can and does occur instantaneously.

Comets unfortunately do leave a trail of misery. I can't remember the name of the foolish cult, whose members committed mass suicide, I think this was from a non-comet maybe. Human beings basically are nuts sometimes.

So are the Baader Planetarium solar eyeglasses safe to wear to view the eclipse? Are they better than the free ones that come with the new Sky at Night magazine? Thanks!

Out of interest, at totality in the Faroes will it then be safe for people to view with the naked eye?

Binastro said:

. Projecting the Sun is quite easy using a small hand mirror with a mask giving a clear mirror of, say, 3 to 5 mm. So don't be put off by the comments of using an astronomical star diagonal.

The refinement using an astronomical star diagonal is complicated by the fact that the mirror is recessed in its housing.


The diameter of the image of the sun on a screen or a white wall is 1/107th the projection distance. This is for a theoretical infinitesimally small mirror.
At a 5 m projection distance such an image would be 46.6 mm across. Using a real 3 mm mirror this, I think, gives an image 49.6 mm across. So the sun's image is 5 cm across as mentioned previously.

Click to expand...

I played around with an old prism diagonal over the weekend. Unscrewed the nosepiece and eyepiece barrels and placed it on top of a photo tripod. Projected the image into my living room over a distance of about 10 meters or so.

I now understand that a small mirror is needed to get a sharper image, but making it too small would render the image too dim.

I have an unused mirror diagonal laying around somewhere that I could cannibalize.
Would be cool to get the iris out of an old camera lens so that the effective projection diameter could be adjusted instantly.

You can use the filters from welding visors, but I believe that the advice is that these should be shade 14 or darker for direct viewing (but they shouldn't be used with binoculars or telescopes though).

I remember an eclipse (must have been partial) down in Kent maybe 10 years ago where I viewed the image inside a cardboard box through the scope.

Presumably older scopes would be still ok for this? (it was mentioned upthread the innards can be damaged?)

. Firstly, why do I get an advert for Bed bug removal just above this message box? Very strange.

Anyway, Grando,
I think that Baader planetarium eclipse specs may be pretty similar to the free ones. Maybe one is better at resisting scratches or less likely to have pinholes. Somebody else will have to advise.

This morning, with a very clear transparent sky at 0850 UTC I got a good but slightly strange coloured view of the Sun. It looks orange, which is not unpleasant, using the sky at night free solar specs.
It was high pressure 1038Hp. Just now in the Street I again got a good view, however the Sun looked a bit dimmer. I think that the reason was that looking out of the kitchen window the pupil size of my eyes was larger than when I was out in the Street in very bright sunlight. The free solar specs seem to be the correct shade.

There were no sunspots visible today with protected unaided eyes. There are two close sunspots, which are nearing the limb of the Sun, as it rotates, but these are too small to be seen without a properly filtered telescope. I think that they may be too small even for binocular projection.

I also viewed the Sun this morning with an H Alpha telescope. There was medium activity, some prominences not large, some filaments, and a few small sunspots.
But the activity on the Sun changes constantly, and it is quite likely next week there may be some larger sunspots.

For consideration of safety I will quote what is written on the inside right part of the free solar specs.

' SAFE FOR DIRECT SOLAR VIEWING. Maximum continuous viewing three minutes; intermittent viewing several hours. Do not use if lenses have scratches, pinholes or tears. Do not clean or disinfect. Do not use with other optical devices. Do not move around when wearing glasses. Do not wear if you have an eye disease or after eye surgery. This is not a Toy: use by children under adult supervision only.

WARNING: NEVER LOOK AT THE SUN WITHOUT SPECIAL EYE PROTECTION. Use these glasses to protect your eyes from solar radiation any time you look directly at the Sun or its reflection, no matter how small a part of it is visible.

On the left side of the free specs are the European standards specifications, which is good I was not aware that there are now official transmittance requirements, also maybe for Australia and New Zealand. These free specs are manufactured or at least supplied from America.

One slight problem that I had was that although they stayed on easily without glasses, when I was wearing my distance glasses then I had to put the free solar specs just in front of my glasses, and although they did hold, they did not do this very well.

So you may have to hold them with your fingers if you use your glasses with the free solar specs in front of them. This is to ensure that they don't fall off or slip so that you might accidentally view the Sun without protection.

. Hi dantheman,
. Really old telescopes, such as 60 mm, 3 inch and 80 mm long focus refractors from the 1950s and 1960s were usually made of brass or aluminium. These will not be affected by the Sun. Later telescopes may have plastic parts, perhaps in the focusing unit, which could melt.
Two element uncemented eyepieces are best. You can also find these with microscopes, and they cost very little. However, the standard fitting for microscopes is about 23.2 mm, rather than the 24.5 mm for older telescopes. My telescope had RAS threads, which are basically 1.25 inch fit, but threaded. The eyepieces are made of brass and will last for ages.
These two element eyepieces only really work properly at F/12 or slower. They might be okay at F/10.
You can easily stop down, even an F/5 telescope, say 100 mm refractor. If you stop it down to 50 mm then it will be F/10.

. Grando,
. During the total part of the eclipse, and only then, it is safe to look at the totally eclipsed Sun with unaided eyes.
There are usually dedicated observers, who call out when totality starts and when totality ends. This is to enable other observers to view the totally eclipsed Sun without protection. And also for them to take images of the event. But extreme caution is needed, especially if you're using optical aid.

I saw the Annular eclipse that came through Southern New York State in the Spring about 15 years ago. I stopped at an exit on Interstate 81 North outside of Cortland, NY. It was a gamble because the weather was calling for clouds.

There were a bunch of people there set up to look at it. A quy was there with his Edmund Astro Scan set up on one of the redwood tables. It had a set up on it to cast a reflection on a screen. He would give it a slight nudge every few minutes to follow it. It worked pretty good. His wife had brought a tub full of Peanut Butter and a large amount of Ritz Crackers for every one to eat and we had a good time.

Another guy came by with his Brandon 92mm (or Vernon) Scope and a set up for it. People driving by on Interstate 81 who hadn't heard about it stopped to find out what was going on and stayed to watch it.

During the period up to the full eclipse there were occasions when we could see it in tiny shadows caused by little pinholes in tree leaves near by. I recall how it got much cooler as the eclipse reached totality. Very shortly after it reached totality a thick cloud came over it and we all could see the annular ring through that cloud.

I had made a box with a little pin hole in it to cast a beam of light onto a white paper on the inside and if I got it lined up with the sun properly I could see the progress of the eclipse in a tiny circle of light cast on the paper.

It was well worth the leave I had to take from work and the 90 mile drive north to see it! :t::king:

Bob

. Hi Bob,
. Thanks for the description of the nice memories that you had.

The 1999 total eclipse in Britain was mainly clouded out, although some people had good views. Unfortunately I was not lucky.
A friend telephoned me from the Devon/Cornwall border and told me that all the cows and other animals were lying down ready to go to sleep.

Me and my mate travelled down to Cornwall to see the 1999 total eclipse. We were absolutely gutted, but not in the least surprised, when it was clouded out. We were sat on a cliff top overlooking St Michael's Mount when it took place. When it got dark large numbers of sea birds took to the wing making a heck of a din, guess they were alarmed and confused with the darkness decending so rapidly during daytime.

. Astronomy Now magazine just arrived.
Unfortunately the coverage of the March 20 Eclipse is not good. Not only that, there are no free Eclipse glasses.

So the Sky at Nght Magazine is definitely the one to get.

One can, I think, get eclipse glasses from the British Astronomical Association, but I have not looked up the price.

At about 1330 UTC today, with a bright sun but with some Cirrus clouds away from the sun, I had a look with filtered unaided eyes. Even though I was braced against a lamppost the wind was blowing me around and I could not get a perfectly steady view. There were no sunspots to be seen. It was 9°C and 1037Hp.

With a properly filtered 10 times instrument, again there was almost nothing to see on the sun's disc, which is unusual over the last few months. There was a tiny elongated sunspot at the 4 o'clock position nearing the limb.