Solar Eclipse in UV: 70% in Central New Jersey

[Andrea B.]

Although my part of the United States did not see the full solar eclipse, the 70% maximum version we got was quite fascinating. I am outdoors a lot, so to me the sunlight became very much dimmer than normal during the eclipse. Michael did not notice the difference quite as much.

 

At the beginning of the eclipse here, my Solartech Solarmeter was reading around 3.5 mW/cm2 UVA+UVB when pointed at the sun. The readings dropped to 0.8 at our maximum shadow - quite a dramatic difference in solar UV output. We had some cloud scrim coming and going, so I tried to only take Solarmeter readings when it was gone. However, please don't take those measurements as anything other than an observation of the relative drop in solar UV output between beginning and maximum of the eclipse here.

 

We did not make note of the temperatures, but it did feel cooler during the maximum shadow.

 

Gear:

Nikon D610 full spectrum conversion

Nikon 105/4.5 UV-Nikkor UV-dedicated lens

 

Filter:

I flipped between these two types of filtration.

Hoya U-340 (4mm)

Hoya U-340 (4mm) + S8612 (0.75mm)

 

In order to try to get a UV photo of the eclipse with between 4.00 - 4.75 mm thick filtration I needed to drop the ISO setting to 100 and stop the UV-Nikkor down to f/16 - f/32 to cut the immense amount of UV getting through.

 

 

 

Reflected Ultraviolet Photograph of 70% Solar Eclipse at Maximum

Location: (North 40-23'39'', West 074-07'02'')

Altitude: 118'/36m.

Exposure: f/32 for 1/1600" @ ISO-100

Filter: Hoya U-340 (4.0mm) only

Monochrome, straight out of camera, cropped. It is easier to control massive amounts of incoming sunlight by simply shooting in black & white mode. The UV color is false anyway.

It came out rather well I think although I doubt NASA would be interested. :D

 

 

 

Raw Composite of Preceding Frame

The file was converted in the Raw Digger app to determine where the UV light was recorded before application of any white balance steps. Light went to the red and green channels. The blue channel was mostly noise.

 

 

Exposure Push of Preceding Frame

Shoot directly at the sun and what do you always get? Flare, reflections and other glowy artifacts. I pushed the exposure here just to show you what was hidden.

 

 

Another Pushed Exposure

Another shot shows that if you shoot at a slightly different angle the flare and reflections just move somewhere else.

 

 

 

Reflected Ultraviolet Photograph of Solar Eclipse at about 50%

f/22 for 1/4000" @ ISO-100

Filter: Hoya U-340 (4.0mm) + S8612 (0.75mm)

Monochrome, straight out of camera, cropped.

 

 

Exposure Push of Preceding Frame

It is kind of fun to see how the light bounces around through all that filtration and optics.

[Hornblende]

Great images Andrea, I can see a sunspot group in your fifth image!

And your first image looks like an upside-down Cheshire Cat!

[Andrea B.]

Thanks! I was so excited that my little impromptu UV fotos managed to capture a sunspot!!

What a fun day it was.

[OlDoinyo]

I viewed the eclipse with my son as we flew into the Monroe County airport in Madisonville, Tennessee. The weather was hazy but mostly clear and totality lasted around 2 minutes and 30 seconds. About 70 other small airplanes flew in, there was a party with food served by the airport manager and associated FBO staff, and the mood was festive and bright. A generally good time was had by all, especially for those of us for whom this eclipse was a first-time experience.

 

Unfortunately, my pictures of the event are basically garbage, and are posted here only as curiosities--they certainly do no justice to this magnificent spectacle. I used the Makowski 500mm mirror optic, which is a fussy optic, but my pictures from Monday are not even up to the standard of my practice shot from last week--something seems to have gone horribly wrong with the focus, such that not even being at f/32 could rescue the situation--and due to the small preview screen on my camera, I was not aware of the issue until too late. I do not own any other long telephoto lens with appreciable UV bandpass, so I used what I had.

 

I managed to fire off four UV frames during totality. the Sony A900 was fitted with the Makowski 500mm mirror optic and the Baader U2 filter. Exposure was 1.6 seconds and display intent is BGR.

 

ISO 100, f/32:

 

 

ISO 800, f/32:

 

 

ISO 800, f/16:

 

 

ISO 800, f/8:

 

 

None of the corona's structure is resolved in any of these images. The three loop-shaped prominences on the right limb (captured by millions of other photographers on the same day) are apparent; that they appear orange-red indicates emission primarily in the 370-400 nm range; the corona shows no chromaticity. There is no argument from incandescence to explain the prominence color; line emission (possibly from ionized calcium) may be the cause of this.

[Andrea B.]

I've had some events myself where the photos didn't turn out so well. But the mental images and excitement from being there and seeing something "for real" will be held in memory forever.

 

I'm thinking that the mirror optics must have gotten a bit jarred?

 

Anyway it is quite interesting to see the false colour you captured for the prominences. Are those what they call the "Baily Beads"?

Thank you for showing us these.

[Cadmium]

Clark, You were more centered in the totality than I was, to get that even of prominences all the way around, and to get that longer totality of 2+ minutes.

If I had driven a little further north I would have had twice the totality time length.

 

Andrea, when I shoot the sun I always stack whatever filter with AstroSolar film in the front. I never shoot with any filter by itself.

This is to protect everything, filter, lens, camera... and even the eyes if using the viewfinder, but I have never used the optical viewfinder,

so far I have always used a loupe with live view.

That protects me totally, and protects the camera gear.

My usual past set up for sunspots and such has been AstroSolar 5.0 OD + Baader U.

This time I have been using AstroSolar 3.8 OD + H-Alpha filter, because 5.0 OD is a bit strong with the H-Alpha, so that stack protects the camera, and gives enough light, but can not be used to view optically.

 

Of course if you are in the totality zone, then you can photograph the totality as long as it lasts in your location without any filters at all, and you can look at it with no eye protection, but not a second before or after totality.

You know when it is total if you are wearing solar glasses, or looking at a filtered live view, because when it is total the view goes dark through the glasses or through the filters.

In my opinion, the best set up to photograph the sun and sunspots on any clear day is simply to stack the Baader U or other UV-Only filter, with the AstroSolar 5.0 OD film, using live view, with a long lens that preferably is at least moderately UV friendly.

Tripod, mirror up, remote shutter... I usually use spot, AP, and play with exposure comp a bit to get the surface of the sun and the detail of the spots optimized. I often use auto focus with lenses that do.

I don't let the camera bake in the sun, I put my rain hat over the end of the lens hood when not shooting, this shades the entire length of the lens and camera, as long as it is pointed directly at the sun.

Personally, I don't think I would shoot the sun with only a UV filter or stack alone. The Baader U and AstroSolar 5.0 OD seem to be a pretty good working pair together, and everything is protected, even if you inadvertently look through the optical viewfinder.

I feel more comfortable with live view myself, and with 5.0 OD film.

DANGER!!!! BE CAREFUL not to get your 5.0 OD film mixed up with 3.8 OD film. They look the same, although you can see the difference if you view a light bulb through them.

I posted a couple pics of my eclipse setup:

http://www.ultraviol...dpost__p__17342