16 replies to this topic

[George9]

Yesterday was a relatively clear day, and the Sun was at about the right height, so I lugged my coronagraph and mount and camera on the subway to West 34th St and 12th Avenue (the Hudson River) to image the solar corona behind the Empire State Building. Here is my first attempt at processing. I hope to improve it. I have lots of shots, but this one captured the corona just passing behind the building and the light refracted through the 102nd floor observation deck's plate glass windows. It was taken at 8:37am on November 2, 2023. The coronal streamers were confirmed by the Solar Dynamics Observatory 211A image, as well as by turning the filter oven off later on and seeing the streamers disappear off band.

 

It proves that even from a sea-level city on a good but not perfect day, you can get the corona with amateur equipment.

 

I will post later with better versions.

 

FYI, here is the coronagraph: https://solarchatfor...pic.php?t=42685

 

George

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Edited by George9, 03 November 2023 - 08:22 AM.

[SNH]

I had no idea such a picture was possible from the ground!

 

Scott H.

[George9]

Here is a better shot at processing, plus an image of the Empire State Building taken 30 minutes earlier to see where the camera was aiming.

George

 

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[George9]

Two photos by my friend, Stan Honda, an excellent photographer, of the set up. The photo with the black rectangle on upper left is a clever shot with an eclipse viewer showing the Sun (yellow half circle) partially covered by the Empire State Building.

 

George

 

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[highfnum]

That's weird 

[lorenzo italy]

Excellent photo George.

I thought that only from high altitude could the solar corona be photographed. What seems most incredible to me is that you managed to transport all the equipment on the subway 

 

Lorenzo

[Klaus_160]

Fantastic image!

You should wait for a day with 'more Corona' to make it even more impressive!

[hopskipson]

Excellent photo George.

I thought that only from high altitude could the solar corona be photographed. What seems most incredible to me is that you managed to transport all the equipment on the subway 

 

Lorenzo

 

As a native NYer, I am thoroughly impressed!

 

Great shot, George!

[R Botero]

Great result!  

[George9]

Thanks, all. You know, it was a pretty clear day ("above average" on ClearSkyClock) but not amazing ("transparent" on ClearSkyClock). I had taken a photo of the horizon on Oct 23, which was a weirdly clear day and on this day, Nov 2, and you can see that Nov 2 was more hazy. So it doesn't have to be a freaky clear day.

 

The 1.2-Angstrom FWHM filter at 5303 Angstroms is the key. I did spend about a year reducing scattered light inside the instrument, but nothing was magical. Klaus and I have gotten to the point where we expect to see at least some corona on every outing (obviously we don't go outside on hazy or cloudy days).

 

I expect someday a manufacturer will produce a corona-viewing coronagraph for amateurs. The 5303 filter makes it easy enough for them to make it safe when the Sun peeks out.

 

George

[LarryAlvarez]

Pretty cool!!!   The pics of you shooting it make the whole thing cool! 

[ch-viladrich]

Amazing George !

 

This is a kind of double-oculter system, with an internal oculter and an external oculter ;-)

 

The periphery of the external oculter should be "dented" to limit diffusion of light by diffraction. Not sure there is a building somewhere with "dented" edges.

[George9]

Ha, yes, you could look at it that way.

 

George

[George9]

Here is a frame from the video with no contrast adjustment, which shows the building better. It is rotated so that the building is upright and reduced in size a bit for posting.

 

I am still deciphering the light sources. The disc in the middle is the shadow of the cone. The level there is miniscule. That implies the scatter beyond the cone is small.

 

The area over the Empire State Building is a dim grey. I wonder if that is scatter from the objective. It is presumably before the cone.

 

The outermost part of the light grey ring shows vignetting. Just inside that is a combination of sky background and instrument scatter.

 

The brightest part just outside the cone is corona, along with the sky background and instrument scatter.

 

George

 

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[Klaus_160]

Wow, that is a fantastic shot, with the Corona right at the bottom!

Klaus

[ch-viladrich]

Here is a frame from the video with no contrast adjustment, which shows the building better. It is rotated so that the building is upright and reduced in size a bit for posting.

 

I am still deciphering the light sources. The disc in the middle is the shadow of the cone. The level there is miniscule. That implies the scatter beyond the cone is small.

 

The area over the Empire State Building is a dim grey. I wonder if that is scatter from the objective. It is presumably before the cone.

 

The outermost part of the light grey ring shows vignetting. Just inside that is a combination of sky background and instrument scatter.

 

The brightest part just outside the cone is corona, along with the sky background and instrument scatter.

 

George

Hi George,

Indeed, this is a splendid way to analyse the difference possible sources of light scattering.

[George9]

I was looking at some photos from that day and an earlier day, and I think they illustrate the quality of the air for seeing the corona. On Oct 23, 2023, it was a truly clear day, what I would call "coronal." Really blue even close to the Sun. Perhaps the clearest day of the fall in New York City. On Nov 2, 2023, when I took the Empire State Building photos above, it was pretty clear but not amazing.

 

Here is a comparison. The challenge is that these are iPhone shots, and the iPhone's AI decides how blue your sky should be. I tried to normalize them, but look at the change in blueness as you approach the horizon. On Nov 2, there is a white band as your approach the horizon and scattered clouds. On Oct 23, it is more blue all the way down; some whitening, but not nearly as white as Nov 2.

 

Therefore, on a good but not perfect day, you can pick up the corona from sea level, as shown in the photos above. If I had taken the Empire State Building photos on Oct 23, the image would have been clearer. It seems to me that if I can get the corona from there on Nov 2, then anyone can build a coronagraph and view the corona occasionally.

 

George

 

 

Nov 2, 2023 (day of the Empire State Building shot)

 

 

Oct 23, 2023 (a "coronal" weather day; note Empire State Building in the background)

 

 

also Oct 23, 2023 (note smoke stacks on the horizon, which are 30 miles away)