Solar corona from yesterday

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george9
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Solar corona from yesterday

Post by george9 »

I got a better session yesterday looking for the corona and got a shot of it. I was using my Baader prominence viewer converted to a coronagraph. Using the Baader cones and projection lens, but new field lens, field stop, Lyot stop, Lyot spot, blackening, etc. And a 2-Angstrom single-cavity 5303A filter. With an f/20 50mm 5/10 scratch-dig singlet in front. This was built in collaboration with Klaus_160. The sky was very good with blue sky right near the Sun.

At 10am yesterday at Utsayantha Mountain in New York (3200 feet), I saw a narrow pyramid-shaped feature coming off the Sun with the filter at 32C, which is the proper temperature for 5303. I then cut the power and let the filter drop to 10C, going off band by about 3.5A, and it disappeared. I went back to 32C and it came back. Down to 6C this time and gone. Back up to 32C and there, back down to 10C again and gone. Meanwhile I saw a known artifact (probably a scratch on the field lens) on the opposite side, with a different shape but similar brightness. It stayed constant with the temperature changes.

To make sure the pyramid was not an artifact, I rotated the scope in the rings about 5 degrees, and the feature moved by 5 degree against a tiny piece of dust on the cone (seen in the image below). Moved it back and restored. Rotated and moved, restored and back again. So it had to be a solar feature.

I looked then in H-alpha (10A triple cavity), and I got my bearings on the solar positioning. There was a very flat small prom below the pyramid.

I took a photo of SDO's 171A at the same time, but did not look at positioning of the regions until after the observation session. I aligned the photos using shots of H-alpha and GONG.

Below are the shots of it in the 5303A (green) and the SDO 171A (orange), one of each and superimposed. The 5303 shot has a white line under the relevant regions. What I was looking at was the one on the left. Not so obvious in this shot but obvious at the time (I suspect the camera was not well positioned to capture the one on the left well). It was only later, going over it with Klaus, that the bigger one to the right became more obvious in the photo. The one on the right shows the probable base of some loops. But in the eyepiece, the one on the left was easy and I did not notice the one on the right (remember that I had not tried to align 171A yet, so I did not know what to look for). It may be because further to the right was my biggest artifact, and that may have distracted me.

Based on the repeated temperatures, the repeated positioning, and the SDO alignment that was done only after the session, I am convinced that it is the corona. Too high for a prominence, plus the wrong frequency. And I have practice viewing proms at other frequencies now.

Now that Klaus has demonstrated that it is possible, even at moderate altitudes and with moderate assembly skills, you can get there, at least with a 5303 filter and a good atmospheric day. Klaus spent 20 years on it, and I spent the past year but benefitting from his knowledge. You have to be a bit neurotic to get rid of all the sources of scatter, but that's the fun. My two goals were to see prominences unfiltered outside of an eclipse and to see the corona outside of an eclipse, so I am pretty happy.

Next step is building a coronagraph without so many artifacts. Mainly needs a new field lens, but given that, might as well redo it. And I just took a class in solar imaging, so I hope to improve there.

But I need a new camera with a bigger sensor. My ASI290, which did not work out yesterday and thus the iPhone shot, would have gotten the left one but would have missed the right one from the field of view. Maybe a 174? Focal length is over 1000mm. The challenge is that the view is fleeting and low clouds were passing by, so I just could not get the ASI290 properly focused with the spacers I had in the time available. I will practice that with an ND filter and the Sun off center.

George
5303 at 32C 20211024 10amET.jpg
5303 at 32C 20211024 10amET.jpg (78.1 KiB) Viewed 522 times
171A 20211024 10amET.jpg
171A 20211024 10amET.jpg (52.83 KiB) Viewed 522 times
5303 at 32C and 171A 20211024 10amET.jpg
5303 at 32C and 171A 20211024 10amET.jpg (55.65 KiB) Viewed 522 times


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Re: Solar corona from yesterday

Post by Montana »

WOW!!!! well done George :bow :bow :bow
do you have an image of the set up and configuration? just wondering whether my Baader prominence viewer can be adapted?

Alexandra


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Re: Solar corona from yesterday

Post by george9 »

I will dig up some images, but in the meantime, here are some quick answers.

1. You need an appropriate objective. I am using a 50mm f/20 uncoated singlet with low scratch and dig. An air-spaced coated doublet is unlikely to work. Then this goes to a Baader cone.

2. You need to add a field stop (say 20mm diameter) between the cone and the field lens. That produced the biggest improvement for me.

3. Make sure your field lens is pristine. Mine was defective, repaired by some previous owner, so I had to replace it, and now I have to replace it again.

4. The iris is not ideal in terms of rejecting light (bright grey, not a knife edge). I replaced it with my own Lyot stop.

5. I added a Lyot spot. Klaus doesn't use one, so maybe not necessary.

6. I use the Baader projection lens but hope to replace it.

7. I use the Baader X-Y adjuster.

8. Whatever filter I am using. H-alpha, H-beta, H-gamma, CaK, helium D3, and now 5303A.

9. I generally use a Beloptik KG3-UR-IR cut for safety, unless the filter is fully blocked from UV to long IR.

10. I blackened the inside of everything with Black 3.0 paint. Problem is that it is sensitive to water, so looking for an alternative.

11. I removed the baffles from my OTA. You don't want the light from the cone to reflect off the baffle and back to your eyepiece.

12. I use a sticky dew shield to help keep dust off the objective.

13. Dust is where half you time will go. Klaus and I have been iterating on different methods. If you can see dust on the objective, forget it. I have gotten to the point where I can remove all visible dust. But if I shine a very bright flashlight through the lens, and it is in front of a Black 3.0 background, then I see say 20 miniscule specks. They don't seem to hurt. They are dimmer than the reflection that the Lyot spot is intended to block. But again if you see the dust just holding the lens, forget it, you see a spray of light in the field. I tried to create a clean room, but not very effective. You also need to clean the field lens, which is harder because it is buried in there. Doesn't add to the background light but produces artifacts in the field of view. E.g., that thing on the far lower right in the photo above is a scratch or dust.

14. My one innovation is that I created an indoor test bench. A very bright LED with a collimation lens in front of a light trap, placed 35 feet away from the scope. Let's me diagnose things without blinding myself. That's how I know the nearly invisible dust is okay. By the way, it looks like it is snowing inside my apartment. Hard to believe how much dust is constantly moving. Those photos from yesterday had the lowest dust in the air that I have seen yet. Normally my photos are filled with dust streaks flying by the telescope.

George


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Re: Solar corona from yesterday

Post by yltansg »

Hi George,

That is an amazing view of the Corona!!

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Re: Solar corona from yesterday

Post by Montana »

George, I have combined the above two images for SPOD, I hope you don't mind :) I am so impressed with your image.
George Corona.jpg
George Corona.jpg (171.97 KiB) Viewed 489 times
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Re: Solar corona from yesterday

Post by banjo »

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Re: Solar corona from yesterday

Post by DSobserver »

amazing

congratulation!


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Re: Solar corona from yesterday

Post by george9 »

Wow, thanks so much for the photos and replies. I am quite honored to have a photo there. George


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Re: Solar corona from yesterday

Post by MapleRidge »

Incredible image George :bow

I hope the continuing refinements improve the performance for you!

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