Solar Eclipse Benton Arkansas

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SVG223
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Solar Eclipse Benton Arkansas

Post by SVG223 »

I'm not sure what is causing this aberration or phenomenon.
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Re: Solar Eclipse Benton Arkansas

Post by christian viladrich »

These are internal reflections.
What is the instrument used ? Refractor ? Lens ?


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Re: Solar Eclipse Benton Arkansas

Post by SVG223 »

christian viladrich wrote: Sun May 05, 2024 5:50 pm These are internal reflections.
What is the instrument used ? Refractor ? Lens ?
Thanks!
Tamron 500mm catadioptric lens with 2x teleconverter.


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Re: Solar Eclipse Benton Arkansas

Post by SVG223 »

One without the reflection.
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Re: Solar Eclipse Benton Arkansas

Post by Montana »

Superb images :bow :bow :bow
but yes, I think the intense light of the diamond ring has caused an internal reflection :(

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Re: Solar Eclipse Benton Arkansas

Post by allhoest »

SVG223 wrote: Sun May 05, 2024 10:27 pm
christian viladrich wrote: Sun May 05, 2024 5:50 pm These are internal reflections.
What is the instrument used ? Refractor ? Lens ?
Thanks!
Tamron 500mm catadioptric lens with 2x teleconverter.
Welcome to the club.
Here is one pic taken just before the totality, also with a Tamron F500 f8 catadrioptric, but without teleconverter.
This optic has a provision for an internal filter, and I had the filter mounted.
100DSC09132_r-v1000.jpg
100DSC09132_r-v1000.jpg (49.54 KiB) Viewed 130 times



It would be interesting to know if you also had the filter mounted.
It would be also interesting to have feedback from other catadrioptric users.

I pre-checked the optic during the night while taking a picture of a street light, with the aim of detecting internal reflection.
I couldn't detect any at that time.


Here, an overexposured (1/250) pic taken 18s before the totality:

100DSC09102_r-v1000.jpg
100DSC09102_r-v1000.jpg (53.29 KiB) Viewed 130 times



CS
Alex


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Re: Solar Eclipse Benton Arkansas

Post by christian viladrich »

This might be internal reflection in the meniscus. I have the same issue with my Mak 127 mm :-(

The way to test it is to use the Moon and the earthshine. You set to Moon away for the center of the field, and you push massively exposure time.
This way, you see whether reflection / diffusion is brighter than the earthshine.
This test is relevant since the Moon has about the same luminosity as prominences, and the earhshine has same luminosity of the corona away from the solar limb.

I made the test with my ZWO 80/600 refractor before the eclipse. It was clear there was an issue with internal reflection (probably at the edge of one of the lenses).
The top image is with the addition of a 75 mm aperture stop (20 s exposure time) => no internal reflection,
The bottom image is without any aperture stop (15 s exposure time) => internal reflection is huge.

http://astrosurf.com/viladrich/astro/te ... ec2024.jpg

With the 75 mm aperture stop, I had no internal reflection even before C2 and after C3. Still, there is diffusion due to the surface roughness and cleanest of the lenses (there are not coronagraphic optics ...).

I am not sure whether an aperture stop would solve the issue with a Mak of catadioptric lens. That would be an interesting test to do.


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Re: Solar Eclipse Benton Arkansas

Post by SVG223 »

It would be interesting to know if you also had the filter mounted.

Yes, I had an 82mm ND100000 filter mounted on the front of the lens.




CS
Alex
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Re: Solar Eclipse Benton Arkansas

Post by thesmiths »

christian viladrich wrote: Wed May 08, 2024 12:25 pm The way to test it is to use the Moon and the earthshine. You set to Moon away for the center of the field, and you push massively exposure time. This way, you see whether reflection / diffusion is brighter than the earthshine. This test is relevant since the Moon has about the same luminosity as prominences, and the earthshine has same luminosity of the corona away from the solar limb. I made the test with my ZWO 80/600 refractor before the eclipse. It was clear there was an issue with internal reflection (probably at the edge of one of the lenses).
Hi Christian, I did some similar Moon tests with the Askar 65 PHQ and the results were quite reasonable even with no aperture stop. I used a medium sized sensor (the ZWO 294MM, similar in size to a 1600MM but with smaller pixels). With this is sensor there were only reflections in two of the corners near the Moon. The off-centre images are the most extreme case to see reflections; when the Moon is centred, there were no visible reflections.

I had earlier done the same tests with an 80mm LOMO triplet from APM with a Tele Vue flattener and the reflections were extremely strong. That was one of the reasons I decided to switch to the Askar 65 PHQ from the 80mm LOMO (the field was also much flatter).

The images below were images that were stacked with our specialised General Relativity software; the Moon has been masked so that dim stars can be identified with high precision (meant to be used during a total eclipse to detect small star deflections).

askar 65 1sec 294MM top.JPG
askar 65 1sec 294MM top.JPG (218.62 KiB) Viewed 84 times
askar 65 1sec 294MM bottom.JPG
askar 65 1sec 294MM bottom.JPG (198.15 KiB) Viewed 84 times


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Re: Solar Eclipse Benton Arkansas

Post by christian viladrich »

Hi Doug,

Your images crowded with so many stars are just incredible !

Do you have some first results of your Eddington experiment ? Or are you still processing the data ?


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Re: Solar Eclipse Benton Arkansas

Post by thesmiths »

christian viladrich wrote: Thu May 09, 2024 3:20 pm Do you have some first results of your Eddington experiment ? Or are you still processing the data ?
We are still analysing data. The data was of lower quality than had been hoped due to non-ideal cloud situation in Mexico. The site in Texas was completely clouded.


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