Solar imaging and techniques

  • #201
sophiecentaur
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They are actually a very respectable Ha solar scope
I suppose that the visual images will be not very stunning through any useful narrow band filter. Monochrome or false colour with the right exposure can do wonders - as it does for nebulae.
 
  • #202
davenn
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What I was looking at was on the edge ('limb"?) and was perhaps a few percent of the diameter of the disc. Whether that was what my companions were referring to is anyone's guess; they may have spotted flares too. But I thought the prominences (?) did change in size.

Yup, definitely prominences, not flares. Ohhh yeah I have often detected changes even in 15 - 30 mins of observing .... it's pretty amazing seeing the sun do stuff in real time.

I was surprised at the apparent speed if you translate it to many thousands of km/hr.
Coronal mass ejections CME's can vary from ~ 20 km/sec to ~ 3000 km/sec

I mean, when you think of the time that stuff ejected by the Sun takes to get here then it doesn't seem to scale with the apparent distances / heights of the features I was seeing. I have obviously got something wrong in my intuition about this.

CME's take on avg 2-3 days to get here (150 million km). those prominences in that last photo I posted will be between 50 and 150 km in height above the sun
 
  • #203
davenn
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I suppose that the visual images will be not very stunning through any useful narrow band filter. Monochrome or false colour with the right exposure can do wonders - as it does for nebulae.

most solar scopes produce a reddish colour for the sun, after all we are viewing down in the red end of the spectrum .... 656.28 nm

Remember a He/Ne laser is 633 nm


D
 
  • #204
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depending on where on the sun it was :)
True! ...
... bright areas on the face of the sun near the active region ...
... flares

or

... the features on the limb of the sun like you see in my above fotos ...
... prominences ...
 
  • #205
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Yup, definitely prominences, not flares.
I agree. I too doubt it was the possible flare candidate B7.2 that started at 11:45 and ended at 11:51 (UTC) ...
[AR 2740 was right on the limb on May 3, not May 5 ... (though close around those days) (https://www.spaceweatherlive.com/en/solar-activity/region/12740)]
 
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  • #206
sophiecentaur
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most solar scopes produce a reddish colour for the sun, after all we are viewing down in the red end of the spectrum .... 656.28 nm
Obvious when you think about it. o:)
But that's what you get from all that false colour in images - example: the 'photos' of that black hole we all saw in the papers and on TV.
 
  • #207
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Don't know anything about the technicalities of solar photography but though this would be a good place to ask following question:

Is it possible to create an "artificial eclipse" ? That is to arrange an blocking disk exactly like the moon in a total eclipse so that one can examine the solar chromosphere. And obtain emission spectra such as the following:

https://apod.nasa.gov/apod/ap170907.html
 
  • #208
russ_watters
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Is it possible to create an "artificial eclipse" ? That is to arrange an blocking disk exactly like the moon in a total eclipse so that one can examine the solar chromosphere.
Yes, that is a technique that is used. Not sure if by amateurs.
 
  • #209
sophiecentaur
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Don't know anything about the technicalities of solar photography but though this would be a good place to ask following question:

Is it possible to create an "artificial eclipse" ? That is to arrange an blocking disk exactly like the moon in a total eclipse so that one can examine the solar chromosphere. And obtain emission spectra such as the following:

https://apod.nasa.gov/apod/ap170907.html
I found this esa link which shows a big boys' solution to the problem.
Coronagraphs have been used for a long time on Earth with varying success.
You made me wonder about the possibility of achieving something (much inferior DIY) for an amateur setup. The problem is that most astrophotography uses Prime Focus imaging, which uses just the telescope objective lens (just like a normal camera lens) and any occulting ( blocking) disc would actually need to be very close to the plane of the image sensor if you want to produce a good sharp shadow. Also, the disc would need to be exactly the right size as there is no 'zoom' facility on an astronomical telescope. It would be hard to achieve with a DSLR camera (a favourite low cost solution) although 'clip filters' do exist for Canon cameras which sit very close to the image sensor.
 
  • #210
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I found this esa link which shows a big boys' solution to the problem.
Coronagraphs have been used for a long time on Earth with varying success.
You made me wonder about the possibility of achieving something (much inferior DIY) for an amateur setup. The problem is that most astrophotography uses Prime Focus imaging, which uses just the telescope objective lens (just like a normal camera lens) and any occulting ( blocking) disc would actually need to be very close to the plane of the image sensor if you want to produce a good sharp shadow. Also, the disc would need to be exactly the right size as there is no 'zoom' facility on an astronomical telescope. It would be hard to achieve with a DSLR camera (a favourite low cost solution) although 'clip filters' do exist for Canon cameras which sit very close to the image sensor.
Many thanks - very cool video on the "big boys' solution". Indeed so! Should yield an excellent very high resolution version of (for eg) the following (can't find anything similar from more recent eclipses):

http://articles.adsabs.harvard.edu//full/1930ApJ....71....1M/0000001.000.html
Would be brilliant if someone could come up with the DIY / amateur solution you mention above. However in terms of resolution I would guess the 150m gap - and precision alignment - in the "big boys'" answer is necessary and not very amenable to DIY solutions.
 
  • #211
sophiecentaur
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not very amenable to DIY solutions.
Yes, For a start, the Sun would move across the horizon very fast if a large, distant occluding disc were used and that would need tracking. I used to have a photograph of my son, standing on a wall with a beachball held overhead and producing a pretty good eclipse. I had to do a lot of "forward backward side to side" to make it work. Then I lost the print!!!! baah.

An internal occluding disc would not have the same problems but some fancy optics would be needed to place the Sun image (exactly the right size, of course) at an intermediate focus and then another lens, to project (in focus) both the Sun and the Disc onto the image sensor. Not too hard if you have a selection of appropriate lenses and extension tubes.

Either way, the contrast and the clubby atmosphere are a big problem. You can go down the road and buy a very narrow band filter (a couple of nm bandwidth) if you have at least 1kGBP. You can actually see prominences forming and changing, so they say.
 
  • #212
davenn
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First solar image for many, many months ( at least 8), between crap weather, skies full of bushfire smoke and the general
lack is significant solar activity.

LUNT LS60THa solar scope, ZWO ASI 1600MM camera

200207 large prom.jpg
 
  • #213
sophiecentaur
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I think I saw that whilst trying to tame a PST.
 
  • #214
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Cool pic - that 'little' flare will of course dwarf the worst any bushfire can throw at you!
 
  • #215
sophiecentaur
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Cool pic - that 'little' flare will of course dwarf the worst any bushfire can throw at you!
Yes, but it is at a comforting arm's length away. :wink:comical
Our subjective appreciation of astronomical stuff is very non-linear. 'Small' solar surface features are as impressive as the whole beast in many ways. The Earth would be lost in that small bubble.
 
  • #216
davenn
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Cool pic - that 'little' flare will of course dwarf the worst any bushfire can throw at you!
Yes, a very nice prominence :smile:
 
  • #217
sophiecentaur
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There were some clear blue patches between the clouds this morning and I got this image with my DSLR on the PST, using a X2 barlow. The Prominence and some hairy bits around it seem fairly clear but I get no texture detail, whatever curve and level settings I use in the processing. Nonetheless, I now have 'features' that I wouldn't see with my shiny Baader filter. I'm on the way.
sun on coronado-8.jpg
 
  • #218
davenn
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The Prominence and some hairy bits around it seem fairly clear but I get no texture detail, whatever curve and level settings I use in the processing.
outstanding !! well done :partytime: I was hoping you had a chance to capture that.
Saw in the solar site that I download daily images from

You will discover, like the rest of us already have, that it's almost impossible to keep the surface features
correctly exposed but still be able to image the prominences at the same time.
The prominences are so faint compared to the disk that you have to overexpose the disk to see the prom's
You can experiment with exposing for the disk and save that image with surface features. Then expose for
the prom's and save that image and then merge the 2 images in photoshop ( or your other fav image app)


cheers
Dave
 
  • #219
davenn
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and I got this image with my DSLR on the PST,
there's another good prom. visible at the moment, you may wanna try and photo it :)
 
  • #220
sophiecentaur
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Thanks for the heads up.
It's a nice sunny day here but there is a layer of whispy cloud. Plus, I don't have a long time-slot in my busy day as a 'retired' person. Where did all the spare time go that I used to have when at work?
 
  • #221
Tom.G
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Where did all the spare time go that I used to have when at work?
Replaced with "Don't Die of Boredom" 'work'. :oldwink:
 
  • #222
davenn
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Thanks for the heads up.
Another large prominence on the limb hopefully you have a clear day to see it :smile:


Dave
 

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