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Angular Diameter of Solar Corona?



 
 
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  #1  
Old May 14th 17, 05:22 PM posted to sci.astro.amateur
Davoud[_1_]
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Posts: 1,989
Default Angular Diameter of Solar Corona?

....for eclipse photography purposes. I will be photographing the
eclipse with a "full-frame" DSLR. I have several 'scopes of varying
focal length and photographic fields of view and I want to ensure that
I do not crop the corona during totality.

Thanks!

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm
  #2  
Old May 14th 17, 06:15 PM posted to sci.astro.amateur
Chris L Peterson
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Default Angular Diameter of Solar Corona?

On Sun, 14 May 2017 12:22:33 -0400, Davoud wrote:

...for eclipse photography purposes. I will be photographing the
eclipse with a "full-frame" DSLR. I have several 'scopes of varying
focal length and photographic fields of view and I want to ensure that
I do not crop the corona during totality.


I've seen images where the diameter of the corona exceeds 3°. It
depends on how tricky you're planning on getting with your processing.
Conventional single shot images tend to yield coronas that extend
perhaps a solar radius from the limb. But HDR imagery pushes this way
out. If you're planning the latter, I'd probably go with no more than
a 400-500 mm focal length. While that costs you some theoretical
resolution, most likely the seeing conditions will be what determines
resolution, and your pixel scale will be finer than the actual
resolution you can reach.

I'm planning on using a 400 mm FL refractor with a full frame camera
for my primary imaging instrument. I'll be running the camera from a
computer to shoot a rapid sequence of different exposures to try and
capture as much dynamic range as possible.
  #3  
Old May 16th 17, 01:52 AM posted to sci.astro.amateur
Davoud[_1_]
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Posts: 1,989
Default Angular Diameter of Solar Corona?

Davoud:
...for eclipse photography purposes. I will be photographing the
eclipse with a "full-frame" DSLR. I have several 'scopes of varying
focal length and photographic fields of view and I want to ensure that
I do not crop the corona during totality.


Chris L Peterson:
I've seen images where the diameter of the corona exceeds 3°. It
depends on how tricky you're planning on getting with your processing.
Conventional single shot images tend to yield coronas that extend
perhaps a solar radius from the limb. But HDR imagery pushes this way
out. If you're planning the latter, I'd probably go with no more than
a 400-500 mm focal length. While that costs you some theoretical
resolution, most likely the seeing conditions will be what determines
resolution, and your pixel scale will be finer than the actual
resolution you can reach.


I'm planning on using a 400 mm FL refractor with a full frame camera
for my primary imaging instrument. I'll be running the camera from a
computer to shoot a rapid sequence of different exposures to try and
capture as much dynamic range as possible.


Thanks. That pretty much matches my perception and my plan. I had hoped
to use my Questar, partly for sentimental reasons: this is the 35th
anniversary year of my purchase from the factory. Indeed, it's at the
factory in New Hope, Pa. getting a complete rehab and drive upgrade @
$2950(!) Experience shows that is is perfectly suited for covering the
solar or lunar disc, but the Q cannot cover the long dimension of a 24
x 36mm frame, even with a .6 reducer (FL 840mm). It can cover a circle
of roughly 2 degrees.

Another advantage to the Questar is the reason I bought it:
portability. I have only to carry the Questar case and its Tristand,
plus camera(s). Nifty.

So that may lead to me taking my Tak FSQ-106, FL 530mm. Easily covers a
24 x 36 sensor with a field approximately 4 deg horiz x 2.5 deg vert.
If the diameter Moon/eclipsed Sun is taken to be about 31 minutes of
arc the image on the sensor will be 4.8mm, which is 13 percent of
sensor width and 20% of height. A little smaller than I would prefer,
but with a 30 megapixel camera, easily enlargeable for screen or print.

If I take the Tak or any 'scope other than the Questar to Tennessee I
have to carry my iOptron mount, not terribly bulky, but more than I had
hoped to have to take.

I have no idea why I'm thinking about this. I know that after driving
11+ hours I'm going to be clouded or rained out on eclipse day.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm
  #4  
Old May 18th 17, 02:21 AM posted to sci.astro.amateur
RichA[_6_]
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Posts: 1,076
Default Angular Diameter of Solar Corona?

On Monday, 15 May 2017 20:52:33 UTC-4, Davoud wrote:
Davoud:
...for eclipse photography purposes. I will be photographing the
eclipse with a "full-frame" DSLR. I have several 'scopes of varying
focal length and photographic fields of view and I want to ensure that
I do not crop the corona during totality.


Chris L Peterson:
I've seen images where the diameter of the corona exceeds 3°. It
depends on how tricky you're planning on getting with your processing.
Conventional single shot images tend to yield coronas that extend
perhaps a solar radius from the limb. But HDR imagery pushes this way
out. If you're planning the latter, I'd probably go with no more than
a 400-500 mm focal length. While that costs you some theoretical
resolution, most likely the seeing conditions will be what determines
resolution, and your pixel scale will be finer than the actual
resolution you can reach.


I'm planning on using a 400 mm FL refractor with a full frame camera
for my primary imaging instrument. I'll be running the camera from a
computer to shoot a rapid sequence of different exposures to try and
capture as much dynamic range as possible.


Thanks. That pretty much matches my perception and my plan. I had hoped
to use my Questar, partly for sentimental reasons: this is the 35th
anniversary year of my purchase from the factory. Indeed, it's at the
factory in New Hope, Pa. getting a complete rehab and drive upgrade @
$2950(!) Experience shows that is is perfectly suited for covering the
solar or lunar disc, but the Q cannot cover the long dimension of a 24
x 36mm frame, even with a .6 reducer (FL 840mm). It can cover a circle
of roughly 2 degrees.

Another advantage to the Questar is the reason I bought it:
portability. I have only to carry the Questar case and its Tristand,
plus camera(s). Nifty.

So that may lead to me taking my Tak FSQ-106, FL 530mm. Easily covers a
24 x 36 sensor with a field approximately 4 deg horiz x 2.5 deg vert.
If the diameter Moon/eclipsed Sun is taken to be about 31 minutes of
arc the image on the sensor will be 4.8mm, which is 13 percent of
sensor width and 20% of height. A little smaller than I would prefer,
but with a 30 megapixel camera, easily enlargeable for screen or print.

If I take the Tak or any 'scope other than the Questar to Tennessee I
have to carry my iOptron mount, not terribly bulky, but more than I had
hoped to have to take.

I have no idea why I'm thinking about this. I know that after driving
11+ hours I'm going to be clouded or rained out on eclipse day.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm


An APS or 4/3rds camera would yield a higher pixel density, in case anyone is trying to tailor the scope/camera and depending on the pixel count of the camera sensor. 1000mm will just fit the sun into a 4/3rds sensor, top to bottom I think.
  #5  
Old May 19th 17, 09:57 AM posted to sci.astro.amateur
Martin Brown[_3_]
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Posts: 189
Default Angular Diameter of Solar Corona?

On 14/05/2017 17:22, Davoud wrote:
...for eclipse photography purposes. I will be photographing the
eclipse with a "full-frame" DSLR. I have several 'scopes of varying
focal length and photographic fields of view and I want to ensure that
I do not crop the corona during totality.

Thanks!


You can't reliably predict it in advance since there will be fainter
emission further further out and streamers may or may not be present.
About 3 degrees is a good working hypothesis.

Taking a look to see what LASCO coronograph sees ahead of time might be
a good way to judge it.

Sun has been so quiet recently that a boring eclipse corona view is
possible with very little else to see when the photosphere is occulted.


--
Regards,
Martin Brown
  #6  
Old May 19th 17, 06:48 PM posted to sci.astro.amateur
Gerald Kelleher
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Posts: 1,551
Default Angular Diameter of Solar Corona?

On Friday, May 19, 2017 at 9:57:01 AM UTC+1, Martin Brown wrote:

Sun has been so quiet recently that a boring eclipse corona view is
possible with very little else to see when the photosphere is occulted.


--
Regards,
Martin Brown


Boring indeed !, with theoretical tumbleweeds rolling through your brain no wonder you would find something boring about this great event but you are best left to you own devices.

The stars which make the constellation Leo ( outside any stellar circumpolar structure) are behind the Sun's glare so it is a rare chance to appreciate the purely heliocentric perspective of a central Sun and the relationship of the stars to the orbital motion of the Earth.

https://www.youtube.com/watch?v=eeQwYrfmvoQ

It gets rid of the theoretical riff- raff and their stellar aberration and brings into sharp focus of the Earth's orbital motion through space as the background stars move from an evening to morning appearance or the left side to the right side of the central Sun.

It is an amazing thing that after the use of dual perspectives between the motion of the inner and outer planets seen from a faster or slower moving Earth is followed by the orbital change in position of the stars using a central Sun and a moving Earth.

I personally don't know how people can ignore it even allowing for the hapless theorists who find astronomy boring and life pointless.

  #7  
Old May 21st 17, 09:50 AM posted to sci.astro.amateur
Gerald Kelleher
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Posts: 1,551
Default Angular Diameter of Solar Corona?

For those who don't know, angular diameter is, the space a celestial object seen from the surface Earth takes up .

http://www.daviddarling.info/images/...r_diameter.jpg


It is observer centric as it takes no account of the relative size of the object compared to Earth and gives no feel for the expanse of the celestial arena and by association the motions of the Earth nor the central Sun. At best angular diameter is a term for a celestial diorama pasted on to a rotating celestial sphere limited to the local horizon.

I came to understand on the topics of the dual twilight events (daily twilight/polar twilight) due t separate rotations and the variations in twilight length daily across latitudes due to diminishing speeds across latitudes that observers here are not only stuck with a flat Earth ideology but their view is bound by a observational diameter of 6 miles,at least at sea level -

https://www.weather.gov/images/fsd/astro/twilight.png

It is not advisable to shame people into looking at what they believe, it is more preferable to discuss the ins and outs of dual twilight and variations in twilight lengths using actual causes but obviously the mind tutored in late 17th century celestial sphere concerns won't allow the new insights in by a refusal to change the pretense upholding their system.

That graphic on twilight says it all, it is the lowest of the low in intellectual,historical and technical terms and people should be ashamed even if the angular diameter types are unable to experience it.

 




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