HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

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christian viladrich
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HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

Post by christian viladrich » Sat Sep 29, 2018 8:35 pm

Hello to all,

This is is real fun ;-)

I have still some images left on my HD taken last August at St Veran .

Here is an image of AR2710 taken with my 300 mm solar scope in G band (430 nm 1.9 nm FWHM). There are many filigrees (bright spots) visible in the intergranular region. Many ombral dots are visible in the ombra of the pore at lower left. There is a kind of ring of umbral dots in the umbra of the spot at right. Some bright spot are visible along the filaments of this same spot.

Image

No comes the interesting thing. Thierry Legault was imaging at the same time with its C14 EdgeHD, 3.8 Astrosolar and OIII Astronomik filter (500 nm FWHM 12 nm). We we only 6 to 8 m apart. We happen to take an image at the same time, meaning the seeing was correlated on a 6-8 m base.

http://spaceweathergallery.com/full_ima ... 212874.jpg
Image

If you download both images and compare them carefully, we will see that :
- the granules look the same (not surprising since we took our images at the same time),
- the bright points in the intergranular region are indeed visible at 500 nm, still with a much lower contrast compared to 430 nm,
- while the theoricial resolution of the N300 at 430 mn is the same as the resolution of the C14 EdgeHD at 500 nm, the effective resolution of the C14EdgeHD is lower than the resolution of the 300 mm solar telescope. Here are some of the reasons why :
    - the collimation of both telescopes were perfect ;
      - the optics of both telescopes are perfect ;
        - however because of the much lower transmission of the Astrosolar 3.8 compared to the uncoated primary mirror, Thierry had to increase the gain of its camera (BTW, we have the same B1920-155), and stacked 150 images while I stacked only 30 images. This results in more noise and less resolution ;
          - the level of diffuse light with the Astrolar is larger than with the uncoated mirror.

          Some additional (second order) reasons :
            - the obstruction of my 300 mm is lower that the obstruction of the C14,
              - the granulation shows more contrast at 430 nm than to 500 nm.

              Still ... the Astrosolar turns the C14 into an amazing solar scope at a minimum budget.

              Having a density 2.5 Astrosolar would be a game changer ...

              Best regards
              Christian Viladrich
              Co-author of "Astronomie Planétaire"
              http://www.astroplanetes.com/
              Co-author of "Astronomie Solaire"
              http://www.astronomiesolaire.com/

              christian viladrich
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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

              Post by christian viladrich » Sat Sep 29, 2018 8:41 pm

              Here is Thierry's image with the C14 :
              Image
              Christian Viladrich
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              Co-author of "Astronomie Solaire"
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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

              Post by Derek Klepp » Sun Sep 30, 2018 8:36 am

              Thanks for this Christian a very good comparison.

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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

              Post by marktownley » Sun Sep 30, 2018 11:51 am

              Interesting and informative comparison Christian, thanks!
              Image
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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

              Post by Montana » Mon Oct 01, 2018 11:04 am

              Both images are an absolute pleasure to view :bow :bow :bow
              Alexandra

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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

              Post by LauraMS » Sat Oct 06, 2018 3:58 am

              That is a great comparison, Christian. And it underlines my conclusions when I compared my images with the EdgeHD11 / AstroSolar3.8 with those. made with your solar newton: with the AstroSolar I do not short enough exposure times.

              Some time ago I had asked Thomas Baader about a lower OD AstroSolar filter but they were not willing to produce one. Although in his Europen Patent from the year 2000 or so he claims it can be produced down to an OD of 2.5 ... Probably not enough demand from customers (that could change), maybe safety and tube seeing concerns since more energy enters the OTA...

              I had tried mylar emergency blankets many years ago but image quality wasn't that great.

              Best, Laura

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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

              Post by Carbon60 » Sat Oct 06, 2018 8:17 am

              I would be delighted with either of these marvellous images, Christian. The seeing conditions here are so much the limiting factor. Maybe one day I'll visit and image from one of these 'golden' locations with optimal conditions :)

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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge

              Post by christian viladrich » Sat Oct 06, 2018 9:02 am

              Thanks to all :-)

              Laura : Yes indeed, an Astrosolar 2.5 would be perfect. We should probably all send a request for that? I might have the opportunity to meet with Mr. Thomas Baader at the end of the month. I'll try to convince him ;-)
              BTW, we also tested a density 2.5 filter for another manufacturer. It was very bad.

              Stu : usually, the seeing conditions is the limiting factor. Here the limit was set by the instruments.
              Christian Viladrich
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              Co-author of "Astronomie Solaire"
              http://www.astronomiesolaire.com/

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              Re: HR images of AR2720 Aug 25, C14 EdgeHD versus 300 mm solar scope challenge@

              Post by LauraMS » Sat Oct 06, 2018 8:41 pm

              Christian, maybe Baader would be willing to produce some test sheets with OD2.5 if there is sufficient interest. That's one of the reason why I mentioned my earlier contact with Thomas Baader ;-) If he would see that there is a sufficient number of people interested and also able to get hires narrowband (i.e. with 2-10nm FWHM) continuum images at e.g. G-Band, TiO, CaK with apertures of 8 inches and more, they may develop a product and could have a new product to offer when the solar minimum is over in two years or so.

              So, if everybody interested would drop a note here, and/or send Baader an email expressing their interest, might convince them. And of course it would be helpful if you, Christian, meet in peerson with him and convince him :-)
              Last edited by LauraMS on Sat Oct 06, 2018 9:10 pm, edited 1 time in total.


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