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Featured Stargazing Solar imaging and techniques

  1. Jun 10, 2018 #151

    sophiecentaur

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    Hi and welcome to PF
    Can you tell us how that image was obtained? I have a Baader ASTF 80 and I'd like to be able to do more interesting images than I have obtained so far - not much more than the more obvious spots.
     
  2. Jun 10, 2018 #152
    I am using a Nikon P900 with a Baader 5.0 filter on a regular camera tripod. Usually shoot at maximum optical, 83x, sports mode for a burst of 7 in 1 second. Greater than a minute between shots, it starts to noticeably blur the final image.

    I'll post some images to walk through the process.

    The spectral response of Baader in the NIR and into the IR appears like an etalon comb response, it is a multilayer metallic sandwich - so maybe. My IR blocking filter extinguishes completely at ~ 750nm, so there are only a few candidates for the NIR terrestrial spectrum making it to my camera.

    'Grain extract' subtracts two images and adds 128. Differences between my images are caused by many things, image stabilization being the most consistent for sub-pixel offsets, then there is my inherent alignment error between the stacks.

    I have spent a few months comparing the SDO and SOHO images to the Baader/differencing technique - I am posting this because the correlations are significant. The thermal envelopes and shock waves are almost like a ghost of the UV activity seen in SDO.

    Working on OpenCV for real time video processing with this technique, will move the design over to an FPGA next month to get the frame rates up.
     

    Attached Files:

  3. Jun 10, 2018 #153
    Sun 6 10 2018 7:51MST
    Nikon P900, 83x, Baader 5.0, sports mode burst on standard camera tripod.

    Horizontal banding appears to be layers of the atmosphere. Differencing technique works well for imaging objects close to, or crossing the Sun.
     

    Attached Files:

  4. Jun 10, 2018 #154

    sophiecentaur

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    @Zeke_D Thanks for that. So you seem to be basically temporal high pass filtering (plus some DC offset) and that removes most of the energy - explaining the high noise, I guess. I would imagine that processing a long sequence of movie frames could allow you to dredge more patterns up from the noise with long sequences of frames (less than one minute, from your comment about gap between frames.)
    It's encouraging to see that worthwhile information can be obtained about the Sun without having to spend vast sums on filters.
     
  5. Jun 11, 2018 #155

    davenn

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    Hi there Zeke_D

    welcome and thanks for posting in the thread. It's good to see something a bit different
    Even with your walk-through of your processing, I have to admit, I'm still not totally sure of what I am looking at … detail wise ??
    Continue to post and keep up the explanations :smile:


    regards

    Dave
     
  6. Jun 11, 2018 #156
  7. Jun 11, 2018 #157

    davenn

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  8. Jun 11, 2018 #158

    sophiecentaur

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    Yes. There is just one image where there is a clear area, to the right of the Sun where 'something is going on' but I think we need some help to make more sense of some of the images in post #152.
     
  9. Jun 16, 2018 #159

    davenn

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    16 June 2018, The Sun in Ha.
    Some small prom's and a large but ( for me, ill defined) active region probably mainly due to poor atmospheric conditions
    LUNT LS60THa and ASI1600MM

    180616 Ha Cap_001.jpg

    180616 Ha Cap_022sm.jpg

    180616 Ha Cap_024.jpg



    Dave
     
  10. Jun 16, 2018 #160

    sophiecentaur

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    Nice images as usual, Dave.
    The first and third images seem to have areas of light as if it's a slightly polished sphere, illuminated from one side. The spherical appearance is quite noticeable. How's that happening, I wonder? It's almost as if the Dodge Tool had been used. :smile:
     
  11. Jun 16, 2018 #161

    davenn

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    Thanks :smile:

    are you referring to the 2 circled areas ?

    180616 Ha Cap_024vvv.jpg

    if yes, then yes, I had to do a bit of editing specially on the right ovalled area …. that region was a lot brighter and I had to darked it down a bit

    The left ovalled area has the active region in the middle of it ad I have done a little enhancing there ( Lightroom clarity control) to bring of as much
    detail as I was able to)
    BTW, that little dark area below the right oval is a real feature … a small filament
    and also image 1 and 3 are the same one. #1 is monochrome version and #3 is tinted with a little yellow.... makes it look a little sun like and I often find it improves the detail a bit

    Here is an unedited version …. so you can really see the difference

    Capture_00015.jpg

    You can see just how bright the right side is. I had to try and tone that down a bit

    OK there are 2 quirky things occurring here … one involves the Ha filter and the other is the CMOS sensor in the camera

    1) The filter …. I have discovered from day one of use, that the view of the sun through the filter is not uniform across the field of view.
    and it is the least sensitive around the outer 1/3 of the FOV … within that area a prominence or active region etc can completely disappear
    from view and as I move area of interest into the central area of the FOV of the filter the details "pop" into view

    2) the second thing now involves when I am imaging and it is a mix of #1 discussed above added to the quirks of the camera(s).
    I can move the sun across the FOV of the camera sensor and it will go through brighter and darker areas ( cant describe it better than that)
    as with the unedited image above. Now I can find an area of the sensor where the whole solar disk has even exposure. but an area of interest
    a prominence or active region is not so clearly seen because of the combined quirk if the #1 comments.
    So for the above image, I had to move the solar disk to the right to get the active region to the best /clearest place in the FOV.
    This resulted in the right side of the disk being a bit overexposed

    Could you follow that ? haha hope so :smile:


    Dave
     
  12. Jun 17, 2018 #162

    sophiecentaur

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    Yes I followed it.
    Yep. I'm pleased that I spotted your bit of tinkering. :smile: They make the image much more attractive. I wonder whether, on a future occasion, it might be worth while rotating the sensor / scope (even) to see the result. Astrophotography is probably less concerned with accuracy of flat fields (except for vignetting) than regular pics so solar images are the only ones where our eye is looking for very subtle facial type features.
    It's hard not to assume that the Sun should be totally uniform at all times. But those images are really good to look at.

    Have you tried a flat to see how the sensor, scope , filter is actually performing? But I really think the pictures are so nice that it's hardly worth bothering except for interest.
     
  13. Jun 17, 2018 #163

    davenn

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    The interesting thing is, when I look through the scope with an eyepiece ( visual observing), I don't see that variation of brightness.
    But I am well aware of the variation in the sensitivity of the Ha filter. So I have to believe it must be the camera sensor in how it is
    reacting to the light level from the sun across it's surface.
    Yes, I have rotated the camera and I still see the same effect


    D
     
  14. Jun 17, 2018 #164

    sophiecentaur

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    . . . . due to the sensor orientation?
    You could deal with that with Flats, n'est-ce pas?
     
  15. Jun 17, 2018 #165

    davenn

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    17 June 2018, The Sun in Ha.

    Todays images.... will just post the active region and one prominence image. There were several other prominences visible
    but they were smaller than this one

    A lot more detail visible in the AR today, tho conditions were still poor …. note the rippled limb
    See the black filament within the AR between the 2 white areas

    180617 Ha Cap_015.jpg

    180617 Ha Capture_003.jpg



    Dave
     
  16. Jun 17, 2018 #166

    davenn

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    yes, even with changing the orientation, a changing brightness is still visible

    Possibly ? doing " flats " is not something I hear guys doing for solar images even when they are stacking
    Stacking for solar, lunar and planets is different than for deep space … ( are probably aware of that ?) ...
    it's done by doing a video clip say 500 - 1000 frames, then using software to stack individual frames of the video
     
  17. Jun 17, 2018 #167

    sophiecentaur

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    If you have any constant variation of sensitivity over any image, a flat would help you. Flats help to give a good even background field and that grey / near black level shows up even small variations but they don't visibly affect the relative brightnesses of stars. AP'ers are obsessed with their quality. I am still too excited at just seeing something new on my images to be too bothered.
    I'm sure it would be worth trying - if you feel the need together rid of those pretty effects.
    Smashing!
    Very sharp looking. Scary when you think just how big it is compared with Earth. Glad they don't get any nearer to us.
     
  18. Jun 23, 2018 at 4:28 AM #168

    davenn

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    The Sun in Ha for 23 June 2018
    A couple of nice active regions and a couple of small prominences
    Lunt LS60THa and a ZWO ASI1600MM Camera

    180623 Cap_001sm.jpg

    180623 Cap_006sm.jpg

    180623 Cap_006-2.jpg




    Dave
     
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