The arrival of my Coronado PST Solar Telescope opened a new field for me, as Imaging and Postprocessing the Sun in Ha is quite different from what I had done so far.
So I experimented and made notes of what I did, and after a while decided to write this Tutorial, so that I would not forget what I learned and also share it with you.
I assume you already know how to handle your PST for visual observation, that you are able to use the (web)camera and also that you are familiar with my Planetary Post Processing Tutorial.
To capture the image discussed in this Tutorial I used the following equipment:
And I used the following software:
IMPORTANT: you CANNOT reach focus in PRIME FOCUS with a standard webcam such as the Philips ToUcam and the like, unless you do THIS !!
My rehoused Trust WB-5400 webcam focuses nicely with the eyepiece holder + spacer installed: no disassembly required.
However I prefer to use my Televue 2.5x Powermate which gives a better scale IMHO.
This is the easy part: with the finder dot of the PST in the centre you will soon see the Sun on your screen.
Oh: I crawl under a dark bath towel so that I can see the laptop screen [warning: onlookers will enjoy this and make funny remarks].
Just do some coarse focusing [fine focusing comes a bit later] and we are off to the next step.
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Imaging the sun [white light or with PST] is not easy, because it is hard to see the screen of the laptop. Therefore I use a dark blue bath towel and hide under it. While on holidays my wife could not resist the temptation and imaged ... me |
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With my PST riding high on my LX200 and when the sun is low during the colder period of the year I cannot see the finder window on top of the PST, unless I climb a small ladder. So on a cloudy day I made this Solar Finder. With the sun centred in the eyepiece I will look where the sun shines through the small hole at the front of the Solar Finder and hits the blind flange: there I will make a mark on the blind flange. |
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The next day there was a hesitating low sun so I mounted my PST on a static tripod and was elated to see the expected bright dot on the blind flange: success ! I made sure that the sun was right in the centre of the eyepiece and then provisionally marked the spot on the blind flange. Re-aiming at the sun was as expected: right in the centre of the eyepiece. And no more climbing as my Solar Finder is at the side of the PST. PS: that front lens surely needs cleaning ! |
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The finishing touch: I made a marker with crosshairs and glued it with double sided tape on the blind flange. To ensure that I glued the crosshairs marker exactly on the right spot I mounted my Televue 2.5x Powermate and Philips Vesta SC3 webcam on my PST, aimed at the sun and centred the sun on the live video screen. Click here to download a Word document with printable crosshairs. My Solar Finder has a bonus: as I do not need the original finder anymore I can cover the hole for the original finder [at the front of the PST] with a piece of tape thus preventing unwanted reflections inside the black house of the PST. |
My demonstration image actually exists out of TWO images, which were combined during the post processing (see later).
One image holds the prominences and the other image contains the 'surface' of the Sun.
To reveal the prominences I recommend to start with an overexposure, whereas the filaments and granulation do require a more normal exposure, with the K3CCDTools Brightness Meter at values in the range 175-225.
To actually capture the prominences I recommend the following settings [but you should experiment yourself of course !]:
Now it is time for fine focusing, for which I use what I call "the granulation setting".
To capture the granulation or the filaments you can use the same setting as for the prominence, but with a much shorter exposure: just decrease the expsure time till the granulation nicely shows up and the K3CCDTools Brightness Meter is in the range of 175-225 or whereabouts.)
Habitually I use this 'granulation' setting for fine focusing: use BOTH the focuser and the etalon tuner ring and use the ZOOM function of K3CCDTools.
When you are happy with the focusing go back to the 'prominence settings' and start scanning the rim of the sun for prominences. Once you spot one try to improve the contrast by gently rotation the etalon tuner and/or by tweaking the brightness and gamma/gain settings of the webcam.
Oh: I almost forgot: make sure that you have North UP, which you can easily check by moving the PST up (=North) and down.
When moving the scope to the North the image should go down etc. This way you can can also adjust the East/West orientation of your camera.
With properly oriented images it will be easy to compare your images with those made by others.
Finally at last you are now ready to image; I recommend for prominences to use sequences of 30 seconds at 10 frames per second, as longer sequences will smear the details because prominences rapidly change. Other solar features can be imaged for 60 secs or more.
After imaging the prominence of course you also image the granulation (do not move the scope around during the imaging session !!)
After imaging it is time for post processing; currently I prefer to use Registax5 and this tutorial and after aligning/stacking/wavelets I have these 2 preliminary results:
Image 1: The prominences
Image 2: The granulation
Note: the above images are shown here as 8-bit jpg files, but in reality they are 16-bit FIT files.
The white borders are a by-product of Registax, where I did the wavelet processing. These borders will be removed in Photoshop.
To process the FIT file[s] I use the Photoshop Plugin FITS Liberator.
I highly recommend this plugin, which is freely downloadable; I also recommend the FITS Liberator Tutorial by Noel Carboni.
I save the output of the FITS Liberator processing as PSB files, each with the suffix "fitslib", so that later I know that this is the result of the FITS Liberator processing.
Both the 'Prominence' and the 'Granulation' images are processed in Photoshop, where I mainly use Levels and Curves (to darken), Contrast/Brightness ofr improves contrast and Filter|Blur|Gaussian Blur to remove noise.
Now it is time to combine the 'Prominence' and the 'Granulation' images into one image.
I use the Magic Wand Tool to select the sky part of the granulation image [use the Tolerance for fine tuning]:
and via Expand by 1 pixel and Select|Invert I select the Solar Disk part of the granulation image:
Next use Copy/Paste to Paste the Solar Disk part of the Granulation image onto the Prominence image:
Use the Move Tool to precisely position the Granulation part:
Flatten the 2 layers via Layer|Flatten and use the Crop Tool to cut off the edges:
Now apply the colours as follows [via Image|Adjustments|Colour Balance or Ctrl-B] followed by Hue/Saturation [Ctrl-U]:
And as I am lazy I have put the above into a Photoshop Action, which you could do yourself too.
Here is the result of using the above colourisation:
And here is the final result:
Oh, the frame around the image is explained here.
For your (and my own) convenience: here is a quick scenario of Don Waid's Hi Pass Masking Tutorial
Here are two examples:
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Hi-Pass Masking Technique - monochrome version Click the thumbnail and move your mouse in/out to see the difference. |
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Hi-Pass Masking Technique - colourised version Click the thumbnail and move your mouse in/out to see the difference. |
Should you consider the colourisation too artificial you might prefer this version:
Here is what I did:
I loaded the 'Prominence' image into Photoshop and used the Wand Tool to select the Sun and then used the lower slider in Levels [Crtl-L] to make the Sun black.
Next I inverted the selection [Select|Invert] and used Curves [Crtl-C] to enhance the prominence a bit.
That's all.
The following example nicely shows what an image in negative version brings:
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Filament with Prominences It is especially nice to see the fainter Prominences erupting from the Filament [best seen in the negative version]. September 22, 2009 09:48 UT. Imaging: Coronado PST [on Acuter Merlin Mount] with Televue Powermate 2.5x operating at f/25 [focal length 1000mm] and Philips Vesta SC3a B/W webcam, Baader Infrared Blocking Filter. Mouse in/out to hide/view the negative version. |
With my PST + 2.5 Televue PowerMate + Vesta SC3a camera I once captured the pieces for a mosaic, so then I had the full width of the sun with this setup.
In Irfanview I cropped this solar mosaic 'from rim to rim' so that I had the width in pixels: 1223 pixels for my setup.
The Sun is 109x Earth, so 'one Earth at the Sun' is 1223/109 = 11.2 pixels for my setup.
After having imaged a prominence I measure (by cropping in Irfanview) the size of the prominence in pixels, divide this by 11.2 and I have an idea of the size of the prominence 'in Earthes'.
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Animation of Prominence: approx. 4.8 x 10.3 Earth. [Click the thumbnail to see the full sized version of 700Kb] Please note the balls of fire going up and down. November 12, 2008 11:06 - 11:48 UT. Imaging: Coronado PST piggybacked on LX200 with Televue Powermate 2.5x and Philips Vesta SC3a B/W webcam, Baader Infrared Blocking Filter. |
Here is how I made the above animation:
I used the Interval Timer of K3CCDTools to automatically image during 15 seconds followed by an interval of 45 seconds.
Processing: the 41 AVIs were aligned and stacked + wavelets in Registax [in Auto mode]; the results were saved as TIFFs.
These TIFFs were imported in K3CCDTools and manually aligned using the Show Difference feature;
the results were upsampled 2x, the caption was added using the Text Output Filter and finally saved as GIF.
The final adjustment of the animation was done in Animagic.
Here is how I use my Trust WB-5400 webcam
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A Big Blank Sun. March 13, 2009 08:49 UT. Imaging: Coronado PST piggybacked on LX200; prime focus with Trust WB-5400 webcam, no additional filters. |
Camera settings of the above image [as recorded by WcCtrl]:
K3CCDTools setting:
Please note the checkmark for Capture Startup Message box !
This means that K3CCDTools will start the actual imaging only AFTER you hit OK, which gives the WB-5400 time to obey your camera settings, though a bit slow ..
I wanted to 'get closer' to the sun, so I used my TeleVue 5x Powermate to increase the focal length of my PST from 400mm to 2000m [from f/10 to f/50] but as you can see this really is too much. With the TeleVue 2.5x Powermate I get nice results, so I will stick to that.
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Huge Filament April 2, 2011 09:32 UT. Imaging: Coronado PST piggybacked on LX200 with Televue Powermate 5x operating at f/50 [focal length 2000mm] and Philips Vesta SC3a B/W RAW webcam, Baader Infrared Blocking Filter. |
Catching a live flare is not easy: you need patience and luck :o)
I use the Interval Timer of K3CCDTools to automatically image during 30 seconds followed by an interval of 90 seconds.
This only works if the camera is running as a VFW (Video For Windows) camera; it does not work under WDM.
So you image and image and hopefully you catch a flare, but the imaging session will take a long time.
During that time - which might be hours - your scope is bound to drift off, so you have to 'babysit' your scope.
Not anymore !!!!!!!!
I found out that autoguiding also works on a sunspot instead of a star !!!
So on April 21, 2011 I imaged [with my PST + 2.5x Powermate + webcam] sunspot AR11195 hoping for a flare and autoguiding [with my LX200 10" f/10 + webcam] Worked like a charm !!!!
Here is how I normally autoguide but as said it also works on a sunspot!
Here is part of a K3CCDTools screenshot while autoguiding on a sunspot with quite some turbulence, but that does not matter too much:
Here are some results [click the thumbnail for the larger version and then browse down for details]:
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Animation of Solar Activity in AR11195 [autoguided] April 22, 2011 09:13 - 10:51 UT. More images like this. More animations. |
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Animation of Solar Activity in AR11195 [autoguided] April 21, 2011 10:23 - 11:49 UT. More Solar images. More animations. |
Well worth a visit: Paul Hyndman's Solar Primer.
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