Tuned CaK Filter - 11th August

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Tuned CaK Filter - 11th August

Post by marktownley »

Thursday dawned with probably the most transparent skies i've had all week, and all the planes passing over left no contrails which is always promising. All week i've been playing with getting the most out of my CaK filter, and it is apparent benefits from being tuned to put the filters operating wavelength on or as close to 393.3nm as possible. This is part stems from the work Douglas and others have done in documenting the views in CaK (and CaH) as the wavelength varies around the centre line.

I'll start of with an 'untuned' image of AR13076 taken at 80mm f27 with the ZWO290mm. Things to notice (I thought!) - the inverse granulation is still visible, plenty of plage, the penumbral fibrils are still visible, but I think looks a little 'flat'. The image is brighter and lacking in as much contrast compared to the tuned image, despite both being exposed the same on the histogram and processed identically in ImPPG.

ImageAR13076-CaK-Untuned-80mm-f27-zwo290mm by Mark Townley, on Flickr

With the tuned image the inverse granulation is much darker, and look at the penumbral fibrils, they have more depth and don't look as flat as previous.

ImageAR13076-CaK-Tuned-80mm-f27-zwo290mm by Mark Townley, on Flickr

These were the last images I took (as the seeing was falling fast with rising temperature), but earlier in the session I was able to use 100mm aperture at f27 (zwo290mm again), and I think the effect of the depth in the penumbral fibrils is more apparent here. I wonder in the untuned image if we are viewing a region lower in the chromosphere, whereas with the tuned image this is higher? With Douglas et als SHG images in CaK I wonder of that view is higher in the chromosphere still? Anyway, follows a selection of todays solar activity, all 100mm f27, zwo290mm.

Imagear13076-CaK-100mm-f27-zwo290mm by Mark Townley, on Flickr

Imagear13077-CaK-100mm-f27-zwo290mm by Mark Townley, on Flickr

Imagear13074-CaK-100mm-f27-zwo-290mm by Mark Townley, on Flickr

Imagear13078-CaK-100mm-f27-zwo290mm by Mark Townley, on Flickr

ImageNew-Spot-CaK-100mm-f27-zwo290mm by Mark Townley, on Flickr

ImageSmall-Pore-100mm-f27-zwo290mm by Mark Townley, on Flickr

Now I have the tuning of the filter sorted, next step tomorrow is clocking it rotationally to shift the slight gradient. That will be tomorrow mornings job. Pleased with how this week has progressed in terms of sorting the CaK filter, it has promise ;)

Hope you like these.

Mark


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Re: Tuned CaK Filter - 11th August

Post by Ibbo »

Looking good Mark.


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Re: Tuned CaK Filter - 11th August

Post by pedro »

very informative Mark, thanks for sharing


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Re: Tuned CaK Filter - 11th August

Post by Martin_S »

Great results Mark your Cak experiments are very rewarding.


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Re: Tuned CaK Filter - 11th August

Post by marktownley »

Thanks guys, be heading out in about half an hour to start todays session.


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Re: Tuned CaK Filter - 11th August

Post by MAURITS »

The tuning has a big difference on the images Mark.


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Re: Tuned CaK Filter - 11th August

Post by Montana »

These are superb Mark :bow :hamster: which filter are you tuning? or all three?

Alexandra


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Re: Tuned CaK Filter - 11th August

Post by ffellah »

Super images and very interesting comparison Mark, thank you.

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Re: Tuned CaK Filter - 11th August

Post by rigel123 »

Great images Mark!


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Re: Tuned CaK Filter - 11th August

Post by Carbon60 »

Great progress, Mark. Excellent results.

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Re: Tuned CaK Filter - 11th August

Post by Valery »

This is your best ever serie of CaK images, Mark. My congratulates!

Thanks for this experiment and sharing it's results with us.


Valery


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Re: Tuned CaK Filter - 11th August

Post by DeepSolar64 »

The spicule layer shows easily on the limb too!!


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Re: Tuned CaK Filter - 11th August

Post by marktownley »

Thanks for the kind words everyone.

I'm tuning my new 'Chroma' filter Alexandra ;) The CaK PST filter works best untilted and perfectly orthogonal to the optical axis (as in the CaK PST).

Optical configuration as follows: Astronomik UV/IR filter, Edmunds Optics 394/10nm, Yellow CaK PST filter, Chroma 393.3/0.1 filter tilted.


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Re: Tuned CaK Filter - 11th August

Post by DeepSolar64 »

I would have never pictured a CaK filter being yellow. 🤔


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Re: Tuned CaK Filter - 11th August

Post by nicspenceryork »

marktownley wrote: Sat Aug 13, 2022 6:48 am Thanks for the kind words everyone.

I'm tuning my new 'Chroma' filter Alexandra ;) The CaK PST filter works best untilted and perfectly orthogonal to the optical axis (as in the CaK PST).

Optical configuration as follows: Astronomik UV/IR filter, Edmunds Optics 394/10nm, Yellow CaK PST filter, Chroma 393.3/0.1 filter tilted.
Fascinating feed Mark with awesome images! I've stacked the CaK I've imaged at various percentages and still faffing with which percentage is best and then how sharp in the processing etc but I'll work it out and as soon as I'm done I'll share it!
I dithered whether to try a UV/IR filter with CaK & didn't with my first try... so using it with CaK is a good thing right? UV/IR definitely improves my WL with the Herschel Wedge.
Can I ask do you use a tilt adapter with CaK & WL as well h alpha? I've just always used one for all things solar!
Nic


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Re: Tuned CaK Filter - 11th August

Post by LeoD »

Excellent and very interesting, Mark!
I took the liberty to pop up spicules as well.
Leo
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Re: Tuned CaK Filter - 11th August

Post by eroel »

Mark:
Super results, thanks for sharing your experimentation on tuning.
Best regards.
Eric.


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Re: Tuned CaK Filter - 11th August

Post by marktownley »

Thanks for to everyone for all your likes and kind comments!
nicspenceryork wrote: Sat Aug 13, 2022 2:36 pm Fascinating feed Mark with awesome images! I've stacked the CaK I've imaged at various percentages and still faffing with which percentage is best and then how sharp in the processing etc but I'll work it out and as soon as I'm done I'll share it!
I dithered whether to try a UV/IR filter with CaK & didn't with my first try... so using it with CaK is a good thing right? UV/IR definitely improves my WL with the Herschel Wedge.
Can I ask do you use a tilt adapter with CaK & WL as well h alpha? I've just always used one for all things solar!
Nic
In terms of my CaK images (indeed all my images) I stack 128 of them in AS3, the original size of the file will depend on seeing and scale. In the case of these I captured 3000 and stacked 128, but I captured 5 files of this (5x3000), if the seeing was really borderline I might capture 10x4000 files with one resultant image being the best of the 10 stacked images. If the seeing is better I might record 5x2000 files, but i'm often push the aperture to the seeing so often are recording more rather than less raw data.

I found if I stack less than this then noise can start creeping in during post processing, stacking more then the stacked image is softer, with less detail and contrast (lower quality value). Stacking more allows for more aggresive post processing, but find if i'm having to do this I was using too large an aperture for the seeing.

I determine which is the best final stacked image by reopening it in AS3 and reading off the quality the value, the higher the quality value the better the image will be when it comes out of ImPPG.

I'm using the UV/IR filter primarily to keep the thermal load off the Edmunds Optics 394/10 filter, this is 25mm diameter and despite it sitting up high in the lightcone so the full aperture is used for energy rejection, if the filters get too hot then you can get wavefront distortion error occuring at their faces which reduces quality. The EO filter is a hard coated filter designed for laser use fundamentally so it should be alright, but I don't fancy testing it to breaking point.

I don't use a camera tilter with CaK - only with my IMX174 chipped camera for Ha as this has Newtons rings. When i'm talking about tilting the filters it is the filters themselves I am tilting not the camera or the optical train.

Tilting filters like this for Ca is nothing new, myself and others have been doing it for quite some time. Indeed the professionals do it with CaH on the 1m Sweedish Solar Telescope ;) I just wish we had access to their fancy software to remove the effects of the atmosphere etc. See the file attached for more info...
aa17305-11.pdf
(1.72 MiB) Downloaded 24 times


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Re: Tuned CaK Filter - 11th August

Post by nicspenceryork »

Reassuring & informative, thanks Mark.

4% of frames looked to be the best which seems to tally with yours.
I'll add number of frames I used etc when I post.

I now understand your use of the UV/IR filter for thermal load. I wouldn't need that for my set up. The reason I didn't use the UV/IR filter was because I half had it in my brain that CaK was 'near ultraviolet'. Now that I know that you've used one and that I've looked it up again, I see CaK is to the LEFT of NEAR ultraviolet so I think I understand now that the UV/IR filter wouldn't filter out anything I needed to catch CaK! I'll try it in future to see what happens.
You live and learn!

Nic


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Re: Tuned CaK Filter - 11th August

Post by arnedanielsen »

Awesome results Mark!

Thanks for sharing your CaK optimizations with us!

Best regards,
Arne


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