13Jun2014 PZ SHG: Ca H images

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13Jun2014 PZ SHG: Ca H images

Post by p_zetner »

I'd hoped for a sunny imaging day on Friday 13 but high cirrus made the sky progressively "milkier" throughout the morning until the big clouds rolled in and shut me down. Early on, the cloud cover did produce a nice solar halo, though:
pic_2446.jpg
Despite the clouds, I was able to do some imaging on the Ca H line. I used this line rather than Ca K because I begin to lose intensity rapidly with decreasing wavelength in the violet - odd, because my current grating is UV blazed!

The results surprised me - not bad considering the cloud cover. Maybe the atmosphere is steadier under these conditions. I have to admit, I didn't have the same luck with H beta. Maybe the finer details for this wavelength are more susceptible to transparency.

Here are full disks.

Ca II H1r:
CaH1R_102858_167-781_proc3.jpg
Ca II H2r:
CaH2R_102858_180-768_proc.jpg
Ca II H3:
CaH3_102858_187-761_proc.jpg
The (reciprocal) dispersion of my spectrometer is 0.028A/px while the bandpass (fwhm) is about (better than?) 0.14A.
The images were made from 2px slices taken out of the spectrum.

Cheers.
Peter.


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Re: 13Jun2014 PZ SHG: Ca H images

Post by marktownley »

Very nice results Peter!


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Re: 13Jun2014 PZ SHG: Ca H images

Post by Wah »

Very nice details!

Let me remove the horizontal bands...
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Re: 13Jun2014 PZ SHG: Ca H images

Post by Carbon60 »

Excellent images, Peter.

That's a nice setup, which is working extremely well.


Stu.


H-alpha, WL and Ca II K imaging kit for various image scales.
Fluxgate Magnetometers (1s and 150s Cadence).
Radio meteor detector.
More images at http://www.flickr.com/photos/solarcarbon60/
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Re: 13Jun2014 PZ SHG: Ca H images

Post by marktownley »

Great treatment wah!


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Re: 13Jun2014 PZ SHG: Ca H images

Post by alex »

Great work! :geek: :geek:


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Re: 13Jun2014 PZ SHG: Ca H images

Post by p_zetner »

Thanks, everyone!

Wah: Great job!

Is this your procedure?
1. Crop a vertical band near the centre (as featureless as possible).
2. Resize crop to 1px width.
3. Expand cropped / resized image to full width to generate a "flat".
4. Divide by flat.

I've tried this with only questionable success. Am I missing something?

Thanks.
Peter.


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Re: 13Jun2014 PZ SHG: Ca H images

Post by Wah »

During the flat field create process, we need to remove the bright and dark features as much as possible before resizing to 1px width.
I was using layers and layer masks to do the job, that would be quit time spending.


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Re: 13Jun2014 PZ SHG: Ca H images

Post by p_zetner »

Thanks for that advice, Wah.

This makes sense and it is something I haven't been doing.

Processing these SHG images can be very time consuming for a nice result!

Cheers.
Peter.


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Re: 13Jun2014 PZ SHG: Ca H images

Post by swisswalter »

Hi Peter

top results


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
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Re: 13Jun2014 PZ SHG: Ca H images

Post by DSobserver »

Wah wrote:During the flat field create process, we need to remove the bright and dark features as much as possible before resizing to 1px width.
I was using layers and layer masks to do the job, that would be quit time spending.
and what about a FFT treatment?


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Re: 13Jun2014 PZ SHG: Ca H images

Post by Wah »

DSobserver, FFT treatment will work for some fixed width / frequency bands. I don't think the slit irregularity can be applied to this processing method.
Actually, I did try converting the images to frequency domain, but didn't find bright spots in the FFT diagram...


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Re: 13Jun2014 PZ SHG: Ca H images

Post by Montana »

Wow!! amazing shots :bow :bow :bow

Out of interest, why are the poles brighter?

Alexandra


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Re: 13Jun2014 PZ SHG: Ca H images

Post by p_zetner »

Thanks Alexandra and Walter.

Alexandra:

The bright poles are a processing artifact. I have to be a bit more careful (and follow Wah's example)!

Wah and Vincent:

ImageJ has a fft bandpass filter which includes suppression of horizontal or vertical lines. Wah, this software looks for the appropriate "lines" pattern (spots) in frequency space and blocks automatically (with a direction tolerance that you set). Below is a comparison of images with and without this processing. A sky background subtraction has been applied to the image on the left and the image on the right is the ImageJ filtered version. You can see that the horizontal lines are mostly eliminated but some dark banding has been introduced, the proms are wiped out and a complex sky background has been reintroduced! (A very slight levels adjustment has been made - same to both images - but no other processing.)

Cheers.
Peter.
102858_180-768_2px_siz_bkg-sub.jpg


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Re: 13Jun2014 PZ SHG: Ca H images

Post by Wah »

I use your raw image to remove the bands.
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Re: 13Jun2014 PZ SHG: Ca H images

Post by Derek Klepp »

Peter and Wah thank you for a great result so much more to see than with the straight diagonal


Anthony

Re: 13Jun2014 PZ SHG: Ca H images

Post by Anthony »

Fantastic work.


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