CaH SHG 80mm f6 stacked image

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CaH SHG 80mm f6 stacked image

Post by thesmiths »

We upgraded our Calcium SHG in a few ways. First, we attached a 80mm f6 triplet APO to try for a bit more spatial resolution. Next, we installed a 2400 l/mm diffraction grating to get more spectral resolution. Everything else was essentially the same as our previous Calcium imaging run (see viewtopic.php?t=36730). Here is how the setup looks (without the shroud we put over it to block out ambient light).

SHG setup with 80mm f6 APO refractor; 2400 l/mm grating, 50mm x 50mm; 9 micron x 12mm lithographic slit; ZWO 178MM camera; 135mm f4 collimator; 150mm f4.5 camera lens. This configuration assures that the slit is orientated quite precisely in the RA direction. This means that scanning is done in DEC. The mount was a Vixen GP2 with upgraded motors. The grating is mounted on an ADM dovetail clamp so it can be interchanged or removed for safe storage.
SHG setup with 80mm f6 APO refractor; 2400 l/mm grating, 50mm x 50mm; 9 micron x 12mm lithographic slit; ZWO 178MM camera; 135mm f4 collimator; 150mm f4.5 camera lens. This configuration assures that the slit is orientated quite precisely in the RA direction. This means that scanning is done in DEC. The mount was a Vixen GP2 with upgraded motors. The grating is mounted on an ADM dovetail clamp so it can be interchanged or removed for safe storage.
1420.jpg (348.43 KiB) Viewed 558 times

Once all the focusing is set, we retreat indoors and run things via Remote Desktop. Below is a screenshot of the FireCapture and EqMod controller we use for image capture and scanning. The actual acquisition parameters are visible in the screenshot. Since the slit is oriented quite precisely in RA (due to the grating being mounted on a dovetail bar), the ROI shown is a line in the E-W direction (probably across the active region just above the equator). Scanning is done is DEC, so the slit traverses N-S for a scan, the recording is stopped; restarted and then the slit travels S-N in the next scan (hence the feature in our software to do a "mirror flip" in the reconstruction).

FireCapture and EqMod image acquisition (via Remote Desktop). Acquisition parameters are visible: 20X sidereal rate scan; 322 fps; 2ms exposure; ROI 2400x150.
FireCapture and EqMod image acquisition (via Remote Desktop). Acquisition parameters are visible: 20X sidereal rate scan; 322 fps; 2ms exposure; ROI 2400x150.
Calcium H desktop.JPG (165.47 KiB) Viewed 558 times

Here is the Calcium H image we created using our v3.4 software, AS3, imppg and Photoshop. The stacking was done from the best 25% of 58 SHG images, so a large amount of data (around 140 GB). Note that the imaging was done between 15:00 and 15:30 UTC and I was able to get the image processed by the evening -- so a relatively quick turnaround.

CaH, stack of best 25% of 58 SHG images
CaH, stack of best 25% of 58 SHG images
070722-CaH-stack58,25-imppg.jpg (189.37 KiB) Viewed 558 times

There is a bit of a focus issue such that the left side is sharp but the right side is a bit out of focus. This I think was because I chose to focus the telescope on the left side of the Sun since that was where there was more structure to focus on (see the screenshot of the FireCapture ROI). There must be some optical tilt somewhere (this was the first attempt with this setup). It looks like there are some edge effects at the North and South rim. This looks like a stacking problem (and maybe incorrect imppg usage?).

I should mention that for the stacking, I used images where there was no transversalium removal done. The lithographic slit is almost without any structure and it was cleaned well before assembly. The transversalium removal function does introduce some slight artefacts and I found that with stacking, the need for their removal in the input images is unnecessary.

It's interesting to compare this image to H-alpha etalon and CaK filter images taken on the same day and around the same time (the afternoon of July 7): see viewtopic.php?t=36959. I've taken the great H-alpha and CaK images from Arne and made a mosaic with our CaH SHG image so it's easier to see where there are similarities and differences.

H-alpha (Coronado 60mm); CaH (SHG); and CaK (Lunt CaK 1200)
H-alpha (Coronado 60mm); CaH (SHG); and CaK (Lunt CaK 1200)
070722-CaH-Halpha-CaK.jpg (601.36 KiB) Viewed 558 times


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Re: CaH SHG 80mm f6 stacked image

Post by Montana »

Oh my!! what a breath taking image :bow :bow :bow you should be very proud of all your hard work :)

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Re: CaH SHG 80mm f6 stacked image

Post by torsinadoc »

Really impressive to see these details in CaH. This set up is the holy grail for Ca imaging


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Re: CaH SHG 80mm f6 stacked image

Post by fulvio.mete »

Great images!

Fulvio


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Re: CaH SHG 80mm f6 stacked image

Post by christian viladrich »

One of the best Ca K images I seen taken with a SHG. The filaments have very nice contrast.
Well done !


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Re: CaH SHG 80mm f6 stacked image

Post by marktownley »

Very impressive indeed Douglas


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