H-alpha SHG through the living room window on Nov 4

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thesmiths
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H-alpha SHG through the living room window on Nov 4

Post by thesmiths »

It was a sunny clear autumn day in London and there was a glimpse of clear sun around 11:30am through my upstairs window. The obstacles were roofs, tree branches and some window frames. This lead to less than ideal seeing conditions and I could see many scans had distortions caused by turbulence. Nevertheless, with some luck and persistence, I was able to get some acceptable data.

H-alpha SHG. 90mm 910mm doublet refractor. 2400 l/mm grating 30mm x 30mm. 135mm f3.5 collimator, 150mm f4.5 camera lens. 183MM camera, 2x2 binning. 4ms exposure, gain 51 (11%). Stack of best 7 of 21 scans. 11:30 UTC to 11:37 UTC.
H-alpha SHG. 90mm 910mm doublet refractor. 2400 l/mm grating 30mm x 30mm. 135mm f3.5 collimator, 150mm f4.5 camera lens. 183MM camera, 2x2 binning. 4ms exposure, gain 51 (11%). Stack of best 7 of 21 scans. 11:30 UTC to 11:37 UTC.
041122-Ha-4-910mm-2400g-stack-7.jpg (883.37 KiB) Viewed 197 times

Using Tilting Sun, I rotated the above image so that the solar equator was approximately horizontal, cropped the northern hemisphere and inverted. Click on the image to see at higher resolution.

H-alpha SHG. Rotated by 24 degrees, cropped and inverted. FireCapture, AS!3, ImPPG, Photoshop Elements.
H-alpha SHG. Rotated by 24 degrees, cropped and inverted. FireCapture, AS!3, ImPPG, Photoshop Elements.
041122-Ha-4-910mm-2400g-stack-7-crop-invert.jpg (454.45 KiB) Viewed 197 times

I recently attached a Sky-Watcher Auto Focuser to the Sky-Watcher Evostar 90 achromat and this turned out to be very helpful. The focus mechanism on the telescope does not allow much fine control and also makes the field of view shake a lot. Focusing is very critical for good SHG imaging and the electronic focuser makes it much easier. I have a ZWO EAF on my other SHG setup (which has a triplet APO with a Feather Touch focuser) and this turned out to be such a useful addition, I decided to add an electronic focuser to the Sky-Watcher also.


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Re: H-alpha SHG through the living room window on Nov 4

Post by highfnum »

sheesh thru a window no less


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Re: H-alpha SHG through the living room window on Nov 4

Post by marktownley »

Stunning image Douglas!


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Re: H-alpha SHG through the living room window on Nov 4

Post by thesmiths »

My sense is this SHG setup using the 90mm 910mm achromat does not provide the image quality of my other setup based around a 106mm 720mm triplet. The optical components of the SHG itself are not too dissimilar now between the two so I think it comes down to the quality of the telescope itself. The Sky-Watcher achromat is one I picked up off of eBay for a nominal amount while the triplet has a very nice Russian APO lens and always gives excellent results throughout the visible range.

But the Sky-Watcher is really lightweight, as is the foamboard SHG, so I can put it onto a lightweight Vixen GP2 mount and move it around inside the house (and carry the whole thing outside too). The triplet setup needs to be mounted on something like an HEQ5 at a minimum and is therefore not very mobile.

When I say the image quality is better, I am actually judging by how the details within the spectral line appear, not on a full disk scan, which can be distorted by momentary changes in seeing.


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Re: H-alpha SHG through the living room window on Nov 4

Post by rsfoto »

Excellent


regards Rainer

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Re: H-alpha SHG through the living room window on Nov 4

Post by Montana »

Incredible, looks like the Sun is ready to pop :bow :hamster:

Alexandra


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Re: H-alpha SHG through the living room window on Nov 4

Post by thesmiths »

I would say the current 90mm aperture SHG setup described here compares favourably with a Lunt 60 double stack: viewtopic.php?t=38704

I actually have a Lunt 60 PT and also have the front mounted etalon in order to double stack. I found that in my case, the double stack was not so easy to get good full disk results with due to uneven illumination (which could probably be remedied with taking flats, etc).

My better 106mm aperture SHG compares favourably with approximately a 80mm double stack. In both cases, although it takes a bit of work to get good results, the initial investment cost of the SHG is a small fraction of what a double stack etalon goes for these days. And of course, you can look at a few different wavelengths with the same instrument, which makes it even more of a bargain.


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Re: H-alpha SHG through the living room window on Nov 4

Post by StarHugger »

Thanks, the images are stunning and the information is welcome indeed.


Aaron.
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