I LOVE finding out about different ways to appreciate the Sun and light in general. Use this forum to post your info or questions about various outside the mainstream ways to appreciate our life giving star!
Lovely weather in London today. The morning offered good seeing and I was able to do tests with various setups: my 106mm APO triplet, 140mm Vixen NA, and Skywatcher 80mm f6.5. In this post, I show the results from the 106mm / 720mm refractor, which were the best. I only imaged to do the H-alpha and Ca-H lines. Open in a new tab to view at full resolution (there are a lot of details: the solar disk diameter is 2680 pixels).
H-alpha SHG. 106mm aperture. 2.5ms exposure, gain zero. ZWO 183MM camera. ROI 3304x100 pixels. 385 fps. Stack of 9 frames (out of 21 scans). 0753-0759 UTC.
070723-Ha-2-106mm-stack9.jpg (1.79 MiB) Viewed 1711 times
Ca-H SHG. 72mm aperture, f/10. 3.0ms exposure, gain 17%. 318 fps. ROI 3304x120. Stack of 9 frames (from 20 scans). 0846-0852 UTC.
070723-CaH-72mm-stack9.jpg (1.74 MiB) Viewed 1711 times
H-alpha SHG, inverted.
070723-Ha-2-106mm-stack9-invert.jpg (1.87 MiB) Viewed 1711 times
Ca-H SHG, inverted.
070723-CaH-72mm-stack9-invert.jpg (2.07 MiB) Viewed 1711 times
Last edited by thesmiths on Fri Jul 07, 2023 10:19 pm, edited 1 time in total.
I made a small modification to my dovetail SHG that helps to focus the two Pentax lenses that I use as the collimator and imaging lenses. I put foamboard disks over the helical focusers, which makes it much easier to make small adjustments. This is similar to a trick I saw some people use with SCT focusers.
Lunt 50THa solar scope
Lunt CaK B12 module
SW Evostar 72ED for full disk imaging
Sol'Ex SHG
80mm f/7 achromat used with pressure tune module off the Lunt with Lunt 100mm ERF
Bresser 90 f/10 achromat used for CaK & white light imaging & PST mod with Lunt 100mm ERF
Coronado SM40 (pre Meade) and BF10 filter set + SMII 60 richview DS etalon
Skywatcher EQ6 Pro and Ioptron CEM60
Then there is all the night kit which is far too long a list to write up here!
More images on view on my Flickr page...https://www.flickr.com/photos/alun_h/
Having some expereince with Sol'Ex, I know how dependent we are on excellent seeing but also cannot minimize the skill of the operator- these are exemplary!
Does daytime seeing follow a pattern in London or is it more random in nature?
I also am curious to know if you have to refocus the objective lens when going from Ha to CaH? and at what f/stop are your collimator and objective?
NM_mike wrote: ↑Mon Jul 10, 2023 1:07 pm
Does daytime seeing follow a pattern in London or is it more random in nature? I also am curious to know if you have to refocus the objective lens when going from Ha to CaH? and at what f/stop are your collimator and objective?
Yes, I found early in the morning is the best in London. Where I live it's kind of green and not so much concrete.
I have to refocus the camera going from 650nm to 400nm. The telescope also needs refocusing. The collimator seems to require less refocusing for some reason.
You should use the collimator and objective with as wide an f-stop as the lens allows. I'm using 150mm f/4 lenses.
christian viladrich wrote: ↑Sat Jul 08, 2023 5:22 pm
The comparison with the TS image taken by Pedro is quite interesting.
We can see that the SHG has better spectral resolution than a triple-stack combination. The contrast of the fainter filaments is higher.
And the resolution of Doug's image is quite amazing !
I think Christian is referring to this particular image from Pedro. The title says "LUNT60, TS SM60/SM40". To my mind, the spectral resolution is fairly similar, but of course Pedro's triple stack has only (I believe) a 40mm aperture while I am using 106mm. So it's to be expected that the spatial resolution is better. I think it's very difficult to separate the effects of spectral and spatial resolution. I suspect an 80mm triple stack might be better than a 106mm SHG image -- but that kind of equipment would be difficult to assemble. The theoretical spectral resolution of my SHG is 0.1 angstrom at H-alpha, but it reality it's probably more like 0.2 angstrom. I suspect also that the spatial resolution isn't entirely limited by the telescope optics but is probably slightly degraded by the internal optics of the spectrometer. That's why I suggested that it might be more equivalent to something like a 80-90mm aperture triple stack.
http://brierleyhillsolar.blogspot.co.uk/ Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
Simply stunning images!
