I tried a new approach to the stacking process for the CaH image. I used the best 75% of 35 SHG images (which were already hand selected to some degree) in AutoStakkert . I then used Registax 6 wavelets , followed by a little Photoshop. The result was quite good. It's definitely sharper than the fir...

p_zetner wrote: ↑Thu Jun 23, 2022 2:14 am I’m a little surprised that you claim a spectral resolution of 0.16 angstroms. How did you measure this?

I only used Ken's SimSpec SHG v1_3b spreadsheet to calculate the spectral resolution, rather than measuring it.

I also include a CaH image taken shortly after the H-beta and H-alpha images. For this, I again used my 600mm all-camera lens SGH. This one does not yet have as good resolution as my main one based on a 700mm APO triplet telescope. I again attempted stacking to improve noise, this time with 35 indiv...

Another good day of weather in London and the SHG was set up for Hydrogen imaging. Rather than try stacking again, which is hard work, I took a huge number of gigabytes of scans and found a few with excellent individual quality. These were full disk images which were cropped to better preserve the r...

I used the pixel shift feature in our software to create a series of images from 0 to +11 pixel shift and created a mosaic. 151109_shift_0_11_clahe_small.jpg When I compare to Stuart Green's CaK filter image from the same day ( https://www.flickr.com/photos/solarcarbon60/52163380338/ ), it seems to ...

I decided to revisit an older SHG setup and to install one of the new long chrome-on-quartz stilts in order to image around the Calcium lines. This way, I could keep my 106mm aperture 700mm FL telescope with the 2400 l/mm grating reserved for the H-beta to H-alpha range of wavelengths. The 400nm par...

When I look at the K and H lines through a spectrometer, I can see that the slightly longer wavelength (H) is considerably brighter, at least on a camera sensor. That may not make enough difference visually though. It can lead to better shutter-speed/gain settings so for the same bandwidth, H ought ...

There is always a characteristic “spiky” appearance to features I capture in my spectroheliograms. I assume this is due to seeing variations over the course of my (slow) scan. What surprises me is that these spiky variations don’t seem to appear in your raw (fast) scans. I would expect that they oc...

Some more experimental background : the unfiltered solar radiation on the chrome-on-quartz slit does not seems to have have affected the slit after quite a few hours of exposure. I do try to put on the telescope lens cap when I am not imaging (that is probably good advice for all solar equipment). ...

I don't recall trying H-beta before as it was somewhat featureless in the images I had seen. But with my new full-disk, high spatial resolution capability (due to the long chrome-on-quartz slits), I am pleasantly surprised by the gentle and subtle features that H-beta can show. Fortuitously, the Sun...

What about the camera you used? Fulvio I was using the ZWO 178MM but I recently decided to "upgrade" to a ZWO 183MM . The sensor is essentially the same, as far as I can tell; it is just larger (and the dimensions of the case is slightly different too, which changes the focal point). The ...

p_zetner wrote: ↑Fri Jun 17, 2022 2:38 am Your results are making wonder if I should give the "fast scan" technique a try!

Fast scanning is definitely the way to go. You get a much higher probability of success (but a lot more disk space used).

For those who know about Russian optics : does anyone know the difference between LOMO and LZOS ? I ordered an 80mm f6 refractor from Markus at APM some years ago (I think he said it was the last run of small APOs he would be doing, using up all the parts he had around). It came with a LOMO lens. T...

I will add here a reduced size side-by-side comparison, which enables matching the small features more easily, in particular the filaments . I think filaments only appear clearly with quite narrowband imaging. 111512_124201_small.jpg There was a small camera rotation done between the two images so t...

Hi Franco, what's your impression of CaH vs CaK?

Is your photo rotated slightly counter-clockwise on purpose?

The sky over London was clear and the air was quite still today so even better results were obtained in the most recent testing of the long chrome/quartz slits (for the previous test run see https://solarchatforum.com/viewtopic.php?t=36602 ). I used the setup from the day before to take four H-alpha...

The sky over London was clear and the air was quite still today so even better results were obtained in the most recent testing of the long chrome/quartz slits (for the previous test run see https://solarchatforum.com/viewtopic.php?t=36602 ). I used the setup from the day before to take four H-alpha...

my concern with the usual M42 focusers we can find in astro (Borg, TS or others), is that they are not strong enough to support the weight of the SHG The Asahi Pentax version (also called the "Pentax helicoid extension tube") is considered the king of helical focusers. They are a little h...

Could you post a picture of the M42 focuser arrangement for the collimating lens? There are of course two types of M42 (I have one of each): the "Pentax" camera thread is 1.0mm pitch and the "T-mount", which has a 0.75mm thread pitch. My SHG setup uses the Pentax type lenses and...

We made a few minor improvements to the previous setup described here: https://solarchatforum.com/viewtopic.php?t=36537 . To aid with focusing , an M42 helical focuser was inserted between the collimator lens and the slit holder. This finally allowed good focus to be achieved after much playing arou...

you made this or bought it? I had these made for me by a mask design shop. So in that sense, I did not do the photolithography myself (it is a rather specialised business to get sub-micron accuracy). I did have to make a lot of design decisions though (no doubt, some of which will probably turn out...

I made a quick spectroheliograph scan today to follow-up on the previous initial thermal test https://solarchatforum.com/viewtopic.php?t=36508 . I was able to do a full-disk scan using my 106mm, 700mm FL APO refractor. This telescope has typically performed very well for solar imaging in white light...

In a previous post https://solarchatforum.com/viewtopic.php?t=36503 , I described my motivation and design thoughts for making a chrome on fused quartz SHG slit. One design parameter I did not go into was the choice of optical density (OD) for the chrome mask. The way the semiconductor masks are mad...

I almost totally agree about your analysis of slit type for solar spectrographs. Your option of quartz slits seems interesting, but I'm afraid the cost of your slit plate could be high. Like with all things related to semiconductor processing, the fixed cost is high but the unit cost can be quite l...

I'm wondering if a too thin slit wouldn't be counterproductive: I mean at the focal plane of the main telescope you image the Sun's image on the entrance slit. That means that the size of the smallest image point will have a certain physical size depending on the diameter, seeing and focal length. ...