rsfoto wrote: ↑Sat Jun 03, 2023 3:35 pm I have some diagonals and will test if my new little SVBONY 70mm f/6 can focus after two diagonals.

A short refractor with 420mm focal length will have proportionately less back focus than a long refractor with 900mm focal length.

The telescope focuser supports only the weight of the two diagonals. I would dare to say that in this construction the focuser has no weight to carry at all as the SHG is resting on top of the telescope. No, that is not how it is constructed. The two diagonals are installed into the telescope focus...

Using 2 diagonals needs a lot of backfocus, did he shorten the telescope tube ? No shortening was required. Most of the telescopes I've used for SHG need a huge number of extensions in order to focus on a slit. A few notes on the construction. The telescope focuser supports only the weight of the t...

Maurice sometimes posts to iceinspace but says he is not an active participant in many online astronomy forums. I said I would like to show some of his work to inspire others. I attach some of his more recent images: Ha_MPV_260523_am_sml.jpg CaH_MPV_270523_am_sml.jpg helium_D3_ps_diff_method2_sml.jp...

Maurice from Melbourne Australia contacted me in February to ask me to send him one of my quartz SHG slits. He had already built a Solex and used it with a 70mm f/6 refractor. His plan was to build a larger instrument based on the 100mm f/9 Orion telescope. He decided to use a folded design, which i...

The first commercial H alpha solar telescope that I know of was the one I first looked through in 1968. It had been advertised in Sky & Telescope beginning in the late 1960's. The solar prominence telescope that Marvin called "The New Realm Telescope," used an H alpha filter which was...

It is not clear to me who actually made the first use of mica-spaced etalon for solar observation : Doug Martin or Kononovitch & Shcheglov. I mentioned the Russian work because it is the one cited by both Harvard University and the American Institute of Physics (academics put priority to publis...

The first use of a Fabry-Perot etalon for solar observation was done at the Crimean Astronomical Observatory in the summer of 1966. The results were published in 1968 in Astronomicheskii Zhurnal (English translation attached). As shown in Figure 2, the bandwidth of the etalon was 0.7 angstrom, simil...

I have been testing my Skywatcher 80ED (600mm focal length, f/7.5) with a quartz slit and no attenuation at all: no ND filter, no Herschel wedge, and even no UV/IR filter. I was able to get a little higher shutter speed as a result. So far, I have seen no degradation of the chrome mask layer. I thin...

we have a lot of pins on this section now Maybe too many pins! I thought some should be moved (or is it copied?) to the Solar Reference Library . I would move (or copy) this current one on Helium imaging, the Zoom call one https://solarchatforum.com/viewtopic.php?t=40847 and the Christian Buil one ...

This question came up in the recent Zoom call. Valerie listened to the replay and kindly posted the following on the https://groups.io/g/Solex-English message board: https://groups.io/g/Solex-English/message/1006 I replied to her post with some of my experiences with the Helium line: https://groups....

I am still fine tuning my 80mm / 600mm refractor with accompanying spectroheliograph (SHG). I could only manage a short session late in the day and it was windy and a bit cloudy -- extremely non-ideal for the SHG technique. I managed a few scans in H-alpha that were of moderate quality. I then decid...

As you go further south, the sun is also higher in the sky (closer to noon local time), which has some advantages. It might also last a bit longer.

I did a few experiments with different telescopes today and the conditions deteriorated as time went on. Here are are pair Hydrogen Balmer images -- H-alpha and H-beta -- which I took with my 80mm aperture, 600mm focal length refractor towards the end of the session. Click on the image to see at hig...

There is a "feel" about the Ha which is very different - more organic - than classic Ha etalon photos. Is that b/c of the SHG? I'm sorry I missed the zoom on SHG you gave as we had guests - did that end up being recorded? Yes, there was a recording made. You can find it here: https://sola...

I am presuming the red spot is the Sun Yes, it is. I didn't expect to see that. But then I realised that the attenuation is specified as OD5, which is the same as Baader solar film (the visual kind). Apparently, thin metal films become more transparent with longer wavelength so that's why it looks ...

I had some good feedback on the Solarchat 14 May 2023 Zoom call. I posted an edited version of the slides I used in the original Zoom announcement thread, but I'm afraid that will eventually become hard to find (it's now in the SPOD Archive). I've put the slides in this new post and perhaps one of t...

In This is Solarchat I posted a mosaic of these three wavelengths: https://solarchatforum.com/viewtopic.php?t=40803 . I will post the individual images here. 106mm aperture, 720mm focal length telescope. The Ca-H image was done with a 72mm aperture mask (and probably the H-beta might have benefited ...

In This is Solarchat I posted a mosaic of these three wavelengths: https://solarchatforum.com/viewtopic.php?t=40803 . I will post the individual images here. 106mm aperture, 720mm focal length telescope. The Ca-H image was done with a 72mm aperture mask (and probably the H-beta might have benefited ...

Here's a mosaic of three wavelengths taken on May 21 using my 106mm aperture spectroheliograph (SHG). Click on the image to see at higher resolution. To see full details, open the image in a new tab (each disk is around 3000 pixels in diameter).

Have you tried to measure the temperature rise of the copper heat sink? Just curious about heat transfer. I have not directly measured the temperature of the copper disk. I often will touch the M42 tube into which the disk is mounted and I haven't noticed any external temperature rise. I deliberate...

Before the sun went behind the trees, I thought I would try a quick experiment to answer the question: how hard is it to attach a spectroheliograph to a Newtonian? It turns out, not as difficult as I had thought. I was only able to do a single scan before clouds and trees prevented further imaging. ...

The weather was too unpredictable to bring out the spectroheliograph, so I spent late Saturday afternoon playing with an instrument I had not brought out in a long time: the 130mm f5 solar Newtonian (primary mirror stripped of its reflective coating). I took a few full-disk SER files with the Baader...

How big is the secondary? Secondary mirror is 18 mm. That's very good (and somewhat unusual). It makes sense for narrow field of view imaging. Most Newtonians have secondaries that are bigger than necessary (in order to maximise the field of view). In this case, only 9% of the diameter is obstructe...

The optics look very good -- but I'm a bit sceptical of their focuser. What's your opinion?

Those eyepieces look just like the Japanese microscope eyepieces from that period. I'm guessing around 1970?