Updated foamboard spectroheliograph (with larger optics)

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Updated foamboard spectroheliograph (with larger optics)

Post by thesmiths »

Since we first built our "foamboard SHG" last year viewtopic.php?t=32136 we made incremental improvements (changing the grating, the slit, the collimator lens, including an external helical focuser for the collimator). I thought I would post some photos of the most recent version, which is now upgraded with larger optics in order to work with longer focal length telescopes (i.e. a larger projected solar disk).

Our original version worked with 100m f4 lens (i.e. 25mm diameter), which essentially matched the Solex design http://www.astrosurf.com/solex/sol-ex-c ... on-en.html. After getting very good results with our "dovetail SHG" -- which uses Asahi Pentax 135mm f3.5 and 150mm f4 lenses viewtopic.php?t=38214 -- we decided to upgrade the optics of our foamboard SHG to make them roughly similar to our dovetail SHG. This would allow attaching the foamboard SHG to larger telescopes (like our 140mm / 800mm refractor viewtopic.php?t=38418 or possibly an 8-inch SCT).

We had a 135mm f3.5 macro bellows lens and a 150mm f4.5 enlarger lens in our stockpile of lenses. We did some surgery on the foamboard, slicing away some pieces of foamboard with a scalpel, inserting the new optical components and putting everything back together with a hot glue gun. This time, we decided to add Asahi Pentax helicoid focusers on both the camera and collimator sides of the SHG. An Astronomik L1 filter was added in front of a chrome on fused quartz slit. The final result is shown in the photos below: with the top lid removed (first photo); with the top lid installed and showing the bottom side with the grating adjustment screws (second photo); and a recent H-alpha SHG image from Nov 4 taken using a long focal length refractor viewtopic.php?t=38703.

Upgraded foamboard SHG (top lid removed)
Upgraded foamboard SHG (top lid removed)
1597-annotated.jpg (621.77 KiB) Viewed 244 times
Upgraded foamboard SHG (top lid in place)
Upgraded foamboard SHG (top lid in place)
1590-annotated.jpg (126.57 KiB) Viewed 244 times
H-alpha image from Nov 4 -- foamboard SHG installed on 90mm / 910mm refractor
H-alpha image from Nov 4 -- foamboard SHG installed on 90mm / 910mm refractor
041122-Ha-4-910mm-2400g-stack-7-crop-invert.jpg (454.45 KiB) Viewed 244 times

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Re: Updated foamboard spectroheliograph (with larger optics)

Post by marktownley »

An excellent setup!

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Re: Updated foamboard spectroheliograph (with larger optics)

Post by DeepSolar64 »

I love SHGs. They can image any spectral line. I just wish someone sold a completed one commercially.

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