My folded SHG and Ha image from 3rd June 23

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Alun_H
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My folded SHG and Ha image from 3rd June 23

Post by Alun_H »

After having watched Douglas Smiths interesting Zoom presentation on YouTube I was intrigued seeing Maurice's folded spectroheliograph and spent the last few days adapting my foam board constructed SHG to sit piggybacked to my 90mm f/10 achromat due mainly to the fact the focuser on the scope cannot hold the weight without flexing. Foam board casing is bolted down on to a Losmandy plate which is then bolted to the top of the scopes tube rings,two 2" mirror diagonals feeding the image from the scope onto the quartz slit which then passes through a 135mm Pentax lens collimator to a 25x25 2400l/mm grating then to a 150mm Pentax imaging lens/QHY5III 178M. At 900mm focal length full disk isn't attainable with the 178 so mosaics
are required until such a time I can replace camera with possibly a 183. The scope tube had been shortened when I used it for a PST mod and at the moment I am using the Hoya Pro ND16 on the front of the scope so aperture is reduced to 82mm,will eventually replace this with a 2" Astronomik L1
UV/IR block. The rig rides on my NEQ6 Pro,scanning in RA with no problems,haven't weighed the scope/SHG so not sure of the exact weight.

Image from yesterday (3rd June) is a two pane mosaic each pane is a stack of four scans stacked and stitched in Affinity Photo,processed in Astrosurface and PS CS2.
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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! :lol:
More images on view on my Flickr page...https://www.flickr.com/photos/alun_h/
thesmiths
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Re: My folded SHG and Ha image from 3rd June 23

Post by thesmiths »

Alun, that looks really good. I think the folded design shows a lot of promise and you showed it’s not too difficult to implement. There are probably a lot of shortened refractors around from PST mods. F/10 is a bit longer than ideal but has some optical advantages with regards to abberations and also focus depth.

Didn’t you tell me before that you swapped around the 135/150 lenses? As I recall, the way you have it now (collimator 135 and camera 150) maximises the spectral resolution on a 2.4 micron sensor, so that’s an advantage. At the end of the day, splurging on the IMX183 sensor is worth it.


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Re: My folded SHG and Ha image from 3rd June 23

Post by thesmiths »

By the way, you can probably easily fit the fairly inexpensive Skywatcher autofocuser on that scope. It works better than manual focusing. But in my experience, the ZWO EAF, although more expensive and sometimes trickier to install, is miles ahead.


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Re: My folded SHG and Ha image from 3rd June 23

Post by Alun_H »

Thank you Douglas,I had a 150/150 combination at one time but reverted back to the 135 collimator. IMX183 is on the cards,working with mosaics when
clouds are drifting through can be troublesome,as you no doubt know yourself. As to the autofocuser,I just mounted the SW unit to the focuser today after having made up an adapter for it to fit the spindle.

Alun


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! :lol:
More images on view on my Flickr page...https://www.flickr.com/photos/alun_h/
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Re: My folded SHG and Ha image from 3rd June 23

Post by rsfoto »

Hi,

Very well done. Excellent.

I think this is going to be standard procedure for the future of SHG's. SHG and scope really fixed in a stable position the the only moving thing is the Diagonals at the focuser.

Honestly I have always wondered how Christian Buil achieves those results with hanging the Sol'Ex on his telescopes and adjusting every by hand... after seeing my set up and having to run back- and forwards to achieve any adjustment. Nearly impossible unless I have a helper moving all the knobs and me shouting from the PC good or not good :lol:

Doug mentioned that the connection between second diagonal and scope does not need to be fixed as stray light is no problem there due to the very high illumination of the slit bu the focused telescope.


regards Rainer

Observatorio Real de 14
San Luis Potosi Mexico

North 22° West 101°
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