Sol'Ex with quartz slit

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Alun_H
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Sol'Ex with quartz slit

Post by Alun_H »

Back on the 27th March I had some sunshine to allow me to set up my Sol'Ex with a quartz slit (thank you Douglas). Was planning on using a UV/IR block filter from Baader but found it cuts way too much UV (CaK line totally missing) so will need to remain with Hoya ND16 on front of the 72ED until
I can get an Astronomik L1 filter. By the time I had got the SHG sorted and focused the clouds had once again rolled in and the wind dropped resulting in the clouds literally sitting in the sky,no movement whatsoever :cry: Although I had run a few scans in various wavelengths the only usable images not hampered by the cloud came from the Hydrogen Beta line,and then I realized after recording the data I had forgot to remove the 40mm aperture mask from the scope which I have in place for scanning in the CaK line,mistake seems to have paid off though. So,72ED with Hoya ND16 full aperture filter,Sol'Ex with 9um quartz slit/QHY5III 178M,16x sidereal speed used on CEM60,single scan but with slight processing in Photoshop CS2 (sharpen,brightness/gamma level adjustment,noise reduction) Also added false colour to the image.
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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: Sol'Ex with quartz slit

Post by thesmiths »

Looks like, despite clouds, you got a good first result with the new quartz slit. Did you think the aperture stop helped the H-beta?

You'll have to explain more fully at some stage how you integrated the slit into a Solex. I think you're only the second person to have tried it.


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Re: Sol'Ex with quartz slit

Post by rsfoto »

You'll have to explain more fully at some stage how you integrated the slit into a Solex. I think you're only the second person to have tried it.
I was going to ask the same before I saw Doug's comment :)

Now I have to ask. What is the advantage of the Quartz slit over the slit delivered by Shelyak in the Sol'Ex optical kit ? It is quite an additional investment...

Thanks


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Re: Sol'Ex with quartz slit

Post by thesmiths »

rsfoto wrote: Thu Mar 30, 2023 5:15 pm What is the advantage of the Quartz slit over the slit delivered by Shelyak in the Sol'Ex optical kit ?
There are two main advantages. First, the quartz slit is longer, 12mm vs 4.5mm. That means you can use it with a longer focal length telescope and still image a full disk with a single scan. With the Solex slit you would need to stitch two (or even three) scans together to get a full disk at longer focal lengths. The quartz still is also slightly narrower (9 micron vs 10 micron) which should give slightly better spectral resolution.

Second, quartz has a much lower thermal expansion coefficient than glass (which is what all the other slits use). This means it is much less sensitive to thermal shock. Therefore, an ND filter or Herschel wedge is unnecessary. A UV/IR filter is, however, recommended.

The following link has a pdf document that describes the quartz slit in more detail:
https://github.com/thelondonsmiths/Sole ... -SHG-slits


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Re: Sol'Ex with quartz slit

Post by rsfoto »

thesmiths wrote: Thu Mar 30, 2023 7:57 pm
rsfoto wrote: Thu Mar 30, 2023 5:15 pm What is the advantage of the Quartz slit over the slit delivered by Shelyak in the Sol'Ex optical kit ?
There are two main advantages. First, the quartz slit is longer, 12mm vs 4.5mm. That means you can use it with a longer focal length telescope and still image a full disk with a single scan. With the Solex slit you would need to stitch two (or even three) scans together to get a full disk at longer focal lengths. The quartz still is also slightly narrower (9 micron vs 10 micron) which should give slightly better spectral resolution.

Second, quartz has a much lower thermal expansion coefficient than glass (which is what all the other slits use). This means it is much less sensitive to thermal shock. Therefore, an ND filter or Herschel wedge is unnecessary. A UV/IR filter is, however, recommended.

The following link has a pdf document that describes the quartz slit in more detail:
https://github.com/thelondonsmiths/Sole ... -SHG-slits
Thanks Doug,

Thank you for the explanation. I think iin that case I do not need it. Thanks.

I have been using my Sol'Ex with the original slit with a 240mm focal length and aperture mask of 41mm (= f/5.85) and only a UV/IR filter in front for H-alpha and so far it still exists after letting it run for hours.

For Calcium I stopped down now to 24mm aperture (f/10) according to some recommendations I got.

Rainer


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Re: Sol'Ex with quartz slit

Post by Alun_H »

Thank you Douglas,I do believe reducing to 40mm helps,I tried an experiment earlier today in the Hbeta,one scan at full 72mm and another at 40mm
and by reducing the aperture focus was that much sharper. Will post images later when I have sorted them out. I can do a write up of how I installed the slit sometime,but basically I had a M42 threaded ring and the filter insert from a Geoptik Canon lens to CCD adapter which when padded out with suitable tape accepted the quartz slit cell and slid into the front of the Sol'ex much the same way as the ZWO T2 to filter adapter would work. Adjustment for focus of slit to collimator lens was now limited due to support tube being just sightly too short and moving slit housing forward placed the locking screws just outside of their channel in the support tube causing the housing to shift when locking down,but I got round this by moving the collimator lens forward in its tube and gently locked it in position by three equally spaced M3 grubb screws along with a spacer ring for the lens to sit on,housing is now pushed back to its original position and less twisting action when tightening down.

Rainer,I changed the slit because I was losing light when using the Herschel wedge so had to increase the exposure times along with gain resulting in slower frames per second and noisy images,especially in the Halpha. With the quartz slit and (for the time being) the Hoya ND 16 I am running at zero gain and around 1-2ms exposures,slightly more though in the CaK I think I was running at around 6-8ms and gain of 3-5. I will eventually get myself an Astronomik L1 UV/IR block so as to get rid of the ND 16 (unless I capture magnetogram images using the 3D glasses based filters) allowing even less exposure times and more FPS.

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: Sol'Ex with quartz slit

Post by thesmiths »

To Alun: with regards to Calcium imaging, Ca-H is not really much different for Ca-K, as you probably already know.

By the way, if you want to do magnetograms (detection of circular polarisation), I would actually use the technique of using a glass linear polariser behind an Edmund Optics quarter wave film. This is hinted at in C. Buil's YouTube video, as I recall. In the end, I think he chose to demonstrate the technique using two circular polarisers from 3D glasses and swapping them in a filter drawer. The more traditional way to do it is to rotate the linear polariser thereby continuously changing from right to left polarisation. I did this a few years ago in the context of detection of the Zeeman effect with a neon discharge tube: see viewtopic.php?p=285761#p285761. I think the optical quality will be higher than using 3D glasses.

Also, I don't see why the circular polariser necessarily has to be in front of the slit (thereby exposing it to quite intense radiation). It could be attached to the front of the collimator lens or even, I believe, to the front of the camera lens. The light though the slit should certainly maintain circular polarisation, and so should the light coming off the grating (although there could be a 180 degree rotation due to reflection).

I believe you could even put a quarter wave film on the front of the collimator and then a rotatable glass linear polariser on the front of the camera lens. These configuration could all be tested with a circularly polarised light source before testing on the sun.


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Re: Sol'Ex with quartz slit

Post by Alun_H »

Hi Douglas,

Thank you for the info regarding polariser filters,have found them on Edmund optics site and bookmarked (shopping list is getting longer still) I have got one of those drawer units for the Sol'Ex along with a couple pairs of 3D glasses so will play around with these for the time being. I think Christian mentioned in his video that the 3D glasses filters need to be as close to the slit as possible due to the fact that the image quality will be poor.
The placing of filters in front of the collimating and camera lenses and then adjusting during use isn't easy on the Sol'Ex as it involves loosening the locking bolts and removing the tubes holding the lenses,upsetting alignment of camera each time or possible loss of collimator focus on slit. For these more advanced projects I am going to have to build another SHG using camera lenses (I have a fair few lying around).

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: Sol'Ex with quartz slit

Post by thesmiths »

To Alun: you're quite right, the Solex design is not very conducive to making adjustments for elements inside the box. I think I could manage it with my Pentax lens design. There is a polarisation preference for light reflecting off a grating (see the Thorlabs grating specs) and Christian discusses this with regard to the orientation of circular polarising filters. I'll have to think a bit about this but I think putting the quarter wave film on the front of collimator lens and then rotating the linear polariser on the camera lens should work. In my earlier Zeeman experiments I used a 49mm Hoya linear polariser which simply screwed into the front filter threads of the Pentax lens. With my Pentax lens SHG, I can just reach in and turn the helical focusers so I should be able to also rotate the polariser. It's actually kind of crazy to put the polariser in front of the slit where all kinds of bad things can happen to it.

By the way, the Edmund Optics quarter wave film comes with opaque protective film (on both sides, as I recall). The optical film is really thin and delicate and I actually partially tore my piece while taking off the protective film. It wasn't so important for the experiment I was previously doing but just be aware that you need to (1) remove the protective film and (2) avoid damaging the optical film.


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Re: Sol'Ex with quartz slit

Post by Montana »

This is spectacular Alun :bow :hamster:

Alexandra


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Re: Sol'Ex with quartz slit

Post by Alun_H »

Thank you Alexandra.

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: Sol'Ex with quartz slit

Post by DN7 »

thesmiths wrote: Thu Mar 30, 2023 7:57 pm The following link has a pdf document that describes the quartz slit in more detail:
https://github.com/thelondonsmiths/Sole ... -SHG-slits
Wondering if that 9um crome over fused quartz slit is obtainable from you? If so, how can I obtain one?
Last edited by DN7 on Mon Apr 17, 2023 11:53 pm, edited 1 time in total.


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Re: Sol'Ex with quartz slit

Post by thesmiths »

DN7 wrote: Mon Apr 17, 2023 10:24 pm Wondering if that 9um chrome on fused quartz slit is obtainable from you? If so, how can I obtain one?
Yes, I still have some available. You can send an email to the address shown on the GitHub.


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