New telescope ~400mm focal length for SHG

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New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi,

I am biting the bullet and 99% on the way to buy a better scope for my Sol'Ex

Skywatcher 62mm?

Skywatcher 72mm?

Skywatcher 82mm?

or any other brand.

I have a Takahashi Sky90 f/5.0 450mm focal length but it is not collimated and collimating that scope is a Nightmare even for the Takahashi technicians ...

I do not want to exchange the slit which is the original Sol'Ex 4.5mm wide and 10µm which means theoretically I could go up to 450mm focal length?


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Re: New telescope ~400mm focal length for SHG

Post by thesmiths »

For the original Solex design, the best scope is the Skywatcher 72ED (420mm focal length).


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

thesmiths wrote: Mon May 15, 2023 6:05 pm For the original Solex design, the best scope is the Skywatcher 72ED (420mm focal length).
Thanks but what I do not like on this scope is the Crayford focuser.. I do not like Crayford focusers at all. They slip to easily, but I have a Rack & Pinion Feathertouch on a unused RC from Astrotech.

I could 3D print an adapter. There is a good offer right now on the Smiley AWS company.

SkyWatcher 72mm


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi Doug,

May I ask why ? Is it because of the slit width of 4.5mm and 420mm focal length? In any case I have 46mm ND filters so I would stop it down to f/9.1

There is also a good price for the SkyWatcher EvoLux 62mm. with 400mm focal length and stopping down to 46mm gives me f/8.7

Decisions decisions decisions ... :lol: :lol: :lol: :lol:


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Re: New telescope ~400mm focal length for SHG

Post by thesmiths »

72mm aperture is the largest commonly available telescope that will fit easily on the 4.5mm slit of the traditional Solex. Normally, you would not want to mask the aperture to lose spatial resolution (except for the Calcium lines). If you are ok with merging several scans in a mosaic, you could look at a longer focal length. I'm sure you can find similar scopes with rack and pinion focusers (typically Vixen used R&P).


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Re: New telescope ~400mm focal length for SHG

Post by Jean-Francois »

Hello,

Here an example done with my TSAPO72F6 (the last image from last month).
TSAPO72F6_1x1_AS_3-19.jpg
TSAPO72F6_1x1_AS_3-19.jpg (996.61 KiB) Viewed 2216 times

And my setup ... please note that I use an EQ8 mount, not the LX75 on the picture.
The TSAPO72F6 telescope has a focal length of 432 mm. That is not a problem to center it in the "178" camera.

The telescope has a rack and pinion focuser. You can see that I use the Laserta 2" Herschel prism ... that is not a lightweight part.
I have no problem. In the meantime, I have an electric focuser mounted on the telescope.

And If you think that the Sol'Ex is not standard ... it is correct. I redesign completely the Sol'Ex.
I add a double planetary gear with 36x reduction. One complete rotation of the button rotates the grating with 10°.
TSAPO72F6_SolEx.jpg
TSAPO72F6_SolEx.jpg (316.5 KiB) Viewed 2216 times

Regards,
Jean-Francois


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi All,

Thank You


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

.. Normally, you would not want to mask the aperture to lose spatial resolution.
Hi Doug,

Interesting how many opinions about " To Mask or Not To Mask"

:lol:

Thanks Rainer
Last edited by rsfoto on Fri Jun 02, 2023 4:12 pm, edited 1 time in total.


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi SHG experts,

I just placed an order for a 70mm f/6 420mm focal length telescope as well as some ND filters (2 0.3), 4(0.6), 8(0.9) and 16(1.2) and a UV/IR filter.

https://cdn.mos.cms.futurecdn.net/w6MED ... aEaU2M.jpg

What ND filter do you think I will need in order to avoid the cracking of the standard Sol'Ex slit ?


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

What ND filter do you think I will need in order to avoid the cracking of the standard Sol'Ex slit ?
OK, I will start with all 4 and taking off one by one until it cracks and so I will know which one not to use :lol:

and then order the slit from Doug ... aka the smiths ...


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Re: New telescope ~400mm focal length for SHG

Post by thesmiths »

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 think with this relatively small aperture and fairly slow focal ratio, the intensity is not too high to damage the chrome. I did see some damage to the chrome with a 140mm aperture at 800mm focal length (f/5.7). But the quartz substrate itself is impervious (it is the same material used to make the windows on the SR71 Blackbird).


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi Doug,

Thanks. I will do the same test I made with my 60mm f/4 scope. Focus on the Sun and put a temperature sensor at the focus and see how high it goes.

BTW, I bought a SVBONY SV503 70mm f/6 which was US $ 120.00 cheaper then the StarWatcher. I missed the offer the other day. The SkyWatcher was at MXN $ 9,500.00 a few weeks ago and now it is at MXN $ 11,679.00 and the SVBONY I got it for MXN $ 9500.00 last week. Today the SVBONY is also at MXN $ 11,917.00

regqards Rainer


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Re: New telescope ~400mm focal length for SHG

Post by Alun_H »

rsfoto wrote: Sat May 27, 2023 8:00 pm What ND filter do you think I will need in order to avoid the cracking of the standard Sol'Ex slit ?
I use the Hoya pro ND16 with my 72ED and Sol'ex with no problems to the glass slit and the kit is pointing at the Sun for hours on end . The weaker versions I have read cause fringes,again no problem with the ND16,focus though can be a bit soft when compared to when using Herschel wedge.

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: New telescope ~400mm focal length for SHG

Post by rsfoto »

Alun_H wrote: Wed May 31, 2023 4:34 pm
rsfoto wrote: Sat May 27, 2023 8:00 pm What ND filter do you think I will need in order to avoid the cracking of the standard Sol'Ex slit ?
I use the Hoya pro ND16 with my 72ED and Sol'ex with no problems to the glass slit and the kit is pointing at the Sun for hours on end . The weaker versions I have read cause fringes,again no problem with the ND16,focus though can be a bit soft when compared to when using Herschel wedge.

Alun
Hi Alun,

Do you also use an UV/IR filter at the front?

regards Rainer


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Re: New telescope ~400mm focal length for SHG

Post by NM_mike »

Sounds like a nice scope for Solex.

I have similar setup with a stock Solex slit. To get started I tried a stack of filters ( R band CCD, moon ND) and made sure that I could hold my hand at the focal point for ~ one minute comfortably- no burning sensation. I can detect warmth and I think that is ok. I had the SHG setup for several hours continuously with no apparent harm. This solution got me up and running for Ha. I am still waiting on a Lacerta wedge. I decided to go a different route rather than the Hoya filters.. I have also received a 2" Baader 0.8 ND filter that I screwed into a Baader 2" to M42( T thread) adapter. This then screws into the front of Solex. I will report back when I have an opportunity to test. I would expect the Baader filters to perform very well. They can also be stacked if needed.

-Mike
rsfoto wrote: Sat May 27, 2023 8:00 pm Hi SHG experts,

I just placed an order for a 70mm f/6 420mm focal length telescope as well as some ND filters (2 0.3), 4(0.6), 8(0.9) and 16(1.2) and a UV/IR filter.

https://cdn.mos.cms.futurecdn.net/w6MED ... aEaU2M.jpg

What ND filter do you think I will need in order to avoid the cracking of the standard Sol'Ex slit ?


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi,

The smiley company just delivered the Telescope.

What a beautiful and very well made scope. The Rack&Pinion focuser soft like butter but not as soft as a ride on my Land Rover SII 1961 :lol:

Now I am well armed in any case ...

Winchester_30-30_1894_2.jpg
Winchester_30-30_1894_2.jpg (133.28 KiB) Viewed 1998 times
Winchester_30-30_1894_1.jpg
Winchester_30-30_1894_1.jpg (123.87 KiB) Viewed 1998 times

SORRY ¡ WRONG images ! :lol: :lol: :lol: :lol: :lol:

Below the correct one

SVBONY_70mm_f6_420mm_S.jpg
SVBONY_70mm_f6_420mm_S.jpg (147.8 KiB) Viewed 1998 times


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi,

I finished adapting the EAF telescope focuser from the Sol'Ex to the SVBONY and below a test on some red lamps using a 77mm0UV/IR filter threaded with a 3D printed adapter M88x1.0 into the Sun shade.

Here a quality test of the optics. I have to say tis is perfectly collimated.

Out of focus outside and Out fo Focus Inside as well as focused


Some artificial stars on the chimney

Chimney_1.5km.JPG
Chimney_1.5km.JPG (63.22 KiB) Viewed 1957 times

Out of focus OUT

SSBONY_70mm_outoffocus.JPG
SSBONY_70mm_outoffocus.JPG (24.42 KiB) Viewed 1957 times

Out of focus IN

SSBONY_70mm_inoffocus.JPG
SSBONY_70mm_inoffocus.JPG (23.97 KiB) Viewed 1957 times

In focus

SSBONY_70mm_infocus.JPG
SSBONY_70mm_infocus.JPG (21.38 KiB) Viewed 1957 times


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi,

Below some images of the SVBONY focuser using a salvaged ZWO EAF focuser. The EAF focuser from ZWO is limited by driver to 60.000 steps and I think that is a stupidity.

First design and It will perhaps improved. The resolution I ahve per step is 0.4 micron. Putting the drive on the 1.1wheel would increase the resolution to about 4 micron. They say it is a 10:1 reduction but that is not the case. It is about 9.7 to 9.8... need to think about how to use the blck knoab instead of the fine adjustment. The focuser trube tavels 90mm and this gices me 225,000 steps and the EAF is not able to do that.

On the black knob I would have about 22500 steps and so I could use the full focuser tube travel.

SCBONY_Focuser_1.jpg
SCBONY_Focuser_1.jpg (81.95 KiB) Viewed 1950 times
SCBONY_Focuser_2.jpg
SCBONY_Focuser_2.jpg (114.34 KiB) Viewed 1950 times
SCBONY_Focuser_3.jpg
SCBONY_Focuser_3.jpg (48.96 KiB) Viewed 1950 times


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi,

Today I received two 1.25" diagonals for a primary test. They were cheap ones and cost me both about US $ 30.00. If it works I will buy some dielectric ones which cost each about US $ 50.00.

Now after the fact that I was able to get the backfocus of the Sun yesterday using a Baader film I measured 135mm.

Now comes the difficult part as all this is without shortening the length of the telescope :shock:

The two 1.25" diagonals take up 2x 42mm and the distance I need for the Telescope center to Solex center is 86mm which means a ditance of the two diagonal equal to 44mm. Summing up all this gives me 42+44+42 = 128mm which gives me 7mm of clearance at the focuser tube body. All this using a 0 zero space adapter at the focuser tube in order to connect the first diagonal to the telescope.

Anybody please tell me what is the range you need for focusing the telescope on the slit.
Thank You

As far as I measured the slit is 1mm outside of the front flange at the Sol'Ex.

Now I need to make a plate for mounting the Sol'Ex on top of the SVBONY as well as a shade for the slit.

Then I will see what happens :roll:

SVBONY_Sol'EX_mirror_1.jpg
SVBONY_Sol'EX_mirror_1.jpg (85.41 KiB) Viewed 1904 times
SVBONY_Sol'EX_mirror_2.jpg
SVBONY_Sol'EX_mirror_2.jpg (81.93 KiB) Viewed 1904 times


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi,

More or less finished the folded arrangement of my Sol-Ex on top of my new SVBONY 70mm f!6 420mm focal length.

The position of the focuser was found by mounting the telescope on my mount and tracking the sun. The focuser draw tube sits in focus at 10.5mm when placing a piece of sandwich paper and measuring the sun diameter which is for June at about 3.85mm.

The slit between mirrir base and 1.25" diagonal is about 6.77mm

Will I reach focus or not by moving the focuser inward+ I guess if I move 1mm the focuser tube in this arrangement the focused SUn moves two millimeters. On the other side this does not fit into my theretical calculation. The center of the telescope is at 41mm, the ring has 10mm height, I added 8mm plate and the center of the Sol-Ex is at 25mm so this gives me from center to center 41+10+8+25 = 84mm. the right angle from the front so I have to add 42 mm and this gives me 126mm and the Sun focuses in straigt way at 135mm so I theoretically get 9mm at the focuser draw tube, correct?
SVBONY_SHG_folded_3.jpg
SVBONY_SHG_folded_3.jpg (164.96 KiB) Viewed 1870 times
If I buy some mirrors and design a double diagonal I think I will get more backfocus. Need to make a drawing.

On Sunday I will mount it on the mount and test the focus on the Sun

I think we need to convince the Telescope producers to deliver us telescopes with a bigger backfocus :lol:

The other solution is to cut the telescope tube and print an adapter :shock:

SVBONY_SHG_folded_1.jpg
SVBONY_SHG_folded_1.jpg (186.86 KiB) Viewed 1870 times
SVBONY_SHG_folded_2.jpg
SVBONY_SHG_folded_2.jpg (173.24 KiB) Viewed 1870 times


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Re: New telescope ~400mm focal length for SHG

Post by rsfoto »

Hi,

Continuing with my new set up :lol: I was able to test but decided to stop as the ambient temperature reached a high of 37°C half an hour ago.

Have some adjustement problems but telescope reaches nice focus on the slit. Right on the Position I had found oout and a tiny bit of focus correction gave me a sharp edge.

There is not yet light shielding in the gap between diagonal and slit holder of Sol'Ex.

First problem were Newton rings but that was solved by taking off one of the ND filters. Had put a ND16 and a ND 8 filter and that gave me Newton rings. I am also using a UV/IR filter in the light path and that one is 77mm Ø with a clear pass of 72 mm so this filter can not produce vignetting. The ND filters are 82mm Ø. I took off one ND16 and left ND 8 and they disappeared and my Spectrum was clean as I knew from the normal SHG setup. Glass Mirror did not crack. THe Newton rings started to disappear from Magnesium triplet towards the Calcium lines. Did not take screenshots after taking off the ND 16 filter.

Another problem is that I need to center the double diagonal against the Sol'Ex. I have to analyze from where comes the problem and possibly print some new plates.

The most critical problem is the terrible vignetting I have at the edges. Seems like I need a wider slit then 4mm (Sol'Ex standard glass slit 4mm wide and 10µm slit). The Sun takes up 3.85mm.

Sharpness of everything looks good.

RS-Cam-Cool (registered trade Mark :lol:) maintains my camera at ambient temperature which is a good sign.

Below some images I was able to take on the Sun.

Newton rings at Hydrogen Alpha
Newton rings at Hydrogen Alpha
Sol'Ex_Folded_SVBONY_70mm_1.JPG (219.64 KiB) Viewed 1841 times

Both Edges
Both Edges
Sol'Ex_Folded_SVBONY_70mm_2.JPG (66.29 KiB) Viewed 1841 times

Calcium lines
Calcium lines
Sol'Ex_Folded_SVBONY_70mm_Ca2X.JPG (214.49 KiB) Viewed 1841 times

Hydrogen Beta
Hydrogen Beta
Sol'Ex_Folded_SVBONY_70mm_Hb.JPG (187.16 KiB) Viewed 1841 times

Left Edge
Left Edge
Sol'Ex_Folded_SVBONY_70mm_L_edge.JPG (71.65 KiB) Viewed 1841 times

Right Edge
Right Edge
Sol'Ex_Folded_SVBONY_70mm_R_edge.JPG (56.94 KiB) Viewed 1841 times

Magnesium Triplet
Magnesium Triplet
Sol'Ex_Folded_SVBONY_70mm_MgT.JPG (172.86 KiB) Viewed 1841 times

Sodium Doublet
Sodium Doublet
Sol'Ex_Folded_SVBONY_70mm_NaD.JPG (178.47 KiB) Viewed 1841 times

Temp_36°C_20230610.JPG
Temp_36°C_20230610.JPG (193.98 KiB) Viewed 1841 times

Temp_36°C_20230610_b.jpg
Temp_36°C_20230610_b.jpg (79.61 KiB) Viewed 1841 times


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Re: New telescope ~400mm focal length for SHG

Post by inhapi »

Jean-Francois wrote: Tue May 16, 2023 7:01 pm Hello,


And If you think that the Sol'Ex is not standard ... it is correct. I redesign completely the Sol'Ex.
I add a double planetary gear with 36x reduction. One complete rotation of the button rotates the grating with 10°.
TSAPO72F6_SolEx.jpg


Regards,
Jean-Francois
Intersting. It seems you also made other changes to the Sol'ex design, apart from the fine rotation of the grating, did you improve ohter aspects ? Are your STL files available (If you allow me to ask).


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Re: New telescope ~400mm focal length for SHG

Post by thesmiths »

To revisit this old topic, I recently got an Askar 65PHQ for another project (eclipse related) and it occurred to me that it is a good choice for SolEx. The focal length is 416mm and the focal ration is f/6.4. Christian Buil has used the similarly designed 80PHQ and 107PHQ (actually the identical ZWO versions) with SolEx and StarEx and found them both very good. He noted the violet correction is excellent (as the manufacturer's spot diagrams suggest).


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