Dream come true!

Use this section to discuss "standard" Baader/Coronado/ Lunt SolarView/ Daystar, etc… filters, cameras and scopes. No mods, just questions/ answers and reviews.
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Bob Yoesle
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Dream come true!

Post by Bob Yoesle » Mon Mar 30, 2015 5:18 am

I've just realized one of my dreams, the "Holy Grail" of solar filters - the Coronado SM140 with an internal SM90 double-stacking module:
IMGP3593 SM crp.jpg
IMGP3593 SM crp.jpg (364.33 KiB) Viewed 11514 times

Only six SM140's - so far the largest commercial production H alpha filters - were made by Coronado Tucson -- three by Andy Lunt and three by Brian Stephens (both now with Lunt Solar of course), and only two were equipped with double stacking modules. One (allegedly with an internal SM60 module) is used at the Vatican Observatory in Rome, and the other was presented at Hands On The Sun (HOTS) in Tucson late in 2005 using the SM90 internal module installed in a TAK FS 152 f8, as shown here:
784582-6.jpg
784582-6.jpg (35.35 KiB) Viewed 11514 times
I was able to view through it first-hand then, and the image was pretty darn awesome. I recently informed Greg Piepol (who also attended) about getting this set, and he remarked
Boy, do I remember that SM140! I skipped a talk at HOTS 2005 to spend some quality time looking through it. In all my years, that filter combination was the best solar view I've seen.
I will be putting this system together with a 150 f8 achromat (no real need to use a Fluorite APO), and as luck would have it (just as with the SM90) the filter threads for the T-Max tuner are identical the objective cell, and no front filter adapter is necessary:
IMGP3599 crp SM.jpg
IMGP3599 crp SM.jpg (255.76 KiB) Viewed 11514 times
The internal module outer rings are removable, and can be easily adapted to the new OTA inside diameter once the internal baffles are removed, and the tube shortened slightly for bino-viewer use:
IMGP3597 crp SM.jpg
IMGP3597 crp SM.jpg (247.09 KiB) Viewed 11514 times
Given the ratios of the objective effective aperture to etalon are similar to the ratio of the objective to collimator focal length, a field angle magnification can be estimated at 140/90 = 1.6, therefore the field angle of the sun’s limb should subtend only about 0.25 x 1.6 = 0.40 degree, well within the diameter for pretty good full-disk contrast uniformity. Regardless, I’m looking forward to the increased resolution; and the existing SM90 system will be kept if needed for full-disk work. I will keep my progress posted.
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Re: Dream come true!

Post by marktownley » Mon Mar 30, 2015 6:57 am

You very lucky man Bob! When is the party round your house?
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Re: Dream come true!

Post by Helios GER » Mon Mar 30, 2015 8:47 am

Awsome Set Bob! Can´t wai to see more pictures :D
Best regards from germany, Chris

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Re: Dream come true!

Post by Montana » Mon Mar 30, 2015 9:05 am

:hamster: :hamster: :hamster: I can't imagine what the view would be like :hamster: :hamster: :hamster: please show us :)

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Re: Dream come true!

Post by GuillermoBarrancos » Mon Mar 30, 2015 9:13 am

That is some very nice gear! :)

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Re: Dream come true!

Post by Bill Edelen » Mon Mar 30, 2015 2:52 pm

Nice.... Can't wait for results.... :cool:

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Re: Dream come true!

Post by swisswalter » Tue Mar 31, 2015 4:16 am

Hi Bob

congratulations, good luck with the holy grail
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Re: Dream come true!

Post by Bob Yoesle » Tue Mar 31, 2015 5:17 am

Thanks everyone, I'm hoping I will have some fine details worked out and a bit of additional modifications. and the new scope up and running soon. Imaging will then commence with SM90/90 vs. SM140/90 comparisons...

Of course any solar geek is always welcome to visit!

More soon.
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Re: Dream come true!

Post by Carbon60 » Tue Mar 31, 2015 6:01 am

Oh wow. The results should be stunning.

Stu.
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Re: Dream come true!

Post by Valery » Tue Mar 31, 2015 6:35 am

Very nice upgrade, Bob!

Glad to know you are in progress. I think you finally sold the
pair of 100mm filters.

Valery.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

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Re: Dream come true!

Post by Bob Yoesle » Thu Apr 02, 2015 2:51 pm

;) I originally bought the DSF100's (which have a top-notch reputation and seemed for $10,000 USD too good to pass up, as OPT list them for $32,000 USD) in order to compare and contrast to the DS SM90/90's, and would sell whichever one lost the contest -- and either way I hopefully would not lose financially. I'll just say there were some fly's in the ointment (as we say here in the States), as Montana can attest...

Whether or not I now keep my Lunt-era Coronado Tucson SM90/90 DS filters will depend on just how good a job the SM140/90 does on full-disc imaging, as the SM90's are flat-out amazing, and as it turned out somewhat better than the SolarScope DSF 100's on contrast and disc uniformity -- even after they reach a relative thermal equilibrium:
Caompare Image2 enhanced comp.jpg
Identically processed images.

I attribute this to the presence of the central spacer of the SM90 - the unobstructed DSF100 SolarScope filters apparently can't completely thermally stabilize well enough to maintain a perfectly uniform etalon gap spacing, and therefore were not quite able to equal the contrast performance of DS SM90s - and they sometimes took an hour or more to be sufficiently on-band to allow tuning. Therefore I conclude the advantage of a large unobstructed etalon is also its Achilles Heel (greatly exaggerated):
Etalon DS thermal stability.jpg
Etalon DS thermal stability.jpg (52.77 KiB) Viewed 11358 times
See: http://www.sunsteinlaw.com/media/Sidori ... ilters.pdf

Pre-warming to ambient and use of a DERF to suppress the residual IR (especially from 700-750 nm) passed by the SolarScope ERF proved very helpful:
Sol-ERF-lin.jpg
Sol-ERF-lin.jpg (859.76 KiB) Viewed 11358 times
Baader-D-ERF.jpg
Baader-D-ERF.jpg (415.65 KiB) Viewed 11358 times
The DSF100's did have slightly more detail when seeing allowed, which I attribute to the larger aperture; but in the end better contrast and overall "snap" ruled in favor of keeping the SM90's.

The great thing is that the SM140/90 filter arrangement should not only have greater resolution than my DS SM90's, but also should have good contrast performance for full disc (as well as close up) viewing and imaging, due to the large internal etalon size and resulting relatively small field angle magnification. I looked through these filters at HOTS in 2005 and it made my SM90's envious ;-) The SM140 double stacked with internal SM90 uses a custom made negative collimating lens, with a custom refocusing lens which restores the 1200 mm focal length of the objective. Brian at Lunt Solar (who made the filters when at Coronado Tucson in 2005) told me this custom module alone was a $10,000 USD item. The SM140 by itself originally cost $15,000+ USD, and the BF30 they came with goes for $1,600 USD. So given I traded the DSF100 system for the SM140/90/BF30 system, I think I did alright...

Interestingly, Brian told me the internal etalon is not tuned by tilting (or pressure). Rather it was made to be on the "high" side of the H alpha line -- e.g. to the red side. The front SM140 is tilted for tuning to the blue side, and therefore the narrower bandpass and transmission shaping are the result of both filter's transmission curves convoluting and CWL shifting - which might be a bit different than the usual method, but in practical terms little different:
image017.gif
image017.gif (5.25 KiB) Viewed 11358 times
Right now I'm thinking about adding a DERF 110 installed in a tilted filter holder just before the collimation lens of the internal SM90. This way I can use the telescope single stacked with the BF30 which has the RG630 ITF, and when double stacked I can use the BF30 in which I have replaced the ITF with Oliver Smie's (BelOptik) KG3 UV/IR filter. And of course I could go crazy with adding the existing SM90/90 to the front for a triple (or quad) stack SM90 system :band2 just to see what happens...
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Re: Dream come true!

Post by Derek Klepp » Thu Apr 02, 2015 11:37 pm

Thanks Bob and good luck with the outcome.I always enjoy these posts.

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Re: Dream come true!

Post by Valery » Fri Apr 03, 2015 12:20 am

Hi Bob,

Very interesting ifo about your upgrade project.

BTW You writes:
"Interestingly, Brian told me the internal etalon is not tuned by tilting (or pressure). Rather it was made to be on the "high" side of the H alpha line -- e.g. to the red side. The front SM140 is tilted for tuning to the blue side, and therefore the narrower bandpass and transmission shaping are the result of both filter's transmission curves convoluting and CWL shifting - which might be a bit different than the usual method, but in practical terms little different:"

This is not good solution. If you measure the FWHM of two combinations of ideally coincide CWL and overlapped as in your given case the FWHM is the same, but the fidelity of ideally coincide filters is much higher.

The only reason of this overlapped "design" is that SM90 is not tilted and so, no banding = full disk more uniform.

The same approach I do use in my internally double stacked LS50F etalons.


Valery.
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.

Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.

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Re: Dream come true!

Post by swisswalter » Fri Apr 03, 2015 7:21 am

Hi Bob

thanks for the detailed information
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Dream come true!

Post by Bob Yoesle » Fri Apr 03, 2015 2:24 pm

Hi Valery
If you measure the FWHM of two combinations of ideally coincide CWL and overlapped as in your given case the FWHM is the same, but the fidelity of ideally coincide filters is much higher.
Yes - I agree. But in my dual front etalon DS, both the filters have slightly different CWL's, and both are made to be on the "red side" for tilting to be on-band. They also require tilting and consequently shifted CWLs to eliminate retroreflections between the two etalons -- so it seems that "in real life" neither appear to have the exact same CWL that would be ideal. But the performance is pretty darn good nonetheless... I won't really know until I have the SM140 system set up and can see how it all works against the "reference" SM90s. This reminds me of the importance of doing side-by-side tests (or objective A-B test as done in audio component evaluations), as memories can be deceptively inaccurate.
DSF100 v SM90DS.jpg
Ultimately I might employ pressure tuning for the internal module - it would actually require applying a vacuum to the sealed etalon chamber. Feels like more tinkering ahead...
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Re: Dream come true!

Post by Valery » Fri Apr 03, 2015 5:58 pm

Bob,

What is your observatory altitude?


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Re: Dream come true!

Post by swisswalter » Fri Apr 03, 2015 10:01 pm

Hi Bob

another losmady setup, just great ;)
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Dream come true!

Post by michael.h.f.wilkinson » Wed Apr 08, 2015 7:49 am

Stunning set-up. That SM140-90 is going to be just stunning
Solar kit: GP-C8 with Thousand Oaks Solar filter, APM 80mm F/6, Lunt Herschel Wedge, Solar Spectrum 0.3Å H-alpha filter, Beloptic Tri-Band ERF (80mm free aperture), Thousand Oaks 90mm ERF, Coronado SolarMax II 60mm with Double Stack Unit. Lunt straight B1800 Ca-K module.

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Re: Dream come true!

Post by Bob Yoesle » Sun Apr 12, 2015 2:12 pm

As usual, plans need to change.

The CR-6 OTA has too small an ID to allow use of the Internal module without significant modification. I don't want to risk this, so a new OTA using only the objective cell will likely be implemented. Hastings tubing looks to be a perfect match - it will incorporate ~ 50 mm longitudinal slots for fine positioning of the internal module. A new end-ring for the AP 2.7 FT focuser will be needed, and the matching end-ring for the objective cell...
IMGP3606 srp SM.jpg
IMGP3606 srp SM.jpg (181.1 KiB) Viewed 11127 times
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Re: Dream come true!

Post by marktownley » Sun Apr 12, 2015 3:54 pm

thanks for the update :)
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Re: Dream come true!

Post by swisswalter » Mon Apr 13, 2015 4:56 pm

Hi Bob

that looks very interesting. The same here, plans change, come and go. A never ending story. Good luck with the mod
Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)

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Re: Dream come true!

Post by Bob Yoesle » Tue Apr 21, 2015 2:43 pm

Working out the OTA dimensions, sans the internal etalon -- a key figure is to see how short the tube needs to be for use with my Celestron-Baader binoviewers... work continues. This photo gives a good representation of the size differences between the SM90 and SM140 systems.
SM140 - SM90 single.jpg
SM140 - SM90 single.jpg (109.6 KiB) Viewed 11009 times
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Re: Dream come true!

Post by GuillermoBarrancos » Thu Apr 23, 2015 7:44 am

Nice! I bought the WO binoviewers myself last week and love it! No way I can go back to single EP viewing again.

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Re: Dream come true!

Post by marktownley » Thu Apr 23, 2015 8:12 am

That scope is a beast Bob!

BTW, we are over in Silverton for the eclipse in 2017, doesn't look too far(?) from Goldendale, maybe we can catch up at some point then if you are around?
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Re: Dream come true!

Post by Bob Yoesle » Thu Apr 23, 2015 3:10 pm

That would be wonderful Mark! It's a beautiful area of the country, if you have time I'd love to show you around.
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