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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Dream come true!

Post by Bob Yoesle »

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 18466 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 18466 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 18466 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 18466 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 »

You very lucky man Bob! When is the party round your house?


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Re: Dream come true!

Post by Helios GER »

Awsome Set Bob! Can´t wai to see more pictures :D


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Re: Dream come true!

Post by Montana »

: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 »

That is some very nice gear! :)


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Re: Dream come true!

Post by Bill Edelen »

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


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Re: Dream come true!

Post by swisswalter »

Hi Bob

congratulations, good luck with the holy grail


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Re: Dream come true!

Post by Bob Yoesle »

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 »

Oh wow. The results should be stunning.

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Re: Dream come true!

Post by Valery »

Very nice upgrade, Bob!

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

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Re: Dream come true!

Post by Bob Yoesle »

;) 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 18310 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 18310 times
Baader-D-ERF.jpg
Baader-D-ERF.jpg (415.65 KiB) Viewed 18310 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 18310 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 »

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


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Re: Dream come true!

Post by Valery »

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.


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Re: Dream come true!

Post by swisswalter »

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 :)

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Re: Dream come true!

Post by Bob Yoesle »

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 »

Bob,

What is your observatory altitude?


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Re: Dream come true!

Post by swisswalter »

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 :)

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Re: Dream come true!

Post by michael.h.f.wilkinson »

Stunning set-up. That SM140-90 is going to be just stunning


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Re: Dream come true!

Post by Bob Yoesle »

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 18080 times


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Re: Dream come true!

Post by marktownley »

thanks for the update :)


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Re: Dream come true!

Post by swisswalter »

Hi Bob

that looks very interesting. The same here, plans change, come and go. A never ending story. Good luck with the mod


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Re: Dream come true!

Post by Bob Yoesle »

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
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Re: Dream come true!

Post by GuillermoBarrancos »

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 »

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 »

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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Re: Dream come true!

Post by astroshot »

Very interesting read Bob. Well done! You must be chuffed!


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Re: Dream come true!

Post by Marcello »

Hi Bob, congratulations, a great and unique set up!

I didn't know about the Vatican observatory, I have to consider a pilgrimage!


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Re: Dream come true!

Post by Solar B »

Aye :)
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Re: Dream come true!

Post by Bob Yoesle »

Hi everyone, and thanks for the great comments and encouragement!

Brian -- where did you find that image of the HOTS 2005 conference which introduced the SM140? I think I recognize that guy in the background looking through the side x side twin refractors with the HW and DS SM90's ;-)
HOTS 2005 w arrow.jpg
HOTS 2005 w arrow.jpg (267.62 KiB) Viewed 13815 times
Marcello - I wouldn't make that pilgrimage just yet. I contacted the Vatican in order to obtain additional information on their 'scopes implementation, and they deny having such a telescope! The only scope they are aware of is this SM90 DS dedicated scope from the period:
Vatican Observatory Coronado.jpg
You might have to seek out the Swiss Guard or Opus Dei to see what happened to it!
Swiss-Guards.jpg
Swiss-Guards.jpg (95.7 KiB) Viewed 13815 times
So as it may turn out, I might have the only such filter system now in existence...

Work is progressing slowly on the SM140 telescope; still waiting on a set of new spacer rings for the SM90 internal module -- a local school for machinists has graciously volunteered to make them, but they are on summer vacation. I'm also looking into the optical theory for how to determine the exact focal length of the negative collimator lens, as this spacing is critical to optimum contrast performance, and no records apparently exist from the original scope design for specifying its focal length -- but the procedure looks pretty straightforward.

Another issue has cropped up -- upon close inspection the SM140's RG630 ERF is covered with fine sleeks, and has a significantly abraded area:
IMGP3629 sm.jpg
IMGP3629 sm.jpg (506.1 KiB) Viewed 13815 times
IMGP3629 crop sm.jpg
IMGP3629 crop sm.jpg (589.04 KiB) Viewed 13815 times
While these might not significantly harm the images, I just can't see having these defects with such a unique and valuable filter system, so I'm considering various options. Re-polishing is an option, but I also would want to re-coat the ERF with an IR blocking coating (blocking filter conservation, etalon stability), and so far I've only been able to obtain two quotes from firms willing to do a one-off IR hot mirror coating job, and it's $2500 - $3000 minimum! So I'm also considering a Baader DERF 160 which will fit within the existing tilted ERF cell, and using my spare RG630 ERF from my second SM90 to mount within the internal SM90 module in its original tilted cell - this should be a viable solution, and perhaps improve on the original as far as thermal protection and stability is concerned.

The OTA itself has been completed, and I have implemented a second-hand Astro-Physics 2.7 focuser, which was machined and adapted to the OEM focuser back plate:
New CR6 focuser.jpg
New CR6 focuser.jpg (209.82 KiB) Viewed 13815 times
In order to accommodate the longer focuser and use the BF30 and a binoviewer, the OTA was shortened about 50 mm, and I had an auto-body shop paint it white to give it that classy refractor look:
New CR6 OTA.jpg
I'll post again when significant additional progress is made.

B-)


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Re: Dream come true!

Post by marktownley »

sexy time! :D


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Re: Dream come true!

Post by Bob Yoesle »

I guess they should be sexy since we use them to look at "heavenly bodies." ;)

BTW - found out the real scoop -- The SM140 Markus thought went to the Vatican actually was a 140 with an internal 60 DS module (as used with the 90) that went to Mexico. The Vatican did get a single stack SM140 on loan, but it was returned. So I guess there was only one 140/90 filter set ever made...


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Re: Dream come true!

Post by arnedanielsen »

Wow! Big congratulations Bob! I'm looking forward to reading more about this project and of course see the resulting pictures!!

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Re: Dream come true!

Post by Montana »

Wow!! have you asked Ken at Solarscope whether he would do it for you? I know you are best friends :)

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Re: Dream come true!

Post by Solar B »

Hi Bob

I remember seeing the pic on "Coronado Solar Chat" at the time .... as to the identity of the gentleman with the dual 90s/wedge set up who knows ?? :)

Im sure I speak for all in wishing you the very best with your 140s development.
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Re: Dream come true!

Post by Derek Klepp »

Thanks for the update


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Re: Dream come true!

Post by marktownley »

Montana wrote:Wow!! have you asked Ken at Solarscope whether he would do it for you? I know you are best friends :)

Alexandra
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Re: Dream come true!

Post by Bob Yoesle »

Thanks Guys!

Re: Ken @ SolarScope: I have nothing but the utmost respect for Ken and that he is a true perfectionist in trying to meet the needs of a very small niche market, and carve out a special area for such products in a small business environment. For example Ken was more responsive than I found Meade Coronado in answering email inquiries. Therefore I am grateful I had a chance to deal with him directly and honestly regarding my findings, and found him nothing but professional. Hopefully others will benefit from my difficulties, but moreover Ken's willingness to do all he reasonably could to address and correct most all of them.

BTW - As I mentioned previously Greg Piepol ( http://sungazer.net/ ) was also at HOTS 2005, made this whimsical image following our visit.
SM140 Piepol stack.jpg
SM140 Piepol stack.jpg (57.25 KiB) Viewed 13702 times
He, Paul Hyndman ( http://www.astro-nut.com/ ) and I (e.g: guess who ?!) all had/have Coronado DS 90's from that era, and had a great time under the sun down in Tucson that year... And we were all pretty amazed by the SM140/90 views -- just hoping I can duplicate what I remember...

B-)


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Re: Dream come true!

Post by Solar B »

Here's a pic from HOTS 2005 ... I recognise Gary & Greg .... I wish it was 05 again to (my first PST) .... ;-) .... Brian
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Re: Dream come true!

Post by Bob Yoesle »

Hi Brian - yep I recognize most of these guys; left to right - Bill Dean from Coronado, and solar imaging pioneers Gary Palmer ( http://www.solarminimum.com/ ), Greg Piepol, and Paul Hyndman... Indeed good times.
Last edited by Bob Yoesle on Sun Sep 13, 2015 11:39 pm, edited 1 time in total.


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Re: Dream come true!

Post by solarchat »

yep, I recognize those guys...


Piepol Palmer Ramsden.jpg
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Stephen W. Ramsden
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Founder/Director Charlie Bates Solar Astronomy Project
http://www.solarastronomy.org
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Re: Dream come true!

Post by Bob Yoesle »

Some cool dudes there!

DEFR 160 arrives this week. Damaged ERF removed, getting prepped for ERF cell removal -- it's threaded pretty tight and it looks like some heat may be needed. The etalon cell and gold cover are much thicker than the SM90:
IMGP3632 sm.jpg


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Re: Dream come true!

Post by Solar B »

Let us not forget that its Mr Palmers image that adorns the PST box :)

Hi Bob ... Is the SM/ERF then encased in a small cell that we cant see and will
the 160 DERF fit perfectly in place of the existing ?

Brian
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Re: Dream come true!

Post by Bob Yoesle »

Here you go Brian -- a bit more progress as the DERF 160 arrived courtesy of Bob Luffel at Alpine Astronomical (great guy and service), and per the usual Baader fashion well packaged and in impeccable condition. The DERF 160 is larger in diameter than the OEM ERF by 15 mm -- but I determined it would fit directly in the OEM ERF cell if I used the retaining ring area for the DERF, and I would have a millimeter or two to spare all around. Thus I would not have to worry about turning down a delicate optic, releasing internal stresses, other unforeseen hazards, etc. It would be just a matter of using a different retaining method...

The first problem was removing the OEM ERF cell from the etalon cover, which required a special tool with the seating pins to fit the holes in the ERF cell... Once removed, three small holes were drilled and tapped around the periphery for the retaining bolts which would hold the DERF 160 in the larger circumference which held the OEM ERF retaining ring:
ERF cell mod.jpg
Note I used small pieces of black tape to ensure no direct metal to glass contact.

Below the DERF 160 is installed in the OEM ERF cell. It is shown from the eyepiece side in the cell sitting on the tape as noted above, and was centered using thin cardboard shims. Black silicone adhesive was used in multiple applications around the periphery to hold the DERF laterally, as is done with the etalon plates themselves. Finally, trimmed rubber washers secured through the retaining bolts act as restraining "clips" to prevent the DERF from ever falling onto the etalon plates themselves. One of the bolt/washers (shown at top) required a second partial washer to take up the space created by the tilt of the DERF in the OEM ERF cell:
DERF & cell mod.jpg
The OEM cell with the new DERF 160 fitted within the etalon cover:
DERF w cell-cover.jpg
The "acid test" would be if everything still worked when the cover was installed (e.g. the restraining bolts did not prevent full seating of the cover) - no issues there, and the DERF 160 looks as good (or better ;-) than the OEM, and retains the tilt of the original ERF:
DERF 160 installed.jpg
I'm very happy with this mod, as the DERF 160 should prevent any significant thermal issues affecting the front etalon itself (possible to some degree with such a large etalon in spite of the central spacer) and yield much better overall thermal stability. Additionally, it should protect the subsequent internal etalon and blocking filters from experiencing significant thermal loading an cycling. Moreover, it is used only for 88% of it's diameter which should avoid any possible edge issues, and Brian Stephens (Coronado Tucson / Lunt) told me that due to the large size, the BK7 substrate used for the DERF would have significantly less striae and better homogeneity than the RG630 ERF originally used. And obviously I have none of the OEM ERF sleaks and abrasions to deal with.

This week the machining students should have the internal SM90 RG630 ERF retaining ring and internal etalon centering rings completed, and further progress can be made ;-)


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Re: Dream come true!

Post by Solar B »

I'm loving it , loving it , loving it :)

Yes I do really like it !

Brian


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Re: Dream come true!

Post by marktownley »

I look forward to these updates Bob!


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Re: Dream come true!

Post by Bob Yoesle »

Getting much closer to first light! Yesterday was a busy day...

One of the main issues is how to determine as accurately as possible the focal length of the negative collimation lens, as it typically can not form a real image. However, there are methods. One, which is pretty straightforward, is a measurement of where the image of the sun (e.g. at infinity) produces a circular image exactly twice as large as the clear aperture:
negative lens FL simple method jpeg.jpg
negative lens FL simple method jpeg.jpg (15.61 KiB) Viewed 13451 times
This, however, might be subject to various inaccuracies, so I decided to go a more traditional route of optical bench testing, as described here: http://stao.ca/VLresources/sci-tie-data ... nt(060.pdf

All I needed was to find an optical bench. Luckily most college physics courses do an optics lab and have such equipment. I made contact with Yakima Valley Community College, and Dr. Stephen Rodrigue was quite enthusiastic about the project. I knew the objective/collimtor focal length(s) would be roughly the same ratio as the etalon diameters. Therefore a "ball park" focal length of 90/140 x the objective FL would be a close approximation: ~ 90/140 x 1200 = 771 mm.

We made multiple measurements at several lens spacing's in order to get a reliable and statistically valid sample. Dr. Rodrigue had an even more rigorous data reduction methodology than the referenced paper in the link above, and applied a inverted parameter of the scatter plot to derive a best fit line, with a 99% fit accuracy:
Dr Stephen Rodrigue YVCC.jpg
Here Dr. Rodrigue is working on the data reduction, with the optical bench in the foreground. The data indicate a focal length of - 77.7 cm:
Neg lens data.jpg
Neg lens data.jpg (160.36 KiB) Viewed 13451 times
I really enjoyed my time with Dr. Rodrigue, and he gets one of the first looks through the new instrument ;-)

The students working under the direction of Dan Steinmetz at Perry Technical Institute ( https://perrytech.edu/programs.html?programid=9 ) got back from summer vacation, and the internal etalon centering rings and the internal SM90 ERF retaining ring were completed this week. They also get a "first look." Here the rings are shown in preparation for painting:
New internal rings & SM90ERF retainer.jpg
So now just about everything is ready. Here is a photo of all the components worked on so far and/or ready for assembly:
Parts - final.jpg
Going left to right, top row: AP2.7 focuser machined and adapted to CR6 focuser end plate, shortened and painted CR6 OTA.
Second row: SM140 front etalon, DERF 160 in OEM ERF cell, etalon cover (now painted flat black on interior), SM140 T-Max tilt-tuner
Third row: forward internal etalon centering ring, negative collimator lens in cell, SM90 internal etalon in housing, refocusing lens in cell, rear internal etalon module centering ring, SM140 etalon cover
Bottom row: SM90 RG630 internal ERF in OEM tilt-cell, internal ERF cell retaining ring, original SM140 product warranty - dated May 11, 2005.

So it won't be long now - I have to make the internal etalon fixation rings or device - likely will adapt the OTA's OEM internal baffles, and finalize the mechanics of the front etalon adjustment rod.

To be continued...
Last edited by Bob Yoesle on Sun Sep 13, 2015 3:08 pm, edited 2 times in total.


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Re: Dream come true!

Post by marktownley »

You're having a lot of fun with this Bob :)


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Re: Dream come true!

Post by Carbon60 »

Immaculately engineered, Bob. We're all on tenterhooks waiting for first light.

I hope the viewing conditions do it justice!

Good luck.

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Re: Dream come true!

Post by astroshot »

Great to see your progress Bob.
Thanks for posting the updates.


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Re: Dream come true!

Post by MapleRidge »

An amazing project Bob...can't wait to see the first images form this assembly.

Brian


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