Dream come true!

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Re: Dream come true!

Post by Marcello »

Hi Bob,
congratulation for the happy of this long story, and to Mr. Andy for the excellent assistance!

The image looks great, I can only guess how wonderful is the view at the eyepiece!

cheers
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Re: Dream come true!

Post by Solar B »

Fantastic news Bob and it does appear to be onband in the image even giving
the poor seeing :cool:

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Re: Dream come true!

Post by marktownley »

Brilliant! Bring on spring!


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Re: Dream come true!

Post by Valery »

Congratulates, Bob!

Looking for your DS images full disk and high res.


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Re: Dream come true!

Post by Derek Klepp »

Good to hear Bob.


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Re: Dream come true!

Post by Bob Yoesle »

I have a bit of progress to report on this seemingly endless project - a lot of time and effort which is turning out to be worth it in the end.

Views through the scope in the early spring were good, but not quite what I had hoped for. While I had hoped the mechanical internal etalon tuning would work, it proved to be impractical - as once the setting was chosen, the telescope then became fixed with the internal etalon tuning, and would require complete disassembly to adjust further. Changing atmospheric pressure and temperature seemed to prevent optimum performance.

So I decided the only way to go would be pressure tuning. Once again I relied on the wonderful help of Dan Steinmetz and his students at Perry Technical Institute.

I didn't want to disassemble the etalon from its housing, and Dan advised there was plenty of clearance around the etalon to drill and tap an access for a vacuum fitting. A bit nerve racking waiting for the process, but all went well!
20160727_131959(0) SM.jpg
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20160727_132826 SM.jpg
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Next was determining how to seal the etalon collimator module. I decided on a silicone gasket and vacuum grease approach. Here's my dining room table workbench. I purchased the gasket material, and Perry Tech cut custom gaskets for both the collimator and refocusing lens cells, and the cell mounts themselves.
IMGP3898 SM.jpg
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Applying vacuum grease to the lens cell:
IMGP3900 SM.jpg
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My look of disappointment when seeing the vacuum would not hold:
IMGP3905 SM.jpg
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I tried redoing the seals several times, and in the end all I had were sore wrists from the multiple assembly and disassembly tries (silicone grease is thick - and quite messy) -- and no sealing. A quick call to Lunt, who advised sealing the lens itself with clear RTV silicone applied inside the cell, and applying the same to the outside of the lens cells to achieve the best seal possible. This did the trick:
IMGP3914 SM.jpg
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Here's the completed internal module, with a Lunt IR blocking ERF ahead of the negative collimator lens, the vacuum fitting, and OTA positioning bolts:
IMGP3916 SM.jpg
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Perry Tech cut longitudinal slots along the OTA which were necessary to allow adjustment/optimizing the position of the internal module, and passage of the vacuum fitting. Note the nice brass setting bolts on the curved aluminum pressure blocks (which I faced with felt to protect the OTA finish):
IMGP3917 SM.jpg
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The completed OTA with a Ralston Instruments precision vacuum/pressure hand pump attached:
IMGP3921 SM.jpg
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Here's the OTA in place, with the ball check valve and disconnect. The OTA is quite heavy at 40 pounds with both etalons:
IMGP3929 SM.jpg
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A close up of the Ralston Instruments pump, showing the days optimum vacuum of -4.5 PSI. The level of pressure is roughly set by the hand pump on the right side, and the fine adjustment is accomplished by the threaded fine-tuning knob of the left side -- very fine adjustment is possible. I found this preferable to the pressure tuners I have used, due to the fact that the adjustment is accomplished off-scope and no movement of the image is involved during tuning.
IMGP3924 SM.jpg
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Initial evaluation was performed yesterday just before the weather deteriorated here in the Pacific Northwest. Despite poor transparency, everything was perfectly on band! I first viewed the image single stack with the internal 90 mm etalon, and tuned it up perfectly. Adding the SM140 removed the double limb and showed much improved contrast. But boy is the seeing aperture-limiting. Therefore no imaging was attempted. Additional fine tuning of the collimator position, OTA finish details, and possible addition of a 105 mm B+W Kaesemann circular polarizer behind the ERF lie ahead - weather dependent and it might be spring until these issues can be optimized.

And being somewhat OCD, I'm looking to adapt a defunct Helios etalon assembly as an internal triple stacking module for use within the AP 2.7 inch focusers I use for my H alpha scopes:
IMGP3938 SM.jpg
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Looking forward to some steady clear weather for my first real observation and imaging attempts. Might have to get down to California for the winter shake down.
IMGP3933 SM.jpg
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IMGP3936 SM.jpg
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Re: Dream come true!

Post by christian viladrich »

What a beautiful and amazing work !
I am delighted you start having good results paying back your effort.

BTW, if I run the math, I find you will have a 0.67° sweet spot (in diameter) with the 140/90 etalons. This is if we allow a CWL shift of only 0.25 A at the edge of the sweet spot.


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Re: Dream come true!

Post by marktownley »

It's looking fantastic Bob!


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Re: Dream come true!

Post by Bob Yoesle »

Thanks Mark and Christian - and thanks Christian for the sweet spot calculation ;-)


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Re: Dream come true!

Post by george9 »

Amazing, Bob! Good luck on the tuning. George


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Re: Dream come true!

Post by MapleRidge »

The scope looks great Bob...eager to see how the refinements work out.

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Re: Dream come true!

Post by Montana »

Wow! I'm looking forward to the first image through it :hamster:

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Re: Dream come true!

Post by Solar B »

In Awe of your fastidious work as ever Robert :bow

Now that's one Bino view I'd like to take :cool:

Oh and triple stack ... that should cut down on leakage !!

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Re: Dream come true!

Post by Bob Yoesle »

Thanks everyone! I have learned to be patient with this endeavor. I've also heard from Bill Dean that there may be additional 140/90's in existence somewhere, and that indeed the Vatican's was one of the first 90/60 DS scopes.

As it turns out the Helios might be totally unsalvageable - not only won't it come on-band in it's current state - it's put together with some kind of Loctite material. I will have to apply a hack saw or C4 to it to get it apart.

In the meantime, I'm also going to play around with a 105 mm Schneider (B+W) Kasemann circular polarizer for both the new telescope and the DS 90's. My previous experience with a smaller Kasemann for the CaK module indicates these appear to have very good optical quality. The advertised specifications show high quality components for an off-the-shelf photography CP:

"The Kasemann circular polarizer filter is completely edge-sealed for maximum durability under extreme climatic conditions. Lesser non-sealed circular polarizer filters can suffer from foil separation at the filter edges when used in these conditions. Käsemann polarizing foils are neutral in color, have a higher efficiency than conventional polarizing foils, and are cemented between high-grade plano-parallel optical glass, using a special cementing technique that resists delamination in humid climates. The resulting sandwich is then precision-polished again to achieve highly accurate plano-parallel surfaces... They are well suited for applications that require the highest possible imaging quality, especially with high-speed telephoto lenses and apochromatic lenses. " [Schneider Optics]

We'll see if they live up to this level of quality for solar telescope use. Hoping the weather may soon cooperate.


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Re: Dream come true!

Post by marktownley »

Thanks Bob, very interesting about the CP filter, i've just been googling them.


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Re: Dream come true!

Post by Spectral Joe »

Bob

Before getting violent with the Helios (not that I have anything against C4 in the proper place, having used hundreds of pounds of it in a previous career) I can try getting the relevant parts out without damaging them. If you're heading down to California in the future it would be a good thing to attempt together. I'm also working on some new equipment for bandpass measurement that you might find interesting.

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Re: Dream come true!

Post by antonello »

Hello Bob

Also I have had a dream for a long time and I worked for achieve it. For this purpose I have built a slight Truss (see picture 1)
1.jpg
1.jpg (88.16 KiB) Viewed 12700 times

for a 150 mm H-alpha Istar lens. After, I have purchased a Lunt Etalon, the model for 60 mm Double stack, for to put it inside the telescope. For this purpose, I have designed and made a 65 mm lenses collimator with a negative lens and a positive lens, to be used as shown in the second image (all this is attached to the end of the truss ....).
2.jpg
2.jpg (91.44 KiB) Viewed 12700 times
The whole system works perfectly, but my real dream was to have an Etalon of type "pressure" from 60 mm, promised for years by Lunt, but never realized.
My dream was to make (easily) a sealed cylinder for my Etalon (the two lenses help much) and to get the same H-alpha tuning not by inclination, but through the reduction in pressure within the cylinder sealed Etalon.
I thought it was a difficult thing because I've never seen him do this ... but then I saw your solution and I think that my dream It could be achieved. I saw that you are using a Hand vacuum pump Ralston
This pump is very expensive ($ 400). Is it necessary to such a precise pump? Would not be enough a more simpler pump, by that very Lunt used in "Etalon pressure type" (type syringe) used not for pressure, but for to create a vacuum?
Last thing. You or anyone is reading, know a formula that allows to calculate the shift of the frequency as a function of pressure?

Many thanks

Antonello


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Re: Dream come true!

Post by christian viladrich »

Hello Antonello,
I was just wondering where did you find the 65 / 400 mm lenses ?
BTW, in your case the diameter of the sweet spot is 22 arcmin, if you accept a max 0.25 A CWL shift at the edge of the sweet spot.
I've got an EXCEL file from Gert Gottschalk which calculates the CWL as a function of pressure. If you don't find it on the web, you can drop me a message.


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Re: Dream come true!

Post by Bob Yoesle »

Hi Mark - the Kasemann should arrive today and I'm looking forward to seeing what it can do and how much the decrease in image brightness occurs... unfortunately it might be a week or more until some sun arrives :-(

Hi Joe - would love to visit you again sometime for some "demolition" :) - I'll PM you...

Hi Antonello - what a beautiful telescope implementation!
You or anyone is reading, know a formula that allows to calculate the shift of the frequency as a function of pressure?
I think you can get to it by the formula's on these pages - get the air pressure and resultant refractive index put into the etalon wavelength formula:

https://www.gribble.org/cycling/air_density.html

and

http://emtoolbox.nist.gov/Wavelength/Documentation.asp

This graphic shows the relationship between refractive index and pressure, temperature, and humidity:
Effects of temperature pressure and humidity on refractive index of air.jpg
Effects of temperature pressure and humidity on refractive index of air.jpg (91.9 KiB) Viewed 12669 times
Depending on how high the etalon is tuned, I don't think you'd need more than - 5 PSI or so of vacuum - right now I'm finding about - 2 PSI is ideal for my internal 90.

You could first try one of these type of Mityvac automotive vacuum hand pumps to see if it would work:
MV8000.jpg
MV8000.jpg (121.33 KiB) Viewed 12669 times


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Re: Dream come true!

Post by Solar B »

That's a wonderful assembly you've got going on there Antonello !!
Loving the adonized red features to :cool:

If I may I think etalons that exhibit good finesse do/would benefit from pressure tuning ... however a regular
or average etalon perhaps not so and tilting would suffice ... this just from my rudimentary understanding.

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Re: Dream come true!

Post by Bob Yoesle »

Update.

I had some good weather and decent seeing for a couple of hours this past weekend, and finally had the views I have hoped for.

First single stacked; the internal SM90 etalon is quite uniform and superb in contrast, and is only slightly off-band high. About - 2.0 PSI of vacuum was required to bring the filter on-band (maximum filament density), and the range of adjustment is quite generous: +/- 0.5 PSI or greater. The increased aperture is awesome in good seeing!

Next: double stacked with the SM140 was a delight, no double limb, and the full-disc contrast was quite good, though not quite up to the DS SM90's - apparently nothing can touch them - DS ghosting required more tilt than I preferred to remove the ghost completely from the FOV.

Next I added the Schneider B+W 105 mm Kasemann circular polarizer - and solar Nirvana has been achieved! Though the image is dimmer, using my BelOptik KG3 BF30 still provided good image brightness, I could see no degradation in image quality at the 90 x magnification I used, and I couldn't get the grin off my face with binoviewing :-)

Some final tweaks and refinements are underway, and when I have good seeing I'll grab some images to post for the community.


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Re: Dream come true!

Post by robert »

Amazing journey to this point. Thanks for sharing it.
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Re: Dream come true!

Post by george9 »

Great to hear, Bob. George


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Re: Dream come true!

Post by marktownley »

Fantastic news Bob!


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Re: Dream come true!

Post by antonello »

Hello Christian

I designed the collimator with OSLO and optimized with Zemax so that none of the surfaces of the lens was flat, then I built the lambda/10 lenses from an important national industry. The system is expensive, but it is perfect.

This is the spots diagram with a perfect 150 mm f:10 lens
1_150mm_f10_perfect_lens_with_satta_collimator .jpg
1_150mm_f10_perfect_lens_with_satta_collimator .jpg (41.32 KiB) Viewed 12487 times
and this is the spots diagram with a commercial achromatic (150 mm f: 10)
2_150mm_f10_achromatic_with_satta_collimator .jpg
2_150mm_f10_achromatic_with_satta_collimator .jpg (42.34 KiB) Viewed 12487 times
The project was created for commercial purposes, but the result is still good when using catalog lenses with a flat side, as in this drawing
img010.jpg
img010.jpg (14.37 KiB) Viewed 12487 times
In this case, the quality is however still inside the diffraction
3_1_150mm_f10_perfect_lens_with_plano_concave_plano_convex_collimator .jpg
3_1_150mm_f10_perfect_lens_with_plano_concave_plano_convex_collimator .jpg (43.72 KiB) Viewed 12487 times
4_150mm_f10_achromatic_with_plano_concave_plano_convex_collimator .jpg
4_150mm_f10_achromatic_with_plano_concave_plano_convex_collimator .jpg (44.32 KiB) Viewed 12487 times
The important thing is that the two lenses are placed exactly as in the drawing above

You are right about the sweet spot, but I have realized the 150 mm to see details of the sun. To see the full surface of the sun I use the same Etalon and the same collimator system in a 100 mm f:10 telescope (Tal 100).
Here it is
tal_100_modified.jpg
tal_100_modified.jpg (89.78 KiB) Viewed 12487 times
The block collimator with etalon is universal and fits on all telescopes F: 10 or more, just put the first lens to F- 400 mm from the lens obiectiv (the precise value is achieved with Oslo (or ZEMAX).

Hello Bob
Thank you for all your interesting graphics. Thanks also to the information on the necessary pressure. Less 0.2 Bar, are a very small value. much smaller than I thought. Thanks also to the photograph of the economical aspirator vacuum. I had already thought of use one such tool that is used to suck oil from the brakes of cars, but you must change the tool for fine adjustment of the pressure. Precisely for this reason now I'm following a new road, testing a simply small piston for vacuum with adjustment by screw self made. I will experience everything as soon as the sun comes out.
Many thanks


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Re: Dream come true!

Post by christian viladrich »

Thanks a lot Antonello,
You've done a beautifull work and wonderfull design.
Just wondering ... you're using F/6.6 collimating lens on a 150 mm F/10 objective ? Just to be sure.
Best regards
Christian


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Re: Dream come true!

Post by Bob Yoesle »

Thanks for the OSLO spot diagrams Antonello! This provides confidence that such designs can have very good optical performance, even with a design with a larger sweet spot. Your modular approach is quite nice ;-)
The important thing is that the two lenses are placed exactly as in the drawing above.
Obviously the negative collimator must be the first optic following the objective, followed by the etalon and refocus lens. Are you referring to the plano surface facing outward for each optic? I note this is also the orientation as originally designed for my SM90 internal etalon.


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Re: Dream come true!

Post by Valery »

Hi Bob,

My congratulations with the success!

Looking for your first imaging session.


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Re: Dream come true!

Post by antonello »

Hello Bob

Yes, the two lenses (in a system with a plano concave and a plano convex lens standard) must be placed as in the drawing, with the plano surfaces facing outward for each optic. Only so the quality of the telescope it is maintained.

Hello Christian

Yes the lens has an f: 6.6, but this is the focal ratio of the collimator (needed for marginal beams in a telescope of 200-250 mm of diameter).
The real beam of the my 150 mm telescope (parallel rays of a particular of the Sun on the optical axis) intercepts the collimator (negative lens) at 1078 mm from the objective, where the diameter of the lens used is of 42.2 mm, then the focal ratio of the collimator is 400 / 42.2 = 9.5

For my 150 mm, they would have been sufficient smaller lenses (about 50 mm), but they were available glass disks of BK7 of diameter 65mm and then I did the lenses with this diameter, useful if one day I were to have a telescope 200-250 mm of diameter, which is unlikely, but not impossible :-)


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Re: Dream come true!

Post by Bob Yoesle »

Well, it's now going on almost two years since I started this project, and I'm hoping there will soon be "light at the end of the tunnel" - pun intended!

Some of the most recent, and hopefully final, developments:

Back in October when I got some very brief great views before the weather turned bad, I did note a slight degradation of image quality when I used the front SM140 with the internal SM90. I suspected I might have a DERF 160 issue due to the colder fall temperatures, and the securing method I used (black automotive silicone). Sure enough, removing the DERF (still had the internal SM90 EFR in place), solved the problem - I had a much improved hi-contrast view. I consulted with Brian Stephens at Lunt, who agreed stiff silicone was likely the culprit and that most silicone's are not suitable for optical use, and recommended the same Loctite Superflex 575 RTV used to seal the collimator optics and lens cells (hard to find locally, had to order on-line: https://www.zoro.com/loctite-rtv-silico ... lsrc=aw.ds).

First, I removed the old silicone and installed some additional safety retaining bolts and rubber washers; the washers do not actually touch the optic itself:
IMGP4043 SM.jpg
IMGP4043 SM.jpg (371.2 KiB) Viewed 11392 times
I used a syringe and a cut-off 16 gauge IV catheter to squeeze in some blobs of the RTV between the filter and cell wall, similar to how an etalon plate is held in its cell:
IMGP4045 SM.jpg
IMGP4045 SM.jpg (325.11 KiB) Viewed 11392 times
IMGP4047 SM.jpg
IMGP4047 SM.jpg (203.98 KiB) Viewed 11392 times
This should hopefully solve the issue of warping of the DERF with changing temperature, while offering a secure hold and prevent the remote chance of a failure from damaging the etalon itself. At some future point I may opt for a completely new DERF filter cell, but for now I hope this will work without untoward effects.

Next up was a better internal ERF and circular polarizer implementation. My original 105 mm B+W Kaesemann filter proved to be too small for the SM90 ERF filter cell I had widened up to 100 mm, as it had an actual OD of only 101 mm. So I acquired another B+W Kaesemann filter, this time the 112 mm, which has an actual filter diameter of 106 mm (almost identical to the Lunt ERF, which is 105 mm in OD)- which was perfect. Both B+W Kaesemann CP filters had to be sent to Schneider Optics in California in order to remove the filter from the filter cell, as there is no easy way to to this yourself without risking breaking the filter.

In order to have tilted filter components, I also ordered a Lunt 100 mm filter ERF cover, and had it machined to fit within the internal etalon mount front ring. I attached the SM90 ERF cell to the rear of this ring, and was careful to align both ERF filter cells so that they would have opposite tilts to minimize any chances of unwanted reflections:
IMGP4037 SM.jpg
IMGP4037 SM.jpg (244.11 KiB) Viewed 11392 times
The completed ERF and CP equipped front etalon ring. The ERF precedes the CP in the optical path in order to protect the CP from excessive heat and possible damage when used in single stack mode.
IMGP4039 SM.jpg
IMGP4039 SM.jpg (256.18 KiB) Viewed 11392 times
The completed internal etalon assembly, with ERF and CP, minus the vacuum assembly:
IMGP4042 SM.jpg
IMGP4042 SM.jpg (234.56 KiB) Viewed 11392 times
So at this point, I'm hoping I've done just about all that I can to optimize the filter system and telescope's performance. It should now be completely suitable for both for single and double stack use. Time will tell, as now I have to wait for suitable weather conditions. Current temperatures are well below freezing, and I have a couple of feet of snow to contend with in the path to the observatory... This may be the only sun I see fore awhile ;-)
IMGP4012 SM.JPG
IMGP4012 SM.JPG (304.78 KiB) Viewed 11392 times
Either that, or an exploratory trip to visit California when the weather improves there. In the meantime, maybe this thread needs to be moved to the "solar scope modifications" category!


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Re: Dream come true!

Post by marktownley »

Always very interesting to read the developments here Bob. You should hopefully be having some good fun with it this year. Interesting gems to keep for future reference regards the B+W filter and the silicone seal used.


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Re: Dream come true!

Post by GUS »

Hi Bob, I'm not sure if you mentioned this before, but how do you know which side of the Lunt ERF faces the sun. I have the 100 and 75mm ERF's and there is nothing to indicate which side to point to the sun. I've been told that there should be an arrow on the edge, but can't see any on either ERF.
And thanks for posting this thread Bob, it's been interesting to following your progress.

Ivan.


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Re: Dream come true!

Post by Bob Yoesle »

Thank you Mark and Ivan, I hope some of what I've learned will be of use to others.

Ivan, the Lunt ERF's don't have an arrow (the thicker Baader DERF's do). The lunt ERF's do have a sunward side, which can be discerned by tilting the ERF at about 45 degrees or more to a bright light source. It then will have a bright metallic rose-pink appearance. You can see some of this brighter reflected light falling on the etalon module ring in the photo above:
IMGP4037 SM 2.jpg
IMGP4037 SM 2.jpg (222.16 KiB) Viewed 11307 times
So while from near normal angles the RG630 looks very deep transparent red, when tilted at 45 degrees or more you will see this bright metallic rose-pink reflective coating:
Lunt ERF.jpg
Lunt ERF.jpg (292.95 KiB) Viewed 11140 times
The other side has a standard anti-reflection coating and will not have such a bright reflective coating. Hope this helps.


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Re: Dream come true!

Post by Bob Yoesle »

Still working on DERF issues, but there has not been much activity lately. So when a hot day with no wind appeared, I hefted the the heavy double stacked scope with the Lunt internal ERF and a B+W circular polarizer installed onto the Losmandy G11, and I discovered AR 2665 on July 5th:
IMGP3926 SM crp.jpg
IMGP3926 SM crp.jpg (226.59 KiB) Viewed 9233 times
140DS 1200mm_050717_225627.jpg
140DS 1200mm_050717_225627.jpg (491.5 KiB) Viewed 9233 times
140DS 2400mm_050717_174300.jpg
140DS 2400mm_050717_174300.jpg (471.9 KiB) Viewed 9233 times
140DS 2400mm_050717_174129.jpg
140DS 2400mm_050717_174129.jpg (179.23 KiB) Viewed 9233 times
The internal etalon required only - 1.5 PSI to be on-band, and contrast uniformity is excellent! Seeing was only average, so it appears I will have to wait for some excellent seeing to get the most out of this scope, but after a long journey I'm quite pleased with these results ;-)


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Re: Dream come true!

Post by Montana »

Well done Bob!! :hamster: :hamster: :hamster:

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Re: Dream come true!

Post by Roman »

Wow! I just finished reading this thread and I must say - hands down. What am I complaining about :D? This was real torture you just came through, but as I see, it was really worth it. That images are incredible right now. Can't wait what you post here when the weather will cooperate :).


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Re: Dream come true!

Post by marktownley »

Really quite excellent results there Bob, i'm glad this project is working out for you :)


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Re: Dream come true!

Post by Bob Yoesle »

Thank you very much Alexandra, Roman, and Mark!


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Re: Dream come true!

Post by Solar B »

Superb images and Update on the beasties performance .... love it.


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