Dream come true!
Re: Dream come true!
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
Marcello
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
Marcello
Play in the sunshine, we're gonna get over !!
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Re: Dream come true!
Fantastic news Bob and it does appear to be onband in the image even giving
the poor seeing
Brian
the poor seeing
Brian
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Re: Dream come true!
Brilliant! Bring on spring!
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Re: Dream come true!
Congratulates, Bob!
Looking for your DS images full disk and high res.
Valery
Looking for your DS images full disk and high res.
Valery
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Re: Dream come true!
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!
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.
Applying vacuum grease to the lens cell:
My look of disappointment when seeing the vacuum would not hold:
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:
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:
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):
The completed OTA with a Ralston Instruments precision vacuum/pressure hand pump attached:
Here's the OTA in place, with the ball check valve and disconnect. The OTA is quite heavy at 40 pounds with both etalons:
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.
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:
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.
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!
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.
Applying vacuum grease to the lens cell:
My look of disappointment when seeing the vacuum would not hold:
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:
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:
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):
The completed OTA with a Ralston Instruments precision vacuum/pressure hand pump attached:
Here's the OTA in place, with the ball check valve and disconnect. The OTA is quite heavy at 40 pounds with both etalons:
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.
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:
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.
Diagonally parked in a parallel universe.
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Re: Dream come true!
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.
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.
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
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Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
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Re: Dream come true!
It's looking fantastic Bob!
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Re: Dream come true!
Thanks Mark and Christian - and thanks Christian for the sweet spot calculation ;-)
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Re: Dream come true!
The scope looks great Bob...eager to see how the refinements work out.
Brian
Brian
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Photos: https://www.flickr.com/photos/185395281@N08/albums
10'x15 Roll-off Roof Observatory
Takahashi EM400 Mount carrying:
C14 + Lunt 80ED
Deep Sky Work - ASI294MM Pro+EFW 7x36/Canon 60D (Ha mod), ONAG
Planetary Work - SBIG CFW10, ASI462MM
2.2m Diameter Dome
iOptron CEM70G Mount carrying:
Orion EON 130ED, f7 OTA for Day & Night Use
Ha Setup: Lunt LS80PT/LS75FHa/B1200Ha + Home Brew Lunt Double Stack/B1800Ha on the Orion OTA + Daystar Quantum
WL, G-Band & CaK Setup: Lunt Wedge & Lunt B1800CaK, Baader K-Line and Altair 2nm G-Band filter
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Re: Dream come true!
In Awe of your fastidious work as ever Robert
Now that's one Bino view I'd like to take
Oh and triple stack ... that should cut down on leakage !!
Brian
Now that's one Bino view I'd like to take
Oh and triple stack ... that should cut down on leakage !!
Brian
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Re: Dream come true!
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.
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!
Thanks Bob, very interesting about the CP filter, i've just been googling them.
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Re: Dream come true!
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.
Joe
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.
Joe
Observing the Sun with complex optical systems since 1966, and still haven't burned, melted or damaged anything.
Not blind yet, either!
Light pollution? I only observe the Sun, magnitude -26.74. Pollute that!
Not blind yet, either!
Light pollution? I only observe the Sun, magnitude -26.74. Pollute that!
Re: Dream come true!
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)
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 ....).
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
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)
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 ....).
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!
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.
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.
Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
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Re: Dream come true!
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!
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:
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:
Hi Joe - would love to visit you again sometime for some "demolition" - I'll PM you...
Hi Antonello - what a beautiful telescope implementation!
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:You or anyone is reading, know a formula that allows to calculate the shift of the frequency as a function of pressure?
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:
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:
Diagonally parked in a parallel universe.
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Re: Dream come true!
That's a wonderful assembly you've got going on there Antonello !!
Loving the adonized red features to
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.
Brian
Loving the adonized red features to
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.
Brian
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Re: Dream come true!
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.
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!
Amazing journey to this point. Thanks for sharing it.
Robert
Robert
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Re: Dream come true!
Fantastic news Bob!
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
Re: Dream come true!
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
and this is the spots diagram with a commercial achromatic (150 mm f: 10)
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
In this case, the quality is however still inside the diffraction
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
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
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
and this is the spots diagram with a commercial achromatic (150 mm f: 10)
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
In this case, the quality is however still inside the diffraction
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
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!
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
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
Christian Viladrich
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Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
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- Bob Yoesle
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Re: Dream come true!
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 ;-)
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.The important thing is that the two lenses are placed exactly as in the drawing above.
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Re: Dream come true!
Hi Bob,
My congratulations with the success!
Looking for your first imaging session.
Valery
My congratulations with the success!
Looking for your first imaging session.
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.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.
Re: Dream come true!
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 :-)
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!
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:
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:
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:
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.
The completed internal etalon assembly, with ERF and CP, minus the vacuum assembly:
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 ;-)
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!
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:
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:
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:
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.
The completed internal etalon assembly, with ERF and CP, minus the vacuum assembly:
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 ;-)
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!
Diagonally parked in a parallel universe.
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
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Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
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- marktownley
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Re: Dream come true!
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!
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.
And thanks for posting this thread Bob, it's been interesting to following your progress.
Ivan.
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Re: Dream come true!
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: 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: The other side has a standard anti-reflection coating and will not have such a bright reflective coating. Hope this helps.
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: 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: The other side has a standard anti-reflection coating and will not have such a bright reflective coating. Hope this helps.
Diagonally parked in a parallel universe.
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
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Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
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- Bob Yoesle
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Re: Dream come true!
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:
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 ;-)
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 ;-)
Diagonally parked in a parallel universe.
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Re: Dream come true!
Wow! I just finished reading this thread and I must say - hands down. What am I complaining about ? 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!
Really quite excellent results there Bob, i'm glad this project is working out for you
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Re: Dream come true!
Thank you very much Alexandra, Roman, and Mark!
Diagonally parked in a parallel universe.
Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
Dark-Sky Defenders
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Curiosity is the father of knowledge; uncertainty is the mother of wisdom.
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