SolarMax internal etalon size (old SM70 and SM90II)

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
Post Reply
User avatar
Pablito
Ohhhhhh My!
Ohhhhhh My!
Posts: 155
Joined: Tue Mar 06, 2012 8:20 pm
Been thanked: 13 times

SolarMax internal etalon size (old SM70 and SM90II)

Post by Pablito »

Hello,

Does anyone know what size have internal etalons in SolarMax 70 (old model) and SolarMax 90 II?

I know that SM 60 II has 35mm aperture with central obstruction. What about others? I have old SolarMax 70 on my eye but know nothing about it and I'm not sure how it will work in bigger aperture mod. It's focal ratio almost fits my 5" refractor.

Thanks for any help :)


User avatar
Bob Yoesle
Almost There...
Almost There...
Posts: 994
Joined: Thu Mar 08, 2012 7:24 pm
Has thanked: 540 times
Been thanked: 807 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Bob Yoesle »

Hi Pablito,

The SolarMax 70 was the same as the Helios (I think); I believe it is a ~ 50 mm OD etalon with a clear aperture of 35 mm - almost identical to the current Lunt 60 internal etalon in that regard. I don't have any idea on the current SM90II, but I believe the original (Tucson) SM90 internal module etalon was an SM60.


Diagonally parked in a parallel universe.

Curiosity is the father of knowledge; uncertainty is the mother of wisdom.

Dark-Sky Defenders
Goldendale Observatory
User avatar
Pablito
Ohhhhhh My!
Ohhhhhh My!
Posts: 155
Joined: Tue Mar 06, 2012 8:20 pm
Been thanked: 13 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Pablito »

Thanks Bob, it helps me much :)

Do you kow why Lunt or Coronado cut clear aperture in internal etalons?


User avatar
Bob Yoesle
Almost There...
Almost There...
Posts: 994
Joined: Thu Mar 08, 2012 7:24 pm
Has thanked: 540 times
Been thanked: 807 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Bob Yoesle »

Hi Pablito,

The internal etalons Coronado and Lunt use are air-spaced etalons:

In the solid spacer type of etalon, the mirror coating is applied to the ends of the solid material - cleaved mica in the case of the DayStar and Solar Spectrum filters. Therefore the entire face of the filter is usually coated, and the "etalon gap" is the substrate itself.

With the air-spaced etalons (Coroandao, Lunt, Solar Scope) the interfering reflections occur between the inside faces of the optically polished etalon plates, and they are separated by very thin low-expansion spacers, which are small chips broken off from a larger uniformly thin wafer of polished low-expansion glass (see below). These multiple spacers must be optically contacted ( https://en.wikipedia.org/wiki/Optical_contact_bonding ) to the un-coated faces of the mirror substrates around the periphery - therefore the mirror coating does not extend all the way to the edge of the substrate, and the etalon is effectively smaller than the substrate itself.

Coronado patented the use of a central spacer to maintain the etalon gap spacing under changing thermal loads encountered in solar observation, and Lunt patented the "Root 3" three central spacer method to do the same thing in it's larger 100 mm etalons. These spacers are also optically contacted between un-coated areas of the substrate, and therefore require a reflective "mask" in front and behind the uncoated area to prevent stray and direct sunlight from getting through.

The Coronado SM90 etalon has an effective coated diameter of 90 mm, the optical substrates themselves are 105 mm in diameter:
SM90 s ERF crp SM.jpg
SM90 s ERF crp SM.jpg (286.16 KiB) Viewed 7734 times
Hope this helps. B-)
Last edited by Bob Yoesle on Tue Aug 23, 2016 10:14 pm, edited 1 time in total.


Diagonally parked in a parallel universe.

Curiosity is the father of knowledge; uncertainty is the mother of wisdom.

Dark-Sky Defenders
Goldendale Observatory
User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 4059
Joined: Sun Nov 18, 2012 3:13 pm
Has thanked: 156 times
Been thanked: 893 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Valery »

Bob Yoesle wrote:Hi Pablito,

The SolarMax 70 was the same as the Helios (I think); I believe it is a ~ 50 mm OD etalon with a clear aperture of 35 mm - almost identical to the current Lunt 60 internal etalon in that regard. I don't have any idea on the current SM90II, but I believe the original (Tucson) SM90 internal module etalon was an SM60.
Thanks a lot, Bob!

Much appreciated.


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.
User avatar
Pablito
Ohhhhhh My!
Ohhhhhh My!
Posts: 155
Joined: Tue Mar 06, 2012 8:20 pm
Been thanked: 13 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Pablito »

All is clear now. Thank you very much Bob!


User avatar
Bob Yoesle
Almost There...
Almost There...
Posts: 994
Joined: Thu Mar 08, 2012 7:24 pm
Has thanked: 540 times
Been thanked: 807 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Bob Yoesle »

You're very welcome Valery and Pablito ;-)

BTW, here's some interesting and I hope informative pics I got on my March 2015 visit to Lunt which shows some of what goes into making today's H alpha solar telescopes:

On the way down, beautiful Arizona desert scenery:
IMG_20150323_162618757 crp SM.jpg
IMG_20150323_162618757 crp SM.jpg (103.98 KiB) Viewed 7717 times
The optical components are polished flat on large orbital polishers; note the grey tube at upper right which supplies the polishing slurry to the huge rotating polishing lap. The large central weight deforms the lap as needed to produce the desired polishing shape:
Polishing.jpg
Polishing.jpg (121.07 KiB) Viewed 7717 times
Spacer discs are attached to larger discs for polishing to the precise thickness required for the etalon gap:
Spacer polishing.jpg
Spacer polishing.jpg (58.42 KiB) Viewed 7717 times
A LS60 etalon plate with mirror coating:
Coated plate.jpg
Coated plate.jpg (74.18 KiB) Viewed 7717 times
Multiple etalon plates grouped and awaiting assembly:
Etalon plates.jpg
Etalon plates.jpg (94.65 KiB) Viewed 7717 times
A spacer disc with portions removed for spacer assembly placement:
Spacer chips.jpg
Spacer chips.jpg (85.47 KiB) Viewed 7717 times
Spacer assembly testing station:
Spacer etalon assembly sm.jpg
Spacer etalon assembly sm.jpg (62.31 KiB) Viewed 7717 times
Workstation for spacer placement and etalon assembly:
IMG_20150323_111451219_HDR crop SM.jpg
IMG_20150323_111451219_HDR crop SM.jpg (89.93 KiB) Viewed 7717 times
Completed LS60 etalon (camera focused on ceiling tiles!):
completed etalon.jpg
completed etalon.jpg (71.06 KiB) Viewed 7717 times
Checking an etalon fringe pattern using a laboratory Hydrogen spectrum tube:
Test crp SM.jpg
Test crp SM.jpg (57.47 KiB) Viewed 7717 times
In-house CNC machining of OTA components:
Raw and finished.jpg
Raw and finished.jpg (118.97 KiB) Viewed 7717 times
Pressure tuners being assembled:
Pressure tuner assembly.jpg
Pressure tuner assembly.jpg (137 KiB) Viewed 7717 times
A tilt-tuned etalon in it's "basket cell":
Tilt tuned etalon.jpg
Tilt tuned etalon.jpg (121.47 KiB) Viewed 7717 times
Finished LS50's and 60's awaiting final testing an shipment:
Awaiting final testing.jpg
Awaiting final testing.jpg (104.91 KiB) Viewed 7717 times
On my way home through the Nevada Great Basin - wonderful dark-skies ;-)
IMG_20150324_145805848 crp SM.jpg
IMG_20150324_145805848 crp SM.jpg (321.77 KiB) Viewed 7717 times
Thanks again to all the wonderful folks at LUNT Solar for their help and hospitality!

B-)


Diagonally parked in a parallel universe.

Curiosity is the father of knowledge; uncertainty is the mother of wisdom.

Dark-Sky Defenders
Goldendale Observatory
User avatar
Pablito
Ohhhhhh My!
Ohhhhhh My!
Posts: 155
Joined: Tue Mar 06, 2012 8:20 pm
Been thanked: 13 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Pablito »

WOW! :)


User avatar
Marcello
Im an EXPERT!
Im an EXPERT!
Posts: 384
Joined: Sat Dec 28, 2013 5:06 pm
Been thanked: 25 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Marcello »

Hi Bob, very interesting report, thanks!

The reflection of the ceiling is impressive!


Play in the sunshine, we're gonna get over !!
User avatar
marktownley
Librarian
Librarian
Posts: 42272
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20440 times
Been thanked: 10246 times
Contact:

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by marktownley »

A good story there Bob! :)


Image
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!
User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 4059
Joined: Sun Nov 18, 2012 3:13 pm
Has thanked: 156 times
Been thanked: 893 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Valery »

Thanks, Bob, for the story.


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.
christian viladrich
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2150
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Has thanked: 1 time
Been thanked: 2713 times
Contact:

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by christian viladrich »

Thanks Bob for sharing these images !


Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
christian viladrich
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 2150
Joined: Sun Jun 14, 2015 4:46 pm
Location: France
Has thanked: 1 time
Been thanked: 2713 times
Contact:

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by christian viladrich »

BTW, an information there ... I don't know if it is relevant at all in the discussion :
- in an "optimal" system, the F/D of the refractor lens (or telescope) should be equal to the f/d of the divergent (or convergent) lens of the collimating system,
- once this is true, the radius of the sweet spot simply depends on the ratio : diameters of etalon /diameter of the etalon.
So the bigger the internal etalon, the larger the sweet spot, but of course there are some practical issues ....


Christian Viladrich
Co-author of "Planetary Astronomy"
http://planetary-astronomy.com/
Editor of "Solar Astronomy"
http://www.astronomiesolaire.com/
User avatar
Valery
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 4059
Joined: Sun Nov 18, 2012 3:13 pm
Has thanked: 156 times
Been thanked: 893 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Valery »

"diameters of etalon /diameter of the etalon." (C.V)

You, obviously, just mistaken, miswritten. Should be diameters of an objective/diameter of an etalon.

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.
Sungazer
Ohhhhhh My!
Ohhhhhh My!
Posts: 58
Joined: Wed Apr 02, 2014 1:59 pm
Location: N.Hants
Been thanked: 3 times

Re: SolarMax internal etalon size (old SM70 and SM90II)

Post by Sungazer »

Many thanks Bob for the very informative photos of Etalon production. I had often wondered how they where manufactured. Quite a change from,The old system of half plates and Polaroid sheets interleaved ,which was used in the 1960s. D :bow2


Post Reply