What's and Etalon, and How do I Make One?

For those who have googled "what's an etalon?" the returned results outlining complex looking optical equations, mathmatical relationships, and technical references probably didn't do much to answer the question. Unless you are an Optical Physicist of course. (I love that stuff)

An etalon refers to an interference type filter typically used in Solar Telescopes because of the desire for an ultra narrow bandpass.

An etalon is probably one of the simplest designs for an optical filter utilizing some of the most precise optical specifications. Due to it both being simple and the need for precision, there are many compromises that can influence the quality of an etalon filter.

An etalon is comprised of 2 flat and parallel optical surface that have been optically coated with a high reflective dielectric layer with the high reflector layer peaking at the desired bandpass point for best results. These optical surfaces are seperated by a gap. This gap can be either air or a solid material. The light resonates in the gap by internal reflection off the highly reflective layers on the surfaces. Thru interference at this gap, only light meeting the correct angle of incidence to the surface and is not "interfered with" can pass, all other light is lost.

The main parameters that define an etalon are:

Bandpass: This is the width of the curve that defines the transmitance of the filter at 50% of the total transmision of the filter. An etalon's transmission has a broad base and a sharp peak. Typically the peak transmission should be between 80-90%, so the bandpass of the etalon will be measured between the 40-45% points. For Solar applications it is generally accepted that the lower this number, the better. Typical Solar Etalons have a bandpass of <1.0.

Bandpass is a function of the gap size between the high reflector plates. The larger the gap size, the narrower the bandpass.

Bandpass is also a function of the reflectivity of the etalon high reflector plates. The higher the reflectivity, the narrower the bandpass.

Peak Transmission: In order to obtain good contrast it is important to maximize the peak transmission while minimizing the "out of band" transmission. To explain this statement, a surface that had zero reflectivity would have 100% peak transmission. However, because there is no reflectivity in the cavity, there is no interference, and thus, no filter (bandpass). A surface with 100% R would reflect all light before it entered the cavity, thus having zero T. The compromise is somewhere in between..

Peak transmission is a function of the reflectivity of the surfaces. The higher the R, the lower the peak transmission. (in reality it isn't quite that simple)

Free Spectral Range: The free spectral range is defined as the gap between the peaks of transmission plotted againt wavelength. Huh?? An etalon produces a "comb" of peak transmission across a broad range of the visible spectrum. This would be like a hair comb. One tooth of the comb would represent a peak transmission. This comb would then be missing about 12-14 teeth before the next peak transmission, or tooth. In our case the FSR is more than 10 Angstroms. This becomes important to our ability to block the unwanted peak transmissions utilizing simpler filters. The narrower the FSR, the harder it is to block the transmissions you don't want. Letting another leak transmission thru will wash out the details.

FSR is a function of gap size. The narrower the gap, the wider the FSR.

Optical Flatness and Parallism: Probably the most critical aspects of the etalon performance.... To put it simply, the better the flatness and the parallism, the better the etalon.

The quality of an etalon is very much the function of precision polishing and gap maintainance.

When it comes to the specification of a Solar Telescope I often hear the bandpass stated out as a matter of fact. However, this bandpass is typically the theoretical value of the system based on the known paramaters of reflectivity, gap size, and optical flatness. What one should realize is that bandpass is not the all defining specification of a quality system.

I could quite easily manufacture a 0.3A bandpass filter and everyone would be happy.. Right??

Not if it's performance was any factor.. An etalon with a peak transmission of 40% and a FSR of 4A is quite easy to manufacture. But I assure you, you wouldn't want it in your scope.

When it comes to Etalons there are typically a few things to look at.. The bandpass, is of course, of very high concern as long as all other aspects of the optical system have been addressed. An FSR of greater than 10A is required in order to prevent out of band leaks. (the camel peaking it's nose under the tent) a phrase I liked when I heard it.

Peak T is also important as long as it comes with a zero baseline. Signal to noise ratio is critical because it is what makes the brights bright, and the darks dark. No-one want to see a significant orange glow in the space around the Sun's image, this simply washes out the edge details.

Contrast is just as important as bandpass in my opinion. However, there really isn't any specification for contrast ratio.

End of Part 1

Next: How do we make them?

Etalons: External and Internal

Which is Better??

The defining difference between an External etalon vs an Internal etalon has typically been Price vs Performance... Well that gap is getting very narrow.

External etalons are used on the front of an existing scope, and the user typically asks that the etalon be full aperture. Internal etalons are situated internally to the scope, allowing for a full aperture objective to pass the light thru a smaller etalon due it being placed further down the optical path.

The basic rule of thumb for an etalon is the price is a function of the area. That adds up fast.

Another rule of thumb that I have heard is that the acceptance angle of an airspaced etalon is 0.5 degrees. What one should keep in mind is that, in any case, an etalon specified by surface reflection at the interface of the internal plates, thickness of gap, and gap medium only, will NOT perform to that optimal specification should there be anything other than collimated light passing thru it.

F30 does not apply specifically to airspaced etalons due to the higher index material utilized at the gap of the solid design. In most cases for solar this is solid material is Mica, and in some cases it is fused silica. All solid etalons that I have made for space flight have been fused silica.

The Sun is not a point source. In fact, the Sun is a very large extended source. It may look small at 93M miles away, but it is 865,000 miles in diameter. To put that in perspective, if the Sun were an objective and the front of your filter was the focal plane (I don't think we need to look at filter size in this example ;) the system would have an F107 ratio. That's still not entirely collimated..

Seeing the Sun at Sunset or Sunrise in relation to a distant mountain also puts it's size into perspective.

Even so, the best position for an etalon filter is on the front of the scope. However, this etalon is still compromised from ideal by the Sun's angle. These errors are small.
The use of tilt at the front etalon is simply a method of shifting the bandpass (the frequency of light passing thru the etalon). Due to the acceptance angle of the etalon, this tilt must remain very small. The more the tilt, the wider the bandpass becomes, and the non-collimated Sun angles begin to play a factor.

Tilting was introduced many years ago as a way of allowing etalons to be mass produced at slightly above the Ha line. They could then be tilted on line to accomodate the users changes in altitude and changes in barometric pressure at any given location. Without tilt, Solar Telescopes would be many times more expensive than they are today.

The move to internal etalons was done in order to bring the manufacturing costs of the Solar Telescopes down to less than 1k. By utilizing an etalon that was half the diameter of one required for the front, the cost of the etalon was cut by more than half. Even with the added cost of re-collimating and re-focus lenses, the system realized significant gains in affordability.

One of the huge benefits to internal etalons has been the fact that we only deal in one wavelength of light. This allows for the optimization of the internal lens system to remain fairly simple and straight forward. Ha! Right.. Simply aligning and collimating 4 optics now..

The evolution of internal etalons has taken several steps.
The original systems had internal fixed etalons that sat behind a re-collimating lens set (these lenses work to bring the light rays back to parallel). The light from the etalon was then re-focused back to the image plane.

These systems cannot compensate for changes in altitude and air pressure. Taking this system from sea level to 8,000ft would not work.

The next step is the introduction of some tilt. This works similar to the tilt on the front of a system. However, due to both off axis light rays that could not be re-collimated with a simple lens, and the angles created by the Sun's size, the etalon can only be tilted thru a fraction of a front mounted system. These etalons have been designed to be only very slightly higher than the Ha line so minimal tilt is required. Front mounted etalon designs can be used for this process, but recent innovations to coatings on the etalon cannot be used due to the new design's slightly narrower acceptance angle.

These systems maintain a very good flat field of narrow bandpass due to the optimization of the collimating set at Ha over about 80% of the entire field. Etalons with a theoretical bandpass of 0.65A are used, but are specified internally at 0.75A over the entire field due to the compromise of the ray angles. The center portion of these systems is typically better than 0.7A.

The current technology is the Doppler True tuning design.
The technology came about for the simple reason that tilted internal etalons are not optimized. The ideal design calls for an internal etalon (to reduce cost) in a perfectly collimated system, without the need for tilt, while also compensating for altitude and pressure changes (or being isolated from).
The new system may be simple, but it addresses 99% of all the relevant issues.

The incorporation of the air pressure system (see other blog entries for description of how this works ) has allowed us to improve the technology of the high reflector layers.
For a given optical system, we have been able to modify the design of the HR. We are still working on tweaks and changes, but have already seen some improvement to resolution, field flatness, and contrast. The new designs are moving in an area that provides for blacker backgrounds and sharper features. There's still room for improvement..

So which is better? External or Internal??

The jury is still out on that one. It is still a function of Price vs Performance.

The new evolution of internal design has certainly gone a long way to improving the performance of internal systems. However, the added cost of the pressure system has now made the external system seem more affordable.

In my opinion the best option is to buy as much double stack system as you can afford ;)

All kidding aside. Going with an internal PT system is probably the most ideal start. Buying a system that you know you can DS later without much problem is good. The dedicated system is fully optimized and ready to go. We are familiar with these systems and can help with technical issues. We test every system that goes out. I cannot test a Lunt Filter on Your scope. I cannot answer questions about in focus etc. for Your scope.

The removal of the tilting from the internal system is providing stunning results. The ability to Doppler Shift instantly to and away from you adds a 3D feel to the image that cannot be matched. This technology has certainly improved the dedicated system.

Now... What about all that tilt on the front??

The see-saw of performance is about to swing again. Lunt will be introducing the front mounted filter system with the Pressure Tune capability in mid next year (or maybe sooner ;). These systems will be manual control and also remote operable. For those that don't have 6 foot arms for your LS160F on that really long scope, this will certainly be a must.

Next blog: What is an Etalon and how do we make them?

Help Needed on Lunt Forum

The New Lunt Solar Forum is live..

We are looking for a few enthusiasatic helpers who are familiar with this type of forum to do moderating and help set up the catagories etc..

Please let us know if you can help out by sending an e-mail to sales@luntsolarsystems.com

Working with us on the Lunt Forum will entitle you to discounts on Lunt Products. We can also arrange to send new products to you for test and review.

Thanks in advance...

Sky and Telescope Hot Product 2010!!

We certainly appreciate being recognized by Sky and Telescope for a Hot Product of 2010 Award.

This award has been presented to Lunt Solar for the LS60T/Ha/PT system.

The Pressure Tuned System received an overwhelmingly positive response when shown at NEAF, RTMC, and PATS in 2009. I will be writing a full editorial about the Doppler True tuning system with insights into how to get the most from this system, and why this new technology is such an innovation to the Solar Telescope.

Thanks again to all the folks at Sky and Telescope for picking Lunt Solar and the LS60T/PT. I am very proud of this scope and enjoy testing them every chance I get.

NEAF shirt spotted in Peru!!

I'll have to get Rikki to do a little write up about what it's like living in Peru.

Here is an image of Rikki with Jesus, the guy who drives her too and from "work" every day.

Is that a NEAF shirt that Jesus is wearing??

As some people know, Rikki lives in Peru. She runs the Lunt office from a small office in the town near where she lives. It must be nice to be chauffeured to and from work.

When I get into the office in the morning, I see the mouse cursor on her virtual terminal moving around. She uses an internet based program to chat with Jen in the office all day for free!! You know she's here all day, but you never see her...

I won't say that it hasn't been without it's small glitches, but I have to say that the virtual commuting really works even over thousands of miles to a developing country..

What else does Rikki do in Peru and how did we get this worked out?? I'll have to get her write up a little blog and send in some pics..

Stay tuned..

Great Activity Today !!!

Tucson, Arizona has cooled some from last week. One week ago today it was 90 degrees, today we are in the low 70s.. oooh that's chilly...

Along with the cooled temps has come some nice transparent skies. I was testing today and I am very delighted to see several good active areas and as many as 4-5 small developing areas. In addition there are filaments on the surface.. woooHooo!

I hope you get a chance to get outside and view, it's very nice to see the significant increase in activity over the last few months..

Let me know what you see..

Limited Edition LS75F/HR Un-Obstructed

A HR LS75F Un-obstructed filter with matchable BF at <0.6Angstroms (single stack).

During the process of R&D I have been working with new coating technologies that are very low stress and very high finesse. As you know, these coatings will be made available in the new LS152T.

One of our recent projects was the manufacture of some un-obstructed larger 75mm Hydrogen-alpha etalons. My intention was to build one and keep it for myself.

Due to batch costs, it was just as costly to make one as it was to make a few :)

As luck would have it, we have been able to produce a couple of these etalons and I have decided to make maybe 5 available. These filters are not part of our normal production and when they are gone, they are gone, we will not take any orders for more. They are a limited edition signature series filter. There is the possibility of matching 2 for a single DS system.

A little about the etalons:

Internal aperture obstructions are used to maintain the parallelism of the high reflector plates typical to an etalon.
Removing the internal obstructions, or feet, requires that the etalon plates be manufactured to the highest specification for flatness possible. Generally better than 100th wave.
In order to prevent stress to the plates (bending) after the coating process, the coating has to be done in a system that can put down a hard, accurate, dielectric at very low heat. This process is often refered to as ion assisted deposition.

In order to decrease the bandwidth, we had to improve the high reflector dielectric properties. However, in general the trade off has been that plates flat enough to take advantage of the improved coating, were too costly to produce. (higher R needed better flatness).

The coatings that we are currently introducing have higher finesse and lower bandpass. While also providing higher contrast (noise to signal and all that). We are making the blacker, black, and the brighter, bright. Sort of like HD for solar viewing..

I will discuss more about the coatings in a future blog..

The specifications are as follows:

Type: Single Etalon Front Mount Filter
Size: 75mm Un-obstructed
Bandpass: <0.6
FSR: 11 Angstroms
Blocking Filter: Price includes B1200
Adapter Plate: Not Included (POR)
Price: US$3,985.00
Availability: Limited from Stock (check your local dealer or call us)

These are subject to prior sale and we will NOT take orders after they are gone.

Each filter will be signed and dated.

We have a few other fun things coming up, so you will have to check back here to hear about them first. (How about an unobstructed 150????) ;)~

One Thousand Dollar Giveaway :)

In the spirit of awards and the launch of our new website, Lunt Solar will be giving away a total of US$1,000.00 in gift cards to be used toward the purchase of any Lunt product at any authorized Lunt dealer worldwide..

Entries for this event should be received by December 31st 2009. All entries received after that will be included in January 2010. Award winners will be notified in early January.

How do you enter??

Simply submit; a series of images with related text, an editorial article, a "how to" article, educational article, etc.. Keep the submission relevant and original to anything Solar. It doesn't have to be observing related.

All submissions will be reviewed and prizes will be awarded to those that are interesting, fun, creative, and entertaining.

Submissions will be placed into our blog or on our website.

Please include return contact information in all submissions.

Submissions and questions should be sent to: sales@luntsolarsystems.com
Please use the sales e-mail until we have finished uploading the completed website and accounts this coming week....

Check back often for more info and updates.

This is what Solar Minimum looked like ;)

Greg Piepol sent this image of the Sun a few weeks back. I am not sure when it was taken.

Assuming this was just a couple os weeks ago, we can certainly appreciate that the Sun has become a little more active in that timeframe.

Although we still have a long way to go before we see the amazing events that the Sun displays during it's Solar Maximum, I think we can all feel good about the fact that Solar Minimum is over.

Hopefully we won't be receiving any more images like the one attached for a while ;)

I am going to stop the further developement of the Adobe Photoshop Solar Features plugin package. The plugin would have allowed for the "enhancement" of Solar Minimum images.

We have received a few recent images and I will be getting those added to the website soon. There's still alot of work to be done on that site.. Keep the submissions coming, and feel free to comment and ask questions..

Popular Science Best of What's New 2009

A quote....

"For 22 years, Popular Science has honored the innovations that surprise and amaze us - those that make a positive impact on our world today and challenge our views of what's possible in the future." said Mark Jannot, Editor-in-Chief of Popular Science.
"The Best of What's New Award is the magazine's top honor, and the the 100 winners - chosen from among thousands of entrants - represent the highest level of achievement in their fields."

We are obviously very pleased to have received the BOWN 2009 award in the Recreational Catagory for the New LS60 Pressure Tuned Telescope. See page 58 of the December issue, or check on line when it goes live.

Although it has long been known that altitude changes move the center bandpass of an air spaced filter, it wasn't until June of this year that the reality of a system that incorporates this technology was brought out into the mainstream. A simple system that simply increases and decreases the air pressure inside a sealed cavity.
This change in air pressure results in a change in refractive index which alters the interference of the light as it enters the cavity. Simplicity! This system basically does the same job as heat would do to a solid design, but instantly, without power, at the turn of a wrist.

Look for some exciting new developements from Lunt Solar in the next 6 months. Along with some R&D projects which I will continue to discuss as I can, we are close to completion on the developement of several new products..

Thanks! to Popular Science for recognizing Lunt Solar as a leader in it's field.

First Week of November (Last Part)

As of November 1st we officially began to move into our new expanded facilities next door. Our landlord, Steve, has been nice enough to let us store our cases, shipping containers etc. over there for the last few months until the facilities were ready. The new facilities increased our square footage by about another 40%.

The expansion incudes a few more offices, a nice education/AV area with kitchen and restrooms, and in mid area a nice big fully climate controlled room for our upcoming coating facilities with large double doors to our current assembly area. The back of the area has been heated and cooled, but is currently used as a main storage area. During the buildout of our current area, we had the fore thought to put 800 Amps of 3 phase power in, so the new area has plenty of juice to keep us going.

I'll have to get some pictures up, but it's hard to believe that we first moved in to the current building in February of 2008. The building had a small kitchen, and a lobby. There were NO bathroom facilities. (We made friends with the neighbors very quickly ;). The first 2 Continuous Polishers were working in the kitchen area on very long extension cords. I had an electric heater on one wall and an air conditioner on the other, both fighting to keep the un-insulated room at +/-1 degree.

6 months later we were able to move out of the kitchen and populate the new building just in time for our open house..

14 months later we are still expanding and I am still working very hard to increase our capacity to meet the ever growing demand.

First Week of November (Part 2)

During this week we finally finished our 6th Continuous Polisher.

All the polishers at Lunt are custom designed and fabricated on site. They are currently all 48" diameter with a capacity for about a 12" part. In our application we use plastic fixtures on the lap to hold multiple sizes. We also utilize a large conditioning wheel that runs continiuously on the lap to maintain the required flatness to the parts being polished.

The 48" granite lap is supported on a thick steel plate which mounts via a very heavy duty machine bearing to our custom tables. Our tables are designed and manufactured to be very solid. The lap is driven by a 5HP motor with a large gear reducer, all controlled by a variable speed controller. Due to the fact that our laps generally run 24 hours a day, 7 days a week, we have ensured that all components are over sized for the job.

The granite forms the solid and thermally stable foundation for the polishing pitch. We use a Gugolz fine pitch. We heat the pitch up in a very large pot and once fully liquid, we add secondary components to ensure that the lap will remain firm and stable for long periods of time.
These additions make the lap very "hard". The trade off is that it takes many hours just to push a lap 1/4 wave in each direction. The benefit is that the lap remains flat for extended periods of time, allowing us to finish an entire batch of glass in that timeframe. This also ensures that the laps cannot drift too far while being run overnight. The hardness of the lap and the fine polishing compound assure that our flats are very precise and have no roll off at the edge.

Our next project is the fabrication of a 36" Continuous Grinder. David, our glass grinder, spends 8 hours a day grinding glass from rough cut to fine grind. A second machine will allow us to provide just a little more ground parts than the optics shop currently needs freeing David to hekp in other areas.

In addition to the 6 48" CPs, we are in the middle of construction on our 72" Continuous Polisher. The granite has arrived, and the steel base is finished. This machine will be used to manufacture precision flats up to 24" in diameter. Recent large flats were finished on a large draper style machine. Although we eventually met the specifications of 1/10th wave over 20", we have certainly concluded that a large CP is the way to go.

Outreach in Riverside, CA

I wanted to share my experience with this new gear.

I don't know what Andy does when he matches this scopes and filters up but I am just completely blown away by the views with the new LS60THa scope and my original LS50FHa filter. This set up starts to mimics views I had years back with a buddies older Coronado Solarmax 90 filter on a TV101 scope! I knew double stacking was the way to go but seeing it real time with this latest technology really reinforces it.

I got first sunlight Saturday morning and could see so much detail on a new emerging active region that day. The bright spot with detailed twisting was very easy to see and study. The orange peel was so intense that the sun's globe was starting to show the classic 3D quality of truly high end H-Alpha rigs. And, amazingly, the double stack even at 50mm aperture was still able to show the prominences extremely well even while showing all this surface detail. How can this be!!? Most smaller aperture double stack H-Alpha filters and scopes in the past just showed higher surface detail at the strong expense of easily seen edge detail. Not both at the same time. This little additional gift to the views is just more iceing on the solar cake.

Using the scope and filter set up at the large STEP Conference outreach here in Riverside for the last two days presented easily seen surface detail for every single student and teacher. Every single one. No guessing. There was never any......"well I see it sort of but I'm not sure". Even the younger children could view the orange peel, filaments and active regions clearly. Lots of smiles or "that's so cool!" or "that's really our sun? Are you kidding me?....awwwwesome!!"

I now have the ultimate solar outreach tool that can be use to share our star with many thousands of the public of all ages over the years. I have tools to do serious outreach all day long. Not just at night. For an outreach junkie like me this is true Nirvana.
I thank all of you guys involved at Lunt Solar Systems for bringing this company to market. You folks really are continuing the vision of bringing H-Alpha observing to the masses. All I can say is your service and products speak for themselves.

.....Thanks for these very kind words, we look forward to hearing about ongoing outreach from Riverside and in your area.....

Thanks again,
P. Agins
Riverside Astronomical Society
Outreach program

The NEW Website!!

The new Lunt Solar Website is almost finished!
........It is almost finished... right?..........

With DNS transfer scheduled for Wednesday, November 11th I am excited about finally starting on a website dedicated to everything Solar. With live streams in Ha and CaK, news and events, forums, galleries, and editorials provided by the users of solar equipment.

We would like to see Solar enthusiasts get involved. Jot down a few stories, ideas or experiences and submit them for the site. We will be featuring articles on past and upcoming events, your local outreach efforts, and a chance to share you knowledge of observing and imaging. And please include pictures!!

The new community area will be dedicated to everything solar it does NOT matter what brand of scope you use. I have been involved in the solar filter business since about 1998, I understand that Lunt is not the only manufacture of Solar equipment, the fact is we all share the same interests and should do what we can to promote the hobby of Solar to everyone. I am certainly proud of the equipment I helped produce before Lunt, and it is a result of that experience that I am able to push it's continued evolution..

So put pen to paper and submit "articles of interest" to editorial@luntsolarsystems.com

We also need to get the word out about the new website and the blogs (there are 11 of us in this area).

The blog will be attached to the new site once the site is live..

First Week of November (Part 1)

The first week of November has flown by. A week ago today we were getting ready for Holloween night, it'll be Thanksgiving before you know it!!.

Testing, new products, and website were the projects of the week.

The image at left is the New LS152T/PT. This is currently the largest dedicated telescope that we manufacture. This is a working prototype and was on display at PATS. It had been my intention to take it outside on the Sunday, but the mount that I was going to borrow was sold on Saturday. I did try the mount it was displayed on, but that was a drop waiting to happen.

The internal lens sets for the system are almost finished. The prototype lenses were "off the shelf" and weren't quite optimized for the system proviving only about a 70% sweetspot in the center of field. The production lenses have been designed to the optical system. They are also slightly larger than the prototype given more aperture to the beam.

The LS152 contains an unobstructed 60mm HR (high resolution) etalon. This is a new etalon design and provides for high signal to noise ratio which greatly darkens that background allowing for stunning contrast on edge details.

I have already had one person ask about the unobstructed 60mm, and before the questions are raised and the assumptions made in other forums, I will state that we will not be introducing the LS60F until Summer of 2010. Due to the very high demand for the other products, we will not be tooling this particular size at the expense of current production. Our LS60F production is currently limited to the LS152T, and takes the place of the production schedule for the LS200T.

The estimated US$ retail for this instrument is $7,495.00 (this does NOT include the CaK module). For those that have the LS200T on order you will be receiving the LS152T at no additional cost. If you purchased the CaK option for the LS200T you will also be receiving that at no additional cost. As you know, the LS200T was introduced at 5k. It was the intention to increase this price once the system was shipping and had good reviews. As I will explain in another post, the LS200T could never meet both the performance requirements that I had set for it, while also meeting the strict safety requirements. The trade offs were leading to unacceptable compromizes on both sides. Safety will always be of the highest priority to ANY solar product.

For those that choose to accept the exchange, I promise that you will be receiving a solar system that exceeds my expectaions for what the LS200T was going to do. By defualt the delays have allowed for the incorporation of a 60mm etalon instead of a 50mm. The new HR (high resolution) coatings will be incorporated standard, and the value of the package itself will provide a good return on investment should you ever choose to sell.

For those that cannot accept the exchange, we will refund any deposit in full.

Recent Trip to Mt Lemmon Sky Center

This image was recently e-mailed to me from my Landlord. He and a group from his church spent the day and part of the evening at the Mt Lemmon Sky Center.
For those that attended the Open House at Lunt Solar a year ago, you will remember the visit to 9,000 ft. It was about this time of year and although the weather was clear and sunny, the temperatures were very cold.
Shortly after the visit we donated a LS100T/PT to the facility in appreciation of their hosting the event and providing everyone with a look thru some of their large scopes. Everyone had a great time.

We chose the LS100T/PT specifically because of the high altitude. A large aperture scope in great skies without the issues of air pressure to the air spaced etalon.

I hadn't given much thought to the scope on Mt Lemmon until I received this picture. Steve and the group were wandering around the domes, when Steve recognized the name on the 100T. He'd never actually looked thru one of my larger scopes before and expressed his excitment at having the chance to look thru one of our systems "in the wild". He was very pleased with the view. Everyone in the group had a chance to view the active region of last week.

This scope was provided to allow the Center to provide visitors a chance to view the Sun. The Mt Lemmon Sky Center is open to the public, and often receives large groups of children and adults who are interested in learning more about astronomy as well as the nature of the mountain.

For more information on the Sky Center you can visit http://skycenter.arizona.edu/

The facilities were remodeled about a year ago and I have to say that they did a fantastic job. From large kitchen areas, to private bedrooms, and a first rate meeting/audio visual area.

We are hoping to visit the center at our next Solar event which is now tentatively planned for March 2010.