2009 LUNT LS100T/Ha REVIEW Review by Stephen W. Ramsden (spike@solarastrophotography.com)

Tuesday, April 21, 2009

MANUFACTURERS INFORMATION

100mm H-alpha Solar-Telescope with B1200 blocking filter

The LS100T/Ha is a complete Solar Telescope. The refractor based system has a precision aligned singlet chromatic lens with a 100 mm aperture. The front singlet lens reduces the stray-light over an achromat by half. With the matched collimation lens set, it also fully corrects on axis coma, astigmatism and de-centering aberrations and provides a full spherically corrected flat-field Solar-Telescope. The focal length is 800 mm providing a ~7.3 mm image thru a 12 mm blocking filter. Course focus adjustment is via a slide tube. Focusing is achieved with a High Precision 2" Starlight Feather Touch Friction focuser with the a 10:1 reduction as standard equipment. An internal etalon with tune adjustment allows for a <0.7 Angstrom bandpass. Additionally the system may also be purchased with the 100mm external, front mounted Double Stack Etalon LS100FHa for a bandpass of <0.5 Angstrom. See the link at optional accessories down at this side. Specifikations: • Aperture: 100mm • Bandpass: <0.7 Angstrom • Focal length: 800mm • Blocking filter diameter: 12mm • 2" Feather-Touch focuser with 10:1 reduction • Tube diameter: 121mm • Tube length with blocking filter: 634mm • Weight: 5 kg Delivered with order: • optical tube with 2" feather touch focuser with 2.5" travel, includes adapter • tube ring • B1200 blocking filter • dovetail • sol-searcher • transport case Pre-orders will be shipped in the order they are received. Prices are subject to change without notice.

Price 4,498.00 $

REVIEW:

The LUNT LS100T/Ha dedicated solar telescope came was double boxed in white/brown cardboard boxes with the standard LUNT shipping tape. The internal box was surrounded by shipping peanuts and the internal box had a hard-shell case inside of it which had firm foam padding cut to fit the scope. Three layers of cushioned protection kept the scope in flawless condition through the rigors of shipping. I took delivery of this scope at NEAF and carried it home to Atlanta on an airplane myself. That’s another story in itself but suffice it to say that this case survived a monster truck ride in the trunk of my buddies Jeep for over 30 miles between NEAF and the White Plains airport.

The box contained:

1 LS100T/Ha telescope

1 B1200 Halpha Blocking Filter

2 LUNT Mounting rings and a standard 2 inch dovetail plate

1 Televue Sol Searcher

1 Feathertouch 2 inch focuser manual

1 LUNT LS100T/Ha Users Manual

1 LUNT 5 year warranty card

From one end of the scope to the other were a metal LUNT branded, screw on lens cap over the objective, a large white OTA with 2 mounting rings of high quality, an rubber and brass air pressure activated tuning system knob, a televue sol searcher, a very high quality 2 inch Feathertouch focuser, a 1.25 inch B1200 blocking filter and a plastic eyepiece plug.

(the LUNT zoom eyepieces were also exceptional but are not included in the price)

The LUNT LS100T/Ha had an exceptionally sturdy feel to it when handled. The scope had been autographed by Andy Lunt just under the air pressure tuner. The scope was well balanced and I gotta’ tell you the Feathertouch focuser was a real beauty.

I guess I should start by explaining the Barometric chamber for the internal etalon and its regulated air pressure tuning system as I understand it. I spoke at length with LUNT officials at the Northeast Astronomy Forum about this advancement in technology. They were very excited to get it out to the public as this was something that they had been working on offering for some time now. The system is presently available as an add-on option for all scopes 60mm and above that use an internal etalon. It is also available as a retrofit from LUNT if you want to send your scope in for a couple of weeks. It is not an option for externally mounted etalons as of yet so the LS35 does not have the option available. The simplicity and accuracy of this system was astounding.

The system replaces the tilting etalon configuration which is standard in the industry with an airtight chamber which contains the etalon surfaces. There is a large rubber knob on the outside of the scope which controls the internal air pressure inside the chamber. Varying the air pressure between and around the etalon changes the refractive index of the air between the surfaces and effectively tunes the internal etalon plus or minus towards the blue or red end of the Halpha spike. The knob must be fully removed initially to allow for venting of the chamber in order to equalize it with your ambient air pressure. Then you screw on the sealed rubber knob to create an air tight chamber. Screwing the knob in increases the air pressure by a maximum of 3 psi. This system keeps the etalon surfaces perfectly parallel at all times and does not stress or move the etalon surfaces in any way. The etalon is consistently usable up to 12,000 feet MSL and between -50 to +200 degrees centigrade It is really quite ingenious in design and simplicity. There is a collimating lens on the front of the etalon chamber and a refocusing lens on the rear.

I mounted the Telescope using my standard Celestron CGE mount on my favorite Pinnacle Portable Pier from Shahin at PWTech. I also mounted a Coronado SM90 single etalon Halpha scope and the new LUNT LS35 Double stacked Halpha scope for comparison and for a future review that I am working on.

The Sun was extremely calm with only 1 tiny AR and 2 discernable prominences through the best of my scopes. No, the tractor trailer in the background did not carry my equipment to the field. I was joined by a State of Georgia parks employee who was graciously mowing down the grass on my clubs astronomy field 45 miles E/SE of Atlanta. This is where I go for all of my solar photography. I whipped out my trusty LUNT “extra geeky” solar observers hat and got started.

The sky conditions were partly cloudy and the air temperature was 76 degrees F. The surface wind was from the NW at 6mph with Gusts to 17mph. In my opinion it was a 6 out of 10 day for solar viewing. There were 30 minute periods of uninterrupted viewing intermixed with 5-10 minute periods of clouds covering the Sun.

My first light view through the LUNT LS100T/Ha was absolutely incredible! The Suns surface was alive with mottling and there was a small, very faint loop prominence on the limb as well as a few bulging “piles” of Hydrogen plasma waiting to erupt into proms. One corner of the Sun had a peculiar little brighter area in which others on the Cloudy Nights Solar Forum were able to identify a miniscule white light Sunspot during the same time. The LUNT view was bright and crisp with a nice, dark background. It was everything I expected, and then some, for the price and aperture. I began to turn the air pressure regulator knob and watched as small features came in and out of view. The Feather touch focuser was superb and made even the most minute of focus changes easily controllable.

There was a very noticeable lack of a sweet spot or the “band of clarity” noticed in my other scopes when using the air tuner. The disk stayed evenly bright as features popped in and out of view. I was able to adjust the tuner from one extreme to the other with ease and it felt firm the entire way. I was very pleased with the control and the very fine adjustments of the bandwidth available with the new tuning system. It seemed to have much more precise control than the brass tuning wheel on my other scopes.

When compared visually with the single etalon Coronado SM90 (with the external 90mm etalon removed), the LUNT 100 had significantly more surface detail and was easily tuned to show many different surface features. The Coronado internal etalon on the SM90 was not adjustable but it still provided a good deal of surface detail just not nearly as much as the LUNT. The faint prominences were easily visible in both scopes and they both gave high contrast dark backgrounds. I would have to say that visually the LUNT 100 edged out the Coronado because of the added surface detail but was just slightly better resolution on the prominences.

I took a look through the LUNT LS35 to see whether the proms were even visible in it and they were just barely there. I don’t think that I would have seen them in the LS35 had I not known were to look and known to keep tuning it until I found them. They were VERY faint. This is a testament to both larger scopes power of resolution and quality of engineering. It was becoming a real shootout of the big guns.

I attached my DMK31 monochrome camera and took some avi’s in both scopes in an attempt to show their respective resolution of surface details and prominences. Be advised that the Sun was relatively quiet today to most Solar observers. I happen to very much enjoy the plain disk with no features just as much as the big proms as I believe that a “quiet” Sun is just as beautiful and telling of a telescopes abilities as a Sun filled with spots, filaments and prominences.

The images below were shot within 10 minutes of each other and were processed using Registax 4.0 with exactly the same settings from start to finish. I did not colorize any of the shots so that their native resolution could more easily be seen by the reader. No photo-shopping of these images.

Here are the results:

LUNT LS100T/Ha Single Etalon/DMK31

Coronado SM90-single etalon/DMK31

THE BOTTOM LINE

THIS TELESCOPE ROCKS!!!

Pros-

The technical advancements found on the LUNT 100 are state of the art.

The Feathertouch focuser is absolutely superior to anything out there and it blew away the Helical focuser on the SM90.

The included accessories make it ready to mount out of the box.

The air pressure tuning system far outperforms anything else I have seen in Halpha

This scope is priced well below any other Halpha solar scope of its size on the market.

The LUNT customer service is exceptionally good

The supplied case is very sturdy, roomy and solid

The surface feature resolution is comparable to a double stacked system from other manufacturers

The prominence clarity is unsurpassed in single stacked dedicated scopes

Great Job LUNT!

Cons-

Uhhh……………gimme a minute…..uhhh. I can’t think of a single con to list with regards to this scope.

Thank you for reading,

Stephen W. Ramsden

www.solarastrophotography.com www.charliebates.org

spike@solarastrophotography.com