LS60THa 60mm f/8.33 double stack, 12mm blocking filter, Feather Touch focuser

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The Lunt LS60THa double stack 60mm solar refractor with Feather Touch focuser upgrade is designed for serious high resolution Hydrogen-alpha solar viewing. The H-alpha views through the Lunt 60mm solar refractor show you much more of the living Sun than ordinary glass or Mylar white light solar filters that show only sunspots. With the Lunt LS60/Ha, you see the violent ever-changing tapestry of multiple prominences leaping off the edges of the solar disk and the explosive upheavals of flares and filaments on the face of the Sun. All of this is visible in addition to sunspots and surface features in exquisite detail.

In addition, the best and most-detailed H-alpha views of the Sun are undoubtedly seen thru a dual etalon (double stacked) scope like this Lunt 60mm. The reduction in passband from a single etalon’s under 0.8 Ångstroms to under 0.55 Ångstroms with the double stack system seems to bring the Sun's surface to life with a palpable Wow! reaction from virtually all who experience a double stack Sun. However, adding a second etalon to an existing etalon is not quite as simple as it may seem. Both etalons need to be brought on line (tuned) and both need to be tiltable such that all ghosts are eliminated when viewing or imaging. Ideally the transmission curves should overlap perfectly when on band to provide for the best possible resolution and contrast.

The Lunt LS60THa consists of a 500mm focal length 60mm aperture f/8.33 refractor with an integrated double stack Hydrogen-alpha solar filter. The factory-matched tunable external/internal double etalon system allows use at both a wider <0.8 Ångstroms passband for brighter prominences and a narrower <0.55 Ångstroms passband for higher contrast views of surface features.

The three-part filter uses a single pass 60mm etalon, a single pass 50mm etalon, and a 12mm blocking filter built into the standard equipment 1.25” star diagonal. There is also an infrared reflecting window (Energy Reflecting Filter or ERF) early in the optical path to remove unwanted heat from the system. Both etalons in the system are matched at the factory to provide a system optimized for maximum performance and the elimination of ghosting. A tuning mechanism built into the system lets you center the passband precisely on the H-alpha line for maximum contrast, as well as perform off-band observations of Doppler-shifted disk features to determine whether they are moving towards you or away from you.

The scope’s singlet objective lens is fully multicoated. It is not necessary to use an achromatic doublet in a small solar scope to correct for chromatic aberration in the violet end of the visible spectrum. Solar scopes are designed to observe only a single wavelength of red light at the opposite end of the spectrum. Why pay for two lenses to cure a problem that a solar scope is incapable of showing you in the first place? In addition, the front singlet lens design reduces the stray light of a two-lens achromat’s internal reflections by half. With the matched collimation lens set built into the scope, it also fully corrects for on-axis coma, astigmatism, and de-centering aberrations and provides a spherically corrected flat-field image.

If the scope is used without the removable external etalon, the system has a <0.8 Ångstrom passband, centered on the 6562.8 Ångstrom H-alpha line. The sub-Ångstrom passband width gives you balanced views of feathery prominences and low-contrast surface detail alike. If the external etalon is added to the scope, the passband narrows to <0.55 Ångstroms for substantially higher contrast surface details, although with a slight loss of prominence brightness. The filter is thermally stable, so there is no drifting off the H-alpha line as the filter heats up during use. The 12mm clear aperture of the blocking filter portion of the H-alpha system (which is built into the star diagonal housing) is ideally matched to the focal length of the telescope to give you an approximately 4.5mm diameter image of the full disk of the Sun at prime focus. The 12mm B1200 blocking filter is better suited for binoviewer use and for imagers who need a wider illuminated field for use with cameras needing a long back focus.

Coarse focus is via a sliding drawtube. Very precise focusing is achieved using the upgraded premium 2” Feather Touch 1.5” drawtube travel dual-speed Crayford focuser that has a 10:1 reduction ratio for precision focusing on the smallest of solar details. Large ribbed focusing knobs make it easy for you to reach a precise focus, even if you are observing in the dead of winter while wearing gloves or mittens.

You can use virtually any 1.25” eyepiece with the 60mm Lunt solar refractor. A typical 20mm 1.25” Plössl will give you a magnification of 25x and a little over a 2° field of view compared with the 0.5° diameter disk of the Sun. A 15mm Plössl will give you 33.3x and about a 1.5° field, giving you plenty of dark sky background around the solar disk to show off the prominences.

The Lunt LS60THa comes with a clamshell-type mounting ring with 1/4”-20 thread holes that will let you mount the scope directly on a photo tripod for a quick peek at the Sun. You can also mount the clamshell ring on a dovetail plate and install it on an altazimuth or equatorial mount for extended observing and tracking of the Sun. A foam-lined hard case is standard equipment for transporting and storing your Lunt scope.

Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

500mm
Focal Ratio:
This is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. The smaller the f/number, the lower the magnification, the wider the field, and the brighter the image with any given eyepiece or camera.

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are usually better suited to higher power lunar, planetary, and binary star observing and high power photography. Medium f/6 to f/10 focal ratios work well with either.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, are recorded based on the aperture, however, rather than the focal ratio – so that the larger the aperture, the fainter the star you can see or photograph, no matter what the focal ratio.

f/8.33
Resolution:
This is the ability of a telescope to separate closely-spaced binary stars into two distinct objects, measured in seconds of arc. One arc second equals 1/3600th of a degree and is about the width of a 25-cent coin at a distance of three miles! In essence, resolution is a measure of how much detail a telescope can reveal. The resolution values on our website are derived using the Dawes’ limit formula.

Dawes’ limit only applies to point sources of light (stars). Smaller separations can be resolved in extended objects, such as the planets. For example, Cassini’s Division in the rings of Saturn (0.5 arc seconds across), was discovered using a 2.5” telescope – which has a Dawes’ limit of 1.8 arc seconds!

The ability of a telescope to resolve to Dawes’ limit is usually much more affected by seeing conditions, by the difference in brightness between the binary star components, and by the observer’s visual acuity, than it is by the optical quality of the telescope.

a1.93 rc seconds
Aperture:
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
2.4"
Warranty:
1 year
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  • Dual etalon H-alpha filter
  • Dual-speed 2” Feather Touch Crayford focuser
  • Dust cover
  • Hard carrying case
  • 1.25” star diagonal with integral 12mm blocking filter
  • Clamshell mounting ring
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Lunt Solar Systems - LS60THa 60mm f/8.33 solar refractor with 12mm blocking filter and Feather Touch upgrade

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Lunt Solar Systems - LS60THa 60mm f/8.33 solar refractor with 12mm blocking filter and Feather Touch upgrade
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Our Product #: L60TDS2F
Manufacturer Product #: LS60THaDS50/B1200/FT
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This Lunt 60mm dual etalon (double stacked) solar telescope with a Feather Touch focuser upgrade provides very high resolution Hydrogen-alpha images of explosive solar flares and prominences as well as sunspot and surface features in exquisite detail . . .





. . . our 35th year