This Lunt LS60THa/B600CPT Pressure Tuning 60mm solar refractor represents an economical new approach to serious high resolution Hydrogen-alpha solar viewing. It has a True Doppler Tuning (Pressure Tuning) system that allows you to shift the scope's passband to either side of the H-Alpha band. This emphasizes features that are moving either towards or away from you, adding a 3D-like component to your viewing.
Pressure tuning has a minimal effect on prominences, due to their being at the edge of the disk, but it clearly improves your view of filaments and active regions on the surface. While looking at a filament at the center of the Sun, for example, you have the ability to Doppler shift from the base of the filament to the tip. You can follow the filament thru its structure toward you and away from you. This allows for enhanced visual and imaging capability for the observer as well as a research tool for the avid hobbyist.
This Lunt LS60THa/B600CPT consists of a 500mm focal length 60mm aperture f/8.33 refractor with an integrated Hydrogen-alpha solar filter. The two-part filter uses an internal etalon behind the objective lens and a 6mm blocking filter built into the standard equipment 1.25” star diagonal. There is also an infrared reflecting window (Energy Reflecting Filter or ERF) in the optical path to remove unwanted heat from the system. A turn or two of the Pressure Tuning mechanism built into side of the system lets you center the passband precisely on the H-alpha line for maximum contrast, as well as quickly perform off-band observations of Doppler-shifted disk features.
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 and all other portions of the visible spectrum are filtered out. 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 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.
The filter has a <0.75 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. The filter is thermally stable, so there is no drifting off the H-alpha line as the filter heats up during use.
The 6mm clear aperture of the blocking filter portion of the H-alpha system in the star diagonal is ideally matched to the focal length of the telescope for visual observing of the approximately 4.5mm diameter prime focus full disk image of the Sun. While this 6mm blocking filter aperture is well suited for visual observing, DSLR imagers will get better results with the larger 12mm aperture blocking filter used in the Lunt #L60T12P, as will those observers using a binoviewer.
This Lunt LS60THa/B600CPT uses a dual-speed Crayford focuser with 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” eyepieces with this 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.
This Lunt LS60THa/B600CPT 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 with slow motion controls for easier extended observing and tracking of the Sun. A foam-lined hard case is standard equipment for transporting and storing your Lunt scope.