LS50THa 50mm f/7 refractor, 6mm blocking filter, Pressure Tuning

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This Lunt L50T600 50mm Hydrogen-alpha solar refractor with Pressure Tuning is an economical new approach to serious high resolution Hydrogen-alpha solar viewing and imaging. It has an internal True Doppler Tuning (Pressure Tuning) system that allows you to shift the scope's passband to either side of the H-Alpha band. This lets you emphasize 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, a turn or two of the Pressure Tuning mechanism built into side of the filter lets you gradually 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 L50T600 consists of a 350mm focal length 50mm aperture f/7 refractor with a helical focuser and an integrated Hydrogen-alpha solar filter. The two-part filter consists of a Pressure Tuned etalon built into the rear of the scope body 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. The scope’s achromatic cemented doublet objective lens is fully multicoated for high light transmission.

The internal H-alpha filter has a <0.75 Ångstrom passband, centered on the 6562.8 Ångstrom H-alpha line. This 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. A separate double stack filter module is available as an option to reduce the scope's passband to <0.5 Ångstrom to show you even more surface detail and contrast.

The Sun's disk at prime focus in the scope is 3.5mm in diameter. The 4mm blocking filter version of the scope (our #L60T400) provides a full disk image visually. However, if you are planning on DSLR imaging, this 6mm clear aperture blocking filter version of the LS50THa is needed to get a full disk image.

You can use virtually any 1.25” eyepieces with this 50mm Lunt solar refractor. A typical 15mm 1.25” Plössl will give you a magnification of 23.3x and a little over a 2.1° field of view compared with the 0.5° diameter disk of the Sun, giving you plenty of dark sky background around the solar disk to show off the prominences.. A 9mm Plössl will give you 43.3x and about a 1.15° field for more close-up views of prominences and disc features.

This Lunt L50T600 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 for transporting and storing your Lunt scope is optional, as is a safe solar finder that mounts on the clamshell ring.
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.

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.

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.

2.32 arc seconds
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.
Telescope Type:
The optical design of a telescope.  Telescope type is classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, or by the task they perform.
1 year
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LS50THa 50mm f/7 refractor, 6mm blocking filter, Pressure Tuning

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LS50THa 50mm f/7 refractor, 6mm blocking filter, Pressure Tuning
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Our Product #: L50T600
Manufacturer Product #: LS50THa/B600PT
Price: $949.00  FREE ground shipping - Click for more info
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Clear skies,

This Lunt 50mm solar telescope has a 6mm blocking filter and True Doppler Tuning (Pressure Tuning) to give you economical high resolution visual and DSLR Hydrogen-alpha images of explosive solar flares and prominences as well as sunspot and surface features in exquisite detail.

. . . our 38th year