Lunt 80mm H-Alpha Solar Telescopes

For the advanced solar observer Lunt offer this ED refractor with an aperture of 80 mm and 560 mm focal length, of course fully unobstructed. The H-alpha telescope is equipped as standard with the air-pressure tuning system “Pressure Tuner”, whereby the internal Etalon achieves a bandwidth of <0.7 Angstrom. The telescope has both a 1/4”-20 connection for photo-tripods, and a dovetail plate for astronomical mounts. A Sol-Searcher, a zoom-eyepiece, and a transport case are also included.

Like the smaller LS60THa this telescope is available alternatively with different blocking filters (B1200 or B1800), and with standard Crayford or Feather Touch focuser.

This telescope is already prepared for the new double stack system DSII from Lunt Solar Systems. The DSII eliminates the need for an external front mounted filter for double stacking. In this system both Etalons are internally installed in the telescope, and both Etalons are equipped with the tuning system “Pressure Tuner”!

What is the „Pressure Tuner“ system?

The air pressure of the atmosphere varies, depending on if you are at sea level or on a mountain. Unfortunately also the sensitive Etalon filter systems respond to these air pressure variations. The wavelength range that is allowed through the filters, shifts as a function of the air pressure. This shifting is indeed minimal, but at bandwidths of less than one Angstrom it is already clearly visible. If the filter is not adjusted precisely to the H-alpha wavelength, the image of the sun through the telescope degrades, prominences and surface details are no longer visible.

Therefore, the Etalon filter systems have to be adjusted to the prevailing air pressure at the observation location. This “Tuning” called adjustment is typically done by a mechanical tilting of the filter. At sizes of a few Angstrom, it is obviously not easy to achieve the exact adjustment by mechanical tilting. And because the filter is no longer perfectly straight in the beam path, but slightly oblique, there may also be optical failures.

The new air-pressure system “Pressure Tuner” by Lunt Solar Systems takes a different path. The Etalon filter will not be tilted to only simulate a balance to the air pressure, but the air pressure in the filter system is in fact adapted by 100 percent to the real external air pressure. Thereafter the air surrounding the Etalon can simply be compressed or decompressed by the tuning system in order to change the air pressure between the surfaces. This allows the Etalon surfaces to always remain at the same perfect angle to the light waves but changes the diffractive index of the air in the chamber and thus accomplishes the same tuning expect that it goes around + or - 0.4 Angstrom on either side of the centerline. Therefore, the patent-pending “Pressure Tuner” system from Lunt Solar Systems is also called “True Doppler Tuning”, and it achieves much better results than conventional tuning systems.
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