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Applying their solar-viewing experience and technologies to a nighttime scope, Lunt Solar Systems created the 4" / 102mm f/6.6 ED Doublet Refractor. It employs extra-low dispersion (ED) glass with a doublet lens system to correct for chromatic aberration to virtually eliminate color fringing and comas. Further enhancing the optical properties of the scope are fully multicoated optics that increase light transmission to create bright and clear images. Its 4" aperture and 714mm focal length produce a respectable f/6.6 focal ratio, making it an ideal scope for observing and imaging near-space objects such as the Moon and planets, and brighter deep-sky objects like nebulae, galaxies, and globular clusters.
To ensure users can achieve tack-sharp images, Lunt outfitted the scope with a 2" Crayford-style focuser. Unlike a traditional rack-and-pinion focuser, the Crayford-style uses a steel rod held tightly against the drawtube to provide a toothless friction system that eliminates backlash and enables ultra-fine precision focusing. It features a larger coarse-focus knob and a smaller micro-focusing knob with a 10:1 reduction for ultra-fine focusing capabilities. To expand the usability of the OTA, a 2"-to-1.25" adapter is included for the focuser allowing for a wider array of eyepieces and accessories.
The scope is offered here without a mount or tripod, but can be easily mounted with the addition of an optional Vixen or Losmandy-style dovetail plate. Holes on the top of the OTA provide a mounting point for a user-supplied finderscope.
4" / 102mm aperture
f/6.6 focal ratio
714mm focal length
Doublet refractor optical path
Anti-reflection fully multicoated optics
Extra-low dispersion (ED) glass
Corrects for chromatic aberration by focusing all wavelengths to the same point, eliminating color fringing - especially at high magnifications
2" diameter drawtube with 1.25" adapter
Coarse-focus knob, 10:1 fine-focus knob
Crayford focusers use a toothless friction system that allows for super-fine precision focusing without backlash
Brass compression ring to protect eyepieces and accessories
Etched focusing scale for precise repeatability
1.65" (4.19cm) focus travel
Requires user-supplied mount and tripod
Mounting holes on bottom for plate
Mounting holes on top of OTA for finderscope bracket
In the Box
Lunt Solar Systems 4" / 102mm f/6.6 ED Doublet Refractor (OTA Only)
Foam-Lined Carry Case
Limited Five-Year Warranty
Table of Contents
4" / 102 mm
Eyepiece Barrel Diameter
2" directly to focuser 1.25" with included adapter