Tele-Vue Panoptic 41mm - Used

A 46mm Field Stop: The Maximum True Field in a 2-inch Barrel

The fundamental limit on an eyepiece's true field of view (TFoV) is its field stop, the internal metal ring that defines the edge of the view. The Panoptic 41mm has a 46mm field stop, the maximum for 2" eyepieces; Tele Vue's 55mm Plössl shares it. The true field of both is the largest possible in a 2-inch barrel eyepiece.

You can calculate the true field for your specific telescope using the formula: TFoV = (Eyepiece Field Stop ÷ Telescope Focal Length) × 57.3. For an SCT with a 2800mm focal length, the Panoptic 41mm yields a true field of (46 ÷ 2800) × 57.3 = 0.94°, nearly two full Moons across, enough for the Lagoon Nebula's (M8) bright core with room around it.

9.1mm to 2.9mm Exit Pupils: Performance from f/4.5 to f/14

An eyepiece's exit pupil determines image brightness and is critical for matching the optic to your telescope and observing conditions. The Panoptic 41mm produces a range of exit pupils suited for various instruments, from a very large 9.1mm on a fast f/4.5 Dobsonian to a more moderate 2.9mm on a slow f/14 Maksutov-Cassegrain. Tele Vue's chart gives 9.1, 7.9, 5.9, 4.1 and 2.9mm at f/4.5, f/5.2, f/7, f/10 and f/14.

Avoid exit pupils larger than 7mm in reflecting telescopes; refractors have no upper limit. In an f/4.5 or f/5.2 reflector the 41mm exceeds that 7mm, so a shorter eyepiece suits those telescopes better. The eyeguard also helps minimize "pupil shadowing".

27mm Eye Relief for Eyeglass and Dioptrx Use

With 27mm of eye relief, more than the 15mm to 20mm suggested for eyeglass wearers, the Panoptic 41mm suits observers who wear glasses. Eyeglass wearers can completely unscrew and remove the eyeguard housing for maximum eye relief. The Adjustable Height Eyeguard Adapter positions your eye in the exit pupil and reduces stray light; its soft rubber eyeguard can be used extended, rolled back or removed.

The 41mm accepts Tele Vue's Dioptrx, which locks onto the top of the eyepiece and replaces glasses for astigmatism. Astigmatism is likely to be visible with long focal length eyepieces that produce large exit pupils. Dioptrx comes in ¼ to 3½ diopter.

Panoptic 41mm vs. Plössl 55mm and Nagler 31mm

• vs. Tele Vue 55mm Plössl: Both have a 46.0mm field stop and show the same true field. The 55mm gives lower power and a larger exit pupil, useful in slow telescopes, with 38mm of eye relief. The 41mm gives more magnification across a 68° field; for a given field stop, the shorter focal length and wider apparent field show more detail and fainter stars.
• vs. Tele Vue 31mm Nagler: The 31mm Nagler has an 82° apparent field and a 42.0mm field stop, so it shows slightly less sky, with 19mm of eye relief. The Panoptic has 27mm of eye relief and weighs 33.6 oz against the Nagler's 2.2 lbs.

Handling and Care

The Tele Vue Panoptic 41mm weighs 33.6 oz (2.10 lb) and has 6 elements in 4 groups, with multi-coatings and blackened lens edges. Do not unscrew the chrome barrel, or the lenses will fall out.

Clean the eyelens only when necessary. Unscrew the eyeguard housing completely for access. Use a bulb-type puffer to blow off loose dust, then clean the surface with a gently moistened (not soaked) Q-Tip in a circular motion. Never pour liquid directly on the lens: capillary action can carry it into the eyepiece and dissolve the lens edge blackening.

A Note on Used Condition

This Tele Vue Panoptic 41mm is a used eyepiece in really good condition. It comes with its two dust caps and its original Tele Vue boxes, and offers the same views as a new one at a lower price. This used eyepiece is sold without warranty.