TeleVue Plössl 32mm 50° Eyepiece - 1.25"

The 27mm Field Stop: Maximizing the 1.25" Format

The true field, the circle of sky you see, depends on the field stop diameter and the telescope's focal length. The 32mm Plössl's 27mm field stop is the 1¼" maximum in Al Nagler's guide, shared with the 40mm Plössl and 24mm Panoptic.

You can calculate the true field of view (TFoV) for your telescope using Tele Vue's formula: TFoV = (Eyepiece Field Stop ÷ Telescope Focal Length) x 57.3. For an 8" f/10 Schmidt-Cassegrain with a 2032mm focal length, the 32mm Plössl yields a true field of (27mm ÷ 2032mm) x 57.3 = 0.76 degrees. This is wide enough to frame the entire full Moon, which is about 0.5 degrees across, with room to spare.

Design and Fast Reflectors

The 32mm Plössl has 4 elements in 2 groups; Al Nagler's guide gives Plössls a 50° apparent field.

For observers with fast Newtonian or Dobsonian reflectors (f/5 or faster), coma can soften stars at the edge of the field. Tele Vue's Paracorr Type-2 eliminates coma, and scopes faster than f/5.0 see the greatest results. It has a 1.15x magnification factor, so the 32mm acts like a 27.8mm.

• Higher Powers: Tele Vue makes Barlows and Powermates in 2x, 2.5x, 3x, 4x and 5x. A 2x makes the 32mm act like a 16mm.
• Nebula Observation: It takes 1¼" filters (M28.5x0.6), and Tele Vue's insert lists BandMate Nebustar, O-III and H-Beta, which pass select wavelengths and darken the sky so nebulae "pop out".

22mm Eye Relief and 6.2 oz Weight: Comfort and Compatibility

The 32mm Plössl has 22mm of eye relief, more than the 15mm to 20mm recommended for observers who wear glasses to correct astigmatism. It accepts DIOPTRX (Y in the chart), which locks onto the top; you're more likely to see a sharper, higher contrast image with it than with eyeglasses. It also accepts the Eyeguard Extender (EGE-0020), which raises the eyeguard by 8mm and can be stacked.

It weighs 6.2 oz (176 g) and has an optical length of 2.8" (71 mm). Do not unscrew the chrome barrel! The lenses will fall out, voiding the warranty.

Calculating Exit Pupils from 7.1mm to 2.3mm for Your Telescope

The exit pupil, calculated as Eyepiece Focal Length ÷ Telescope f-ratio, determines the brightness of the image background. Tele Vue's chart gives:

Avoid exit pupils above 7mm in reflectors; light that misses your eye's pupil is lost.

• Fast Reflector (f/4.5): 7.1mm exit pupil, at the 7mm limit for reflectors.
• Dobsonian (f/5.2): 6.2mm exit pupil.
• Apochromatic Refractor (f/7): 4.6mm exit pupil.
• Schmidt-Cassegrain (f/10): 3.2mm exit pupil.
• Maksutov-Cassegrain (f/14): 2.3mm exit pupil.

TeleVue 32mm Plössl vs. 40mm Plössl: A 27mm Field Stop Comparison

Both have a 27.0mm field stop in Tele Vue's chart, so they show the same sky in a given telescope.

Al Nagler's guide notes that for each field stop size, shorter focal lengths with larger apparent fields show more detail and fainter stars, with a smaller exit pupil. The 32mm has a 50° field against the 40mm's 43°.

• 32mm Plössl Advantage: More magnification, a darker sky background and a 50° apparent field.
• 40mm Plössl Advantage: Lower magnification and a larger exit pupil (e.g., 4.0mm vs. 3.2mm in an f/10 scope). It has 28mm of eye relief against 22mm.