Tele Vue DeLite 3mm 62° Eyepiece - 1.25"

The DeLite Philosophy: A 62° Field with 20mm of Eye Relief

Tele Vue's DeLite manual says each DeLite has 20mm of eye relief and a 62° apparent field, and that it is designed for optimum viewing whether or not you wear eyeglasses.

Drawing on Tele Vue's Delos design experience, the DeLite keeps the size and weight down while achieving the best sharpness, linearity (freedom from pincushion distortion) and ghost suppression over the entire field for any speed (f/#) telescope.

3mm Magnification: Exit Pupils from 0.7mm to 0.2mm

Magnification is the telescope's focal length divided by 3. The atmosphere usually limits planetary observing to about 300x, which this eyepiece reaches at 900mm: 160x in a TV-76 (480mm) and 200x in a TV-85 (600mm) stay under it.

Exit pupils are 0.7, 0.6, 0.4, 0.3 and 0.2mm at f/4.5, f/5.2, f/7, f/10 and f/14. Avoid exit pupils below 0.5mm in reflectors, so in reflectors it suits f/5 and faster.

• f/4.5 System: 0.7mm Exit Pupil
• f/5.2 System: 0.6mm Exit Pupil
• f/7.0 System: 0.4mm Exit Pupil
• f/10.0 System: 0.3mm Exit Pupil
• f/14.0 System: 0.2mm Exit Pupil

The Locking Eyeguard and DIOPTRX Astigmatism Correction

The adjustable, locking eyeguard housing is in two pieces and gives eyeglass wearers full eye relief in the down position. Without glasses, grasp a grip ring in each hand, twist the lower one to the left to loosen it, pull the eyeguard fully out, then slide it down while looking through the eyepiece until you just see the full field with your peripheral vision.

Note the height with the green indicator lines and lock it by twisting the lower ring to the right; be careful not to unscrew the lower barrel section. The DeLite is ideal for DIOPTRX (Y in the chart), though at exit pupils of 1mm or less, as here, you probably will not need eyeglasses at all.

Calculating True Field from the 3.2mm Field Stop

The true field, how much sky you see, depends on the field stop diameter and the telescope's focal length. The DeLite manual lists 3.2mm for the 3mm. Tele Vue's formula: True Field = (Eyepiece Field Stop ÷ Telescope Focal Length) × 57.3.

For example, in a telescope with a 1000mm focal length, the 3mm DeLite would yield a true field of (3.2mm / 1000mm) × 57.3 = 0.18 degrees. That suits planets, double stars and small lunar regions.

System Integration: Paracorr, Powermates, and Bandmate Filter Compatibility

Its 1¼" barrel takes M28.5x0.6 filters, and the DeLite manual lists BandMate filters and the FoneMate smartphone adapter (SFA-0001), which clamps to the eyepiece for still, video or timelapse images.

Tele Vue's Paracorr Type-2 eliminates the coma of Newtonians and Dobsonians; those faster than f/5.0 see the greatest results. Its 1.15x factor makes the 3mm act like a 2.6mm. Tele Vue's Barlows and Powermates (2x to 5x) add more power than the atmosphere usually allows with a 3mm eyepiece.

DeLite 3mm vs. Delos 3.5mm and Nagler Zoom 3-6mm

Comparisons from Tele Vue's chart:

• vs. Delos 3.5mm: 72° apparent field and a 4.4mm field stop, with the same 20mm of eye relief; it weighs 17.6 oz against the DeLite's 7.8 oz.
• vs. Nagler Zoom 3-6mm: The Nagler Zoom provides the flexibility of multiple focal lengths in one eyepiece. It has a 50° field, 10mm of eye relief and no Dioptrx (N); the DeLite 3mm has 62°, 20mm and Dioptrx (Y).