Tele Vue DeLite 5mm 62° Eyepiece - 1.25"

DeLite Optical Design: A 62° Field with 20mm of Eye Relief

Each DeLite has 20mm of eye relief and a 62° apparent field. Based on Tele Vue's Delos design experience, it 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.

20mm of eye relief is at the top of the 15mm to 20mm recommended for observers who wear glasses to correct astigmatism, and it minimizes eye lens fogging in cold weather. At exit pupils of 1mm or less you probably will not need glasses, and this eyepiece gives 1.1mm or less in every telescope in the chart.

The Adjustable Locking Eyeguard

The adjustable, locking eyeguard housing is in two pieces. In the down position it gives eyeglass wearers full eye relief; an eye too far in or out causes edge darkening and field loss.

To adjust, you simply grasp the upper and lower rubber grip rings and twist the lower ring to the left to loosen the assembly. Without glasses, pull it 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 when rotating the housing.

True Field and Exit Pupil from f/4.5 to f/14

The true field of view (TFoV) your telescope delivers with the DeLite 5mm depends on your instrument's focal length. You can calculate it by dividing the eyepiece's 5.3mm field stop diameter by your telescope's focal length in mm, then multiplying by 57.3. For example, in a refractor with a 700mm focal length, the TFoV would be (5.3 / 700) * 57.3 = 0.43 degrees.

The exit pupil, which determines image brightness, is calculated by dividing the 5mm focal length by your telescope's f-ratio. Tele Vue's chart gives 1.1, 1.0, 0.7, 0.5 and 0.4mm at f/4.5, f/5.2, f/7, f/10 and f/14:

• At f/4.5 (Fast Dobsonian): 1.1mm exit pupil, for double stars and planets.
• At f/7 (Apochromatic Refractor): 0.7mm exit pupil, for the Moon.
• At f/10 (SCT): 0.5mm exit pupil, the smallest advisable in reflectors and a power few nights support.
• At f/14 (Maksutov-Cassegrain): 0.4mm exit pupil, below 0.5mm and more power than most nights allow.

System Integration: Use with Dioptrx, Paracorr, and Powermates

Tele Vue's DeLite manual lists these:

• Dioptrx Ready: The DeLite is ideal for DIOPTRX (Y in the chart), which locks onto the top and corrects astigmatism in place of glasses.
• Paracorr for Fast Reflectors: 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 5mm act like a 4.3mm.
• Barlows and Powermates: Tele Vue makes them in 2x, 2.5x, 3x, 4x and 5x. With a 5mm eyepiece they mostly suit short telescopes: a 2x in a TV-76 (480mm) gives 192x.
• Filters and Imaging: The barrel takes M28.5x0.6 filters, and the insert lists BandMate filters. The FoneMate smartphone adapter (SFA-0001) clamps to the eyepiece for still, video or timelapse images.

DeLite 5mm vs. Delos 4.5mm and Nagler 5mm

Comparisons from Tele Vue's chart:

• vs. Tele Vue Delos 4.5mm: 72° apparent field, 5.6mm field stop and the same 20mm of eye relief; it weighs 17.6 oz against the DeLite's 7.5 oz.
• vs. Tele Vue Nagler 5mm Type 6: 82° apparent field and a 7.0mm field stop, so more sky at the same power, with 12mm of eye relief and Dioptrx with an adapter (Y*).

For high powers, choose eyepieces by magnification ratios rather than field stops. Aim for at least 150x for planetary and double star work and no more than about 300x, the usual atmospheric limit. In a 1000mm telescope the DeLite 5mm gives 200x.