Tele Vue DeLite 9mm 62° Eyepiece - 1.25"

The DeLite Line

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.

A 20mm Eye Relief with an Adjustable Locking Eyeguard

Every DeLite has 20mm of eye relief, at the top of the 15mm to 20mm recommended for eyeglass wearers. The adjustable, locking eyeguard housing gives eyeglass wearers full eye relief in the down position.

Without glasses, grasp a grip ring in each hand and 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. An eye too far in or out causes edge darkening and field loss; take care not to unscrew the lower barrel section when rotating the housing.

Calculating True Field and Exit Pupil with the 9.6mm Field Stop

The true field of view (TFoV) your telescope delivers with the DeLite 9mm is determined by its 9.6mm field stop diameter. You can calculate it precisely with the formula: TFoV = (Eyepiece Field Stop ÷ Telescope Focal Length) × 57.3. For a telescope with a 2000mm focal length, the DeLite 9mm yields a true field of (9.6mm ÷ 2000mm) × 57.3 = 0.275°.

The exit pupil, which determines image brightness, is calculated by dividing the eyepiece focal length by the telescope's f-ratio. Tele Vue's chart gives 2.0, 1.7, 1.3, 0.9 and 0.6mm at f/4.5, f/5.2, f/7, f/10 and f/14:

• f/14 Maksutov-Cassegrain: 0.6mm exit pupil.
• f/10 Schmidt-Cassegrain: 0.9mm exit pupil, for the Moon and planets.
• f/7 Refractor: 1.3mm exit pupil, for small planetary nebulae.
• f/4.5 Dobsonian: 2.0mm exit pupil, for globular clusters.

DeLite 9mm vs. Nagler and Delos: A Field Stop Comparison

Comparisons from Tele Vue's chart:

• vs. Nagler 9mm Type 6: 82° apparent field and a 12.4mm field stop, so more sky at the same power, with 12mm of eye relief and Dioptrx with an adapter (Y*).
• vs. Delos 10mm: 72° apparent field, 12.7mm field stop, the same 20mm of eye relief, and 14.4 oz against the DeLite's 7.3 oz.

Use field stop ratios such as 1.4 or 2.0 for low and medium powers and magnification ratios for high powers. The 9mm's 9.6mm is a 1.4 step below the 13mm DeLite (13.8mm) and a factor 2 below the 18.2mm (19.1mm).

System Integration: Paracorr, Dioptrx, and Barlow Compatibility

Tele Vue's DeLite manual lists these:

• Paracorr Type-2: It eliminates the coma of Newtonians and Dobsonians, and those faster than f/5.0 see the greatest results. Its 1.15x factor makes the 9mm act like a 7.8mm.
• DIOPTRX™ Astigmatism Corrector: The DeLite is ideal for DIOPTRX (Y in the chart), which attaches and locks onto the top and corrects astigmatism in place of glasses.
• Barlows and Powermates: Tele Vue makes them in 2x, 2.5x, 3x, 4x and 5x. A 2x makes the 9mm act like a 4.5mm.
• Bandmate™ Filters: The barrel takes M28.5x0.6 filters, and the insert lists Nebustar, O-III and H-Beta.
• FoneMate™: The smartphone adapter (SFA-0001) clamps to the eyepiece for still, video or timelapse images.