Tele Vue Delos 14mm 72° Eyepiece - 1.25"

The Delos 14mm: A 72° Field for Any Focal Ratio

The Delos series was developed from Tele Vue's experience with the Ethos line, and it keeps size and weight down while achieving sharpness, linearity (freedom from pincushion distortion) and ghost suppression over the entire field for any speed (f/#) telescope. In Tele Vue's range the 72° Delos sits between the 68° Panoptic and the 82° Nagler.

Field Geometry: Understanding the 17.3mm Field Stop and True Field

An eyepiece's true field of view (how much sky it actually shows) is determined by its field stop diameter and the telescope's focal length. The Delos 14mm has a 17.3mm field stop, which is the physical aperture inside the eyepiece that defines the edge of the view. You can calculate the true field in degrees using Tele Vue's formula: True Field = (Eyepiece Field Stop ÷ Telescope Focal Length) x 57.3.

For example, in a telescope with a 1200mm focal length, the Delos 14mm would yield a true field of (17.3mm / 1200mm) x 57.3 = 0.83 degrees. That frames the Hercules Globular Cluster (M13) or the Dumbbell Nebula (M27) with sky around them.

Magnification & Exit Pupil: The 14mm Delos at f/4.5, f/7, and f/10

The 14mm focal length provides a versatile medium-to-high magnification for most telescopes. 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 3.1, 2.7, 2.0, 1.4 and 1.0mm at f/4.5, f/5.2, f/7, f/10 and f/14.

• At f/4.5 (Fast Dobsonian): The exit pupil is 3.1mm, for bright views of nebulae and galaxies.
• At f/7 (Apochromatic Refractor): The exit pupil is 2.0mm, suited to globular clusters and observing detail in brighter planetary nebulae.
• At f/10 (Schmidt-Cassegrain): The exit pupil is 1.4mm, which darkens the sky background; for planetary detail most observers go to higher power.

Ergonomics: 20mm of Eye Relief and the Locking Eyeguard

Every 1¼" Delos has 20mm of eye relief. The Delos is designed for optimum viewing whether or not you wear eyeglasses, with full eye relief for eyeglass wearers when the eyeguard housing is down, and the generous eye relief also minimizes eye lens fogging in cold weather.

To manage this long eye relief, the Delos has an adjustable, locking eyeguard housing. By twisting the lower grip ring, you can slide the housing up or down to find the height where you just see the full field. Green indicator lines on the barrel help you note your preferred setting. Once set, you can lock it in place, and the system minimizes extraneous outside light.

Sharpness, Linearity and Ghost Suppression

Tele Vue's own words: the Delos achieves "the best sharpness, linearity (freedom from pincushion distortion) and ghost suppression over the entire field for any speed (f/#) telescope." Linearity means straight lines stay straight across the field.

Tele Vue does not publish the glass, coatings or element count of the Delos.

System Integration: Pairing with Paracorr, Barlows, and Powermates

For owners of fast Newtonian and Dobsonian reflectors (f/5 or faster), mirror coma makes off-centre stars look like little comets. The Tele Vue Paracorr Type-2 eliminates it, with the greatest results in scopes faster than f/5.0. The Paracorr acts as a 1.15x amplifier, effectively turning the 14mm Delos into a 12.2mm eyepiece.

To increase magnification for planetary observing, the Delos 14mm can be used with Tele Vue's Barlows and Powermates. A 2x Powermate transforms it into a high-power 7mm eyepiece, while a 3x Barlow yields a 4.7mm equivalent, for steady nights on the planets.

Delos 14mm vs. Ethos 13mm: Field Stop, Eye Relief, and Immersion

Within the Tele Vue lineup, the main trade-off between the Delos 14mm and its wider-field siblings is apparent field against eye relief.

• vs. Ethos 13mm (100°): The Ethos provides a 100° field with a larger 22.3mm field stop, showing more true field. However, the Delos 14mm counters with 20mm of eye relief versus the Ethos's 15mm, which suits eyeglass wearers.
• Field Stop Framing: Build an eyepiece set based on field stop increments. The Delos 14mm (17.3mm field stop) and Ethos 13mm (22.3mm field stop) represent two distinct steps in this methodology. The Delos provides higher magnification for a given true field size, often preferred for resolving detail within an object, while the Ethos frames that object within more surrounding sky.

Accessory Ecosystem: Dioptrx, FoneMate, and BandMate Filters

The Delos manual lists these Tele Vue accessories:

• Dioptrx Ready: The Delos is ideal for Tele Vue's Dioptrx astigmatism corrector, which locks onto the top of the eyepiece and is always completely aligned to the eyepiece optics, unlike eyeglasses.
• FoneMate Compatible: You can attach the Tele Vue FoneMate smartphone adapter to capture images and videos through the eyepiece, still, video or timelapse.
• BandMate Filters: The eyepiece has 1¼" filter threads. BandMate Nebustar, OIII and H-beta filters make nebulae "pop out" by passing select wavelengths and darkening the sky.