Tele Vue Delos 6mm 72° Eyepiece - 1.25"

The Delos 6mm: A 72° Window for High-Power Observing

Tele Vue's Ethos design experience made it possible to keep Delos size and weight down. Each Delos model in the instruction sheet has 20mm of eye relief with a 72° apparent field. At high power a wider field keeps an object in view longer in a telescope without a drive, such as a Dobsonian.

The Delos achieves sharpness, linearity (freedom from pincushion distortion) and ghost suppression over the entire field for any speed (f/#) telescope.

Calculating True Field: The 7.6mm Field Stop in Practice

An eyepiece's true field of view (TFoV), how much sky it actually shows, is determined by its field stop diameter and the focal length of the telescope. The Tele Vue Delos 6mm has a 7.6mm field stop. To calculate the true field, you use Tele Vue's formula:

True Field (°) = (Eyepiece Field Stop in mm ÷ Telescope Focal Length in mm) x 57.3

For example, in a telescope with a 1200mm focal length, such as an 8" f/6 Dobsonian, the Delos 6mm yields a true field of 0.36° at 200x, a power for Jupiter and close double stars.

Exit Pupil Performance: From a 1.3mm Pupil at f/4.5 to 0.4mm at f/14

The exit pupil is the beam of light that leaves the eyepiece, and its size is critical for matching the eyepiece to your telescope and observing goals. The Delos 6mm gives small exit pupils, for high-power viewing. The exit pupil is calculated as: Eyepiece Focal Length ÷ Telescope f/#.

Tele Vue provides precise exit pupil data for the Delos 6mm across a range of common telescope speeds:

• f/4.5 Telescope: 1.3mm exit pupil
• f/5.2 Telescope: 1.2mm exit pupil
• f/7 Telescope: 0.9mm exit pupil
• f/10 Telescope: 0.6mm exit pupil
• f/14 Telescope: 0.4mm exit pupil

With exit pupils from 1.3mm down to 0.4mm, the Delos 6mm is a high-power eyepiece in any of these telescopes; below about 0.5mm, steady seeing matters most.

Comfort at High Power: 20mm Eye Relief and the Locking Eyeguard

The Delos is designed for optimum viewing whether or not you wear eyeglasses; with the eyeguard housing down, eyeglass wearers get the full 20mm of eye relief. The generous eye relief also minimizes eye lens fogging from eye moisture in cold weather.

To manage this eye relief, the Delos 6mm has an adjustable, locking eyeguard housing. An eye too far in or too far out causes edge darkening and field loss. To use it:

• To Adjust: Grasp the upper and lower rubber grip rings and twist the lower ring to the left to loosen the housing. Without glasses, slide it fully out, then down while looking through the eyepiece until you just see the full field with your peripheral vision.
• To Lock: While holding both grip rings, twist the lower ring to the right to lock the position. You can use the green indicator lines on the inner barrel to note your preferred setting for quick setup in the future.

Sharpness and Linearity at Any f/#

Tele Vue's design goal for the Delos is sharpness over the entire field for any speed (f/#) telescope. A fast Newtonian's own coma still needs a corrector (see below).

Linearity means freedom from pincushion distortion, so straight lines stay straight and objects keep their shape as they drift toward the edge. Ghost suppression is also among the Delos design goals.

Achieving Higher Powers with Barlows & Paracorr 1.15x

The Delos 6mm can be paired with Tele Vue's Barlows and Powermates to reach even higher magnifications, which is practical only on nights of very steady seeing. A 2x Barlow would turn the 6mm into a 3mm eyepiece, doubling the power for critical study of planetary details or splitting extremely close double stars.

Fast Newtonians show coma, which no eyepiece removes. The Tele Vue Paracorr Type-2 eliminates it, with the greatest results in scopes faster than f/5.0. Its 1.15x magnification factor makes the Delos 6mm act like a 5.2mm eyepiece.

Astigmatism Correction: DIOPTRX Compatibility for the Sharpest View

The 20mm eye relief leaves room for glasses. The Delos is also ideal for Tele Vue's DIOPTRX astigmatism corrector, available from ¼ to 3½ diopter.

DIOPTRX attaches and locks onto the top of the eyepiece, so you observe without your glasses. Its benefits:

• Perfect Alignment: DIOPTRX is always completely aligned to the eyepiece optics, and it rotates to match your astigmatic axis.
• Coatings: DIOPTRX likely has better multi-coatings than eyeglasses.
• Enhanced Contrast: DIOPTRX allows your normal maximum contrast, which eyeglasses can diminish.

Delos 6mm vs. The Field: Building a Tele Vue Eyepiece Set

Comparisons from Tele Vue's chart:

• Delos 6mm vs. Ethos 6mm: The 6mm Ethos has a 100° apparent field and a 10.4mm field stop, with 15mm of eye relief. The Delos 6mm has 20mm of eye relief and a 7.6mm field stop.
• Delos 6mm vs. Nagler 5mm (Type 6): The 5mm Nagler has an 82° field, a 7.0mm field stop and 12mm of eye relief, and needs an adapter for Dioptrx (Y*). The Delos 6mm has 20mm of eye relief and is Dioptrx ready (Y).

Choose low and medium power eyepieces in ratios of field stop diameter, such as 1.4 or 2.0, and higher power eyepieces in ratios of magnification. The Delos 6mm is a high-power eyepiece, so step to it by magnification: from the 8mm Delos it is 1.33x more power, and the 4.5mm Delos is 1.33x more again.