Tele Vue Nagler T7 14mm 82° Eyepiece - 2"

The "Spacewalk" View, Now with 19mm of Eye Relief

The original 13mm Nagler was the first eyepiece to give well-corrected wide "spacewalk" views with an 82° apparent field. If you have been waiting for a Nagler series for eyeglass wearers, the Type 7 is it.

Observers who wear glasses to correct astigmatism should look for 15mm to 20mm of eye relief, and the Type 7 has 19mm. The generous eye relief also minimizes eye lens fogging from eye moisture in cold weather.

Calculating True Field with the 20.5mm Field Stop

While the apparent field determines the immersive quality of the view, the eyepiece's 20.5mm field stop diameter determines the actual patch of sky you see. You can calculate the true field of view (TFoV) in your specific telescope using Tele Vue's formula: TFoV = (Eyepiece Field Stop ÷ Telescope Focal Length) x 57.3.

• Example 1 (Dobsonian): In a 10-inch f/5 Dobsonian with a 1250mm focal length, the Nagler T7 14mm yields a true field of (20.5mm ÷ 1250mm) x 57.3 ≈ 0.94°. That holds the Hercules Cluster (M13) with plenty of sky around it.
• Example 2 (SCT): In an 8-inch f/10 SCT with a 2032mm focal length, the true field is (20.5mm ÷ 2032mm) x 57.3 ≈ 0.58°. Room for the Whirlpool Galaxy (M51) and its companion.

Magnification & Exit Pupil from f/4.5 to f/14

The exit pupil, the beam of light leaving the eyepiece, sets image brightness.

Tele Vue's chart gives:

• f/4.5 Telescope: 3.1mm exit pupil, for nebulae under dark skies.
• f/5.2 Telescope: 2.7mm exit pupil, for galaxies and star clusters.
• f/7 Telescope: 2.0mm exit pupil, for globular clusters.
• f/10 Telescope: 1.4mm exit pupil, for planetary nebulae and double stars.
• f/14 Telescope: 1.0mm exit pupil, for double stars and planets.

Eyeglass & DIOPTRX Use: 19mm of Relief and the Adjustable Eyeguard

The Type 7 is designed for optimum viewing whether or not you wear eyeglasses. The adjustable, locking eyeguard is there for observers who don't: it helps position your eye at the exit pupil so you don't get too close to the eyelens.

Twist the lower grip ring to the left to loosen the two-piece housing, 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 on the green indicator lines and twist the lower ring to the right to lock it. This also blocks contrast-robbing stray light.

• DIOPTRX Ready: The Type 7 is ideal for DIOPTRX, and the chart marks the 14mm Dioptrx ready (Y). DIOPTRX is always completely aligned to the eyepiece optics, so you're more likely to see a sharper, higher contrast image than through glasses.

Parfocality

Nagler Type 7 eyepieces are parfocal with each other when used in 2" mode, so the 14mm and the other Type 7s need little or no refocusing when swapped.

They are also parfocal with most other 1¼" Tele Vue eyepieces when those eyepieces are used in the Tele Vue Hi-Hat 1¼" to 2" adapter (ASF-8125).

Performance in Fast Newtonians with Paracorr Type-2

Newtonian and Dobsonian telescopes show coma, which makes off-center stars look like little comets. No eyepiece removes it; the Tele Vue Paracorr Type-2 eliminates it, and scopes faster than f/5.0 see the greatest results.

The Paracorr goes into your 2" focuser like a Barlow and has a 1.15x magnification factor, so the 14mm acts like a 12.2mm. The Type-2 lets an f/3 parabolic mirror perform like an f/12 without it.

Reaching Higher Powers with Barlows & Powermates

Al Nagler's guide suggests choosing a long focal length eyepiece with comfortable eye relief and using image amplifiers to increase power. Tele Vue makes Barlows and Powermates in 2x, 2.5x, 3x, 4x and 5x.

A 2x Barlow effectively turns the 14mm into a 7mm eyepiece, doubling the magnification for planetary observing. A 4x Powermate makes it act like a 3.5mm.

The Nagler T7 14mm in Context: Choosing Your Tele Vue Eyepiece

Comparisons from Tele Vue's chart:

• vs. Nagler T6 13mm: The 13mm Type 6 has a 1¼" barrel, a 17.6mm field stop and 12mm of eye relief, and needs an adapter for Dioptrx (Y*). The T7 14mm has 19mm of eye relief and the larger 20.5mm field stop.
• vs. Delos 14mm: The 14mm Delos has 20mm of eye relief, a 72° apparent field and a 17.3mm field stop, in a 1¼" barrel. The Nagler T7 14mm shows more sky with its 82° field and 20.5mm field stop.
• Building a Set: Choose uniform steps in field stop. From the 31mm Nagler's 42mm, a factor of 2 lands near the 14mm's 20.5mm, and the next step near 10mm.

Build, Accessories, and Lifetime Warranty

The Nagler T7 14mm weighs 1.23 lbs (556 g) and has a 2" barrel. Do not remove the chrome barrel, to avoid getting dust and dirt into the eyepiece. It comes with top and bottom dust caps.

Tele Vue accessories for the Type 7:

• Filter Compatibility: Tele Vue's BandMate Nebustar, O-III and H-Beta nebula filters, which pass select wavelengths and darken the sky.
• Smartphone Imaging: The Type 7 table marks the 14mm Y for FoneMate, Tele Vue's smartphone adapter for still, video or timelapse images.
• Warranty: Like all Tele Vue eyepieces, the Nagler T7 14mm is covered by a Lifetime Limited Warranty against defects in material or workmanship.