A short-focal-length eyepiece usually asks you to give something up. You get the magnification you want, but often with tighter eye relief, a smaller viewing window, or an eyepiece that simply becomes less comfortable the longer you use it.
The Tele Vue 5.5mm Nagler Type 7 takes a different approach. It combines the high magnification of a 5.5mm eyepiece with an expansive 82° apparent field and 19mm of eye relief, giving you a high-power view that still feels open and relaxed. For observers who wear glasses, that long eye relief may be the most important feature of all. For everyone else, it simply makes high-power observing easier to settle into.
The Type 7 design was developed as a natural extension of Tele Vue's limited-production Apollo 11 eyepiece, with the goal of carrying its full-field sharpness, contrast, distortion control, and comfortable eye placement into an eyeglass-friendly Nagler series. In the 5.5mm, that philosophy is aimed squarely at the Moon, planets, double stars, globular clusters, planetary nebulae, and any other target that rewards magnification.
High Power Without the Tunnel
One of the pleasures of using an 82° eyepiece at high magnification is that the object doesn't feel trapped inside a narrow field. The Moon has room around it. Jupiter and Saturn remain surrounded by enough sky to make the view feel natural. Globular clusters can fill the center of the field without the edges closing in around them.
That wide apparent field is particularly useful in a manually tracked Dobsonian. At high power, objects move through the eyepiece quickly. An 82° field gives you more observing time between nudges, which means more time studying the target and less time repositioning the telescope.
The exact magnification depends on your telescope. Divide the telescope's focal length by 5.5mm to find the power. In a 1200mm telescope, for example, the 5.5mm produces about 218×. In a 700mm refractor, it produces about 127×. That makes the same eyepiece a very different tool depending on the instrument behind it.
19mm of Eye Relief
The 5.5mm Type 7 provides 19mm of eye relief, which is unusually generous for an eyepiece delivering this much magnification. Tele Vue designed the Type 7 specifically so observers who wear glasses can still take advantage of the full 82° field without having to crowd the eye lens.
If you observe without glasses, the adjustable locking eye guard lets you set a comfortable viewing position and helps keep your eye from getting too close to the lens. It also blocks peripheral stray light, which can make a noticeable difference when you're trying to hold subtle planetary detail or tease out a faint companion star.
The large eye lens adds to that comfort. Instead of feeling as though you're peering into a small opening, the Type 7 presents a broad viewing window that is easy to return to night after night.
Optical Performance
Tele Vue's design goal for the Type 7 was straightforward: each focal length had to equal or exceed the Apollo 11 eyepiece in full-field sharpness, contrast, distortion correction, eye relief, and pupil comfort while delivering the traditional Nagler 82° apparent field.
The 5.5mm uses Tele Vue's fully multi-coated optics and internal baffling to control reflections and stray light. At high magnification, those details matter. Planetary observing depends on contrast, double stars benefit from a clean field around the diffraction pattern, and faint structure inside globular clusters or planetary nebulae is easier to see when unwanted light is kept out of the view.
The goal isn't to make the eyepiece call attention to itself. A good high-power eyepiece should disappear once your eye settles into position and let you concentrate on the target.
Dual 1.25-Inch and 2-Inch Compatibility
The 5.5mm Type 7 can be used in either 1.25-inch or 2-inch focusers and diagonals. That makes it easy to move between telescopes without adding unnecessary adapters to every setup.
The Type 7 series belongs to Tele Vue's B parfocal group when used in 2-inch mode. The 5.5mm can also be made parfocal with most other 1.25-inch Tele Vue eyepieces by using the Tele Vue Hi-Hat 1.25-inch-to-2-inch adapter. That means changing magnification can require little or no refocusing when the eyepieces are configured appropriately.
The 5.5mm is also suitable for binoviewer use and is compatible with Tele Vue Dioptrx astigmatism correctors and the FoneMate smartphone adapter.
Under the Night Sky
This is an eyepiece for nights when the atmosphere lets you use some power.
On the Moon, 5.5mm can bring crater walls, rilles, mountain ranges, and fine structure along the terminator into a scale where you can spend a long time studying a surprisingly small piece of lunar terrain.
On Jupiter and Saturn, the wide field gives the planet room to sit naturally in the view while the short focal length supplies the image scale needed to look for finer detail. Mars becomes particularly interesting near opposition when its apparent diameter is large enough to reward higher power.
Double stars are another natural use. The combination of magnification, field correction, and contrast makes the 5.5mm well suited to tight pairs when the seeing cooperates. Globular clusters can also be excellent targets, with higher magnification helping resolve stars farther into the cluster while the 82° field keeps the view from feeling cramped.
As with any high-power eyepiece, the telescope and the atmosphere decide how often you can use it. A 5.5mm can be an everyday high-power eyepiece in a short refractor and a serious seeing-night eyepiece in a long focal-length SCT or Dobsonian. The focal length of your telescope matters more than any generic target list.
Frequently Asked Questions
How much magnification will the 5.5mm Type 7 give me?
Divide your telescope's focal length by 5.5. A 600mm telescope gives about 109×, a 1000mm telescope about 182×, and a 1200mm telescope about 218×. Whether that magnification is practical on a particular night depends on the telescope, target, and atmospheric seeing.
Is the 5.5mm Type 7 comfortable with eyeglasses?
That is one of its primary design goals. Tele Vue specifies 19mm of eye relief, giving many eyeglass wearers enough room to see the full 82° apparent field. The exact experience will depend on the shape and position of your glasses.
Does it fit a 1.25-inch focuser?
Yes. The 5.5mm Type 7 has a dual 1.25-inch/2-inch barrel and can be used in either size focuser or diagonal.
Can I use it in a binoviewer?
Yes. Tele Vue lists the 5.5mm Type 7 as suitable for binoviewer use. Remember that you will need a matched pair.
Is it Dioptrx compatible?
Yes. The 5.5mm Type 7 accepts Tele Vue Dioptrx astigmatism correctors for observers who prefer to remove their eyeglasses at the telescope.
Is the 5.5mm parfocal with other Tele Vue eyepieces?
It belongs to Tele Vue's B parfocal group when used in 2-inch mode. Parfocality with most Tele Vue 1.25-inch eyepieces can also be achieved with the Tele Vue Hi-Hat 1.25-inch-to-2-inch adapter.
Is 5.5mm too much magnification for my telescope?
That depends entirely on the telescope's focal length and the conditions. In a 700mm refractor it produces about 127×, which may be useful very often. In a 2000mm SCT it produces about 364×, which requires excellent seeing and is much more specialized. Calculate the magnification before deciding whether 5.5mm fits your observing setup.
Final Thoughts
The appeal of the 5.5mm Nagler Type 7 is that it doesn't make high magnification feel like a compromise. You get the image scale expected from a short focal-length eyepiece, but you still have an 82° field, a large eye lens, and 19mm of eye relief.
For eyeglass wearers, that combination is particularly unusual. For observers who don't wear glasses, it simply makes a high-power eyepiece more comfortable to use.
If 5.5mm gives your telescope the magnification range you want for the Moon, planets, double stars, globular clusters, and other compact targets, the Type 7 gives you that power without giving up the wide-field Nagler experience to get it.
