Tele Vue 2.5mm Nagler Type 6


Availability: More on the way

This is an optically superb and exceptionally short focal length ultra wide field eyepiece . . .
Our Product #: TN02
TeleVue Product #: EN6-02.5
Recommended Accessories

Product Description

This is an optically superb and exceptionally short focal length ultra wide field eyepiece. This latest premium 1.25" TeleVue Nagler Type 6 uses seven optical elements for optimized performance across a very wide field of view. Several different extra low dispersion glass types and specialized coatings are employed for improved contrast and longer eye relief than previous Nagler designs, even those acclaimed as being among the finest wide field eyepieces available. At a usable eye relief of 12mm, the 2.5mm Nagler would normally vignette the field of view for eyeglass wearers. However, since the 82 degree field is so wide that you can't see the full field without having to move your head from side to side to take it all in anyway, vignetting in the conventional sense is not a problem.

The 2.5mm Nagler is designed for very high magnification observing with short focal length refractors and fast focal ratio/short focal length reflectors. While it can also be used with longer focal ratio Schmidt-Cassegrains and Maksutov-Cassegrains, its exit pupil becomes prohibitively small and the images very dim with these scopes. For example, using it with a 2000mm 8" f/10 Schmidt-Cassegrain will result in 800x (100x per inch of aperture) and a 0.25mm exit pupil (about 1/100th of an inch across). Both of these figures far exceed the rule of thumb maximum values of 50-60x per inch of aperture and a 0.5mm exit pupil for usable observing under good to very good seeing conditions for a reasonably experienced observer.

The optical performance is typical TeleVue - well corrected and sharp from edge to edge. There is a slight loss of contrast when compared to an eyepiece with fewer elements, due to the additional lenses needed to achieve the unique combination of a very short focal length and very wide field. The loss is minimal though, on a par with the contrast loss in an eyepiece/Barlow combination with the same effective focal length. In the eyes of many observers, however, the "picture window on space" observing experience of its exceptionally wide field more than makes up for any slight contrast loss.

Supplied plastic caps seal both ends of the eyepiece to keep it dust free. A rubber grip ring gives a secure and comfortable grip in all temperature extremes. A groove machined into the chrome barrel of the eyepiece acts as a safety stop to keep the eyepiece secure should the focuser thumbscrew loosen slightly while using the eyepiece.

Tech Details

Barrel Size 1.25"
Eye Relief 12mm
Field of view 82
Focal Length 2.5mm
Number of optical elements 7
Weight 9 oz.
Warranty Limited Lifetime


Review by:
I am so happy to have had a 2.5T6 for several years for just those few nights when the highest magnifications were possible. I have used this eyepiece to show our club president M57's central star at 839x and we held it steadily in direct vision when he actually thought it could never be seen at all. Extragalactic details in such objects as the NGC4038/4039 pair or NGC6946 are revealed better at highest mag on the best nights. You should snag one of these NOW as TV no longer makes 'em and that rare night is lurking in your future. (Posted on 10/30/2018)
Review by:
I had the opportunity to use one of these with my small apo refractor and even at exceedingly high magnification, the eyepiece performed very well. Obviously this is pushing the scope to the limits. I viewed thru various TeleVue eyepieces and having never looked thru a Tele Vue before, it was an eye opener (no pun intended). the 2.5mm was amazing but provides too much magnification for my tastes, although it performed better than any other high power eyepiece I have ever used, and a at good site, Jupiter had excellent clarity and contrast. I give it 5 stars because the teleview naglers were definitely the finest eyepieces i have ever viewed thru. I feel that some other much less expensive eyepieces come very close to this performance ( the Meade 5000 Ultrawides for example) but as with anything else, you'll pay a premium for the very best out there, and televue delivers as usual. If you have the means to invest in such fine eyepieces you wont be disappointed. (Posted on 10/28/2018)
How do you rate this product? *