15mm Titan 1.25" 70° field super wide angle

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 Very limited quantity. This Astro-Tech 15mm Titan is a very wide 70° field medium power 1.25” eyepiece at a very economical price. It is ideal for lunar observing, resolving globular clusters, picking up detail in emission and reflection nebulas, etc. Its 15mm focal length nicely fills the gap between the 25/26mm eyepiece that typically comes as standard equipment with most telescopes and an 8/10mm high power planetary/binary star splitting eyepiece.

With short focal length refractors and fast focal ratio reflectors, it gives an extraordinary “picture window on space” image. A f/4 Meade 8” Schmidt-Newtonian reflector, for example, yields a 3.75mm exit pupil, 54x, and a generous 1.3° field of view that’s good for observing open clusters such as the Pleiades; large nebulas such as the Lagoon, Veil, and Orion; and large globulars such as M-13 and Omega Centauri. All will fit nicely into the field of view, with a framework of black velvet sky around them to set off their subtleties. Globular clusters and nebulas are vivid and nearly three-dimensional.

The 66mm f/6 Astro-Tech AT-66 refractor, on the other hand, has a magnification of 27x with this eyepiece, with a 2.5mm exit pupil and an immense 2.63° field (over five times as wide as the full Moon).

Even medium and long focal length telescopes provide impressive views. Use this 15mm Titan on an 8” f/10 catadioptric scope and you still get a 0.52° field at 133x, perfect for the Moon and globular clusters like M9, M13, and M22.

The 7mm eye relief is somewhat short for those who must wear eyeglasses while observing due to astigmatism, and will somewhat vignette the field. This is of minor concern, as even those who don’t have to wear glasses while observing will find they have to move their head from side to side while observing to see the entire huge field of view.

Field of view:
The field of view (FOV) is the amount of observable world one can see at any given moment.
70°
Eye Relief:
Eye relief is the distance from the last surface of the eye lens of an eyepiece to the plane behind the eyepiece where all the light rays of the exit pupil come to a focus and the circular image is formed, sometimes called the “Ramsden Disk.” This is where your eye should be positioned to see the full field of view of the eyepiece. If you must wear glasses because of astigmatism, you’ll usually need at least 15mm of eye relief or longer if you want to see the full field of view with your glasses on.

A note on our eye relief figures: Quite often, our eye relief figures will differ from those of the manufacturer. This is because we measure the “usable” eye relief, while the manufacturers specify their usually-longer (but technically correct) “designed” eye relief.

The eye lens of the eyepiece is normally recessed below the rubber eyeguard or rubber rim of the eyepiece to keep the lens from being scratched during use. An eyepiece might have a “designed” eye relief of 15mm (and the eye relief will truly measure 15mm from the eye lens to where the image forms). However, if the eye lens is recessed 3mm below the eye guard, the Ramsden Disk forms only 12mm above the eyepiece body (the 15mm “designed” eye relief, less the 3mm of eye relief made unusable by having the eye lens recessed into the body of the eyepiece). This “usable” eye relief of 12mm (measured from the rolled-down eyeguard – the closest point you can get your eye to the eye lens – to where the image forms) is the eye relief figure we would measure and list in this website.

Why is it important to list the “usable” eye relief? For those people who don’t wear eyeglasses while observing, a few mm difference between the eye relief they expect from the manufacturer’s literature and the shorter eye relief they actually get in real life doesn’t mean a lot. They can simply move a little closer to the eyepiece to see the full field, and never realize that the eye relief is a little shorter than they expected. However, some people must wear eyeglasses while observing, because of severe astigmatism. These observers can’t move closer to the eyepiece if the eye relief is shorter than expected because their glasses get in the way. For these people, the real life “usable” eye relief is more important than the technically correct but sometimes not fully usable “designed” eye relief. We measure and list the actual usable eye relief so that people in the real world can pick the eyepieces that will work best for them.

7mm
Focal Length:
This is the length of the effective optical path of a telescopeor eyepiece (the distance from the main mirror or lens where the lightis gathered to the point where the prime focus image is formed). Focallength is typically expressed in millimeters.

The longer the focallength, the higher the magnification and the narrower the field of viewwith any given eyepiece. The shorter the focal length, the lower themagnification and the wider the field of view with the same eyepiece.

15mm
Number of optical elements:
5
Barrel Size:
The industry standard diameter, as of 2011, is 1.25" and is the most common.  Other sizes available are .965" and 2".
1.25"
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Overall Product Rating: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics(5.00)   # of Ratings: 1   (Only registered customers can rate)

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1. Curt on 4/30/2013, said: AstronomicsAstronomicsAstronomicsAstronomicsAstronomics
This eyepiece held its own against my TV 15mm Panoptic. Every bit as bright. No differnce in on-axis sharpness. In my f/7 refractor images were sharp to about 75% to edge of field. In my f/10 schmidt-cass images were sharp almost to the edge. Color correction was comparable. Eye relief was slightly less than the 15mm panoptic. All-in-all a strong performer and a real bargain, especially when on sale!
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Astro-Tech - 15mm Titan 1.25" 70° field super wide angle

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Astro-Tech - 15mm Titan 1.25" 70° field super wide angleImage showing a typical Astro-Tech Titan with its twist-up eyecup both extended and retracted. Note the safety groove machined into the barrel.
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This 15mm Astro-Tech Titan is a good quality medium power eyepiece with a very wide 70° field of view that will add expansive deep space vistas to your observing kit at a price only a fraction that of exotic wide field designs with a similar field of view . . .





. . . our 34th year