The TMB® 100 16 – named a Sky & Telescope Hot Product for 2010 – is a new and surprisingly affordable 2” 16mm 100° field eyepiece designed for “picture window on space” medium power deep space use with telescopes using a 2” focuser or star diagonal and having a focal ratio as fast as f/4. It is exceptionally effective on nebulas with fast f/ratio reflectors, such as Dobsonians, giving both an immense field and a good exit pupil (over 3.5mm with the typical f/4.5 Dob).
The very wide field of The TMB® 100 16 also makes it great for moderate power globular cluster observing with Dobsonians, as you have much longer to observe before the cluster drifts out of the field and the scope has to be repositioned. That said, it is worth noting that the new 16mm TMB® 100 is marvelous for open clusters, nebulas, galaxy clusters, and globular clusters with any telescope.
The 100° apparent field of this new 16mm TMB® eyepiece is nearly 50% larger in area than the field of 82° eyepieces. You could get a similar true field with a longer focal length (but narrower apparent field) eyepiece, but the 16mm TMB® 100 has the benefits of the higher power and darker sky backgrounds that are inherent in its shorter focal length. You can use the field of view calculator below to see just how much sky the 16mm TMB® 100 can reveal with your telescope.
There is a soft rolldown eyecup to shield your eye from ambient light (from a neighbor’s security light, for example) and improve your image contrast. This eyecup has been carefully sized to position your eye at the correct eyepoint to avoid vignetting of the image, unlike similar eyepieces with overly long eyecups. At a true usable eye relief of 12mm, the TMB® 100 16 would normally somewhat vignette the field of view for eyeglass wearers. However, since the 100° 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.
Then why, you might ask, do you need a 100° field eyepiece if your eye can’t take in its full field? It’s what we call the “picture window on space” effect. Stand a few feet back from an ordinary window in your house and look out at the world. The window frame on either side cuts off your view of the world and you see only part of the landscape. That’s the view though a conventional eyepiece. The eyepiece field stop acts like a window frame and cuts off part of your view. Now stand a few feet back from a picture window and look out again. The window frame is outside your eye’s field of view and all you see is the outside world. That’s the view through the 100° field 16mm TMB® 100. The eyepiece simply seems to disappear and you are looking out at space through a picture window. Which would you prefer – the cramped view through an ordinary window, or the unobstructed view through a picture window? The 16mm TMB® 100 gives you that wide screen “picture window” view of the heavens most people find simply enchanting.
The 16mm TMB® 100 has high contrast, comfortable eye relief, and full field sharpness – with well-controlled astigmatism, field curvature, geometric distortion, and lateral color. Its eight lens elements are fully-multicoated on all air-to-glass surfaces for high light transmission and contrast. The optical plan is shown in the feature image below. The eyepiece body is encased in a broad rubber grip ring that provides a sure and comfortable grip in cold weather or heavy dew conditions.
The affordable 16mm TMB® 100 is smaller and lighter than competitive 100° field eyepieces of similar focal length. It measures only 4.25” long with the rolldown eyecup extended, and 4” long with it rolled down. It weighs only 14.4 ounces, far less than competitive eyepieces of similar focal length that can weigh up to 2 pounds. This makes balancing a Dobsonian less of an issue when using this TMB® eyepiece than it can be with competitive 100° field eyepieces.
The 16mm TMB® 100 fits 2" focusers and star diagonals only. Its 2" barrel is threaded to accept standard 2" neutral density, light pollution, and color filters. The eyepiece comes with dust caps for both ends of the eyepiece. A plastic bolt-type storage case is standard equipment. | 
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