| This Meade Ultra Wide eyepiece is an excellent low power, wide field eyepiece that’s particularly well-matched to big Dobsonian scopes. While the longer focal length 30mm Ultra Wide provides an even wider field of view with an f/4.5 scope, it also has a very large 6.7mm exit pupil, larger than many observers’ eyes can dilate. That effectively wastes some of the scope’s light gathering capacity, as some of the full light cone falls on the observer’s iris, rather than entering his or her eye. This 24mm Ultra Wide, on the other hand, has a 5.3mm exit pupil with an f/4.5 scope. That’s an exit pupil more in line with the maximum dilated pupil of most observers’ eyes. With this 24mm, you get the full light-gathering your scope is capable of, while still keeping nearly the same wide “picture window on space" field of view as the 30mm Ultra Wide. The six-lens design uses multiple rare earth glass elements. It is primarily designed for no-holds-barred low power deep space use with scopes having focal ratios down to f/4. It is marvelous for open clusters, nebulas, and globular clusters with any scope, but is particularly effective with fast f/ratio reflectors. That being said, it must also be noted that its very wide field also makes it convenient for moderate power lunar and planetary observing with Dobsonians, as you have much longer to observe before the planet drifts out of the field and the scope has to be repositioned. Please note the 35 ounce weight of this superb eyepiece. It may pose a balance problem with some Dobsonians when switching to it from a much lighter shorter focal length 1.25" eyepiece. Its use may require some temporary rebalancing of your scope, or the use of a TeleVue #TVEQC equalizing adapter with 1.25" eyepieces to avoid balance problems.
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