{"id":107124,"date":"2026-04-17T14:35:12","date_gmt":"2026-04-17T12:35:12","guid":{"rendered":"https:\/\/www.telescoop.nl\/?post_type=product&p=107124"},"modified":"2026-07-20T12:26:21","modified_gmt":"2026-07-20T10:26:21","slug":"televue-ethos-21mm-100-degree-eyepiece","status":"publish","type":"product","link":"https:\/\/www.telescoop.nl\/en\/televue-ethos-21mm-100-2-oculair\/","title":{"rendered":"TeleVue Ethos 21mm - 100\u00b0 2\" Eyepiece"},"content":{"rendered":"

TeleVue Ethos 21mm: 100\u00b0 2\" Eyepiece: Ethos eyepiece with 100-degree field of view<\/strong><\/h2>\n\n\n\n

The Ethos 21mm is the model with the largest true field of view in the series. The 36.2mm field stop brings the field of view close to that of a 35mm Panoptic, while the exit pupil remains much smaller.<\/p>\n\n\n\n

In an f\/4 Dobsonian, that exit pupil is approximately 5.25 mm instead of 8.75 mm with a 35mm Panoptic. For older eyes and for observers under a light-polluted sky, that's a significant difference.<\/p>\n\n\n\n

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What a 100-degree field of view does<\/h4>\n\n\n\n

A classic Ploessl has 50 degrees, a Nagler has 82 degrees. At 100 degrees, your eye can no longer take in the field at once: you\u2019re looking around the image instead of *at* it. That\u2019s the effect the Ethos series is known for.<\/p>\n\n\n\n

Practically, this also means that objects remain in view for longer. On a manually tracked Dobson, this saves constant readjustment.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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The maximum field of view within a 2-inch pitch<\/h4>\n\n\n\n

At this focal length, the design is reaching the mechanical limit of the 2-inch holder. TeleVue is achieving the largest possible true field of view without significant edge vignetting.<\/p>\n\n\n\n

The eyepiece is parfocal with the 31mm Nagler Type 5. Keep in mind that at over a kilo, it's the heaviest model in the series: check the balance of your mount.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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Viewing Comfort and Dioptrx<\/h4>\n\n\n\n

The eye relief is 15 mm at every focal length in the series. The height of the foldable eyecup is adjustable, so your eye is always in the same position.<\/p>\n\n\n\n

If you wear glasses due to astigmatism, you can replace them with Dioptrx on the eyepiece. This corrects your own cylindrical aberration without the eyeglass lenses costing contrast and eye distance.<\/p>\n<\/div>\n<\/div>\n\n\n\n

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In your telescope<\/h4>\n\n\n\n

In a telescope with a focal length of 1200 mm, this eyepiece provides approximately 57x with a true field of view of about 1.73 degrees. You can calculate this for your own telescope using the field stop: true field of view = 57.3 x field stop divided by the telescope's focal length.<\/p>\n\n\n\n

The field stop on this model is 36.2 mm. That number\u2014and not just the focal length\u2014determines how much of the sky you actually see.<\/p>\n<\/div>\n<\/div>\n\n\n\n

Included<\/h3>\n\n\n\n