This high power Omni eyepiece is a 4 -element premium symmetrical Plossl optical design. Features include blackened lens edges to minimize internal reflection and maximize contrast, multi-layer coating group on each lens surface to maximize light transmission and contrast, and each Omni goes through a two-step anodizing process to prevent reflection from the top eyepiece barrel, unlike most other manufactures who use reflective surfaces. Threaded barrels accept 1-1/4" Celestron thread-in filters.
Product carries two-year manufacturer limited warranty (within US/Canada only).
Important note: Depending on your telescope, this eyepiece may provide magnifications that are too high! While it can be very useful for viewing the Sun, Moon, brighter planets and terrestrial objects, it is not for everyone or for common viewing conditions.
Before buying, please make sure that you are using realistic magnifications with your telescope. A good rule of thumb is that under very good conditions and with a very good telescope, the maximum power you will be able to use is about 50x of magnification per inch of telescope aperture. With average telescopes and/or average conditions, you might be limited to 30x of magnification per inch of telescope aperture. So for example, if you have a 5" telescope, under typical conditions you might typically use 5x30 = 150x of magnification, and 5x50 = 250x of magnification at best. If your telescope has a focal length of, say, 1200mm, then this eyepiece will result in a magnification of 1200 / 4 = 300x which is probably too much for this telescope.
Also, when you magnify an object, its light is spread over a larger area. Since the brightness of the object being viewed hasn't changed, this means that the image you see will be fainter. Double the magnification and the image will get 4 times fainter. This is a basic law of physics, but people often forget this and complain that the "image is not bright enough" when they increase the magnification to very high powers.
Boosting the magnification beyond the recommended maximum for your telescope aperture is not realistic. This is bound to result in image break-down, causing faint, fuzzy images, focusing difficulties, increased color around objects and general disappointment. Use the eyepiece in the right settings and with the correct expectations, and you will enjoy it.
Sep 5, 2014
Works well, but the view is limitedPros: Cons:
Difficult To FocusComments:
My 4mm eyepiece works just fine in both my 8" and 12" Dobs. However, it's about at the upper magnification limit in both Dobs. Saturn and Jupiter are a bit fuzzy from my driveway anyway, due to atmospheric distortion, and with a 4mm eyepiece, you end up with a blob that's 'too close' and too fuzzy to appreciate the beauty of what you're seeing. Don't expect a closer cleaner view of ANYTHING with any brand of 4mm eyepiece. The atmosphere won't let you have crisp edges.
I would recommend that folks with 8-12" Dobs get a 6mm instead of 4mm (to add to their starter eyepiece set of 30mm and 9mm). I think the views would be more enjoyable overall.
Quality of the Celestron lens looks good though, so I will recommend their eyepiece series as good hobby astronomy choices overall.
This review was provided courtesy of AgenaAstro.comSort by
|Apparent Field of View
|Bolt Case Included
|Yes - Free Agena Eyepiece Container
|Bolt Case Size
|Eye Relief by Design
|Standard 1.25" Filter Thread (M28.5 x 0.6)
|Rubber Eye Guard
|Blackened Lens Edges
|Eyepiece Focal Length
|5mm and Under
|Eyepiece Field of View
|51 - 60 degrees
|With safety undercut