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4.3 out of 5 stars
4.3 out of 5 stars
Style Name: SkyMaster 25 x 70 Porro Prism|Change
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on 9 December 2009
This posting begins with a discussion of some core information about binoculars for astronomical viewing that should help potential purchasers make a more informed purchase decision.

If you have other viewing objectives than astronomical objects, or are already familiar with binocular specifications, you may want to stop here or just read the latter part of this review before going on to other postings; otherwise, read-on.

There are two main styles of "true" binoculars. Here, binoculars that do not use prisms such as opera glasses, are not discussed further. Most binoculars use one of two type prisms, either roof prisms or Porro prisms. Roof prisms are more modern and have a straight through appearance, i.e., the binocular cylinders form straight tubes. Porro prism binoculars (named after Ignazio Porro) have a tell-tale right angle bend. These usually are manufactured with two prism on each side of the binoculars, i.e., double Porro prisms. Although considerably larger in size, because of their improved optical qualities Porro prism binoculars, such as the model reviewed here, are preferred over roof prism binoculars for astronomical viewing.

Another important aspect of binoculars is the size of their exit pupil. Younger folks have pupils that can open, dilate, to a maximum size of slightly over 7mm. However, as one gets older the size of this window into the eye reduces. Over the age of thirty most folks have a reduction in their dark adapted pupil size of approximately 1mm every 20 years. The exit pupils for a pair of binoculars should ideally approximate the entry pupil of the observer's eye. Although some studies suggest an even smaller exit pupil size, see below. The size of a binoculars' exit pupil is found by dividing aperture by magnification. For example, common 7 x 50 binoculars (7 power by 50mm) have an exit pupil of approximately 7.14mm. In practice, this exit pupil size is larger than many adult's dark-adapted pupil size, particularly when some extraneous light is also present. In most viewing environments such as in or near a city such extraneous "light pollution" is almost always present. In addition, the periphery of the eye's lens exhibits some inherent optical degradation. Thus, an exit pupil size around 5mm may be preferred, although some experimental evidence suggests an exit pupil even less than 4mm may be most appropriate. These 15 x 70mm binoculars have an exit pupil of approximately 4.7mm resulting in more of the light exiting the lenses entering the eye than might occur with e.g., 7 x 50mm binoculars.

One of the most important considerations when choosing binoculars is their light gathering ability. Binoculars are essentially "light buckets". The human eye at its widest has a 7mm plus entry window. The 70mm objective lenses here have over 50 times the light gathering area of the human eye. Another factor affecting the light transmitted by binoculars are the materials used in their lenses and lens coatings. The least expensive binoculars have uncoated lenses or single coated lenses. Multi-coated binocular lenses and BaK-4, barium crown glass prisms, as in these Celestrons, are typically more expensive but improve light transmission resulting in sharper and brighter images.

The best eye relief, i.e., the distance your eyes needs to be behind the exit pupil of a binocular to see the full exit image is probably between 15mm and 20mm. These binoculars provide 18mm and additionally come with rubber eyecups. Thus, I've been able to use these both with and without glasses. I use lightly tinted sunglasses when viewing the moon to see more detail. In this case I leave the eyecups raised. When viewing without glasses I leave the eyecups down.

In use, I've found the images sharp and with adequate contrast to enjoy star clusters, the moon and planets. This pair's primary negative is its size and weight. These binoculars are really big. Owing both to their size and weight and as well as the relatively high magnification they are not comfortable to use hand-held for any but the shortest period of time. Because of their magnification, the slightest shake moves the astronomical object out of the field of view. Fortunately, they come with a tripod adapter. However, for some the need to use a tripod may defeat the value of having a "portable" pair of hand-held binoculars. For these observer's a smaller 50mm binocular is more appropriate. A minor problem is the carrying case, mine arrive with missed stitching on about a 1" section of a vertical seam, letting light through and possibly rain. The case is also a bit tight making it more difficult to easily insert and remove the binoculars, a better degree of quality control for the case, and a slightly larger size would seem more appropriate. Simply holding the case to the light and looking inward will reveal any stitching missed.

However, even recognizing that these binoculars cannot be hand-held for any extended period, they are probably one of the best choices for astronomical observers who need relative portability compared to a probably more cumbersome and expensive telescope. Perhaps surprisingly, they are also an extremely useful adjunct for those who use telescopes.

In summary, these binoculars allow for considerable additional exploration of astronomical objects compared to the naked eye. However, a tripod is required for any extended observations. Highly recommended.
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on 1 June 2015
Let me start by saying I did not have a clue about stargazing/astronomy until Christmas 2014 when I was bought a pair of 10x50 bins (tech term for binoculars, apparently) and a stargazing book to begin my foray into amateur astronomy. If, like me, you could stare at the night sky for hours and just bask in the wonder that is our solar system, then I could not recommend a better way to start it.

Six months later and I’ve decided to upgrade to these 25x70 beasts. I was tempted to go for the 25x100 but didn’t want to make the mistake of trying to run before I could walk. I ordered them Friday afternoon and took delivery the following morning. I could barely contain my excitement in opening the box!

The packaging itself is basic, but not too complicated. I had the binoculars, the carry bag (with strap), a wipe-cloth, neck strap, standard instructions and – the most important – a tripod mount. I haven’t bought a tripod yet but may well be making a purchase this week, as these bins aren’t exactly heavy but it’s difficult to maintain a steady focus on, say, the Moon (which by the way looks BEAUTIFUL through these).

So far – and I’m only two days into using them – I’m very, very impressed. Thankfully it was a clear night last night and where I live (Wales, UK) I was able to see the Moon, Venus, Jupiter and its moons, and Saturn! Although the latter was a mere blemish in my lens, I could clearly make out its rings (the planet is almost an oval-shape) and I couldn’t believe my eyes.

The build quality is superb. They feel heavy, but they’re not that heavy if you know what I mean. Of course, buying a tripod will both give you amazing images and give your arms a rest, but for now I’m happy using my garden table as a stabiliser for my elbows. The focus wheel is a little stiff, but being 31 I’ve had some good practice with my fingers over the years. The eye piece protector is a little flimsy, but to be honest I’ll hardly use it as it’ll spend more time out of its carry case than in it.

Before I had my first pair of bins, I assumed that astronomy was for balding single men with grey beards and adenoids, looking up through telescopes the size of a Ford Galaxy (pardon the pun), but with a simple pair of binoculars you can gaze at the stars for hours and see way, way more than the naked eye. Orion’s Nebula is simply breathtaking.

To sum up, if you’re looking to upgrade from a pair of 10x50s, these are the bins for you. If you’re just starting out, then I’d recommend these but no higher (or heavier) than these. Like I said, by starting small and working your way up gives you much more appreciation of what you can see. I can honestly see myself never buying a telescope and instead upgrading my bins every year or so. They are THAT good.

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on 22 October 2011
I've been an amateur astronomer for a while now and have a couple of telescopes both of which are pretty bulky. I also had a pair of 10x50 bins which are highly portable of course but with only 10 magnification and not a lot of light gathering ability, they were never going to show much detail. I bought these as a grab and go for when you just want to have a quick look at Jupiter and its moons or a scan of the lunar surface. At the price, I was only expecting something that was a bit better than my 10x50s but wow, the viewing through these is terrific and I hadn't quite appreciated just how much better they would be. The moon is a joy to view through these, they are very easy to focus and have an excellent quality feel to them. The tripod mount adapter is pretty wobbly to be honest but that's not the real purpose of these. If you're in the mood to set up tripods then get an astroscope but these are small and light enough to hold without any problems.

I really am very very pleased. Another brilliant low cost item from Celestron.
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on 27 October 2011
My wife and I bought a pair of these recently and we are well impressed. These 20x80 binoculars are great! Faint objects are really prominent due to the immense light gathering power of the 80mm lenses.

The 20x magnification meant that we recently got splendid views of the moon and Jupiter with them. It was quite amazing that Jupiter's shape and also it's four brightest moons were easily visible. And I have to add that the sky wasn't all that clear at the time either (it was a little bit hazy) so we're really keen to see what they'll do when we start getting proper winter clear skies!

The instrument feels well built and the optics are well aligned.

Be aware though that these binoculars are heavy so you'll need some sort of tripod in order to keep them steady.

We went for 20x80 binoculars after reading about different types for astronomy in "Stargazing with binoculars" (published by Firefly), which we'd bought from Amazon some weeks before. We decided to go for something more powerful than the usual 10x50 binoculars as we wanted to get better views of dimmer objects, the moon and the planets. If you don't want to pay this sort of money though, note that Celestron also do cheaper (and lighter) 15x70 and 25x70 models for around half the price. However, if you want even more light gathering power, there is also a 25x100 model but that is around twice the price of these 20x80 binoculars.

Overall, these binoculars have performed well and we don't regret the purchase.
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on 11 October 2011
Having read conflicting reviews, I cautiously purchased these binos, they arrived and... Brilliant!

Very robust, good quality and well designed, they look good too. I think the price is very good too. Crisp, clear image and no problems with collimation as reported by a few reviews. Easy to perform the initial set-up and the tripod adapter works really well.

Not as heavy as I was expecting, although I brought a monopod in the end which gives me the perfect mix of stability and manouverability with less weight.

What have I seen so far: Lots of clouds (I live in London), The Full Moon with such clear detail of craters and blemishes and all and Jupiter and 4 of its Moons (amazing to see sometinh so far away as almost pea-sized).
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on 7 February 2012
My wife and I are just getting into astronomy, she has the telescope so I decided to get a good set of binoculars. I cannot beleive how good these binoculars are. The close ups are amazing. The clarity of the images superb!!!! All moons of Jupiter are clearly visable, Mars, WOW, Venus, amazingly bright and the Moon is simply sensational(especially when full) I could go on and on about how good these bins are. If you want a great piece of kit to get going into astronomy or bird watching then I can only say one thing about these binoculars, BUY SOME!!!!! You wont be disappointed
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on 26 December 2012
My Celestron Skymaster 20x80 binoculars were received a few weeks before Christmas, but as they were a Christmas present bought for me I didn't get any chance to test them out before they were all wrapped up ready for the big day! So now I've had chance and these are my findings after using them for about four or five hours solid.

Firstly, I can confirm that mine were NOT out of collimation. I'd been reading all about collimation as a number of people on the net had reported this problem with various Celestron binoculars (and others) so I did absolutely loads of research on the net in case mine needed collimating. In a nutshell, collimation means that the prisms are slightly misaligned causing a sort of slight doubling of the image. Apparently, the manufacturers of Celestron binoculars in China don't have the best quality control system in place and it seems that unfortunately some of these models ship already out of collimation. If you don't know what to look out for chances are you'll just put up with it as it can be barely noticeable, but it can cause eye strain and headaches as your eyes try to 'correct' the image. So, I've been lucky with mine as they are certainly not out of collimation. The image through the 20x80s is great, nice and bright and I found they snapped to a good focus. Focusing on a dark vertical post against a bright sky background revealed a little color fringing, certainly not enough to be a problem, but this will be present in just about any binocular optics anyway unless you go very expensive. All movable mechanisms like the focus wheel and the dioptre (right eye piece) adjustment are nice and smooth with no sign of stiffness thoughout it's range.

Finally I thought I'd mention the weight issue as a lot of people mention this. They are pretty heavy yes. unfortunately this is a trade off for the large 80mm objective lenses. If your only using them to grab and use for just a minute or two before putting them down again then you really shouldn't have too much of a problem, but then I'd have to wonder why you would go for something of this size and weight if you never plan to use a tripod. Mounting them on a tripod is without doubt where you will appreciate them most, especially as this is what this model is designed for with the built in tripod adapter. Had a good look at the stars during a brief break in the clouds and it was great. Now looking forward to clearer skies and getting away from all this light pollution. I hope this helps a little. I'm really pleased with mine and wouldn't change them.
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on 26 November 2012

I bought these binoculars a month ago and am delighted with them. Here's why:

Firstly, you're paying a very low price for a very good piece of equipment. Just as good during daytime use, these are becoming the standard for astronomical viewing and if you're paying hundreds and hundreds for optics of the same magnification then you're a fool. Celestron now pretty much has the market covered in terms of good optics at a knock-down price. These are the binos I see at just about every astronomy gathering I attend. People love them.

Secondly, they're not heavy to transport at all... unless you're five years old or generally given to moaning. I regularly trek out with these plus the Hama tripod on my back without any problems whatsoever. Granted, the bag is not thick enough but with a little bit of common sense you can pad it out with cheap foam lining as I did.

Thirdly, I cannot tell you how many times I've knocked these things against a wall or chair and found they're in perfect order; they're solid, reliable, and pleasant to hold.

My tips would be these:
1) Buy the tripod with them (it'll be down in the "Others bought these with it" thing lower down the page), you'll need it for steady viewing.
2) Don't bother with the 25x100 version unless you're going to buy an expensive liquid head tripod.
3) Do NOT be tempted to use anything other than a special optics cloth to wipe the lenses.
4) If you're going to be out in the garden at night a lot don't forget to leave these outside to cool down for quite some time prior - if you don't, they'll gather condensation on a cold night just like any piece of optical equipment.

Through these binos I've managed with ease the following:

Seen binary stars in clear separation, taken a lovely look at the Orion Nebula, been blown away by full and clear views of the Pleiades and the Hyades, seen four of Jupiter's moons AND the red bands on Jupiter, sat for an hour just staring up at the Andromeda Galaxy, seen dozens of star clusters in perfect clarity, and had the most jaw-droppingly brilliant views of our own moon in all its glory.

Drawbacks? Criticisms? None other than that the bag is too thin.
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on 23 November 2011
For a little over £100 it is very difficult to find fault with these binos.
These binos can be quickly set up on a tripod, and given the wide field of view and the 'straight through' nature of binocular viewing (as opposed to the 90 or 45 degree viewpoint of a telescope, they are quick to align to whatever object you are looking at. You do need a heavy duty robust tripod however, and I would highly recommend getting a fluid head type as used for video cameras, as this gives a smooth resistive movement and avoids the motion sickness that jerky movements will give you when viewing at x20 magnification.
Viewing stars through binos is a lot less tiring than using one eye through a telescope, and the view is more 3 dimensional, this is especially true if you are able to get away from light pollution. What you loose in magnification compared to a scope, you gain in magnificent wide views of starfields. I had lovely views of Jupiter and four of it's moons on a recent clear night, although I could not make out surface detail.
These binos have a rubberised coating that allows a good grip, and a large focus wheel that is easy to turn with gloves on...important when it is cold on winter nights. Good firm lens caps at the big end actually stay on very well, and the whole kit has a canvas carry bag, which is not padded but what do you expect for the money? can store the caps when you are using the binos.
The only area I would mark it down is the tripod mount. It is a metal locking nut which slides along a bar which runs the length of the spine of the binos. the base of this nut screws into a standard 1/4 inch tripod or adaptor plate. The trouble is that the base of the nut is only around 1 inch in diameter so does not provide a very wide solid foot to mount the binos on. The silk finish of the metal bar does not provide a good grip when you screw the knurled nut hard down, which does mean that the binos can slip a little around their axis. This is not too much of a problem if you do not hold the binos whilst on the tripod...just a light touch on the focus wheel and avoid pushing your eyes against the eyecups!
I have used these binos for daytime observation from an old hillfort on the Mendips. The view was nice and bright, but the 80mm objective lenses magnified the effects of heat haze on that summer day, which affected their performance. A recent trip to the same spot last week gave a good clear view right across the Bristol Channel some 30 miles away through the crisp autumn air, so I would give a cautious endorsement to daytime terrestrial use.
It is just about possible to hand hold these binos if you hold them as close to the end of the lenses as possible, but whilst they are not really would not want to be doing it for long...these are definately not for casual wildlife viewing! They are big make sure you have enough cupboard space to store them.
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on 14 June 2011
excellent night sky views from these bino's. I was a little skeptical when buying but was pleasantly surprised. These are quite bright and with good sharpness from the centre to soft ish at outer edges of focus.contrast is middling to good . For the money these are a great bargain but they aint too strong and some tender loving care is advised and what ever you do dont drop them.
you can just make out the shape of saturn, ring is visible
the moon looks amazingly big and sharp with some tight colour fringing on the outside edge
stars seem a little warmer in colour but resolve to pin points of light
As the seeing at this time of the year varies from crap to really crap I cant comment on any deep sky stuff.

if you want super contrasty super sharp binos go elsewhere and add another 1000 or 2 or as far as you want to go, to your budget.
I would recommend these binoculars to someone to start off with in astronomy as they will see so much more with these compared to the rubbish telescopes that most people start of with.
you also need a good tripod as they are quite heavy to hold still.
The pair i received seem to have good collimation but from the reports i have read it is a bit of a lucky bag in this respect.I was lucky far.......... ENJOY

Sharpness 7/10
contrast 7/10
focus 7/10
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