Friday, 24 October 2014

Barska X-Trail 15x70 Binoculars - A Quick Review

Like all self-respecting amateur astronomers, I have a bad case of “Aperture Fever” - you never have enough aperture, and you can certainly never have too much!

I've been using my Pentax XCF 10x50 binoculars for stargazing for the past few months, and I'm still very happy with them - they deliver a lovely bright, sharp, wide-angle image. But I wanted more …

As is my habit, I started browsing eBay and other online shopping sites for something affordable in the 15x70 “giant” class, and I kept coming across the Barska X-Trail 15x70s 

The key specs are as follows:

  • Magnification: 15x
  • Objective Lens: 70 mm
  • Prism type: Porro, BAK-4
  • Exit Pupil: 4.7 mm (70 mm / 15x)
  • Optical Coating: Fully Coated
  • Field of View: 77 m @ 1000 m (4.4 degrees Actual FoV; 65 degrees Apparent FoV)
  • Close Focus: 15 m
  • Eye Relief: 20 mm
  • Weight: 1270 g
  • Included Accessories: Mini Table-Top Tripod, Tripod Adaptor, Soft Carrying Case, Neck Strap, Lens Covers and Lens Cloth

They ticked pretty well all of the boxes for me. About the only thing I could criticize is that they are only “Fully Coated” rather than “Fully Multi-Coated” - but for the low asking price, I figured I could live with this “omission”.

Plus of course, there's the open question of build and optical quality … They seemed to get good reviews overall, and they are certainly affordable, so there was only one way to find out….

I found an international seller who offered them for AU$94.95, including expedited delivery to Australia, so I took the plunge and ordered a pair on Thursday last week - and they were delivered in Brisbane exactly one week later - very happy with that!

The binoculars came very well packed, and arrived without any damage. I unpacked them and took a look at what I had bought.

The binoculars themselves feel solidly built and have a nice “heft” and balance. The fold-down cup on the right eyepiece is a bit "buckled" (I guess it has been "crushed" in the box for some time) - I'm not sure if it will straighten out over time, but it doesn't detract form the use of the binoculars. Apart from that, no problems at all.

The table-top tripod and tripod adapter are somewhat surprisingly not complete rubbish - the tripod is metal and seems quite sturdy,  but I'm not sure how often I will have a table to set them up on, and in any case, you can really only use them near-horizontal on such a small tripod, so it is really only useful for terrestrial viewing.

The carry case and neck strap are pretty basic (the neck strap is really WAY too thin for hanging these babies around your neck!), so an upgrade to a better wider padded strap is on the cards. The case is thin and soft, with minimal padding, so won't provide much protection from bumps and knocks, but my binoculars will live safely at home, and the case is really only going to be  a dust cover, so I can live with that.

I was pleased to find they were perfectly collimated, and provide a bright, sharp image all the way to the edge of the 65-degree apparent field of view (4.4-degrees actual field of view at 15x magnification).

There’s a bit of distortion and Chromatic Aberration at the edge of the field of view, if you look hard, but because these have a nice wide field of view, it really doesn't detract from the overall view. The distortion is there, but you can only really see it if you position a straight line (such as a building or power pole) near the edge of the field of view; it’s basically not noticeable on more “natural” targets. The CA is only apparent on bright, high-contrast targets near the edge of the field of view. These defects are only apparent if you switch your gaze from the centre to the periphery, and the effect disappears if you swing the binoculars to bring the main target more central.

But of course it was really their night-time use that I really wanted to test out!

When the Sun had set, and family duties had been attended to, I settled down in a camping chair in the back yard with my Pentax 10x50s, my new Barska 15x70s, and a couple of tripods. It’s New Moon at the moment, so checking out the Moon is out of the question for a few days, so my first targets were some old favourites that were favourably positioned - the globular cluster 47 Tucanae (NGC 104), the Great Nebula in Orion (M42), Andromeda Galaxy (M31), and Ptolemy’s Cluster (M7). I swapped back and forth between the two binoculars a few times on each target, to compare the views. 

And I was very impressed!

Stars were shown as pin-sharp points of light across the field - the CA and distortion that could be picked up by selecting suitable “test targets” in daylight really isn't apparent at all for stargazing use. (I suspect it will be more apparent on a bright target like the Moon, but again, should only be noticeable at the periphery rather than in the central view.)

The 15x70s show significantly more stars than the 10x50s, and the higher magnification tends to darken the background sky as well, which also helps in seeing very faint stars, and brings diffuse targets such as nebulae and galaxies into better contrast against the sky. Looking at nebulae and galaxies revealed a bigger apparent area (as the fainter edges could be resolved more clearly), and showed more detail and "structure" within the “body” of the nebulae as well - and all at 50% higher magnification than the 10x50s. The 4.4 degree field of view is ample for viewing pretty well any night-sky target, apart perhaps from seeing an entire constellation in a single view, for which the 10x50s with their 6.5 degree field might be preferable.

The 10x50s are light and compact enough to be held steady for extended periods, but the bigger  and heavier 15x70s definitely test your endurance after a short period. My tripods just aren’t the right size and shape for convenient binocular stargazing use while sitting in a  comfortable chair (you really need a parallelogram arm for this), and of course the higher magnification amplifies the shakes. However, I found that folding up the legs of a tripod to make a monopod worked very well (especially with the pan / tilt head) - just plant the base of the “monopod” on the ground ahead of you, and lean it back to bring the binoculars up to your face, and use the pan / tilt to get the alignment just right; then lock the pan / tilt, and you have a nice steady platform which requires virtually no arm support other than a bit of light guiding.

While playing around, I also found that the supplied table-top tripod also makes a handy “pistol grip” mount, which allows you to hand-hold the binoculars much more steady than conventional hand-held use. I folded the three legs together to make a single “grip” for my left hand, and turned the pan / tilt handle 90 degrees to the right (rather than it's normal orientation in-line with the binoculars); then holding the pan / tilt handle in my right, it is actually possible to hold the binoculars much more steadily and comfortably than the normal handheld position. I'm not sure why this is - it’s probably because your arms are comfortably resting down on your chest rather than being held elbows-out in front of your chest, but if you doubt me, try it - it might work for you too!

All in all, I’m very happy with my purchase! My only quibble is that I now have even more equipment to cart around - the 10x50s give a wonderful wide view for hand-held terrestrial and “wide sky” use (e.g. meteor spotting), and are light enough to throw in a backpack, but the 15x70s will be my “go to” binoculars for stargazing use, especially when I have a chair and a “monopod” to make them comfortable to use for extended viewing sessions.