Telescope Reviews: Strathspey 15x70 vs Helios Stellar 15x70

Following another thread a short while ago I decided to buy a pair of the Strathspey as a means to “upgrade” some Helios 15x70 binoculars I already owned.

BACKGROUND

I regard myself as a relative beginner to binocular astronomy despite the fact that I have owned the Helios for a couple of years. I purchased them as a reasonably priced, large aperture instrument, but being fully aware of the cost of buying premium grade optical equipment in the UK, my expectations for the Helios’ performance were modest. I was initially impressed with their light gathering ability and high magnification but over a relatively short period of time became disillusioned with the short eye-relief and other aberrations I see. For these reasons the Helios has been used relatively little.

My original intention was to try the latest “premium” Astro-Physics or equivalent, but was put off this idea after much thought by the weight of these products and by the fact that I would have to import one into the UK. Thus, came about the idea of the Strathspey, which I believe comes from the same factory as the Oberwerk Giant series. These are significantly lighter than the aforementioned premium models and thus conceivably can be handheld at least for short periods, and in the UK are very reasonably priced. At this point in time I preferred not to splash out on much more expensive equipment.

My general experience with bins is limited compared to many on this forum, but I have previously owned both Zeiss and Leica compact 8x20’s for travelling, and briefly looked through larger Leica and Swarovski models. I also own a pair of Opticron 10x42 HR wide field.

Although I have tried to describe my thoughts, I would suggest you bear in mind that I am still inexperienced in testing binoculars!

So how do they compare?

a) THE PACKAGES

Both come with caps for the objectives and eyepieces. The Helios comes with a nice “hard case” and the Strat with a much cheaper looking soft nylon case. The Strat costs £95.75 incl delivery and the Helios has a recommended price of £154.99 excluding delivery – it may be available cheaper?

b) SOME PHYSICAL CHARACTERISTICS AND SPECS

• The Strat is slightly longer and heavier (1.8kg vs 1.29kg) than the Helios, but it doesn’t feel unduly so.

• It also has a slightly wider specified FOV (4.5 deg vs 4 deg).

• Eye relief is clearly longer (18mm) than the Helios (unknown, but I vaguely remember seeing a figure of 14mm somewhere – perhaps someone can confirm?).

• The Strat has much larger aperture eyepieces (2.2cm vs 1.4cm) and larger eyecups. Consequentially, the space between eyecups is also less. For my face, eyes and nose, I find the Strat to be a little uncomfortable if I am not wearing glasses, but with glasses and eyecups pushed back (which mostly will be the case for astronomical use) there is no problem.

• Re the coatings, both look pretty good to me although I am definitely no expert in assessing this. Looking into either, my own reflection is minimal. Strathspey’s website describes the coatings as “broadband coatings on all surfaces including the prisms”. Colour is purple / green. The website of Helios’ UK importer says this model has “multi-coatings on every lens surface” but there is no mention of the prisms. Coatings are blue / green. Coatings on neither product show any obvious blemishes.

• One feature of the Strat that I find a little odd is the setting I have to use for the right dioptre adjustment. Despite my eyes being not that different, I find I have to set it well into the “-“ end of the scale. By contrast, the Helios’s setting is much more central.

• The Helios’ build quality is definitely superior. It feels more solid despite being lighter, and overall there seems to have been a bit more attention to detail in the quality of the finish.

c) PERFORMANCE

• The Helios’ appalling eye-relief for eye-glass wearers is immediately obvious. Even with the eye-cups pushed back, I cannot see much more than half way to the edge of the field from the centre; let’s be generous and say 60% of the way to the edge. This means the area viewed through each eye is only 36% of the specified FOV! By contrast I can see the entire FOV of the Strat, which also has a slightly wider specified FOV. Without glasses, however, I am able to see the entire FOV in the Helios with both eyes open, but looking through one eye only I have to push the eyepiece right “into my eye-socket” to see the full field.

• One issue I have had with the Strat is occasional “blackout / kidney beaning”. I understand this may be due to not having my eye properly lined up with the exit pupil, which I guess may be a function of a) the longer eye-relief, and perhaps also b) the Strat’s much larger eyepiece aperture, both of which I suspect make it more difficult to get optimum eye placement. As I have become more used to using them, this is becoming slightly less of a problem although I still find it irritating when it happens.

• On-axis the Helios is slightly sharper. For example, testing during the day on some deer at a distance of 200 yards or so, the texture of the fur was slightly clearer with the Helios. At night, with a nearly full moon as subject, surface detail was also a little sharper. Off-axis, the Strat remains pretty good to about ¾ of the way out to the edge of the FOV and even beyond that it remains perfectly acceptable IMO. By contrast, my impression is that sharpness falls off more quickly with the Helios, and is relatively poor near the edge of the FOV.

• Both instruments do show some false colour. Testing with a nearly full moon as subject, the Helios showed a fair amount of yellow and green fringing around opposite sides of the moon’s disk, whilst the Strat fared a little better. On bright stars I have been experiencing some CA but at this stage I am hesitant to conclude too much from this because generally I have had poor atmospheric conditions - it seems like aeons since “seeing” has been good! Nevertheless, the odd “steadier moment” has led me to suspect the Strat is again a little better here. Daytime testing on subjects such as tree branches and TV aerials against a bright grey sky leads me to the same conclusion.

• Recently, I have been able to view Saturn from my back garden. Both instruments produce a touch of glare / reflection (I’m not sure if these are one and the same thing or if not how you distinguish between them). Testing on Sirius, both have shown a pale “halo” around the star. To be honest, at this stage I wouldn’t want to read too much into these features because they may have been exacerbated by ambient light or the turbulent atmospheric conditions. Also, in the case of the Strat, I have already mentioned the difficulties I’ve had with getting “optimum eye-placement” and I’ve noticed the amount of glare / reflection I’ve had is sensitive to eye placement. Further testing is required to draw a fair conclusion.

• For me the biggest thrill has been viewing the Orion area and also the Pleiades. Although subjects of this sort look good in the Helios, the Strat’s much larger effective FOV produces a much more immersive experience.

• So far I’ve not noticed any major difference in the darkness of the background sky, but it’s still early days!

• For daytime users, the Helios’ closest focus point is much nearer at about 20 paces vs 30 paces. I measured these wearing glasses but noticed slightly shorter distances without. I guess this discrepancy is due to the extent of my eye-glass correction.

CONCLUSION

Unsurprisingly, both products have good and bad points. I prefer the ergonomics, finish and build quality of the Helios but the Strat’s superior eye-relief, better off-axis performance and slightly lower levels of false colour. Let’s be honest – neither of these is “pin sharp” and both suffer from some aberrations, but it would be ridiculous to expect them to perform as well as “top models” selling at many times the price – something has to give.

For me, the eye-relief and overall optical performance of the Strat is good enough to provide some very enjoyable views of the night sky and that, together with its modest price, makes it an excellent buy in the UK.

My eyesight is such that I do need to wear glasses to enable me to “line up” intended targets. However, even then, the Helios’ substantially restricted FOV caused by its appalling eye-relief makes finding a target that much more difficult. The hassle of constantly putting them on and taking them off is just not worth while and thus for me the Helios comes second in this comparison, especially given its higher price.

John

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