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Binocular Observing

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clx's picture
Binocular Observing

     Is there on optimum size for binoculars for viewing of variable Stars?  I have three pair of binoculars, 7X50, 15X60 and a pair of  tripod mounted 11X70's.   I ask this in anticipation of acquiring a universal binocular mount for my tripod, and possibly new bino's (Oberwerks 70mm /45 deg or Celestron 25X100).  I might buy these new bino's regardless; they might all be suitable.

     I would like to hear from some seasoned binocular observers on this matter

Aldebaran's picture
Binocular observing

No, there isn't any optimal size for binocular observing. With smaller bino's you can observe only the brighter stars but with larger, many also fainter stars are well observable for you! The only thing that matters, is that you select suitable stars to your observing program. It's important to not choose too faint stars, because it is very difficult to make any reliable estimates of too faint stars.

Your set of binoculars is really impressive! There are hundreds of stars available with that set of binos! Just use any of the binos, and choose suitable stars for them. Brighter stars for smaller binos, and fainter stars for the larger ones. You can also follow some large-amplitude mira -stars, for example Omi Cet, X Oph or R Aql are well observable with your larger binos also during the minimum of these stars! When these are in their maximum, you can well observe them with the smaller binos. Some small-amplitude semiregular -stars can be observed with one pair of binos throughout their entire cycle. With that arsenal of binoculars, there are huge amount of stars that you can observe, even if you would use only one pair of the binos that you have!

Good observing and clear skies,

Juha Ojanperä (OJMA)

Turku, Finland

pox's picture
Sometimes it's easy to go for

Sometimes it's easy to go for the 'obvious' ones - bright Miras near maximum and so on. But don't forget the unpredictable stars - AB Aur, CH Cyg, AG Dra and (especially with your larger binos) stars like XY Per and CQ Tau which often hover around 9th mag. With a pair of 25 x 100's you'll essentially be a 'telescopic' observer. Even with the smaller sizes you can catch U Gem and SS Cyg near maximum!

mdrapp's picture
It's all about balance

As a beginner I'll give my two cents.....

I find 10x50s an excellent size for binocular variable star observing.  One, while I like to use them mounted, they work just fine for a quick estimate if I need to.  Also, 10x50s tend to have a larger field of view than larger bincoulars, thus making it easier for me to find the field and comparison stars.

--Michael in Houston (RMW)

cutterboyus's picture

As a beginner I had good luck with 10x50s also.  Easy to hand hold and a good field of view to identify variable fields.  Go for quality, you wont be sorry in the long run.  Hard to go below 7.5 mag with my skies though.

lmk's picture
OK in a pinch

Having done a lot of visual observing with telescopes (mostly) and binos, here's my 2c on the issue:

1. Binos are useful for "grab and go" quick estimates, or when you are travelling or away from your regular telescopes.

2. Given a choice, however, I'd go with even small telescopes (eg. Edmund Astroscan) over binos because:

a. Typical mass produced binos have rather poor optics. If you cannot focus stars to sharp points, you lose quite a bit of fainter star ability (just defocus a good scope and you will quickly lose many tenths to a full magnitude due to the blurring of the image over a wider area).

b. The fixed eyepieces and generally low powers, image distortion from simple achromatic lenses, limit your ability to resolve variables, comp stars from close companions.

c. Holding binoculars over your head and bending your neck backwards at sharp angles gets to be very uncomfortable quickly. Its tough to keep steady as your arms tire. A recliner helps a lot, and binocular stand/mounts are good, but then you are talking about a lot of extra equipment to lug around, even more than a small telescope!

3. Binos have some positive though:

a. Ubiquitous and inexpensive, anybody can buy anywhere and use one.

b. Both eyes in use. Can make viewing more comfortable or natural, BUT only if properly aligned, otherwise a lot of eyestrain negates the advantage.

So, in summary, if you have a choice, get a nice small telescope rather than a pair of binos (unless you already have a pair, and dont want to sell). You will appreciate having something that comfortably points to what you want to see, and stays put without any athletics. Putting binos down to check the chart, and back and forth again to find the field in the sky, is somewhat inconvenient.  Plus, you have choices of great eyepieces to use, such as Naglers and Ethos for stupendous wide views, and various high magnifications!

Mike LMK

BBI's picture
You can never have enough

You can never have enough binoculars :-). I use a 8x40 handheld for bright stars,12x60 on a long monopod for fainter ones and a 20x80 on a parallelogram. I'm dreaming of a giant ...x100 (45° or 90°) from Oberwerk or Garrett Optical or ? with a sturdy mount like this one "Universal Astronomics Millennium Unimount" ( No neck pain with this one!

There are always tradeoffs; more than one pair is best

Over the past 25 years, I have used many different binoculars in observing, from 7x20 up to 11x80.  Currently I use a 7x35 Nikon wide angle for stars down to about magnitude 7 or 7.5 (or mag 5.5 near a full moon), and a 12x60 Celestron for most non-telescopic fainter stars that I'm following.  Both of these were very reasonably priced and provide superb images.  I still use my 14x70 sometimes, but only rarely; when the 12x60 won't show a target reliably, I often switch to telescope instead.  The 7x35 works surprisingly well, and the 12x60 is a recently acquired instrument that I absolutely love.  I'm very myopic and, when not wearing contact lenses, much prefer to use an instrument that will bring stars into focus without my glasses so I can obtain optimum contrast, light throughput, and shielding from ambient light.  The Nikon and Celestron both do that, but not the 14x70.  Hope this helps...I admire your stable of binoculars and agree with your strategy!

williampme's picture
Bino observing

I guess I will add my .00022 cents.  I have been observing since 1988 and my best estimate for bino vs telescope observing is 80% bino 20% telescope.  The main reason for this is that I do not use more instrument than I need to get a good estimate.  The vast majority of observations are of M or SRV types and near maximum many of these are mag 8 or brighter.   I have 7x35, 7x50, 10x50, 15x70, and 25/40x100 binoculars.  The 10x50 and larger glasses have parallelogram mounts.  the 7x glasses are for handholding and serve for variables brighter than 6th magnitude.  The parallelogram mount also facilitates zenith observing.  The 15x70 glasses will work down to mag 10 - I can follow Z UMa through it's entire cycle just using these, for example, and have been doing so for years.  The 25x100's will allow reliable estimates to mag 11 or so and the 40x eyepieces down to 11.5.  I have decent but not outstanding observing conditions so the numbers could change if I were in a city or a remote desert.  There are MANY stars within the grasp of 50-70mm glasses, so you could construct an observing list that would keep you busy for the entire year.

LKR's picture
Binocs and mounts

I've used 10X 50 and 20X 70 but the latter only with a mount. Depends on the situation and the stars I am going for. Both have been good in their respective situations.



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