Miyauchi Bs-iB 20x77

4.0 Miyauchi, Bs-77ib

> Excellent Optics
> True binocular
> Small & light in comparison

> Easily lost caps
> Unsecure Eyepieces
> Chromatic Aberration on bright objects

General purpose binoculars are an excellent way to scan the night sky. The Miyauchi Bs-77ib "Exceed" are a great 'next step' for sweeping star fields, viewing comets, and generally observing the night sky right side up. Hand held binoculars have a limited magnification and objective size before jiggles and tremors destroy the image beyond recognition. Moving up to large objective, higher magnification astronomical binoculars requires a mount, the sturdier the better. While there are several entries into the larger astronomical binocular group, the Miyauch's are a smaller, lighter weight than most and have a 45° angled ocular that makes higher angle viewing much easier than straight through binoculars. The extra magnification without much of an increase in bulk makes these a great binocular for a sturdy camera mount making movement, aiming, and "Grab-n-Go" use easier than many of the others in this class. While the Miyauchi Bs-77ib "Exceed" do not replace standard binoculars for hand-held scanning at low power, they do provide a brighter image revealing fainter stars, nebulae, and galaxies. The higher magnification and slightly larger objectives definitely shows star clusters and fields to better advantage.

The Miyauchi Bs-77ib "Exceed" are well constructed, solidly build, and should last a lifetime provided care is taken in two mildly annoying areas. First, the front lens covers do not attach with a very positive hold. They stay in place but can easily be knocked loose with a minor bump. Over time these become increasing loose and need the felt replaced to retain any real positive hold. Second the 20x and 30x eyepieces while positively seated with an O-Ring can become dislodged if the binoculars are inverted and jarred. Fortunately, I was told about this possibility and tried it over a bed with a comforter from only a few inches in height. Turning the binoculars upside down and lightly rapping the base with the heel of your hand can cause an eyepiece to fall out. While neither of these issues is devastating as long as you are aware and careful, it can be annoying. So be fore warned, both the objective and eyepiece caps come off easily and can be easily lost. Remove the caps inside and place them in a safe location before you use the binoculars. Do not turn your binoculars upside down without 1st removing the eyepieces. Other than these two issues the binoculars are very solid and well built with excellent construction.

The 77mm Objective have a built in Dew Shield which is convenient but does not allow for the lens caps to be attached when extended. The objectives themselves are a semi-Apochromatic, 4-element, f/5.2 design using an ED (extra-dispersive) element for improved color correction. The lenses are multi-coated which is clearly visible as multiple red and green reflections when they are held up to the light. The eyepieces are held in place by a neoprene O-ring around the upper part of the barrel and are easily removed with a firm pull. [sometimes too easily] I have read the eyepieces are Reverse-Kellner design and the 20x = 2.5° FOV with an exit pupil of 3.85 while the 30x = 2.2° FOV. Eye relief is a little less than 20mm which is nice for eyeglass wearers but the short rubber eye shields do not fold down. If you are an eyeglass wearer you may find it easier to remove the eye shields which are very easily removed by just slipping them off.

At about 6 1/2 lbs the Miyauchi Bs-77ib "Exceed" are not much larger than the 16X70 Fujinons or the 18X70 Nikon Astroluxe and have the advantage of 20x or 30x plus the 45° angled ocular. Most well made camera tripods will handle these binoculars and on a study mount like a Bogen 3011 are easy to move and use. These binoculars can be mounted using the either a 'circular plate on post' with a standard ¼" x 20 TPI thread which will fit a standard camera tripod, or there are lateral mounting points on the sides that accept Miyauchi's fork mount. I have used both but general find that mounting them on a heavy camera tripod is more convenient for my style of viewing. Being able to swap to the 30x wide field is a nice feature when viewing smaller targets but does require the mount to be more stable.

The interior of the Bs-77ib binoculars are well baffled and blackened to prevent reflections and combined with the antireflective lens coatings do not present ghost imaging. Interpupilliary distance is adjusted by pushing the two eyepieces together or apart. The scissor mechanism that controls the interocular turret adjustment seems to work well on mine although others have reported theirs have loosened over time. If you have never used individual eyepiece focusing, there is a knack which is quickly learned and not having a central focusing mechanism is no real hardship. The eye point on these binoculars is somewhat critical and moving your head off-axis by much causes chromatic aberration or blackout.

Optically the Miyauchi Bs-77ib "Exceed" are excellent for any deep sky objects but not something I normally choose for Lunar observation. These binoculars are do not excell at Lunar or Planetary observing. They are marginal with fringe color (Chromatic Aberration) on the moon and the flaring on bright objects like planets. Compared to my Fujinon and Vixen binoculars in this objective range, the Miyauchi Bs-77ib "Exceed" have the worst chormatic aberration. While this is surprising since they're a Semi-APO with ED element, I've found the fringe on these worse than the 16x70 Fuji, 18x70 Astroluxe, or Vixen BT-80s. (The advantage here going to the BT-80s since you can use standard 1 1/4" "Fringe Killing" filters.) Also I don't tend to use them for planetary viewing mostly because I like a higher magnification for planetary work. But for DSOs and star field views they are excellent. For wide field use the Bs-77ib have a exceptionally flat field with no noticeable aberrations.

When viewing Orion's M42, you can split 4 stars in the Trapezium across 90+% of the FOV with bluish color seen in the nebula and a hint of the arc detail clearly noticeable. The image gets just the least bit soft with a reduced contrast and detail at the very edge of the FOV. M42s companion Nebula M43, showed discernible nebulosity with a faint nebular glow. The Planetary Nebula M27 is clearly seen as an Hourglass shape. Bright star clusters like M35, M37, and M38 looked terrific with pin-point star images. The Pleiades Cluster reveals about 80 stars very clear and crisp. No distortion of star images is seen even at the edges of this open cluster. These binoculars provide fantastic star colors that are beautifully defined with exceptionally clear color contrast at such low power. Alberio is easily split at 20x into deep orange and blue colored stars. While there are no issues with false color fringing under were normal DSO viewing, a definite color fringe is detectable on Jupiter when you look for it although both main equatorial belts are clearly visible. Saturn’s rings are clearly visible as distinctly separate from the planet body. When turned to Venus there are definite signs of fringe but it's phases are visible at 30x.

Overall the Miyauchi Bs-77ib "Exceed" are an excellent binocular for viewing star fields and DSO. With the exception of the mechanical issues stated regarding the lens covers and eyepiece O-Rings, they are very well manufactured and have the best optics in their size class. Light through put, contrast, and detail are excellent with no noticeable ghosting or internal reflections. They are sharp across 90% of the FOV with only the slightest softening at the very edge. There is no sign of any pin cushion or barrel distortions and no spherical aberration. While I'm not going to sell my 10x70 Fujis or Vixen BT-80s, the performance of these binoculars has convinced me to sell my 16x70 Fujinions. The Miyauchi Bs-77ib "Exceed" have too many advantages over the Fujis to keep both. The Miyauchis are almost the same size and bulk but at easier to use and more flexible. If you're in the market for a pair of 70 to 80mm actual binoculars, I suggest you look at the Miyauchi Bs-77ib "Exceed".