CN FORUMS ARCHIVE Telescope Reviews: Anttler Optics Sky Sweeper 20x80

Anttler 20x80

This is a less expensive 20x80 for those in the market that don’t want to pay $279 or $299 for the 20x80 triplets that are available.

It is light weight for a 20x80. It weighs in at 4# 10oz. Most of this binocular is made out of plastic.

This binocular measures f# = 4.5.

It has a multi-coated objective lens, but the rest of the components are single coated.

I’ve measured the field of view several times. Once I measured only 3.5°. But further use and more precise measures indicate it is closer to 3.7°.

Chromatic aberration is apparent on the moon and also when viewing dark tree limbs against a bright sky background. On the moon there is greater CA when it is off-axis, but there is still a thin blue and yellow band even when the moon is on-axis.

The exit pupil does not measure 4mm. It measures 4.25 to 4.3mm. Now if the exit pupil were smaller than it is supposed to be, we need to question whether it is caused by an eyepiece that is not providing the stated magnification or whether it is caused by an internal aperture stop. BUT when the exit pupil is larger than it is supposed to be and the aperture measures the full 80mm, there is only one thing that can cause this. The eyepiece that is being used is a longer focal length than it should be and the binocular is lower magnification than stated. This binocular has a magnification of about 18.6x to 18.8x.

With a magnification of 18.8x and a field of view of 3.7°, this eyepiece has an Afov of 70°. There is no apparent aperture stop, however, the outer 5% or so of the image is significantly darkened. This could be occurring because it uses such a wide angle eyepiece.

The eye relief is 17mm from the lens to the eye point. But there is a 3mm recess to the lens, so usable eye relief is 14mm. For me with my thin glasses, there is a slight cutoff of the outer field of view.

IPD range is 57mm to 72mm.

The point collimation is merged, but the field of view is off by several arcminutes, although not enough to make the view uncomfortable.

From the prisms back to the eyepieces, this binocular is an exact duplicate of the Burgess LW 20x80. I’ve compared the prism shelf, the housing and the dials and they all match. The only difference in this binocular and the Burgess 20x80 LW is the way the Anttler closes the objective housing. The plastic screw on parts are a little different. One minor difference is the eyepieces. The Burgess has a slightly smaller eye lens and the magnification is distinctly slightly higher in the Burgess.

The eyepiece is 4 elements in 3 groups. The field lens is a cemented doublet. All 6 surfaces are single MgF coated. The edges are not blackened. The eyepiece housing is all plastic.

The prisms are also MgF single coated. Only the objective lens is multi-coated. That qualifies this binocular to be classified as a multi-coated binocular. The single coated lenses are very faint blue in color. The objective is quite green, although if you tilt it at a steep enough angle you can see a purple tint. Even for a multi-coating, these are not premium coatings. Quite a bit of reflection can be seen in the multi-coating.

The contrast is not quite as good as some of the better binoculars. In comparisons to another 20x80 that I own, it was a bit more difficult to see objects like M33 and M1. However, clusters like M38, M37 and M35 were seen just as well. Although the reflections off the objective lens were relatively low, I did notice some minor internal ghosting. This would indicate possibly some internal reflections off the single coated surfaces.

On axis resolution is just a bit below my better binoculars. I could not split the equal double Mesartim at 7.8”. I've split this one is several other 20x80s.

In mag 5 skies I could see stars down to mag 10.7. This is only about 0.1 or 0.2 mag less than better 20x80s.

Sharpness across the field of view was pretty equal all the way around. However, it is not sharp very far out from center. I could see an 18” double at 50% out, but not at 60% out. That’s about 340 arcseconds of resolution at 50% out in the field. That is less sharp than most other binoculars, however it is almost identical to the Burgess 20x80 LW. Most other better binoculars can see 340 arcseconds all the way out to between 65% and 75% in the field of view. I did clearly see Alberio at 80% out from center and that gives 640 arcseconds at 80% out, better than the Burgess LW which drops off to 720 arcseconds at 75% out from center, the poorest sharpness out at that point of any binocular I've ever tested.

This binocular does have a vertical mount post attached to a center rod and the front objective is braced. That is probably what accounts for the difference in the objective housing difference between this and the Burgess 20x80 LW. If it wasn’t for this center post and front brace, this binocular is nearly identical to the now discontinued Burgess 20x80 LW.

This is a fairly inexpensive binocular available from Anttler optics. Called the Sky Sweeper, and regular priced at $179, it currently is selling for only $149. It would appear that the exact same binocular is also available from DBA astronomy.

I’d have to say, this binocular works just fine. No, it is not a premium binocular. But it doesn’t carry a premium price tag either. This binocular provides a decent value in a less expensive package for the observer that is shopping in that price range.

See the Vendor Announcements forum for links to the dealer, Anttler Optics.

edz

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