For observers seeking a compact achromat
, the Borg 76SWII could be a fine choice.
Gathering 44 percent more light than its sibling (the Meade AR-5), this refractor is a 6-inch (152-mm), 1,220-mm-focallength (f/8) achromat
with an LXD55 German equatorial mount, built-in dual-axis worm-drive systems, an illuminated polar-alignment viewfinder, and an adjustable tripod.
My 6-inch f/8 achromat
gathers more than twice as much light as its smaller 4-inch f/9.8 cousin, and it also exhibits far more secondary spectrum.
For one of my tests I set up an older 80-mm f/11 achromat
(a good scope in its own right) next to the Orion.
For the Nighthawk, advertised as an achromat
with a "proprietary" Stellarvue lens, the answer is, Surprisingly little.
Under extremely favorable conditions I pushed the scope in excess of 285x on the Moon--a respectable feat for an achromat
of these specifications.
" brings red and blue light to one focal point.
Spatial and temporal limits of vision in the achromat
. Journal of Physiology, 377, 365-385.
On that basis, he declared that an achromat
: An objective lens system constructed of glass with limited quality of correction for color and spherical aberration.
Despite its spherical mirror, Baby provides pretty good low- and medium-power views when used with the MA (modified achromat
) eyepieces supplied with Mama and Papa.
However, observing the crater Muller on 2008 October 8 with my 100mm Borg Achromat
I did gain the impression of a darker streak running along and down the crater wall and aligned with the distinct crater chain beyond.