The price for high-quality refractors has fallen dramatically in recent years, and you can now purchase a 4-to-5-inch extra-low dispersion (ED) apochromatic (APO) telescope that's almost entirely free of the false color that plagues achromats
for a fraction of the cost commonly seen a decade ago.
In point of fact, there may well be phenomenal differences between, e.g., achromats
and normally sighted people.
The sun blinds people with achromatopsia, known as achromats
, when they are outside, and some people are so sensitive to light that they are even uncomfortable indoors in a normally lit room.
Like all fast achromats
, the Infinity 90 shows violet halos around the Moon and planets, but the planetary views are otherwise quite attractive and detailed.
, the most inexpensive models, produce a bluish-purple halo of unfocused light around bright subjects such as the Moon and planets.
DayStar recommends using achromats
or apochomatic refractors without additional correcting elements near the focuser.
* Inexpensive refractors (ones called achromats
) are unable to focus all colors to the same point, which results in a halo of blue light around bright objects.
These include a pair of D&G Optical 5-inch f/30 achromats
in oversized tubes that are intended primarily for solar observing.
That $20 telescope fired her imagination, just as many other lowly 50-mm achromats
have done for others (I still fondly remember my first 50-mm Tasco).