From the April 2013 issue

How much color should I be able to see in sky objects through a 10-inch telescope?

Dennis Holt, Concordia, Kansas
By | Published: April 22, 2013 | Last updated on May 18, 2023
The Blue Snowball (NGC 7662) is one planetary nebula in which you should be able to see color through a 10-inch telescope. // Dave Lassiter
Unfortunately, when you look at distant galaxies and nebulae, you won’t see much color through your telescope. That’s because you’re viewing objects that are too faint to trigger your eyes’ color receptors. (This is the same reason why on Earth we see lots of color in the daytime but not much at night.)
However, two classes of celestial objects — double stars and planetary nebulae — break this rule. The reason is their sizes. Stars are point sources, and planetaries typically measure less than 1 arcminute across. (As a comparison, the Full Moon spans 31 arcminutes.) So although they’re not really all that bright, their light concentrates over a small area. In astronomical terms, their surface brightnesses are high. The table above (“Color test”) provides 10 colorful objects to observe.

Here are five colorful double stars and five planetary nebulae in which you should see color; they are organized by group and then right ascension. You’ll find the positions of all these objects using Astronomy’s interactive star atlas at
Designation Colors
Beta (β) Cygni
Blue and gold
Eta (η) Cassiopeiae
Yellow and red
Al Rischa
Alpha (α) Piscium
Yellow and blue
Almach  Gamma (γ) Andromedae  Yellow and blue
Kaffaljidhma  Gamma Ceti  White and blue
The Little Gem  NGC 6818  Green
The Blue Flash  NGC 6905  Blue
The Saturn Nebula  NGC 7009


The Blue Snowball  NGC 7662  Blue
Cleopatra’s Eye  NGC 1535  Blue
Michael E. Bakich
Senior Editor