Gary Imm

GaryI

About

A backyard amateur astrophotographer enjoying retirement with my wife on beautiful Lake Livingston in Onalaska, Texas, about 90 minutes north of Houston.

(read more)

Stats

Member since
...

Last seen online
...

Total integration time
8822.2 hours

Average integration time
5.0 hours

Forum posts written
88

Comments written
29207

Comments received
42590

Likes received
173677

Views received
485714

The Hickson catalog is a collection of 100 galaxy groups by Paul Hickson in 1982. Hickson compact galaxy groups are tightly spaced relative to other space objects. A typical Hickson group has 4 galaxies, but can have up to 8. The criteria for a Hickson Galaxy Group is specific and detailed in his paper, but basically it boils down to 3 simple things: 1. The group must have at least 4 galaxies, all with decent brightness; 2. The group must be isolated and not just part of a large cluster; and 3. The group has to be compact, with spacing between them similar to their sizes. The galaxies are generally small, distant and a challenge to image. The diameter of a circle which surrounds each entire group ranges from 1 arc-minute to 16 arc-minutes. The brightest galaxy in each group is usually about magnitude 14. The objects below are listed in order of their Hickson number.