What is the Caldwell List?

What is the Caldwell List?

Caldwell Catalogue poster

Poster by Roberto Mura

You may have heard about the Caldwell List or Caldwell Catalogue and wondered what it is. The Caldwell list was invented by Sir Patrick Moore. He put the list together after observing the Perseus Sword-handle and realised that many of the bright and interesting objects in the night sky weren't included in the Messier list (for more information on the Messier list visit What is the Messier List here). As Charles Messier had already utilised the letter 'M' to designate his list of deep space objects that weren't comets, Sir Patrick Moore used his proper hyphenated name Caldwell-Moore. Hence, this is why each space object is prefixed with a 'C'.

The list comprises 109 deep space objects to mirror the Messier list and is usually the next step an amateur astronomer takes in observing deep space objects after the Messier list.

The Caldwell list contains a wide range of interesting deep space objects. These include galaxies, globular clusters, nebulae, star clusters, dark nebulae, planetary nebulae and supernova remnants. Many of these are included in the Learn Astronomy HQ's constellation and DSO guide.

Iris nebula

The Beautiful Iris Nebula, C4. Image by Hewholooks

The list contains objects ranging from magnitude 1 to 13 and should be in the range of a 6 inch telescope. It covers a declination from +85 to -85 degrees. So there is something for everyone in both the northern and southern hemispheres. Unlike the Messier list where the objects are numbered in the order they were discovered, the Caldwell list numbers the objects from most northerly to most southernly. This means that in order to observe the whole list you would need to travel to the opposite hemisphere. Time to make some astronomical friends or take a fun astronomy holiday.

If you do plan to try and see all the Caldwell List objects be sure to register with the Astronomical League as they have an award for this achievement.

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