About the NPO's Object List
The National Public Observatory’s Object List contains 109 celestial objects (for amateur telescopes) beyond the Messier and Caldwell lists!
Want to explore the sky beyond these two famous lists, without taking on the daunting task of sifting for gems in the New General Catalog's 7,650 celestial objects?
The challenge was to construct a list, using the traditional 109 total objects, that were interesting and still within the range of the average amateur sized telescope (8 to 10 inches). Other criterias of object brightness or interest had to be considered to make the list interesting even though composed of generally lesser known objects. Generally galaxies of less than the 10th magnitude were only considered for the list, however if a galaxy was located near a bright star or other known object it was considered for inclusion. The limits for globular clusters and planetary nebulas was less stringent as they tend to have higher surface brightness. Open clusters were, on average, less bright than many on the Messier & Caldwell lists. In the end, a range of fascinating objects were included in the NPO Object List, to help guide you to a deeper understanding of the remarkable objects available to you in the night sky with an amateur telescope.
About Values Displayed
Celestial Coordinate System Right
Ascension Right
Ascension is measured in hours, minutes, and seconds beginning in the First point of Aries and going eastward. Hours lines of Right Ascension are space 15 degrees apart at the equator and converge like spokes going towards a hub at the north and south celestial poles. Hours (h) of right ascension (RA) are further divided into sixty minutes (m), and each minute is divided into sixty seconds (s).
Declination
Declination is analogous to latitude on the surface of the earth whereas RA is analogous to longitude. A star's declination (DEC) is distance from the north and south celestial equator measured in degrees from 0 degrees to 90 degrees. A + sign is used to designate DEC north and a - sign is used to designate DEC south. Often by convention the + sign will be omitted and just assumed. Declination is further divided into sixty minutes, and sixty seconds of arc just as Right Ascension is but these units always represent the same arc distances whereas RA arc distances are converted by the cosine of the declination.
Size Figures
Size figures are expressed as apparent sizes in minutes of arc. Some sizes had to be estimated. Objects with irregular shapes may have two sizes given in the description.
Magnitude Figures
Magnitude is a measurement of brightness, and is expressed as apparent visual magnitude where the data was available. A few of the objects magnitudes had to be estimated because limited data was readily available. If anyone has more concrete magnitude data for any of these objects that look to be substantially in error, we would welcome the appropriate corrections.
Credits
The National Public Observatory’s Object List was compiled for the NPO by John Gilkison, Jeff Jenkins, Bill Chrisly & Nicholas Patterson.