Deep-Sky Object Explorer
Explore the 109 objects in NASA HEASARC’s electronic Messier set, then add your location, date and observing time to see where each target sits in your sky.
Make the catalogue relevant to your sky
Location and time are used only in your browser. They let the explorer estimate each target's altitude at the selected time and its highest sampled altitude between 18:00 and 06:00 local time.
About this data
The explorer covers the 109 records in NASA HEASARC’s electronic Messier catalogue. HEASARC omits M102 because it treats that historical entry as spurious and identified with M101. Right ascension, declination, visual magnitude and representative dimensions are used for planning and educational display. The browser applies a standard sidereal-time transformation to estimate local altitude and does not apply precession, nutation, refraction, terrain or weather corrections.
Choose targets by position, contrast and field size
Altitude tells you how high an object sits above the geometric horizon. Objects higher in the sky usually suffer less atmospheric extinction than objects near the horizon. Magnitude describes integrated brightness, while angular size tells you how much sky the object spans. Extended galaxies and nebulae can remain difficult even when their total magnitude looks bright because their light is spread over a large area.
Use Find in my sky for a dedicated altitude and azimuth calculation, then use Check framing to compare the object's angular extent with your telescope setup.