Sharpless 148

Sh2-148 is a compact emission nebula in Cepheus with an angular size of just 3.0′ × 1.6′, making it a demanding small-scale target that rewards long focal lengths and steady seeing. Because it lies roughly 18,900 light-years away yet spans only about 17 light-years across, it appears as a tight glowing knot rather than a sprawling cloud, so hydrogen-alpha narrowband filtering is essential to pull its structure from the rich Milky Way background. It sits immediately beside its catalog neighbor Sharpless 149 (also cataloged as LBN 516), which shares nearly the same patch of sky and lies at a comparable distance of about 17,800 light-years, so the two are almost always framed together. The nearby Sharpless 147, at roughly 10,200 light-years, rounds out this trio of independently cataloged emission nebulae that visually blend into one photographic field.

Names and Catalog numbers

• Sh2-148 (Sharpless 148)
• Sh2-147 (Sharpless 147) (associated object: Sh2-147)
• Sh2-149 (Sharpless 149) (associated object: Sh2-149)
• LBN 516 (associated object: Sh2-149)

Position and the cosmic neighborhood

Sh2-148 lies deep in the northern constellation Cepheus at right ascension 22h 56m 18s and declination +58° 31′, embedded in one of the densest star fields of the autumn Milky Way. Its close companion Sharpless 149 (LBN 516) sits barely an arcminute away at 22h 56m 17s, +58° 31′, so wide-field images capture both nebulae as a single luminous complex despite their being listed as separate objects. A short distance to the west lies Sharpless 147 at 22h 55m 42s, +58° 28′, and although it appears part of the same region on the sky, it is a distinct emission nebula at a very different distance. Together the three make a compact but layered target for anyone framing this crowded corner of Cepheus.

Nice to Know

• Although Sh2-148, Sharpless 149 (LBN 516) and Sharpless 147 photograph as one blended region, the catalogs list them as three separate, independent emission nebulae.
• Sh2-148 spans only about 17 light-years across yet lies some 18,900 light-years away, explaining its tiny 3.0′ × 1.6′ angular footprint.
• Sh2-148 and Sharpless 149 sit at nearly the same distance — 18,900 and 17,800 light-years respectively — while Sharpless 147, at about 10,200 light-years, is a foreground object only apparently associated with the pair.
• The trio’s small angular size and rich Cepheus surroundings make narrowband hydrogen-alpha imaging and long focal lengths the preferred approach for resolving detail.

Brightness, distance and size

It lies about 18,900 light-years from Earth and spans roughly 17 light-years across. On the sky it appears about 3.0′ × 1.6′ in size.