H-NGC7243
Open Cluster in Lacerta
About
A loose cluster of mostly blue-white stars in Lacerta, about 2,800 light-years away; age estimates run from 100 to 250 million years. A 2016 survey of it found 37 eclipsing binaries and 26 pulsating variables. Herschel 400 entry, found by William Herschel in 1788.
Imaging tips
- It spans roughly 30′, about the width of the full Moon, so it needs a wide field: a short focal length or a fast, short refractor.
- A sparse field led by a few magnitude 8–9 stars, with a close double near the centre (magnitudes 9.3 and 9.7, under 10″ apart). The star colours are the subject: shoot broadband.
- One published colour image used only 16 × 1.5 min each of R, G and B with no narrowband data, so a short session is enough.
- Best in August and September; it passes almost overhead from 50°N, peaking near 90°.
Facts
- Size
- 30.6′
- Magnitude
- 6.4
- Coordinates
- RA 22h 15.3m, Dec +49° 53′
- Framing, APS-C
- 790–1320 mm
- Framing, full frame
- 1210–2020 mm
- Best months
- Aug, Sep
- Peak altitude
- 90° from 50°N, 75° from 35°N