Sh2-108 — Gamma Cygni Nebula

About

Also catalogued as IC 1318, a very large complex of glowing hydrogen around Sadr (γ Cygni), the star at the centre of Cygnus's cross. Dark nebulae run through it. One visual observer reported that it overfills a 4° finder field.

Imaging tips

• At 130–220 mm on APS-C (210–340 mm full frame) the whole complex fits, as it is about 180′ across.
• An emission nebula, so narrowband suits it: one imager combined 6 nm Hα, OIII and SII with RGB for the stars, 12 hours 46 minutes in all, through a 72 mm f/5.6 astrograph.
• Another imager built a two-pane mosaic over four nights, 10 hours 40 minutes in total, covering about 2.9 × 2.4°; the Hα was shot as 5-minute subs.
• The open cluster NGC 6910 lies about 74′ away and M29 about 78′, both in the same wide field; the Crescent Nebula is about 125′ off.
• Best in July and August; it passes almost overhead, about 80° altitude from 50°N.