M26

About

An open cluster in Scutum, about 5,160 light-years away and roughly 85 million years old. Its core has a region of unusually low star density, and as of 2015 there was still no clear explanation for it.

Imaging tips

• About 15′ across: roughly 1,620–2,690 mm on APS-C spans a third to half of the frame. Imagers say a long focal length suits it, while a wide field can also catch the dark Milky Way clouds around it.
• M11 lies nearby. A wide lens can frame both, but the Galactic Hunter authors prefer to image them separately with a larger telescope.
• The star field is crowded: one first stack looked noisy, and star masks, or removing the stars to work on the background, helped in processing.
• Sparse stars allow long subs: 180–300 seconds are suggested, and one 2-panel mosaic used 8 hours of 5-minute frames. Best around June and July; about 31° altitude at most from 50°N.