Hercules

Keystone of Hercules

Hercules Keystone

common observer pattern · high confidence

The lopsided four-star keystone anchors Hercules and points the way to M13 on the western edge. From 50°N it is a high summer pattern, best when the Milky Way is climbing.

Central RA: 16^h 54^m 52.6^s
Central Dec: +34° 33′ 55″
Brightest member: V 2.81
Best months from 50°N: June–September evenings
Suggested instrument: naked-eye
Approx. span: 8.8°

Finder context

Use the nearby bright stars to locate the gold box, then move to the larger chart for the pattern itself.

Framing: Approximate member-star span: 8.8°; use at least 12.3° field for context.

Observing and imaging

Naked eye

Start with the unaided eye. Suburban skies usually show the main stars.

Binoculars

Binoculars are optional: use them to check colours, nearby doubles, or richer Milky Way background.

Small scope

A telescope is usually too narrow for the whole shape; use it after the pattern has guided you to a target.

Imaging

Frame a 12° field around Hercules to include the pattern and its nearby stars.

Tonight from your latitude

Set your location and date to see a useful window, peak altitude, sky visibility, and Moon conditions. Use Month to compare the season ahead.

Latitude 50°NLongitude -114°Date Month Sky darkness Bortle 4 · limit V 6.1

Naked-eye visibility by sky class

Bortle class rates night-sky brightness. The atlas counts a pattern as recognisable when at least 70% of its defining stars are visible.

Bortle 3: 4/4 stars — fully visibleBortle 5: 4/4 stars — fully visibleBortle 7: 4/4 stars — fully visible

Moon impact

For 50°N in the best month, green dates mark at least two hours with the pattern above 20° and the Moon below the horizon.

01020304050607080910111213141516171819202122232425262728293031

Member stars

Name	Bayer / Flamsteed	HR	RA J2000	Dec J2000	V mag
40Zet Her	40Zet Her	HR 6212	16^h 41^m 17.2^s	+31° 36′ 11″	2.81
67Pi Her	67Pi Her	HR 6418	17^h 15^m 02.8^s	+36° 48′ 33″	3.16
44Eta Her	44Eta Her	HR 6220	16^h 42^m 53.8^s	+38° 55′ 20″	3.53
58Eps Her	58Eps Her	HR 6324	17^h 00^m 17.4^s	+30° 55′ 35″	3.92

Source and confidence

common observer pattern; high confidence. A commonly used constellation-part or seasonal guide pattern.

Citations

Bright Star Catalogue, 5th Revised Ed.: Hoffleit, D. & Warren, W.H. Jr. (1991). Positions, V magnitudes, Bayer/Flamsteed identifiers. source
Star Tales: Ridpath, I. Constellation and asterism notes used to cross-check common sky-pattern names. source
The Hipparcos and Tycho Catalogues: ESA SP-1200 (1997). Used as the modern astrometric reference named by the atlas; the MVP pages expose BSC5 J2000 fields for the plotted bright-star members.