Leo

Sickle of Leo

Leo's Sickle

common observer pattern · high confidence

A backward question mark above Regulus sketches the lion's head and mane. It is one of the easiest ways to find Leo before the spring galaxy fields rise.

Central RA: 10^h 05^m 10.0^s
Central Dec: +20° 17′ 42″
Brightest member: V 1.35
Best months from 50°N: March–June evenings
Suggested instrument: naked-eye
Approx. span: 14.5°

Finder context

This wider chart is deliberately schematic: it uses nearby bright-star context and boxes the asterism’s member-star footprint, but it does not draw official constellation boundaries or promise horizon/season precision.

Framing: Approximate member-star span: 14.5°; use at least 20.3° field for context.

Observing and imaging

Naked eye

Primary naked-eye pattern; suburban skies should show the main stars unless the description notes a low horizon or dark-sky need.

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 as a wide-field scene in/near Leo; a field of view around 20° keeps context without claiming exact constellation boundaries.

Observability from your latitude

Uses this asterism’s centroid RA/Dec: transit altitude, hours above 20°, and a month-scale evening window. Default is Edmonton-ish 50°N.

Latitude 50°NMonth

Naked-eye visibility by sky class

Approximate limiting magnitudes: Bortle 3 ≈ V 6.6, Bortle 5 ≈ V 5.6, Bortle 7 ≈ V 4.6. The shape is counted recognisable when at least 70% of defining stars clear the limit.

Bortle 3: 6/6 stars — fully visibleBortle 5: 6/6 stars — fully visibleBortle 7: 6/6 stars — fully visible

Member stars

Name	Bayer / Flamsteed	HR	RA J2000	Dec J2000	V mag
Regulus	32Alp Leo	HR 3982	10^h 08^m 22.3^s	+11° 58′ 02″	1.35
Algieba	41Gam1Leo	HR 4057	10^h 19^m 58.3^s	+19° 50′ 30″	2.61
17Eps Leo	17Eps Leo	HR 3873	09^h 45^m 51.1^s	+23° 46′ 27″	2.98
36Zet Leo	36Zet Leo	HR 4031	10^h 16^m 41.4^s	+23° 25′ 02″	3.44
30Eta Leo	30Eta Leo	HR 3975	10^h 07^m 20.0^s	+16° 45′ 46″	3.52
24Mu Leo	24Mu Leo	HR 3905	09^h 52^m 45.8^s	+26° 00′ 25″	3.88

Source and confidence

common observer pattern; high confidence. Commonly used constellation-part or seasonal guide-pattern name, with member-star positions plotted from BSC5.

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.