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Early warning for newly discovered comets and unconfirmed objects.

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123P

123P/West-Hartley

CometClass Ecatalogued
Northern hemisphere

Difficult — CCD / large telescope. Around mag 14.8. A large amateur CCD or a professional telescope is required.

Active comet in COBS

JSONCSV

Right ascension

10h 49m 18s

J2000

Declination

+18° 47′ 24″

J2000

Estimated magnitude

14.8

CCD / citizen telescope · COBS consensus

Confidence

33

Class E · priority 76

Observations

343

80.00 d arc

Last observation

8d ago

Tue, 08 Sep 2026 19:57:21 GMT · COBS consensus

Perihelion

2026-09-21

2.160 au

Peak window

2026-09-18 → 2026-10-12

COBS peak mag 14.8 on 2026-10-09 · perihelion 2026-09-21. Window is those dates ±3 days — not a light-curve fit.

Historic peak

14.8

COBS / analyzed peak 2026-10-09

Catalog ingest

13m ago

Venator last wrote this row 2026-09-16 22:00:03 UTC

Light curve

Brightness over time (V mag)

Gold = reported observations. Steel dashed family = ensemble (nominal / outburst / fade / disruption).

Tail length

Converted to degrees from COBS (d / arcmin / arcsec). Empty until analysis has pulled the archive.

Ensemble is a first-pass H0/n photometric model plus observed samples — not a trained ML forecast yet. The background analyzer walks the catalog one object at a time so COBS is not flooded. Disruption track rises after perihelion to stand in for solar-wind stripping.

Orbital elements

q

2.160 au

e

0.4450

i

15.30°

Ω

45.90°

ω

104.00°

a

3.890 au

MOID

—

H

—

H0 / n

7.0 / 8.5

NEO score

—

PHA score

—

RMS

—

Elongation

20°

Reporting sources

  • COBS comet list

    ok

    Comet Observation Database magnitudes and perihelion data for the full COBS list (active and inactive).

  • COBS orbits

    ok

    Osculating elements and photometric parameters (H0, n) for active comets.

Name history

  • 123P/West-Hartley

    123P · 2026-09-08 02:09:56 UTC → current

Discoverers

  • West-Hartley

    Discoverer · parsed-name · 2026-09-08 17:27:23 UTC → current

Contributors

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Pips are observation weight on this object (log of report count). Hover for catalog-wide weight.