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Early warning for newly discovered comets and unconfirmed objects.

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C/2025 A6

C/2025 A6 (Lemmon)

CometClass Ecatalogued
Southern hemisphere

Difficult — CCD / large telescope. Around mag 17.5. A large amateur CCD or a professional telescope is required. Historic peak was mag 4.2.

Active comet in COBS

JSONCSV

Right ascension

09h 29m 15s

J2000

Declination

−12° 05′ 55″

J2000

Estimated magnitude

17.5

CCD / citizen telescope · COBS consensus

Confidence

33

Class E · priority 66

Observations

1134

Arc unknown

Last observation

114d ago

Wed, 15 Jul 2026 18:28:47 GMT · COBS consensus

Perihelion

2025-11-08

0.530 au

Peak window

2025-11-05 → 2025-11-11

COBS peak mag 4.2 on 2025-11-08 · perihelion 2025-11-08. Window is those dates ±3 days — not a light-curve fit.

Historic peak

4.2

COBS / analyzed peak 2025-11-08

Catalog ingest

13m ago

Venator last wrote this row 2026-11-07 03:00:09 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

0.530 au

e

0.9960

i

144.00°

Ω

108.00°

ω

133.00°

a

121.000 au

MOID

—

H

—

H0 / n

6.9 / 3.8

NEO score

—

PHA score

—

RMS

—

Elongation

77°

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

  • C/2025 A6 (Lemmon)

    Informal: Lemmon

    C/2025 A6 · 2026-09-13 22:21:23 UTC → current

Discoverers

  • Lemmon

    Discoverer · parsed-name · 2026-09-13 22:21:23 UTC → current

Contributors

1–40 of 131

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