Comet C/2025 A6 (Lemmon)

Comet C/2025 A6 (Lemmon) was discovered on 3 January 2025 by D. Carson Fuls during the Mount Lemmon Survey in Arizona. At the time, it appeared extremely faint (magnitude ~21.5) and was initially mistaken for an asteroid, until subsequent observations revealed a condensed coma and a short tail.

It is a long-period comet, arriving from the outer reaches of the Solar System with an inbound orbital period of around 1,350 years.

Its closest approach to Earth will occur on 21 October 2025, while perihelion will take place on 8 November 2025. The orbit is highly inclined (~143.7°), making it retrograde (moving opposite to the planets).

In recent months, the comet has been brightening faster than predicted. Forecasts now suggest it could peak around magnitude 3–4, becoming visible in binoculars and possibly even to the naked eye under dark skies.

The image was acquired with a Takahashi TOA-150 and an STL-11000M camera: 72 × 30-second luminance exposures, together with 26 × 20-second RGB frames obtained through an FSQ-106N.

Colour calibration was performed using the SpectrophotometricColorCalibration module, taking a G2V star as white reference on an auxiliary star-registered image, then transferring the calibration coefficients to the comet-registered stack following the method described by Vicent Peris.

Data were acquired simultaneously and synchronized with two cameras under AstroArt. control.

Click on the images for full resolution versions, or go to the Gallery section for full exposure details.

Image processing: Pixinsight.

Observatory automation and remote operation with Talon6.