If you’re looking for a celestial treat in the coming nights, keep your eyes on the northwest sky just after sunset — Comet C/2025 A6 (Lemmon) is making its way into evening visibility, and Delmarva is in a prime spot to catch it.
Discovered in January 2025 by the Mount Lemmon Survey, Comet Lemmon has become one of the most talked-about comets of the year. Originally expected to remain faint, the comet has surprised astronomers by brightening faster than forecast.
Lemmon will make its closest approach to Earth on October 21, 2025, at about 0.596 AU (roughly 89 million km) away. It reaches perihelion (its closest point to the Sun) on November 8, 2025.
Currently, the comet is estimated to be around magnitude 5 to 6, making it not quite prominent to the naked eye in most skies — but definitely within reach of binoculars or small telescopes in a dark location. Some predictions are more optimistic, suggesting it might brighten to magnitude ~4 around late October, which would make it more noticeable even to unaided eyes under favorable conditions.
One of the exciting features now is that Lemmon will be about 42° away from the Sun during its closest approach — meaning it should be visible low in the western sky about an hour after sunset. The star Arcturus (in the constellation Boötes) and the double star Izar are being cited as useful reference points to help find it.
By mid-to-late October, it should shift from being a dawn object into the evening sky, which greatly improves viewing opportunities for observers who aren’t night-owls.
What Delmarva Observers Need to Know
When & Where to Look
- The comet will be best seen just after nautical twilight, once the sky is fairly dark but before it sinks too close to the horizon.
- Start scanning the northwest to west-northwest horizon — the comet will be relatively low.
- Use a low horizon (free from trees or buildings) to maximize your view.
- For timing, expect prime viewing windows roughly 30 to 90 minutes after sunset, though this will shift slightly each evening as the comet’s position changes.
Sky Conditions
- Fortunately, forecasts suggest clear skies are likely — ideal conditions for comet watching.
- Minimize light pollution: try to get to a darker spot (away from street lights or heavy urban glow) to boost your chances of spotting Lemmon.
- Use apps like Stellarium, SkySafari, or TheSkyLive to track its nightly position against the background stars.
Tips for Viewing & Photographing Comet Lemmon
For Visual Observers (Binoculars / Telescopes)
- Start with 10×50 or 10×60 binoculars — these will likely pick up the comet before your eyes can.
- Use a low-power eyepiece in a telescope (e.g. 40–60×) to get a wider field of view and more context.
- Try averted vision (looking slightly to the side of the comet) — your peripheral vision is better at detecting faint objects.
- Take time to let your eyes acclimate to the dark (about 20–30 minutes).
For Astrophotographers
- Use a wide-field lens (e.g. 24–50 mm) on a full-frame or APS-C camera, or a modest focal length if using a telescope.
- Aim for exposures of 30–120 seconds, depending on your tracking capability and sky conditions.
- Use a star-track mount or equatorial tracker if possible, so you can lengthen exposure without the stars trailing.
- Stack multiple frames in post-processing to improve signal-to-noise and bring out tail structure.
- Consider taking sequences over several nights — the comet’s movement will allow you to show motion or tail changes.
- Use dark, flat, and bias calibration frames to clean up the images.
Caution / Tips
- Because the comet is low, atmospheric extinction and scattering may dim it. Give yourself some margin.
- Watch for fog, haze, or humidity near the horizon, which could obscure faint details.
- Be patient — the comet’s brightness can vary, and fainter comets often require persistence and ideal conditions.
Why This Is a Special Opportunity
Comet Lemmon is not a frequently returning visitor — its inbound orbital period is estimated at about 1,350 years, and after its perihelion passage that period may shorten to around 1,150 years. It last visited Earth’s vicinity more than a millennium ago, and this may be our best chance to glimpse it in our lifetime.
If conditions hold, Lemmon could become the brightest comet of 2025 — a rare and beautiful sight in the autumn sky.
So, clear your evening calendar (or at least a half hour), pack your binoculars or camera gear, and look northwest after sunset over Delmarva. With luck and clear skies, you may witness a stunning visitor from the outer reaches of the solar system.