Meteor Showers and Smart Telescopes: Use the Right Tool

Every August and December, forums fill with people asking how to photograph the Perseids or the Geminids with a smart telescope, and the honest answer is unwelcome: you cannot, usefully, and trying will ruin an evening that would otherwise be one of the best of the year.

It is worth explaining why, because the reasoning illuminates what these instruments are for, and because there is a genuinely good way to spend those nights.

Why the format is wrong for meteors

Field of view. A smart telescope sees one to two degrees. Meteors appear anywhere in a sky spanning 180 degrees. The odds of one crossing your specific patch during any given exposure are very low, and you cannot improve them by pointing more carefully, because meteors do not have a location until they happen.

Exposure strategy. Deep-sky imaging takes many short exposures and stacks them. Meteor photography wants long single exposures covering a wide area, so that a bright transient event lands somewhere in the frame and is recorded in one go.

Stacking actively removes them. This is the part people find most counter-intuitive. Outlier rejection during stacking is designed to eliminate anything appearing in only one frame: satellites, aircraft, cosmic ray hits. A meteor is exactly that signature. Your telescope is engineered to delete meteors, and it is good at it.^[1]

What actually works for meteors

A camera with a wide or fisheye lens, on a fixed tripod, taking continuous exposures of ten to thirty seconds at a wide aperture and moderately high ISO, pointed at a large area of sky roughly 40-50 degrees from the radiant.

Then you let it run for hours and review afterwards. Most frames contain nothing. A few contain something, and that is the whole technique. A phone on a tripod with a night mode and an intervalometer app does a creditable job of this at zero cost.

Pointing away from the radiant rather than at it is the counter-intuitive part: meteors near the radiant are foreshortened into short streaks, while those further away show their full length.

What to do with the telescope on shower night

Here is the constructive answer. The nights of major showers are usually chosen for good reasons: they are often clear, often moonless, and you are outside anyway.

Run a normal deep-sky session. Set the telescope on a target that suits the season, start a long integration, and then lie back and watch the shower with your own eyes while it works. The instrument does not need supervision, which is precisely its advantage.

This is the best of both: you get an image from a night you would otherwise spend only looking, and you get to watch the shower properly rather than through a screen.

One caveat worth knowing. If a bright meteor does cross your telescope's field, stacking rejection will usually remove it from the final image. If you want to keep it, you would need the individual frames rather than the stack, and even then you have a short streak across a small field rather than a memorable photograph.

Watching a shower properly

Since the telescope is running itself, the practical advice for the human is straightforward:

• Lie down. A reclining chair or a mat. Craning upward for an hour is genuinely uncomfortable and you will give up early.
• Look at a large area, not the radiant. Peripheral vision catches meteors well.
• Give it time. Rates quoted for showers are theoretical maxima under perfect skies. Real counts are lower, and they come in clusters with long gaps.
• Stay dark-adapted. No phone. This is easier said than done while a telescope is asking for attention, which is another argument for setting a long single target and leaving it alone.
• Best hours are after midnight, when your side of the planet turns to face the direction of travel.

Then check what the telescope collected in the morning. Two things from one night, and neither compromised the other.

Notes & sources

1. Outlier rejection in image stacking and its removal of single-frame transients including meteors and satellite trails. Siril documentation, stacking and rejection ↩