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Can Satellites Orbiting the Moon Be Seen with a 4″ Optical Telescope?

-- Jay | June 20, 2020

Question:

Is there satellites orbiting the Moon? And are they visible through a 4″ telescope with a focal length of 1325mm? Reason I ask is I believe I spotted two of them orbiting the Moon one afternoon just before dark, the Moon was a Waning Crescent and above the dark portion of the Moon was an object gleaming brighter than the Moon itself and was within what I would consider orbit range of the Moon’s crust. It appeared to get closer to the Moon the longer I looked at it and before I could snap a photo of it, it disappeared into what I guess was the shadow of the Moon blocking the sunlight at that point. Another dimmer light I was able to spot drifting slowly down the side of the Moon and I was able to watch as it orbited the Moon to a lower portion where it finally became too dim to longer follow. Do you believe that these were satellites orbiting the Moon that I saw?
Thanks much, Jay

-- Jay

Answer:

I believe that there is only one known artificial satellite orbiting the Moon at the moment, that being the Lunar Reconnaissance Orbiter (LRO). I don’t believe that artificial satellites orbiting the Moon can be seen from Earth with a 4 inch optical telescope, and especially before sunset. The LRO is only about 5 meters in size, which would make it appear to be an unresolved point of light from Earth. Very roughly, the gain in sensitivity you get from a 4 inch telescope beyond what your eye can detect is about 9 magnitudes. If your eye can detect objects down to magnitude 6 then, the LRO would have to be at least magnitude 15 to be detectable with your telescope. For reference, Pluto’s moon Charon is about magnitude 15 at its brightest, which I believe is difficult to detect with telescopes that are significantly larger in diameter than 4 inches. So, I suspect that what you saw were not artificial satellites orbiting around the Moon.

-- Jeff Mangum

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