Those who know even little bit about telescopes will be flabbergasted that this question even gets asked, but it does. Every now and then someone asks us in the store or via email “Will this telescope will let me see the Lunar Lander/Flag on the Moon?”
After first resisting the urge to Facepalm we then go on to explain why this is not going to happen with pretty much any telescope used on Earth, or heck even from telescopes in orbit.
First of all go to Google Images and look for telescope images of the Lunar Lander remains. You won’t find any. The shots that come up from such a search are from the Lunar Reconnaissance Orbiter that photographed the Lunar Surface FROM LUNAR ORBIT in 2009. Keep in mind that the LRO was probably in a lower orbit than the spy satellites we use around Earth and it still has the Lander remains showing up as a few pixels casting a longer shadow. This was all that the probe in Lunar orbit could do. The Hubble couldn’t even do that, and your terrestrial-based telescope can’t either.
Why not? Well it all comes down to a little things called resolution. What that means is how much your telescope can differentiate one object from another, or how small an object you can see. Resolution is measured in parts of a degree called arc seconds. How much this resolution translates to size depends on how far the object being viewed is from you. Close to the telescope and you can count individuals’ buttons on someone’s shirt, get to deep space and that same resolution now makes up billions of miles.
For the Moon? Well, a large home telescope (12″ or larger), under perfect circumstances has maxed out viewing limit of .5 arc seconds. Sounds good (and it is) but once you get just to the Moon that .5 arc seconds is measured in miles. Keep in mind that the Lunar lander was only a few yards across!
Simple logic and common sense should tell most folks this if they think about it, but we are often told tales of spy satellites that can read our license plates from orbit, or have it in our heads that optics work the way we want rather than being governed by certain optical laws. It doesn’t help that cheap department store telescopes often come in boxes that show pictures of the Moon taken from the Apollo landers!
BTW, do not expect to see the flag on the Moon. Ever. The flags were made of plastic and have been bombarded with direct UV for over 40 years. The result has most likely destroyed the flags. The footprints the astronauts left on the moon will last for ages – the plastic flags they hung up? Not so much! UPDATE – 7/31/2012. Seems that is wrong, the flags are still there!