What is the smallest detail I can see on the moon

[beamer3.6m]

If I use my 8" Skywatcher Explorer could you tell me how to calculate the smallest features I will be able to see on the moon in km.

I.e, what would be the smallest object I could see on the moon in terms of its size.

Hope that makes sense.

[Roy Batty]

... errrr Tiny Clanger

But seriously... i read somewhere that with an 8" newt you should be able to resolve objects about the size of a football pitch if that makes sense. By resolve i mean able to tell two objects as separate objects.

RB

[Ant]

just found this on the internet...

The Hubble Space Telescope was recently trained on the Moon for the first time. It can theoretically resolve lunar features down to 85 metres (280 feet) across, which means that although it could never directly observe the lunar module's base section (much less the flag) it could possibly see its shadow near lunar sunrise or sunset. No Earth-bound telescope could match this feat.

A football pitch (I've just been told is 100yards) is around 92metres... So an 8" newt could not see something that small.

Hope that helps

Ant

[Ant]

according to Dawes limit (http://en.wikipedia.org/wiki/Dawes'_limit)

an 8" scope would be able to resolve to 0.58 arc seconds.

Lets assume the moon is 30 arc minutes (1800 arc seconds). The moons diameter is c3473km.

So 3474/1800 = 1.93 KM per arc second.

1.93 *0.58 = 1.12km

So in your scope you can resolve down to 1.12km.

This issue is further clouded (if you excuse the pun) by atmospherics, the quality of the equipment used, collimation and the wave length of light your observing.

Ant

[Roy Batty]

sorry for getting a bit mixed up here :? . . Ant's right

the anecdote about being able to see a football pitch is actually a stadium using the most powerful earth based telescope would appear as a single pixel.

still looking out for those damn clangers anyway

RB

[Ant]

Don't worry about getting mixed up... did you see MY calculation on the comet size - I was half a million km out

[Hugh]

Plus (or minus if you like), the visual accuity of the observer ... ?

[saturn5]

Don't worry about getting mixed up... did you see MY calculation on the comet size - I was half a million km out

I think you should get a pat on the back for knowing the maths to be able to calculate it,whether the answer is right or wrong.I wouldn't know where to start :withstupid:

[Black Shuck]

Don't worry about getting mixed up... did you see MY calculation on the comet size - I was half a million km out

When the distances are so large and the angles so small the mathematical errors are likely to be large. Half a million kms error over a distance of 243800000kms (the distance of Comet Holmes) is an error of 0.2% !!!

As I said to my friend who is a Physics and Mathematics graduate (who was 0.3 million kms out) what is a few thousand kms between friends apart from a long way to meet up for a beer?

Both interesting threads - makes you think about the scale of the things we view/image and sometimes take for granted on a daily basis!

Cheers

Bill£

[Casus belli]

... errrr Tiny Clanger

RB

Tiny Clanger? No chance. The soup dragon is only just visible in a 12" Dob :wave:

[Astroman]

Good post, Ant. You've pegged the "theoretical" limits. In practice, during excellent seeing, (which I'm very lucky to get from time to time), with an 8" I've seen craters as small as 5km across, and rilles ~2km across. When asked by the public, I generally say the smallest object they could see, given their lack of experience among other factors, is about 10km across under any given conditions. It may have large "error bars", but it still gives them some sense of scale.

[philsail1]

At last, I can stop straining my eyeballs out looking for Neil Armstrong's footprints!

Regards,

philsail1

[Tiny]

There should be lots of them - he took small steps. Isn't he a hermit now?

[supernova]

At last, I can stop straining my eyeballs out looking for Neil Armstrong's footprints!

Regards,

philsail1

You should see through my scope,

Did you know he had a drawing pin stuck in his left boot

He cant be a hermit he didn't walk sideways :nono:

[lunator]

Ant

excellent calculation. I remember having a discussion about this at my astro society and conclusion was n 8" scope could see craters down to 1km. Unfortunately being in London means that the real figure is quite a bit larger.

Cheers

Ian