question ?

[bruno106a]

Hi everybody can anyone remember the site of the moon calculator with the camera lenses on it I think it was by a french bloke, I think his name started with an x did have it on my other computer but now dead so i can't retrieve it thanks for any help andy

 

[MWHCVT]

Sorry to say I have no idea what your referring to so I'll be intrigued as to what the answer turns out to be

 

[graphilly]

http://xjubier.free.fr/en/site_pages/astronomy/MoonExposureCalculator.html ???

 

[MWHCVT]

http://xjubier.free.fr/en/site_pages/astronomy/MoonExposureCalculator.html ???

That is actually quite a cool little tool

 

[Goody13]

Have just had a play with it and the interesting this is that the exposure limit without tracking is 1/1.6s for a 12MP sensor and 1/2.5s for a 21MP camera. Why would that be?

 

[MWHCVT]

Have just had a play with it and the interesting this is that the exposure limit without tracking is 1/1.6s for a 12MP sensor and 1/2.5s for a 21MP camera. Why would that be?

Most likely down to the fact that any longer than that and you'll suffer from the rotation of the earth without a tracking mount..I've not calculated the figures to be sure though

 

[Goody13]

I'd worked that bit out, but why the difference according to the no. of MP only?

 

[StewartR]

I'd worked that bit out, but why the difference according to the no. of MP only?

For a given focal length and a given sensor size, the moon takes up a defined portion of the sensor, right? You can see previews of this on that site you mentioned. (Incidentally they aren't accurate but that's another story.) Obviously the more pixels you have on your sensor, the bigger the image of the moon in terms of pixels, if all else is equal.

Now the moon appears to move in the sky due to the earth's rotation, and it moves a distance equal to its diameter every two minutes. So the bigger the moon in terms of pixels, the more pixels it moves in a given time. The numbers on that web site are meant to be the time it takes the moon to move by one pixel.

 

[Goody13]

Obviously the more pixels you have on your sensor, the bigger the image of the moon in terms of pixels

Thanks, that sort of makes sense, but I am still a little puzzled by the above statement. If you have more pixels, doesn't it just mean there are more pixels used in making up the image of the moon on the sensor?

 

[StewartR]

Thanks, that sort of makes sense, but I am still a little puzzled by the above statement. If you have more pixels, doesn't it just mean there are more pixels used in making up the image of the moon on the sensor?

That's what I said. What's puzzling about it?

 

[AJQS]

More pixels for the same diameter of moon = more blur for the same exposure time.

 

[Goody13]

That's what I said. What's puzzling about it?

How it would work, but I think Alan has clarified it. Thanks all.

 

[bruno106a]

thanks for that graphilly, and to all the others who enlightened peter

 

[JulesP]

Thanks for that - added to my favourites list
Should come in handy