Is it true that with higher magnification for a given scope the range of details seen diminshes?

Question

With so much literature flying around outside. i came across the mention that on increasing mag the details diminshes and the picture gets less sharper. While I agree with the sharpness I am not sure as to why the details degrad. It does not make practical sense, perhaps Im wrong but I was able to see saturn better with a 10mm eye piece than a 25mm eye piece for a 130mm 650 focal newtonian.

Have heard so many different opinions on this that perhaps I would have to end up buying a pair of barlows to see what is pratically sensible. It would help however is someone having genuinue knoweldge in the field of optics and clearly define and explain the anomoly before I go out spending money on lenses.

Again perhaps using a eyes of shorter focal length to increase mag might be better than barlow due to light bending etc I suppose.

regards

Answer 1

Well Saturn's really tiny so making it bigger makes it look better.
Planets and double stars want the highest magnification the condition allows. The details degrade because the view gets darker when magnified, but that doesn't matter with bright stars or planets.

Diffuse things like nebulae and galaxies can actually dissapear when overmagnified however, because the surface brightness is low. In that case you want to use a magnification as low as 1/5 to 1/7 of the aperture in millimeters.

If you buy a barlow you might get a 2x one, and now you have 4 eyepieces 26x, 52x, 65x, and 130x

It also might depend on whether you prefer a larger slightly blurry Saturn or a very tiny diamond-sharp Saturn. Don't buy a barlow to see planets if you don't like blurry.
Because at 65x you're already seeing as much detail that you'll ever see and if you get a 2x barlow then Saturn will be twice as big, twice as blurry and four times as dim.
But if you want more magnification and don't mind less sharpness then go ahead. Don't get a 3x barlow though, that's too much for the telescope.


It's those ones that say 675x MAGNIFICATION!!! with 3X BARLOW ONLY $19.99! that they might be complaining about.

Answer 2

Details may not actually diminish, but, above a certain power, the image is not clearer and you see no more detail, just blur. Which isn't very pleasant.

With your 10mm eyepiece on a 650mm focal length scope you're at 65 power, which is still fine. With a 130mm diameter scope you could go to about 130 power, on a good clear night. Beyond that, you'll see little more detail, you'll just magnify the blur. Some people say 50X per inch, but that assumes perfect optics and a perfect night. With a consumer grade telescope and an average clear night 25X is more like it.

Barlows are maybe a little less clear. People like them because one Barlow can be used on several different eyepieces. If you're clever about choosing focal lengths, that can essentially double the number of eyepieces you have.

Answer 3

It's a bit like looking closer, and closer at a photograph. For awhile you see more details, but eventually you begin to see pixels or grain (depending on whether you are looking at a digital or a film picture) and no further detail is possible. If you think of the grain or pixel as atmospheric distortion and optical imperfection you get the idea.