magnification

[quimby44]

hi all you stargazers i am using a zennox 76 x 700 with a 1.5x erecting lens with a H20 lens which i got with the telescope am i at my maximum whats the best lens to get its a 1.25 cheers stephen 

[jambouk]

Max mag is 30-50x per inch (but varies and 50x unlikely with smaller scopes)

Currently: 700 / 20 = 35 x 1.5 = 52x mag

Max theoretical mag: 3 x 30 = 90x

Highest power eye piece: 90 = 700 / ?

700 / 90 = 8mm

So highest power eye piece i'd say would be in the region of 8-10mm. Best to try an eye piece in this range before buying one as the view you get may be awful as it just magnifies things too much without offering any clarity.

(Calculations done in my head so may be a touch out (or very out)).

James

[ronin]

As above you will presently be getting 52x, Your "max" will be sort of anywhere from 75x to 150x depending on what you read or want to believe.

Realistically you will I suspect top out at 100x which is a 7mm eyepiece, an 8mm will give 87x.

The H20 lens is a Huygens design and they are not that good, they are 2 simple plano-convex lens.

Wikipedia has this to say about the Huygens eyepieces:

"This optical design is now considered obsolete since with today's shorter focal length telescopes the eyepiece suffers from short eye relief, high image distortion, chromatic aberration, and a very narrow apparent field of view."

As you can read not a great deal of praise for them.

Do you need eye relief for glasses?

If so then a shortish plossl may be ruled out.

If eye relief is required then you are looking at around the £50-60 area for cost, although there are others that may be fine at a little less, however plossl's are £35ish and BST's are £49 so not a huge difference in some respect.

[quimby44]

Max mag is 30-50x per inch (but varies and 50x unlikely with smaller scopes)

Currently: 700 / 20 = 35 x 1.5 = 52x mag

Max theoretical mag: 3 x 30 = 90x

Highest power eye piece: 90 = 700 / ?

700 / 90 = 8mm

So highest power eye piece i'd say would be in the region of 8-10mm. Best to try an eye piece in this range before buying one as the view you get may be awful as it just magnifies things too much without offering any clarity.

(Calculations done in my head so may be a touch out (or very out)).

James

thanks james

[quimby44]

As above you will presently be getting 52x, Your "max" will be sort of anywhere from 75x to 150x depending on what you read or want to believe.

Realistically you will I suspect top out at 100x which is a 7mm eyepiece, an 8mm will give 87x.

The H20 lens is a Huygens design and they are not that good, they are 2 simple plano-convex lens.

Wikipedia has this to say about the Huygens eyepieces:

"This optical design is now considered obsolete since with today's shorter focal length telescopes the eyepiece suffers from short eye relief, high image distortion, chromatic aberration, and a very narrow apparent field of view."

As you can read not a great deal of praise for them.

Do you need eye relief for glasses?

If so then a shortish plossl may be ruled out.

If eye relief is required then you are looking at around the £50-60 area for cost, although there are others that may be fine at a little less, however plossl's are £35ish and BST's are £49 so not a huge difference in some respect.

thank you ronin will keep that in mind i ware glasses so think it will cost me the £50.£60 mark will have a word with the club i am joining