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Another 2" ep question


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Whats the lowest 2" eyepeice i can use on my 12" f/5 1500mm dob?

Can somebody also explain(i must be a bit thick) the diference when using say a 32mm ep with 55fov & a 32mm ep with 68fov, how does it display more when the magnification is the same?

It's probably obvious when the right diagram is found:o

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Dunno about 2" ep's really, but the FOV is basically how big the visual circle is... For example, a ridiculously narrow FOV will be like looking through a straw, whereas a wide one will be large enough for you to actually move your eyeball left to right and look around inside the eyepiece. Both would give the same mag, but it's basically just a bigger "window".

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A 32mm eyepiece will give you x47, so...

The 55° eyepiece will give an actual field of 1.17°

The 68° eyepiece will give an actual field of 1.45°

If you had a 31mm Nagler, that would give you 1.69° and is as wide as you can get.

Any longer focal length than 32mm and the exit pupil will be too large.

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Whats the lowest 2" eyepeice i can use on my 12" f/5 1500mm dob?

Can somebody also explain(i must be a bit thick) the diference when using say a 32mm ep with 55fov & a 32mm ep with 68fov, how does it display more when the magnification is the same?

It's probably obvious when the right diagram is found:o

Unfortunately every software I know try to cram up the view on a circle the same size, even for different FOVs.

As jimmyjamjoejoe explained. If you look through a small window, then through a large window you'll see a lot more to the sides. Your eyes will give you the same magnification for both windows, so things will have the same size.

Edited by pvaz
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Unfortunately every software I know try to cram up the view on a circle the same size, even for different FOVs.

^This was what confused me.

It all makes sense now, thank you.

A 31mm Nagler would be nice but I was after something err....alot less £. Any suggestions?

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Check my paint skills

i vote POW for this. should be supplied with every beginners scope. as for a serious answer - the 32mm panaview get nice things said about it, for 80 quid. i have the 38mm, which wasn't sharp to the edge at f6 but i still really like it.

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