h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Choosing a Telescope Eyepiece - A87847429
Author: Gnomon - U151503

This was in Peer Review before.

Previous Peer Review conversation: F22144398?thread=8312680

I enjoyed reading this the first time it was in Peer Review.

I don't have any telescope experience, but it reads well.
There are questions I think that will arise and so will need answers prepared. These are around the 2.4 v 2 rule. Where you have written 'Some people say that you can push the magnification as far as 2.4 times the aperture in millimetres' I can't help but wonder who these people are, and similarly when you later say 'Experience shows that this is not really achievable' I wonder whose experience.

Is it a case of 'if you are, say, a University and have type X of extra-expensive telescopic equipment 2.4 works, but for most people the standard the limit is 2?' Or is it just that there are circumstances in which increased blur does not matter as much, but for the majority practical purposes 2 is the benchmark? Or has a recognised astronomy authority, such as Patrick Moore, supported the limit of 2? Maybe a little footnote to explain further might help?

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At MMF's request in another thread, I've changed the title of this to:

"Choosing an Eyepiece for an Astronomical Telescope"

Good point Bluebottle. It seems to be that the telescope manufacturers claim magnifications of as high as 2.4 x aperture, but many websites suggest that this would only be achievable in very good viewing conditions, and a figure of 2.0 is more realistic.

Thank you, Gnomon. Didn't want to create a problem, but I thought it was a more accurate title for the entry.



MMF

Ah, it's a manufacturers' claim – that explains it perfectly.

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I'm still looking into this issue.

I've restated that section to state specifically that the figures of 2.4 and 2.0 are by telescope manufacturers and amateur astronomy websites respectively:

Telescope manufacturers say that you can push the magnification as far as 2.4 times the aperture in millimetres, which would give a maximum magnification of 240&times; for the same 100mm telescope. This is the equivalent of multiplying the aperture in inches by 60. Most amateur astronomy sites agree that this is being optimistic - the viewing conditions would have to be very good for a clear view at this magnification.

Well, this was a delightfully informative read.

I did need to read your new paragraph (2.4 vs 2.0) twice just to make sure I was following fully - but I think I see what my difficulty was. You end the paragraph immediately before (para. numbered 3.) with '...upwards to the highest magnification possible on your telescope.'

Then paragraph numbered 4. starts with 'The highest magnification practical on your telescope can be...' which i carelessly glossed over and was still thinking in terms of highest possible. So, anyway - does one really want a range of eyepieces up to the highest possible (which might not be practical)? or to the highest practical, in which case the whole thing comes together.

Thanks

Thanks Pailaway. I'm away this evening but will have a careful read through tomorrow evening with these points in mind.

You're right, Pailaway. The distinction between highest possible and highest practical magnification confused even me. I meant to say 'highest practical' both times. But that leads to repitition which can be equally confusing, so I've reword the end of section 3 to be:

"As a result, it's a good idea to have a range of eyepieces that give you different magnifications upwards from about 15&times; to whatever your telescope is capable of."

Excellent! is there any possibility of a section of regarding camera eyepiece adaptors for photography

I don't know anythingabout that, bob, so I won't write about it.

I have been trying to find recommendations, it was just an idea

Have you considered a link to: A827309 How to Choose an Astronomical Telescope

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Good idea!

I've added a link in the references section.

Had another read-through and have nothing more to add, unless you wanted to include links to other astronomy articles, such as:
A301870 - Astronomy for Amateurs
A346844 - What's the Point of Astronomy?

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I've added an introductory paragraph, and have put a few links in it, including the two you suggested here.