Making a small Refractor.

[Wedge]

Hi All.

I am planning to make a small refractor for part of my GCSE coursework.

I was wondering what sort of lenses would I need? (IE biconvex etc)

Does anybody ave a useful guide which they could link me to?

Thanks!

Remy.

[GazOC]

Are you making a reflector or a refractor?

[Wedge]

I did say refractor.

I mentioned it in both the post and title

:oops:

[GazOC]

I did say refractor.

I mentioned it in both the post and title

Then you asked about mirrors in your first post......

[Wedge]

Ah Yes :oops:

Seems I confused myself then!

How embarrassing!

[GazOC]

No worries mate!

FWIW its lot easier (and cheaper) to make a decent reflector yourself than decent refractor.

[jcm]

You can make a simple refractor from two convex lenses , one long focus and one a short focus (eyepiece) and a couple of sliding cardboard tubes. This will give you a magnified image but with lots of distortion and colour fringing.

It depends on how good you want your final image.

John

[Wedge]

No worries mate!

FWIW its lot easier (and cheaper) to make a decent reflector yourself than decent refractor.

Perhaps.

But decent it doesn't have to be...

I mean, I am not going to use it instead of my normal telescope, It only really needs to be VERY simple.

My teacher said that he could provide me the lenses, if I were to report back which sort I needed.

[GazOC]

Ah, fair enough..I thought you might want to use it.

[jcm]

Its not too important as long as the focal lengths are different. If you had a 30cm fl lens ( the longer the fl of this the longer the tube) and with a 5cm fl lens you would get a mag of 6X. Cardboard is easy to cut and you could always paint the tubes to make it look better.

John

[Brass n glass]

Ian Poyser does refractor kits for GCSE. Have a look at http://www.irpoyser.co.uk/educational.php

[Wedge]

OK Thanks,

So my a 30cm fl lens, you mean focal length?

Is that the same as diameter?

[jcm]

OK Thanks,

So my a 30cm fl lens, you mean focal length?

Is that the same as diameter?

Yep , fl = focal length. Its not the same as the diameter. Its the distance from the lens to the point a sharp image is formed.

Objective diam - say 5cm (2") , eyepiece diam say 2.5cm (1") - but you not have to stick to these measurements.

If the school is providing the lenses see what they have got.

John

[Wedge]

OK that is good in fact.

I thought that I would need a lens with a 30cm diameter :shock:

Thanks for the help.

[jcm]

No problem.

Post again if you need any further help.

John

[Wedge]

OK, I will, Thanks

Good luck on your 1000th post

[The Warthog]

I've occasionally, in the absence of a real scope, checked out the view in a new ep by holding up a largish magnifying glass and examining the image to get an idea of eye relief, etc. This would work as the front elephant of the scope.

If your teacher's going to supply the lenses, though, tell him you want an 80mm APO triplet with a focal ratio of f/6.