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Any suggestions for a 5mm - 10mm telescope eyepiece? Answered

I am currently using a home built 3'' refracting telescope, and want to build a shorter focal length eyepiece to get some detail for observing planets (lunar surface, rings on Saturn, more of the moons of Jupiter. The current setup uses a plossl eyepiece with about a 25mm focal length, giving 30 to 40x magnification, and allowing very clear viewing of the moon, and will pick out three of Jupiters moons on a clear night.

Ideally I'd like a 5mm to 10mm focal length, for a 100 to 200x magnification. I've considered using the lens out of a DVD drive, which looks as though it could work, although I've only seen one example of it done before. I also have a selection of reasonable quality prisms and lenses about 1'' diameter, with focal lengths from about 2'' to 4''.

So, how well would a DVD drive lens work, and are there any interesting designs that make an eyepiece with a focal length significantly shorter than any of its component lenses (in the same way the focal length of a plossl is about 1/2 the focal length of the lenses used).

Thanks in advance for any help. (Would this get better response in the photography section)

Discussions

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mathup

3 years ago

i have also tried with a dvd lens of 10 mm focal length and a 1000 mm focal length as objective. It is very difficult to see through the eyepiece but it has amazing power of 100x which can be used to see saturn

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mathupmathup

Reply 3 years ago

well done mathu you done it very well

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mathupmathup

Reply 3 years ago

well done mathu you done it very well

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steveastrouk

7 years ago

AFAIK the lens of DVD player is not achromatic - it doesn't need to be, and is also not spherical !

Take a look at the rings around a star under focus and over focus.

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The Skinnerzsteveastrouk

Reply 7 years ago

Thanks for sharing the knowledge. Still waiting for the weather to clear up enough to see anything.

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steveastroukThe Skinnerz

Reply 7 years ago

Ah British optical astronomy. Is it any wonder we pioneered radio astronomy ?

I actually looked up yesterday, and it was pretty good where I am at the moment, tonight, not so much.

If you REALLY want to make your own eyepieces, I suggest you look at "SurplusShed" in the USA who have THE BEST supplies of surplus lenses AND eyepiece kits imaginable, Plossl, Erfle, orthos, all sorts of stuff.

Steve

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The Skinnerzsteveastrouk

Reply 7 years ago

I would prefer to build my own eyepieces, and it is even more work to adapt the telescope to take standard components, as when I built it I didn't really think about ever wanting to add different parts, so partial disassembly is needed to change the eyepiece.

At the moment, I was just thinking of doing something useful with the optics I had around, but I'll have a look at that US supplier if I get around to doing it properly. (I got the original lenses from I.R.Poyser in Wales)

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The Skinnerzsteveastrouk

Reply 7 years ago

Still appears to be going, and providing a very good service. In fact, my telescope is based on some of his designs which were provided when I ordered the lenses.

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The Skinnerz

7 years ago

Just finished mounting the DVD player lens, and initial results are surprisingly good. Apart from a number of fine rings around the edge of the image, probably from the grinding of the lens or the mould. I'll see how well it works on Jupiter once the cloud clears. So far, I can clearly see the fixings on a streetlight from a fair distance.