[meteorite-list] [OT-Off Topic] telescope

From: Galactic Stone & Ironworks <*meteoritemike_at_meteoritecentral.com*> Date: Tue, 10 Jan 2012 18:16:21 -0500 Message-ID: <CAKBPJW-6fPBcmPvd=FXF2cMY024jicu3S13LKb6cNAvuukGh2A_at_mail.gmail.com> · meteoritemike_at_meteoritecentral.com

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Galactic Stone & Ironworks - Meteorites & Amber (Michael Gilmer)
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On 1/10/12, Peter Scherff <peterscherff at rcn.com> wrote:
> Hi John,
>
> I have a similar rig. I find that I can use it to look at objects on the
> horizon. Unfortunately it is a killer when you turn it near the zenith.
> Without a diagonal you will kill your neck.
>
> Thanks,
>
> Peter
>
> -----Original Message-----
> From: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Pict
> Sent: Tuesday, January 10, 2012 11:15 AM
> To: Benjamin P. Sun; meteorite-list at meteoritecentral.com
> Subject: Re: [meteorite-list] telescope
>
> Benjamin,
>
> Haven't had a chance to play with this yet but I just managed to find a
> Nikon Lens scope converter. They were discontinued some time ago and are
> rare - been looking for a couple of years for a reasonably priced one. You
> mount it onto a manual focus F mount telephoto and it turns the lens into a
> telescope with a magnification 1/10th the focal length in mm.
>
> Now I have a 600mm f4, two 1.4X teleconverters, and a 2X teleconverter. So
> in theory I could stack all the teleconverters on and have a 2400mm f16
> lens. The front objective on this lens is 160mm in diameter so according to
> your rule of thumb it should be good for a useful magnification of
> (50/25)x160 = 320, whereas the actual magnification will be 2400/10=240,
> well within this.
>
> I was assuming the lens would be too dark at f16 to see much. Is this setup
> comparable to a telescope in the sense that your guidelines for maximum
> useable magnification still apply? I'd be delighted to hear that I do have a
> chance of it being useable at this magnification. What do you think? It will
> be monstrously unwieldy, but I do have a substantial tripod and gimbal head
> so should be possible to keep it reasonably steady.
>
> Regards,
> John
>
>
> On 10/01/2012 04:13, "Benjamin P. Sun" <bpsun2009 at gmail.com> wrote:
>
>>On a limited budget, a small refractor is best for casual planetary and
>>lunar viewing.
>>
>>Small reflectors are more suited for viewing deep space objects, such
>>as galaxies and nebulas.
>>Avoid reflectors under 100mm in aperture. Their large central
>>obstruction from the secondary mirror blocks out too much light. You'd
>>get a better, brighter, sharper image through a 60mm refractor than
>>through a 80mm reflector.
>>
>>I started out in astronomy decades ago with a quality 60mm tabletop
>>spotting scope with a zoom eyepiece. I could easily see all 4 of
>>Jupiters' moons, the rings of Saturn, the orange disk of Mars, the
>>phases of Venus, 7 stars of Pleiades, and Orion's nebula with it.
>>Ignore all the magnification power hype. A useful magnification
>>guideline is 50-60x per inch of aperture. So 60mm(2.4 inches) will
>>yield a maximum useful magnification of about 140x. More than enough
>>for the casual astronomer. Beyond that magnification and everything
>>begins to look crappy, dark and fuzzy.
>>
>>Remember, even on a low budget, you can still find a good quality
>>scope. Look for a coated(multi-coated if you're lucky) air-spaced
>>achromatic lens and good multi-element .965" or 1.25" sized eyepieces.
>>A finderscope is a non-essential accessory and usually useless junk
>>anyways.
>>______________________________________________
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>
>
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