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Not all lenses are meant to be used as telescope objectives.
On Friday, March 25, 2022 at 7:43:39 AM UTC-6, W wrote:
Not all lenses are meant to be used as telescope objectives.I can attest to that, as I wear eyeglasses, and I also own a camera - in addition to a
smartphone with a camera.
However, a lens that is 74 mm in diameter, but with a focal length of
3,000 mm, I would suspect, _is_ intended to be used as a telescope
objective.
But maybe not. 74 mm diameter is the kind of aperture one would associate with a department store special telescope. If diffraction limited, a telescope
with such an objective could magnify up to 180x. Divide 3000 by 180, and
you get 16 2/3. They do make eyepieces with focal lengths that big, so one _could_ use that lens in a telescope, impractical though it might be.
John Savard
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On Friday, March 25, 2022 at 7:43:39 AM UTC-6, W wrote:
Not all lenses are meant to be used as telescope objectives.I can attest to that, as I wear eyeglasses, and I also own a camera - in addition to a
smartphone with a camera.
However, a lens that is 74 mm in diameter, but with a focal length of
3,000 mm, I would suspect, _is_ intended to be used as a telescope
objective.
But maybe not. 74 mm diameter is the kind of aperture one would associate with a department store special telescope. If diffraction limited, a telescope
with such an objective could magnify up to 180x. Divide 3000 by 180, and
you get 16 2/3. They do make eyepieces with focal lengths that big, so one _could_ use that lens in a telescope, impractical though it might be.
On Friday, March 25, 2022 at 2:05:25 AM UTC-7, RichA wrote:ext_f=%7B%22sku_id%22%3A%2210000004778721146%22%7D&pdp_pi=-1%3B42.26%3B-1%3B-1%40salePrice%3BCAD%3Bsearch-mainSearch
https://www.aliexpress.com/item/4000640306730.html?spm=a2g0o.productlist.0.0.6f302331VGkoXt&algo_pvid=c0b2e880-ec51-4bb6-b05a-f14d156bc3c9&aem_p4p_detail=20220217225309433165067225700107795225&algo_exp_id=c0b2e880-ec51-4bb6-b05a-f14d156bc3c9-9&pdp_
I already have a 10-ft telescope and don't need another!
https://www.cloudynights.com/uploads/monthly_06_2006/post-12572-14070975670902_thumb.jpg
On Friday, 25 March 2022 at 23:47:31 UTC-4, palsing wrote:ext_f=%7B%22sku_id%22%3A%2210000004778721146%22%7D&pdp_pi=-1%3B42.26%3B-1%3B-1%40salePrice%3BCAD%3Bsearch-mainSearch
On Friday, March 25, 2022 at 2:05:25 AM UTC-7, RichA wrote:
https://www.aliexpress.com/item/4000640306730.html?spm=a2g0o.productlist.0.0.6f302331VGkoXt&algo_pvid=c0b2e880-ec51-4bb6-b05a-f14d156bc3c9&aem_p4p_detail=20220217225309433165067225700107795225&algo_exp_id=c0b2e880-ec51-4bb6-b05a-f14d156bc3c9-9&pdp_
I already have a 10-ft telescope and don't need another!
https://www.cloudynights.com/uploads/monthly_06_2006/post-12572-14070975670902_thumb.jpg
Impressive. Most will fold (optically or physically) the lens.
On Sunday, March 27, 2022 at 8:41:38 PM UTC-7, RichA wrote:pdp_ext_f=%7B%22sku_id%22%3A%2210000004778721146%22%7D&pdp_pi=-1%3B42.26%3B-1%3B-1%40salePrice%3BCAD%3Bsearch-mainSearch
On Friday, 25 March 2022 at 23:47:31 UTC-4, palsing wrote:
On Friday, March 25, 2022 at 2:05:25 AM UTC-7, RichA wrote:
https://www.aliexpress.com/item/4000640306730.html?spm=a2g0o.productlist.0.0.6f302331VGkoXt&algo_pvid=c0b2e880-ec51-4bb6-b05a-f14d156bc3c9&aem_p4p_detail=20220217225309433165067225700107795225&algo_exp_id=c0b2e880-ec51-4bb6-b05a-f14d156bc3c9-9&
I already have a 10-ft telescope and don't need another!
https://www.cloudynights.com/uploads/monthly_06_2006/post-12572-14070975670902_thumb.jpg
Impressive. Most will fold (optically or physically) the lens.There is no lens in this telescope, just 2 mirrors... it is just a simple Dobsonian mount Newtonian, one of the simplest designs of all...
On Friday, March 25, 2022 at 7:43:39 AM UTC-6, W wrote:
Not all lenses are meant to be used as telescope objectives.
I can attest to that, as I wear eyeglasses, and I also own a camera - in addition to a
smartphone with a camera.
However, a lens that is 74 mm in diameter, but with a focal length of
3,000 mm, I would suspect, _is_ intended to be used as a telescope
objective.
But maybe not. 74 mm diameter is the kind of aperture one would associate with a department store special telescope. If diffraction limited, a telescope
with such an objective could magnify up to 180x. Divide 3000 by 180, and
you get 16 2/3. They do make eyepieces with focal lengths that big, so one _could_ use that lens in a telescope, impractical though it might be.
Folks, if you don't like a thread, please just skip it; thanks!
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