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Can you tell a difference visually from a eyepiece with coatings


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Would FmC Coated eyepieces be better visually than a non coated eyepiece

Can I ask you a question ?

You have been a member of the Cloudynights forum since 2009 and have apparently owned many eyepieces and scopes from the threads you have started on that forum. With respect, surely you have picked up the answers to these sort of basic questions by now ?.

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John I like to listen to other astronomers on what they feel about these questions and I like to associate with people that may have a different point of view with things Sure job I know most of these questions but I like to share my experiences with other Astronomers I hope you understand that

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I think the answer to this question is potentially very varied. if you live in any sort of light pollution and are observing without a hood and observing bright objects then coatings will certainly be important. ghosting and reflection would be a major issue as would reflections from the eye. from a dark site with a hood and observing very faint objects you might find that no coatings is actually beneficial to light transmission.

most people observe somewhere between these extremes and therefore I feel good coatings are more beneficial to most people than no coatings.

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Moonshine i tend to agree I have not so good skies here they not deep sky viewing skies here on most nights I only can see 5th mag stars but with cold fronts in the winter We can get to 6th mag stars here

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Is It easier to see the stars using a telescope :grin: I just thought I would ask, it has coatings on the corrector plate :grin:

Edited by Pig
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II do not think many people on SGL have ever looked through an uncoated EP (or at least one where the ens figure was half decent). Our school had a 70mm scope with an ancient Huygens EP in RAS thread. That was uncoated as I remember. Even with just 4 air-glass interfaces, you got ghosting and glare (this did not prevent us from having loads of fun with it). We later got a coated (single MgF2 coating) MA 40mm which blew it completely out of the water in terms of quality. The MA40 was by no means a quality EP in modern terms, but the addition of coatings makes a big difference in transmission. Assuming 5% light loss at each air-glass interface, the Huygens transmitted 0.954 = 0.8145 times less than the ideal transmission, or 18.55% loss (0.22 magnitudes). The MgF2 coating increased transmission to about 0.994= 0.96 or 4% loss (0.044 magnitudes).

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I've tried uncoated high-power EPs (microscope, adapted) for double stars and there are major issues. Light scatter from the primary star made seeing a fainter secondary star almost impossible. I imagine any observation when the Moon was "out and about" would be subject to the same issues!

Chris

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Imagine a 6-element, 4-group design without coating: 0.958= 0.6634 transmission or 33.66% losses. And about half that light will be bounced towards the viewer as glare and ghost images. The ratio of signal to glare is roughly 0.6634/(0.5 x 0.3366) = 3.94. With modern multicoatings the transmission goes up to 0.9841 or just 1.59% loss. The signal to glare ratio is roughly 124 or 31 times better than without coatings

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Moonshine i tend to agree I have not so good skies here they not deep sky viewing skies here on most nights I only can see 5th mag stars but with cold fronts in the winter We can get to 6th mag stars here

You should be so lucky with "only mag 5 skies.. and mag 6 in winter" - swap my orange mag 2.5 skies and maybe mag 4 twice a year - any day :police: . Pointless EP ? BTW.
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