Anonymous
Unregistered
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What is UHTC and what EXACTLY on a telescope is coated with it? I mean what exact parts of the telescope come with UHTC? 
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NJ Night Sky
Reged: 03/25/04
Posts: 833
Loc: Hillsborough, NJ
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UHTC increases total transmission and image brightness by nearly 20% over standard coatings. Objects will appear bright. Well so they say it is a coating on the front lens of the scope.
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Jim
NJ Night Sky- J&T Telescope - MicroStock Photography - Shop4Scopes
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sixela
Postmaster
Reged: 12/23/04
Posts: 13991
Loc: Boechout, Belgium
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Quote:
UHTC increases total transmission and image brightness by nearly 20% over standard coatings. Objects will appear bright. Well so they say it is a coating on the front lens of the scope.
I doubt it's only the lens -- I think they have special coatings enhancing transmission on the corrector and special coatings to enhance reflectivity on the mirrors, and they're just calling them all "UHTC".
I wonder which "standard" coatings they're comparing against would be. 86% reflectivity for an enhanced Al + SiO (becoming Al+SiO2) is already very common these days. I think it's going to be hard finding that 103.2% reflectivity coating.
Unless there's some typical Meade small print and that 20% means they're talking about *system* reflectivity of corrector, primary and secondary mirror, of course. Yup, that looks about right.
They wouldn't mention the supplied diagonal, I bet (which, IIRC, isn't usually a dielectrically coated or UHTC diagonal and may even be a so-so prism diagonal - it's easy to lose 10% of the 20% of light you just won using the latter, if you compare it with a dielectrically coated diagonal).
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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Skywatcher 130mm f/5 BlackLine (finder, widefield scope and solar continuum scope)
Sumerian 250mm f/4.8 Alkaid (as travelscope without platform and on Tom O. platform above).
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cwstad
sage
Reged: 07/22/04
Posts: 305
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maybe this will help
Emission Line Wavelength
(nm.) Transmission: Standard
Coating (%) Transmission: UHTC
Group (%) Increase*
Hydrogen-alpha (Ha) 656 76.7 88.46 15.33%
Hydrogen-beta (Hb) 486 76.8 89.22 16.17%
Oxygen III 496 77.6 89.78 15.7%
Oxygen III 501 77.9 88.98 15.51%
Helium II 469 75 87.63 16.84%
Helium I 588 79.2 90.1 13.76%
Nitrogen II 655 76.7 88.5 15.38%
Nitrogen II 658 76.6 88.39 15.39%
Sulfur II 673 75.7 87.79 15.97%
if you need any further info check out the link
http://www.meade.com/catalog/uhtc/index.html
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Celestron 80EQ
Meade ETX 125
Homepage http://www.farstar.co.uk
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sixela
Postmaster
Reged: 12/23/04
Posts: 13991
Loc: Boechout, Belgium
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It still doesn't say whether it's system or single mirror throughput. From the numbers, I'd say it's system throughput, which would make the mirror coatings 96% reflective rather than 87% reflective for your typical AL+SiO (becoming Al+SiO2) coating.
Nothing earth-shattering - almost all coaters have similar options.
I'd be interested to know if these UHTC coatings last as long as the others...
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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Skywatcher 130mm f/5 BlackLine (finder, widefield scope and solar continuum scope)
Sumerian 250mm f/4.8 Alkaid (as travelscope without platform and on Tom O. platform above).
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JGlover
sage
Reged: 08/19/04
Posts: 364
Loc: Naperville, IL
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Quote:
What is UHTC and what EXACTLY on a telescope is coated with it? I mean what exact parts of the telescope come with UHTC?
Both the front and back of the corrector plate are coated, along with the surfaces of both the primary and secondary mirror.
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John Glover
Napervile, IL
Orion 120ST, WO 102ED/SV, Vixen A70Lf, WO ZS66SD
Celestron ASGT and SLT, Vixen Porta
PST
ETX105
DSH6
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Rainbow
professor emeritus
Reged: 08/27/04
Posts: 662
Loc: Norfolk, UK
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I was lead to believe that in UHT spec the corrector had the extra UHT coating surfaces on both sides whilst the Primary and secondary still have 'Standard' Meade coatings.
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Meade ETX 90 UHTC, 497 Autostar, 884 tripod, right angle finder.
CALIBRATE MOTORS and TRAIN DRIVES!
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sixela
Postmaster
Reged: 12/23/04
Posts: 13991
Loc: Boechout, Belgium
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Quote:
I was lead to believe that in UHT spec the corrector had the extra UHT coating surfaces on both sides whilst the Primary and secondary still have 'Standard' Meade coatings.
I doubt it: the light loss on mirrors is much larger than that through a corrector plate.
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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Skywatcher 130mm f/5 BlackLine (finder, widefield scope and solar continuum scope)
Sumerian 250mm f/4.8 Alkaid (as travelscope without platform and on Tom O. platform above).
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kc6zut
scholastic sledgehammer
Reged: 04/26/04
Posts: 790
Loc: Manhattan Beach CA
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IMHO UHTC and the similar Celestron option are revenue enhancement devices. You pay more for little practical improvement. Throughput gains on the order of 20% make little difference visually or photographically. Just as in audio, a 1dB difference is practically unnoticable. Vision and hearing respond logarithmicly so it takes a large change to make a noticable improvement. Just my 2 cents.
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minutas cantorum, minutas balorum, minutas carboratum desendus pantorum
73 de kc6zut, Max
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Greg_Klugie
super member
Reged: 04/29/04
Posts: 114
Loc: Garland, Texas
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I have a few related questions...
1. How does "more" light transfer through a piece of clear glass after additional coating(s) are put on it? It would seem logical that any coating would decrease photon transmission. ( isn't that why you wear sunglasses on a bright day??.... my sunglasses always let in LESS light)
2. If the coating deal is genuine... is it truly applicable and worthwhile is small aperture scopes?
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JGlover
sage
Reged: 08/19/04
Posts: 364
Loc: Naperville, IL
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Quote:
1. How does "more" light transfer through a piece of clear glass after additional coating(s) are put on it? It would seem logical that any coating would decrease photon transmission. ( isn't that why you wear sunglasses on a bright day??.... my sunglasses always let in LESS light)
Optical coatings enhance light transmission by reducing scattering of the light as it passes through the glass. Less scattered light means more light throughput.
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John Glover
Napervile, IL
Orion 120ST, WO 102ED/SV, Vixen A70Lf, WO ZS66SD
Celestron ASGT and SLT, Vixen Porta
PST
ETX105
DSH6
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sixela
Postmaster
Reged: 12/23/04
Posts: 13991
Loc: Boechout, Belgium
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Quote:
Optical coatings enhance light transmission by reducing scattering of the light as it passes through the glass.
Fixing absorption *in* the glass in beyond the power of a coating (which, by definition, is only at the interface between the element and the outside world with another refractive index).
What a coating does is reduce the slight amount of light not transmitted but reflected on an interface.
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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Skywatcher 130mm f/5 BlackLine (finder, widefield scope and solar continuum scope)
Sumerian 250mm f/4.8 Alkaid (as travelscope without platform and on Tom O. platform above).
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Rainbow
professor emeritus
Reged: 08/27/04
Posts: 662
Loc: Norfolk, UK
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Destructive interference
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Meade ETX 90 UHTC, 497 Autostar, 884 tripod, right angle finder.
CALIBRATE MOTORS and TRAIN DRIVES!
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Greg_Klugie
super member
Reged: 04/29/04
Posts: 114
Loc: Garland, Texas
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Thanks Glove, Six, And Rain. Your explanations make sense. I still have thrift related problems on paying the extra bucks on UHTC for small ( < 125mm ) scopes.
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Meade 2080
Meade DSX-90
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Rainbow
professor emeritus
Reged: 08/27/04
Posts: 662
Loc: Norfolk, UK
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Go for it - an etx 90 with UHT performs vary similarly to a 105 with standard coatings - but without the extra weight - yay!
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Meade ETX 90 UHTC, 497 Autostar, 884 tripod, right angle finder.
CALIBRATE MOTORS and TRAIN DRIVES!
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sixela
Postmaster
Reged: 12/23/04
Posts: 13991
Loc: Boechout, Belgium
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Being my pedantic self -- given the area is proportional to the *square* of the aperture, a scope with 20% more light output per aperture is equivalent to another one with "standard" output with an aperture that is sqrt(1.20) times larger.
That would be a 98 with standard coatings.
If you take 15% as the increased efficiency, the "effective aperture" increases by 7% [the fact it's again "roughly half as big" is not a coincidence -- the slope of the square root around one is 0.5].
All ignoring the effect of the differences in central obstruction - that is left as an exercise to the reader  .
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400mm f/4.46 self made Dobsonian on Tom Osypowski equatorial platform
Skywatcher 130mm f/5 BlackLine (finder, widefield scope and solar continuum scope)
Sumerian 250mm f/4.8 Alkaid (as travelscope without platform and on Tom O. platform above).
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Rainbow
professor emeritus
Reged: 08/27/04
Posts: 662
Loc: Norfolk, UK
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Belgium man, Belgium!
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Meade ETX 90 UHTC, 497 Autostar, 884 tripod, right angle finder.
CALIBRATE MOTORS and TRAIN DRIVES!
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MarkHilt
super member
Reged: 01/26/05
Posts: 152
Loc: West Amboy, New York, United S...
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Maters not how it works, that 15 percent more light really does make the diff. My buddy has a 105 and my 90 keeps up for half the money. There is a really techy page about it on the mead site that expains it. LOL
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ETX-90RA UHTC
80mm Widefield Refractor/Finder
5 inch Meade on Alt/Az mount
IBM T23/LPI (imaging)
10" Dob [my winter project]
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jrcrilly
Refractor wienie no more
Reged: 04/30/03
Posts: 30716
Loc: NE Ohio
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Quote:
IMHO UHTC and the similar Celestron option are revenue enhancement devices. You pay more for little practical improvement.
That's more true with the Celestrons than the Meades. Celestron's "standard" coatings are quite good (best in the industry for many years) while Meade's "standard" coatings have been downgraded to plain MgFL. Meade's not publishing the improvement made by UHTC over the premium EMC coatings they replaced (which were standard equipment).
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John C
Battle Cry of Reno
http://www.wadsworthobservatory.com
My Cloudy Nights gallery
AT12RC
AT65EDQ
QSI683WSG-8
Roper Scientific Quantix 6303E "project" camera
mystery EQ mount on the way
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