Questions about light transmission

[chrisyeo]

I am unaware that manufacturers list the light transmission capabilities of their scopes. It seems that everything is gauged by the aperture. however:

1. How does a reflector contrast with, say, a mak of similar aperture? It seems that a reflector will have better contrast since it's got less glass/surfaces?

2. How does UHTC (meade) compare with Starbright (Celestron?) coatings?

4. How about UHTC vs. Reflector?

3. How can we easily measure the light transmission of a particular scope?

Thanks !.
Chris

[VinSnr]

I am unaware that manufacturers list the light transmission capabilities of their scopes. It seems that everything is gauged by the aperture. however:

1. How does a reflector contrast with, say, a mak of similar aperture? It seems that a reflector will have better contrast since it's got less glass/surfaces?

2. How does UHTC (meade) compare with Starbright (Celestron?) coatings?

4. How about UHTC vs. Reflector?

3. How can we easily measure the light transmission of a particular scope?

Thanks !.
Chris

1. Reflector will give better views. It's brighter. The Mak has much larger CO. Also, like you say, less glass.

2.Meade will tell you UHTC is better. Your eyes will tell you no difference.

3. UHTC vs reflector? I can tell you if that reflector has a good mirror, it will beat any SCT coatings in this world.

4. Measure light transmission? Not sure, but you can email to Dr. Clay of Arkansas Observatory.

[weixing]

Hi,
From the information in the Celestron and Meade website, the UHTC and Starbright use similar material for coating, so I think it should be around the same. Anyway, as what VinSnr said you may not notice any difference at all.

Also, UHTC is just a name give to the more expensive coating use by Meade. It got two type of coating, one for the Mirror - to increase reflectivity and one for the Corrector Lens - to reduce reflection and increase light transmission.

Anyway, all astronomical lens and mirror will need some sort of coating to enchance light transmission and reduce reflection for lens and increase reflectivity for mirror. Also, some coating will act as a protection layer to the other more sensitive coating, mirror and lens from the elements.

Have a nice day and happy Chinese New Year!!

[Kelvin]

Anyway, all astronomical lens and mirror will need some sort of coating to enchance light transmission and reduce reflection for lens and increase reflectivity for mirror. Also, some coating will act as a protection layer to the other more sensitive coating, mirror and lens from the elements.

yup i heard about it too, alot of ppl told me that the outcome is the same, pretty little difference in viewing images,

The more inportant ones are the protection layer coatings. without them, the coating WILL WEAR OUT like mine spotting scope after 5~8 years.

[Airconvent]

Anyway, all astronomical lens and mirror will need some sort of coating to enchance light transmission and reduce reflection for lens and increase reflectivity for mirror. Also, some coating will act as a protection layer to the other more sensitive coating, mirror and lens from the elements.

yup i heard about it too, alot of ppl told me that the outcome is the same, pretty little difference in viewing images,

The more inportant ones are the protection layer coatings. without them, the coating WILL WEAR OUT like mine spotting scope after 5~8 years.

someone from the US tested his scopes after several years of use and noted that exotic coatings like UHTC, UMC and Starbright outperform standard coatings significantly but they also deteriorate faster as the exotic materials degrade. After 5-8 years, the scope with standard coatings would marginally outperform the scope with exotic coatings as they deteriorate slower....

DR Clay from Arkansas Observatory did some comparison on UHTC and the findings can be seen below:


http://www.arksky.org/cgi-bin/ib/ikonbo ... T;f=3;t=79


rich