Who in OZ Aluminizes mirrors to >90% ?

[Gama]

Hi all,

Its time for my mirror to be re aluminized, but all i can find is around mid 80% reflectivity from the mobs i rung. This is too much loss for me to swallow, i really am looking at better than 90 % reflectivity.
Anyone know of some one ?.
The mirror is 22" so its not a small mirror.

Thanks.

Theo

[Geoff45]

I'm afraid that aluminium is just not reflective enough for your needs. According to Sidgwick (Amateur Astronomers Handbook p111) Al has a reflectance of 89% in the uv, 88% in blue/green and 87% in red.
Geoff
PS: You could DYI and try silver like we used to do in the old days. Gets up to 96% in the red.

[Gama]

Doesnt then have to be coated, as it would start to tarnish.

The

[Screwdriverone]

Astro Optical does mirrors, as do these people,

http://www.telescopes-astronomy.com.au/telescopes036.htm

Chris

[Gama]

The issue Chris, is how well its reflectivity is going to be. Many advertise under 90%, but thats a heap of % to lose. Thus my quest for a high % coat.

Theo.

[Screwdriverone]

The internet site link talks about >90% reflectivity, check it out.

Chris

[Geoff45]

I presume you are referring to silver. Yes you can coat it with DYI. However I was not being entirely serious when referring to silvering. Probably these days if you tried to buy the chemicals they'd arrest you as a terrorist suspect. I'm sure you can't just go to the chemist as I did as a teenager and buy the stuff with no questions asked.

[Gama]

Gone to the Astro site, but makes no mention of %. So im not sure where you got that value.

Theo.

[MrB]

"The aluminium coating placed onto the surface of the glass returns about 90% reflectivity.
The overall reflectivity combined with the secondary mirror drops down to about 80%.
Different enhanced coatings brought out by manufacturers can bring this figure back up to
around 90%."
and....
"The following aluminsisng prices include enhanced overcoating for maximum reflectivity."

So yes, they do... the second 90% they quote is total system reflectivity(including secondary), or, 90%^0.5 = 94.89%, so approx 95% per enhanced coated reflective surface.

[Gama]

I'll give them a call tomorrow and see what they say.

Tell ya what though, it aint like the U.S, with up to 98 %. Jeepers..

90 % i lose about 2 inches of aperature.
Oh well, im losing more now i suppose.

Thanks guys.

Theo.

[Screwdriverone]

Theo,

the link that I meant wasnt the Astro Optical mention, it was for Telescopes-astronomy that MrB quoted you on the content of the website, the contact number for them is (08) 8381 3188

Cheers

Chris