Bolometric night sky temperature and subcooling of telescope structures

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Table A.1.

Properties of some materials commonly used in telescopes with derived characteristic lengths ξ and relaxation times τ, all for w = 10 mm and h = 4.5 W K⁻¹ m⁻².

Quantity	Unit	Steel	Stainless	Al	Schott
		S355 ^(a)	steel 304 ^(b)	5754 ^(b)	Zerodur^(c)^(d)
k_m	W K⁻¹ m⁻¹	45	16	125	1.46
ρ_m	kg m⁻³	7850	8020	2670	2530
c_m	J K⁻¹ kg⁻¹	450	480	900	821
	%	n/a	10–45	6–20	90

ξ	m	0.32	0.19	0.53	0.06
τ	hours	2.18	2.38	1.48	1.28

Notes.

^(a)

http://www.matweb.com;

^(b)

Valencia & Quested (2010);

^(c)

https://www.schott.com/en-gb/products/zerodur/technical-details;

^(d)

Banyal & Ravindra (2011).

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