WRAK
scholastic sledgehammer
Reged: 02/18/12

Relationship LP and Telescope magnitude limit
#5538310  11/25/12 06:17 AM

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There are established algorithms for calculating the theoretical magnitude limit of a telescope depending on aperture. Do you know of a similar proven formula for light polluted skies based not only on aperture but also on the naked eye magnitude limit? Wilfried

csa/montana
Den Mama
Reged: 05/14/05
Loc: montana

Re: Relationship LP and Telescope magnitude limit
[Re: WRAK]
#5540008  11/26/12 09:57 AM

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Here's one that might be of interest:
Naked eye limiting magnitude

WRAK
scholastic sledgehammer
Reged: 02/18/12

Re: Relationship LP and Telescope magnitude limit
[Re: csa/montana]
#5541508  11/27/12 04:20 AM

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Thanks, certainly of interest  but what I am looking for exactly would be an extension to the formula for calculating the Telescope Limiting Magnitude like for example "TLM=2,7+5*LOG10(D_mm)f(NELM)". Wilfried

derangedhermit
PoohBah
Reged: 10/07/09
Loc: USA

Re: Relationship LP and Telescope magnitude limit
[Re: WRAK]
#5542455  11/27/12 04:41 PM

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NELM is not a useful measurement of light pollution for use in such a formula. It is too dependent on the observer.

Tony Flanders
Postmaster
Reged: 05/18/06
Loc: Cambridge, MA, USA

Re: Relationship LP and Telescope magnitude limit
[Re: WRAK]
#5542827  11/27/12 09:10 PM

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Quote:
Thanks, certainly of interest  but what I am looking for exactly would be an extension to the formula for calculating the Telescope Limiting Magnitude like for example "TLM=2,7+5*LOG10(D_mm)f(NELM)". Wilfried
I'd say that a fair approximation for binoculars is:
BLM = NELM + 2.5*LOG10(mm/7 * mag)
However, this isn't really linear with magnification; it's faster than linear for low magnifications, and magnification becomes almost irrelevant at exit pupils smaller than 1 mm.
Binocular vision is worth about 1/4 magnitude. So subtract 1/4 mag for monocular telescopes.

WRAK
scholastic sledgehammer
Reged: 02/18/12

Re: Relationship LP and Telescope magnitude limit
[Re: Tony Flanders]
#5543691  11/28/12 11:39 AM

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Tony, thanks  I have checked this and found good values with strong light pollution with NELM around 3 but not these good with less light pollution giving values above the standard TLM formula. But this should be resolvable with some adaptions. Wilfried

GeneT
Ely Kid
Reged: 11/07/08
Loc: South Texas

Re: Relationship LP and Telescope magnitude limit
[Re: csa/montana]
#5552959  12/03/12 10:08 PM

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Quote:
Here's one that might be of interest:
Naked eye limiting magnitude
Nice chart!
