Calibrating the luminosity of nearby stars to refine calculations of universe age and expansion

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notFritzArgelander
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Calibrating the luminosity of nearby stars to refine calculations of universe age and expansion

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Post by notFritzArgelander »


https://phys.org/news/2022-09-calibrati ... efine.html

Looks like they are using a 4" Takahashi with a Celestron finder.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: Calibrating the luminosity of nearby stars to refine calculations of universe age and expansion

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Post by ThinkerX »


one of the bigger annoyances with my long-ago photometric distance project was the margin of error for the magnitudes of given stars - often by as much as half a magnitude.

That said, I was under the impression that Gaia's magnitudes are insanely accurate and includes excellent distances to pretty much every star within at least fifty parsecs, so the point of this exercise leaves me a bit puzzled.
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Re: Calibrating the luminosity of nearby stars to refine calculations of universe age and expansion

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Post by notFritzArgelander »


ThinkerX wrote: Sat Sep 24, 2022 9:56 pm one of the bigger annoyances with my long-ago photometric distance project was the margin of error for the magnitudes of given stars - often by as much as half a magnitude.

That said, I was under the impression that Gaia's magnitudes are insanely accurate and includes excellent distances to pretty much every star within at least fifty parsecs, so the point of this exercise leaves me a bit puzzled.
The relative precision of Gaia is ~0.002 mag. Which I don't think is insanely accurate.

https://www.aanda.org/articles/aa/full_ ... 8.html#S10
The internal analysis of the data shows that the photometric calibrations can reach a precision as low as 2 mmag on individual CCD measurements. Other tests show that systematic effects are present in the data at the 10 mmag level.
The point of the exercise is to eliminate systematic errors due to relying on older less precise measurements of the standards. Since the standard measurements are decades old, it makes sense to revisit them.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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Re: Calibrating the luminosity of nearby stars to refine calculations of universe age and expansion

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Post by ThinkerX »


The relative precision of Gaia is ~0.002 mag. Which I don't think is insanely accurate.
Compared to the 0.2 - 0.5 margins of error in the older catalogues, it is insanely accurate. (Yes, there were precise magnitude measures for a few stars...very few.)

That said, I suspect that because of atmospheric distortion if naught else, the Gaia measurements will be superior to this program.
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Re: Calibrating the luminosity of nearby stars to refine calculations of universe age and expansion

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Post by notFritzArgelander »


ThinkerX wrote: Sun Sep 25, 2022 3:08 am
The relative precision of Gaia is ~0.002 mag. Which I don't think is insanely accurate.
Compared to the 0.2 - 0.5 margins of error in the older catalogues, it is insanely accurate. (Yes, there were precise magnitude measures for a few stars...very few.)
Errors that large are common for photographic photometry. Photoelectric photometry would regularly reach 0.05 or 0.01 errors. A few stars would be done to 0.005 magnitude errors.

The big catalogs old like HD, CD, CPD, etc were late 19th early 20th century efforts and precision photometry was not an aim. There were a lot of visual (!) and photographic measures. More recent Hipparcos data were not that precise but were better.
That said, I suspect that because of atmospheric distortion if naught else, the Gaia measurements will be superior to this program.
It might be as precise but not more so. Most astronomical observations remain ground based and it is essential to calibrate carefully for atmospheric effects and relate Gaia observations to ground based observations. This work is scientifically valuable in that regard. Relying solely on Gaia observations without cross checks from efforts like this runs the risk of systematic offsets. Reproducibility by independent means is an important part of scientific measurement methodology.
Scopes: Refs: Orion ST80, SV 80EDA f7, TS 102ED f11 Newts: AWB 130mm, f5, Z12 f5; Cats: VMC110L, Intes MK66,VMC200L f9.75 EPs: KK Fujiyama Orthoscopics, 2x Vixen NPLs (40-6mm) and BCOs, Baader Mark IV zooms, TV Panoptics, Delos, Plossl 32-8mm. Mixed brand Masuyama/Astroplans Binoculars: Nikon Aculon 10x50, Celestron 15x70, Baader Maxbright. Mounts: Star Seeker IV, Vixen Porta II, Celestron CG5
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