Quote:
Originally Posted by BPO
Hi. At a truly dark site during new moon you'll approach 22*, so long as you aim the SQM at a "dark" part of the sky, but under overcast skies you'll easily exceed 22.
On Unihedron's site there are readings in the 23+ range from places such as Cherry Springs. Those were taken under heavy cloud cover. Had it been clear the readings would have been much reduced, probably around upper 20 to 21ish.
*Reading from my dark mountain site have slightly exceeded 22, but I remain unconvinced, although it's been claimed that SQMs in deepest darkest Namibia and the Aussie outback have also handily beat the 22 limit. Anthony Trekatch at Unihedron told me that he suspects low 22 readings (eg 22.0 to 22.05) from such sites may be accurate.
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That sounds 100% accurate to me and consistent with my experience. Any readings over very low 22s would indicate to me the batteries are depleted. I have seen mine and Andrew Murrell's unit read 1.5 lower when we put fresh batteries in and it was obvious the intitial readings were inflated.
I have achieved readings of just under 22.0 from very dark skies and would expect readings up to 22.1 or thereabouts, from the darkest places on the planet. The 23 + readings from the USA, which is the most light polluted continent on the planet, are clearly in error IMO.
Cheers,
John B
Cheers,
John B