Telescope Reviews: Re: Ground Truth for the Bortle Scale

"Summer" place near Halcottsville, NY (in Catskills, elevation = 2050 ft):

1. Distance to nearest major light source.

(Straight-line distances in nautical miles)

Nearby (under 10 NMi):

1. - Halcottsville (13 streetlights)
2. - Denver (few streetlights)
2.5 - Kelly Corners (few streetlights)
3. - New Kingston (few streetlights)
4. - Roxbury (about 65 streetlights -- both sides of main street)
4.5 - Arkville (many streetlights)
5. - Margaretville (many streetlights)
6. - Fleischmanns (many streetlights)
7. - Highmount (some streetlights)
8. - Andes (quite a few streetlights)
8. - Bovina center (some streetlights)
8.5 - Pine Hill (quite a few streetlights)
9. - Hobart (some streetlights)
9.5 - Grand Gorge (quite a few streetlights)
9.5 - Prattsville (quite a few streetlights)

Bigger nearby cities:

10.5 - Stamford
14. - Delhi
24. - Walton
24. - Oneonta
26. - Liberty
27. - Cobbleskill (etc.)
34. - Monticello
37. - Kingston
45. - Albany (etc.)
85. - New York City (etc.)

2. Color zone in Light Pollution Atlas.

Blue, near border with green (back in 1998? anyway)

3. Sky-Quality Meter reading.

On a good night (with leaves) 21.6 or so. Can be as bad as 21.25 with fresh snow, and if it's murky. On one recent occasion, I couldn't get the reading to go below 21.71 (numerically) even with repeated attempts.

4. Visibility of Milky Way.

Visible (obvious when overhead) Dark patches are visible seemingly out in front of the brighter background. Usually, on good nights, my eyes don't have a chance to get fully dark-adapterd, since I need to tend to the images being captured at the laptop.

5. Naked-eye visibility of various DSOs.

I don't go looking for these (I mainly do imaging), but M45, M31 are certainly visible, maybe others.

6. Are clouds bright or dark?

Low clouds down to the south and southeast are bright (Margaretville/Arkville or Kingston/Shokan/Boiceville area?) Clouds to the west or overhead are not visible, so they can sneak up on you (unless there's a moon out). You have to look for missing stars to detect clouds.

7. Other indicators used in Bortle scale.

Don't do much visual observing. The Milky Way does not cast shadows. The whole sky glows. The glow is least near the zenith. There are light domes all around (except west). If you put your hand a few inches above something, it's darker underneath, so the whole sky casts fuzzy shadows.

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Hutech 30D, SBIG ST-402 autoguider
SV80S, SV66 guidescope
AP900, G-11, Barndoor tracker

http://www.pbase.com/s58y

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