Achray Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Achray Campground clear sky chart from 2005-11-06 to 2024-03-23.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	17% 11% 4 8% 7% 3 5% 4 5% 6% 30%	78844
	Night	16% 12% 5% 9% 7% 3 4 4 5% 6% 29%	81023
Transparency	Day	55% 5% 10% 19% 10% 1	78549
	Night	56% 5% 11% 18% 9% 1	80852
Seeing	Day	23% 16% 31% 19% 9% 2	13724
	Night	23% 13% 30% 25% 9% 1	22820

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 15% 8% 13% 9% 4 4 4 4 4 21%	2517
	11th to 20th	Day	12% 12% 6% 15% 12% 5% 4 4 4 7% 19%	2520
	21st to end	Day	16% 21% 9% 12% 7% 4 5% 4 3 3 18%	3032
February	1st to 10th	Day	10% 16% 6% 14% 11% 4 6% 4 4 5% 20%	1710
	11th to 20th	Day	12% 15% 7% 11% 7% 5% 5% 5% 5% 5% 23%	1663
	21st to end	Day	17% 15% 6% 8% 8% 5% 5% 5% 5% 5% 23%	1479
March	1st to 10th	Day	14% 16% 7% 9% 6% 3 4 4 4 5% 29%	1999
	11th to 20th	Day	13% 13% 5% 11% 8% 4 5% 4 4 5% 27%	2090
	21st to end	Day	16% 11% 4 7% 6% 3 4 3 4 5% 37%	2244
April	1st to 10th	Day	22% 12% 4 7% 7% 3 4 3 4 5% 29%	2160
	11th to 20th	Day	21% 10% 3 7% 6% 3 3 4 4 5% 35%	2154
	21st to end	Day	22% 10% 3 7% 6% 3 3 4 4 4 33%	2340
May	1st to 10th	Day	18% 9% 4 6% 6% 3 4 4 5% 6% 34%	2488
	11th to 20th	Day	19% 9% 3 7% 6% 3 5% 4 4 6% 35%	2478
	21st to end	Day	15% 7% 3 6% 5% 3 5% 4 4 7% 40%	2725
June	1st to 10th	Day	21% 7% 4 6% 6% 3 5% 5% 6% 6% 31%	2520
	11th to 20th	Day	15% 6% 2 6% 5% 3 5% 5% 6% 8% 37%	2543
	21st to end	Day	17% 7% 3 6% 6% 4 5% 5% 6% 8% 33%	2700
July	1st to 10th	Day	13% 5% 3 5% 6% 3 5% 6% 7% 8% 39%	2592
	11th to 20th	Day	12% 6% 3 5% 6% 4 6% 6% 7% 9% 37%	2520
	21st to end	Day	13% 5% 2 6% 6% 4 7% 6% 7% 10% 35%	2744
August	1st to 10th	Day	12% 7% 3 6% 7% 4 5% 6% 6% 9% 35%	2373
	11th to 20th	Day	13% 6% 3 6% 6% 4 5% 6% 6% 7% 37%	2303
	21st to end	Day	15% 7% 3 6% 6% 4 5% 7% 7% 9% 33%	2440
September	1st to 10th	Day	15% 7% 3 4 5% 3 5% 5% 5% 8% 41%	2160
	11th to 20th	Day	15% 7% 2 7% 5% 3 4 5% 5% 6% 43%	2160
	21st to end	Day	19% 8% 2 7% 5% 3 4 5% 5% 6% 34%	1881
October	1st to 10th	Day	18% 11% 3 7% 5% 3 4 5% 4 7% 34%	1800
	11th to 20th	Day	24% 14% 3 8% 6% 3 4 4 4 6% 24%	1800
	21st to end	Day	28% 15% 5% 7% 6% 3 4 4 4 5% 21%	1913
November	1st to 10th	Day	15% 13% 5% 7% 5% 4 4 4 6% 7% 30%	1558
	11th to 20th	Day	17% 16% 7% 9% 6% 4 5% 4 4 5% 24%	1520
	21st to end	Day	22% 16% 7% 11% 8% 3 4 4 4 5% 17%	1520
December	1st to 10th	Day	20% 18% 7% 10% 9% 4 4 3 4 4 15%	1520
	11th to 20th	Day	18% 18% 6% 10% 7% 4 5% 4 3 5% 19%	1906
	21st to end	Day	24% 19% 7% 13% 7% 3 2 3 2 3 17%	2772
January	1st to 10th	Night	15% 18% 9% 13% 9% 3 6% 4 4 5% 15%	4429
	11th to 20th	Night	11% 13% 5% 15% 11% 5% 7% 5% 4 5% 19%	4440
	21st to end	Night	13% 20% 9% 11% 8% 5% 5% 4 4 4 17%	4622
February	1st to 10th	Night	11% 14% 7% 11% 9% 5% 6% 5% 5% 7% 21%	2470
	11th to 20th	Night	12% 14% 5% 11% 10% 4 5% 4 4 5% 26%	2403
	21st to end	Night	13% 14% 5% 10% 9% 4 5% 5% 4 6% 25%	1975
March	1st to 10th	Night	15% 12% 6% 9% 7% 4 5% 4 4 5% 30%	2166
	11th to 20th	Night	13% 13% 6% 8% 6% 2 5% 4 5% 7% 29%	2089
	21st to end	Night	13% 10% 5% 8% 7% 3 4 4 4 6% 37%	2157
April	1st to 10th	Night	20% 11% 4 8% 6% 3 4 5% 4 5% 31%	1800
	11th to 20th	Night	20% 10% 4 5% 5% 3 3 4 5% 6% 36%	1771
	21st to end	Night	21% 11% 3 7% 5% 3 4 4 4 5% 31%	1620
May	1st to 10th	Night	19% 9% 3 5% 5% 4 4 5% 5% 6% 37%	1471
	11th to 20th	Night	18% 8% 3 5% 5% 3 4 4 4 7% 39%	1415
	21st to end	Night	12% 6% 3 4 6% 4 4 5% 6% 7% 43%	1550
June	1st to 10th	Night	17% 7% 3 7% 5% 3 4 6% 5% 7% 35%	1440
	11th to 20th	Night	15% 5% 2 5% 4 4 4 5% 6% 8% 43%	1407
	21st to end	Night	17% 6% 2 5% 6% 3 5% 6% 6% 8% 37%	1260
July	1st to 10th	Night	10% 6% 2 4 5% 2 5% 5% 5% 8% 48%	1358
	11th to 20th	Night	11% 5% 2 5% 4 3 5% 5% 5% 8% 46%	1440
	21st to end	Night	8% 5% 2 4 6% 4 5% 6% 7% 9% 43%	1574
August	1st to 10th	Night	11% 5% 2 6% 6% 3 4 4 6% 8% 44%	1563
	11th to 20th	Night	10% 4 3 5% 5% 2 6% 6% 7% 8% 45%	1598
	21st to end	Night	12% 6% 3 5% 4 3 5% 5% 5% 8% 43%	1896
September	1st to 10th	Night	11% 6% 3 5% 5% 3 4 4 6% 8% 46%	1800
	11th to 20th	Night	15% 7% 3 5% 4 2 3 4 5% 7% 47%	1800
	21st to end	Night	17% 8% 3 6% 4 3 3 4 4 7% 42%	2076
October	1st to 10th	Night	22% 8% 3 5% 4 2 3 3 4 5% 40%	2160
	11th to 20th	Night	22% 11% 3 7% 6% 3 4 5% 6% 5% 28%	2160
	21st to end	Night	24% 14% 4 7% 6% 3 3 4 5% 6% 25%	2443
November	1st to 10th	Night	18% 10% 4 7% 6% 3 5% 4 5% 6% 32%	2518
	11th to 20th	Night	16% 13% 6% 9% 8% 4 5% 4 5% 6% 25%	2660
	21st to end	Night	21% 16% 6% 11% 7% 4 4 3 4 5% 21%	2660
December	1st to 10th	Night	21% 19% 7% 11% 7% 3 5% 4 4 4 15%	2660
	11th to 20th	Night	17% 18% 6% 11% 7% 4 4 4 4 5% 21%	3288
	21st to end	Night	25% 19% 6% 13% 7% 3 3 3 3 4 14%	4884

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	67% 5% 12% 10% 6%	2518
	11th to 20th	Day	67% 4 10% 12% 7% 1	2520
	21st to end	Day	72% 5% 6% 12% 5% 1	3032
February	1st to 10th	Day	67% 4 9% 14% 5% 1	1710
	11th to 20th	Day	61% 5% 11% 13% 8% 1	1672
	21st to end	Day	62% 4 8% 14% 10% 1	1479
March	1st to 10th	Day	58% 4 10% 16% 11% 1	2002
	11th to 20th	Day	60% 4 8% 16% 10% 1	2090
	21st to end	Day	51% 4 8% 19% 13% 5%	2244
April	1st to 10th	Day	60% 3 7% 18% 10% 3	2160
	11th to 20th	Day	53% 3 6% 22% 13% 2	2154
	21st to end	Day	55% 3 7% 17% 15% 3	2340
May	1st to 10th	Day	50% 4 9% 19% 13% 5%	2488
	11th to 20th	Day	51% 4 7% 21% 15% 2	2482
	21st to end	Day	45% 6% 11% 22% 13% 4	2725
June	1st to 10th	Day	53% 5% 10% 19% 12% 1	2520
	11th to 20th	Day	43% 6% 10% 24% 14% 2	2543
	21st to end	Day	48% 7% 11% 22% 12% 1	2700
July	1st to 10th	Day	40% 7% 12% 26% 14% 1	2522
	11th to 20th	Day	41% 7% 12% 26% 12% 1	2445
	21st to end	Day	43% 7% 13% 28% 9%	2591
August	1st to 10th	Day	45% 8% 13% 22% 11% 1	2359
	11th to 20th	Day	43% 7% 15% 25% 9% 1	2303
	21st to end	Day	45% 9% 13% 23% 9% 1	2440
September	1st to 10th	Day	42% 6% 13% 27% 12%	2160
	11th to 20th	Day	42% 5% 11% 30% 11%	2160
	21st to end	Day	50% 6% 12% 24% 8%	1881
October	1st to 10th	Day	51% 6% 11% 20% 12% 1	1800
	11th to 20th	Day	62% 5% 12% 16% 4	1800
	21st to end	Day	66% 5% 10% 13% 5% 1	1913
November	1st to 10th	Day	53% 5% 14% 21% 7%	1558
	11th to 20th	Day	62% 5% 12% 14% 6% 1	1520
	21st to end	Day	71% 5% 10% 10% 4 1	1520
December	1st to 10th	Day	74% 4 8% 10% 4	1520
	11th to 20th	Day	69% 4 7% 12% 8% 1	1906
	21st to end	Day	75% 3 6% 14% 3	2772
January	1st to 10th	Night	72% 5% 10% 9% 3	4429
	11th to 20th	Night	67% 6% 12% 11% 4	4440
	21st to end	Night	71% 5% 7% 10% 7%	4622
February	1st to 10th	Night	64% 5% 11% 13% 7% 1	2470
	11th to 20th	Night	60% 3 10% 19% 6% 1	2405
	21st to end	Night	60% 4 9% 18% 8% 1	1975
March	1st to 10th	Night	57% 5% 10% 16% 10% 2	2176
	11th to 20th	Night	55% 4 11% 17% 12% 1	2090
	21st to end	Night	49% 4 8% 21% 15% 4	2157
April	1st to 10th	Night	57% 4 7% 18% 12% 2	1800
	11th to 20th	Night	50% 4 8% 24% 14% 2	1771
	21st to end	Night	56% 4 6% 16% 15% 3	1620
May	1st to 10th	Night	48% 5% 7% 21% 16% 4	1471
	11th to 20th	Night	46% 5% 7% 24% 17% 3	1416
	21st to end	Night	40% 7% 13% 21% 16% 4	1551
June	1st to 10th	Night	47% 7% 11% 21% 13% 1	1440
	11th to 20th	Night	39% 6% 11% 26% 16% 2	1407
	21st to end	Night	43% 8% 15% 21% 13% 1	1260
July	1st to 10th	Night	32% 8% 12% 28% 19% 2	1318
	11th to 20th	Night	38% 6% 13% 29% 14% 1	1392
	21st to end	Night	35% 7% 17% 31% 10%	1486
August	1st to 10th	Night	38% 7% 16% 25% 14%	1553
	11th to 20th	Night	33% 8% 19% 29% 10% 1	1598
	21st to end	Night	37% 7% 17% 29% 9% 1	1896
September	1st to 10th	Night	35% 7% 14% 30% 13%	1800
	11th to 20th	Night	38% 5% 14% 32% 10%	1800
	21st to end	Night	43% 5% 14% 29% 9%	2076
October	1st to 10th	Night	48% 5% 11% 23% 13%	2160
	11th to 20th	Night	56% 6% 13% 19% 6%	2160
	21st to end	Night	61% 5% 10% 15% 8%	2443
November	1st to 10th	Night	53% 5% 14% 20% 8%	2518
	11th to 20th	Night	60% 5% 12% 15% 7% 1	2660
	21st to end	Night	67% 5% 11% 14% 3	2660
December	1st to 10th	Night	74% 4 8% 10% 3	2660
	11th to 20th	Night	66% 5% 8% 14% 7%	3288
	21st to end	Night	77% 3 6% 11% 4	4884

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	20% 23% 34% 19% 4	180
	11th to 20th	Day	22% 17% 39% 16% 5% 1	180
	21st to end	Day	22% 18% 35% 18% 6% 1	272
February	1st to 10th	Day	27% 26% 33% 10% 3 1	270
	11th to 20th	Day	26% 28% 39% 7% 1	270
	21st to end	Day	34% 21% 33% 11% 1	291
March	1st to 10th	Day	27% 21% 34% 15% 3	460
	11th to 20th	Day	26% 19% 32% 18% 4 1	460
	21st to end	Day	32% 20% 27% 16% 4 1	470
April	1st to 10th	Day	29% 20% 30% 15% 5% 1	420
	11th to 20th	Day	34% 18% 22% 15% 8% 3	412
	21st to end	Day	29% 17% 31% 14% 6% 2	420
May	1st to 10th	Day	29% 14% 27% 20% 7% 3	423
	11th to 20th	Day	24% 18% 28% 18% 9% 4	447
	21st to end	Day	20% 15% 32% 20% 11% 2	485
June	1st to 10th	Day	24% 11% 36% 22% 7% 1	450
	11th to 20th	Day	19% 14% 30% 24% 11% 3	473
	21st to end	Day	20% 13% 33% 22% 11% 2	630
July	1st to 10th	Day	12% 9% 34% 33% 11% 2	517
	11th to 20th	Day	14% 11% 34% 25% 14% 3	444
	21st to end	Day	14% 8% 37% 28% 11% 3	488
August	1st to 10th	Day	15% 7% 33% 28% 13% 5%	446
	11th to 20th	Day	15% 7% 27% 27% 18% 6%	439
	21st to end	Day	16% 14% 31% 20% 13% 6%	495
September	1st to 10th	Day	15% 12% 30% 22% 15% 6%	450
	11th to 20th	Day	18% 10% 27% 20% 20% 6%	450
	21st to end	Day	21% 14% 26% 21% 14% 5%	450
October	1st to 10th	Day	25% 16% 25% 18% 11% 4	450
	11th to 20th	Day	31% 19% 28% 14% 6% 1	450
	21st to end	Day	35% 17% 25% 18% 4	462
November	1st to 10th	Day	25% 21% 33% 14% 6% 1	252
	11th to 20th	Day	28% 19% 38% 10% 5% 1	180
	21st to end	Day	31% 25% 29% 12% 2 1	180
December	1st to 10th	Day	32% 16% 37% 11% 6%	180
	11th to 20th	Day	33% 24% 30% 9% 2 1	180
	21st to end	Day	31% 20% 33% 13% 3 1	198
January	1st to 10th	Night	25% 15% 34% 21% 5%	760
	11th to 20th	Night	26% 17% 28% 22% 6%	760
	21st to end	Night	18% 14% 34% 27% 6% 1	836
February	1st to 10th	Night	20% 18% 37% 21% 4	760
	11th to 20th	Night	22% 18% 37% 19% 3	743
	21st to end	Night	23% 21% 31% 23% 2	628
March	1st to 10th	Night	24% 19% 32% 22% 4	760
	11th to 20th	Night	24% 18% 34% 18% 6% 1	760
	21st to end	Night	19% 15% 35% 23% 7%	801
April	1st to 10th	Night	29% 15% 31% 21% 4	720
	11th to 20th	Night	27% 15% 28% 21% 8%	707
	21st to end	Night	29% 10% 27% 23% 11% 1	540
May	1st to 10th	Night	22% 8% 29% 30% 11%	391
	11th to 20th	Night	23% 9% 32% 27% 9%	354
	21st to end	Night	14% 9% 34% 31% 12%	389
June	1st to 10th	Night	18% 8% 39% 29% 4 1	360
	11th to 20th	Night	19% 7% 27% 33% 13% 1	360
	21st to end	Night	20% 7% 29% 32% 12% 1	360
July	1st to 10th	Night	11% 5% 32% 37% 14% 1	350
	11th to 20th	Night	12% 5% 28% 39% 16% 1	348
	21st to end	Night	10% 5% 32% 37% 16% 1	394
August	1st to 10th	Night	13% 5% 25% 35% 21% 1	489
	11th to 20th	Night	12% 4 21% 39% 22% 3	534
	21st to end	Night	15% 6% 29% 31% 17% 2	708
September	1st to 10th	Night	15% 8% 28% 30% 18% 2	720
	11th to 20th	Night	19% 6% 25% 27% 20% 3	720
	21st to end	Night	22% 8% 23% 28% 18% 2	720
October	1st to 10th	Night	26% 10% 27% 25% 11% 2	720
	11th to 20th	Night	28% 13% 29% 21% 8% 1	720
	21st to end	Night	32% 13% 27% 24% 3	792
November	1st to 10th	Night	25% 15% 27% 25% 7% 1	740
	11th to 20th	Night	25% 17% 34% 16% 9% 1	760
	21st to end	Night	32% 14% 26% 23% 4	760
December	1st to 10th	Night	33% 16% 31% 16% 4	760
	11th to 20th	Night	28% 17% 32% 20% 3 1	760
	21st to end	Night	35% 14% 28% 19% 3 1	836

Page generated at 2024-03-19 23:31:06. Version ac07

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