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 2024-11-03.

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	16% 11% 4 9% 5% 5% 4 3 5% 6% 31%	101941
	Night	16% 12% 4 10% 5% 5% 4 3 5% 6% 30%	97042
Transparency	Day	52% 5% 11% 21% 10% 1	101699
	Night	55% 5% 11% 19% 9% 1	96904
Seeing	Day	23% 16% 31% 19% 9% 2	14634
	Night	23% 13% 30% 25% 9% 1	23500

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	15% 16% 7% 14% 7% 5% 4 3 4 4 20%	2517
	11th to 20th	Day	11% 13% 6% 18% 9% 6% 4 3 4 6% 19%	2520
	21st to end	Day	15% 21% 9% 13% 5% 5% 4 3 3 3 18%	3032
February	1st to 10th	Day	10% 17% 6% 16% 9% 5% 5% 3 5% 5% 20%	1710
	11th to 20th	Day	11% 17% 6% 11% 6% 6% 5% 4 5% 5% 23%	1663
	21st to end	Day	17% 15% 5% 9% 7% 6% 5% 4 5% 5% 23%	1479
March	1st to 10th	Day	17% 18% 6% 9% 4 3 3 3 4 5% 27%	3296
	11th to 20th	Day	10% 18% 6% 13% 6% 5% 4 3 5% 5% 25%	3480
	21st to end	Day	11% 9% 4 9% 5% 5% 4 2 5% 5% 41%	3900
April	1st to 10th	Day	22% 14% 4 8% 6% 4 4 2 4 5% 28%	2280
	11th to 20th	Day	22% 11% 3 8% 5% 4 3 3 4 4 34%	2276
	21st to end	Day	22% 10% 3 8% 5% 4 4 3 4 4 33%	2470
May	1st to 10th	Day	19% 10% 3 7% 5% 5% 4 3 5% 6% 31%	4380
	11th to 20th	Day	16% 9% 3 7% 4 4 4 3 5% 8% 36%	4398
	21st to end	Day	17% 7% 2 7% 4 5% 4 3 5% 7% 39%	4837
June	1st to 10th	Day	21% 8% 3 8% 5% 4 5% 4 6% 6% 30%	2660
	11th to 20th	Day	15% 6% 2 6% 5% 4 6% 4 7% 8% 37%	2685
	21st to end	Day	17% 8% 3 7% 5% 5% 5% 4 6% 8% 32%	2850
July	1st to 10th	Day	14% 7% 3 7% 5% 5% 6% 5% 7% 8% 33%	4568
	11th to 20th	Day	12% 6% 3 6% 6% 5% 5% 5% 7% 8% 38%	4440
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 6% 7% 46%	4814
August	1st to 10th	Day	13% 7% 3 8% 6% 6% 6% 5% 6% 8% 33%	4178
	11th to 20th	Day	17% 6% 2 7% 4 5% 5% 4 6% 8% 35%	4044
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 5% 8% 10% 39%	4286
September	1st to 10th	Day	15% 7% 2 6% 4 4 5% 4 5% 7% 41%	2280
	11th to 20th	Day	14% 7% 2 7% 3 3 4 3 5% 6% 45%	2280
	21st to end	Day	19% 8% 2 9% 4 5% 4 4 5% 6% 34%	1985
October	1st to 10th	Day	17% 11% 3 8% 4 4 4 4 4 6% 34%	1900
	11th to 20th	Day	23% 14% 3 9% 5% 4 4 3 4 6% 25%	1900
	21st to end	Day	27% 15% 4 8% 5% 4 4 3 4 5% 21%	2019
November	1st to 10th	Day	15% 14% 4 8% 4 4 4 3 6% 7% 30%	1576
	11th to 20th	Day	16% 17% 6% 10% 6% 5% 4 3 4 5% 24%	1520
	21st to end	Day	21% 17% 7% 12% 6% 5% 4 3 4 5% 17%	1520
December	1st to 10th	Day	20% 20% 6% 12% 7% 6% 3 3 4 4 15%	1520
	11th to 20th	Day	18% 19% 5% 12% 6% 5% 4 3 3 5% 19%	1906
	21st to end	Day	24% 20% 6% 15% 5% 4 2 2 2 3 17%	2772
January	1st to 10th	Night	14% 19% 9% 14% 7% 5% 5% 3 4 5% 15%	4429
	11th to 20th	Night	11% 14% 5% 18% 9% 7% 6% 4 5% 5% 18%	4440
	21st to end	Night	13% 21% 8% 12% 7% 7% 4 3 4 4 17%	4622
February	1st to 10th	Night	11% 15% 7% 11% 8% 6% 6% 4 5% 6% 20%	2470
	11th to 20th	Night	12% 15% 5% 12% 9% 5% 5% 3 4 5% 26%	2403
	21st to end	Night	13% 15% 4 12% 8% 5% 4 3 5% 6% 24%	1975
March	1st to 10th	Night	16% 14% 4 8% 5% 5% 4 3 4 5% 31%	3542
	11th to 20th	Night	13% 18% 6% 11% 6% 4 5% 3 5% 6% 23%	3479
	21st to end	Night	11% 9% 4 10% 7% 5% 5% 4 5% 6% 34%	3732
April	1st to 10th	Night	20% 13% 4 9% 5% 4 4 3 4 5% 30%	1900
	11th to 20th	Night	20% 11% 3 6% 4 4 3 3 5% 5% 36%	1870
	21st to end	Night	22% 11% 3 8% 5% 4 4 3 4 5% 32%	1710
May	1st to 10th	Night	20% 9% 3 6% 5% 5% 4 4 6% 6% 34%	2559
	11th to 20th	Night	17% 9% 3 8% 5% 4 4 3 5% 7% 35%	2495
	21st to end	Night	12% 8% 3 7% 5% 5% 3 4 6% 6% 40%	2738
June	1st to 10th	Night	17% 8% 3 9% 5% 4 4 5% 5% 7% 34%	1520
	11th to 20th	Night	15% 6% 2 6% 4 5% 3 4 6% 8% 42%	1485
	21st to end	Night	18% 7% 2 6% 5% 4 4 4 6% 8% 37%	1330
July	1st to 10th	Night	11% 7% 2 8% 6% 4 5% 4 5% 7% 40%	2386
	11th to 20th	Night	13% 7% 2 7% 3 4 5% 4 5% 7% 43%	2520
	21st to end	Night	9% 5% 2 5% 4 5% 4 4 6% 8% 47%	2739
August	1st to 10th	Night	12% 5% 2 6% 4 4 5% 4 6% 8% 44%	2749
	11th to 20th	Night	16% 5% 3 6% 4 3 5% 4 5% 7% 43%	2785
	21st to end	Night	13% 5% 2 6% 4 4 4 4 5% 9% 45%	3336
September	1st to 10th	Night	11% 6% 3 5% 4 4 4 3 6% 8% 47%	1900
	11th to 20th	Night	14% 7% 2 5% 3 3 3 3 5% 6% 49%	1900
	21st to end	Night	18% 8% 2 6% 4 4 3 3 4 7% 41%	2192
October	1st to 10th	Night	21% 8% 3 6% 4 3 4 2 5% 5% 40%	2280
	11th to 20th	Night	21% 12% 3 9% 5% 3 4 3 6% 5% 29%	2280
	21st to end	Night	23% 14% 4 8% 4 4 3 3 5% 6% 25%	2579
November	1st to 10th	Night	17% 11% 5% 8% 5% 4 4 3 5% 6% 32%	2545
	11th to 20th	Night	16% 14% 5% 10% 6% 5% 5% 4 5% 5% 25%	2660
	21st to end	Night	21% 17% 5% 12% 6% 5% 4 2 4 5% 20%	2660
December	1st to 10th	Night	20% 21% 6% 11% 6% 5% 5% 3 4 4 15%	2660
	11th to 20th	Night	16% 19% 5% 12% 6% 4 4 3 4 5% 21%	3288
	21st to end	Night	25% 20% 6% 15% 5% 3 2 2 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	60% 4 10% 15% 11% 1	3299
	11th to 20th	Day	60% 5% 10% 15% 9% 1	3480
	21st to end	Day	45% 4 8% 23% 16% 4	3900
April	1st to 10th	Day	59% 3 7% 19% 10% 3	2280
	11th to 20th	Day	54% 3 6% 22% 13% 2	2276
	21st to end	Day	55% 3 6% 17% 15% 3	2470
May	1st to 10th	Day	51% 6% 8% 22% 10% 3	4394
	11th to 20th	Day	45% 7% 11% 27% 9% 1	4402
	21st to end	Day	45% 6% 11% 20% 16% 3	4837
June	1st to 10th	Day	53% 5% 10% 19% 12% 1	2660
	11th to 20th	Day	43% 6% 11% 24% 14% 2	2685
	21st to end	Day	48% 7% 11% 21% 12% 1	2850
July	1st to 10th	Day	46% 6% 13% 25% 9% 1	4498
	11th to 20th	Day	40% 7% 15% 29% 9% 1	4365
	21st to end	Day	36% 6% 12% 34% 12%	4661
August	1st to 10th	Day	47% 6% 13% 24% 9%	4164
	11th to 20th	Day	44% 6% 16% 26% 8%	4083
	21st to end	Day	37% 7% 13% 32% 10% 1	4286
September	1st to 10th	Day	42% 5% 13% 27% 12%	2280
	11th to 20th	Day	40% 5% 12% 30% 12%	2280
	21st to end	Day	50% 6% 12% 23% 9%	1985
October	1st to 10th	Day	50% 6% 11% 21% 11% 1	1900
	11th to 20th	Day	61% 5% 12% 17% 4	1900
	21st to end	Day	66% 5% 10% 13% 5% 1	2019
November	1st to 10th	Day	53% 5% 14% 21% 7%	1576
	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	55% 6% 12% 17% 9% 1	3552
	11th to 20th	Night	60% 6% 11% 15% 7% 1	3480
	21st to end	Night	48% 5% 7% 22% 15% 2	3732
April	1st to 10th	Night	57% 4 7% 18% 12% 2	1900
	11th to 20th	Night	50% 4 7% 24% 13% 2	1870
	21st to end	Night	55% 4 6% 17% 15% 3	1710
May	1st to 10th	Night	47% 7% 10% 23% 10% 2	2565
	11th to 20th	Night	46% 9% 9% 24% 11% 1	2496
	21st to end	Night	42% 7% 11% 23% 14% 2	2739
June	1st to 10th	Night	47% 7% 11% 21% 13% 1	1520
	11th to 20th	Night	39% 6% 11% 27% 16% 2	1485
	21st to end	Night	44% 8% 14% 21% 13% 1	1330
July	1st to 10th	Night	42% 7% 14% 23% 13% 1	2346
	11th to 20th	Night	40% 6% 14% 31% 9% 1	2472
	21st to end	Night	33% 7% 13% 33% 14%	2651
August	1st to 10th	Night	37% 6% 15% 27% 14%	2739
	11th to 20th	Night	39% 7% 18% 28% 8%	2812
	21st to end	Night	35% 6% 16% 30% 11% 2	3336
September	1st to 10th	Night	35% 7% 14% 31% 13%	1900
	11th to 20th	Night	36% 5% 14% 32% 12%	1900
	21st to end	Night	44% 5% 14% 27% 10%	2192
October	1st to 10th	Night	47% 5% 11% 24% 13%	2280
	11th to 20th	Night	55% 6% 13% 19% 7%	2280
	21st to end	Night	61% 5% 11% 15% 7%	2579
November	1st to 10th	Night	54% 5% 14% 20% 8%	2545
	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	30% 21% 29% 15% 4 1	506
April	1st to 10th	Day	30% 19% 31% 15% 5% 1	460
	11th to 20th	Day	36% 19% 22% 14% 7% 3	452
	21st to end	Day	30% 18% 30% 14% 6% 2	460
May	1st to 10th	Day	29% 15% 27% 19% 7% 3	463
	11th to 20th	Day	22% 17% 28% 20% 10% 3	487
	21st to end	Day	21% 16% 32% 20% 10% 2	529
June	1st to 10th	Day	24% 11% 35% 22% 7% 1	490
	11th to 20th	Day	18% 13% 31% 25% 11% 2	515
	21st to end	Day	20% 15% 33% 21% 10% 2	680
July	1st to 10th	Day	13% 10% 33% 33% 10% 2	561
	11th to 20th	Day	14% 12% 35% 24% 13% 3	484
	21st to end	Day	14% 8% 35% 29% 11% 4	532
August	1st to 10th	Day	15% 7% 32% 27% 13% 5%	486
	11th to 20th	Day	16% 8% 26% 27% 18% 5%	479
	21st to end	Day	15% 13% 32% 22% 14% 5%	539
September	1st to 10th	Day	16% 12% 30% 21% 14% 6%	490
	11th to 20th	Day	16% 9% 25% 20% 21% 9%	490
	21st to end	Day	20% 14% 25% 21% 14% 5%	490
October	1st to 10th	Day	24% 17% 26% 18% 11% 4	490
	11th to 20th	Day	30% 20% 28% 15% 6% 1	490
	21st to end	Day	34% 17% 26% 18% 4	502
November	1st to 10th	Day	26% 21% 34% 14% 6% 1	258
	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% 16% 35% 22% 7%	836
April	1st to 10th	Night	30% 14% 30% 21% 4	760
	11th to 20th	Night	28% 16% 28% 21% 8%	746
	21st to end	Night	29% 10% 27% 22% 11% 1	570
May	1st to 10th	Night	22% 8% 29% 31% 11%	412
	11th to 20th	Night	23% 9% 32% 28% 9%	374
	21st to end	Night	15% 9% 34% 31% 11%	411
June	1st to 10th	Night	18% 8% 39% 30% 4 1	380
	11th to 20th	Night	19% 8% 28% 32% 13% 1	380
	21st to end	Night	20% 8% 29% 31% 11% 1	380
July	1st to 10th	Night	11% 5% 32% 37% 14% 1	370
	11th to 20th	Night	12% 5% 27% 40% 15% 1	368
	21st to end	Night	10% 5% 31% 36% 17%	416
August	1st to 10th	Night	13% 5% 24% 36% 21% 1	517
	11th to 20th	Night	12% 4 21% 39% 21% 3	564
	21st to end	Night	15% 6% 28% 32% 17% 2	748
September	1st to 10th	Night	15% 8% 28% 30% 17% 2	760
	11th to 20th	Night	18% 5% 23% 26% 23% 3	760
	21st to end	Night	22% 8% 23% 28% 18% 2	760
October	1st to 10th	Night	25% 9% 28% 25% 11% 2	760
	11th to 20th	Night	27% 14% 28% 22% 8% 1	760
	21st to end	Night	32% 14% 27% 23% 4	836
November	1st to 10th	Night	25% 16% 27% 25% 7% 1	749
	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 2024-10-31 03:39:20. Version ac07

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