Orion Acres
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Orion Acres clear sky chart from 2005-11-06 to 2026-04-02.

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	13% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	131413
	Night	13% 8% 3 7% 4 4 4 3 5% 7% 41%	130464
Transparency	Day	43% 5% 11% 21% 16% 4	135151
	Night	41% 5% 11% 21% 17% 5%	134797
Seeing	Day	20% 12% 24% 22% 15% 7%	16441
	Night	18% 10% 22% 28% 18% 3	26545

By Month

Percentage Cloud Cover SE (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	18% 10% 6% 8% 4 3 3 3 4 5% 36%	5258
	11th to 20th	Day	13% 6% 3 11% 3 2 3 2 3 4 49%	5280
	21st to end	Day	20% 8% 4 8% 4 3 3 3 4 6% 36%	6173
February	1st to 10th	Day	17% 11% 4 7% 4 4 4 4 4 5% 35%	2100
	11th to 20th	Day	22% 9% 3 7% 6% 4 4 3 5% 5% 33%	2048
	21st to end	Day	18% 10% 3 8% 4 4 4 3 5% 5% 36%	1730
March	1st to 10th	Day	18% 11% 4 8% 5% 5% 4 4 5% 5% 32%	4580
	11th to 20th	Day	12% 7% 3 7% 4 4 4 3 5% 5% 47%	5034
	21st to end	Day	14% 8% 3 7% 5% 4 4 3 5% 7% 40%	5620
April	1st to 10th	Day	12% 9% 2 6% 5% 4 4 4 6% 7% 40%	2412
	11th to 20th	Day	13% 8% 3 6% 4 3 4 4 4 7% 43%	2374
	21st to end	Day	13% 7% 3 6% 5% 5% 4 4 6% 7% 39%	2501
May	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 5% 7% 8% 29%	5862
	11th to 20th	Day	17% 9% 3 10% 6% 7% 5% 4 6% 7% 26%	5861
	21st to end	Day	16% 8% 2 6% 5% 5% 4 4 5% 7% 37%	6433
June	1st to 10th	Day	10% 7% 2 8% 5% 6% 6% 5% 7% 9% 35%	2600
	11th to 20th	Day	5% 5% 2 7% 6% 5% 7% 6% 8% 10% 40%	2600
	21st to end	Day	6% 5% 2 7% 6% 5% 7% 6% 9% 10% 36%	2600
July	1st to 10th	Day	6% 5% 2 7% 7% 6% 7% 6% 8% 10% 35%	5900
	11th to 20th	Day	8% 6% 2 7% 6% 8% 8% 7% 10% 11% 27%	5900
	21st to end	Day	11% 9% 4 10% 7% 7% 7% 6% 8% 10% 20%	6424
August	1st to 10th	Day	6% 4 2 5% 5% 6% 6% 5% 8% 10% 42%	4170
	11th to 20th	Day	6% 4 2 7% 5% 7% 7% 6% 8% 10% 36%	3849
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 6% 7% 46%	4312
September	1st to 10th	Day	12% 6% 2 8% 5% 6% 6% 5% 5% 7% 37%	2297
	11th to 20th	Day	13% 7% 3 7% 5% 4 5% 5% 6% 7% 39%	2200
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 3 5% 6% 43%	2200
October	1st to 10th	Day	10% 5% 2 6% 4 4 4 3 4 6% 51%	2200
	11th to 20th	Day	11% 4 2 4 3 4 3 3 5% 6% 55%	2152
	21st to end	Day	14% 6% 3 4 4 3 4 3 5% 6% 48%	2063
November	1st to 10th	Day	11% 6% 2 6% 4 3 4 3 4 4 53%	1852
	11th to 20th	Day	12% 7% 2 6% 4 4 3 3 5% 6% 48%	1890
	21st to end	Day	15% 9% 2 6% 3 4 4 4 5% 6% 42%	1890
December	1st to 10th	Day	15% 10% 3 6% 3 4 4 3 4 5% 44%	3020
	11th to 20th	Day	17% 14% 4 9% 5% 5% 4 3 3 5% 32%	3463
	21st to end	Day	19% 10% 6% 7% 4 3 3 3 5% 9% 32%	4565
January	1st to 10th	Night	16% 11% 3 8% 3 2 3 3 4 6% 40%	7635
	11th to 20th	Night	14% 10% 4 8% 4 3 3 2 3 4 46%	7680
	21st to end	Night	17% 12% 4 6% 4 4 4 2 3 4 38%	8006
February	1st to 10th	Night	16% 9% 4 7% 5% 4 4 3 6% 6% 37%	2520
	11th to 20th	Night	21% 10% 3 8% 5% 4 5% 3 4 3 34%	2458
	21st to end	Night	22% 10% 3 7% 4 4 4 3 5% 5% 34%	2076
March	1st to 10th	Night	20% 11% 4 7% 5% 5% 4 3 5% 6% 29%	5493
	11th to 20th	Night	11% 7% 2 6% 4 4 4 3 5% 6% 48%	5143
	21st to end	Night	14% 8% 3 8% 5% 5% 5% 3 4 5% 41%	5588
April	1st to 10th	Night	13% 6% 2 5% 4 4 5% 4 5% 7% 45%	2015
	11th to 20th	Night	12% 7% 2 5% 3 2 3 3 5% 8% 48%	1975
	21st to end	Night	11% 7% 2 5% 4 4 4 4 6% 8% 44%	1896
May	1st to 10th	Night	14% 9% 3 8% 6% 5% 5% 4 6% 8% 32%	4033
	11th to 20th	Night	19% 10% 3 9% 5% 5% 5% 3 5% 7% 29%	4032
	21st to end	Night	13% 7% 3 8% 4 4 5% 4 6% 9% 36%	4421
June	1st to 10th	Night	9% 6% 3 7% 5% 5% 5% 3 7% 9% 40%	1800
	11th to 20th	Night	5% 3 2 4 3 4 5% 4 7% 12% 51%	1800
	21st to end	Night	5% 5% 2 5% 4 5% 4 5% 8% 12% 45%	1800
July	1st to 10th	Night	7% 5% 2 6% 5% 4 6% 5% 8% 11% 40%	4058
	11th to 20th	Night	7% 5% 2 5% 4 5% 6% 5% 8% 13% 39%	4057
	21st to end	Night	9% 10% 3 8% 5% 5% 6% 5% 8% 12% 29%	4427
August	1st to 10th	Night	3 3 1 4 4 5% 5% 4 7% 11% 51%	2974
	11th to 20th	Night	6% 5% 1 6% 5% 5% 4 5% 7% 10% 47%	3200
	21st to end	Night	6% 3 1 4 4 3 4 5% 7% 9% 54%	3586
September	1st to 10th	Night	9% 6% 2 6% 5% 5% 5% 4 6% 8% 45%	2081
	11th to 20th	Night	13% 6% 2 5% 4 5% 4 4 7% 7% 45%	2200
	21st to end	Night	11% 6% 2 5% 3 4 4 3 6% 6% 51%	2200
October	1st to 10th	Night	10% 4 2 4 4 3 3 2 5% 6% 59%	2200
	11th to 20th	Night	12% 6% 2 6% 3 3 4 3 4 5% 52%	2246
	21st to end	Night	14% 8% 2 5% 3 3 3 2 3 6% 51%	2773
November	1st to 10th	Night	12% 7% 2 6% 3 3 4 3 5% 6% 50%	2666
	11th to 20th	Night	11% 8% 2 6% 3 3 3 2 6% 5% 49%	2730
	21st to end	Night	15% 10% 3 7% 4 3 3 3 5% 5% 42%	2730
December	1st to 10th	Night	18% 9% 3 7% 4 4 4 2 4 5% 41%	4380
	11th to 20th	Night	19% 13% 4 6% 3 3 3 3 4 4 36%	4952
	21st to end	Night	19% 8% 7% 8% 5% 5% 4 3 5% 6% 30%	6633

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	50% 3 8% 23% 15% 2	5259
	11th to 20th	Day	40% 3 4 16% 33% 4	5280
	21st to end	Day	50% 2 7% 22% 13% 6%	6173
February	1st to 10th	Day	50% 3 7% 19% 17% 3	2100
	11th to 20th	Day	53% 4 7% 17% 15% 4	2058
	21st to end	Day	48% 4 8% 15% 19% 6%	1730
March	1st to 10th	Day	52% 5% 6% 11% 18% 8%	4580
	11th to 20th	Day	40% 3 6% 19% 20% 11%	5034
	21st to end	Day	43% 5% 9% 27% 14% 2	5622
April	1st to 10th	Day	41% 7% 11% 21% 16% 3	2412
	11th to 20th	Day	40% 5% 8% 20% 23% 5%	2374
	21st to end	Day	42% 6% 10% 27% 13% 2	2501
May	1st to 10th	Day	50% 7% 12% 21% 9% 1	5897
	11th to 20th	Day	53% 8% 15% 18% 7%	5865
	21st to end	Day	46% 6% 8% 22% 15% 2	6447
June	1st to 10th	Day	41% 9% 15% 21% 12% 1	2600
	11th to 20th	Day	35% 9% 18% 23% 13% 2	2600
	21st to end	Day	36% 11% 20% 17% 13% 3	2600
July	1st to 10th	Day	40% 7% 18% 22% 11% 1	5835
	11th to 20th	Day	45% 6% 26% 18% 4 1	5831
	21st to end	Day	55% 7% 18% 16% 3	6240
August	1st to 10th	Day	33% 7% 13% 33% 13% 1	4157
	11th to 20th	Day	38% 7% 16% 23% 14% 1	3885
	21st to end	Day	34% 6% 11% 31% 16% 2	4311
September	1st to 10th	Day	43% 9% 12% 17% 15% 5%	2297
	11th to 20th	Day	43% 7% 10% 20% 18% 2	2200
	21st to end	Day	39% 7% 11% 21% 17% 5%	2200
October	1st to 10th	Day	25% 3 5% 17% 37% 13%	3590
	11th to 20th	Day	22% 2 5% 21% 33% 16%	3483
	21st to end	Day	31% 2 6% 25% 25% 11%	3313
November	1st to 10th	Day	35% 4 8% 20% 27% 6%	1852
	11th to 20th	Day	37% 4 7% 23% 23% 6%	1890
	21st to end	Day	41% 4 7% 21% 22% 4	1890
December	1st to 10th	Day	44% 2 5% 21% 24% 3	3020
	11th to 20th	Day	55% 3 6% 17% 14% 4	3460
	21st to end	Day	49% 3 12% 22% 11% 2	4565
January	1st to 10th	Night	47% 3 13% 21% 15% 2	7636
	11th to 20th	Night	43% 2 5% 17% 27% 6%	7680
	21st to end	Night	51% 2 7% 15% 19% 7%	8006
February	1st to 10th	Night	47% 4 10% 19% 17% 3	2520
	11th to 20th	Night	54% 5% 6% 16% 15% 5%	2459
	21st to end	Night	52% 4 6% 16% 17% 5%	2076
March	1st to 10th	Night	53% 5% 6% 13% 18% 4	5493
	11th to 20th	Night	37% 4 6% 20% 19% 14%	5143
	21st to end	Night	45% 4 8% 24% 16% 3	5588
April	1st to 10th	Night	36% 6% 12% 22% 20% 3	2015
	11th to 20th	Night	34% 5% 9% 23% 23% 7%	1975
	21st to end	Night	37% 5% 14% 27% 16% 1	1896
May	1st to 10th	Night	48% 8% 15% 19% 9% 1	4060
	11th to 20th	Night	54% 7% 14% 16% 8%	4033
	21st to end	Night	42% 8% 14% 24% 12% 1	4429
June	1st to 10th	Night	39% 8% 16% 23% 13% 2	1800
	11th to 20th	Night	24% 8% 20% 31% 15% 2	1800
	21st to end	Night	30% 9% 19% 26% 13% 4	1800
July	1st to 10th	Night	35% 8% 21% 23% 11% 1	4015
	11th to 20th	Night	34% 6% 32% 22% 5% 2	4006
	21st to end	Night	46% 8% 24% 17% 4 1	4297
August	1st to 10th	Night	26% 7% 14% 38% 14% 1	2963
	11th to 20th	Night	30% 8% 22% 25% 15% 1	3230
	21st to end	Night	27% 7% 14% 32% 20% 1	3586
September	1st to 10th	Night	34% 9% 16% 20% 15% 5%	2081
	11th to 20th	Night	37% 8% 12% 21% 21% 2	2200
	21st to end	Night	34% 5% 12% 23% 21% 6%	2200
October	1st to 10th	Night	20% 2 6% 25% 30% 17%	3590
	11th to 20th	Night	21% 3 5% 20% 32% 18%	3654
	21st to end	Night	28% 2 5% 25% 29% 11%	4473
November	1st to 10th	Night	35% 5% 8% 21% 24% 8%	2666
	11th to 20th	Night	36% 4 7% 21% 26% 8%	2730
	21st to end	Night	44% 3 6% 21% 21% 5%	2730
December	1st to 10th	Night	47% 3 5% 18% 24% 3	4380
	11th to 20th	Night	50% 3 6% 18% 20% 3	4954
	21st to end	Night	52% 4 10% 22% 10% 1	6633

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	37% 20% 29% 12% 2	330
	11th to 20th	Day	38% 23% 26% 8% 3 1	330
	21st to end	Day	29% 30% 29% 10% 1	363
February	1st to 10th	Day	32% 23% 32% 11% 2	330
	11th to 20th	Day	45% 24% 25% 5% 1	330
	21st to end	Day	40% 25% 26% 7% 2	273
March	1st to 10th	Day	33% 22% 33% 10% 2 1	330
	11th to 20th	Day	30% 23% 25% 17% 4 1	510
	21st to end	Day	25% 21% 34% 14% 6% 1	594
April	1st to 10th	Day	27% 15% 30% 19% 9% 1	504
	11th to 20th	Day	21% 17% 33% 19% 9% 1	492
	21st to end	Day	22% 14% 32% 20% 10% 2	500
May	1st to 10th	Day	20% 17% 30% 20% 9% 4	503
	11th to 20th	Day	15% 11% 29% 24% 15% 7%	527
	21st to end	Day	18% 8% 22% 26% 14% 12%	573
June	1st to 10th	Day	14% 8% 20% 25% 20% 13%	530
	11th to 20th	Day	7% 5% 17% 33% 23% 15%	530
	21st to end	Day	8% 4 24% 27% 20% 17%	530
July	1st to 10th	Day	9% 3 17% 30% 24% 17%	525
	11th to 20th	Day	10% 4 11% 27% 27% 21%	524
	21st to end	Day	11% 3 10% 28% 28% 19%	576
August	1st to 10th	Day	13% 4 15% 27% 25% 16%	526
	11th to 20th	Day	12% 4 18% 26% 29% 10%	519
	21st to end	Day	13% 4 11% 26% 31% 15%	583
September	1st to 10th	Day	11% 3 19% 26% 30% 12%	530
	11th to 20th	Day	13% 5% 15% 28% 29% 10%	530
	21st to end	Day	16% 6% 18% 28% 27% 5%	530
October	1st to 10th	Day	13% 7% 21% 32% 19% 7%	530
	11th to 20th	Day	14% 13% 28% 28% 15% 3	530
	21st to end	Day	21% 11% 31% 22% 13% 2	446
November	1st to 10th	Day	22% 13% 34% 22% 9% 2	330
	11th to 20th	Day	18% 19% 39% 20% 4	330
	21st to end	Day	25% 18% 34% 15% 7% 1	330
December	1st to 10th	Day	34% 18% 31% 14% 2 1	330
	11th to 20th	Day	28% 22% 28% 16% 6%	330
	21st to end	Day	34% 19% 31% 13% 4	363
January	1st to 10th	Night	27% 18% 31% 21% 3	840
	11th to 20th	Night	26% 19% 30% 21% 5%	840
	21st to end	Night	21% 19% 34% 23% 3	924
February	1st to 10th	Night	23% 16% 31% 25% 4	840
	11th to 20th	Night	31% 20% 28% 19% 2	823
	21st to end	Night	30% 20% 27% 20% 2	692
March	1st to 10th	Night	22% 15% 33% 25% 4	840
	11th to 20th	Night	21% 16% 30% 25% 7% 1	840
	21st to end	Night	19% 15% 31% 26% 8%	924
April	1st to 10th	Night	17% 14% 28% 30% 10%	608
	11th to 20th	Night	17% 13% 32% 28% 10% 1	593
	21st to end	Night	15% 9% 28% 33% 14% 1	600
May	1st to 10th	Night	12% 8% 31% 30% 19% 2	600
	11th to 20th	Night	15% 7% 20% 31% 21% 5%	591
	21st to end	Night	11% 4 14% 36% 29% 6%	650
June	1st to 10th	Night	10% 5% 15% 35% 31% 5%	600
	11th to 20th	Night	6% 2 11% 33% 37% 12%	600
	21st to end	Night	7% 2 10% 34% 38% 10%	600
July	1st to 10th	Night	10% 1 9% 28% 42% 10%	585
	11th to 20th	Night	9% 4 7% 25% 40% 15%	582
	21st to end	Night	9% 2 6% 29% 42% 12%	657
August	1st to 10th	Night	8% 2 8% 26% 47% 9%	597
	11th to 20th	Night	10% 3 11% 31% 37% 8%	594
	21st to end	Night	13% 1 8% 29% 40% 9%	660
September	1st to 10th	Night	12% 2 11% 31% 36% 8%	681
	11th to 20th	Night	15% 4 13% 28% 35% 6%	800
	21st to end	Night	13% 3 15% 31% 34% 4	800
October	1st to 10th	Night	12% 6% 19% 28% 29% 7%	800
	11th to 20th	Night	16% 9% 25% 31% 19% 2	800
	21st to end	Night	19% 9% 22% 33% 14% 2	880
November	1st to 10th	Night	17% 9% 23% 32% 17% 2	820
	11th to 20th	Night	17% 15% 28% 30% 10% 1	840
	21st to end	Night	22% 14% 24% 29% 10% 1	840
December	1st to 10th	Night	27% 15% 26% 28% 5%	840
	11th to 20th	Night	24% 13% 28% 28% 7% 1	840
	21st to end	Night	27% 15% 25% 28% 5%	924

Page generated at 2026-03-30 01:18:43. Version ac07

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