Stoney Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stoney Hill Observatory clear sky chart from 2005-11-06 to 2024-11-10.

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	14% 8% 3 8% 5% 5% 5% 4 6% 8% 34%	101445
	Night	15% 9% 3 8% 5% 5% 5% 4 6% 7% 35%	97709
Transparency	Day	45% 8% 14% 21% 11% 1	104952
	Night	46% 7% 14% 21% 11% 1	102291
Seeing	Day	20% 17% 30% 21% 9% 3	14845
	Night	20% 15% 32% 25% 7% 1	23903

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	12% 10% 4 10% 6% 6% 6% 4 6% 6% 29%	2517
	11th to 20th	Day	14% 13% 5% 12% 6% 5% 6% 4 6% 5% 24%	2520
	21st to end	Day	17% 12% 5% 10% 6% 6% 4 5% 5% 6% 23%	2879
February	1st to 10th	Day	14% 12% 4 9% 7% 5% 6% 5% 5% 6% 27%	1710
	11th to 20th	Day	11% 10% 4 10% 7% 5% 5% 6% 6% 6% 30%	1818
	21st to end	Day	16% 11% 4 9% 6% 5% 3 3 6% 6% 30%	1570
March	1st to 10th	Day	22% 13% 5% 9% 5% 4 4 3 4 5% 28%	3116
	11th to 20th	Day	11% 11% 4 10% 5% 5% 5% 4 6% 7% 32%	3310
	21st to end	Day	17% 9% 3 7% 5% 5% 5% 3 5% 5% 36%	4153
April	1st to 10th	Day	16% 10% 3 8% 5% 4 4 3 5% 6% 35%	2280
	11th to 20th	Day	15% 8% 3 7% 5% 5% 4 4 5% 6% 37%	2254
	21st to end	Day	18% 8% 2 7% 5% 4 5% 4 5% 7% 34%	2356
May	1st to 10th	Day	21% 9% 3 8% 5% 5% 4 3 5% 7% 30%	4192
	11th to 20th	Day	15% 8% 3 7% 5% 5% 5% 4 6% 8% 33%	4398
	21st to end	Day	10% 5% 2 6% 5% 4 5% 5% 8% 9% 40%	4837
June	1st to 10th	Day	13% 6% 2 8% 6% 6% 6% 4 7% 8% 33%	2660
	11th to 20th	Day	14% 5% 3 6% 5% 5% 6% 6% 7% 10% 34%	2660
	21st to end	Day	14% 6% 2 8% 6% 5% 5% 4 7% 8% 34%	2660
July	1st to 10th	Day	7% 6% 3 7% 5% 6% 6% 5% 8% 10% 35%	4440
	11th to 20th	Day	8% 5% 2 7% 5% 6% 7% 5% 8% 10% 37%	4440
	21st to end	Day	11% 6% 3 7% 6% 5% 6% 5% 7% 8% 35%	4814
August	1st to 10th	Day	14% 7% 2 7% 6% 5% 6% 4 7% 8% 33%	4392
	11th to 20th	Day	10% 8% 3 8% 5% 7% 6% 5% 7% 10% 32%	3730
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 12% 39%	4180
September	1st to 10th	Day	12% 5% 1 6% 5% 5% 5% 4 6% 7% 43%	2280
	11th to 20th	Day	11% 6% 2 5% 4 4 4 4 5% 8% 48%	2198
	21st to end	Day	16% 5% 2 6% 4 4 4 5% 7% 8% 40%	2090
October	1st to 10th	Day	17% 8% 3 7% 5% 5% 5% 4 5% 6% 35%	1976
	11th to 20th	Day	13% 7% 3 7% 5% 5% 4 4 5% 7% 39%	1900
	21st to end	Day	21% 9% 2 7% 4 5% 5% 4 5% 7% 32%	1897
November	1st to 10th	Day	12% 8% 3 5% 4 4 5% 4 5% 7% 43%	1752
	11th to 20th	Day	14% 8% 3 8% 6% 5% 4 5% 5% 5% 38%	1710
	21st to end	Day	16% 9% 2 8% 5% 5% 5% 4 5% 7% 34%	1558
December	1st to 10th	Day	17% 13% 3 10% 6% 6% 5% 4 6% 6% 24%	1520
	11th to 20th	Day	21% 10% 3 7% 5% 4 3 3 4 7% 32%	1906
	21st to end	Day	23% 15% 5% 10% 6% 4 4 3 4 6% 21%	2772
January	1st to 10th	Night	14% 11% 4 9% 6% 4 4 3 5% 7% 33%	4429
	11th to 20th	Night	12% 12% 5% 11% 6% 5% 4 4 5% 6% 28%	4440
	21st to end	Night	21% 12% 4 10% 6% 5% 5% 4 5% 5% 24%	4774
February	1st to 10th	Night	13% 12% 4 10% 7% 5% 5% 4 6% 6% 29%	2470
	11th to 20th	Night	10% 9% 4 10% 6% 6% 5% 5% 7% 7% 30%	2247
	21st to end	Night	16% 10% 3 8% 6% 4 5% 5% 6% 7% 30%	1884
March	1st to 10th	Night	23% 10% 2 8% 5% 5% 5% 4 5% 6% 28%	3724
	11th to 20th	Night	14% 10% 4 7% 6% 5% 5% 4 5% 5% 34%	3645
	21st to end	Night	14% 10% 3 8% 5% 6% 5% 4 5% 5% 35%	3477
April	1st to 10th	Night	17% 9% 4 7% 5% 4 5% 4 5% 6% 33%	1900
	11th to 20th	Night	18% 7% 2 7% 6% 4 5% 3 5% 7% 35%	1875
	21st to end	Night	19% 6% 3 6% 5% 3 4 4 5% 7% 38%	1823
May	1st to 10th	Night	21% 9% 3 8% 5% 5% 4 5% 5% 6% 31%	2776
	11th to 20th	Night	15% 9% 3 9% 6% 6% 6% 3 6% 7% 31%	2495
	21st to end	Night	11% 6% 3 7% 5% 6% 5% 4 7% 8% 39%	2738
June	1st to 10th	Night	14% 8% 3 7% 4 4 5% 4 6% 7% 39%	1520
	11th to 20th	Night	13% 5% 2 6% 4 4 5% 4 8% 10% 39%	1520
	21st to end	Night	11% 5% 2 6% 5% 4 5% 4 6% 9% 42%	1520
July	1st to 10th	Night	8% 6% 3 7% 6% 6% 5% 5% 6% 9% 40%	2520
	11th to 20th	Night	10% 6% 3 7% 4 5% 6% 4 7% 8% 40%	2520
	21st to end	Night	11% 6% 3 8% 4 6% 5% 5% 5% 8% 40%	2739
August	1st to 10th	Night	17% 7% 3 6% 4 4 5% 4 7% 9% 35%	2532
	11th to 20th	Night	12% 7% 2 7% 5% 5% 5% 4 7% 7% 39%	3066
	21st to end	Night	9% 6% 2 5% 4 4 4 3 6% 9% 48%	3476
September	1st to 10th	Night	12% 7% 2 6% 4 4 4 4 6% 7% 45%	1900
	11th to 20th	Night	13% 4 2 4 3 3 4 3 5% 7% 53%	1981
	21st to end	Night	13% 6% 2 6% 5% 5% 4 4 5% 7% 44%	2090
October	1st to 10th	Night	16% 9% 2 7% 5% 4 4 4 6% 5% 38%	2199
	11th to 20th	Night	14% 6% 2 7% 4 4 5% 4 6% 7% 41%	2280
	21st to end	Night	20% 8% 3 6% 4 4 4 3 6% 7% 34%	2699
November	1st to 10th	Night	13% 8% 3 6% 4 4 4 4 5% 6% 43%	2531
	11th to 20th	Night	16% 8% 3 6% 5% 4 5% 4 5% 7% 37%	2470
	21st to end	Night	15% 8% 2 7% 6% 5% 6% 4 5% 6% 38%	2617
December	1st to 10th	Night	17% 11% 4 8% 5% 5% 5% 4 6% 8% 27%	2660
	11th to 20th	Night	20% 9% 3 7% 5% 5% 5% 4 6% 6% 31%	3288
	21st to end	Night	24% 13% 5% 9% 5% 5% 4 3 4 6% 24%	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	49% 9% 15% 21% 6% 1	2518
	11th to 20th	Day	59% 8% 12% 15% 6% 1	2520
	21st to end	Day	59% 7% 13% 15% 5% 1	2879
February	1st to 10th	Day	54% 9% 12% 15% 8% 1	1710
	11th to 20th	Day	51% 7% 12% 19% 10% 1	1827
	21st to end	Day	53% 6% 12% 16% 12% 1	1570
March	1st to 10th	Day	57% 5% 12% 15% 8% 1	3119
	11th to 20th	Day	46% 8% 17% 18% 9% 2	3310
	21st to end	Day	49% 5% 8% 17% 18% 3	4153
April	1st to 10th	Day	50% 5% 10% 21% 11% 2	2280
	11th to 20th	Day	46% 7% 10% 20% 14% 2	2254
	21st to end	Day	48% 7% 11% 17% 13% 3	2356
May	1st to 10th	Day	52% 8% 11% 16% 11% 1	4206
	11th to 20th	Day	47% 7% 16% 20% 9% 1	4402
	21st to end	Day	35% 10% 15% 25% 14% 1	4837
June	1st to 10th	Day	46% 9% 14% 20% 11% 1	2660
	11th to 20th	Day	42% 10% 15% 20% 12% 1	2660
	21st to end	Day	45% 8% 15% 20% 11% 1	2660
July	1st to 10th	Day	39% 10% 14% 22% 14% 1	4370
	11th to 20th	Day	39% 9% 16% 24% 12% 1	4365
	21st to end	Day	42% 9% 16% 20% 13% 1	4661
August	1st to 10th	Day	47% 9% 15% 19% 9% 1	4378
	11th to 20th	Day	45% 8% 16% 25% 6%	3766
	21st to end	Day	36% 8% 17% 28% 11% 1	4180
September	1st to 10th	Day	38% 8% 13% 25% 15% 1	2280
	11th to 20th	Day	33% 7% 12% 26% 19% 1	2198
	21st to end	Day	40% 8% 13% 24% 13% 2	2090
October	1st to 10th	Day	41% 6% 11% 21% 20% 1	3288
	11th to 20th	Day	35% 4 13% 29% 18% 1	3140
	21st to end	Day	34% 7% 16% 27% 14% 2	3097
November	1st to 10th	Day	40% 6% 15% 25% 13% 1	1752
	11th to 20th	Day	46% 7% 12% 19% 14% 1	1710
	21st to end	Day	47% 8% 17% 19% 8% 1	1558
December	1st to 10th	Day	59% 7% 13% 14% 7% 1	1520
	11th to 20th	Day	52% 6% 18% 17% 7% 1	1906
	21st to end	Day	63% 7% 11% 14% 4	2772
January	1st to 10th	Night	48% 8% 16% 19% 9% 1	4429
	11th to 20th	Night	54% 7% 13% 16% 8% 1	4440
	21st to end	Night	61% 8% 10% 15% 6% 1	4774
February	1st to 10th	Night	54% 7% 13% 17% 8% 1	2470
	11th to 20th	Night	51% 8% 13% 18% 10% 1	2249
	21st to end	Night	51% 6% 15% 18% 9% 2	1884
March	1st to 10th	Night	54% 7% 12% 17% 9% 1	3734
	11th to 20th	Night	49% 7% 14% 22% 8% 1	3646
	21st to end	Night	49% 5% 9% 17% 16% 3	3477
April	1st to 10th	Night	50% 6% 12% 19% 11% 1	1900
	11th to 20th	Night	46% 8% 11% 18% 16% 1	1875
	21st to end	Night	45% 7% 12% 18% 15% 3	1823
May	1st to 10th	Night	54% 6% 12% 14% 11% 2	2782
	11th to 20th	Night	50% 8% 14% 19% 8% 1	2496
	21st to end	Night	39% 9% 16% 20% 15% 1	2739
June	1st to 10th	Night	42% 7% 13% 24% 12% 2	1520
	11th to 20th	Night	38% 9% 17% 23% 12%	1520
	21st to end	Night	37% 9% 16% 25% 13% 1	1520
July	1st to 10th	Night	40% 7% 16% 20% 16% 1	2480
	11th to 20th	Night	38% 7% 17% 24% 14%	2472
	21st to end	Night	41% 7% 14% 25% 12% 1	2651
August	1st to 10th	Night	45% 8% 17% 22% 8%	2522
	11th to 20th	Night	42% 7% 17% 25% 9%	3096
	21st to end	Night	32% 7% 15% 35% 11% 1	3476
September	1st to 10th	Night	39% 6% 13% 26% 15% 1	1900
	11th to 20th	Night	31% 5% 14% 26% 23% 1	1981
	21st to end	Night	39% 6% 13% 24% 17% 1	2090
October	1st to 10th	Night	45% 5% 14% 21% 14%	3667
	11th to 20th	Night	32% 5% 14% 26% 22% 1	3779
	21st to end	Night	38% 6% 15% 30% 11% 1	4449
November	1st to 10th	Night	40% 7% 12% 21% 18% 2	2531
	11th to 20th	Night	46% 7% 13% 21% 12% 2	2470
	21st to end	Night	45% 7% 18% 22% 7% 1	2617
December	1st to 10th	Night	53% 8% 15% 18% 7%	2660
	11th to 20th	Night	52% 7% 16% 15% 10% 1	3288
	21st to end	Night	60% 7% 12% 15% 5%	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	24% 28% 32% 11% 5%	180
	11th to 20th	Day	33% 28% 23% 14% 2 1	180
	21st to end	Day	21% 28% 32% 13% 5%	231
February	1st to 10th	Day	30% 28% 34% 8% 1	270
	11th to 20th	Day	28% 28% 33% 10% 1	426
	21st to end	Day	29% 23% 32% 14% 2	382
March	1st to 10th	Day	27% 22% 33% 16% 3	460
	11th to 20th	Day	26% 26% 30% 14% 3 1	460
	21st to end	Day	31% 22% 26% 13% 5% 1	506
April	1st to 10th	Day	28% 24% 27% 14% 5% 1	460
	11th to 20th	Day	27% 25% 27% 14% 6% 1	452
	21st to end	Day	25% 22% 33% 13% 5% 2	460
May	1st to 10th	Day	29% 18% 30% 15% 6% 2	463
	11th to 20th	Day	17% 16% 35% 23% 8% 2	487
	21st to end	Day	14% 12% 33% 26% 11% 3	529
June	1st to 10th	Day	15% 17% 32% 24% 10% 2	490
	11th to 20th	Day	15% 13% 32% 26% 13% 2	490
	21st to end	Day	17% 15% 30% 26% 10% 3	490
July	1st to 10th	Day	11% 10% 28% 32% 14% 4	485
	11th to 20th	Day	11% 7% 32% 31% 17% 3	484
	21st to end	Day	12% 6% 35% 30% 15% 3	532
August	1st to 10th	Day	9% 8% 30% 32% 16% 5%	486
	11th to 20th	Day	13% 7% 29% 29% 16% 6%	479
	21st to end	Day	10% 12% 28% 29% 17% 5%	539
September	1st to 10th	Day	15% 9% 27% 23% 19% 6%	490
	11th to 20th	Day	12% 11% 26% 22% 18% 12%	490
	21st to end	Day	19% 12% 25% 25% 15% 5%	490
October	1st to 10th	Day	22% 10% 28% 23% 13% 4	490
	11th to 20th	Day	17% 18% 31% 23% 9% 2	490
	21st to end	Day	27% 15% 31% 21% 5% 1	436
November	1st to 10th	Day	22% 17% 28% 21% 11% 1	392
	11th to 20th	Day	23% 24% 31% 16% 4 1	370
	21st to end	Day	24% 24% 27% 22% 2	218
December	1st to 10th	Day	23% 28% 31% 14% 4 1	180
	11th to 20th	Day	30% 22% 37% 8% 2	180
	21st to end	Day	23% 24% 37% 13% 2 1	198
January	1st to 10th	Night	20% 20% 38% 20% 2	760
	11th to 20th	Night	26% 19% 34% 19% 2	760
	21st to end	Night	19% 21% 39% 19% 2	836
February	1st to 10th	Night	24% 18% 38% 18% 2	760
	11th to 20th	Night	20% 24% 40% 17%	743
	21st to end	Night	25% 22% 32% 18% 3	628
March	1st to 10th	Night	24% 22% 35% 17% 2	760
	11th to 20th	Night	24% 23% 33% 18% 2	760
	21st to end	Night	23% 24% 32% 17% 4	836
April	1st to 10th	Night	23% 22% 33% 19% 2	760
	11th to 20th	Night	23% 19% 33% 19% 5%	751
	21st to end	Night	22% 20% 31% 23% 4	683
May	1st to 10th	Night	22% 18% 31% 21% 7%	538
	11th to 20th	Night	16% 17% 36% 25% 5% 1	374
	21st to end	Night	11% 12% 32% 36% 9%	411
June	1st to 10th	Night	18% 8% 34% 30% 10% 1	380
	11th to 20th	Night	16% 7% 34% 33% 10%	380
	21st to end	Night	10% 7% 34% 37% 11% 1	380
July	1st to 10th	Night	12% 5% 25% 42% 16% 1	370
	11th to 20th	Night	12% 6% 22% 42% 16% 1	368
	21st to end	Night	12% 4 25% 47% 12%	416
August	1st to 10th	Night	11% 3 23% 44% 18% 1	391
	11th to 20th	Night	12% 5% 25% 36% 19% 3	731
	21st to end	Night	14% 7% 22% 36% 20% 1	836
September	1st to 10th	Night	15% 5% 29% 34% 16% 1	760
	11th to 20th	Night	16% 6% 26% 30% 18% 5%	760
	21st to end	Night	15% 7% 29% 34% 13% 2	760
October	1st to 10th	Night	20% 11% 27% 27% 14% 1	760
	11th to 20th	Night	16% 13% 32% 30% 8%	760
	21st to end	Night	25% 15% 33% 24% 4	836
November	1st to 10th	Night	19% 16% 33% 25% 7%	779
	11th to 20th	Night	21% 16% 36% 20% 6% 1	760
	21st to end	Night	20% 19% 32% 23% 5%	760
December	1st to 10th	Night	24% 19% 37% 16% 3	760
	11th to 20th	Night	25% 18% 33% 22% 2	760
	21st to end	Night	28% 20% 33% 17% 1	836

Page generated at 2024-11-07 06:55:45. Version ac07

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