Stony Creek Ranch Resort Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stony Creek Ranch Resort Observatory clear sky chart from 2005-11-06 to 2024-11-01.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	101409
	Night	16% 9% 3 8% 5% 4 4 4 5% 6% 35%	97550
Transparency	Day	47% 9% 13% 19% 10% 1	101165
	Night	47% 9% 13% 19% 11% 1	97413
Seeing	Day	22% 17% 30% 20% 9% 3	14745
	Night	19% 14% 30% 27% 9% 1	23760

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	11% 13% 5% 11% 5% 6% 5% 4 5% 6% 28%	2517
	11th to 20th	Day	16% 15% 7% 13% 8% 5% 4 3 4 4 22%	2520
	21st to end	Day	15% 15% 6% 11% 6% 5% 5% 4 5% 6% 22%	2835
February	1st to 10th	Day	12% 13% 4 10% 7% 6% 6% 5% 6% 6% 26%	1710
	11th to 20th	Day	10% 11% 6% 11% 7% 5% 6% 5% 5% 5% 29%	1800
	21st to end	Day	18% 11% 5% 8% 6% 4 3 3 5% 5% 32%	1570
March	1st to 10th	Day	21% 17% 4 9% 4 4 3 3 3 5% 26%	3116
	11th to 20th	Day	12% 12% 4 9% 6% 5% 5% 4 6% 6% 30%	3306
	21st to end	Day	17% 11% 3 7% 5% 4 4 3 4 5% 37%	4156
April	1st to 10th	Day	19% 12% 3 7% 4 4 4 3 4 6% 35%	2280
	11th to 20th	Day	17% 9% 2 6% 5% 6% 4 4 5% 6% 36%	2254
	21st to end	Day	20% 10% 3 8% 5% 5% 5% 3 5% 6% 31%	2380
May	1st to 10th	Day	22% 12% 3 7% 4 4 5% 3 5% 6% 28%	4251
	11th to 20th	Day	17% 7% 3 7% 4 6% 5% 4 7% 8% 31%	4398
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 39%	4837
June	1st to 10th	Day	16% 7% 3 7% 6% 5% 5% 5% 7% 8% 30%	2660
	11th to 20th	Day	17% 5% 3 6% 6% 4 5% 5% 7% 8% 33%	2660
	21st to end	Day	17% 7% 2 7% 5% 5% 5% 4 7% 9% 30%	2660
July	1st to 10th	Day	10% 5% 2 7% 6% 6% 6% 5% 7% 9% 36%	4440
	11th to 20th	Day	10% 5% 2 6% 5% 6% 6% 5% 9% 12% 33%	4440
	21st to end	Day	13% 6% 2 6% 5% 6% 6% 5% 7% 7% 36%	4814
August	1st to 10th	Day	15% 5% 2 7% 5% 6% 6% 5% 7% 8% 35%	4423
	11th to 20th	Day	14% 7% 2 7% 5% 6% 6% 5% 8% 10% 31%	3777
	21st to end	Day	12% 6% 3 6% 4 5% 6% 5% 8% 9% 37%	4180
September	1st to 10th	Day	13% 4 2 6% 4 5% 5% 4 6% 8% 43%	2280
	11th to 20th	Day	14% 5% 2 5% 4 4 4 3 5% 8% 47%	2199
	21st to end	Day	17% 5% 2 6% 4 4 4 4 6% 6% 40%	2090
October	1st to 10th	Day	21% 8% 3 9% 5% 5% 5% 3 5% 5% 32%	1971
	11th to 20th	Day	15% 8% 3 7% 4 4 5% 4 6% 7% 36%	1900
	21st to end	Day	22% 10% 3 7% 5% 4 4 3 5% 6% 29%	1881
November	1st to 10th	Day	12% 9% 3 7% 5% 4 5% 4 6% 7% 37%	1671
	11th to 20th	Day	15% 10% 4 6% 5% 5% 5% 4 5% 7% 34%	1710
	21st to end	Day	17% 10% 4 7% 5% 4 5% 4 5% 7% 32%	1525
December	1st to 10th	Day	19% 15% 4 10% 6% 5% 4 3 5% 6% 24%	1520
	11th to 20th	Day	21% 11% 3 8% 5% 5% 4 4 5% 5% 30%	1906
	21st to end	Day	22% 16% 5% 11% 5% 5% 3 3 3 5% 21%	2772
January	1st to 10th	Night	14% 11% 5% 9% 6% 5% 4 4 5% 5% 32%	4429
	11th to 20th	Night	11% 12% 6% 13% 7% 6% 5% 4 5% 7% 23%	4440
	21st to end	Night	19% 14% 5% 9% 6% 5% 4 3 4 4 27%	4820
February	1st to 10th	Night	11% 11% 4 10% 7% 6% 6% 5% 7% 6% 26%	2470
	11th to 20th	Night	10% 10% 4 10% 7% 4 5% 5% 6% 6% 33%	2266
	21st to end	Night	14% 9% 3 9% 6% 5% 4 4 6% 7% 33%	1884
March	1st to 10th	Night	23% 13% 3 7% 4 4 4 4 5% 6% 28%	3724
	11th to 20th	Night	13% 11% 4 8% 6% 4 4 5% 5% 6% 34%	3650
	21st to end	Night	15% 13% 3 9% 5% 4 4 3 4 5% 35%	3476
April	1st to 10th	Night	18% 8% 3 7% 6% 4 5% 4 5% 5% 36%	1900
	11th to 20th	Night	18% 9% 3 6% 5% 3 4 4 5% 7% 37%	1875
	21st to end	Night	19% 9% 2 7% 4 4 3 3 6% 5% 37%	1800
May	1st to 10th	Night	22% 11% 4 8% 5% 4 3 4 5% 7% 28%	2719
	11th to 20th	Night	18% 9% 4 9% 6% 4 4 3 4 7% 31%	2495
	21st to end	Night	13% 5% 2 6% 5% 5% 5% 5% 7% 8% 40%	2738
June	1st to 10th	Night	18% 6% 1 5% 4 5% 5% 4 6% 7% 39%	1520
	11th to 20th	Night	16% 7% 2 6% 4 4 5% 3 6% 9% 39%	1520
	21st to end	Night	16% 5% 2 6% 5% 4 6% 4 5% 7% 40%	1520
July	1st to 10th	Night	9% 5% 3 7% 5% 5% 5% 5% 7% 8% 40%	2520
	11th to 20th	Night	13% 4 2 5% 5% 4 4 4 6% 8% 45%	2520
	21st to end	Night	13% 6% 2 6% 5% 5% 4 3 6% 7% 42%	2739
August	1st to 10th	Night	17% 7% 2 7% 5% 4 5% 3 5% 6% 39%	2506
	11th to 20th	Night	16% 6% 2 7% 4 4 4 4 6% 7% 41%	3002
	21st to end	Night	9% 5% 2 5% 4 4 5% 5% 6% 9% 46%	3476
September	1st to 10th	Night	11% 5% 2 5% 4 3 4 3 7% 8% 47%	1900
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 4 5% 53%	1981
	21st to end	Night	15% 6% 2 4 4 5% 4 4 4 6% 46%	2090
October	1st to 10th	Night	19% 6% 3 8% 4 4 5% 4 5% 6% 34%	2205
	11th to 20th	Night	15% 6% 3 7% 5% 4 6% 3 6% 6% 40%	2280
	21st to end	Night	22% 9% 3 7% 4 4 4 4 6% 7% 31%	2717
November	1st to 10th	Night	13% 8% 3 8% 5% 5% 4 3 5% 6% 41%	2414
	11th to 20th	Night	18% 7% 3 7% 4 4 4 3 6% 7% 36%	2470
	21st to end	Night	15% 9% 3 7% 5% 4 5% 4 6% 7% 35%	2652
December	1st to 10th	Night	16% 13% 4 9% 6% 6% 4 3 6% 6% 27%	2660
	11th to 20th	Night	20% 10% 3 8% 6% 5% 4 4 5% 5% 30%	3288
	21st to end	Night	23% 13% 6% 11% 5% 4 4 3 5% 5% 22%	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	51% 11% 14% 17% 6% 1	2518
	11th to 20th	Day	62% 8% 11% 12% 5% 2	2520
	21st to end	Day	61% 9% 11% 12% 5% 1	2835
February	1st to 10th	Day	55% 10% 11% 16% 6% 1	1710
	11th to 20th	Day	54% 8% 11% 15% 10% 2	1809
	21st to end	Day	54% 6% 11% 16% 12% 1	1570
March	1st to 10th	Day	60% 7% 11% 11% 10% 2	3119
	11th to 20th	Day	48% 13% 15% 13% 10% 2	3306
	21st to end	Day	48% 8% 7% 15% 19% 3	4156
April	1st to 10th	Day	51% 6% 9% 19% 12% 3	2280
	11th to 20th	Day	47% 7% 11% 19% 14% 2	2254
	21st to end	Day	53% 7% 10% 15% 12% 3	2380
May	1st to 10th	Day	51% 10% 10% 18% 10% 1	4265
	11th to 20th	Day	46% 13% 14% 17% 8% 1	4402
	21st to end	Day	35% 11% 16% 25% 11% 1	4837
June	1st to 10th	Day	47% 11% 14% 16% 10% 1	2660
	11th to 20th	Day	45% 9% 14% 18% 12% 1	2660
	21st to end	Day	48% 10% 14% 19% 10% 1	2660
July	1st to 10th	Day	39% 9% 16% 23% 13%	4370
	11th to 20th	Day	39% 9% 17% 27% 7%	4365
	21st to end	Day	43% 8% 16% 22% 10%	4661
August	1st to 10th	Day	43% 9% 16% 19% 12% 1	4409
	11th to 20th	Day	43% 10% 16% 25% 6%	3814
	21st to end	Day	39% 8% 16% 26% 10%	4180
September	1st to 10th	Day	37% 10% 13% 29% 11% 1	2280
	11th to 20th	Day	34% 7% 13% 28% 17% 1	2199
	21st to end	Day	41% 8% 15% 22% 13% 1	2090
October	1st to 10th	Day	53% 7% 10% 17% 12% 1	1971
	11th to 20th	Day	43% 10% 15% 22% 8% 1	1900
	21st to end	Day	54% 8% 13% 14% 9% 1	1881
November	1st to 10th	Day	42% 10% 16% 20% 11%	1671
	11th to 20th	Day	47% 8% 14% 15% 14% 2	1710
	21st to end	Day	50% 10% 16% 16% 7% 1	1525
December	1st to 10th	Day	61% 8% 11% 13% 6% 1	1520
	11th to 20th	Day	55% 8% 16% 14% 6% 1	1906
	21st to end	Day	65% 8% 9% 11% 8%	2772
January	1st to 10th	Night	50% 10% 15% 15% 9% 1	4429
	11th to 20th	Night	57% 11% 13% 11% 7% 1	4440
	21st to end	Night	60% 7% 12% 13% 8% 1	4820
February	1st to 10th	Night	55% 9% 12% 16% 7% 1	2470
	11th to 20th	Night	48% 9% 12% 18% 12% 1	2268
	21st to end	Night	48% 8% 14% 20% 8% 2	1884
March	1st to 10th	Night	53% 9% 11% 15% 11% 1	3734
	11th to 20th	Night	48% 10% 12% 19% 10% 1	3651
	21st to end	Night	49% 7% 8% 16% 16% 3	3476
April	1st to 10th	Night	48% 7% 11% 20% 14% 2	1900
	11th to 20th	Night	46% 8% 11% 20% 14% 1	1875
	21st to end	Night	45% 8% 11% 18% 14% 4	1800
May	1st to 10th	Night	51% 12% 11% 14% 10% 1	2725
	11th to 20th	Night	51% 11% 13% 16% 9% 1	2496
	21st to end	Night	37% 12% 15% 19% 15% 2	2739
June	1st to 10th	Night	43% 9% 15% 20% 12% 2	1520
	11th to 20th	Night	40% 8% 17% 21% 13% 1	1520
	21st to end	Night	41% 10% 14% 22% 12% 1	1520
July	1st to 10th	Night	38% 10% 16% 22% 14% 1	2480
	11th to 20th	Night	36% 8% 18% 24% 14%	2472
	21st to end	Night	39% 8% 14% 27% 11% 1	2651
August	1st to 10th	Night	43% 8% 15% 23% 10%	2496
	11th to 20th	Night	41% 7% 17% 26% 9%	3030
	21st to end	Night	32% 8% 16% 33% 11%	3476
September	1st to 10th	Night	33% 9% 16% 28% 13% 1	1900
	11th to 20th	Night	34% 6% 13% 28% 19% 1	1981
	21st to end	Night	38% 8% 14% 23% 15% 2	2090
October	1st to 10th	Night	48% 9% 12% 18% 12% 1	2205
	11th to 20th	Night	43% 9% 15% 22% 10% 1	2280
	21st to end	Night	51% 8% 13% 18% 9% 1	2717
November	1st to 10th	Night	43% 7% 14% 20% 13% 2	2414
	11th to 20th	Night	45% 8% 12% 21% 11% 2	2470
	21st to end	Night	47% 9% 16% 18% 9% 1	2652
December	1st to 10th	Night	56% 9% 14% 15% 6%	2660
	11th to 20th	Night	53% 9% 13% 14% 10% 1	3288
	21st to end	Night	61% 10% 10% 13% 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	22% 22% 33% 16% 8%	180
	11th to 20th	Day	24% 28% 31% 13% 2 1	180
	21st to end	Day	16% 27% 38% 14% 5% 1	216
February	1st to 10th	Day	27% 33% 32% 8% 1	270
	11th to 20th	Day	22% 32% 33% 12% 1	408
	21st to end	Day	31% 21% 30% 16% 3	382
March	1st to 10th	Day	27% 17% 35% 18% 3	460
	11th to 20th	Day	26% 25% 30% 14% 4 1	460
	21st to end	Day	29% 25% 24% 14% 7% 2	506
April	1st to 10th	Day	33% 20% 25% 14% 6% 1	460
	11th to 20th	Day	31% 23% 24% 13% 7% 2	452
	21st to end	Day	28% 20% 31% 14% 5% 2	460
May	1st to 10th	Day	30% 18% 30% 13% 7% 2	463
	11th to 20th	Day	17% 17% 35% 22% 6% 2	487
	21st to end	Day	18% 15% 31% 23% 11% 2	529
June	1st to 10th	Day	19% 16% 32% 22% 10% 2	490
	11th to 20th	Day	16% 16% 32% 25% 10% 2	490
	21st to end	Day	20% 14% 33% 21% 8% 3	490
July	1st to 10th	Day	15% 9% 31% 28% 15% 3	485
	11th to 20th	Day	15% 8% 31% 30% 14% 3	484
	21st to end	Day	14% 9% 36% 27% 10% 3	532
August	1st to 10th	Day	12% 10% 28% 28% 16% 5%	486
	11th to 20th	Day	18% 8% 25% 28% 13% 8%	479
	21st to end	Day	12% 12% 30% 26% 14% 6%	539
September	1st to 10th	Day	15% 9% 27% 25% 16% 9%	490
	11th to 20th	Day	14% 10% 26% 22% 18% 11%	490
	21st to end	Day	18% 10% 31% 23% 11% 7%	490
October	1st to 10th	Day	26% 14% 25% 17% 13% 4	490
	11th to 20th	Day	20% 18% 29% 23% 9% 2	490
	21st to end	Day	30% 14% 30% 19% 6% 1	429
November	1st to 10th	Day	24% 16% 25% 21% 13% 1	365
	11th to 20th	Day	25% 22% 27% 19% 6% 1	370
	21st to end	Day	28% 18% 35% 17% 2	185
December	1st to 10th	Day	26% 24% 29% 16% 3 1	180
	11th to 20th	Day	28% 24% 33% 12% 3	180
	21st to end	Day	27% 22% 35% 13% 4 1	198
January	1st to 10th	Night	19% 18% 37% 24% 3	760
	11th to 20th	Night	21% 19% 33% 23% 3	760
	21st to end	Night	14% 19% 37% 25% 4	836
February	1st to 10th	Night	17% 19% 41% 22% 2	760
	11th to 20th	Night	17% 22% 40% 20% 2	743
	21st to end	Night	22% 19% 37% 19% 3	628
March	1st to 10th	Night	23% 18% 34% 23% 2	760
	11th to 20th	Night	24% 18% 33% 21% 4	760
	21st to end	Night	22% 19% 31% 21% 7%	836
April	1st to 10th	Night	24% 18% 31% 23% 4	760
	11th to 20th	Night	23% 18% 32% 20% 7%	751
	21st to end	Night	26% 16% 28% 24% 7%	660
May	1st to 10th	Night	25% 15% 28% 23% 9%	507
	11th to 20th	Night	18% 16% 32% 26% 7% 1	374
	21st to end	Night	15% 9% 27% 35% 14% 1	411
June	1st to 10th	Night	19% 6% 27% 34% 12% 1	380
	11th to 20th	Night	18% 7% 25% 36% 13%	380
	21st to end	Night	16% 6% 28% 39% 11% 1	380
July	1st to 10th	Night	11% 5% 24% 40% 19% 1	370
	11th to 20th	Night	13% 2 24% 40% 20% 1	368
	21st to end	Night	11% 4 25% 43% 16% 1	416
August	1st to 10th	Night	10% 2 24% 44% 19% 1	378
	11th to 20th	Night	14% 6% 21% 36% 21% 3	691
	21st to end	Night	15% 6% 19% 39% 21% 1	836
September	1st to 10th	Night	13% 5% 25% 36% 18% 2	760
	11th to 20th	Night	15% 7% 24% 27% 22% 5%	760
	21st to end	Night	16% 6% 30% 30% 16% 2	760
October	1st to 10th	Night	23% 11% 25% 26% 14% 1	760
	11th to 20th	Night	19% 12% 28% 31% 10% 1	760
	21st to end	Night	25% 14% 30% 25% 6%	836
November	1st to 10th	Night	17% 15% 32% 28% 8%	743
	11th to 20th	Night	22% 19% 28% 24% 6% 1	760
	21st to end	Night	19% 16% 34% 23% 6% 1	760
December	1st to 10th	Night	24% 16% 36% 21% 4	760
	11th to 20th	Night	24% 17% 31% 23% 4	760
	21st to end	Night	25% 18% 34% 21% 2	836

Page generated at 2024-10-29 11:20:46. Version ac07

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