Standing Stone Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Standing Stone Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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% 9% 3 7% 5% 5% 5% 4 6% 7% 35%	101223
	Night	14% 9% 4 7% 5% 4 5% 4 5% 7% 36%	97780
Transparency	Day	45% 8% 12% 20% 13% 2	104899
	Night	44% 8% 12% 21% 13% 3	102243
Seeing	Day	22% 14% 24% 21% 13% 6%	15207
	Night	20% 13% 21% 29% 16% 2	25280

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	15% 15% 7% 10% 6% 4 3 2 4 6% 27%	2836
	11th to 20th	Day	13% 15% 8% 12% 9% 5% 3 2 3 3 25%	2840
	21st to end	Day	17% 17% 4 9% 5% 4 3 2 4 5% 29%	3124
February	1st to 10th	Day	13% 12% 4 10% 6% 4 5% 4 5% 7% 32%	1710
	11th to 20th	Day	17% 10% 5% 8% 5% 5% 4 3 5% 7% 31%	1739
	21st to end	Day	18% 12% 3 9% 5% 4 3 3 5% 5% 32%	1604
March	1st to 10th	Day	22% 11% 4 6% 4 3 3 4 5% 6% 31%	3435
	11th to 20th	Day	13% 8% 3 8% 3 3 4 3 4 6% 45%	3480
	21st to end	Day	17% 10% 3 7% 5% 4 5% 3 6% 6% 34%	3815
April	1st to 10th	Day	12% 11% 2 7% 5% 5% 4 4 5% 7% 40%	2133
	11th to 20th	Day	13% 8% 3 7% 5% 4 4 3 4 7% 41%	2255
	21st to end	Day	17% 8% 3 6% 5% 4 5% 3 6% 7% 37%	2470
May	1st to 10th	Day	18% 10% 4 8% 6% 6% 5% 4 7% 7% 27%	4082
	11th to 20th	Day	21% 8% 3 7% 5% 6% 5% 4 6% 8% 27%	4081
	21st to end	Day	9% 6% 2 6% 6% 5% 7% 6% 7% 10% 36%	4476
June	1st to 10th	Day	12% 6% 2 7% 5% 5% 6% 5% 6% 8% 38%	2470
	11th to 20th	Day	10% 6% 2 7% 6% 5% 6% 5% 8% 10% 36%	2470
	21st to end	Day	9% 6% 2 6% 6% 6% 6% 5% 8% 9% 37%	2470
July	1st to 10th	Day	7% 5% 2 7% 5% 6% 6% 4 8% 9% 40%	4120
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 5% 8% 11% 38%	4120
	21st to end	Day	15% 10% 4 10% 6% 7% 6% 5% 6% 7% 25%	4466
August	1st to 10th	Day	12% 7% 2 8% 6% 6% 6% 6% 8% 11% 28%	4104
	11th to 20th	Day	10% 5% 2 7% 6% 6% 6% 5% 8% 9% 34%	4044
	21st to end	Day	6% 4 1 5% 5% 5% 5% 5% 7% 11% 47%	4286
September	1st to 10th	Day	12% 6% 2 5% 5% 5% 4 5% 7% 7% 43%	2197
	11th to 20th	Day	12% 9% 3 8% 5% 5% 5% 4 5% 6% 38%	2090
	21st to end	Day	20% 7% 2 7% 5% 5% 4 4 5% 6% 35%	2090
October	1st to 10th	Day	15% 6% 2 6% 4 3 4 3 5% 7% 44%	1940
	11th to 20th	Day	16% 9% 2 6% 4 3 3 3 4 6% 43%	1900
	21st to end	Day	15% 10% 3 7% 3 4 3 3 3 6% 43%	2090
November	1st to 10th	Day	11% 8% 2 4 5% 3 4 3 5% 6% 48%	1879
	11th to 20th	Day	11% 10% 3 7% 4 5% 5% 3 5% 6% 40%	1710
	21st to end	Day	13% 10% 4 6% 4 5% 4 4 5% 6% 40%	1710
December	1st to 10th	Day	19% 13% 4 9% 4 4 5% 4 5% 6% 27%	1710
	11th to 20th	Day	17% 13% 4 7% 3 3 3 3 5% 8% 35%	2153
	21st to end	Day	18% 14% 4 9% 5% 5% 5% 4 6% 7% 23%	3124
January	1st to 10th	Night	12% 19% 8% 10% 6% 5% 4 4 5% 5% 23%	4109
	11th to 20th	Night	17% 12% 4 10% 6% 4 4 3 4 5% 33%	4120
	21st to end	Night	19% 14% 5% 7% 8% 4 4 3 4 4 27%	4532
February	1st to 10th	Night	14% 11% 4 8% 5% 5% 5% 3 5% 7% 32%	2470
	11th to 20th	Night	19% 10% 4 9% 6% 5% 5% 4 4 6% 28%	2325
	21st to end	Night	16% 11% 5% 8% 6% 4 5% 3 5% 6% 31%	1848
March	1st to 10th	Night	21% 13% 4 7% 4 4 4 3 4 5% 31%	3418
	11th to 20th	Night	12% 8% 7% 6% 4 3 4 3 5% 6% 41%	3480
	21st to end	Night	15% 8% 2 5% 4 4 4 4 6% 7% 41%	3817
April	1st to 10th	Night	11% 11% 3 7% 5% 5% 4 3 5% 7% 39%	2047
	11th to 20th	Night	13% 7% 3 6% 5% 4 4 4 6% 8% 41%	1875
	21st to end	Night	14% 6% 3 6% 4 4 4 5% 6% 7% 40%	1724
May	1st to 10th	Night	20% 11% 4 8% 5% 4 4 4 5% 7% 29%	2813
	11th to 20th	Night	20% 9% 4 7% 5% 4 4 3 4 7% 33%	2812
	21st to end	Night	10% 7% 3 7% 4 6% 6% 5% 7% 9% 37%	3079
June	1st to 10th	Night	7% 6% 3 6% 4 5% 4 4 7% 10% 43%	1710
	11th to 20th	Night	9% 6% 2 6% 4 4 5% 5% 6% 10% 44%	1710
	21st to end	Night	9% 5% 2 5% 5% 4 5% 5% 7% 10% 44%	1710
July	1st to 10th	Night	7% 4 2 8% 5% 5% 6% 5% 9% 10% 38%	2840
	11th to 20th	Night	8% 5% 2 5% 4 4 4 3 7% 10% 47%	2840
	21st to end	Night	11% 8% 4 11% 6% 5% 5% 5% 6% 9% 30%	3087
August	1st to 10th	Night	12% 7% 3 10% 5% 6% 6% 4 6% 8% 33%	2825
	11th to 20th	Night	11% 6% 3 8% 5% 4 6% 4 7% 8% 38%	2785
	21st to end	Night	6% 4 2 5% 4 4 4 4 7% 8% 53%	3338
September	1st to 10th	Night	10% 6% 2 6% 4 5% 4 4 6% 6% 47%	1980
	11th to 20th	Night	12% 6% 3 6% 5% 4 5% 3 5% 8% 44%	2090
	21st to end	Night	14% 8% 3 6% 4 5% 5% 4 5% 6% 39%	2090
October	1st to 10th	Night	13% 6% 2 5% 4 4 5% 3 5% 6% 46%	2238
	11th to 20th	Night	12% 8% 3 7% 4 4 5% 3 4 6% 44%	2280
	21st to end	Night	13% 9% 2 6% 5% 3 4 3 5% 5% 45%	2508
November	1st to 10th	Night	12% 7% 3 6% 4 3 4 3 5% 6% 48%	2296
	11th to 20th	Night	12% 10% 3 7% 4 4 5% 4 5% 6% 41%	2470
	21st to end	Night	13% 10% 3 7% 5% 4 5% 3 5% 5% 40%	2470
December	1st to 10th	Night	18% 12% 4 9% 5% 4 4 4 5% 6% 28%	2470
	11th to 20th	Night	15% 11% 6% 9% 5% 4 4 4 5% 6% 31%	3042
	21st to end	Night	16% 16% 6% 9% 5% 5% 5% 4 5% 6% 24%	4532

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	58% 5% 7% 19% 10% 1	2837
	11th to 20th	Day	64% 5% 7% 13% 9% 2	2840
	21st to end	Day	57% 5% 8% 17% 12% 1	3124
February	1st to 10th	Day	52% 6% 8% 20% 13% 1	1710
	11th to 20th	Day	53% 5% 10% 17% 12% 3	1748
	21st to end	Day	54% 5% 9% 15% 14% 3	1604
March	1st to 10th	Day	51% 7% 10% 21% 9% 2	3435
	11th to 20th	Day	41% 6% 10% 21% 20% 3	3480
	21st to end	Day	48% 9% 9% 19% 12% 2	3815
April	1st to 10th	Day	44% 8% 11% 19% 15% 4	2133
	11th to 20th	Day	44% 6% 11% 22% 15% 3	2255
	21st to end	Day	46% 8% 12% 21% 11% 2	2470
May	1st to 10th	Day	54% 10% 9% 17% 8% 1	4120
	11th to 20th	Day	52% 10% 12% 19% 6% 1	4085
	21st to end	Day	38% 12% 17% 19% 12% 3	4489
June	1st to 10th	Day	41% 11% 14% 21% 13%	2470
	11th to 20th	Day	41% 11% 16% 18% 14% 1	2470
	21st to end	Day	40% 11% 14% 21% 12% 2	2470
July	1st to 10th	Day	37% 13% 19% 19% 9% 4	4055
	11th to 20th	Day	36% 11% 18% 25% 9% 1	4051
	21st to end	Day	56% 9% 11% 15% 8% 1	4324
August	1st to 10th	Day	45% 12% 18% 19% 6%	4091
	11th to 20th	Day	41% 12% 13% 23% 11%	4083
	21st to end	Day	29% 12% 18% 26% 15% 1	4286
September	1st to 10th	Day	38% 9% 14% 18% 17% 4	2197
	11th to 20th	Day	45% 7% 10% 21% 17% 1	2090
	21st to end	Day	49% 7% 11% 18% 14% 1	2090
October	1st to 10th	Day	30% 7% 10% 20% 26% 7%	3226
	11th to 20th	Day	31% 5% 11% 24% 16% 13%	3140
	21st to end	Day	30% 4 9% 31% 16% 11%	3428
November	1st to 10th	Day	36% 5% 10% 22% 23% 3	1879
	11th to 20th	Day	44% 5% 8% 20% 19% 3	1710
	21st to end	Day	44% 5% 11% 21% 16% 2	1710
December	1st to 10th	Day	57% 6% 9% 16% 9% 2	1710
	11th to 20th	Day	49% 4 9% 19% 17% 1	2150
	21st to end	Day	57% 9% 10% 17% 7%	3124
January	1st to 10th	Night	61% 7% 7% 12% 11% 1	4109
	11th to 20th	Night	54% 6% 7% 18% 13% 3	4120
	21st to end	Night	58% 6% 8% 17% 10% 1	4532
February	1st to 10th	Night	52% 6% 11% 17% 13% 1	2470
	11th to 20th	Night	57% 6% 7% 16% 11% 3	2327
	21st to end	Night	54% 6% 10% 17% 9% 4	1848
March	1st to 10th	Night	54% 6% 10% 18% 10% 2	3418
	11th to 20th	Night	42% 7% 9% 25% 17% 1	3480
	21st to end	Night	40% 8% 13% 20% 17% 2	3817
April	1st to 10th	Night	45% 8% 11% 19% 14% 3	2047
	11th to 20th	Night	39% 6% 14% 20% 16% 4	1875
	21st to end	Night	41% 8% 14% 25% 11% 1	1724
May	1st to 10th	Night	53% 10% 11% 17% 8% 1	2840
	11th to 20th	Night	48% 11% 15% 20% 6%	2813
	21st to end	Night	37% 14% 18% 21% 6% 4	3087
June	1st to 10th	Night	35% 12% 17% 23% 13% 1	1710
	11th to 20th	Night	33% 11% 19% 23% 13% 1	1710
	21st to end	Night	32% 12% 19% 23% 14% 2	1710
July	1st to 10th	Night	35% 14% 20% 18% 11% 2	2795
	11th to 20th	Night	31% 10% 19% 31% 7% 2	2786
	21st to end	Night	46% 13% 13% 20% 7%	2988
August	1st to 10th	Night	45% 11% 18% 21% 5%	2814
	11th to 20th	Night	40% 10% 14% 25% 10%	2812
	21st to end	Night	26% 10% 15% 33% 14% 1	3338
September	1st to 10th	Night	37% 9% 14% 19% 16% 5%	1980
	11th to 20th	Night	36% 8% 12% 24% 18% 2	2090
	21st to end	Night	43% 8% 12% 22% 13% 1	2090
October	1st to 10th	Night	33% 8% 9% 21% 25% 4	3732
	11th to 20th	Night	32% 6% 9% 23% 20% 10%	3779
	21st to end	Night	26% 4 11% 29% 21% 10%	4120
November	1st to 10th	Night	37% 6% 11% 21% 22% 4	2296
	11th to 20th	Night	43% 5% 9% 19% 19% 4	2470
	21st to end	Night	45% 6% 9% 21% 16% 3	2470
December	1st to 10th	Night	57% 6% 9% 18% 8% 2	2470
	11th to 20th	Night	53% 6% 9% 17% 14% 1	3044
	21st to end	Night	58% 8% 10% 14% 9%	4532

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	39% 26% 21% 9% 4 1	270
	11th to 20th	Day	42% 24% 27% 7% 1	270
	21st to end	Day	38% 26% 24% 10% 3	297
February	1st to 10th	Day	33% 25% 27% 12% 3	270
	11th to 20th	Day	52% 21% 19% 7% 1	270
	21st to end	Day	44% 22% 25% 7% 2	259
March	1st to 10th	Day	33% 21% 22% 18% 4 1	460
	11th to 20th	Day	31% 27% 23% 13% 5% 1	460
	21st to end	Day	29% 24% 26% 14% 6%	506
April	1st to 10th	Day	26% 26% 24% 15% 8% 1	460
	11th to 20th	Day	25% 18% 28% 17% 10% 2	452
	21st to end	Day	29% 21% 23% 15% 10% 2	460
May	1st to 10th	Day	26% 18% 27% 15% 9% 4	463
	11th to 20th	Day	22% 13% 27% 20% 13% 5%	487
	21st to end	Day	15% 11% 25% 23% 17% 9%	529
June	1st to 10th	Day	13% 12% 26% 24% 16% 8%	490
	11th to 20th	Day	10% 11% 28% 25% 18% 8%	490
	21st to end	Day	11% 11% 26% 27% 15% 9%	490
July	1st to 10th	Day	12% 6% 20% 29% 21% 13%	485
	11th to 20th	Day	6% 5% 21% 36% 19% 13%	484
	21st to end	Day	14% 6% 21% 28% 19% 11%	532
August	1st to 10th	Day	15% 6% 23% 23% 22% 12%	486
	11th to 20th	Day	14% 6% 22% 23% 22% 13%	479
	21st to end	Day	10% 4 18% 27% 25% 16%	539
September	1st to 10th	Day	12% 6% 20% 26% 23% 13%	490
	11th to 20th	Day	14% 4 18% 27% 26% 11%	490
	21st to end	Day	22% 12% 21% 27% 15% 3	490
October	1st to 10th	Day	17% 9% 23% 27% 19% 6%	490
	11th to 20th	Day	20% 16% 21% 24% 16% 3	490
	21st to end	Day	23% 14% 24% 22% 14% 3	539
November	1st to 10th	Day	21% 13% 28% 24% 12% 3	453
	11th to 20th	Day	31% 17% 25% 19% 7%	270
	21st to end	Day	27% 19% 30% 19% 5% 1	270
December	1st to 10th	Day	36% 24% 25% 10% 4 1	270
	11th to 20th	Day	33% 20% 26% 15% 6% 1	270
	21st to end	Day	33% 21% 24% 14% 7% 1	297
January	1st to 10th	Night	30% 23% 25% 18% 3	760
	11th to 20th	Night	34% 20% 24% 19% 3	760
	21st to end	Night	31% 21% 28% 18% 2	836
February	1st to 10th	Night	27% 18% 29% 24% 2	760
	11th to 20th	Night	34% 25% 23% 17%	743
	21st to end	Night	26% 25% 29% 18% 1	628
March	1st to 10th	Night	26% 19% 28% 23% 4	760
	11th to 20th	Night	28% 22% 23% 20% 7%	760
	21st to end	Night	23% 19% 29% 23% 7%	836
April	1st to 10th	Night	20% 22% 27% 25% 6%	760
	11th to 20th	Night	19% 16% 26% 27% 12%	751
	21st to end	Night	16% 16% 25% 35% 8%	584
May	1st to 10th	Night	18% 14% 23% 31% 13% 1	570
	11th to 20th	Night	16% 10% 22% 34% 17% 1	561
	21st to end	Night	11% 6% 16% 34% 28% 5%	617
June	1st to 10th	Night	7% 6% 19% 38% 27% 3	570
	11th to 20th	Night	11% 4 13% 35% 36% 2	570
	21st to end	Night	10% 4 14% 40% 30% 2	570
July	1st to 10th	Night	10% 2 11% 39% 33% 5%	555
	11th to 20th	Night	6% 3 9% 33% 45% 5%	552
	21st to end	Night	8% 3 10% 36% 38% 5%	624
August	1st to 10th	Night	12% 2 11% 35% 37% 3	567
	11th to 20th	Night	13% 2 12% 32% 36% 5%	564
	21st to end	Night	10% 2 9% 33% 40% 6%	750
September	1st to 10th	Night	11% 5% 11% 33% 34% 6%	760
	11th to 20th	Night	12% 4 13% 33% 34% 4	760
	21st to end	Night	16% 7% 19% 30% 26% 1	760
October	1st to 10th	Night	14% 9% 19% 30% 25% 3	760
	11th to 20th	Night	17% 15% 20% 29% 18% 1	760
	21st to end	Night	20% 12% 20% 33% 13% 2	836
November	1st to 10th	Night	17% 9% 23% 34% 15% 1	760
	11th to 20th	Night	24% 15% 20% 30% 10% 1	760
	21st to end	Night	20% 17% 21% 32% 8% 1	760
December	1st to 10th	Night	31% 20% 25% 19% 6%	760
	11th to 20th	Night	25% 19% 26% 25% 5%	760
	21st to end	Night	27% 17% 26% 27% 3	836

Page generated at 2024-11-03 02:11:27. Version ac07

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