Payne's Starfield Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Payne's Starfield Observatory clear sky chart from 2005-11-06 to 2025-02-06.

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	15% 11% 4 9% 5% 5% 5% 4 5% 7% 31%	109151
	Night	15% 11% 4 9% 5% 4 4 3 5% 6% 32%	109027
Transparency	Day	51% 6% 11% 20% 11% 1	112844
	Night	50% 5% 11% 20% 12% 2	113475
Seeing	Day	20% 15% 27% 20% 12% 5%	15369
	Night	19% 12% 28% 27% 12% 2	25295

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	14% 17% 9% 18% 8% 5% 4 3 4 5% 12%	4056
	11th to 20th	Day	12% 21% 7% 14% 7% 6% 6% 3 3 4 15%	4060
	21st to end	Day	21% 17% 9% 11% 8% 6% 5% 3 3 3 12%	4466
February	1st to 10th	Day	18% 17% 4 11% 7% 5% 3 4 4 4 23%	1755
	11th to 20th	Day	15% 13% 5% 15% 6% 4 4 3 4 7% 24%	1793
	21st to end	Day	18% 15% 4 10% 5% 3 4 3 5% 5% 28%	1570
March	1st to 10th	Day	21% 14% 7% 10% 5% 4 4 3 5% 5% 22%	3280
	11th to 20th	Day	12% 11% 4 10% 5% 4 4 3 4 6% 35%	3480
	21st to end	Day	21% 10% 4 9% 5% 4 4 3 4 6% 31%	3815
April	1st to 10th	Day	14% 14% 5% 8% 6% 5% 4 3 5% 6% 31%	2118
	11th to 20th	Day	16% 12% 3 7% 5% 4 3 3 5% 6% 35%	2420
	21st to end	Day	18% 9% 3 8% 6% 4 4 4 5% 7% 32%	2470
May	1st to 10th	Day	20% 11% 3 7% 5% 5% 5% 4 5% 6% 28%	4082
	11th to 20th	Day	21% 8% 3 6% 4 4 4 3 5% 8% 34%	4081
	21st to end	Day	11% 7% 2 7% 5% 5% 6% 5% 7% 10% 35%	4476
June	1st to 10th	Day	11% 7% 2 8% 5% 5% 5% 5% 7% 9% 36%	2470
	11th to 20th	Day	11% 8% 2 7% 5% 5% 5% 5% 6% 8% 36%	2483
	21st to end	Day	11% 5% 2 6% 6% 5% 6% 5% 8% 9% 37%	2660
July	1st to 10th	Day	9% 7% 3 8% 6% 5% 6% 4 6% 10% 37%	4312
	11th to 20th	Day	9% 4 2 6% 5% 4 5% 5% 8% 11% 41%	4120
	21st to end	Day	10% 7% 2 7% 5% 5% 5% 5% 7% 10% 36%	4466
August	1st to 10th	Day	9% 7% 3 7% 5% 5% 6% 4 7% 10% 37%	4104
	11th to 20th	Day	9% 6% 3 6% 5% 5% 6% 5% 8% 10% 37%	4044
	21st to end	Day	7% 5% 2 7% 5% 6% 6% 5% 7% 10% 41%	4496
September	1st to 10th	Day	13% 6% 2 6% 4 4 5% 3 5% 8% 46%	2090
	11th to 20th	Day	9% 6% 2 6% 5% 5% 4 3 6% 10% 44%	2090
	21st to end	Day	20% 7% 2 5% 5% 4 3 3 4 6% 40%	2090
October	1st to 10th	Day	14% 7% 2 7% 5% 4 4 4 5% 7% 42%	2016
	11th to 20th	Day	14% 9% 3 6% 4 5% 4 4 6% 6% 39%	1900
	21st to end	Day	19% 10% 3 8% 5% 4 4 3 5% 7% 32%	2042
November	1st to 10th	Day	10% 8% 2 6% 5% 4 4 4 6% 7% 44%	1762
	11th to 20th	Day	17% 12% 5% 8% 5% 4 4 3 4 5% 32%	1800
	21st to end	Day	18% 15% 6% 9% 5% 4 4 3 4 6% 26%	1800
December	1st to 10th	Day	17% 14% 6% 15% 6% 4 3 3 4 5% 22%	2683
	11th to 20th	Day	22% 16% 7% 11% 6% 4 3 3 3 4 20%	3335
	21st to end	Day	24% 22% 7% 11% 5% 4 4 2 3 3 14%	4466
January	1st to 10th	Night	14% 19% 8% 19% 7% 5% 4 2 4 4 15%	5889
	11th to 20th	Night	12% 17% 9% 16% 7% 8% 6% 4 4 4 13%	5900
	21st to end	Night	20% 15% 7% 12% 6% 4 4 3 4 5% 21%	6490
February	1st to 10th	Night	19% 14% 4 11% 6% 5% 5% 4 4 5% 24%	2536
	11th to 20th	Night	15% 13% 4 11% 7% 4 5% 4 5% 5% 26%	2270
	21st to end	Night	19% 14% 4 11% 6% 5% 4 3 5% 4 26%	1884
March	1st to 10th	Night	20% 14% 5% 7% 4 4 4 3 4 5% 30%	3559
	11th to 20th	Night	12% 9% 4 8% 4 4 4 3 5% 7% 40%	3480
	21st to end	Night	18% 9% 3 7% 5% 4 4 3 5% 6% 37%	3817
April	1st to 10th	Night	15% 11% 3 6% 5% 4 4 5% 5% 7% 35%	2077
	11th to 20th	Night	15% 8% 3 7% 5% 5% 5% 3 6% 7% 36%	1707
	21st to end	Night	14% 8% 3 7% 5% 5% 4 3 6% 8% 36%	1710
May	1st to 10th	Night	23% 12% 3 8% 5% 5% 4 3 5% 6% 27%	2813
	11th to 20th	Night	18% 8% 2 7% 4 3 3 3 5% 8% 38%	2812
	21st to end	Night	9% 6% 2 5% 4 4 5% 5% 7% 11% 43%	3079
June	1st to 10th	Night	9% 7% 2 6% 5% 6% 5% 4 5% 8% 45%	1710
	11th to 20th	Night	8% 5% 2 5% 5% 4 6% 5% 6% 10% 42%	1686
	21st to end	Night	9% 4 2 7% 5% 4 5% 5% 7% 10% 43%	1520
July	1st to 10th	Night	10% 6% 2 6% 4 4 4 3 6% 8% 46%	2644
	11th to 20th	Night	8% 4 2 5% 4 4 5% 4 6% 10% 48%	2840
	21st to end	Night	8% 5% 3 6% 5% 5% 5% 5% 6% 9% 43%	3087
August	1st to 10th	Night	9% 7% 3 7% 5% 5% 6% 5% 7% 9% 37%	2825
	11th to 20th	Night	9% 8% 4 8% 5% 4 4 3 6% 7% 43%	2785
	21st to end	Night	5% 4 2 5% 4 5% 5% 5% 7% 9% 50%	3138
September	1st to 10th	Night	11% 5% 2 5% 3 4 5% 3 5% 6% 51%	2074
	11th to 20th	Night	9% 4 2 5% 4 3 3 3 5% 8% 55%	2090
	21st to end	Night	15% 7% 2 5% 4 4 3 3 6% 7% 44%	2090
October	1st to 10th	Night	10% 6% 3 5% 4 4 4 4 5% 7% 48%	2163
	11th to 20th	Night	15% 8% 3 7% 4 5% 3 4 4 7% 41%	2280
	21st to end	Night	20% 9% 2 6% 5% 4 4 3 4 8% 35%	2555
November	1st to 10th	Night	12% 7% 3 6% 5% 5% 4 3 5% 6% 45%	2536
	11th to 20th	Night	16% 11% 4 8% 5% 4 4 3 6% 6% 34%	2600
	21st to end	Night	18% 14% 4 9% 5% 4 4 4 5% 6% 27%	2600
December	1st to 10th	Night	16% 13% 6% 11% 6% 5% 5% 3 5% 6% 23%	4464
	11th to 20th	Night	18% 17% 7% 12% 5% 4 4 3 5% 5% 20%	4827
	21st to end	Night	22% 21% 7% 11% 5% 4 3 3 4 5% 15%	6490

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	74% 5% 8% 11% 3	4057
	11th to 20th	Day	73% 3 9% 7% 7%	4060
	21st to end	Day	77% 4 5% 8% 5%	4466
February	1st to 10th	Day	64% 5% 9% 14% 7% 1	1755
	11th to 20th	Day	62% 6% 8% 15% 9% 1	1803
	21st to end	Day	58% 5% 11% 17% 7% 2	1570
March	1st to 10th	Day	63% 5% 9% 18% 5%	3280
	11th to 20th	Day	49% 5% 11% 26% 9% 1	3480
	21st to end	Day	54% 4 11% 22% 8%	3815
April	1st to 10th	Day	53% 5% 12% 17% 12% 1	2118
	11th to 20th	Day	50% 5% 12% 17% 13% 2	2420
	21st to end	Day	51% 6% 11% 19% 11% 2	2470
May	1st to 10th	Day	54% 7% 11% 20% 7% 1	4120
	11th to 20th	Day	48% 7% 13% 22% 9% 1	4085
	21st to end	Day	40% 9% 14% 21% 12% 4	4489
June	1st to 10th	Day	42% 8% 12% 24% 15% 1	2470
	11th to 20th	Day	42% 9% 13% 21% 13% 1	2483
	21st to end	Day	40% 9% 14% 20% 14% 2	2660
July	1st to 10th	Day	42% 8% 11% 22% 15% 2	4247
	11th to 20th	Day	33% 7% 14% 26% 19% 1	4051
	21st to end	Day	40% 8% 14% 17% 19% 3	4324
August	1st to 10th	Day	41% 8% 16% 22% 13%	4091
	11th to 20th	Day	38% 8% 12% 27% 14% 1	4083
	21st to end	Day	37% 7% 14% 29% 12% 3	4496
September	1st to 10th	Day	38% 6% 12% 21% 19% 4	2090
	11th to 20th	Day	36% 5% 12% 25% 18% 3	2090
	21st to end	Day	45% 5% 10% 21% 19% 1	2090
October	1st to 10th	Day	28% 4 11% 33% 23% 1	3354
	11th to 20th	Day	38% 5% 10% 25% 18% 4	3140
	21st to end	Day	40% 4 13% 24% 18% 2	3344
November	1st to 10th	Day	38% 6% 11% 26% 16% 2	1762
	11th to 20th	Day	54% 4 9% 20% 10% 2	1800
	21st to end	Day	61% 4 9% 16% 9% 1	1800
December	1st to 10th	Day	65% 5% 12% 15% 3	2683
	11th to 20th	Day	68% 4 10% 13% 5%	3332
	21st to end	Day	77% 3 7% 8% 5%	4466
January	1st to 10th	Night	73% 4 6% 12% 4	5889
	11th to 20th	Night	75% 3 9% 7% 5%	5900
	21st to end	Night	68% 3 11% 12% 6% 2	6490
February	1st to 10th	Night	62% 5% 10% 15% 7% 1	2536
	11th to 20th	Night	59% 5% 9% 17% 9% 1	2271
	21st to end	Night	62% 5% 10% 12% 9% 2	1884
March	1st to 10th	Night	55% 5% 10% 20% 9% 1	3559
	11th to 20th	Night	43% 6% 12% 28% 9% 2	3480
	21st to end	Night	47% 6% 10% 26% 11% 1	3817
April	1st to 10th	Night	48% 6% 12% 19% 14% 2	2077
	11th to 20th	Night	47% 5% 12% 16% 17% 3	1707
	21st to end	Night	45% 7% 12% 19% 16% 2	1710
May	1st to 10th	Night	57% 7% 7% 19% 8% 2	2840
	11th to 20th	Night	44% 6% 11% 26% 11% 1	2813
	21st to end	Night	32% 9% 15% 27% 14% 3	3087
June	1st to 10th	Night	37% 7% 13% 23% 18% 2	1710
	11th to 20th	Night	33% 8% 16% 24% 17% 2	1686
	21st to end	Night	34% 9% 14% 24% 16% 3	1520
July	1st to 10th	Night	36% 6% 12% 23% 17% 6%	2601
	11th to 20th	Night	30% 7% 14% 31% 17% 1	2786
	21st to end	Night	35% 8% 14% 21% 19% 3	2988
August	1st to 10th	Night	40% 9% 14% 22% 13% 1	2814
	11th to 20th	Night	40% 6% 10% 25% 19% 1	2812
	21st to end	Night	28% 9% 15% 30% 16% 2	3138
September	1st to 10th	Night	33% 7% 11% 24% 19% 6%	2074
	11th to 20th	Night	28% 4 12% 27% 25% 3	2090
	21st to end	Night	39% 6% 11% 20% 22% 2	2090
October	1st to 10th	Night	28% 4 8% 29% 30% 2	3605
	11th to 20th	Night	33% 5% 11% 27% 20% 5%	3779
	21st to end	Night	36% 4 9% 28% 19% 4	4203
November	1st to 10th	Night	40% 4 12% 23% 18% 3	2536
	11th to 20th	Night	51% 5% 9% 20% 12% 3	2600
	21st to end	Night	57% 5% 11% 19% 7% 1	2600
December	1st to 10th	Night	62% 5% 10% 17% 5%	4464
	11th to 20th	Night	66% 4 12% 13% 4	4829
	21st to end	Night	72% 4 9% 11% 4	6490

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	28% 27% 32% 8% 5%	300
	11th to 20th	Day	29% 28% 35% 6% 2	300
	21st to end	Day	30% 28% 28% 12% 2	330
February	1st to 10th	Day	34% 26% 26% 12% 2	285
	11th to 20th	Day	30% 31% 29% 9%	270
	21st to end	Day	31% 36% 26% 6%	225
March	1st to 10th	Day	27% 24% 32% 15% 2	365
	11th to 20th	Day	28% 22% 32% 13% 5%	460
	21st to end	Day	31% 19% 30% 16% 4	506
April	1st to 10th	Day	24% 21% 29% 16% 8% 1	460
	11th to 20th	Day	24% 21% 28% 15% 8% 4	452
	21st to end	Day	24% 19% 33% 16% 6% 2	460
May	1st to 10th	Day	25% 18% 31% 16% 7% 3	463
	11th to 20th	Day	24% 11% 29% 20% 11% 5%	487
	21st to end	Day	14% 9% 25% 26% 20% 6%	529
June	1st to 10th	Day	13% 9% 28% 30% 14% 5%	490
	11th to 20th	Day	15% 9% 27% 27% 19% 4	503
	21st to end	Day	13% 9% 31% 27% 15% 4	680
July	1st to 10th	Day	14% 6% 20% 26% 22% 13%	599
	11th to 20th	Day	11% 5% 26% 27% 21% 10%	484
	21st to end	Day	11% 5% 22% 30% 23% 9%	532
August	1st to 10th	Day	13% 4 18% 29% 23% 13%	486
	11th to 20th	Day	14% 6% 25% 26% 19% 10%	479
	21st to end	Day	9% 6% 19% 30% 25% 11%	539
September	1st to 10th	Day	13% 6% 22% 25% 24% 10%	490
	11th to 20th	Day	11% 4 16% 28% 28% 13%	490
	21st to end	Day	24% 10% 21% 24% 15% 6%	490
October	1st to 10th	Day	12% 11% 28% 25% 19% 6%	490
	11th to 20th	Day	17% 19% 29% 22% 10% 3	490
	21st to end	Day	24% 20% 30% 20% 5% 1	491
November	1st to 10th	Day	15% 24% 35% 15% 9% 2	300
	11th to 20th	Day	28% 19% 31% 14% 7% 1	300
	21st to end	Day	27% 25% 37% 9% 2	300
December	1st to 10th	Day	29% 29% 26% 11% 4 2	227
	11th to 20th	Day	27% 25% 34% 11% 3	287
	21st to end	Day	35% 20% 33% 11% 2	330
January	1st to 10th	Night	25% 22% 35% 16% 3	800
	11th to 20th	Night	26% 22% 33% 16% 3	800
	21st to end	Night	24% 21% 34% 19% 3	880
February	1st to 10th	Night	27% 16% 37% 18% 2	781
	11th to 20th	Night	23% 21% 35% 18% 2	743
	21st to end	Night	29% 17% 35% 16% 2	628
March	1st to 10th	Night	23% 17% 34% 23% 4	760
	11th to 20th	Night	21% 18% 34% 20% 6% 1	760
	21st to end	Night	24% 13% 32% 24% 6%	836
April	1st to 10th	Night	19% 16% 35% 23% 6%	747
	11th to 20th	Night	20% 13% 33% 23% 9% 2	563
	21st to end	Night	19% 11% 38% 24% 7% 1	570
May	1st to 10th	Night	21% 11% 30% 29% 9% 1	570
	11th to 20th	Night	21% 6% 28% 30% 13% 2	561
	21st to end	Night	10% 4 24% 37% 23% 2	617
June	1st to 10th	Night	12% 4 26% 40% 18% 1	570
	11th to 20th	Night	11% 4 21% 44% 18% 2	570
	21st to end	Night	10% 5% 26% 37% 20% 2	570
July	1st to 10th	Night	11% 3 17% 40% 23% 7%	555
	11th to 20th	Night	7% 3 20% 38% 28% 4	552
	21st to end	Night	9% 4 16% 39% 30% 2	624
August	1st to 10th	Night	8% 2 14% 43% 27% 5%	567
	11th to 20th	Night	9% 4 15% 40% 27% 4	564
	21st to end	Night	7% 2 16% 35% 33% 6%	627
September	1st to 10th	Night	13% 4 20% 32% 26% 5%	744
	11th to 20th	Night	11% 3 13% 38% 30% 5%	760
	21st to end	Night	19% 6% 23% 29% 19% 4	760
October	1st to 10th	Night	13% 7% 27% 30% 20% 3	760
	11th to 20th	Night	19% 12% 31% 24% 12% 1	760
	21st to end	Night	24% 15% 30% 23% 9%	836
November	1st to 10th	Night	17% 13% 31% 26% 12% 1	780
	11th to 20th	Night	23% 16% 31% 23% 7% 1	800
	21st to end	Night	26% 17% 29% 22% 6% 1	800
December	1st to 10th	Night	28% 17% 33% 18% 4	800
	11th to 20th	Night	26% 17% 34% 20% 3	800
	21st to end	Night	29% 16% 32% 20% 3	880

Page generated at 2025-02-03 03:05:52. Version ac07

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