Warren Rupp Observatory
Clear Sky Chart
History

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

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 8% 5% 5% 5% 4 5% 7% 31%	101283
	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	97693
Transparency	Day	51% 3 10% 22% 12% 1	104962
	Night	50% 3 10% 22% 13% 2	102154
Seeing	Day	21% 15% 28% 21% 11% 5%	15023
	Night	20% 13% 28% 26% 12% 2	24942

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	17% 20% 7% 13% 5% 5% 4 3 5% 6% 14%	2836
	11th to 20th	Day	14% 23% 8% 11% 6% 6% 7% 3 4 5% 14%	2840
	21st to end	Day	25% 20% 10% 13% 6% 5% 3 2 3 3 10%	3124
February	1st to 10th	Day	18% 17% 6% 10% 7% 5% 3 2 4 4 23%	1710
	11th to 20th	Day	14% 14% 5% 13% 7% 5% 5% 3 5% 5% 24%	1783
	21st to end	Day	17% 15% 5% 11% 5% 4 4 3 4 5% 27%	1570
March	1st to 10th	Day	21% 15% 7% 9% 5% 4 4 3 4 6% 23%	3298
	11th to 20th	Day	12% 13% 4 10% 5% 4 5% 3 4 6% 34%	3480
	21st to end	Day	21% 11% 4 9% 5% 4 4 3 4 6% 29%	3815
April	1st to 10th	Day	14% 15% 4 8% 5% 5% 4 3 5% 6% 30%	2111
	11th to 20th	Day	17% 12% 4 7% 4 4 4 3 5% 6% 35%	2428
	21st to end	Day	20% 10% 2 8% 5% 4 5% 3 4 7% 32%	2470
May	1st to 10th	Day	20% 11% 3 8% 6% 5% 4 4 5% 6% 29%	4082
	11th to 20th	Day	20% 9% 3 7% 4 4 4 3 5% 8% 33%	4081
	21st to end	Day	12% 6% 2 7% 5% 5% 6% 5% 7% 9% 35%	4476
June	1st to 10th	Day	12% 7% 3 7% 6% 5% 5% 4 7% 8% 36%	2470
	11th to 20th	Day	11% 8% 3 7% 6% 5% 6% 4 6% 9% 35%	2476
	21st to end	Day	11% 5% 2 6% 6% 6% 5% 5% 8% 9% 37%	2660
July	1st to 10th	Day	11% 7% 3 8% 5% 5% 5% 4 6% 10% 36%	4290
	11th to 20th	Day	9% 4 2 7% 5% 5% 5% 5% 8% 11% 40%	4120
	21st to end	Day	11% 6% 2 7% 6% 5% 6% 5% 7% 9% 37%	4466
August	1st to 10th	Day	11% 8% 3 7% 5% 6% 5% 4 6% 9% 36%	4104
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 6% 8% 9% 35%	4044
	21st to end	Day	7% 6% 2 7% 5% 5% 7% 4 7% 10% 40%	4510
September	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 5% 7% 45%	2100
	11th to 20th	Day	9% 7% 3 6% 5% 4 4 5% 6% 8% 43%	2090
	21st to end	Day	20% 8% 3 6% 4 4 4 2 4 6% 40%	2090
October	1st to 10th	Day	14% 7% 2 7% 4 3 4 4 5% 8% 42%	2009
	11th to 20th	Day	15% 10% 3 7% 4 4 4 4 5% 6% 38%	1900
	21st to end	Day	19% 13% 3 7% 5% 4 3 4 5% 7% 31%	2047
November	1st to 10th	Day	10% 9% 3 6% 4 4 4 3 6% 7% 43%	1717
	11th to 20th	Day	17% 14% 5% 8% 5% 4 4 3 4 6% 32%	1710
	21st to end	Day	18% 16% 5% 9% 4 4 4 3 4 5% 27%	1690
December	1st to 10th	Day	18% 18% 7% 12% 6% 4 4 3 4 5% 19%	1520
	11th to 20th	Day	17% 16% 7% 12% 5% 5% 4 3 4 6% 20%	2042
	21st to end	Day	23% 25% 9% 10% 5% 3 3 2 4 3 12%	3124
January	1st to 10th	Night	15% 21% 8% 15% 5% 4 4 3 4 4 17%	4109
	11th to 20th	Night	14% 18% 9% 17% 7% 5% 6% 4 3 4 13%	4120
	21st to end	Night	24% 20% 7% 14% 5% 3 3 2 3 3 14%	4532
February	1st to 10th	Night	19% 14% 5% 11% 6% 4 4 3 5% 5% 23%	2470
	11th to 20th	Night	15% 14% 5% 10% 7% 5% 5% 3 5% 6% 25%	2280
	21st to end	Night	19% 15% 5% 11% 6% 5% 4 4 4 5% 25%	1884
March	1st to 10th	Night	20% 15% 5% 7% 4 4 3 2 4 4 31%	3554
	11th to 20th	Night	12% 10% 3 7% 5% 4 4 4 5% 7% 39%	3480
	21st to end	Night	18% 10% 3 7% 5% 4 3 3 4 5% 37%	3817
April	1st to 10th	Night	15% 12% 3 7% 5% 4 4 4 5% 8% 33%	2085
	11th to 20th	Night	15% 8% 3 7% 5% 4 5% 3 5% 7% 36%	1699
	21st to end	Night	14% 10% 3 6% 5% 5% 5% 3 6% 8% 35%	1710
May	1st to 10th	Night	23% 12% 3 7% 5% 5% 4 3 5% 6% 27%	2813
	11th to 20th	Night	18% 9% 3 6% 3 4 3 3 6% 7% 39%	2812
	21st to end	Night	9% 5% 1 6% 4 4 5% 4 7% 10% 44%	3079
June	1st to 10th	Night	9% 7% 2 6% 6% 4 4 4 5% 8% 44%	1710
	11th to 20th	Night	8% 5% 2 6% 4 5% 4 5% 9% 9% 42%	1693
	21st to end	Night	10% 5% 2 7% 4 4 5% 5% 6% 10% 44%	1520
July	1st to 10th	Night	10% 6% 2 6% 4 4 4 4 6% 9% 46%	2654
	11th to 20th	Night	9% 4 1 5% 4 4 5% 5% 7% 9% 49%	2840
	21st to end	Night	7% 6% 2 7% 4 5% 5% 5% 6% 10% 43%	3087
August	1st to 10th	Night	11% 8% 3 7% 5% 5% 5% 5% 6% 9% 37%	2825
	11th to 20th	Night	10% 9% 3 7% 4 3 4 4 5% 7% 43%	2785
	21st to end	Night	6% 4 2 6% 4 4 6% 4 7% 9% 50%	3124
September	1st to 10th	Night	12% 5% 2 5% 3 4 4 3 5% 6% 51%	2065
	11th to 20th	Night	9% 4 2 5% 3 3 4 4 5% 7% 55%	2090
	21st to end	Night	16% 7% 2 6% 4 3 3 3 6% 7% 43%	2090
October	1st to 10th	Night	11% 7% 2 5% 4 4 4 4 5% 7% 48%	2171
	11th to 20th	Night	15% 9% 3 7% 5% 4 4 3 5% 7% 40%	2280
	21st to end	Night	21% 9% 2 6% 4 4 4 3 4 6% 35%	2550
November	1st to 10th	Night	13% 8% 2 6% 4 4 4 3 5% 7% 43%	2483
	11th to 20th	Night	15% 13% 3 8% 5% 4 4 3 5% 6% 33%	2470
	21st to end	Night	19% 13% 5% 9% 5% 4 4 4 6% 6% 27%	2482
December	1st to 10th	Night	19% 17% 6% 11% 5% 4 4 4 4 5% 21%	2660
	11th to 20th	Night	16% 15% 6% 11% 5% 4 4 3 5% 6% 24%	3138
	21st to end	Night	22% 20% 10% 10% 6% 4 4 3 4 4 14%	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	72% 2 8% 15% 3	2837
	11th to 20th	Day	75% 2 9% 11% 4	2840
	21st to end	Day	82% 2 5% 8% 3 1	3124
February	1st to 10th	Day	67% 2 9% 15% 7% 1	1710
	11th to 20th	Day	63% 4 7% 16% 9% 1	1792
	21st to end	Day	60% 1 11% 18% 7% 2	1570
March	1st to 10th	Day	66% 1 7% 21% 5%	3298
	11th to 20th	Day	53% 2 8% 27% 9% 1	3480
	21st to end	Day	57% 2 10% 23% 8%	3815
April	1st to 10th	Day	55% 3 11% 18% 12% 1	2111
	11th to 20th	Day	51% 3 11% 18% 14% 2	2428
	21st to end	Day	53% 3 10% 21% 12% 2	2470
May	1st to 10th	Day	57% 2 10% 22% 8% 1	4120
	11th to 20th	Day	50% 3 12% 25% 9% 1	4085
	21st to end	Day	44% 5% 12% 22% 13% 4	4489
June	1st to 10th	Day	44% 4 11% 26% 14% 1	2470
	11th to 20th	Day	45% 4 13% 23% 14% 1	2476
	21st to end	Day	42% 4 14% 22% 15% 2	2660
July	1st to 10th	Day	44% 5% 10% 23% 16% 2	4225
	11th to 20th	Day	35% 5% 13% 26% 19% 1	4051
	21st to end	Day	42% 6% 13% 18% 19% 3	4324
August	1st to 10th	Day	44% 5% 13% 24% 14%	4091
	11th to 20th	Day	40% 6% 11% 29% 12% 1	4083
	21st to end	Day	38% 5% 13% 29% 12% 3	4510
September	1st to 10th	Day	39% 5% 11% 23% 19% 4	2100
	11th to 20th	Day	38% 3 11% 26% 18% 3	2090
	21st to end	Day	47% 3 9% 22% 19% 1	2090
October	1st to 10th	Day	29% 3 12% 33% 22% 1	3334
	11th to 20th	Day	41% 4 8% 25% 19% 3	3140
	21st to end	Day	41% 2 12% 25% 18% 1	3349
November	1st to 10th	Day	41% 2 12% 26% 16% 2	1717
	11th to 20th	Day	56% 3 8% 21% 10% 2	1710
	21st to end	Day	60% 3 9% 18% 8% 1	1690
December	1st to 10th	Day	70% 2 9% 15% 4	1520
	11th to 20th	Day	67% 3 7% 18% 5%	2039
	21st to end	Day	79% 1 9% 7% 3	3124
January	1st to 10th	Night	72% 2 7% 15% 5%	4109
	11th to 20th	Night	79% 1 7% 10% 3	4120
	21st to end	Night	77% 2 6% 12% 3	4532
February	1st to 10th	Night	65% 3 9% 16% 7% 1	2470
	11th to 20th	Night	61% 3 8% 18% 8% 1	2282
	21st to end	Night	64% 3 8% 15% 9% 2	1884
March	1st to 10th	Night	59% 2 8% 22% 9% 1	3554
	11th to 20th	Night	46% 3 10% 29% 10% 2	3480
	21st to end	Night	50% 2 8% 28% 11% 1	3817
April	1st to 10th	Night	50% 4 11% 19% 15% 2	2085
	11th to 20th	Night	48% 3 11% 18% 17% 3	1699
	21st to end	Night	47% 4 10% 22% 15% 2	1710
May	1st to 10th	Night	59% 2 8% 21% 9% 1	2840
	11th to 20th	Night	47% 3 10% 26% 12% 2	2813
	21st to end	Night	36% 4 13% 29% 16% 3	3087
June	1st to 10th	Night	38% 5% 12% 25% 18% 2	1710
	11th to 20th	Night	35% 5% 16% 25% 17% 2	1693
	21st to end	Night	36% 5% 14% 26% 16% 3	1520
July	1st to 10th	Night	36% 4 11% 25% 17% 6%	2610
	11th to 20th	Night	31% 5% 14% 32% 17% 1	2786
	21st to end	Night	36% 5% 14% 22% 20% 3	2988
August	1st to 10th	Night	43% 6% 13% 23% 14% 1	2814
	11th to 20th	Night	40% 4 10% 28% 18%	2812
	21st to end	Night	31% 5% 15% 32% 15% 2	3124
September	1st to 10th	Night	34% 4 11% 27% 18% 6%	2065
	11th to 20th	Night	29% 4 10% 29% 26% 3	2090
	21st to end	Night	41% 3 9% 23% 21% 2	2090
October	1st to 10th	Night	29% 3 7% 30% 29% 2	3626
	11th to 20th	Night	36% 3 11% 26% 20% 4	3779
	21st to end	Night	38% 3 9% 30% 18% 3	4198
November	1st to 10th	Night	42% 3 11% 24% 17% 3	2483
	11th to 20th	Night	53% 3 8% 22% 13% 2	2470
	21st to end	Night	58% 2 12% 20% 7% 1	2482
December	1st to 10th	Night	67% 3 9% 15% 6% 1	2660
	11th to 20th	Night	62% 3 10% 20% 5%	3140
	21st to end	Night	75% 2 9% 11% 3	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	30% 27% 29% 9% 4	270
	11th to 20th	Day	30% 27% 33% 7% 2	270
	21st to end	Day	30% 29% 29% 9% 1	297
February	1st to 10th	Day	37% 23% 27% 12% 2	270
	11th to 20th	Day	31% 30% 30% 8%	270
	21st to end	Day	31% 36% 27% 6%	225
March	1st to 10th	Day	30% 24% 30% 14% 2	370
	11th to 20th	Day	29% 21% 32% 13% 5% 1	460
	21st to end	Day	33% 18% 28% 16% 4	506
April	1st to 10th	Day	25% 21% 31% 15% 7% 2	460
	11th to 20th	Day	26% 23% 26% 15% 7% 3	452
	21st to end	Day	28% 17% 33% 15% 5% 2	460
May	1st to 10th	Day	26% 17% 31% 16% 6% 3	463
	11th to 20th	Day	24% 11% 31% 18% 11% 5%	487
	21st to end	Day	13% 11% 26% 27% 16% 7%	529
June	1st to 10th	Day	16% 8% 32% 28% 11% 5%	490
	11th to 20th	Day	17% 9% 27% 28% 16% 3	496
	21st to end	Day	14% 11% 33% 25% 13% 4	680
July	1st to 10th	Day	15% 5% 21% 27% 20% 12%	590
	11th to 20th	Day	12% 5% 27% 27% 19% 10%	484
	21st to end	Day	10% 5% 23% 32% 21% 8%	532
August	1st to 10th	Day	12% 6% 20% 30% 20% 12%	486
	11th to 20th	Day	14% 5% 27% 27% 18% 9%	479
	21st to end	Day	9% 6% 22% 31% 22% 11%	539
September	1st to 10th	Day	13% 6% 24% 24% 22% 10%	490
	11th to 20th	Day	10% 4 17% 31% 26% 12%	490
	21st to end	Day	26% 9% 21% 24% 14% 6%	490
October	1st to 10th	Day	13% 12% 29% 24% 17% 5%	490
	11th to 20th	Day	21% 17% 28% 21% 10% 3	490
	21st to end	Day	27% 18% 31% 19% 4 1	496
November	1st to 10th	Day	16% 24% 34% 15% 9% 1	285
	11th to 20th	Day	29% 20% 30% 16% 6% 1	270
	21st to end	Day	29% 24% 35% 11% 1	260
December	1st to 10th	Day	24% 32% 29% 9% 4 2	180
	11th to 20th	Day	25% 28% 35% 9% 4	220
	21st to end	Day	35% 22% 31% 11% 1	297
January	1st to 10th	Night	27% 23% 32% 15% 2	760
	11th to 20th	Night	28% 24% 31% 14% 3	760
	21st to end	Night	25% 22% 31% 18% 3	836
February	1st to 10th	Night	28% 19% 35% 16% 2	760
	11th to 20th	Night	25% 23% 32% 18% 2	743
	21st to end	Night	29% 20% 34% 15% 2	628
March	1st to 10th	Night	24% 19% 32% 22% 4	760
	11th to 20th	Night	23% 19% 33% 19% 6% 1	760
	21st to end	Night	26% 13% 33% 21% 6%	836
April	1st to 10th	Night	23% 16% 34% 22% 5%	755
	11th to 20th	Night	21% 13% 35% 21% 9% 2	563
	21st to end	Night	19% 11% 39% 24% 6% 1	570
May	1st to 10th	Night	22% 9% 32% 28% 9% 1	570
	11th to 20th	Night	22% 7% 29% 28% 13% 2	561
	21st to end	Night	11% 4 25% 34% 23% 3	617
June	1st to 10th	Night	12% 4 28% 39% 17% 1	570
	11th to 20th	Night	12% 4 25% 41% 17% 2	570
	21st to end	Night	11% 5% 28% 36% 19% 2	570
July	1st to 10th	Night	12% 2 19% 40% 23% 5%	555
	11th to 20th	Night	7% 3 22% 38% 26% 4	552
	21st to end	Night	9% 4 15% 42% 27% 2	624
August	1st to 10th	Night	10% 4 13% 44% 25% 5%	567
	11th to 20th	Night	11% 2 17% 39% 27% 4	564
	21st to end	Night	8% 3 17% 36% 30% 5%	627
September	1st to 10th	Night	14% 5% 20% 31% 26% 4	748
	11th to 20th	Night	11% 3 15% 37% 30% 5%	760
	21st to end	Night	20% 8% 21% 29% 18% 4	760
October	1st to 10th	Night	15% 7% 26% 31% 19% 3	760
	11th to 20th	Night	21% 14% 29% 24% 11% 2	760
	21st to end	Night	25% 14% 30% 23% 7%	836
November	1st to 10th	Night	18% 14% 30% 24% 12% 1	764
	11th to 20th	Night	25% 17% 30% 21% 7% 1	760
	21st to end	Night	26% 18% 30% 20% 5% 1	760
December	1st to 10th	Night	31% 17% 32% 17% 3	760
	11th to 20th	Night	26% 19% 33% 19% 3	760
	21st to end	Night	29% 18% 33% 17% 3	836

Page generated at 2024-11-03 13:19:02. Version ac07

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