Schoonover Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Schoonover Observatory clear sky chart from 2005-11-06 to 2025-02-21.

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% 10% 4 8% 5% 4 4 4 5% 7% 33%	108841
	Night	15% 11% 4 9% 5% 4 4 3 5% 6% 33%	109820
Transparency	Day	49% 5% 11% 21% 12% 1	112484
	Night	50% 4 11% 21% 13% 2	114316
Seeing	Day	18% 10% 27% 23% 15% 6%	15843
	Night	19% 9% 28% 29% 13% 1	25760

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% 18% 9% 18% 6% 4 3 3 3 4 18%	3617
	11th to 20th	Day	13% 17% 7% 14% 8% 6% 7% 5% 3 3 17%	3688
	21st to end	Day	21% 17% 8% 14% 6% 4 3 3 3 4 16%	4466
February	1st to 10th	Day	18% 16% 6% 13% 7% 5% 3 4 4 5% 20%	1835
	11th to 20th	Day	15% 14% 6% 15% 7% 4 4 3 4 5% 23%	1948
	21st to end	Day	17% 15% 6% 10% 4 4 3 3 5% 7% 26%	1570
March	1st to 10th	Day	21% 20% 5% 9% 5% 4 3 3 3 5% 22%	3166
	11th to 20th	Day	14% 11% 3 7% 5% 4 4 4 6% 6% 36%	3480
	21st to end	Day	20% 13% 5% 10% 4 5% 4 3 4 6% 27%	3815
April	1st to 10th	Day	15% 14% 4 8% 5% 4 4 4 5% 6% 31%	2233
	11th to 20th	Day	18% 10% 2 7% 4 4 4 3 5% 7% 35%	2348
	21st to end	Day	19% 9% 2 8% 5% 5% 5% 3 5% 7% 33%	2470
May	1st to 10th	Day	20% 9% 3 8% 5% 5% 5% 4 5% 7% 29%	4082
	11th to 20th	Day	18% 7% 2 5% 5% 4 4 4 6% 7% 36%	4081
	21st to end	Day	10% 6% 2 7% 5% 5% 5% 5% 6% 9% 40%	4476
June	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 5% 6% 8% 39%	2572
	11th to 20th	Day	11% 6% 2 5% 5% 5% 6% 4 7% 10% 41%	2660
	21st to end	Day	11% 5% 2 5% 6% 6% 6% 5% 8% 9% 37%	2660
July	1st to 10th	Day	12% 6% 3 7% 5% 5% 5% 4 7% 10% 36%	4440
	11th to 20th	Day	8% 4 2 5% 4 4 5% 4 7% 10% 47%	4419
	21st to end	Day	8% 6% 2 6% 5% 6% 5% 5% 7% 9% 40%	4466
August	1st to 10th	Day	9% 6% 2 5% 4 4 4 4 7% 10% 44%	4104
	11th to 20th	Day	8% 5% 2 5% 4 5% 6% 5% 8% 10% 41%	4044
	21st to end	Day	8% 4 2 5% 5% 5% 5% 4 6% 10% 46%	4322
September	1st to 10th	Day	13% 6% 2 5% 4 4 4 4 5% 7% 47%	2161
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 6% 9% 45%	2090
	21st to end	Day	17% 7% 2 5% 4 3 3 3 5% 6% 43%	2090
October	1st to 10th	Day	12% 7% 3 6% 4 4 5% 3 5% 7% 44%	2085
	11th to 20th	Day	16% 7% 2 7% 4 5% 5% 4 5% 6% 40%	1900
	21st to end	Day	19% 9% 3 7% 5% 4 5% 4 6% 7% 31%	1933
November	1st to 10th	Day	10% 10% 3 7% 3 3 3 4 5% 6% 47%	1762
	11th to 20th	Day	17% 14% 4 7% 5% 5% 4 3 5% 6% 32%	1800
	21st to end	Day	19% 17% 5% 8% 4 3 3 3 5% 5% 28%	1800
December	1st to 10th	Day	15% 15% 6% 11% 5% 4 4 4 4 5% 27%	2930
	11th to 20th	Day	16% 19% 8% 11% 5% 4 5% 3 4 5% 20%	3346
	21st to end	Day	23% 22% 8% 11% 6% 4 4 2 3 4 13%	3982
January	1st to 10th	Night	15% 18% 8% 17% 6% 4 4 2 3 4 19%	6348
	11th to 20th	Night	11% 19% 9% 16% 8% 6% 5% 4 3 3 14%	6272
	21st to end	Night	22% 15% 6% 10% 5% 4 4 3 4 4 22%	6490
February	1st to 10th	Night	19% 15% 5% 11% 6% 5% 4 3 3 5% 24%	2561
	11th to 20th	Night	14% 14% 5% 11% 5% 4 5% 3 5% 6% 27%	2338
	21st to end	Night	21% 14% 4 10% 5% 4 4 3 4 5% 26%	1885
March	1st to 10th	Night	19% 15% 4 6% 4 4 3 2 3 5% 34%	3685
	11th to 20th	Night	11% 9% 3 5% 5% 4 3 4 6% 7% 43%	3480
	21st to end	Night	18% 10% 4 8% 5% 4 4 3 4 5% 36%	3817
April	1st to 10th	Night	15% 11% 3 7% 4 4 4 4 6% 6% 36%	1962
	11th to 20th	Night	18% 8% 3 6% 4 5% 4 4 6% 7% 35%	1779
	21st to end	Night	17% 9% 3 8% 5% 4 4 3 5% 7% 36%	1710
May	1st to 10th	Night	20% 10% 3 8% 5% 5% 4 4 5% 6% 30%	2813
	11th to 20th	Night	20% 6% 2 5% 4 4 4 3 6% 8% 38%	2812
	21st to end	Night	10% 5% 2 5% 4 4 5% 4 6% 10% 44%	3079
June	1st to 10th	Night	10% 5% 2 6% 4 4 5% 4 5% 7% 47%	1603
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 3 7% 9% 46%	1520
	21st to end	Night	9% 5% 3 5% 5% 5% 4 4 7% 9% 44%	1520
July	1st to 10th	Night	10% 5% 2 6% 4 4 5% 3 6% 9% 46%	2530
	11th to 20th	Night	7% 4 1 5% 4 3 4 5% 7% 9% 51%	2547
	21st to end	Night	9% 6% 2 7% 5% 4 5% 4 6% 8% 44%	3087
August	1st to 10th	Night	12% 7% 2 6% 4 5% 4 4 6% 9% 40%	2825
	11th to 20th	Night	9% 8% 2 6% 4 4 4 3 6% 8% 46%	2785
	21st to end	Night	5% 4 2 7% 5% 4 5% 4 6% 8% 50%	3330
September	1st to 10th	Night	11% 6% 2 5% 3 4 4 3 4 7% 51%	2000
	11th to 20th	Night	10% 5% 1 4 3 3 4 3 5% 7% 55%	2090
	21st to end	Night	13% 6% 2 7% 4 4 4 4 4 5% 46%	2090
October	1st to 10th	Night	11% 4 2 6% 4 3 4 3 5% 7% 51%	2093
	11th to 20th	Night	18% 8% 3 7% 4 4 4 3 5% 6% 40%	2280
	21st to end	Night	20% 8% 2 6% 5% 3 4 4 5% 7% 37%	2662
November	1st to 10th	Night	13% 9% 3 6% 4 4 4 3 5% 6% 44%	2536
	11th to 20th	Night	15% 13% 4 8% 4 3 3 3 5% 6% 35%	2600
	21st to end	Night	18% 15% 5% 8% 5% 4 4 3 4 6% 27%	2600
December	1st to 10th	Night	13% 13% 6% 10% 6% 5% 5% 4 6% 7% 26%	4250
	11th to 20th	Night	18% 18% 7% 12% 5% 4 4 3 4 4 21%	4845
	21st to end	Night	24% 21% 6% 9% 5% 4 4 3 4 5% 14%	6996

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% 3 7% 13% 5%	3618
	11th to 20th	Day	73% 3 8% 5% 9% 1	3688
	21st to end	Day	75% 2 7% 9% 7%	4466
February	1st to 10th	Day	66% 4 10% 13% 6% 1	1835
	11th to 20th	Day	65% 5% 7% 16% 7%	1958
	21st to end	Day	58% 5% 12% 15% 7% 2	1570
March	1st to 10th	Day	66% 5% 8% 16% 5%	3166
	11th to 20th	Day	46% 6% 11% 26% 10% 1	3480
	21st to end	Day	58% 6% 12% 19% 4	3815
April	1st to 10th	Day	53% 6% 12% 18% 12%	2233
	11th to 20th	Day	48% 5% 11% 21% 12% 2	2348
	21st to end	Day	50% 6% 11% 20% 10% 2	2470
May	1st to 10th	Day	52% 8% 11% 20% 9% 1	4120
	11th to 20th	Day	45% 7% 14% 25% 9% 1	4085
	21st to end	Day	37% 9% 13% 21% 17% 3	4489
June	1st to 10th	Day	42% 6% 11% 24% 14% 2	2572
	11th to 20th	Day	37% 6% 14% 24% 16% 2	2660
	21st to end	Day	39% 9% 15% 19% 14% 4	2660
July	1st to 10th	Day	43% 5% 11% 22% 16% 2	4371
	11th to 20th	Day	32% 5% 14% 29% 19% 1	4344
	21st to end	Day	38% 6% 13% 20% 19% 3	4324
August	1st to 10th	Day	35% 5% 16% 27% 16% 1	4091
	11th to 20th	Day	35% 5% 13% 31% 14% 1	4083
	21st to end	Day	33% 5% 13% 34% 12% 3	4321
September	1st to 10th	Day	36% 6% 12% 23% 19% 4	2161
	11th to 20th	Day	34% 7% 9% 25% 22% 3	2090
	21st to end	Day	40% 6% 10% 23% 20% 1	2090
October	1st to 10th	Day	28% 3 11% 35% 21% 1	3462
	11th to 20th	Day	38% 3 11% 25% 22% 1	3140
	21st to end	Day	43% 4 9% 24% 19% 1	3157
November	1st to 10th	Day	38% 5% 11% 26% 19% 1	1762
	11th to 20th	Day	54% 3 9% 20% 11% 2	1800
	21st to end	Day	58% 4 10% 18% 8% 1	1800
December	1st to 10th	Day	62% 3 13% 20% 3	2930
	11th to 20th	Day	66% 3 12% 14% 4	3343
	21st to end	Day	77% 3 6% 10% 4	3982
January	1st to 10th	Night	70% 4 6% 15% 5%	6348
	11th to 20th	Night	76% 3 7% 8% 6%	6272
	21st to end	Night	66% 3 12% 12% 7% 1	6490
February	1st to 10th	Night	64% 4 10% 14% 7% 1	2561
	11th to 20th	Night	58% 5% 11% 16% 9% 1	2339
	21st to end	Night	61% 4 9% 15% 10% 1	1885
March	1st to 10th	Night	54% 4 9% 24% 9% 1	3685
	11th to 20th	Night	38% 7% 13% 27% 14% 1	3480
	21st to end	Night	50% 5% 10% 25% 8% 1	3817
April	1st to 10th	Night	48% 6% 11% 21% 13% 1	1962
	11th to 20th	Night	47% 6% 11% 17% 17% 2	1779
	21st to end	Night	47% 6% 11% 19% 14% 3	1710
May	1st to 10th	Night	53% 8% 9% 19% 9% 2	2840
	11th to 20th	Night	43% 7% 13% 25% 11% 1	2813
	21st to end	Night	32% 8% 15% 26% 17% 2	3087
June	1st to 10th	Night	35% 7% 12% 24% 19% 3	1603
	11th to 20th	Night	33% 8% 14% 25% 17% 3	1520
	21st to end	Night	35% 7% 15% 23% 17% 3	1520
July	1st to 10th	Night	36% 5% 10% 28% 16% 5%	2490
	11th to 20th	Night	29% 5% 14% 30% 21% 1	2499
	21st to end	Night	38% 5% 15% 19% 18% 5%	2988
August	1st to 10th	Night	41% 5% 14% 25% 14% 1	2814
	11th to 20th	Night	36% 4 11% 31% 17% 1	2812
	21st to end	Night	32% 5% 14% 29% 17% 3	3330
September	1st to 10th	Night	33% 5% 13% 25% 18% 6%	2000
	11th to 20th	Night	29% 5% 10% 27% 26% 3	2090
	21st to end	Night	39% 5% 10% 23% 20% 3	2090
October	1st to 10th	Night	24% 3 8% 30% 33% 1	3496
	11th to 20th	Night	35% 3 10% 27% 23% 1	3779
	21st to end	Night	35% 3 7% 31% 20% 3	4388
November	1st to 10th	Night	41% 4 10% 24% 18% 2	2536
	11th to 20th	Night	50% 3 10% 20% 14% 3	2600
	21st to end	Night	58% 5% 10% 19% 8%	2600
December	1st to 10th	Night	58% 3 12% 21% 6%	4250
	11th to 20th	Night	67% 3 12% 11% 6% 1	4847
	21st to end	Night	74% 3 9% 11% 3	6996

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	23% 19% 35% 17% 4 1	300
	11th to 20th	Day	26% 18% 39% 12% 4 1	300
	21st to end	Day	30% 16% 34% 15% 5% 1	330
February	1st to 10th	Day	29% 17% 37% 14% 3	300
	11th to 20th	Day	24% 21% 35% 16% 5%	300
	21st to end	Day	25% 20% 43% 10% 2	225
March	1st to 10th	Day	23% 18% 40% 14% 4	290
	11th to 20th	Day	27% 13% 31% 21% 7% 2	460
	21st to end	Day	30% 14% 33% 17% 6%	506
April	1st to 10th	Day	22% 15% 30% 24% 7% 3	460
	11th to 20th	Day	21% 19% 28% 18% 10% 4	452
	21st to end	Day	24% 13% 30% 24% 7% 2	460
May	1st to 10th	Day	24% 13% 28% 24% 8% 3	463
	11th to 20th	Day	23% 8% 25% 24% 13% 7%	487
	21st to end	Day	10% 7% 26% 27% 21% 9%	529
June	1st to 10th	Day	11% 9% 25% 30% 18% 6%	592
	11th to 20th	Day	13% 5% 26% 28% 22% 6%	680
	21st to end	Day	12% 8% 26% 30% 17% 6%	680
July	1st to 10th	Day	13% 2 19% 29% 21% 16%	671
	11th to 20th	Day	8% 3 24% 30% 22% 13%	660
	21st to end	Day	9% 4 16% 29% 27% 15%	532
August	1st to 10th	Day	10% 2 14% 29% 27% 17%	486
	11th to 20th	Day	11% 4 19% 30% 24% 11%	479
	21st to end	Day	10% 3 15% 26% 31% 15%	539
September	1st to 10th	Day	16% 2 15% 26% 28% 13%	490
	11th to 20th	Day	9% 2 16% 23% 34% 17%	490
	21st to end	Day	20% 10% 18% 24% 19% 9%	490
October	1st to 10th	Day	10% 7% 25% 30% 19% 9%	490
	11th to 20th	Day	16% 14% 31% 24% 12% 2	490
	21st to end	Day	25% 11% 37% 21% 5% 1	382
November	1st to 10th	Day	16% 12% 37% 21% 10% 4	300
	11th to 20th	Day	26% 17% 29% 17% 11%	300
	21st to end	Day	28% 17% 35% 18% 2	300
December	1st to 10th	Day	22% 20% 36% 16% 6% 1	300
	11th to 20th	Day	24% 15% 39% 17% 5%	300
	21st to end	Day	29% 18% 33% 17% 3	330
January	1st to 10th	Night	23% 15% 36% 20% 5%	1000
	11th to 20th	Night	26% 15% 37% 17% 4 1	964
	21st to end	Night	25% 16% 35% 21% 4	880
February	1st to 10th	Night	26% 12% 35% 24% 2	800
	11th to 20th	Night	23% 14% 37% 24% 2	783
	21st to end	Night	27% 13% 37% 19% 3	629
March	1st to 10th	Night	21% 13% 33% 27% 6% 1	760
	11th to 20th	Night	19% 13% 35% 27% 6%	760
	21st to end	Night	24% 11% 29% 26% 8% 1	836
April	1st to 10th	Night	19% 13% 36% 27% 5%	632
	11th to 20th	Night	20% 12% 33% 25% 8% 1	563
	21st to end	Night	20% 8% 37% 24% 10% 1	570
May	1st to 10th	Night	24% 7% 30% 31% 8% 1	570
	11th to 20th	Night	23% 5% 27% 30% 14% 1	561
	21st to end	Night	11% 3 26% 35% 22% 3	617
June	1st to 10th	Night	11% 2 24% 45% 17%	570
	11th to 20th	Night	11% 3 22% 44% 18% 1	570
	21st to end	Night	11% 2 24% 38% 24% 1	570
July	1st to 10th	Night	10% 2 15% 41% 28% 4	555
	11th to 20th	Night	7% 3 17% 40% 29% 4	552
	21st to end	Night	9% 2 12% 44% 30% 2	624
August	1st to 10th	Night	10% 1 13% 43% 29% 4	567
	11th to 20th	Night	11% 3 12% 42% 29% 4	564
	21st to end	Night	7% 2 13% 38% 35% 4	627
September	1st to 10th	Night	12% 3 16% 36% 28% 4	670
	11th to 20th	Night	11% 2 14% 37% 31% 5%	760
	21st to end	Night	15% 5% 22% 34% 22% 2	760
October	1st to 10th	Night	14% 5% 24% 35% 19% 4	760
	11th to 20th	Night	21% 11% 29% 27% 11% 1	760
	21st to end	Night	25% 11% 30% 27% 7%	836
November	1st to 10th	Night	18% 9% 34% 26% 13% 1	780
	11th to 20th	Night	23% 14% 31% 24% 7% 1	800
	21st to end	Night	25% 13% 33% 24% 5%	800
December	1st to 10th	Night	23% 14% 36% 21% 5%	800
	11th to 20th	Night	27% 12% 35% 22% 4	810
	21st to end	Night	31% 15% 32% 19% 3	1100

Page generated at 2025-02-18 03:26:30. Version ac07

Copyright © 2025 Attilla Danko.