Walter E. Schuele Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walter E. Schuele Planetarium 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	15% 11% 4 9% 5% 4 4 4 5% 7% 31%	109071
	Night	16% 13% 5% 10% 5% 4 4 3 5% 6% 29%	109474
Transparency	Day	50% 7% 12% 19% 10% 1	112746
	Night	54% 7% 11% 17% 10% 1	113940
Seeing	Day	18% 11% 27% 26% 14% 4	15260
	Night	22% 11% 26% 27% 13% 2	24872

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% 21% 7% 23% 6% 4 3 2 3 3 13%	4056
	11th to 20th	Day	14% 23% 7% 17% 8% 6% 5% 3 3 3 11%	4060
	21st to end	Day	22% 20% 9% 14% 7% 5% 3 2 3 3 12%	4466
February	1st to 10th	Day	17% 19% 6% 12% 7% 5% 4 3 5% 4 20%	1800
	11th to 20th	Day	14% 15% 7% 16% 8% 4 5% 3 3 5% 20%	1828
	21st to end	Day	19% 13% 5% 11% 6% 5% 5% 4 6% 6% 22%	1570
March	1st to 10th	Day	21% 14% 6% 9% 4 4 3 2 4 6% 27%	3329
	11th to 20th	Day	13% 13% 5% 11% 5% 5% 4 3 4 5% 33%	3480
	21st to end	Day	19% 13% 5% 9% 5% 3 4 3 4 5% 29%	3815
April	1st to 10th	Day	14% 14% 3 7% 5% 4 4 4 6% 7% 32%	2113
	11th to 20th	Day	18% 11% 3 6% 4 4 4 4 4 6% 35%	2442
	21st to end	Day	20% 10% 3 7% 4 4 4 3 4 6% 34%	2470
May	1st to 10th	Day	18% 10% 3 8% 5% 5% 5% 3 5% 6% 32%	4082
	11th to 20th	Day	17% 9% 3 6% 4 4 4 4 6% 7% 36%	4081
	21st to end	Day	10% 6% 3 6% 4 5% 5% 4 7% 9% 41%	4476
June	1st to 10th	Day	12% 7% 2 6% 5% 5% 5% 4 6% 8% 39%	2654
	11th to 20th	Day	11% 5% 2 6% 5% 5% 4 4 7% 8% 41%	2719
	21st to end	Day	10% 6% 2 6% 4 4 5% 5% 7% 10% 40%	2801
July	1st to 10th	Day	9% 6% 2 7% 5% 4 4 4 6% 10% 41%	4358
	11th to 20th	Day	9% 5% 2 5% 4 4 5% 4 6% 11% 46%	4120
	21st to end	Day	10% 5% 3 6% 5% 5% 6% 4 6% 9% 42%	4466
August	1st to 10th	Day	12% 7% 3 7% 4 5% 4 4 6% 9% 40%	4104
	11th to 20th	Day	11% 6% 3 7% 5% 4 5% 5% 7% 9% 38%	4044
	21st to end	Day	9% 5% 2 6% 4 5% 5% 5% 7% 9% 41%	4485
September	1st to 10th	Day	14% 5% 2 5% 5% 4 5% 5% 5% 8% 42%	2154
	11th to 20th	Day	10% 7% 2 6% 5% 4 4 4 6% 8% 45%	2090
	21st to end	Day	18% 9% 3 6% 4 4 3 4 5% 6% 38%	2090
October	1st to 10th	Day	14% 6% 3 8% 4 4 4 3 7% 8% 39%	1980
	11th to 20th	Day	20% 9% 3 7% 4 5% 4 3 5% 6% 34%	1900
	21st to end	Day	22% 11% 3 8% 5% 5% 4 3 6% 6% 27%	2054
November	1st to 10th	Day	14% 12% 3 8% 4 5% 3 3 6% 7% 34%	1762
	11th to 20th	Day	18% 18% 4 9% 5% 4 3 3 5% 6% 26%	1800
	21st to end	Day	19% 19% 6% 10% 6% 5% 5% 3 6% 6% 16%	1600
December	1st to 10th	Day	17% 18% 7% 13% 7% 5% 5% 3 5% 5% 16%	2600
	11th to 20th	Day	21% 21% 6% 12% 6% 4 4 4 5% 6% 12%	2990
	21st to end	Day	23% 22% 7% 15% 6% 5% 3 3 4 4 9%	4232
January	1st to 10th	Night	15% 19% 9% 23% 6% 3 3 2 3 4 12%	5889
	11th to 20th	Night	11% 21% 10% 19% 8% 5% 5% 3 4 4 9%	5900
	21st to end	Night	21% 20% 7% 14% 5% 3 3 3 3 3 17%	6490
February	1st to 10th	Night	20% 16% 5% 13% 7% 4 4 4 4 4 20%	2600
	11th to 20th	Night	17% 17% 5% 12% 6% 6% 5% 3 4 5% 21%	2453
	21st to end	Night	20% 15% 5% 12% 6% 5% 4 3 5% 5% 22%	1885
March	1st to 10th	Night	22% 15% 3 6% 4 3 3 2 4 5% 33%	3523
	11th to 20th	Night	15% 12% 5% 6% 4 4 4 4 5% 6% 35%	3480
	21st to end	Night	17% 12% 4 7% 5% 4 4 3 5% 5% 33%	3817
April	1st to 10th	Night	16% 14% 3 7% 5% 3 4 5% 6% 6% 31%	2067
	11th to 20th	Night	16% 10% 2 7% 5% 4 4 4 6% 6% 33%	1701
	21st to end	Night	16% 9% 3 6% 5% 4 5% 4 6% 7% 36%	1710
May	1st to 10th	Night	21% 10% 4 7% 4 4 4 4 5% 8% 28%	2813
	11th to 20th	Night	15% 8% 3 7% 5% 4 5% 4 5% 8% 36%	2812
	21st to end	Night	11% 5% 2 5% 4 5% 5% 4 6% 9% 46%	3079
June	1st to 10th	Night	11% 7% 3 6% 4 5% 5% 3 6% 6% 43%	1520
	11th to 20th	Night	10% 4 2 7% 5% 5% 5% 5% 7% 9% 40%	1453
	21st to end	Night	10% 5% 3 6% 5% 5% 4 4 7% 10% 42%	1373
July	1st to 10th	Night	10% 6% 2 6% 4 4 4 4 6% 9% 46%	2590
	11th to 20th	Night	9% 4 2 5% 4 4 4 4 6% 9% 48%	2840
	21st to end	Night	7% 6% 3 6% 4 5% 5% 5% 7% 10% 43%	3087
August	1st to 10th	Night	11% 6% 3 7% 4 5% 5% 4 5% 10% 41%	2825
	11th to 20th	Night	13% 8% 3 7% 4 4 4 3 5% 6% 42%	2785
	21st to end	Night	8% 5% 3 7% 5% 5% 6% 4 6% 8% 44%	3138
September	1st to 10th	Night	11% 6% 3 6% 4 4 6% 4 5% 6% 44%	2023
	11th to 20th	Night	10% 5% 2 6% 4 4 4 3 6% 7% 49%	2090
	21st to end	Night	17% 7% 3 6% 6% 4 5% 3 5% 6% 38%	2090
October	1st to 10th	Night	14% 6% 3 6% 4 5% 5% 4 5% 7% 42%	2199
	11th to 20th	Night	21% 10% 3 7% 4 3 4 3 5% 6% 33%	2280
	21st to end	Night	26% 10% 3 7% 4 3 4 4 5% 6% 27%	2541
November	1st to 10th	Night	16% 12% 3 7% 5% 4 4 3 6% 5% 35%	2536
	11th to 20th	Night	18% 17% 4 10% 5% 4 4 3 4 5% 25%	2600
	21st to end	Night	23% 17% 5% 8% 5% 5% 4 3 4 6% 20%	2795
December	1st to 10th	Night	16% 18% 7% 12% 6% 5% 5% 4 4 6% 17%	4580
	11th to 20th	Night	19% 22% 7% 11% 5% 3 4 3 4 5% 17%	5205
	21st to end	Night	23% 21% 6% 12% 6% 5% 4 3 4 5% 12%	6705

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	77% 5% 8% 6% 3 1	4057
	11th to 20th	Day	78% 6% 10% 4 2	4060
	21st to end	Day	77% 5% 6% 9% 3	4466
February	1st to 10th	Day	65% 6% 13% 11% 5%	1800
	11th to 20th	Day	64% 8% 10% 14% 5% 1	1837
	21st to end	Day	59% 8% 14% 12% 6% 1	1570
March	1st to 10th	Day	56% 8% 10% 21% 5%	3329
	11th to 20th	Day	48% 10% 16% 19% 6% 1	3480
	21st to end	Day	52% 10% 12% 15% 9% 1	3815
April	1st to 10th	Day	48% 8% 13% 17% 14% 1	2113
	11th to 20th	Day	48% 7% 12% 17% 14% 2	2442
	21st to end	Day	49% 7% 12% 20% 10% 2	2470
May	1st to 10th	Day	48% 9% 11% 21% 9% 1	4120
	11th to 20th	Day	43% 11% 15% 21% 9% 2	4085
	21st to end	Day	34% 11% 14% 19% 16% 6%	4489
June	1st to 10th	Day	40% 8% 12% 25% 14% 1	2654
	11th to 20th	Day	36% 10% 15% 21% 15% 2	2719
	21st to end	Day	35% 8% 14% 23% 16% 3	2801
July	1st to 10th	Day	37% 6% 13% 25% 17% 3	4291
	11th to 20th	Day	30% 6% 14% 29% 19% 1	4051
	21st to end	Day	36% 6% 18% 20% 19% 2	4324
August	1st to 10th	Day	40% 7% 15% 26% 13%	4091
	11th to 20th	Day	38% 7% 13% 32% 8% 1	4083
	21st to end	Day	35% 7% 15% 29% 12% 2	4485
September	1st to 10th	Day	38% 8% 16% 20% 15% 3	2154
	11th to 20th	Day	35% 8% 14% 25% 17% 1	2090
	21st to end	Day	45% 7% 11% 19% 17%	2090
October	1st to 10th	Day	34% 6% 15% 27% 18% 1	3292
	11th to 20th	Day	47% 6% 11% 19% 17% 1	3140
	21st to end	Day	44% 5% 13% 22% 15% 1	3368
November	1st to 10th	Day	48% 7% 13% 19% 12% 1	1762
	11th to 20th	Day	59% 6% 11% 14% 9% 1	1800
	21st to end	Day	66% 9% 8% 11% 5%	1600
December	1st to 10th	Day	71% 5% 16% 7% 2	2600
	11th to 20th	Day	77% 5% 9% 8% 2	2986
	21st to end	Day	80% 5% 8% 6% 1	4232
January	1st to 10th	Night	76% 6% 7% 8% 3	5889
	11th to 20th	Night	80% 6% 7% 6% 2	5900
	21st to end	Night	72% 5% 10% 9% 5%	6490
February	1st to 10th	Night	66% 7% 11% 11% 4	2600
	11th to 20th	Night	63% 7% 10% 14% 5%	2455
	21st to end	Night	63% 7% 9% 13% 7% 1	1885
March	1st to 10th	Night	54% 5% 14% 19% 8%	3523
	11th to 20th	Night	44% 10% 17% 17% 10% 1	3480
	21st to end	Night	49% 9% 12% 21% 8% 1	3817
April	1st to 10th	Night	52% 6% 13% 16% 12% 2	2067
	11th to 20th	Night	47% 7% 13% 16% 14% 3	1701
	21st to end	Night	44% 7% 13% 19% 14% 3	1710
May	1st to 10th	Night	50% 9% 11% 17% 11% 2	2840
	11th to 20th	Night	43% 9% 13% 20% 13% 2	2813
	21st to end	Night	30% 10% 15% 23% 18% 4	3087
June	1st to 10th	Night	39% 8% 11% 24% 14% 3	1520
	11th to 20th	Night	36% 9% 15% 21% 17% 3	1453
	21st to end	Night	35% 9% 13% 25% 17% 1	1373
July	1st to 10th	Night	34% 5% 13% 24% 18% 6%	2549
	11th to 20th	Night	32% 6% 13% 27% 19% 3	2786
	21st to end	Night	34% 7% 15% 20% 21% 3	2988
August	1st to 10th	Night	39% 7% 13% 25% 14% 1	2814
	11th to 20th	Night	41% 7% 10% 29% 12% 1	2812
	21st to end	Night	37% 6% 12% 28% 15% 2	3138
September	1st to 10th	Night	38% 8% 13% 23% 15% 4	2023
	11th to 20th	Night	33% 7% 13% 25% 20% 2	2090
	21st to end	Night	46% 7% 11% 19% 16% 1	2090
October	1st to 10th	Night	32% 6% 8% 28% 24% 1	3667
	11th to 20th	Night	48% 5% 9% 20% 17%	3779
	21st to end	Night	44% 5% 10% 25% 15% 1	4177
November	1st to 10th	Night	50% 7% 12% 18% 12% 2	2536
	11th to 20th	Night	61% 6% 10% 13% 8% 2	2600
	21st to end	Night	67% 6% 10% 13% 4	2795
December	1st to 10th	Night	71% 5% 14% 8% 2	4580
	11th to 20th	Night	72% 5% 11% 11% 2	5208
	21st to end	Night	74% 7% 10% 8% 1	6705

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	26% 19% 37% 12% 7% 1	300
	11th to 20th	Day	25% 24% 38% 9% 4	300
	21st to end	Day	26% 21% 33% 17% 2 1	330
February	1st to 10th	Day	24% 20% 40% 14% 2	300
	11th to 20th	Day	28% 19% 34% 17% 1	300
	21st to end	Day	24% 26% 35% 13% 1	225
March	1st to 10th	Day	21% 20% 30% 25% 4	388
	11th to 20th	Day	21% 17% 33% 22% 6% 1	460
	21st to end	Day	28% 14% 31% 23% 5%	506
April	1st to 10th	Day	18% 14% 36% 23% 8% 1	460
	11th to 20th	Day	21% 15% 29% 23% 8% 3	452
	21st to end	Day	24% 11% 32% 23% 8% 2	460
May	1st to 10th	Day	24% 10% 28% 27% 9% 2	463
	11th to 20th	Day	19% 7% 26% 30% 16% 3	487
	21st to end	Day	12% 5% 24% 34% 20% 6%	529
June	1st to 10th	Day	14% 4 26% 38% 14% 3	490
	11th to 20th	Day	12% 6% 23% 36% 19% 4	549
	21st to end	Day	12% 6% 25% 35% 18% 3	680
July	1st to 10th	Day	9% 4 21% 32% 26% 8%	630
	11th to 20th	Day	12% 5% 17% 35% 24% 7%	484
	21st to end	Day	9% 4 22% 35% 24% 6%	532
August	1st to 10th	Day	11% 4 19% 32% 26% 8%	486
	11th to 20th	Day	12% 3 20% 34% 23% 7%	479
	21st to end	Day	11% 5% 19% 33% 25% 8%	539
September	1st to 10th	Day	16% 4 20% 27% 26% 7%	490
	11th to 20th	Day	12% 3 15% 32% 25% 12%	490
	21st to end	Day	22% 9% 22% 25% 14% 8%	490
October	1st to 10th	Day	14% 8% 25% 27% 19% 7%	490
	11th to 20th	Day	22% 14% 29% 23% 9% 3	490
	21st to end	Day	26% 18% 28% 21% 7%	503
November	1st to 10th	Day	18% 21% 26% 23% 10% 2	300
	11th to 20th	Day	27% 21% 31% 14% 7%	300
	21st to end	Day	30% 19% 32% 18% 2	200
December	1st to 10th	Day	24% 24% 30% 18% 5% 1	200
	11th to 20th	Day	26% 25% 31% 17% 3	200
	21st to end	Day	29% 20% 33% 17% 1	278
January	1st to 10th	Night	29% 20% 32% 15% 4	800
	11th to 20th	Night	31% 18% 31% 16% 4	800
	21st to end	Night	28% 16% 31% 22% 4	880
February	1st to 10th	Night	30% 13% 31% 22% 4	800
	11th to 20th	Night	25% 15% 33% 23% 3	783
	21st to end	Night	26% 15% 36% 20% 3	629
March	1st to 10th	Night	23% 12% 32% 26% 7%	760
	11th to 20th	Night	20% 14% 33% 25% 8% 1	760
	21st to end	Night	25% 9% 28% 27% 10% 1	836
April	1st to 10th	Night	21% 12% 31% 29% 7% 1	760
	11th to 20th	Night	19% 9% 34% 26% 10% 2	577
	21st to end	Night	19% 8% 32% 32% 8% 1	570
May	1st to 10th	Night	21% 7% 23% 34% 13% 1	570
	11th to 20th	Night	20% 6% 24% 31% 17% 2	561
	21st to end	Night	12% 2 18% 36% 27% 4	617
June	1st to 10th	Night	13% 4 23% 40% 19% 1	380
	11th to 20th	Night	11% 3 22% 40% 23% 1	380
	21st to end	Night	10% 3 21% 39% 26%	423
July	1st to 10th	Night	10% 4 12% 39% 31% 4	555
	11th to 20th	Night	12% 4 17% 34% 28% 6%	552
	21st to end	Night	9% 3 16% 40% 30% 2	624
August	1st to 10th	Night	11% 3 14% 38% 29% 5%	567
	11th to 20th	Night	13% 4 13% 36% 30% 4	564
	21st to end	Night	13% 3 16% 33% 29% 5%	628
September	1st to 10th	Night	14% 5% 17% 32% 27% 5%	760
	11th to 20th	Night	13% 3 15% 31% 32% 6%	760
	21st to end	Night	21% 7% 21% 28% 19% 5%	760
October	1st to 10th	Night	18% 10% 21% 27% 20% 4	760
	11th to 20th	Night	26% 13% 27% 23% 9% 1	760
	21st to end	Night	31% 15% 24% 25% 5%	836
November	1st to 10th	Night	24% 13% 28% 25% 9% 1	780
	11th to 20th	Night	30% 17% 29% 17% 6% 2	800
	21st to end	Night	33% 17% 30% 16% 5%	800
December	1st to 10th	Night	31% 18% 31% 16% 5%	800
	11th to 20th	Night	30% 19% 30% 17% 4	800
	21st to end	Night	31% 16% 31% 19% 3	880

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

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