Leitner Observatory and Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leitner Observatory and Planetarium 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	18% 7% 2 6% 4 4 4 4 5% 7% 40%	101251
	Night	19% 7% 2 6% 4 4 4 3 5% 6% 41%	97804
Transparency	Day	42% 6% 12% 22% 16% 2	104798
	Night	43% 5% 12% 22% 15% 2	102346
Seeing	Day	20% 16% 31% 22% 9% 2	15036
	Night	21% 13% 32% 26% 8% 1	24069

By Month

Percentage Cloud Cover NE (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% 6% 2 6% 3 4 3 3 5% 5% 46%	2517
	11th to 20th	Day	17% 9% 3 7% 4 4 4 5% 5% 5% 37%	2520
	21st to end	Day	22% 10% 3 7% 4 4 4 4 5% 5% 32%	2868
February	1st to 10th	Day	17% 7% 3 6% 5% 5% 5% 3 5% 7% 38%	1776
	11th to 20th	Day	15% 7% 2 5% 4 4 4 4 6% 8% 43%	1848
	21st to end	Day	21% 8% 3 5% 4 4 3 3 6% 6% 37%	1570
March	1st to 10th	Day	27% 9% 2 5% 3 4 3 3 4 5% 34%	3116
	11th to 20th	Day	11% 5% 1 4 4 4 5% 5% 7% 8% 46%	3263
	21st to end	Day	21% 7% 2 6% 4 3 4 3 4 6% 40%	4166
April	1st to 10th	Day	19% 8% 2 5% 4 4 4 3 5% 6% 39%	2280
	11th to 20th	Day	20% 6% 2 6% 4 4 4 3 3 7% 42%	2254
	21st to end	Day	21% 5% 2 5% 4 3 5% 3 5% 5% 41%	2380
May	1st to 10th	Day	28% 9% 2 5% 3 3 3 3 5% 7% 31%	4106
	11th to 20th	Day	24% 7% 2 6% 4 4 4 3 5% 7% 33%	4260
	21st to end	Day	16% 5% 2 4 3 3 4 3 6% 8% 46%	4837
June	1st to 10th	Day	18% 5% 2 5% 4 4 5% 5% 6% 8% 37%	2660
	11th to 20th	Day	16% 6% 2 5% 5% 4 4 4 6% 10% 38%	2660
	21st to end	Day	13% 7% 2 5% 5% 5% 5% 4 6% 8% 40%	2660
July	1st to 10th	Day	14% 6% 2 7% 5% 5% 5% 4 7% 9% 36%	4440
	11th to 20th	Day	15% 5% 2 6% 4 4 5% 4 7% 9% 40%	4440
	21st to end	Day	17% 8% 3 7% 5% 4 5% 4 6% 7% 34%	4814
August	1st to 10th	Day	20% 6% 2 7% 5% 5% 5% 4 6% 8% 33%	4247
	11th to 20th	Day	12% 6% 2 6% 4 3 4 3 6% 9% 44%	3736
	21st to end	Day	8% 5% 2 6% 5% 4 4 4 6% 10% 46%	4180
September	1st to 10th	Day	13% 5% 2 5% 5% 4 4 4 5% 6% 46%	2280
	11th to 20th	Day	13% 5% 2 4 3 4 4 3 5% 6% 52%	2149
	21st to end	Day	20% 6% 2 5% 5% 4 4 3 4 6% 41%	2090
October	1st to 10th	Day	21% 7% 2 5% 4 3 3 3 4 6% 41%	2061
	11th to 20th	Day	15% 4 1 5% 4 3 3 4 5% 7% 48%	1889
	21st to end	Day	20% 6% 1 4 4 4 4 4 5% 7% 41%	1881
November	1st to 10th	Day	14% 7% 2 5% 4 4 3 3 4 6% 49%	1708
	11th to 20th	Day	20% 6% 2 4 2 3 3 2 5% 7% 47%	1710
	21st to end	Day	17% 6% 2 5% 4 3 4 3 5% 6% 45%	1687
December	1st to 10th	Day	19% 6% 3 5% 4 5% 4 5% 5% 6% 38%	1520
	11th to 20th	Day	23% 6% 1 4 3 3 3 2 4 6% 45%	1906
	21st to end	Day	19% 11% 3 6% 4 4 4 3 5% 6% 34%	2772
January	1st to 10th	Night	17% 6% 2 5% 3 3 3 4 4 7% 46%	4429
	11th to 20th	Night	18% 9% 3 7% 4 3 3 2 4 4 44%	4440
	21st to end	Night	25% 11% 3 6% 4 3 3 3 4 5% 33%	4787
February	1st to 10th	Night	17% 9% 3 6% 4 3 3 3 4 5% 41%	2402
	11th to 20th	Night	17% 8% 3 5% 4 3 3 3 4 7% 42%	2218
	21st to end	Night	20% 8% 2 5% 4 3 4 3 3 6% 41%	1884
March	1st to 10th	Night	26% 11% 2 5% 3 3 3 3 4 5% 35%	3724
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 4 5% 6% 44%	3690
	21st to end	Night	21% 9% 2 5% 3 3 3 3 5% 5% 41%	3466
April	1st to 10th	Night	19% 7% 2 6% 4 4 4 4 6% 7% 37%	1900
	11th to 20th	Night	21% 6% 2 6% 4 3 3 3 5% 6% 42%	1875
	21st to end	Night	20% 7% 2 7% 5% 3 4 3 4 5% 42%	1800
May	1st to 10th	Night	25% 11% 3 7% 5% 3 4 3 5% 6% 29%	2834
	11th to 20th	Night	23% 8% 3 7% 4 4 4 4 4 6% 31%	2660
	21st to end	Night	19% 8% 2 4 3 4 4 3 4 6% 42%	2738
June	1st to 10th	Night	19% 6% 2 6% 5% 4 4 4 5% 6% 39%	1520
	11th to 20th	Night	17% 7% 2 5% 4 3 4 4 5% 9% 40%	1520
	21st to end	Night	14% 6% 2 6% 4 5% 4 3 5% 9% 42%	1520
July	1st to 10th	Night	14% 8% 2 7% 5% 4 5% 4 7% 8% 35%	2520
	11th to 20th	Night	18% 7% 2 5% 4 5% 5% 4 7% 9% 35%	2520
	21st to end	Night	21% 8% 2 6% 5% 4 4 4 7% 7% 33%	2739
August	1st to 10th	Night	24% 6% 2 7% 5% 5% 5% 5% 6% 7% 29%	2650
	11th to 20th	Night	15% 6% 3 7% 4 4 6% 4 5% 7% 40%	3088
	21st to end	Night	10% 4 1 4 3 3 4 3 5% 8% 55%	3476
September	1st to 10th	Night	15% 5% 3 5% 4 4 4 3 4 7% 44%	1900
	11th to 20th	Night	15% 5% 2 4 3 3 3 3 4 6% 53%	2030
	21st to end	Night	18% 7% 3 5% 4 4 4 3 4 5% 43%	2090
October	1st to 10th	Night	20% 7% 2 6% 4 4 4 2 4 6% 41%	2117
	11th to 20th	Night	15% 5% 2 6% 3 3 3 2 5% 6% 50%	2289
	21st to end	Night	22% 7% 2 5% 3 3 4 3 5% 5% 42%	2717
November	1st to 10th	Night	13% 6% 2 5% 4 3 4 3 5% 6% 49%	2470
	11th to 20th	Night	20% 7% 2 4 3 3 3 3 4 6% 47%	2470
	21st to end	Night	16% 6% 1 5% 4 4 4 3 5% 7% 46%	2489
December	1st to 10th	Night	21% 7% 2 6% 3 4 4 3 5% 5% 40%	2660
	11th to 20th	Night	21% 6% 2 5% 3 3 5% 3 5% 5% 42%	3288
	21st to end	Night	22% 11% 3 6% 3 3 3 3 4 5% 37%	4884

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	39% 4 11% 31% 12% 3	2518
	11th to 20th	Day	48% 5% 12% 23% 11% 1	2520
	21st to end	Day	52% 7% 8% 20% 10% 2	2868
February	1st to 10th	Day	45% 6% 13% 20% 14% 2	1776
	11th to 20th	Day	40% 6% 11% 24% 16% 3	1857
	21st to end	Day	47% 6% 11% 19% 14% 3	1570
March	1st to 10th	Day	53% 4 13% 17% 11% 2	3119
	11th to 20th	Day	33% 7% 16% 29% 14% 2	3263
	21st to end	Day	46% 4 8% 17% 20% 5%	4166
April	1st to 10th	Day	45% 6% 10% 20% 16% 4	2280
	11th to 20th	Day	43% 5% 11% 20% 18% 3	2254
	21st to end	Day	44% 6% 10% 21% 16% 4	2380
May	1st to 10th	Day	52% 7% 15% 14% 11% 2	4120
	11th to 20th	Day	48% 8% 14% 19% 9% 2	4264
	21st to end	Day	35% 7% 13% 25% 18% 2	4837
June	1st to 10th	Day	43% 8% 13% 23% 12% 1	2660
	11th to 20th	Day	40% 8% 15% 23% 13% 1	2660
	21st to end	Day	39% 9% 14% 23% 14% 1	2660
July	1st to 10th	Day	44% 9% 11% 20% 16% 1	4370
	11th to 20th	Day	40% 6% 17% 22% 14% 1	4365
	21st to end	Day	48% 6% 13% 17% 15% 2	4661
August	1st to 10th	Day	48% 8% 15% 21% 8%	4233
	11th to 20th	Day	37% 6% 14% 31% 11% 1	3772
	21st to end	Day	34% 7% 13% 27% 17% 2	4180
September	1st to 10th	Day	37% 8% 12% 22% 19% 2	2280
	11th to 20th	Day	33% 6% 11% 23% 24% 2	2149
	21st to end	Day	44% 6% 8% 20% 19% 3	2090
October	1st to 10th	Day	36% 5% 10% 20% 23% 6%	3425
	11th to 20th	Day	27% 4 10% 24% 32% 4	3117
	21st to end	Day	31% 5% 14% 25% 23% 3	3081
November	1st to 10th	Day	39% 4 13% 21% 21% 3	1708
	11th to 20th	Day	39% 4 12% 22% 20% 3	1710
	21st to end	Day	40% 5% 13% 26% 13% 3	1687
December	1st to 10th	Day	46% 5% 14% 18% 15% 1	1520
	11th to 20th	Day	42% 3 16% 19% 18% 2	1906
	21st to end	Day	52% 5% 11% 22% 10% 1	2772
January	1st to 10th	Night	39% 4 11% 30% 12% 4	4429
	11th to 20th	Night	45% 4 12% 23% 13% 3	4440
	21st to end	Night	55% 4 8% 20% 11% 2	4787
February	1st to 10th	Night	44% 6% 12% 23% 12% 2	2402
	11th to 20th	Night	43% 5% 10% 20% 17% 4	2220
	21st to end	Night	46% 4 9% 22% 15% 4	1884
March	1st to 10th	Night	52% 4 10% 20% 12% 2	3734
	11th to 20th	Night	38% 6% 16% 22% 15% 3	3691
	21st to end	Night	46% 3 8% 12% 25% 6%	3466
April	1st to 10th	Night	46% 5% 10% 20% 16% 3	1900
	11th to 20th	Night	44% 5% 11% 19% 20% 1	1875
	21st to end	Night	46% 4 9% 22% 15% 4	1800
May	1st to 10th	Night	56% 7% 12% 14% 10% 1	2840
	11th to 20th	Night	53% 9% 13% 14% 9% 2	2661
	21st to end	Night	42% 5% 15% 24% 13% 1	2739
June	1st to 10th	Night	45% 6% 10% 20% 17% 2	1520
	11th to 20th	Night	40% 7% 14% 27% 12% 1	1520
	21st to end	Night	40% 8% 13% 25% 14%	1520
July	1st to 10th	Night	46% 9% 13% 18% 12% 1	2480
	11th to 20th	Night	45% 6% 17% 23% 9% 1	2472
	21st to end	Night	49% 6% 14% 15% 15% 2	2651
August	1st to 10th	Night	54% 7% 14% 15% 9% 1	2640
	11th to 20th	Night	43% 6% 14% 28% 8% 1	3118
	21st to end	Night	28% 5% 15% 33% 18% 1	3476
September	1st to 10th	Night	39% 6% 10% 25% 18% 2	1900
	11th to 20th	Night	33% 5% 10% 24% 25% 3	2030
	21st to end	Night	44% 5% 8% 20% 20% 3	2090
October	1st to 10th	Night	39% 4 12% 23% 19% 2	3533
	11th to 20th	Night	25% 4 9% 27% 31% 4	3800
	21st to end	Night	32% 4 13% 27% 21% 2	4467
November	1st to 10th	Night	37% 4 12% 22% 20% 4	2470
	11th to 20th	Night	41% 4 10% 24% 18% 4	2470
	21st to end	Night	39% 4 13% 29% 13% 2	2489
December	1st to 10th	Night	47% 5% 12% 20% 15% 1	2660
	11th to 20th	Night	44% 5% 15% 17% 18% 2	3288
	21st to end	Night	50% 4 12% 22% 12% 1	4884

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% 26% 28% 21% 2	180
	11th to 20th	Day	23% 32% 29% 14% 1 1	180
	21st to end	Day	21% 27% 34% 11% 5% 2	225
February	1st to 10th	Day	25% 25% 34% 15% 1	336
	11th to 20th	Day	22% 29% 36% 13% 1	456
	21st to end	Day	27% 24% 31% 14% 4	382
March	1st to 10th	Day	21% 25% 35% 16% 3	460
	11th to 20th	Day	20% 27% 34% 14% 3 1	460
	21st to end	Day	25% 24% 36% 11% 4 1	506
April	1st to 10th	Day	24% 25% 32% 13% 6% 1	460
	11th to 20th	Day	27% 20% 31% 17% 5% 1	452
	21st to end	Day	25% 18% 34% 17% 4 2	460
May	1st to 10th	Day	27% 21% 30% 16% 6% 1	463
	11th to 20th	Day	21% 15% 36% 22% 5% 1	487
	21st to end	Day	19% 10% 30% 27% 12% 2	529
June	1st to 10th	Day	17% 12% 32% 26% 12% 2	490
	11th to 20th	Day	17% 11% 34% 27% 10% 1	490
	21st to end	Day	16% 10% 33% 27% 12% 2	490
July	1st to 10th	Day	16% 5% 28% 31% 17% 3	485
	11th to 20th	Day	13% 6% 28% 34% 15% 4	484
	21st to end	Day	15% 7% 32% 33% 9% 2	532
August	1st to 10th	Day	14% 7% 28% 33% 14% 5%	486
	11th to 20th	Day	13% 6% 29% 30% 18% 5%	479
	21st to end	Day	11% 9% 30% 29% 14% 6%	539
September	1st to 10th	Day	17% 9% 28% 25% 17% 4	490
	11th to 20th	Day	15% 6% 32% 26% 14% 8%	490
	21st to end	Day	22% 11% 32% 22% 10% 3	490
October	1st to 10th	Day	27% 11% 24% 22% 12% 4	490
	11th to 20th	Day	16% 18% 29% 27% 9% 2	483
	21st to end	Day	25% 16% 32% 18% 8% 2	429
November	1st to 10th	Day	16% 17% 30% 24% 11% 3	378
	11th to 20th	Day	24% 24% 26% 21% 5%	370
	21st to end	Day	19% 22% 29% 22% 7%	347
December	1st to 10th	Day	21% 20% 36% 17% 6%	180
	11th to 20th	Day	27% 27% 32% 13% 2	180
	21st to end	Day	25% 21% 34% 14% 6% 1	198
January	1st to 10th	Night	21% 20% 37% 19% 3	760
	11th to 20th	Night	28% 19% 32% 19% 3	760
	21st to end	Night	20% 21% 37% 19% 3	836
February	1st to 10th	Night	22% 20% 34% 23% 2	760
	11th to 20th	Night	22% 21% 40% 16% 2	743
	21st to end	Night	26% 18% 35% 17% 3	628
March	1st to 10th	Night	23% 18% 36% 19% 4	760
	11th to 20th	Night	22% 15% 38% 21% 4 1	760
	21st to end	Night	23% 19% 36% 19% 3	836
April	1st to 10th	Night	23% 17% 35% 21% 4	760
	11th to 20th	Night	22% 14% 36% 24% 4	751
	21st to end	Night	22% 14% 37% 21% 6%	660
May	1st to 10th	Night	25% 12% 33% 22% 7%	570
	11th to 20th	Night	23% 11% 38% 22% 6%	474
	21st to end	Night	20% 5% 23% 40% 10%	411
June	1st to 10th	Night	22% 5% 29% 33% 10% 1	380
	11th to 20th	Night	19% 4 29% 35% 12%	380
	21st to end	Night	16% 6% 26% 41% 10% 1	380
July	1st to 10th	Night	14% 5% 24% 41% 16% 1	370
	11th to 20th	Night	14% 2 20% 45% 17% 1	368
	21st to end	Night	16% 3 25% 42% 13% 1	416
August	1st to 10th	Night	12% 3 28% 40% 15% 1	457
	11th to 20th	Night	16% 3 20% 42% 17% 2	741
	21st to end	Night	14% 4 24% 37% 19% 3	836
September	1st to 10th	Night	17% 4 28% 33% 15% 3	760
	11th to 20th	Night	17% 5% 25% 31% 19% 3	760
	21st to end	Night	22% 6% 27% 29% 16% 1	760
October	1st to 10th	Night	23% 10% 26% 26% 13% 3	760
	11th to 20th	Night	19% 13% 31% 28% 9% 1	760
	21st to end	Night	26% 11% 34% 21% 8%	836
November	1st to 10th	Night	16% 14% 34% 24% 11% 1	760
	11th to 20th	Night	23% 16% 34% 20% 6% 1	760
	21st to end	Night	22% 17% 32% 24% 5% 1	760
December	1st to 10th	Night	26% 16% 31% 20% 5% 1	760
	11th to 20th	Night	25% 19% 31% 21% 3	760
	21st to end	Night	26% 17% 37% 18% 2	836

Page generated at 2024-11-03 02:11:26. Version ac07

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