Lenore and Walter Hawley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lenore and Walter Hawley Observatory 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	17% 7% 3 7% 5% 4 5% 4 5% 7% 37%	101303
	Night	18% 8% 2 6% 4 4 4 3 5% 6% 38%	97739
Transparency	Day	45% 6% 11% 21% 14% 2	104828
	Night	44% 6% 12% 22% 14% 2	102303
Seeing	Day	24% 17% 29% 19% 8% 2	14941
	Night	22% 14% 31% 25% 7% 1	23824

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	14% 8% 3 6% 5% 4 4 4 5% 6% 41%	2517
	11th to 20th	Day	15% 8% 4 9% 5% 4 4 4 5% 6% 37%	2520
	21st to end	Day	18% 11% 3 8% 5% 5% 4 3 5% 5% 33%	2772
February	1st to 10th	Day	17% 9% 2 6% 5% 6% 5% 5% 5% 6% 34%	1716
	11th to 20th	Day	12% 8% 3 9% 5% 4 5% 4 6% 7% 38%	1848
	21st to end	Day	16% 10% 3 8% 5% 4 4 3 5% 6% 36%	1570
March	1st to 10th	Day	23% 14% 3 7% 5% 4 4 3 4 4 28%	3116
	11th to 20th	Day	14% 8% 3 8% 5% 4 5% 5% 6% 7% 36%	3313
	21st to end	Day	20% 9% 3 7% 4 4 4 3 6% 7% 33%	4060
April	1st to 10th	Day	19% 9% 3 7% 4 4 4 4 4 5% 37%	2280
	11th to 20th	Day	18% 6% 2 7% 5% 5% 5% 4 6% 6% 37%	2270
	21st to end	Day	21% 7% 3 7% 5% 4 4 4 5% 5% 34%	2470
May	1st to 10th	Day	23% 11% 3 9% 5% 4 4 4 5% 6% 27%	4106
	11th to 20th	Day	20% 7% 3 8% 5% 4 5% 3 5% 7% 31%	4256
	21st to end	Day	14% 6% 2 5% 4 4 5% 4 6% 8% 42%	4837
June	1st to 10th	Day	19% 7% 2 7% 5% 5% 5% 4 6% 8% 32%	2660
	11th to 20th	Day	16% 6% 3 7% 4 5% 5% 4 6% 8% 37%	2660
	21st to end	Day	19% 7% 2 7% 5% 5% 5% 4 6% 8% 32%	2660
July	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 5% 7% 10% 36%	4440
	11th to 20th	Day	10% 5% 2 6% 5% 5% 6% 5% 7% 10% 38%	4440
	21st to end	Day	16% 6% 3 8% 5% 5% 5% 4 6% 7% 36%	4814
August	1st to 10th	Day	14% 6% 3 7% 5% 5% 6% 4 6% 8% 36%	4233
	11th to 20th	Day	14% 8% 3 6% 5% 5% 5% 4 6% 8% 36%	3996
	21st to end	Day	8% 5% 2 6% 4 5% 5% 4 6% 9% 44%	4180
September	1st to 10th	Day	12% 5% 2 5% 5% 4 4 5% 6% 6% 46%	2280
	11th to 20th	Day	15% 5% 2 5% 3 3 2 2 5% 6% 53%	2101
	21st to end	Day	16% 6% 3 6% 3 4 4 3 4 7% 45%	2090
October	1st to 10th	Day	22% 7% 2 6% 3 4 4 3 5% 5% 38%	2090
	11th to 20th	Day	16% 6% 1 5% 4 4 4 4 4 7% 44%	1829
	21st to end	Day	23% 7% 3 5% 4 4 4 3 3 6% 38%	1881
November	1st to 10th	Day	15% 7% 2 5% 4 4 3 3 5% 6% 48%	1708
	11th to 20th	Day	19% 6% 2 5% 3 3 3 4 5% 5% 46%	1710
	21st to end	Day	20% 7% 2 5% 4 4 4 4 4 6% 40%	1682
December	1st to 10th	Day	18% 9% 3 7% 5% 4 5% 3 6% 7% 34%	1520
	11th to 20th	Day	21% 8% 2 6% 4 3 4 4 4 4 40%	1906
	21st to end	Day	24% 11% 3 7% 5% 4 4 3 4 5% 30%	2772
January	1st to 10th	Night	17% 8% 2 5% 4 4 4 3 5% 5% 44%	4429
	11th to 20th	Night	14% 8% 3 9% 5% 5% 5% 3 6% 6% 36%	4440
	21st to end	Night	21% 14% 4 8% 5% 4 4 3 4 4 30%	4884
February	1st to 10th	Night	15% 9% 3 7% 5% 4 5% 3 6% 7% 37%	2458
	11th to 20th	Night	12% 9% 2 7% 4 4 5% 4 7% 6% 39%	2218
	21st to end	Night	16% 9% 2 6% 4 4 4 4 5% 7% 39%	1884
March	1st to 10th	Night	27% 10% 2 6% 4 4 3 3 5% 5% 32%	3724
	11th to 20th	Night	12% 9% 3 8% 6% 4 6% 4 5% 6% 36%	3645
	21st to end	Night	24% 8% 2 6% 3 4 4 4 6% 6% 33%	3567
April	1st to 10th	Night	20% 8% 3 7% 4 3 4 4 5% 6% 36%	1900
	11th to 20th	Night	21% 8% 2 6% 4 4 4 4 4 5% 40%	1857
	21st to end	Night	20% 7% 2 7% 4 4 3 4 5% 6% 38%	1710
May	1st to 10th	Night	26% 10% 3 7% 5% 4 4 3 5% 6% 26%	2834
	11th to 20th	Night	17% 8% 3 9% 6% 6% 6% 4 7% 7% 27%	2667
	21st to end	Night	16% 6% 3 6% 4 4 4 5% 6% 8% 40%	2738
June	1st to 10th	Night	19% 8% 3 7% 5% 3 4 3 5% 6% 37%	1520
	11th to 20th	Night	19% 6% 2 6% 4 5% 4 3 6% 8% 36%	1520
	21st to end	Night	18% 7% 3 5% 5% 5% 4 4 5% 9% 37%	1520
July	1st to 10th	Night	11% 5% 1 6% 6% 5% 7% 5% 7% 9% 39%	2520
	11th to 20th	Night	12% 6% 2 6% 5% 4 5% 4 7% 8% 41%	2520
	21st to end	Night	15% 7% 2 5% 4 3 5% 4 5% 7% 42%	2739
August	1st to 10th	Night	21% 6% 3 7% 5% 4 5% 3 5% 6% 35%	2666
	11th to 20th	Night	13% 8% 3 7% 5% 5% 5% 4 6% 8% 38%	2814
	21st to end	Night	9% 4 2 4 3 3 4 3 6% 10% 53%	3476
September	1st to 10th	Night	12% 6% 2 6% 3 3 3 3 4 7% 51%	1900
	11th to 20th	Night	14% 6% 1 4 3 2 3 2 4 6% 53%	2078
	21st to end	Night	15% 6% 2 5% 4 3 3 3 5% 6% 48%	2090
October	1st to 10th	Night	22% 6% 3 6% 4 5% 3 3 4 5% 40%	2090
	11th to 20th	Night	15% 7% 2 5% 4 4 4 4 6% 8% 42%	2349
	21st to end	Night	22% 7% 2 6% 4 4 4 3 5% 6% 37%	2717
November	1st to 10th	Night	15% 7% 3 7% 4 3 4 3 5% 6% 45%	2470
	11th to 20th	Night	17% 6% 3 6% 4 3 4 2 5% 5% 45%	2470
	21st to end	Night	16% 8% 2 5% 4 4 4 3 5% 7% 41%	2493
December	1st to 10th	Night	20% 9% 3 7% 4 4 4 3 5% 6% 37%	2660
	11th to 20th	Night	20% 8% 3 5% 3 3 4 4 5% 6% 39%	3288
	21st to end	Night	22% 10% 3 8% 5% 4 3 3 5% 5% 33%	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	42% 5% 11% 31% 10% 1	2518
	11th to 20th	Day	47% 6% 15% 21% 10% 1	2520
	21st to end	Day	51% 6% 10% 22% 9% 2	2772
February	1st to 10th	Day	49% 5% 12% 21% 10% 2	1716
	11th to 20th	Day	44% 6% 12% 21% 14% 3	1857
	21st to end	Day	49% 5% 9% 20% 14% 2	1570
March	1st to 10th	Day	59% 5% 9% 13% 11% 3	3119
	11th to 20th	Day	41% 10% 14% 19% 13% 3	3313
	21st to end	Day	49% 5% 7% 17% 17% 5%	4060
April	1st to 10th	Day	49% 5% 8% 19% 15% 4	2280
	11th to 20th	Day	45% 7% 11% 19% 16% 3	2270
	21st to end	Day	51% 6% 8% 16% 17% 3	2470
May	1st to 10th	Day	57% 8% 9% 15% 9% 1	4120
	11th to 20th	Day	51% 8% 14% 15% 10% 2	4260
	21st to end	Day	37% 9% 13% 23% 17% 2	4837
June	1st to 10th	Day	49% 7% 12% 20% 11%	2660
	11th to 20th	Day	44% 7% 11% 19% 16% 3	2660
	21st to end	Day	49% 8% 11% 18% 13% 1	2660
July	1st to 10th	Day	42% 6% 13% 22% 16% 1	4370
	11th to 20th	Day	40% 7% 15% 24% 13%	4365
	21st to end	Day	46% 6% 12% 20% 14% 1	4661
August	1st to 10th	Day	45% 8% 15% 21% 11% 1	4219
	11th to 20th	Day	45% 7% 14% 25% 8% 1	4035
	21st to end	Day	35% 7% 12% 28% 16% 2	4180
September	1st to 10th	Day	36% 6% 13% 24% 19% 2	2280
	11th to 20th	Day	34% 5% 8% 27% 23% 2	2101
	21st to end	Day	39% 6% 9% 24% 20% 3	2090
October	1st to 10th	Day	45% 5% 8% 22% 17% 2	3480
	11th to 20th	Day	35% 5% 10% 28% 20% 3	3006
	21st to end	Day	36% 3 8% 31% 18% 3	3081
November	1st to 10th	Day	39% 4 13% 25% 17% 2	1708
	11th to 20th	Day	41% 4 11% 22% 20% 3	1710
	21st to end	Day	46% 4 16% 20% 12% 1	1682
December	1st to 10th	Day	49% 6% 14% 17% 12% 1	1520
	11th to 20th	Day	47% 6% 11% 17% 16% 4	1906
	21st to end	Day	55% 6% 12% 17% 10% 1	2772
January	1st to 10th	Night	41% 6% 13% 27% 11% 3	4429
	11th to 20th	Night	44% 8% 13% 22% 10% 3	4440
	21st to end	Night	56% 5% 10% 17% 10% 1	4884
February	1st to 10th	Night	46% 7% 12% 20% 13% 2	2458
	11th to 20th	Night	44% 6% 10% 21% 16% 3	2220
	21st to end	Night	43% 6% 11% 24% 13% 4	1884
March	1st to 10th	Night	54% 5% 10% 19% 11% 3	3734
	11th to 20th	Night	45% 9% 11% 19% 15% 2	3646
	21st to end	Night	48% 6% 7% 14% 19% 6%	3567
April	1st to 10th	Night	48% 5% 10% 18% 17% 3	1900
	11th to 20th	Night	46% 6% 7% 22% 18% 1	1857
	21st to end	Night	46% 6% 11% 18% 16% 4	1710
May	1st to 10th	Night	57% 8% 10% 16% 8% 2	2840
	11th to 20th	Night	52% 10% 14% 14% 9% 2	2668
	21st to end	Night	40% 9% 16% 21% 12% 2	2739
June	1st to 10th	Night	48% 6% 11% 21% 12% 1	1520
	11th to 20th	Night	45% 8% 13% 19% 13% 2	1520
	21st to end	Night	44% 9% 12% 21% 12% 1	1520
July	1st to 10th	Night	39% 9% 16% 22% 13% 1	2480
	11th to 20th	Night	40% 8% 14% 24% 15%	2472
	21st to end	Night	41% 6% 11% 26% 14% 1	2651
August	1st to 10th	Night	50% 8% 11% 20% 10%	2656
	11th to 20th	Night	44% 9% 15% 21% 11%	2841
	21st to end	Night	28% 6% 17% 31% 18% 1	3476
September	1st to 10th	Night	34% 6% 13% 26% 19% 1	1900
	11th to 20th	Night	33% 5% 10% 28% 22% 2	2078
	21st to end	Night	37% 6% 10% 28% 18% 2	2090
October	1st to 10th	Night	43% 6% 15% 23% 13% 2	3480
	11th to 20th	Night	32% 5% 11% 25% 24% 3	3911
	21st to end	Night	37% 4 10% 31% 15% 2	4467
November	1st to 10th	Night	40% 5% 10% 24% 18% 2	2470
	11th to 20th	Night	42% 4 10% 24% 18% 3	2470
	21st to end	Night	43% 5% 14% 25% 12% 1	2493
December	1st to 10th	Night	49% 6% 11% 22% 11% 1	2660
	11th to 20th	Night	45% 6% 13% 17% 17% 1	3288
	21st to end	Night	53% 5% 10% 23% 10% 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	28% 26% 25% 18% 3	180
	11th to 20th	Day	31% 23% 32% 11% 2 2	180
	21st to end	Day	22% 30% 30% 15% 4	198
February	1st to 10th	Day	32% 26% 27% 13% 2	321
	11th to 20th	Day	32% 28% 25% 14% 2	456
	21st to end	Day	31% 23% 29% 14% 3	382
March	1st to 10th	Day	31% 18% 33% 16% 2	460
	11th to 20th	Day	32% 26% 26% 11% 3 1	460
	21st to end	Day	32% 20% 28% 12% 5% 2	506
April	1st to 10th	Day	35% 18% 28% 11% 5% 2	460
	11th to 20th	Day	31% 21% 27% 13% 5% 2	452
	21st to end	Day	30% 20% 30% 13% 6% 2	460
May	1st to 10th	Day	33% 20% 27% 14% 4 2	463
	11th to 20th	Day	20% 20% 35% 18% 5% 2	487
	21st to end	Day	20% 15% 33% 23% 8% 1	529
June	1st to 10th	Day	21% 14% 37% 19% 8% 1	490
	11th to 20th	Day	18% 17% 31% 22% 9% 2	490
	21st to end	Day	20% 18% 32% 21% 7% 3	490
July	1st to 10th	Day	17% 9% 33% 27% 12% 2	485
	11th to 20th	Day	15% 8% 33% 30% 11% 3	484
	21st to end	Day	14% 11% 33% 29% 10% 3	532
August	1st to 10th	Day	13% 10% 30% 30% 14% 2	486
	11th to 20th	Day	17% 10% 29% 26% 13% 5%	479
	21st to end	Day	12% 10% 32% 26% 15% 5%	539
September	1st to 10th	Day	17% 11% 25% 24% 16% 7%	490
	11th to 20th	Day	18% 14% 26% 16% 16% 10%	490
	21st to end	Day	19% 12% 29% 22% 13% 6%	490
October	1st to 10th	Day	27% 12% 23% 21% 11% 4	490
	11th to 20th	Day	24% 14% 29% 19% 11% 3	435
	21st to end	Day	31% 14% 27% 21% 6%	429
November	1st to 10th	Day	24% 17% 25% 24% 9% 1	378
	11th to 20th	Day	33% 17% 25% 19% 5% 1	370
	21st to end	Day	31% 18% 28% 16% 5% 1	342
December	1st to 10th	Day	27% 26% 26% 17% 4	180
	11th to 20th	Day	34% 21% 32% 11% 3	180
	21st to end	Day	35% 18% 28% 13% 5% 1	198
January	1st to 10th	Night	23% 21% 34% 20% 3	760
	11th to 20th	Night	28% 19% 32% 18% 3	760
	21st to end	Night	22% 19% 36% 20% 3	836
February	1st to 10th	Night	22% 17% 37% 21% 3	760
	11th to 20th	Night	23% 21% 36% 19% 2	743
	21st to end	Night	25% 21% 29% 22% 3	628
March	1st to 10th	Night	27% 18% 34% 18% 3	760
	11th to 20th	Night	25% 20% 30% 20% 4	760
	21st to end	Night	27% 18% 32% 19% 4	836
April	1st to 10th	Night	27% 18% 31% 20% 4	760
	11th to 20th	Night	26% 18% 31% 19% 5%	733
	21st to end	Night	26% 16% 33% 22% 3	570
May	1st to 10th	Night	26% 12% 35% 21% 6% 1	570
	11th to 20th	Night	21% 14% 32% 28% 5%	481
	21st to end	Night	20% 9% 30% 33% 8%	411
June	1st to 10th	Night	19% 9% 34% 29% 8% 1	380
	11th to 20th	Night	18% 11% 27% 34% 10% 1	380
	21st to end	Night	18% 9% 29% 37% 7%	380
July	1st to 10th	Night	16% 5% 28% 42% 10% 1	370
	11th to 20th	Night	13% 5% 24% 42% 15% 2	368
	21st to end	Night	15% 4 27% 39% 13% 1	416
August	1st to 10th	Night	17% 4 22% 42% 14%	473
	11th to 20th	Night	16% 8% 28% 32% 14% 2	581
	21st to end	Night	16% 5% 23% 37% 18% 2	836
September	1st to 10th	Night	15% 6% 30% 31% 17% 1	760
	11th to 20th	Night	16% 8% 28% 28% 18% 3	760
	21st to end	Night	17% 9% 30% 29% 14% 2	760
October	1st to 10th	Night	24% 12% 23% 28% 12% 1	760
	11th to 20th	Night	19% 11% 33% 24% 11% 1	760
	21st to end	Night	25% 15% 29% 24% 6%	836
November	1st to 10th	Night	20% 14% 32% 26% 7% 1	760
	11th to 20th	Night	23% 18% 30% 22% 7% 1	760
	21st to end	Night	24% 18% 29% 22% 6%	760
December	1st to 10th	Night	26% 18% 33% 19% 4	760
	11th to 20th	Night	27% 19% 32% 19% 3	760
	21st to end	Night	27% 19% 32% 20% 3	836

Page generated at 2024-11-03 02:11:14. Version ac07

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