Hawk Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawk 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	12% 7% 3 7% 5% 4 5% 4 5% 7% 42%	101439
	Night	10% 7% 3 7% 4 4 4 3 5% 7% 45%	97686
Transparency	Day	40% 6% 13% 25% 14% 2	105056
	Night	38% 6% 13% 25% 16% 2	102201
Seeing	Day	15% 10% 31% 29% 13% 2	15935
	Night	13% 8% 34% 34% 10% 1	25808

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	11% 13% 4 14% 9% 8% 7% 4 5% 4 21%	2446
	11th to 20th	Day	5% 14% 6% 11% 6% 5% 9% 3 8% 10% 23%	2662
	21st to end	Day	7% 13% 6% 14% 9% 8% 7% 4 5% 6% 23%	3135
February	1st to 10th	Day	9% 11% 3 10% 8% 7% 7% 4 6% 6% 27%	1710
	11th to 20th	Day	9% 10% 3 9% 7% 6% 6% 4 5% 6% 35%	1687
	21st to end	Day	11% 10% 3 9% 5% 5% 5% 4 5% 7% 36%	1570
March	1st to 10th	Day	12% 8% 4 8% 4 3 3 3 4 6% 43%	3306
	11th to 20th	Day	9% 8% 3 7% 4 3 4 3 4 7% 47%	3480
	21st to end	Day	25% 12% 4 9% 4 4 4 3 5% 5% 25%	3814
April	1st to 10th	Day	16% 8% 2 7% 5% 4 4 3 5% 6% 38%	2149
	11th to 20th	Day	19% 8% 3 6% 4 3 5% 4 5% 6% 37%	2442
	21st to end	Day	21% 8% 2 6% 3 4 3 3 5% 6% 38%	2470
May	1st to 10th	Day	17% 6% 2 6% 5% 4 5% 4 6% 7% 38%	4082
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 4 6% 48%	4082
	21st to end	Day	18% 6% 2 6% 4 4 4 3 6% 7% 40%	4789
June	1st to 10th	Day	12% 5% 2 5% 4 3 4 4 5% 8% 48%	2759
	11th to 20th	Day	14% 5% 2 5% 4 4 4 4 5% 7% 43%	2850
	21st to end	Day	8% 5% 2 4 4 4 4 4 7% 8% 49%	2850
July	1st to 10th	Day	10% 4 2 6% 5% 5% 5% 4 7% 10% 42%	4723
	11th to 20th	Day	6% 3 1 4 3 3 4 3 5% 7% 59%	4373
	21st to end	Day	4 3 2 5% 4 4 5% 4 8% 10% 53%	4465
August	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 4 6% 9% 45%	4104
	11th to 20th	Day	16% 8% 3 6% 4 4 5% 4 6% 7% 37%	4041
	21st to end	Day	9% 4 2 6% 4 4 5% 3 5% 7% 52%	4532
September	1st to 10th	Day	14% 5% 2 4 3 3 3 2 4 6% 53%	2209
	11th to 20th	Day	10% 4 2 4 4 3 3 3 5% 6% 56%	2090
	21st to end	Day	10% 4 2 5% 4 3 4 3 6% 6% 54%	2090
October	1st to 10th	Day	16% 6% 1 5% 3 3 2 3 5% 6% 49%	1962
	11th to 20th	Day	13% 7% 2 4 3 2 3 3 4 5% 53%	1900
	21st to end	Day	16% 7% 3 7% 3 3 2 2 5% 5% 46%	2007
November	1st to 10th	Day	10% 7% 2 6% 4 3 3 4 6% 8% 46%	1709
	11th to 20th	Day	8% 8% 3 12% 5% 5% 4 4 4 6% 41%	1582
	21st to end	Day	12% 8% 3 7% 4 4 5% 4 5% 7% 41%	1520
December	1st to 10th	Day	8% 10% 3 11% 6% 4 4 4 7% 7% 36%	1520
	11th to 20th	Day	7% 13% 5% 10% 7% 6% 6% 4 5% 7% 31%	1887
	21st to end	Day	17% 7% 5% 15% 5% 4 4 3 6% 7% 25%	2442
January	1st to 10th	Night	10% 11% 3 13% 10% 6% 6% 4 5% 6% 25%	4504
	11th to 20th	Night	4 10% 4 11% 7% 5% 8% 5% 9% 8% 28%	4304
	21st to end	Night	6% 12% 6% 13% 5% 6% 6% 5% 5% 7% 29%	4532
February	1st to 10th	Night	9% 11% 3 10% 6% 5% 3 4 6% 6% 37%	2470
	11th to 20th	Night	8% 10% 3 8% 5% 5% 4 3 5% 7% 41%	2396
	21st to end	Night	8% 8% 3 8% 6% 4 4 4 6% 6% 43%	1884
March	1st to 10th	Night	9% 7% 2 6% 3 3 3 3 5% 7% 51%	3551
	11th to 20th	Night	9% 7% 2 6% 3 4 4 3 6% 8% 49%	3480
	21st to end	Night	24% 12% 4 7% 6% 4 4 2 5% 6% 27%	3817
April	1st to 10th	Night	14% 8% 2 6% 4 5% 4 4 5% 7% 40%	2027
	11th to 20th	Night	18% 8% 2 6% 4 3 3 2 4 6% 44%	1689
	21st to end	Night	17% 7% 2 6% 4 3 4 3 6% 6% 41%	1710
May	1st to 10th	Night	18% 5% 2 4 3 3 3 3 5% 7% 46%	2823
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 5% 8% 51%	2823
	21st to end	Night	16% 5% 2 5% 4 4 4 3 5% 7% 44%	2776
June	1st to 10th	Night	7% 5% 1 5% 2 3 4 3 5% 8% 55%	1416
	11th to 20th	Night	7% 4 2 5% 4 4 4 4 6% 8% 52%	1330
	21st to end	Night	7% 4 1 3 3 2 4 4 6% 8% 58%	1330
July	1st to 10th	Night	9% 4 2 5% 3 3 5% 4 6% 8% 50%	2242
	11th to 20th	Night	5% 2 1 3 3 3 4 3 4 7% 67%	2596
	21st to end	Night	3 2 1 3 3 3 5% 4 6% 11% 59%	3098
August	1st to 10th	Night	6% 4 2 6% 4 4 6% 5% 6% 8% 49%	2836
	11th to 20th	Night	12% 5% 2 4 4 3 4 3 5% 8% 49%	2798
	21st to end	Night	8% 4 1 4 3 4 4 3 6% 8% 56%	3135
September	1st to 10th	Night	9% 3 2 4 3 2 3 3 5% 7% 59%	1966
	11th to 20th	Night	9% 4 2 3 3 3 2 3 5% 7% 58%	2090
	21st to end	Night	9% 5% 1 3 2 3 3 4 4 7% 59%	2090
October	1st to 10th	Night	15% 5% 1 4 3 3 3 2 4 6% 54%	2199
	11th to 20th	Night	12% 5% 3 5% 3 3 4 3 4 5% 54%	2280
	21st to end	Night	14% 7% 2 5% 3 3 3 3 4 6% 50%	2589
November	1st to 10th	Night	10% 5% 1 4 4 3 5% 4 4 7% 52%	2470
	11th to 20th	Night	8% 7% 3 8% 4 4 4 3 6% 8% 45%	2597
	21st to end	Night	9% 8% 2 6% 4 4 3 3 5% 7% 48%	2660
December	1st to 10th	Night	8% 9% 3 9% 5% 5% 4 4 6% 7% 40%	2660
	11th to 20th	Night	10% 9% 3 8% 5% 4 5% 4 5% 7% 39%	3293
	21st to end	Night	18% 10% 4 14% 5% 4 4 3 4 5% 28%	5225

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	63% 6% 12% 14% 5%	2447
	11th to 20th	Day	55% 5% 10% 23% 7%	2662
	21st to end	Day	61% 7% 14% 13% 6%	3135
February	1st to 10th	Day	55% 6% 14% 15% 9% 1	1710
	11th to 20th	Day	49% 6% 14% 20% 10% 1	1696
	21st to end	Day	47% 8% 12% 20% 11% 1	1570
March	1st to 10th	Day	42% 5% 12% 32% 8% 1	3306
	11th to 20th	Day	37% 5% 10% 32% 13% 3	3480
	21st to end	Day	61% 8% 13% 14% 3 1	3814
April	1st to 10th	Day	46% 5% 12% 23% 12% 1	2149
	11th to 20th	Day	48% 6% 10% 22% 13% 2	2442
	21st to end	Day	46% 6% 12% 24% 11% 1	2470
May	1st to 10th	Day	42% 8% 10% 24% 16%	4120
	11th to 20th	Day	35% 6% 12% 28% 16% 3	4086
	21st to end	Day	42% 7% 10% 25% 15% 1	4802
June	1st to 10th	Day	33% 7% 15% 29% 13% 2	2759
	11th to 20th	Day	38% 7% 13% 25% 15% 3	2850
	21st to end	Day	31% 8% 14% 29% 15% 3	2850
July	1st to 10th	Day	36% 7% 19% 25% 12% 1	4649
	11th to 20th	Day	24% 5% 13% 33% 20% 4	4298
	21st to end	Day	24% 8% 16% 29% 21% 2	4325
August	1st to 10th	Day	34% 7% 15% 29% 13% 2	4090
	11th to 20th	Day	45% 7% 14% 25% 9% 1	4080
	21st to end	Day	31% 7% 16% 27% 16% 3	4531
September	1st to 10th	Day	33% 5% 10% 31% 18% 2	2209
	11th to 20th	Day	29% 6% 15% 33% 15% 1	2090
	21st to end	Day	30% 6% 10% 31% 21% 2	2090
October	1st to 10th	Day	25% 3 8% 27% 33% 4	3261
	11th to 20th	Day	29% 4 15% 27% 21% 4	3140
	21st to end	Day	39% 4 13% 24% 18% 2	3288
November	1st to 10th	Day	35% 5% 17% 26% 14% 3	1709
	11th to 20th	Day	43% 6% 14% 23% 13% 1	1582
	21st to end	Day	41% 7% 15% 24% 13% 1	1520
December	1st to 10th	Day	45% 5% 17% 22% 10% 1	1520
	11th to 20th	Day	51% 6% 18% 20% 5%	1884
	21st to end	Day	57% 5% 13% 17% 7% 1	2442
January	1st to 10th	Night	58% 6% 10% 18% 7%	4504
	11th to 20th	Night	49% 6% 13% 21% 9% 1	4304
	21st to end	Night	53% 9% 14% 15% 8%	4532
February	1st to 10th	Night	47% 5% 12% 23% 11% 1	2470
	11th to 20th	Night	43% 5% 12% 24% 13% 3	2397
	21st to end	Night	40% 5% 13% 24% 14% 3	1884
March	1st to 10th	Night	33% 5% 12% 28% 21% 2	3551
	11th to 20th	Night	33% 6% 10% 30% 19% 2	3480
	21st to end	Night	58% 6% 14% 16% 5% 1	3817
April	1st to 10th	Night	41% 7% 14% 23% 14% 1	2027
	11th to 20th	Night	44% 4 9% 22% 18% 2	1689
	21st to end	Night	43% 6% 11% 24% 14% 2	1710
May	1st to 10th	Night	37% 7% 13% 22% 19% 2	2850
	11th to 20th	Night	31% 7% 11% 26% 21% 4	2824
	21st to end	Night	39% 7% 10% 27% 16% 1	2784
June	1st to 10th	Night	26% 8% 15% 29% 18% 3	1416
	11th to 20th	Night	28% 7% 15% 27% 19% 4	1330
	21st to end	Night	23% 6% 16% 30% 22% 2	1330
July	1st to 10th	Night	31% 6% 21% 27% 13% 2	2207
	11th to 20th	Night	19% 5% 14% 39% 20% 4	2548
	21st to end	Night	19% 8% 18% 31% 22% 3	2999
August	1st to 10th	Night	30% 8% 14% 30% 16% 2	2826
	11th to 20th	Night	34% 7% 16% 29% 13% 2	2825
	21st to end	Night	26% 7% 17% 25% 22% 4	3135
September	1st to 10th	Night	25% 7% 12% 30% 22% 4	1966
	11th to 20th	Night	26% 5% 14% 34% 18% 2	2090
	21st to end	Night	25% 5% 10% 33% 24% 3	2090
October	1st to 10th	Night	20% 3 6% 24% 43% 4	3667
	11th to 20th	Night	26% 3 13% 29% 26% 3	3779
	21st to end	Night	38% 4 12% 30% 16% 1	4263
November	1st to 10th	Night	31% 5% 15% 24% 21% 4	2470
	11th to 20th	Night	36% 5% 15% 26% 16% 2	2597
	21st to end	Night	35% 5% 15% 28% 16% 1	2660
December	1st to 10th	Night	42% 5% 18% 25% 9%	2660
	11th to 20th	Night	43% 6% 21% 24% 7%	3295
	21st to end	Night	58% 4 11% 19% 7% 1	5225

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	14% 11% 34% 26% 12% 2	270
	11th to 20th	Day	17% 13% 33% 29% 7% 1	270
	21st to end	Day	16% 10% 37% 26% 10% 1	297
February	1st to 10th	Day	11% 19% 39% 29% 3	270
	11th to 20th	Day	15% 15% 41% 22% 6% 1	270
	21st to end	Day	20% 13% 43% 19% 4	225
March	1st to 10th	Day	19% 17% 40% 19% 4 1	270
	11th to 20th	Day	21% 9% 41% 18% 11% 1	270
	21st to end	Day	28% 13% 35% 18% 5% 1	297
April	1st to 10th	Day	25% 18% 36% 17% 4	329
	11th to 20th	Day	26% 15% 31% 22% 5% 1	640
	21st to end	Day	27% 14% 26% 21% 10% 2	650
May	1st to 10th	Day	18% 14% 32% 26% 9% 1	653
	11th to 20th	Day	20% 12% 29% 25% 12% 3	675
	21st to end	Day	21% 7% 29% 30% 10% 2	734
June	1st to 10th	Day	9% 7% 26% 35% 20% 4	680
	11th to 20th	Day	14% 8% 36% 25% 14% 3	680
	21st to end	Day	10% 7% 33% 33% 15% 2	680
July	1st to 10th	Day	7% 4 21% 40% 23% 5%	671
	11th to 20th	Day	6% 6% 28% 37% 20% 3	668
	21st to end	Day	5% 3 25% 41% 22% 4	739
August	1st to 10th	Day	8% 3 26% 38% 21% 4	676
	11th to 20th	Day	11% 4 25% 34% 21% 5%	665
	21st to end	Day	8% 5% 27% 36% 21% 4	748
September	1st to 10th	Day	17% 7% 28% 29% 17% 3	419
	11th to 20th	Day	9% 5% 38% 31% 15% 3	300
	21st to end	Day	13% 16% 31% 25% 12% 3	300
October	1st to 10th	Day	19% 9% 29% 27% 10% 5%	300
	11th to 20th	Day	15% 18% 32% 26% 8% 1	300
	21st to end	Day	22% 15% 36% 21% 7%	330
November	1st to 10th	Day	21% 11% 36% 20% 9% 3	282
	11th to 20th	Day	13% 19% 41% 22% 5%	270
	21st to end	Day	21% 16% 33% 21% 9%	270
December	1st to 10th	Day	11% 11% 45% 24% 8% 1	270
	11th to 20th	Day	18% 11% 41% 26% 5%	270
	21st to end	Day	23% 15% 35% 25% 3	297
January	1st to 10th	Night	12% 9% 37% 30% 10% 1	950
	11th to 20th	Night	13% 11% 35% 33% 7% 1	950
	21st to end	Night	14% 10% 38% 31% 7%	1045
February	1st to 10th	Night	15% 11% 38% 30% 5% 1	950
	11th to 20th	Night	13% 10% 39% 30% 7% 1	922
	21st to end	Night	13% 7% 38% 32% 9% 1	628
March	1st to 10th	Night	13% 8% 41% 32% 6% 1	655
	11th to 20th	Night	15% 11% 38% 32% 4	570
	21st to end	Night	21% 9% 35% 27% 8%	627
April	1st to 10th	Night	18% 14% 39% 27% 3	570
	11th to 20th	Night	22% 14% 31% 27% 6% 1	563
	21st to end	Night	19% 13% 33% 25% 9% 1	570
May	1st to 10th	Night	18% 7% 36% 29% 10%	570
	11th to 20th	Night	16% 11% 31% 31% 11% 1	561
	21st to end	Night	18% 7% 32% 30% 13%	617
June	1st to 10th	Night	10% 7% 25% 43% 15% 1	570
	11th to 20th	Night	8% 5% 35% 41% 11% 1	570
	21st to end	Night	9% 3 27% 46% 15%	570
July	1st to 10th	Night	6% 2 24% 41% 26% 1	555
	11th to 20th	Night	4 2 26% 51% 17%	552
	21st to end	Night	5% 2 23% 53% 16% 1	624
August	1st to 10th	Night	6% 3 25% 46% 19% 1	567
	11th to 20th	Night	9% 3 23% 39% 24% 1	564
	21st to end	Night	6% 3 28% 44% 19% 1	627
September	1st to 10th	Night	10% 5% 26% 43% 15% 2	570
	11th to 20th	Night	9% 5% 33% 36% 13% 3	570
	21st to end	Night	13% 6% 32% 35% 12% 1	570
October	1st to 10th	Night	16% 9% 33% 29% 12% 1	679
	11th to 20th	Night	16% 11% 37% 29% 7%	760
	21st to end	Night	17% 12% 35% 27% 9%	917
November	1st to 10th	Night	12% 10% 36% 33% 9% 1	950
	11th to 20th	Night	13% 11% 39% 30% 7%	950
	21st to end	Night	13% 9% 38% 33% 7%	950
December	1st to 10th	Night	13% 9% 38% 32% 7%	950
	11th to 20th	Night	17% 7% 36% 31% 8%	950
	21st to end	Night	21% 11% 34% 28% 6%	1045

Page generated at 2024-11-03 01:11:13. Version ac07

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