Hawk's Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawk's Hollow Observatory clear sky chart from 2005-11-06 to 2024-11-28.

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	13% 10% 4 8% 5% 5% 4 4 5% 7% 34%	101473
	Night	15% 12% 4 9% 5% 4 4 3 5% 6% 32%	98117
Transparency	Day	47% 6% 12% 21% 13% 1	105044
	Night	51% 6% 11% 19% 12% 1	102687
Seeing	Day	17% 12% 29% 24% 13% 5%	15898
	Night	19% 9% 28% 31% 12% 1	25764

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% 22% 7% 16% 8% 6% 4 3 4 4 12%	2527
	11th to 20th	Day	13% 17% 8% 18% 14% 9% 4 3 3 4 7%	2530
	21st to end	Day	22% 22% 8% 17% 8% 5% 4 2 2 3 8%	2783
February	1st to 10th	Day	11% 17% 7% 15% 10% 6% 4 4 4 4 17%	1743
	11th to 20th	Day	13% 14% 6% 15% 9% 6% 5% 3 4 5% 21%	1848
	21st to end	Day	15% 15% 6% 13% 4 5% 5% 4 5% 5% 22%	1570
March	1st to 10th	Day	15% 13% 3 9% 5% 5% 5% 3 5% 7% 30%	3120
	11th to 20th	Day	11% 8% 5% 10% 7% 5% 5% 4 5% 7% 32%	3373
	21st to end	Day	19% 13% 6% 9% 6% 4 3 3 4 5% 28%	3973
April	1st to 10th	Day	19% 14% 4 7% 5% 4 4 3 5% 6% 30%	2280
	11th to 20th	Day	17% 11% 3 7% 4 3 4 3 6% 6% 36%	2300
	21st to end	Day	17% 9% 3 7% 5% 4 4 3 5% 6% 35%	2470
May	1st to 10th	Day	16% 8% 2 6% 5% 4 4 4 5% 8% 37%	4082
	11th to 20th	Day	14% 7% 2 6% 4 4 4 4 6% 8% 40%	4104
	21st to end	Day	11% 6% 2 5% 4 4 5% 4 6% 8% 45%	4824
June	1st to 10th	Day	10% 6% 2 6% 4 4 5% 4 5% 9% 44%	2660
	11th to 20th	Day	10% 5% 2 5% 5% 4 4 3 5% 8% 47%	2660
	21st to end	Day	11% 6% 2 6% 4 4 4 4 6% 10% 42%	2660
July	1st to 10th	Day	11% 7% 4 6% 5% 5% 5% 4 7% 9% 37%	4440
	11th to 20th	Day	7% 4 2 5% 3 4 5% 6% 7% 9% 50%	4440
	21st to end	Day	8% 6% 2 6% 4 4 5% 4 6% 10% 45%	4813
August	1st to 10th	Day	11% 6% 2 6% 4 3 5% 4 7% 10% 41%	4167
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 5% 8% 46%	4044
	21st to end	Day	7% 6% 2 7% 4 4 5% 4 7% 8% 46%	4215
September	1st to 10th	Day	11% 6% 3 7% 4 5% 5% 3 6% 8% 45%	2256
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 3 6% 8% 48%	2090
	21st to end	Day	12% 7% 3 7% 6% 4 5% 3 5% 8% 41%	2090
October	1st to 10th	Day	15% 7% 2 7% 5% 4 4 3 4 6% 43%	2090
	11th to 20th	Day	20% 10% 4 8% 5% 5% 5% 4 5% 7% 26%	1846
	21st to end	Day	23% 11% 2 9% 6% 6% 5% 3 4 7% 23%	1881
November	1st to 10th	Day	13% 12% 3 7% 5% 4 5% 4 5% 7% 35%	1762
	11th to 20th	Day	16% 18% 5% 11% 6% 5% 4 3 5% 5% 21%	1800
	21st to end	Day	21% 17% 6% 9% 4 4 4 3 4 7% 21%	1773
December	1st to 10th	Day	13% 23% 8% 15% 7% 6% 3 3 3 5% 14%	1558
	11th to 20th	Day	13% 21% 9% 16% 6% 6% 5% 4 4 4 13%	1918
	21st to end	Day	21% 25% 7% 13% 6% 5% 3 3 3 4 9%	2783
January	1st to 10th	Night	16% 22% 10% 16% 7% 4 4 2 3 3 13%	4428
	11th to 20th	Night	14% 18% 10% 19% 11% 6% 4 2 3 3 10%	4440
	21st to end	Night	23% 21% 8% 13% 7% 4 4 3 4 4 10%	4884
February	1st to 10th	Night	13% 18% 5% 13% 10% 5% 4 3 4 5% 19%	2432
	11th to 20th	Night	12% 16% 6% 12% 6% 5% 4 4 4 5% 24%	2218
	21st to end	Night	16% 16% 4 10% 6% 5% 5% 4 4 5% 25%	1884
March	1st to 10th	Night	16% 9% 4 8% 4 5% 4 4 5% 6% 36%	3733
	11th to 20th	Night	9% 8% 3 6% 4 4 4 4 6% 8% 44%	3586
	21st to end	Night	17% 12% 5% 8% 6% 4 5% 4 6% 6% 28%	3674
April	1st to 10th	Night	15% 12% 3 7% 5% 4 4 4 4 6% 36%	1900
	11th to 20th	Night	20% 9% 3 6% 4 3 4 4 5% 5% 37%	1828
	21st to end	Night	16% 10% 3 6% 4 4 4 4 5% 7% 38%	1710
May	1st to 10th	Night	15% 9% 4 8% 4 4 4 4 5% 6% 37%	2813
	11th to 20th	Night	17% 7% 2 6% 4 3 4 3 5% 6% 42%	2786
	21st to end	Night	15% 7% 3 7% 5% 4 4 4 5% 6% 41%	2743
June	1st to 10th	Night	11% 6% 2 5% 4 4 4 5% 5% 9% 45%	1520
	11th to 20th	Night	8% 7% 2 6% 5% 4 5% 3 7% 10% 43%	1520
	21st to end	Night	10% 5% 2 5% 5% 5% 5% 5% 7% 9% 44%	1520
July	1st to 10th	Night	9% 6% 3 8% 5% 4 5% 4 7% 8% 42%	2530
	11th to 20th	Night	7% 4 2 4 3 5% 3 4 6% 7% 56%	2530
	21st to end	Night	7% 5% 2 6% 5% 5% 4 3 5% 8% 50%	2750
August	1st to 10th	Night	9% 6% 2 5% 4 4 4 3 6% 8% 49%	2764
	11th to 20th	Night	11% 5% 2 5% 3 3 4 4 6% 7% 49%	2785
	21st to end	Night	8% 6% 2 8% 5% 4 5% 4 6% 7% 45%	3438
September	1st to 10th	Night	9% 6% 2 6% 3 4 4 3 5% 7% 51%	1905
	11th to 20th	Night	10% 4 2 5% 3 4 3 3 4 6% 55%	2090
	21st to end	Night	13% 8% 3 6% 5% 4 4 3 5% 7% 44%	2090
October	1st to 10th	Night	17% 5% 2 4 3 4 4 3 4 7% 47%	2090
	11th to 20th	Night	21% 10% 3 8% 4 4 3 3 5% 6% 34%	2330
	21st to end	Night	23% 10% 3 6% 4 4 4 3 5% 6% 32%	2717
November	1st to 10th	Night	15% 12% 3 7% 4 4 4 3 5% 6% 37%	2536
	11th to 20th	Night	16% 17% 5% 11% 5% 4 4 4 6% 6% 23%	2600
	21st to end	Night	18% 18% 6% 9% 5% 4 3 4 4 6% 24%	2562
December	1st to 10th	Night	16% 24% 8% 13% 6% 5% 4 3 4 5% 14%	2618
	11th to 20th	Night	16% 20% 8% 14% 7% 5% 4 3 4 4 16%	3279
	21st to end	Night	26% 22% 6% 10% 5% 4 4 3 4 4 12%	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	75% 8% 9% 7% 1	2528
	11th to 20th	Day	82% 5% 8% 4 1	2530
	21st to end	Day	83% 5% 5% 5% 2	2783
February	1st to 10th	Day	70% 5% 9% 13% 3	1743
	11th to 20th	Day	65% 5% 9% 14% 7%	1858
	21st to end	Day	62% 6% 12% 14% 5% 1	1570
March	1st to 10th	Day	54% 5% 13% 20% 8%	3120
	11th to 20th	Day	48% 7% 16% 20% 8% 1	3373
	21st to end	Day	58% 5% 11% 18% 7% 1	3973
April	1st to 10th	Day	54% 5% 10% 19% 11% 1	2280
	11th to 20th	Day	47% 5% 11% 22% 13% 2	2300
	21st to end	Day	48% 6% 12% 18% 14% 2	2470
May	1st to 10th	Day	43% 6% 13% 23% 14% 1	4120
	11th to 20th	Day	39% 6% 15% 24% 14% 3	4108
	21st to end	Day	35% 7% 13% 22% 22% 2	4837
June	1st to 10th	Day	35% 7% 13% 27% 16% 2	2660
	11th to 20th	Day	35% 6% 13% 25% 20% 2	2660
	21st to end	Day	36% 7% 15% 22% 18% 2	2660
July	1st to 10th	Day	42% 5% 14% 21% 15% 3	4371
	11th to 20th	Day	28% 6% 15% 30% 19% 2	4365
	21st to end	Day	34% 6% 14% 22% 22% 2	4662
August	1st to 10th	Day	37% 6% 12% 30% 15% 1	4152
	11th to 20th	Day	34% 6% 12% 29% 17% 1	4083
	21st to end	Day	35% 5% 14% 27% 17% 2	4214
September	1st to 10th	Day	37% 6% 15% 26% 14% 2	2256
	11th to 20th	Day	32% 6% 13% 31% 17% 1	2090
	21st to end	Day	41% 5% 13% 24% 16%	2090
October	1st to 10th	Day	30% 3 8% 39% 19% 1	3480
	11th to 20th	Day	42% 5% 13% 25% 15%	3036
	21st to end	Day	50% 5% 12% 23% 8% 1	3081
November	1st to 10th	Day	48% 8% 12% 21% 11% 1	1762
	11th to 20th	Day	65% 5% 10% 15% 5% 1	1800
	21st to end	Day	64% 6% 13% 12% 4	1773
December	1st to 10th	Day	75% 6% 8% 9% 2	1558
	11th to 20th	Day	74% 6% 10% 9% 1	1915
	21st to end	Day	79% 5% 7% 8% 1	2783
January	1st to 10th	Night	76% 5% 8% 7% 4	4428
	11th to 20th	Night	81% 5% 6% 5% 3	4440
	21st to end	Night	78% 6% 9% 5% 2	4884
February	1st to 10th	Night	68% 5% 9% 12% 5%	2432
	11th to 20th	Night	62% 6% 8% 17% 6%	2219
	21st to end	Night	60% 6% 11% 15% 6% 1	1884
March	1st to 10th	Night	48% 7% 13% 25% 7% 1	3733
	11th to 20th	Night	36% 7% 15% 26% 14% 3	3586
	21st to end	Night	55% 7% 11% 17% 9% 1	3674
April	1st to 10th	Night	48% 6% 11% 21% 13% 1	1900
	11th to 20th	Night	48% 5% 8% 18% 18% 4	1828
	21st to end	Night	45% 5% 12% 19% 15% 3	1710
May	1st to 10th	Night	45% 7% 12% 20% 14% 2	2840
	11th to 20th	Night	42% 6% 9% 22% 18% 3	2787
	21st to end	Night	42% 7% 9% 19% 21% 2	2751
June	1st to 10th	Night	35% 6% 11% 29% 17% 3	1520
	11th to 20th	Night	36% 7% 13% 24% 19% 2	1520
	21st to end	Night	34% 8% 15% 25% 16% 3	1520
July	1st to 10th	Night	39% 5% 13% 25% 12% 7%	2490
	11th to 20th	Night	27% 5% 14% 28% 24% 2	2482
	21st to end	Night	34% 6% 13% 19% 26% 3	2662
August	1st to 10th	Night	33% 5% 13% 31% 17% 1	2755
	11th to 20th	Night	33% 7% 10% 32% 17% 1	2812
	21st to end	Night	37% 5% 10% 27% 18% 2	3438
September	1st to 10th	Night	32% 8% 12% 27% 19% 3	1905
	11th to 20th	Night	30% 5% 11% 32% 20% 2	2090
	21st to end	Night	40% 6% 12% 27% 14% 1	2090
October	1st to 10th	Night	28% 4 9% 36% 21% 2	3480
	11th to 20th	Night	42% 3 13% 23% 19%	3879
	21st to end	Night	44% 4 10% 27% 15%	4467
November	1st to 10th	Night	49% 6% 10% 23% 12% 1	2536
	11th to 20th	Night	60% 6% 12% 15% 6% 1	2600
	21st to end	Night	62% 6% 14% 15% 2	2562
December	1st to 10th	Night	73% 6% 8% 9% 4	2618
	11th to 20th	Night	71% 7% 11% 8% 3	3281
	21st to end	Night	76% 5% 10% 7% 2	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	20% 17% 32% 24% 5% 2	270
	11th to 20th	Day	23% 16% 40% 17% 4	270
	21st to end	Day	27% 14% 32% 22% 5% 1	297
February	1st to 10th	Day	18% 27% 28% 22% 3 2	270
	11th to 20th	Day	18% 23% 37% 19% 4	270
	21st to end	Day	24% 27% 36% 11% 2	225
March	1st to 10th	Day	21% 23% 41% 11% 4	270
	11th to 20th	Day	21% 16% 29% 24% 9% 1	392
	21st to end	Day	27% 15% 29% 20% 7% 1	506
April	1st to 10th	Day	26% 14% 32% 22% 6% 1	460
	11th to 20th	Day	25% 19% 27% 20% 5% 3	452
	21st to end	Day	23% 13% 31% 19% 11% 2	460
May	1st to 10th	Day	22% 14% 30% 23% 8% 3	463
	11th to 20th	Day	16% 11% 29% 24% 15% 4	497
	21st to end	Day	15% 10% 26% 28% 16% 6%	734
June	1st to 10th	Day	11% 9% 33% 29% 13% 5%	680
	11th to 20th	Day	13% 9% 29% 31% 13% 5%	680
	21st to end	Day	13% 9% 32% 29% 13% 4	680
July	1st to 10th	Day	8% 5% 26% 30% 21% 9%	671
	11th to 20th	Day	10% 6% 25% 32% 18% 8%	668
	21st to end	Day	9% 4 29% 33% 18% 8%	739
August	1st to 10th	Day	10% 4 22% 26% 24% 14%	524
	11th to 20th	Day	11% 5% 19% 29% 25% 11%	479
	21st to end	Day	11% 4 21% 29% 24% 10%	539
September	1st to 10th	Day	14% 4 23% 29% 20% 10%	490
	11th to 20th	Day	9% 4 19% 27% 28% 13%	490
	21st to end	Day	15% 12% 21% 26% 19% 8%	490
October	1st to 10th	Day	16% 13% 26% 26% 16% 4	490
	11th to 20th	Day	22% 16% 31% 25% 5% 1	384
	21st to end	Day	30% 14% 38% 11% 4 2	330
November	1st to 10th	Day	22% 16% 31% 23% 7% 1	300
	11th to 20th	Day	22% 23% 35% 14% 5%	300
	21st to end	Day	27% 14% 43% 12% 4	291
December	1st to 10th	Day	26% 23% 29% 14% 7% 1	270
	11th to 20th	Day	20% 21% 38% 16% 5%	270
	21st to end	Day	25% 24% 34% 14% 4	297
January	1st to 10th	Night	21% 15% 32% 24% 7% 1	950
	11th to 20th	Night	25% 12% 32% 25% 5% 1	950
	21st to end	Night	23% 9% 30% 33% 5%	1045
February	1st to 10th	Night	22% 10% 36% 27% 4	798
	11th to 20th	Night	20% 13% 35% 26% 6%	743
	21st to end	Night	24% 13% 40% 20% 3	628
March	1st to 10th	Night	19% 10% 35% 27% 8% 1	760
	11th to 20th	Night	16% 13% 34% 29% 7% 1	760
	21st to end	Night	21% 11% 31% 29% 8% 1	757
April	1st to 10th	Night	19% 9% 35% 30% 6%	570
	11th to 20th	Night	23% 10% 33% 26% 7% 1	563
	21st to end	Night	21% 9% 30% 31% 8% 1	570
May	1st to 10th	Night	18% 8% 31% 35% 9% 1	570
	11th to 20th	Night	20% 5% 29% 35% 12%	561
	21st to end	Night	14% 4 24% 36% 20% 2	617
June	1st to 10th	Night	11% 5% 26% 40% 17%	570
	11th to 20th	Night	11% 4 29% 39% 16%	570
	21st to end	Night	12% 4 22% 42% 19% 1	570
July	1st to 10th	Night	8% 3 15% 43% 29% 2	555
	11th to 20th	Night	7% 4 18% 43% 25% 3	552
	21st to end	Night	8% 1 17% 44% 28% 1	624
August	1st to 10th	Night	9% 2 15% 45% 27% 2	567
	11th to 20th	Night	12% 2 13% 43% 26% 4	564
	21st to end	Night	10% 4 15% 40% 29% 3	627
September	1st to 10th	Night	10% 4 18% 40% 24% 4	575
	11th to 20th	Night	11% 4 17% 37% 27% 4	760
	21st to end	Night	14% 8% 22% 32% 21% 4	760
October	1st to 10th	Night	18% 6% 22% 35% 18% 1	760
	11th to 20th	Night	26% 11% 24% 28% 10% 1	760
	21st to end	Night	28% 10% 31% 24% 7%	836
November	1st to 10th	Night	22% 11% 30% 28% 9%	780
	11th to 20th	Night	25% 14% 32% 23% 6% 1	800
	21st to end	Night	26% 11% 31% 27% 5%	789
December	1st to 10th	Night	27% 13% 31% 23% 6%	908
	11th to 20th	Night	25% 13% 35% 23% 4	950
	21st to end	Night	31% 10% 36% 20% 2	1045

Page generated at 2024-11-25 00:22:19. Version ac07

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