Humarock Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Humarock 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% 8% 2 6% 4 4 4 4 5% 7% 39%	101168
	Night	18% 8% 3 6% 4 4 4 3 5% 7% 38%	97890
Transparency	Day	24% 48% 7% 12% 8% 1	104734
	Night	24% 48% 7% 12% 8% 1	102413
Seeing	Day	18% 6% 22% 31% 18% 4	15141
	Night	20% 8% 28% 29% 13% 2	23990

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	16% 9% 2 5% 2 4 4 4 5% 6% 44%	2517
	11th to 20th	Day	18% 10% 3 5% 3 3 3 3 5% 5% 41%	2520
	21st to end	Day	23% 11% 3 9% 4 4 4 3 4 6% 31%	2773
February	1st to 10th	Day	21% 9% 3 4 4 5% 5% 4 5% 6% 34%	1798
	11th to 20th	Day	14% 9% 3 5% 4 4 4 4 5% 7% 40%	1848
	21st to end	Day	17% 8% 3 5% 4 4 4 4 6% 6% 36%	1570
March	1st to 10th	Day	25% 14% 2 6% 3 3 3 3 4 5% 30%	3116
	11th to 20th	Day	12% 7% 3 7% 4 4 4 3 6% 7% 43%	3380
	21st to end	Day	24% 8% 2 5% 4 4 4 3 4 5% 35%	3960
April	1st to 10th	Day	18% 9% 2 6% 4 3 4 3 6% 5% 39%	2280
	11th to 20th	Day	16% 8% 2 5% 4 4 4 4 5% 7% 41%	2292
	21st to end	Day	18% 6% 2 6% 4 4 4 3 6% 7% 40%	2470
May	1st to 10th	Day	23% 12% 4 8% 5% 4 3 3 5% 6% 27%	4106
	11th to 20th	Day	24% 9% 3 7% 4 4 4 2 5% 6% 33%	4081
	21st to end	Day	14% 6% 2 5% 3 3 4 3 5% 8% 46%	4798
June	1st to 10th	Day	19% 6% 2 4 4 4 4 5% 7% 9% 35%	2660
	11th to 20th	Day	15% 6% 2 5% 5% 4 4 5% 6% 10% 38%	2660
	21st to end	Day	15% 5% 2 6% 6% 5% 4 5% 7% 8% 37%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 6% 5% 5% 7% 10% 36%	4440
	11th to 20th	Day	9% 6% 2 7% 5% 5% 6% 5% 6% 10% 39%	4440
	21st to end	Day	17% 6% 3 6% 4 4 4 5% 5% 8% 37%	4766
August	1st to 10th	Day	14% 7% 2 7% 5% 5% 6% 5% 7% 9% 33%	4105
	11th to 20th	Day	11% 8% 3 8% 4 5% 5% 4 6% 7% 39%	4045
	21st to end	Day	8% 4 1 5% 4 5% 5% 5% 7% 9% 47%	4190
September	1st to 10th	Day	13% 6% 2 5% 4 4 4 3 6% 7% 48%	2247
	11th to 20th	Day	15% 5% 2 4 3 3 3 3 4 6% 53%	2090
	21st to end	Day	19% 6% 2 5% 4 3 4 3 5% 6% 44%	2090
October	1st to 10th	Day	23% 5% 2 5% 3 3 4 3 4 6% 43%	2090
	11th to 20th	Day	14% 6% 2 4 3 4 4 3 5% 8% 47%	1874
	21st to end	Day	19% 6% 2 5% 3 3 4 3 5% 6% 43%	1881
November	1st to 10th	Day	18% 7% 2 5% 4 2 4 2 4 7% 45%	1708
	11th to 20th	Day	18% 8% 2 4 4 4 4 3 5% 6% 43%	1710
	21st to end	Day	18% 7% 2 5% 3 4 5% 3 5% 6% 41%	1710
December	1st to 10th	Day	17% 10% 2 6% 4 4 4 3 4 7% 38%	1615
	11th to 20th	Day	20% 9% 3 5% 5% 3 3 3 4 6% 39%	1906
	21st to end	Day	22% 10% 3 7% 4 4 4 3 4 6% 32%	2772
January	1st to 10th	Night	19% 7% 1 5% 3 3 3 3 4 6% 45%	4429
	11th to 20th	Night	15% 11% 4 8% 4 3 3 3 4 5% 38%	4440
	21st to end	Night	23% 14% 5% 8% 4 3 4 3 4 5% 26%	4881
February	1st to 10th	Night	17% 10% 3 7% 4 4 4 4 5% 7% 35%	2380
	11th to 20th	Night	17% 9% 3 6% 4 3 4 4 6% 6% 37%	2218
	21st to end	Night	18% 8% 2 5% 4 4 3 3 5% 5% 42%	1884
March	1st to 10th	Night	30% 10% 2 5% 3 3 3 3 4 5% 31%	3724
	11th to 20th	Night	11% 10% 3 6% 5% 5% 5% 4 5% 6% 40%	3578
	21st to end	Night	26% 9% 2 6% 4 4 5% 4 4 4 33%	3670
April	1st to 10th	Night	18% 10% 3 7% 5% 4 4 2 6% 7% 36%	1900
	11th to 20th	Night	18% 9% 1 6% 5% 5% 5% 3 5% 6% 38%	1835
	21st to end	Night	18% 7% 2 7% 5% 4 5% 3 5% 5% 38%	1710
May	1st to 10th	Night	24% 11% 4 7% 4 3 4 3 4 7% 28%	2834
	11th to 20th	Night	24% 10% 3 8% 4 5% 5% 4 5% 7% 25%	2813
	21st to end	Night	16% 6% 2 6% 4 5% 4 3 7% 8% 38%	2804
June	1st to 10th	Night	18% 8% 3 6% 4 3 4 4 7% 7% 37%	1520
	11th to 20th	Night	16% 8% 3 7% 5% 3 5% 4 5% 8% 37%	1520
	21st to end	Night	16% 7% 2 6% 3 5% 4 4 6% 10% 38%	1520
July	1st to 10th	Night	9% 6% 3 8% 5% 4 5% 5% 7% 10% 36%	2520
	11th to 20th	Night	9% 6% 2 7% 5% 5% 4 5% 9% 9% 38%	2520
	21st to end	Night	17% 8% 3 7% 4 4 5% 5% 5% 8% 34%	2754
August	1st to 10th	Night	16% 7% 3 8% 5% 5% 6% 5% 7% 9% 29%	2825
	11th to 20th	Night	9% 9% 3 7% 4 5% 6% 4 8% 7% 38%	2782
	21st to end	Night	9% 3 2 4 3 4 3 4 6% 8% 54%	3464
September	1st to 10th	Night	11% 6% 2 6% 5% 3 4 4 6% 7% 47%	1933
	11th to 20th	Night	14% 5% 2 5% 3 3 3 3 5% 7% 52%	2090
	21st to end	Night	18% 6% 2 6% 3 3 4 4 6% 6% 42%	2090
October	1st to 10th	Night	22% 5% 3 5% 4 3 3 3 4 5% 42%	2090
	11th to 20th	Night	15% 6% 2 6% 3 3 4 3 5% 7% 46%	2303
	21st to end	Night	21% 8% 2 6% 3 4 4 3 5% 5% 39%	2717
November	1st to 10th	Night	16% 6% 2 6% 4 3 4 4 5% 6% 45%	2470
	11th to 20th	Night	17% 9% 2 6% 3 3 3 3 4 6% 44%	2470
	21st to end	Night	16% 6% 2 5% 4 3 5% 3 5% 8% 41%	2470
December	1st to 10th	Night	19% 9% 3 6% 4 4 4 3 5% 6% 37%	2560
	11th to 20th	Night	18% 8% 2 6% 4 3 4 3 6% 7% 38%	3288
	21st to end	Night	20% 10% 3 7% 4 4 3 3 5% 6% 34%	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	25% 37% 7% 23% 7% 1	2518
	11th to 20th	Day	26% 39% 5% 19% 8% 1	2520
	21st to end	Day	39% 42% 6% 10% 3 1	2773
February	1st to 10th	Day	18% 65% 6% 6% 4 1	1798
	11th to 20th	Day	17% 64% 4 8% 7% 1	1857
	21st to end	Day	14% 66% 5% 9% 5% 1	1570
March	1st to 10th	Day	40% 41% 6% 6% 6% 1	3119
	11th to 20th	Day	18% 44% 12% 15% 9% 1	3380
	21st to end	Day	35% 41% 3 8% 8% 4	3960
April	1st to 10th	Day	19% 65% 3 7% 5% 1	2280
	11th to 20th	Day	14% 66% 4 9% 6% 1	2292
	21st to end	Day	17% 65% 3 7% 7% 1	2470
May	1st to 10th	Day	36% 46% 7% 7% 4	4120
	11th to 20th	Day	35% 42% 10% 9% 3	4085
	21st to end	Day	21% 42% 8% 15% 14%	4798
June	1st to 10th	Day	14% 66% 5% 9% 6%	2660
	11th to 20th	Day	12% 66% 6% 9% 6% 1	2660
	21st to end	Day	14% 64% 5% 9% 8%	2660
July	1st to 10th	Day	26% 40% 11% 11% 11% 1	4370
	11th to 20th	Day	24% 40% 12% 14% 9%	4365
	21st to end	Day	30% 38% 9% 14% 8% 1	4614
August	1st to 10th	Day	31% 40% 12% 13% 4	4092
	11th to 20th	Day	28% 40% 8% 19% 5%	4084
	21st to end	Day	15% 40% 11% 21% 12%	4190
September	1st to 10th	Day	14% 60% 5% 13% 8%	2247
	11th to 20th	Day	15% 60% 3 10% 9% 1	2090
	21st to end	Day	19% 60% 4 9% 7%	2090
October	1st to 10th	Day	23% 39% 8% 17% 12% 1	3480
	11th to 20th	Day	16% 37% 3 20% 20% 2	3090
	21st to end	Day	16% 38% 8% 23% 13% 1	3081
November	1st to 10th	Day	19% 58% 6% 9% 6% 1	1708
	11th to 20th	Day	18% 60% 4 7% 10% 1	1710
	21st to end	Day	16% 60% 6% 11% 6% 2	1710
December	1st to 10th	Day	21% 61% 6% 5% 7%	1615
	11th to 20th	Day	23% 49% 7% 8% 9% 3	1906
	21st to end	Day	33% 40% 9% 11% 6%	2772
January	1st to 10th	Night	24% 38% 8% 22% 6% 2	4429
	11th to 20th	Night	29% 38% 7% 16% 9% 1	4440
	21st to end	Night	43% 41% 5% 7% 4 1	4881
February	1st to 10th	Night	18% 65% 5% 6% 5% 1	2380
	11th to 20th	Night	18% 64% 3 7% 7% 1	2220
	21st to end	Night	15% 65% 3 8% 7% 2	1884
March	1st to 10th	Night	39% 41% 5% 8% 5% 2	3734
	11th to 20th	Night	22% 45% 9% 10% 13% 1	3579
	21st to end	Night	38% 41% 4 4 8% 5%	3670
April	1st to 10th	Night	20% 65% 2 6% 5% 1	1900
	11th to 20th	Night	15% 66% 4 7% 6% 1	1835
	21st to end	Night	17% 65% 4 6% 7% 1	1710
May	1st to 10th	Night	35% 44% 9% 9% 3	2840
	11th to 20th	Night	37% 45% 10% 6% 2	2814
	21st to end	Night	24% 45% 9% 13% 9% 1	2805
June	1st to 10th	Night	14% 66% 5% 9% 6%	1520
	11th to 20th	Night	13% 66% 5% 9% 6%	1520
	21st to end	Night	14% 65% 4 10% 7% 1	1520
July	1st to 10th	Night	26% 40% 7% 13% 13%	2480
	11th to 20th	Night	25% 40% 13% 14% 8%	2472
	21st to end	Night	32% 39% 8% 11% 9% 1	2666
August	1st to 10th	Night	35% 41% 9% 10% 5% 1	2813
	11th to 20th	Night	26% 43% 10% 16% 5%	2809
	21st to end	Night	13% 39% 11% 18% 18%	3464
September	1st to 10th	Night	14% 61% 5% 12% 7% 1	1933
	11th to 20th	Night	16% 60% 3 9% 11% 1	2090
	21st to end	Night	19% 61% 3 8% 8%	2090
October	1st to 10th	Night	25% 39% 8% 19% 7% 1	3480
	11th to 20th	Night	12% 37% 6% 17% 26% 2	3826
	21st to end	Night	17% 37% 7% 23% 14% 1	4467
November	1st to 10th	Night	19% 59% 5% 10% 7% 1	2470
	11th to 20th	Night	17% 60% 4 8% 9% 2	2470
	21st to end	Night	16% 60% 6% 12% 5% 1	2470
December	1st to 10th	Night	21% 60% 5% 7% 6%	2560
	11th to 20th	Night	23% 50% 6% 8% 12% 1	3288
	21st to end	Night	32% 39% 8% 15% 6%	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	26% 12% 32% 23% 7% 1	180
	11th to 20th	Day	20% 16% 32% 27% 6%	180
	21st to end	Day	20% 8% 40% 24% 8% 1	199
February	1st to 10th	Day	25% 11% 35% 25% 4	412
	11th to 20th	Day	20% 14% 43% 21% 3	456
	21st to end	Day	18% 13% 31% 30% 7% 1	382
March	1st to 10th	Day	21% 10% 35% 28% 7%	460
	11th to 20th	Day	16% 11% 37% 30% 6% 1	460
	21st to end	Day	23% 9% 33% 24% 9% 2	506
April	1st to 10th	Day	24% 8% 28% 27% 10% 2	460
	11th to 20th	Day	21% 5% 27% 37% 9%	452
	21st to end	Day	23% 4 23% 37% 12% 2	460
May	1st to 10th	Day	26% 5% 25% 31% 11% 2	463
	11th to 20th	Day	17% 2 22% 40% 16% 3	487
	21st to end	Day	17% 3 15% 36% 24% 4	529
June	1st to 10th	Day	19% 2 14% 39% 23% 4	490
	11th to 20th	Day	15% 3 15% 41% 21% 5%	490
	21st to end	Day	14% 3 11% 42% 25% 4	490
July	1st to 10th	Day	14% 3 10% 33% 33% 8%	485
	11th to 20th	Day	10% 3 10% 32% 37% 8%	484
	21st to end	Day	12% 2 8% 37% 37% 3	532
August	1st to 10th	Day	10% 2 9% 39% 35% 5%	486
	11th to 20th	Day	12% 3 11% 33% 33% 9%	479
	21st to end	Day	13% 3 10% 33% 32% 10%	539
September	1st to 10th	Day	17% 3 13% 29% 29% 10%	490
	11th to 20th	Day	17% 5% 16% 27% 24% 12%	490
	21st to end	Day	21% 4 17% 32% 20% 6%	490
October	1st to 10th	Day	23% 4 19% 26% 22% 5%	490
	11th to 20th	Day	15% 6% 29% 25% 22% 3	420
	21st to end	Day	23% 6% 27% 29% 12% 3	429
November	1st to 10th	Day	16% 8% 24% 34% 16% 2	378
	11th to 20th	Day	25% 11% 30% 23% 10% 1	370
	21st to end	Day	20% 14% 30% 25% 9% 1	370
December	1st to 10th	Day	21% 9% 40% 23% 7%	275
	11th to 20th	Day	24% 13% 32% 26% 4	180
	21st to end	Day	25% 13% 32% 22% 8% 1	198
January	1st to 10th	Night	22% 12% 41% 21% 4	760
	11th to 20th	Night	26% 16% 35% 19% 3	760
	21st to end	Night	20% 15% 40% 21% 4 1	836
February	1st to 10th	Night	22% 14% 38% 24% 3	760
	11th to 20th	Night	23% 14% 42% 17% 3	743
	21st to end	Night	21% 14% 36% 23% 6%	628
March	1st to 10th	Night	24% 11% 35% 24% 6%	760
	11th to 20th	Night	21% 10% 36% 26% 7% 1	760
	21st to end	Night	23% 8% 35% 25% 9% 1	836
April	1st to 10th	Night	22% 7% 34% 29% 8%	760
	11th to 20th	Night	21% 5% 31% 34% 9%	711
	21st to end	Night	20% 5% 28% 35% 12% 1	570
May	1st to 10th	Night	26% 5% 23% 34% 10% 2	570
	11th to 20th	Night	20% 4 27% 34% 15% 1	562
	21st to end	Night	19% 4 14% 46% 15% 2	451
June	1st to 10th	Night	20% 3 15% 38% 21% 3	380
	11th to 20th	Night	18% 3 16% 42% 19% 2	380
	21st to end	Night	17% 3 14% 47% 19% 1	380
July	1st to 10th	Night	12% 2 9% 48% 27% 2	370
	11th to 20th	Night	12% 3 9% 45% 29% 3	368
	21st to end	Night	13% 3 11% 44% 29% 1	419
August	1st to 10th	Night	8% 3 11% 45% 31% 2	568
	11th to 20th	Night	12% 3 10% 43% 30% 3	562
	21st to end	Night	13% 2 9% 37% 33% 6%	824
September	1st to 10th	Night	13% 2 16% 38% 29% 3	760
	11th to 20th	Night	16% 3 15% 34% 25% 7%	760
	21st to end	Night	19% 3 18% 33% 22% 5%	760
October	1st to 10th	Night	24% 5% 19% 28% 20% 4	760
	11th to 20th	Night	17% 6% 30% 29% 16% 2	760
	21st to end	Night	25% 7% 31% 25% 10% 1	836
November	1st to 10th	Night	18% 6% 29% 31% 13% 1	760
	11th to 20th	Night	21% 15% 32% 22% 9% 1	760
	21st to end	Night	19% 16% 33% 25% 6% 1	760
December	1st to 10th	Night	24% 13% 37% 19% 6%	760
	11th to 20th	Night	21% 17% 38% 20% 4	760
	21st to end	Night	23% 13% 40% 21% 3	836

Page generated at 2024-11-03 02:11:22. Version ac07

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