Hoback
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hoback clear sky chart from 2005-11-06 to 2024-10-25.

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	5% 12% 4 9% 5% 4 4 3 5% 6% 43%	101944
	Night	5% 13% 5% 10% 4 4 4 3 5% 6% 43%	97061
Transparency	Day	41% 6% 10% 19% 16% 8%	101694
	Night	42% 6% 12% 20% 15% 6%	96901
Seeing	Day	15% 19% 32% 24% 9% 2	15608
	Night	13% 11% 25% 35% 15% 1	25201

By Month

Percentage Cloud Cover SW (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	2 20% 11% 18% 6% 4 3 3 4 5% 23%	2643
	11th to 20th	Day	4 18% 7% 17% 7% 3 3 3 4 6% 27%	2860
	21st to end	Day	3 28% 8% 13% 4 3 3 2 3 5% 27%	3146
February	1st to 10th	Day	4 23% 9% 16% 6% 4 4 3 5% 5% 21%	1710
	11th to 20th	Day	3 23% 9% 15% 7% 3 4 2 4 5% 26%	1665
	21st to end	Day	4 20% 8% 19% 8% 4 4 3 4 4 21%	1517
March	1st to 10th	Day	3 21% 8% 16% 5% 4 3 3 3 5% 30%	3400
	11th to 20th	Day	4 16% 5% 8% 4 3 3 3 4 5% 44%	3490
	21st to end	Day	6% 26% 9% 15% 7% 5% 4 3 4 5% 15%	3825
April	1st to 10th	Day	8% 19% 7% 11% 6% 4 3 3 6% 6% 27%	2185
	11th to 20th	Day	7% 16% 5% 13% 7% 5% 4 3 5% 6% 29%	2379
	21st to end	Day	8% 18% 5% 10% 5% 5% 4 3 5% 8% 30%	2470
May	1st to 10th	Day	9% 18% 4 9% 6% 5% 5% 4 5% 6% 28%	4110
	11th to 20th	Day	6% 7% 2 6% 5% 4 5% 5% 7% 8% 44%	4166
	21st to end	Day	8% 14% 5% 9% 5% 5% 4 4 5% 5% 35%	4825
June	1st to 10th	Day	10% 8% 2 6% 5% 4 4 5% 7% 9% 40%	2660
	11th to 20th	Day	8% 7% 3 7% 4 5% 4 4 6% 6% 46%	2798
	21st to end	Day	2 2 1 5% 3 4 4 4 5% 7% 63%	2850
July	1st to 10th	Day	2 2 1 3 2 2 3 3 5% 6% 72%	4740
	11th to 20th	Day	1 2 1 4 3 4 4 4 5% 7% 65%	4238
	21st to end	Day	3 3 1 4 4 4 5% 4 6% 7% 58%	4454
August	1st to 10th	Day	3 3 1 4 3 5% 6% 4 7% 8% 55%	4092
	11th to 20th	Day	2 2 1 4 3 4 4 4 5% 7% 63%	4028
	21st to end	Day	3 2 1 4 2 3 4 3 5% 6% 66%	4465
September	1st to 10th	Day	4 4 2 5% 4 4 4 3 5% 6% 62%	2261
	11th to 20th	Day	7% 5% 2 6% 3 4 4 3 4 6% 56%	2090
	21st to end	Day	7% 5% 2 5% 3 3 3 3 3 5% 60%	2090
October	1st to 10th	Day	9% 11% 3 8% 4 4 3 2 4 5% 46%	1935
	11th to 20th	Day	8% 11% 3 5% 4 3 4 3 5% 5% 49%	1900
	21st to end	Day	8% 12% 4 7% 3 4 3 3 5% 7% 44%	2008
November	1st to 10th	Day	12% 15% 6% 9% 4 3 3 2 4 6% 37%	1664
	11th to 20th	Day	8% 18% 4 11% 4 3 3 2 4 7% 36%	1520
	21st to end	Day	2 18% 7% 13% 5% 4 3 3 5% 4 37%	1520
December	1st to 10th	Day	5% 21% 7% 14% 6% 4 3 3 4 5% 28%	1520
	11th to 20th	Day	5% 23% 7% 15% 6% 4 4 2 5% 6% 23%	1926
	21st to end	Day	4 16% 5% 13% 6% 5% 5% 4 5% 9% 29%	2794
January	1st to 10th	Night	3 16% 9% 21% 6% 4 4 3 4 5% 26%	4339
	11th to 20th	Night	3 20% 9% 22% 6% 3 3 2 3 5% 24%	4110
	21st to end	Night	4 30% 8% 12% 4 3 3 2 3 5% 26%	4521
February	1st to 10th	Night	3 21% 10% 16% 7% 5% 4 3 3 5% 23%	2470
	11th to 20th	Night	4 20% 9% 14% 6% 4 3 3 4 3 30%	2402
	21st to end	Night	4 19% 8% 18% 8% 5% 4 2 4 5% 24%	1935
March	1st to 10th	Night	3 21% 7% 17% 5% 3 3 2 4 5% 30%	3473
	11th to 20th	Night	2 12% 5% 8% 3 3 3 4 5% 7% 47%	3490
	21st to end	Night	5% 21% 9% 12% 6% 5% 4 4 5% 5% 25%	3828
April	1st to 10th	Night	6% 17% 5% 9% 5% 3 4 3 5% 7% 35%	1995
	11th to 20th	Night	6% 13% 5% 9% 5% 5% 5% 4 6% 5% 36%	1746
	21st to end	Night	8% 12% 3 7% 4 3 5% 3 5% 7% 43%	1710
May	1st to 10th	Night	9% 20% 4 7% 3 4 4 3 5% 6% 36%	2860
	11th to 20th	Night	4 4 2 5% 4 3 4 4 7% 9% 54%	2723
	21st to end	Night	7% 11% 3 7% 4 4 5% 4 6% 7% 43%	2762
June	1st to 10th	Night	8% 7% 2 6% 4 4 5% 3 7% 10% 44%	1520
	11th to 20th	Night	7% 6% 2 4 3 4 3 4 5% 8% 53%	1376
	21st to end	Night	2 1 1 3 2 3 3 2 5% 7% 71%	1330
July	1st to 10th	Night	1 1 2 2 3 3 4 6% 6% 72%	2220
	11th to 20th	Night	1 1 2 2 2 3 3 6% 8% 71%	2697
	21st to end	Night	1 1 1 3 2 3 3 4 7% 8% 66%	3109
August	1st to 10th	Night	3 3 1 4 3 3 4 4 6% 9% 60%	2847
	11th to 20th	Night	2 2 1 4 3 4 4 4 6% 8% 61%	2811
	21st to end	Night	3 2 1 3 2 2 2 2 5% 6% 72%	3201
September	1st to 10th	Night	4 3 2 4 2 3 3 3 5% 5% 67%	1914
	11th to 20th	Night	6% 4 2 5% 3 3 3 4 5% 8% 58%	2090
	21st to end	Night	8% 5% 2 3 3 1 2 2 3 6% 64%	2090
October	1st to 10th	Night	11% 9% 3 6% 3 3 3 3 4 6% 49%	2244
	11th to 20th	Night	9% 8% 3 5% 3 3 3 3 4 5% 54%	2280
	21st to end	Night	6% 10% 3 6% 4 3 4 4 5% 6% 49%	2449
November	1st to 10th	Night	11% 14% 4 9% 3 4 4 3 5% 5% 39%	2405
	11th to 20th	Night	7% 16% 4 9% 4 5% 4 3 6% 6% 37%	2650
	21st to end	Night	4 15% 6% 10% 5% 4 3 4 5% 7% 39%	2660
December	1st to 10th	Night	4 20% 7% 14% 6% 5% 3 2 3 5% 29%	2660
	11th to 20th	Night	5% 21% 7% 16% 5% 4 4 3 4 5% 26%	3271
	21st to end	Night	4 19% 6% 13% 5% 4 4 3 5% 7% 30%	4873

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% 11% 16% 4 1	2644
	11th to 20th	Day	59% 6% 13% 12% 8% 2	2860
	21st to end	Day	61% 6% 11% 14% 8% 1	3146
February	1st to 10th	Day	65% 7% 11% 12% 4 1	1710
	11th to 20th	Day	62% 6% 12% 12% 5% 3	1674
	21st to end	Day	67% 6% 7% 13% 5% 2	1517
March	1st to 10th	Day	58% 5% 9% 16% 12% 1	3400
	11th to 20th	Day	42% 7% 14% 26% 10% 1	3490
	21st to end	Day	71% 9% 9% 10% 2	3825
April	1st to 10th	Day	57% 8% 12% 15% 7% 1	2185
	11th to 20th	Day	55% 7% 12% 18% 7% 1	2382
	21st to end	Day	53% 8% 12% 22% 5%	2470
May	1st to 10th	Day	51% 9% 11% 20% 7% 1	4110
	11th to 20th	Day	30% 9% 13% 31% 13% 3	4169
	21st to end	Day	46% 8% 12% 25% 8%	4825
June	1st to 10th	Day	38% 8% 18% 25% 11% 1	2660
	11th to 20th	Day	36% 8% 11% 19% 19% 8%	2798
	21st to end	Day	19% 5% 9% 22% 33% 12%	2850
July	1st to 10th	Day	12% 4 6% 14% 35% 29%	4666
	11th to 20th	Day	17% 4 7% 12% 24% 36%	4164
	21st to end	Day	22% 6% 7% 15% 35% 16%	4314
August	1st to 10th	Day	23% 7% 8% 15% 31% 17%	4078
	11th to 20th	Day	20% 5% 7% 22% 32% 14%	4067
	21st to end	Day	18% 5% 7% 19% 31% 20%	4464
September	1st to 10th	Day	23% 5% 8% 17% 32% 14%	2261
	11th to 20th	Day	29% 6% 10% 22% 25% 8%	2090
	21st to end	Day	27% 4 11% 26% 26% 5%	2090
October	1st to 10th	Day	41% 6% 10% 24% 16% 4	1935
	11th to 20th	Day	38% 6% 14% 29% 10% 3	1900
	21st to end	Day	41% 7% 16% 24% 12% 1	2008
November	1st to 10th	Day	50% 5% 13% 20% 9% 2	1664
	11th to 20th	Day	50% 6% 17% 17% 9% 1	1520
	21st to end	Day	51% 6% 14% 18% 9% 1	1520
December	1st to 10th	Day	60% 8% 10% 11% 8% 3	1520
	11th to 20th	Day	63% 6% 12% 13% 5%	1924
	21st to end	Day	52% 6% 10% 14% 11% 7%	2794
January	1st to 10th	Night	60% 7% 9% 17% 6%	4339
	11th to 20th	Night	65% 5% 10% 12% 5% 1	4110
	21st to end	Night	63% 5% 11% 13% 6% 1	4521
February	1st to 10th	Night	65% 7% 10% 12% 6%	2470
	11th to 20th	Night	59% 6% 10% 15% 8% 1	2403
	21st to end	Night	64% 6% 10% 13% 4 3	1935
March	1st to 10th	Night	57% 5% 10% 17% 12%	3473
	11th to 20th	Night	35% 9% 17% 26% 11% 1	3490
	21st to end	Night	59% 11% 12% 16% 2 1	3828
April	1st to 10th	Night	49% 9% 15% 16% 9% 2	1995
	11th to 20th	Night	46% 10% 14% 21% 8% 1	1746
	21st to end	Night	39% 10% 17% 25% 9%	1710
May	1st to 10th	Night	46% 8% 12% 23% 11% 1	2860
	11th to 20th	Night	22% 9% 17% 35% 14% 2	2724
	21st to end	Night	36% 10% 13% 30% 10% 2	2762
June	1st to 10th	Night	34% 9% 18% 25% 12% 1	1520
	11th to 20th	Night	28% 7% 13% 23% 20% 8%	1376
	21st to end	Night	14% 5% 8% 24% 34% 15%	1330
July	1st to 10th	Night	11% 4 8% 14% 40% 23%	2185
	11th to 20th	Night	10% 3 5% 18% 32% 32%	2649
	21st to end	Night	13% 4 9% 21% 35% 17%	3011
August	1st to 10th	Night	20% 5% 8% 15% 35% 16%	2838
	11th to 20th	Night	20% 5% 8% 26% 25% 15%	2838
	21st to end	Night	15% 3 7% 21% 34% 20%	3201
September	1st to 10th	Night	19% 5% 7% 18% 32% 19%	1914
	11th to 20th	Night	24% 6% 11% 22% 26% 10%	2090
	21st to end	Night	24% 4 9% 28% 29% 6%	2090
October	1st to 10th	Night	36% 6% 12% 24% 18% 4	2244
	11th to 20th	Night	35% 4 13% 31% 14% 2	2280
	21st to end	Night	34% 8% 17% 28% 12% 1	2449
November	1st to 10th	Night	48% 7% 12% 21% 9% 3	2405
	11th to 20th	Night	47% 7% 15% 20% 8% 1	2650
	21st to end	Night	46% 7% 14% 20% 10% 2	2660
December	1st to 10th	Night	59% 6% 14% 11% 6% 3	2660
	11th to 20th	Night	61% 6% 13% 14% 6%	3272
	21st to end	Night	54% 6% 10% 16% 8% 6%	4873

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	22% 12% 28% 29% 9% 1	270
	11th to 20th	Day	14% 18% 35% 20% 11% 1	270
	21st to end	Day	13% 18% 37% 25% 6% 1	297
February	1st to 10th	Day	24% 29% 31% 14% 2	270
	11th to 20th	Day	22% 26% 30% 19% 3	270
	21st to end	Day	19% 29% 32% 15% 4	329
March	1st to 10th	Day	23% 28% 32% 13% 2	460
	11th to 20th	Day	16% 25% 33% 21% 5%	460
	21st to end	Day	22% 28% 33% 15% 2	506
April	1st to 10th	Day	27% 25% 29% 15% 4 1	460
	11th to 20th	Day	25% 27% 31% 13% 4 1	452
	21st to end	Day	25% 20% 25% 21% 7% 2	460
May	1st to 10th	Day	17% 22% 32% 21% 7% 1	463
	11th to 20th	Day	16% 18% 33% 22% 10% 1	544
	21st to end	Day	22% 12% 26% 24% 13% 3	734
June	1st to 10th	Day	11% 18% 26% 27% 14% 3	680
	11th to 20th	Day	14% 22% 36% 19% 9%	680
	21st to end	Day	5% 14% 34% 29% 15% 2	680
July	1st to 10th	Day	4 10% 32% 36% 15% 2	671
	11th to 20th	Day	3 14% 43% 26% 12% 1	555
	21st to end	Day	4 12% 38% 32% 12% 3	531
August	1st to 10th	Day	7% 13% 40% 31% 9% 2	487
	11th to 20th	Day	5% 11% 38% 28% 15% 4	477
	21st to end	Day	5% 16% 35% 28% 13% 3	539
September	1st to 10th	Day	5% 16% 33% 29% 13% 4	490
	11th to 20th	Day	12% 17% 33% 23% 10% 4	490
	21st to end	Day	10% 17% 30% 27% 14% 3	490
October	1st to 10th	Day	13% 17% 29% 22% 16% 3	335
	11th to 20th	Day	16% 20% 20% 26% 14% 4	300
	21st to end	Day	20% 20% 30% 25% 5% 1	311
November	1st to 10th	Day	27% 19% 26% 18% 6% 3	270
	11th to 20th	Day	16% 20% 33% 23% 5% 2	270
	21st to end	Day	13% 19% 32% 28% 8%	270
December	1st to 10th	Day	20% 15% 31% 24% 9% 1	270
	11th to 20th	Day	20% 21% 36% 19% 5%	270
	21st to end	Day	22% 19% 31% 18% 8% 2	297
January	1st to 10th	Night	15% 14% 28% 34% 9% 1	898
	11th to 20th	Night	14% 15% 29% 29% 11% 2	760
	21st to end	Night	15% 10% 32% 33% 9% 1	836
February	1st to 10th	Night	16% 15% 36% 27% 6% 1	760
	11th to 20th	Night	15% 15% 33% 30% 7% 1	744
	21st to end	Night	14% 17% 35% 27% 7%	628
March	1st to 10th	Night	14% 19% 29% 31% 6% 1	760
	11th to 20th	Night	10% 14% 27% 36% 12% 1	760
	21st to end	Night	15% 14% 29% 31% 10%	836
April	1st to 10th	Night	15% 16% 28% 31% 9% 1	665
	11th to 20th	Night	14% 15% 30% 31% 9%	563
	21st to end	Night	15% 9% 25% 34% 15% 1	570
May	1st to 10th	Night	16% 10% 22% 36% 16% 1	570
	11th to 20th	Night	12% 6% 25% 34% 22% 1	561
	21st to end	Night	17% 9% 20% 36% 18% 1	617
June	1st to 10th	Night	11% 12% 21% 32% 23% 1	570
	11th to 20th	Night	10% 11% 27% 38% 15%	426
	21st to end	Night	3 2 15% 50% 27% 3	380
July	1st to 10th	Night	2 15% 49% 33% 2	370
	11th to 20th	Night	2 3 16% 51% 28%	534
	21st to end	Night	2 2 13% 50% 31% 1	624
August	1st to 10th	Night	6% 2 14% 48% 28% 2	567
	11th to 20th	Night	3 3 12% 51% 29% 2	564
	21st to end	Night	5% 4 18% 41% 30% 2	627
September	1st to 10th	Night	6% 4 15% 43% 29% 2	584
	11th to 20th	Night	8% 3 20% 38% 28% 4	760
	21st to end	Night	11% 5% 18% 37% 25% 4	760
October	1st to 10th	Night	15% 7% 21% 36% 20% 2	760
	11th to 20th	Night	13% 10% 19% 36% 20% 2	760
	21st to end	Night	13% 10% 20% 42% 11% 3	812
November	1st to 10th	Night	19% 12% 25% 31% 12% 1	740
	11th to 20th	Night	16% 14% 30% 33% 6% 1	940
	21st to end	Night	13% 13% 26% 35% 11% 1	950
December	1st to 10th	Night	19% 12% 32% 31% 5% 1	950
	11th to 20th	Night	18% 14% 31% 30% 6%	950
	21st to end	Night	19% 16% 31% 25% 9% 1	1045

Page generated at 2024-10-22 18:21:06. Version ac07

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