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 2024-03-01.

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	6% 12% 5% 8% 6% 3 4 4 5% 6% 40%	79082
	Night	5% 13% 5% 9% 5% 3 4 4 5% 6% 40%	80381
Transparency	Day	44% 7% 11% 18% 14% 5%	78792
	Night	45% 7% 12% 19% 13% 5%	80193
Seeing	Day	15% 18% 32% 24% 9% 2	14621
	Night	13% 11% 25% 35% 15% 1	24433

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 19% 12% 15% 8% 3 3 4 4 5% 24%	2643
	11th to 20th	Day	4 17% 8% 14% 9% 3 4 4 4 6% 27%	2860
	21st to end	Day	3 27% 9% 11% 6% 2 3 3 3 5% 27%	3146
February	1st to 10th	Day	5% 22% 9% 15% 7% 3 4 4 5% 5% 22%	1710
	11th to 20th	Day	3 21% 10% 14% 8% 2 4 3 4 5% 26%	1665
	21st to end	Day	5% 18% 10% 18% 9% 3 4 5% 3 4 21%	1517
March	1st to 10th	Day	5% 16% 8% 14% 7% 4 6% 4 4 5% 28%	1948
	11th to 20th	Day	5% 16% 7% 10% 5% 3 5% 4 6% 7% 32%	1980
	21st to end	Day	7% 22% 8% 11% 8% 4 4 4 5% 6% 21%	2178
April	1st to 10th	Day	8% 17% 7% 10% 7% 4 4 4 5% 6% 27%	2070
	11th to 20th	Day	8% 15% 6% 12% 8% 4 4 4 5% 6% 28%	2252
	21st to end	Day	8% 17% 5% 9% 6% 3 4 4 5% 8% 31%	2340
May	1st to 10th	Day	9% 11% 5% 9% 8% 4 6% 6% 5% 7% 31%	2340
	11th to 20th	Day	9% 9% 3 6% 7% 4 6% 7% 8% 8% 33%	2354
	21st to end	Day	13% 12% 5% 10% 7% 4 5% 6% 6% 6% 25%	2724
June	1st to 10th	Day	10% 8% 3 5% 5% 3 5% 6% 7% 9% 39%	2520
	11th to 20th	Day	8% 7% 3 6% 5% 4 5% 5% 5% 7% 45%	2650
	21st to end	Day	2 2 1 4 4 3 5% 4 5% 7% 63%	2700
July	1st to 10th	Day	2 2 1 3 4 2 4 5% 7% 8% 62%	2700
	11th to 20th	Day	2 3 1 3 4 3 5% 4 5% 7% 63%	2426
	21st to end	Day	4 3 1 3 5% 3 4 5% 5% 7% 57%	2545
August	1st to 10th	Day	5% 4 1 5% 4 3 6% 5% 7% 7% 52%	2328
	11th to 20th	Day	2 2 2 4 4 3 3 4 5% 7% 63%	2299
	21st to end	Day	5% 4 1 4 4 3 4 6% 5% 7% 59%	2544
September	1st to 10th	Day	4 4 2 4 5% 3 4 4 5% 5% 61%	2142
	11th to 20th	Day	7% 5% 2 5% 4 3 4 4 5% 6% 57%	1980
	21st to end	Day	7% 5% 2 5% 4 2 4 3 3 5% 59%	1980
October	1st to 10th	Day	10% 11% 4 7% 5% 3 4 3 4 5% 44%	1834
	11th to 20th	Day	9% 11% 3 4 5% 2 4 4 4 6% 48%	1800
	21st to end	Day	8% 12% 5% 6% 4 3 4 4 4 6% 44%	1963
November	1st to 10th	Day	13% 14% 6% 8% 5% 2 4 2 4 5% 37%	1664
	11th to 20th	Day	9% 17% 5% 10% 5% 2 4 3 4 7% 36%	1520
	21st to end	Day	2 17% 8% 12% 5% 3 4 4 5% 4 37%	1520
December	1st to 10th	Day	5% 20% 7% 12% 8% 4 3 3 4 5% 28%	1520
	11th to 20th	Day	5% 23% 7% 14% 7% 3 4 3 5% 6% 23%	1926
	21st to end	Day	5% 15% 6% 11% 7% 4 5% 5% 5% 9% 29%	2794
January	1st to 10th	Night	3 15% 9% 19% 8% 3 4 4 4 5% 26%	4339
	11th to 20th	Night	3 19% 10% 19% 9% 3 3 3 3 5% 24%	4110
	21st to end	Night	5% 29% 9% 11% 5% 3 3 3 3 5% 26%	4521
February	1st to 10th	Night	3 20% 11% 14% 8% 4 5% 4 3 4 23%	2470
	11th to 20th	Night	4 19% 10% 13% 7% 3 3 4 4 3 30%	2402
	21st to end	Night	4 17% 9% 16% 10% 4 4 3 3 5% 24%	1935
March	1st to 10th	Night	4 17% 9% 13% 8% 3 5% 4 4 6% 29%	2017
	11th to 20th	Night	4 13% 5% 9% 5% 3 5% 6% 5% 8% 38%	1980
	21st to end	Night	6% 18% 6% 10% 7% 3 4 5% 5% 6% 30%	2178
April	1st to 10th	Night	7% 16% 5% 8% 6% 2 4 4 5% 8% 35%	1890
	11th to 20th	Night	7% 12% 6% 8% 6% 4 5% 5% 5% 6% 36%	1654
	21st to end	Night	8% 11% 4 6% 5% 2 5% 4 5% 7% 44%	1620
May	1st to 10th	Night	10% 9% 4 6% 4 3 5% 4 5% 7% 43%	1620
	11th to 20th	Night	7% 7% 2 6% 6% 3 4 5% 8% 11% 43%	1539
	21st to end	Night	11% 9% 3 7% 6% 3 5% 6% 7% 8% 36%	1552
June	1st to 10th	Night	8% 7% 2 6% 5% 3 4 4 6% 11% 45%	1440
	11th to 20th	Night	8% 5% 3 4 4 3 3 5% 5% 8% 53%	1304
	21st to end	Night	2 1 1 2 3 2 3 3 5% 7% 71%	1260
July	1st to 10th	Night	1 1 2 3 3 5% 6% 7% 9% 63%	1260
	11th to 20th	Night	2 1 1 2 2 2 3 4 6% 8% 70%	1527
	21st to end	Night	2 2 1 3 3 2 4 5% 5% 7% 66%	1773
August	1st to 10th	Night	4 4 1 4 4 3 3 6% 5% 9% 58%	1611
	11th to 20th	Night	2 2 1 2 3 2 3 4 6% 8% 66%	1602
	21st to end	Night	4 2 1 3 3 2 3 3 5% 7% 66%	1811
September	1st to 10th	Night	5% 3 2 4 3 2 3 3 5% 5% 67%	1813
	11th to 20th	Night	5% 4 1 5% 4 2 3 4 5% 8% 59%	1980
	21st to end	Night	9% 5% 2 3 3 1 2 3 3 6% 63%	1980
October	1st to 10th	Night	12% 9% 3 6% 3 3 3 3 4 6% 47%	2125
	11th to 20th	Night	10% 8% 3 5% 3 2 3 3 4 6% 54%	2160
	21st to end	Night	7% 10% 3 6% 4 2 4 5% 5% 6% 49%	2389
November	1st to 10th	Night	12% 12% 5% 8% 4 3 4 4 5% 5% 39%	2405
	11th to 20th	Night	7% 15% 5% 8% 5% 4 5% 4 5% 6% 37%	2650
	21st to end	Night	4 13% 7% 9% 6% 3 3 4 5% 7% 39%	2660
December	1st to 10th	Night	5% 19% 8% 13% 8% 5% 4 3 3 5% 29%	2660
	11th to 20th	Night	6% 20% 8% 15% 6% 3 4 4 4 5% 27%	3271
	21st to end	Night	4 18% 6% 12% 7% 3 4 4 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	66% 7% 8% 13% 5% 2	1517
March	1st to 10th	Day	59% 6% 12% 15% 6% 1	1948
	11th to 20th	Day	51% 9% 14% 16% 8% 2	1980
	21st to end	Day	64% 8% 10% 14% 3	2178
April	1st to 10th	Day	57% 8% 12% 14% 7% 1	2070
	11th to 20th	Day	57% 7% 12% 17% 6% 1	2255
	21st to end	Day	53% 7% 12% 22% 5%	2340
May	1st to 10th	Day	50% 9% 12% 21% 8% 1	2340
	11th to 20th	Day	43% 11% 13% 25% 8%	2357
	21st to end	Day	56% 9% 14% 15% 5%	2724
June	1st to 10th	Day	38% 8% 18% 24% 11% 1	2520
	11th to 20th	Day	36% 8% 11% 19% 18% 8%	2650
	21st to end	Day	19% 6% 9% 22% 33% 11%	2700
July	1st to 10th	Day	18% 6% 9% 20% 32% 14%	2626
	11th to 20th	Day	20% 4 8% 16% 26% 25%	2352
	21st to end	Day	24% 6% 9% 14% 26% 21%	2404
August	1st to 10th	Day	28% 7% 10% 17% 24% 13%	2313
	11th to 20th	Day	21% 5% 8% 22% 31% 14%	2299
	21st to end	Day	23% 5% 8% 18% 31% 13%	2544
September	1st to 10th	Day	24% 5% 8% 16% 31% 15%	2142
	11th to 20th	Day	28% 6% 11% 22% 25% 9%	1980
	21st to end	Day	29% 4 11% 26% 26% 4	1980
October	1st to 10th	Day	43% 6% 10% 24% 13% 3	1834
	11th to 20th	Day	39% 6% 14% 28% 10% 3	1800
	21st to end	Day	41% 7% 16% 24% 12% 1	1963
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	58% 6% 12% 17% 7%	2017
	11th to 20th	Night	45% 10% 14% 21% 8% 2	1980
	21st to end	Night	55% 10% 14% 17% 3 1	2178
April	1st to 10th	Night	49% 9% 15% 16% 10% 2	1890
	11th to 20th	Night	47% 9% 14% 21% 7% 1	1654
	21st to end	Night	38% 10% 17% 26% 9%	1620
May	1st to 10th	Night	39% 8% 14% 28% 12%	1620
	11th to 20th	Night	32% 12% 18% 26% 12%	1540
	21st to end	Night	44% 11% 17% 21% 6%	1552
June	1st to 10th	Night	34% 9% 19% 24% 12% 1	1440
	11th to 20th	Night	28% 8% 14% 23% 20% 8%	1304
	21st to end	Night	14% 5% 9% 25% 34% 13%	1260
July	1st to 10th	Night	15% 6% 12% 22% 31% 13%	1225
	11th to 20th	Night	12% 4 6% 21% 31% 26%	1479
	21st to end	Night	16% 5% 10% 17% 30% 22%	1674
August	1st to 10th	Night	23% 6% 11% 18% 25% 16%	1602
	11th to 20th	Night	15% 6% 8% 24% 32% 15%	1602
	21st to end	Night	19% 4 9% 20% 31% 17%	1811
September	1st to 10th	Night	20% 5% 7% 17% 31% 19%	1813
	11th to 20th	Night	23% 6% 11% 23% 26% 11%	1980
	21st to end	Night	26% 4 9% 28% 28% 5%	1980
October	1st to 10th	Night	38% 6% 13% 24% 15% 4	2125
	11th to 20th	Night	35% 4 14% 31% 14% 2	2160
	21st to end	Night	35% 8% 17% 27% 13% 1	2389
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% 30% 31% 15% 4	329
March	1st to 10th	Day	23% 29% 32% 14% 2	421
	11th to 20th	Day	16% 27% 33% 20% 4	420
	21st to end	Day	23% 28% 33% 15% 2	462
April	1st to 10th	Day	27% 25% 28% 15% 4 1	420
	11th to 20th	Day	26% 27% 31% 11% 3 1	412
	21st to end	Day	25% 20% 25% 21% 7% 2	420
May	1st to 10th	Day	15% 22% 33% 22% 8% 1	423
	11th to 20th	Day	15% 18% 33% 22% 11% 2	501
	21st to end	Day	22% 12% 26% 24% 13% 4	679
June	1st to 10th	Day	11% 17% 26% 27% 15% 3	630
	11th to 20th	Day	14% 21% 36% 19% 9%	630
	21st to end	Day	5% 13% 33% 30% 17% 2	630
July	1st to 10th	Day	3 9% 33% 36% 16% 2	621
	11th to 20th	Day	3 15% 44% 26% 11% 1	512
	21st to end	Day	4 11% 39% 32% 12% 2	487
August	1st to 10th	Day	7% 12% 40% 31% 9% 1	447
	11th to 20th	Day	4 10% 37% 28% 16% 4	437
	21st to end	Day	5% 15% 35% 29% 13% 3	495
September	1st to 10th	Day	6% 16% 34% 29% 12% 3	450
	11th to 20th	Day	12% 17% 33% 24% 10% 4	450
	21st to end	Day	10% 18% 30% 28% 13% 2	450
October	1st to 10th	Day	15% 18% 29% 21% 15% 3	304
	11th to 20th	Day	17% 21% 20% 27% 13% 3	270
	21st to end	Day	21% 20% 29% 25% 5% 1	297
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% 18% 30% 31% 6% 1	722
	11th to 20th	Night	10% 14% 27% 36% 12% 1	720
	21st to end	Night	15% 14% 30% 31% 10%	792
April	1st to 10th	Night	15% 15% 28% 31% 10% 1	630
	11th to 20th	Night	14% 16% 30% 31% 9%	533
	21st to end	Night	15% 9% 25% 34% 16% 1	540
May	1st to 10th	Night	14% 9% 22% 37% 17% 1	540
	11th to 20th	Night	13% 6% 24% 34% 23% 1	531
	21st to end	Night	17% 8% 20% 36% 18% 1	584
June	1st to 10th	Night	12% 11% 21% 31% 23% 1	540
	11th to 20th	Night	10% 11% 26% 38% 15%	404
	21st to end	Night	3 2 13% 50% 29% 3	360
July	1st to 10th	Night	2 15% 49% 33% 2	350
	11th to 20th	Night	2 3 16% 51% 27%	505
	21st to end	Night	2 2 13% 48% 32% 2	591
August	1st to 10th	Night	6% 2 14% 48% 28% 2	537
	11th to 20th	Night	3 2 10% 51% 31% 2	534
	21st to end	Night	5% 4 17% 41% 31% 2	594
September	1st to 10th	Night	7% 5% 16% 42% 29% 2	553
	11th to 20th	Night	8% 3 19% 38% 29% 4	720
	21st to end	Night	12% 5% 18% 37% 25% 4	720
October	1st to 10th	Night	15% 8% 21% 34% 20% 2	720
	11th to 20th	Night	14% 10% 19% 35% 19% 3	720
	21st to end	Night	13% 10% 20% 42% 11% 3	792
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 2024-02-27 04:30:12. Version ac07

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