Hyampom
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hyampom clear sky chart from 2005-11-06 to 2026-02-16.

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	7% 7% 2 5% 3 3 3 3 4 6% 56%	139942
	Night	9% 8% 3 7% 4 4 4 3 5% 5% 49%	138330
Transparency	Day	30% 5% 9% 21% 22% 14%	134775
	Night	36% 6% 10% 18% 19% 12%	134491
Seeing	Day	15% 13% 25% 25% 16% 6%	16725
	Night	14% 8% 18% 31% 25% 5%	25956

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	14% 17% 4 11% 6% 6% 5% 3 5% 6% 23%	4824
	11th to 20th	Day	12% 9% 2 4 3 3 3 2 3 4 54%	5340
	21st to end	Day	15% 8% 2 7% 4 4 4 3 5% 6% 42%	5843
February	1st to 10th	Day	16% 10% 3 7% 4 5% 4 4 5% 5% 38%	1890
	11th to 20th	Day	11% 13% 3 9% 5% 5% 4 4 5% 7% 34%	1801
	21st to end	Day	14% 15% 4 8% 4 3 4 3 5% 8% 33%	1613
March	1st to 10th	Day	13% 21% 5% 10% 4 3 4 3 4 4 29%	4952
	11th to 20th	Day	14% 14% 4 9% 5% 4 3 3 3 6% 37%	5000
	21st to end	Day	13% 15% 4 12% 6% 6% 4 3 4 6% 25%	5486
April	1st to 10th	Day	13% 12% 3 8% 5% 5% 5% 3 6% 8% 32%	2388
	11th to 20th	Day	13% 11% 3 6% 4 3 3 3 5% 7% 41%	2369
	21st to end	Day	7% 9% 3 5% 5% 3 4 4 6% 8% 46%	2496
May	1st to 10th	Day	5% 7% 2 4 3 3 3 3 5% 7% 58%	5880
	11th to 20th	Day	3 3 1 4 3 3 4 3 5% 6% 64%	6074
	21st to end	Day	4 3 1 2 2 2 3 3 6% 7% 67%	6902
June	1st to 10th	Day	7% 5% 2 5% 4 4 4 4 5% 7% 54%	2800
	11th to 20th	Day	3 3 1 4 3 3 3 3 5% 7% 66%	2800
	21st to end	Day	3 2 1 2 2 2 3 2 4 4 76%	2800
July	1st to 10th	Day	1 1 1 1 1 1 1 2 3 87%	6319
	11th to 20th	Day	1 1 1 1 1 1 1 2 2 87%	6104
	21st to end	Day	1 1 1 1 2 2 4 5% 83%	6402
August	1st to 10th	Day	1 1 1 2 1 1 2 2 4 5% 81%	5777
	11th to 20th	Day	1 1 1 3 2 3 3 2 4 4 77%	5796
	21st to end	Day	1 1 1 2 2 2 2 2 4 6% 78%	6028
September	1st to 10th	Day	1 1 1 2 1 2 2 2 3 4 80%	2400
	11th to 20th	Day	3 2 1 5% 3 3 4 3 5% 7% 64%	2336
	21st to end	Day	4 3 1 4 2 3 2 2 4 6% 69%	2139
October	1st to 10th	Day	4 2 1 3 2 3 3 2 4 5% 71%	3280
	11th to 20th	Day	6% 3 1 4 3 4 5% 4 5% 8% 56%	3261
	21st to end	Day	8% 5% 2 7% 5% 7% 5% 4 6% 7% 44%	3558
November	1st to 10th	Day	13% 8% 2 8% 5% 5% 4 3 6% 8% 38%	2003
	11th to 20th	Day	14% 9% 2 8% 6% 5% 5% 4 8% 9% 30%	1701
	21st to end	Day	12% 9% 2 7% 5% 5% 4 3 5% 7% 41%	1680
December	1st to 10th	Day	7% 5% 3 6% 5% 5% 5% 3 6% 8% 47%	2700
	11th to 20th	Day	24% 12% 4 10% 7% 6% 6% 4 5% 6% 18%	3108
	21st to end	Day	18% 15% 4 12% 7% 6% 6% 4 5% 5% 18%	4092
January	1st to 10th	Night	16% 17% 5% 11% 6% 5% 4 3 5% 5% 21%	8058
	11th to 20th	Night	10% 9% 3 7% 4 4 3 3 4 6% 50%	7650
	21st to end	Night	16% 10% 3 7% 4 4 5% 3 5% 6% 37%	8371
February	1st to 10th	Night	13% 11% 3 8% 5% 5% 5% 3 5% 7% 35%	2730
	11th to 20th	Night	11% 13% 4 10% 6% 5% 4 3 6% 6% 31%	2597
	21st to end	Night	11% 11% 4 9% 5% 6% 5% 4 5% 7% 35%	2015
March	1st to 10th	Night	12% 19% 7% 10% 5% 4 4 4 5% 6% 24%	4942
	11th to 20th	Night	12% 13% 3 9% 5% 4 4 3 4 5% 38%	5000
	21st to end	Night	11% 19% 7% 13% 7% 4 4 3 5% 5% 23%	5489
April	1st to 10th	Night	11% 11% 4 9% 5% 5% 5% 3 7% 7% 32%	2010
	11th to 20th	Night	8% 10% 4 8% 6% 4 4 4 5% 7% 40%	1979
	21st to end	Night	6% 9% 2 8% 5% 3 4 4 6% 8% 45%	1900
May	1st to 10th	Night	5% 7% 2 5% 3 3 4 3 4 5% 58%	4100
	11th to 20th	Night	2 5% 4 8% 4 3 4 3 4 5% 58%	3811
	21st to end	Night	2 2 1 2 2 2 3 3 4 7% 71%	3972
June	1st to 10th	Night	5% 5% 3 6% 4 4 4 4 7% 8% 52%	1600
	11th to 20th	Night	3 2 1 2 3 2 2 3 5% 7% 71%	1600
	21st to end	Night	3 2 1 2 1 2 1 2 3 4 78%	1600
July	1st to 10th	Night	1 1 1 1 1 1 1 2 3 89%	3640
	11th to 20th	Night	1 1 1 1 1 1 1 2 2 88%	3861
	21st to end	Night	1 2 1 1 2 2 4 5% 82%	4472
August	1st to 10th	Night	1 1 2 2 2 2 4 4 81%	4035
	11th to 20th	Night	2 3 1 3 2 2 3 3 4 3 75%	4052
	21st to end	Night	2 1 1 3 2 2 2 2 3 4 79%	4967
September	1st to 10th	Night	1 2 1 3 1 2 2 2 3 4 79%	2000
	11th to 20th	Night	2 3 2 5% 3 3 3 3 4 7% 64%	2060
	21st to end	Night	3 3 1 6% 3 3 3 3 4 5% 66%	2260
October	1st to 10th	Night	4 2 1 5% 3 3 3 3 4 4 68%	3920
	11th to 20th	Night	6% 6% 3 8% 5% 4 4 3 5% 6% 51%	3897
	21st to end	Night	7% 5% 3 9% 6% 5% 6% 4 5% 6% 43%	4253
November	1st to 10th	Night	12% 8% 3 8% 6% 6% 5% 5% 5% 6% 37%	2513
	11th to 20th	Night	14% 9% 3 8% 6% 6% 6% 5% 6% 8% 29%	2914
	21st to end	Night	12% 7% 3 7% 4 4 4 3 6% 8% 41%	2940
December	1st to 10th	Night	10% 6% 4 6% 3 3 3 4 6% 8% 46%	4700
	11th to 20th	Night	24% 13% 3 8% 5% 6% 6% 4 5% 6% 20%	5316
	21st to end	Night	23% 13% 4 10% 6% 5% 5% 4 5% 5% 20%	7106

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	59% 8% 8% 14% 10% 1	4825
	11th to 20th	Day	35% 4 5% 10% 21% 25%	5340
	21st to end	Day	41% 5% 9% 12% 19% 14%	5843
February	1st to 10th	Day	47% 6% 9% 17% 14% 7%	1890
	11th to 20th	Day	48% 6% 10% 18% 15% 3	1810
	21st to end	Day	49% 8% 11% 15% 13% 4	1613
March	1st to 10th	Day	58% 5% 6% 18% 12% 2	4952
	11th to 20th	Day	49% 6% 11% 15% 17% 2	5000
	21st to end	Day	58% 7% 12% 19% 4 1	5486
April	1st to 10th	Day	49% 8% 14% 17% 11% 2	2388
	11th to 20th	Day	42% 7% 12% 21% 13% 5%	2372
	21st to end	Day	34% 8% 16% 24% 16% 2	2496
May	1st to 10th	Day	25% 5% 12% 24% 28% 6%	5880
	11th to 20th	Day	20% 4 12% 26% 31% 7%	6077
	21st to end	Day	16% 4 14% 52% 13%	6904
June	1st to 10th	Day	28% 7% 13% 30% 19% 3	2800
	11th to 20th	Day	18% 5% 12% 27% 30% 8%	2800
	21st to end	Day	13% 3 8% 24% 35% 18%	2800
July	1st to 10th	Day	6% 2 4 18% 30% 41%	6251
	11th to 20th	Day	6% 1 2 11% 28% 52%	6029
	21st to end	Day	6% 2 7% 29% 30% 27%	6217
August	1st to 10th	Day	8% 2 5% 18% 34% 34%	4206
	11th to 20th	Day	10% 2 7% 26% 35% 20%	4195
	21st to end	Day	10% 2 7% 24% 40% 17%	4343
September	1st to 10th	Day	9% 3 6% 15% 32% 36%	2400
	11th to 20th	Day	20% 4 8% 24% 34% 10%	2336
	21st to end	Day	17% 4 9% 21% 29% 21%	2139
October	1st to 10th	Day	17% 3 6% 20% 19% 36%	3280
	11th to 20th	Day	26% 4 11% 32% 19% 8%	3261
	21st to end	Day	36% 7% 9% 20% 18% 10%	3558
November	1st to 10th	Day	43% 7% 10% 19% 14% 8%	2003
	11th to 20th	Day	48% 7% 12% 14% 11% 8%	1701
	21st to end	Day	43% 6% 9% 15% 16% 12%	1680
December	1st to 10th	Day	35% 4 8% 18% 26% 10%	2700
	11th to 20th	Day	65% 7% 8% 10% 7% 3	3108
	21st to end	Day	65% 8% 7% 10% 8% 2	4092
January	1st to 10th	Night	61% 9% 9% 11% 9% 2	8058
	11th to 20th	Night	36% 5% 6% 11% 19% 23%	7650
	21st to end	Night	47% 5% 7% 11% 17% 14%	8371
February	1st to 10th	Night	48% 6% 9% 17% 14% 6%	2730
	11th to 20th	Night	52% 7% 9% 16% 13% 4	2599
	21st to end	Night	47% 8% 13% 18% 11% 3	2015
March	1st to 10th	Night	57% 6% 9% 19% 7% 2	4942
	11th to 20th	Night	45% 7% 13% 18% 12% 4	5000
	21st to end	Night	60% 9% 13% 13% 4 1	5489
April	1st to 10th	Night	48% 9% 16% 16% 9% 2	2010
	11th to 20th	Night	42% 8% 15% 19% 11% 5%	1979
	21st to end	Night	34% 8% 18% 26% 13% 2	1900
May	1st to 10th	Night	25% 5% 13% 23% 29% 6%	4097
	11th to 20th	Night	27% 6% 11% 19% 30% 7%	3811
	21st to end	Night	13% 4 18% 48% 16%	3972
June	1st to 10th	Night	29% 6% 13% 31% 18% 2	1600
	11th to 20th	Night	13% 4 13% 34% 28% 8%	1600
	21st to end	Night	12% 2 7% 27% 35% 18%	1600
July	1st to 10th	Night	5% 1 3 20% 31% 40%	3600
	11th to 20th	Night	6% 1 2 9% 31% 50%	3813
	21st to end	Night	6% 1 8% 25% 34% 26%	4345
August	1st to 10th	Night	9% 2 5% 19% 32% 34%	2929
	11th to 20th	Night	9% 3 10% 19% 37% 22%	2929
	21st to end	Night	11% 2 6% 25% 39% 16%	3573
September	1st to 10th	Night	10% 2 6% 16% 33% 33%	2000
	11th to 20th	Night	19% 4 10% 26% 30% 10%	2060
	21st to end	Night	20% 5% 9% 20% 24% 23%	2260
October	1st to 10th	Night	19% 3 8% 13% 24% 34%	3920
	11th to 20th	Night	31% 5% 11% 28% 17% 8%	3897
	21st to end	Night	37% 6% 10% 17% 20% 10%	4253
November	1st to 10th	Night	45% 7% 12% 14% 15% 8%	2513
	11th to 20th	Night	49% 9% 12% 14% 10% 6%	2914
	21st to end	Night	41% 7% 9% 14% 18% 11%	2940
December	1st to 10th	Night	35% 5% 10% 18% 22% 11%	4700
	11th to 20th	Night	62% 7% 8% 13% 9% 2	5316
	21st to end	Night	62% 9% 10% 11% 7% 2	7106

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	39% 14% 21% 19% 7% 1	257
	11th to 20th	Day	27% 12% 24% 17% 14% 5%	430
	21st to end	Day	23% 15% 21% 22% 15% 4	473
February	1st to 10th	Day	26% 15% 25% 19% 13% 2	430
	11th to 20th	Day	29% 19% 22% 18% 9% 2	411
	21st to end	Day	27% 19% 24% 19% 9% 1	391
March	1st to 10th	Day	32% 23% 25% 15% 4 1	500
	11th to 20th	Day	29% 18% 25% 17% 9% 2	500
	21st to end	Day	31% 21% 24% 17% 6% 1	550
April	1st to 10th	Day	26% 19% 27% 19% 8% 1	500
	11th to 20th	Day	26% 17% 25% 21% 9% 2	492
	21st to end	Day	16% 22% 29% 18% 11% 3	500
May	1st to 10th	Day	18% 17% 31% 20% 11% 3	503
	11th to 20th	Day	17% 20% 28% 21% 10% 4	528
	21st to end	Day	14% 12% 30% 24% 15% 5%	573
June	1st to 10th	Day	11% 15% 26% 29% 13% 6%	530
	11th to 20th	Day	11% 17% 32% 23% 12% 5%	530
	21st to end	Day	3 10% 33% 28% 18% 8%	530
July	1st to 10th	Day	3 7% 29% 33% 18% 9%	526
	11th to 20th	Day	1 5% 27% 34% 25% 9%	524
	21st to end	Day	1 3 23% 36% 25% 13%	575
August	1st to 10th	Day	1 3 29% 35% 22% 10%	527
	11th to 20th	Day	2 6% 26% 33% 21% 13%	517
	21st to end	Day	3 4 23% 33% 28% 9%	583
September	1st to 10th	Day	2 9% 23% 38% 21% 7%	530
	11th to 20th	Day	7% 8% 25% 32% 22% 5%	530
	21st to end	Day	8% 8% 25% 31% 22% 6%	530
October	1st to 10th	Day	9% 10% 25% 26% 21% 9%	530
	11th to 20th	Day	13% 10% 18% 27% 25% 7%	530
	21st to end	Day	16% 11% 21% 27% 19% 6%	583
November	1st to 10th	Day	19% 12% 24% 24% 14% 7%	479
	11th to 20th	Day	19% 13% 20% 25% 17% 7%	231
	21st to end	Day	20% 10% 20% 24% 21% 6%	220
December	1st to 10th	Day	20% 11% 20% 22% 15% 11%	220
	11th to 20th	Day	28% 17% 17% 21% 9% 8%	220
	21st to end	Day	29% 15% 21% 20% 13% 2	242
January	1st to 10th	Night	27% 9% 23% 26% 12% 3	840
	11th to 20th	Night	21% 9% 20% 29% 16% 5%	840
	21st to end	Night	21% 10% 21% 26% 18% 4	924
February	1st to 10th	Night	21% 10% 22% 33% 13% 2	840
	11th to 20th	Night	22% 9% 23% 28% 16% 3	804
	21st to end	Night	19% 13% 25% 30% 12% 1	660
March	1st to 10th	Night	24% 16% 22% 23% 12% 3	800
	11th to 20th	Night	24% 10% 19% 28% 17% 2	800
	21st to end	Night	25% 14% 24% 23% 13% 1	880
April	1st to 10th	Night	17% 13% 25% 27% 16% 2	800
	11th to 20th	Night	17% 12% 23% 28% 17% 4	791
	21st to end	Night	13% 10% 23% 31% 20% 3	700
May	1st to 10th	Night	10% 9% 24% 32% 23% 4	600
	11th to 20th	Night	8% 7% 21% 29% 30% 4	485
	21st to end	Night	9% 7% 23% 32% 26% 3	433
June	1st to 10th	Night	6% 7% 20% 35% 30% 3	400
	11th to 20th	Night	4 6% 23% 42% 25% 1	400
	21st to end	Night	4 2 12% 40% 40% 3	400
July	1st to 10th	Night	2 1 10% 42% 41% 4	390
	11th to 20th	Night	2 7% 35% 49% 6%	479
	21st to end	Night	1 4 27% 56% 12%	657
August	1st to 10th	Night	1 5% 34% 49% 10%	597
	11th to 20th	Night	1 1 8% 37% 45% 9%	594
	21st to end	Night	1 1 9% 38% 44% 6%	858
September	1st to 10th	Night	2 2 13% 38% 37% 8%	800
	11th to 20th	Night	4 4 14% 36% 34% 9%	800
	21st to end	Night	5% 5% 15% 30% 36% 8%	800
October	1st to 10th	Night	8% 5% 19% 30% 35% 4	800
	11th to 20th	Night	11% 4 17% 30% 32% 7%	800
	21st to end	Night	14% 6% 14% 34% 24% 8%	880
November	1st to 10th	Night	16% 8% 20% 31% 21% 5%	820
	11th to 20th	Night	18% 9% 21% 31% 18% 3	840
	21st to end	Night	17% 9% 18% 33% 20% 3	840
December	1st to 10th	Night	20% 8% 19% 30% 19% 4	840
	11th to 20th	Night	28% 11% 17% 28% 14% 3	840
	21st to end	Night	30% 13% 19% 26% 10% 2	924

Page generated at 2026-02-12 22:42:14. Version ac07

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