Redman Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Redman Observatory clear sky chart from 2005-11-06 to 2026-03-18.

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	3 3 1 4 3 3 3 3 4 6% 68%	139506
	Night	4 4 2 5% 3 3 4 3 5% 6% 63%	139502
Transparency	Day	18% 4 8% 19% 27% 24%	134529
	Night	22% 5% 9% 18% 25% 21%	135459
Seeing	Day	5% 6% 19% 33% 27% 10%	17301
	Night	5% 3 13% 38% 34% 7%	26956

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	6% 4 2 6% 4 5% 5% 4 6% 8% 51%	5040
	11th to 20th	Day	4 4 1 4 3 3 3 3 6% 7% 62%	5340
	21st to end	Day	6% 5% 2 7% 5% 5% 5% 5% 6% 9% 46%	5843
February	1st to 10th	Day	10% 6% 2 6% 4 3 3 3 5% 6% 52%	1951
	11th to 20th	Day	7% 6% 2 7% 4 4 4 4 5% 7% 49%	2050
	21st to end	Day	8% 6% 2 6% 3 3 5% 5% 4 8% 51%	1730
March	1st to 10th	Day	8% 5% 2 7% 5% 6% 5% 5% 7% 9% 40%	4770
	11th to 20th	Day	5% 4 1 6% 5% 4 4 3 5% 6% 56%	5078
	21st to end	Day	4 5% 2 7% 6% 5% 6% 6% 7% 9% 43%	5719
April	1st to 10th	Day	6% 6% 2 4 4 3 4 4 5% 8% 55%	2400
	11th to 20th	Day	5% 4 2 5% 3 3 4 3 5% 8% 58%	2369
	21st to end	Day	4 3 1 4 3 3 3 3 5% 8% 63%	2400
May	1st to 10th	Day	2 2 1 2 2 2 2 2 4 5% 77%	5440
	11th to 20th	Day	1 2 1 3 2 2 2 2 3 5% 77%	5655
	21st to end	Day	1 2 1 2 1 1 2 2 3 6% 80%	6902
June	1st to 10th	Day	2 2 1 3 2 3 3 2 4 8% 71%	2800
	11th to 20th	Day	1 1 2 2 1 1 2 2 4 84%	2800
	21st to end	Day	1 1 1 2 1 1 3 3 85%	2800
July	1st to 10th	Day	1 1 1 1 1 2 3 90%	6319
	11th to 20th	Day	1 1 2 2 2 2 2 3 4 82%	5924
	21st to end	Day	1 2 2 2 2 2 4 5% 80%	6402
August	1st to 10th	Day	1 1 1 1 1 2 1 3 5% 84%	5564
	11th to 20th	Day	1 1 1 1 2 2 3 90%	5364
	21st to end	Day	1 1 1 2 2 2 3 4 83%	5984
September	1st to 10th	Day	1 1 2 1 2 1 2 2 4 84%	2400
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 5% 78%	2400
	21st to end	Day	1 2 1 3 2 2 2 2 4 6% 73%	2190
October	1st to 10th	Day	1 1 2 2 2 3 2 5% 5% 75%	3280
	11th to 20th	Day	1 2 1 4 3 3 2 2 3 4 74%	3261
	21st to end	Day	2 2 2 4 3 3 4 3 4 7% 67%	3558
November	1st to 10th	Day	3 4 1 3 3 3 3 3 5% 6% 65%	1978
	11th to 20th	Day	5% 4 1 4 4 3 4 3 5% 7% 60%	1890
	21st to end	Day	5% 4 2 6% 4 3 4 4 4 6% 59%	1890
December	1st to 10th	Day	3 5% 2 6% 4 4 4 4 6% 9% 52%	2815
	11th to 20th	Day	10% 5% 3 6% 5% 4 4 4 6% 8% 44%	3108
	21st to end	Day	10% 7% 3 9% 6% 5% 5% 5% 7% 10% 34%	4092
January	1st to 10th	Night	8% 6% 3 7% 4 4 4 3 5% 7% 50%	7852
	11th to 20th	Night	4 4 2 4 3 4 3 3 5% 6% 61%	7650
	21st to end	Night	8% 7% 3 8% 6% 5% 5% 4 6% 7% 41%	8371
February	1st to 10th	Night	8% 6% 2 5% 4 4 5% 3 4 5% 54%	2667
	11th to 20th	Night	7% 4 2 5% 4 3 4 4 6% 7% 54%	2458
	21st to end	Night	7% 5% 2 5% 4 4 4 3 4 6% 56%	2076
March	1st to 10th	Night	6% 8% 3 8% 5% 5% 6% 5% 6% 7% 41%	5327
	11th to 20th	Night	4 4 2 5% 4 4 5% 4 6% 7% 55%	5077
	21st to end	Night	7% 6% 2 8% 5% 5% 4 4 5% 6% 49%	5254
April	1st to 10th	Night	5% 4 2 4 3 4 4 3 5% 7% 60%	2000
	11th to 20th	Night	4 4 1 4 3 3 3 3 5% 5% 65%	1979
	21st to end	Night	3 4 2 4 3 3 3 2 4 7% 65%	2000
May	1st to 10th	Night	1 1 1 3 2 2 2 3 4 6% 76%	4560
	11th to 20th	Night	1 2 1 5% 3 4 4 3 5% 6% 68%	4245
	21st to end	Night	1 1 2 2 2 3 2 3 5% 79%	3972
June	1st to 10th	Night	2 2 1 2 2 3 4 4 6% 6% 68%	1600
	11th to 20th	Night	2 1 2 2 2 2 2 4 5% 78%	1600
	21st to end	Night	1 1 1 1 2 1 3 4 85%	1600
July	1st to 10th	Night	1 1 1 2 2 2 4 87%	3640
	11th to 20th	Night	1 1 2 1 1 3 3 5% 5% 78%	4048
	21st to end	Night	1 3 3 4 5% 5% 6% 7% 65%	4472
August	1st to 10th	Night	1 1 1 1 2 2 3 4 85%	4254
	11th to 20th	Night	1 1 1 1 1 2 2 91%	4506
	21st to end	Night	1 1 1 2 2 3 4 85%	5015
September	1st to 10th	Night	1 1 1 2 2 1 2 2 3 4 83%	2000
	11th to 20th	Night	1 2 1 3 2 2 3 2 3 5% 76%	2000
	21st to end	Night	1 2 1 2 2 2 2 2 3 4 80%	2203
October	1st to 10th	Night	1 2 1 2 2 2 2 2 3 5% 78%	3920
	11th to 20th	Night	1 2 2 4 3 3 3 3 3 4 71%	3897
	21st to end	Night	2 3 1 4 2 2 3 2 4 6% 71%	4253
November	1st to 10th	Night	3 3 1 4 3 2 3 3 4 6% 68%	2539
	11th to 20th	Night	3 4 1 5% 3 3 4 4 5% 6% 62%	2730
	21st to end	Night	4 4 2 5% 4 4 3 4 6% 7% 58%	2730
December	1st to 10th	Night	5% 4 1 5% 3 4 5% 4 7% 8% 55%	4585
	11th to 20th	Night	8% 7% 3 8% 5% 5% 5% 5% 7% 8% 40%	5316
	21st to end	Night	8% 8% 4 11% 7% 6% 6% 4 6% 8% 32%	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	27% 6% 13% 28% 17% 9%	5041
	11th to 20th	Day	22% 4 8% 11% 22% 33%	5340
	21st to end	Day	29% 7% 11% 14% 27% 12%	5843
February	1st to 10th	Day	32% 5% 8% 19% 21% 16%	1951
	11th to 20th	Day	32% 5% 10% 22% 22% 9%	2060
	21st to end	Day	31% 5% 13% 21% 23% 7%	1730
March	1st to 10th	Day	34% 8% 14% 15% 24% 5%	4770
	11th to 20th	Day	27% 6% 10% 31% 17% 9%	5078
	21st to end	Day	31% 9% 17% 24% 16% 3	5719
April	1st to 10th	Day	27% 5% 13% 26% 22% 8%	2400
	11th to 20th	Day	25% 5% 12% 25% 25% 8%	2372
	21st to end	Day	20% 6% 13% 26% 28% 7%	2400
May	1st to 10th	Day	12% 2 7% 28% 39% 12%	5440
	11th to 20th	Day	12% 3 9% 32% 35% 9%	5658
	21st to end	Day	9% 3 8% 28% 43% 10%	6904
June	1st to 10th	Day	15% 4 11% 25% 30% 15%	2800
	11th to 20th	Day	8% 2 6% 17% 39% 28%	2800
	21st to end	Day	7% 2 4 14% 33% 40%	2800
July	1st to 10th	Day	3 1 2 6% 23% 66%	6251
	11th to 20th	Day	7% 2 3 7% 20% 61%	5854
	21st to end	Day	7% 2 3 14% 34% 39%	6217
August	1st to 10th	Day	7% 2 3 12% 33% 43%	4048
	11th to 20th	Day	4 2 2 8% 30% 54%	3880
	21st to end	Day	6% 1 3 12% 29% 49%	4311
September	1st to 10th	Day	6% 2 4 11% 32% 45%	2400
	11th to 20th	Day	10% 2 5% 20% 38% 25%	2400
	21st to end	Day	12% 2 6% 17% 36% 27%	2190
October	1st to 10th	Day	11% 2 6% 13% 24% 44%	3280
	11th to 20th	Day	13% 4 7% 19% 36% 21%	3261
	21st to end	Day	18% 3 6% 13% 33% 27%	3558
November	1st to 10th	Day	20% 3 8% 22% 30% 17%	1978
	11th to 20th	Day	23% 5% 10% 20% 25% 17%	1890
	21st to end	Day	26% 3 8% 19% 24% 20%	1890
December	1st to 10th	Day	27% 4 7% 16% 26% 20%	2815
	11th to 20th	Day	34% 7% 12% 18% 19% 9%	3108
	21st to end	Day	37% 10% 16% 21% 12% 4	4092
January	1st to 10th	Night	31% 6% 12% 25% 20% 7%	7852
	11th to 20th	Night	21% 5% 8% 12% 24% 29%	7650
	21st to end	Night	36% 8% 10% 14% 20% 12%	8371
February	1st to 10th	Night	32% 4 8% 19% 23% 15%	2667
	11th to 20th	Night	27% 4 11% 23% 25% 11%	2459
	21st to end	Night	29% 6% 10% 23% 24% 9%	2076
March	1st to 10th	Night	35% 9% 12% 17% 22% 5%	5327
	11th to 20th	Night	26% 7% 14% 26% 18% 8%	5077
	21st to end	Night	33% 8% 15% 25% 16% 3	5254
April	1st to 10th	Night	25% 4 15% 27% 19% 10%	2000
	11th to 20th	Night	22% 4 12% 29% 24% 9%	1979
	21st to end	Night	21% 5% 10% 29% 28% 8%	2000
May	1st to 10th	Night	12% 4 11% 27% 31% 15%	4557
	11th to 20th	Night	16% 4 13% 25% 31% 11%	4246
	21st to end	Night	9% 5% 13% 26% 37% 9%	3972
June	1st to 10th	Night	16% 5% 14% 22% 28% 14%	1600
	11th to 20th	Night	12% 3 6% 18% 34% 27%	1600
	21st to end	Night	8% 1 4 16% 32% 39%	1600
July	1st to 10th	Night	5% 1 3 7% 20% 65%	3600
	11th to 20th	Night	11% 1 6% 8% 17% 57%	3996
	21st to end	Night	22% 2 7% 13% 26% 30%	4345
August	1st to 10th	Night	9% 1 3 13% 32% 42%	3088
	11th to 20th	Night	4 1 3 7% 26% 59%	3256
	21st to end	Night	7% 1 3 13% 28% 48%	3608
September	1st to 10th	Night	9% 2 3 11% 27% 47%	2000
	11th to 20th	Night	12% 2 6% 16% 35% 28%	2000
	21st to end	Night	11% 2 6% 16% 37% 29%	2203
October	1st to 10th	Night	11% 2 4 13% 25% 46%	3920
	11th to 20th	Night	14% 5% 7% 18% 33% 23%	3897
	21st to end	Night	16% 2 5% 15% 38% 25%	4253
November	1st to 10th	Night	17% 4 8% 20% 30% 21%	2539
	11th to 20th	Night	21% 4 12% 19% 25% 19%	2730
	21st to end	Night	25% 5% 11% 18% 24% 19%	2730
December	1st to 10th	Night	24% 4 6% 17% 32% 17%	4585
	11th to 20th	Night	37% 7% 11% 18% 17% 10%	5316
	21st to end	Night	43% 10% 13% 20% 10% 4	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	14% 10% 29% 32% 13% 2	330
	11th to 20th	Day	9% 9% 25% 35% 19% 3	430
	21st to end	Day	9% 8% 24% 34% 21% 4	473
February	1st to 10th	Day	11% 11% 25% 29% 19% 5%	463
	11th to 20th	Day	12% 12% 24% 31% 18% 3	535
	21st to end	Day	8% 9% 27% 37% 15% 3	446
March	1st to 10th	Day	10% 15% 25% 34% 16% 1	540
	11th to 20th	Day	10% 11% 26% 31% 19% 2	529
	21st to end	Day	9% 14% 29% 32% 14% 3	550
April	1st to 10th	Day	11% 8% 24% 29% 22% 6%	500
	11th to 20th	Day	6% 12% 24% 33% 20% 5%	492
	21st to end	Day	3 7% 26% 33% 21% 9%	500
May	1st to 10th	Day	6% 8% 24% 30% 24% 7%	503
	11th to 20th	Day	2 8% 21% 38% 22% 8%	528
	21st to end	Day	4 9% 20% 33% 23% 10%	573
June	1st to 10th	Day	3 4 16% 32% 31% 14%	530
	11th to 20th	Day	1 4 20% 35% 27% 14%	530
	21st to end	Day	2 14% 32% 33% 18%	530
July	1st to 10th	Day	8% 38% 34% 20%	526
	11th to 20th	Day	2 3 34% 37% 23%	524
	21st to end	Day	8% 30% 37% 25%	575
August	1st to 10th	Day	1 13% 35% 33% 18%	527
	11th to 20th	Day	1 1 8% 32% 38% 21%	517
	21st to end	Day	2 1 7% 29% 42% 20%	583
September	1st to 10th	Day	1 1 12% 28% 39% 19%	530
	11th to 20th	Day	2 3 13% 32% 38% 12%	530
	21st to end	Day	2 4 14% 31% 37% 13%	530
October	1st to 10th	Day	2 5% 14% 39% 31% 9%	530
	11th to 20th	Day	4 4 20% 33% 30% 9%	530
	21st to end	Day	3 4 14% 36% 34% 8%	583
November	1st to 10th	Day	5% 5% 18% 31% 31% 9%	454
	11th to 20th	Day	9% 6% 18% 38% 24% 4	330
	21st to end	Day	5% 6% 22% 41% 22% 4	330
December	1st to 10th	Day	9% 7% 21% 41% 17% 5%	258
	11th to 20th	Day	8% 5% 22% 34% 26% 5%	220
	21st to end	Day	15% 13% 27% 30% 13% 2	242
January	1st to 10th	Night	12% 6% 19% 41% 18% 3	840
	11th to 20th	Night	8% 3 17% 49% 22% 3	840
	21st to end	Night	11% 3 16% 45% 22% 3	924
February	1st to 10th	Night	11% 5% 15% 42% 24% 3	840
	11th to 20th	Night	9% 5% 19% 43% 20% 3	824
	21st to end	Night	9% 4 18% 49% 17% 2	692
March	1st to 10th	Night	9% 6% 19% 44% 20% 2	840
	11th to 20th	Night	7% 4 18% 40% 26% 4	828
	21st to end	Night	8% 4 21% 39% 25% 2	880
April	1st to 10th	Night	6% 4 20% 41% 27% 2	800
	11th to 20th	Night	6% 4 20% 38% 28% 4	791
	21st to end	Night	4 3 23% 35% 29% 7%	800
May	1st to 10th	Night	3 2 18% 41% 31% 6%	800
	11th to 20th	Night	3 2 14% 38% 37% 6%	672
	21st to end	Night	2 1 18% 40% 32% 6%	433
June	1st to 10th	Night	2 1 9% 40% 44% 5%	400
	11th to 20th	Night	1 1 12% 37% 43% 7%	400
	21st to end	Night	1 1 4 33% 53% 9%	400
July	1st to 10th	Night	1 2 25% 61% 12%	390
	11th to 20th	Night	1 1 10% 64% 25%	558
	21st to end	Night	1 1 1 13% 58% 27%	657
August	1st to 10th	Night	1 2 25% 53% 17%	691
	11th to 20th	Night	1 3 26% 55% 15%	792
	21st to end	Night	2 21% 60% 16%	880
September	1st to 10th	Night	1 3 25% 57% 14%	800
	11th to 20th	Night	3 1 7% 34% 44% 12%	800
	21st to end	Night	2 1 7% 32% 48% 10%	800
October	1st to 10th	Night	4 1 8% 38% 43% 6%	800
	11th to 20th	Night	3 3 9% 38% 41% 6%	800
	21st to end	Night	4 2 8% 43% 34% 8%	880
November	1st to 10th	Night	5% 2 13% 41% 35% 4	820
	11th to 20th	Night	5% 3 15% 47% 27% 4	840
	21st to end	Night	5% 2 18% 47% 25% 4	840
December	1st to 10th	Night	10% 3 16% 46% 23% 3	840
	11th to 20th	Night	12% 3 16% 48% 21% 2	840
	21st to end	Night	11% 5% 24% 42% 16% 2	924

Page generated at 2026-03-14 23:23:53. Version ac07

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