Malpas Observatory West
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Malpas Observatory West clear sky chart from 2005-11-06 to 2026-02-01.

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	3 5% 2 5% 4 4 4 3 5% 6% 61%	136563
	Night	2 4 2 4 3 3 4 3 5% 6% 64%	132973
Transparency	Day	23% 4 6% 16% 28% 23%	131395
	Night	20% 3 6% 17% 30% 24%	129140
Seeing	Day	9% 14% 27% 29% 16% 5%	16561
	Night	6% 8% 21% 34% 26% 5%	26797

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 6% 3 7% 4 3 4 3 4 5% 60%	4188
	11th to 20th	Day	1 3 2 5% 4 3 3 2 3 5% 69%	4190
	21st to end	Day	4 11% 3 5% 3 3 4 3 4 5% 55%	4609
February	1st to 10th	Day	2 8% 3 5% 4 3 3 3 6% 5% 59%	1850
	11th to 20th	Day	3 8% 3 6% 5% 3 4 3 4 6% 56%	1950
	21st to end	Day	4 9% 3 6% 3 3 3 3 4 6% 56%	1650
March	1st to 10th	Day	2 8% 3 5% 3 3 3 3 5% 6% 59%	4907
	11th to 20th	Day	1 10% 4 7% 6% 6% 5% 3 6% 7% 45%	5000
	21st to end	Day	2 6% 3 5% 4 3 4 4 6% 8% 57%	5486
April	1st to 10th	Day	2 5% 2 5% 4 4 3 4 5% 7% 59%	2200
	11th to 20th	Day	2 4 2 4 3 3 3 2 5% 4 68%	2344
	21st to end	Day	2 5% 1 4 4 3 3 2 5% 6% 65%	2600
May	1st to 10th	Day	5% 5% 2 5% 4 4 4 3 4 5% 60%	5880
	11th to 20th	Day	2 3 1 4 4 4 4 3 5% 6% 64%	5841
	21st to end	Day	1 2 1 3 3 2 3 2 3 4 75%	6423
June	1st to 10th	Day	2 2 1 3 3 3 3 3 4 6% 70%	2600
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 4 81%	2600
	21st to end	Day	2 2 2 4 3 3 4 3 3 5% 70%	2600
July	1st to 10th	Day	1 2 1 3 3 3 3 3 4 5% 71%	5879
	11th to 20th	Day	4 4 2 7% 6% 7% 8% 6% 8% 8% 41%	5880
	21st to end	Day	3 3 1 6% 5% 5% 5% 4 5% 6% 56%	6401
August	1st to 10th	Day	3 4 2 6% 6% 6% 6% 4 6% 7% 50%	5779
	11th to 20th	Day	2 2 2 5% 4 4 5% 5% 6% 8% 57%	5798
	21st to end	Day	4 5% 2 7% 5% 7% 6% 5% 6% 8% 46%	6041
September	1st to 10th	Day	4 5% 2 7% 6% 6% 5% 4 6% 8% 48%	2200
	11th to 20th	Day	3 3 1 4 3 3 4 3 4 4 68%	2200
	21st to end	Day	3 2 1 4 3 4 4 3 4 5% 67%	2200
October	1st to 10th	Day	3 4 1 5% 3 3 3 2 4 4 68%	3539
	11th to 20th	Day	2 4 1 3 1 2 2 2 3 5% 74%	3250
	21st to end	Day	1 2 1 3 2 3 3 3 3 5% 75%	3548
November	1st to 10th	Day	3 3 1 2 2 3 3 2 4 6% 71%	2002
	11th to 20th	Day	2 3 1 3 3 3 4 4 3 5% 69%	1890
	21st to end	Day	3 7% 1 5% 3 2 2 2 4 5% 63%	1890
December	1st to 10th	Day	3 3 1 4 2 2 3 3 5% 7% 67%	3040
	11th to 20th	Day	2 4 2 5% 4 4 4 3 7% 10% 53%	3499
	21st to end	Day	4 7% 3 6% 5% 4 4 3 5% 8% 53%	4609
January	1st to 10th	Night	1 5% 3 6% 3 3 3 3 4 6% 62%	5997
	11th to 20th	Night	2 4 2 4 3 2 3 2 4 5% 69%	6010
	21st to end	Night	3 9% 3 7% 4 4 4 3 5% 5% 54%	6611
February	1st to 10th	Night	1 6% 2 5% 3 3 3 3 5% 6% 63%	2545
	11th to 20th	Night	3 6% 2 5% 4 3 4 3 4 7% 59%	2338
	21st to end	Night	3 9% 2 5% 3 3 4 2 4 6% 57%	1980
March	1st to 10th	Night	1 9% 3 5% 4 4 4 3 5% 6% 57%	4986
	11th to 20th	Night	2 7% 3 9% 5% 5% 6% 5% 6% 6% 46%	5000
	21st to end	Night	2 5% 1 4 3 3 4 3 6% 7% 61%	5489
April	1st to 10th	Night	2 4 1 4 3 3 3 3 4 6% 66%	2200
	11th to 20th	Night	2 4 1 4 3 3 4 3 3 5% 70%	1996
	21st to end	Night	2 2 1 3 2 2 3 2 4 6% 73%	1800
May	1st to 10th	Night	3 3 1 4 3 3 3 3 5% 5% 67%	4100
	11th to 20th	Night	1 2 1 3 2 3 3 2 4 5% 73%	4074
	21st to end	Night	1 2 2 2 2 2 3 5% 80%	4474
June	1st to 10th	Night	2 3 1 2 3 2 3 2 4 6% 73%	1800
	11th to 20th	Night	1 1 2 2 1 2 2 3 4 81%	1800
	21st to end	Night	2 2 1 2 3 3 2 2 4 5% 75%	1800
July	1st to 10th	Night	1 1 1 3 2 3 3 3 4 5% 74%	4100
	11th to 20th	Night	1 2 1 5% 4 5% 6% 5% 8% 9% 53%	4100
	21st to end	Night	2 3 1 4 3 4 4 5% 7% 9% 58%	4472
August	1st to 10th	Night	1 2 1 4 4 4 5% 5% 7% 12% 53%	4033
	11th to 20th	Night	1 1 1 2 2 3 3 3 7% 10% 67%	4051
	21st to end	Night	2 3 2 5% 4 5% 6% 5% 8% 8% 54%	4915
September	1st to 10th	Night	2 3 1 4 4 4 5% 4 7% 7% 58%	2200
	11th to 20th	Night	2 2 1 2 1 2 4 3 3 3 77%	2200
	21st to end	Night	1 1 1 3 2 2 2 2 3 4 76%	2200
October	1st to 10th	Night	2 2 1 3 3 3 4 2 4 5% 71%	3657
	11th to 20th	Night	3 3 1 3 2 2 2 2 4 6% 71%	3898
	21st to end	Night	1 1 1 3 2 2 3 2 4 6% 75%	4252
November	1st to 10th	Night	1 3 1 3 3 3 2 2 4 5% 73%	2513
	11th to 20th	Night	1 3 1 4 2 2 3 3 5% 6% 70%	2730
	21st to end	Night	2 6% 2 5% 3 3 3 3 4 5% 64%	2730
December	1st to 10th	Night	3 4 1 2 2 2 3 2 5% 7% 69%	4370
	11th to 20th	Night	3 4 2 4 3 3 3 3 5% 7% 62%	4941
	21st to end	Night	3 5% 2 5% 4 4 3 3 4 6% 61%	6611

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	26% 3 4 21% 31% 15%	4189
	11th to 20th	Day	19% 3 6% 19% 20% 33%	4190
	21st to end	Day	31% 2 4 13% 30% 20%	4609
February	1st to 10th	Day	26% 3 7% 16% 26% 22%	1850
	11th to 20th	Day	30% 3 5% 20% 24% 19%	1960
	21st to end	Day	30% 3 6% 16% 24% 21%	1650
March	1st to 10th	Day	25% 4 4 17% 32% 18%	4907
	11th to 20th	Day	34% 6% 7% 20% 23% 9%	5000
	21st to end	Day	25% 4 8% 29% 25% 9%	5486
April	1st to 10th	Day	24% 3 6% 19% 32% 16%	2200
	11th to 20th	Day	19% 3 4 16% 34% 24%	2347
	21st to end	Day	20% 3 5% 17% 39% 16%	2600
May	1st to 10th	Day	24% 4 6% 14% 35% 17%	5880
	11th to 20th	Day	18% 5% 5% 12% 37% 23%	5844
	21st to end	Day	14% 2 4 7% 35% 38%	6424
June	1st to 10th	Day	15% 3 4 12% 32% 34%	2600
	11th to 20th	Day	10% 2 2 6% 27% 52%	2600
	21st to end	Day	18% 3 4 9% 26% 41%	2600
July	1st to 10th	Day	15% 3 5% 9% 19% 48%	5816
	11th to 20th	Day	34% 7% 10% 17% 18% 13%	5811
	21st to end	Day	26% 6% 11% 12% 24% 21%	6217
August	1st to 10th	Day	40% 9% 15% 14% 11% 11%	4208
	11th to 20th	Day	25% 8% 11% 20% 22% 14%	4197
	21st to end	Day	30% 6% 9% 23% 22% 11%	4344
September	1st to 10th	Day	31% 7% 9% 14% 19% 19%	2200
	11th to 20th	Day	18% 4 6% 13% 33% 26%	2200
	21st to end	Day	20% 4 4 15% 31% 27%	2200
October	1st to 10th	Day	20% 2 5% 11% 23% 40%	3539
	11th to 20th	Day	15% 2 4 12% 44% 24%	3250
	21st to end	Day	13% 2 4 14% 34% 33%	3548
November	1st to 10th	Day	17% 2 4 23% 33% 21%	2002
	11th to 20th	Day	17% 3 5% 17% 32% 26%	1890
	21st to end	Day	24% 2 4 16% 33% 21%	1890
December	1st to 10th	Day	18% 3 5% 19% 30% 25%	3040
	11th to 20th	Day	26% 2 5% 19% 34% 13%	3498
	21st to end	Day	30% 3 7% 22% 26% 11%	4609
January	1st to 10th	Night	23% 3 4 19% 34% 17%	5997
	11th to 20th	Night	18% 2 6% 21% 25% 29%	6010
	21st to end	Night	31% 3 5% 10% 26% 25%	6611
February	1st to 10th	Night	23% 3 7% 18% 27% 22%	2545
	11th to 20th	Night	25% 3 5% 20% 26% 19%	2339
	21st to end	Night	28% 3 4 16% 27% 22%	1980
March	1st to 10th	Night	27% 4 5% 16% 31% 17%	4986
	11th to 20th	Night	33% 6% 6% 20% 24% 10%	5000
	21st to end	Night	21% 3 8% 29% 29% 10%	5489
April	1st to 10th	Night	20% 3 6% 19% 36% 17%	2200
	11th to 20th	Night	18% 2 4 15% 35% 25%	1996
	21st to end	Night	13% 2 5% 21% 41% 18%	1800
May	1st to 10th	Night	18% 5% 6% 18% 33% 20%	4097
	11th to 20th	Night	12% 2 5% 13% 42% 25%	4075
	21st to end	Night	9% 1 4 8% 42% 37%	4474
June	1st to 10th	Night	13% 4 3 10% 33% 37%	1800
	11th to 20th	Night	9% 2 3 8% 27% 53%	1800
	21st to end	Night	12% 3 3 9% 23% 50%	1800
July	1st to 10th	Night	12% 3 5% 10% 20% 49%	4055
	11th to 20th	Night	23% 5% 12% 23% 23% 14%	4046
	21st to end	Night	21% 5% 15% 14% 22% 23%	4344
August	1st to 10th	Night	27% 9% 21% 18% 12% 13%	2928
	11th to 20th	Night	13% 6% 17% 23% 25% 17%	2928
	21st to end	Night	19% 4 9% 20% 32% 15%	3538
September	1st to 10th	Night	22% 7% 10% 16% 24% 21%	2200
	11th to 20th	Night	13% 3 5% 16% 34% 30%	2200
	21st to end	Night	13% 3 5% 13% 33% 33%	2200
October	1st to 10th	Night	15% 3 6% 10% 25% 41%	3657
	11th to 20th	Night	16% 1 4 13% 43% 23%	3898
	21st to end	Night	12% 1 4 12% 34% 36%	4252
November	1st to 10th	Night	16% 2 4 19% 36% 24%	2513
	11th to 20th	Night	15% 3 5% 18% 32% 28%	2730
	21st to end	Night	23% 2 5% 17% 28% 24%	2730
December	1st to 10th	Night	16% 2 4 19% 31% 28%	4370
	11th to 20th	Night	22% 3 4 17% 36% 18%	4941
	21st to end	Night	25% 3 6% 24% 28% 15%	6611

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	15% 19% 29% 23% 12% 2	330
	11th to 20th	Day	11% 14% 34% 26% 12% 4	330
	21st to end	Day	10% 16% 30% 27% 15% 3	363
February	1st to 10th	Day	14% 19% 29% 24% 10% 5%	350
	11th to 20th	Day	13% 23% 32% 25% 7% 1	495
	21st to end	Day	14% 25% 29% 23% 7% 1	414
March	1st to 10th	Day	15% 26% 29% 21% 8% 1	500
	11th to 20th	Day	16% 20% 28% 22% 11% 2	500
	21st to end	Day	14% 25% 33% 20% 7% 1	550
April	1st to 10th	Day	10% 21% 36% 18% 13% 3	500
	11th to 20th	Day	14% 26% 32% 20% 7% 2	492
	21st to end	Day	11% 25% 30% 19% 12% 3	500
May	1st to 10th	Day	10% 23% 32% 26% 8% 2	503
	11th to 20th	Day	10% 17% 30% 24% 14% 4	528
	21st to end	Day	7% 17% 35% 26% 11% 3	573
June	1st to 10th	Day	5% 11% 32% 31% 18% 4	530
	11th to 20th	Day	4 14% 34% 30% 14% 4	530
	21st to end	Day	5% 7% 32% 35% 16% 4	530
July	1st to 10th	Day	2 3 29% 36% 24% 6%	526
	11th to 20th	Day	5% 2 16% 41% 25% 10%	524
	21st to end	Day	8% 4 15% 31% 30% 13%	575
August	1st to 10th	Day	7% 3 19% 40% 22% 9%	527
	11th to 20th	Day	5% 2 14% 44% 25% 10%	517
	21st to end	Day	9% 5% 15% 33% 27% 11%	583
September	1st to 10th	Day	7% 5% 20% 33% 25% 9%	530
	11th to 20th	Day	5% 12% 29% 32% 17% 5%	530
	21st to end	Day	6% 12% 25% 31% 22% 6%	530
October	1st to 10th	Day	8% 13% 29% 24% 21% 5%	495
	11th to 20th	Day	7% 12% 26% 28% 22% 5%	330
	21st to end	Day	7% 16% 22% 29% 21% 5%	363
November	1st to 10th	Day	11% 15% 23% 28% 19% 4	330
	11th to 20th	Day	9% 12% 26% 28% 20% 5%	330
	21st to end	Day	13% 15% 22% 30% 16% 4	330
December	1st to 10th	Day	8% 13% 25% 32% 18% 4	330
	11th to 20th	Day	5% 13% 30% 30% 18% 4	330
	21st to end	Day	18% 19% 24% 29% 9% 1	363
January	1st to 10th	Night	10% 11% 26% 30% 16% 8%	840
	11th to 20th	Night	10% 8% 26% 34% 16% 6%	840
	21st to end	Night	10% 14% 25% 31% 17% 4	924
February	1st to 10th	Night	7% 10% 29% 33% 16% 5%	800
	11th to 20th	Night	7% 12% 30% 34% 14% 3	784
	21st to end	Night	11% 14% 29% 30% 14% 2	660
March	1st to 10th	Night	9% 14% 29% 32% 13% 2	800
	11th to 20th	Night	10% 12% 24% 29% 21% 5%	800
	21st to end	Night	6% 12% 29% 34% 17% 2	880
April	1st to 10th	Night	4 13% 32% 33% 16% 2	800
	11th to 20th	Night	6% 14% 31% 32% 15% 2	669
	21st to end	Night	4 11% 31% 34% 17% 4	600
May	1st to 10th	Night	3 9% 27% 42% 18% 1	600
	11th to 20th	Night	4 7% 26% 34% 26% 4	591
	21st to end	Night	3 8% 27% 38% 21% 3	650
June	1st to 10th	Night	4 4 19% 43% 28% 2	600
	11th to 20th	Night	1 5% 24% 41% 25% 4	600
	21st to end	Night	2 2 17% 38% 37% 4	600
July	1st to 10th	Night	3 9% 39% 43% 6%	585
	11th to 20th	Night	4 1 3 28% 55% 10%	582
	21st to end	Night	3 1 5% 24% 54% 12%	657
August	1st to 10th	Night	3 1 5% 28% 50% 12%	597
	11th to 20th	Night	3 1 4 30% 54% 9%	594
	21st to end	Night	3 2 5% 26% 53% 12%	760
September	1st to 10th	Night	3 2 7% 29% 48% 11%	800
	11th to 20th	Night	4 3 13% 35% 39% 6%	800
	21st to end	Night	2 6% 15% 35% 33% 8%	800
October	1st to 10th	Night	4 6% 22% 36% 29% 3	800
	11th to 20th	Night	6% 4 20% 41% 24% 6%	800
	21st to end	Night	4 6% 21% 34% 25% 10%	880
November	1st to 10th	Night	4 8% 22% 37% 22% 6%	820
	11th to 20th	Night	5% 8% 21% 40% 21% 6%	840
	21st to end	Night	8% 8% 24% 35% 19% 5%	840
December	1st to 10th	Night	8% 9% 21% 35% 23% 4	840
	11th to 20th	Night	10% 8% 22% 36% 21% 3	840
	21st to end	Night	12% 12% 26% 32% 15% 3	924

Page generated at 2026-01-28 23:21:40. Version ac07

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