CAMSAT Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the CAMSAT Observatory clear sky chart from 2005-11-06 to 2026-04-17.

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	15% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	131817
	Night	15% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	130327
Transparency	Day	46% 7% 13% 21% 11% 1	135407
	Night	48% 7% 13% 20% 12% 1	134823
Seeing	Day	17% 11% 27% 27% 14% 4	16186
	Night	19% 9% 29% 29% 12% 2	25692

By Month

Percentage Cloud Cover NE (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	17% 11% 4 9% 5% 6% 5% 3 5% 5% 30%	4661
	11th to 20th	Day	10% 18% 7% 17% 8% 6% 5% 4 4 4 16%	4985
	21st to end	Day	14% 14% 6% 13% 7% 5% 5% 4 5% 5% 21%	5780
February	1st to 10th	Day	15% 15% 5% 12% 6% 6% 5% 4 5% 5% 23%	1890
	11th to 20th	Day	13% 13% 6% 12% 6% 5% 4 4 4 6% 26%	1843
	21st to end	Day	18% 13% 5% 10% 5% 6% 4 3 5% 5% 27%	1607
March	1st to 10th	Day	19% 9% 4 8% 5% 4 4 3 5% 6% 32%	5042
	11th to 20th	Day	12% 11% 4 9% 5% 5% 5% 4 6% 8% 30%	5090
	21st to end	Day	18% 10% 3 8% 4 4 4 3 5% 5% 35%	5586
April	1st to 10th	Day	18% 12% 3 9% 5% 4 4 4 5% 7% 29%	2502
	11th to 20th	Day	20% 9% 3 6% 4 3 5% 4 4 6% 35%	2496
	21st to end	Day	19% 8% 3 7% 5% 5% 5% 4 5% 5% 34%	2600
May	1st to 10th	Day	20% 8% 3 7% 5% 5% 5% 4 6% 7% 32%	5933
	11th to 20th	Day	16% 9% 3 8% 5% 4 4 3 5% 7% 35%	6318
	21st to end	Day	18% 6% 2 6% 4 4 4 3 6% 7% 39%	6949
June	1st to 10th	Day	14% 7% 2 7% 5% 5% 5% 5% 7% 8% 37%	2800
	11th to 20th	Day	11% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	2800
	21st to end	Day	14% 5% 2 6% 4 4 5% 4 7% 9% 39%	2800
July	1st to 10th	Day	9% 5% 2 7% 5% 5% 5% 4 6% 10% 42%	6360
	11th to 20th	Day	8% 4 2 5% 4 5% 5% 4 6% 9% 48%	6360
	21st to end	Day	6% 4 2 5% 5% 5% 5% 5% 6% 9% 48%	6574
August	1st to 10th	Day	15% 6% 2 6% 4 5% 5% 4 6% 7% 40%	4234
	11th to 20th	Day	11% 6% 3 7% 5% 4 5% 4 7% 11% 38%	4174
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 45%	4459
September	1st to 10th	Day	12% 4 2 6% 4 5% 5% 4 6% 7% 45%	2400
	11th to 20th	Day	11% 5% 2 4 4 4 4 3 6% 8% 49%	2314
	21st to end	Day	13% 6% 3 7% 5% 4 4 4 6% 8% 39%	2140
October	1st to 10th	Day	16% 7% 2 6% 4 5% 5% 4 5% 6% 39%	2000
	11th to 20th	Day	18% 9% 3 7% 5% 4 5% 4 6% 6% 32%	2000
	21st to end	Day	22% 10% 4 8% 5% 5% 5% 4 5% 7% 26%	2200
November	1st to 10th	Day	15% 9% 3 8% 5% 5% 5% 3 6% 8% 33%	1766
	11th to 20th	Day	14% 11% 4 9% 6% 6% 6% 5% 6% 7% 26%	1680
	21st to end	Day	19% 12% 4 9% 6% 4 6% 3 5% 8% 23%	1680
December	1st to 10th	Day	18% 15% 5% 11% 7% 6% 7% 5% 6% 6% 15%	2680
	11th to 20th	Day	20% 14% 4 9% 5% 5% 4 3 5% 6% 25%	3066
	21st to end	Day	27% 15% 6% 11% 6% 4 4 3 4 4 16%	4048
January	1st to 10th	Night	15% 13% 4 10% 5% 5% 5% 4 6% 6% 28%	8234
	11th to 20th	Night	13% 15% 5% 13% 8% 6% 6% 4 6% 6% 19%	7896
	21st to end	Night	13% 12% 5% 10% 5% 5% 6% 4 6% 7% 26%	8401
February	1st to 10th	Night	13% 15% 5% 9% 6% 5% 5% 4 5% 6% 26%	2730
	11th to 20th	Night	14% 12% 5% 10% 6% 5% 4 4 5% 6% 28%	2663
	21st to end	Night	14% 12% 4 10% 5% 5% 5% 5% 5% 6% 29%	2195
March	1st to 10th	Night	17% 9% 4 7% 6% 5% 5% 3 5% 6% 33%	5018
	11th to 20th	Night	11% 8% 3 8% 5% 5% 4 5% 6% 8% 37%	5089
	21st to end	Night	21% 7% 3 6% 4 4 4 3 4 5% 39%	5588
April	1st to 10th	Night	18% 10% 3 7% 5% 4 5% 4 5% 6% 33%	2117
	11th to 20th	Night	16% 7% 2 7% 6% 5% 5% 4 5% 6% 39%	2003
	21st to end	Night	16% 7% 3 7% 5% 4 5% 4 6% 7% 36%	1800
May	1st to 10th	Night	24% 7% 3 6% 4 4 4 4 5% 5% 35%	4007
	11th to 20th	Night	15% 7% 2 7% 4 5% 6% 4 5% 7% 37%	3575
	21st to end	Night	18% 5% 2 5% 4 4 4 3 5% 7% 42%	3926
June	1st to 10th	Night	12% 6% 2 6% 4 5% 5% 4 6% 7% 43%	1600
	11th to 20th	Night	8% 5% 2 6% 6% 6% 4 5% 6% 9% 44%	1600
	21st to end	Night	12% 6% 2 5% 4 5% 5% 4 6% 9% 43%	1600
July	1st to 10th	Night	7% 6% 2 6% 5% 4 5% 4 6% 9% 47%	3600
	11th to 20th	Night	10% 4 2 5% 4 4 4 3 6% 8% 50%	3600
	21st to end	Night	9% 5% 2 4 3 4 3 4 6% 8% 53%	4261
August	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 6% 8% 48%	2915
	11th to 20th	Night	12% 4 2 5% 4 3 4 3 5% 7% 51%	2875
	21st to end	Night	10% 4 2 6% 4 4 4 4 6% 7% 48%	3406
September	1st to 10th	Night	9% 5% 2 6% 4 5% 4 5% 5% 8% 48%	2000
	11th to 20th	Night	10% 4 1 4 4 4 3 3 5% 7% 56%	2083
	21st to end	Night	16% 7% 2 7% 4 3 4 3 5% 6% 43%	2260
October	1st to 10th	Night	14% 7% 2 6% 5% 4 4 4 5% 6% 43%	2400
	11th to 20th	Night	19% 8% 3 6% 5% 4 5% 4 5% 6% 34%	2400
	21st to end	Night	20% 9% 3 6% 4 5% 6% 4 5% 7% 32%	2640
November	1st to 10th	Night	17% 7% 2 7% 5% 4 4 4 5% 7% 38%	2747
	11th to 20th	Night	15% 11% 3 8% 6% 5% 5% 4 6% 7% 30%	2940
	21st to end	Night	20% 11% 3 8% 5% 5% 5% 4 7% 7% 25%	2940
December	1st to 10th	Night	17% 13% 5% 10% 6% 5% 6% 5% 6% 7% 20%	4720
	11th to 20th	Night	17% 15% 4 9% 5% 5% 5% 4 5% 5% 25%	5348
	21st to end	Night	25% 13% 7% 11% 5% 5% 4 4 5% 5% 16%	7150

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	54% 7% 14% 14% 11%	4662
	11th to 20th	Day	70% 6% 10% 9% 5%	5018
	21st to end	Day	62% 6% 11% 11% 9%	5780
February	1st to 10th	Day	61% 8% 10% 16% 5% 1	1890
	11th to 20th	Day	58% 7% 12% 16% 7% 1	1852
	21st to end	Day	57% 6% 12% 18% 6%	1607
March	1st to 10th	Day	52% 6% 14% 14% 14% 1	5045
	11th to 20th	Day	49% 7% 18% 16% 7% 2	5090
	21st to end	Day	49% 5% 10% 20% 15% 1	5586
April	1st to 10th	Day	52% 7% 11% 18% 11% 1	2502
	11th to 20th	Day	48% 6% 11% 21% 13% 1	2496
	21st to end	Day	49% 7% 12% 18% 12% 3	2600
May	1st to 10th	Day	49% 7% 13% 16% 12% 4	5942
	11th to 20th	Day	47% 10% 11% 15% 15% 1	6322
	21st to end	Day	42% 7% 13% 23% 12% 3	6949
June	1st to 10th	Day	42% 9% 13% 21% 15% 1	2800
	11th to 20th	Day	37% 8% 13% 25% 15% 1	2800
	21st to end	Day	38% 8% 16% 23% 14% 1	2800
July	1st to 10th	Day	35% 7% 15% 27% 15% 2	6290
	11th to 20th	Day	31% 6% 14% 34% 15% 1	6285
	21st to end	Day	31% 8% 14% 31% 16%	6386
August	1st to 10th	Day	41% 8% 14% 22% 14% 1	4221
	11th to 20th	Day	37% 7% 17% 28% 10% 1	4213
	21st to end	Day	32% 8% 14% 36% 10% 1	4459
September	1st to 10th	Day	35% 9% 14% 29% 11% 1	2400
	11th to 20th	Day	31% 8% 15% 31% 14% 1	2314
	21st to end	Day	41% 9% 14% 26% 10%	2140
October	1st to 10th	Day	35% 6% 15% 27% 15% 1	3260
	11th to 20th	Day	37% 6% 17% 25% 14%	3240
	21st to end	Day	49% 7% 15% 22% 6%	3538
November	1st to 10th	Day	48% 8% 14% 20% 9% 1	1766
	11th to 20th	Day	54% 9% 14% 15% 8% 1	1680
	21st to end	Day	58% 7% 15% 16% 3	1680
December	1st to 10th	Day	67% 8% 14% 8% 3	2680
	11th to 20th	Day	60% 8% 13% 10% 9%	3066
	21st to end	Day	70% 8% 6% 10% 5%	4048
January	1st to 10th	Night	54% 7% 14% 19% 6%	8234
	11th to 20th	Night	64% 9% 10% 11% 7% 1	7938
	21st to end	Night	56% 7% 12% 13% 12% 1	8401
February	1st to 10th	Night	56% 8% 12% 18% 5% 1	2730
	11th to 20th	Night	57% 6% 12% 16% 8%	2665
	21st to end	Night	53% 7% 12% 19% 8% 1	2195
March	1st to 10th	Night	52% 5% 11% 17% 13% 3	5028
	11th to 20th	Night	43% 6% 18% 22% 10% 2	5090
	21st to end	Night	46% 4 11% 20% 17% 2	5588
April	1st to 10th	Night	51% 4 11% 19% 13% 1	2117
	11th to 20th	Night	47% 6% 10% 19% 16% 2	2003
	21st to end	Night	46% 8% 10% 19% 15% 2	1800
May	1st to 10th	Night	51% 6% 11% 14% 13% 6%	4014
	11th to 20th	Night	45% 8% 13% 18% 13% 2	3576
	21st to end	Night	41% 7% 13% 23% 15% 2	3927
June	1st to 10th	Night	39% 7% 11% 24% 16% 2	1600
	11th to 20th	Night	37% 6% 12% 23% 21% 2	1600
	21st to end	Night	37% 8% 13% 24% 17% 1	1600
July	1st to 10th	Night	34% 6% 15% 24% 19% 2	3560
	11th to 20th	Night	32% 6% 13% 32% 17% 1	3552
	21st to end	Night	30% 6% 12% 29% 22% 1	4134
August	1st to 10th	Night	35% 5% 14% 28% 15% 2	2904
	11th to 20th	Night	33% 6% 15% 32% 13% 1	2902
	21st to end	Night	33% 6% 13% 32% 14% 1	3406
September	1st to 10th	Night	33% 8% 14% 29% 14% 1	2000
	11th to 20th	Night	28% 6% 13% 34% 18%	2083
	21st to end	Night	41% 7% 12% 26% 13% 1	2260
October	1st to 10th	Night	34% 4 9% 28% 24% 1	3920
	11th to 20th	Night	42% 5% 14% 28% 10%	3899
	21st to end	Night	40% 6% 15% 27% 11% 1	4252
November	1st to 10th	Night	45% 7% 13% 22% 13% 1	2747
	11th to 20th	Night	51% 7% 15% 17% 9% 1	2940
	21st to end	Night	56% 9% 16% 15% 4	2940
December	1st to 10th	Night	61% 7% 14% 14% 4	4720
	11th to 20th	Night	59% 8% 11% 12% 9% 1	5348
	21st to end	Night	69% 9% 9% 8% 5%	7150

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% 21% 29% 19% 8%	220
	11th to 20th	Day	24% 21% 34% 15% 5% 1	282
	21st to end	Day	25% 19% 33% 19% 3	363
February	1st to 10th	Day	22% 22% 35% 16% 5% 1	330
	11th to 20th	Day	22% 21% 38% 16% 3	330
	21st to end	Day	25% 23% 33% 17% 2	313
March	1st to 10th	Day	21% 16% 36% 22% 5%	540
	11th to 20th	Day	21% 19% 32% 22% 6%	540
	21st to end	Day	26% 14% 32% 22% 6% 1	594
April	1st to 10th	Day	20% 17% 31% 25% 5%	540
	11th to 20th	Day	25% 13% 29% 21% 10% 2	516
	21st to end	Day	21% 12% 35% 20% 10% 2	500
May	1st to 10th	Day	20% 8% 26% 30% 10% 5%	503
	11th to 20th	Day	15% 5% 26% 33% 17% 4	527
	21st to end	Day	15% 3 22% 34% 20% 5%	573
June	1st to 10th	Day	14% 7% 28% 34% 15% 2	530
	11th to 20th	Day	12% 5% 25% 36% 21% 2	530
	21st to end	Day	15% 4 23% 37% 16% 5%	530
July	1st to 10th	Day	7% 3 20% 36% 27% 6%	525
	11th to 20th	Day	12% 3 19% 34% 23% 8%	524
	21st to end	Day	7% 3 22% 41% 20% 6%	576
August	1st to 10th	Day	11% 3 17% 35% 24% 10%	526
	11th to 20th	Day	10% 4 18% 31% 28% 9%	519
	21st to end	Day	11% 3 19% 37% 21% 9%	583
September	1st to 10th	Day	12% 6% 21% 30% 21% 11%	530
	11th to 20th	Day	8% 4 15% 31% 26% 16%	530
	21st to end	Day	15% 5% 28% 29% 16% 7%	530
October	1st to 10th	Day	18% 8% 26% 25% 17% 6%	530
	11th to 20th	Day	19% 13% 35% 24% 7% 2	530
	21st to end	Day	24% 14% 31% 22% 8% 1	583
November	1st to 10th	Day	21% 16% 29% 24% 10% 1	317
	11th to 20th	Day	18% 20% 35% 21% 6%	220
	21st to end	Day	24% 18% 38% 16% 4	220
December	1st to 10th	Day	22% 18% 32% 21% 5% 2	220
	11th to 20th	Day	25% 24% 29% 17% 5%	220
	21st to end	Day	29% 18% 38% 12% 2	242
January	1st to 10th	Night	24% 15% 38% 17% 5%	840
	11th to 20th	Night	26% 16% 33% 22% 3	840
	21st to end	Night	19% 13% 36% 25% 6% 1	924
February	1st to 10th	Night	20% 15% 39% 23% 3	840
	11th to 20th	Night	22% 15% 36% 23% 5%	823
	21st to end	Night	21% 14% 40% 21% 4	692
March	1st to 10th	Night	19% 13% 36% 28% 4 1	840
	11th to 20th	Night	21% 13% 34% 26% 5% 1	840
	21st to end	Night	20% 10% 31% 28% 10%	924
April	1st to 10th	Night	24% 10% 32% 28% 6%	840
	11th to 20th	Night	17% 10% 32% 30% 10% 1	783
	21st to end	Night	20% 6% 30% 32% 11%	600
May	1st to 10th	Night	20% 4 26% 31% 17% 2	580
	11th to 20th	Night	16% 3 27% 38% 16% 1	394
	21st to end	Night	10% 3 19% 43% 22% 2	433
June	1st to 10th	Night	13% 3 24% 41% 18% 1	400
	11th to 20th	Night	10% 3 25% 40% 22% 2	400
	21st to end	Night	12% 3 21% 42% 22% 1	400
July	1st to 10th	Night	6% 2 15% 46% 29% 2	390
	11th to 20th	Night	11% 3 15% 42% 27% 2	388
	21st to end	Night	9% 2 15% 46% 25% 2	581
August	1st to 10th	Night	10% 1 13% 40% 33% 4	597
	11th to 20th	Night	8% 2 14% 37% 33% 5%	594
	21st to end	Night	11% 2 20% 37% 26% 3	765
September	1st to 10th	Night	10% 5% 21% 34% 24% 6%	800
	11th to 20th	Night	12% 4 17% 29% 30% 8%	800
	21st to end	Night	18% 5% 19% 31% 22% 5%	800
October	1st to 10th	Night	17% 5% 28% 28% 21% 2	800
	11th to 20th	Night	22% 10% 29% 29% 9% 1	800
	21st to end	Night	24% 9% 30% 30% 6% 1	880
November	1st to 10th	Night	21% 10% 26% 32% 10% 1	820
	11th to 20th	Night	21% 14% 30% 26% 6% 2	840
	21st to end	Night	25% 11% 34% 24% 6%	840
December	1st to 10th	Night	28% 13% 33% 22% 4	840
	11th to 20th	Night	22% 15% 38% 22% 4	840
	21st to end	Night	30% 11% 36% 20% 2	924

Page generated at 2026-04-14 02:44:27. Version ac07

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