Chamberlain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chamberlain Observatory clear sky chart from 2005-11-06 to 2024-12-02.

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	12% 7% 3 6% 4 4 4 4 6% 8% 42%	101507
	Night	13% 8% 3 6% 4 4 4 3 5% 7% 43%	98206
Transparency	Day	39% 5% 12% 26% 17% 2	105100
	Night	40% 4 10% 25% 18% 3	102742
Seeing	Day	15% 8% 26% 27% 17% 6%	15732
	Night	17% 8% 29% 31% 14% 2	25571

By Month

Percentage Cloud Cover SE (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	11% 12% 6% 11% 6% 5% 5% 4 6% 7% 30%	2527
	11th to 20th	Day	13% 9% 4 9% 7% 8% 3 4 6% 6% 31%	2667
	21st to end	Day	21% 18% 6% 8% 4 3 3 2 4 4 28%	3135
February	1st to 10th	Day	15% 11% 4 8% 5% 4 4 4 5% 7% 33%	1710
	11th to 20th	Day	15% 11% 3 7% 5% 5% 4 3 5% 7% 36%	1838
	21st to end	Day	15% 11% 3 7% 4 4 4 3 5% 5% 39%	1570
March	1st to 10th	Day	18% 12% 3 6% 3 3 3 2 4 4 41%	3135
	11th to 20th	Day	11% 8% 3 5% 3 4 4 3 5% 8% 47%	3480
	21st to end	Day	16% 10% 3 8% 5% 4 5% 3 5% 7% 33%	4051
April	1st to 10th	Day	12% 7% 2 7% 5% 5% 4 3 6% 8% 41%	2280
	11th to 20th	Day	15% 9% 3 6% 5% 4 4 3 5% 6% 41%	2254
	21st to end	Day	17% 6% 3 7% 5% 5% 4 3 5% 6% 38%	2280
May	1st to 10th	Day	13% 7% 3 8% 5% 5% 5% 4 8% 11% 32%	3915
	11th to 20th	Day	17% 8% 2 6% 5% 4 5% 4 6% 7% 36%	4349
	21st to end	Day	9% 6% 2 6% 4 5% 5% 4 6% 7% 46%	4824
June	1st to 10th	Day	8% 5% 2 5% 4 4 5% 4 6% 10% 48%	2660
	11th to 20th	Day	8% 4 2 5% 4 4 4 5% 6% 9% 49%	2660
	21st to end	Day	5% 4 1 6% 5% 5% 5% 5% 7% 10% 47%	2660
July	1st to 10th	Day	13% 5% 2 6% 4 5% 5% 4 7% 9% 40%	4440
	11th to 20th	Day	5% 4 1 6% 4 5% 5% 4 7% 11% 48%	4440
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 5% 8% 11% 41%	4656
August	1st to 10th	Day	5% 4 2 5% 4 4 4 4 7% 9% 52%	4077
	11th to 20th	Day	13% 5% 2 6% 5% 5% 5% 4 6% 9% 41%	3729
	21st to end	Day	5% 4 2 5% 4 4 4 4 7% 9% 51%	4180
September	1st to 10th	Day	13% 5% 2 4 3 4 3 2 5% 8% 51%	2280
	11th to 20th	Day	9% 5% 1 5% 4 4 3 4 5% 8% 51%	2242
	21st to end	Day	8% 5% 2 5% 4 4 4 4 5% 7% 52%	2090
October	1st to 10th	Day	10% 5% 2 4 3 4 4 3 4 6% 56%	1914
	11th to 20th	Day	15% 5% 2 5% 3 3 3 3 4 6% 51%	1900
	21st to end	Day	17% 7% 2 6% 4 3 3 2 5% 5% 46%	2043
November	1st to 10th	Day	12% 5% 2 5% 4 3 3 3 4 7% 52%	1762
	11th to 20th	Day	14% 9% 2 5% 3 3 3 4 4 6% 47%	1800
	21st to end	Day	15% 12% 4 7% 4 5% 3 2 5% 6% 39%	1730
December	1st to 10th	Day	13% 12% 4 8% 4 4 4 4 4 6% 38%	1528
	11th to 20th	Day	14% 10% 4 6% 5% 4 5% 4 5% 5% 37%	1918
	21st to end	Day	20% 15% 5% 9% 4 5% 5% 3 5% 6% 24%	2783
January	1st to 10th	Night	14% 10% 6% 10% 4 4 4 3 4 5% 34%	4428
	11th to 20th	Night	14% 12% 5% 11% 5% 6% 7% 4 3 5% 28%	4299
	21st to end	Night	23% 17% 5% 9% 4 3 3 2 4 5% 25%	4532
February	1st to 10th	Night	15% 12% 5% 8% 5% 4 4 4 5% 5% 34%	2470
	11th to 20th	Night	15% 8% 3 7% 5% 4 4 3 5% 6% 41%	2227
	21st to end	Night	16% 10% 4 7% 5% 3 3 3 4 5% 41%	1884
March	1st to 10th	Night	21% 11% 2 5% 4 3 3 3 3 4 41%	3733
	11th to 20th	Night	14% 6% 2 5% 2 3 3 2 4 7% 51%	3494
	21st to end	Night	18% 9% 3 7% 5% 4 4 4 5% 6% 34%	3578
April	1st to 10th	Night	12% 7% 2 5% 5% 4 4 4 5% 7% 46%	1900
	11th to 20th	Night	14% 7% 2 6% 4 4 4 3 5% 8% 45%	1875
	21st to end	Night	18% 7% 3 8% 4 4 3 3 4 6% 40%	1900
May	1st to 10th	Night	17% 8% 2 6% 4 4 5% 4 6% 8% 38%	2978
	11th to 20th	Night	13% 7% 3 6% 4 4 4 4 4 7% 44%	2551
	21st to end	Night	8% 5% 2 7% 5% 4 6% 5% 6% 9% 42%	2743
June	1st to 10th	Night	8% 4 2 6% 3 4 4 4 6% 10% 50%	1520
	11th to 20th	Night	6% 4 2 5% 4 3 5% 4 7% 8% 53%	1520
	21st to end	Night	5% 3 2 5% 4 4 4 5% 6% 10% 51%	1520
July	1st to 10th	Night	12% 5% 2 5% 4 3 4 3 6% 10% 45%	2530
	11th to 20th	Night	4 3 1 5% 4 4 4 3 6% 9% 56%	2530
	21st to end	Night	8% 6% 2 7% 5% 5% 6% 5% 7% 10% 40%	2903
August	1st to 10th	Night	5% 3 1 4 3 3 4 4 6% 9% 58%	2861
	11th to 20th	Night	10% 5% 2 6% 3 4 4 4 5% 7% 50%	3100
	21st to end	Night	5% 3 1 3 3 4 4 3 5% 10% 58%	3476
September	1st to 10th	Night	10% 5% 2 4 3 4 3 3 4 8% 54%	1900
	11th to 20th	Night	9% 4 2 5% 4 4 5% 3 7% 7% 51%	1918
	21st to end	Night	9% 4 2 5% 3 4 4 4 5% 6% 54%	2090
October	1st to 10th	Night	9% 3 1 5% 4 3 3 3 4 7% 58%	2261
	11th to 20th	Night	13% 6% 2 5% 2 3 3 3 5% 6% 53%	2280
	21st to end	Night	18% 7% 2 5% 3 3 3 3 4 6% 46%	2553
November	1st to 10th	Night	10% 6% 2 4 3 3 4 3 4 5% 55%	2536
	11th to 20th	Night	12% 7% 2 5% 4 3 3 3 5% 7% 48%	2600
	21st to end	Night	18% 9% 2 6% 3 4 4 2 5% 5% 42%	2666
December	1st to 10th	Night	15% 11% 3 7% 5% 5% 4 4 6% 6% 34%	2687
	11th to 20th	Night	17% 8% 3 6% 4 4 3 3 4 5% 42%	3279
	21st to end	Night	20% 19% 5% 9% 5% 5% 4 3 4 4 21%	4884

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	53% 4 10% 23% 9% 1	2528
	11th to 20th	Day	53% 3 15% 19% 10%	2667
	21st to end	Day	62% 2 8% 17% 10% 1	3135
February	1st to 10th	Day	50% 4 12% 23% 10% 1	1710
	11th to 20th	Day	47% 4 10% 23% 14% 2	1848
	21st to end	Day	48% 4 9% 23% 14% 3	1570
March	1st to 10th	Day	48% 3 7% 23% 17% 2	3135
	11th to 20th	Day	35% 5% 13% 25% 17% 4	3480
	21st to end	Day	48% 6% 16% 23% 6% 1	4051
April	1st to 10th	Day	41% 4 12% 26% 16% 1	2280
	11th to 20th	Day	45% 3 9% 25% 15% 3	2254
	21st to end	Day	46% 4 12% 24% 13% 1	2280
May	1st to 10th	Day	44% 7% 16% 25% 8%	3950
	11th to 20th	Day	46% 6% 11% 26% 11%	4353
	21st to end	Day	36% 5% 12% 24% 22% 1	4837
June	1st to 10th	Day	32% 5% 14% 29% 16% 3	2660
	11th to 20th	Day	30% 6% 13% 25% 23% 3	2660
	21st to end	Day	30% 6% 17% 25% 17% 4	2660
July	1st to 10th	Day	39% 5% 11% 29% 14% 2	4371
	11th to 20th	Day	28% 7% 14% 30% 19% 2	4365
	21st to end	Day	34% 8% 18% 27% 12% 1	4510
August	1st to 10th	Day	27% 5% 15% 38% 15% 1	4063
	11th to 20th	Day	38% 5% 13% 26% 17%	3765
	21st to end	Day	27% 6% 16% 33% 15% 3	4179
September	1st to 10th	Day	33% 3 9% 29% 21% 5%	2280
	11th to 20th	Day	31% 4 8% 27% 26% 3	2242
	21st to end	Day	31% 5% 8% 30% 23% 3	2090
October	1st to 10th	Day	19% 3 6% 19% 47% 7%	3174
	11th to 20th	Day	24% 2 7% 21% 38% 7%	3140
	21st to end	Day	35% 2 6% 29% 26% 2	3345
November	1st to 10th	Day	33% 3 12% 27% 21% 4	1762
	11th to 20th	Day	39% 3 9% 25% 19% 5%	1800
	21st to end	Day	48% 4 9% 26% 13%	1730
December	1st to 10th	Day	48% 4 13% 24% 11%	1528
	11th to 20th	Day	48% 3 10% 24% 12% 3	1915
	21st to end	Day	62% 3 11% 15% 8% 1	2783
January	1st to 10th	Night	53% 3 11% 24% 9% 1	4428
	11th to 20th	Night	59% 4 7% 20% 9%	4299
	21st to end	Night	63% 3 8% 18% 7% 1	4532
February	1st to 10th	Night	52% 4 10% 21% 12% 1	2470
	11th to 20th	Night	45% 4 10% 22% 17% 2	2228
	21st to end	Night	48% 2 10% 23% 15% 3	1884
March	1st to 10th	Night	48% 4 7% 25% 14% 2	3733
	11th to 20th	Night	35% 4 11% 26% 20% 5%	3494
	21st to end	Night	50% 5% 10% 26% 7% 1	3578
April	1st to 10th	Night	38% 5% 10% 27% 17% 4	1900
	11th to 20th	Night	38% 4 11% 24% 19% 4	1875
	21st to end	Night	45% 4 8% 23% 17% 3	1900
May	1st to 10th	Night	43% 7% 17% 20% 13% 1	3008
	11th to 20th	Night	40% 5% 13% 28% 13% 1	2552
	21st to end	Night	36% 6% 13% 23% 19% 2	2751
June	1st to 10th	Night	30% 5% 15% 27% 20% 4	1520
	11th to 20th	Night	27% 5% 12% 28% 25% 4	1520
	21st to end	Night	27% 6% 15% 28% 17% 7%	1520
July	1st to 10th	Night	35% 4 12% 31% 16% 3	2490
	11th to 20th	Night	23% 5% 11% 39% 19% 2	2482
	21st to end	Night	36% 7% 18% 24% 13% 1	2811
August	1st to 10th	Night	22% 6% 16% 38% 17% 1	2851
	11th to 20th	Night	34% 5% 12% 26% 22% 1	3130
	21st to end	Night	23% 5% 15% 36% 18% 3	3476
September	1st to 10th	Night	31% 3 9% 27% 23% 7%	1900
	11th to 20th	Night	31% 3 9% 28% 25% 5%	1918
	21st to end	Night	30% 4 9% 24% 28% 4	2090
October	1st to 10th	Night	17% 2 6% 20% 48% 6%	3768
	11th to 20th	Night	24% 3 7% 23% 37% 7%	3779
	21st to end	Night	32% 3 8% 27% 25% 6%	4201
November	1st to 10th	Night	31% 4 11% 26% 22% 6%	2536
	11th to 20th	Night	37% 2 9% 27% 21% 4	2600
	21st to end	Night	44% 3 10% 26% 16% 1	2666
December	1st to 10th	Night	50% 4 11% 22% 12% 1	2687
	11th to 20th	Night	45% 3 10% 26% 14% 1	3281
	21st to end	Night	66% 4 8% 13% 7% 1	4884

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% 16% 36% 20% 6%	270
	11th to 20th	Day	28% 16% 36% 17% 3	270
	21st to end	Day	21% 17% 44% 14% 4	297
February	1st to 10th	Day	25% 14% 42% 14% 4	270
	11th to 20th	Day	24% 21% 31% 19% 4 1	270
	21st to end	Day	25% 16% 42% 17% 1	225
March	1st to 10th	Day	19% 16% 44% 19% 2	270
	11th to 20th	Day	28% 19% 32% 16% 5%	270
	21st to end	Day	30% 13% 33% 17% 6%	431
April	1st to 10th	Day	17% 12% 40% 21% 8% 1	460
	11th to 20th	Day	20% 14% 30% 23% 11% 2	452
	21st to end	Day	23% 13% 33% 21% 9% 2	460
May	1st to 10th	Day	19% 10% 32% 27% 11% 2	463
	11th to 20th	Day	18% 7% 28% 26% 18% 4	638
	21st to end	Day	13% 5% 29% 29% 16% 8%	734
June	1st to 10th	Day	8% 5% 22% 32% 23% 10%	680
	11th to 20th	Day	9% 4 21% 35% 25% 7%	680
	21st to end	Day	6% 5% 29% 34% 20% 7%	680
July	1st to 10th	Day	12% 1 15% 28% 29% 15%	671
	11th to 20th	Day	7% 3 15% 36% 30% 10%	668
	21st to end	Day	9% 2 16% 32% 31% 11%	739
August	1st to 10th	Day	8% 2 14% 36% 29% 11%	662
	11th to 20th	Day	13% 4 14% 28% 30% 11%	479
	21st to end	Day	9% 2 12% 29% 35% 13%	539
September	1st to 10th	Day	12% 4 15% 32% 24% 13%	490
	11th to 20th	Day	9% 2 12% 32% 31% 13%	490
	21st to end	Day	11% 6% 23% 28% 24% 8%	490
October	1st to 10th	Day	11% 7% 24% 36% 16% 6%	314
	11th to 20th	Day	14% 16% 31% 26% 11% 2	300
	21st to end	Day	28% 15% 29% 22% 7%	330
November	1st to 10th	Day	16% 10% 36% 21% 13% 5%	300
	11th to 20th	Day	19% 17% 34% 16% 11% 2	300
	21st to end	Day	28% 11% 30% 24% 6% 1	300
December	1st to 10th	Day	13% 14% 44% 18% 7% 4	273
	11th to 20th	Day	20% 13% 37% 26% 3	270
	21st to end	Day	25% 18% 38% 15% 4	297
January	1st to 10th	Night	17% 14% 38% 25% 6%	950
	11th to 20th	Night	22% 14% 37% 22% 5%	950
	21st to end	Night	21% 13% 38% 26% 2	1045
February	1st to 10th	Night	21% 14% 37% 24% 4	950
	11th to 20th	Night	18% 15% 39% 26% 2	752
	21st to end	Night	23% 15% 35% 25% 2	628
March	1st to 10th	Night	22% 12% 38% 23% 5%	760
	11th to 20th	Night	25% 10% 33% 26% 6%	584
	21st to end	Night	26% 10% 31% 28% 5%	627
April	1st to 10th	Night	16% 12% 38% 27% 6%	570
	11th to 20th	Night	17% 10% 35% 29% 10% 1	563
	21st to end	Night	22% 5% 37% 27% 8%	570
May	1st to 10th	Night	18% 6% 31% 34% 10% 1	570
	11th to 20th	Night	17% 4 24% 39% 16% 1	561
	21st to end	Night	10% 4 24% 40% 19% 3	617
June	1st to 10th	Night	10% 2 20% 39% 28% 1	570
	11th to 20th	Night	9% 2 19% 46% 21% 3	570
	21st to end	Night	6% 3 21% 43% 25% 2	570
July	1st to 10th	Night	12% 1 8% 34% 36% 8%	555
	11th to 20th	Night	4 1 14% 43% 34% 3	552
	21st to end	Night	7% 1 12% 39% 37% 3	624
August	1st to 10th	Night	8% 2 10% 43% 34% 3	567
	11th to 20th	Night	8% 2 11% 42% 33% 5%	564
	21st to end	Night	5% 1 10% 39% 39% 6%	627
September	1st to 10th	Night	12% 2 14% 35% 32% 5%	570
	11th to 20th	Night	10% 3 14% 34% 34% 5%	588
	21st to end	Night	11% 5% 23% 31% 26% 4	760
October	1st to 10th	Night	11% 2 26% 32% 25% 4	760
	11th to 20th	Night	17% 9% 30% 30% 13% 1	760
	21st to end	Night	22% 9% 33% 30% 6%	836
November	1st to 10th	Night	13% 7% 39% 31% 9% 1	780
	11th to 20th	Night	16% 13% 35% 29% 6% 1	800
	21st to end	Night	24% 11% 33% 25% 6%	866
December	1st to 10th	Night	22% 10% 36% 27% 5% 1	960
	11th to 20th	Night	23% 8% 33% 30% 6%	950
	21st to end	Night	28% 14% 32% 24% 2	1045

Page generated at 2024-11-29 09:43:10. Version ac07

Copyright © 2024 Attilla Danko.