McCauley Lake Observatory
Clear Sky Chart
History

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

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	16% 12% 4 9% 5% 5% 4 4 5% 6% 30%	101929
	Night	15% 13% 5% 10% 6% 5% 4 3 5% 6% 29%	97012
Transparency	Day	53% 7% 11% 20% 9% 1	101686
	Night	54% 7% 11% 18% 9% 1	96874
Seeing	Day	23% 18% 32% 19% 7% 2	14658
	Night	22% 16% 32% 22% 8% 1	23540

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	14% 18% 7% 16% 7% 5% 4 2 4 5% 19%	2517
	11th to 20th	Day	11% 14% 7% 19% 11% 6% 5% 3 5% 5% 15%	2520
	21st to end	Day	16% 21% 11% 14% 5% 4 3 2 3 3 17%	3092
February	1st to 10th	Day	10% 17% 6% 15% 11% 5% 4 3 4 4 20%	1710
	11th to 20th	Day	11% 15% 6% 14% 7% 6% 5% 3 4 5% 24%	1663
	21st to end	Day	15% 17% 5% 11% 7% 5% 5% 4 5% 4 22%	1469
March	1st to 10th	Day	15% 19% 5% 10% 5% 4 4 3 4 6% 26%	3331
	11th to 20th	Day	9% 19% 7% 13% 6% 4 4 3 4 5% 25%	3480
	21st to end	Day	11% 11% 5% 9% 5% 5% 3 3 4 6% 39%	3872
April	1st to 10th	Day	20% 15% 4 9% 4 4 4 3 4 6% 27%	2280
	11th to 20th	Day	21% 12% 3 8% 3 4 4 3 4 4 34%	2287
	21st to end	Day	21% 12% 4 8% 4 4 3 3 5% 4 33%	2470
May	1st to 10th	Day	19% 10% 3 9% 4 5% 4 3 5% 6% 31%	4326
	11th to 20th	Day	16% 10% 3 7% 5% 4 4 3 6% 7% 35%	4398
	21st to end	Day	17% 8% 3 6% 4 4 4 3 5% 6% 39%	4837
June	1st to 10th	Day	21% 9% 3 7% 6% 5% 4 4 5% 7% 29%	2660
	11th to 20th	Day	16% 7% 2 6% 5% 5% 5% 4 6% 8% 36%	2692
	21st to end	Day	18% 7% 3 7% 5% 5% 6% 4 5% 8% 32%	2850
July	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 5% 7% 9% 32%	4578
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 5% 6% 8% 38%	4440
	21st to end	Day	11% 6% 2 6% 5% 5% 4 4 6% 8% 44%	4814
August	1st to 10th	Day	15% 8% 3 8% 6% 5% 6% 5% 6% 8% 31%	4114
	11th to 20th	Day	17% 8% 3 6% 5% 5% 5% 4 6% 8% 33%	4044
	21st to end	Day	10% 6% 2 5% 5% 6% 5% 5% 7% 10% 39%	4309
September	1st to 10th	Day	16% 7% 3 5% 4 5% 4 4 6% 8% 39%	2280
	11th to 20th	Day	14% 8% 3 6% 4 4 4 3 5% 7% 43%	2265
	21st to end	Day	20% 9% 3 7% 5% 4 4 3 5% 6% 33%	1991
October	1st to 10th	Day	18% 11% 3 7% 4 5% 3 4 5% 6% 33%	1900
	11th to 20th	Day	22% 16% 3 9% 6% 5% 3 3 4 5% 24%	1900
	21st to end	Day	26% 17% 5% 9% 5% 4 4 2 3 5% 19%	2043
November	1st to 10th	Day	15% 16% 5% 9% 4 4 4 3 6% 6% 28%	1559
	11th to 20th	Day	16% 18% 6% 11% 7% 5% 4 3 4 5% 22%	1520
	21st to end	Day	19% 19% 8% 13% 6% 5% 4 3 3 4 14%	1520
December	1st to 10th	Day	17% 23% 8% 12% 7% 4 3 2 3 4 15%	1520
	11th to 20th	Day	16% 19% 8% 13% 8% 5% 4 2 4 4 18%	1906
	21st to end	Day	21% 22% 8% 15% 6% 2 2 2 3 4 15%	2772
January	1st to 10th	Night	13% 19% 8% 15% 8% 5% 5% 4 5% 5% 13%	4429
	11th to 20th	Night	10% 14% 6% 19% 11% 9% 7% 4 5% 5% 13%	4440
	21st to end	Night	13% 18% 9% 15% 6% 6% 6% 3 4 4 15%	4564
February	1st to 10th	Night	11% 17% 6% 12% 8% 6% 4 4 5% 6% 18%	2470
	11th to 20th	Night	10% 16% 6% 13% 7% 6% 4 3 6% 4 25%	2403
	21st to end	Night	11% 17% 5% 12% 7% 5% 5% 4 4 6% 24%	1984
March	1st to 10th	Night	16% 14% 4 11% 6% 4 4 3 3 6% 29%	3505
	11th to 20th	Night	13% 17% 7% 11% 5% 4 4 3 5% 6% 25%	3479
	21st to end	Night	11% 11% 5% 10% 6% 4 4 3 6% 7% 33%	3759
April	1st to 10th	Night	19% 15% 4 9% 4 3 3 3 5% 5% 30%	1900
	11th to 20th	Night	18% 11% 3 7% 5% 4 3 3 4 5% 36%	1857
	21st to end	Night	18% 11% 5% 8% 5% 5% 4 3 4 5% 31%	1710
May	1st to 10th	Night	18% 11% 3 6% 3 4 4 3 5% 8% 35%	2613
	11th to 20th	Night	17% 9% 3 7% 4 4 4 4 5% 7% 36%	2495
	21st to end	Night	12% 9% 3 7% 5% 4 4 3 5% 7% 41%	2738
June	1st to 10th	Night	16% 9% 3 6% 4 5% 6% 4 5% 8% 34%	1520
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 7% 8% 43%	1477
	21st to end	Night	16% 8% 3 7% 5% 4 4 5% 6% 6% 37%	1330
July	1st to 10th	Night	11% 8% 3 7% 5% 5% 5% 3 5% 7% 40%	2365
	11th to 20th	Night	14% 8% 2 6% 4 4 4 3 5% 6% 43%	2520
	21st to end	Night	9% 7% 2 5% 4 4 5% 3 6% 8% 48%	2739
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 7% 9% 44%	2813
	11th to 20th	Night	16% 6% 3 6% 3 4 5% 3 5% 7% 42%	2785
	21st to end	Night	14% 5% 1 4 3 4 4 4 6% 9% 45%	3314
September	1st to 10th	Night	12% 6% 1 5% 4 4 5% 4 5% 8% 46%	1900
	11th to 20th	Night	14% 8% 2 6% 3 3 3 3 4 6% 49%	1912
	21st to end	Night	17% 9% 3 6% 3 4 4 3 5% 6% 40%	2188
October	1st to 10th	Night	19% 10% 3 6% 4 3 4 3 5% 6% 38%	2280
	11th to 20th	Night	19% 14% 4 7% 5% 5% 4 3 4 6% 28%	2280
	21st to end	Night	23% 17% 4 8% 5% 5% 4 3 4 5% 22%	2553
November	1st to 10th	Night	16% 14% 4 8% 5% 4 4 4 4 5% 29%	2538
	11th to 20th	Night	16% 15% 5% 10% 7% 6% 5% 3 5% 6% 24%	2660
	21st to end	Night	18% 19% 6% 12% 8% 5% 4 3 4 6% 16%	2660
December	1st to 10th	Night	17% 22% 8% 13% 7% 5% 4 4 4 4 13%	2660
	11th to 20th	Night	14% 22% 8% 12% 6% 4 4 3 4 4 19%	3288
	21st to end	Night	23% 21% 7% 15% 7% 4 3 2 3 4 11%	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	67% 8% 10% 9% 6%	2518
	11th to 20th	Day	70% 6% 8% 9% 6% 1	2520
	21st to end	Day	73% 4 6% 10% 6% 1	3092
February	1st to 10th	Day	67% 6% 8% 13% 6% 1	1710
	11th to 20th	Day	63% 5% 9% 13% 9% 2	1672
	21st to end	Day	63% 6% 8% 12% 10% 1	1469
March	1st to 10th	Day	59% 6% 11% 11% 11% 1	3334
	11th to 20th	Day	60% 6% 11% 14% 8% 1	3480
	21st to end	Day	46% 5% 9% 22% 15% 3	3872
April	1st to 10th	Day	59% 4 8% 18% 9% 3	2280
	11th to 20th	Day	53% 5% 7% 22% 12% 1	2287
	21st to end	Day	55% 5% 7% 17% 13% 3	2470
May	1st to 10th	Day	50% 8% 10% 20% 11% 2	4339
	11th to 20th	Day	46% 7% 12% 24% 9% 1	4402
	21st to end	Day	44% 8% 11% 18% 16% 3	4837
June	1st to 10th	Day	52% 8% 10% 18% 10% 1	2660
	11th to 20th	Day	44% 8% 12% 22% 13% 2	2692
	21st to end	Day	49% 8% 12% 20% 11% 1	2850
July	1st to 10th	Day	44% 8% 14% 23% 10% 1	4508
	11th to 20th	Day	40% 8% 15% 28% 9%	4365
	21st to end	Day	37% 7% 11% 31% 13%	4661
August	1st to 10th	Day	48% 8% 12% 23% 8%	4100
	11th to 20th	Day	45% 9% 15% 25% 6% 1	4083
	21st to end	Day	37% 7% 14% 31% 10%	4309
September	1st to 10th	Day	41% 8% 14% 26% 11% 1	2280
	11th to 20th	Day	40% 6% 14% 27% 13%	2265
	21st to end	Day	50% 8% 11% 23% 9%	1991
October	1st to 10th	Day	52% 7% 11% 20% 11% 1	1900
	11th to 20th	Day	63% 7% 10% 14% 5% 1	1900
	21st to end	Day	68% 5% 9% 12% 5% 1	2043
November	1st to 10th	Day	54% 7% 14% 18% 6% 1	1559
	11th to 20th	Day	63% 7% 10% 12% 7% 1	1520
	21st to end	Day	73% 6% 8% 9% 4 1	1520
December	1st to 10th	Day	74% 5% 8% 10% 4	1520
	11th to 20th	Day	70% 6% 7% 9% 7% 1	1906
	21st to end	Day	75% 3 5% 13% 3	2772
January	1st to 10th	Night	71% 8% 10% 8% 3	4429
	11th to 20th	Night	68% 11% 9% 7% 4 1	4440
	21st to end	Night	71% 7% 7% 8% 6%	4564
February	1st to 10th	Night	66% 6% 11% 12% 6% 1	2470
	11th to 20th	Night	60% 5% 10% 16% 8% 1	2405
	21st to end	Night	59% 6% 9% 18% 8% 1	1984
March	1st to 10th	Night	57% 5% 11% 14% 10% 1	3515
	11th to 20th	Night	57% 8% 13% 15% 7% 1	3480
	21st to end	Night	46% 7% 10% 21% 13% 2	3759
April	1st to 10th	Night	56% 4 8% 18% 12% 2	1900
	11th to 20th	Night	50% 5% 8% 22% 14% 1	1857
	21st to end	Night	55% 5% 8% 16% 15% 2	1710
May	1st to 10th	Night	45% 9% 12% 23% 10% 2	2619
	11th to 20th	Night	44% 10% 11% 24% 10% 1	2496
	21st to end	Night	39% 9% 12% 23% 15% 2	2739
June	1st to 10th	Night	46% 8% 12% 21% 12% 1	1520
	11th to 20th	Night	38% 7% 13% 26% 15% 1	1477
	21st to end	Night	45% 8% 15% 19% 12%	1330
July	1st to 10th	Night	41% 9% 16% 19% 14% 1	2325
	11th to 20th	Night	39% 6% 13% 31% 10%	2472
	21st to end	Night	34% 7% 13% 31% 15%	2651
August	1st to 10th	Night	36% 7% 16% 26% 13% 1	2803
	11th to 20th	Night	39% 9% 18% 26% 8% 1	2812
	21st to end	Night	35% 7% 15% 30% 10% 2	3314
September	1st to 10th	Night	34% 7% 17% 28% 12% 1	1900
	11th to 20th	Night	38% 5% 14% 31% 13%	1912
	21st to end	Night	44% 7% 13% 26% 10%	2188
October	1st to 10th	Night	47% 6% 13% 20% 14%	2280
	11th to 20th	Night	57% 6% 13% 17% 7%	2280
	21st to end	Night	63% 6% 11% 13% 7% 1	2553
November	1st to 10th	Night	55% 6% 14% 18% 7%	2538
	11th to 20th	Night	60% 7% 12% 14% 6% 1	2660
	21st to end	Night	69% 7% 10% 11% 3	2660
December	1st to 10th	Night	73% 6% 9% 9% 3	2660
	11th to 20th	Night	67% 6% 7% 12% 7% 1	3288
	21st to end	Night	78% 4 5% 9% 3	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% 24% 35% 13% 4 1	180
	11th to 20th	Day	28% 16% 37% 16% 2 2	180
	21st to end	Day	25% 19% 34% 18% 5%	288
February	1st to 10th	Day	28% 28% 33% 8% 2 1	270
	11th to 20th	Day	26% 31% 36% 6% 1	270
	21st to end	Day	36% 22% 32% 9% 1	281
March	1st to 10th	Day	24% 23% 37% 14% 2	460
	11th to 20th	Day	24% 21% 35% 15% 4 1	460
	21st to end	Day	28% 25% 30% 13% 4	506
April	1st to 10th	Day	27% 21% 33% 13% 5%	460
	11th to 20th	Day	35% 22% 21% 13% 7% 2	452
	21st to end	Day	29% 18% 33% 12% 6% 1	460
May	1st to 10th	Day	24% 19% 30% 18% 7% 2	463
	11th to 20th	Day	21% 18% 30% 20% 9% 2	487
	21st to end	Day	19% 19% 30% 20% 9% 2	529
June	1st to 10th	Day	21% 14% 38% 20% 6% 1	490
	11th to 20th	Day	18% 15% 35% 20% 10% 2	522
	21st to end	Day	20% 15% 34% 21% 7% 1	680
July	1st to 10th	Day	15% 10% 37% 29% 8% 2	571
	11th to 20th	Day	13% 14% 36% 25% 11% 2	484
	21st to end	Day	12% 12% 33% 30% 10% 2	532
August	1st to 10th	Day	15% 11% 29% 29% 10% 5%	486
	11th to 20th	Day	15% 9% 26% 30% 14% 5%	479
	21st to end	Day	16% 12% 33% 24% 11% 4	539
September	1st to 10th	Day	17% 12% 33% 21% 12% 5%	490
	11th to 20th	Day	17% 9% 26% 23% 17% 8%	490
	21st to end	Day	22% 17% 24% 21% 12% 4	490
October	1st to 10th	Day	24% 19% 26% 18% 10% 3	490
	11th to 20th	Day	29% 26% 26% 14% 4 1	490
	21st to end	Day	35% 19% 29% 14% 3	514
November	1st to 10th	Day	29% 22% 33% 12% 4	247
	11th to 20th	Day	31% 20% 33% 12% 3 1	180
	21st to end	Day	30% 23% 37% 6% 3 1	180
December	1st to 10th	Day	28% 23% 33% 15% 1	180
	11th to 20th	Day	33% 26% 28% 10% 1 1	180
	21st to end	Day	31% 24% 27% 15% 3 1	198
January	1st to 10th	Night	23% 22% 36% 16% 3 1	760
	11th to 20th	Night	25% 19% 31% 18% 5% 1	760
	21st to end	Night	17% 16% 36% 23% 7% 1	836
February	1st to 10th	Night	21% 22% 39% 15% 4	760
	11th to 20th	Night	19% 21% 40% 17% 4	743
	21st to end	Night	22% 23% 32% 20% 2	628
March	1st to 10th	Night	21% 21% 36% 19% 3	760
	11th to 20th	Night	20% 20% 36% 17% 5% 1	760
	21st to end	Night	19% 18% 35% 21% 6%	836
April	1st to 10th	Night	26% 17% 33% 19% 4	760
	11th to 20th	Night	25% 20% 28% 18% 9%	733
	21st to end	Night	22% 15% 30% 22% 11%	570
May	1st to 10th	Night	22% 10% 28% 30% 10% 1	440
	11th to 20th	Night	21% 12% 31% 28% 8%	374
	21st to end	Night	14% 12% 35% 28% 11%	411
June	1st to 10th	Night	18% 9% 37% 29% 6% 1	380
	11th to 20th	Night	18% 10% 30% 30% 11%	380
	21st to end	Night	20% 10% 28% 31% 10% 1	380
July	1st to 10th	Night	11% 7% 32% 35% 14% 1	370
	11th to 20th	Night	15% 7% 30% 32% 15% 1	368
	21st to end	Night	9% 7% 37% 33% 12% 1	416
August	1st to 10th	Night	12% 5% 27% 35% 19% 2	555
	11th to 20th	Night	11% 5% 25% 36% 21% 3	564
	21st to end	Night	15% 8% 29% 30% 15% 2	739
September	1st to 10th	Night	14% 9% 30% 29% 16% 2	760
	11th to 20th	Night	17% 9% 27% 25% 18% 4	760
	21st to end	Night	21% 11% 23% 25% 17% 2	760
October	1st to 10th	Night	25% 14% 28% 22% 10% 2	760
	11th to 20th	Night	27% 18% 31% 16% 7% 1	760
	21st to end	Night	31% 18% 29% 18% 4	836
November	1st to 10th	Night	27% 17% 31% 20% 5% 1	745
	11th to 20th	Night	24% 23% 31% 15% 7%	760
	21st to end	Night	31% 18% 29% 18% 3 1	760
December	1st to 10th	Night	29% 21% 34% 11% 5%	760
	11th to 20th	Night	25% 22% 33% 16% 3 1	760
	21st to end	Night	33% 19% 30% 14% 3 1	836

Page generated at 2024-10-30 01:22:57. Version ac07

Copyright © 2024 Attilla Danko.