Crow's Nest Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crow's Nest 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	18% 7% 2 6% 4 4 4 4 5% 7% 39%	100820
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 37%	98128
Transparency	Day	24% 49% 7% 12% 7% 1	100579
	Night	25% 50% 6% 11% 7% 1	97990
Seeing	Day	20% 9% 29% 28% 12% 2	15006
	Night	22% 10% 29% 27% 11% 1	23930

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	15% 8% 3 6% 4 4 4 3 5% 6% 42%	2517
	11th to 20th	Day	18% 6% 2 5% 5% 4 4 4 5% 6% 43%	2520
	21st to end	Day	18% 12% 3 6% 3 3 4 3 5% 5% 38%	2772
February	1st to 10th	Day	18% 9% 2 6% 4 5% 4 4 5% 6% 37%	1700
	11th to 20th	Day	13% 8% 3 7% 6% 5% 5% 4 6% 6% 38%	1839
	21st to end	Day	16% 11% 3 6% 5% 5% 3 4 5% 5% 37%	1570
March	1st to 10th	Day	26% 11% 2 6% 4 4 4 3 4 5% 31%	3116
	11th to 20th	Day	16% 7% 2 6% 4 4 4 3 5% 7% 41%	3437
	21st to end	Day	25% 8% 2 6% 3 3 4 3 5% 5% 35%	3878
April	1st to 10th	Day	20% 9% 3 6% 4 3 4 4 5% 6% 36%	2280
	11th to 20th	Day	18% 5% 2 6% 4 4 4 3 5% 7% 41%	2360
	21st to end	Day	22% 7% 2 6% 5% 4 4 3 5% 5% 37%	2470
May	1st to 10th	Day	22% 9% 3 7% 5% 5% 4 4 6% 6% 29%	4106
	11th to 20th	Day	19% 8% 3 7% 5% 4 4 4 6% 8% 34%	4099
	21st to end	Day	17% 6% 2 5% 4 5% 4 4 6% 7% 39%	4837
June	1st to 10th	Day	22% 7% 3 6% 4 3 4 3 5% 7% 35%	2660
	11th to 20th	Day	17% 7% 2 5% 5% 3 4 4 5% 7% 41%	2660
	21st to end	Day	22% 6% 3 6% 5% 4 4 4 6% 6% 34%	2660
July	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 4 6% 9% 34%	4440
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 7% 10% 41%	4440
	21st to end	Day	19% 7% 2 5% 4 4 4 3 6% 8% 38%	4795
August	1st to 10th	Day	16% 6% 3 7% 4 4 5% 4 5% 8% 38%	4105
	11th to 20th	Day	16% 8% 2 7% 4 4 4 4 6% 8% 37%	4045
	21st to end	Day	8% 4 1 4 4 4 5% 4 6% 9% 50%	4358
September	1st to 10th	Day	12% 5% 2 4 4 3 4 3 5% 8% 50%	2223
	11th to 20th	Day	12% 6% 2 4 3 2 4 3 4 6% 54%	2090
	21st to end	Day	17% 7% 2 5% 3 3 3 3 5% 7% 45%	2090
October	1st to 10th	Day	18% 7% 3 6% 3 4 3 3 4 6% 42%	2090
	11th to 20th	Day	18% 6% 2 6% 5% 3 4 3 4 5% 44%	1838
	21st to end	Day	22% 8% 2 5% 3 4 3 3 5% 6% 41%	1881
November	1st to 10th	Day	16% 7% 1 4 4 3 3 3 4 6% 48%	1680
	11th to 20th	Day	20% 5% 2 4 3 3 4 3 5% 5% 46%	1710
	21st to end	Day	21% 8% 2 5% 3 2 3 3 3 5% 44%	1687
December	1st to 10th	Day	22% 9% 3 5% 5% 4 3 3 4 5% 38%	1387
	11th to 20th	Day	23% 8% 2 4 3 3 3 3 4 6% 41%	1708
	21st to end	Day	25% 9% 3 7% 4 3 4 4 5% 6% 30%	2772
January	1st to 10th	Night	16% 9% 3 6% 4 3 3 3 5% 6% 43%	4429
	11th to 20th	Night	13% 8% 3 9% 6% 5% 4 4 5% 5% 37%	4440
	21st to end	Night	20% 11% 3 7% 4 4 4 3 4 6% 34%	4884
February	1st to 10th	Night	17% 9% 3 6% 5% 5% 5% 4 5% 6% 36%	2478
	11th to 20th	Night	14% 10% 3 6% 5% 5% 4 4 5% 5% 39%	2223
	21st to end	Night	15% 10% 3 6% 4 4 4 3 6% 5% 40%	1884
March	1st to 10th	Night	29% 10% 2 6% 3 4 3 2 4 5% 32%	3724
	11th to 20th	Night	13% 8% 4 9% 5% 5% 5% 4 6% 8% 33%	3521
	21st to end	Night	25% 9% 3 6% 4 3 4 3 6% 5% 31%	3739
April	1st to 10th	Night	21% 10% 2 5% 4 4 4 3 4 6% 37%	1900
	11th to 20th	Night	19% 6% 2 5% 5% 4 5% 4 6% 7% 38%	1768
	21st to end	Night	23% 7% 2 6% 5% 4 4 3 5% 5% 36%	1710
May	1st to 10th	Night	23% 8% 3 7% 4 4 5% 4 7% 7% 28%	2834
	11th to 20th	Night	18% 9% 3 7% 6% 6% 6% 5% 6% 9% 26%	2813
	21st to end	Night	18% 9% 4 7% 4 4 4 4 6% 7% 34%	2747
June	1st to 10th	Night	22% 9% 3 6% 5% 5% 5% 3 5% 6% 31%	1520
	11th to 20th	Night	17% 8% 2 6% 4 3 4 4 6% 8% 38%	1520
	21st to end	Night	24% 8% 2 5% 4 4 5% 4 6% 7% 31%	1520
July	1st to 10th	Night	15% 8% 3 8% 5% 4 5% 5% 7% 9% 31%	2520
	11th to 20th	Night	13% 7% 2 8% 5% 5% 5% 4 6% 9% 35%	2520
	21st to end	Night	15% 6% 3 6% 5% 5% 4 4 7% 8% 37%	2739
August	1st to 10th	Night	21% 8% 3 8% 5% 5% 4 3 6% 7% 30%	2811
	11th to 20th	Night	16% 9% 3 7% 5% 4 5% 4 6% 8% 32%	2782
	21st to end	Night	11% 5% 2 5% 4 4 4 3 6% 8% 47%	3282
September	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 5% 6% 48%	1957
	11th to 20th	Night	15% 8% 2 4 3 2 4 2 4 6% 51%	2090
	21st to end	Night	15% 6% 2 5% 4 3 5% 3 4 6% 47%	2090
October	1st to 10th	Night	19% 6% 2 5% 4 4 4 3 6% 7% 39%	2090
	11th to 20th	Night	16% 6% 2 6% 3 4 4 3 6% 6% 43%	2337
	21st to end	Night	24% 7% 2 5% 4 4 3 3 5% 5% 38%	2717
November	1st to 10th	Night	17% 6% 2 5% 4 3 4 4 5% 5% 45%	2421
	11th to 20th	Night	18% 5% 2 5% 4 4 5% 4 5% 5% 44%	2470
	21st to end	Night	16% 8% 2 6% 5% 3 4 3 5% 7% 42%	2489
December	1st to 10th	Night	22% 10% 3 5% 4 4 3 4 4 6% 35%	2790
	11th to 20th	Night	23% 6% 2 5% 4 3 3 3 5% 6% 40%	3485
	21st to end	Night	24% 10% 3 6% 4 4 4 2 4 6% 34%	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	28% 38% 10% 17% 6%	2518
	11th to 20th	Day	26% 39% 8% 18% 8% 1	2520
	21st to end	Day	32% 42% 7% 13% 6%	2772
February	1st to 10th	Day	17% 65% 5% 6% 5% 1	1700
	11th to 20th	Day	18% 64% 4 7% 7% 1	1848
	21st to end	Day	15% 65% 4 8% 6% 2	1570
March	1st to 10th	Day	39% 41% 4 6% 9% 1	3119
	11th to 20th	Day	24% 43% 7% 13% 10% 2	3437
	21st to end	Day	34% 41% 2 8% 11% 4	3878
April	1st to 10th	Day	19% 64% 3 7% 5% 2	2280
	11th to 20th	Day	15% 66% 4 8% 5% 1	2360
	21st to end	Day	19% 65% 3 7% 6%	2470
May	1st to 10th	Day	32% 47% 9% 9% 3	4120
	11th to 20th	Day	30% 44% 11% 11% 3	4103
	21st to end	Day	24% 43% 11% 12% 9%	4837
June	1st to 10th	Day	15% 65% 5% 9% 4	2660
	11th to 20th	Day	14% 65% 4 8% 7% 1	2660
	21st to end	Day	16% 64% 4 10% 6%	2660
July	1st to 10th	Day	30% 39% 8% 15% 8%	4370
	11th to 20th	Day	23% 38% 12% 18% 8%	4365
	21st to end	Day	30% 37% 9% 15% 9% 1	4642
August	1st to 10th	Day	30% 39% 10% 16% 5%	4092
	11th to 20th	Day	31% 40% 12% 13% 4	4084
	21st to end	Day	16% 40% 11% 20% 14%	4358
September	1st to 10th	Day	11% 61% 6% 13% 8%	2223
	11th to 20th	Day	16% 60% 4 11% 8% 1	2090
	21st to end	Day	15% 60% 4 13% 7%	2090
October	1st to 10th	Day	19% 60% 4 9% 7% 2	2090
	11th to 20th	Day	15% 60% 5% 13% 7%	1838
	21st to end	Day	21% 59% 5% 8% 5% 1	1881
November	1st to 10th	Day	17% 59% 6% 11% 6% 1	1680
	11th to 20th	Day	17% 59% 4 8% 9% 2	1710
	21st to end	Day	18% 60% 7% 8% 7% 1	1687
December	1st to 10th	Day	20% 61% 5% 9% 6%	1387
	11th to 20th	Day	24% 49% 4 11% 9% 4	1708
	21st to end	Day	36% 40% 6% 11% 6% 2	2772
January	1st to 10th	Night	26% 38% 9% 18% 6% 2	4429
	11th to 20th	Night	27% 39% 9% 14% 9% 2	4440
	21st to end	Night	36% 42% 5% 12% 5%	4884
February	1st to 10th	Night	17% 65% 5% 6% 5% 2	2478
	11th to 20th	Night	17% 64% 3 7% 8% 1	2225
	21st to end	Night	17% 64% 4 7% 5% 3	1884
March	1st to 10th	Night	37% 41% 6% 8% 6% 2	3734
	11th to 20th	Night	27% 43% 6% 14% 8% 2	3522
	21st to end	Night	37% 42% 2 7% 8% 4	3739
April	1st to 10th	Night	19% 65% 2 6% 7% 1	1900
	11th to 20th	Night	18% 66% 3 7% 6% 1	1768
	21st to end	Night	19% 65% 3 6% 5% 2	1710
May	1st to 10th	Night	32% 45% 11% 8% 3	2840
	11th to 20th	Night	33% 44% 11% 9% 3	2814
	21st to end	Night	28% 45% 9% 10% 8% 1	2748
June	1st to 10th	Night	18% 66% 3 8% 5%	1520
	11th to 20th	Night	14% 66% 7% 8% 5%	1520
	21st to end	Night	18% 64% 4 9% 4	1520
July	1st to 10th	Night	31% 39% 8% 12% 10%	2480
	11th to 20th	Night	29% 38% 8% 16% 9%	2472
	21st to end	Night	29% 37% 8% 17% 8%	2651
August	1st to 10th	Night	38% 38% 9% 10% 4	2800
	11th to 20th	Night	33% 40% 9% 12% 5%	2809
	21st to end	Night	19% 40% 11% 17% 13%	3282
September	1st to 10th	Night	13% 61% 6% 12% 7% 1	1957
	11th to 20th	Night	18% 60% 4 11% 7% 1	2090
	21st to end	Night	15% 60% 4 15% 5% 1	2090
October	1st to 10th	Night	18% 60% 5% 10% 5% 1	2090
	11th to 20th	Night	13% 60% 6% 13% 7% 1	2337
	21st to end	Night	21% 60% 4 9% 5% 1	2717
November	1st to 10th	Night	19% 59% 3 11% 6% 1	2421
	11th to 20th	Night	18% 60% 3 8% 10% 1	2470
	21st to end	Night	17% 61% 6% 9% 7% 1	2489
December	1st to 10th	Night	22% 60% 3 8% 7%	2790
	11th to 20th	Night	23% 49% 5% 9% 12% 1	3486
	21st to end	Night	36% 38% 7% 11% 8% 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	24% 20% 27% 23% 6%	180
	11th to 20th	Day	26% 17% 28% 23% 5% 1	180
	21st to end	Day	18% 12% 38% 24% 8% 1	198
February	1st to 10th	Day	24% 13% 38% 21% 4	360
	11th to 20th	Day	18% 17% 44% 19% 2	452
	21st to end	Day	20% 15% 37% 22% 6%	382
March	1st to 10th	Day	23% 13% 36% 25% 4	460
	11th to 20th	Day	17% 15% 42% 21% 5%	460
	21st to end	Day	24% 15% 34% 18% 7% 3	506
April	1st to 10th	Day	24% 15% 32% 20% 7% 2	460
	11th to 20th	Day	23% 9% 35% 23% 9% 1	452
	21st to end	Day	26% 8% 33% 25% 7% 1	460
May	1st to 10th	Day	25% 6% 33% 26% 8% 2	463
	11th to 20th	Day	19% 5% 36% 29% 10% 2	487
	21st to end	Day	20% 6% 31% 32% 10% 2	529
June	1st to 10th	Day	21% 5% 26% 35% 11% 1	490
	11th to 20th	Day	17% 5% 29% 34% 12% 3	490
	21st to end	Day	22% 4 27% 30% 14% 2	490
July	1st to 10th	Day	18% 3 20% 39% 17% 3	485
	11th to 20th	Day	15% 2 20% 39% 20% 3	484
	21st to end	Day	14% 2 18% 42% 20% 4	532
August	1st to 10th	Day	15% 3 20% 37% 22% 3	486
	11th to 20th	Day	17% 2 19% 35% 20% 6%	479
	21st to end	Day	12% 3 20% 38% 22% 5%	539
September	1st to 10th	Day	13% 5% 25% 31% 22% 4	490
	11th to 20th	Day	14% 7% 26% 29% 18% 7%	490
	21st to end	Day	18% 6% 25% 29% 17% 4	490
October	1st to 10th	Day	20% 8% 22% 30% 17% 4	490
	11th to 20th	Day	21% 8% 29% 25% 14% 3	390
	21st to end	Day	28% 10% 28% 25% 9%	429
November	1st to 10th	Day	18% 14% 29% 26% 10% 2	368
	11th to 20th	Day	24% 12% 34% 21% 8% 1	370
	21st to end	Day	24% 15% 32% 21% 8% 1	370
December	1st to 10th	Day	26% 11% 39% 15% 8%	237
	11th to 20th	Day	25% 18% 34% 18% 4 1	180
	21st to end	Day	25% 21% 29% 18% 7% 1	198
January	1st to 10th	Night	21% 18% 37% 20% 4	760
	11th to 20th	Night	23% 20% 35% 18% 4	760
	21st to end	Night	20% 17% 38% 20% 4	836
February	1st to 10th	Night	22% 18% 35% 21% 4	760
	11th to 20th	Night	20% 18% 40% 20% 2	743
	21st to end	Night	19% 15% 37% 23% 6%	628
March	1st to 10th	Night	23% 15% 37% 21% 3	760
	11th to 20th	Night	22% 11% 35% 23% 8% 1	760
	21st to end	Night	24% 12% 31% 26% 6% 1	836
April	1st to 10th	Night	27% 10% 32% 25% 6%	760
	11th to 20th	Night	21% 7% 33% 29% 8% 1	644
	21st to end	Night	26% 5% 28% 28% 11% 1	570
May	1st to 10th	Night	24% 3 27% 32% 12% 2	570
	11th to 20th	Night	23% 5% 26% 32% 12% 2	562
	21st to end	Night	27% 3 20% 33% 15% 2	420
June	1st to 10th	Night	25% 4 18% 34% 15% 3	380
	11th to 20th	Night	19% 4 18% 39% 17% 3	380
	21st to end	Night	25% 3 16% 40% 15% 1	380
July	1st to 10th	Night	21% 2 11% 44% 21% 2	370
	11th to 20th	Night	20% 3 14% 39% 23% 2	368
	21st to end	Night	17% 2 13% 41% 25% 2	416
August	1st to 10th	Night	16% 3 14% 43% 23% 2	554
	11th to 20th	Night	16% 2 14% 41% 23% 4	562
	21st to end	Night	15% 3 15% 36% 27% 4	720
September	1st to 10th	Night	15% 2 19% 37% 25% 3	760
	11th to 20th	Night	19% 3 22% 28% 23% 5%	760
	21st to end	Night	18% 4 23% 33% 19% 3	760
October	1st to 10th	Night	22% 6% 21% 29% 19% 2	760
	11th to 20th	Night	19% 8% 30% 29% 11% 3	760
	21st to end	Night	28% 10% 28% 25% 8%	836
November	1st to 10th	Night	20% 8% 34% 28% 9% 2	745
	11th to 20th	Night	20% 15% 34% 22% 8% 1	760
	21st to end	Night	19% 17% 35% 22% 7%	769
December	1st to 10th	Night	27% 12% 38% 16% 7%	850
	11th to 20th	Night	24% 18% 36% 19% 3	835
	21st to end	Night	28% 14% 34% 19% 4	836

Page generated at 2024-10-30 01:22:56. Version ac07

Copyright © 2024 Attilla Danko.