Echo Hill Outdoor School
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Echo Hill Outdoor School clear sky chart from 2005-11-06 to 2024-11-28.

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	14% 6% 2 6% 4 4 4 4 6% 8% 43%	101435
	Night	15% 7% 2 6% 4 4 4 4 5% 7% 42%	98033
Transparency	Day	21% 47% 7% 14% 9% 2	105066
	Night	22% 47% 6% 14% 9% 2	102540
Seeing	Day	16% 7% 23% 27% 19% 8%	15080
	Night	17% 7% 27% 32% 15% 2	24476

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	16% 5% 2 5% 3 3 3 3 5% 7% 48%	2517
	11th to 20th	Day	14% 10% 3 8% 6% 4 4 3 4 5% 39%	2744
	21st to end	Day	19% 7% 2 6% 4 5% 4 3 5% 6% 38%	3124
February	1st to 10th	Day	16% 7% 2 6% 4 4 5% 4 5% 7% 40%	1710
	11th to 20th	Day	17% 8% 2 5% 4 4 4 3 6% 7% 42%	1769
	21st to end	Day	18% 9% 3 7% 3 4 3 3 5% 5% 40%	1570
March	1st to 10th	Day	23% 5% 2 5% 3 3 3 3 5% 7% 41%	3238
	11th to 20th	Day	10% 5% 2 4 4 4 5% 3 6% 7% 50%	3480
	21st to end	Day	21% 6% 2 6% 4 3 3 3 4 5% 43%	3969
April	1st to 10th	Day	14% 6% 2 5% 4 4 5% 4 6% 7% 42%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 6% 7% 47%	2254
	21st to end	Day	17% 5% 3 5% 3 3 4 4 6% 7% 43%	2280
May	1st to 10th	Day	25% 8% 2 5% 4 3 4 4 5% 7% 32%	3948
	11th to 20th	Day	21% 7% 2 7% 4 4 4 4 6% 8% 31%	4398
	21st to end	Day	10% 4 2 6% 3 4 4 4 7% 9% 47%	4823
June	1st to 10th	Day	10% 5% 2 5% 5% 5% 5% 5% 7% 11% 42%	2660
	11th to 20th	Day	10% 5% 2 5% 5% 4 5% 5% 6% 9% 44%	2660
	21st to end	Day	10% 3 2 5% 3 4 4 4 7% 10% 48%	2660
July	1st to 10th	Day	5% 4 2 5% 5% 5% 5% 5% 9% 11% 44%	4440
	11th to 20th	Day	9% 4 2 5% 5% 5% 5% 4 8% 12% 41%	4440
	21st to end	Day	9% 6% 2 6% 5% 5% 7% 5% 8% 10% 37%	4540
August	1st to 10th	Day	15% 6% 2 5% 3 4 5% 5% 7% 10% 36%	4104
	11th to 20th	Day	11% 4 2 6% 4 4 5% 4 6% 10% 45%	3775
	21st to end	Day	9% 4 2 6% 3 4 4 4 6% 8% 49%	4180
September	1st to 10th	Day	13% 4 2 5% 4 3 4 4 5% 8% 47%	2280
	11th to 20th	Day	11% 5% 1 5% 3 4 4 4 5% 8% 50%	2280
	21st to end	Day	18% 7% 3 6% 4 4 4 4 5% 7% 38%	2038
October	1st to 10th	Day	16% 7% 2 5% 3 3 3 3 6% 7% 47%	1900
	11th to 20th	Day	14% 6% 2 4 3 3 3 3 5% 6% 51%	1900
	21st to end	Day	14% 6% 2 6% 3 3 4 3 5% 5% 49%	2090
November	1st to 10th	Day	13% 5% 2 4 3 3 4 3 5% 6% 52%	1766
	11th to 20th	Day	13% 5% 2 4 3 5% 4 3 5% 7% 49%	1800
	21st to end	Day	14% 6% 2 5% 4 3 4 3 5% 5% 48%	1616
December	1st to 10th	Day	18% 6% 2 6% 4 3 4 4 5% 7% 42%	1520
	11th to 20th	Day	17% 8% 2 5% 4 3 3 2 5% 7% 42%	1910
	21st to end	Day	15% 6% 3 6% 5% 6% 4 4 5% 7% 39%	2772
January	1st to 10th	Night	16% 8% 3 6% 4 4 4 3 4 6% 43%	4429
	11th to 20th	Night	18% 8% 2 5% 4 4 3 3 4 6% 43%	4212
	21st to end	Night	21% 8% 2 6% 4 3 3 3 4 5% 40%	4532
February	1st to 10th	Night	16% 8% 2 5% 5% 4 4 3 5% 6% 41%	2470
	11th to 20th	Night	19% 7% 2 6% 4 3 3 3 4 5% 44%	2295
	21st to end	Night	18% 8% 2 5% 4 3 4 4 4 5% 42%	1884
March	1st to 10th	Night	22% 8% 2 5% 4 3 3 3 4 6% 40%	3611
	11th to 20th	Night	12% 5% 2 5% 4 4 3 4 5% 7% 49%	3480
	21st to end	Night	16% 8% 3 6% 3 4 3 3 3 5% 46%	3663
April	1st to 10th	Night	15% 7% 3 6% 3 4 4 4 5% 7% 41%	1900
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 5% 6% 45%	1875
	21st to end	Night	18% 6% 2 4 3 4 3 3 5% 8% 45%	1900
May	1st to 10th	Night	22% 9% 3 6% 5% 4 5% 3 5% 6% 32%	2959
	11th to 20th	Night	22% 9% 3 7% 4 5% 4 4 6% 7% 29%	2495
	21st to end	Night	11% 5% 2 7% 4 4 4 4 6% 9% 43%	2732
June	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 5% 9% 46%	1520
	11th to 20th	Night	10% 6% 2 7% 5% 5% 5% 4 6% 10% 41%	1520
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 7% 11% 42%	1520
July	1st to 10th	Night	7% 5% 3 7% 5% 6% 6% 5% 8% 10% 39%	2520
	11th to 20th	Night	10% 5% 2 6% 6% 4 6% 4 7% 11% 38%	2520
	21st to end	Night	14% 7% 3 7% 5% 5% 5% 5% 6% 8% 36%	3009
August	1st to 10th	Night	16% 6% 3 7% 4 4 6% 4 7% 9% 33%	2825
	11th to 20th	Night	11% 7% 3 7% 5% 5% 6% 4 6% 8% 38%	3007
	21st to end	Night	10% 5% 2 5% 4 4 5% 3 5% 7% 49%	3476
September	1st to 10th	Night	12% 6% 3 7% 3 4 4 3 6% 7% 46%	1900
	11th to 20th	Night	10% 6% 2 5% 4 3 3 3 5% 7% 52%	1900
	21st to end	Night	18% 7% 3 7% 5% 5% 4 3 5% 6% 39%	2139
October	1st to 10th	Night	18% 7% 2 6% 4 3 3 3 4 5% 43%	2280
	11th to 20th	Night	15% 5% 2 4 4 3 3 3 5% 6% 51%	2280
	21st to end	Night	16% 5% 1 4 4 4 3 3 4 6% 50%	2508
November	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 5% 6% 53%	2529
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 5% 6% 48%	2600
	21st to end	Night	13% 5% 1 6% 5% 4 4 3 6% 7% 47%	2714
December	1st to 10th	Night	18% 6% 3 6% 4 3 4 4 5% 6% 40%	2660
	11th to 20th	Night	18% 5% 2 6% 4 4 4 3 5% 7% 42%	3285
	21st to end	Night	15% 8% 3 6% 4 5% 5% 5% 6% 8% 36%	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	23% 37% 5% 22% 10% 3	2518
	11th to 20th	Day	33% 37% 4 14% 9% 2	2744
	21st to end	Day	30% 40% 10% 13% 6% 1	3124
February	1st to 10th	Day	17% 66% 7% 7% 3 1	1710
	11th to 20th	Day	15% 64% 3 10% 7% 2	1778
	21st to end	Day	17% 65% 4 7% 5% 1	1570
March	1st to 10th	Day	31% 41% 5% 14% 5% 3	3238
	11th to 20th	Day	16% 42% 3 23% 14% 2	3480
	21st to end	Day	27% 40% 6% 12% 12% 3	3969
April	1st to 10th	Day	16% 66% 4 7% 6% 1	2280
	11th to 20th	Day	13% 66% 5% 9% 5% 1	2254
	21st to end	Day	15% 65% 5% 8% 7% 1	2280
May	1st to 10th	Day	37% 41% 6% 12% 4 1	3983
	11th to 20th	Day	34% 41% 11% 13% 2	4402
	21st to end	Day	19% 41% 9% 17% 12% 2	4837
June	1st to 10th	Day	14% 66% 4 9% 6% 1	2660
	11th to 20th	Day	12% 66% 3 10% 7% 1	2660
	21st to end	Day	10% 65% 7% 10% 8%	2660
July	1st to 10th	Day	20% 41% 18% 9% 8% 4	4370
	11th to 20th	Day	25% 38% 12% 19% 5% 1	4365
	21st to end	Day	28% 38% 9% 13% 11% 1	4395
August	1st to 10th	Day	28% 40% 11% 18% 4	4091
	11th to 20th	Day	21% 39% 8% 23% 8%	3812
	21st to end	Day	17% 38% 8% 21% 15% 1	4180
September	1st to 10th	Day	14% 60% 7% 10% 7% 2	2280
	11th to 20th	Day	14% 60% 4 11% 9% 2	2280
	21st to end	Day	22% 60% 3 10% 5%	2038
October	1st to 10th	Day	22% 37% 5% 10% 22% 4	3160
	11th to 20th	Day	11% 37% 6% 19% 21% 8%	3140
	21st to end	Day	8% 36% 6% 23% 21% 5%	3428
November	1st to 10th	Day	17% 56% 6% 10% 8% 3	1766
	11th to 20th	Day	13% 57% 4 11% 13% 2	1800
	21st to end	Day	15% 58% 5% 16% 6% 2	1616
December	1st to 10th	Day	21% 60% 6% 8% 5% 1	1520
	11th to 20th	Day	22% 48% 5% 16% 8% 1	1906
	21st to end	Day	30% 38% 10% 14% 7%	2772
January	1st to 10th	Night	29% 37% 5% 17% 9% 3	4429
	11th to 20th	Night	27% 37% 5% 18% 11% 2	4212
	21st to end	Night	31% 39% 4 17% 7% 1	4532
February	1st to 10th	Night	16% 65% 6% 9% 3 1	2470
	11th to 20th	Night	16% 63% 2 7% 9% 1	2297
	21st to end	Night	16% 64% 5% 8% 5% 3	1884
March	1st to 10th	Night	34% 40% 5% 15% 5% 1	3611
	11th to 20th	Night	17% 41% 6% 23% 11% 3	3480
	21st to end	Night	25% 40% 4 11% 16% 3	3663
April	1st to 10th	Night	16% 65% 2 8% 7% 1	1900
	11th to 20th	Night	14% 66% 5% 9% 5% 2	1875
	21st to end	Night	15% 65% 4 8% 7% 1	1900
May	1st to 10th	Night	36% 41% 6% 12% 5% 1	2989
	11th to 20th	Night	36% 42% 9% 10% 3	2496
	21st to end	Night	23% 41% 10% 13% 10% 3	2739
June	1st to 10th	Night	14% 66% 4 9% 7%	1520
	11th to 20th	Night	13% 67% 4 10% 6%	1520
	21st to end	Night	11% 65% 5% 12% 6% 1	1520
July	1st to 10th	Night	25% 40% 15% 10% 8% 2	2480
	11th to 20th	Night	27% 38% 14% 16% 4 1	2472
	21st to end	Night	33% 38% 8% 13% 9%	2913
August	1st to 10th	Night	33% 40% 12% 11% 4	2814
	11th to 20th	Night	26% 39% 7% 20% 7%	3035
	21st to end	Night	19% 38% 5% 22% 15%	3476
September	1st to 10th	Night	14% 61% 6% 11% 6% 2	1900
	11th to 20th	Night	14% 60% 3 10% 11% 2	1900
	21st to end	Night	22% 60% 4 7% 6%	2139
October	1st to 10th	Night	28% 38% 5% 12% 14% 3	3800
	11th to 20th	Night	11% 37% 7% 15% 25% 5%	3779
	21st to end	Night	10% 36% 7% 24% 17% 5%	4120
November	1st to 10th	Night	15% 57% 6% 11% 8% 3	2529
	11th to 20th	Night	16% 57% 3 10% 12% 3	2600
	21st to end	Night	14% 58% 5% 13% 8% 1	2714
December	1st to 10th	Night	20% 60% 6% 9% 5%	2660
	11th to 20th	Night	21% 49% 5% 10% 11% 3	3288
	21st to end	Night	30% 39% 9% 15% 6%	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	19% 18% 35% 20% 6% 2	180
	11th to 20th	Day	18% 22% 31% 20% 8%	243
	21st to end	Day	18% 14% 40% 20% 7% 1	297
February	1st to 10th	Day	21% 9% 39% 21% 9% 1	270
	11th to 20th	Day	24% 16% 35% 21% 3 1	377
	21st to end	Day	26% 13% 33% 23% 5% 1	382
March	1st to 10th	Day	16% 13% 34% 30% 6% 1	460
	11th to 20th	Day	19% 12% 35% 23% 8% 2	460
	21st to end	Day	21% 10% 29% 29% 8% 2	506
April	1st to 10th	Day	20% 8% 36% 25% 8% 3	460
	11th to 20th	Day	14% 13% 27% 26% 16% 5%	452
	21st to end	Day	20% 9% 24% 32% 13% 2	460
May	1st to 10th	Day	24% 9% 23% 25% 15% 3	463
	11th to 20th	Day	18% 6% 22% 30% 18% 6%	487
	21st to end	Day	17% 2 15% 24% 29% 13%	529
June	1st to 10th	Day	11% 4 18% 29% 26% 13%	490
	11th to 20th	Day	12% 3 17% 29% 27% 11%	490
	21st to end	Day	10% 3 16% 33% 26% 12%	490
July	1st to 10th	Day	10% 1 9% 31% 31% 18%	485
	11th to 20th	Day	5% 1 7% 33% 36% 18%	484
	21st to end	Day	10% 2 11% 31% 35% 11%	532
August	1st to 10th	Day	12% 2 9% 29% 33% 15%	486
	11th to 20th	Day	11% 3 8% 29% 34% 15%	479
	21st to end	Day	9% 2 13% 31% 29% 17%	539
September	1st to 10th	Day	17% 2 15% 24% 24% 18%	490
	11th to 20th	Day	11% 3 14% 29% 29% 15%	490
	21st to end	Day	24% 6% 17% 29% 19% 6%	490
October	1st to 10th	Day	19% 4 19% 27% 19% 11%	490
	11th to 20th	Day	15% 7% 26% 27% 19% 6%	490
	21st to end	Day	16% 6% 28% 28% 18% 4	539
November	1st to 10th	Day	15% 7% 30% 26% 17% 5%	398
	11th to 20th	Day	12% 14% 33% 28% 12% 2	400
	21st to end	Day	13% 13% 32% 27% 12% 3	234
December	1st to 10th	Day	20% 9% 35% 27% 8% 1	180
	11th to 20th	Day	21% 16% 29% 24% 10%	180
	21st to end	Day	21% 9% 31% 27% 10% 2	198
January	1st to 10th	Night	19% 11% 42% 24% 4	760
	11th to 20th	Night	22% 13% 32% 27% 5%	760
	21st to end	Night	19% 12% 38% 30% 2	836
February	1st to 10th	Night	20% 9% 36% 32% 3	760
	11th to 20th	Night	23% 14% 40% 22% 1	743
	21st to end	Night	22% 14% 35% 25% 4	628
March	1st to 10th	Night	18% 12% 37% 27% 6%	760
	11th to 20th	Night	18% 12% 37% 26% 7% 1	760
	21st to end	Night	19% 7% 36% 30% 7% 1	836
April	1st to 10th	Night	19% 10% 38% 26% 7%	760
	11th to 20th	Night	16% 8% 31% 34% 12%	751
	21st to end	Night	19% 8% 29% 33% 11%	760
May	1st to 10th	Night	21% 7% 24% 36% 12% 1	667
	11th to 20th	Night	19% 8% 23% 37% 14%	374
	21st to end	Night	13% 3 14% 42% 25% 2	411
June	1st to 10th	Night	12% 3 19% 43% 22% 2	380
	11th to 20th	Night	11% 2 18% 43% 25% 2	380
	21st to end	Night	11% 4 17% 45% 22% 1	380
July	1st to 10th	Night	7% 3 14% 42% 29% 4	370
	11th to 20th	Night	6% 1 10% 42% 38% 3	368
	21st to end	Night	7% 2 11% 46% 30% 3	572
August	1st to 10th	Night	10% 3 10% 40% 34% 4	567
	11th to 20th	Night	11% 4 11% 36% 33% 5%	696
	21st to end	Night	12% 3 11% 36% 33% 6%	836
September	1st to 10th	Night	15% 1 15% 34% 29% 6%	760
	11th to 20th	Night	13% 3 11% 36% 32% 6%	760
	21st to end	Night	21% 4 18% 32% 23% 2	760
October	1st to 10th	Night	21% 5% 19% 31% 21% 4	760
	11th to 20th	Night	17% 6% 26% 34% 16% 1	760
	21st to end	Night	18% 6% 29% 32% 14% 1	836
November	1st to 10th	Night	15% 5% 31% 34% 13% 2	780
	11th to 20th	Night	19% 12% 29% 31% 9% 1	800
	21st to end	Night	16% 13% 31% 30% 9% 1	789
December	1st to 10th	Night	23% 10% 34% 24% 9% 1	760
	11th to 20th	Night	17% 9% 37% 30% 6%	760
	21st to end	Night	19% 8% 35% 34% 4	836

Page generated at 2024-11-25 00:22:21. Version ac07

Copyright © 2024 Attilla Danko.