Weathertop Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Weathertop Observatory clear sky chart from 2005-11-06 to 2024-10-20.

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	17% 10% 3 7% 5% 4 5% 4 5% 7% 33%	101253
	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 32%	97449
Transparency	Day	49% 8% 13% 19% 10% 1	101009
	Night	52% 8% 12% 18% 9% 1	97313
Seeing	Day	23% 18% 27% 20% 9% 3	14782
	Night	23% 16% 27% 26% 8% 1	23781

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% 15% 5% 10% 6% 4 4 3 5% 5% 27%	2517
	11th to 20th	Day	16% 13% 7% 12% 6% 5% 5% 3 5% 5% 23%	2520
	21st to end	Day	20% 18% 5% 9% 5% 4 5% 3 4 4 22%	2833
February	1st to 10th	Day	15% 15% 5% 9% 8% 5% 5% 4 5% 6% 24%	1710
	11th to 20th	Day	13% 15% 5% 12% 7% 4 4 3 4 6% 26%	1833
	21st to end	Day	19% 15% 4 9% 7% 4 4 3 4 4 28%	1570
March	1st to 10th	Day	24% 14% 4 9% 5% 4 3 2 4 5% 27%	3116
	11th to 20th	Day	15% 16% 4 8% 5% 4 4 3 5% 6% 30%	3290
	21st to end	Day	20% 11% 3 11% 4 4 4 3 4 4 32%	4166
April	1st to 10th	Day	19% 13% 4 6% 5% 4 3 3 5% 4 34%	2280
	11th to 20th	Day	17% 9% 3 7% 5% 4 5% 4 5% 5% 36%	2254
	21st to end	Day	21% 9% 3 7% 4 4 4 4 5% 5% 33%	2384
May	1st to 10th	Day	25% 10% 3 7% 4 4 5% 4 5% 6% 29%	4165
	11th to 20th	Day	17% 8% 3 7% 6% 5% 5% 4 6% 7% 33%	4398
	21st to end	Day	12% 6% 2 6% 5% 4 4 4 7% 9% 42%	4837
June	1st to 10th	Day	16% 8% 3 7% 5% 5% 5% 5% 6% 8% 32%	2660
	11th to 20th	Day	18% 6% 2 6% 4 4 5% 5% 7% 10% 33%	2660
	21st to end	Day	16% 9% 2 6% 5% 5% 4 4 6% 9% 33%	2660
July	1st to 10th	Day	11% 6% 3 6% 5% 5% 5% 5% 7% 10% 38%	4440
	11th to 20th	Day	10% 5% 2 7% 5% 5% 6% 5% 8% 9% 38%	4440
	21st to end	Day	14% 7% 2 7% 6% 5% 5% 5% 6% 7% 35%	4814
August	1st to 10th	Day	16% 7% 2 7% 5% 5% 6% 4 7% 8% 33%	4399
	11th to 20th	Day	13% 7% 2 7% 5% 5% 5% 5% 7% 8% 35%	3762
	21st to end	Day	12% 5% 3 6% 4 5% 5% 5% 6% 9% 40%	4180
September	1st to 10th	Day	13% 5% 2 5% 4 3 4 4 6% 7% 45%	2280
	11th to 20th	Day	15% 6% 1 5% 3 4 4 3 4 8% 48%	2181
	21st to end	Day	16% 6% 3 5% 4 4 4 3 6% 8% 41%	2090
October	1st to 10th	Day	21% 8% 3 7% 5% 4 4 4 4 5% 35%	2000
	11th to 20th	Day	15% 8% 3 6% 4 4 6% 3 5% 7% 38%	1882
	21st to end	Day	25% 11% 3 8% 5% 3 4 3 5% 6% 28%	1782
November	1st to 10th	Day	14% 10% 3 6% 4 3 4 3 5% 7% 42%	1671
	11th to 20th	Day	17% 10% 3 7% 6% 4 5% 3 5% 5% 35%	1710
	21st to end	Day	18% 11% 4 8% 5% 4 4 5% 5% 6% 30%	1571
December	1st to 10th	Day	18% 17% 5% 9% 5% 4 5% 3 5% 5% 24%	1520
	11th to 20th	Day	21% 16% 4 7% 4 3 3 3 4 4 31%	1906
	21st to end	Day	24% 17% 6% 10% 5% 3 4 3 3 4 21%	2772
January	1st to 10th	Night	15% 14% 5% 10% 5% 4 4 3 4 5% 30%	4429
	11th to 20th	Night	13% 13% 6% 14% 7% 5% 5% 3 5% 5% 23%	4440
	21st to end	Night	24% 14% 4 11% 6% 4 4 3 4 4 22%	4820
February	1st to 10th	Night	16% 13% 4 11% 7% 5% 5% 4 5% 5% 25%	2470
	11th to 20th	Night	12% 13% 5% 13% 7% 5% 4 3 5% 6% 27%	2233
	21st to end	Night	17% 14% 4 10% 4 3 5% 3 5% 6% 28%	1884
March	1st to 10th	Night	23% 11% 3 10% 5% 4 5% 4 5% 5% 26%	3724
	11th to 20th	Night	15% 15% 4 8% 6% 4 5% 3 5% 6% 30%	3667
	21st to end	Night	20% 15% 4 10% 4 4 3 2 3 4 31%	3466
April	1st to 10th	Night	20% 12% 2 7% 4 4 5% 3 5% 7% 31%	1900
	11th to 20th	Night	21% 9% 3 7% 5% 4 4 3 5% 6% 33%	1875
	21st to end	Night	21% 10% 3 6% 4 3 3 4 5% 6% 36%	1796
May	1st to 10th	Night	27% 9% 2 7% 4 4 4 3 5% 5% 29%	2804
	11th to 20th	Night	17% 9% 3 9% 7% 5% 5% 5% 6% 5% 29%	2495
	21st to end	Night	13% 7% 2 6% 6% 5% 5% 4 5% 8% 38%	2738
June	1st to 10th	Night	20% 7% 3 6% 4 5% 4 3 5% 7% 36%	1520
	11th to 20th	Night	18% 5% 2 5% 4 5% 4 4 6% 8% 39%	1520
	21st to end	Night	14% 5% 2 6% 5% 5% 4 4 6% 9% 40%	1520
July	1st to 10th	Night	12% 7% 3 8% 6% 5% 5% 4 7% 8% 36%	2520
	11th to 20th	Night	14% 8% 3 7% 5% 4 5% 4 5% 8% 37%	2520
	21st to end	Night	14% 7% 3 7% 5% 5% 4 5% 5% 7% 39%	2739
August	1st to 10th	Night	22% 8% 3 7% 4 4 4 3 5% 8% 33%	2506
	11th to 20th	Night	16% 6% 3 7% 5% 5% 5% 4 6% 6% 37%	3053
	21st to end	Night	12% 6% 3 6% 4 4 4 4 6% 9% 42%	3476
September	1st to 10th	Night	14% 7% 3 6% 4 3 4 3 6% 6% 44%	1900
	11th to 20th	Night	15% 5% 2 4 4 3 3 3 4 7% 51%	1998
	21st to end	Night	15% 6% 2 6% 4 4 4 4 4 6% 44%	2090
October	1st to 10th	Night	21% 7% 3 7% 4 5% 4 4 4 6% 35%	2175
	11th to 20th	Night	15% 8% 2 7% 4 4 5% 3 6% 6% 38%	2281
	21st to end	Night	25% 10% 3 6% 4 5% 4 3 5% 6% 29%	2574
November	1st to 10th	Night	15% 10% 3 7% 4 4 5% 4 4 5% 39%	2407
	11th to 20th	Night	17% 9% 3 7% 5% 5% 5% 4 5% 5% 35%	2470
	21st to end	Night	17% 11% 4 8% 5% 4 4 3 5% 6% 33%	2607
December	1st to 10th	Night	20% 15% 4 9% 6% 3 4 4 5% 6% 24%	2660
	11th to 20th	Night	23% 13% 4 8% 5% 4 4 3 5% 6% 26%	3288
	21st to end	Night	26% 16% 6% 8% 4 3 3 3 4 4 22%	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	57% 10% 12% 18% 4	2518
	11th to 20th	Day	62% 10% 12% 11% 4 1	2520
	21st to end	Day	65% 8% 10% 12% 4 1	2833
February	1st to 10th	Day	60% 8% 12% 14% 6% 1	1710
	11th to 20th	Day	61% 6% 9% 15% 8% 1	1842
	21st to end	Day	59% 7% 10% 14% 9% 1	1570
March	1st to 10th	Day	61% 6% 12% 13% 7% 1	3119
	11th to 20th	Day	52% 10% 16% 12% 8% 2	3290
	21st to end	Day	52% 7% 7% 14% 17% 2	4166
April	1st to 10th	Day	54% 6% 8% 20% 10% 2	2280
	11th to 20th	Day	48% 8% 11% 18% 14% 1	2254
	21st to end	Day	52% 7% 9% 17% 12% 3	2384
May	1st to 10th	Day	55% 8% 11% 17% 9% 1	4179
	11th to 20th	Day	47% 10% 14% 19% 8% 1	4402
	21st to end	Day	37% 10% 14% 25% 13% 1	4837
June	1st to 10th	Day	47% 9% 15% 18% 10% 1	2660
	11th to 20th	Day	45% 9% 14% 19% 12% 1	2660
	21st to end	Day	48% 10% 13% 19% 10% 1	2660
July	1st to 10th	Day	40% 10% 13% 24% 13% 1	4370
	11th to 20th	Day	39% 10% 16% 25% 10%	4365
	21st to end	Day	44% 9% 16% 20% 11%	4661
August	1st to 10th	Day	46% 9% 15% 21% 8%	4385
	11th to 20th	Day	43% 9% 18% 24% 6% 1	3799
	21st to end	Day	37% 9% 16% 28% 9% 1	4180
September	1st to 10th	Day	36% 9% 13% 27% 14% 1	2280
	11th to 20th	Day	36% 7% 12% 24% 20% 1	2181
	21st to end	Day	40% 7% 13% 25% 12% 2	2090
October	1st to 10th	Day	51% 7% 11% 18% 11% 2	2000
	11th to 20th	Day	44% 8% 16% 23% 8% 1	1882
	21st to end	Day	57% 8% 11% 14% 9% 1	1782
November	1st to 10th	Day	43% 7% 15% 22% 12% 1	1671
	11th to 20th	Day	50% 8% 12% 17% 12% 1	1710
	21st to end	Day	53% 7% 16% 17% 6% 1	1571
December	1st to 10th	Day	62% 8% 12% 11% 6% 1	1520
	11th to 20th	Day	58% 7% 14% 16% 6% 1	1906
	21st to end	Day	66% 8% 8% 12% 5%	2772
January	1st to 10th	Night	56% 9% 14% 13% 7% 1	4429
	11th to 20th	Night	60% 10% 11% 13% 5% 1	4440
	21st to end	Night	66% 7% 10% 12% 5% 1	4820
February	1st to 10th	Night	60% 8% 12% 13% 6% 1	2470
	11th to 20th	Night	57% 8% 12% 14% 9% 1	2235
	21st to end	Night	55% 7% 13% 15% 8% 2	1884
March	1st to 10th	Night	58% 9% 8% 17% 8% 1	3734
	11th to 20th	Night	53% 9% 12% 18% 7% 1	3668
	21st to end	Night	55% 6% 7% 13% 16% 3	3466
April	1st to 10th	Night	53% 6% 12% 18% 10% 1	1900
	11th to 20th	Night	50% 8% 10% 18% 13% 1	1875
	21st to end	Night	49% 7% 10% 16% 14% 4	1796
May	1st to 10th	Night	55% 8% 11% 15% 10% 1	2810
	11th to 20th	Night	52% 11% 12% 16% 8% 1	2496
	21st to end	Night	41% 11% 12% 19% 15% 1	2739
June	1st to 10th	Night	46% 8% 13% 23% 10% 1	1520
	11th to 20th	Night	42% 8% 16% 22% 12%	1520
	21st to end	Night	40% 11% 14% 23% 12% 1	1520
July	1st to 10th	Night	43% 9% 14% 19% 14% 1	2480
	11th to 20th	Night	43% 10% 13% 23% 12%	2472
	21st to end	Night	43% 9% 11% 26% 10% 1	2651
August	1st to 10th	Night	49% 8% 15% 21% 7%	2496
	11th to 20th	Night	44% 10% 18% 20% 8%	3082
	21st to end	Night	34% 9% 16% 30% 10%	3476
September	1st to 10th	Night	41% 7% 12% 26% 14% 1	1900
	11th to 20th	Night	34% 6% 12% 28% 19% 1	1998
	21st to end	Night	41% 8% 11% 24% 15% 1	2090
October	1st to 10th	Night	49% 7% 11% 21% 10% 2	2175
	11th to 20th	Night	44% 9% 16% 21% 10% 1	2281
	21st to end	Night	55% 8% 13% 15% 9% 1	2574
November	1st to 10th	Night	46% 7% 11% 20% 14% 2	2407
	11th to 20th	Night	50% 8% 13% 16% 11% 2	2470
	21st to end	Night	52% 7% 16% 17% 7%	2607
December	1st to 10th	Night	62% 8% 13% 13% 5%	2660
	11th to 20th	Night	59% 8% 14% 12% 7%	3288
	21st to end	Night	65% 7% 9% 15% 4	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	29% 23% 28% 16% 4	180
	11th to 20th	Day	33% 25% 28% 11% 2 1	180
	21st to end	Day	21% 25% 36% 12% 6%	215
February	1st to 10th	Day	31% 34% 27% 7% 1	270
	11th to 20th	Day	28% 30% 29% 11% 2	441
	21st to end	Day	30% 25% 28% 16% 2	382
March	1st to 10th	Day	29% 23% 27% 18% 3	460
	11th to 20th	Day	30% 27% 26% 14% 3 1	460
	21st to end	Day	32% 24% 23% 14% 6% 2	506
April	1st to 10th	Day	36% 19% 25% 13% 7%	460
	11th to 20th	Day	30% 25% 23% 13% 7% 1	452
	21st to end	Day	30% 17% 30% 16% 4 2	460
May	1st to 10th	Day	33% 17% 29% 12% 6% 2	463
	11th to 20th	Day	20% 17% 33% 21% 6% 2	487
	21st to end	Day	18% 15% 27% 26% 10% 4	529
June	1st to 10th	Day	18% 16% 29% 25% 11% 2	490
	11th to 20th	Day	19% 15% 30% 24% 11% 2	490
	21st to end	Day	20% 17% 29% 22% 11% 2	490
July	1st to 10th	Day	14% 10% 30% 27% 16% 3	485
	11th to 20th	Day	12% 6% 35% 32% 13% 2	484
	21st to end	Day	14% 9% 36% 26% 12% 2	532
August	1st to 10th	Day	13% 12% 25% 29% 17% 5%	486
	11th to 20th	Day	17% 8% 27% 29% 13% 7%	479
	21st to end	Day	14% 12% 25% 28% 16% 6%	539
September	1st to 10th	Day	18% 11% 21% 25% 17% 8%	490
	11th to 20th	Day	16% 13% 22% 20% 19% 11%	490
	21st to end	Day	20% 12% 24% 22% 16% 6%	490
October	1st to 10th	Day	25% 14% 23% 20% 13% 5%	490
	11th to 20th	Day	21% 19% 27% 21% 10% 2	482
	21st to end	Day	31% 15% 27% 21% 5% 1	396
November	1st to 10th	Day	19% 22% 25% 19% 14% 1	365
	11th to 20th	Day	28% 25% 23% 18% 5% 1	370
	21st to end	Day	29% 23% 28% 17% 4	231
December	1st to 10th	Day	31% 22% 33% 11% 3 1	180
	11th to 20th	Day	37% 19% 29% 13% 2	180
	21st to end	Day	32% 25% 27% 15% 2	198
January	1st to 10th	Night	24% 24% 31% 19% 2	760
	11th to 20th	Night	27% 23% 28% 20% 2	760
	21st to end	Night	22% 20% 35% 20% 3	836
February	1st to 10th	Night	24% 21% 35% 18% 1	760
	11th to 20th	Night	22% 25% 34% 17% 2	743
	21st to end	Night	27% 22% 30% 17% 3	628
March	1st to 10th	Night	26% 22% 30% 19% 2	760
	11th to 20th	Night	26% 25% 28% 18% 3	760
	21st to end	Night	27% 21% 25% 19% 7%	836
April	1st to 10th	Night	29% 18% 29% 22% 3	760
	11th to 20th	Night	26% 18% 29% 21% 6%	751
	21st to end	Night	27% 17% 28% 23% 6%	656
May	1st to 10th	Night	27% 16% 26% 24% 7% 1	553
	11th to 20th	Night	18% 16% 30% 30% 6% 1	374
	21st to end	Night	13% 10% 27% 37% 11% 1	411
June	1st to 10th	Night	22% 6% 26% 35% 11% 1	380
	11th to 20th	Night	19% 7% 23% 39% 11%	380
	21st to end	Night	15% 6% 26% 42% 11% 1	380
July	1st to 10th	Night	13% 5% 23% 44% 15%	370
	11th to 20th	Night	15% 5% 20% 44% 15% 1	368
	21st to end	Night	14% 4 23% 45% 13% 1	416
August	1st to 10th	Night	13% 4 22% 42% 18% 1	378
	11th to 20th	Night	17% 3 21% 37% 19% 3	718
	21st to end	Night	15% 6% 22% 36% 20% 1	836
September	1st to 10th	Night	17% 6% 26% 33% 17% 1	760
	11th to 20th	Night	18% 7% 20% 29% 21% 5%	760
	21st to end	Night	18% 9% 24% 32% 15% 2	760
October	1st to 10th	Night	26% 10% 21% 28% 13% 2	760
	11th to 20th	Night	20% 11% 29% 30% 10%	759
	21st to end	Night	30% 14% 28% 23% 5%	792
November	1st to 10th	Night	21% 17% 27% 26% 8%	740
	11th to 20th	Night	23% 19% 31% 20% 6% 1	760
	21st to end	Night	23% 19% 31% 21% 6% 1	760
December	1st to 10th	Night	29% 22% 30% 15% 4	760
	11th to 20th	Night	26% 22% 28% 21% 3	760
	21st to end	Night	29% 22% 30% 17% 2	836

Page generated at 2024-10-17 13:09:43. Version ac07

Copyright © 2024 Attilla Danko.