StonyHill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the StonyHill Observatory clear sky chart from 2005-11-06 to 2024-11-30.

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% 7% 2 6% 4 4 4 3 5% 7% 41%	101487
	Night	17% 7% 3 6% 4 4 4 3 5% 7% 40%	98123
Transparency	Day	40% 7% 14% 22% 15% 2	105033
	Night	42% 6% 12% 22% 15% 2	102666
Seeing	Day	18% 6% 23% 31% 17% 4	15135
	Night	20% 7% 29% 30% 12% 2	24227

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	16% 5% 2 6% 4 3 3 3 5% 6% 46%	2517
	11th to 20th	Day	17% 8% 3 6% 4 5% 5% 4 5% 6% 37%	2520
	21st to end	Day	22% 12% 4 7% 4 3 4 3 4 5% 32%	2930
February	1st to 10th	Day	18% 7% 3 7% 5% 3 4 3 5% 7% 40%	1768
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 6% 46%	1848
	21st to end	Day	18% 8% 2 7% 4 4 3 3 4 5% 40%	1570
March	1st to 10th	Day	26% 10% 2 5% 3 2 3 3 4 5% 37%	3116
	11th to 20th	Day	9% 5% 1 4 4 4 5% 5% 7% 9% 48%	3272
	21st to end	Day	20% 7% 2 6% 3 3 3 3 5% 6% 42%	4166
April	1st to 10th	Day	17% 8% 3 5% 4 4 4 3 6% 7% 40%	2280
	11th to 20th	Day	16% 7% 1 5% 5% 4 4 3 5% 6% 44%	2254
	21st to end	Day	19% 6% 2 4 3 4 5% 3 5% 7% 43%	2348
May	1st to 10th	Day	26% 9% 2 5% 3 3 3 3 5% 7% 33%	4106
	11th to 20th	Day	24% 7% 2 6% 5% 3 4 3 5% 7% 35%	4266
	21st to end	Day	13% 5% 2 5% 3 3 4 3 6% 8% 47%	4837
June	1st to 10th	Day	16% 6% 2 5% 4 3 3 4 5% 9% 42%	2660
	11th to 20th	Day	13% 7% 2 5% 4 5% 5% 4 6% 9% 41%	2660
	21st to end	Day	10% 6% 2 5% 5% 4 4 4 6% 9% 44%	2660
July	1st to 10th	Day	9% 5% 3 8% 5% 6% 6% 5% 7% 10% 38%	4440
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 41%	4440
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 6% 7% 36%	4814
August	1st to 10th	Day	18% 6% 2 6% 4 5% 4 4 7% 9% 34%	4205
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 5% 9% 46%	3730
	21st to end	Day	9% 5% 2 5% 4 4 4 4 6% 9% 49%	4180
September	1st to 10th	Day	13% 6% 2 5% 4 4 5% 3 5% 7% 47%	2280
	11th to 20th	Day	12% 6% 2 5% 3 3 3 3 5% 7% 52%	2161
	21st to end	Day	18% 7% 2 6% 4 4 4 3 5% 6% 41%	2090
October	1st to 10th	Day	21% 6% 2 5% 2 3 3 3 5% 7% 43%	2042
	11th to 20th	Day	15% 5% 2 5% 4 4 3 3 5% 6% 48%	1900
	21st to end	Day	19% 5% 1 6% 4 3 4 3 5% 7% 42%	1895
November	1st to 10th	Day	14% 5% 2 5% 4 3 3 3 4 6% 50%	1761
	11th to 20th	Day	17% 6% 2 5% 3 3 3 2 4 7% 49%	1800
	21st to end	Day	15% 8% 2 5% 3 3 4 4 5% 7% 44%	1773
December	1st to 10th	Day	17% 6% 3 7% 4 4 4 3 7% 7% 36%	1520
	11th to 20th	Day	21% 8% 2 4 2 3 3 3 5% 6% 44%	1906
	21st to end	Day	18% 10% 3 9% 4 4 5% 3 5% 7% 33%	2772
January	1st to 10th	Night	18% 7% 2 5% 4 4 3 2 4 8% 44%	4429
	11th to 20th	Night	17% 9% 3 7% 3 3 3 3 4 5% 43%	4440
	21st to end	Night	24% 10% 4 8% 4 3 3 3 4 5% 32%	4724
February	1st to 10th	Night	16% 9% 3 5% 4 4 4 3 5% 6% 41%	2410
	11th to 20th	Night	18% 7% 3 5% 5% 3 4 4 5% 6% 40%	2218
	21st to end	Night	20% 7% 2 5% 3 4 4 3 5% 6% 41%	1884
March	1st to 10th	Night	23% 11% 3 6% 3 3 3 2 4 5% 36%	3724
	11th to 20th	Night	13% 6% 2 6% 5% 5% 4 4 5% 7% 44%	3683
	21st to end	Night	22% 9% 2 5% 3 3 3 3 5% 5% 40%	3466
April	1st to 10th	Night	18% 7% 3 6% 4 4 4 4 6% 6% 38%	1900
	11th to 20th	Night	18% 7% 3 6% 4 3 4 3 4 7% 40%	1875
	21st to end	Night	18% 8% 3 6% 4 3 3 3 4 5% 42%	1829
May	1st to 10th	Night	24% 10% 4 7% 4 4 4 3 4 8% 29%	2834
	11th to 20th	Night	24% 9% 3 7% 5% 4 4 3 5% 6% 30%	2655
	21st to end	Night	16% 8% 2 6% 3 4 4 3 5% 7% 42%	2738
June	1st to 10th	Night	17% 8% 2 4 5% 5% 3 3 4 8% 41%	1520
	11th to 20th	Night	15% 7% 2 6% 3 3 4 4 6% 9% 41%	1520
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 5% 6% 10% 40%	1520
July	1st to 10th	Night	10% 9% 3 7% 5% 5% 6% 5% 7% 9% 34%	2520
	11th to 20th	Night	12% 7% 4 7% 4 4 5% 5% 6% 10% 36%	2520
	21st to end	Night	17% 9% 3 6% 5% 5% 4 4 6% 8% 33%	2739
August	1st to 10th	Night	21% 7% 3 6% 4 5% 5% 4 7% 7% 31%	2688
	11th to 20th	Night	13% 7% 3 7% 4 4 5% 4 7% 8% 39%	3097
	21st to end	Night	8% 5% 1 5% 3 4 4 4 5% 7% 53%	3476
September	1st to 10th	Night	13% 5% 2 6% 4 4 5% 3 6% 6% 45%	1900
	11th to 20th	Night	14% 4 2 6% 3 2 4 3 4 7% 51%	2017
	21st to end	Night	18% 6% 2 7% 5% 4 3 3 4 6% 42%	2090
October	1st to 10th	Night	19% 8% 2 7% 4 4 3 3 4 6% 40%	2136
	11th to 20th	Night	15% 4 2 5% 4 3 3 3 5% 7% 49%	2280
	21st to end	Night	21% 6% 2 6% 4 4 3 3 4 7% 41%	2703
November	1st to 10th	Night	12% 6% 2 6% 4 3 4 3 5% 5% 49%	2537
	11th to 20th	Night	18% 7% 2 4 3 3 3 3 4 5% 47%	2600
	21st to end	Night	15% 6% 2 5% 4 3 4 3 6% 6% 46%	2619
December	1st to 10th	Night	20% 8% 2 6% 4 4 4 3 5% 7% 38%	2660
	11th to 20th	Night	20% 7% 2 5% 3 4 4 3 5% 6% 42%	3288
	21st to end	Night	20% 9% 3 7% 4 4 4 3 5% 6% 37%	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	39% 5% 12% 30% 12% 2	2518
	11th to 20th	Day	43% 7% 13% 24% 12% 1	2520
	21st to end	Day	52% 8% 9% 20% 9% 1	2930
February	1st to 10th	Day	44% 5% 14% 23% 13% 1	1768
	11th to 20th	Day	40% 5% 11% 25% 17% 2	1857
	21st to end	Day	46% 6% 11% 21% 13% 3	1570
March	1st to 10th	Day	47% 7% 13% 20% 10% 2	3119
	11th to 20th	Day	28% 10% 16% 30% 14% 1	3272
	21st to end	Day	43% 5% 10% 17% 21% 5%	4166
April	1st to 10th	Day	43% 6% 11% 20% 16% 4	2280
	11th to 20th	Day	41% 5% 13% 21% 17% 3	2254
	21st to end	Day	41% 7% 11% 21% 17% 4	2348
May	1st to 10th	Day	50% 8% 16% 14% 11% 1	4120
	11th to 20th	Day	48% 10% 15% 17% 9% 2	4270
	21st to end	Day	33% 9% 16% 23% 17% 2	4837
June	1st to 10th	Day	39% 9% 14% 22% 15% 2	2660
	11th to 20th	Day	39% 8% 14% 24% 13% 2	2660
	21st to end	Day	36% 9% 16% 22% 15% 1	2660
July	1st to 10th	Day	42% 10% 13% 19% 15% 1	4370
	11th to 20th	Day	38% 8% 18% 22% 13% 1	4365
	21st to end	Day	45% 8% 13% 17% 14% 2	4661
August	1st to 10th	Day	46% 8% 16% 21% 9%	4191
	11th to 20th	Day	36% 7% 15% 32% 9% 1	3766
	21st to end	Day	31% 7% 14% 26% 20% 2	4180
September	1st to 10th	Day	37% 7% 14% 20% 20% 2	2280
	11th to 20th	Day	33% 6% 12% 24% 24% 2	2161
	21st to end	Day	45% 6% 11% 18% 19% 2	2090
October	1st to 10th	Day	34% 6% 12% 20% 22% 5%	3393
	11th to 20th	Day	25% 5% 11% 23% 32% 4	3140
	21st to end	Day	29% 5% 15% 26% 22% 2	3095
November	1st to 10th	Day	36% 6% 13% 22% 21% 2	1761
	11th to 20th	Day	38% 4 10% 23% 22% 3	1800
	21st to end	Day	39% 6% 15% 27% 11% 2	1773
December	1st to 10th	Day	44% 6% 17% 18% 14% 1	1520
	11th to 20th	Day	42% 4 15% 20% 17% 2	1906
	21st to end	Day	47% 10% 13% 21% 8%	2772
January	1st to 10th	Night	38% 5% 12% 29% 12% 3	4429
	11th to 20th	Night	44% 5% 13% 24% 12% 2	4440
	21st to end	Night	53% 6% 9% 20% 11% 1	4724
February	1st to 10th	Night	43% 6% 13% 23% 12% 2	2410
	11th to 20th	Night	44% 5% 11% 19% 16% 4	2220
	21st to end	Night	44% 4 9% 23% 16% 4	1884
March	1st to 10th	Night	51% 5% 10% 20% 11% 3	3734
	11th to 20th	Night	36% 7% 14% 26% 15% 3	3684
	21st to end	Night	45% 5% 8% 14% 22% 6%	3466
April	1st to 10th	Night	45% 6% 11% 18% 17% 3	1900
	11th to 20th	Night	44% 6% 10% 18% 20% 1	1875
	21st to end	Night	44% 6% 10% 20% 16% 5%	1829
May	1st to 10th	Night	54% 9% 11% 15% 9% 1	2840
	11th to 20th	Night	53% 8% 14% 14% 9% 1	2656
	21st to end	Night	40% 8% 15% 22% 13% 2	2739
June	1st to 10th	Night	43% 7% 11% 20% 18% 1	1520
	11th to 20th	Night	38% 9% 14% 26% 12% 1	1520
	21st to end	Night	38% 9% 15% 24% 13% 1	1520
July	1st to 10th	Night	46% 10% 14% 18% 12% 1	2480
	11th to 20th	Night	43% 8% 15% 24% 10% 1	2472
	21st to end	Night	48% 7% 14% 16% 13% 1	2651
August	1st to 10th	Night	49% 9% 17% 17% 8% 1	2678
	11th to 20th	Night	40% 7% 15% 28% 9% 1	3127
	21st to end	Night	28% 7% 13% 33% 18% 1	3476
September	1st to 10th	Night	39% 8% 10% 24% 18% 1	1900
	11th to 20th	Night	33% 6% 11% 24% 22% 3	2017
	21st to end	Night	43% 7% 9% 20% 19% 3	2090
October	1st to 10th	Night	39% 6% 11% 23% 19% 2	3565
	11th to 20th	Night	24% 4 11% 26% 31% 4	3779
	21st to end	Night	31% 5% 13% 28% 21% 2	4453
November	1st to 10th	Night	35% 6% 13% 22% 20% 3	2537
	11th to 20th	Night	40% 4 10% 23% 19% 4	2600
	21st to end	Night	37% 5% 14% 29% 13% 2	2619
December	1st to 10th	Night	46% 5% 14% 21% 13% 1	2660
	11th to 20th	Night	43% 5% 12% 19% 18% 2	3288
	21st to end	Night	46% 7% 13% 23% 11% 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	21% 12% 33% 25% 8% 1	180
	11th to 20th	Day	17% 16% 39% 23% 5% 1	180
	21st to end	Day	21% 5% 39% 26% 8% 2	243
February	1st to 10th	Day	24% 8% 35% 30% 4	328
	11th to 20th	Day	19% 11% 39% 29% 3	456
	21st to end	Day	24% 12% 31% 26% 7% 1	382
March	1st to 10th	Day	16% 10% 37% 30% 8%	460
	11th to 20th	Day	16% 8% 39% 30% 6% 1	460
	21st to end	Day	23% 8% 32% 28% 8% 2	506
April	1st to 10th	Day	21% 9% 32% 26% 11% 1	460
	11th to 20th	Day	19% 6% 25% 35% 13% 1	452
	21st to end	Day	24% 6% 23% 34% 11% 2	460
May	1st to 10th	Day	26% 5% 25% 32% 10% 2	463
	11th to 20th	Day	20% 3 20% 38% 18% 1	487
	21st to end	Day	17% 2 13% 33% 30% 5%	529
June	1st to 10th	Day	18% 3 13% 36% 26% 4	490
	11th to 20th	Day	15% 3 17% 39% 22% 3	490
	21st to end	Day	12% 3 16% 36% 28% 5%	490
July	1st to 10th	Day	11% 3 13% 33% 31% 9%	485
	11th to 20th	Day	9% 4 11% 34% 33% 9%	484
	21st to end	Day	13% 3 14% 35% 31% 4	532
August	1st to 10th	Day	12% 2 11% 39% 27% 9%	486
	11th to 20th	Day	14% 4 10% 35% 30% 7%	479
	21st to end	Day	10% 4 13% 37% 26% 10%	539
September	1st to 10th	Day	18% 3 16% 29% 23% 12%	490
	11th to 20th	Day	16% 2 13% 32% 26% 12%	490
	21st to end	Day	23% 3 20% 31% 18% 5%	490
October	1st to 10th	Day	25% 4 19% 27% 18% 8%	490
	11th to 20th	Day	14% 7% 28% 31% 17% 4	490
	21st to end	Day	22% 8% 30% 25% 13% 2	436
November	1st to 10th	Day	15% 9% 25% 32% 15% 3	395
	11th to 20th	Day	18% 15% 34% 26% 7% 1	400
	21st to end	Day	19% 13% 30% 28% 10% 1	375
December	1st to 10th	Day	19% 10% 37% 22% 12%	180
	11th to 20th	Day	27% 15% 26% 26% 6%	180
	21st to end	Day	21% 12% 34% 24% 8% 1	198
January	1st to 10th	Night	19% 14% 40% 23% 4	760
	11th to 20th	Night	24% 12% 34% 27% 3	760
	21st to end	Night	19% 13% 40% 25% 3	836
February	1st to 10th	Night	20% 10% 38% 28% 3	760
	11th to 20th	Night	22% 9% 45% 22% 2	743
	21st to end	Night	24% 10% 37% 24% 5%	628
March	1st to 10th	Night	21% 8% 39% 26% 6%	760
	11th to 20th	Night	19% 8% 40% 26% 6% 1	760
	21st to end	Night	22% 7% 38% 26% 6% 1	836
April	1st to 10th	Night	22% 7% 35% 30% 6% 1	760
	11th to 20th	Night	20% 7% 31% 33% 10%	751
	21st to end	Night	21% 4 29% 36% 8% 1	689
May	1st to 10th	Night	24% 5% 27% 31% 11% 2	570
	11th to 20th	Night	22% 4 29% 33% 11%	469
	21st to end	Night	20% 3 12% 37% 25% 2	411
June	1st to 10th	Night	21% 2 19% 37% 19% 2	380
	11th to 20th	Night	17% 3 13% 45% 20% 2	380
	21st to end	Night	10% 4 17% 48% 19% 2	380
July	1st to 10th	Night	12% 3 14% 41% 27% 2	370
	11th to 20th	Night	12% 3 11% 46% 23% 4	368
	21st to end	Night	15% 2 14% 46% 21% 1	416
August	1st to 10th	Night	10% 1 14% 45% 27% 2	482
	11th to 20th	Night	15% 3 13% 33% 32% 3	750
	21st to end	Night	14% 3 14% 36% 28% 5%	836
September	1st to 10th	Night	16% 2 21% 35% 21% 5%	760
	11th to 20th	Night	17% 3 16% 37% 22% 6%	760
	21st to end	Night	21% 3 22% 32% 19% 3	760
October	1st to 10th	Night	24% 7% 24% 26% 16% 4	760
	11th to 20th	Night	18% 8% 27% 33% 13% 1	760
	21st to end	Night	24% 8% 32% 27% 9%	836
November	1st to 10th	Night	15% 8% 32% 30% 13% 2	780
	11th to 20th	Night	21% 12% 34% 24% 9% 1	800
	21st to end	Night	18% 13% 33% 27% 8% 1	800
December	1st to 10th	Night	24% 13% 34% 23% 6% 1	760
	11th to 20th	Night	22% 11% 38% 24% 4	760
	21st to end	Night	23% 12% 38% 23% 4	836

Page generated at 2024-11-27 17:30:49. Version ac07

Copyright © 2024 Attilla Danko.