Artis Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Artis Observatory clear sky chart from 2005-11-06 to 2024-11-01.

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	6% 3 1 3 2 2 3 2 4 5% 68%	101021
	Night	9% 4 1 3 2 2 3 2 4 5% 65%	98135
Transparency	Day	19% 4 8% 17% 24% 28%	100771
	Night	22% 4 10% 19% 22% 23%	97975
Seeing	Day	7% 5% 20% 34% 25% 8%	15268
	Night	9% 2 12% 39% 32% 7%	24734

By Month

Percentage Cloud Cover SW (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	13% 9% 3 7% 5% 4 5% 4 7% 7% 35%	2539
	11th to 20th	Day	14% 6% 3 8% 6% 7% 6% 4 6% 6% 35%	2746
	21st to end	Day	19% 7% 2 6% 4 5% 5% 4 7% 8% 33%	3146
February	1st to 10th	Day	15% 6% 1 5% 3 3 3 4 5% 6% 49%	1783
	11th to 20th	Day	11% 6% 2 4 3 4 4 4 5% 7% 50%	1850
	21st to end	Day	16% 6% 2 5% 4 4 3 3 4 6% 48%	1570
March	1st to 10th	Day	13% 8% 2 7% 5% 4 5% 5% 8% 9% 34%	3138
	11th to 20th	Day	9% 5% 2 3 2 3 3 3 4 6% 61%	3447
	21st to end	Day	15% 6% 3 5% 3 4 4 4 6% 7% 43%	4070
April	1st to 10th	Day	10% 5% 2 4 3 3 3 2 4 7% 58%	2280
	11th to 20th	Day	9% 5% 1 4 3 3 3 3 5% 6% 59%	2249
	21st to end	Day	6% 3 1 3 3 3 3 3 5% 6% 64%	2280
May	1st to 10th	Day	5% 2 1 2 1 2 1 1 2 4 78%	3882
	11th to 20th	Day	2 1 1 2 1 1 2 2 3 5% 81%	4122
	21st to end	Day	3 1 2 1 2 2 2 3 4 80%	4813
June	1st to 10th	Day	3 2 1 2 2 2 2 3 4 7% 72%	2660
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 87%	2660
	21st to end	Day	1 1 1 1 1 1 1 2 3 86%	2660
July	1st to 10th	Day	1 1 1 1 2 2 92%	4420
	11th to 20th	Day	1 1 1 1 1 1 2 2 3 3 84%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4519
August	1st to 10th	Day	2 1 1 1 1 1 1 2 2 3 85%	3916
	11th to 20th	Day	1 1 1 1 1 3 91%	3724
	21st to end	Day	1 1 1 1 1 1 1 1 2 90%	4180
September	1st to 10th	Day	1 1 1 1 2 1 2 2 88%	2280
	11th to 20th	Day	2 2 2 1 1 1 2 3 4 82%	2237
	21st to end	Day	2 1 1 2 1 1 1 2 3 4 83%	2090
October	1st to 10th	Day	2 3 1 3 2 2 3 2 4 4 73%	1962
	11th to 20th	Day	3 1 1 2 1 3 2 2 4 4 77%	1900
	21st to end	Day	5% 2 1 3 2 2 3 1 4 6% 72%	2085
November	1st to 10th	Day	8% 4 1 3 3 4 3 3 5% 7% 61%	1674
	11th to 20th	Day	8% 3 1 4 3 3 3 4 5% 7% 61%	1710
	21st to end	Day	10% 5% 1 4 3 4 3 3 4 7% 58%	1710
December	1st to 10th	Day	14% 5% 1 3 4 4 3 3 5% 6% 51%	1577
	11th to 20th	Day	23% 8% 2 6% 5% 4 4 2 3 7% 37%	1928
	21st to end	Day	12% 6% 3 8% 5% 5% 6% 5% 6% 8% 34%	2794
January	1st to 10th	Night	15% 8% 3 6% 4 3 3 3 5% 6% 44%	4406
	11th to 20th	Night	18% 7% 3 6% 3 4 5% 4 5% 7% 38%	4203
	21st to end	Night	21% 7% 2 5% 4 4 3 3 5% 8% 40%	4521
February	1st to 10th	Night	16% 5% 1 4 2 3 3 3 4 6% 52%	2394
	11th to 20th	Night	13% 4 1 4 2 3 3 3 5% 6% 56%	2218
	21st to end	Night	15% 6% 2 5% 3 3 2 3 4 6% 52%	1884
March	1st to 10th	Night	18% 6% 2 6% 3 4 5% 3 6% 6% 42%	3736
	11th to 20th	Night	11% 4 1 4 2 2 2 2 4 5% 62%	3530
	21st to end	Night	19% 6% 2 4 3 3 4 3 4 6% 46%	3581
April	1st to 10th	Night	11% 4 1 4 2 2 2 3 5% 7% 59%	1900
	11th to 20th	Night	6% 4 1 3 2 3 3 3 5% 6% 64%	1879
	21st to end	Night	5% 3 1 2 2 3 3 2 3 5% 70%	1900
May	1st to 10th	Night	4 1 1 3 1 1 1 2 3 4 79%	3094
	11th to 20th	Night	2 1 1 1 1 1 1 2 3 4 82%	2775
	21st to end	Night	2 1 1 2 1 1 1 1 2 4 84%	2762
June	1st to 10th	Night	3 2 1 2 2 2 2 2 3 6% 75%	1520
	11th to 20th	Night	1 1 1 1 1 2 2 3 88%	1520
	21st to end	Night	1 1 1 1 1 2 1 2 3 87%	1520
July	1st to 10th	Night	1 1 1 1 1 1 2 94%	2540
	11th to 20th	Night	2 2 1 2 2 2 2 2 3 4 80%	2540
	21st to end	Night	1 1 1 1 1 2 2 2 4 85%	3037
August	1st to 10th	Night	1 2 1 1 1 1 2 1 3 4 83%	3027
	11th to 20th	Night	1 1 1 1 1 2 2 91%	3126
	21st to end	Night	2 1 1 1 1 1 1 1 2 89%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 2 90%	1900
	11th to 20th	Night	1 2 2 1 1 1 1 3 3 83%	1942
	21st to end	Night	2 1 1 1 1 2 1 1 2 4 84%	2090
October	1st to 10th	Night	3 3 1 2 2 3 2 2 3 4 76%	2214
	11th to 20th	Night	4 1 1 2 1 2 2 2 4 5% 77%	2280
	21st to end	Night	5% 1 1 2 1 1 2 1 3 5% 78%	2511
November	1st to 10th	Night	8% 3 1 3 3 2 3 2 4 6% 65%	2411
	11th to 20th	Night	6% 3 1 3 3 2 2 2 4 7% 66%	2470
	21st to end	Night	9% 3 2 4 3 3 3 3 5% 6% 60%	2470
December	1st to 10th	Night	13% 5% 2 5% 3 3 3 3 4 6% 53%	2598
	11th to 20th	Night	21% 8% 2 5% 4 3 3 3 5% 7% 39%	3276
	21st to end	Night	15% 7% 2 7% 4 5% 6% 4 6% 8% 37%	4862

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	43% 9% 22% 18% 8% 1	2539
	11th to 20th	Day	45% 11% 13% 16% 10% 6%	2746
	21st to end	Day	46% 9% 15% 17% 11% 2	3146
February	1st to 10th	Day	35% 6% 11% 24% 18% 6%	1783
	11th to 20th	Day	33% 5% 11% 25% 21% 6%	1860
	21st to end	Day	36% 7% 14% 25% 17% 2	1570
March	1st to 10th	Day	41% 7% 18% 18% 14% 2	3138
	11th to 20th	Day	23% 6% 13% 32% 16% 11%	3447
	21st to end	Day	36% 6% 17% 24% 14% 3	4070
April	1st to 10th	Day	28% 3 13% 28% 20% 8%	2280
	11th to 20th	Day	25% 5% 10% 27% 23% 9%	2252
	21st to end	Day	20% 5% 12% 29% 28% 7%	2280
May	1st to 10th	Day	13% 3 7% 25% 34% 19%	3882
	11th to 20th	Day	9% 2 6% 25% 41% 17%	4125
	21st to end	Day	10% 2 6% 27% 38% 17%	4814
June	1st to 10th	Day	13% 3 10% 20% 31% 22%	2660
	11th to 20th	Day	5% 1 5% 15% 38% 35%	2660
	21st to end	Day	6% 2 2 8% 29% 53%	2660
July	1st to 10th	Day	3 1 1 3 12% 79%	4351
	11th to 20th	Day	7% 2 3 5% 15% 69%	4345
	21st to end	Day	6% 1 2 5% 26% 60%	4376
August	1st to 10th	Day	8% 1 2 5% 25% 59%	3901
	11th to 20th	Day	3 1 5% 24% 66%	3760
	21st to end	Day	5% 1 2 7% 27% 59%	4179
September	1st to 10th	Day	6% 1 3 6% 27% 57%	2280
	11th to 20th	Day	8% 2 3 19% 38% 30%	2237
	21st to end	Day	8% 2 3 17% 37% 34%	2090
October	1st to 10th	Day	13% 3 6% 18% 26% 33%	1962
	11th to 20th	Day	12% 2 6% 22% 29% 27%	1900
	21st to end	Day	16% 2 7% 21% 31% 23%	2085
November	1st to 10th	Day	24% 4 12% 22% 25% 12%	1674
	11th to 20th	Day	24% 5% 14% 25% 25% 7%	1710
	21st to end	Day	28% 5% 12% 20% 27% 9%	1710
December	1st to 10th	Day	34% 7% 12% 20% 18% 10%	1577
	11th to 20th	Day	49% 6% 11% 17% 13% 5%	1928
	21st to end	Day	45% 10% 18% 17% 8% 3	2794
January	1st to 10th	Night	39% 8% 20% 20% 10% 2	4406
	11th to 20th	Night	44% 7% 19% 15% 9% 7%	4203
	21st to end	Night	43% 7% 13% 21% 12% 3	4521
February	1st to 10th	Night	33% 5% 11% 24% 20% 8%	2394
	11th to 20th	Night	27% 4 12% 27% 23% 6%	2219
	21st to end	Night	34% 4 13% 27% 18% 4	1884
March	1st to 10th	Night	39% 7% 15% 19% 18% 3	3736
	11th to 20th	Night	25% 3 14% 30% 19% 9%	3530
	21st to end	Night	38% 5% 14% 26% 14% 3	3581
April	1st to 10th	Night	25% 4 14% 27% 21% 8%	1900
	11th to 20th	Night	22% 4 11% 30% 25% 9%	1879
	21st to end	Night	17% 3 12% 30% 31% 6%	1900
May	1st to 10th	Night	11% 2 9% 29% 35% 14%	3094
	11th to 20th	Night	8% 2 5% 24% 43% 18%	2776
	21st to end	Night	8% 2 6% 28% 45% 11%	2762
June	1st to 10th	Night	12% 3 9% 24% 31% 21%	1520
	11th to 20th	Night	5% 2 4 17% 39% 34%	1520
	21st to end	Night	5% 2 3 8% 26% 57%	1520
July	1st to 10th	Night	2 1 2 13% 81%	2500
	11th to 20th	Night	9% 2 2 5% 14% 68%	2492
	21st to end	Night	6% 1 2 5% 24% 62%	2942
August	1st to 10th	Night	8% 1 1 6% 22% 61%	3018
	11th to 20th	Night	4 1 2 4 18% 72%	3156
	21st to end	Night	6% 1 1 6% 25% 61%	3498
September	1st to 10th	Night	4 1 2 6% 25% 62%	1900
	11th to 20th	Night	8% 2 4 14% 40% 32%	1942
	21st to end	Night	8% 2 2 14% 37% 37%	2090
October	1st to 10th	Night	13% 3 5% 16% 26% 37%	2214
	11th to 20th	Night	11% 3 7% 21% 30% 29%	2280
	21st to end	Night	12% 2 5% 23% 34% 26%	2511
November	1st to 10th	Night	22% 3 10% 24% 25% 17%	2411
	11th to 20th	Night	19% 4 12% 27% 25% 13%	2470
	21st to end	Night	24% 4 11% 22% 29% 10%	2470
December	1st to 10th	Night	33% 4 12% 20% 19% 12%	2598
	11th to 20th	Night	44% 6% 13% 17% 16% 5%	3276
	21st to end	Night	43% 8% 16% 21% 9% 3	4862

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	26% 5% 23% 27% 14% 4	180
	11th to 20th	Day	16% 5% 16% 34% 21% 8%	308
	21st to end	Day	17% 4 18% 35% 18% 8%	407
February	1st to 10th	Day	18% 7% 21% 26% 20% 9%	405
	11th to 20th	Day	15% 7% 26% 30% 17% 5%	455
	21st to end	Day	13% 9% 27% 32% 16% 2	382
March	1st to 10th	Day	15% 9% 26% 33% 14% 3	460
	11th to 20th	Day	13% 11% 28% 25% 18% 4	460
	21st to end	Day	17% 11% 27% 28% 14% 2	506
April	1st to 10th	Day	13% 13% 25% 28% 17% 4	460
	11th to 20th	Day	12% 12% 25% 33% 15% 4	452
	21st to end	Day	4 11% 27% 32% 19% 7%	460
May	1st to 10th	Day	4 10% 34% 32% 14% 5%	463
	11th to 20th	Day	6% 7% 26% 34% 20% 6%	488
	21st to end	Day	6% 9% 19% 36% 23% 7%	529
June	1st to 10th	Day	2 5% 24% 33% 27% 9%	490
	11th to 20th	Day	2 5% 24% 38% 24% 8%	490
	21st to end	Day	1 3 18% 40% 28% 10%	490
July	1st to 10th	Day	1 10% 42% 35% 11%	486
	11th to 20th	Day	1 7% 36% 40% 15%	484
	21st to end	Day	1 9% 40% 37% 13%	531
August	1st to 10th	Day	3 1 14% 43% 27% 11%	487
	11th to 20th	Day	1 1 16% 40% 30% 12%	477
	21st to end	Day	2 1 10% 39% 36% 13%	539
September	1st to 10th	Day	1 2 13% 40% 31% 12%	490
	11th to 20th	Day	3 3 22% 37% 28% 7%	490
	21st to end	Day	2 3 18% 36% 34% 8%	490
October	1st to 10th	Day	2 4 21% 34% 31% 9%	490
	11th to 20th	Day	3 4 21% 33% 30% 9%	490
	21st to end	Day	4 5% 16% 32% 34% 8%	534
November	1st to 10th	Day	9% 5% 16% 30% 31% 10%	270
	11th to 20th	Day	6% 3 16% 36% 28% 12%	270
	21st to end	Day	10% 3 18% 32% 30% 8%	270
December	1st to 10th	Day	15% 2 15% 36% 25% 7%	207
	11th to 20th	Day	16% 4 21% 30% 20% 9%	180
	21st to end	Day	21% 4 23% 29% 20% 5%	198
January	1st to 10th	Night	18% 2 13% 34% 24% 9%	760
	11th to 20th	Night	12% 3 13% 38% 27% 8%	760
	21st to end	Night	18% 2 10% 38% 25% 6%	836
February	1st to 10th	Night	17% 3 12% 37% 22% 9%	760
	11th to 20th	Night	14% 4 15% 34% 27% 7%	744
	21st to end	Night	17% 3 13% 45% 19% 4	628
March	1st to 10th	Night	18% 4 14% 40% 21% 4	760
	11th to 20th	Night	13% 4 18% 33% 27% 7%	760
	21st to end	Night	15% 2 19% 38% 24% 2	836
April	1st to 10th	Night	11% 4 21% 36% 25% 3	760
	11th to 20th	Night	7% 5% 23% 38% 23% 5%	751
	21st to end	Night	6% 3 22% 38% 25% 6%	760
May	1st to 10th	Night	4 4 21% 44% 23% 4	713
	11th to 20th	Night	5% 2 20% 46% 27% 1	529
	21st to end	Night	4 3 20% 43% 29% 2	411
June	1st to 10th	Night	4 2 17% 48% 26% 3	380
	11th to 20th	Night	1 1 16% 52% 31% 1	380
	21st to end	Night	1 11% 52% 34% 2	380
July	1st to 10th	Night	5% 48% 44% 2	370
	11th to 20th	Night	3 4 44% 46% 3	368
	21st to end	Night	1 6% 28% 56% 10%	578
August	1st to 10th	Night	2 8% 41% 42% 7%	668
	11th to 20th	Night	1 1 5% 42% 45% 7%	752
	21st to end	Night	2 4 32% 54% 8%	836
September	1st to 10th	Night	1 5% 34% 51% 8%	760
	11th to 20th	Night	1 2 9% 41% 37% 10%	760
	21st to end	Night	2 1 8% 35% 44% 10%	760
October	1st to 10th	Night	4 1 8% 41% 39% 8%	760
	11th to 20th	Night	4 1 8% 39% 38% 10%	760
	21st to end	Night	5% 10% 36% 32% 16%	836
November	1st to 10th	Night	9% 3 9% 33% 34% 13%	742
	11th to 20th	Night	6% 1 10% 42% 31% 9%	760
	21st to end	Night	10% 12% 38% 30% 9%	760
December	1st to 10th	Night	15% 2 12% 39% 26% 7%	760
	11th to 20th	Night	19% 1 11% 40% 23% 6%	760
	21st to end	Night	19% 2 14% 41% 20% 4	836

Page generated at 2024-10-29 08:20:47. Version ac07

Copyright © 2024 Attilla Danko.