Chiaro Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chiaro Observing Site 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	16% 7% 2 6% 4 4 4 4 6% 7% 39%	101507
	Night	17% 7% 2 6% 4 4 4 3 5% 7% 42%	98028
Transparency	Day	41% 7% 12% 22% 16% 2	105052
	Night	41% 6% 11% 23% 17% 3	102559
Seeing	Day	19% 13% 31% 23% 10% 3	15125
	Night	19% 10% 32% 28% 9% 1	24325

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% 9% 3 5% 4 4 3 3 4 5% 46%	2517
	11th to 20th	Day	16% 9% 3 8% 5% 4 4 3 5% 6% 38%	2520
	21st to end	Day	23% 12% 3 7% 4 4 3 2 4 5% 33%	3074
February	1st to 10th	Day	15% 8% 3 7% 5% 4 3 3 5% 6% 41%	1724
	11th to 20th	Day	16% 8% 2 6% 4 3 4 3 4 5% 43%	1848
	21st to end	Day	17% 10% 3 6% 4 4 3 3 5% 6% 38%	1570
March	1st to 10th	Day	27% 7% 2 5% 3 3 4 3 3 5% 37%	3116
	11th to 20th	Day	9% 5% 1 5% 5% 4 5% 4 6% 7% 48%	3371
	21st to end	Day	20% 8% 2 5% 4 3 4 2 4 5% 43%	4120
April	1st to 10th	Day	17% 8% 2 6% 4 4 4 4 4 7% 39%	2280
	11th to 20th	Day	15% 7% 2 5% 4 4 4 3 7% 7% 42%	2254
	21st to end	Day	17% 6% 2 6% 4 4 4 4 6% 7% 40%	2280
May	1st to 10th	Day	24% 10% 3 7% 4 4 4 3 5% 7% 28%	4095
	11th to 20th	Day	27% 9% 2 6% 4 4 4 4 4 6% 31%	4352
	21st to end	Day	13% 5% 2 5% 4 5% 4 4 6% 8% 42%	4837
June	1st to 10th	Day	14% 6% 2 5% 5% 5% 5% 5% 7% 9% 38%	2660
	11th to 20th	Day	13% 7% 2 6% 5% 5% 5% 4 6% 8% 39%	2660
	21st to end	Day	10% 6% 2 6% 5% 5% 6% 4 7% 9% 39%	2660
July	1st to 10th	Day	8% 5% 2 7% 6% 6% 7% 6% 8% 10% 35%	4440
	11th to 20th	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 10% 35%	4440
	21st to end	Day	12% 8% 3 8% 6% 6% 6% 5% 7% 8% 30%	4814
August	1st to 10th	Day	18% 6% 3 7% 5% 5% 5% 5% 7% 8% 30%	4079
	11th to 20th	Day	13% 6% 3 6% 4 5% 5% 4 7% 9% 39%	3730
	21st to end	Day	10% 5% 1 6% 4 5% 4 4 7% 9% 44%	4180
September	1st to 10th	Day	14% 6% 2 6% 5% 4 4 3 5% 8% 44%	2280
	11th to 20th	Day	12% 5% 2 5% 3 4 4 4 5% 8% 48%	2206
	21st to end	Day	20% 7% 2 7% 4 3 4 4 5% 6% 38%	2090
October	1st to 10th	Day	20% 6% 2 4 3 3 4 3 5% 6% 43%	1973
	11th to 20th	Day	15% 6% 2 4 3 3 3 3 4 6% 51%	1900
	21st to end	Day	18% 6% 2 6% 3 3 3 3 4 6% 46%	1967
November	1st to 10th	Day	13% 5% 2 5% 4 3 3 2 4 6% 52%	1761
	11th to 20th	Day	16% 6% 2 6% 4 3 4 3 5% 6% 47%	1800
	21st to end	Day	16% 6% 1 4 4 4 4 3 4 8% 45%	1711
December	1st to 10th	Day	17% 8% 3 7% 3 4 3 3 5% 7% 40%	1520
	11th to 20th	Day	19% 7% 3 4 4 3 4 3 4 5% 44%	1906
	21st to end	Day	16% 7% 3 6% 4 5% 5% 4 7% 6% 37%	2772
January	1st to 10th	Night	17% 7% 2 4 4 3 3 3 4 5% 48%	4429
	11th to 20th	Night	18% 9% 2 6% 4 3 3 3 4 5% 44%	4440
	21st to end	Night	23% 10% 2 6% 4 3 3 3 4 5% 36%	4564
February	1st to 10th	Night	16% 9% 3 6% 3 4 3 3 5% 7% 41%	2456
	11th to 20th	Night	18% 9% 2 6% 4 3 3 3 5% 6% 42%	2218
	21st to end	Night	19% 7% 2 5% 3 3 3 3 5% 6% 43%	1884
March	1st to 10th	Night	22% 12% 3 6% 3 3 2 2 3 5% 38%	3724
	11th to 20th	Night	12% 6% 2 6% 5% 4 4 3 5% 6% 47%	3585
	21st to end	Night	20% 9% 3 6% 4 3 3 2 3 4 43%	3510
April	1st to 10th	Night	17% 9% 3 6% 4 4 4 3 5% 6% 41%	1900
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 4 6% 42%	1875
	21st to end	Night	17% 6% 2 5% 3 3 5% 3 5% 7% 42%	1900
May	1st to 10th	Night	23% 10% 3 7% 5% 4 4 3 5% 8% 28%	2844
	11th to 20th	Night	26% 10% 3 6% 4 4 2 3 4 7% 31%	2570
	21st to end	Night	14% 7% 3 6% 3 4 4 4 5% 8% 41%	2738
June	1st to 10th	Night	14% 7% 2 6% 5% 4 4 3 6% 8% 42%	1520
	11th to 20th	Night	13% 6% 2 7% 4 4 4 4 6% 8% 41%	1520
	21st to end	Night	9% 5% 2 6% 5% 5% 6% 5% 7% 10% 40%	1520
July	1st to 10th	Night	8% 6% 3 9% 6% 6% 6% 5% 7% 10% 36%	2520
	11th to 20th	Night	11% 7% 3 6% 5% 4 4 4 7% 10% 38%	2520
	21st to end	Night	16% 8% 3 7% 4 5% 5% 4 8% 8% 33%	2739
August	1st to 10th	Night	23% 7% 2 6% 4 4 5% 4 6% 9% 31%	2814
	11th to 20th	Night	12% 6% 3 7% 4 5% 4 4 6% 8% 42%	3097
	21st to end	Night	8% 5% 2 6% 3 4 4 3 5% 8% 51%	3476
September	1st to 10th	Night	13% 6% 2 7% 4 4 5% 4 4 6% 45%	1900
	11th to 20th	Night	12% 6% 2 4 4 3 4 3 5% 6% 52%	1972
	21st to end	Night	19% 7% 3 6% 3 3 3 2 6% 6% 41%	2090
October	1st to 10th	Night	19% 6% 3 5% 3 4 4 3 4 5% 43%	2204
	11th to 20th	Night	14% 5% 2 5% 3 4 3 3 5% 6% 51%	2280
	21st to end	Night	18% 7% 2 5% 3 3 4 3 4 5% 47%	2631
November	1st to 10th	Night	12% 5% 2 5% 4 3 4 3 5% 6% 53%	2537
	11th to 20th	Night	18% 6% 2 5% 3 3 4 3 4 5% 48%	2600
	21st to end	Night	13% 6% 2 5% 4 5% 4 3 5% 7% 46%	2619
December	1st to 10th	Night	20% 7% 2 6% 4 3 4 3 4 6% 41%	2660
	11th to 20th	Night	18% 5% 2 5% 5% 4 3 3 6% 7% 43%	3288
	21st to end	Night	18% 8% 3 6% 4 4 4 4 5% 6% 38%	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	40% 5% 11% 26% 15% 3	2518
	11th to 20th	Day	45% 5% 11% 22% 14% 2	2520
	21st to end	Day	54% 6% 8% 20% 10% 2	3074
February	1st to 10th	Day	45% 5% 13% 23% 13% 2	1724
	11th to 20th	Day	43% 5% 9% 23% 16% 3	1857
	21st to end	Day	47% 5% 10% 21% 13% 5%	1570
March	1st to 10th	Day	49% 5% 9% 25% 9% 2	3119
	11th to 20th	Day	32% 7% 12% 31% 15% 3	3371
	21st to end	Day	44% 5% 9% 17% 21% 5%	4120
April	1st to 10th	Day	44% 6% 11% 19% 16% 5%	2280
	11th to 20th	Day	40% 6% 13% 22% 16% 3	2254
	21st to end	Day	42% 7% 11% 18% 18% 4	2280
May	1st to 10th	Day	54% 9% 11% 15% 10% 1	4109
	11th to 20th	Day	53% 7% 13% 18% 9% 1	4356
	21st to end	Day	36% 9% 12% 24% 17% 2	4837
June	1st to 10th	Day	40% 9% 13% 21% 15% 2	2660
	11th to 20th	Day	40% 9% 13% 23% 12% 2	2660
	21st to end	Day	38% 10% 14% 21% 17% 1	2660
July	1st to 10th	Day	40% 12% 15% 19% 13% 1	4370
	11th to 20th	Day	41% 9% 17% 19% 13% 1	4365
	21st to end	Day	47% 8% 12% 18% 14% 1	4661
August	1st to 10th	Day	48% 9% 14% 20% 8%	4065
	11th to 20th	Day	39% 8% 13% 26% 12% 1	3766
	21st to end	Day	33% 8% 12% 27% 19% 2	4180
September	1st to 10th	Day	38% 7% 13% 19% 20% 3	2280
	11th to 20th	Day	35% 6% 11% 22% 24% 3	2206
	21st to end	Day	45% 6% 10% 17% 20% 2	2090
October	1st to 10th	Day	36% 5% 11% 17% 25% 5%	3272
	11th to 20th	Day	24% 4 10% 23% 33% 6%	3140
	21st to end	Day	27% 4 14% 24% 27% 4	3218
November	1st to 10th	Day	34% 4 14% 26% 20% 2	1761
	11th to 20th	Day	38% 4 10% 22% 23% 3	1800
	21st to end	Day	38% 5% 13% 29% 12% 2	1711
December	1st to 10th	Day	44% 5% 14% 21% 15% 1	1520
	11th to 20th	Day	41% 5% 13% 26% 13% 2	1906
	21st to end	Day	44% 8% 12% 23% 12% 1	2772
January	1st to 10th	Night	38% 4 10% 31% 13% 4	4429
	11th to 20th	Night	44% 4 11% 25% 14% 3	4440
	21st to end	Night	50% 5% 8% 22% 13% 2	4564
February	1st to 10th	Night	43% 5% 14% 23% 13% 2	2456
	11th to 20th	Night	44% 4 10% 19% 19% 5%	2220
	21st to end	Night	42% 5% 8% 23% 18% 4	1884
March	1st to 10th	Night	50% 4 8% 24% 12% 3	3734
	11th to 20th	Night	36% 6% 12% 25% 17% 3	3586
	21st to end	Night	46% 4 7% 16% 22% 5%	3510
April	1st to 10th	Night	44% 5% 9% 19% 18% 5%	1900
	11th to 20th	Night	43% 6% 9% 19% 20% 3	1875
	21st to end	Night	41% 6% 9% 20% 20% 4	1900
May	1st to 10th	Night	53% 8% 11% 18% 10% 1	2850
	11th to 20th	Night	54% 6% 13% 16% 10% 2	2571
	21st to end	Night	38% 9% 14% 21% 16% 2	2739
June	1st to 10th	Night	41% 8% 11% 21% 18% 1	1520
	11th to 20th	Night	39% 8% 13% 26% 12% 1	1520
	21st to end	Night	36% 10% 16% 21% 15% 2	1520
July	1st to 10th	Night	41% 10% 16% 18% 12% 2	2480
	11th to 20th	Night	40% 8% 17% 24% 11% 1	2472
	21st to end	Night	45% 8% 15% 17% 14% 1	2651
August	1st to 10th	Night	50% 8% 18% 15% 9% 1	2804
	11th to 20th	Night	39% 6% 13% 30% 11% 1	3127
	21st to end	Night	30% 6% 11% 31% 21% 2	3476
September	1st to 10th	Night	40% 7% 10% 21% 19% 2	1900
	11th to 20th	Night	33% 6% 11% 22% 25% 4	1972
	21st to end	Night	44% 6% 7% 21% 20% 2	2090
October	1st to 10th	Night	38% 6% 10% 22% 22% 2	3672
	11th to 20th	Night	24% 4 10% 27% 30% 5%	3779
	21st to end	Night	27% 4 10% 30% 25% 4	4330
November	1st to 10th	Night	33% 5% 12% 24% 22% 4	2537
	11th to 20th	Night	40% 4 8% 23% 20% 4	2600
	21st to end	Night	37% 5% 13% 27% 17% 2	2619
December	1st to 10th	Night	45% 5% 11% 23% 15% 2	2660
	11th to 20th	Night	41% 5% 12% 20% 17% 4	3288
	21st to end	Night	45% 6% 12% 24% 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% 23% 37% 15% 3 1	180
	11th to 20th	Day	29% 32% 23% 14% 3	180
	21st to end	Day	25% 20% 33% 16% 4 1	285
February	1st to 10th	Day	24% 23% 39% 11% 2 1	284
	11th to 20th	Day	26% 21% 39% 12% 2	456
	21st to end	Day	27% 21% 34% 15% 3	382
March	1st to 10th	Day	24% 21% 34% 17% 4	460
	11th to 20th	Day	20% 24% 36% 14% 4 1	460
	21st to end	Day	26% 22% 31% 16% 4 1	506
April	1st to 10th	Day	22% 22% 35% 14% 5% 1	460
	11th to 20th	Day	21% 17% 36% 17% 7% 2	452
	21st to end	Day	25% 18% 34% 17% 5% 2	460
May	1st to 10th	Day	27% 15% 33% 16% 6% 2	463
	11th to 20th	Day	22% 13% 36% 21% 7% 2	487
	21st to end	Day	19% 9% 25% 29% 15% 4	529
June	1st to 10th	Day	16% 9% 32% 27% 13% 2	490
	11th to 20th	Day	14% 11% 33% 28% 11% 3	490
	21st to end	Day	13% 6% 33% 32% 14% 2	490
July	1st to 10th	Day	12% 6% 25% 31% 19% 6%	485
	11th to 20th	Day	9% 3 24% 36% 22% 5%	484
	21st to end	Day	12% 6% 31% 32% 15% 4	532
August	1st to 10th	Day	14% 3 25% 35% 17% 6%	486
	11th to 20th	Day	13% 5% 22% 33% 21% 6%	479
	21st to end	Day	12% 5% 27% 30% 17% 9%	539
September	1st to 10th	Day	16% 7% 28% 23% 17% 9%	490
	11th to 20th	Day	13% 4 30% 30% 13% 10%	490
	21st to end	Day	25% 9% 28% 23% 11% 4	490
October	1st to 10th	Day	26% 8% 23% 22% 14% 6%	490
	11th to 20th	Day	16% 14% 30% 25% 12% 3	490
	21st to end	Day	20% 13% 33% 21% 11% 2	474
November	1st to 10th	Day	14% 14% 35% 23% 12% 2	395
	11th to 20th	Day	21% 18% 33% 22% 7%	400
	21st to end	Day	22% 15% 33% 22% 7% 1	329
December	1st to 10th	Day	23% 24% 34% 11% 7% 1	180
	11th to 20th	Day	30% 21% 32% 12% 6%	180
	21st to end	Day	24% 17% 34% 20% 5% 1	198
January	1st to 10th	Night	19% 17% 40% 20% 4	760
	11th to 20th	Night	25% 15% 33% 22% 4	760
	21st to end	Night	19% 16% 41% 22% 2	836
February	1st to 10th	Night	21% 15% 39% 23% 2	760
	11th to 20th	Night	23% 19% 42% 15% 1	743
	21st to end	Night	23% 19% 36% 18% 3	628
March	1st to 10th	Night	21% 15% 39% 20% 4	760
	11th to 20th	Night	22% 15% 39% 19% 4 1	760
	21st to end	Night	21% 12% 41% 21% 5%	836
April	1st to 10th	Night	20% 16% 39% 20% 5%	760
	11th to 20th	Night	19% 12% 36% 27% 5%	751
	21st to end	Night	20% 12% 36% 27% 5% 1	760
May	1st to 10th	Night	23% 11% 34% 25% 7% 1	580
	11th to 20th	Night	23% 8% 35% 28% 5%	423
	21st to end	Night	18% 3 23% 41% 13% 1	411
June	1st to 10th	Night	17% 6% 25% 39% 12%	380
	11th to 20th	Night	13% 4 26% 42% 16%	380
	21st to end	Night	9% 4 24% 49% 13%	380
July	1st to 10th	Night	12% 3 23% 44% 16% 2	370
	11th to 20th	Night	11% 3 20% 44% 21% 1	368
	21st to end	Night	11% 3 23% 46% 16%	416
August	1st to 10th	Night	12% 3 17% 46% 20% 2	556
	11th to 20th	Night	11% 3 22% 38% 23% 3	750
	21st to end	Night	14% 3 18% 40% 22% 3	836
September	1st to 10th	Night	16% 4 24% 34% 19% 3	760
	11th to 20th	Night	16% 4 20% 34% 22% 5%	760
	21st to end	Night	22% 5% 23% 32% 16% 2	760
October	1st to 10th	Night	22% 6% 26% 26% 16% 4	760
	11th to 20th	Night	16% 10% 29% 33% 11%	760
	21st to end	Night	22% 8% 36% 25% 9% 1	836
November	1st to 10th	Night	15% 8% 37% 28% 11% 1	780
	11th to 20th	Night	20% 14% 32% 26% 8% 1	800
	21st to end	Night	16% 15% 37% 25% 7% 1	789
December	1st to 10th	Night	25% 16% 33% 18% 7% 1	760
	11th to 20th	Night	21% 13% 40% 23% 4	760
	21st to end	Night	21% 13% 40% 25% 3	836

Page generated at 2024-11-25 00:22:15. Version ac07

Copyright © 2024 Attilla Danko.