D'Auria Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the D'Auria Observatory clear sky chart from 2005-11-06 to 2025-05-26.

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% 5% 2 8% 6% 7% 7% 6% 8% 10% 35%	114131
	Night	6% 5% 2 6% 5% 5% 5% 5% 7% 10% 44%	115108
Transparency	Day	38% 10% 17% 20% 11% 3	117854
	Night	33% 10% 19% 23% 13% 3	119524
Seeing	Day	7% 3 17% 30% 25% 18%	16743
	Night	7% 2 14% 32% 32% 13%	26928

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	6% 5% 2 6% 4 4 5% 4 7% 11% 46%	4056
	11th to 20th	Day	14% 8% 3 9% 6% 6% 5% 4 6% 9% 30%	4060
	21st to end	Day	8% 8% 3 8% 6% 6% 5% 4 6% 7% 41%	4650
February	1st to 10th	Day	7% 6% 2 6% 5% 6% 6% 4 6% 11% 41%	2000
	11th to 20th	Day	6% 3 2 6% 3 4 5% 5% 8% 10% 48%	2061
	21st to end	Day	5% 5% 2 6% 5% 4 7% 4 8% 9% 46%	1815
March	1st to 10th	Day	3 3 2 6% 5% 6% 7% 6% 9% 9% 45%	4935
	11th to 20th	Day	3 2 1 4 3 4 4 4 6% 9% 59%	4980
	21st to end	Day	6% 4 2 7% 5% 5% 5% 5% 7% 10% 44%	5465
April	1st to 10th	Day	4 3 2 6% 5% 5% 5% 6% 8% 11% 46%	2200
	11th to 20th	Day	4 4 2 7% 5% 6% 6% 5% 9% 11% 42%	2241
	21st to end	Day	6% 4 2 6% 5% 5% 6% 5% 6% 10% 46%	2400
May	1st to 10th	Day	2 2 1 4 4 5% 5% 5% 7% 11% 55%	3885
	11th to 20th	Day	5% 4 2 6% 5% 6% 5% 5% 7% 11% 42%	3913
	21st to end	Day	5% 4 2 8% 7% 7% 8% 6% 8% 10% 34%	4541
June	1st to 10th	Day	13% 9% 4 11% 10% 9% 8% 6% 7% 8% 16%	2470
	11th to 20th	Day	8% 7% 4 11% 11% 11% 9% 6% 8% 9% 16%	2470
	21st to end	Day	6% 8% 3 12% 11% 9% 10% 7% 8% 9% 17%	2470
July	1st to 10th	Day	5% 6% 2 8% 7% 8% 8% 6% 10% 14% 25%	4120
	11th to 20th	Day	5% 5% 3 9% 7% 8% 9% 7% 10% 14% 24%	4120
	21st to end	Day	3 4 2 7% 7% 8% 8% 7% 10% 14% 30%	4466
August	1st to 10th	Day	3 5% 3 11% 9% 9% 9% 9% 10% 12% 20%	4023
	11th to 20th	Day	5% 6% 2 9% 7% 8% 8% 8% 11% 14% 22%	3678
	21st to end	Day	5% 4 2 8% 8% 10% 10% 8% 11% 14% 20%	3828
September	1st to 10th	Day	6% 6% 3 12% 9% 10% 8% 8% 11% 11% 17%	2090
	11th to 20th	Day	8% 8% 4 13% 9% 8% 8% 7% 8% 9% 19%	2090
	21st to end	Day	10% 10% 4 12% 7% 7% 7% 7% 8% 8% 21%	2090
October	1st to 10th	Day	7% 6% 4 12% 8% 7% 7% 6% 9% 12% 21%	2019
	11th to 20th	Day	10% 5% 3 9% 7% 8% 7% 7% 8% 10% 26%	1900
	21st to end	Day	10% 7% 3 8% 7% 6% 6% 5% 7% 10% 33%	2090
November	1st to 10th	Day	6% 6% 2 6% 6% 6% 6% 6% 8% 9% 39%	1957
	11th to 20th	Day	8% 6% 3 9% 8% 7% 6% 5% 8% 7% 35%	2000
	21st to end	Day	7% 5% 2 7% 7% 6% 5% 5% 7% 9% 42%	2000
December	1st to 10th	Day	4 4 1 4 4 4 4 3 6% 9% 55%	3209
	11th to 20th	Day	8% 5% 2 7% 5% 6% 5% 5% 8% 11% 38%	3373
	21st to end	Day	11% 6% 3 9% 7% 7% 7% 5% 8% 9% 29%	4466
January	1st to 10th	Night	5% 5% 2 6% 5% 5% 5% 5% 8% 10% 44%	5889
	11th to 20th	Night	14% 9% 3 8% 6% 5% 5% 4 6% 7% 34%	5900
	21st to end	Night	9% 7% 3 7% 5% 4 5% 4 5% 7% 43%	6288
February	1st to 10th	Night	6% 6% 2 5% 4 4 4 4 6% 9% 48%	2400
	11th to 20th	Night	5% 3 1 5% 4 3 4 4 6% 7% 57%	2221
	21st to end	Night	5% 3 1 4 4 3 4 3 6% 10% 58%	1815
March	1st to 10th	Night	3 3 2 6% 4 5% 5% 4 6% 9% 51%	4918
	11th to 20th	Night	3 3 1 3 3 3 4 3 5% 8% 63%	4980
	21st to end	Night	5% 3 2 5% 4 5% 5% 4 6% 8% 52%	5467
April	1st to 10th	Night	3 2 1 4 3 3 4 4 7% 9% 60%	2200
	11th to 20th	Night	4 3 1 4 3 4 4 4 6% 10% 55%	2105
	21st to end	Night	5% 3 2 5% 3 4 5% 5% 6% 10% 53%	2000
May	1st to 10th	Night	1 2 1 3 3 3 3 3 6% 9% 66%	3230
	11th to 20th	Night	5% 3 2 5% 4 4 5% 4 7% 10% 53%	3214
	21st to end	Night	4 4 1 5% 4 4 5% 5% 8% 11% 49%	3130
June	1st to 10th	Night	11% 8% 3 8% 6% 6% 6% 6% 8% 11% 26%	1710
	11th to 20th	Night	6% 6% 2 6% 6% 5% 7% 7% 8% 14% 32%	1710
	21st to end	Night	4 4 2 6% 6% 6% 8% 8% 10% 14% 32%	1710
July	1st to 10th	Night	3 5% 2 7% 5% 5% 6% 5% 11% 16% 35%	2840
	11th to 20th	Night	3 4 2 6% 5% 5% 6% 6% 11% 14% 37%	2840
	21st to end	Night	2 4 2 6% 5% 5% 6% 6% 10% 15% 41%	3087
August	1st to 10th	Night	3 3 2 8% 6% 7% 7% 6% 10% 14% 34%	2875
	11th to 20th	Night	3 4 2 6% 5% 6% 7% 6% 10% 14% 37%	3129
	21st to end	Night	4 3 2 7% 5% 7% 8% 8% 13% 16% 27%	3828
September	1st to 10th	Night	4 3 2 7% 6% 7% 7% 7% 9% 14% 33%	2090
	11th to 20th	Night	6% 7% 3 8% 8% 7% 7% 6% 8% 11% 28%	2090
	21st to end	Night	6% 7% 3 10% 7% 6% 7% 6% 10% 11% 28%	2090
October	1st to 10th	Night	7% 5% 3 9% 7% 7% 7% 6% 9% 11% 29%	2159
	11th to 20th	Night	8% 6% 3 8% 5% 5% 6% 5% 8% 11% 35%	2280
	21st to end	Night	9% 6% 3 8% 5% 5% 5% 4 6% 8% 41%	2508
November	1st to 10th	Night	7% 4 2 7% 5% 5% 5% 5% 7% 9% 47%	2341
	11th to 20th	Night	8% 8% 2 6% 6% 5% 5% 6% 6% 9% 39%	2400
	21st to end	Night	6% 4 2 5% 5% 5% 5% 4 6% 8% 49%	2400
December	1st to 10th	Night	5% 4 2 5% 3 3 3 4 6% 8% 57%	3952
	11th to 20th	Night	10% 7% 3 7% 5% 4 4 4 6% 8% 44%	4822
	21st to end	Night	9% 8% 3 9% 6% 6% 6% 5% 7% 8% 31%	6490

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	30% 7% 11% 30% 16% 6%	4057
	11th to 20th	Day	49% 8% 14% 20% 7% 2	4060
	21st to end	Day	41% 5% 8% 25% 17% 4	4650
February	1st to 10th	Day	34% 6% 11% 25% 20% 4	2000
	11th to 20th	Day	27% 6% 11% 27% 23% 5%	2071
	21st to end	Day	29% 6% 11% 22% 24% 8%	1815
March	1st to 10th	Day	27% 9% 14% 23% 24% 3	4935
	11th to 20th	Day	19% 7% 14% 30% 18% 13%	4980
	21st to end	Day	31% 7% 11% 27% 19% 5%	5465
April	1st to 10th	Day	27% 8% 14% 32% 17% 3	2200
	11th to 20th	Day	29% 10% 15% 23% 18% 5%	2241
	21st to end	Day	29% 7% 13% 26% 21% 4	2400
May	1st to 10th	Day	19% 7% 12% 34% 23% 3	3920
	11th to 20th	Day	31% 8% 18% 36% 7%	3917
	21st to end	Day	37% 13% 13% 28% 9% 1	4554
June	1st to 10th	Day	62% 10% 16% 10% 3	2470
	11th to 20th	Day	59% 12% 18% 11% 1	2470
	21st to end	Day	54% 15% 21% 8% 1	2470
July	1st to 10th	Day	40% 14% 30% 16%	4055
	11th to 20th	Day	40% 14% 36% 10%	4051
	21st to end	Day	33% 17% 34% 15% 1	4324
August	1st to 10th	Day	45% 17% 25% 10% 2	4010
	11th to 20th	Day	41% 16% 30% 13%	3714
	21st to end	Day	45% 17% 32% 6% 1	3828
September	1st to 10th	Day	51% 16% 21% 11%	2090
	11th to 20th	Day	56% 15% 18% 9% 2	2090
	21st to end	Day	57% 13% 13% 12% 5%	2090
October	1st to 10th	Day	47% 11% 20% 15% 5% 1	3357
	11th to 20th	Day	49% 13% 16% 14% 8% 1	3140
	21st to end	Day	39% 7% 12% 25% 14% 3	3428
November	1st to 10th	Day	36% 7% 14% 17% 19% 6%	1957
	11th to 20th	Day	44% 7% 9% 18% 17% 5%	2000
	21st to end	Day	37% 7% 12% 17% 23% 4	2000
December	1st to 10th	Day	25% 6% 11% 31% 24% 4	3209
	11th to 20th	Day	35% 7% 15% 21% 18% 4	3370
	21st to end	Day	47% 8% 15% 15% 14% 1	4466
January	1st to 10th	Night	32% 8% 14% 27% 17% 3	5889
	11th to 20th	Night	48% 7% 15% 19% 9% 2	5900
	21st to end	Night	39% 6% 10% 27% 15% 3	6288
February	1st to 10th	Night	31% 5% 14% 26% 20% 4	2400
	11th to 20th	Night	24% 6% 12% 25% 23% 9%	2222
	21st to end	Night	22% 6% 13% 23% 28% 8%	1815
March	1st to 10th	Night	26% 8% 12% 24% 24% 6%	4918
	11th to 20th	Night	18% 6% 17% 28% 19% 11%	4980
	21st to end	Night	27% 7% 13% 27% 21% 5%	5467
April	1st to 10th	Night	19% 6% 16% 37% 18% 3	2200
	11th to 20th	Night	23% 8% 17% 25% 21% 5%	2105
	21st to end	Night	25% 7% 15% 28% 22% 3	2000
May	1st to 10th	Night	13% 8% 17% 44% 16% 3	3260
	11th to 20th	Night	23% 10% 18% 38% 11%	3215
	21st to end	Night	24% 10% 20% 35% 11%	3138
June	1st to 10th	Night	48% 12% 22% 15% 3	1710
	11th to 20th	Night	39% 15% 25% 18% 3	1710
	21st to end	Night	37% 16% 36% 11%	1710
July	1st to 10th	Night	31% 15% 36% 18%	2795
	11th to 20th	Night	30% 14% 43% 12%	2786
	21st to end	Night	27% 16% 39% 16% 1	2988
August	1st to 10th	Night	36% 16% 31% 15% 2	2864
	11th to 20th	Night	32% 15% 36% 16% 1	3159
	21st to end	Night	37% 19% 36% 7% 1	3828
September	1st to 10th	Night	36% 18% 30% 14% 2	2090
	11th to 20th	Night	46% 17% 24% 11% 2	2090
	21st to end	Night	46% 14% 21% 14% 6%	2090
October	1st to 10th	Night	45% 13% 19% 18% 4 1	3601
	11th to 20th	Night	48% 10% 19% 13% 9% 1	3779
	21st to end	Night	38% 7% 12% 25% 15% 3	4120
November	1st to 10th	Night	32% 7% 14% 22% 20% 5%	2341
	11th to 20th	Night	40% 7% 11% 24% 15% 4	2400
	21st to end	Night	31% 8% 14% 21% 22% 5%	2400
December	1st to 10th	Night	24% 7% 12% 36% 17% 4	3952
	11th to 20th	Night	37% 6% 13% 21% 17% 5%	4824
	21st to end	Night	47% 9% 14% 16% 13% 1	6490

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	8% 7% 34% 39% 11% 1	300
	11th to 20th	Day	12% 10% 37% 31% 9% 1	300
	21st to end	Day	10% 10% 42% 29% 9%	330
February	1st to 10th	Day	5% 8% 33% 38% 16% 1	300
	11th to 20th	Day	7% 4 25% 42% 19% 3	414
	21st to end	Day	4 4 25% 38% 26% 2	414
March	1st to 10th	Day	4 6% 33% 39% 16% 2	500
	11th to 20th	Day	5% 5% 32% 34% 21% 3	500
	21st to end	Day	4 4 29% 36% 22% 4	550
April	1st to 10th	Day	4 4 29% 38% 18% 6%	500
	11th to 20th	Day	3 4 30% 36% 19% 9%	492
	21st to end	Day	4 3 24% 37% 23% 9%	500
May	1st to 10th	Day	2 2 18% 37% 27% 14%	503
	11th to 20th	Day	8% 3 20% 31% 23% 14%	527
	21st to end	Day	8% 3 9% 29% 27% 24%	549
June	1st to 10th	Day	12% 2 12% 27% 26% 21%	490
	11th to 20th	Day	8% 2 7% 24% 27% 32%	490
	21st to end	Day	4 1 3 17% 28% 46%	490
July	1st to 10th	Day	5% 2 16% 29% 48%	485
	11th to 20th	Day	5% 1 3 14% 37% 40%	484
	21st to end	Day	5% 1 2 17% 31% 45%	532
August	1st to 10th	Day	6% 1 6% 16% 30% 41%	486
	11th to 20th	Day	6% 1 2 17% 29% 45%	479
	21st to end	Day	7% 1 6% 24% 29% 32%	539
September	1st to 10th	Day	6% 1 4 18% 30% 41%	490
	11th to 20th	Day	7% 2 6% 16% 30% 40%	490
	21st to end	Day	9% 3 6% 23% 26% 33%	490
October	1st to 10th	Day	7% 2 12% 37% 31% 11%	490
	11th to 20th	Day	10% 2 15% 31% 29% 14%	490
	21st to end	Day	9% 3 17% 36% 27% 8%	539
November	1st to 10th	Day	6% 4 23% 35% 25% 7%	495
	11th to 20th	Day	11% 4 21% 36% 23% 5%	500
	21st to end	Day	7% 3 23% 37% 26% 4	500
December	1st to 10th	Day	9% 4 20% 39% 25% 3	475
	11th to 20th	Day	8% 5% 24% 40% 18% 5%	300
	21st to end	Day	10% 5% 28% 37% 17% 4	330
January	1st to 10th	Night	7% 4 20% 43% 24% 3	800
	11th to 20th	Night	10% 4 25% 41% 19% 1	800
	21st to end	Night	7% 6% 28% 43% 16% 1	880
February	1st to 10th	Night	8% 5% 21% 43% 23% 1	800
	11th to 20th	Night	5% 4 23% 44% 22% 2	783
	21st to end	Night	5% 2 19% 48% 24% 1	660
March	1st to 10th	Night	5% 4 25% 44% 21% 1	800
	11th to 20th	Night	4 3 22% 46% 23% 2	800
	21st to end	Night	5% 3 24% 45% 23% 1	880
April	1st to 10th	Night	4 3 20% 47% 25% 2	800
	11th to 20th	Night	5% 2 21% 46% 25% 1	791
	21st to end	Night	5% 3 17% 46% 28% 2	800
May	1st to 10th	Night	3 14% 45% 35% 3	800
	11th to 20th	Night	8% 2 15% 39% 33% 3	786
	21st to end	Night	7% 2 6% 23% 48% 14%	634
June	1st to 10th	Night	14% 1 5% 23% 42% 15%	570
	11th to 20th	Night	8% 2 3 12% 43% 32%	570
	21st to end	Night	4 1 3 11% 42% 41%	570
July	1st to 10th	Night	5% 1 2 6% 45% 41%	555
	11th to 20th	Night	2 1 2 10% 42% 43%	552
	21st to end	Night	3 1 2 8% 39% 48%	624
August	1st to 10th	Night	6% 1 3 8% 46% 37%	591
	11th to 20th	Night	3 1 2 12% 45% 38%	750
	21st to end	Night	8% 1 5% 17% 40% 29%	836
September	1st to 10th	Night	6% 4 12% 41% 37%	760
	11th to 20th	Night	8% 2 5% 13% 38% 34%	760
	21st to end	Night	10% 2 6% 16% 40% 26%	760
October	1st to 10th	Night	9% 2 8% 33% 37% 10%	760
	11th to 20th	Night	10% 1 9% 29% 40% 11%	760
	21st to end	Night	13% 2 15% 35% 29% 7%	836
November	1st to 10th	Night	8% 2 20% 37% 30% 3	780
	11th to 20th	Night	9% 4 16% 34% 33% 4	800
	21st to end	Night	8% 2 16% 45% 27% 3	800
December	1st to 10th	Night	6% 2 17% 41% 32% 3	800
	11th to 20th	Night	9% 3 16% 40% 29% 3	800
	21st to end	Night	7% 4 18% 39% 28% 3	880

Page generated at 2025-05-23 09:20:57. Version ac07

Copyright © 2025 Attilla Danko.