DaVinci Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DaVinci Observatory clear sky chart from 2005-11-06 to 2026-05-17.

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% 12% 4 9% 5% 5% 4 4 5% 7% 29%	132230
	Night	16% 13% 5% 10% 6% 5% 4 3 5% 6% 27%	130587
Transparency	Day	53% 7% 12% 18% 9% 1	135822
	Night	56% 7% 11% 17% 9% 1	135081
Seeing	Day	26% 17% 29% 17% 8% 3	16400
	Night	25% 16% 28% 22% 8% 1	25883

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% 21% 7% 18% 8% 4 4 2 3 3 12%	4661
	11th to 20th	Day	11% 25% 9% 21% 9% 5% 4 3 3 3 7%	5042
	21st to end	Day	15% 15% 8% 17% 12% 10% 6% 3 4 3 8%	5780
February	1st to 10th	Day	18% 19% 6% 14% 8% 5% 6% 2 3 4 14%	1890
	11th to 20th	Day	14% 18% 8% 17% 8% 5% 4 3 3 4 15%	1843
	21st to end	Day	20% 16% 5% 13% 8% 6% 5% 2 5% 4 16%	1628
March	1st to 10th	Day	17% 14% 6% 12% 6% 5% 3 2 3 5% 27%	5041
	11th to 20th	Day	10% 18% 5% 9% 5% 5% 5% 3 5% 6% 29%	5090
	21st to end	Day	20% 13% 4 10% 5% 4 4 3 5% 6% 27%	5586
April	1st to 10th	Day	18% 15% 4 8% 6% 4 4 3 4 6% 28%	2515
	11th to 20th	Day	20% 12% 3 7% 4 4 4 3 4 6% 33%	2499
	21st to end	Day	21% 10% 3 8% 4 4 4 3 4 5% 34%	2730
May	1st to 10th	Day	22% 10% 3 8% 5% 4 4 3 5% 6% 30%	6054
	11th to 20th	Day	17% 11% 3 8% 5% 4 5% 4 5% 7% 31%	6402
	21st to end	Day	20% 8% 3 6% 3 4 4 4 6% 6% 36%	6949
June	1st to 10th	Day	17% 7% 2 6% 4 4 5% 4 6% 8% 37%	2800
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 5% 7% 9% 37%	2800
	21st to end	Day	15% 6% 2 6% 4 4 4 4 7% 8% 40%	2800
July	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 7% 10% 42%	6360
	11th to 20th	Day	11% 6% 3 6% 5% 5% 5% 5% 7% 10% 39%	6360
	21st to end	Day	9% 5% 2 6% 4 4 5% 4 7% 9% 45%	6543
August	1st to 10th	Day	18% 6% 2 6% 4 4 5% 4 6% 8% 37%	4234
	11th to 20th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 10% 33%	4174
	21st to end	Day	12% 5% 2 6% 4 4 4 4 6% 10% 42%	4413
September	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 5% 9% 42%	2400
	11th to 20th	Day	12% 5% 2 5% 4 4 6% 4 6% 7% 44%	2336
	21st to end	Day	15% 7% 3 8% 5% 6% 5% 4 6% 8% 32%	2125
October	1st to 10th	Day	20% 6% 3 7% 5% 4 4 3 5% 7% 36%	2000
	11th to 20th	Day	20% 11% 4 9% 6% 4 4 4 4 7% 28%	2000
	21st to end	Day	26% 13% 4 9% 5% 4 4 4 4 5% 22%	2200
November	1st to 10th	Day	16% 12% 3 9% 5% 5% 5% 4 5% 6% 30%	1821
	11th to 20th	Day	14% 16% 5% 10% 5% 5% 4 4 5% 6% 26%	1680
	21st to end	Day	20% 18% 5% 10% 6% 4 4 4 4 6% 19%	1680
December	1st to 10th	Day	19% 22% 6% 12% 5% 5% 4 4 5% 6% 12%	2680
	11th to 20th	Day	21% 19% 6% 12% 5% 4 4 3 5% 4 18%	3066
	21st to end	Day	23% 21% 6% 14% 7% 5% 4 3 3 4 11%	4048
January	1st to 10th	Night	16% 19% 7% 18% 8% 5% 4 2 3 4 14%	8234
	11th to 20th	Night	12% 20% 9% 20% 9% 6% 5% 3 4 4 10%	7841
	21st to end	Night	16% 17% 6% 17% 10% 9% 4 3 4 4 10%	8401
February	1st to 10th	Night	17% 19% 5% 13% 7% 5% 4 3 4 4 18%	2730
	11th to 20th	Night	15% 15% 6% 13% 7% 5% 6% 4 4 5% 19%	2663
	21st to end	Night	17% 17% 6% 13% 7% 5% 4 3 5% 6% 18%	2175
March	1st to 10th	Night	18% 12% 5% 9% 7% 5% 4 3 4 5% 28%	5018
	11th to 20th	Night	15% 14% 4 7% 4 4 4 3 5% 7% 33%	5089
	21st to end	Night	19% 11% 4 9% 4 4 3 3 5% 6% 32%	5588
April	1st to 10th	Night	20% 13% 4 9% 6% 4 4 3 4 4 29%	2105
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 4 5% 6% 34%	2075
	21st to end	Night	17% 9% 3 7% 4 4 5% 4 5% 7% 34%	1902
May	1st to 10th	Night	25% 11% 4 8% 4 3 4 3 4 5% 29%	4107
	11th to 20th	Night	13% 7% 3 9% 5% 6% 5% 4 7% 8% 35%	3623
	21st to end	Night	19% 7% 3 7% 4 4 4 4 6% 7% 36%	3926
June	1st to 10th	Night	12% 6% 3 7% 6% 6% 6% 5% 7% 8% 34%	1600
	11th to 20th	Night	11% 6% 2 6% 5% 5% 6% 4 6% 7% 41%	1600
	21st to end	Night	13% 7% 2 6% 4 5% 5% 4 6% 8% 41%	1600
July	1st to 10th	Night	9% 7% 2 7% 4 4 4 4 7% 9% 42%	3600
	11th to 20th	Night	10% 6% 2 7% 4 4 5% 3 6% 9% 44%	3600
	21st to end	Night	10% 5% 2 5% 3 4 4 4 6% 7% 50%	4305
August	1st to 10th	Night	10% 6% 2 7% 5% 5% 4 4 6% 9% 42%	2915
	11th to 20th	Night	14% 7% 3 7% 4 4 4 4 6% 7% 40%	2875
	21st to end	Night	9% 5% 2 5% 4 5% 5% 4 7% 10% 44%	3450
September	1st to 10th	Night	12% 7% 3 5% 4 4 4 3 5% 7% 45%	2000
	11th to 20th	Night	12% 5% 2 5% 4 3 3 3 5% 6% 51%	2060
	21st to end	Night	17% 8% 3 6% 4 4 3 4 6% 8% 37%	2275
October	1st to 10th	Night	16% 7% 3 7% 5% 3 5% 3 5% 7% 40%	2400
	11th to 20th	Night	21% 10% 3 9% 4 5% 3 3 5% 6% 31%	2400
	21st to end	Night	26% 11% 3 7% 5% 4 4 3 5% 5% 27%	2640
November	1st to 10th	Night	16% 11% 3 8% 5% 4 3 4 5% 5% 36%	2692
	11th to 20th	Night	15% 13% 4 9% 6% 6% 5% 4 6% 6% 26%	2940
	21st to end	Night	18% 16% 5% 9% 6% 4 6% 5% 5% 6% 20%	2940
December	1st to 10th	Night	17% 22% 8% 12% 7% 5% 5% 3 4 6% 12%	4720
	11th to 20th	Night	19% 22% 6% 10% 5% 5% 4 3 4 4 19%	5348
	21st to end	Night	24% 18% 6% 11% 7% 5% 4 3 4 5% 13%	7150

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	77% 7% 8% 6% 2	4662
	11th to 20th	Day	81% 5% 5% 5% 3 1	5076
	21st to end	Day	81% 6% 8% 3 1	5780
February	1st to 10th	Day	74% 4 10% 10% 1	1890
	11th to 20th	Day	73% 7% 7% 10% 2	1852
	21st to end	Day	71% 5% 9% 10% 4	1628
March	1st to 10th	Day	60% 5% 12% 15% 8%	5044
	11th to 20th	Day	53% 7% 17% 14% 7% 1	5090
	21st to end	Day	57% 5% 9% 20% 8% 1	5586
April	1st to 10th	Day	58% 5% 9% 18% 9% 1	2515
	11th to 20th	Day	53% 5% 10% 20% 12% 1	2499
	21st to end	Day	53% 5% 9% 19% 12% 2	2730
May	1st to 10th	Day	55% 5% 10% 16% 9% 4	6063
	11th to 20th	Day	51% 7% 10% 18% 12% 1	6406
	21st to end	Day	47% 6% 12% 20% 12% 2	6949
June	1st to 10th	Day	44% 6% 12% 21% 15% 1	2800
	11th to 20th	Day	42% 6% 14% 23% 13% 1	2800
	21st to end	Day	40% 7% 14% 23% 15% 1	2800
July	1st to 10th	Day	35% 8% 13% 27% 16% 1	6290
	11th to 20th	Day	37% 8% 14% 25% 14% 1	6285
	21st to end	Day	34% 8% 14% 28% 16%	6356
August	1st to 10th	Day	42% 8% 15% 22% 12% 1	4221
	11th to 20th	Day	43% 9% 16% 24% 8% 1	4213
	21st to end	Day	36% 6% 14% 32% 11% 1	4413
September	1st to 10th	Day	40% 7% 13% 28% 11% 1	2400
	11th to 20th	Day	36% 8% 13% 28% 14% 1	2336
	21st to end	Day	49% 6% 14% 21% 9% 1	2125
October	1st to 10th	Day	39% 7% 16% 24% 13% 1	3260
	11th to 20th	Day	48% 5% 15% 19% 13%	3240
	21st to end	Day	50% 6% 15% 20% 7% 1	3538
November	1st to 10th	Day	54% 7% 10% 18% 9% 1	1821
	11th to 20th	Day	58% 6% 14% 15% 6% 1	1680
	21st to end	Day	68% 5% 12% 11% 4	1680
December	1st to 10th	Day	73% 8% 12% 7% 1	2680
	11th to 20th	Day	68% 8% 8% 9% 6%	3066
	21st to end	Day	78% 6% 9% 6% 2	4048
January	1st to 10th	Night	74% 8% 8% 8% 2	8234
	11th to 20th	Night	77% 7% 8% 5% 3	7882
	21st to end	Night	77% 7% 7% 6% 3	8401
February	1st to 10th	Night	70% 5% 9% 12% 4	2730
	11th to 20th	Night	67% 6% 11% 12% 4	2665
	21st to end	Night	66% 5% 11% 12% 5%	2175
March	1st to 10th	Night	59% 5% 12% 17% 7%	5028
	11th to 20th	Night	50% 6% 16% 19% 8% 2	5090
	21st to end	Night	52% 7% 10% 20% 11% 1	5588
April	1st to 10th	Night	58% 5% 8% 18% 10% 1	2105
	11th to 20th	Night	50% 6% 10% 20% 12% 2	2075
	21st to end	Night	49% 6% 10% 20% 14% 2	1902
May	1st to 10th	Night	58% 5% 9% 14% 11% 4	4114
	11th to 20th	Night	45% 8% 15% 19% 12% 1	3624
	21st to end	Night	46% 7% 10% 21% 15% 1	3927
June	1st to 10th	Night	44% 8% 10% 21% 16% 2	1600
	11th to 20th	Night	40% 7% 13% 21% 18% 2	1600
	21st to end	Night	41% 6% 14% 21% 17% 2	1600
July	1st to 10th	Night	37% 6% 13% 25% 17% 1	3560
	11th to 20th	Night	35% 8% 13% 27% 16% 1	3552
	21st to end	Night	32% 7% 14% 25% 22% 1	4177
August	1st to 10th	Night	38% 6% 16% 26% 13% 1	2904
	11th to 20th	Night	42% 7% 16% 26% 10%	2902
	21st to end	Night	32% 8% 16% 31% 12% 1	3450
September	1st to 10th	Night	37% 7% 14% 29% 13% 1	2000
	11th to 20th	Night	33% 5% 12% 32% 17% 1	2060
	21st to end	Night	45% 7% 13% 22% 12% 1	2275
October	1st to 10th	Night	40% 7% 10% 25% 17% 1	3920
	11th to 20th	Night	48% 5% 13% 20% 12% 1	3899
	21st to end	Night	45% 6% 15% 25% 8% 1	4252
November	1st to 10th	Night	49% 5% 11% 22% 10% 2	2692
	11th to 20th	Night	57% 6% 13% 16% 8% 1	2940
	21st to end	Night	63% 8% 13% 13% 3	2940
December	1st to 10th	Night	72% 9% 11% 7% 1	4720
	11th to 20th	Night	70% 6% 7% 11% 6% 1	5348
	21st to end	Night	74% 6% 10% 8% 3	7150

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	37% 27% 24% 8% 3 1	220
	11th to 20th	Day	34% 32% 23% 8% 2 1	292
	21st to end	Day	34% 26% 28% 11% 2	363
February	1st to 10th	Day	36% 28% 28% 6% 1	330
	11th to 20th	Day	36% 32% 27% 4 1	330
	21st to end	Day	43% 25% 25% 7% 1	344
March	1st to 10th	Day	32% 23% 29% 12% 3	540
	11th to 20th	Day	36% 21% 30% 10% 2 1	540
	21st to end	Day	34% 22% 27% 13% 3 1	594
April	1st to 10th	Day	34% 20% 30% 11% 4 1	540
	11th to 20th	Day	37% 19% 23% 14% 5% 1	532
	21st to end	Day	30% 20% 31% 13% 6% 1	540
May	1st to 10th	Day	29% 17% 31% 16% 5% 3	543
	11th to 20th	Day	25% 14% 30% 20% 8% 3	551
	21st to end	Day	21% 14% 32% 20% 9% 3	573
June	1st to 10th	Day	21% 18% 36% 18% 5% 1	530
	11th to 20th	Day	18% 13% 35% 23% 9% 2	530
	21st to end	Day	21% 14% 36% 21% 7% 2	530
July	1st to 10th	Day	12% 9% 33% 28% 16% 3	525
	11th to 20th	Day	15% 10% 30% 28% 14% 3	524
	21st to end	Day	13% 9% 35% 28% 12% 3	576
August	1st to 10th	Day	13% 10% 26% 30% 15% 6%	526
	11th to 20th	Day	13% 8% 30% 27% 15% 6%	519
	21st to end	Day	15% 12% 29% 25% 12% 8%	583
September	1st to 10th	Day	16% 12% 26% 24% 15% 7%	530
	11th to 20th	Day	12% 6% 25% 26% 20% 11%	530
	21st to end	Day	18% 16% 28% 20% 12% 5%	530
October	1st to 10th	Day	24% 13% 26% 21% 12% 4	530
	11th to 20th	Day	30% 19% 28% 16% 5% 1	530
	21st to end	Day	37% 17% 27% 13% 4	583
November	1st to 10th	Day	32% 19% 30% 12% 5% 1	370
	11th to 20th	Day	34% 24% 30% 8% 3 2	220
	21st to end	Day	41% 20% 29% 9%	220
December	1st to 10th	Day	40% 21% 27% 9% 3	220
	11th to 20th	Day	41% 23% 26% 9% 1	220
	21st to end	Day	42% 26% 22% 7% 2 1	242
January	1st to 10th	Night	33% 25% 27% 11% 3	840
	11th to 20th	Night	35% 25% 26% 12% 2	840
	21st to end	Night	28% 24% 29% 16% 3	924
February	1st to 10th	Night	31% 26% 27% 14% 1	840
	11th to 20th	Night	28% 28% 27% 15% 2	823
	21st to end	Night	30% 26% 29% 14% 1	692
March	1st to 10th	Night	27% 20% 33% 16% 4	840
	11th to 20th	Night	30% 20% 29% 18% 3	840
	21st to end	Night	26% 16% 33% 18% 6% 1	924
April	1st to 10th	Night	29% 19% 31% 19% 2	840
	11th to 20th	Night	27% 16% 31% 19% 6%	831
	21st to end	Night	22% 12% 34% 25% 7%	642
May	1st to 10th	Night	23% 11% 29% 24% 11% 2	620
	11th to 20th	Night	15% 10% 35% 31% 8%	406
	21st to end	Night	15% 11% 28% 33% 12% 1	433
June	1st to 10th	Night	14% 8% 37% 32% 8%	400
	11th to 20th	Night	14% 9% 31% 37% 10%	400
	21st to end	Night	15% 8% 36% 36% 6% 1	400
July	1st to 10th	Night	10% 6% 28% 40% 14% 1	390
	11th to 20th	Night	11% 6% 30% 37% 15% 2	388
	21st to end	Night	12% 4 30% 36% 17% 2	599
August	1st to 10th	Night	11% 3 23% 42% 19% 2	597
	11th to 20th	Night	12% 5% 22% 36% 24% 2	594
	21st to end	Night	13% 5% 28% 33% 19% 2	796
September	1st to 10th	Night	17% 8% 25% 33% 15% 2	800
	11th to 20th	Night	14% 6% 21% 32% 24% 4	800
	21st to end	Night	20% 11% 26% 27% 14% 3	800
October	1st to 10th	Night	19% 10% 29% 25% 15% 2	800
	11th to 20th	Night	29% 16% 27% 21% 6% 1	800
	21st to end	Night	34% 15% 29% 20% 3	880
November	1st to 10th	Night	27% 16% 28% 22% 7% 1	820
	11th to 20th	Night	28% 17% 29% 17% 7% 1	840
	21st to end	Night	31% 22% 27% 15% 5%	840
December	1st to 10th	Night	36% 23% 24% 13% 4	840
	11th to 20th	Night	33% 25% 27% 12% 2	840
	21st to end	Night	38% 21% 26% 13% 2	924

Page generated at 2026-05-14 01:58:53. Version ac07

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