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 2025-01-22.

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% 4 5% 4 5% 7% 30%	105198
	Night	17% 13% 4 9% 5% 5% 4 3 5% 6% 28%	104173
Transparency	Day	52% 7% 12% 19% 9% 1	108801
	Night	55% 7% 12% 18% 9% 1	108658
Seeing	Day	25% 17% 29% 18% 8% 3	14697
	Night	25% 16% 28% 22% 8% 1	24196

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% 23% 7% 14% 7% 4 4 2 3 3 16%	2597
	11th to 20th	Day	12% 24% 9% 21% 10% 5% 3 2 3 3 8%	2807
	21st to end	Day	22% 21% 9% 12% 8% 5% 4 3 4 3 9%	3133
February	1st to 10th	Day	18% 19% 5% 14% 8% 5% 6% 2 3 4 15%	1710
	11th to 20th	Day	13% 18% 9% 17% 8% 5% 5% 3 3 4 16%	1663
	21st to end	Day	20% 15% 5% 13% 8% 5% 5% 2 5% 4 17%	1477
March	1st to 10th	Day	19% 13% 5% 10% 5% 5% 3 3 4 5% 27%	3431
	11th to 20th	Day	10% 22% 5% 8% 5% 5% 5% 3 5% 5% 27%	3480
	21st to end	Day	17% 12% 3 10% 5% 4 4 3 6% 7% 30%	3815
April	1st to 10th	Day	18% 15% 4 8% 5% 3 4 3 4 6% 29%	2275
	11th to 20th	Day	20% 11% 3 7% 4 4 3 3 4 6% 35%	2259
	21st to end	Day	21% 11% 3 8% 4 4 4 3 4 5% 33%	2470
May	1st to 10th	Day	20% 10% 3 7% 5% 4 4 3 5% 7% 32%	4130
	11th to 20th	Day	16% 10% 3 8% 6% 4 5% 4 6% 7% 29%	4398
	21st to end	Day	12% 7% 2 6% 3 4 4 4 6% 7% 46%	4837
June	1st to 10th	Day	17% 7% 2 6% 4 4 5% 4 6% 8% 37%	2660
	11th to 20th	Day	13% 6% 2 6% 5% 4 5% 5% 7% 9% 38%	2660
	21st to end	Day	15% 6% 2 5% 4 4 4 4 7% 8% 40%	2660
July	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 5% 6% 10% 43%	4440
	11th to 20th	Day	12% 6% 2 6% 4 5% 5% 5% 7% 10% 39%	4440
	21st to end	Day	8% 5% 2 7% 5% 5% 6% 5% 8% 10% 40%	4543
August	1st to 10th	Day	18% 6% 2 6% 4 4 5% 4 6% 8% 36%	4104
	11th to 20th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 10% 33%	4044
	21st to end	Day	13% 5% 2 6% 4 4 4 4 6% 10% 42%	4278
September	1st to 10th	Day	14% 7% 2 6% 4 4 4 4 5% 9% 41%	2280
	11th to 20th	Day	13% 5% 2 5% 4 4 6% 4 6% 7% 43%	2219
	21st to end	Day	15% 7% 3 8% 5% 6% 5% 4 6% 8% 32%	2019
October	1st to 10th	Day	21% 6% 3 7% 5% 4 4 3 5% 7% 33%	1900
	11th to 20th	Day	20% 11% 4 9% 6% 4 4 4 4 6% 28%	1900
	21st to end	Day	26% 13% 4 9% 5% 4 4 4 4 5% 22%	2090
November	1st to 10th	Day	15% 12% 3 9% 5% 5% 5% 4 5% 6% 30%	1733
	11th to 20th	Day	14% 16% 5% 10% 4 5% 4 4 5% 7% 26%	1600
	21st to end	Day	20% 18% 5% 10% 6% 4 4 3 4 6% 19%	1600
December	1st to 10th	Day	19% 22% 6% 12% 5% 5% 5% 4 5% 6% 12%	2600
	11th to 20th	Day	22% 19% 6% 11% 5% 4 4 3 5% 4 18%	2986
	21st to end	Day	23% 21% 6% 13% 7% 5% 4 3 3 4 11%	3960
January	1st to 10th	Night	18% 21% 6% 13% 7% 5% 4 2 3 4 16%	4569
	11th to 20th	Night	14% 20% 9% 17% 9% 6% 4 3 4 4 11%	4371
	21st to end	Night	24% 21% 6% 15% 7% 5% 3 3 3 3 10%	4546
February	1st to 10th	Night	17% 19% 5% 13% 7% 4 4 3 4 4 18%	2470
	11th to 20th	Night	15% 15% 6% 13% 7% 5% 6% 4 4 5% 19%	2403
	21st to end	Night	17% 16% 6% 13% 6% 5% 4 4 4 6% 19%	1974
March	1st to 10th	Night	21% 12% 4 9% 5% 5% 3 3 3 4 31%	3408
	11th to 20th	Night	19% 16% 4 8% 5% 4 4 3 5% 6% 26%	3479
	21st to end	Night	16% 10% 3 8% 4 4 3 3 5% 6% 38%	3817
April	1st to 10th	Night	20% 13% 4 8% 5% 4 3 3 4 4 30%	1905
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 4 5% 6% 35%	1875
	21st to end	Night	17% 10% 3 7% 4 5% 5% 4 5% 7% 34%	1721
May	1st to 10th	Night	22% 9% 3 8% 4 3 4 3 5% 6% 32%	2811
	11th to 20th	Night	14% 7% 3 8% 5% 6% 5% 4 7% 8% 33%	2495
	21st to end	Night	13% 5% 2 5% 4 4 4 4 6% 8% 44%	2738
June	1st to 10th	Night	12% 6% 2 7% 6% 6% 6% 5% 7% 8% 34%	1520
	11th to 20th	Night	11% 6% 2 6% 5% 5% 5% 4 6% 8% 41%	1520
	21st to end	Night	13% 7% 2 6% 4 5% 5% 4 6% 8% 40%	1520
July	1st to 10th	Night	9% 8% 2 7% 4 4 4 4 7% 9% 42%	2520
	11th to 20th	Night	11% 6% 2 6% 4 4 5% 3 6% 9% 45%	2520
	21st to end	Night	10% 5% 2 5% 3 4 5% 5% 6% 7% 48%	3006
August	1st to 10th	Night	11% 6% 2 7% 5% 5% 4 4 6% 9% 41%	2825
	11th to 20th	Night	14% 8% 3 7% 4 4 4 4 6% 7% 39%	2785
	21st to end	Night	9% 5% 2 5% 4 5% 5% 4 7% 10% 44%	3344
September	1st to 10th	Night	12% 7% 3 5% 4 4 4 3 5% 7% 45%	1900
	11th to 20th	Night	13% 5% 2 5% 4 3 3 3 5% 6% 50%	1957
	21st to end	Night	17% 8% 3 6% 4 4 3 4 6% 8% 36%	2161
October	1st to 10th	Night	17% 7% 3 7% 5% 3 5% 3 5% 7% 38%	2280
	11th to 20th	Night	21% 10% 3 9% 4 5% 3 3 5% 6% 30%	2280
	21st to end	Night	26% 12% 3 7% 5% 4 4 3 5% 5% 25%	2508
November	1st to 10th	Night	16% 11% 4 8% 5% 4 3 4 5% 5% 37%	2561
	11th to 20th	Night	16% 13% 4 9% 6% 6% 5% 4 6% 6% 27%	2800
	21st to end	Night	18% 16% 5% 9% 6% 4 5% 5% 5% 7% 20%	2800
December	1st to 10th	Night	17% 21% 8% 12% 7% 5% 5% 3 4 6% 12%	4580
	11th to 20th	Night	19% 22% 6% 10% 5% 5% 4 3 4 4 19%	5208
	21st to end	Night	24% 18% 6% 11% 7% 6% 4 3 4 5% 13%	6996

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	74% 8% 7% 7% 3	2598
	11th to 20th	Day	84% 4 5% 5% 2	2807
	21st to end	Day	80% 6% 9% 4 1	3133
February	1st to 10th	Day	74% 4 10% 10% 1	1710
	11th to 20th	Day	72% 7% 7% 11% 3	1672
	21st to end	Day	71% 5% 9% 10% 4	1477
March	1st to 10th	Day	59% 5% 10% 19% 6%	3434
	11th to 20th	Day	56% 9% 14% 13% 7% 1	3480
	21st to end	Day	53% 6% 12% 22% 7% 1	3815
April	1st to 10th	Day	57% 5% 9% 18% 9% 1	2275
	11th to 20th	Day	51% 4 10% 20% 13% 2	2259
	21st to end	Day	54% 5% 9% 19% 13% 2	2470
May	1st to 10th	Day	51% 5% 12% 19% 11% 2	4142
	11th to 20th	Day	51% 8% 13% 20% 7% 1	4402
	21st to end	Day	36% 6% 14% 25% 16% 3	4837
June	1st to 10th	Day	44% 6% 13% 20% 15% 2	2660
	11th to 20th	Day	41% 6% 15% 23% 14% 1	2660
	21st to end	Day	40% 7% 14% 23% 14% 1	2660
July	1st to 10th	Day	35% 7% 13% 28% 16% 2	4370
	11th to 20th	Day	36% 9% 15% 26% 13%	4365
	21st to end	Day	36% 9% 16% 24% 14% 1	4398
August	1st to 10th	Day	43% 8% 15% 22% 12% 1	4091
	11th to 20th	Day	43% 9% 16% 24% 7% 1	4083
	21st to end	Day	36% 6% 14% 32% 11% 1	4278
September	1st to 10th	Day	40% 7% 14% 27% 11% 1	2280
	11th to 20th	Day	37% 8% 13% 27% 14% 1	2219
	21st to end	Day	49% 6% 14% 21% 9% 1	2019
October	1st to 10th	Day	40% 8% 16% 23% 12%	3160
	11th to 20th	Day	48% 5% 16% 19% 13%	3140
	21st to end	Day	50% 6% 15% 21% 7%	3428
November	1st to 10th	Day	54% 7% 11% 18% 9% 1	1733
	11th to 20th	Day	58% 6% 14% 15% 7% 1	1600
	21st to end	Day	68% 5% 12% 11% 4	1600
December	1st to 10th	Day	73% 8% 12% 6% 1	2600
	11th to 20th	Day	68% 8% 8% 9% 7%	2986
	21st to end	Day	78% 6% 8% 6% 2	3960
January	1st to 10th	Night	71% 10% 9% 7% 3	4569
	11th to 20th	Night	77% 7% 9% 5% 2	4371
	21st to end	Night	79% 7% 6% 6% 2	4546
February	1st to 10th	Night	71% 5% 9% 12% 3	2470
	11th to 20th	Night	67% 6% 10% 12% 4	2405
	21st to end	Night	66% 5% 12% 13% 5%	1974
March	1st to 10th	Night	57% 5% 10% 21% 6%	3418
	11th to 20th	Night	58% 6% 14% 15% 6% 1	3480
	21st to end	Night	44% 7% 11% 24% 13% 1	3817
April	1st to 10th	Night	57% 5% 8% 19% 10% 1	1905
	11th to 20th	Night	49% 7% 9% 20% 13% 2	1875
	21st to end	Night	50% 6% 10% 19% 14% 2	1721
May	1st to 10th	Night	52% 5% 11% 18% 12% 2	2818
	11th to 20th	Night	47% 8% 17% 20% 8% 1	2496
	21st to end	Night	35% 7% 12% 24% 20% 2	2739
June	1st to 10th	Night	44% 8% 10% 21% 16% 1	1520
	11th to 20th	Night	40% 7% 12% 21% 19% 2	1520
	21st to end	Night	42% 7% 14% 21% 16% 1	1520
July	1st to 10th	Night	38% 6% 13% 23% 18% 2	2480
	11th to 20th	Night	36% 7% 14% 28% 14% 1	2472
	21st to end	Night	33% 8% 17% 24% 17% 2	2910
August	1st to 10th	Night	38% 6% 15% 27% 12% 1	2814
	11th to 20th	Night	42% 6% 16% 26% 9%	2812
	21st to end	Night	32% 8% 16% 31% 12% 1	3344
September	1st to 10th	Night	38% 7% 14% 27% 13% 1	1900
	11th to 20th	Night	34% 5% 12% 30% 17% 1	1957
	21st to end	Night	44% 7% 13% 22% 12% 1	2161
October	1st to 10th	Night	41% 8% 10% 24% 16% 1	3800
	11th to 20th	Night	49% 5% 14% 20% 12% 1	3779
	21st to end	Night	46% 6% 15% 25% 7% 1	4120
November	1st to 10th	Night	49% 5% 11% 22% 10% 2	2561
	11th to 20th	Night	57% 6% 13% 16% 8% 1	2800
	21st to end	Night	63% 8% 13% 13% 3	2800
December	1st to 10th	Night	73% 9% 11% 7% 1	4580
	11th to 20th	Night	70% 6% 7% 11% 6% 1	5208
	21st to end	Night	74% 6% 9% 8% 2	6996

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% 25% 25% 9% 4 1	200
	11th to 20th	Day	32% 32% 24% 9% 2 1	265
	21st to end	Day	31% 25% 29% 12% 2	300
February	1st to 10th	Day	36% 30% 26% 6% 1	270
	11th to 20th	Day	33% 34% 27% 4 1	270
	21st to end	Day	41% 26% 25% 8% 1	289
March	1st to 10th	Day	31% 22% 31% 12% 4	460
	11th to 20th	Day	32% 22% 32% 11% 2 1	460
	21st to end	Day	33% 21% 27% 14% 4 1	506
April	1st to 10th	Day	32% 20% 31% 13% 4 1	460
	11th to 20th	Day	35% 19% 23% 16% 6% 2	452
	21st to end	Day	30% 20% 31% 12% 6% 1	460
May	1st to 10th	Day	28% 15% 30% 17% 6% 3	463
	11th to 20th	Day	23% 13% 31% 22% 9% 3	487
	21st to end	Day	18% 14% 32% 22% 10% 3	529
June	1st to 10th	Day	21% 18% 36% 18% 6% 1	490
	11th to 20th	Day	18% 12% 34% 24% 10% 2	490
	21st to end	Day	21% 14% 36% 21% 7% 2	490
July	1st to 10th	Day	12% 9% 33% 27% 17% 4	485
	11th to 20th	Day	15% 10% 30% 28% 13% 4	484
	21st to end	Day	13% 10% 35% 28% 12% 3	532
August	1st to 10th	Day	14% 10% 27% 28% 15% 6%	486
	11th to 20th	Day	12% 8% 31% 27% 15% 6%	479
	21st to end	Day	15% 10% 28% 26% 12% 8%	539
September	1st to 10th	Day	16% 12% 27% 24% 14% 7%	490
	11th to 20th	Day	13% 7% 24% 25% 20% 11%	490
	21st to end	Day	19% 17% 28% 19% 12% 5%	490
October	1st to 10th	Day	26% 14% 26% 20% 11% 4	490
	11th to 20th	Day	30% 19% 27% 17% 6% 1	490
	21st to end	Day	37% 17% 28% 12% 5%	539
November	1st to 10th	Day	32% 18% 30% 13% 6% 1	342
	11th to 20th	Day	33% 24% 32% 8% 2 2	200
	21st to end	Day	39% 22% 29% 10% 1	200
December	1st to 10th	Day	39% 22% 27% 9% 3 1	200
	11th to 20th	Day	41% 23% 25% 10% 1	200
	21st to end	Day	40% 26% 23% 7% 3 1	220
January	1st to 10th	Night	33% 25% 27% 12% 4	800
	11th to 20th	Night	33% 25% 26% 13% 2	800
	21st to end	Night	27% 22% 30% 17% 4	841
February	1st to 10th	Night	32% 27% 26% 13% 1	760
	11th to 20th	Night	27% 28% 28% 14% 2	743
	21st to end	Night	30% 26% 29% 14% 2	628
March	1st to 10th	Night	26% 20% 33% 17% 4	760
	11th to 20th	Night	29% 20% 29% 19% 4 1	760
	21st to end	Night	25% 15% 34% 19% 7% 1	836
April	1st to 10th	Night	28% 19% 31% 20% 2	760
	11th to 20th	Night	26% 16% 31% 19% 6% 1	751
	21st to end	Night	23% 11% 33% 24% 8%	581
May	1st to 10th	Night	22% 10% 28% 26% 11% 2	561
	11th to 20th	Night	15% 10% 34% 33% 8%	374
	21st to end	Night	14% 10% 28% 35% 13% 1	411
June	1st to 10th	Night	15% 8% 37% 32% 8%	380
	11th to 20th	Night	14% 9% 29% 38% 10%	380
	21st to end	Night	15% 8% 35% 35% 6% 1	380
July	1st to 10th	Night	11% 6% 28% 39% 15% 1	370
	11th to 20th	Night	11% 6% 31% 36% 14% 2	368
	21st to end	Night	12% 4 30% 36% 16% 2	569
August	1st to 10th	Night	11% 4 24% 41% 19% 2	567
	11th to 20th	Night	12% 5% 23% 35% 24% 2	564
	21st to end	Night	13% 4 27% 33% 20% 2	756
September	1st to 10th	Night	17% 8% 25% 33% 15% 2	760
	11th to 20th	Night	14% 6% 22% 30% 23% 4	760
	21st to end	Night	20% 11% 25% 26% 14% 4	760
October	1st to 10th	Night	19% 11% 29% 25% 14% 2	760
	11th to 20th	Night	30% 16% 26% 21% 6% 1	760
	21st to end	Night	34% 15% 28% 19% 3	836
November	1st to 10th	Night	26% 16% 28% 22% 7% 1	780
	11th to 20th	Night	28% 17% 29% 17% 7% 1	800
	21st to end	Night	31% 22% 27% 16% 5%	800
December	1st to 10th	Night	37% 23% 23% 13% 4	800
	11th to 20th	Night	34% 24% 27% 13% 3	800
	21st to end	Night	38% 21% 26% 13% 2	880

Page generated at 2025-01-19 03:06:49. Version ac07

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