Dreamy Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dreamy Skies Observatory clear sky chart from 2005-11-06 to 2026-08-15.

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	13% 11% 4 10% 5% 5% 5% 4 5% 7% 32%	143134
	Night	13% 12% 5% 10% 6% 5% 4 3 5% 6% 31%	138973
Transparency	Day	49% 7% 11% 20% 12% 1	146640
	Night	51% 7% 12% 19% 10% 1	143541
Seeing	Day	21% 17% 33% 19% 7% 2	17940
	Night	20% 15% 32% 24% 8% 1	27439

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	14% 17% 7% 21% 8% 4 3 2 4 5% 15%	4691
	11th to 20th	Day	10% 18% 8% 21% 10% 8% 6% 3 4 3 10%	4679
	21st to end	Day	11% 14% 8% 15% 8% 6% 6% 4 5% 6% 17%	5173
February	1st to 10th	Day	10% 16% 6% 15% 11% 5% 6% 4 4 5% 18%	1890
	11th to 20th	Day	12% 14% 6% 15% 9% 6% 5% 3 4 4 22%	1977
	21st to end	Day	10% 19% 6% 13% 7% 4 5% 4 4 4 22%	1730
March	1st to 10th	Day	12% 11% 4 12% 5% 4 4 4 5% 6% 33%	4578
	11th to 20th	Day	12% 13% 6% 11% 5% 5% 5% 4 7% 7% 26%	5086
	21st to end	Day	20% 12% 7% 11% 5% 4 4 3 5% 5% 24%	5599
April	1st to 10th	Day	17% 18% 4 8% 4 4 5% 3 5% 4 28%	2520
	11th to 20th	Day	18% 13% 3 7% 4 3 4 3 4 5% 35%	2660
	21st to end	Day	15% 12% 3 9% 5% 4 4 3 5% 6% 32%	2730
May	1st to 10th	Day	15% 9% 3 8% 6% 5% 5% 4 6% 8% 33%	7642
	11th to 20th	Day	14% 8% 3 7% 5% 4 4 4 5% 6% 40%	7626
	21st to end	Day	14% 7% 2 6% 4 4 4 3 5% 6% 44%	9186
June	1st to 10th	Day	12% 7% 2 6% 5% 5% 4 4 6% 8% 41%	3150
	11th to 20th	Day	13% 7% 3 7% 4 5% 5% 5% 6% 8% 38%	3150
	21st to end	Day	13% 8% 3 6% 5% 5% 5% 5% 6% 8% 37%	3150
July	1st to 10th	Day	12% 6% 2 7% 5% 4 5% 4 6% 9% 39%	8401
	11th to 20th	Day	8% 5% 2 6% 5% 5% 6% 4 7% 9% 44%	8280
	21st to end	Day	8% 6% 2 7% 4 4 5% 4 6% 9% 44%	8992
August	1st to 10th	Day	9% 5% 2 7% 5% 5% 6% 6% 8% 10% 37%	4366
	11th to 20th	Day	13% 6% 2 7% 5% 5% 4 4 6% 6% 41%	4226
	21st to end	Day	12% 6% 3 8% 5% 5% 5% 3 6% 7% 40%	4618
September	1st to 10th	Day	11% 7% 3 6% 5% 4 5% 4 7% 8% 40%	2315
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 3 5% 7% 47%	2200
	21st to end	Day	15% 10% 3 6% 4 4 5% 3 6% 9% 35%	2200
October	1st to 10th	Day	17% 8% 3 8% 4 4 4 3 5% 7% 38%	2159
	11th to 20th	Day	21% 14% 3 8% 6% 5% 5% 4 4 5% 26%	1962
	21st to end	Day	18% 17% 4 10% 6% 6% 5% 4 4 5% 22%	1980
November	1st to 10th	Day	14% 16% 4 8% 5% 4 4 3 6% 8% 27%	1852
	11th to 20th	Day	12% 18% 6% 12% 5% 6% 5% 4 5% 6% 21%	1884
	21st to end	Day	18% 18% 6% 13% 6% 4 4 3 4 5% 19%	1680
December	1st to 10th	Day	11% 25% 8% 18% 7% 5% 3 4 4 4 11%	2435
	11th to 20th	Day	14% 21% 9% 14% 7% 6% 4 3 4 4 14%	2691
	21st to end	Day	23% 22% 9% 18% 5% 3 3 2 2 3 9%	3676
January	1st to 10th	Night	12% 14% 7% 24% 10% 6% 4 3 3 4 14%	8233
	11th to 20th	Night	10% 18% 9% 17% 12% 8% 5% 4 4 4 9%	8236
	21st to end	Night	8% 14% 8% 16% 9% 7% 6% 4 5% 5% 17%	9025
February	1st to 10th	Night	9% 16% 6% 14% 9% 7% 6% 4 5% 6% 19%	2730
	11th to 20th	Night	11% 15% 5% 14% 7% 6% 4 3 5% 6% 23%	2527
	21st to end	Night	13% 16% 6% 12% 7% 5% 4 4 5% 4 25%	2076
March	1st to 10th	Night	14% 10% 4 9% 6% 4 4 3 5% 6% 36%	5482
	11th to 20th	Night	11% 12% 5% 9% 4 5% 5% 4 6% 7% 33%	5090
	21st to end	Night	18% 13% 5% 10% 5% 3 4 3 4 4 31%	5588
April	1st to 10th	Night	17% 13% 3 8% 5% 4 4 4 5% 7% 31%	2116
	11th to 20th	Night	18% 12% 3 6% 4 3 4 3 5% 6% 34%	1908
	21st to end	Night	16% 10% 4 8% 4 5% 5% 4 5% 5% 36%	1890
May	1st to 10th	Night	11% 7% 3 7% 5% 4 5% 4 5% 8% 40%	5257
	11th to 20th	Night	13% 10% 3 6% 4 4 4 3 6% 7% 40%	5234
	21st to end	Night	16% 6% 2 5% 4 4 3 3 5% 7% 46%	5012
June	1st to 10th	Night	13% 5% 2 5% 5% 4 4 4 6% 7% 45%	1470
	11th to 20th	Night	9% 5% 3 6% 5% 4 5% 4 7% 8% 44%	1470
	21st to end	Night	11% 6% 2 7% 6% 4 5% 4 5% 6% 45%	1470
July	1st to 10th	Night	10% 5% 2 6% 4 4 5% 4 7% 11% 41%	4582
	11th to 20th	Night	7% 5% 2 5% 3 4 4 4 7% 8% 51%	4710
	21st to end	Night	10% 5% 2 5% 3 3 4 4 6% 8% 50%	5118
August	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 8% 46%	3000
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 5% 7% 49%	2911
	21st to end	Night	10% 6% 2 6% 4 4 4 4 6% 7% 48%	3278
September	1st to 10th	Night	10% 7% 3 5% 3 4 3 3 5% 7% 49%	2065
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 5% 7% 50%	2200
	21st to end	Night	16% 7% 2 6% 5% 4 4 3 5% 7% 40%	2200
October	1st to 10th	Night	15% 9% 2 7% 4 3 4 3 4 7% 43%	2240
	11th to 20th	Night	17% 14% 4 8% 5% 4 4 3 4 5% 33%	2435
	21st to end	Night	21% 13% 3 8% 5% 4 4 3 5% 6% 29%	2860
November	1st to 10th	Night	12% 13% 4 8% 5% 4 5% 4 6% 8% 31%	2666
	11th to 20th	Night	12% 17% 5% 11% 7% 5% 5% 4 4 6% 25%	2734
	21st to end	Night	17% 19% 6% 10% 5% 5% 4 4 5% 6% 21%	2940
December	1st to 10th	Night	12% 16% 6% 15% 7% 6% 5% 4 5% 6% 17%	4958
	11th to 20th	Night	10% 23% 8% 15% 7% 5% 4 3 4 5% 17%	5736
	21st to end	Night	21% 24% 9% 13% 5% 4 3 3 3 3 11%	7526

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	72% 5% 10% 8% 3 1	4692
	11th to 20th	Day	76% 6% 5% 8% 4	4710
	21st to end	Day	66% 6% 11% 10% 6%	5173
February	1st to 10th	Day	65% 7% 9% 14% 3	1890
	11th to 20th	Day	64% 7% 9% 13% 7% 1	1986
	21st to end	Day	62% 6% 11% 15% 6% 1	1730
March	1st to 10th	Day	50% 6% 15% 16% 10% 3	4580
	11th to 20th	Day	52% 7% 15% 17% 7% 2	5086
	21st to end	Day	60% 6% 9% 16% 9%	5599
April	1st to 10th	Day	57% 5% 11% 16% 9% 1	2520
	11th to 20th	Day	50% 5% 10% 18% 15% 1	2660
	21st to end	Day	51% 6% 13% 15% 13% 3	2730
May	1st to 10th	Day	46% 8% 10% 20% 14% 2	7651
	11th to 20th	Day	43% 7% 9% 23% 16% 2	7630
	21st to end	Day	39% 6% 9% 21% 21% 5%	9186
June	1st to 10th	Day	39% 7% 13% 24% 15% 2	3150
	11th to 20th	Day	41% 8% 12% 21% 16% 2	3150
	21st to end	Day	42% 9% 12% 23% 13% 1	3150
July	1st to 10th	Day	39% 7% 14% 23% 15% 2	8333
	11th to 20th	Day	33% 7% 12% 32% 16% 1	8205
	21st to end	Day	33% 8% 13% 28% 17% 1	8794
August	1st to 10th	Day	38% 9% 12% 26% 14% 1	4352
	11th to 20th	Day	41% 8% 12% 25% 13% 1	4265
	21st to end	Day	41% 7% 13% 26% 11% 1	4617
September	1st to 10th	Day	40% 9% 13% 23% 14% 1	2315
	11th to 20th	Day	35% 7% 15% 28% 15%	2200
	21st to end	Day	45% 7% 14% 22% 11%	2200
October	1st to 10th	Day	34% 5% 9% 33% 18% 1	3510
	11th to 20th	Day	52% 5% 8% 20% 14%	3178
	21st to end	Day	58% 7% 11% 18% 6%	3180
November	1st to 10th	Day	54% 7% 12% 19% 8%	1852
	11th to 20th	Day	61% 7% 16% 11% 5%	1884
	21st to end	Day	67% 7% 12% 10% 3 1	1680
December	1st to 10th	Day	75% 8% 8% 8% 1	2435
	11th to 20th	Day	72% 6% 8% 11% 2	2691
	21st to end	Day	82% 4 4 5% 5%	3676
January	1st to 10th	Night	71% 8% 8% 8% 3 1	8233
	11th to 20th	Night	74% 7% 8% 7% 3	8280
	21st to end	Night	65% 7% 8% 13% 7%	9025
February	1st to 10th	Night	62% 8% 10% 13% 6% 1	2730
	11th to 20th	Night	59% 7% 12% 17% 5% 1	2529
	21st to end	Night	60% 6% 12% 16% 6%	2076
March	1st to 10th	Night	48% 5% 16% 19% 11% 1	5493
	11th to 20th	Night	45% 8% 20% 20% 7% 1	5091
	21st to end	Night	53% 7% 11% 17% 11% 1	5588
April	1st to 10th	Night	52% 6% 10% 18% 12% 2	2116
	11th to 20th	Night	48% 6% 9% 20% 15% 2	1908
	21st to end	Night	49% 7% 10% 17% 14% 3	1890
May	1st to 10th	Night	40% 7% 12% 20% 19% 3	5264
	11th to 20th	Night	41% 7% 11% 25% 16% 1	5235
	21st to end	Night	38% 5% 10% 23% 20% 4	5013
June	1st to 10th	Night	37% 6% 12% 25% 19% 1	1470
	11th to 20th	Night	36% 7% 14% 24% 17% 2	1470
	21st to end	Night	38% 7% 13% 25% 14% 3	1470
July	1st to 10th	Night	36% 8% 17% 21% 14% 4	4542
	11th to 20th	Night	29% 6% 12% 36% 15% 1	4662
	21st to end	Night	32% 8% 14% 31% 15%	5002
August	1st to 10th	Night	34% 7% 14% 30% 14% 1	2990
	11th to 20th	Night	32% 8% 17% 30% 13% 1	2938
	21st to end	Night	32% 8% 17% 28% 15% 1	3278
September	1st to 10th	Night	33% 8% 14% 27% 17% 1	2065
	11th to 20th	Night	31% 7% 16% 32% 14%	2200
	21st to end	Night	42% 7% 15% 25% 10% 1	2200
October	1st to 10th	Night	31% 6% 12% 33% 17% 1	3656
	11th to 20th	Night	46% 6% 9% 24% 15%	3958
	21st to end	Night	48% 6% 13% 25% 7%	4610
November	1st to 10th	Night	49% 8% 13% 21% 8% 1	2666
	11th to 20th	Night	59% 7% 14% 14% 7% 1	2734
	21st to end	Night	62% 8% 15% 12% 3 1	2940
December	1st to 10th	Night	64% 9% 13% 12% 2	4958
	11th to 20th	Night	66% 7% 10% 11% 5%	5735
	21st to end	Night	76% 7% 6% 5% 6%	7526

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	29% 20% 36% 12% 2	330
	11th to 20th	Day	25% 27% 36% 9% 2	330
	21st to end	Day	29% 15% 41% 11% 3 1	363
February	1st to 10th	Day	25% 31% 33% 7% 3 1	330
	11th to 20th	Day	27% 31% 33% 7% 1	330
	21st to end	Day	34% 26% 33% 5% 1	273
March	1st to 10th	Day	28% 30% 33% 8% 1	330
	11th to 20th	Day	30% 19% 34% 14% 3	536
	21st to end	Day	33% 19% 28% 16% 4	594
April	1st to 10th	Day	31% 21% 28% 16% 4	540
	11th to 20th	Day	33% 19% 28% 11% 6% 2	532
	21st to end	Day	27% 18% 31% 18% 6% 2	540
May	1st to 10th	Day	25% 19% 34% 15% 6% 2	543
	11th to 20th	Day	20% 18% 31% 21% 8% 2	567
	21st to end	Day	17% 16% 35% 23% 7% 2	825
June	1st to 10th	Day	16% 19% 37% 20% 7% 1	780
	11th to 20th	Day	18% 16% 36% 22% 5% 2	780
	21st to end	Day	15% 14% 40% 24% 5% 2	780
July	1st to 10th	Day	11% 12% 36% 29% 10% 3	771
	11th to 20th	Day	11% 14% 35% 26% 10% 4	768
	21st to end	Day	11% 11% 38% 27% 9% 4	849
August	1st to 10th	Day	10% 11% 28% 27% 15% 8%	568
	11th to 20th	Day	11% 10% 25% 31% 16% 8%	535
	21st to end	Day	16% 10% 32% 24% 14% 4	583
September	1st to 10th	Day	15% 13% 29% 23% 13% 7%	530
	11th to 20th	Day	12% 9% 24% 30% 15% 9%	530
	21st to end	Day	19% 12% 26% 28% 11% 4	530
October	1st to 10th	Day	24% 18% 27% 17% 13% 2	530
	11th to 20th	Day	30% 17% 33% 17% 3	492
	21st to end	Day	29% 26% 31% 11% 2	363
November	1st to 10th	Day	31% 18% 33% 14% 3 1	330
	11th to 20th	Day	29% 23% 33% 12% 2 1	326
	21st to end	Day	27% 25% 35% 11% 1	220
December	1st to 10th	Day	31% 21% 31% 13% 3 1	220
	11th to 20th	Day	30% 27% 34% 7% 2	220
	21st to end	Day	38% 26% 26% 8% 2	272
January	1st to 10th	Night	23% 22% 34% 17% 4	1050
	11th to 20th	Night	23% 22% 33% 18% 4	1050
	21st to end	Night	20% 17% 38% 20% 5%	1148
February	1st to 10th	Night	18% 23% 38% 18% 3	840
	11th to 20th	Night	25% 23% 30% 18% 4	823
	21st to end	Night	26% 20% 35% 16% 3	692
March	1st to 10th	Night	19% 20% 37% 19% 5%	840
	11th to 20th	Night	24% 20% 32% 20% 4	840
	21st to end	Night	24% 16% 35% 21% 4 1	924
April	1st to 10th	Night	24% 19% 33% 18% 5%	646
	11th to 20th	Night	28% 15% 28% 22% 6% 1	623
	21st to end	Night	21% 13% 33% 27% 5% 1	630
May	1st to 10th	Night	13% 13% 38% 27% 7% 1	630
	11th to 20th	Night	19% 12% 29% 30% 9%	621
	21st to end	Night	16% 8% 34% 30% 12%	625
June	1st to 10th	Night	15% 9% 34% 35% 7% 1	420
	11th to 20th	Night	10% 10% 37% 32% 10%	420
	21st to end	Night	13% 8% 31% 34% 13% 1	420
July	1st to 10th	Night	8% 6% 25% 44% 16% 1	565
	11th to 20th	Night	8% 5% 29% 39% 17% 3	612
	21st to end	Night	10% 6% 24% 42% 17% 1	690
August	1st to 10th	Night	9% 4 26% 37% 23% 1	627
	11th to 20th	Night	11% 6% 20% 35% 25% 2	606
	21st to end	Night	14% 5% 25% 38% 17% 1	660
September	1st to 10th	Night	13% 7% 27% 29% 20% 4	665
	11th to 20th	Night	13% 8% 25% 30% 20% 4	800
	21st to end	Night	20% 9% 24% 28% 16% 3	800
October	1st to 10th	Night	20% 11% 29% 27% 12% 1	800
	11th to 20th	Night	26% 15% 32% 20% 6%	800
	21st to end	Night	28% 15% 30% 21% 4	880
November	1st to 10th	Night	21% 18% 35% 18% 6% 1	820
	11th to 20th	Night	22% 23% 32% 18% 4	840
	21st to end	Night	28% 18% 37% 15% 3	840
December	1st to 10th	Night	24% 22% 35% 16% 4	987
	11th to 20th	Night	25% 22% 35% 14% 4	1050
	21st to end	Night	31% 19% 32% 15% 2	1155

Page generated at 2026-08-12 03:37:17. Version ac07

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