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 2024-02-25.

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	14% 11% 5% 8% 7% 4 5% 5% 5% 7% 30%	78078
	Night	14% 12% 5% 9% 7% 4 5% 5% 5% 6% 29%	81229
Transparency	Day	52% 7% 12% 17% 10% 1	77784
	Night	53% 8% 12% 17% 9% 1	81058
Seeing	Day	21% 17% 33% 20% 7% 3	14497
	Night	20% 15% 32% 24% 8% 1	24276

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% 18% 9% 13% 6% 4 4 3 5% 6% 18%	2527
	11th to 20th	Day	13% 17% 7% 14% 12% 8% 7% 4 5% 5% 9%	2530
	21st to end	Day	19% 18% 11% 12% 8% 3 5% 4 4 6% 12%	2787
February	1st to 10th	Day	11% 15% 7% 14% 12% 4 5% 5% 5% 5% 17%	1710
	11th to 20th	Day	12% 13% 6% 14% 10% 5% 5% 4 4 4 23%	1783
	21st to end	Day	10% 19% 7% 11% 8% 4 4 5% 4 5% 22%	1520
March	1st to 10th	Day	12% 12% 5% 10% 8% 4 5% 5% 5% 6% 28%	1798
	11th to 20th	Day	13% 12% 5% 8% 7% 4 5% 4 4 6% 33%	1976
	21st to end	Day	17% 13% 4 7% 6% 3 4 4 6% 6% 31%	2178
April	1st to 10th	Day	18% 16% 5% 7% 5% 2 5% 4 5% 5% 28%	2160
	11th to 20th	Day	19% 13% 4 7% 4 2 4 4 4 5% 35%	2276
	21st to end	Day	16% 12% 4 8% 6% 3 5% 4 5% 7% 32%	2340
May	1st to 10th	Day	17% 8% 4 6% 7% 3 5% 5% 6% 7% 32%	2340
	11th to 20th	Day	17% 7% 3 7% 5% 4 4 5% 5% 6% 38%	2301
	21st to end	Day	11% 6% 3 5% 6% 3 6% 5% 6% 7% 42%	2752
June	1st to 10th	Day	13% 6% 2 5% 6% 4 4 5% 5% 9% 40%	2700
	11th to 20th	Day	13% 6% 3 6% 5% 3 5% 5% 6% 8% 39%	2700
	21st to end	Day	13% 7% 3 6% 6% 3 5% 5% 6% 8% 38%	2700
July	1st to 10th	Day	8% 5% 2 5% 5% 3 5% 6% 7% 8% 46%	2558
	11th to 20th	Day	10% 6% 3 5% 6% 3 6% 5% 7% 8% 41%	2520
	21st to end	Day	9% 6% 3 7% 6% 3 6% 6% 7% 8% 40%	2743
August	1st to 10th	Day	9% 5% 2 7% 7% 5% 6% 7% 7% 10% 35%	2329
	11th to 20th	Day	10% 6% 3 6% 6% 4 5% 5% 6% 7% 42%	2303
	21st to end	Day	12% 6% 3 6% 5% 3 4 4 6% 9% 40%	2547
September	1st to 10th	Day	12% 7% 4 5% 6% 3 5% 5% 6% 8% 40%	2084
	11th to 20th	Day	13% 6% 2 5% 5% 3 5% 4 5% 7% 45%	1980
	21st to end	Day	15% 9% 3 6% 5% 3 5% 5% 6% 9% 33%	1980
October	1st to 10th	Day	19% 9% 4 8% 5% 2 4 4 5% 7% 35%	1944
	11th to 20th	Day	23% 14% 4 6% 8% 4 4 5% 4 5% 24%	1766
	21st to end	Day	20% 17% 4 9% 6% 4 5% 5% 4 5% 21%	1782
November	1st to 10th	Day	14% 15% 5% 7% 6% 3 4 4 6% 9% 27%	1672
	11th to 20th	Day	13% 16% 7% 11% 7% 4 5% 5% 5% 5% 21%	1706
	21st to end	Day	18% 17% 6% 11% 8% 3 5% 4 3 5% 20%	1520
December	1st to 10th	Day	13% 20% 8% 13% 8% 4 4 4 5% 5% 16%	1386
	11th to 20th	Day	16% 18% 7% 12% 8% 4 5% 4 4 6% 16%	1671
	21st to end	Day	23% 23% 11% 16% 7% 3 3 3 2 3 6%	2509
January	1st to 10th	Night	14% 16% 8% 15% 8% 5% 5% 4 4 5% 18%	4428
	11th to 20th	Night	12% 15% 8% 15% 13% 6% 6% 5% 4 4 11%	4440
	21st to end	Night	15% 17% 10% 14% 9% 4 5% 5% 4 5% 12%	4879
February	1st to 10th	Night	10% 15% 6% 12% 10% 6% 7% 6% 5% 6% 18%	2470
	11th to 20th	Night	11% 14% 6% 13% 8% 5% 5% 4 5% 6% 23%	2281
	21st to end	Night	14% 16% 5% 11% 8% 4 5% 4 4 4 25%	1831
March	1st to 10th	Night	11% 11% 5% 8% 6% 3 4 4 5% 6% 36%	2149
	11th to 20th	Night	14% 11% 4 7% 5% 4 4 5% 4 6% 36%	1980
	21st to end	Night	17% 10% 3 8% 4 3 4 4 5% 6% 35%	2178
April	1st to 10th	Night	18% 12% 4 6% 6% 3 3 5% 5% 7% 30%	1814
	11th to 20th	Night	18% 10% 3 5% 5% 2 4 4 6% 7% 35%	1633
	21st to end	Night	16% 9% 4 7% 6% 3 5% 5% 5% 5% 36%	1620
May	1st to 10th	Night	13% 8% 4 6% 6% 4 5% 6% 5% 8% 35%	1620
	11th to 20th	Night	15% 9% 3 6% 5% 3 5% 5% 6% 8% 37%	1592
	21st to end	Night	12% 4 2 4 5% 3 4 4 6% 9% 46%	1515
June	1st to 10th	Night	14% 5% 2 4 5% 3 4 5% 7% 7% 45%	1260
	11th to 20th	Night	9% 5% 3 5% 5% 3 5% 5% 7% 9% 46%	1260
	21st to end	Night	10% 5% 2 6% 6% 3 5% 5% 5% 6% 47%	1260
July	1st to 10th	Night	6% 3 2 4 4 2 4 5% 6% 12% 53%	1396
	11th to 20th	Night	5% 4 3 6% 5% 3 5% 5% 6% 8% 49%	1440
	21st to end	Night	8% 5% 3 5% 4 2 4 5% 7% 7% 51%	1575
August	1st to 10th	Night	7% 4 2 4 4 3 5% 6% 6% 8% 50%	1606
	11th to 20th	Night	9% 4 2 4 4 3 3 4 5% 8% 54%	1598
	21st to end	Night	12% 5% 2 4 5% 3 4 5% 6% 8% 46%	1807
September	1st to 10th	Night	11% 7% 3 5% 4 3 4 4 6% 7% 48%	1858
	11th to 20th	Night	13% 4 3 5% 4 3 4 4 5% 7% 49%	1980
	21st to end	Night	17% 6% 3 5% 5% 3 4 4 4 8% 40%	1980
October	1st to 10th	Night	16% 9% 2 6% 5% 2 4 4 4 6% 40%	2016
	11th to 20th	Night	18% 13% 4 7% 6% 3 4 4 4 5% 32%	2191
	21st to end	Night	23% 13% 4 7% 6% 3 4 4 4 5% 27%	2574
November	1st to 10th	Night	12% 12% 5% 7% 6% 3 5% 5% 6% 8% 32%	2406
	11th to 20th	Night	13% 15% 6% 10% 8% 4 6% 5% 4 6% 24%	2473
	21st to end	Night	18% 16% 6% 8% 6% 4 4 5% 5% 6% 23%	2660
December	1st to 10th	Night	14% 15% 8% 12% 8% 5% 5% 5% 5% 6% 18%	2793
	11th to 20th	Night	13% 17% 6% 14% 9% 4 6% 5% 5% 6% 15%	3526
	21st to end	Night	22% 26% 9% 12% 7% 3 4 3 3 3 9%	5140

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	67% 7% 13% 9% 3	2528
	11th to 20th	Day	76% 9% 8% 6% 2	2530
	21st to end	Day	74% 6% 12% 5% 2	2787
February	1st to 10th	Day	66% 7% 9% 14% 3	1710
	11th to 20th	Day	63% 7% 9% 13% 7% 1	1792
	21st to end	Day	62% 6% 11% 14% 6% 1	1520
March	1st to 10th	Day	56% 6% 12% 16% 8% 2	1800
	11th to 20th	Day	53% 6% 11% 19% 8% 3	1976
	21st to end	Day	53% 6% 11% 19% 11% 1	2178
April	1st to 10th	Day	57% 5% 11% 16% 9% 1	2160
	11th to 20th	Day	50% 6% 11% 17% 15% 1	2276
	21st to end	Day	52% 6% 13% 13% 13% 3	2340
May	1st to 10th	Day	49% 8% 11% 19% 11% 2	2340
	11th to 20th	Day	45% 7% 11% 21% 14% 2	2305
	21st to end	Day	39% 9% 14% 22% 15% 2	2752
June	1st to 10th	Day	40% 7% 14% 23% 15% 2	2700
	11th to 20th	Day	40% 8% 12% 21% 17% 2	2700
	21st to end	Day	42% 8% 13% 23% 13% 1	2700
July	1st to 10th	Day	33% 8% 14% 24% 18% 2	2489
	11th to 20th	Day	38% 7% 15% 23% 15% 2	2445
	21st to end	Day	38% 9% 14% 21% 16% 2	2591
August	1st to 10th	Day	41% 10% 14% 23% 11% 1	2315
	11th to 20th	Day	39% 9% 13% 24% 13% 2	2303
	21st to end	Day	40% 8% 14% 23% 14% 1	2547
September	1st to 10th	Day	41% 9% 13% 21% 14% 2	2084
	11th to 20th	Day	37% 7% 16% 28% 12% 1	1980
	21st to end	Day	47% 7% 15% 22% 9%	1980
October	1st to 10th	Day	49% 7% 10% 23% 11% 1	1944
	11th to 20th	Day	61% 7% 10% 16% 5%	1766
	21st to end	Day	63% 7% 12% 11% 6%	1782
November	1st to 10th	Day	53% 7% 13% 18% 8%	1672
	11th to 20th	Day	62% 7% 16% 10% 5%	1706
	21st to end	Day	66% 7% 13% 10% 3 1	1520
December	1st to 10th	Day	69% 8% 10% 10% 2	1386
	11th to 20th	Day	67% 8% 11% 12% 2	1671
	21st to end	Day	84% 5% 5% 4 2	2509
January	1st to 10th	Night	65% 10% 9% 12% 4	4428
	11th to 20th	Night	73% 8% 9% 8% 2	4440
	21st to end	Night	73% 8% 9% 8% 2	4879
February	1st to 10th	Night	62% 9% 10% 13% 6% 1	2470
	11th to 20th	Night	59% 7% 12% 16% 5% 1	2283
	21st to end	Night	61% 6% 11% 14% 7%	1831
March	1st to 10th	Night	48% 5% 13% 22% 10% 1	2160
	11th to 20th	Night	47% 7% 12% 21% 12% 2	1981
	21st to end	Night	49% 6% 12% 19% 12% 2	2178
April	1st to 10th	Night	51% 7% 11% 18% 12% 2	1814
	11th to 20th	Night	46% 6% 10% 21% 14% 2	1633
	21st to end	Night	48% 7% 10% 17% 14% 3	1620
May	1st to 10th	Night	45% 8% 14% 19% 12% 3	1620
	11th to 20th	Night	43% 8% 10% 23% 13% 3	1593
	21st to end	Night	34% 7% 16% 24% 15% 3	1516
June	1st to 10th	Night	37% 6% 13% 26% 17% 1	1260
	11th to 20th	Night	34% 8% 15% 24% 17% 2	1260
	21st to end	Night	36% 7% 13% 26% 15% 3	1260
July	1st to 10th	Night	23% 7% 18% 31% 19% 2	1356
	11th to 20th	Night	31% 7% 15% 29% 17% 1	1392
	21st to end	Night	30% 10% 16% 27% 17% 1	1487
August	1st to 10th	Night	30% 8% 18% 29% 14% 1	1596
	11th to 20th	Night	28% 8% 18% 30% 15% 1	1598
	21st to end	Night	33% 8% 17% 25% 14% 2	1807
September	1st to 10th	Night	34% 8% 13% 26% 17% 2	1858
	11th to 20th	Night	33% 7% 16% 33% 11%	1980
	21st to end	Night	43% 8% 16% 26% 8%	1980
October	1st to 10th	Night	42% 8% 13% 23% 12% 1	2016
	11th to 20th	Night	54% 7% 12% 20% 6% 1	2191
	21st to end	Night	57% 7% 12% 16% 7%	2574
November	1st to 10th	Night	48% 8% 14% 21% 8% 1	2406
	11th to 20th	Night	60% 7% 14% 13% 6%	2473
	21st to end	Night	61% 8% 16% 12% 3 1	2660
December	1st to 10th	Night	65% 8% 11% 13% 3	2793
	11th to 20th	Night	65% 9% 13% 9% 3	3525
	21st to end	Night	78% 7% 7% 5% 3	5140

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	27% 20% 37% 13% 3	270
	11th to 20th	Day	24% 25% 37% 11% 3	270
	21st to end	Day	30% 13% 41% 12% 3 1	297
February	1st to 10th	Day	24% 31% 34% 7% 3 1	270
	11th to 20th	Day	26% 33% 33% 7% 1	270
	21st to end	Day	34% 26% 33% 7% 1	210
March	1st to 10th	Day	28% 30% 32% 9% 1	240
	11th to 20th	Day	25% 18% 37% 16% 4	416
	21st to end	Day	30% 18% 28% 18% 5%	462
April	1st to 10th	Day	28% 21% 28% 18% 5%	420
	11th to 20th	Day	32% 17% 30% 12% 8% 2	412
	21st to end	Day	27% 18% 30% 17% 6% 2	420
May	1st to 10th	Day	25% 19% 32% 15% 6% 3	423
	11th to 20th	Day	20% 17% 32% 21% 8% 3	447
	21st to end	Day	15% 14% 36% 25% 8% 2	662
June	1st to 10th	Day	16% 19% 35% 21% 8% 1	630
	11th to 20th	Day	17% 13% 36% 25% 6% 3	630
	21st to end	Day	15% 13% 38% 26% 5% 2	630
July	1st to 10th	Day	10% 11% 34% 30% 11% 3	621
	11th to 20th	Day	11% 14% 33% 28% 10% 4	618
	21st to end	Day	11% 12% 37% 26% 9% 4	684
August	1st to 10th	Day	10% 11% 29% 25% 15% 9%	448
	11th to 20th	Day	10% 10% 23% 31% 17% 9%	439
	21st to end	Day	17% 9% 33% 23% 15% 3	495
September	1st to 10th	Day	15% 12% 31% 23% 13% 7%	450
	11th to 20th	Day	14% 10% 26% 30% 13% 7%	450
	21st to end	Day	21% 12% 24% 27% 11% 5%	450
October	1st to 10th	Day	26% 17% 27% 16% 13% 2	450
	11th to 20th	Day	33% 17% 31% 15% 3	416
	21st to end	Day	33% 25% 30% 10% 2	297
November	1st to 10th	Day	29% 16% 36% 15% 3 1	270
	11th to 20th	Day	25% 26% 34% 11% 3 1	268
	21st to end	Day	25% 24% 39% 10% 2 1	180
December	1st to 10th	Day	28% 22% 33% 12% 3 2	180
	11th to 20th	Day	28% 27% 36% 8% 2	180
	21st to end	Day	34% 27% 28% 8% 2	222
January	1st to 10th	Night	22% 22% 34% 18% 4	950
	11th to 20th	Night	23% 20% 32% 19% 5%	950
	21st to end	Night	20% 15% 39% 20% 5%	1040
February	1st to 10th	Night	18% 22% 38% 18% 3	760
	11th to 20th	Night	25% 21% 31% 19% 4	743
	21st to end	Night	27% 19% 33% 18% 2	611
March	1st to 10th	Night	19% 19% 36% 20% 5%	720
	11th to 20th	Night	23% 20% 33% 20% 4	720
	21st to end	Night	24% 15% 34% 22% 4 1	792
April	1st to 10th	Night	24% 18% 33% 19% 6% 1	554
	11th to 20th	Night	26% 14% 29% 24% 6% 1	533
	21st to end	Night	19% 14% 33% 28% 6% 1	540
May	1st to 10th	Night	15% 13% 38% 26% 7% 2	540
	11th to 20th	Night	19% 12% 28% 30% 10%	531
	21st to end	Night	15% 7% 33% 31% 13% 1	535
June	1st to 10th	Night	16% 8% 33% 35% 8% 1	360
	11th to 20th	Night	10% 9% 35% 34% 12%	360
	21st to end	Night	10% 8% 30% 37% 14% 1	360
July	1st to 10th	Night	6% 5% 26% 44% 17% 1	481
	11th to 20th	Night	7% 5% 29% 37% 18% 3	522
	21st to end	Night	11% 5% 26% 41% 17% 1	591
August	1st to 10th	Night	8% 4 28% 37% 23% 1	537
	11th to 20th	Night	10% 6% 22% 34% 26% 2	534
	21st to end	Night	15% 5% 25% 36% 17% 1	594
September	1st to 10th	Night	13% 6% 28% 30% 19% 4	598
	11th to 20th	Night	14% 8% 26% 30% 17% 4	720
	21st to end	Night	21% 9% 24% 27% 16% 4	720
October	1st to 10th	Night	22% 11% 28% 26% 12% 1	720
	11th to 20th	Night	27% 15% 33% 19% 6%	720
	21st to end	Night	31% 15% 30% 20% 4 1	792
November	1st to 10th	Night	19% 18% 36% 18% 7% 1	740
	11th to 20th	Night	22% 22% 33% 18% 4 1	760
	21st to end	Night	27% 17% 37% 16% 3	760
December	1st to 10th	Night	24% 22% 35% 16% 4	893
	11th to 20th	Night	24% 22% 36% 14% 4	950
	21st to end	Night	30% 18% 34% 16% 2	1045

Page generated at 2024-02-22 06:05:45. Version ac07

Copyright 2024 Attilla Danko