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 2024-10-24.

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 9% 5% 5% 5% 4 5% 7% 32%	101082
	Night	13% 12% 5% 9% 5% 5% 4 4 5% 6% 31%	97771
Transparency	Day	50% 8% 12% 18% 11% 1	100838
	Night	51% 8% 13% 19% 9% 1	97634
Seeing	Day	21% 17% 33% 20% 7% 3	15517
	Night	20% 15% 32% 24% 8% 1	25048

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% 19% 8% 15% 5% 5% 3 3 5% 6% 18%	2527
	11th to 20th	Day	13% 17% 7% 17% 9% 10% 6% 3 5% 5% 8%	2530
	21st to end	Day	19% 19% 10% 13% 6% 5% 4 3 4 6% 12%	2787
February	1st to 10th	Day	10% 17% 6% 15% 11% 5% 6% 4 4 5% 17%	1710
	11th to 20th	Day	11% 14% 6% 16% 9% 5% 5% 3 4 4 22%	1783
	21st to end	Day	10% 19% 6% 12% 7% 4 5% 4 4 4 23%	1570
March	1st to 10th	Day	12% 14% 4 10% 5% 4 5% 4 5% 5% 31%	3118
	11th to 20th	Day	11% 13% 6% 13% 5% 5% 4 4 5% 6% 27%	3476
	21st to end	Day	16% 14% 6% 11% 7% 5% 5% 3 6% 5% 24%	3828
April	1st to 10th	Day	17% 18% 4 8% 4 4 5% 3 5% 4 28%	2280
	11th to 20th	Day	18% 13% 4 7% 4 2 4 3 4 5% 35%	2404
	21st to end	Day	16% 12% 3 9% 5% 4 4 3 5% 6% 33%	2470
May	1st to 10th	Day	15% 8% 3 8% 5% 5% 5% 4 6% 7% 34%	4108
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 5% 7% 43%	4081
	21st to end	Day	11% 6% 2 6% 4 4 4 3 5% 8% 46%	4906
June	1st to 10th	Day	13% 7% 2 6% 5% 5% 4 4 6% 8% 39%	2850
	11th to 20th	Day	12% 6% 2 7% 4 5% 5% 4 6% 8% 39%	2850
	21st to end	Day	14% 8% 3 6% 5% 5% 5% 4 6% 7% 37%	2850
July	1st to 10th	Day	14% 7% 3 8% 6% 4 5% 5% 6% 7% 36%	4506
	11th to 20th	Day	8% 5% 2 6% 5% 5% 6% 5% 7% 9% 42%	4440
	21st to end	Day	8% 6% 2 8% 5% 5% 5% 5% 7% 8% 40%	4814
August	1st to 10th	Day	9% 5% 2 7% 5% 6% 6% 6% 8% 10% 37%	4106
	11th to 20th	Day	13% 6% 2 7% 5% 5% 4 4 6% 6% 41%	4044
	21st to end	Day	12% 7% 3 8% 5% 5% 5% 3 5% 7% 40%	4477
September	1st to 10th	Day	11% 8% 3 6% 5% 4 5% 4 7% 8% 40%	2199
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 3 5% 7% 46%	2090
	21st to end	Day	15% 10% 3 6% 5% 4 5% 3 6% 9% 34%	2090
October	1st to 10th	Day	18% 9% 3 8% 4 4 4 3 4 7% 37%	2051
	11th to 20th	Day	21% 15% 3 8% 6% 5% 5% 4 4 5% 25%	1864
	21st to end	Day	20% 18% 3 10% 5% 5% 5% 4 4 5% 21%	1809
November	1st to 10th	Day	13% 16% 4 8% 6% 4 4 3 6% 9% 27%	1672
	11th to 20th	Day	12% 18% 7% 12% 5% 6% 4 4 5% 5% 21%	1706
	21st to end	Day	18% 17% 5% 13% 6% 4 5% 3 4 5% 20%	1520
December	1st to 10th	Day	13% 21% 8% 14% 7% 5% 3 4 4 5% 16%	1386
	11th to 20th	Day	16% 19% 6% 13% 7% 6% 4 4 4 6% 16%	1671
	21st to end	Day	23% 24% 10% 18% 6% 4 3 2 2 3 6%	2509
January	1st to 10th	Night	14% 16% 8% 17% 6% 6% 4 3 4 5% 17%	4428
	11th to 20th	Night	12% 15% 8% 17% 11% 8% 6% 3 4 4 11%	4440
	21st to end	Night	15% 18% 9% 15% 8% 6% 5% 4 4 5% 11%	4879
February	1st to 10th	Night	10% 16% 6% 14% 9% 7% 6% 4 5% 5% 18%	2470
	11th to 20th	Night	11% 15% 5% 14% 7% 6% 4 4 5% 6% 23%	2281
	21st to end	Night	13% 17% 5% 12% 7% 5% 4 4 5% 4 25%	1884
March	1st to 10th	Night	14% 10% 4 7% 4 4 3 3 5% 6% 39%	3722
	11th to 20th	Night	10% 13% 5% 8% 4 4 5% 4 5% 6% 37%	3480
	21st to end	Night	13% 13% 6% 11% 6% 4 4 3 5% 5% 31%	3817
April	1st to 10th	Night	18% 13% 3 7% 6% 4 4 4 5% 7% 30%	1914
	11th to 20th	Night	18% 11% 3 6% 4 3 4 3 6% 7% 34%	1724
	21st to end	Night	16% 9% 4 7% 4 4 5% 4 5% 5% 36%	1710
May	1st to 10th	Night	13% 8% 3 7% 5% 4 5% 4 5% 7% 40%	2833
	11th to 20th	Night	12% 8% 3 6% 4 4 5% 4 6% 9% 40%	2812
	21st to end	Night	15% 6% 2 5% 4 4 3 3 5% 8% 44%	2672
June	1st to 10th	Night	14% 6% 2 5% 5% 4 4 4 6% 6% 44%	1330
	11th to 20th	Night	8% 5% 3 6% 5% 4 5% 4 7% 8% 46%	1330
	21st to end	Night	11% 6% 2 6% 6% 4 5% 4 5% 6% 46%	1330
July	1st to 10th	Night	10% 6% 3 6% 4 4 5% 5% 7% 11% 41%	2458
	11th to 20th	Night	7% 4 2 5% 4 4 5% 3 6% 7% 52%	2530
	21st to end	Night	8% 5% 2 6% 4 3 4 4 7% 8% 50%	2750
August	1st to 10th	Night	9% 5% 2 6% 4 5% 5% 4 6% 8% 46%	2820
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 7% 50%	2785
	21st to end	Night	10% 6% 2 6% 4 4 4 4 6% 7% 48%	3177
September	1st to 10th	Night	10% 7% 2 5% 3 4 3 3 5% 7% 49%	1962
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 5% 7% 50%	2090
	21st to end	Night	17% 7% 2 6% 4 4 4 3 5% 7% 40%	2090
October	1st to 10th	Night	15% 9% 2 7% 4 3 4 3 4 7% 41%	2128
	11th to 20th	Night	17% 14% 4 8% 5% 4 4 3 4 5% 33%	2313
	21st to end	Night	23% 13% 3 8% 5% 4 4 3 5% 5% 27%	2614
November	1st to 10th	Night	11% 12% 4 8% 5% 4 5% 4 6% 8% 31%	2406
	11th to 20th	Night	12% 17% 5% 11% 7% 6% 5% 4 4 6% 24%	2473
	21st to end	Night	17% 17% 6% 9% 5% 5% 4 4 5% 6% 22%	2660
December	1st to 10th	Night	14% 17% 6% 13% 7% 6% 5% 4 5% 6% 18%	2793
	11th to 20th	Night	13% 17% 6% 16% 8% 6% 5% 4 5% 6% 15%	3526
	21st to end	Night	21% 27% 8% 13% 5% 4 3 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	1570
March	1st to 10th	Day	53% 7% 12% 18% 9% 1	3120
	11th to 20th	Day	53% 8% 13% 18% 6% 2	3476
	21st to end	Day	58% 7% 10% 14% 10% 1	3828
April	1st to 10th	Day	57% 5% 11% 16% 9% 1	2280
	11th to 20th	Day	50% 6% 11% 18% 15% 1	2404
	21st to end	Day	51% 6% 13% 14% 14% 3	2470
May	1st to 10th	Day	44% 10% 12% 16% 17% 2	4120
	11th to 20th	Day	37% 9% 14% 25% 14% 1	4085
	21st to end	Day	35% 7% 13% 20% 21% 4	4906
June	1st to 10th	Day	40% 8% 14% 23% 14% 2	2850
	11th to 20th	Day	40% 8% 11% 21% 17% 2	2850
	21st to end	Day	43% 8% 12% 23% 13% 1	2850
July	1st to 10th	Day	45% 7% 12% 19% 15% 1	4437
	11th to 20th	Day	33% 8% 15% 28% 15% 1	4365
	21st to end	Day	35% 10% 13% 21% 19% 1	4662
August	1st to 10th	Day	38% 9% 12% 26% 14% 1	4092
	11th to 20th	Day	41% 8% 11% 25% 13% 1	4083
	21st to end	Day	42% 7% 13% 26% 11% 1	4476
September	1st to 10th	Day	40% 8% 13% 23% 14% 1	2199
	11th to 20th	Day	36% 7% 15% 28% 15%	2090
	21st to end	Day	46% 7% 14% 22% 11%	2090
October	1st to 10th	Day	47% 6% 10% 24% 12% 1	2051
	11th to 20th	Day	60% 7% 10% 16% 6%	1864
	21st to end	Day	63% 7% 12% 12% 6%	1809
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% 15% 7%	1884
March	1st to 10th	Night	45% 6% 16% 23% 9% 1	3733
	11th to 20th	Night	42% 9% 16% 23% 9% 1	3481
	21st to end	Night	50% 9% 13% 18% 8% 1	3817
April	1st to 10th	Night	51% 7% 11% 18% 12% 2	1914
	11th to 20th	Night	47% 6% 10% 21% 14% 2	1724
	21st to end	Night	48% 8% 10% 17% 14% 3	1710
May	1st to 10th	Night	40% 8% 15% 16% 18% 3	2840
	11th to 20th	Night	36% 9% 13% 25% 14% 2	2813
	21st to end	Night	37% 7% 15% 20% 16% 5%	2673
June	1st to 10th	Night	38% 6% 12% 26% 17% 1	1330
	11th to 20th	Night	34% 7% 15% 24% 18% 2	1330
	21st to end	Night	37% 7% 12% 26% 15% 3	1330
July	1st to 10th	Night	36% 7% 15% 24% 13% 4	2418
	11th to 20th	Night	29% 7% 12% 37% 14% 1	2482
	21st to end	Night	30% 10% 16% 26% 17% 1	2662
August	1st to 10th	Night	34% 7% 14% 30% 14% 1	2810
	11th to 20th	Night	33% 7% 17% 30% 13% 1	2812
	21st to end	Night	32% 8% 17% 28% 15% 1	3177
September	1st to 10th	Night	33% 8% 13% 27% 17% 1	1962
	11th to 20th	Night	32% 6% 15% 33% 14%	2090
	21st to end	Night	42% 7% 15% 25% 9%	2090
October	1st to 10th	Night	41% 7% 13% 25% 13% 1	2128
	11th to 20th	Night	53% 7% 12% 20% 8% 1	2313
	21st to end	Night	57% 7% 12% 17% 7%	2614
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	33% 27% 34% 5% 1	225
March	1st to 10th	Day	27% 29% 34% 9% 1	270
	11th to 20th	Day	26% 18% 37% 16% 3	456
	21st to end	Day	30% 19% 29% 17% 4	506
April	1st to 10th	Day	29% 21% 29% 17% 4	460
	11th to 20th	Day	33% 18% 29% 11% 7% 2	452
	21st to end	Day	27% 18% 30% 17% 6% 2	460
May	1st to 10th	Day	25% 18% 33% 15% 6% 2	463
	11th to 20th	Day	19% 16% 32% 23% 8% 3	487
	21st to end	Day	15% 14% 36% 26% 8% 2	717
June	1st to 10th	Day	16% 20% 35% 20% 8% 1	680
	11th to 20th	Day	17% 15% 37% 24% 5% 3	680
	21st to end	Day	16% 15% 37% 25% 5% 2	680
July	1st to 10th	Day	11% 12% 34% 29% 10% 3	671
	11th to 20th	Day	11% 15% 33% 28% 10% 4	668
	21st to end	Day	11% 11% 37% 27% 10% 4	739
August	1st to 10th	Day	10% 12% 29% 25% 15% 9%	488
	11th to 20th	Day	11% 10% 24% 31% 17% 9%	479
	21st to end	Day	17% 10% 32% 23% 14% 3	539
September	1st to 10th	Day	15% 12% 30% 23% 13% 6%	490
	11th to 20th	Day	13% 9% 25% 30% 14% 8%	490
	21st to end	Day	20% 12% 26% 27% 11% 4	490
October	1st to 10th	Day	26% 18% 27% 16% 12% 2	490
	11th to 20th	Day	31% 17% 33% 15% 3	454
	21st to end	Day	32% 25% 31% 10% 2	306
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% 20% 34% 18% 2	628
March	1st to 10th	Night	19% 19% 37% 20% 5%	760
	11th to 20th	Night	22% 20% 33% 21% 4	760
	21st to end	Night	24% 15% 34% 23% 4 1	836
April	1st to 10th	Night	24% 17% 34% 19% 5% 1	584
	11th to 20th	Night	26% 16% 29% 23% 6% 1	563
	21st to end	Night	20% 13% 33% 28% 5% 1	570
May	1st to 10th	Night	14% 13% 37% 27% 7% 2	570
	11th to 20th	Night	19% 12% 28% 31% 10%	561
	21st to end	Night	16% 7% 33% 31% 13% 1	565
June	1st to 10th	Night	16% 8% 33% 34% 7% 1	380
	11th to 20th	Night	9% 9% 36% 34% 11%	380
	21st to end	Night	12% 7% 31% 35% 14% 1	380
July	1st to 10th	Night	7% 6% 26% 44% 17% 1	509
	11th to 20th	Night	7% 5% 29% 38% 18% 3	552
	21st to end	Night	10% 5% 25% 41% 18% 1	624
August	1st to 10th	Night	8% 4 28% 37% 23% 1	567
	11th to 20th	Night	10% 6% 21% 35% 26% 2	564
	21st to end	Night	15% 5% 25% 37% 17% 1	627
September	1st to 10th	Night	13% 7% 28% 29% 19% 4	632
	11th to 20th	Night	13% 8% 26% 30% 19% 4	760
	21st to end	Night	20% 9% 24% 28% 16% 3	760
October	1st to 10th	Night	21% 12% 29% 26% 12% 1	760
	11th to 20th	Night	26% 15% 33% 20% 6%	760
	21st to end	Night	31% 15% 30% 20% 4	805
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 2024-10-21 02:20:03. Version ac07

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