Stardust Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stardust Observatory clear sky chart from 2005-11-06 to 2024-11-11.

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	12% 8% 3 7% 5% 4 4 4 6% 8% 39%	101365
	Night	13% 9% 3 7% 4 4 4 3 5% 7% 41%	97857
Transparency	Day	42% 5% 12% 24% 15% 2	104942
	Night	42% 4 11% 24% 16% 2	102420
Seeing	Day	16% 9% 27% 26% 17% 5%	15740
	Night	17% 9% 29% 31% 13% 1	25559

By Month

Percentage Cloud Cover SE (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	12% 13% 7% 14% 6% 5% 5% 3 5% 5% 24%	2527
	11th to 20th	Day	12% 11% 5% 12% 8% 7% 8% 5% 7% 6% 19%	2534
	21st to end	Day	19% 19% 9% 10% 4 4 3 3 4 6% 20%	3135
February	1st to 10th	Day	15% 13% 4 12% 6% 4 4 3 3 6% 30%	1710
	11th to 20th	Day	13% 10% 4 7% 6% 6% 5% 4 5% 8% 32%	1838
	21st to end	Day	16% 12% 5% 10% 5% 4 3 4 4 6% 31%	1570
March	1st to 10th	Day	18% 14% 3 7% 4 4 4 2 3 5% 35%	3120
	11th to 20th	Day	9% 9% 3 5% 5% 4 4 3 6% 8% 45%	3415
	21st to end	Day	18% 11% 4 10% 5% 4 5% 4 4 7% 28%	4089
April	1st to 10th	Day	14% 9% 3 7% 5% 4 4 3 6% 7% 37%	2280
	11th to 20th	Day	14% 10% 3 6% 5% 4 4 4 5% 5% 39%	2254
	21st to end	Day	18% 8% 2 7% 5% 5% 5% 3 5% 6% 36%	2280
May	1st to 10th	Day	14% 8% 3 7% 5% 5% 5% 4 7% 9% 31%	4019
	11th to 20th	Day	17% 7% 3 6% 5% 5% 5% 3 5% 8% 36%	4362
	21st to end	Day	10% 5% 2 6% 5% 4 4 4 6% 8% 45%	4824
June	1st to 10th	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 46%	2660
	11th to 20th	Day	8% 5% 2 6% 3 5% 4 4 6% 7% 50%	2660
	21st to end	Day	7% 5% 2 7% 6% 5% 5% 4 7% 10% 42%	2660
July	1st to 10th	Day	12% 6% 2 6% 5% 5% 4 5% 7% 11% 38%	4440
	11th to 20th	Day	5% 5% 2 7% 4 4 5% 4 7% 10% 47%	4440
	21st to end	Day	8% 5% 2 6% 4 5% 5% 5% 8% 10% 41%	4813
August	1st to 10th	Day	6% 4 2 5% 4 4 4 4 8% 11% 48%	4082
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 7% 10% 42%	3729
	21st to end	Day	5% 4 2 6% 4 5% 6% 5% 7% 10% 47%	4180
September	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 5% 7% 49%	2280
	11th to 20th	Day	9% 4 2 6% 4 4 5% 4 4 7% 51%	2223
	21st to end	Day	9% 6% 2 5% 4 4 4 3 6% 8% 49%	2090
October	1st to 10th	Day	10% 5% 2 5% 4 3 4 3 5% 6% 52%	1943
	11th to 20th	Day	15% 8% 3 6% 4 3 4 3 3 6% 46%	1900
	21st to end	Day	18% 10% 2 7% 3 3 3 3 5% 6% 39%	1990
November	1st to 10th	Day	11% 8% 2 6% 4 3 4 3 5% 7% 49%	1762
	11th to 20th	Day	16% 9% 4 6% 4 3 3 3 5% 7% 41%	1710
	21st to end	Day	16% 11% 3 8% 5% 4 3 3 4 4 38%	1625
December	1st to 10th	Day	14% 12% 5% 8% 6% 4 3 3 6% 6% 32%	1520
	11th to 20th	Day	14% 11% 4 9% 5% 5% 5% 3 5% 8% 31%	1918
	21st to end	Day	22% 17% 8% 13% 4 4 4 3 4 4 18%	2783
January	1st to 10th	Night	13% 13% 6% 10% 5% 5% 4 3 4 5% 31%	4428
	11th to 20th	Night	13% 18% 6% 10% 5% 5% 7% 4 5% 3 24%	4431
	21st to end	Night	22% 17% 7% 10% 4 3 4 2 3 5% 22%	4532
February	1st to 10th	Night	16% 12% 5% 9% 5% 4 3 4 4 7% 32%	2470
	11th to 20th	Night	13% 10% 4 8% 6% 3 4 3 6% 6% 38%	2227
	21st to end	Night	17% 11% 3 8% 6% 3 3 3 4 5% 37%	1884
March	1st to 10th	Night	19% 12% 3 6% 3 3 3 3 4 5% 38%	3733
	11th to 20th	Night	12% 7% 2 5% 3 4 3 3 5% 5% 51%	3560
	21st to end	Night	19% 10% 4 8% 6% 4 4 3 5% 5% 30%	3541
April	1st to 10th	Night	12% 7% 4 6% 5% 4 5% 4 5% 6% 42%	1900
	11th to 20th	Night	14% 7% 2 6% 4 4 4 3 5% 7% 44%	1875
	21st to end	Night	20% 7% 3 8% 4 4 3 4 4 6% 38%	1900
May	1st to 10th	Night	16% 8% 2 8% 5% 5% 5% 4 5% 8% 34%	2862
	11th to 20th	Night	15% 6% 3 6% 4 5% 4 4 6% 7% 40%	2538
	21st to end	Night	8% 6% 2 6% 5% 4 5% 3 6% 9% 46%	2743
June	1st to 10th	Night	9% 4 1 5% 4 3 3 3 7% 10% 51%	1520
	11th to 20th	Night	8% 5% 2 5% 3 5% 5% 4 6% 8% 51%	1520
	21st to end	Night	6% 5% 2 7% 5% 4 5% 4 7% 10% 45%	1520
July	1st to 10th	Night	12% 5% 2 7% 5% 5% 5% 3 7% 9% 41%	2530
	11th to 20th	Night	3 3 1 4 3 4 4 4 6% 9% 57%	2530
	21st to end	Night	6% 5% 2 6% 4 4 5% 4 8% 9% 45%	2750
August	1st to 10th	Night	5% 3 1 5% 3 3 4 3 5% 11% 56%	2852
	11th to 20th	Night	7% 4 2 5% 5% 3 4 4 6% 8% 52%	3100
	21st to end	Night	4 4 2 4 3 5% 4 5% 7% 9% 53%	3476
September	1st to 10th	Night	10% 5% 2 5% 4 3 3 2 4 7% 55%	1900
	11th to 20th	Night	7% 5% 2 5% 3 4 3 3 5% 8% 54%	1937
	21st to end	Night	8% 6% 2 5% 4 3 4 3 5% 8% 50%	2090
October	1st to 10th	Night	10% 4 2 5% 3 3 4 3 4 6% 55%	2232
	11th to 20th	Night	14% 6% 2 4 3 3 4 2 4 7% 51%	2280
	21st to end	Night	18% 9% 2 6% 4 3 4 3 4 5% 42%	2608
November	1st to 10th	Night	10% 7% 2 6% 4 3 3 2 5% 6% 52%	2536
	11th to 20th	Night	12% 7% 3 6% 4 4 4 3 5% 7% 45%	2477
	21st to end	Night	17% 10% 3 6% 4 4 4 3 4 6% 40%	2552
December	1st to 10th	Night	15% 12% 3 8% 5% 5% 4 3 5% 7% 33%	2660
	11th to 20th	Night	15% 10% 3 9% 5% 4 4 3 4 5% 38%	3279
	21st to end	Night	21% 20% 6% 11% 5% 4 4 3 4 4 18%	4884

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	61% 4 9% 19% 7% 1	2528
	11th to 20th	Day	64% 4 12% 14% 6%	2534
	21st to end	Day	67% 4 9% 15% 5%	3135
February	1st to 10th	Day	57% 4 10% 18% 9% 1	1710
	11th to 20th	Day	51% 4 11% 21% 12% 1	1848
	21st to end	Day	54% 4 8% 22% 10% 2	1570
March	1st to 10th	Day	54% 4 8% 18% 14% 2	3120
	11th to 20th	Day	37% 5% 14% 26% 17% 1	3415
	21st to end	Day	56% 5% 15% 20% 4	4089
April	1st to 10th	Day	46% 5% 11% 24% 13% 1	2280
	11th to 20th	Day	46% 5% 9% 24% 14% 3	2254
	21st to end	Day	49% 5% 12% 20% 12% 2	2280
May	1st to 10th	Day	47% 6% 15% 23% 9% 1	4056
	11th to 20th	Day	46% 6% 12% 27% 9% 1	4366
	21st to end	Day	35% 6% 11% 22% 24% 2	4837
June	1st to 10th	Day	34% 6% 14% 28% 16% 4	2660
	11th to 20th	Day	33% 5% 11% 25% 23% 3	2660
	21st to end	Day	36% 7% 14% 22% 17% 3	2660
July	1st to 10th	Day	39% 6% 13% 27% 13% 2	4371
	11th to 20th	Day	30% 6% 15% 29% 19% 1	4365
	21st to end	Day	34% 8% 20% 22% 15% 1	4662
August	1st to 10th	Day	28% 6% 20% 33% 11% 1	4067
	11th to 20th	Day	36% 7% 13% 29% 14% 1	3765
	21st to end	Day	30% 7% 16% 29% 14% 4	4179
September	1st to 10th	Day	34% 5% 10% 26% 20% 6%	2280
	11th to 20th	Day	32% 4 9% 26% 22% 6%	2223
	21st to end	Day	33% 4 8% 30% 22% 2	2090
October	1st to 10th	Day	23% 3 7% 20% 43% 3	3229
	11th to 20th	Day	28% 3 8% 22% 35% 5%	3140
	21st to end	Day	40% 3 8% 26% 21% 2	3254
November	1st to 10th	Day	36% 3 14% 25% 18% 4	1762
	11th to 20th	Day	45% 3 10% 26% 15% 2	1710
	21st to end	Day	52% 3 10% 23% 12%	1625
December	1st to 10th	Day	52% 5% 13% 21% 9% 1	1520
	11th to 20th	Day	51% 5% 9% 26% 6% 2	1915
	21st to end	Day	70% 4 9% 12% 5%	2783
January	1st to 10th	Night	56% 4 11% 20% 8%	4428
	11th to 20th	Night	65% 3 9% 16% 7% 1	4431
	21st to end	Night	66% 3 9% 16% 6% 1	4532
February	1st to 10th	Night	53% 4 11% 19% 11% 2	2470
	11th to 20th	Night	47% 3 11% 23% 14% 2	2228
	21st to end	Night	49% 3 10% 22% 12% 3	1884
March	1st to 10th	Night	49% 3 10% 24% 12% 1	3733
	11th to 20th	Night	36% 4 9% 27% 20% 3	3560
	21st to end	Night	54% 5% 12% 22% 7% 1	3541
April	1st to 10th	Night	41% 4 12% 24% 15% 3	1900
	11th to 20th	Night	40% 4 10% 26% 17% 4	1875
	21st to end	Night	48% 4 10% 20% 15% 3	1900
May	1st to 10th	Night	47% 7% 13% 22% 10% 1	2889
	11th to 20th	Night	41% 6% 14% 28% 11% 1	2539
	21st to end	Night	33% 7% 12% 22% 22% 4	2751
June	1st to 10th	Night	28% 5% 15% 29% 18% 5%	1520
	11th to 20th	Night	30% 5% 12% 25% 24% 5%	1520
	21st to end	Night	33% 6% 16% 23% 18% 4	1520
July	1st to 10th	Night	39% 6% 12% 28% 13% 2	2490
	11th to 20th	Night	22% 6% 14% 32% 24% 2	2482
	21st to end	Night	32% 6% 19% 23% 16% 3	2662
August	1st to 10th	Night	24% 5% 18% 33% 19% 1	2843
	11th to 20th	Night	29% 6% 13% 33% 17% 1	3130
	21st to end	Night	25% 7% 16% 33% 15% 4	3476
September	1st to 10th	Night	30% 4 9% 26% 22% 8%	1900
	11th to 20th	Night	29% 4 8% 27% 27% 5%	1937
	21st to end	Night	33% 4 9% 27% 22% 5%	2090
October	1st to 10th	Night	22% 3 6% 23% 41% 4	3726
	11th to 20th	Night	24% 2 8% 25% 37% 5%	3779
	21st to end	Night	36% 3 10% 23% 24% 4	4294
November	1st to 10th	Night	34% 4 11% 27% 20% 5%	2536
	11th to 20th	Night	39% 3 12% 26% 19% 2	2477
	21st to end	Night	46% 3 10% 25% 15% 1	2552
December	1st to 10th	Night	52% 4 12% 22% 10% 1	2660
	11th to 20th	Night	49% 4 12% 25% 10% 1	3281
	21st to end	Night	71% 4 7% 12% 5% 1	4884

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	26% 20% 29% 18% 8%	270
	11th to 20th	Day	27% 17% 36% 17% 4	270
	21st to end	Day	20% 19% 34% 23% 5%	297
February	1st to 10th	Day	24% 16% 39% 17% 4	270
	11th to 20th	Day	23% 20% 29% 22% 6%	270
	21st to end	Day	26% 15% 42% 15% 2	225
March	1st to 10th	Day	24% 17% 40% 16% 3	270
	11th to 20th	Day	27% 14% 37% 16% 6%	270
	21st to end	Day	32% 12% 33% 17% 4 1	456
April	1st to 10th	Day	22% 12% 34% 25% 7%	460
	11th to 20th	Day	20% 17% 30% 23% 8% 2	452
	21st to end	Day	25% 12% 35% 20% 8% 1	460
May	1st to 10th	Day	21% 10% 32% 25% 10% 2	463
	11th to 20th	Day	19% 10% 26% 26% 16% 2	651
	21st to end	Day	13% 6% 32% 27% 14% 7%	734
June	1st to 10th	Day	9% 5% 24% 31% 24% 7%	680
	11th to 20th	Day	10% 4 22% 34% 24% 6%	680
	21st to end	Day	9% 5% 29% 31% 21% 5%	680
July	1st to 10th	Day	12% 2 14% 31% 25% 16%	671
	11th to 20th	Day	7% 2 21% 30% 28% 10%	668
	21st to end	Day	10% 2 15% 33% 32% 7%	739
August	1st to 10th	Day	9% 2 14% 35% 30% 11%	666
	11th to 20th	Day	10% 5% 16% 29% 26% 14%	479
	21st to end	Day	7% 2 15% 29% 35% 11%	539
September	1st to 10th	Day	13% 2 20% 28% 27% 9%	490
	11th to 20th	Day	9% 3 12% 29% 33% 13%	490
	21st to end	Day	12% 9% 22% 26% 24% 8%	490
October	1st to 10th	Day	11% 8% 27% 29% 20% 5%	343
	11th to 20th	Day	17% 18% 31% 24% 8% 2	300
	21st to end	Day	31% 13% 34% 18% 5%	330
November	1st to 10th	Day	14% 12% 35% 26% 9% 4	300
	11th to 20th	Day	23% 15% 31% 19% 10% 2	270
	21st to end	Day	29% 9% 34% 23% 5%	270
December	1st to 10th	Day	16% 19% 37% 18% 7% 3	270
	11th to 20th	Day	20% 15% 41% 19% 4	270
	21st to end	Day	27% 16% 40% 14% 2	297
January	1st to 10th	Night	17% 15% 39% 24% 5%	950
	11th to 20th	Night	21% 14% 38% 21% 5%	950
	21st to end	Night	22% 13% 35% 26% 3	1045
February	1st to 10th	Night	23% 13% 35% 25% 4	950
	11th to 20th	Night	20% 13% 36% 28% 3	752
	21st to end	Night	24% 15% 37% 21% 2	628
March	1st to 10th	Night	21% 14% 37% 24% 4	760
	11th to 20th	Night	20% 11% 35% 28% 6%	624
	21st to end	Night	24% 10% 35% 25% 6%	627
April	1st to 10th	Night	17% 14% 36% 27% 6%	570
	11th to 20th	Night	18% 13% 32% 28% 9%	563
	21st to end	Night	24% 7% 35% 27% 7%	570
May	1st to 10th	Night	18% 7% 36% 32% 7% 1	570
	11th to 20th	Night	18% 4 26% 39% 12% 2	561
	21st to end	Night	12% 4 26% 34% 22% 2	617
June	1st to 10th	Night	10% 3 21% 48% 19%	570
	11th to 20th	Night	10% 2 22% 45% 19% 2	570
	21st to end	Night	8% 3 28% 39% 21% 1	570
July	1st to 10th	Night	10% 2 11% 37% 34% 6%	555
	11th to 20th	Night	4 3 16% 45% 30% 3	552
	21st to end	Night	7% 1 13% 44% 33% 2	624
August	1st to 10th	Night	8% 1 10% 47% 31% 3	567
	11th to 20th	Night	8% 2 10% 43% 31% 5%	564
	21st to end	Night	6% 2 14% 36% 41% 2	627
September	1st to 10th	Night	12% 4 15% 38% 27% 4	570
	11th to 20th	Night	8% 3 15% 39% 31% 4	607
	21st to end	Night	10% 8% 22% 33% 24% 3	760
October	1st to 10th	Night	11% 4 28% 33% 21% 2	760
	11th to 20th	Night	17% 11% 29% 29% 13% 1	760
	21st to end	Night	23% 10% 34% 26% 7%	836
November	1st to 10th	Night	13% 9% 39% 27% 10% 1	780
	11th to 20th	Night	17% 13% 36% 26% 7% 1	763
	21st to end	Night	22% 12% 35% 25% 6%	842
December	1st to 10th	Night	22% 10% 38% 25% 5%	950
	11th to 20th	Night	23% 10% 34% 28% 5% 1	950
	21st to end	Night	28% 15% 32% 23% 2	1045

Page generated at 2024-11-08 05:44:51. Version ac07

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