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 2024-11-02.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	101305
	Night	16% 9% 3 8% 5% 4 4 4 5% 7% 35%	97616
Transparency	Day	49% 6% 11% 21% 11% 1	101106
	Night	48% 6% 11% 22% 12% 1	97485
Seeing	Day	22% 13% 27% 22% 12% 4	14761
	Night	21% 12% 25% 29% 12% 1	24209

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	15% 17% 7% 10% 5% 4 4 3 3 5% 27%	2526
	11th to 20th	Day	11% 18% 9% 15% 8% 5% 4 3 4 4 19%	2840
	21st to end	Day	20% 19% 7% 12% 6% 4 4 3 4 4 17%	3124
February	1st to 10th	Day	15% 16% 5% 10% 7% 5% 4 3 4 6% 24%	1710
	11th to 20th	Day	14% 11% 5% 11% 6% 6% 5% 4 7% 5% 26%	1663
	21st to end	Day	18% 12% 4 10% 5% 5% 4 3 4 6% 28%	1544
March	1st to 10th	Day	21% 11% 3 6% 5% 5% 4 3 5% 7% 29%	3428
	11th to 20th	Day	12% 11% 4 9% 5% 4 4 4 5% 6% 34%	3480
	21st to end	Day	15% 10% 3 7% 6% 5% 4 3 5% 6% 37%	3833
April	1st to 10th	Day	17% 11% 3 8% 6% 5% 5% 4 5% 6% 32%	2280
	11th to 20th	Day	16% 11% 2 7% 4 5% 4 3 6% 6% 36%	2254
	21st to end	Day	21% 7% 3 6% 5% 5% 4 4 5% 6% 33%	2361
May	1st to 10th	Day	28% 7% 2 7% 4 4 4 3 5% 6% 29%	4082
	11th to 20th	Day	23% 8% 3 7% 6% 4 5% 3 5% 7% 29%	4320
	21st to end	Day	12% 6% 2 6% 5% 5% 5% 5% 6% 9% 40%	4823
June	1st to 10th	Day	14% 7% 2 6% 6% 6% 5% 4 6% 8% 35%	2660
	11th to 20th	Day	15% 5% 2 6% 6% 6% 5% 4 6% 9% 36%	2660
	21st to end	Day	13% 5% 2 7% 4 5% 5% 4 7% 9% 39%	2660
July	1st to 10th	Day	8% 5% 3 7% 6% 6% 6% 4 8% 9% 38%	4440
	11th to 20th	Day	8% 5% 2 7% 6% 5% 6% 5% 7% 10% 39%	4376
	21st to end	Day	11% 7% 3 8% 5% 5% 5% 5% 6% 7% 38%	4466
August	1st to 10th	Day	20% 6% 3 6% 5% 5% 5% 5% 7% 8% 30%	4104
	11th to 20th	Day	14% 6% 2 7% 6% 7% 6% 4 7% 7% 35%	4017
	21st to end	Day	15% 5% 2 5% 3 5% 4 4 6% 8% 43%	4180
September	1st to 10th	Day	17% 5% 2 6% 5% 3 5% 3 4 6% 44%	2280
	11th to 20th	Day	15% 5% 2 4 4 3 4 3 5% 7% 48%	2256
	21st to end	Day	23% 6% 3 6% 4 4 3 4 6% 6% 35%	1995
October	1st to 10th	Day	17% 8% 3 6% 4 5% 4 3 5% 6% 39%	1900
	11th to 20th	Day	18% 7% 3 7% 4 4 5% 4 6% 6% 36%	1900
	21st to end	Day	17% 9% 2 7% 4 4 5% 3 5% 6% 37%	2090
November	1st to 10th	Day	11% 7% 3 7% 4 5% 4 5% 5% 6% 42%	1767
	11th to 20th	Day	16% 12% 3 7% 5% 5% 5% 3 6% 6% 31%	1564
	21st to end	Day	17% 12% 2 8% 7% 6% 4 4 6% 6% 29%	1520
December	1st to 10th	Day	18% 15% 5% 10% 6% 5% 5% 4 5% 6% 21%	1520
	11th to 20th	Day	18% 15% 6% 9% 4 4 4 4 4 6% 26%	1910
	21st to end	Day	22% 17% 6% 10% 6% 5% 5% 4 4 4 17%	2772
January	1st to 10th	Night	14% 13% 7% 11% 6% 5% 4 4 6% 6% 25%	4415
	11th to 20th	Night	15% 15% 6% 13% 5% 5% 4 3 5% 6% 22%	4120
	21st to end	Night	23% 13% 6% 12% 5% 5% 4 3 4 4 21%	4532
February	1st to 10th	Night	15% 11% 5% 10% 5% 5% 4 4 4 7% 30%	2470
	11th to 20th	Night	16% 10% 3 9% 6% 5% 6% 5% 5% 6% 30%	2403
	21st to end	Night	16% 11% 3 10% 5% 6% 4 3 5% 5% 32%	1908
March	1st to 10th	Night	22% 13% 3 6% 5% 3 4 3 4 5% 33%	3423
	11th to 20th	Night	11% 9% 6% 7% 5% 4 5% 4 6% 6% 36%	3480
	21st to end	Night	15% 9% 2 7% 4 4 3 3 4 5% 44%	3797
April	1st to 10th	Night	17% 12% 3 9% 5% 4 3 4 5% 6% 32%	1900
	11th to 20th	Night	16% 8% 2 6% 5% 4 4 4 5% 6% 38%	1875
	21st to end	Night	18% 6% 2 6% 5% 4 4 4 5% 7% 38%	1834
May	1st to 10th	Night	28% 8% 2 7% 4 4 4 3 3 6% 30%	2813
	11th to 20th	Night	26% 10% 3 6% 3 4 4 3 5% 6% 30%	2569
	21st to end	Night	13% 6% 2 6% 5% 5% 4 4 7% 10% 39%	2732
June	1st to 10th	Night	13% 6% 2 6% 5% 4 3 3 6% 8% 44%	1520
	11th to 20th	Night	12% 6% 2 7% 4 4 4 4 8% 9% 40%	1520
	21st to end	Night	11% 5% 2 5% 3 4 5% 4 8% 10% 42%	1520
July	1st to 10th	Night	9% 5% 3 7% 6% 4 5% 4 6% 8% 42%	2520
	11th to 20th	Night	7% 4 2 6% 4 5% 5% 5% 7% 11% 45%	2580
	21st to end	Night	13% 6% 2 7% 5% 5% 4 4 5% 7% 42%	3087
August	1st to 10th	Night	17% 6% 3 6% 4 5% 4 4 6% 9% 37%	2825
	11th to 20th	Night	16% 6% 2 6% 4 4 5% 4 6% 6% 41%	2785
	21st to end	Night	15% 4 2 5% 3 4 4 3 6% 7% 47%	3471
September	1st to 10th	Night	17% 4 2 5% 4 4 4 3 5% 8% 45%	1900
	11th to 20th	Night	12% 6% 2 5% 2 3 3 3 4 8% 52%	1921
	21st to end	Night	20% 6% 2 6% 3 5% 4 3 4 7% 39%	2184
October	1st to 10th	Night	17% 6% 2 6% 3 3 4 3 4 7% 45%	2280
	11th to 20th	Night	16% 7% 2 6% 4 3 3 4 5% 6% 43%	2280
	21st to end	Night	20% 8% 3 5% 4 4 4 3 5% 6% 39%	2508
November	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 4 6% 49%	2343
	11th to 20th	Night	17% 10% 3 6% 5% 4 5% 3 5% 6% 35%	2612
	21st to end	Night	16% 11% 4 7% 4 4 5% 4 6% 6% 33%	2660
December	1st to 10th	Night	18% 11% 3 9% 5% 5% 5% 4 6% 7% 26%	2660
	11th to 20th	Night	18% 12% 4 9% 5% 4 5% 4 5% 5% 29%	3285
	21st to end	Night	20% 13% 5% 9% 6% 5% 5% 4 6% 6% 21%	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	59% 6% 11% 17% 5% 2	2527
	11th to 20th	Day	69% 3 8% 12% 7% 1	2840
	21st to end	Day	72% 4 7% 12% 4 1	3124
February	1st to 10th	Day	61% 4 12% 15% 7% 1	1710
	11th to 20th	Day	55% 6% 9% 22% 8% 1	1672
	21st to end	Day	57% 3 11% 19% 8% 3	1544
March	1st to 10th	Day	55% 5% 10% 24% 6%	3428
	11th to 20th	Day	49% 6% 15% 21% 9% 2	3480
	21st to end	Day	48% 5% 11% 22% 13% 1	3833
April	1st to 10th	Day	52% 4 10% 20% 12% 2	2280
	11th to 20th	Day	48% 5% 10% 19% 16% 3	2254
	21st to end	Day	51% 4 8% 22% 13% 2	2361
May	1st to 10th	Day	55% 6% 8% 20% 9% 1	4120
	11th to 20th	Day	54% 6% 13% 18% 7% 1	4324
	21st to end	Day	39% 7% 13% 26% 13% 2	4837
June	1st to 10th	Day	45% 6% 10% 23% 14% 1	2660
	11th to 20th	Day	45% 6% 12% 21% 14% 2	2660
	21st to end	Day	40% 6% 13% 27% 14% 1	2660
July	1st to 10th	Day	40% 7% 14% 25% 11% 2	4370
	11th to 20th	Day	37% 9% 14% 25% 15% 1	4301
	21st to end	Day	42% 7% 10% 24% 16% 1	4324
August	1st to 10th	Day	49% 8% 13% 21% 9%	4091
	11th to 20th	Day	44% 7% 11% 27% 10% 1	4056
	21st to end	Day	39% 5% 11% 28% 15% 2	4180
September	1st to 10th	Day	42% 4 9% 24% 18% 3	2280
	11th to 20th	Day	36% 4 11% 27% 20% 2	2256
	21st to end	Day	48% 5% 10% 20% 16% 1	1995
October	1st to 10th	Day	46% 5% 11% 21% 16% 2	1900
	11th to 20th	Day	47% 6% 10% 24% 12% 1	1900
	21st to end	Day	47% 5% 11% 23% 12% 1	2090
November	1st to 10th	Day	41% 5% 13% 21% 17% 3	1767
	11th to 20th	Day	54% 4 10% 20% 10% 2	1564
	21st to end	Day	55% 4 12% 21% 8%	1520
December	1st to 10th	Day	62% 6% 12% 14% 6%	1520
	11th to 20th	Day	59% 5% 12% 19% 5%	1906
	21st to end	Day	69% 6% 10% 11% 3	2772
January	1st to 10th	Night	57% 4 12% 19% 7% 1	4415
	11th to 20th	Night	62% 5% 13% 14% 6% 1	4120
	21st to end	Night	67% 3 8% 16% 5% 1	4532
February	1st to 10th	Night	54% 5% 12% 21% 8% 1	2470
	11th to 20th	Night	53% 5% 10% 19% 12% 1	2405
	21st to end	Night	55% 5% 9% 19% 11% 2	1908
March	1st to 10th	Night	53% 5% 10% 22% 9% 1	3423
	11th to 20th	Night	44% 9% 12% 25% 9% 1	3480
	21st to end	Night	43% 4 7% 24% 19% 3	3797
April	1st to 10th	Night	53% 4 9% 19% 14% 1	1900
	11th to 20th	Night	44% 6% 10% 22% 15% 2	1875
	21st to end	Night	45% 4 10% 23% 15% 3	1834
May	1st to 10th	Night	56% 6% 7% 18% 11% 2	2840
	11th to 20th	Night	54% 7% 12% 17% 9% 1	2570
	21st to end	Night	38% 8% 15% 22% 12% 4	2739
June	1st to 10th	Night	38% 6% 14% 26% 15% 2	1520
	11th to 20th	Night	38% 8% 14% 23% 15% 2	1520
	21st to end	Night	35% 8% 13% 29% 14% 1	1520
July	1st to 10th	Night	38% 8% 13% 21% 16% 3	2480
	11th to 20th	Night	32% 9% 15% 26% 17% 1	2532
	21st to end	Night	40% 7% 13% 18% 20% 2	2988
August	1st to 10th	Night	45% 8% 14% 23% 10%	2814
	11th to 20th	Night	41% 7% 11% 28% 13% 1	2812
	21st to end	Night	36% 6% 12% 32% 13% 2	3471
September	1st to 10th	Night	38% 5% 11% 24% 18% 3	1900
	11th to 20th	Night	32% 5% 10% 31% 20% 2	1921
	21st to end	Night	45% 5% 10% 22% 17% 1	2184
October	1st to 10th	Night	40% 5% 13% 25% 15% 1	2280
	11th to 20th	Night	41% 5% 12% 25% 15% 2	2280
	21st to end	Night	46% 4 10% 24% 15% 1	2508
November	1st to 10th	Night	37% 4 13% 25% 18% 3	2343
	11th to 20th	Night	47% 5% 10% 23% 13% 3	2612
	21st to end	Night	50% 4 13% 23% 9% 1	2660
December	1st to 10th	Night	56% 7% 13% 18% 6%	2660
	11th to 20th	Night	56% 5% 11% 20% 7%	3288
	21st to end	Night	61% 7% 12% 16% 3	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	28% 23% 32% 10% 5% 2	184
	11th to 20th	Day	35% 20% 32% 12% 1	270
	21st to end	Day	26% 19% 36% 14% 4 1	297
February	1st to 10th	Day	30% 20% 34% 13% 3	270
	11th to 20th	Day	35% 21% 35% 9% 1	270
	21st to end	Day	35% 17% 29% 17% 2	356
March	1st to 10th	Day	29% 19% 29% 20% 4	460
	11th to 20th	Day	30% 20% 30% 15% 5% 1	460
	21st to end	Day	28% 20% 30% 15% 5% 2	506
April	1st to 10th	Day	28% 18% 29% 18% 6% 1	460
	11th to 20th	Day	21% 21% 25% 19% 10% 4	452
	21st to end	Day	29% 15% 32% 15% 7% 2	460
May	1st to 10th	Day	30% 14% 30% 13% 11% 3	463
	11th to 20th	Day	25% 14% 27% 17% 13% 4	487
	21st to end	Day	19% 8% 26% 24% 16% 6%	529
June	1st to 10th	Day	19% 13% 26% 26% 12% 4	490
	11th to 20th	Day	20% 8% 24% 29% 15% 4	490
	21st to end	Day	16% 9% 30% 27% 14% 4	490
July	1st to 10th	Day	14% 6% 25% 27% 18% 10%	485
	11th to 20th	Day	9% 5% 29% 30% 20% 8%	484
	21st to end	Day	14% 6% 27% 30% 18% 5%	532
August	1st to 10th	Day	13% 6% 24% 27% 20% 9%	486
	11th to 20th	Day	13% 6% 23% 27% 19% 11%	479
	21st to end	Day	16% 5% 23% 28% 16% 13%	539
September	1st to 10th	Day	19% 6% 19% 28% 19% 9%	490
	11th to 20th	Day	16% 3 18% 28% 23% 11%	490
	21st to end	Day	29% 8% 22% 21% 14% 6%	490
October	1st to 10th	Day	22% 9% 20% 25% 19% 6%	490
	11th to 20th	Day	21% 14% 29% 23% 11% 2	490
	21st to end	Day	23% 13% 32% 24% 7% 1	539
November	1st to 10th	Day	18% 15% 29% 24% 13% 2	411
	11th to 20th	Day	25% 21% 29% 16% 8%	224
	21st to end	Day	24% 17% 38% 18% 2 1	180
December	1st to 10th	Day	32% 19% 34% 9% 5% 1	180
	11th to 20th	Day	27% 22% 31% 18% 2	180
	21st to end	Day	29% 18% 30% 17% 6%	198
January	1st to 10th	Night	24% 19% 33% 20% 4	760
	11th to 20th	Night	29% 14% 31% 23% 3	760
	21st to end	Night	23% 18% 33% 23% 3	836
February	1st to 10th	Night	26% 17% 29% 26% 2	760
	11th to 20th	Night	28% 21% 32% 18% 1	743
	21st to end	Night	28% 16% 32% 21% 2	628
March	1st to 10th	Night	25% 15% 33% 25% 3	760
	11th to 20th	Night	26% 16% 29% 23% 5% 1	760
	21st to end	Night	23% 15% 32% 22% 6%	836
April	1st to 10th	Night	26% 16% 30% 23% 5%	760
	11th to 20th	Night	21% 13% 32% 26% 7% 1	751
	21st to end	Night	22% 12% 28% 31% 7%	694
May	1st to 10th	Night	25% 7% 24% 32% 11% 1	570
	11th to 20th	Night	20% 7% 27% 35% 10%	422
	21st to end	Night	13% 6% 21% 37% 20% 2	411
June	1st to 10th	Night	14% 6% 20% 40% 19% 1	380
	11th to 20th	Night	15% 5% 22% 39% 19% 1	380
	21st to end	Night	12% 6% 22% 44% 17% 1	380
July	1st to 10th	Night	12% 6% 15% 44% 19% 4	370
	11th to 20th	Night	8% 2 16% 43% 28% 2	402
	21st to end	Night	11% 3 17% 45% 24% 1	624
August	1st to 10th	Night	10% 2 14% 43% 30% 2	567
	11th to 20th	Night	15% 5% 10% 39% 26% 5%	564
	21st to end	Night	14% 4 16% 34% 30% 3	831
September	1st to 10th	Night	18% 4 16% 35% 24% 4	760
	11th to 20th	Night	15% 4 15% 32% 29% 5%	760
	21st to end	Night	22% 8% 18% 30% 20% 3	760
October	1st to 10th	Night	20% 7% 20% 29% 21% 3	760
	11th to 20th	Night	20% 13% 24% 31% 11% 1	760
	21st to end	Night	24% 12% 23% 32% 8% 1	836
November	1st to 10th	Night	17% 11% 27% 33% 12% 1	748
	11th to 20th	Night	23% 17% 24% 26% 8% 1	760
	21st to end	Night	24% 15% 28% 28% 5% 1	760
December	1st to 10th	Night	29% 15% 30% 21% 5%	760
	11th to 20th	Night	26% 16% 29% 26% 4	760
	21st to end	Night	26% 15% 29% 27% 2	836

Page generated at 2024-10-30 13:19:23. Version ac07

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