Starlifter Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starlifter Observatory clear sky chart from 2005-11-06 to 2024-08-15.

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	16% 11% 4 10% 6% 5% 5% 4 5% 6% 27%	95549
	Night	16% 12% 4 11% 7% 5% 5% 4 5% 5% 26%	93166
Transparency	Day	55% 8% 11% 17% 8% 1	95268
	Night	58% 8% 11% 15% 8% 1	93001
Seeing	Day	24% 19% 29% 18% 8% 2	14417
	Night	22% 16% 26% 25% 9% 1	23304

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	12% 14% 8% 20% 10% 6% 4 3 4 4 15%	2517
	11th to 20th	Day	12% 15% 6% 20% 10% 6% 5% 3 4 4 14%	2520
	21st to end	Day	12% 19% 9% 13% 6% 8% 5% 3 4 4 16%	2772
February	1st to 10th	Day	12% 14% 6% 13% 11% 7% 5% 3 5% 5% 19%	1636
	11th to 20th	Day	9% 15% 7% 16% 10% 7% 6% 4 4 4 18%	1838
	21st to end	Day	12% 14% 5% 14% 9% 6% 4 5% 5% 5% 21%	1570
March	1st to 10th	Day	20% 16% 5% 12% 7% 5% 4 4 3 4 20%	3116
	11th to 20th	Day	13% 17% 7% 13% 7% 4 4 3 4 5% 22%	3243
	21st to end	Day	16% 13% 5% 13% 5% 4 3 3 3 4 31%	4166
April	1st to 10th	Day	18% 16% 5% 9% 5% 5% 3 3 4 6% 26%	2280
	11th to 20th	Day	17% 12% 4 7% 5% 5% 4 3 5% 6% 32%	2254
	21st to end	Day	22% 11% 3 8% 5% 4 4 3 5% 6% 27%	2467
May	1st to 10th	Day	23% 12% 3 8% 5% 5% 4 3 5% 5% 26%	4188
	11th to 20th	Day	16% 9% 3 9% 7% 6% 5% 4 6% 7% 28%	4398
	21st to end	Day	14% 6% 3 7% 5% 5% 5% 5% 7% 9% 34%	4837
June	1st to 10th	Day	24% 7% 3 7% 5% 5% 5% 4 6% 7% 27%	2660
	11th to 20th	Day	16% 8% 3 6% 5% 4 6% 4 6% 9% 33%	2660
	21st to end	Day	20% 9% 3 8% 6% 5% 5% 4 6% 7% 27%	2660
July	1st to 10th	Day	12% 8% 3 6% 6% 6% 5% 5% 7% 10% 32%	4440
	11th to 20th	Day	11% 6% 3 8% 6% 5% 7% 5% 8% 11% 31%	4440
	21st to end	Day	14% 8% 2 7% 5% 5% 6% 5% 6% 8% 35%	4814
August	1st to 10th	Day	15% 8% 2 7% 5% 5% 6% 5% 7% 8% 31%	2634
	11th to 20th	Day	13% 7% 3 8% 6% 5% 6% 4 7% 9% 33%	2316
	21st to end	Day	14% 7% 3 7% 5% 5% 5% 4 7% 9% 35%	2376
September	1st to 10th	Day	15% 7% 3 6% 4 4 4 4 7% 8% 40%	2160
	11th to 20th	Day	16% 8% 2 5% 3 3 3 4 4 8% 44%	2037
	21st to end	Day	15% 8% 2 7% 5% 5% 4 4 5% 8% 36%	1980
October	1st to 10th	Day	22% 11% 3 8% 4 4 4 4 5% 6% 28%	1935
	11th to 20th	Day	15% 12% 3 9% 5% 5% 5% 4 6% 6% 30%	1725
	21st to end	Day	21% 21% 5% 7% 4 4 5% 3 4 3 23%	1782
November	1st to 10th	Day	14% 15% 4 8% 7% 4 5% 4 5% 6% 28%	1671
	11th to 20th	Day	15% 16% 6% 12% 5% 5% 5% 3 4 5% 22%	1710
	21st to end	Day	16% 15% 6% 13% 5% 4 4 4 6% 6% 21%	1549
December	1st to 10th	Day	16% 20% 8% 15% 7% 5% 4 2 4 4 15%	1520
	11th to 20th	Day	18% 16% 7% 10% 6% 5% 4 2 5% 5% 22%	1906
	21st to end	Day	20% 15% 7% 16% 7% 6% 5% 3 3 3 15%	2772
January	1st to 10th	Night	13% 15% 6% 21% 9% 6% 5% 3 5% 4 13%	4429
	11th to 20th	Night	10% 14% 6% 20% 13% 7% 5% 3 4 4 13%	4440
	21st to end	Night	14% 19% 8% 15% 6% 6% 4 4 4 3 16%	4884
February	1st to 10th	Night	11% 14% 5% 15% 12% 7% 6% 4 4 5% 18%	2542
	11th to 20th	Night	9% 13% 6% 14% 10% 8% 6% 4 5% 5% 20%	2226
	21st to end	Night	11% 14% 4 14% 8% 7% 5% 3 5% 6% 24%	1884
March	1st to 10th	Night	19% 16% 4 9% 6% 5% 4 3 4 5% 24%	3724
	11th to 20th	Night	13% 17% 6% 11% 6% 5% 4 3 3 4 27%	3698
	21st to end	Night	14% 16% 5% 13% 7% 4 4 2 3 3 29%	3466
April	1st to 10th	Night	18% 14% 4 9% 5% 5% 4 4 5% 5% 27%	1900
	11th to 20th	Night	18% 12% 2 7% 7% 6% 4 3 5% 5% 32%	1875
	21st to end	Night	19% 11% 3 7% 5% 4 5% 3 5% 7% 31%	1711
May	1st to 10th	Night	24% 13% 3 7% 4 4 4 4 4 6% 28%	2781
	11th to 20th	Night	19% 8% 3 9% 5% 4 4 4 5% 6% 32%	2495
	21st to end	Night	15% 7% 2 7% 5% 4 5% 4 6% 8% 37%	2738
June	1st to 10th	Night	23% 8% 3 7% 5% 4 5% 3 5% 8% 30%	1520
	11th to 20th	Night	16% 6% 2 6% 5% 6% 4 4 6% 8% 36%	1520
	21st to end	Night	21% 7% 3 6% 5% 5% 5% 4 6% 8% 32%	1520
July	1st to 10th	Night	12% 7% 3 8% 5% 5% 7% 5% 6% 7% 33%	2520
	11th to 20th	Night	14% 7% 2 8% 5% 5% 5% 5% 6% 7% 36%	2520
	21st to end	Night	13% 7% 3 7% 5% 5% 6% 4 6% 6% 37%	2739
August	1st to 10th	Night	13% 6% 2 6% 5% 5% 4 5% 6% 9% 40%	1512
	11th to 20th	Night	13% 6% 3 7% 5% 4 4 3 5% 7% 42%	1673
	21st to end	Night	15% 6% 3 6% 4 4 4 4 5% 8% 40%	1980
September	1st to 10th	Night	13% 6% 2 6% 4 4 6% 4 5% 7% 43%	1800
	11th to 20th	Night	15% 7% 2 5% 3 3 3 3 4 7% 46%	1922
	21st to end	Night	17% 7% 2 5% 5% 4 4 4 4 7% 42%	1980
October	1st to 10th	Night	21% 9% 3 7% 4 5% 5% 3 5% 6% 32%	2024
	11th to 20th	Night	17% 12% 3 9% 5% 5% 5% 4 5% 6% 30%	2234
	21st to end	Night	22% 15% 3 8% 6% 5% 6% 3 5% 6% 22%	2574
November	1st to 10th	Night	15% 14% 3 9% 5% 5% 5% 4 5% 5% 30%	2407
	11th to 20th	Night	15% 14% 6% 12% 6% 4 4 3 5% 5% 27%	2470
	21st to end	Night	15% 14% 7% 14% 7% 6% 4 3 5% 5% 21%	2626
December	1st to 10th	Night	17% 19% 8% 13% 9% 5% 5% 4 4 4 12%	2660
	11th to 20th	Night	18% 17% 7% 15% 7% 5% 4 3 4 3 16%	3288
	21st to end	Night	20% 15% 5% 18% 7% 5% 4 3 3 4 15%	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	72% 6% 10% 10% 2	2518
	11th to 20th	Day	72% 7% 8% 9% 4 1	2520
	21st to end	Day	71% 6% 10% 8% 4 1	2772
February	1st to 10th	Day	65% 8% 7% 12% 6% 1	1636
	11th to 20th	Day	69% 5% 8% 12% 5% 1	1847
	21st to end	Day	63% 7% 9% 11% 8% 2	1570
March	1st to 10th	Day	68% 6% 8% 9% 7% 1	3119
	11th to 20th	Day	65% 5% 10% 10% 9% 2	3243
	21st to end	Day	58% 4 6% 15% 16% 2	4166
April	1st to 10th	Day	60% 5% 8% 17% 9% 2	2280
	11th to 20th	Day	54% 6% 9% 18% 12% 1	2254
	21st to end	Day	58% 7% 9% 15% 9% 2	2467
May	1st to 10th	Day	60% 6% 9% 18% 6% 1	4202
	11th to 20th	Day	53% 9% 14% 15% 7% 1	4402
	21st to end	Day	43% 10% 12% 25% 9% 1	4837
June	1st to 10th	Day	55% 8% 11% 17% 9%	2660
	11th to 20th	Day	47% 8% 12% 21% 12% 1	2660
	21st to end	Day	55% 8% 11% 18% 8% 1	2660
July	1st to 10th	Day	41% 10% 15% 23% 10%	4370
	11th to 20th	Day	41% 11% 17% 27% 5%	4365
	21st to end	Day	44% 9% 11% 27% 9%	4661
August	1st to 10th	Day	46% 10% 16% 20% 7%	2620
	11th to 20th	Day	45% 8% 17% 21% 8%	2316
	21st to end	Day	43% 9% 14% 22% 12% 1	2376
September	1st to 10th	Day	40% 8% 13% 27% 12% 1	2160
	11th to 20th	Day	40% 6% 10% 28% 15% 1	2037
	21st to end	Day	45% 9% 13% 21% 10% 2	1980
October	1st to 10th	Day	57% 6% 10% 18% 9%	1935
	11th to 20th	Day	52% 9% 15% 17% 7%	1725
	21st to end	Day	66% 6% 8% 12% 6% 2	1782
November	1st to 10th	Day	54% 9% 12% 17% 8%	1671
	11th to 20th	Day	63% 7% 9% 11% 7% 2	1710
	21st to end	Day	62% 8% 13% 12% 3 1	1549
December	1st to 10th	Day	73% 7% 8% 9% 3	1520
	11th to 20th	Day	65% 6% 9% 14% 6%	1906
	21st to end	Day	74% 5% 7% 9% 4	2772
January	1st to 10th	Night	71% 8% 12% 6% 2	4429
	11th to 20th	Night	73% 7% 10% 7% 3	4440
	21st to end	Night	72% 5% 9% 8% 4 1	4884
February	1st to 10th	Night	67% 8% 8% 10% 5%	2542
	11th to 20th	Night	65% 7% 8% 13% 7%	2228
	21st to end	Night	61% 7% 9% 14% 8% 1	1884
March	1st to 10th	Night	62% 5% 10% 13% 8% 1	3734
	11th to 20th	Night	61% 6% 7% 14% 10% 1	3699
	21st to end	Night	60% 5% 5% 14% 13% 1	3466
April	1st to 10th	Night	58% 6% 10% 15% 10% 1	1900
	11th to 20th	Night	53% 7% 9% 19% 12%	1875
	21st to end	Night	53% 8% 9% 15% 13% 3	1711
May	1st to 10th	Night	57% 7% 9% 18% 8% 1	2787
	11th to 20th	Night	50% 10% 13% 17% 9% 1	2496
	21st to end	Night	42% 10% 14% 19% 15% 1	2739
June	1st to 10th	Night	53% 8% 10% 21% 8% 1	1520
	11th to 20th	Night	44% 8% 15% 20% 10% 2	1520
	21st to end	Night	48% 11% 13% 19% 8%	1520
July	1st to 10th	Night	45% 10% 16% 18% 11%	2480
	11th to 20th	Night	41% 11% 13% 26% 8%	2472
	21st to end	Night	43% 11% 13% 23% 10%	2651
August	1st to 10th	Night	39% 10% 17% 26% 7%	1502
	11th to 20th	Night	41% 9% 16% 22% 11%	1673
	21st to end	Night	40% 10% 14% 24% 12%	1980
September	1st to 10th	Night	39% 9% 14% 27% 10% 1	1800
	11th to 20th	Night	39% 7% 12% 30% 12% 1	1922
	21st to end	Night	43% 7% 12% 24% 12% 2	1980
October	1st to 10th	Night	52% 7% 12% 19% 10%	2024
	11th to 20th	Night	54% 8% 13% 19% 6%	2234
	21st to end	Night	62% 7% 10% 12% 7% 1	2574
November	1st to 10th	Night	53% 9% 13% 16% 8% 1	2407
	11th to 20th	Night	59% 6% 10% 15% 7% 2	2470
	21st to end	Night	64% 8% 10% 13% 4	2626
December	1st to 10th	Night	75% 7% 8% 7% 2	2660
	11th to 20th	Night	72% 7% 7% 9% 5%	3288
	21st to end	Night	74% 7% 6% 10% 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	20% 27% 33% 16% 4	180
	11th to 20th	Day	29% 26% 29% 11% 3 1	180
	21st to end	Day	20% 27% 35% 13% 5%	198
February	1st to 10th	Day	32% 33% 25% 7% 2	236
	11th to 20th	Day	29% 24% 35% 10% 3	446
	21st to end	Day	30% 22% 31% 14% 3	382
March	1st to 10th	Day	31% 20% 30% 17% 3	460
	11th to 20th	Day	28% 27% 29% 13% 3	460
	21st to end	Day	31% 23% 25% 12% 8% 1	506
April	1st to 10th	Day	35% 18% 25% 15% 5% 1	460
	11th to 20th	Day	31% 26% 22% 14% 6% 2	452
	21st to end	Day	34% 19% 27% 12% 7% 1	460
May	1st to 10th	Day	31% 20% 27% 13% 6% 2	463
	11th to 20th	Day	18% 19% 34% 20% 6% 2	487
	21st to end	Day	20% 20% 32% 20% 7% 1	529
June	1st to 10th	Day	26% 17% 32% 16% 8% 1	490
	11th to 20th	Day	21% 16% 30% 22% 10% 2	490
	21st to end	Day	23% 20% 32% 17% 7% 1	490
July	1st to 10th	Day	17% 14% 32% 24% 11% 2	485
	11th to 20th	Day	14% 12% 36% 25% 11% 2	484
	21st to end	Day	17% 12% 35% 25% 10% 2	532
August	1st to 10th	Day	16% 12% 29% 28% 12% 3	486
	11th to 20th	Day	16% 13% 29% 24% 13% 6%	456
	21st to end	Day	16% 17% 28% 23% 12% 5%	495
September	1st to 10th	Day	16% 15% 29% 20% 16% 6%	450
	11th to 20th	Day	20% 13% 24% 19% 16% 8%	450
	21st to end	Day	16% 15% 29% 22% 12% 6%	450
October	1st to 10th	Day	28% 14% 23% 18% 13% 4	450
	11th to 20th	Day	23% 22% 25% 21% 8% 1	412
	21st to end	Day	36% 20% 22% 18% 5%	396
November	1st to 10th	Day	27% 18% 24% 22% 8% 1	365
	11th to 20th	Day	28% 25% 25% 14% 7% 1	370
	21st to end	Day	33% 15% 32% 18% 1 1	209
December	1st to 10th	Day	27% 22% 31% 15% 4	180
	11th to 20th	Day	31% 27% 29% 12% 2	180
	21st to end	Day	33% 23% 30% 12% 2 1	198
January	1st to 10th	Night	22% 24% 31% 19% 4	760
	11th to 20th	Night	25% 23% 29% 20% 4	760
	21st to end	Night	17% 22% 33% 24% 4 1	836
February	1st to 10th	Night	19% 21% 36% 21% 3	760
	11th to 20th	Night	22% 24% 31% 20% 3	743
	21st to end	Night	21% 21% 31% 23% 3	628
March	1st to 10th	Night	25% 18% 29% 24% 4	760
	11th to 20th	Night	24% 21% 26% 21% 6%	760
	21st to end	Night	25% 21% 25% 21% 7% 1	836
April	1st to 10th	Night	28% 18% 27% 21% 5%	760
	11th to 20th	Night	25% 19% 26% 22% 8% 1	751
	21st to end	Night	28% 15% 28% 22% 6%	571
May	1st to 10th	Night	27% 14% 27% 24% 8% 1	543
	11th to 20th	Night	18% 13% 30% 28% 8% 2	374
	21st to end	Night	17% 12% 23% 36% 11%	411
June	1st to 10th	Night	26% 9% 24% 28% 12% 1	380
	11th to 20th	Night	20% 7% 22% 34% 16% 1	380
	21st to end	Night	19% 10% 18% 39% 13% 1	380
July	1st to 10th	Night	15% 5% 24% 39% 16% 1	370
	11th to 20th	Night	12% 5% 21% 42% 19% 1	368
	21st to end	Night	14% 5% 20% 44% 16%	416
August	1st to 10th	Night	14% 7% 16% 42% 22%	378
	11th to 20th	Night	13% 8% 22% 32% 21% 3	579
	21st to end	Night	18% 6% 21% 33% 21% 2	792
September	1st to 10th	Night	15% 9% 23% 33% 18% 2	720
	11th to 20th	Night	18% 8% 20% 29% 21% 3	720
	21st to end	Night	19% 11% 25% 25% 18% 2	720
October	1st to 10th	Night	27% 12% 19% 26% 14% 2	720
	11th to 20th	Night	23% 17% 21% 27% 12% 1	720
	21st to end	Night	28% 19% 24% 23% 5%	792
November	1st to 10th	Night	23% 20% 24% 23% 9% 1	740
	11th to 20th	Night	24% 20% 27% 19% 8% 2	760
	21st to end	Night	27% 20% 27% 19% 7% 1	760
December	1st to 10th	Night	27% 23% 28% 19% 4	760
	11th to 20th	Night	27% 21% 26% 21% 5%	760
	21st to end	Night	28% 23% 26% 19% 3	836

Page generated at 2024-08-12 09:52:47. Version ac07

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