Payne's Starfield Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Payne's Starfield Observatory clear sky chart from 2005-11-06 to 2024-01-27.

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	15% 10% 4 7% 6% 3 5% 5% 5% 7% 32%	75153
	Night	15% 10% 4 7% 6% 3 5% 5% 5% 7% 34%	74850
Transparency	Day	51% 6% 11% 19% 11% 1	74876
	Night	49% 6% 11% 20% 12% 2	74648
Seeing	Day	20% 14% 27% 20% 13% 5%	13996
	Night	19% 12% 28% 27% 13% 2	23938

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	17% 15% 8% 10% 9% 4 5% 5% 4 5% 18%	1706
	11th to 20th	Day	17% 18% 9% 11% 8% 5% 4 3 4 4 16%	1710
	21st to end	Day	17% 17% 9% 11% 9% 4 5% 4 4 5% 16%	1836
February	1st to 10th	Day	19% 17% 5% 10% 9% 4 4 4 4 4 21%	1620
	11th to 20th	Day	16% 13% 6% 14% 7% 3 4 4 4 7% 22%	1696
	21st to end	Day	18% 15% 5% 9% 6% 3 4 4 4 5% 28%	1480
March	1st to 10th	Day	18% 11% 6% 7% 6% 4 4 5% 5% 6% 28%	1890
	11th to 20th	Day	17% 13% 5% 9% 6% 3 4 4 5% 7% 28%	1980
	21st to end	Day	24% 10% 4 7% 7% 3 4 4 4 6% 27%	2178
April	1st to 10th	Day	14% 12% 5% 7% 7% 3 4 4 5% 7% 32%	2006
	11th to 20th	Day	17% 11% 4 7% 6% 3 4 4 5% 7% 35%	2291
	21st to end	Day	19% 8% 4 7% 6% 3 5% 5% 4 7% 32%	2340
May	1st to 10th	Day	18% 9% 3 6% 6% 3 6% 4 6% 7% 30%	2340
	11th to 20th	Day	21% 8% 3 6% 6% 3 5% 4 6% 8% 30%	2301
	21st to end	Day	10% 6% 2 6% 6% 4 6% 7% 7% 9% 36%	2531
June	1st to 10th	Day	12% 6% 3 6% 6% 4 6% 5% 6% 9% 36%	2340
	11th to 20th	Day	11% 7% 2 7% 6% 4 6% 7% 6% 9% 36%	2352
	21st to end	Day	11% 4 3 5% 6% 4 5% 7% 8% 10% 37%	2520
July	1st to 10th	Day	11% 6% 3 5% 6% 4 6% 5% 6% 11% 37%	2448
	11th to 20th	Day	10% 5% 2 5% 6% 3 5% 6% 7% 10% 41%	2340
	21st to end	Day	10% 6% 3 6% 5% 4 5% 7% 7% 10% 37%	2547
August	1st to 10th	Day	9% 5% 3 5% 6% 4 6% 6% 8% 10% 38%	2327
	11th to 20th	Day	10% 6% 3 5% 7% 4 6% 6% 8% 9% 37%	2303
	21st to end	Day	9% 5% 2 6% 6% 4 6% 6% 7% 10% 40%	2566
September	1st to 10th	Day	14% 6% 2 5% 5% 3 5% 4 5% 8% 44%	1980
	11th to 20th	Day	10% 6% 3 5% 6% 3 4 5% 6% 10% 43%	1980
	21st to end	Day	18% 6% 2 5% 5% 3 4 4 5% 6% 42%	1980
October	1st to 10th	Day	14% 7% 2 6% 6% 3 4 4 5% 8% 40%	1910
	11th to 20th	Day	15% 9% 3 5% 5% 3 5% 5% 6% 7% 38%	1800
	21st to end	Day	20% 10% 4 7% 6% 2 4 4 5% 7% 31%	1935
November	1st to 10th	Day	10% 8% 3 5% 6% 3 4 4 5% 7% 44%	1672
	11th to 20th	Day	17% 12% 5% 7% 5% 4 4 4 4 5% 33%	1710
	21st to end	Day	19% 13% 6% 9% 5% 3 4 4 3 5% 28%	1710
December	1st to 10th	Day	18% 17% 8% 11% 8% 3 4 4 4 5% 19%	1575
	11th to 20th	Day	18% 15% 7% 11% 8% 3 4 5% 4 5% 21%	2129
	21st to end	Day	24% 23% 9% 9% 6% 3 4 3 3 4 12%	3124
January	1st to 10th	Night	16% 15% 7% 10% 8% 3 6% 4 4 4 22%	2459
	11th to 20th	Night	18% 16% 7% 12% 7% 4 4 4 4 4 20%	2470
	21st to end	Night	16% 16% 7% 11% 8% 4 5% 5% 4 5% 21%	2664
February	1st to 10th	Night	20% 13% 5% 10% 7% 4 5% 4 4 5% 23%	2340
	11th to 20th	Night	16% 12% 5% 10% 8% 4 5% 5% 5% 5% 26%	2147
	21st to end	Night	19% 13% 6% 9% 6% 4 4 4 5% 4 25%	1776
March	1st to 10th	Night	16% 11% 5% 8% 6% 4 4 5% 4 6% 32%	2070
	11th to 20th	Night	14% 9% 4 6% 5% 3 5% 4 5% 8% 36%	1980
	21st to end	Night	19% 9% 4 8% 6% 3 4 4 5% 6% 33%	2178
April	1st to 10th	Night	15% 9% 3 5% 6% 3 5% 6% 5% 7% 36%	1968
	11th to 20th	Night	15% 7% 4 6% 5% 4 5% 4 6% 7% 36%	1616
	21st to end	Night	15% 7% 4 6% 6% 4 5% 4 5% 8% 36%	1620
May	1st to 10th	Night	16% 10% 3 6% 7% 4 5% 5% 6% 7% 31%	1620
	11th to 20th	Night	18% 8% 3 7% 5% 2 4 4 6% 8% 37%	1592
	21st to end	Night	7% 5% 3 4 5% 2 6% 7% 8% 11% 41%	1744
June	1st to 10th	Night	9% 6% 2 5% 5% 4 5% 5% 5% 8% 46%	1620
	11th to 20th	Night	8% 5% 2 4 6% 3 5% 6% 6% 11% 42%	1598
	21st to end	Night	9% 3 3 5% 5% 2 5% 5% 6% 11% 44%	1440
July	1st to 10th	Night	8% 5% 3 6% 5% 3 5% 4 6% 8% 46%	1502
	11th to 20th	Night	7% 3 3 5% 4 3 5% 6% 7% 11% 47%	1620
	21st to end	Night	8% 5% 3 5% 5% 3 6% 5% 6% 8% 44%	1771
August	1st to 10th	Night	5% 5% 2 6% 5% 3 6% 6% 8% 10% 44%	1611
	11th to 20th	Night	7% 6% 3 7% 5% 4 4 5% 7% 8% 45%	1598
	21st to end	Night	7% 4 2 3 4 3 5% 6% 7% 8% 51%	1782
September	1st to 10th	Night	12% 5% 3 4 4 3 5% 4 5% 6% 49%	1964
	11th to 20th	Night	9% 4 2 4 4 3 3 4 5% 8% 55%	1980
	21st to end	Night	13% 6% 2 4 5% 2 3 4 6% 7% 46%	1980
October	1st to 10th	Night	11% 5% 3 5% 5% 3 4 5% 5% 7% 47%	2049
	11th to 20th	Night	16% 8% 3 6% 6% 4 4 4 4 7% 40%	2160
	21st to end	Night	21% 8% 3 5% 6% 3 5% 4 4 7% 34%	2420
November	1st to 10th	Night	13% 7% 3 5% 6% 4 4 4 5% 6% 44%	2406
	11th to 20th	Night	16% 10% 5% 7% 5% 3 4 4 5% 6% 34%	2470
	21st to end	Night	18% 12% 4 8% 6% 3 4 5% 5% 6% 28%	2470
December	1st to 10th	Night	20% 14% 7% 10% 7% 4 5% 4 4 6% 21%	2586
	11th to 20th	Night	17% 12% 7% 10% 6% 3 4 4 6% 6% 25%	3047
	21st to end	Night	22% 19% 9% 9% 6% 3 4 4 4 4 15%	4532

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	68% 5% 9% 13% 5%	1707
	11th to 20th	Day	72% 4 11% 10% 3	1710
	21st to end	Day	72% 5% 7% 11% 4 1	1836
February	1st to 10th	Day	68% 5% 9% 12% 6% 1	1620
	11th to 20th	Day	63% 6% 9% 14% 8% 1	1706
	21st to end	Day	59% 4 11% 17% 7% 2	1480
March	1st to 10th	Day	57% 5% 11% 20% 7% 1	1890
	11th to 20th	Day	57% 5% 10% 17% 9% 2	1980
	21st to end	Day	59% 4 9% 20% 7% 1	2178
April	1st to 10th	Day	52% 5% 13% 17% 12% 1	2006
	11th to 20th	Day	51% 5% 12% 16% 14% 2	2291
	21st to end	Day	52% 6% 10% 19% 11% 2	2340
May	1st to 10th	Day	51% 7% 13% 18% 9% 1	2340
	11th to 20th	Day	51% 8% 12% 16% 11% 1	2305
	21st to end	Day	42% 9% 14% 22% 12% 1	2531
June	1st to 10th	Day	42% 8% 12% 23% 14% 1	2340
	11th to 20th	Day	43% 10% 13% 21% 12% 1	2352
	21st to end	Day	40% 9% 14% 21% 14% 2	2520
July	1st to 10th	Day	41% 10% 12% 21% 14% 2	2383
	11th to 20th	Day	37% 8% 14% 25% 15% 2	2271
	21st to end	Day	38% 9% 15% 23% 12% 2	2405
August	1st to 10th	Day	38% 9% 16% 23% 13% 1	2314
	11th to 20th	Day	40% 10% 14% 25% 11% 2	2303
	21st to end	Day	38% 8% 13% 22% 15% 5%	2566
September	1st to 10th	Day	39% 6% 12% 21% 18% 3	1980
	11th to 20th	Day	37% 6% 13% 25% 16% 3	1980
	21st to end	Day	42% 5% 10% 21% 20% 1	1980
October	1st to 10th	Day	43% 6% 10% 23% 17% 1	1910
	11th to 20th	Day	44% 5% 13% 22% 14% 2	1800
	21st to end	Day	53% 5% 13% 19% 9% 2	1935
November	1st to 10th	Day	39% 6% 12% 25% 16% 2	1672
	11th to 20th	Day	53% 4 9% 20% 10% 2	1710
	21st to end	Day	59% 4 10% 17% 9% 1	1710
December	1st to 10th	Day	68% 6% 8% 14% 3 1	1575
	11th to 20th	Day	65% 5% 8% 16% 5%	2126
	21st to end	Day	78% 4 8% 6% 3	3124
January	1st to 10th	Night	65% 5% 8% 16% 7%	2459
	11th to 20th	Night	68% 4 11% 11% 4	2470
	21st to end	Night	66% 5% 9% 14% 5% 1	2664
February	1st to 10th	Night	64% 5% 10% 14% 6% 1	2340
	11th to 20th	Night	60% 5% 10% 16% 8% 1	2148
	21st to end	Night	62% 5% 9% 13% 9% 2	1776
March	1st to 10th	Night	52% 6% 11% 19% 11% 1	2070
	11th to 20th	Night	47% 5% 12% 23% 10% 3	1980
	21st to end	Night	52% 6% 9% 20% 12% 2	2178
April	1st to 10th	Night	47% 6% 13% 19% 14% 2	1968
	11th to 20th	Night	46% 5% 12% 16% 17% 3	1616
	21st to end	Night	45% 7% 12% 19% 15% 2	1620
May	1st to 10th	Night	51% 7% 10% 18% 11% 3	1620
	11th to 20th	Night	46% 6% 11% 20% 15% 3	1593
	21st to end	Night	34% 10% 16% 24% 14% 2	1745
June	1st to 10th	Night	36% 7% 13% 23% 17% 2	1620
	11th to 20th	Night	34% 9% 15% 24% 17% 2	1598
	21st to end	Night	33% 9% 13% 25% 17% 3	1440
July	1st to 10th	Night	35% 8% 12% 22% 18% 5%	1459
	11th to 20th	Night	29% 9% 15% 27% 19% 2	1566
	21st to end	Night	33% 8% 14% 26% 15% 3	1672
August	1st to 10th	Night	31% 9% 16% 25% 17% 1	1600
	11th to 20th	Night	35% 8% 15% 24% 17% 1	1598
	21st to end	Night	26% 10% 15% 24% 20% 4	1782
September	1st to 10th	Night	34% 7% 12% 23% 18% 6%	1964
	11th to 20th	Night	29% 4 12% 28% 25% 2	1980
	21st to end	Night	37% 7% 11% 21% 23% 2	1980
October	1st to 10th	Night	35% 6% 12% 25% 20% 2	2049
	11th to 20th	Night	45% 6% 9% 25% 15% 1	2160
	21st to end	Night	51% 5% 9% 21% 12% 2	2420
November	1st to 10th	Night	41% 4 12% 22% 18% 3	2406
	11th to 20th	Night	51% 5% 9% 20% 13% 2	2470
	21st to end	Night	56% 5% 11% 19% 7% 1	2470
December	1st to 10th	Night	65% 5% 9% 15% 5% 1	2586
	11th to 20th	Night	60% 5% 11% 19% 5%	3049
	21st to end	Night	73% 5% 9% 10% 3	4532

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% 27% 31% 9% 6%	270
	11th to 20th	Day	30% 25% 36% 7% 2	270
	21st to end	Day	30% 27% 28% 12% 2	282
February	1st to 10th	Day	38% 24% 26% 11% 1	240
	11th to 20th	Day	31% 33% 27% 9%	240
	21st to end	Day	31% 37% 27% 5% 1	198
March	1st to 10th	Day	26% 25% 33% 14% 2	330
	11th to 20th	Day	28% 20% 33% 13% 5%	420
	21st to end	Day	32% 18% 29% 17% 4	462
April	1st to 10th	Day	24% 20% 30% 17% 9% 1	420
	11th to 20th	Day	24% 20% 27% 16% 8% 4	412
	21st to end	Day	26% 18% 33% 15% 6% 2	420
May	1st to 10th	Day	25% 17% 31% 16% 7% 4	423
	11th to 20th	Day	24% 11% 30% 20% 11% 4	447
	21st to end	Day	14% 9% 25% 26% 20% 7%	485
June	1st to 10th	Day	13% 7% 30% 31% 15% 5%	450
	11th to 20th	Day	15% 9% 26% 26% 19% 4	462
	21st to end	Day	13% 9% 30% 28% 15% 4	630
July	1st to 10th	Day	14% 4 18% 26% 23% 14%	553
	11th to 20th	Day	11% 4 25% 28% 22% 11%	444
	21st to end	Day	12% 4 22% 29% 24% 10%	488
August	1st to 10th	Day	13% 3 17% 28% 24% 14%	446
	11th to 20th	Day	14% 5% 24% 26% 20% 11%	439
	21st to end	Day	10% 6% 20% 29% 23% 11%	495
September	1st to 10th	Day	14% 5% 22% 24% 25% 10%	450
	11th to 20th	Day	12% 4 16% 27% 28% 13%	450
	21st to end	Day	21% 9% 21% 25% 16% 7%	450
October	1st to 10th	Day	12% 11% 28% 24% 18% 6%	450
	11th to 20th	Day	18% 19% 30% 22% 10% 2	450
	21st to end	Day	26% 20% 30% 19% 4 1	450
November	1st to 10th	Day	14% 25% 35% 15% 9% 2	270
	11th to 20th	Day	28% 19% 30% 15% 8% 1	270
	21st to end	Day	26% 25% 38% 10% 2	270
December	1st to 10th	Day	29% 29% 26% 11% 4 2	205
	11th to 20th	Day	24% 26% 36% 11% 3	258
	21st to end	Day	34% 20% 33% 11% 2	297
January	1st to 10th	Night	25% 22% 34% 16% 3	760
	11th to 20th	Night	27% 21% 33% 16% 3	760
	21st to end	Night	23% 21% 34% 19% 3	820
February	1st to 10th	Night	28% 16% 37% 18% 2	720
	11th to 20th	Night	24% 20% 36% 18% 2	703
	21st to end	Night	29% 17% 36% 16% 2	592
March	1st to 10th	Night	23% 17% 34% 22% 4	720
	11th to 20th	Night	20% 17% 35% 21% 7% 1	720
	21st to end	Night	25% 13% 31% 25% 6% 1	792
April	1st to 10th	Night	19% 16% 36% 23% 6%	708
	11th to 20th	Night	20% 13% 33% 23% 9% 2	533
	21st to end	Night	20% 10% 38% 24% 7% 1	540
May	1st to 10th	Night	21% 10% 31% 29% 9% 1	540
	11th to 20th	Night	21% 6% 28% 30% 13% 2	531
	21st to end	Night	10% 4 23% 36% 24% 3	584
June	1st to 10th	Night	11% 3 26% 41% 18% 1	540
	11th to 20th	Night	12% 4 21% 42% 18% 2	540
	21st to end	Night	11% 5% 24% 38% 21% 2	540
July	1st to 10th	Night	10% 3 16% 40% 24% 7%	525
	11th to 20th	Night	7% 3 19% 37% 29% 5%	522
	21st to end	Night	9% 4 17% 38% 30% 2	591
August	1st to 10th	Night	8% 2 14% 44% 27% 5%	537
	11th to 20th	Night	9% 3 15% 39% 29% 5%	534
	21st to end	Night	7% 2 17% 34% 32% 6%	594
September	1st to 10th	Night	14% 4 20% 30% 27% 5%	704
	11th to 20th	Night	12% 3 14% 37% 30% 5%	720
	21st to end	Night	17% 6% 23% 29% 20% 4	720
October	1st to 10th	Night	13% 7% 27% 30% 20% 3	720
	11th to 20th	Night	20% 12% 32% 25% 11%	720
	21st to end	Night	25% 15% 29% 23% 8%	792
November	1st to 10th	Night	17% 13% 31% 25% 13% 1	740
	11th to 20th	Night	22% 16% 31% 23% 8% 1	760
	21st to end	Night	24% 17% 29% 22% 6% 1	760
December	1st to 10th	Night	28% 17% 32% 18% 4	760
	11th to 20th	Night	25% 17% 35% 20% 4	760
	21st to end	Night	28% 17% 33% 19% 3	836

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