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 2026-06-01.

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	14% 10% 4 9% 5% 5% 5% 4 5% 7% 31%	132544
	Night	14% 11% 4 9% 5% 5% 5% 4 5% 7% 32%	130533
Transparency	Day	51% 6% 11% 20% 11% 1	136193
	Night	50% 5% 11% 20% 12% 2	134956
Seeing	Day	21% 15% 27% 20% 12% 5%	17142
	Night	19% 12% 28% 27% 12% 2	27017

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	16% 17% 8% 16% 7% 5% 5% 3 4 6% 13%	5258
	11th to 20th	Day	10% 19% 7% 16% 9% 7% 5% 3 3 4 16%	5280
	21st to end	Day	18% 15% 8% 12% 9% 6% 5% 3 4 4 15%	5780
February	1st to 10th	Day	17% 17% 4 11% 7% 5% 3 3 4 5% 23%	1890
	11th to 20th	Day	16% 13% 5% 15% 6% 4 4 3 4 7% 23%	1988
	21st to end	Day	16% 15% 4 11% 5% 3 4 3 5% 6% 28%	1730
March	1st to 10th	Day	17% 11% 8% 13% 5% 4 4 3 4 4 26%	4815
	11th to 20th	Day	11% 10% 4 10% 5% 4 4 3 4 6% 39%	5090
	21st to end	Day	19% 11% 4 10% 5% 5% 4 3 5% 5% 29%	5586
April	1st to 10th	Day	15% 13% 5% 8% 6% 5% 4 3 6% 6% 30%	2341
	11th to 20th	Day	15% 11% 3 8% 5% 4 3 3 5% 7% 35%	2678
	21st to end	Day	17% 9% 3 8% 6% 4 4 4 5% 7% 33%	2730
May	1st to 10th	Day	21% 10% 3 8% 5% 5% 5% 4 5% 5% 28%	5992
	11th to 20th	Day	19% 9% 3 7% 5% 4 5% 3 5% 8% 33%	5991
	21st to end	Day	17% 7% 2 6% 4 5% 5% 5% 7% 8% 33%	6576
June	1st to 10th	Day	12% 7% 2 8% 5% 5% 5% 5% 7% 9% 37%	2600
	11th to 20th	Day	11% 8% 2 7% 6% 5% 5% 5% 7% 8% 35%	2614
	21st to end	Day	11% 5% 2 6% 6% 5% 5% 5% 8% 9% 37%	2800
July	1st to 10th	Day	9% 6% 3 7% 5% 5% 5% 4 6% 10% 40%	6176
	11th to 20th	Day	10% 6% 2 7% 5% 5% 6% 5% 8% 11% 34%	5900
	21st to end	Day	10% 7% 3 7% 4 5% 5% 5% 7% 10% 37%	6424
August	1st to 10th	Day	9% 7% 3 7% 5% 5% 6% 4 7% 9% 38%	4234
	11th to 20th	Day	8% 6% 3 6% 5% 5% 6% 5% 8% 10% 37%	4174
	21st to end	Day	7% 5% 2 7% 5% 6% 6% 5% 7% 10% 41%	4639
September	1st to 10th	Day	13% 6% 2 5% 4 4 5% 3 5% 8% 47%	2200
	11th to 20th	Day	9% 6% 2 6% 5% 4 4 4 6% 10% 45%	2200
	21st to end	Day	20% 7% 2 5% 5% 4 4 3 4 6% 40%	2200
October	1st to 10th	Day	13% 7% 2 7% 4 4 4 4 5% 7% 44%	2122
	11th to 20th	Day	14% 9% 2 6% 4 5% 4 4 6% 7% 41%	2000
	21st to end	Day	19% 10% 4 8% 5% 4 4 3 5% 7% 32%	2149
November	1st to 10th	Day	11% 8% 2 6% 5% 4 4 4 6% 7% 43%	1852
	11th to 20th	Day	17% 12% 5% 7% 5% 4 4 4 4 5% 32%	1890
	21st to end	Day	18% 15% 6% 10% 5% 4 4 3 4 6% 26%	1890
December	1st to 10th	Day	17% 14% 6% 15% 6% 4 4 3 4 5% 22%	2766
	11th to 20th	Day	22% 16% 7% 11% 6% 4 3 3 4 4 20%	3424
	21st to end	Day	24% 22% 7% 11% 5% 4 4 2 3 3 14%	4565
January	1st to 10th	Night	13% 18% 7% 18% 8% 5% 5% 3 4 4 14%	7635
	11th to 20th	Night	10% 16% 9% 17% 7% 8% 7% 4 4 4 15%	7680
	21st to end	Night	17% 14% 6% 11% 6% 6% 5% 3 4 5% 23%	8401
February	1st to 10th	Night	18% 13% 4 11% 7% 5% 4 4 4 5% 24%	2730
	11th to 20th	Night	16% 12% 4 12% 7% 4 5% 4 5% 5% 25%	2515
	21st to end	Night	18% 14% 5% 11% 6% 5% 4 3 4 5% 26%	2076
March	1st to 10th	Night	19% 13% 5% 7% 5% 4 4 3 4 5% 32%	5244
	11th to 20th	Night	12% 8% 3 7% 4 4 4 4 6% 8% 40%	5090
	21st to end	Night	17% 9% 3 8% 5% 4 4 3 5% 6% 36%	5588
April	1st to 10th	Night	16% 11% 3 6% 5% 4 4 5% 5% 7% 34%	2295
	11th to 20th	Night	14% 8% 3 7% 5% 5% 5% 3 6% 7% 36%	1889
	21st to end	Night	14% 9% 3 7% 5% 5% 4 3 6% 8% 36%	1890
May	1st to 10th	Night	23% 12% 3 8% 5% 5% 5% 3 5% 6% 26%	4123
	11th to 20th	Night	17% 9% 3 7% 4 3 3 3 5% 9% 37%	4122
	21st to end	Night	13% 7% 2 6% 5% 5% 5% 4 6% 9% 38%	4520
June	1st to 10th	Night	9% 7% 2 6% 5% 6% 4 3 5% 8% 45%	1800
	11th to 20th	Night	9% 6% 2 5% 5% 4 6% 5% 6% 10% 42%	1774
	21st to end	Night	9% 4 2 7% 5% 4 5% 5% 7% 10% 43%	1600
July	1st to 10th	Night	9% 6% 2 6% 4 4 5% 4 6% 9% 44%	3784
	11th to 20th	Night	9% 5% 2 7% 5% 5% 5% 5% 7% 10% 41%	4057
	21st to end	Night	8% 6% 3 6% 4 5% 5% 5% 6% 9% 43%	4427
August	1st to 10th	Night	9% 7% 3 7% 5% 5% 5% 5% 7% 9% 38%	2915
	11th to 20th	Night	8% 8% 4 8% 5% 4 4 3 5% 7% 44%	2875
	21st to end	Night	5% 4 2 5% 4 5% 5% 5% 8% 9% 50%	3237
September	1st to 10th	Night	11% 5% 2 5% 3 4 4 3 5% 6% 52%	2183
	11th to 20th	Night	8% 4 2 4 4 3 3 3 5% 8% 56%	2200
	21st to end	Night	15% 7% 2 5% 4 4 3 3 6% 7% 44%	2200
October	1st to 10th	Night	10% 5% 3 5% 4 4 4 4 5% 7% 49%	2277
	11th to 20th	Night	14% 7% 3 7% 4 5% 3 4 4 7% 42%	2400
	21st to end	Night	19% 8% 2 6% 5% 4 4 3 4 8% 36%	2690
November	1st to 10th	Night	12% 7% 3 6% 5% 4 4 3 5% 6% 45%	2666
	11th to 20th	Night	15% 10% 4 8% 5% 4 4 3 6% 6% 34%	2730
	21st to end	Night	18% 14% 4 9% 5% 4 4 4 5% 6% 27%	2730
December	1st to 10th	Night	16% 13% 6% 12% 6% 5% 5% 3 5% 6% 23%	4600
	11th to 20th	Night	18% 17% 7% 12% 5% 4 4 3 5% 5% 21%	4957
	21st to end	Night	22% 20% 7% 11% 5% 4 3 3 4 5% 15%	6633

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	71% 4 11% 11% 2	5259
	11th to 20th	Day	73% 3 8% 7% 9%	5280
	21st to end	Day	74% 4 7% 12% 4	5780
February	1st to 10th	Day	64% 5% 9% 14% 7% 1	1890
	11th to 20th	Day	63% 5% 8% 15% 8% 1	1998
	21st to end	Day	57% 4 12% 18% 7% 2	1730
March	1st to 10th	Day	61% 4 8% 21% 7% 1	4815
	11th to 20th	Day	46% 4 12% 27% 9% 2	5090
	21st to end	Day	56% 4 10% 21% 9% 1	5586
April	1st to 10th	Day	54% 5% 13% 16% 11% 1	2341
	11th to 20th	Day	50% 5% 13% 17% 13% 2	2678
	21st to end	Day	50% 5% 11% 21% 11% 2	2730
May	1st to 10th	Day	56% 7% 9% 17% 9% 2	6027
	11th to 20th	Day	50% 6% 12% 22% 10% 1	5995
	21st to end	Day	45% 7% 12% 22% 11% 3	6590
June	1st to 10th	Day	42% 8% 12% 23% 15% 1	2600
	11th to 20th	Day	43% 9% 13% 21% 13% 1	2614
	21st to end	Day	39% 9% 14% 21% 15% 2	2800
July	1st to 10th	Day	39% 6% 10% 28% 14% 2	6111
	11th to 20th	Day	40% 7% 15% 22% 15% 1	5831
	21st to end	Day	40% 7% 12% 19% 19% 2	6240
August	1st to 10th	Day	40% 8% 16% 23% 13%	4221
	11th to 20th	Day	38% 8% 12% 28% 14% 1	4213
	21st to end	Day	36% 7% 14% 29% 12% 3	4639
September	1st to 10th	Day	37% 6% 11% 22% 20% 4	2200
	11th to 20th	Day	35% 5% 12% 26% 19% 3	2200
	21st to end	Day	44% 5% 10% 20% 20% 1	2200
October	1st to 10th	Day	28% 4 11% 33% 23% 1	3460
	11th to 20th	Day	37% 5% 10% 25% 18% 4	3240
	21st to end	Day	40% 4 12% 24% 18% 2	3451
November	1st to 10th	Day	39% 6% 12% 26% 16% 2	1852
	11th to 20th	Day	54% 4 10% 20% 10% 2	1890
	21st to end	Day	61% 4 9% 17% 8% 1	1890
December	1st to 10th	Day	65% 5% 12% 14% 3	2766
	11th to 20th	Day	68% 4 10% 14% 5%	3421
	21st to end	Day	77% 3 7% 8% 5%	4565
January	1st to 10th	Night	74% 4 7% 11% 4	7636
	11th to 20th	Night	73% 3 9% 8% 6% 1	7680
	21st to end	Night	64% 3 11% 14% 7% 1	8401
February	1st to 10th	Night	61% 5% 10% 16% 7% 1	2730
	11th to 20th	Night	61% 5% 9% 16% 8% 1	2516
	21st to end	Night	62% 5% 10% 13% 9% 2	2076
March	1st to 10th	Night	55% 4 9% 21% 10% 1	5244
	11th to 20th	Night	40% 5% 13% 30% 10% 2	5090
	21st to end	Night	49% 4 10% 21% 15% 2	5588
April	1st to 10th	Night	49% 5% 12% 19% 13% 2	2295
	11th to 20th	Night	46% 6% 12% 17% 16% 3	1889
	21st to end	Night	45% 7% 11% 20% 16% 1	1890
May	1st to 10th	Night	58% 6% 8% 15% 10% 3	4150
	11th to 20th	Night	45% 5% 10% 25% 13% 1	4123
	21st to end	Night	41% 7% 13% 26% 11% 2	4528
June	1st to 10th	Night	37% 7% 13% 23% 19% 2	1800
	11th to 20th	Night	35% 8% 15% 24% 16% 2	1774
	21st to end	Night	34% 9% 14% 24% 17% 3	1600
July	1st to 10th	Night	36% 6% 13% 24% 17% 4	3743
	11th to 20th	Night	37% 8% 15% 27% 13% 1	4006
	21st to end	Night	36% 7% 13% 20% 21% 2	4297
August	1st to 10th	Night	39% 8% 14% 23% 13% 1	2904
	11th to 20th	Night	40% 5% 10% 26% 19% 1	2902
	21st to end	Night	28% 9% 15% 30% 16% 2	3237
September	1st to 10th	Night	32% 7% 11% 25% 20% 5%	2183
	11th to 20th	Night	27% 4 11% 29% 25% 3	2200
	21st to end	Night	40% 6% 11% 20% 23% 2	2200
October	1st to 10th	Night	27% 4 8% 29% 30% 2	3719
	11th to 20th	Night	33% 4 11% 26% 21% 5%	3899
	21st to end	Night	36% 4 9% 29% 19% 3	4338
November	1st to 10th	Night	40% 4 12% 24% 18% 3	2666
	11th to 20th	Night	50% 5% 9% 21% 12% 3	2730
	21st to end	Night	58% 5% 11% 19% 7% 1	2730
December	1st to 10th	Night	62% 5% 10% 17% 6%	4600
	11th to 20th	Night	66% 4 12% 13% 4	4959
	21st to end	Night	72% 4 9% 11% 4	6633

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% 27% 32% 8% 5%	330
	11th to 20th	Day	31% 28% 33% 6% 2	330
	21st to end	Day	31% 27% 29% 11% 1	363
February	1st to 10th	Day	32% 26% 27% 13% 2	330
	11th to 20th	Day	33% 29% 28% 8%	330
	21st to end	Day	29% 35% 30% 6%	273
March	1st to 10th	Day	27% 25% 32% 14% 1	435
	11th to 20th	Day	31% 21% 30% 12% 5% 1	540
	21st to end	Day	30% 20% 31% 16% 3	594
April	1st to 10th	Day	25% 22% 30% 15% 7% 1	540
	11th to 20th	Day	24% 22% 28% 16% 7% 3	532
	21st to end	Day	23% 19% 32% 17% 7% 3	540
May	1st to 10th	Day	27% 19% 30% 15% 6% 3	543
	11th to 20th	Day	23% 12% 30% 20% 10% 4	567
	21st to end	Day	17% 11% 26% 24% 18% 6%	617
June	1st to 10th	Day	13% 10% 28% 30% 14% 5%	530
	11th to 20th	Day	15% 9% 27% 27% 18% 4	544
	21st to end	Day	13% 9% 30% 28% 15% 4	730
July	1st to 10th	Day	13% 6% 19% 27% 23% 12%	645
	11th to 20th	Day	11% 5% 26% 27% 21% 10%	524
	21st to end	Day	11% 5% 22% 30% 24% 9%	576
August	1st to 10th	Day	12% 4 18% 29% 24% 13%	526
	11th to 20th	Day	13% 6% 23% 26% 21% 11%	519
	21st to end	Day	9% 6% 20% 30% 25% 10%	583
September	1st to 10th	Day	13% 6% 21% 25% 24% 11%	530
	11th to 20th	Day	10% 4 15% 28% 29% 14%	530
	21st to end	Day	23% 9% 21% 24% 15% 7%	530
October	1st to 10th	Day	12% 11% 27% 24% 20% 6%	530
	11th to 20th	Day	17% 18% 30% 23% 9% 3	530
	21st to end	Day	23% 21% 31% 19% 5% 1	532
November	1st to 10th	Day	17% 22% 36% 15% 8% 2	330
	11th to 20th	Day	31% 18% 30% 13% 7% 1	330
	21st to end	Day	28% 25% 38% 8% 2	330
December	1st to 10th	Day	28% 30% 27% 11% 3 2	250
	11th to 20th	Day	28% 25% 34% 10% 3	316
	21st to end	Day	36% 20% 33% 10% 2	363
January	1st to 10th	Night	25% 22% 34% 16% 3	840
	11th to 20th	Night	26% 24% 32% 15% 3	840
	21st to end	Night	24% 21% 34% 18% 3	924
February	1st to 10th	Night	25% 16% 37% 19% 2	840
	11th to 20th	Night	23% 21% 34% 19% 2	823
	21st to end	Night	28% 17% 36% 17% 2	692
March	1st to 10th	Night	24% 17% 34% 22% 4	840
	11th to 20th	Night	22% 18% 35% 19% 6% 1	840
	21st to end	Night	24% 15% 32% 23% 5%	924
April	1st to 10th	Night	21% 17% 34% 23% 5%	825
	11th to 20th	Night	19% 15% 33% 23% 8% 2	623
	21st to end	Night	20% 10% 37% 25% 7% 1	630
May	1st to 10th	Night	21% 11% 30% 29% 8% 1	630
	11th to 20th	Night	20% 7% 28% 31% 12% 2	621
	21st to end	Night	12% 4 24% 37% 21% 2	683
June	1st to 10th	Night	12% 4 26% 40% 18% 1	600
	11th to 20th	Night	12% 4 21% 44% 18% 2	600
	21st to end	Night	10% 5% 25% 37% 21% 2	600
July	1st to 10th	Night	11% 3 16% 40% 24% 6%	585
	11th to 20th	Night	7% 3 20% 38% 28% 4	582
	21st to end	Night	8% 4 16% 39% 31% 2	657
August	1st to 10th	Night	8% 2 14% 44% 26% 5%	597
	11th to 20th	Night	9% 4 14% 39% 29% 4	594
	21st to end	Night	7% 2 17% 36% 33% 6%	660
September	1st to 10th	Night	13% 4 20% 31% 27% 5%	783
	11th to 20th	Night	11% 2 13% 38% 31% 5%	800
	21st to end	Night	19% 6% 23% 29% 20% 3	800
October	1st to 10th	Night	13% 7% 26% 30% 21% 3	800
	11th to 20th	Night	19% 12% 31% 25% 12% 1	800
	21st to end	Night	23% 15% 31% 23% 8%	880
November	1st to 10th	Night	17% 13% 32% 26% 12% 1	820
	11th to 20th	Night	23% 17% 30% 23% 7% 1	840
	21st to end	Night	27% 17% 29% 21% 6%	840
December	1st to 10th	Night	28% 18% 33% 18% 4	840
	11th to 20th	Night	26% 17% 35% 20% 3	840
	21st to end	Night	29% 17% 32% 19% 3	924

Page generated at 2026-05-29 01:53:26. Version ac07

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