Aubright Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Aubright Observatory clear sky chart from 2005-11-06 to 2026-09-29.

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	8% 6% 2 7% 5% 5% 6% 5% 7% 10% 38%	148635
	Night	9% 6% 2 7% 5% 5% 5% 4 7% 9% 42%	142765
Transparency	Day	40% 7% 16% 18% 13% 6%	152346
	Night	38% 7% 16% 18% 15% 7%	147126
Seeing	Day	11% 8% 23% 25% 21% 12%	18010
	Night	11% 6% 22% 32% 24% 5%	28020

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	7% 6% 2 6% 4 4 4 3 5% 7% 53%	5258
	11th to 20th	Day	18% 8% 3 7% 4 4 4 3 5% 7% 38%	5280
	21st to end	Day	9% 6% 2 6% 4 4 4 4 5% 8% 48%	5818
February	1st to 10th	Day	14% 7% 2 5% 5% 3 4 4 4 5% 46%	2100
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 5% 6% 48%	2048
	21st to end	Day	11% 7% 2 6% 4 4 4 3 5% 6% 49%	1798
March	1st to 10th	Day	14% 8% 3 7% 4 4 4 4 5% 7% 40%	5045
	11th to 20th	Day	7% 3 2 4 3 3 4 4 5% 7% 57%	5090
	21st to end	Day	12% 5% 2 5% 3 4 4 4 5% 9% 47%	5586
April	1st to 10th	Day	9% 5% 2 5% 5% 4 4 4 6% 8% 47%	2310
	11th to 20th	Day	8% 6% 3 6% 4 5% 5% 4 6% 8% 46%	2345
	21st to end	Day	4 4 2 5% 5% 5% 5% 4 7% 8% 51%	2579
May	1st to 10th	Day	8% 6% 2 7% 6% 5% 5% 5% 7% 10% 39%	7616
	11th to 20th	Day	10% 5% 2 6% 4 4 4 5% 6% 9% 44%	7626
	21st to end	Day	4 4 2 7% 6% 7% 7% 6% 9% 12% 37%	8391
June	1st to 10th	Day	11% 6% 2 9% 6% 7% 6% 6% 8% 10% 28%	2730
	11th to 20th	Day	5% 5% 3 8% 7% 7% 8% 8% 9% 11% 29%	2730
	21st to end	Day	7% 6% 3 9% 7% 7% 7% 6% 9% 11% 28%	2730
July	1st to 10th	Day	5% 6% 3 9% 8% 8% 9% 8% 9% 11% 24%	7680
	11th to 20th	Day	3 4 2 7% 7% 8% 9% 6% 10% 15% 29%	7680
	21st to end	Day	3 3 2 7% 6% 7% 8% 7% 10% 15% 32%	8340
August	1st to 10th	Day	11% 8% 3 10% 8% 8% 8% 6% 8% 12% 20%	6014
	11th to 20th	Day	5% 4 2 7% 6% 6% 8% 6% 9% 13% 35%	5912
	21st to end	Day	7% 5% 3 9% 7% 8% 8% 6% 9% 13% 26%	5566
September	1st to 10th	Day	11% 8% 4 10% 8% 8% 8% 5% 9% 9% 22%	2310
	11th to 20th	Day	14% 7% 3 9% 7% 7% 8% 6% 7% 9% 24%	2310
	21st to end	Day	12% 7% 3 9% 5% 5% 6% 5% 7% 7% 35%	2288
October	1st to 10th	Day	12% 6% 3 8% 5% 6% 5% 5% 8% 8% 34%	2171
	11th to 20th	Day	7% 5% 2 6% 5% 4 4 4 5% 7% 52%	2000
	21st to end	Day	8% 5% 2 5% 4 4 4 3 6% 8% 50%	2200
November	1st to 10th	Day	10% 5% 2 5% 5% 4 4 4 6% 9% 46%	2057
	11th to 20th	Day	9% 6% 2 6% 5% 4 4 4 6% 7% 46%	2089
	21st to end	Day	11% 5% 3 6% 5% 4 3 3 6% 7% 47%	1890
December	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 6% 7% 54%	3020
	11th to 20th	Day	13% 7% 2 7% 5% 4 5% 4 6% 7% 39%	3463
	21st to end	Day	14% 9% 3 7% 4 4 4 3 4 6% 42%	4565
January	1st to 10th	Night	8% 6% 2 4 3 3 3 3 5% 7% 55%	7635
	11th to 20th	Night	15% 7% 2 7% 4 4 5% 4 7% 7% 38%	7680
	21st to end	Night	13% 8% 3 6% 4 3 4 3 6% 7% 42%	8359
February	1st to 10th	Night	13% 5% 2 6% 5% 4 4 3 5% 6% 48%	2520
	11th to 20th	Night	13% 7% 2 6% 4 4 3 3 4 6% 48%	2458
	21st to end	Night	11% 7% 2 6% 4 4 4 3 4 6% 49%	2006
March	1st to 10th	Night	17% 9% 3 6% 4 4 3 3 4 6% 41%	5028
	11th to 20th	Night	5% 5% 2 4 3 3 4 4 6% 10% 54%	5090
	21st to end	Night	9% 6% 2 6% 4 4 4 3 6% 7% 50%	5588
April	1st to 10th	Night	8% 5% 1 5% 5% 4 4 4 6% 8% 48%	2310
	11th to 20th	Night	8% 6% 2 5% 3 4 4 2 5% 7% 54%	2222
	21st to end	Night	6% 3 2 4 4 4 4 5% 7% 9% 52%	2056
May	1st to 10th	Night	7% 6% 3 7% 5% 5% 5% 4 6% 9% 43%	5237
	11th to 20th	Night	9% 7% 3 7% 4 4 5% 4 7% 10% 42%	5234
	21st to end	Night	4 5% 2 7% 5% 5% 6% 4 8% 12% 41%	5761
June	1st to 10th	Night	10% 5% 2 7% 4 5% 5% 6% 8% 12% 35%	1890
	11th to 20th	Night	6% 5% 2 7% 6% 6% 6% 6% 10% 11% 35%	1890
	21st to end	Night	7% 5% 1 7% 6% 6% 5% 6% 9% 12% 36%	1890
July	1st to 10th	Night	6% 6% 3 9% 7% 6% 7% 6% 9% 14% 27%	5278
	11th to 20th	Night	3 4 2 7% 7% 6% 8% 6% 10% 14% 33%	5277
	21st to end	Night	4 5% 2 8% 6% 6% 7% 6% 10% 12% 34%	5736
August	1st to 10th	Night	8% 8% 3 10% 7% 7% 7% 6% 9% 13% 22%	4135
	11th to 20th	Night	3 4 2 6% 5% 6% 6% 6% 9% 13% 39%	4115
	21st to end	Night	5% 6% 2 8% 6% 6% 8% 6% 9% 12% 31%	5511
September	1st to 10th	Night	11% 8% 3 7% 6% 6% 6% 6% 8% 10% 28%	2310
	11th to 20th	Night	11% 7% 3 9% 6% 7% 6% 5% 9% 10% 28%	2310
	21st to end	Night	8% 7% 2 8% 5% 5% 5% 4 6% 10% 40%	2289
October	1st to 10th	Night	11% 6% 2 7% 5% 4 5% 4 7% 7% 42%	2227
	11th to 20th	Night	7% 4 2 5% 4 4 3 3 5% 6% 56%	2400
	21st to end	Night	9% 5% 2 5% 4 4 4 3 5% 8% 51%	2640
November	1st to 10th	Night	10% 5% 2 5% 4 4 3 4 6% 8% 49%	2461
	11th to 20th	Night	10% 6% 3 6% 4 4 4 3 5% 7% 49%	2527
	21st to end	Night	11% 6% 2 5% 4 4 4 4 5% 7% 47%	2730
December	1st to 10th	Night	11% 6% 1 5% 4 3 4 3 4 6% 54%	4380
	11th to 20th	Night	12% 8% 2 7% 4 4 4 3 5% 6% 45%	4952
	21st to end	Night	13% 9% 3 7% 4 4 4 3 5% 6% 41%	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	33% 2 12% 15% 26% 13%	5259
	11th to 20th	Day	47% 2 5% 14% 16% 16%	5280
	21st to end	Day	35% 4 8% 24% 16% 12%	5818
February	1st to 10th	Day	40% 5% 9% 14% 21% 12%	2100
	11th to 20th	Day	37% 5% 9% 16% 22% 12%	2058
	21st to end	Day	36% 5% 10% 18% 19% 13%	1798
March	1st to 10th	Day	42% 5% 9% 15% 18% 10%	5045
	11th to 20th	Day	26% 5% 11% 18% 19% 22%	5090
	21st to end	Day	35% 4 9% 21% 19% 11%	5586
April	1st to 10th	Day	33% 7% 11% 20% 18% 12%	2310
	11th to 20th	Day	35% 7% 8% 17% 23% 9%	2345
	21st to end	Day	28% 7% 12% 22% 23% 8%	2579
May	1st to 10th	Day	37% 9% 14% 24% 13% 3	7651
	11th to 20th	Day	35% 6% 13% 30% 14% 2	7630
	21st to end	Day	36% 8% 21% 22% 12% 2	8405
June	1st to 10th	Day	47% 11% 16% 15% 10% 1	2730
	11th to 20th	Day	42% 14% 19% 19% 5%	2730
	21st to end	Day	45% 14% 21% 14% 6%	2730
July	1st to 10th	Day	50% 9% 28% 13% 1	7615
	11th to 20th	Day	41% 9% 36% 12% 2	7611
	21st to end	Day	38% 9% 28% 23% 2	8156
August	1st to 10th	Day	55% 9% 26% 8% 1	6001
	11th to 20th	Day	38% 8% 29% 18% 7%	5951
	21st to end	Day	47% 9% 24% 19% 2	5566
September	1st to 10th	Day	53% 14% 15% 10% 7% 1	2310
	11th to 20th	Day	53% 12% 14% 14% 7%	2310
	21st to end	Day	46% 8% 14% 17% 13% 3	2288
October	1st to 10th	Day	52% 6% 9% 10% 14% 8%	3535
	11th to 20th	Day	27% 4 5% 15% 35% 13%	3240
	21st to end	Day	26% 4 6% 20% 35% 9%	3538
November	1st to 10th	Day	34% 7% 10% 20% 18% 11%	2057
	11th to 20th	Day	36% 6% 9% 17% 22% 11%	2089
	21st to end	Day	37% 5% 10% 18% 21% 9%	1890
December	1st to 10th	Day	30% 5% 11% 24% 20% 11%	3020
	11th to 20th	Day	44% 5% 9% 16% 18% 8%	3460
	21st to end	Day	45% 3 7% 19% 20% 6%	4565
January	1st to 10th	Night	29% 3 11% 16% 30% 11%	7636
	11th to 20th	Night	45% 3 7% 15% 18% 13%	7680
	21st to end	Night	41% 5% 9% 19% 16% 11%	8359
February	1st to 10th	Night	38% 5% 8% 16% 20% 13%	2520
	11th to 20th	Night	37% 5% 9% 19% 18% 12%	2459
	21st to end	Night	36% 5% 9% 20% 18% 12%	2006
March	1st to 10th	Night	45% 5% 9% 16% 16% 10%	5028
	11th to 20th	Night	25% 5% 12% 20% 19% 19%	5090
	21st to end	Night	34% 4 10% 20% 18% 13%	5588
April	1st to 10th	Night	33% 6% 14% 20% 16% 10%	2310
	11th to 20th	Night	30% 6% 8% 24% 23% 10%	2222
	21st to end	Night	25% 7% 16% 26% 20% 6%	2056
May	1st to 10th	Night	36% 9% 17% 23% 12% 3	5264
	11th to 20th	Night	37% 6% 18% 25% 11% 3	5235
	21st to end	Night	34% 9% 20% 22% 14% 1	5771
June	1st to 10th	Night	37% 12% 22% 19% 9%	1890
	11th to 20th	Night	37% 13% 24% 22% 5%	1890
	21st to end	Night	37% 14% 24% 19% 5% 1	1890
July	1st to 10th	Night	44% 11% 30% 13% 1	5235
	11th to 20th	Night	38% 13% 36% 12% 2	5226
	21st to end	Night	38% 9% 30% 21% 1	5606
August	1st to 10th	Night	51% 12% 28% 7% 1	4124
	11th to 20th	Night	34% 9% 31% 19% 7%	4142
	21st to end	Night	43% 13% 25% 17% 2	5511
September	1st to 10th	Night	46% 14% 19% 14% 6% 1	2310
	11th to 20th	Night	47% 14% 16% 17% 7%	2310
	21st to end	Night	38% 9% 16% 21% 13% 3	2289
October	1st to 10th	Night	50% 6% 10% 13% 13% 7%	3643
	11th to 20th	Night	28% 3 5% 18% 35% 10%	3899
	21st to end	Night	24% 4 7% 22% 33% 11%	4252
November	1st to 10th	Night	33% 6% 12% 20% 17% 12%	2461
	11th to 20th	Night	35% 6% 8% 18% 21% 11%	2527
	21st to end	Night	36% 5% 11% 19% 19% 10%	2730
December	1st to 10th	Night	33% 4 10% 21% 18% 14%	4380
	11th to 20th	Night	41% 4 9% 21% 16% 9%	4954
	21st to end	Night	44% 5% 10% 18% 18% 5%	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	10% 19% 47% 19% 5% 1	330
	11th to 20th	Day	13% 15% 39% 24% 8% 1	330
	21st to end	Day	15% 21% 47% 15% 2	363
February	1st to 10th	Day	13% 18% 39% 22% 7% 1	330
	11th to 20th	Day	18% 18% 40% 17% 7%	330
	21st to end	Day	14% 17% 38% 25% 7%	341
March	1st to 10th	Day	11% 15% 35% 26% 11% 1	540
	11th to 20th	Day	13% 13% 36% 24% 12% 3	540
	21st to end	Day	13% 13% 34% 26% 13% 2	594
April	1st to 10th	Day	13% 14% 33% 23% 14% 3	540
	11th to 20th	Day	10% 12% 31% 26% 14% 7%	532
	21st to end	Day	5% 7% 31% 28% 18% 10%	540
May	1st to 10th	Day	6% 9% 29% 29% 18% 9%	543
	11th to 20th	Day	9% 3 26% 30% 21% 11%	567
	21st to end	Day	9% 3 16% 27% 29% 16%	617
June	1st to 10th	Day	12% 4 14% 32% 23% 15%	570
	11th to 20th	Day	7% 3 16% 23% 27% 24%	570
	21st to end	Day	5% 2 12% 23% 32% 26%	570
July	1st to 10th	Day	7% 2 5% 22% 33% 31%	565
	11th to 20th	Day	5% 1 6% 18% 38% 34%	564
	21st to end	Day	6% 2 7% 21% 37% 26%	620
August	1st to 10th	Day	11% 2 10% 19% 31% 27%	566
	11th to 20th	Day	7% 2 5% 19% 33% 34%	559
	21st to end	Day	11% 3 7% 24% 32% 24%	627
September	1st to 10th	Day	12% 5% 10% 22% 28% 23%	570
	11th to 20th	Day	14% 2 16% 27% 25% 17%	570
	21st to end	Day	13% 4 11% 26% 30% 16%	562
October	1st to 10th	Day	16% 4 25% 31% 18% 5%	530
	11th to 20th	Day	8% 7% 21% 31% 26% 6%	530
	21st to end	Day	9% 7% 25% 36% 19% 4	583
November	1st to 10th	Day	14% 8% 27% 29% 18% 4	535
	11th to 20th	Day	12% 10% 33% 26% 15% 3	529
	21st to end	Day	11% 14% 38% 24% 12% 1	330
December	1st to 10th	Day	10% 18% 34% 24% 13% 2	330
	11th to 20th	Day	16% 15% 34% 28% 6%	330
	21st to end	Day	15% 12% 34% 29% 9% 2	363
January	1st to 10th	Night	14% 12% 35% 31% 8% 1	840
	11th to 20th	Night	14% 13% 28% 34% 10% 1	840
	21st to end	Night	18% 12% 36% 29% 5%	924
February	1st to 10th	Night	16% 9% 29% 35% 9%	840
	11th to 20th	Night	16% 12% 33% 32% 7%	823
	21st to end	Night	15% 11% 34% 35% 5%	692
March	1st to 10th	Night	11% 11% 33% 36% 9%	840
	11th to 20th	Night	10% 12% 35% 32% 11% 1	840
	21st to end	Night	10% 10% 34% 35% 11%	924
April	1st to 10th	Night	11% 9% 32% 36% 11%	840
	11th to 20th	Night	10% 9% 31% 34% 15%	831
	21st to end	Night	7% 5% 29% 43% 16% 1	796
May	1st to 10th	Night	5% 4 23% 46% 20% 2	630
	11th to 20th	Night	8% 2 20% 38% 29% 3	621
	21st to end	Night	8% 1 11% 38% 37% 6%	683
June	1st to 10th	Night	12% 2 11% 36% 34% 5%	630
	11th to 20th	Night	7% 2 10% 30% 39% 13%	630
	21st to end	Night	7% 2 9% 25% 42% 15%	630
July	1st to 10th	Night	6% 1 7% 25% 44% 16%	615
	11th to 20th	Night	6% 4 20% 51% 19%	612
	21st to end	Night	4 6% 24% 52% 13%	690
August	1st to 10th	Night	9% 1 6% 23% 45% 16%	627
	11th to 20th	Night	5% 1 4 20% 51% 20%	624
	21st to end	Night	12% 3 10% 23% 38% 15%	901
September	1st to 10th	Night	14% 2 8% 23% 43% 11%	840
	11th to 20th	Night	13% 2 12% 29% 37% 8%	840
	21st to end	Night	11% 3 13% 30% 36% 8%	833
October	1st to 10th	Night	15% 2 21% 32% 28% 3	800
	11th to 20th	Night	8% 5% 18% 37% 29% 3	800
	21st to end	Night	10% 4 21% 37% 25% 2	880
November	1st to 10th	Night	12% 5% 24% 36% 22% 1	820
	11th to 20th	Night	14% 7% 26% 34% 18% 2	840
	21st to end	Night	13% 8% 28% 33% 17% 1	840
December	1st to 10th	Night	15% 8% 28% 31% 18% 1	840
	11th to 20th	Night	15% 8% 26% 35% 15% 1	840
	21st to end	Night	15% 9% 28% 34% 14%	924

Page generated at 2026-09-26 04:18:45. Version ac07

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