UpUp Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UpUp Observatory clear sky chart from 2005-11-06 to 2026-03-18.

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 9% 5% 4 4 3 5% 6% 32%	132030
	Night	16% 13% 5% 10% 5% 4 4 3 4 6% 28%	129399
Transparency	Day	52% 6% 11% 20% 10% 1	135612
	Night	56% 5% 11% 18% 10% 1	133904
Seeing	Day	23% 15% 30% 20% 9% 3	16589
	Night	23% 13% 28% 25% 10% 1	25594

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	16% 15% 7% 12% 6% 4 4 3 5% 5% 24%	4351
	11th to 20th	Day	10% 22% 9% 19% 10% 7% 5% 3 3 3 9%	4948
	21st to end	Day	10% 17% 8% 16% 8% 6% 6% 3 5% 5% 16%	5780
February	1st to 10th	Day	12% 20% 7% 16% 8% 5% 4 4 3 4 19%	1890
	11th to 20th	Day	14% 17% 6% 13% 6% 6% 4 3 4 5% 23%	1843
	21st to end	Day	16% 18% 6% 11% 6% 5% 4 4 5% 5% 20%	1588
March	1st to 10th	Day	18% 14% 5% 9% 6% 4 3 3 4 5% 29%	5039
	11th to 20th	Day	13% 14% 5% 9% 6% 6% 6% 3 6% 7% 26%	5057
	21st to end	Day	19% 15% 5% 8% 4 3 3 3 4 5% 33%	5465
April	1st to 10th	Day	20% 13% 4 8% 5% 4 4 3 4 5% 30%	2365
	11th to 20th	Day	21% 12% 2 6% 4 4 4 3 4 5% 36%	2488
	21st to end	Day	22% 10% 4 6% 4 3 3 4 4 5% 34%	2600
May	1st to 10th	Day	19% 9% 3 7% 4 4 4 4 4 7% 35%	5934
	11th to 20th	Day	15% 9% 3 7% 4 4 4 3 5% 7% 39%	6318
	21st to end	Day	22% 9% 2 6% 4 4 4 3 5% 6% 36%	6949
June	1st to 10th	Day	18% 8% 2 5% 5% 4 4 4 5% 8% 36%	2800
	11th to 20th	Day	13% 6% 2 6% 4 5% 4 4 6% 8% 40%	2993
	21st to end	Day	18% 8% 2 6% 4 4 4 4 6% 8% 36%	3000
July	1st to 10th	Day	15% 5% 2 6% 4 4 5% 4 6% 9% 39%	6819
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 5% 7% 48%	6462
	21st to end	Day	9% 5% 2 6% 4 4 5% 3 6% 8% 50%	6612
August	1st to 10th	Day	14% 7% 2 7% 5% 4 5% 4 5% 8% 39%	4234
	11th to 20th	Day	16% 7% 2 6% 4 4 5% 4 7% 9% 37%	4174
	21st to end	Day	9% 5% 2 6% 4 4 5% 4 7% 9% 45%	4543
September	1st to 10th	Day	15% 6% 3 6% 5% 4 4 4 6% 7% 41%	2400
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 6% 8% 45%	2280
	21st to end	Day	18% 7% 3 8% 5% 4 5% 4 5% 6% 35%	2161
October	1st to 10th	Day	21% 8% 2 7% 4 5% 4 3 4 7% 35%	2000
	11th to 20th	Day	25% 10% 3 9% 6% 5% 4 4 5% 6% 25%	2000
	21st to end	Day	28% 11% 4 10% 5% 4 4 4 4 5% 22%	2200
November	1st to 10th	Day	20% 15% 4 8% 6% 5% 3 3 6% 7% 25%	1705
	11th to 20th	Day	17% 15% 4 10% 6% 5% 5% 4 5% 6% 21%	1680
	21st to end	Day	20% 22% 5% 10% 5% 6% 5% 4 4 5% 15%	1680
December	1st to 10th	Day	17% 28% 6% 10% 5% 4 5% 3 5% 5% 14%	2680
	11th to 20th	Day	18% 22% 8% 16% 5% 3 3 2 3 4 16%	3066
	21st to end	Day	24% 19% 5% 15% 5% 4 4 3 3 3 16%	3926
January	1st to 10th	Night	13% 19% 9% 17% 7% 5% 4 3 3 4 17%	8517
	11th to 20th	Night	11% 20% 8% 18% 8% 6% 5% 3 4 4 13%	7921
	21st to end	Night	10% 17% 8% 15% 8% 6% 4 3 4 5% 20%	8401
February	1st to 10th	Night	12% 19% 6% 15% 9% 5% 4 3 4 5% 19%	2730
	11th to 20th	Night	13% 17% 7% 12% 6% 5% 4 3 4 5% 23%	2663
	21st to end	Night	16% 16% 5% 10% 7% 5% 5% 3 4 5% 23%	2214
March	1st to 10th	Night	17% 12% 5% 10% 4 4 4 3 5% 6% 30%	5020
	11th to 20th	Night	11% 13% 6% 9% 5% 5% 6% 4 5% 7% 29%	5057
	21st to end	Night	22% 11% 5% 7% 4 4 4 3 5% 5% 31%	5467
April	1st to 10th	Night	21% 12% 4 8% 6% 3 4 3 5% 5% 29%	2035
	11th to 20th	Night	19% 10% 3 7% 5% 4 3 3 5% 5% 36%	1877
	21st to end	Night	18% 11% 4 7% 5% 5% 4 4 5% 6% 31%	1800
May	1st to 10th	Night	18% 8% 3 6% 5% 5% 5% 4 5% 7% 35%	3991
	11th to 20th	Night	13% 8% 3 6% 5% 4 4 3 5% 7% 42%	3575
	21st to end	Night	18% 7% 2 7% 5% 4 4 4 5% 6% 38%	3926
June	1st to 10th	Night	15% 8% 3 7% 4 5% 5% 4 5% 8% 37%	1600
	11th to 20th	Night	11% 6% 2 5% 5% 4 5% 4 6% 9% 44%	1401
	21st to end	Night	15% 7% 3 7% 5% 4 4 4 6% 7% 38%	1400
July	1st to 10th	Night	13% 6% 3 7% 5% 4 5% 4 6% 8% 41%	3160
	11th to 20th	Night	14% 5% 2 5% 4 4 3 3 4 7% 47%	3498
	21st to end	Night	10% 6% 2 5% 3 3 4 3 4 8% 50%	4237
August	1st to 10th	Night	11% 6% 2 6% 4 4 5% 4 6% 8% 45%	2915
	11th to 20th	Night	16% 6% 2 7% 4 4 4 3 4 6% 44%	2875
	21st to end	Night	15% 5% 2 5% 4 4 4 4 5% 6% 48%	3322
September	1st to 10th	Night	11% 7% 3 6% 4 4 5% 4 6% 7% 45%	2000
	11th to 20th	Night	13% 5% 2 6% 4 4 3 3 5% 7% 49%	2117
	21st to end	Night	18% 6% 2 7% 4 4 4 4 4 7% 40%	2237
October	1st to 10th	Night	18% 8% 3 7% 4 4 5% 3 5% 7% 36%	2400
	11th to 20th	Night	26% 11% 2 8% 5% 3 4 3 5% 6% 27%	2400
	21st to end	Night	25% 12% 4 9% 5% 4 4 3 5% 5% 24%	2640
November	1st to 10th	Night	19% 14% 4 7% 6% 4 4 3 4 5% 29%	2811
	11th to 20th	Night	16% 18% 5% 10% 5% 4 5% 3 5% 7% 23%	2940
	21st to end	Night	22% 21% 5% 10% 5% 4 3 4 5% 5% 15%	2940
December	1st to 10th	Night	19% 27% 6% 12% 5% 4 4 3 4 5% 13%	4720
	11th to 20th	Night	16% 22% 9% 17% 6% 5% 4 3 4 4 11%	5348
	21st to end	Night	23% 21% 6% 16% 5% 4 3 2 3 3 13%	7244

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	62% 5% 10% 15% 8%	4352
	11th to 20th	Day	80% 4 6% 6% 4	4980
	21st to end	Day	69% 5% 9% 9% 8%	5780
February	1st to 10th	Day	71% 4 7% 13% 4 1	1890
	11th to 20th	Day	64% 6% 8% 13% 8% 1	1852
	21st to end	Day	65% 6% 7% 15% 6%	1588
March	1st to 10th	Day	58% 5% 12% 10% 14% 1	5042
	11th to 20th	Day	57% 5% 13% 16% 7% 1	5057
	21st to end	Day	54% 4 8% 20% 11% 1	5465
April	1st to 10th	Day	56% 4 10% 19% 10% 1	2365
	11th to 20th	Day	52% 4 8% 23% 13% 1	2488
	21st to end	Day	52% 5% 9% 18% 13% 3	2600
May	1st to 10th	Day	48% 6% 11% 20% 10% 5%	5943
	11th to 20th	Day	44% 6% 11% 19% 18% 1	6322
	21st to end	Day	49% 5% 12% 19% 13% 3	6949
June	1st to 10th	Day	46% 6% 10% 24% 13%	2800
	11th to 20th	Day	40% 7% 12% 25% 15% 1	2993
	21st to end	Day	45% 7% 14% 22% 12% 1	3000
July	1st to 10th	Day	40% 6% 15% 27% 11% 1	6746
	11th to 20th	Day	35% 6% 11% 33% 14%	6384
	21st to end	Day	32% 6% 13% 34% 15%	6423
August	1st to 10th	Day	42% 7% 14% 25% 11% 1	4221
	11th to 20th	Day	42% 8% 16% 25% 9%	4213
	21st to end	Day	34% 7% 14% 35% 10% 1	4543
September	1st to 10th	Day	41% 7% 13% 28% 10% 1	2400
	11th to 20th	Day	36% 7% 14% 30% 12%	2280
	21st to end	Day	49% 7% 11% 24% 9%	2161
October	1st to 10th	Day	44% 6% 13% 26% 10% 1	3260
	11th to 20th	Day	50% 6% 13% 23% 8%	3240
	21st to end	Day	57% 6% 13% 17% 6%	3538
November	1st to 10th	Day	58% 5% 14% 18% 5%	1705
	11th to 20th	Day	63% 5% 15% 12% 4 1	1680
	21st to end	Day	71% 5% 10% 10% 3	1680
December	1st to 10th	Day	72% 5% 12% 9% 2	2680
	11th to 20th	Day	73% 3 8% 11% 5%	3066
	21st to end	Day	74% 3 6% 10% 6%	3926
January	1st to 10th	Night	71% 5% 7% 11% 6%	8517
	11th to 20th	Night	74% 6% 6% 8% 6%	7963
	21st to end	Night	66% 5% 9% 10% 10% 1	8401
February	1st to 10th	Night	67% 4 9% 15% 5%	2730
	11th to 20th	Night	64% 4 10% 15% 7%	2665
	21st to end	Night	63% 4 10% 16% 6%	2214
March	1st to 10th	Night	54% 5% 12% 14% 11% 4	5030
	11th to 20th	Night	54% 7% 15% 16% 7% 1	5058
	21st to end	Night	55% 4 9% 18% 12% 2	5467
April	1st to 10th	Night	57% 5% 9% 18% 11% 1	2035
	11th to 20th	Night	49% 5% 7% 22% 14% 2	1877
	21st to end	Night	53% 5% 9% 15% 16% 1	1800
May	1st to 10th	Night	47% 6% 11% 19% 13% 5%	3998
	11th to 20th	Night	40% 6% 12% 23% 18% 1	3576
	21st to end	Night	45% 6% 11% 24% 13% 1	3927
June	1st to 10th	Night	45% 6% 10% 22% 16% 1	1600
	11th to 20th	Night	37% 6% 12% 26% 19% 1	1401
	21st to end	Night	44% 7% 13% 23% 13% 1	1400
July	1st to 10th	Night	40% 6% 13% 25% 14% 2	3125
	11th to 20th	Night	36% 5% 12% 31% 15%	3453
	21st to end	Night	33% 5% 9% 36% 16% 1	4111
August	1st to 10th	Night	37% 5% 15% 27% 15% 1	2904
	11th to 20th	Night	41% 6% 16% 23% 13%	2902
	21st to end	Night	35% 6% 11% 35% 11% 1	3322
September	1st to 10th	Night	36% 7% 16% 27% 12% 1	2000
	11th to 20th	Night	35% 5% 15% 31% 14%	2117
	21st to end	Night	44% 6% 13% 26% 11%	2237
October	1st to 10th	Night	38% 6% 12% 28% 17%	3920
	11th to 20th	Night	49% 6% 14% 23% 8%	3899
	21st to end	Night	52% 7% 14% 20% 7%	4252
November	1st to 10th	Night	56% 6% 12% 19% 7%	2811
	11th to 20th	Night	61% 6% 13% 14% 6% 1	2940
	21st to end	Night	70% 6% 11% 10% 3	2940
December	1st to 10th	Night	74% 5% 12% 7% 2	4720
	11th to 20th	Night	76% 5% 8% 8% 3	5348
	21st to end	Night	77% 4 6% 8% 5%	7244

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	22% 26% 32% 14% 5%	220
	11th to 20th	Day	24% 24% 34% 12% 5% 1	275
	21st to end	Day	26% 18% 33% 18% 4	363
February	1st to 10th	Day	30% 25% 31% 9% 4	330
	11th to 20th	Day	27% 25% 37% 10% 1	330
	21st to end	Day	38% 20% 33% 10%	273
March	1st to 10th	Day	25% 21% 36% 15% 3	537
	11th to 20th	Day	28% 19% 32% 17% 4	528
	21st to end	Day	34% 15% 29% 16% 6% 1	550
April	1st to 10th	Day	29% 20% 29% 15% 7% 1	500
	11th to 20th	Day	36% 16% 22% 16% 7% 3	492
	21st to end	Day	32% 14% 31% 15% 6% 2	500
May	1st to 10th	Day	26% 12% 31% 21% 7% 3	503
	11th to 20th	Day	20% 14% 30% 22% 11% 3	527
	21st to end	Day	20% 14% 30% 21% 11% 5%	573
June	1st to 10th	Day	21% 14% 28% 27% 7% 1	530
	11th to 20th	Day	17% 13% 32% 25% 11% 3	723
	21st to end	Day	21% 11% 34% 23% 9% 2	730
July	1st to 10th	Day	12% 10% 30% 29% 15% 4	721
	11th to 20th	Day	14% 12% 26% 29% 14% 5%	571
	21st to end	Day	13% 9% 31% 28% 13% 5%	576
August	1st to 10th	Day	15% 7% 24% 31% 15% 8%	526
	11th to 20th	Day	15% 6% 24% 29% 16% 9%	519
	21st to end	Day	15% 10% 29% 23% 16% 7%	583
September	1st to 10th	Day	18% 8% 28% 25% 13% 8%	530
	11th to 20th	Day	12% 7% 25% 24% 21% 11%	530
	21st to end	Day	20% 12% 25% 26% 14% 3	530
October	1st to 10th	Day	25% 13% 26% 18% 13% 5%	530
	11th to 20th	Day	27% 19% 32% 16% 6%	530
	21st to end	Day	34% 17% 31% 15% 4	583
November	1st to 10th	Day	33% 18% 29% 15% 5%	254
	11th to 20th	Day	27% 21% 35% 13% 3	220
	21st to end	Day	28% 23% 35% 12% 2	220
December	1st to 10th	Day	31% 23% 25% 17% 3	220
	11th to 20th	Day	36% 25% 25% 11% 2	220
	21st to end	Day	36% 23% 28% 11% 2	242
January	1st to 10th	Night	30% 17% 32% 16% 4 1	944
	11th to 20th	Night	30% 17% 31% 17% 5% 1	840
	21st to end	Night	22% 13% 32% 25% 7% 1	924
February	1st to 10th	Night	23% 19% 32% 22% 4	840
	11th to 20th	Night	23% 17% 34% 22% 5%	823
	21st to end	Night	27% 19% 28% 21% 4	692
March	1st to 10th	Night	23% 18% 34% 22% 3	840
	11th to 20th	Night	23% 17% 33% 22% 4 1	829
	21st to end	Night	23% 14% 31% 24% 8%	880
April	1st to 10th	Night	29% 15% 29% 23% 5%	800
	11th to 20th	Night	27% 13% 27% 22% 10% 1	693
	21st to end	Night	24% 12% 28% 26% 10% 1	600
May	1st to 10th	Night	21% 8% 23% 34% 12% 1	577
	11th to 20th	Night	19% 9% 31% 30% 12%	394
	21st to end	Night	14% 6% 29% 36% 14%	433
June	1st to 10th	Night	16% 8% 30% 36% 10% 1	400
	11th to 20th	Night	14% 9% 27% 39% 12%	400
	21st to end	Night	19% 6% 23% 38% 14% 1	400
July	1st to 10th	Night	8% 4 21% 48% 17% 2	390
	11th to 20th	Night	12% 7% 23% 37% 21% 1	388
	21st to end	Night	11% 5% 24% 37% 22% 1	570
August	1st to 10th	Night	11% 5% 17% 39% 25% 3	597
	11th to 20th	Night	12% 4 17% 36% 28% 3	594
	21st to end	Night	16% 6% 22% 31% 23% 2	720
September	1st to 10th	Night	13% 8% 26% 30% 19% 4	800
	11th to 20th	Night	14% 6% 22% 30% 23% 5%	800
	21st to end	Night	21% 7% 20% 33% 17% 3	800
October	1st to 10th	Night	21% 12% 27% 26% 13% 1	800
	11th to 20th	Night	31% 12% 25% 22% 8% 1	800
	21st to end	Night	30% 16% 30% 20% 4	880
November	1st to 10th	Night	28% 14% 28% 21% 7% 1	820
	11th to 20th	Night	27% 18% 30% 19% 5%	840
	21st to end	Night	35% 15% 29% 17% 3	840
December	1st to 10th	Night	34% 19% 27% 15% 4	840
	11th to 20th	Night	27% 20% 34% 15% 3 1	840
	21st to end	Night	34% 16% 30% 17% 3	966

Page generated at 2026-03-15 02:23:52. Version ac07

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