DSO - Upham
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DSO - Upham clear sky chart from 2005-11-06 to 2025-01-07.

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	3 2 1 3 3 3 3 3 5% 7% 67%	108448
	Night	3 3 1 4 3 3 4 3 5% 7% 64%	109358
Transparency	Day	16% 4 6% 16% 29% 29%	108212
	Night	19% 4 6% 15% 29% 27%	109183
Seeing	Day	5% 8% 17% 27% 26% 17%	14508
	Night	4 4 21% 42% 26% 2	24950

By Month

Percentage Cloud Cover SW (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	2 3 2 4 2 3 3 3 5% 6% 68%	2912
	11th to 20th	Day	2 2 1 2 2 2 3 2 5% 7% 72%	2860
	21st to end	Day	7% 4 2 4 3 3 3 4 6% 6% 59%	3146
February	1st to 10th	Day	2 3 1 3 2 2 3 4 4 6% 70%	1752
	11th to 20th	Day	4 4 1 4 3 2 3 3 4 5% 68%	1849
	21st to end	Day	3 2 1 2 3 3 2 3 5% 5% 71%	1598
March	1st to 10th	Day	3 3 1 4 3 3 3 3 4 6% 67%	3444
	11th to 20th	Day	6% 3 2 4 4 3 4 3 5% 6% 61%	3490
	21st to end	Day	1 3 2 4 3 3 4 4 6% 8% 62%	3847
April	1st to 10th	Day	2 2 2 2 2 3 3 4 7% 73%	2280
	11th to 20th	Day	3 2 1 3 2 2 2 2 3 4 77%	2251
	21st to end	Day	2 2 1 2 2 2 2 2 3 5% 80%	2280
May	1st to 10th	Day	1 1 1 1 1 1 2 1 2 4 84%	3800
	11th to 20th	Day	1 1 1 2 2 2 2 3 4 7% 75%	3765
	21st to end	Day	1 1 1 1 1 1 1 2 3 87%	4471
June	1st to 10th	Day	2 2 1 3 3 2 3 3 5% 8% 69%	2470
	11th to 20th	Day	2 1 1 2 1 1 2 2 4 5% 78%	2470
	21st to end	Day	5% 3 1 4 3 4 5% 4 7% 7% 58%	2470
July	1st to 10th	Day	3 3 1 4 4 4 5% 4 8% 8% 55%	4110
	11th to 20th	Day	2 1 1 4 4 4 4 4 8% 10% 59%	4110
	21st to end	Day	3 4 2 5% 4 5% 6% 6% 9% 12% 44%	4454
August	1st to 10th	Day	3 1 1 4 3 3 5% 5% 9% 13% 52%	3925
	11th to 20th	Day	3 2 1 3 3 3 4 4 6% 10% 62%	3726
	21st to end	Day	3 2 1 4 4 4 5% 5% 8% 10% 53%	4180
September	1st to 10th	Day	6% 3 2 5% 3 4 4 3 6% 9% 54%	2280
	11th to 20th	Day	6% 3 1 3 3 3 4 3 6% 7% 61%	2280
	21st to end	Day	3 3 1 3 2 2 2 3 5% 5% 72%	2028
October	1st to 10th	Day	2 2 1 2 2 1 2 2 3 4 80%	3170
	11th to 20th	Day	2 2 1 2 2 3 3 2 4 4 75%	3150
	21st to end	Day	1 1 1 1 1 1 1 1 2 3 86%	3438
November	1st to 10th	Day	2 2 1 3 2 2 2 2 3 6% 75%	1959
	11th to 20th	Day	2 3 1 3 2 2 3 3 4 6% 71%	2000
	21st to end	Day	6% 4 1 3 4 2 3 3 5% 6% 62%	1856
December	1st to 10th	Day	5% 3 1 4 3 2 3 3 4 6% 65%	2817
	11th to 20th	Day	3 3 3 4 3 3 2 2 4 6% 67%	3300
	21st to end	Day	2 2 1 2 2 3 3 2 5% 6% 73%	4510
January	1st to 10th	Night	3 4 2 4 3 3 3 3 4 5% 64%	4175
	11th to 20th	Night	2 2 1 2 2 2 3 3 5% 6% 71%	4110
	21st to end	Night	7% 5% 2 5% 4 3 3 3 7% 6% 54%	4521
February	1st to 10th	Night	2 3 1 3 2 3 4 3 4 6% 69%	2427
	11th to 20th	Night	5% 4 2 3 3 2 3 3 4 5% 66%	2218
	21st to end	Night	2 3 1 3 3 3 4 4 5% 6% 67%	1851
March	1st to 10th	Night	4 5% 1 3 2 3 3 3 4 7% 66%	3430
	11th to 20th	Night	8% 4 1 4 3 3 3 3 5% 6% 59%	3490
	21st to end	Night	2 3 1 4 4 3 3 3 6% 8% 62%	3803
April	1st to 10th	Night	1 2 1 2 3 3 4 3 5% 6% 69%	1900
	11th to 20th	Night	3 3 1 3 2 3 3 3 4 7% 68%	1877
	21st to end	Night	1 1 1 2 2 2 3 4 4 5% 76%	1900
May	1st to 10th	Night	2 1 1 1 1 2 1 3 4 83%	3170
	11th to 20th	Night	3 3 1 4 3 4 4 3 5% 7% 64%	3140
	21st to end	Night	1 1 1 1 2 2 2 2 2 4 83%	3111
June	1st to 10th	Night	2 3 1 3 3 4 4 4 7% 7% 63%	1710
	11th to 20th	Night	2 2 1 2 2 3 4 3 5% 5% 70%	1710
	21st to end	Night	3 3 1 5% 5% 5% 6% 6% 8% 9% 48%	1710
July	1st to 10th	Night	3 3 2 5% 5% 5% 6% 5% 10% 11% 45%	2860
	11th to 20th	Night	2 3 1 6% 5% 6% 6% 6% 8% 10% 48%	2860
	21st to end	Night	4 5% 2 8% 6% 7% 7% 6% 10% 12% 34%	3109
August	1st to 10th	Night	2 2 1 5% 5% 6% 6% 6% 11% 15% 39%	3001
	11th to 20th	Night	3 3 1 4 4 5% 5% 4 8% 12% 51%	3113
	21st to end	Night	3 4 2 8% 7% 7% 8% 6% 9% 10% 35%	3487
September	1st to 10th	Night	5% 4 2 6% 4 4 6% 6% 7% 9% 48%	1900
	11th to 20th	Night	6% 3 1 4 4 3 4 4 6% 8% 57%	1900
	21st to end	Night	4 2 1 3 3 3 3 2 5% 6% 67%	2143
October	1st to 10th	Night	2 2 1 3 2 2 2 3 4 5% 75%	3800
	11th to 20th	Night	4 2 2 3 2 2 3 2 3 4 73%	3778
	21st to end	Night	2 1 1 1 1 1 2 1 3 5% 82%	4120
November	1st to 10th	Night	3 2 1 1 2 2 3 2 4 5% 76%	2340
	11th to 20th	Night	2 3 1 2 2 2 3 3 4 5% 74%	2400
	21st to end	Night	6% 4 1 4 2 3 2 2 5% 7% 65%	2515
December	1st to 10th	Night	4 3 1 3 2 2 2 3 4 5% 71%	4368
	11th to 20th	Night	2 2 1 4 3 4 4 3 5% 7% 66%	4943
	21st to end	Night	3 2 1 3 2 2 2 2 4 6% 72%	6468

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	16% 3 3 15% 44% 19%	2913
	11th to 20th	Day	13% 2 5% 20% 45% 15%	2860
	21st to end	Day	24% 4 6% 25% 28% 13%	3146
February	1st to 10th	Day	15% 2 5% 17% 29% 32%	1752
	11th to 20th	Day	19% 3 3 15% 32% 27%	1859
	21st to end	Day	16% 2 2 10% 30% 39%	1598
March	1st to 10th	Day	18% 3 2 8% 37% 32%	3444
	11th to 20th	Day	22% 6% 3 18% 27% 24%	3490
	21st to end	Day	17% 5% 3 15% 33% 27%	3847
April	1st to 10th	Day	11% 2 2 11% 31% 41%	2280
	11th to 20th	Day	13% 2 1 7% 25% 51%	2254
	21st to end	Day	10% 2 2 10% 29% 47%	2280
May	1st to 10th	Day	8% 2 1 5% 21% 64%	3800
	11th to 20th	Day	10% 4 4 11% 26% 45%	3768
	21st to end	Day	6% 1 1 5% 14% 72%	4471
June	1st to 10th	Day	14% 3 4 13% 26% 40%	2470
	11th to 20th	Day	11% 2 2 7% 21% 57%	2470
	21st to end	Day	23% 5% 7% 15% 19% 31%	2470
July	1st to 10th	Day	22% 6% 12% 18% 19% 23%	4046
	11th to 20th	Day	18% 6% 12% 26% 31% 7%	4041
	21st to end	Day	27% 7% 15% 28% 20% 3	4314
August	1st to 10th	Day	18% 7% 12% 33% 25% 4	3911
	11th to 20th	Day	17% 5% 11% 19% 36% 12%	3762
	21st to end	Day	24% 6% 14% 28% 22% 7%	4179
September	1st to 10th	Day	26% 5% 8% 20% 22% 18%	2280
	11th to 20th	Day	21% 5% 6% 18% 28% 22%	2280
	21st to end	Day	15% 3 5% 17% 33% 27%	2028
October	1st to 10th	Day	11% 2 4 9% 26% 47%	3170
	11th to 20th	Day	14% 2 4 13% 31% 36%	3150
	21st to end	Day	7% 1 1 12% 33% 45%	3438
November	1st to 10th	Day	13% 2 4 17% 36% 28%	1959
	11th to 20th	Day	15% 3 3 18% 29% 32%	2000
	21st to end	Day	23% 3 4 17% 32% 21%	1856
December	1st to 10th	Day	21% 3 4 21% 32% 19%	2817
	11th to 20th	Day	22% 2 3 15% 40% 18%	3299
	21st to end	Day	14% 2 4 19% 40% 21%	4510
January	1st to 10th	Night	21% 3 3 17% 41% 15%	4175
	11th to 20th	Night	14% 3 5% 18% 46% 15%	4110
	21st to end	Night	28% 3 7% 21% 30% 12%	4521
February	1st to 10th	Night	18% 2 4 18% 26% 32%	2427
	11th to 20th	Night	21% 3 4 13% 30% 29%	2218
	21st to end	Night	17% 4 4 10% 28% 38%	1851
March	1st to 10th	Night	18% 3 2 10% 37% 29%	3430
	11th to 20th	Night	24% 5% 4 16% 30% 22%	3490
	21st to end	Night	19% 3 4 14% 37% 23%	3803
April	1st to 10th	Night	15% 3 3 9% 32% 38%	1900
	11th to 20th	Night	16% 4 2 11% 23% 44%	1877
	21st to end	Night	10% 4 2 11% 31% 42%	1900
May	1st to 10th	Night	8% 2 1 6% 19% 65%	3170
	11th to 20th	Night	16% 6% 6% 9% 22% 42%	3141
	21st to end	Night	8% 2 2 5% 13% 70%	3111
June	1st to 10th	Night	17% 4 5% 15% 22% 36%	1710
	11th to 20th	Night	15% 3 4 9% 18% 51%	1710
	21st to end	Night	26% 7% 9% 15% 17% 26%	1710
July	1st to 10th	Night	27% 8% 15% 18% 16% 17%	2815
	11th to 20th	Night	27% 7% 12% 19% 27% 8%	2806
	21st to end	Night	36% 8% 18% 24% 10% 3	3011
August	1st to 10th	Night	27% 8% 13% 31% 17% 4	2992
	11th to 20th	Night	24% 6% 13% 15% 32% 11%	3143
	21st to end	Night	38% 8% 14% 20% 16% 4	3487
September	1st to 10th	Night	29% 6% 11% 17% 19% 17%	1900
	11th to 20th	Night	24% 5% 8% 18% 21% 24%	1900
	21st to end	Night	18% 3 6% 15% 32% 25%	2143
October	1st to 10th	Night	13% 3 5% 9% 24% 46%	3800
	11th to 20th	Night	17% 2 3 12% 24% 41%	3778
	21st to end	Night	9% 1 2 9% 31% 48%	4120
November	1st to 10th	Night	12% 3 3 16% 34% 32%	2340
	11th to 20th	Night	13% 3 2 17% 33% 32%	2400
	21st to end	Night	21% 2 5% 18% 31% 24%	2515
December	1st to 10th	Night	17% 2 4 22% 35% 19%	4368
	11th to 20th	Night	19% 2 5% 14% 39% 21%	4943
	21st to end	Night	16% 2 3 18% 41% 20%	6468

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	9% 8% 17% 42% 19% 5%	288
	11th to 20th	Day	7% 5% 17% 39% 24% 8%	270
	21st to end	Day	5% 7% 22% 34% 25% 7%	297
February	1st to 10th	Day	6% 9% 20% 36% 21% 8%	270
	11th to 20th	Day	13% 7% 24% 37% 17% 2	270
	21st to end	Day	9% 20% 24% 31% 11% 5%	253
March	1st to 10th	Day	8% 17% 31% 31% 11% 3	460
	11th to 20th	Day	10% 17% 22% 27% 18% 5%	460
	21st to end	Day	6% 23% 33% 25% 11% 3	506
April	1st to 10th	Day	7% 16% 29% 26% 15% 8%	460
	11th to 20th	Day	5% 20% 33% 25% 15% 3	452
	21st to end	Day	5% 18% 30% 26% 15% 5%	460
May	1st to 10th	Day	3 12% 34% 26% 18% 6%	463
	11th to 20th	Day	2 9% 28% 29% 23% 9%	488
	21st to end	Day	2 10% 29% 35% 19% 6%	529
June	1st to 10th	Day	3 5% 19% 31% 26% 17%	490
	11th to 20th	Day	4 4 19% 30% 28% 15%	490
	21st to end	Day	5% 3 10% 26% 28% 27%	490
July	1st to 10th	Day	4 1 4 21% 36% 33%	486
	11th to 20th	Day	2 1 2 17% 38% 40%	484
	21st to end	Day	3 2 2 13% 33% 46%	531
August	1st to 10th	Day	4 1 2 12% 34% 47%	487
	11th to 20th	Day	4 2 4 17% 36% 37%	477
	21st to end	Day	5% 1 2 16% 34% 42%	539
September	1st to 10th	Day	7% 1 5% 22% 37% 27%	490
	11th to 20th	Day	3 2 8% 26% 40% 21%	490
	21st to end	Day	4 4 9% 25% 38% 21%	368
October	1st to 10th	Day	4 3 12% 23% 35% 23%	300
	11th to 20th	Day	9% 5% 11% 22% 32% 21%	300
	21st to end	Day	5% 7% 10% 25% 34% 20%	330
November	1st to 10th	Day	6% 3 18% 34% 29% 9%	300
	11th to 20th	Day	1 5% 14% 30% 37% 13%	300
	21st to end	Day	8% 9% 19% 34% 22% 7%	300
December	1st to 10th	Day	10% 3 17% 36% 27% 8%	300
	11th to 20th	Day	6% 6% 21% 39% 19% 9%	300
	21st to end	Day	8% 7% 24% 38% 19% 4	330
January	1st to 10th	Night	6% 5% 21% 49% 17% 2	784
	11th to 20th	Night	4 4 25% 49% 17% 1	760
	21st to end	Night	6% 6% 25% 46% 16% 1	836
February	1st to 10th	Night	4 4 28% 45% 18% 1	760
	11th to 20th	Night	8% 6% 31% 44% 11%	744
	21st to end	Night	4 8% 43% 37% 8%	628
March	1st to 10th	Night	6% 7% 31% 44% 10%	760
	11th to 20th	Night	4 8% 28% 43% 16% 1	760
	21st to end	Night	3 9% 36% 39% 12%	823
April	1st to 10th	Night	2 9% 42% 39% 9%	570
	11th to 20th	Night	5% 9% 39% 37% 9%	563
	21st to end	Night	2 10% 38% 42% 8% 1	570
May	1st to 10th	Night	3 6% 36% 46% 9%	570
	11th to 20th	Night	2 3 27% 50% 16% 1	561
	21st to end	Night	2 5% 30% 50% 13%	617
June	1st to 10th	Night	3 3 20% 49% 24% 1	570
	11th to 20th	Night	2 1 19% 54% 23%	570
	21st to end	Night	4 1 9% 44% 39% 3	570
July	1st to 10th	Night	5% 2 4 36% 48% 6%	555
	11th to 20th	Night	4 1 3 25% 59% 8%	552
	21st to end	Night	5% 3 2 23% 57% 10%	624
August	1st to 10th	Night	4 1 3 23% 56% 13%	567
	11th to 20th	Night	5% 1 4 24% 57% 10%	564
	21st to end	Night	3 2 3 25% 59% 8%	627
September	1st to 10th	Night	6% 2 4 33% 50% 4	570
	11th to 20th	Night	6% 1 5% 41% 46% 1	570
	21st to end	Night	5% 1 8% 45% 39% 2	694
October	1st to 10th	Night	5% 3 13% 47% 31% 2	760
	11th to 20th	Night	5% 1 16% 48% 29% 1	760
	21st to end	Night	3 3 15% 41% 33% 4	836
November	1st to 10th	Night	4 2 16% 45% 30% 2	780
	11th to 20th	Night	3 2 18% 46% 29% 3	800
	21st to end	Night	8% 4 22% 43% 22% 1	915
December	1st to 10th	Night	7% 4 19% 49% 19% 1	1000
	11th to 20th	Night	5% 4 23% 49% 18% 1	880
	21st to end	Night	4 5% 26% 48% 16% 1	880

Page generated at 2025-01-04 01:23:58. Version ac07

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