Adolphson Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Adolphson Observatory clear sky chart from 2005-11-06 to 2024-10-24.

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	12% 8% 3 7% 5% 4 4 4 6% 8% 39%	101317
	Night	13% 9% 3 7% 4 4 4 3 5% 6% 41%	97528
Transparency	Day	42% 7% 13% 23% 13% 1	101106
	Night	42% 6% 12% 23% 14% 2	97410
Seeing	Day	15% 10% 28% 26% 16% 5%	15752
	Night	16% 10% 31% 30% 12% 1	25557

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	11% 12% 6% 14% 7% 6% 5% 3 4 6% 26%	2527
	11th to 20th	Day	12% 12% 4 12% 9% 7% 8% 4 5% 5% 23%	2576
	21st to end	Day	15% 19% 9% 13% 7% 4 4 3 3 5% 18%	3135
February	1st to 10th	Day	15% 12% 5% 10% 6% 6% 5% 3 4 6% 28%	1710
	11th to 20th	Day	14% 10% 3 8% 5% 5% 5% 4 4 7% 35%	1765
	21st to end	Day	14% 13% 4 11% 6% 3 3 3 4 6% 34%	1570
March	1st to 10th	Day	16% 12% 4 7% 3 4 3 3 4 5% 39%	3167
	11th to 20th	Day	9% 8% 2 5% 4 4 4 4 6% 7% 46%	3480
	21st to end	Day	19% 13% 4 10% 5% 4 4 3 5% 6% 27%	4023
April	1st to 10th	Day	15% 12% 3 7% 5% 4 3 3 5% 7% 36%	2280
	11th to 20th	Day	15% 10% 3 7% 5% 4 4 3 5% 5% 38%	2254
	21st to end	Day	21% 7% 3 8% 5% 4 4 3 5% 6% 34%	2280
May	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 7% 9% 35%	4123
	11th to 20th	Day	17% 7% 2 6% 4 4 3 4 5% 8% 39%	4399
	21st to end	Day	11% 6% 2 5% 4 4 4 4 5% 7% 45%	4824
June	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 46%	2660
	11th to 20th	Day	7% 6% 2 6% 5% 4 5% 3 6% 7% 49%	2660
	21st to end	Day	10% 6% 2 6% 6% 5% 4 4 7% 10% 41%	2660
July	1st to 10th	Day	9% 7% 2 7% 5% 6% 6% 5% 8% 10% 36%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 5% 4 6% 10% 50%	4440
	21st to end	Day	7% 4 2 6% 5% 5% 6% 5% 8% 12% 40%	4754
August	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 4 8% 12% 43%	4104
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 4 6% 10% 41%	3829
	21st to end	Day	6% 5% 2 5% 4 5% 4 4 6% 9% 50%	4180
September	1st to 10th	Day	11% 5% 2 5% 4 4 3 3 6% 7% 50%	2280
	11th to 20th	Day	10% 4 1 4 4 3 4 3 5% 8% 52%	2268
	21st to end	Day	9% 5% 2 6% 4 4 5% 4 6% 8% 48%	2057
October	1st to 10th	Day	12% 6% 2 5% 4 3 3 3 4 5% 51%	1900
	11th to 20th	Day	15% 9% 2 7% 4 3 3 2 4 6% 45%	1900
	21st to end	Day	20% 9% 2 5% 3 3 3 3 4 6% 40%	1948
November	1st to 10th	Day	10% 7% 2 5% 5% 3 4 4 6% 7% 47%	1672
	11th to 20th	Day	15% 11% 3 8% 4 4 3 3 4 8% 37%	1710
	21st to end	Day	16% 13% 3 7% 4 4 3 2 4 5% 39%	1521
December	1st to 10th	Day	14% 13% 5% 9% 6% 4 5% 3 4 5% 33%	1520
	11th to 20th	Day	14% 12% 3 8% 6% 4 4 3 6% 5% 34%	1918
	21st to end	Day	21% 19% 9% 13% 5% 3 3 2 4 4 17%	2783
January	1st to 10th	Night	12% 13% 6% 14% 5% 5% 4 3 4 5% 30%	4428
	11th to 20th	Night	12% 17% 7% 11% 6% 5% 5% 4 8% 4 23%	4379
	21st to end	Night	18% 16% 6% 14% 5% 3 3 3 4 4 24%	4532
February	1st to 10th	Night	15% 11% 5% 9% 5% 4 5% 3 5% 6% 33%	2470
	11th to 20th	Night	13% 10% 3 7% 5% 4 4 4 5% 7% 37%	2301
	21st to end	Night	14% 11% 4 8% 4 3 3 3 4 5% 41%	1884
March	1st to 10th	Night	18% 11% 3 6% 3 4 4 3 4 5% 39%	3715
	11th to 20th	Night	12% 7% 2 5% 3 3 3 2 5% 6% 51%	3480
	21st to end	Night	21% 11% 5% 10% 5% 5% 4 3 5% 6% 25%	3608
April	1st to 10th	Night	14% 9% 3 7% 5% 4 3 3 5% 7% 40%	1900
	11th to 20th	Night	15% 10% 2 6% 3 4 3 3 6% 5% 43%	1875
	21st to end	Night	17% 6% 3 7% 5% 4 4 3 5% 7% 38%	1900
May	1st to 10th	Night	18% 8% 3 7% 5% 4 4 3 6% 8% 33%	2772
	11th to 20th	Night	12% 7% 2 6% 4 5% 4 3 6% 8% 42%	2506
	21st to end	Night	7% 5% 2 6% 4 4 5% 4 6% 8% 49%	2743
June	1st to 10th	Night	8% 4 2 5% 5% 4 3 5% 6% 9% 50%	1520
	11th to 20th	Night	7% 6% 2 5% 4 3 4 3 7% 10% 48%	1520
	21st to end	Night	9% 5% 2 5% 4 4 4 4 6% 8% 47%	1520
July	1st to 10th	Night	13% 6% 2 6% 5% 4 6% 4 7% 9% 39%	2530
	11th to 20th	Night	4 3 1 4 4 4 4 4 6% 9% 58%	2530
	21st to end	Night	6% 4 2 6% 4 4 5% 4 7% 9% 48%	2805
August	1st to 10th	Night	4 4 2 4 4 3 4 4 5% 9% 57%	2836
	11th to 20th	Night	6% 5% 2 5% 4 4 4 3 5% 7% 54%	3001
	21st to end	Night	5% 4 2 5% 4 4 4 4 6% 8% 55%	3476
September	1st to 10th	Night	11% 5% 1 4 2 3 3 2 5% 7% 57%	1900
	11th to 20th	Night	10% 4 2 5% 4 3 4 4 6% 7% 52%	1900
	21st to end	Night	8% 5% 2 5% 5% 4 4 4 6% 9% 50%	2110
October	1st to 10th	Night	10% 6% 2 5% 4 3 3 3 4 5% 54%	2280
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 5% 6% 50%	2280
	21st to end	Night	16% 9% 2 6% 4 4 4 4 5% 6% 40%	2473
November	1st to 10th	Night	11% 7% 2 5% 3 2 3 2 5% 7% 52%	2406
	11th to 20th	Night	13% 9% 3 6% 4 3 4 3 6% 7% 41%	2470
	21st to end	Night	16% 10% 3 7% 4 4 3 3 4 6% 39%	2655
December	1st to 10th	Night	13% 12% 4 8% 5% 4 4 3 5% 6% 35%	2660
	11th to 20th	Night	14% 12% 4 9% 5% 4 4 3 4 5% 36%	3279
	21st to end	Night	21% 17% 6% 12% 6% 5% 4 3 3 4 19%	4884

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	58% 7% 11% 18% 6%	2528
	11th to 20th	Day	62% 6% 10% 14% 8%	2576
	21st to end	Day	69% 5% 9% 11% 6%	3135
February	1st to 10th	Day	57% 5% 13% 17% 6% 2	1710
	11th to 20th	Day	49% 6% 12% 21% 11% 1	1774
	21st to end	Day	52% 5% 11% 22% 9% 2	1570
March	1st to 10th	Day	48% 6% 11% 19% 14% 2	3167
	11th to 20th	Day	35% 7% 15% 25% 18%	3480
	21st to end	Day	55% 8% 15% 18% 4 1	4023
April	1st to 10th	Day	48% 6% 12% 23% 12%	2280
	11th to 20th	Day	46% 6% 10% 23% 13% 2	2254
	21st to end	Day	50% 6% 10% 19% 13% 1	2280
May	1st to 10th	Day	42% 10% 13% 21% 14% 1	4159
	11th to 20th	Day	43% 7% 11% 29% 10%	4403
	21st to end	Day	36% 8% 11% 22% 21% 2	4837
June	1st to 10th	Day	33% 8% 15% 25% 16% 2	2660
	11th to 20th	Day	34% 7% 11% 24% 22% 3	2660
	21st to end	Day	37% 8% 15% 22% 15% 2	2660
July	1st to 10th	Day	41% 7% 14% 25% 11% 2	4371
	11th to 20th	Day	28% 7% 17% 28% 18% 2	4365
	21st to end	Day	33% 8% 22% 21% 15% 1	4604
August	1st to 10th	Day	30% 8% 18% 31% 11% 1	4090
	11th to 20th	Day	38% 7% 15% 27% 14% 1	3867
	21st to end	Day	30% 7% 14% 31% 15% 3	4179
September	1st to 10th	Day	32% 7% 12% 24% 21% 4	2280
	11th to 20th	Day	29% 5% 12% 27% 23% 4	2268
	21st to end	Day	32% 7% 12% 28% 20% 2	2057
October	1st to 10th	Day	35% 6% 10% 26% 22% 2	1900
	11th to 20th	Day	42% 4 8% 25% 19% 2	1900
	21st to end	Day	45% 4 13% 21% 14% 3	1948
November	1st to 10th	Day	35% 6% 16% 24% 15% 4	1672
	11th to 20th	Day	46% 5% 11% 24% 12% 1	1710
	21st to end	Day	49% 5% 13% 23% 9% 1	1521
December	1st to 10th	Day	53% 6% 12% 20% 9% 1	1520
	11th to 20th	Day	49% 6% 11% 23% 8% 2	1915
	21st to end	Day	71% 5% 7% 11% 5%	2783
January	1st to 10th	Night	54% 8% 12% 18% 8%	4428
	11th to 20th	Night	61% 5% 11% 15% 8% 1	4379
	21st to end	Night	64% 5% 10% 16% 5% 1	4532
February	1st to 10th	Night	53% 4 12% 19% 11% 1	2470
	11th to 20th	Night	46% 5% 12% 24% 12% 1	2302
	21st to end	Night	47% 3 8% 25% 14% 2	1884
March	1st to 10th	Night	46% 7% 9% 24% 12% 1	3715
	11th to 20th	Night	34% 6% 11% 30% 16% 4	3480
	21st to end	Night	57% 9% 13% 16% 5% 1	3608
April	1st to 10th	Night	42% 6% 11% 25% 14% 2	1900
	11th to 20th	Night	42% 5% 10% 22% 17% 4	1875
	21st to end	Night	45% 6% 12% 20% 14% 3	1900
May	1st to 10th	Night	46% 9% 14% 18% 13% 1	2801
	11th to 20th	Night	37% 11% 15% 26% 11%	2507
	21st to end	Night	30% 8% 13% 24% 23% 2	2751
June	1st to 10th	Night	29% 9% 16% 24% 18% 4	1520
	11th to 20th	Night	29% 7% 12% 25% 23% 5%	1520
	21st to end	Night	34% 7% 16% 19% 20% 3	1520
July	1st to 10th	Night	40% 6% 15% 23% 13% 2	2490
	11th to 20th	Night	23% 6% 14% 32% 24% 2	2482
	21st to end	Night	30% 7% 19% 22% 19% 3	2716
August	1st to 10th	Night	22% 7% 18% 33% 18% 2	2826
	11th to 20th	Night	29% 6% 16% 32% 17% 1	3029
	21st to end	Night	26% 7% 16% 31% 16% 4	3476
September	1st to 10th	Night	27% 5% 12% 26% 25% 5%	1900
	11th to 20th	Night	29% 7% 11% 26% 21% 6%	1900
	21st to end	Night	31% 6% 12% 25% 24% 3	2110
October	1st to 10th	Night	32% 5% 10% 24% 25% 4	2280
	11th to 20th	Night	35% 5% 10% 25% 22% 3	2280
	21st to end	Night	44% 6% 10% 20% 18% 2	2473
November	1st to 10th	Night	32% 5% 13% 26% 20% 4	2406
	11th to 20th	Night	41% 6% 12% 24% 16% 2	2470
	21st to end	Night	46% 5% 11% 24% 13% 1	2655
December	1st to 10th	Night	49% 5% 13% 22% 10% 1	2660
	11th to 20th	Night	49% 6% 12% 25% 8% 1	3281
	21st to end	Night	69% 6% 8% 11% 5%	4884

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	21% 18% 33% 20% 7% 1	270
	11th to 20th	Day	25% 20% 37% 13% 5%	270
	21st to end	Day	21% 21% 33% 19% 6%	297
February	1st to 10th	Day	23% 17% 40% 17% 4	270
	11th to 20th	Day	21% 18% 34% 21% 4 1	270
	21st to end	Day	24% 17% 41% 16% 2	225
March	1st to 10th	Day	19% 18% 43% 18% 3	270
	11th to 20th	Day	27% 17% 32% 15% 9%	270
	21st to end	Day	29% 18% 32% 15% 6% 1	416
April	1st to 10th	Day	24% 13% 34% 23% 5%	460
	11th to 20th	Day	19% 17% 32% 20% 11% 1	452
	21st to end	Day	25% 13% 33% 20% 8% 2	460
May	1st to 10th	Day	20% 10% 34% 26% 8% 2	547
	11th to 20th	Day	19% 13% 28% 24% 13% 2	675
	21st to end	Day	15% 8% 30% 26% 15% 7%	734
June	1st to 10th	Day	8% 5% 26% 31% 23% 6%	680
	11th to 20th	Day	7% 4 28% 36% 20% 4	680
	21st to end	Day	10% 9% 31% 31% 15% 5%	680
July	1st to 10th	Day	10% 4 17% 32% 25% 13%	671
	11th to 20th	Day	9% 3 23% 36% 21% 9%	668
	21st to end	Day	8% 3 19% 35% 28% 7%	739
August	1st to 10th	Day	6% 3 21% 35% 27% 8%	676
	11th to 20th	Day	9% 6% 18% 29% 28% 11%	543
	21st to end	Day	6% 4 15% 33% 31% 11%	539
September	1st to 10th	Day	12% 6% 17% 31% 26% 8%	490
	11th to 20th	Day	8% 2 17% 35% 26% 11%	490
	21st to end	Day	12% 8% 27% 25% 23% 7%	457
October	1st to 10th	Day	12% 8% 30% 28% 17% 5%	300
	11th to 20th	Day	19% 18% 30% 20% 12% 1	300
	21st to end	Day	31% 15% 30% 18% 5% 1	306
November	1st to 10th	Day	11% 11% 39% 26% 10% 3	270
	11th to 20th	Day	21% 16% 34% 20% 7% 1	270
	21st to end	Day	26% 13% 32% 25% 4	270
December	1st to 10th	Day	14% 17% 38% 21% 6% 3	270
	11th to 20th	Day	20% 15% 38% 20% 7%	270
	21st to end	Day	23% 21% 37% 16% 3	297
January	1st to 10th	Night	15% 16% 42% 20% 6%	950
	11th to 20th	Night	19% 15% 39% 21% 5% 1	950
	21st to end	Night	19% 13% 37% 28% 3	1045
February	1st to 10th	Night	22% 12% 39% 23% 5%	950
	11th to 20th	Night	18% 15% 37% 26% 3	826
	21st to end	Night	20% 15% 41% 20% 3	628
March	1st to 10th	Night	21% 13% 39% 22% 4	755
	11th to 20th	Night	19% 12% 35% 28% 7%	570
	21st to end	Night	25% 12% 35% 25% 4	627
April	1st to 10th	Night	19% 13% 38% 26% 4	570
	11th to 20th	Night	20% 13% 33% 27% 7%	563
	21st to end	Night	20% 10% 34% 30% 6%	570
May	1st to 10th	Night	15% 10% 37% 31% 6% 1	570
	11th to 20th	Night	17% 7% 27% 35% 13% 1	561
	21st to end	Night	11% 6% 31% 32% 19% 1	617
June	1st to 10th	Night	10% 4 24% 44% 17% 1	570
	11th to 20th	Night	9% 4 26% 40% 20%	570
	21st to end	Night	11% 4 30% 37% 18% 1	570
July	1st to 10th	Night	9% 2 12% 41% 32% 4	555
	11th to 20th	Night	5% 1 20% 45% 26% 3	552
	21st to end	Night	6% 2 13% 47% 30% 1	624
August	1st to 10th	Night	6% 1 15% 46% 29% 3	567
	11th to 20th	Night	7% 2 16% 41% 29% 5%	564
	21st to end	Night	7% 1 14% 45% 32% 2	627
September	1st to 10th	Night	12% 4 18% 38% 25% 3	570
	11th to 20th	Night	12% 3 18% 36% 27% 4	570
	21st to end	Night	10% 6% 24% 35% 21% 3	751
October	1st to 10th	Night	11% 7% 29% 32% 19% 2	760
	11th to 20th	Night	16% 12% 32% 29% 12%	760
	21st to end	Night	21% 12% 34% 25% 7%	805
November	1st to 10th	Night	16% 9% 40% 27% 8% 1	740
	11th to 20th	Night	17% 15% 38% 24% 6%	760
	21st to end	Night	21% 12% 36% 25% 6%	945
December	1st to 10th	Night	18% 13% 39% 24% 4 1	950
	11th to 20th	Night	22% 11% 34% 26% 6%	950
	21st to end	Night	26% 16% 34% 23% 2	1045

Page generated at 2024-10-21 01:20:05. Version ac07

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