Appold Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Appold Planetarium clear sky chart from 2005-11-06 to 2024-03-08.

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	15% 10% 4 7% 6% 3 5% 5% 5% 7% 33%	78702
	Night	16% 10% 4 7% 6% 3 4 4 5% 6% 34%	80892
Transparency	Day	50% 6% 12% 20% 11% 1	78414
	Night	51% 6% 11% 19% 12% 1	80701
Seeing	Day	20% 12% 29% 22% 12% 5%	14600
	Night	20% 10% 28% 27% 12% 1	24592

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	19% 18% 7% 10% 7% 3 4 5% 4 4 19%	2527
	11th to 20th	Day	16% 19% 6% 10% 7% 5% 9% 6% 4 5% 12%	2530
	21st to end	Day	27% 20% 10% 10% 5% 2 3 3 3 4 12%	3122
February	1st to 10th	Day	15% 15% 5% 9% 8% 4 6% 5% 5% 5% 22%	1710
	11th to 20th	Day	15% 11% 5% 10% 9% 5% 6% 4 5% 5% 26%	1831
	21st to end	Day	17% 13% 5% 8% 5% 3 5% 4 5% 7% 27%	1570
March	1st to 10th	Day	17% 12% 5% 8% 6% 3 4 5% 5% 7% 28%	1901
	11th to 20th	Day	15% 13% 4 7% 6% 3 3 4 5% 7% 33%	1980
	21st to end	Day	22% 13% 5% 7% 6% 3 4 5% 4 4 26%	2178
April	1st to 10th	Day	16% 11% 4 6% 6% 3 6% 5% 5% 7% 31%	2101
	11th to 20th	Day	19% 9% 3 6% 5% 3 5% 5% 5% 8% 33%	2255
	21st to end	Day	20% 9% 3 6% 4 3 4 4 5% 7% 34%	2340
May	1st to 10th	Day	17% 8% 3 7% 6% 3 5% 4 6% 8% 33%	2340
	11th to 20th	Day	19% 8% 3 7% 5% 3 5% 4 6% 7% 33%	2301
	21st to end	Day	11% 5% 3 5% 6% 4 6% 6% 7% 8% 40%	2531
June	1st to 10th	Day	12% 5% 2 5% 5% 3 6% 6% 6% 8% 41%	2474
	11th to 20th	Day	10% 6% 2 5% 5% 4 5% 6% 6% 8% 43%	2520
	21st to end	Day	11% 5% 3 6% 5% 4 6% 6% 7% 10% 39%	2520
July	1st to 10th	Day	9% 5% 2 4 5% 3 5% 5% 6% 9% 46%	2520
	11th to 20th	Day	9% 3 2 5% 4 3 5% 6% 6% 11% 45%	2520
	21st to end	Day	8% 5% 2 5% 6% 4 6% 6% 6% 9% 43%	2567
August	1st to 10th	Day	8% 4 2 4 6% 3 6% 5% 7% 8% 46%	2327
	11th to 20th	Day	10% 5% 2 5% 7% 4 6% 5% 8% 10% 39%	2303
	21st to end	Day	11% 5% 2 5% 6% 3 4 6% 6% 10% 43%	2513
September	1st to 10th	Day	13% 6% 3 5% 5% 3 5% 5% 6% 8% 42%	2039
	11th to 20th	Day	9% 5% 2 6% 5% 3 6% 6% 6% 9% 45%	1980
	21st to end	Day	15% 6% 2 4 4 3 4 6% 5% 8% 42%	1980
October	1st to 10th	Day	13% 5% 3 6% 5% 3 4 5% 6% 7% 43%	1951
	11th to 20th	Day	20% 9% 2 6% 5% 3 5% 4 5% 6% 35%	1800
	21st to end	Day	20% 8% 3 7% 6% 4 5% 5% 6% 6% 31%	1834
November	1st to 10th	Day	12% 8% 3 7% 4 4 4 5% 6% 8% 41%	1672
	11th to 20th	Day	17% 14% 4 7% 6% 3 4 4 4 5% 33%	1710
	21st to end	Day	20% 12% 5% 6% 6% 2 4 5% 5% 7% 28%	1710
December	1st to 10th	Day	16% 16% 8% 11% 6% 3 4 4 3 5% 22%	1710
	11th to 20th	Day	15% 15% 7% 8% 7% 4 5% 4 5% 7% 23%	2052
	21st to end	Day	25% 21% 7% 12% 5% 3 4 3 4 5% 12%	2783
January	1st to 10th	Night	17% 18% 7% 7% 7% 3 4 4 5% 5% 23%	4428
	11th to 20th	Night	16% 19% 7% 12% 7% 3 5% 6% 4 5% 15%	4440
	21st to end	Night	26% 18% 8% 10% 5% 3 4 3 3 4 16%	4532
February	1st to 10th	Night	17% 15% 6% 9% 7% 4 5% 4 4 6% 25%	2470
	11th to 20th	Night	15% 13% 5% 9% 6% 4 5% 4 5% 6% 28%	2233
	21st to end	Night	21% 12% 4 8% 5% 3 4 4 4 6% 28%	1884
March	1st to 10th	Night	16% 9% 5% 7% 6% 3 4 4 4 5% 35%	2220
	11th to 20th	Night	15% 9% 3 5% 5% 3 4 5% 5% 6% 39%	1980
	21st to end	Night	20% 9% 4 7% 5% 3 4 4 4 7% 33%	2178
April	1st to 10th	Night	16% 8% 4 6% 5% 3 4 4 5% 7% 37%	1872
	11th to 20th	Night	18% 7% 3 6% 5% 3 5% 4 4 7% 37%	1652
	21st to end	Night	17% 9% 3 5% 5% 3 4 5% 5% 6% 38%	1620
May	1st to 10th	Night	19% 7% 3 7% 6% 4 6% 5% 6% 7% 31%	1620
	11th to 20th	Night	19% 7% 2 6% 5% 3 5% 4 5% 7% 39%	1592
	21st to end	Night	9% 5% 2 6% 5% 3 4 6% 6% 9% 44%	1744
June	1st to 10th	Night	10% 4 2 4 5% 3 6% 6% 7% 8% 44%	1481
	11th to 20th	Night	11% 5% 2 6% 5% 3 4 5% 6% 8% 45%	1440
	21st to end	Night	10% 4 2 4 4 3 4 6% 7% 11% 44%	1440
July	1st to 10th	Night	9% 3 2 4 4 3 4 5% 5% 8% 53%	1440
	11th to 20th	Night	8% 4 2 4 5% 2 4 4 6% 8% 53%	1440
	21st to end	Night	6% 3 1 4 6% 3 5% 6% 7% 9% 50%	1748
August	1st to 10th	Night	7% 4 2 4 5% 3 5% 4 6% 9% 51%	1611
	11th to 20th	Night	9% 4 2 3 4 4 5% 6% 6% 9% 48%	1598
	21st to end	Night	9% 4 2 5% 5% 3 4 5% 5% 7% 51%	1840
September	1st to 10th	Night	11% 5% 2 5% 5% 3 4 4 4 8% 48%	1901
	11th to 20th	Night	9% 5% 2 4 5% 3 3 3 4 7% 53%	1980
	21st to end	Night	13% 5% 3 6% 4 3 4 4 5% 6% 47%	1980
October	1st to 10th	Night	14% 6% 2 5% 6% 3 4 3 5% 7% 44%	2008
	11th to 20th	Night	18% 9% 2 6% 5% 3 4 5% 4 6% 37%	2160
	21st to end	Night	22% 8% 3 5% 5% 3 5% 4 4 5% 35%	2520
November	1st to 10th	Night	14% 8% 3 5% 5% 3 4 4 5% 6% 44%	2406
	11th to 20th	Night	16% 10% 4 7% 5% 3 4 4 6% 7% 33%	2470
	21st to end	Night	20% 12% 4 8% 6% 3 4 4 5% 6% 28%	2470
December	1st to 10th	Night	18% 14% 7% 8% 6% 4 4 4 4 6% 24%	2470
	11th to 20th	Night	17% 15% 5% 9% 5% 3 5% 4 5% 5% 27%	3140
	21st to end	Night	29% 19% 7% 8% 6% 3 4 4 4 5% 13%	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	68% 5% 10% 12% 5%	2528
	11th to 20th	Day	74% 5% 10% 7% 3	2530
	21st to end	Day	78% 4 7% 8% 3	3122
February	1st to 10th	Day	63% 6% 11% 14% 6%	1710
	11th to 20th	Day	60% 5% 10% 17% 8%	1841
	21st to end	Day	57% 5% 14% 17% 6% 2	1570
March	1st to 10th	Day	56% 5% 13% 19% 7%	1901
	11th to 20th	Day	52% 4 12% 19% 11% 2	1980
	21st to end	Day	60% 5% 9% 20% 5% 1	2178
April	1st to 10th	Day	53% 6% 12% 17% 13%	2101
	11th to 20th	Day	49% 6% 11% 20% 12% 2	2255
	21st to end	Day	49% 5% 12% 20% 11% 2	2340
May	1st to 10th	Day	49% 6% 12% 20% 12% 1	2340
	11th to 20th	Day	49% 6% 11% 18% 14% 2	2305
	21st to end	Day	41% 7% 14% 24% 13% 2	2531
June	1st to 10th	Day	39% 7% 12% 26% 13% 3	2474
	11th to 20th	Day	38% 6% 14% 22% 16% 3	2520
	21st to end	Day	39% 7% 14% 21% 15% 4	2520
July	1st to 10th	Day	35% 7% 12% 25% 18% 4	2451
	11th to 20th	Day	32% 8% 14% 26% 18% 2	2445
	21st to end	Day	36% 7% 13% 24% 18% 3	2424
August	1st to 10th	Day	32% 7% 16% 29% 14% 1	2314
	11th to 20th	Day	38% 7% 14% 25% 14% 1	2303
	21st to end	Day	35% 8% 12% 25% 18% 3	2513
September	1st to 10th	Day	39% 6% 15% 21% 16% 3	2039
	11th to 20th	Day	34% 7% 11% 31% 17% 1	1980
	21st to end	Day	39% 6% 13% 26% 16% 1	1980
October	1st to 10th	Day	40% 6% 11% 26% 15% 2	1951
	11th to 20th	Day	48% 5% 10% 22% 13% 1	1800
	21st to end	Day	52% 5% 14% 18% 10% 1	1834
November	1st to 10th	Day	42% 5% 13% 24% 16% 1	1672
	11th to 20th	Day	54% 5% 11% 18% 11% 1	1710
	21st to end	Day	56% 5% 13% 18% 7%	1710
December	1st to 10th	Day	67% 5% 10% 14% 4	1710
	11th to 20th	Day	60% 6% 13% 17% 4	2049
	21st to end	Day	76% 6% 8% 7% 3	2783
January	1st to 10th	Night	63% 5% 10% 15% 6%	4428
	11th to 20th	Night	71% 4 11% 10% 4	4440
	21st to end	Night	73% 4 10% 9% 3	4532
February	1st to 10th	Night	61% 6% 11% 15% 6% 1	2470
	11th to 20th	Night	56% 5% 10% 20% 8% 1	2234
	21st to end	Night	58% 5% 10% 17% 8% 1	1884
March	1st to 10th	Night	52% 5% 11% 22% 10% 1	2220
	11th to 20th	Night	45% 6% 12% 19% 15% 3	1980
	21st to end	Night	51% 5% 9% 25% 9% 2	2178
April	1st to 10th	Night	46% 6% 11% 20% 14% 2	1872
	11th to 20th	Night	47% 5% 10% 19% 17% 2	1652
	21st to end	Night	46% 5% 11% 21% 15% 2	1620
May	1st to 10th	Night	52% 6% 12% 17% 12% 2	1620
	11th to 20th	Night	46% 6% 9% 20% 18% 2	1593
	21st to end	Night	35% 8% 13% 27% 14% 2	1745
June	1st to 10th	Night	35% 6% 12% 27% 17% 2	1481
	11th to 20th	Night	36% 8% 12% 25% 16% 3	1440
	21st to end	Night	33% 8% 14% 25% 19% 1	1440
July	1st to 10th	Night	30% 7% 11% 27% 21% 3	1400
	11th to 20th	Night	29% 7% 15% 27% 20% 2	1392
	21st to end	Night	27% 9% 16% 24% 20% 4	1651
August	1st to 10th	Night	28% 7% 15% 31% 17% 2	1600
	11th to 20th	Night	31% 8% 15% 28% 16% 3	1598
	21st to end	Night	32% 7% 12% 25% 21% 3	1840
September	1st to 10th	Night	36% 6% 13% 25% 17% 4	1901
	11th to 20th	Night	32% 5% 10% 29% 23% 1	1980
	21st to end	Night	37% 6% 13% 26% 17% 2	1980
October	1st to 10th	Night	38% 6% 11% 24% 19% 1	2008
	11th to 20th	Night	47% 6% 10% 20% 16% 1	2160
	21st to end	Night	51% 5% 9% 23% 10% 1	2520
November	1st to 10th	Night	41% 5% 12% 24% 17% 1	2406
	11th to 20th	Night	48% 6% 13% 21% 11% 1	2470
	21st to end	Night	57% 5% 12% 20% 6%	2470
December	1st to 10th	Night	61% 5% 11% 16% 7%	2470
	11th to 20th	Night	59% 6% 14% 14% 7% 1	3142
	21st to end	Night	74% 5% 11% 8% 2	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	27% 21% 30% 18% 2 1	270
	11th to 20th	Day	31% 18% 38% 9% 3 1	270
	21st to end	Day	32% 17% 28% 20% 3	297
February	1st to 10th	Day	29% 20% 36% 11% 3	270
	11th to 20th	Day	28% 20% 38% 11% 2	270
	21st to end	Day	28% 28% 32% 10% 1	225
March	1st to 10th	Day	26% 23% 34% 14% 3	292
	11th to 20th	Day	26% 13% 37% 18% 6% 1	420
	21st to end	Day	32% 15% 30% 16% 7%	462
April	1st to 10th	Day	22% 16% 31% 21% 8% 1	420
	11th to 20th	Day	28% 19% 26% 16% 8% 2	412
	21st to end	Day	28% 14% 34% 14% 9% 2	420
May	1st to 10th	Day	24% 16% 29% 17% 9% 4	423
	11th to 20th	Day	22% 13% 33% 16% 12% 4	447
	21st to end	Day	14% 9% 29% 24% 18% 7%	485
June	1st to 10th	Day	13% 8% 33% 30% 13% 4	584
	11th to 20th	Day	14% 8% 31% 31% 12% 3	630
	21st to end	Day	13% 8% 31% 30% 13% 5%	630
July	1st to 10th	Day	10% 5% 24% 30% 19% 12%	621
	11th to 20th	Day	11% 6% 28% 27% 19% 9%	618
	21st to end	Day	10% 4 27% 30% 20% 9%	508
August	1st to 10th	Day	10% 2 22% 31% 22% 13%	446
	11th to 20th	Day	13% 4 23% 30% 19% 10%	439
	21st to end	Day	12% 5% 22% 31% 21% 10%	495
September	1st to 10th	Day	16% 6% 21% 27% 20% 10%	450
	11th to 20th	Day	11% 4 21% 27% 26% 11%	450
	21st to end	Day	20% 9% 24% 22% 17% 7%	450
October	1st to 10th	Day	16% 9% 28% 25% 15% 8%	450
	11th to 20th	Day	22% 19% 30% 21% 7% 1	450
	21st to end	Day	27% 19% 31% 17% 4 1	349
November	1st to 10th	Day	16% 19% 36% 19% 8% 3	270
	11th to 20th	Day	29% 21% 26% 18% 4 1	270
	21st to end	Day	29% 20% 33% 16% 2	270
December	1st to 10th	Day	28% 27% 27% 11% 7%	270
	11th to 20th	Day	25% 24% 36% 11% 3	270
	21st to end	Day	31% 19% 35% 11% 3	297
January	1st to 10th	Night	25% 17% 32% 20% 5% 1	950
	11th to 20th	Night	28% 16% 33% 17% 5% 1	950
	21st to end	Night	24% 16% 33% 23% 5%	836
February	1st to 10th	Night	26% 14% 33% 23% 4	760
	11th to 20th	Night	24% 14% 35% 24% 3	743
	21st to end	Night	29% 15% 35% 18% 2	628
March	1st to 10th	Night	22% 13% 30% 27% 7% 1	751
	11th to 20th	Night	21% 16% 33% 23% 7%	720
	21st to end	Night	25% 12% 31% 24% 8%	792
April	1st to 10th	Night	21% 14% 33% 26% 5%	612
	11th to 20th	Night	23% 11% 31% 26% 8% 1	533
	21st to end	Night	21% 9% 35% 25% 10%	540
May	1st to 10th	Night	21% 9% 28% 29% 11% 1	540
	11th to 20th	Night	21% 5% 29% 29% 14% 1	531
	21st to end	Night	11% 4 27% 35% 21% 3	584
June	1st to 10th	Night	12% 4 29% 39% 16%	540
	11th to 20th	Night	13% 4 25% 39% 18% 1	540
	21st to end	Night	12% 4 25% 35% 22% 2	540
July	1st to 10th	Night	10% 2 18% 37% 29% 3	525
	11th to 20th	Night	11% 2 21% 39% 22% 4	522
	21st to end	Night	8% 1 18% 43% 28% 3	591
August	1st to 10th	Night	9% 1 18% 41% 28% 3	537
	11th to 20th	Night	12% 2 15% 35% 31% 5%	534
	21st to end	Night	9% 3 16% 35% 32% 4	594
September	1st to 10th	Night	13% 5% 19% 34% 26% 4	641
	11th to 20th	Night	11% 4 18% 34% 29% 3	720
	21st to end	Night	15% 7% 21% 30% 24% 3	720
October	1st to 10th	Night	17% 8% 23% 29% 18% 3	720
	11th to 20th	Night	22% 14% 30% 23% 9% 2	720
	21st to end	Night	27% 12% 30% 24% 7%	792
November	1st to 10th	Night	19% 15% 28% 25% 11% 1	740
	11th to 20th	Night	23% 15% 32% 22% 7% 1	760
	21st to end	Night	28% 12% 32% 22% 5% 1	760
December	1st to 10th	Night	27% 16% 31% 20% 6%	760
	11th to 20th	Night	26% 16% 32% 21% 5%	821
	21st to end	Night	32% 13% 33% 19% 3	1045

Page generated at 2024-03-05 07:23:58. Version ac07

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