Schreder Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Schreder Planetarium 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	11% 3 1 3 2 2 2 2 4 5% 65%	101266
	Night	14% 4 1 3 2 2 3 2 4 5% 59%	97691
Transparency	Day	23% 4 7% 17% 23% 25%	101020
	Night	28% 5% 8% 18% 22% 19%	97526
Seeing	Day	12% 9% 22% 30% 20% 7%	15045
	Night	14% 5% 20% 35% 24% 3	24177

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	22% 9% 3 5% 3 3 3 3 4 7% 38%	2539
	11th to 20th	Day	33% 8% 2 6% 3 2 2 2 3 3 36%	2778
	21st to end	Day	30% 7% 2 5% 3 3 3 2 4 6% 35%	3146
February	1st to 10th	Day	19% 6% 2 4 3 2 4 4 6% 5% 46%	1710
	11th to 20th	Day	19% 4 1 3 3 3 3 2 4 6% 51%	1679
	21st to end	Day	19% 4 2 3 3 3 3 3 5% 8% 47%	1570
March	1st to 10th	Day	28% 11% 3 6% 4 3 3 3 4 5% 30%	3349
	11th to 20th	Day	14% 4 1 3 2 2 2 2 4 6% 58%	3490
	21st to end	Day	22% 8% 2 5% 3 4 4 3 5% 6% 38%	3886
April	1st to 10th	Day	17% 6% 2 4 3 3 3 3 5% 7% 47%	2280
	11th to 20th	Day	13% 4 1 4 2 3 3 3 5% 6% 56%	2249
	21st to end	Day	5% 3 1 4 3 2 3 3 5% 7% 62%	2293
May	1st to 10th	Day	6% 3 1 2 2 3 3 2 4 6% 68%	4110
	11th to 20th	Day	4 2 1 2 1 1 1 2 3 6% 77%	4367
	21st to end	Day	4 2 1 2 2 2 2 2 4 6% 74%	4813
June	1st to 10th	Day	6% 3 1 3 3 3 3 4 5% 7% 62%	2660
	11th to 20th	Day	2 1 1 1 1 2 2 4 5% 79%	2660
	21st to end	Day	4 1 1 2 1 1 1 2 3 3 81%	2660
July	1st to 10th	Day	1 1 1 1 1 2 2 91%	4420
	11th to 20th	Day	2 1 1 1 1 1 2 1 2 3 84%	4420
	21st to end	Day	1 1 1 1 1 2 3 90%	4459
August	1st to 10th	Day	2 2 1 2 1 1 2 2 3 5% 79%	4091
	11th to 20th	Day	1 1 1 1 1 1 1 2 3 88%	3966
	21st to end	Day	2 1 1 1 1 1 1 1 2 3 87%	4180
September	1st to 10th	Day	1 1 1 1 1 1 2 4 89%	2280
	11th to 20th	Day	3 2 3 2 2 2 2 4 6% 75%	2280
	21st to end	Day	2 1 2 2 2 1 2 3 5% 79%	2006
October	1st to 10th	Day	4 2 1 2 2 1 2 2 3 4 75%	1900
	11th to 20th	Day	7% 3 1 2 2 2 2 3 4 6% 69%	1900
	21st to end	Day	12% 2 1 4 2 1 2 2 4 6% 64%	2011
November	1st to 10th	Day	15% 4 2 3 3 3 3 3 4 7% 53%	1741
	11th to 20th	Day	14% 4 2 4 2 3 4 4 6% 9% 50%	1611
	21st to end	Day	13% 4 2 4 3 3 3 3 4 7% 55%	1520
December	1st to 10th	Day	24% 4 1 2 2 3 2 2 4 5% 50%	1520
	11th to 20th	Day	33% 5% 2 6% 3 3 3 3 4 6% 32%	1928
	21st to end	Day	28% 5% 2 4 3 3 3 3 4 6% 38%	2794
January	1st to 10th	Night	23% 6% 1 5% 3 3 4 3 6% 8% 39%	4406
	11th to 20th	Night	30% 6% 2 6% 3 3 3 3 4 5% 35%	4172
	21st to end	Night	29% 9% 3 7% 4 3 4 3 4 4 31%	4521
February	1st to 10th	Night	20% 5% 1 4 3 3 3 3 5% 5% 48%	2470
	11th to 20th	Night	20% 6% 1 4 3 3 3 3 4 6% 48%	2388
	21st to end	Night	17% 6% 1 4 3 4 3 2 4 8% 48%	1884
March	1st to 10th	Night	26% 8% 3 6% 4 3 3 3 3 5% 36%	3522
	11th to 20th	Night	17% 4 1 3 2 2 2 2 4 6% 56%	3490
	21st to end	Night	17% 7% 2 6% 4 4 4 4 6% 7% 38%	3767
April	1st to 10th	Night	16% 6% 2 5% 4 3 3 3 4 7% 48%	1900
	11th to 20th	Night	11% 4 2 4 3 3 3 3 5% 7% 56%	1879
	21st to end	Night	8% 4 1 3 2 2 2 2 6% 8% 62%	1883
May	1st to 10th	Night	8% 3 1 3 2 2 2 2 3 5% 69%	2860
	11th to 20th	Night	4 2 1 2 1 1 2 2 3 4 77%	2526
	21st to end	Night	4 3 1 3 2 2 3 2 4 6% 72%	2762
June	1st to 10th	Night	5% 4 2 4 3 3 3 4 6% 7% 58%	1520
	11th to 20th	Night	3 2 1 2 2 1 2 2 3 5% 78%	1520
	21st to end	Night	2 1 1 2 1 1 2 2 3 3 81%	1520
July	1st to 10th	Night	1 1 1 1 1 1 2 2 91%	2540
	11th to 20th	Night	1 2 1 2 1 1 2 1 3 3 83%	2540
	21st to end	Night	1 1 1 1 2 2 91%	3100
August	1st to 10th	Night	3 2 1 2 1 2 2 2 3 3 79%	2848
	11th to 20th	Night	1 1 1 1 1 2 3 89%	2872
	21st to end	Night	4 2 1 1 1 1 1 1 2 2 85%	3498
September	1st to 10th	Night	1 1 1 1 1 1 1 2 3 88%	1900
	11th to 20th	Night	3 1 2 2 1 2 2 3 6% 77%	1900
	21st to end	Night	4 1 1 2 1 2 2 2 3 5% 78%	2169
October	1st to 10th	Night	5% 2 1 2 2 2 2 2 3 5% 74%	2280
	11th to 20th	Night	7% 2 1 2 2 2 3 2 3 4 72%	2280
	21st to end	Night	11% 2 1 2 2 2 2 2 3 7% 65%	2412
November	1st to 10th	Night	14% 4 1 4 3 3 3 3 5% 7% 52%	2337
	11th to 20th	Night	14% 4 2 4 3 3 4 4 6% 9% 49%	2567
	21st to end	Night	14% 4 1 3 3 3 3 2 4 7% 56%	2660
December	1st to 10th	Night	24% 4 1 2 2 2 2 2 5% 6% 49%	2660
	11th to 20th	Night	35% 6% 1 3 3 2 3 3 4 7% 33%	3276
	21st to end	Night	27% 6% 2 4 3 3 3 3 5% 5% 37%	4862

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	45% 7% 13% 25% 7% 2	2539
	11th to 20th	Day	56% 4 8% 15% 10% 7%	2778
	21st to end	Day	51% 6% 12% 13% 13% 5%	3146
February	1st to 10th	Day	38% 6% 11% 18% 19% 8%	1710
	11th to 20th	Day	36% 4 9% 20% 24% 6%	1688
	21st to end	Day	37% 5% 10% 23% 19% 6%	1570
March	1st to 10th	Day	55% 7% 7% 11% 16% 3	3349
	11th to 20th	Day	29% 4 9% 24% 25% 9%	3490
	21st to end	Day	46% 8% 10% 21% 12% 3	3886
April	1st to 10th	Day	36% 6% 12% 21% 19% 6%	2280
	11th to 20th	Day	29% 6% 11% 22% 21% 11%	2252
	21st to end	Day	21% 5% 12% 26% 28% 9%	2293
May	1st to 10th	Day	16% 6% 11% 20% 28% 20%	4110
	11th to 20th	Day	12% 3 5% 15% 32% 33%	4370
	21st to end	Day	12% 4 11% 29% 32% 13%	4814
June	1st to 10th	Day	21% 6% 10% 20% 26% 17%	2660
	11th to 20th	Day	9% 3 8% 18% 32% 29%	2660
	21st to end	Day	10% 1 4 13% 28% 43%	2660
July	1st to 10th	Day	3 1 2 6% 15% 72%	4351
	11th to 20th	Day	8% 1 3 7% 20% 61%	4345
	21st to end	Day	4 1 2 10% 29% 54%	4318
August	1st to 10th	Day	10% 2 3 10% 24% 53%	4076
	11th to 20th	Day	5% 1 2 15% 36% 41%	4005
	21st to end	Day	7% 1 4 17% 33% 38%	4179
September	1st to 10th	Day	5% 1 3 9% 22% 59%	2280
	11th to 20th	Day	12% 3 7% 19% 34% 25%	2280
	21st to end	Day	11% 3 5% 16% 31% 34%	2006
October	1st to 10th	Day	15% 2 6% 18% 28% 31%	1900
	11th to 20th	Day	19% 4 8% 17% 27% 25%	1900
	21st to end	Day	24% 4 8% 19% 22% 23%	2011
November	1st to 10th	Day	32% 6% 7% 24% 18% 13%	1741
	11th to 20th	Day	33% 7% 12% 22% 16% 10%	1611
	21st to end	Day	31% 4 9% 20% 23% 12%	1520
December	1st to 10th	Day	38% 4 7% 18% 22% 11%	1520
	11th to 20th	Day	56% 4 8% 14% 13% 4	1928
	21st to end	Day	48% 6% 12% 19% 12% 3	2794
January	1st to 10th	Night	43% 8% 17% 21% 8% 3	4406
	11th to 20th	Night	52% 6% 9% 13% 12% 7%	4172
	21st to end	Night	56% 6% 8% 11% 13% 5%	4521
February	1st to 10th	Night	38% 5% 7% 23% 18% 9%	2470
	11th to 20th	Night	38% 5% 9% 19% 22% 7%	2390
	21st to end	Night	36% 5% 11% 22% 20% 7%	1884
March	1st to 10th	Night	49% 8% 13% 14% 13% 3	3522
	11th to 20th	Night	30% 4 9% 25% 22% 10%	3490
	21st to end	Night	40% 10% 14% 23% 10% 2	3767
April	1st to 10th	Night	37% 5% 14% 21% 16% 7%	1900
	11th to 20th	Night	28% 6% 14% 22% 20% 10%	1879
	21st to end	Night	22% 5% 14% 29% 24% 7%	1883
May	1st to 10th	Night	19% 6% 8% 20% 31% 16%	2860
	11th to 20th	Night	13% 4 6% 15% 36% 26%	2526
	21st to end	Night	15% 6% 11% 33% 26% 10%	2762
June	1st to 10th	Night	24% 6% 10% 23% 27% 9%	1520
	11th to 20th	Night	11% 3 8% 19% 33% 26%	1520
	21st to end	Night	10% 2 4 13% 35% 35%	1520
July	1st to 10th	Night	4 1 2 7% 18% 68%	2500
	11th to 20th	Night	9% 2 3 5% 19% 63%	2492
	21st to end	Night	3 1 3 10% 29% 54%	3003
August	1st to 10th	Night	13% 1 3 10% 25% 48%	2839
	11th to 20th	Night	3 2 3 14% 42% 36%	2899
	21st to end	Night	9% 1 2 17% 35% 37%	3498
September	1st to 10th	Night	5% 1 3 8% 24% 58%	1900
	11th to 20th	Night	11% 3 6% 20% 34% 25%	1900
	21st to end	Night	11% 3 6% 18% 26% 36%	2169
October	1st to 10th	Night	16% 3 5% 15% 29% 31%	2280
	11th to 20th	Night	18% 3 6% 23% 24% 27%	2280
	21st to end	Night	22% 3 8% 21% 23% 23%	2412
November	1st to 10th	Night	31% 6% 11% 22% 17% 12%	2337
	11th to 20th	Night	33% 6% 13% 22% 16% 10%	2567
	21st to end	Night	31% 4 10% 21% 21% 13%	2660
December	1st to 10th	Night	38% 4 9% 18% 21% 10%	2660
	11th to 20th	Night	53% 4 7% 15% 18% 3	3276
	21st to end	Night	49% 6% 10% 18% 14% 3	4862

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	42% 5% 19% 21% 10% 3	180
	11th to 20th	Day	29% 9% 21% 22% 14% 5%	327
	21st to end	Day	23% 9% 22% 25% 15% 7%	407
February	1st to 10th	Day	23% 9% 24% 23% 19% 2	370
	11th to 20th	Day	23% 10% 27% 25% 12% 2	371
	21st to end	Day	20% 10% 29% 27% 11% 3	382
March	1st to 10th	Day	32% 13% 25% 20% 7% 3	460
	11th to 20th	Day	24% 11% 22% 25% 14% 4	460
	21st to end	Day	25% 14% 25% 24% 11% 1	506
April	1st to 10th	Day	21% 16% 21% 28% 12% 2	460
	11th to 20th	Day	18% 14% 24% 24% 15% 4	452
	21st to end	Day	6% 14% 34% 25% 16% 5%	460
May	1st to 10th	Day	11% 17% 32% 22% 14% 5%	463
	11th to 20th	Day	10% 9% 29% 26% 19% 6%	488
	21st to end	Day	6% 12% 24% 31% 18% 8%	529
June	1st to 10th	Day	6% 13% 20% 31% 23% 7%	490
	11th to 20th	Day	6% 14% 28% 31% 15% 6%	490
	21st to end	Day	2 6% 24% 33% 26% 9%	490
July	1st to 10th	Day	1 4 22% 39% 22% 12%	486
	11th to 20th	Day	2 17% 39% 28% 13%	484
	21st to end	Day	1 2 11% 41% 32% 13%	531
August	1st to 10th	Day	2 2 16% 36% 28% 15%	487
	11th to 20th	Day	2 3 18% 34% 29% 15%	477
	21st to end	Day	1 5% 17% 35% 30% 13%	539
September	1st to 10th	Day	1 3 19% 38% 29% 11%	490
	11th to 20th	Day	3 7% 21% 35% 24% 10%	490
	21st to end	Day	3 6% 24% 33% 27% 7%	490
October	1st to 10th	Day	4 10% 19% 32% 25% 9%	490
	11th to 20th	Day	8% 5% 22% 32% 23% 9%	490
	21st to end	Day	14% 9% 21% 28% 21% 7%	508
November	1st to 10th	Day	17% 8% 23% 23% 21% 9%	337
	11th to 20th	Day	17% 3 21% 30% 19% 10%	223
	21st to end	Day	14% 6% 26% 31% 17% 6%	180
December	1st to 10th	Day	26% 11% 22% 17% 18% 6%	180
	11th to 20th	Day	28% 4 19% 28% 14% 6%	180
	21st to end	Day	22% 5% 26% 28% 15% 5%	198
January	1st to 10th	Night	26% 4 18% 30% 18% 4	760
	11th to 20th	Night	24% 8% 20% 32% 14% 3	760
	21st to end	Night	23% 5% 22% 29% 17% 4	836
February	1st to 10th	Night	21% 5% 21% 33% 18% 2	760
	11th to 20th	Night	22% 7% 24% 30% 15% 2	744
	21st to end	Night	18% 9% 25% 36% 11% 1	628
March	1st to 10th	Night	27% 8% 23% 26% 14% 2	760
	11th to 20th	Night	22% 6% 21% 30% 20% 1	760
	21st to end	Night	21% 9% 22% 34% 13% 1	836
April	1st to 10th	Night	17% 10% 26% 30% 16% 1	760
	11th to 20th	Night	12% 10% 29% 31% 16% 2	751
	21st to end	Night	9% 7% 31% 33% 19% 1	743
May	1st to 10th	Night	11% 8% 31% 31% 18% 1	570
	11th to 20th	Night	9% 5% 22% 37% 26% 2	384
	21st to end	Night	8% 9% 26% 34% 22% 1	411
June	1st to 10th	Night	7% 6% 26% 39% 22% 1	380
	11th to 20th	Night	3 9% 28% 41% 18% 1	380
	21st to end	Night	3 3 19% 50% 24% 1	380
July	1st to 10th	Night	1 1 15% 44% 37% 3	370
	11th to 20th	Night	2 1 11% 43% 38% 4	368
	21st to end	Night	1 1 6% 39% 48% 6%	615
August	1st to 10th	Night	2 1 9% 34% 46% 7%	567
	11th to 20th	Night	1 1 11% 40% 41% 6%	598
	21st to end	Night	2 1 10% 38% 44% 5%	836
September	1st to 10th	Night	2 1 15% 41% 39% 3	760
	11th to 20th	Night	4 2 12% 38% 39% 5%	760
	21st to end	Night	5% 3 18% 35% 33% 5%	760
October	1st to 10th	Night	6% 7% 18% 36% 29% 4	760
	11th to 20th	Night	8% 3 19% 36% 29% 5%	760
	21st to end	Night	12% 5% 21% 34% 24% 6%	804
November	1st to 10th	Night	13% 5% 16% 36% 27% 4	740
	11th to 20th	Night	16% 4 20% 39% 19% 2	760
	21st to end	Night	16% 6% 20% 36% 19% 3	760
December	1st to 10th	Night	27% 4 19% 32% 16% 3	760
	11th to 20th	Night	30% 4 21% 29% 14% 2	760
	21st to end	Night	25% 5% 24% 32% 13% 1	836

Page generated at 2024-10-20 23:20:00. Version ac07

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