Falls City Starparty
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Falls City Starparty clear sky chart from 2005-11-06 to 2024-11-08.

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	12% 8% 3 8% 5% 5% 5% 4 5% 6% 39%	105465
	Night	13% 9% 3 8% 5% 5% 4 4 5% 6% 40%	102252
Transparency	Day	46% 7% 13% 17% 13% 4	105211
	Night	46% 6% 14% 18% 11% 4	102095
Seeing	Day	16% 12% 23% 27% 17% 4	14736
	Night	17% 7% 20% 34% 19% 2	23655

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	20% 16% 8% 17% 9% 7% 6% 4 4 3 7%	2539
	11th to 20th	Day	28% 11% 3 10% 6% 6% 5% 4 5% 5% 16%	2549
	21st to end	Day	20% 14% 5% 12% 7% 6% 7% 4 5% 6% 13%	3146
February	1st to 10th	Day	22% 13% 3 11% 8% 6% 6% 5% 6% 6% 15%	1710
	11th to 20th	Day	18% 15% 5% 10% 8% 7% 6% 4 5% 4 18%	1665
	21st to end	Day	17% 16% 6% 10% 9% 6% 5% 4 6% 4 18%	1465
March	1st to 10th	Day	13% 13% 5% 12% 7% 8% 7% 5% 5% 7% 19%	3368
	11th to 20th	Day	14% 12% 3 8% 6% 5% 4 3 4 5% 37%	3490
	21st to end	Day	15% 13% 4 12% 9% 8% 6% 4 6% 6% 16%	3853
April	1st to 10th	Day	16% 14% 5% 9% 9% 7% 7% 4 6% 6% 17%	2280
	11th to 20th	Day	18% 12% 4 9% 5% 6% 6% 4 6% 5% 25%	2268
	21st to end	Day	14% 11% 4 9% 8% 6% 6% 5% 6% 7% 24%	2470
May	1st to 10th	Day	15% 10% 3 8% 5% 5% 5% 4 5% 5% 35%	4260
	11th to 20th	Day	9% 5% 2 5% 3 3 3 3 5% 7% 54%	4377
	21st to end	Day	13% 8% 3 7% 6% 7% 7% 6% 8% 7% 29%	4813
June	1st to 10th	Day	16% 9% 3 8% 6% 5% 5% 4 5% 6% 33%	2660
	11th to 20th	Day	11% 8% 3 9% 6% 6% 6% 5% 7% 8% 31%	2660
	21st to end	Day	6% 4 2 5% 5% 4 4 4 5% 7% 54%	2660
July	1st to 10th	Day	3 2 1 3 2 2 2 2 3 5% 74%	4420
	11th to 20th	Day	3 2 1 2 2 2 2 2 3 4 77%	4420
	21st to end	Day	4 2 1 2 2 2 2 2 3 5% 75%	4709
August	1st to 10th	Day	2 3 1 3 3 3 3 2 4 6% 71%	4091
	11th to 20th	Day	5% 4 2 5% 4 4 4 4 6% 7% 54%	4026
	21st to end	Day	6% 5% 1 4 3 3 4 3 5% 7% 59%	4336
September	1st to 10th	Day	4 3 1 4 2 3 3 3 5% 7% 64%	2280
	11th to 20th	Day	8% 6% 2 7% 4 5% 5% 4 6% 8% 46%	2239
	21st to end	Day	12% 6% 3 6% 4 4 3 2 5% 6% 48%	2024
October	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 5% 5% 52%	3180
	11th to 20th	Day	12% 6% 2 8% 7% 6% 7% 5% 7% 9% 32%	3161
	21st to end	Day	14% 9% 3 9% 6% 6% 6% 5% 8% 9% 25%	3448
November	1st to 10th	Day	18% 12% 5% 12% 7% 6% 6% 4 5% 7% 17%	1616
	11th to 20th	Day	19% 14% 5% 10% 7% 6% 5% 4 5% 6% 19%	1520
	21st to end	Day	18% 11% 3 11% 7% 6% 6% 4 5% 5% 22%	1520
December	1st to 10th	Day	19% 13% 5% 10% 8% 6% 5% 3 5% 5% 23%	1520
	11th to 20th	Day	18% 11% 4 13% 8% 7% 7% 6% 7% 7% 13%	1928
	21st to end	Day	22% 16% 6% 16% 8% 6% 5% 5% 5% 4 8%	2794
January	1st to 10th	Night	20% 17% 7% 13% 8% 6% 5% 4 5% 4 11%	4406
	11th to 20th	Night	25% 15% 5% 12% 6% 5% 4 3 4 4 17%	4406
	21st to end	Night	23% 15% 5% 12% 5% 5% 5% 4 5% 5% 16%	4521
February	1st to 10th	Night	15% 13% 5% 12% 8% 7% 5% 4 6% 7% 20%	2470
	11th to 20th	Night	16% 11% 4 9% 6% 6% 6% 5% 6% 5% 26%	2402
	21st to end	Night	16% 12% 5% 10% 7% 6% 7% 4 5% 6% 23%	1989
March	1st to 10th	Night	9% 10% 4 11% 8% 8% 8% 6% 6% 6% 24%	3504
	11th to 20th	Night	10% 8% 3 7% 5% 4 5% 4 5% 6% 44%	3490
	21st to end	Night	14% 15% 4 11% 8% 7% 6% 4 6% 6% 20%	3799
April	1st to 10th	Night	16% 12% 4 8% 7% 6% 6% 4 5% 6% 27%	1900
	11th to 20th	Night	13% 10% 3 7% 6% 5% 5% 3 7% 8% 33%	1855
	21st to end	Night	12% 8% 3 8% 5% 5% 6% 5% 6% 8% 34%	1710
May	1st to 10th	Night	15% 7% 2 6% 4 4 4 4 4 5% 44%	2704
	11th to 20th	Night	6% 5% 1 4 4 4 3 3 5% 5% 60%	2516
	21st to end	Night	7% 5% 3 5% 6% 5% 6% 5% 8% 9% 41%	2762
June	1st to 10th	Night	12% 7% 3 7% 4 5% 4 4 5% 6% 43%	1520
	11th to 20th	Night	8% 7% 2 6% 4 5% 3 4 5% 8% 49%	1520
	21st to end	Night	5% 3 2 5% 3 3 3 2 5% 6% 64%	1434
July	1st to 10th	Night	1 1 1 2 1 2 1 2 2 3 85%	2540
	11th to 20th	Night	3 2 1 2 1 2 1 2 2 3 81%	2540
	21st to end	Night	3 1 1 1 1 1 1 2 4 84%	2842
August	1st to 10th	Night	1 1 1 2 1 2 2 2 4 4 79%	2848
	11th to 20th	Night	4 2 1 3 2 2 3 3 4 7% 68%	2812
	21st to end	Night	5% 3 1 4 2 2 3 2 4 5% 69%	3335
September	1st to 10th	Night	4 2 1 2 2 2 3 3 4 5% 72%	1900
	11th to 20th	Night	7% 4 2 6% 4 4 4 3 5% 7% 54%	1938
	21st to end	Night	8% 5% 1 5% 3 3 4 4 5% 8% 56%	2156
October	1st to 10th	Night	7% 4 2 5% 3 3 3 3 4 7% 59%	3800
	11th to 20th	Night	11% 5% 2 6% 5% 5% 5% 5% 7% 8% 41%	3777
	21st to end	Night	16% 8% 3 9% 5% 5% 5% 4 6% 6% 33%	4121
November	1st to 10th	Night	17% 9% 3 10% 7% 6% 5% 4 6% 6% 26%	2617
	11th to 20th	Night	20% 12% 4 10% 7% 5% 5% 4 5% 5% 23%	2660
	21st to end	Night	16% 10% 3 9% 7% 5% 6% 4 5% 7% 29%	2660
December	1st to 10th	Night	18% 11% 3 9% 6% 6% 6% 4 6% 6% 25%	2660
	11th to 20th	Night	20% 11% 4 11% 7% 6% 5% 4 5% 7% 19%	3276
	21st to end	Night	19% 13% 6% 13% 8% 6% 5% 4 5% 5% 18%	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	82% 5% 7% 3 2 1	2539
	11th to 20th	Day	71% 7% 8% 9% 3 2	2549
	21st to end	Day	74% 6% 8% 7% 5%	3146
February	1st to 10th	Day	69% 9% 8% 10% 4	1710
	11th to 20th	Day	68% 8% 10% 9% 4 2	1674
	21st to end	Day	70% 4 10% 9% 5% 1	1465
March	1st to 10th	Day	64% 7% 15% 11% 3	3368
	11th to 20th	Day	51% 5% 9% 24% 11%	3490
	21st to end	Day	69% 6% 14% 7% 4	3853
April	1st to 10th	Day	68% 6% 12% 11% 3	2280
	11th to 20th	Day	61% 6% 10% 13% 7% 2	2271
	21st to end	Day	58% 8% 12% 13% 7% 1	2470
May	1st to 10th	Day	49% 6% 14% 18% 12%	4260
	11th to 20th	Day	30% 6% 19% 29% 14% 1	4380
	21st to end	Day	50% 10% 25% 14% 2	4814
June	1st to 10th	Day	52% 6% 17% 19% 6% 1	2660
	11th to 20th	Day	48% 8% 21% 16% 6%	2660
	21st to end	Day	31% 6% 20% 27% 12% 4	2660
July	1st to 10th	Day	14% 3 11% 17% 22% 33%	4351
	11th to 20th	Day	13% 3 7% 21% 36% 21%	4345
	21st to end	Day	11% 5% 11% 29% 37% 7%	4560
August	1st to 10th	Day	15% 4 11% 30% 26% 13%	4076
	11th to 20th	Day	25% 11% 18% 27% 15% 4	4065
	21st to end	Day	24% 7% 15% 25% 22% 6%	4335
September	1st to 10th	Day	20% 4 14% 30% 20% 12%	2280
	11th to 20th	Day	35% 8% 15% 20% 16% 6%	2239
	21st to end	Day	38% 5% 14% 23% 14% 6%	2024
October	1st to 10th	Day	32% 8% 9% 24% 26% 2	3180
	11th to 20th	Day	47% 10% 17% 15% 11% 1	3161
	21st to end	Day	51% 9% 12% 16% 10% 1	3448
November	1st to 10th	Day	66% 8% 9% 12% 4	1616
	11th to 20th	Day	66% 8% 10% 8% 6% 2	1520
	21st to end	Day	63% 8% 7% 9% 12% 1	1520
December	1st to 10th	Day	64% 7% 8% 11% 10% 1	1520
	11th to 20th	Day	69% 8% 11% 10% 2	1928
	21st to end	Day	79% 8% 6% 4 2	2794
January	1st to 10th	Night	78% 6% 8% 4 3 1	4406
	11th to 20th	Night	72% 4 8% 10% 3 2	4406
	21st to end	Night	73% 4 8% 8% 6% 1	4521
February	1st to 10th	Night	65% 8% 12% 11% 4	2470
	11th to 20th	Night	60% 7% 14% 11% 6% 2	2404
	21st to end	Night	62% 5% 13% 11% 7% 2	1989
March	1st to 10th	Night	62% 5% 13% 16% 4	3504
	11th to 20th	Night	44% 5% 19% 21% 11% 1	3490
	21st to end	Night	64% 8% 14% 13% 1	3799
April	1st to 10th	Night	59% 7% 17% 11% 6%	1900
	11th to 20th	Night	49% 8% 18% 16% 6% 3	1855
	21st to end	Night	49% 6% 17% 19% 6% 2	1710
May	1st to 10th	Night	43% 6% 16% 24% 9% 1	2704
	11th to 20th	Night	28% 4 17% 34% 15% 2	2516
	21st to end	Night	37% 9% 37% 14% 3	2762
June	1st to 10th	Night	42% 7% 19% 26% 5% 1	1520
	11th to 20th	Night	33% 7% 27% 26% 7%	1520
	21st to end	Night	22% 4 25% 33% 12% 4	1434
July	1st to 10th	Night	9% 2 11% 20% 26% 32%	2500
	11th to 20th	Night	12% 3 8% 20% 28% 29%	2492
	21st to end	Night	7% 4 14% 29% 38% 8%	2753
August	1st to 10th	Night	10% 4 12% 33% 32% 10%	2839
	11th to 20th	Night	16% 7% 22% 38% 12% 5%	2839
	21st to end	Night	19% 6% 16% 28% 24% 7%	3335
September	1st to 10th	Night	15% 5% 16% 30% 23% 11%	1900
	11th to 20th	Night	30% 6% 17% 24% 14% 9%	1938
	21st to end	Night	29% 5% 17% 24% 16% 8%	2156
October	1st to 10th	Night	25% 7% 11% 31% 23% 3	3800
	11th to 20th	Night	40% 7% 21% 20% 10% 2	3777
	21st to end	Night	51% 8% 12% 18% 9% 2	4121
November	1st to 10th	Night	58% 8% 12% 15% 7% 1	2617
	11th to 20th	Night	63% 8% 11% 9% 8% 2	2660
	21st to end	Night	56% 7% 11% 11% 13% 3	2660
December	1st to 10th	Night	61% 5% 12% 11% 11% 1	2660
	11th to 20th	Night	65% 8% 10% 11% 5%	3276
	21st to end	Night	70% 7% 11% 9% 2 1	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	39% 12% 25% 17% 6% 2	180
	11th to 20th	Day	31% 10% 26% 19% 12% 2	189
	21st to end	Day	27% 12% 22% 24% 11% 3	407
February	1st to 10th	Day	27% 18% 22% 19% 12% 2	370
	11th to 20th	Day	26% 18% 28% 17% 9% 2	365
	21st to end	Day	28% 19% 24% 18% 10%	332
March	1st to 10th	Day	26% 15% 27% 23% 7% 1	460
	11th to 20th	Day	25% 13% 24% 24% 11% 3	460
	21st to end	Day	25% 19% 27% 18% 10% 1	506
April	1st to 10th	Day	23% 18% 24% 20% 11% 3	460
	11th to 20th	Day	25% 19% 24% 20% 8% 4	452
	21st to end	Day	20% 16% 31% 20% 11% 2	460
May	1st to 10th	Day	15% 18% 25% 24% 14% 3	463
	11th to 20th	Day	19% 13% 22% 24% 15% 6%	488
	21st to end	Day	13% 11% 23% 27% 21% 5%	529
June	1st to 10th	Day	17% 9% 24% 28% 20% 2	490
	11th to 20th	Day	13% 14% 29% 30% 13% 2	490
	21st to end	Day	4 9% 21% 35% 26% 5%	490
July	1st to 10th	Day	5% 6% 21% 37% 25% 7%	486
	11th to 20th	Day	3 4 23% 37% 25% 7%	484
	21st to end	Day	3 4 16% 38% 31% 8%	531
August	1st to 10th	Day	3 3 16% 37% 30% 11%	487
	11th to 20th	Day	2 4 13% 36% 33% 12%	477
	21st to end	Day	5% 5% 23% 32% 28% 7%	539
September	1st to 10th	Day	5% 7% 22% 30% 29% 7%	490
	11th to 20th	Day	9% 7% 22% 30% 25% 7%	490
	21st to end	Day	12% 9% 24% 34% 17% 4	490
October	1st to 10th	Day	13% 11% 25% 28% 17% 6%	490
	11th to 20th	Day	15% 13% 19% 29% 19% 5%	490
	21st to end	Day	22% 16% 24% 23% 11% 4	539
November	1st to 10th	Day	21% 18% 27% 21% 12% 1	234
	11th to 20th	Day	24% 13% 28% 19% 14% 3	180
	21st to end	Day	25% 16% 21% 22% 16% 1	180
December	1st to 10th	Day	31% 12% 19% 24% 11% 3	180
	11th to 20th	Day	31% 13% 24% 26% 4 2	180
	21st to end	Day	30% 14% 22% 23% 9% 1	198
January	1st to 10th	Night	32% 11% 23% 21% 12% 1	760
	11th to 20th	Night	29% 11% 19% 23% 15% 2	760
	21st to end	Night	24% 7% 17% 34% 15% 3	836
February	1st to 10th	Night	23% 10% 22% 28% 16% 1	760
	11th to 20th	Night	21% 11% 23% 29% 15% 1	744
	21st to end	Night	23% 12% 24% 30% 11%	628
March	1st to 10th	Night	20% 10% 25% 31% 13% 1	760
	11th to 20th	Night	21% 11% 19% 34% 14% 1	760
	21st to end	Night	24% 10% 24% 27% 13% 1	836
April	1st to 10th	Night	23% 11% 21% 28% 16% 1	760
	11th to 20th	Night	18% 10% 24% 32% 15% 1	727
	21st to end	Night	16% 6% 23% 38% 16% 1	570
May	1st to 10th	Night	12% 6% 26% 37% 18% 1	479
	11th to 20th	Night	13% 3 18% 43% 21% 1	374
	21st to end	Night	11% 6% 22% 38% 22% 1	411
June	1st to 10th	Night	15% 4 18% 42% 21%	380
	11th to 20th	Night	9% 3 27% 43% 16% 1	380
	21st to end	Night	7% 2 22% 46% 23%	380
July	1st to 10th	Night	3 2 14% 51% 29% 1	370
	11th to 20th	Night	3 3 18% 52% 24% 1	368
	21st to end	Night	2 1 12% 49% 34% 2	461
August	1st to 10th	Night	2 2 7% 47% 38% 5%	567
	11th to 20th	Night	4 1 7% 42% 44% 3	564
	21st to end	Night	5% 3 15% 43% 31% 2	738
September	1st to 10th	Night	5% 2 18% 41% 33% 2	760
	11th to 20th	Night	8% 4 15% 35% 33% 6%	760
	21st to end	Night	10% 4 17% 41% 26% 3	760
October	1st to 10th	Night	11% 3 24% 34% 24% 3	760
	11th to 20th	Night	15% 6% 17% 36% 23% 5%	760
	21st to end	Night	19% 9% 24% 28% 16% 3	836
November	1st to 10th	Night	21% 8% 22% 33% 15% 1	770
	11th to 20th	Night	26% 13% 21% 28% 12% 1	760
	21st to end	Night	21% 7% 23% 32% 16% 2	760
December	1st to 10th	Night	24% 9% 21% 29% 15% 2	760
	11th to 20th	Night	28% 11% 23% 25% 12% 1	760
	21st to end	Night	29% 13% 24% 24% 10%	836

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