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 2024-01-12.

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	13% 9% 4 7% 7% 4 5% 5% 5% 6% 35%	74718
	Night	13% 8% 3 7% 6% 4 5% 5% 5% 6% 38%	74935
Transparency	Day	50% 6% 13% 17% 11% 3	74424
	Night	48% 6% 14% 18% 10% 3	74750
Seeing	Day	17% 12% 23% 27% 18% 4	13599
	Night	18% 7% 20% 34% 20% 2	22666

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	24% 14% 8% 13% 10% 4 6% 4 3 4 11%	1519
	11th to 20th	Day	22% 11% 4 8% 7% 5% 7% 5% 5% 6% 19%	1460
	21st to end	Day	17% 10% 5% 9% 9% 4 7% 6% 5% 7% 22%	1782
February	1st to 10th	Day	22% 12% 4 10% 9% 5% 7% 6% 6% 6% 16%	1620
	11th to 20th	Day	18% 14% 5% 8% 9% 5% 6% 5% 5% 5% 19%	1575
	21st to end	Day	18% 15% 7% 9% 9% 5% 6% 5% 5% 4 18%	1381
March	1st to 10th	Day	19% 12% 5% 9% 7% 5% 8% 6% 5% 6% 17%	1928
	11th to 20th	Day	21% 14% 5% 8% 8% 4 5% 4 4 7% 19%	1980
	21st to end	Day	19% 13% 5% 11% 11% 5% 7% 4 5% 6% 15%	2194
April	1st to 10th	Day	17% 14% 5% 8% 10% 5% 7% 6% 6% 6% 17%	2160
	11th to 20th	Day	19% 11% 4 8% 7% 5% 6% 5% 6% 5% 24%	2146
	21st to end	Day	14% 10% 5% 8% 8% 4 7% 6% 6% 7% 25%	2340
May	1st to 10th	Day	12% 9% 4 7% 7% 3 6% 5% 6% 7% 35%	2425
	11th to 20th	Day	15% 8% 3 8% 7% 4 5% 5% 7% 7% 31%	2477
	21st to end	Day	15% 7% 3 6% 7% 4 6% 6% 6% 8% 30%	2723
June	1st to 10th	Day	16% 7% 4 7% 7% 4 5% 5% 5% 6% 33%	2520
	11th to 20th	Day	11% 8% 4 8% 7% 4 6% 6% 7% 9% 30%	2520
	21st to end	Day	6% 4 2 5% 5% 3 4 4 5% 6% 54%	2520
July	1st to 10th	Day	4 4 2 4 4 3 3 4 5% 8% 60%	2520
	11th to 20th	Day	6% 3 1 3 3 2 3 4 4 6% 66%	2520
	21st to end	Day	4 2 1 2 2 1 2 2 3 5% 75%	2696
August	1st to 10th	Day	3 3 1 2 4 3 3 3 4 7% 67%	2328
	11th to 20th	Day	4 3 1 3 3 2 3 3 5% 7% 66%	2298
	21st to end	Day	4 4 2 4 4 2 4 4 5% 8% 59%	2467
September	1st to 10th	Day	4 3 1 3 3 3 3 4 5% 7% 64%	2160
	11th to 20th	Day	8% 6% 2 5% 5% 3 5% 5% 5% 8% 46%	2122
	21st to end	Day	12% 6% 3 6% 5% 3 4 3 5% 6% 47%	1918
October	1st to 10th	Day	12% 7% 2 5% 7% 4 4 6% 6% 5% 41%	1800
	11th to 20th	Day	13% 8% 3 6% 8% 5% 7% 5% 5% 8% 32%	1800
	21st to end	Day	15% 10% 4 8% 8% 4 5% 5% 5% 6% 30%	1980
November	1st to 10th	Day	18% 11% 5% 10% 9% 4 6% 6% 5% 7% 17%	1557
	11th to 20th	Day	19% 13% 5% 9% 8% 4 6% 5% 5% 7% 19%	1520
	21st to end	Day	19% 10% 4 10% 8% 5% 6% 6% 5% 5% 22%	1520
December	1st to 10th	Day	19% 11% 6% 9% 8% 4 5% 4 5% 6% 23%	1520
	11th to 20th	Day	18% 11% 4 11% 9% 5% 8% 7% 7% 7% 13%	1928
	21st to end	Day	22% 15% 6% 14% 10% 5% 6% 6% 5% 4 8%	2794
January	1st to 10th	Night	22% 13% 5% 9% 8% 5% 6% 6% 5% 5% 16%	2646
	11th to 20th	Night	21% 12% 4 10% 7% 4 6% 5% 5% 6% 21%	2534
	21st to end	Night	15% 11% 5% 11% 7% 4 5% 5% 5% 6% 28%	2574
February	1st to 10th	Night	14% 12% 5% 11% 8% 5% 6% 5% 6% 7% 20%	2340
	11th to 20th	Night	15% 10% 4 8% 7% 5% 6% 6% 6% 5% 27%	2272
	21st to end	Night	16% 11% 5% 9% 8% 5% 7% 6% 5% 5% 24%	1875
March	1st to 10th	Night	15% 10% 4 9% 7% 5% 7% 7% 6% 5% 25%	2030
	11th to 20th	Night	16% 9% 4 8% 8% 4 7% 5% 6% 7% 26%	1980
	21st to end	Night	18% 11% 4 7% 9% 5% 6% 6% 7% 6% 23%	2161
April	1st to 10th	Night	17% 11% 5% 7% 7% 4 6% 5% 5% 6% 26%	1800
	11th to 20th	Night	13% 9% 4 7% 6% 4 5% 4 7% 8% 33%	1757
	21st to end	Night	12% 7% 3 7% 6% 3 6% 5% 6% 8% 35%	1620
May	1st to 10th	Night	8% 6% 2 7% 5% 4 5% 6% 5% 7% 45%	1534
	11th to 20th	Night	10% 7% 3 6% 7% 4 6% 5% 6% 7% 38%	1416
	21st to end	Night	11% 5% 3 5% 7% 3 4 7% 7% 9% 39%	1552
June	1st to 10th	Night	12% 6% 3 6% 5% 4 5% 5% 5% 7% 43%	1440
	11th to 20th	Night	8% 6% 2 5% 5% 4 4 4 5% 8% 48%	1440
	21st to end	Night	5% 3 2 4 3 2 3 3 4 5% 64%	1358
July	1st to 10th	Night	2 2 1 2 3 2 3 3 3 5% 74%	1440
	11th to 20th	Night	4 2 1 2 1 2 2 3 3 5% 75%	1440
	21st to end	Night	2 1 1 1 1 2 1 3 4 85%	1618
August	1st to 10th	Night	1 1 1 2 2 1 2 4 5% 6% 74%	1611
	11th to 20th	Night	2 2 1 2 2 1 2 2 3 5% 76%	1602
	21st to end	Night	3 2 1 3 3 2 3 3 4 5% 70%	1887
September	1st to 10th	Night	4 2 1 2 2 2 2 4 4 5% 73%	1800
	11th to 20th	Night	7% 4 2 4 5% 3 5% 4 5% 7% 54%	1836
	21st to end	Night	8% 5% 2 5% 4 2 4 4 5% 8% 54%	2042
October	1st to 10th	Night	10% 5% 3 6% 5% 3 3 4 5% 6% 50%	2160
	11th to 20th	Night	11% 6% 2 6% 5% 4 5% 5% 6% 7% 43%	2160
	21st to end	Night	15% 7% 3 7% 5% 3 5% 5% 5% 5% 39%	2376
November	1st to 10th	Night	18% 9% 3 9% 8% 4 5% 5% 6% 6% 27%	2516
	11th to 20th	Night	20% 11% 4 8% 8% 4 5% 6% 5% 5% 23%	2660
	21st to end	Night	16% 9% 3 7% 8% 4 6% 5% 5% 7% 29%	2660
December	1st to 10th	Night	19% 9% 4 8% 7% 4 6% 5% 6% 6% 25%	2660
	11th to 20th	Night	20% 11% 4 10% 8% 5% 6% 5% 5% 7% 19%	3276
	21st to end	Night	19% 12% 6% 11% 10% 4 5% 5% 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	79% 5% 7% 5% 3 1	1519
	11th to 20th	Day	66% 7% 9% 8% 6% 3	1460
	21st to end	Day	63% 7% 9% 11% 9% 1	1782
February	1st to 10th	Day	70% 8% 8% 10% 4	1620
	11th to 20th	Day	67% 7% 10% 9% 4 2	1584
	21st to end	Day	70% 4 10% 9% 5% 2	1381
March	1st to 10th	Day	67% 7% 12% 10% 4	1928
	11th to 20th	Day	66% 4 12% 12% 5% 1	1980
	21st to end	Day	70% 6% 13% 9% 1	2194
April	1st to 10th	Day	68% 6% 12% 10% 4	2160
	11th to 20th	Day	62% 6% 10% 13% 6% 3	2149
	21st to end	Day	58% 9% 12% 13% 7% 1	2340
May	1st to 10th	Day	48% 7% 17% 19% 9%	2425
	11th to 20th	Day	51% 8% 15% 17% 8% 1	2480
	21st to end	Day	52% 8% 18% 18% 4	2724
June	1st to 10th	Day	52% 6% 17% 19% 5% 1	2520
	11th to 20th	Day	49% 8% 22% 16% 6%	2520
	21st to end	Day	31% 5% 21% 26% 12% 4	2520
July	1st to 10th	Day	24% 5% 17% 26% 21% 7%	2451
	11th to 20th	Day	21% 4 11% 29% 28% 7%	2445
	21st to end	Day	12% 4 10% 33% 35% 7%	2546
August	1st to 10th	Day	18% 5% 17% 33% 20% 5%	2312
	11th to 20th	Day	19% 5% 16% 30% 23% 6%	2298
	21st to end	Day	24% 5% 15% 29% 23% 4	2467
September	1st to 10th	Day	20% 4 14% 30% 21% 12%	2160
	11th to 20th	Day	35% 8% 14% 21% 16% 6%	2122
	21st to end	Day	39% 5% 14% 22% 15% 6%	1918
October	1st to 10th	Day	43% 7% 12% 18% 17% 4	1800
	11th to 20th	Day	50% 8% 12% 16% 13% 1	1800
	21st to end	Day	57% 7% 9% 13% 14% 1	1980
November	1st to 10th	Day	67% 8% 9% 12% 4	1557
	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	72% 6% 9% 7% 5% 2	2646
	11th to 20th	Night	66% 5% 10% 10% 6% 4	2534
	21st to end	Night	59% 6% 11% 13% 11% 1	2574
February	1st to 10th	Night	64% 8% 12% 11% 4	2340
	11th to 20th	Night	58% 7% 15% 12% 6% 2	2274
	21st to end	Night	62% 4 13% 11% 7% 2	1875
March	1st to 10th	Night	62% 6% 11% 14% 7%	2030
	11th to 20th	Night	59% 6% 14% 14% 6% 1	1980
	21st to end	Night	62% 9% 14% 14% 2	2161
April	1st to 10th	Night	59% 7% 16% 11% 6%	1800
	11th to 20th	Night	50% 7% 18% 15% 6% 3	1757
	21st to end	Night	49% 7% 17% 19% 7% 2	1620
May	1st to 10th	Night	41% 7% 18% 24% 8% 2	1534
	11th to 20th	Night	45% 7% 19% 20% 7% 3	1416
	21st to end	Night	40% 9% 23% 23% 5%	1552
June	1st to 10th	Night	41% 7% 20% 26% 5% 1	1440
	11th to 20th	Night	34% 7% 28% 24% 7%	1440
	21st to end	Night	23% 4 26% 32% 12% 4	1358
July	1st to 10th	Night	16% 4 19% 31% 23% 7%	1400
	11th to 20th	Night	15% 4 14% 28% 29% 9%	1392
	21st to end	Night	6% 2 12% 36% 33% 10%	1528
August	1st to 10th	Night	13% 5% 19% 39% 18% 6%	1602
	11th to 20th	Night	14% 4 17% 37% 20% 9%	1602
	21st to end	Night	18% 5% 16% 33% 23% 5%	1887
September	1st to 10th	Night	16% 5% 15% 30% 23% 11%	1800
	11th to 20th	Night	30% 6% 16% 23% 15% 9%	1836
	21st to end	Night	31% 5% 17% 21% 17% 8%	2042
October	1st to 10th	Night	35% 6% 13% 24% 17% 5%	2160
	11th to 20th	Night	41% 7% 13% 20% 15% 3	2160
	21st to end	Night	48% 6% 12% 16% 15% 3	2376
November	1st to 10th	Night	58% 7% 12% 15% 7% 1	2516
	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	38% 12% 25% 17% 6% 2	180
	11th to 20th	Day	32% 10% 24% 19% 13% 2	172
	21st to end	Day	27% 10% 21% 26% 12% 3	374
February	1st to 10th	Day	28% 17% 21% 20% 12% 1	340
	11th to 20th	Day	26% 18% 29% 18% 8% 2	335
	21st to end	Day	27% 20% 25% 18% 9%	302
March	1st to 10th	Day	27% 15% 28% 22% 6% 1	420
	11th to 20th	Day	26% 14% 24% 24% 10% 2	420
	21st to end	Day	26% 18% 26% 19% 11% 1	462
April	1st to 10th	Day	25% 19% 22% 20% 10% 4	420
	11th to 20th	Day	27% 17% 24% 20% 8% 4	412
	21st to end	Day	19% 15% 31% 20% 11% 3	420
May	1st to 10th	Day	14% 18% 25% 25% 15% 3	423
	11th to 20th	Day	21% 14% 21% 23% 15% 5%	448
	21st to end	Day	14% 11% 22% 27% 21% 6%	485
June	1st to 10th	Day	17% 9% 24% 27% 21% 2	450
	11th to 20th	Day	14% 14% 28% 30% 13% 2	450
	21st to end	Day	5% 8% 22% 34% 26% 5%	450
July	1st to 10th	Day	5% 5% 20% 37% 26% 7%	446
	11th to 20th	Day	3 5% 24% 37% 25% 7%	444
	21st to end	Day	3 4 16% 38% 32% 8%	487
August	1st to 10th	Day	3 4 16% 36% 30% 12%	447
	11th to 20th	Day	2 4 12% 37% 35% 11%	437
	21st to end	Day	5% 4 23% 33% 29% 7%	495
September	1st to 10th	Day	6% 7% 24% 30% 27% 7%	450
	11th to 20th	Day	9% 7% 21% 30% 26% 7%	450
	21st to end	Day	13% 10% 22% 34% 17% 4	450
October	1st to 10th	Day	14% 11% 24% 28% 18% 6%	450
	11th to 20th	Day	16% 13% 18% 28% 20% 5%	450
	21st to end	Day	22% 15% 23% 23% 12% 5%	495
November	1st to 10th	Day	22% 17% 28% 22% 11% 1	217
	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	28% 11% 19% 24% 16% 2	728
	21st to end	Night	23% 7% 17% 35% 15% 3	792
February	1st to 10th	Night	23% 9% 22% 29% 16% 1	720
	11th to 20th	Night	20% 11% 23% 30% 15% 1	704
	21st to end	Night	23% 12% 23% 31% 11%	592
March	1st to 10th	Night	20% 9% 25% 31% 13% 1	720
	11th to 20th	Night	22% 11% 19% 33% 13% 1	720
	21st to end	Night	24% 10% 22% 28% 13% 2	792
April	1st to 10th	Night	24% 11% 21% 27% 17% 1	720
	11th to 20th	Night	18% 10% 22% 33% 15% 1	689
	21st to end	Night	17% 5% 22% 38% 17% 1	540
May	1st to 10th	Night	10% 6% 26% 38% 19% 1	454
	11th to 20th	Night	14% 3 17% 43% 22% 1	354
	21st to end	Night	12% 5% 22% 38% 22% 2	389
June	1st to 10th	Night	14% 4 18% 42% 22%	360
	11th to 20th	Night	9% 3 27% 43% 17% 1	360
	21st to end	Night	7% 2 22% 46% 23%	360
July	1st to 10th	Night	3 2 13% 51% 30% 1	350
	11th to 20th	Night	3 2 18% 52% 23% 1	348
	21st to end	Night	2 1 11% 50% 35% 1	436
August	1st to 10th	Night	2 2 7% 45% 38% 5%	537
	11th to 20th	Night	4 1 7% 42% 43% 3	534
	21st to end	Night	5% 3 15% 45% 30% 2	699
September	1st to 10th	Night	5% 2 18% 40% 33% 2	720
	11th to 20th	Night	8% 3 14% 34% 34% 6%	720
	21st to end	Night	10% 4 16% 41% 27% 3	720
October	1st to 10th	Night	12% 3 24% 34% 24% 3	720
	11th to 20th	Night	15% 6% 17% 35% 23% 5%	720
	21st to end	Night	20% 8% 24% 28% 17% 4	792
November	1st to 10th	Night	21% 8% 21% 34% 15% 1	740
	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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