Horsethief Lake State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Horsethief Lake State Park clear sky chart from 2005-11-06 to 2024-01-13.

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	8% 7% 3 6% 5% 3 5% 5% 5% 7% 46%	74773
	Night	10% 8% 3 6% 5% 3 5% 5% 5% 7% 42%	74990
Transparency	Day	39% 6% 14% 23% 15% 5%	74476
	Night	42% 7% 15% 21% 12% 3	74808
Seeing	Day	16% 15% 27% 23% 14% 4	13413
	Night	15% 10% 24% 32% 18% 2	22548

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	18% 18% 7% 10% 7% 5% 6% 6% 4 6% 12%	1519
	11th to 20th	Day	19% 14% 8% 10% 9% 4 6% 5% 5% 6% 14%	1459
	21st to end	Day	15% 14% 7% 10% 9% 4 5% 6% 6% 6% 17%	1642
February	1st to 10th	Day	14% 13% 5% 9% 8% 4 5% 6% 5% 8% 23%	1620
	11th to 20th	Day	11% 11% 3 6% 6% 5% 6% 7% 7% 8% 30%	1575
	21st to end	Day	11% 9% 3 7% 8% 5% 6% 7% 8% 7% 29%	1469
March	1st to 10th	Day	12% 9% 5% 7% 7% 4 7% 6% 7% 9% 27%	1800
	11th to 20th	Day	11% 9% 4 8% 8% 4 6% 7% 7% 9% 27%	1975
	21st to end	Day	9% 9% 3 8% 8% 4 7% 7% 7% 9% 28%	2286
April	1st to 10th	Day	9% 7% 4 6% 6% 4 7% 6% 7% 9% 35%	2160
	11th to 20th	Day	7% 9% 3 6% 6% 4 5% 6% 8% 8% 39%	2129
	21st to end	Day	5% 4 2 4 5% 3 5% 6% 8% 11% 47%	2290
May	1st to 10th	Day	5% 3 2 5% 5% 3 5% 5% 6% 7% 53%	2520
	11th to 20th	Day	8% 5% 2 5% 5% 4 5% 5% 7% 11% 44%	2477
	21st to end	Day	8% 4 2 5% 5% 3 5% 6% 6% 8% 49%	2723
June	1st to 10th	Day	7% 4 3 5% 5% 3 5% 5% 6% 9% 49%	2520
	11th to 20th	Day	4 3 2 4 5% 3 4 5% 5% 8% 56%	2520
	21st to end	Day	3 2 1 2 3 2 3 3 4 7% 69%	2520
July	1st to 10th	Day	1 1 1 2 2 2 2 3 4 5% 78%	2520
	11th to 20th	Day	2 2 1 1 2 1 2 3 4 4 78%	2520
	21st to end	Day	2 1 1 1 1 1 1 2 2 4 85%	2741
August	1st to 10th	Day	1 2 1 2 2 1 2 3 3 6% 78%	2463
	11th to 20th	Day	1 1 1 2 1 1 3 3 3 5% 78%	2298
	21st to end	Day	3 1 1 2 3 2 3 3 4 5% 73%	2386
September	1st to 10th	Day	2 2 1 2 2 1 3 3 3 6% 77%	2160
	11th to 20th	Day	4 2 2 3 4 2 5% 5% 5% 6% 61%	2160
	21st to end	Day	7% 4 1 4 4 3 4 4 5% 6% 56%	1928
October	1st to 10th	Day	8% 5% 2 5% 5% 3 4 4 6% 6% 51%	1800
	11th to 20th	Day	8% 5% 2 7% 6% 5% 5% 5% 6% 9% 43%	1800
	21st to end	Day	12% 7% 3 7% 7% 4 7% 5% 6% 7% 36%	1859
November	1st to 10th	Day	15% 10% 4 8% 8% 6% 4 6% 7% 8% 25%	1652
	11th to 20th	Day	14% 13% 5% 9% 7% 4 8% 6% 7% 7% 20%	1520
	21st to end	Day	15% 10% 5% 9% 7% 4 7% 6% 5% 7% 25%	1520
December	1st to 10th	Day	13% 14% 8% 10% 7% 5% 5% 4 6% 6% 23%	1520
	11th to 20th	Day	17% 17% 9% 14% 9% 4 6% 5% 5% 5% 10%	1928
	21st to end	Day	19% 21% 8% 13% 8% 5% 4 4 3 4 12%	2794
January	1st to 10th	Night	19% 16% 7% 11% 7% 4 6% 5% 5% 6% 14%	2646
	11th to 20th	Night	19% 14% 7% 9% 8% 4 6% 4 5% 6% 18%	2562
	21st to end	Night	16% 12% 6% 10% 7% 5% 6% 4 5% 7% 22%	2712
February	1st to 10th	Night	14% 11% 5% 8% 6% 4 6% 6% 5% 8% 28%	2340
	11th to 20th	Night	12% 10% 3 7% 6% 4 5% 5% 5% 7% 37%	2272
	21st to end	Night	10% 12% 4 7% 6% 4 5% 6% 7% 8% 31%	1786
March	1st to 10th	Night	12% 10% 3 8% 5% 4 6% 6% 7% 8% 30%	2160
	11th to 20th	Night	9% 7% 3 7% 7% 4 6% 6% 8% 9% 33%	1981
	21st to end	Night	9% 8% 4 6% 7% 5% 6% 6% 8% 8% 33%	2070
April	1st to 10th	Night	9% 8% 3 6% 5% 3 5% 6% 8% 8% 38%	1800
	11th to 20th	Night	7% 6% 3 6% 5% 3 5% 5% 7% 7% 45%	1779
	21st to end	Night	7% 5% 2 4 5% 3 5% 5% 6% 10% 48%	1666
May	1st to 10th	Night	5% 4 1 4 5% 2 5% 5% 7% 7% 56%	1440
	11th to 20th	Night	7% 3 3 4 4 4 5% 5% 6% 9% 51%	1416
	21st to end	Night	4 5% 2 4 5% 4 5% 6% 6% 11% 49%	1552
June	1st to 10th	Night	9% 4 2 5% 4 4 5% 5% 7% 7% 49%	1440
	11th to 20th	Night	5% 3 2 3 3 3 4 3 6% 8% 60%	1440
	21st to end	Night	2 3 1 3 3 2 4 3 4 5% 70%	1440
July	1st to 10th	Night	2 1 2 2 1 3 3 3 5% 78%	1440
	11th to 20th	Night	1 2 1 2 1 3 3 3 5% 80%	1440
	21st to end	Night	1 1 1 1 1 1 1 2 2 4 85%	1576
August	1st to 10th	Night	1 1 1 2 1 2 3 3 3 5% 78%	1474
	11th to 20th	Night	2 2 1 2 2 2 3 3 4 79%	1602
	21st to end	Night	1 1 1 2 3 2 3 2 4 6% 76%	1970
September	1st to 10th	Night	1 2 1 2 2 1 2 3 4 5% 78%	1800
	11th to 20th	Night	4 3 1 3 4 2 4 4 5% 6% 64%	1800
	21st to end	Night	6% 4 1 3 4 2 3 4 6% 7% 61%	2027
October	1st to 10th	Night	9% 6% 2 5% 4 2 4 4 5% 6% 55%	2160
	11th to 20th	Night	9% 5% 2 4 5% 4 5% 5% 6% 7% 48%	2160
	21st to end	Night	11% 6% 2 6% 5% 3 5% 5% 5% 7% 43%	2497
November	1st to 10th	Night	15% 8% 4 6% 6% 5% 5% 6% 6% 7% 32%	2424
	11th to 20th	Night	16% 12% 4 9% 7% 4 6% 6% 6% 6% 24%	2660
	21st to end	Night	11% 10% 5% 8% 7% 4 7% 7% 6% 7% 29%	2660
December	1st to 10th	Night	16% 13% 7% 10% 7% 3 6% 5% 5% 6% 23%	2660
	11th to 20th	Night	20% 15% 6% 13% 10% 4 6% 4 5% 5% 11%	3276
	21st to end	Night	18% 19% 7% 11% 7% 4 5% 4 4 5% 16%	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	76% 7% 8% 8% 1	1519
	11th to 20th	Day	72% 6% 13% 7% 1	1459
	21st to end	Day	67% 8% 12% 10% 3	1642
February	1st to 10th	Day	61% 8% 17% 11% 2	1620
	11th to 20th	Day	51% 9% 18% 18% 4	1584
	21st to end	Day	51% 9% 17% 15% 8%	1469
March	1st to 10th	Day	52% 9% 14% 18% 7%	1800
	11th to 20th	Day	52% 7% 15% 21% 4	1975
	21st to end	Day	52% 9% 18% 18% 4	2286
April	1st to 10th	Day	45% 8% 18% 21% 9%	2160
	11th to 20th	Day	42% 8% 18% 19% 11% 2	2132
	21st to end	Day	31% 8% 21% 25% 13% 2	2290
May	1st to 10th	Day	30% 6% 17% 31% 16% 1	2520
	11th to 20th	Day	36% 5% 17% 27% 14% 2	2480
	21st to end	Day	33% 7% 20% 28% 11% 1	2724
June	1st to 10th	Day	33% 6% 15% 31% 13% 2	2520
	11th to 20th	Day	27% 4 17% 38% 13% 2	2520
	21st to end	Day	18% 3 15% 35% 21% 8%	2520
July	1st to 10th	Day	11% 3 12% 30% 30% 15%	2451
	11th to 20th	Day	12% 2 8% 22% 35% 20%	2445
	21st to end	Day	7% 2 4 23% 41% 22%	2589
August	1st to 10th	Day	11% 3 10% 28% 34% 14%	2446
	11th to 20th	Day	11% 2 10% 30% 33% 13%	2298
	21st to end	Day	15% 4 9% 33% 32% 7%	2386
September	1st to 10th	Day	12% 2 10% 34% 28% 14%	2160
	11th to 20th	Day	24% 4 16% 25% 24% 7%	2160
	21st to end	Day	30% 4 14% 28% 18% 5%	1928
October	1st to 10th	Day	33% 7% 14% 27% 17% 3	1800
	11th to 20th	Day	39% 7% 18% 22% 13% 1	1800
	21st to end	Day	49% 7% 13% 21% 9%	1859
November	1st to 10th	Day	56% 8% 13% 18% 4	1652
	11th to 20th	Day	62% 10% 13% 12% 3	1520
	21st to end	Day	60% 8% 15% 11% 5% 1	1520
December	1st to 10th	Day	64% 6% 12% 15% 4	1520
	11th to 20th	Day	78% 5% 9% 6% 1	1928
	21st to end	Day	79% 4 7% 8% 1	2794
January	1st to 10th	Night	71% 8% 11% 8% 1	2646
	11th to 20th	Night	67% 6% 12% 10% 4	2562
	21st to end	Night	60% 10% 14% 14% 2 1	2712
February	1st to 10th	Night	55% 9% 19% 14% 3	2340
	11th to 20th	Night	47% 9% 19% 20% 5% 1	2274
	21st to end	Night	48% 9% 17% 19% 5% 1	1786
March	1st to 10th	Night	48% 10% 16% 18% 6% 1	2160
	11th to 20th	Night	46% 7% 19% 22% 6%	1981
	21st to end	Night	48% 8% 20% 19% 5%	2070
April	1st to 10th	Night	42% 8% 19% 22% 8% 1	1800
	11th to 20th	Night	36% 7% 20% 24% 11% 2	1779
	21st to end	Night	31% 9% 19% 27% 11% 2	1666
May	1st to 10th	Night	27% 5% 20% 34% 14% 1	1440
	11th to 20th	Night	29% 6% 21% 29% 12% 2	1416
	21st to end	Night	29% 8% 26% 27% 9% 1	1552
June	1st to 10th	Night	35% 6% 15% 34% 9% 1	1440
	11th to 20th	Night	23% 4 22% 38% 12% 1	1440
	21st to end	Night	19% 3 13% 38% 21% 6%	1440
July	1st to 10th	Night	11% 4 15% 28% 28% 15%	1400
	11th to 20th	Night	9% 3 11% 25% 34% 18%	1392
	21st to end	Night	6% 2 6% 21% 44% 21%	1488
August	1st to 10th	Night	11% 3 9% 32% 32% 13%	1466
	11th to 20th	Night	12% 2 10% 31% 33% 11%	1602
	21st to end	Night	12% 4 9% 33% 34% 8%	1970
September	1st to 10th	Night	11% 3 13% 32% 27% 14%	1800
	11th to 20th	Night	22% 5% 13% 29% 19% 11%	1800
	21st to end	Night	24% 4 15% 29% 22% 6%	2027
October	1st to 10th	Night	31% 5% 12% 26% 24% 2	2160
	11th to 20th	Night	36% 6% 15% 26% 14% 2	2160
	21st to end	Night	39% 8% 14% 23% 15% 1	2497
November	1st to 10th	Night	49% 8% 15% 21% 7%	2424
	11th to 20th	Night	58% 9% 14% 15% 4	2660
	21st to end	Night	52% 9% 16% 17% 5% 1	2660
December	1st to 10th	Night	63% 7% 12% 14% 3	2660
	11th to 20th	Night	74% 8% 10% 6% 1	3276
	21st to end	Night	71% 6% 9% 12% 2	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	34% 17% 17% 17% 13% 3	180
	11th to 20th	Day	34% 10% 19% 26% 9% 1	165
	21st to end	Day	24% 9% 24% 25% 16% 2	234
February	1st to 10th	Day	27% 15% 23% 22% 11% 2	340
	11th to 20th	Day	28% 17% 24% 22% 8%	335
	21st to end	Day	21% 19% 26% 25% 7% 2	342
March	1st to 10th	Day	23% 18% 27% 22% 8% 2	420
	11th to 20th	Day	21% 17% 24% 24% 12% 2	420
	21st to end	Day	23% 20% 27% 20% 9% 1	462
April	1st to 10th	Day	26% 20% 26% 16% 10% 2	420
	11th to 20th	Day	18% 28% 26% 16% 8% 4	412
	21st to end	Day	17% 23% 29% 20% 8% 2	420
May	1st to 10th	Day	15% 20% 30% 21% 11% 3	423
	11th to 20th	Day	20% 14% 30% 18% 14% 4	448
	21st to end	Day	12% 17% 31% 24% 13% 3	485
June	1st to 10th	Day	13% 21% 30% 18% 14% 4	450
	11th to 20th	Day	14% 24% 34% 16% 9% 2	450
	21st to end	Day	6% 17% 33% 26% 14% 4	450
July	1st to 10th	Day	4 12% 44% 25% 13% 2	446
	11th to 20th	Day	5% 14% 36% 27% 15% 3	444
	21st to end	Day	2 11% 34% 25% 19% 9%	487
August	1st to 10th	Day	5% 9% 30% 23% 22% 11%	447
	11th to 20th	Day	2 9% 27% 28% 22% 11%	437
	21st to end	Day	6% 14% 28% 23% 21% 9%	495
September	1st to 10th	Day	4 13% 26% 28% 21% 9%	450
	11th to 20th	Day	10% 11% 25% 25% 24% 5%	450
	21st to end	Day	11% 14% 24% 27% 18% 5%	450
October	1st to 10th	Day	13% 13% 24% 24% 16% 9%	450
	11th to 20th	Day	16% 14% 21% 22% 19% 8%	450
	21st to end	Day	20% 15% 23% 21% 16% 5%	374
November	1st to 10th	Day	25% 12% 20% 27% 13% 3	259
	11th to 20th	Day	31% 11% 22% 24% 9% 3	180
	21st to end	Day	26% 8% 17% 29% 17% 3	180
December	1st to 10th	Day	24% 9% 24% 22% 14% 7%	180
	11th to 20th	Day	34% 10% 22% 26% 7% 1	180
	21st to end	Day	28% 12% 20% 27% 12% 1	198
January	1st to 10th	Night	28% 9% 21% 28% 12% 1	760
	11th to 20th	Night	28% 8% 17% 30% 15% 2	732
	21st to end	Night	23% 8% 17% 31% 19% 2	792
February	1st to 10th	Night	23% 12% 18% 33% 14% 1	720
	11th to 20th	Night	18% 13% 21% 30% 17% 1	704
	21st to end	Night	20% 14% 20% 34% 11% 1	592
March	1st to 10th	Night	18% 12% 21% 34% 14% 1	720
	11th to 20th	Night	15% 11% 23% 36% 14% 1	720
	21st to end	Night	16% 16% 26% 30% 11% 1	792
April	1st to 10th	Night	15% 15% 27% 29% 14% 1	720
	11th to 20th	Night	14% 16% 28% 25% 14% 2	711
	21st to end	Night	10% 16% 33% 27% 13% 1	586
May	1st to 10th	Night	10% 13% 31% 30% 16% 1	360
	11th to 20th	Night	9% 9% 27% 34% 18% 2	354
	21st to end	Night	6% 8% 34% 35% 14% 2	389
June	1st to 10th	Night	12% 13% 33% 28% 14% 1	360
	11th to 20th	Night	9% 17% 38% 27% 9%	360
	21st to end	Night	5% 13% 34% 31% 17% 1	360
July	1st to 10th	Night	3 9% 34% 35% 18% 1	350
	11th to 20th	Night	1 8% 41% 35% 14% 1	348
	21st to end	Night	2 8% 29% 38% 21% 1	394
August	1st to 10th	Night	2 6% 26% 41% 22% 4	400
	11th to 20th	Night	3 5% 17% 34% 33% 8%	534
	21st to end	Night	3 10% 29% 31% 23% 4	782
September	1st to 10th	Night	2 7% 27% 31% 30% 3	720
	11th to 20th	Night	6% 5% 24% 27% 33% 5%	720
	21st to end	Night	7% 7% 21% 33% 28% 4	720
October	1st to 10th	Night	12% 7% 19% 37% 21% 4	720
	11th to 20th	Night	13% 7% 20% 30% 27% 3	720
	21st to end	Night	17% 8% 23% 31% 19% 2	792
November	1st to 10th	Night	17% 9% 21% 37% 14% 1	740
	11th to 20th	Night	24% 9% 21% 31% 13% 1	760
	21st to end	Night	16% 8% 23% 34% 16% 3	760
December	1st to 10th	Night	24% 7% 20% 31% 16% 2	760
	11th to 20th	Night	26% 9% 18% 32% 15% 1	760
	21st to end	Night	28% 11% 20% 31% 9% 1	836

Page generated at 2024-01-10 16:35:19. Version ac07

Copyright 2024 Attilla Danko