Rooster Rock State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rooster Rock State Park clear sky chart from 2005-11-06 to 2025-04-11.

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	25% 12% 3 6% 4 3 3 3 4 5% 34%	117598
	Night	28% 13% 2 5% 3 3 3 2 3 4 32%	119491
Transparency	Day	53% 5% 10% 16% 12% 5%	117341
	Night	56% 4 10% 15% 11% 4	119337
Seeing	Day	31% 9% 22% 25% 10% 2	15038
	Night	36% 7% 16% 26% 15% 2	24169

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	43% 22% 3 5% 3 2 2 2 3 3 12%	3639
	11th to 20th	Day	28% 17% 2 5% 3 3 3 2 3 5% 29%	3640
	21st to end	Day	34% 9% 2 5% 3 3 2 2 3 4 32%	4303
February	1st to 10th	Day	35% 17% 3 5% 5% 3 4 2 4 5% 17%	1800
	11th to 20th	Day	33% 20% 3 6% 5% 3 3 1 3 3 18%	1755
	21st to end	Day	33% 21% 3 6% 2 3 3 2 3 4 19%	1586
March	1st to 10th	Day	22% 18% 5% 9% 5% 4 4 3 5% 5% 19%	4666
	11th to 20th	Day	31% 18% 4 8% 4 3 2 2 2 2 26%	5000
	21st to end	Day	33% 17% 4 9% 5% 5% 4 3 5% 4 11%	5654
April	1st to 10th	Day	34% 19% 3 7% 4 4 3 3 3 4 16%	2400
	11th to 20th	Day	29% 18% 4 6% 4 4 3 2 4 4 22%	2251
	21st to end	Day	31% 14% 3 7% 4 4 4 3 4 5% 22%	2437
May	1st to 10th	Day	26% 15% 3 6% 4 4 3 2 3 5% 31%	4406
	11th to 20th	Day	16% 13% 3 7% 4 4 4 4 4 6% 36%	4377
	21st to end	Day	32% 11% 3 7% 4 4 4 3 4 5% 22%	4813
June	1st to 10th	Day	30% 10% 3 5% 4 3 3 3 5% 6% 29%	2660
	11th to 20th	Day	29% 12% 3 6% 4 4 4 4 5% 6% 24%	2660
	21st to end	Day	14% 7% 2 5% 4 3 3 3 5% 6% 47%	2660
July	1st to 10th	Day	8% 4 1 3 2 2 2 2 4 5% 67%	4420
	11th to 20th	Day	6% 3 1 2 2 2 2 2 3 4 73%	4420
	21st to end	Day	8% 4 1 3 2 2 3 2 4 5% 66%	4790
August	1st to 10th	Day	6% 5% 1 4 3 3 3 3 4 5% 63%	4192
	11th to 20th	Day	7% 5% 2 6% 4 4 4 3 5% 6% 53%	4026
	21st to end	Day	13% 6% 2 5% 4 3 3 3 4 5% 52%	4273
September	1st to 10th	Day	12% 4 1 3 2 3 3 2 4 6% 60%	2280
	11th to 20th	Day	17% 8% 3 6% 3 4 4 3 4 6% 43%	2280
	21st to end	Day	20% 7% 2 6% 2 4 3 3 4 7% 43%	2010
October	1st to 10th	Day	21% 6% 2 4 2 2 3 3 4 5% 48%	3180
	11th to 20th	Day	25% 8% 2 7% 4 3 4 3 5% 7% 32%	3161
	21st to end	Day	36% 11% 2 5% 3 3 3 3 5% 5% 23%	3327
November	1st to 10th	Day	39% 12% 3 8% 4 3 3 2 4 6% 16%	1680
	11th to 20th	Day	41% 11% 3 6% 3 4 3 3 4 4 17%	1600
	21st to end	Day	33% 16% 2 6% 4 3 4 3 3 4 23%	1600
December	1st to 10th	Day	25% 11% 2 5% 3 3 3 3 3 4 38%	2620
	11th to 20th	Day	41% 15% 4 8% 4 3 3 3 3 4 13%	3028
	21st to end	Day	40% 17% 4 8% 4 3 3 2 3 3 13%	4004
January	1st to 10th	Night	42% 18% 2 5% 4 3 3 2 3 3 13%	6306
	11th to 20th	Night	29% 19% 3 4 2 2 2 2 3 5% 30%	6320
	21st to end	Night	33% 11% 2 5% 3 2 2 2 3 4 33%	6661
February	1st to 10th	Night	33% 19% 4 6% 4 3 3 2 4 4 18%	2600
	11th to 20th	Night	35% 17% 3 5% 3 2 3 2 3 4 23%	2532
	21st to end	Night	34% 20% 3 5% 3 3 3 2 4 5% 20%	2043
March	1st to 10th	Night	23% 20% 4 8% 4 4 5% 3 4 5% 20%	5214
	11th to 20th	Night	32% 18% 3 6% 3 2 2 2 2 3 28%	5000
	21st to end	Night	39% 18% 3 7% 4 4 3 3 4 5% 12%	5320
April	1st to 10th	Night	32% 19% 3 7% 5% 4 3 2 3 3 19%	2000
	11th to 20th	Night	28% 16% 3 5% 4 3 3 2 4 6% 27%	1883
	21st to end	Night	33% 15% 2 4 3 3 4 2 4 4 25%	1742
May	1st to 10th	Night	30% 16% 2 5% 2 2 2 1 3 3 34%	2552
	11th to 20th	Night	17% 9% 3 6% 3 3 4 4 4 5% 43%	2516
	21st to end	Night	29% 10% 3 6% 4 3 4 3 5% 6% 27%	2762
June	1st to 10th	Night	28% 9% 2 5% 4 3 3 3 5% 4 34%	1520
	11th to 20th	Night	26% 12% 3 6% 4 2 3 3 4 5% 32%	1520
	21st to end	Night	14% 7% 2 4 3 3 3 3 4 6% 52%	1520
July	1st to 10th	Night	6% 3 1 2 2 2 2 1 2 3 76%	2540
	11th to 20th	Night	5% 2 1 3 2 2 2 2 2 4 74%	2540
	21st to end	Night	6% 3 1 2 1 1 2 2 4 5% 73%	2761
August	1st to 10th	Night	5% 3 1 3 2 2 2 2 3 6% 71%	2742
	11th to 20th	Night	10% 5% 2 5% 4 3 3 3 4 6% 54%	2812
	21st to end	Night	16% 5% 2 4 2 3 2 2 3 5% 58%	3402
September	1st to 10th	Night	11% 3 1 3 2 3 3 2 4 5% 63%	1900
	11th to 20th	Night	19% 7% 2 5% 4 3 3 2 4 5% 45%	1900
	21st to end	Night	18% 8% 1 4 3 3 4 3 4 6% 46%	2166
October	1st to 10th	Night	18% 6% 1 5% 2 3 3 2 3 6% 49%	3800
	11th to 20th	Night	23% 8% 2 5% 3 4 5% 3 5% 7% 34%	3777
	21st to end	Night	38% 11% 2 6% 3 3 3 3 3 4 23%	4237
November	1st to 10th	Night	40% 12% 3 6% 4 3 3 2 4 5% 19%	2615
	11th to 20th	Night	43% 12% 3 5% 4 2 3 2 3 4 19%	2800
	21st to end	Night	33% 14% 2 5% 3 4 3 2 3 5% 26%	2800
December	1st to 10th	Night	25% 11% 2 5% 3 3 2 2 4 6% 37%	4560
	11th to 20th	Night	41% 16% 3 8% 4 3 3 2 3 4 12%	5176
	21st to end	Night	40% 18% 3 8% 4 3 3 2 2 2 13%	6952

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	80% 3 6% 8% 4	3639
	11th to 20th	Day	60% 3 6% 19% 10% 3	3640
	21st to end	Day	58% 4 4 13% 16% 6%	4303
February	1st to 10th	Day	70% 6% 11% 9% 5%	1800
	11th to 20th	Day	72% 4 8% 11% 4 2	1764
	21st to end	Day	70% 4 9% 7% 8% 2	1586
March	1st to 10th	Day	63% 6% 13% 11% 6% 1	4666
	11th to 20th	Day	66% 4 4 19% 6%	5000
	21st to end	Day	74% 7% 9% 6% 2	5654
April	1st to 10th	Day	73% 4 11% 10% 3	2400
	11th to 20th	Day	68% 4 9% 10% 8% 2	2254
	21st to end	Day	65% 5% 10% 11% 7% 2	2437
May	1st to 10th	Day	57% 5% 12% 15% 12%	4406
	11th to 20th	Day	41% 11% 19% 21% 8% 1	4380
	21st to end	Day	63% 9% 15% 12% 2	4814
June	1st to 10th	Day	57% 5% 15% 17% 6%	2660
	11th to 20th	Day	61% 6% 16% 12% 5% 1	2660
	21st to end	Day	37% 5% 16% 27% 10% 4	2660
July	1st to 10th	Day	20% 4 9% 17% 20% 30%	4351
	11th to 20th	Day	16% 3 6% 18% 34% 23%	4345
	21st to end	Day	21% 4 10% 25% 34% 6%	4639
August	1st to 10th	Day	23% 5% 8% 24% 26% 14%	4176
	11th to 20th	Day	30% 6% 15% 32% 12% 5%	4065
	21st to end	Day	34% 5% 10% 23% 18% 10%	4272
September	1st to 10th	Day	27% 4 11% 25% 19% 14%	2280
	11th to 20th	Day	42% 6% 12% 17% 15% 9%	2280
	21st to end	Day	42% 4 13% 19% 15% 7%	2010
October	1st to 10th	Day	39% 5% 6% 21% 25% 4	3180
	11th to 20th	Day	51% 6% 13% 16% 11% 2	3161
	21st to end	Day	63% 6% 6% 16% 9% 1	3327
November	1st to 10th	Day	71% 3 9% 12% 4 1	1680
	11th to 20th	Day	70% 5% 10% 8% 6% 1	1600
	21st to end	Day	66% 5% 6% 9% 12% 1	1600
December	1st to 10th	Day	51% 4 7% 11% 22% 5%	2620
	11th to 20th	Day	77% 3 9% 8% 3	3028
	21st to end	Day	78% 4 8% 8% 2	4004
January	1st to 10th	Night	78% 3 7% 7% 5% 1	6306
	11th to 20th	Night	59% 3 6% 18% 11% 2	6320
	21st to end	Night	58% 3 5% 12% 16% 7%	6661
February	1st to 10th	Night	70% 6% 9% 10% 6% 1	2600
	11th to 20th	Night	67% 5% 9% 11% 6% 2	2534
	21st to end	Night	69% 4 8% 11% 7% 1	2043
March	1st to 10th	Night	63% 7% 11% 13% 3 3	5214
	11th to 20th	Night	63% 4 8% 16% 8% 1	5000
	21st to end	Night	75% 5% 9% 9% 1	5320
April	1st to 10th	Night	71% 4 11% 10% 4	2000
	11th to 20th	Night	60% 6% 13% 11% 7% 3	1883
	21st to end	Night	64% 4 12% 12% 6% 2	1742
May	1st to 10th	Night	57% 4 11% 19% 9% 1	2552
	11th to 20th	Night	39% 7% 22% 23% 7% 2	2516
	21st to end	Night	58% 9% 21% 10% 2	2762
June	1st to 10th	Night	53% 5% 16% 20% 6%	1520
	11th to 20th	Night	57% 4 17% 17% 5%	1520
	21st to end	Night	35% 4 18% 28% 10% 5%	1520
July	1st to 10th	Night	16% 4 7% 23% 25% 25%	2500
	11th to 20th	Night	17% 3 7% 19% 33% 22%	2492
	21st to end	Night	14% 4 13% 26% 36% 7%	2674
August	1st to 10th	Night	18% 3 9% 30% 27% 13%	2734
	11th to 20th	Night	31% 5% 21% 27% 11% 6%	2839
	21st to end	Night	31% 4 11% 26% 13% 14%	3402
September	1st to 10th	Night	24% 4 13% 27% 20% 12%	1900
	11th to 20th	Night	42% 5% 10% 20% 11% 12%	1900
	21st to end	Night	39% 5% 14% 18% 15% 9%	2166
October	1st to 10th	Night	37% 4 8% 22% 26% 3	3800
	11th to 20th	Night	49% 6% 14% 17% 13% 2	3777
	21st to end	Night	64% 5% 6% 14% 9% 2	4237
November	1st to 10th	Night	70% 4 7% 12% 7% 1	2615
	11th to 20th	Night	70% 3 8% 9% 8% 1	2800
	21st to end	Night	62% 4 7% 12% 13% 2	2800
December	1st to 10th	Night	49% 4 8% 13% 22% 4	4560
	11th to 20th	Night	77% 4 8% 7% 4	5176
	21st to end	Night	78% 4 9% 7% 2	6952

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	59% 8% 18% 13% 3	200
	11th to 20th	Day	47% 13% 25% 12% 5% 1	200
	21st to end	Day	48% 10% 17% 19% 6%	350
February	1st to 10th	Day	48% 12% 18% 17% 5% 1	400
	11th to 20th	Day	48% 10% 25% 14% 2 1	395
	21st to end	Day	48% 11% 21% 17% 3	382
March	1st to 10th	Day	42% 14% 25% 13% 6%	500
	11th to 20th	Day	42% 12% 21% 18% 5% 2	500
	21st to end	Day	46% 12% 19% 18% 4	550
April	1st to 10th	Day	46% 11% 17% 19% 6% 1	500
	11th to 20th	Day	40% 15% 23% 15% 6% 2	453
	21st to end	Day	37% 13% 23% 18% 8% 1	460
May	1st to 10th	Day	28% 14% 26% 21% 9% 2	463
	11th to 20th	Day	36% 9% 20% 21% 10% 4	488
	21st to end	Day	32% 9% 19% 25% 11% 3	529
June	1st to 10th	Day	30% 9% 18% 26% 14% 3	490
	11th to 20th	Day	31% 11% 27% 21% 9% 1	490
	21st to end	Day	14% 8% 27% 31% 16% 4	490
July	1st to 10th	Day	12% 7% 23% 41% 14% 3	486
	11th to 20th	Day	8% 7% 23% 41% 16% 4	484
	21st to end	Day	6% 5% 23% 40% 20% 6%	531
August	1st to 10th	Day	9% 3 19% 47% 13% 8%	487
	11th to 20th	Day	7% 5% 21% 40% 21% 6%	477
	21st to end	Day	12% 8% 28% 34% 14% 4	539
September	1st to 10th	Day	15% 5% 28% 33% 15% 4	490
	11th to 20th	Day	20% 7% 25% 30% 15% 2	490
	21st to end	Day	23% 7% 26% 32% 10% 2	490
October	1st to 10th	Day	27% 9% 23% 25% 14% 3	490
	11th to 20th	Day	35% 5% 21% 26% 11% 2	490
	21st to end	Day	42% 10% 20% 18% 9% 1	467
November	1st to 10th	Day	47% 11% 15% 21% 5% 1	257
	11th to 20th	Day	44% 12% 25% 15% 4 2	200
	21st to end	Day	44% 10% 20% 23% 5%	200
December	1st to 10th	Day	44% 12% 21% 20% 3 2	200
	11th to 20th	Day	61% 11% 16% 13% 1	200
	21st to end	Day	57% 9% 20% 9% 5% 1	220
January	1st to 10th	Night	51% 12% 19% 14% 4 1	800
	11th to 20th	Night	47% 9% 21% 18% 5%	800
	21st to end	Night	44% 8% 24% 18% 6% 1	880
February	1st to 10th	Night	44% 9% 20% 21% 6% 1	800
	11th to 20th	Night	46% 10% 14% 22% 7%	784
	21st to end	Night	47% 10% 16% 22% 5%	660
March	1st to 10th	Night	40% 9% 18% 23% 10% 1	800
	11th to 20th	Night	41% 7% 18% 24% 10% 1	800
	21st to end	Night	48% 9% 12% 22% 9% 1	880
April	1st to 10th	Night	43% 8% 14% 24% 10% 1	800
	11th to 20th	Night	36% 8% 18% 24% 13% 2	753
	21st to end	Night	41% 6% 11% 27% 13% 1	602
May	1st to 10th	Night	31% 5% 15% 29% 18% 2	392
	11th to 20th	Night	28% 6% 8% 30% 25% 3	374
	21st to end	Night	31% 4 11% 27% 24% 2	411
June	1st to 10th	Night	31% 4 12% 32% 19% 3	380
	11th to 20th	Night	30% 7% 14% 32% 16%	380
	21st to end	Night	16% 4 12% 40% 26% 1	380
July	1st to 10th	Night	11% 2 8% 41% 37% 1	370
	11th to 20th	Night	9% 2 11% 47% 29% 2	368
	21st to end	Night	5% 2 9% 43% 38% 3	416
August	1st to 10th	Night	9% 3 8% 34% 41% 5%	500
	11th to 20th	Night	8% 2 8% 35% 38% 10%	564
	21st to end	Night	12% 3 12% 40% 27% 5%	779
September	1st to 10th	Night	14% 2 15% 34% 30% 4	760
	11th to 20th	Night	20% 4 11% 31% 29% 5%	760
	21st to end	Night	22% 4 14% 33% 23% 4	760
October	1st to 10th	Night	26% 5% 15% 30% 21% 3	760
	11th to 20th	Night	30% 5% 12% 31% 19% 3	760
	21st to end	Night	40% 5% 19% 23% 10% 3	836
November	1st to 10th	Night	47% 6% 16% 23% 7% 1	780
	11th to 20th	Night	52% 7% 19% 18% 4	800
	21st to end	Night	41% 8% 22% 24% 5%	800
December	1st to 10th	Night	41% 10% 25% 19% 5% 1	800
	11th to 20th	Night	51% 8% 18% 18% 4	800
	21st to end	Night	56% 9% 16% 15% 4	880

Page generated at 2025-04-08 06:17:24. Version ac07

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