Rogue River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rogue River Observatory clear sky chart from 2005-11-06 to 2026-05-02.

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	15% 7% 2 5% 3 3 3 3 4 6% 47%	140899
	Night	19% 9% 2 5% 3 3 3 3 4 6% 42%	139036
Transparency	Day	39% 5% 11% 21% 16% 8%	135684
	Night	43% 6% 10% 18% 15% 9%	135249
Seeing	Day	22% 12% 29% 26% 10% 2	16863
	Night	24% 8% 21% 29% 16% 2	25973

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	32% 18% 4 8% 5% 4 4 3 4 4 16%	4722
	11th to 20th	Day	20% 8% 2 4 3 2 2 2 3 4 51%	5337
	21st to end	Day	22% 9% 3 7% 5% 4 4 3 4 5% 35%	5843
February	1st to 10th	Day	26% 11% 3 7% 4 4 4 3 5% 6% 26%	1890
	11th to 20th	Day	27% 11% 4 8% 5% 4 4 3 3 5% 26%	1845
	21st to end	Day	29% 14% 4 6% 4 4 3 3 4 5% 24%	1642
March	1st to 10th	Day	21% 18% 3 8% 4 4 5% 4 5% 5% 24%	5062
	11th to 20th	Day	28% 11% 3 7% 5% 4 4 2 4 4 28%	5110
	21st to end	Day	32% 14% 3 6% 5% 4 4 4 6% 6% 16%	5607
April	1st to 10th	Day	26% 12% 4 9% 4 5% 4 3 5% 6% 23%	2476
	11th to 20th	Day	24% 11% 2 6% 5% 4 4 3 5% 7% 30%	2509
	21st to end	Day	20% 7% 2 6% 5% 4 3 4 6% 8% 33%	2730
May	1st to 10th	Day	14% 7% 2 6% 4 4 4 3 4 6% 46%	5894
	11th to 20th	Day	12% 7% 3 6% 3 4 4 3 5% 7% 46%	6133
	21st to end	Day	8% 5% 1 4 3 3 3 3 6% 9% 54%	6902
June	1st to 10th	Day	17% 7% 2 5% 4 4 3 4 5% 7% 43%	2800
	11th to 20th	Day	9% 5% 2 4 3 3 3 3 5% 7% 55%	2800
	21st to end	Day	6% 3 1 3 2 3 3 3 4 6% 65%	2800
July	1st to 10th	Day	1 1 1 2 1 1 2 2 3 5% 83%	6319
	11th to 20th	Day	2 1 1 1 1 2 1 2 5% 82%	6196
	21st to end	Day	1 1 1 1 1 2 1 3 6% 82%	6402
August	1st to 10th	Day	1 1 1 2 2 3 3 2 4 8% 73%	5777
	11th to 20th	Day	3 3 1 3 2 2 3 2 4 7% 68%	5796
	21st to end	Day	4 2 1 4 2 3 3 4 5% 7% 65%	6209
September	1st to 10th	Day	2 2 1 4 3 3 3 3 4 5% 71%	2400
	11th to 20th	Day	9% 4 2 5% 3 3 4 3 6% 7% 54%	2275
	21st to end	Day	10% 4 2 4 2 3 3 3 5% 7% 57%	2176
October	1st to 10th	Day	7% 4 2 4 2 2 3 3 5% 6% 63%	3280
	11th to 20th	Day	16% 8% 2 6% 5% 3 4 4 7% 9% 36%	3261
	21st to end	Day	21% 7% 3 7% 4 4 4 4 6% 6% 33%	3558
November	1st to 10th	Day	29% 9% 3 7% 5% 4 4 2 6% 7% 25%	1888
	11th to 20th	Day	26% 12% 3 8% 5% 4 5% 3 5% 7% 23%	1680
	21st to end	Day	22% 10% 3 7% 4 4 4 3 5% 6% 31%	1680
December	1st to 10th	Day	17% 6% 2 6% 3 4 4 3 5% 6% 43%	2700
	11th to 20th	Day	31% 13% 4 10% 6% 5% 5% 3 4 4 16%	3108
	21st to end	Day	37% 14% 4 10% 5% 4 3 3 3 3 14%	4092
January	1st to 10th	Night	40% 14% 3 7% 4 4 4 3 3 4 16%	8172
	11th to 20th	Night	19% 7% 2 4 3 2 2 2 4 5% 49%	7650
	21st to end	Night	25% 10% 3 7% 4 4 3 2 3 4 34%	8371
February	1st to 10th	Night	25% 10% 3 6% 5% 4 4 3 6% 7% 27%	2730
	11th to 20th	Night	25% 13% 4 6% 4 5% 3 3 4 4 29%	2662
	21st to end	Night	28% 13% 3 6% 4 3 4 4 5% 4 26%	2161
March	1st to 10th	Night	21% 19% 3 8% 4 4 5% 4 7% 6% 20%	5052
	11th to 20th	Night	24% 15% 3 7% 4 3 3 3 4 6% 28%	5110
	21st to end	Night	31% 18% 3 7% 4 3 4 3 4 6% 17%	5610
April	1st to 10th	Night	25% 11% 4 7% 5% 5% 4 3 5% 6% 26%	2143
	11th to 20th	Night	21% 12% 3 6% 4 3 4 3 4 5% 34%	2053
	21st to end	Night	20% 8% 3 6% 3 4 4 3 6% 6% 37%	1890
May	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 4 6% 51%	4109
	11th to 20th	Night	12% 7% 3 5% 3 3 4 2 4 5% 52%	3764
	21st to end	Night	8% 6% 2 4 3 3 3 3 5% 6% 57%	3972
June	1st to 10th	Night	16% 7% 2 5% 3 3 3 3 5% 7% 46%	1600
	11th to 20th	Night	7% 4 1 3 2 3 3 3 4 7% 64%	1600
	21st to end	Night	5% 4 1 3 2 2 2 3 3 5% 70%	1600
July	1st to 10th	Night	2 1 1 2 1 2 2 2 3 4 80%	3640
	11th to 20th	Night	1 1 1 1 1 1 2 2 2 8% 79%	3767
	21st to end	Night	2 2 1 2 1 1 2 2 4 6% 78%	4472
August	1st to 10th	Night	1 1 1 3 2 2 3 2 4 8% 74%	4035
	11th to 20th	Night	3 2 1 3 3 3 4 4 5% 9% 64%	4052
	21st to end	Night	3 2 1 3 2 5% 4 3 4 6% 67%	4780
September	1st to 10th	Night	2 3 1 3 2 2 2 2 4 5% 75%	2000
	11th to 20th	Night	6% 4 1 4 3 3 4 3 4 6% 61%	2120
	21st to end	Night	9% 5% 1 4 2 2 3 2 5% 8% 60%	2223
October	1st to 10th	Night	6% 4 2 3 3 3 3 3 4 6% 64%	3920
	11th to 20th	Night	12% 7% 2 7% 4 4 5% 4 5% 7% 42%	3897
	21st to end	Night	25% 9% 3 8% 4 4 4 3 4 5% 31%	4253
November	1st to 10th	Night	24% 10% 2 8% 4 4 4 3 5% 6% 30%	2626
	11th to 20th	Night	27% 13% 3 7% 5% 4 4 3 5% 5% 24%	2940
	21st to end	Night	23% 9% 2 6% 4 4 4 4 5% 6% 33%	2940
December	1st to 10th	Night	16% 8% 3 5% 4 3 4 3 5% 5% 44%	4700
	11th to 20th	Night	34% 12% 3 8% 4 4 4 3 5% 6% 16%	5316
	21st to end	Night	36% 11% 3 8% 4 4 4 3 4 5% 19%	7106

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	71% 6% 8% 8% 6% 1	4723
	11th to 20th	Day	40% 3 3 15% 19% 20%	5337
	21st to end	Day	53% 5% 6% 9% 12% 15%	5843
February	1st to 10th	Day	58% 6% 10% 15% 7% 3	1890
	11th to 20th	Day	62% 6% 10% 14% 7% 2	1854
	21st to end	Day	63% 6% 10% 12% 8% 2	1642
March	1st to 10th	Day	60% 6% 10% 19% 4 1	5062
	11th to 20th	Day	59% 6% 12% 12% 10% 2	5110
	21st to end	Day	66% 10% 11% 9% 3	5607
April	1st to 10th	Day	62% 7% 11% 13% 6% 1	2476
	11th to 20th	Day	54% 8% 11% 16% 10% 2	2512
	21st to end	Day	47% 9% 14% 18% 12% 1	2730
May	1st to 10th	Day	37% 7% 11% 24% 19% 2	5894
	11th to 20th	Day	37% 6% 13% 21% 20% 2	6136
	21st to end	Day	25% 7% 25% 37% 5%	6904
June	1st to 10th	Day	41% 6% 13% 24% 14% 1	2800
	11th to 20th	Day	28% 7% 15% 34% 14% 2	2800
	21st to end	Day	21% 4 13% 35% 22% 5%	2800
July	1st to 10th	Day	7% 2 7% 29% 26% 30%	6251
	11th to 20th	Day	7% 2 7% 14% 29% 42%	6121
	21st to end	Day	6% 2 11% 38% 33% 10%	6217
August	1st to 10th	Day	11% 3 11% 27% 38% 10%	4206
	11th to 20th	Day	15% 4 15% 37% 22% 8%	4195
	21st to end	Day	16% 4 12% 31% 29% 9%	4476
September	1st to 10th	Day	16% 5% 10% 26% 29% 15%	2400
	11th to 20th	Day	28% 7% 13% 30% 17% 5%	2275
	21st to end	Day	27% 6% 12% 25% 22% 9%	2176
October	1st to 10th	Day	22% 6% 11% 18% 23% 20%	3280
	11th to 20th	Day	41% 6% 17% 20% 13% 3	3261
	21st to end	Day	48% 7% 10% 16% 13% 5%	3558
November	1st to 10th	Day	59% 8% 9% 13% 9% 2	1888
	11th to 20th	Day	61% 8% 11% 9% 6% 5%	1680
	21st to end	Day	54% 5% 9% 12% 12% 9%	1680
December	1st to 10th	Day	41% 5% 8% 19% 17% 9%	2700
	11th to 20th	Day	71% 6% 9% 8% 5% 1	3108
	21st to end	Day	76% 5% 5% 9% 4 2	4092
January	1st to 10th	Night	73% 5% 8% 8% 5% 2	8172
	11th to 20th	Night	38% 3 5% 15% 17% 21%	7650
	21st to end	Night	55% 3 5% 8% 14% 15%	8371
February	1st to 10th	Night	55% 6% 12% 13% 9% 3	2730
	11th to 20th	Night	58% 5% 10% 16% 8% 2	2664
	21st to end	Night	59% 9% 10% 12% 9% 3	2161
March	1st to 10th	Night	59% 7% 11% 16% 5% 2	5052
	11th to 20th	Night	57% 7% 12% 11% 10% 4	5110
	21st to end	Night	66% 9% 11% 11% 3	5610
April	1st to 10th	Night	57% 8% 12% 16% 7% 1	2143
	11th to 20th	Night	51% 7% 14% 15% 10% 3	2053
	21st to end	Night	45% 8% 13% 23% 10% 1	1890
May	1st to 10th	Night	32% 7% 10% 26% 21% 3	4106
	11th to 20th	Night	34% 7% 13% 24% 19% 2	3764
	21st to end	Night	24% 9% 27% 33% 6%	3972
June	1st to 10th	Night	39% 7% 12% 30% 13% 1	1600
	11th to 20th	Night	21% 6% 15% 39% 17% 2	1600
	21st to end	Night	17% 5% 12% 37% 24% 6%	1600
July	1st to 10th	Night	9% 2 7% 24% 26% 31%	3600
	11th to 20th	Night	6% 1 5% 15% 30% 42%	3719
	21st to end	Night	8% 2 11% 32% 34% 13%	4345
August	1st to 10th	Night	10% 3 9% 25% 38% 15%	2929
	11th to 20th	Night	14% 6% 11% 36% 23% 10%	2929
	21st to end	Night	15% 3 7% 33% 30% 12%	3438
September	1st to 10th	Night	13% 3 10% 25% 32% 18%	2000
	11th to 20th	Night	23% 6% 13% 31% 20% 6%	2120
	21st to end	Night	25% 6% 13% 21% 20% 15%	2223
October	1st to 10th	Night	21% 5% 11% 18% 20% 25%	3920
	11th to 20th	Night	37% 7% 15% 25% 11% 5%	3897
	21st to end	Night	55% 6% 8% 13% 13% 6%	4253
November	1st to 10th	Night	55% 7% 10% 13% 10% 5%	2626
	11th to 20th	Night	62% 7% 8% 12% 8% 4	2940
	21st to end	Night	50% 7% 10% 11% 13% 8%	2940
December	1st to 10th	Night	41% 5% 7% 17% 19% 10%	4700
	11th to 20th	Night	68% 6% 10% 8% 6% 1	5316
	21st to end	Night	67% 7% 7% 13% 4 1	7106

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	52% 11% 22% 10% 4	220
	11th to 20th	Day	37% 11% 20% 18% 12% 2	427
	21st to end	Day	35% 12% 24% 17% 10% 2	473
February	1st to 10th	Day	34% 13% 26% 20% 7%	430
	11th to 20th	Day	39% 17% 24% 17% 3 1	425
	21st to end	Day	40% 15% 24% 16% 4 1	380
March	1st to 10th	Day	40% 17% 23% 16% 3	540
	11th to 20th	Day	34% 14% 26% 16% 8% 1	540
	21st to end	Day	37% 18% 25% 16% 4	594
April	1st to 10th	Day	32% 15% 26% 21% 6%	540
	11th to 20th	Day	30% 18% 28% 18% 5% 2	532
	21st to end	Day	25% 18% 30% 20% 6% 1	540
May	1st to 10th	Day	17% 18% 36% 19% 9% 1	508
	11th to 20th	Day	26% 14% 27% 21% 9% 2	528
	21st to end	Day	17% 14% 35% 26% 7% 1	573
June	1st to 10th	Day	16% 14% 31% 27% 9% 2	530
	11th to 20th	Day	16% 19% 38% 21% 6%	530
	21st to end	Day	6% 7% 38% 37% 11% 1	530
July	1st to 10th	Day	4 6% 38% 40% 11% 1	526
	11th to 20th	Day	3 5% 41% 38% 10% 2	524
	21st to end	Day	2 2 35% 43% 15% 3	575
August	1st to 10th	Day	1 3 31% 43% 18% 3	527
	11th to 20th	Day	4 3 30% 41% 19% 3	517
	21st to end	Day	6% 3 35% 38% 15% 3	583
September	1st to 10th	Day	4 5% 30% 41% 16% 4	530
	11th to 20th	Day	12% 10% 27% 33% 17% 2	530
	21st to end	Day	14% 9% 31% 31% 12% 2	530
October	1st to 10th	Day	14% 12% 28% 28% 16% 2	530
	11th to 20th	Day	20% 11% 28% 22% 16% 3	530
	21st to end	Day	24% 17% 24% 23% 10% 2	583
November	1st to 10th	Day	33% 14% 22% 19% 9% 2	416
	11th to 20th	Day	38% 13% 18% 17% 11% 2	220
	21st to end	Day	26% 14% 22% 24% 14%	220
December	1st to 10th	Day	25% 16% 22% 22% 11% 4	220
	11th to 20th	Day	44% 12% 18% 20% 5% 2	220
	21st to end	Day	45% 12% 20% 15% 7% 1	242
January	1st to 10th	Night	43% 12% 19% 17% 8% 1	840
	11th to 20th	Night	35% 9% 19% 23% 12% 2	840
	21st to end	Night	33% 8% 19% 27% 12% 1	924
February	1st to 10th	Night	32% 10% 20% 24% 13% 1	840
	11th to 20th	Night	34% 12% 18% 25% 10% 1	824
	21st to end	Night	38% 11% 18% 24% 8%	692
March	1st to 10th	Night	34% 13% 20% 22% 8% 2	840
	11th to 20th	Night	32% 9% 21% 23% 14%	840
	21st to end	Night	38% 13% 20% 20% 8% 1	924
April	1st to 10th	Night	31% 13% 20% 24% 12% 1	840
	11th to 20th	Night	28% 13% 22% 24% 12% 2	805
	21st to end	Night	23% 8% 23% 30% 14% 1	630
May	1st to 10th	Night	18% 9% 29% 30% 13% 1	603
	11th to 20th	Night	18% 9% 20% 31% 21% 2	464
	21st to end	Night	18% 9% 23% 32% 15% 3	433
June	1st to 10th	Night	18% 6% 26% 33% 15% 2	400
	11th to 20th	Night	9% 7% 38% 31% 14% 1	400
	21st to end	Night	8% 4 24% 42% 21% 2	400
July	1st to 10th	Night	5% 22% 43% 29% 1	390
	11th to 20th	Night	3 1 29% 44% 22% 1	437
	21st to end	Night	2 23% 42% 27% 5%	657
August	1st to 10th	Night	1 1 15% 46% 31% 5%	597
	11th to 20th	Night	4 1 12% 44% 32% 7%	594
	21st to end	Night	5% 2 24% 38% 26% 4	775
September	1st to 10th	Night	4 3 17% 44% 30% 3	800
	11th to 20th	Night	7% 5% 17% 32% 31% 8%	800
	21st to end	Night	12% 6% 22% 36% 21% 4	800
October	1st to 10th	Night	12% 6% 24% 33% 21% 3	800
	11th to 20th	Night	19% 8% 19% 30% 20% 4	800
	21st to end	Night	24% 10% 20% 29% 13% 4	880
November	1st to 10th	Night	30% 8% 22% 26% 12% 2	820
	11th to 20th	Night	35% 11% 18% 25% 9% 1	840
	21st to end	Night	27% 11% 21% 29% 11% 1	840
December	1st to 10th	Night	29% 10% 21% 27% 11% 2	840
	11th to 20th	Night	42% 9% 18% 22% 9% 1	840
	21st to end	Night	47% 9% 19% 19% 6%	924

Page generated at 2026-04-28 23:21:40. Version ac07

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