Goldendale Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goldendale Observatory clear sky chart from 2005-11-06 to 2024-03-28.

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	10% 7% 3 6% 5% 3 5% 5% 5% 7% 44%	78673
	Night	12% 8% 3 6% 5% 3 5% 5% 5% 7% 41%	81339
Transparency	Day	38% 9% 14% 20% 15% 5%	78376
	Night	42% 10% 14% 19% 12% 3	81157
Seeing	Day	14% 18% 29% 24% 13% 3	13627
	Night	15% 12% 24% 29% 17% 3	22823

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	19% 19% 6% 11% 8% 4 5% 4 4 5% 13%	2539
	11th to 20th	Day	20% 17% 5% 9% 7% 3 5% 5% 6% 5% 18%	2540
	21st to end	Day	26% 14% 5% 10% 7% 4 5% 5% 5% 5% 14%	2858
February	1st to 10th	Day	15% 14% 5% 9% 6% 3 5% 5% 5% 7% 27%	1710
	11th to 20th	Day	14% 11% 3 7% 7% 3 5% 5% 6% 7% 32%	1665
	21st to end	Day	11% 9% 4 8% 7% 5% 6% 7% 6% 8% 28%	1569
March	1st to 10th	Day	11% 10% 4 8% 6% 4 7% 5% 8% 10% 28%	1900
	11th to 20th	Day	12% 10% 4 7% 6% 4 6% 5% 7% 9% 31%	2067
	21st to end	Day	10% 10% 3 9% 8% 5% 6% 7% 7% 9% 25%	2378
April	1st to 10th	Day	9% 9% 4 7% 6% 4 6% 7% 7% 9% 32%	2160
	11th to 20th	Day	8% 9% 4 6% 6% 3 6% 5% 5% 8% 39%	2129
	21st to end	Day	5% 5% 3 5% 6% 3 6% 5% 7% 9% 45%	2298
May	1st to 10th	Day	6% 5% 2 5% 5% 3 5% 4 7% 8% 50%	2520
	11th to 20th	Day	8% 6% 3 6% 5% 4 5% 7% 8% 10% 38%	2477
	21st to end	Day	9% 5% 2 4 4 4 5% 5% 6% 9% 46%	2723
June	1st to 10th	Day	10% 4 3 5% 4 3 5% 5% 6% 8% 47%	2520
	11th to 20th	Day	5% 4 2 5% 4 3 4 5% 6% 9% 55%	2520
	21st to end	Day	3 3 1 3 3 2 3 4 4 6% 68%	2520
July	1st to 10th	Day	2 1 1 2 2 1 2 3 4 6% 76%	2520
	11th to 20th	Day	3 2 1 2 2 1 3 3 4 5% 76%	2520
	21st to end	Day	2 1 1 1 1 1 2 2 3 85%	2741
August	1st to 10th	Day	3 2 1 2 2 1 2 2 4 5% 76%	2486
	11th to 20th	Day	2 2 1 2 2 1 2 3 3 5% 78%	2298
	21st to end	Day	3 2 1 2 3 2 3 3 4 6% 71%	2376
September	1st to 10th	Day	3 2 1 2 2 1 2 3 4 5% 74%	2160
	11th to 20th	Day	5% 3 1 4 4 3 4 5% 5% 6% 60%	2160
	21st to end	Day	7% 6% 2 4 4 3 4 4 4 6% 56%	1935
October	1st to 10th	Day	8% 6% 2 5% 5% 2 5% 4 7% 7% 50%	1800
	11th to 20th	Day	11% 5% 3 6% 5% 3 5% 5% 6% 8% 44%	1800
	21st to end	Day	15% 8% 2 6% 6% 3 6% 5% 6% 6% 38%	1842
November	1st to 10th	Day	13% 9% 4 9% 7% 4 5% 5% 7% 8% 28%	1660
	11th to 20th	Day	16% 9% 7% 10% 8% 4 6% 6% 6% 7% 22%	1520
	21st to end	Day	14% 9% 6% 9% 7% 3 6% 5% 6% 6% 29%	1520
December	1st to 10th	Day	16% 10% 5% 9% 7% 3 5% 6% 5% 5% 28%	1520
	11th to 20th	Day	18% 15% 6% 13% 10% 5% 6% 5% 4 4 13%	1928
	21st to end	Day	19% 15% 7% 13% 8% 4 5% 5% 4 4 17%	2794
January	1st to 10th	Night	19% 14% 5% 10% 8% 3 5% 6% 6% 6% 17%	4406
	11th to 20th	Night	22% 13% 4 8% 6% 3 5% 4 4 8% 22%	4420
	21st to end	Night	25% 11% 4 8% 7% 5% 7% 5% 4 6% 18%	4796
February	1st to 10th	Night	14% 14% 4 8% 6% 4 4 5% 5% 7% 29%	2470
	11th to 20th	Night	12% 11% 4 6% 7% 3 4 4 5% 6% 36%	2402
	21st to end	Night	11% 12% 6% 7% 6% 3 5% 5% 5% 7% 32%	1884
March	1st to 10th	Night	12% 10% 4 7% 7% 3 6% 5% 6% 8% 33%	2280
	11th to 20th	Night	10% 7% 3 6% 6% 5% 5% 6% 7% 9% 36%	2109
	21st to end	Night	10% 8% 4 7% 6% 5% 6% 6% 7% 7% 33%	2131
April	1st to 10th	Night	9% 8% 4 6% 5% 4 6% 5% 6% 11% 37%	1800
	11th to 20th	Night	9% 6% 2 5% 4 3 4 4 6% 6% 49%	1779
	21st to end	Night	7% 5% 3 6% 5% 3 4 6% 6% 10% 45%	1660
May	1st to 10th	Night	5% 5% 2 4 4 3 5% 4 7% 7% 55%	1440
	11th to 20th	Night	7% 5% 2 3 4 2 5% 6% 7% 10% 50%	1416
	21st to end	Night	5% 6% 3 4 4 2 5% 6% 7% 9% 48%	1552
June	1st to 10th	Night	10% 4 2 4 5% 3 4 5% 6% 8% 50%	1440
	11th to 20th	Night	6% 5% 2 3 4 2 3 3 5% 8% 59%	1440
	21st to end	Night	3 3 2 4 3 2 3 4 4 5% 68%	1440
July	1st to 10th	Night	3 2 1 3 2 2 2 3 3 5% 76%	1440
	11th to 20th	Night	1 2 2 2 1 3 3 3 4 79%	1440
	21st to end	Night	1 1 1 1 1 1 2 2 3 3 84%	1576
August	1st to 10th	Night	2 2 1 2 2 2 2 3 3 4 77%	1449
	11th to 20th	Night	3 2 1 2 2 2 2 2 3 3 77%	1602
	21st to end	Night	2 3 1 2 2 2 3 3 4 5% 75%	1980
September	1st to 10th	Night	3 1 2 2 2 2 3 4 5% 75%	1800
	11th to 20th	Night	4 3 1 3 4 3 4 4 4 5% 64%	1800
	21st to end	Night	6% 4 1 3 3 2 4 4 6% 6% 61%	2023
October	1st to 10th	Night	8% 6% 2 5% 4 3 4 4 5% 6% 55%	2160
	11th to 20th	Night	11% 5% 2 5% 5% 3 5% 4 5% 8% 47%	2160
	21st to end	Night	12% 7% 2 6% 4 3 4 4 5% 6% 46%	2512
November	1st to 10th	Night	16% 8% 3 6% 6% 3 5% 5% 5% 7% 35%	2414
	11th to 20th	Night	18% 9% 4 7% 6% 3 5% 6% 6% 7% 29%	2660
	21st to end	Night	12% 8% 3 9% 6% 4 5% 5% 6% 7% 34%	2660
December	1st to 10th	Night	15% 10% 5% 9% 8% 4 5% 5% 4 6% 30%	2660
	11th to 20th	Night	20% 14% 4 10% 9% 5% 6% 5% 5% 6% 17%	3276
	21st to end	Night	18% 13% 6% 10% 7% 4 5% 4 4 5% 25%	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	68% 10% 12% 8% 1	2539
	11th to 20th	Day	65% 11% 15% 8% 1	2540
	21st to end	Day	69% 14% 10% 5% 2	2858
February	1st to 10th	Day	57% 11% 17% 13% 2	1710
	11th to 20th	Day	49% 13% 16% 16% 5%	1674
	21st to end	Day	51% 12% 17% 13% 7% 1	1569
March	1st to 10th	Day	49% 12% 16% 16% 7%	1900
	11th to 20th	Day	48% 9% 14% 23% 5%	2067
	21st to end	Day	53% 11% 18% 15% 4	2378
April	1st to 10th	Day	45% 11% 16% 18% 9%	2160
	11th to 20th	Day	43% 9% 17% 18% 11% 2	2132
	21st to end	Day	33% 11% 18% 24% 13% 2	2298
May	1st to 10th	Day	30% 8% 17% 28% 16% 1	2520
	11th to 20th	Day	36% 9% 16% 24% 12% 2	2480
	21st to end	Day	33% 9% 20% 27% 10% 1	2724
June	1st to 10th	Day	33% 8% 14% 29% 13% 3	2520
	11th to 20th	Day	25% 7% 17% 34% 15% 2	2520
	21st to end	Day	19% 4 14% 32% 22% 8%	2520
July	1st to 10th	Day	11% 4 11% 26% 33% 15%	2451
	11th to 20th	Day	12% 4 9% 18% 35% 22%	2445
	21st to end	Day	7% 2 6% 19% 43% 23%	2589
August	1st to 10th	Day	12% 4 9% 25% 36% 15%	2469
	11th to 20th	Day	11% 3 10% 27% 36% 13%	2298
	21st to end	Day	16% 4 11% 29% 34% 7%	2376
September	1st to 10th	Day	14% 3 11% 30% 29% 13%	2160
	11th to 20th	Day	24% 7% 12% 26% 23% 8%	2160
	21st to end	Day	29% 7% 15% 26% 18% 5%	1935
October	1st to 10th	Day	33% 8% 15% 26% 16% 2	1800
	11th to 20th	Day	37% 10% 17% 20% 14% 2	1800
	21st to end	Day	45% 10% 14% 20% 11%	1842
November	1st to 10th	Day	52% 11% 15% 17% 5% 1	1660
	11th to 20th	Day	59% 13% 14% 11% 3 1	1520
	21st to end	Day	54% 11% 15% 13% 6% 1	1520
December	1st to 10th	Day	56% 10% 16% 14% 4	1520
	11th to 20th	Day	66% 16% 11% 5% 2	1928
	21st to end	Day	66% 13% 11% 9% 2	2794
January	1st to 10th	Night	64% 15% 12% 8% 2	4406
	11th to 20th	Night	60% 10% 18% 9% 2	4420
	21st to end	Night	65% 15% 10% 8% 1	4796
February	1st to 10th	Night	54% 10% 19% 14% 3	2470
	11th to 20th	Night	49% 9% 16% 19% 7% 1	2404
	21st to end	Night	50% 10% 16% 17% 6% 1	1884
March	1st to 10th	Night	48% 10% 15% 19% 7% 1	2280
	11th to 20th	Night	43% 11% 17% 21% 7% 1	2109
	21st to end	Night	47% 11% 18% 19% 5%	2131
April	1st to 10th	Night	42% 11% 17% 21% 9% 1	1800
	11th to 20th	Night	35% 7% 19% 26% 11% 2	1779
	21st to end	Night	34% 10% 17% 25% 12% 2	1660
May	1st to 10th	Night	26% 8% 17% 33% 15% 1	1440
	11th to 20th	Night	28% 9% 20% 28% 13% 2	1416
	21st to end	Night	28% 12% 22% 28% 10% 1	1552
June	1st to 10th	Night	32% 10% 13% 30% 12% 3	1440
	11th to 20th	Night	24% 6% 18% 35% 17%	1440
	21st to end	Night	19% 5% 12% 33% 24% 7%	1440
July	1st to 10th	Night	13% 4 12% 25% 31% 16%	1400
	11th to 20th	Night	11% 4 9% 22% 32% 23%	1392
	21st to end	Night	7% 2 5% 17% 44% 25%	1488
August	1st to 10th	Night	12% 3 7% 27% 35% 15%	1441
	11th to 20th	Night	13% 2 9% 26% 35% 14%	1602
	21st to end	Night	12% 4 10% 28% 36% 10%	1980
September	1st to 10th	Night	11% 4 11% 30% 29% 15%	1800
	11th to 20th	Night	23% 6% 10% 29% 20% 12%	1800
	21st to end	Night	23% 6% 15% 27% 21% 7%	2023
October	1st to 10th	Night	29% 7% 12% 24% 25% 3	2160
	11th to 20th	Night	37% 7% 13% 24% 16% 2	2160
	21st to end	Night	38% 9% 12% 24% 16% 1	2512
November	1st to 10th	Night	48% 10% 14% 21% 8%	2414
	11th to 20th	Night	54% 12% 14% 15% 4	2660
	21st to end	Night	48% 14% 14% 17% 7%	2660
December	1st to 10th	Night	57% 11% 15% 14% 3	2660
	11th to 20th	Night	64% 15% 13% 7% 1	3276
	21st to end	Night	58% 16% 11% 10% 5%	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	25% 22% 24% 17% 9% 3	180
	11th to 20th	Day	27% 15% 26% 22% 8% 1	180
	21st to end	Day	23% 15% 26% 24% 11% 1	236
February	1st to 10th	Day	26% 19% 28% 21% 6% 1	370
	11th to 20th	Day	27% 23% 25% 19% 5%	365
	21st to end	Day	21% 25% 27% 19% 8% 1	382
March	1st to 10th	Day	19% 24% 33% 17% 7% 1	460
	11th to 20th	Day	18% 21% 28% 22% 9% 2	460
	21st to end	Day	22% 24% 31% 16% 7%	491
April	1st to 10th	Day	24% 22% 28% 17% 7% 2	420
	11th to 20th	Day	18% 28% 29% 16% 7% 2	412
	21st to end	Day	15% 27% 32% 17% 8% 2	420
May	1st to 10th	Day	13% 21% 31% 22% 10% 2	423
	11th to 20th	Day	18% 16% 29% 21% 13% 3	448
	21st to end	Day	12% 16% 29% 28% 12% 3	485
June	1st to 10th	Day	12% 24% 25% 23% 14% 3	450
	11th to 20th	Day	12% 26% 34% 20% 6% 2	450
	21st to end	Day	6% 17% 29% 30% 15% 3	450
July	1st to 10th	Day	3 10% 41% 31% 13% 2	446
	11th to 20th	Day	5% 11% 37% 29% 15% 2	444
	21st to end	Day	2 9% 32% 31% 21% 5%	487
August	1st to 10th	Day	5% 7% 30% 29% 21% 9%	447
	11th to 20th	Day	3 8% 24% 30% 27% 8%	437
	21st to end	Day	7% 12% 31% 26% 18% 5%	495
September	1st to 10th	Day	6% 12% 29% 30% 18% 6%	450
	11th to 20th	Day	9% 10% 30% 29% 19% 3	450
	21st to end	Day	9% 17% 27% 28% 17% 2	450
October	1st to 10th	Day	12% 17% 28% 22% 17% 4	450
	11th to 20th	Day	16% 18% 21% 26% 15% 4	450
	21st to end	Day	19% 20% 27% 17% 13% 4	357
November	1st to 10th	Day	19% 19% 27% 25% 10% 1	264
	11th to 20th	Day	21% 23% 18% 24% 12% 2	180
	21st to end	Day	21% 17% 26% 22% 13% 2	180
December	1st to 10th	Day	22% 17% 24% 19% 11% 7%	180
	11th to 20th	Day	25% 17% 30% 22% 6% 1	180
	21st to end	Day	22% 21% 25% 21% 12%	198
January	1st to 10th	Night	25% 15% 22% 28% 8% 1	760
	11th to 20th	Night	25% 10% 21% 27% 15% 2	760
	21st to end	Night	22% 10% 19% 31% 16% 2	836
February	1st to 10th	Night	22% 14% 23% 25% 13% 1	760
	11th to 20th	Night	18% 16% 24% 28% 13% 1	744
	21st to end	Night	20% 18% 26% 25% 11% 1	628
March	1st to 10th	Night	17% 13% 29% 26% 14% 1	760
	11th to 20th	Night	14% 14% 26% 32% 12% 2	760
	21st to end	Night	15% 19% 30% 23% 10% 2	820
April	1st to 10th	Night	17% 16% 28% 24% 13% 2	720
	11th to 20th	Night	15% 19% 29% 20% 14% 3	711
	21st to end	Night	9% 19% 30% 27% 14% 1	580
May	1st to 10th	Night	7% 16% 28% 32% 16% 3	360
	11th to 20th	Night	12% 8% 25% 32% 21% 3	354
	21st to end	Night	8% 6% 30% 36% 16% 4	389
June	1st to 10th	Night	12% 14% 27% 29% 16% 2	360
	11th to 20th	Night	9% 18% 32% 28% 13% 1	360
	21st to end	Night	5% 13% 22% 39% 21% 1	360
July	1st to 10th	Night	3 5% 27% 42% 22% 1	350
	11th to 20th	Night	1 7% 34% 41% 16% 2	348
	21st to end	Night	2 7% 19% 43% 26% 3	394
August	1st to 10th	Night	2 6% 17% 43% 27% 5%	375
	11th to 20th	Night	4 3 17% 31% 32% 14%	534
	21st to end	Night	3 9% 25% 35% 23% 5%	792
September	1st to 10th	Night	3 6% 24% 35% 28% 4	720
	11th to 20th	Night	6% 6% 23% 28% 29% 8%	720
	21st to end	Night	8% 9% 21% 28% 28% 5%	720
October	1st to 10th	Night	12% 9% 23% 33% 20% 3	720
	11th to 20th	Night	15% 11% 19% 28% 23% 4	720
	21st to end	Night	18% 12% 23% 27% 15% 4	792
November	1st to 10th	Night	19% 12% 24% 33% 12%	740
	11th to 20th	Night	24% 13% 24% 25% 13% 1	760
	21st to end	Night	15% 13% 24% 29% 17% 3	760
December	1st to 10th	Night	18% 12% 24% 29% 15% 2	760
	11th to 20th	Night	25% 10% 24% 29% 11% 1	760
	21st to end	Night	24% 17% 25% 25% 9%	836

Page generated at 2024-03-24 20:37:00. Version ac07

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