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 2024-11-04.

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% 2 6% 4 4 4 4 5% 6% 49%	105356
	Night	10% 8% 3 6% 4 4 4 4 5% 6% 46%	102333
Transparency	Day	18% 48% 7% 13% 10% 6%	105099
	Night	20% 49% 7% 12% 8% 3	102179
Seeing	Day	14% 18% 29% 24% 13% 3	14499
	Night	14% 12% 25% 30% 17% 3	23488

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% 20% 5% 13% 6% 6% 5% 3 4 5% 13%	2539
	11th to 20th	Day	20% 18% 5% 10% 6% 4 4 4 6% 5% 18%	2540
	21st to end	Day	26% 14% 5% 12% 6% 6% 5% 3 5% 4 14%	2858
February	1st to 10th	Day	14% 15% 4 10% 5% 5% 5% 4 5% 6% 27%	1710
	11th to 20th	Day	14% 12% 3 8% 6% 4 5% 4 6% 7% 31%	1665
	21st to end	Day	11% 11% 3 9% 6% 6% 6% 6% 6% 8% 28%	1569
March	1st to 10th	Day	8% 10% 3 8% 5% 5% 6% 4 8% 10% 32%	3138
	11th to 20th	Day	8% 8% 2 6% 4 4 4 3 5% 8% 48%	3455
	21st to end	Day	9% 11% 3 11% 7% 6% 6% 5% 7% 8% 27%	4034
April	1st to 10th	Day	8% 10% 3 8% 6% 6% 6% 5% 7% 9% 33%	2280
	11th to 20th	Day	8% 9% 3 7% 6% 5% 6% 4 5% 8% 39%	2249
	21st to end	Day	5% 6% 3 6% 6% 5% 5% 4 7% 9% 44%	2427
May	1st to 10th	Day	10% 6% 2 4 4 4 4 3 6% 7% 51%	4420
	11th to 20th	Day	5% 3 2 4 3 3 3 4 5% 8% 61%	4377
	21st to end	Day	6% 5% 2 5% 5% 6% 6% 5% 7% 8% 44%	4813
June	1st to 10th	Day	10% 5% 2 5% 4 5% 5% 4 6% 7% 47%	2660
	11th to 20th	Day	4 4 2 5% 3 4 4 4 6% 9% 55%	2660
	21st to end	Day	3 3 1 4 2 2 3 3 4 6% 68%	2660
July	1st to 10th	Day	1 1 1 1 1 1 2 3 4 85%	4420
	11th to 20th	Day	2 2 1 1 1 2 2 3 3 84%	4420
	21st to end	Day	1 1 1 2 1 2 2 2 3 3 82%	4790
August	1st to 10th	Day	3 3 1 3 2 2 2 2 4 5% 74%	4353
	11th to 20th	Day	2 2 1 3 3 2 2 3 5% 6% 72%	4026
	21st to end	Day	4 4 2 4 2 3 3 2 3 5% 67%	4180
September	1st to 10th	Day	3 2 1 2 2 2 3 2 4 6% 73%	2280
	11th to 20th	Day	4 4 1 5% 4 4 4 4 5% 6% 60%	2280
	21st to end	Day	7% 5% 2 4 4 3 4 3 4 6% 58%	2042
October	1st to 10th	Day	5% 4 1 4 2 3 4 3 6% 7% 59%	3180
	11th to 20th	Day	7% 6% 3 7% 5% 5% 5% 4 7% 8% 43%	3161
	21st to end	Day	11% 7% 2 7% 5% 5% 5% 5% 8% 8% 36%	3201
November	1st to 10th	Day	13% 11% 4 10% 5% 5% 5% 4 7% 8% 29%	1687
	11th to 20th	Day	15% 11% 5% 11% 6% 5% 6% 5% 6% 7% 22%	1520
	21st to end	Day	14% 11% 4 10% 7% 5% 6% 4 6% 6% 29%	1520
December	1st to 10th	Day	16% 12% 4 10% 7% 5% 5% 4 5% 5% 28%	1520
	11th to 20th	Day	18% 16% 6% 14% 8% 7% 5% 4 5% 4 13%	1928
	21st to end	Day	19% 16% 7% 14% 6% 5% 4 4 4 4 17%	2794
January	1st to 10th	Night	19% 15% 5% 11% 7% 4 6% 5% 6% 6% 17%	4406
	11th to 20th	Night	22% 14% 4 10% 5% 4 5% 3 4 8% 22%	4420
	21st to end	Night	24% 11% 4 10% 6% 6% 7% 4 5% 6% 18%	4796
February	1st to 10th	Night	14% 15% 4 9% 5% 5% 4 4 5% 6% 29%	2470
	11th to 20th	Night	12% 12% 3 7% 6% 4 4 3 5% 6% 36%	2402
	21st to end	Night	11% 14% 5% 8% 5% 5% 5% 4 6% 7% 32%	1884
March	1st to 10th	Night	8% 10% 3 8% 5% 5% 5% 5% 8% 9% 33%	3736
	11th to 20th	Night	8% 6% 2 6% 4 4 4 4 5% 6% 53%	3521
	21st to end	Night	9% 8% 3 8% 5% 6% 6% 6% 8% 8% 32%	3617
April	1st to 10th	Night	9% 9% 3 7% 5% 5% 5% 4 6% 11% 37%	1900
	11th to 20th	Night	9% 7% 2 5% 4 5% 3 3 6% 6% 49%	1879
	21st to end	Night	6% 5% 2 7% 4 4 4 6% 7% 10% 45%	1751
May	1st to 10th	Night	8% 8% 3 4 3 4 3 3 5% 5% 54%	2540
	11th to 20th	Night	4 3 1 3 2 2 3 3 5% 8% 67%	2516
	21st to end	Night	4 6% 2 4 3 3 4 4 6% 8% 57%	2762
June	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 7% 7% 49%	1520
	11th to 20th	Night	6% 5% 2 3 4 3 3 3 4 8% 60%	1520
	21st to end	Night	2 3 1 5% 3 3 3 3 4 4 68%	1520
July	1st to 10th	Night	1 1 2 1 1 1 2 2 2 86%	2540
	11th to 20th	Night	1 2 1 2 1 2 2 3 3 82%	2540
	21st to end	Night	1 1 1 1 1 1 1 3 4 85%	2761
August	1st to 10th	Night	3 2 1 2 2 2 2 2 3 5% 74%	2574
	11th to 20th	Night	2 2 1 2 2 2 3 3 5% 5% 74%	2812
	21st to end	Night	2 3 1 3 2 2 3 3 4 5% 72%	3498
September	1st to 10th	Night	2 1 2 2 2 2 2 5% 5% 75%	1900
	11th to 20th	Night	4 3 1 4 4 4 4 3 4 5% 63%	1900
	21st to end	Night	6% 4 1 4 3 3 4 3 6% 6% 62%	2136
October	1st to 10th	Night	4 4 1 4 3 3 3 3 5% 7% 64%	3800
	11th to 20th	Night	8% 5% 2 6% 5% 5% 5% 4 7% 9% 45%	3777
	21st to end	Night	10% 6% 2 6% 4 5% 6% 5% 7% 8% 41%	4358
November	1st to 10th	Night	16% 9% 3 8% 5% 4 5% 4 6% 7% 35%	2459
	11th to 20th	Night	17% 10% 3 8% 5% 5% 5% 5% 6% 7% 29%	2660
	21st to end	Night	12% 9% 3 9% 5% 5% 5% 5% 6% 7% 33%	2660
December	1st to 10th	Night	15% 11% 4 10% 7% 5% 4 3 5% 6% 29%	2660
	11th to 20th	Night	20% 14% 4 11% 8% 7% 5% 4 5% 6% 17%	3276
	21st to end	Night	17% 13% 6% 12% 5% 5% 5% 3 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	43% 41% 9% 7%	2539
	11th to 20th	Day	44% 41% 10% 4	2540
	21st to end	Day	50% 45% 2 2	2858
February	1st to 10th	Day	23% 67% 5% 3 1	1710
	11th to 20th	Day	22% 67% 6% 4 1	1674
	21st to end	Day	19% 69% 5% 3 4	1569
March	1st to 10th	Day	23% 45% 10% 17% 5%	3138
	11th to 20th	Day	13% 42% 10% 28% 7%	3455
	21st to end	Day	27% 46% 10% 12% 5%	4034
April	1st to 10th	Day	15% 67% 7% 8% 3	2280
	11th to 20th	Day	14% 67% 7% 6% 5% 1	2252
	21st to end	Day	11% 66% 7% 10% 5% 1	2427
May	1st to 10th	Day	18% 41% 7% 16% 16% 1	4420
	11th to 20th	Day	8% 39% 7% 27% 17% 3	4380
	21st to end	Day	17% 46% 18% 16% 3	4814
June	1st to 10th	Day	8% 65% 5% 13% 8% 1	2660
	11th to 20th	Day	7% 65% 5% 14% 8% 1	2660
	21st to end	Day	5% 63% 5% 13% 11% 2	2660
July	1st to 10th	Day	3 35% 2 6% 18% 36%	4351
	11th to 20th	Day	3 35% 2 5% 15% 39%	4345
	21st to end	Day	7% 35% 4 13% 26% 15%	4639
August	1st to 10th	Day	11% 36% 2 7% 22% 22%	4337
	11th to 20th	Day	10% 37% 7% 30% 14% 2	4065
	21st to end	Day	16% 37% 6% 16% 22% 3	4179
September	1st to 10th	Day	5% 60% 6% 16% 10% 3	2280
	11th to 20th	Day	11% 60% 8% 11% 7% 2	2280
	21st to end	Day	12% 61% 7% 12% 7% 1	2042
October	1st to 10th	Day	12% 37% 8% 23% 18% 1	3180
	11th to 20th	Day	25% 39% 11% 15% 9%	3161
	21st to end	Day	28% 39% 9% 19% 4	3201
November	1st to 10th	Day	21% 61% 6% 9% 2	1687
	11th to 20th	Day	24% 63% 7% 5% 2 1	1520
	21st to end	Day	21% 63% 5% 6% 4 1	1520
December	1st to 10th	Day	29% 62% 4 4 2	1520
	11th to 20th	Day	36% 56% 5% 2 1	1928
	21st to end	Day	42% 45% 6% 6% 1	2794
January	1st to 10th	Night	40% 45% 8% 5% 1	4406
	11th to 20th	Night	41% 41% 13% 5%	4420
	21st to end	Night	46% 48% 3 3	4796
February	1st to 10th	Night	23% 66% 6% 3	2470
	11th to 20th	Night	21% 66% 5% 6% 2	2404
	21st to end	Night	18% 67% 4 8% 3 1	1884
March	1st to 10th	Night	22% 46% 11% 18% 3	3736
	11th to 20th	Night	12% 42% 10% 26% 9%	3521
	21st to end	Night	23% 50% 13% 13% 2	3617
April	1st to 10th	Night	15% 67% 8% 8% 2	1900
	11th to 20th	Night	12% 66% 7% 8% 6%	1879
	21st to end	Night	10% 66% 6% 12% 5% 1	1751
May	1st to 10th	Night	20% 41% 5% 15% 18% 1	2540
	11th to 20th	Night	5% 40% 8% 27% 19% 2	2516
	21st to end	Night	8% 44% 26% 19% 3	2762
June	1st to 10th	Night	9% 65% 5% 15% 6% 1	1520
	11th to 20th	Night	5% 65% 6% 14% 9% 1	1520
	21st to end	Night	7% 63% 4 13% 11% 2	1520
July	1st to 10th	Night	3 34% 2 6% 22% 32%	2500
	11th to 20th	Night	4 34% 3 6% 17% 36%	2492
	21st to end	Night	4 35% 4 14% 25% 18%	2674
August	1st to 10th	Night	10% 36% 1 7% 24% 22%	2566
	11th to 20th	Night	9% 37% 8% 33% 12% 3	2839
	21st to end	Night	11% 37% 8% 18% 19% 7%	3498
September	1st to 10th	Night	5% 60% 7% 12% 12% 4	1900
	11th to 20th	Night	12% 60% 5% 14% 5% 4	1900
	21st to end	Night	10% 60% 6% 14% 8% 2	2136
October	1st to 10th	Night	10% 37% 8% 23% 23%	3800
	11th to 20th	Night	22% 38% 12% 17% 10%	3777
	21st to end	Night	27% 39% 8% 21% 6%	4358
November	1st to 10th	Night	21% 59% 6% 11% 3	2459
	11th to 20th	Night	22% 63% 6% 6% 2	2660
	21st to end	Night	18% 63% 6% 8% 6%	2660
December	1st to 10th	Night	28% 63% 4 4 1	2660
	11th to 20th	Night	35% 56% 6% 3 1	3276
	21st to end	Night	35% 47% 6% 8% 3	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	21% 24% 31% 17% 7%	506
April	1st to 10th	Day	22% 23% 30% 16% 8% 2	460
	11th to 20th	Day	18% 27% 30% 15% 7% 2	452
	21st to end	Day	15% 27% 32% 17% 7% 2	460
May	1st to 10th	Day	15% 20% 31% 22% 10% 2	463
	11th to 20th	Day	17% 17% 30% 21% 13% 3	488
	21st to end	Day	12% 17% 29% 27% 12% 3	529
June	1st to 10th	Day	13% 23% 24% 24% 13% 3	490
	11th to 20th	Day	12% 26% 33% 20% 7% 2	490
	21st to end	Day	7% 17% 29% 31% 14% 3	490
July	1st to 10th	Day	3 10% 40% 29% 15% 2	486
	11th to 20th	Day	4 11% 36% 30% 16% 2	484
	21st to end	Day	2 9% 30% 33% 20% 5%	531
August	1st to 10th	Day	6% 7% 29% 29% 21% 9%	487
	11th to 20th	Day	3 8% 24% 32% 26% 7%	477
	21st to end	Day	8% 12% 30% 26% 19% 6%	539
September	1st to 10th	Day	5% 11% 28% 30% 18% 8%	490
	11th to 20th	Day	9% 10% 30% 30% 18% 3	490
	21st to end	Day	8% 17% 27% 28% 18% 2	490
October	1st to 10th	Day	12% 16% 28% 22% 17% 4	490
	11th to 20th	Day	16% 18% 21% 26% 15% 4	490
	21st to end	Day	18% 19% 27% 19% 12% 4	393
November	1st to 10th	Day	19% 20% 26% 24% 10% 1	273
	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% 24% 10% 2	836
April	1st to 10th	Night	17% 16% 28% 24% 13% 2	760
	11th to 20th	Night	14% 20% 30% 21% 13% 3	751
	21st to end	Night	9% 19% 30% 27% 13% 1	611
May	1st to 10th	Night	8% 17% 28% 31% 15% 2	380
	11th to 20th	Night	11% 8% 26% 32% 21% 2	374
	21st to end	Night	8% 6% 30% 36% 16% 3	411
June	1st to 10th	Night	12% 14% 26% 29% 16% 2	380
	11th to 20th	Night	9% 17% 31% 29% 12% 1	380
	21st to end	Night	5% 12% 22% 39% 20% 1	380
July	1st to 10th	Night	3 5% 26% 42% 22% 1	370
	11th to 20th	Night	1 7% 33% 42% 16% 2	368
	21st to end	Night	1 8% 20% 44% 25% 3	416
August	1st to 10th	Night	3 6% 17% 43% 26% 4	397
	11th to 20th	Night	4 3 18% 31% 30% 13%	564
	21st to end	Night	3 10% 25% 34% 23% 5%	836
September	1st to 10th	Night	3 6% 23% 35% 29% 4	760
	11th to 20th	Night	6% 6% 24% 28% 28% 8%	760
	21st to end	Night	8% 9% 22% 29% 28% 5%	760
October	1st to 10th	Night	11% 9% 23% 34% 21% 3	760
	11th to 20th	Night	15% 11% 20% 28% 22% 4	760
	21st to end	Night	18% 12% 24% 28% 14% 4	836
November	1st to 10th	Night	20% 12% 25% 32% 11%	754
	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 2024-11-01 19:47:34. Version ac07

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