Golden Spike National Historical Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Golden Spike National Historical Park clear sky chart from 2005-11-06 to 2024-12-02.

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	6% 7% 2 6% 4 4 4 3 5% 7% 52%	105480
	Night	7% 8% 3 6% 5% 4 4 3 5% 6% 48%	102805
Transparency	Day	31% 5% 9% 19% 20% 15%	105235
	Night	35% 5% 10% 19% 18% 12%	102639
Seeing	Day	9% 6% 19% 33% 25% 9%	15037
	Night	11% 4 15% 39% 26% 4	24945

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	10% 17% 5% 13% 8% 7% 5% 4 4 4 23%	2550
	11th to 20th	Day	8% 13% 5% 13% 8% 7% 7% 4 5% 5% 24%	2860
	21st to end	Day	12% 19% 5% 17% 11% 6% 4 3 4 3 15%	3146
February	1st to 10th	Day	11% 13% 5% 11% 7% 5% 5% 4 5% 6% 27%	1710
	11th to 20th	Day	10% 12% 4 9% 5% 4 5% 4 7% 8% 31%	1753
	21st to end	Day	6% 12% 5% 11% 5% 5% 5% 4 7% 7% 33%	1570
March	1st to 10th	Day	6% 12% 4 11% 6% 4 4 4 5% 8% 37%	3287
	11th to 20th	Day	7% 7% 3 5% 4 3 4 4 5% 6% 51%	3490
	21st to end	Day	10% 13% 4 9% 6% 5% 5% 4 7% 9% 28%	3825
April	1st to 10th	Day	9% 8% 3 7% 4 5% 4 3 6% 7% 44%	2118
	11th to 20th	Day	8% 8% 2 6% 5% 4 4 4 6% 7% 48%	2432
	21st to end	Day	7% 6% 2 7% 4 4 4 4 6% 9% 47%	2470
May	1st to 10th	Day	6% 8% 2 7% 5% 5% 5% 4 6% 7% 44%	4110
	11th to 20th	Day	4 4 1 5% 3 3 4 4 7% 8% 58%	4071
	21st to end	Day	5% 4 2 5% 4 4 5% 4 6% 7% 54%	4477
June	1st to 10th	Day	4 4 1 3 4 3 5% 3 7% 8% 57%	2546
	11th to 20th	Day	5% 4 2 4 3 3 3 3 5% 8% 60%	2846
	21st to end	Day	2 2 1 3 2 2 2 3 4 6% 72%	2685
July	1st to 10th	Day	2 1 1 2 2 2 3 2 4 5% 79%	4420
	11th to 20th	Day	2 2 1 3 2 3 3 4 7% 7% 66%	4220
	21st to end	Day	3 2 1 3 2 2 3 3 5% 7% 68%	4454
August	1st to 10th	Day	3 2 1 4 3 3 3 2 5% 7% 68%	4092
	11th to 20th	Day	2 2 1 4 3 2 3 3 6% 6% 68%	4028
	21st to end	Day	3 2 1 2 2 2 2 2 4 5% 74%	4521
September	1st to 10th	Day	3 3 1 3 2 3 3 3 4 5% 70%	2135
	11th to 20th	Day	4 2 1 4 3 3 3 3 4 6% 66%	2090
	21st to end	Day	6% 2 1 3 2 3 2 2 5% 6% 68%	2090
October	1st to 10th	Day	5% 3 1 3 2 3 3 3 4 5% 67%	3372
	11th to 20th	Day	4 5% 1 4 3 3 3 3 5% 7% 61%	3150
	21st to end	Day	5% 5% 2 5% 3 3 4 3 4 7% 59%	3300
November	1st to 10th	Day	7% 9% 4 8% 4 3 4 4 5% 7% 46%	1764
	11th to 20th	Day	10% 7% 2 5% 3 3 4 4 7% 9% 46%	1800
	21st to end	Day	8% 12% 3 6% 5% 4 5% 3 5% 7% 42%	1668
December	1st to 10th	Day	10% 13% 5% 11% 6% 4 4 2 3 5% 35%	1528
	11th to 20th	Day	12% 13% 4 13% 9% 7% 6% 5% 5% 7% 20%	1926
	21st to end	Day	9% 12% 4 12% 7% 6% 5% 4 6% 6% 28%	2976
January	1st to 10th	Night	8% 13% 4 9% 6% 6% 6% 4 6% 7% 32%	4372
	11th to 20th	Night	11% 14% 4 11% 6% 5% 5% 4 7% 7% 26%	4110
	21st to end	Night	12% 17% 5% 13% 10% 5% 4 3 4 5% 21%	4521
February	1st to 10th	Night	11% 14% 4 8% 5% 5% 5% 3 6% 7% 32%	2470
	11th to 20th	Night	9% 11% 3 8% 5% 4 5% 3 5% 7% 41%	2313
	21st to end	Night	6% 12% 3 8% 6% 5% 4 4 6% 7% 38%	1884
March	1st to 10th	Night	8% 12% 4 8% 5% 5% 5% 5% 6% 6% 35%	3586
	11th to 20th	Night	5% 6% 2 5% 5% 4 5% 4 6% 7% 49%	3490
	21st to end	Night	9% 9% 4 8% 6% 5% 5% 5% 6% 6% 36%	3828
April	1st to 10th	Night	8% 10% 3 7% 5% 4 4 3 6% 6% 45%	2057
	11th to 20th	Night	10% 8% 2 7% 4 4 4 2 5% 6% 48%	1696
	21st to end	Night	9% 7% 3 6% 5% 4 3 3 6% 6% 49%	1710
May	1st to 10th	Night	8% 8% 3 6% 4 4 4 4 6% 7% 47%	2860
	11th to 20th	Night	6% 5% 2 5% 3 3 3 3 5% 5% 60%	2834
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 5% 5% 52%	3110
June	1st to 10th	Night	5% 4 2 4 3 4 5% 4 6% 8% 54%	1623
	11th to 20th	Night	6% 4 2 4 3 3 4 4 5% 8% 57%	1330
	21st to end	Night	3 2 1 3 3 2 3 2 5% 6% 69%	1484
July	1st to 10th	Night	2 2 1 3 2 3 3 3 4 5% 73%	2540
	11th to 20th	Night	3 3 1 5% 4 4 4 4 6% 8% 58%	2731
	21st to end	Night	2 3 2 5% 3 3 4 3 5% 6% 64%	3109
August	1st to 10th	Night	3 3 1 4 3 4 5% 4 6% 7% 60%	2847
	11th to 20th	Night	2 3 2 6% 3 4 4 3 5% 6% 62%	2811
	21st to end	Night	3 3 1 3 2 2 3 2 3 5% 71%	3146
September	1st to 10th	Night	3 3 1 4 3 3 4 3 4 5% 68%	2040
	11th to 20th	Night	5% 3 1 3 2 2 4 2 4 5% 67%	2090
	21st to end	Night	6% 3 1 4 2 2 3 2 3 3 71%	2090
October	1st to 10th	Night	4 3 1 3 2 2 2 2 3 5% 73%	3604
	11th to 20th	Night	7% 6% 2 4 3 3 3 3 5% 6% 57%	3778
	21st to end	Night	5% 5% 2 5% 4 4 4 4 5% 7% 54%	4241
November	1st to 10th	Night	9% 8% 2 6% 4 4 4 3 5% 7% 49%	2535
	11th to 20th	Night	8% 8% 2 6% 4 3 3 4 6% 7% 49%	2600
	21st to end	Night	6% 9% 3 7% 5% 5% 4 3 6% 7% 45%	2707
December	1st to 10th	Night	10% 10% 4 8% 5% 5% 4 3 6% 7% 38%	2687
	11th to 20th	Night	13% 13% 4 9% 7% 6% 5% 4 5% 8% 26%	3271
	21st to end	Night	10% 11% 4 10% 7% 5% 5% 4 6% 6% 31%	4700

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	63% 8% 14% 12% 2 1	2550
	11th to 20th	Day	59% 10% 14% 13% 2	2860
	21st to end	Day	74% 7% 9% 7% 3 1	3146
February	1st to 10th	Day	57% 6% 14% 16% 5% 1	1710
	11th to 20th	Day	48% 9% 15% 19% 8% 2	1762
	21st to end	Day	47% 8% 14% 21% 8% 1	1570
March	1st to 10th	Day	44% 8% 12% 24% 11% 1	3287
	11th to 20th	Day	31% 6% 11% 33% 18% 1	3490
	21st to end	Day	49% 8% 15% 23% 5% 1	3825
April	1st to 10th	Day	39% 6% 13% 26% 12% 4	2118
	11th to 20th	Day	34% 6% 11% 28% 20% 2	2435
	21st to end	Day	33% 6% 11% 28% 20% 2	2470
May	1st to 10th	Day	34% 5% 10% 25% 21% 5%	4110
	11th to 20th	Day	21% 5% 8% 30% 26% 10%	4074
	21st to end	Day	26% 6% 9% 24% 32% 3	4477
June	1st to 10th	Day	22% 6% 11% 25% 30% 6%	2546
	11th to 20th	Day	23% 4 8% 17% 29% 19%	2846
	21st to end	Day	13% 3 4 13% 31% 35%	2685
July	1st to 10th	Day	10% 2 3 9% 14% 62%	4351
	11th to 20th	Day	15% 3 3 9% 24% 47%	4147
	21st to end	Day	15% 4 3 9% 32% 37%	4314
August	1st to 10th	Day	17% 3 4 14% 28% 34%	4078
	11th to 20th	Day	17% 2 4 14% 36% 27%	4067
	21st to end	Day	14% 2 4 14% 34% 33%	4520
September	1st to 10th	Day	17% 3 5% 16% 29% 30%	2135
	11th to 20th	Day	19% 4 6% 21% 30% 20%	2090
	21st to end	Day	18% 3 8% 21% 37% 13%	2090
October	1st to 10th	Day	20% 3 6% 18% 32% 20%	3372
	11th to 20th	Day	23% 4 8% 32% 27% 6%	3150
	21st to end	Day	25% 4 15% 36% 19% 1	3300
November	1st to 10th	Day	38% 6% 16% 24% 15% 1	1764
	11th to 20th	Day	33% 6% 21% 30% 9% 1	1800
	21st to end	Day	41% 5% 19% 24% 10% 1	1668
December	1st to 10th	Day	53% 6% 15% 16% 8% 1	1528
	11th to 20th	Day	61% 9% 19% 10% 2	1924
	21st to end	Day	54% 9% 14% 13% 9% 1	2976
January	1st to 10th	Night	48% 9% 18% 20% 4 1	4372
	11th to 20th	Night	54% 10% 16% 16% 4 1	4110
	21st to end	Night	65% 7% 14% 9% 4 1	4521
February	1st to 10th	Night	51% 7% 17% 20% 6%	2470
	11th to 20th	Night	43% 6% 15% 22% 14% 1	2314
	21st to end	Night	44% 5% 13% 25% 11% 2	1884
March	1st to 10th	Night	45% 8% 12% 21% 14% 1	3586
	11th to 20th	Night	32% 5% 12% 30% 18% 2	3490
	21st to end	Night	44% 8% 15% 26% 6% 1	3828
April	1st to 10th	Night	39% 5% 11% 25% 13% 7%	2057
	11th to 20th	Night	36% 5% 11% 23% 22% 3	1696
	21st to end	Night	35% 4 10% 24% 23% 4	1710
May	1st to 10th	Night	33% 5% 11% 21% 25% 5%	2860
	11th to 20th	Night	24% 4 7% 24% 32% 9%	2835
	21st to end	Night	32% 5% 8% 23% 30% 2	3110
June	1st to 10th	Night	26% 5% 10% 22% 28% 8%	1623
	11th to 20th	Night	23% 5% 7% 17% 30% 17%	1330
	21st to end	Night	16% 3 3 13% 26% 39%	1484
July	1st to 10th	Night	14% 3 3 8% 14% 57%	2500
	11th to 20th	Night	22% 4 3 7% 22% 42%	2682
	21st to end	Night	20% 3 3 8% 28% 37%	3011
August	1st to 10th	Night	20% 5% 4 10% 27% 34%	2838
	11th to 20th	Night	23% 3 4 13% 27% 29%	2838
	21st to end	Night	16% 3 5% 9% 27% 40%	3146
September	1st to 10th	Night	19% 3 5% 13% 24% 37%	2040
	11th to 20th	Night	20% 3 6% 16% 30% 26%	2090
	21st to end	Night	20% 2 4 18% 32% 23%	2090
October	1st to 10th	Night	16% 2 5% 15% 34% 27%	3604
	11th to 20th	Night	29% 3 4 25% 29% 10%	3778
	21st to end	Night	29% 4 9% 34% 20% 4	4241
November	1st to 10th	Night	35% 5% 13% 26% 19% 3	2535
	11th to 20th	Night	35% 5% 14% 30% 15% 1	2600
	21st to end	Night	38% 5% 14% 31% 11% 2	2707
December	1st to 10th	Night	45% 6% 18% 20% 9% 2	2687
	11th to 20th	Night	55% 7% 17% 16% 4	3272
	21st to end	Night	52% 7% 18% 15% 8%	4700

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	19% 3 13% 33% 18% 13%	186
	11th to 20th	Day	16% 4 17% 31% 24% 8%	270
	21st to end	Day	18% 4 11% 32% 24% 10%	297
February	1st to 10th	Day	19% 4 18% 36% 16% 6%	270
	11th to 20th	Day	13% 5% 18% 41% 17% 5%	358
	21st to end	Day	10% 6% 23% 37% 20% 4	382
March	1st to 10th	Day	12% 7% 17% 37% 23% 5%	460
	11th to 20th	Day	8% 2 16% 39% 26% 8%	460
	21st to end	Day	15% 7% 18% 37% 20% 3	506
April	1st to 10th	Day	14% 8% 17% 34% 20% 7%	460
	11th to 20th	Day	10% 14% 26% 28% 16% 6%	452
	21st to end	Day	12% 9% 25% 29% 20% 5%	460
May	1st to 10th	Day	7% 13% 29% 30% 20% 2	463
	11th to 20th	Day	10% 9% 22% 26% 23% 9%	488
	21st to end	Day	9% 8% 20% 28% 24% 11%	529
June	1st to 10th	Day	4 6% 23% 29% 26% 11%	566
	11th to 20th	Day	9% 6% 24% 33% 24% 5%	680
	21st to end	Day	3 4 24% 36% 26% 7%	515
July	1st to 10th	Day	3 3 19% 38% 27% 9%	486
	11th to 20th	Day	4 2 19% 38% 29% 8%	484
	21st to end	Day	4 2 11% 35% 40% 9%	531
August	1st to 10th	Day	6% 3 17% 34% 29% 11%	487
	11th to 20th	Day	4 5% 14% 32% 34% 12%	477
	21st to end	Day	4 5% 13% 28% 33% 18%	539
September	1st to 10th	Day	3 4 14% 27% 34% 18%	490
	11th to 20th	Day	6% 4 18% 31% 29% 13%	490
	21st to end	Day	7% 5% 16% 25% 34% 12%	490
October	1st to 10th	Day	7% 5% 19% 27% 27% 15%	424
	11th to 20th	Day	6% 7% 20% 26% 22% 19%	300
	21st to end	Day	9% 8% 23% 34% 22% 5%	330
November	1st to 10th	Day	16% 7% 19% 31% 21% 7%	300
	11th to 20th	Day	11% 6% 20% 35% 20% 7%	300
	21st to end	Day	16% 6% 13% 34% 24% 7%	300
December	1st to 10th	Day	15% 4 17% 34% 22% 8%	273
	11th to 20th	Day	17% 2 12% 43% 22% 3	270
	21st to end	Day	18% 6% 18% 32% 19% 6%	264
January	1st to 10th	Night	18% 3 11% 38% 24% 6%	760
	11th to 20th	Night	18% 3 14% 36% 24% 6%	760
	21st to end	Night	18% 3 13% 38% 23% 6%	836
February	1st to 10th	Night	18% 3 18% 41% 19% 2	760
	11th to 20th	Night	15% 3 14% 42% 22% 3	744
	21st to end	Night	11% 7% 18% 43% 19% 2	628
March	1st to 10th	Night	16% 5% 16% 43% 18% 3	760
	11th to 20th	Night	10% 4 15% 44% 24% 3	760
	21st to end	Night	14% 5% 18% 43% 19% 2	836
April	1st to 10th	Night	12% 7% 19% 39% 21% 3	760
	11th to 20th	Night	13% 7% 20% 39% 18% 3	568
	21st to end	Night	12% 6% 18% 38% 22% 3	570
May	1st to 10th	Night	11% 6% 24% 39% 19% 2	570
	11th to 20th	Night	11% 5% 15% 33% 32% 4	561
	21st to end	Night	13% 6% 14% 31% 30% 5%	617
June	1st to 10th	Night	7% 8% 15% 34% 33% 3	568
	11th to 20th	Night	8% 6% 22% 35% 27% 2	380
	21st to end	Night	4 2 19% 43% 28% 4	380
July	1st to 10th	Night	4 2 18% 35% 37% 5%	370
	11th to 20th	Night	4 3 14% 46% 32% 1	480
	21st to end	Night	3 2 9% 42% 40% 5%	624
August	1st to 10th	Night	5% 2 11% 45% 34% 2	567
	11th to 20th	Night	4 4 12% 41% 36% 3	564
	21st to end	Night	5% 4 13% 37% 34% 6%	627
September	1st to 10th	Night	5% 2 12% 37% 37% 7%	739
	11th to 20th	Night	7% 3 11% 38% 34% 7%	760
	21st to end	Night	8% 3 14% 33% 33% 9%	760
October	1st to 10th	Night	8% 3 14% 37% 34% 4	760
	11th to 20th	Night	11% 4 12% 36% 32% 5%	760
	21st to end	Night	8% 4 17% 39% 28% 4	836
November	1st to 10th	Night	12% 5% 13% 41% 25% 4	780
	11th to 20th	Night	13% 3 15% 44% 21% 5%	800
	21st to end	Night	10% 4 15% 42% 26% 4	907
December	1st to 10th	Night	15% 4 12% 44% 22% 2	960
	11th to 20th	Night	21% 3 13% 41% 19% 3	950
	21st to end	Night	20% 5% 17% 39% 17% 2	883

Page generated at 2024-11-29 08:43:06. Version ac07

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