Whiterock Resort
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiterock Resort clear sky chart from 2005-11-06 to 2024-11-05.

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	12% 8% 3 7% 5% 4 4 4 6% 7% 40%	101342
	Night	11% 8% 3 8% 4 4 4 3 5% 7% 44%	97770
Transparency	Day	41% 6% 12% 24% 15% 2	104984
	Night	39% 5% 12% 25% 17% 2	102269
Seeing	Day	15% 11% 31% 27% 13% 3	15851
	Night	15% 10% 34% 30% 10% 1	25692

By Month

Percentage Cloud Cover SE (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	8% 13% 5% 19% 10% 6% 5% 3 4 6% 21%	2637
	11th to 20th	Day	8% 13% 5% 12% 7% 6% 8% 3 5% 7% 27%	2850
	21st to end	Day	12% 13% 7% 16% 6% 4 4 4 5% 5% 22%	3135
February	1st to 10th	Day	10% 14% 5% 10% 7% 6% 4 3 5% 7% 29%	1710
	11th to 20th	Day	10% 10% 4 8% 5% 4 5% 3 4 6% 39%	1664
	21st to end	Day	13% 11% 4 9% 5% 5% 5% 3 5% 5% 35%	1529
March	1st to 10th	Day	14% 9% 3 8% 4 3 3 2 3 5% 44%	3436
	11th to 20th	Day	11% 8% 3 7% 4 4 4 3 5% 6% 44%	3480
	21st to end	Day	23% 14% 6% 9% 6% 4 4 4 4 5% 21%	3814
April	1st to 10th	Day	17% 10% 3 6% 4 4 4 4 5% 6% 37%	2222
	11th to 20th	Day	16% 10% 3 7% 5% 4 3 3 5% 7% 37%	2272
	21st to end	Day	21% 8% 3 6% 5% 4 4 3 5% 6% 35%	2470
May	1st to 10th	Day	18% 9% 2 7% 6% 5% 5% 5% 6% 7% 32%	4082
	11th to 20th	Day	13% 7% 3 6% 5% 4 5% 4 5% 7% 41%	4199
	21st to end	Day	14% 7% 2 6% 5% 4 4 3 6% 8% 40%	4824
June	1st to 10th	Day	10% 6% 2 5% 4 5% 5% 4 6% 9% 44%	2660
	11th to 20th	Day	9% 4 1 5% 5% 5% 5% 5% 7% 9% 45%	2660
	21st to end	Day	7% 6% 2 6% 5% 5% 6% 4 7% 8% 44%	2660
July	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 40%	4440
	11th to 20th	Day	6% 4 1 4 4 4 4 4 5% 7% 58%	4231
	21st to end	Day	4 3 2 5% 5% 5% 6% 5% 7% 12% 47%	4465
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 45%	4104
	11th to 20th	Day	16% 7% 2 6% 4 4 5% 4 6% 8% 40%	4041
	21st to end	Day	7% 5% 2 7% 5% 5% 5% 4 6% 8% 47%	4347
September	1st to 10th	Day	11% 5% 1 4 3 3 4 4 5% 6% 53%	2280
	11th to 20th	Day	9% 6% 2 4 4 4 4 4 5% 7% 52%	2139
	21st to end	Day	10% 5% 2 4 3 3 3 4 5% 8% 52%	2064
October	1st to 10th	Day	13% 6% 2 5% 4 3 4 2 4 6% 50%	1900
	11th to 20th	Day	13% 7% 2 5% 4 3 3 3 4 5% 51%	1900
	21st to end	Day	14% 8% 3 6% 3 4 4 3 5% 6% 43%	2090
November	1st to 10th	Day	11% 6% 2 6% 4 4 3 4 5% 8% 49%	1776
	11th to 20th	Day	12% 8% 3 7% 6% 4 3 4 5% 7% 41%	1520
	21st to end	Day	13% 10% 3 5% 5% 4 3 4 6% 7% 41%	1520
December	1st to 10th	Day	10% 9% 4 8% 5% 4 4 3 6% 6% 38%	1520
	11th to 20th	Day	10% 9% 4 10% 7% 6% 5% 4 6% 8% 33%	1918
	21st to end	Day	18% 13% 5% 17% 6% 5% 4 3 5% 5% 21%	2783
January	1st to 10th	Night	8% 12% 5% 20% 9% 5% 4 3 4 5% 26%	4300
	11th to 20th	Night	8% 13% 5% 10% 6% 5% 7% 4 9% 8% 26%	4120
	21st to end	Night	12% 15% 6% 13% 5% 4 3 2 5% 6% 29%	4532
February	1st to 10th	Night	10% 13% 4 10% 7% 5% 4 3 4 5% 34%	2470
	11th to 20th	Night	10% 11% 3 7% 5% 5% 5% 4 5% 7% 40%	2403
	21st to end	Night	11% 9% 3 10% 4 5% 4 2 4 5% 44%	1940
March	1st to 10th	Night	13% 7% 2 6% 4 3 3 2 4 6% 49%	3419
	11th to 20th	Night	11% 7% 2 5% 3 3 3 2 5% 6% 52%	3480
	21st to end	Night	20% 11% 4 12% 5% 5% 4 4 5% 6% 23%	3817
April	1st to 10th	Night	13% 9% 2 6% 5% 3 4 4 4 6% 44%	1957
	11th to 20th	Night	13% 9% 4 6% 4 3 4 3 5% 7% 42%	1853
	21st to end	Night	16% 8% 3 7% 4 4 3 3 5% 7% 40%	1710
May	1st to 10th	Night	19% 7% 2 5% 4 3 4 3 5% 6% 41%	2823
	11th to 20th	Night	12% 6% 2 5% 4 3 3 3 6% 7% 49%	2706
	21st to end	Night	14% 7% 3 5% 4 3 4 3 6% 7% 45%	2743
June	1st to 10th	Night	6% 5% 2 5% 4 4 5% 4 6% 9% 51%	1520
	11th to 20th	Night	7% 5% 2 4 4 3 4 4 8% 9% 50%	1520
	21st to end	Night	4 4 1 6% 4 5% 4 5% 6% 8% 53%	1520
July	1st to 10th	Night	7% 4 2 5% 4 4 5% 5% 7% 8% 49%	2530
	11th to 20th	Night	4 2 1 3 2 3 3 3 5% 9% 64%	2721
	21st to end	Night	4 3 2 6% 4 4 5% 4 6% 10% 53%	3098
August	1st to 10th	Night	5% 4 1 6% 3 4 4 4 5% 8% 55%	2836
	11th to 20th	Night	10% 7% 2 5% 3 3 4 3 5% 7% 52%	2798
	21st to end	Night	8% 4 2 4 3 3 4 3 5% 8% 56%	3312
September	1st to 10th	Night	8% 4 2 4 4 3 3 3 4 7% 58%	1900
	11th to 20th	Night	9% 5% 2 4 3 3 4 3 6% 7% 55%	2038
	21st to end	Night	9% 4 2 5% 3 3 3 3 4 7% 57%	2096
October	1st to 10th	Night	11% 6% 2 5% 3 3 4 2 4 6% 53%	2280
	11th to 20th	Night	14% 6% 3 5% 3 3 3 2 4 6% 52%	2280
	21st to end	Night	15% 7% 2 7% 3 4 3 3 4 6% 47%	2508
November	1st to 10th	Night	9% 6% 2 5% 3 3 4 3 5% 6% 55%	2397
	11th to 20th	Night	11% 7% 2 7% 4 3 3 3 6% 6% 46%	2660
	21st to end	Night	12% 9% 3 7% 4 3 4 3 5% 6% 45%	2660
December	1st to 10th	Night	9% 10% 3 8% 6% 5% 4 4 6% 6% 38%	2660
	11th to 20th	Night	10% 9% 4 9% 5% 5% 3 4 6% 6% 40%	3279
	21st to end	Night	18% 16% 6% 14% 5% 4 3 3 3 4 25%	4884

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	64% 5% 10% 14% 7%	2638
	11th to 20th	Day	59% 3 9% 22% 7%	2850
	21st to end	Day	63% 4 11% 14% 7%	3135
February	1st to 10th	Day	55% 4 10% 18% 10% 1	1710
	11th to 20th	Day	47% 4 12% 22% 14% 2	1673
	21st to end	Day	50% 5% 12% 19% 11% 3	1529
March	1st to 10th	Day	44% 4 9% 26% 15% 2	3436
	11th to 20th	Day	40% 6% 11% 25% 15% 3	3480
	21st to end	Day	65% 7% 10% 13% 4 1	3814
April	1st to 10th	Day	47% 6% 11% 26% 10% 1	2222
	11th to 20th	Day	48% 5% 12% 21% 13% 2	2272
	21st to end	Day	49% 5% 10% 23% 13%	2470
May	1st to 10th	Day	49% 8% 11% 18% 13% 1	4120
	11th to 20th	Day	42% 7% 9% 28% 13% 1	4203
	21st to end	Day	41% 7% 12% 23% 17% 1	4837
June	1st to 10th	Day	35% 7% 16% 25% 14% 3	2660
	11th to 20th	Day	33% 7% 14% 27% 18% 1	2660
	21st to end	Day	36% 7% 15% 25% 13% 3	2660
July	1st to 10th	Day	37% 8% 16% 28% 9% 2	4371
	11th to 20th	Day	24% 7% 13% 33% 21% 3	4158
	21st to end	Day	26% 9% 19% 26% 18% 2	4325
August	1st to 10th	Day	33% 8% 15% 27% 16% 1	4090
	11th to 20th	Day	42% 6% 11% 29% 12% 1	4080
	21st to end	Day	33% 7% 15% 26% 17% 3	4346
September	1st to 10th	Day	31% 5% 11% 29% 21% 4	2280
	11th to 20th	Day	31% 6% 12% 31% 19% 1	2139
	21st to end	Day	30% 5% 11% 31% 23% 1	2064
October	1st to 10th	Day	21% 3 6% 27% 41% 2	3160
	11th to 20th	Day	25% 3 12% 31% 23% 6%	3140
	21st to end	Day	37% 5% 8% 29% 19% 4	3428
November	1st to 10th	Day	34% 5% 16% 24% 18% 3	1776
	11th to 20th	Day	43% 5% 12% 23% 17% 1	1520
	21st to end	Day	44% 4 14% 24% 14% 1	1520
December	1st to 10th	Day	45% 4 16% 22% 10% 2	1520
	11th to 20th	Day	49% 6% 16% 24% 6%	1915
	21st to end	Day	65% 5% 9% 15% 6% 1	2783
January	1st to 10th	Night	61% 4 10% 15% 10% 1	4300
	11th to 20th	Night	53% 5% 12% 18% 11% 2	4120
	21st to end	Night	58% 5% 11% 16% 10% 1	4532
February	1st to 10th	Night	53% 4 10% 20% 11% 2	2470
	11th to 20th	Night	44% 5% 11% 24% 14% 3	2404
	21st to end	Night	44% 3 11% 21% 18% 3	1940
March	1st to 10th	Night	38% 4 8% 28% 19% 3	3419
	11th to 20th	Night	34% 4 10% 32% 15% 5%	3480
	21st to end	Night	60% 9% 14% 12% 4 1	3817
April	1st to 10th	Night	40% 5% 11% 26% 16% 2	1957
	11th to 20th	Night	43% 5% 10% 24% 16% 3	1853
	21st to end	Night	44% 5% 11% 23% 15% 1	1710
May	1st to 10th	Night	43% 6% 10% 21% 18% 2	2850
	11th to 20th	Night	35% 7% 11% 26% 17% 4	2707
	21st to end	Night	39% 7% 12% 21% 18% 3	2751
June	1st to 10th	Night	29% 6% 15% 31% 15% 4	1520
	11th to 20th	Night	28% 8% 13% 24% 23% 4	1520
	21st to end	Night	27% 7% 15% 29% 19% 3	1520
July	1st to 10th	Night	29% 7% 16% 33% 13% 2	2490
	11th to 20th	Night	18% 6% 18% 34% 22% 2	2672
	21st to end	Night	24% 9% 19% 29% 17% 2	2999
August	1st to 10th	Night	25% 6% 16% 32% 18% 2	2826
	11th to 20th	Night	32% 6% 14% 30% 16% 2	2825
	21st to end	Night	27% 6% 16% 27% 19% 6%	3312
September	1st to 10th	Night	28% 5% 10% 28% 25% 4	1900
	11th to 20th	Night	28% 5% 11% 34% 20% 1	2038
	21st to end	Night	28% 4 9% 31% 25% 3	2096
October	1st to 10th	Night	21% 3 6% 22% 46% 2	3800
	11th to 20th	Night	27% 3 9% 27% 28% 7%	3779
	21st to end	Night	38% 4 10% 27% 19% 2	4120
November	1st to 10th	Night	31% 4 15% 25% 21% 4	2397
	11th to 20th	Night	38% 4 14% 26% 16% 2	2660
	21st to end	Night	41% 4 10% 28% 15% 2	2660
December	1st to 10th	Night	45% 3 14% 26% 11% 1	2660
	11th to 20th	Night	44% 5% 13% 30% 7% 1	3281
	21st to end	Night	64% 4 8% 17% 7% 1	4884

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	20% 16% 34% 22% 7% 1	270
	11th to 20th	Day	21% 14% 41% 21% 2 1	270
	21st to end	Day	22% 11% 38% 24% 4 1	297
February	1st to 10th	Day	18% 17% 44% 17% 3	270
	11th to 20th	Day	16% 21% 38% 20% 4 1	270
	21st to end	Day	24% 20% 38% 16% 3	225
March	1st to 10th	Day	16% 21% 42% 15% 6% 1	270
	11th to 20th	Day	26% 13% 38% 16% 6%	270
	21st to end	Day	32% 17% 34% 14% 3	297
April	1st to 10th	Day	27% 14% 34% 19% 5%	402
	11th to 20th	Day	22% 16% 34% 21% 7%	470
	21st to end	Day	23% 17% 33% 19% 6% 2	650
May	1st to 10th	Day	24% 14% 31% 23% 8% 1	653
	11th to 20th	Day	20% 13% 31% 25% 10% 1	675
	21st to end	Day	18% 10% 29% 25% 15% 3	734
June	1st to 10th	Day	8% 6% 28% 31% 22% 5%	680
	11th to 20th	Day	9% 6% 32% 34% 15% 3	680
	21st to end	Day	8% 8% 39% 28% 14% 3	680
July	1st to 10th	Day	7% 4 21% 34% 25% 10%	671
	11th to 20th	Day	5% 4 27% 35% 21% 8%	668
	21st to end	Day	6% 2 23% 41% 24% 5%	739
August	1st to 10th	Day	9% 5% 22% 38% 21% 5%	676
	11th to 20th	Day	12% 6% 20% 34% 24% 5%	665
	21st to end	Day	10% 3 22% 38% 20% 6%	641
September	1st to 10th	Day	13% 6% 25% 33% 17% 6%	490
	11th to 20th	Day	9% 4 31% 33% 18% 5%	349
	21st to end	Day	12% 13% 27% 32% 13% 2	300
October	1st to 10th	Day	18% 9% 29% 26% 15% 3	300
	11th to 20th	Day	17% 17% 38% 21% 6% 1	300
	21st to end	Day	19% 17% 35% 20% 7% 1	330
November	1st to 10th	Day	15% 16% 39% 21% 7% 2	282
	11th to 20th	Day	20% 19% 36% 18% 7%	270
	21st to end	Day	21% 15% 39% 20% 6%	270
December	1st to 10th	Day	10% 13% 45% 23% 8%	270
	11th to 20th	Day	14% 16% 38% 22% 8% 1	270
	21st to end	Day	24% 18% 42% 13% 3	297
January	1st to 10th	Night	14% 16% 38% 26% 5%	950
	11th to 20th	Night	16% 15% 39% 23% 6% 1	950
	21st to end	Night	20% 11% 37% 26% 5%	1045
February	1st to 10th	Night	18% 12% 42% 24% 4	950
	11th to 20th	Night	17% 14% 40% 24% 4	929
	21st to end	Night	15% 17% 42% 20% 4 2	684
March	1st to 10th	Night	18% 11% 39% 24% 7% 1	570
	11th to 20th	Night	18% 9% 37% 28% 8%	570
	21st to end	Night	24% 13% 37% 20% 6% 1	627
April	1st to 10th	Night	19% 15% 38% 22% 5%	570
	11th to 20th	Night	18% 14% 34% 28% 5% 1	563
	21st to end	Night	19% 13% 35% 24% 8% 1	570
May	1st to 10th	Night	19% 9% 35% 29% 8%	570
	11th to 20th	Night	18% 9% 29% 32% 11%	561
	21st to end	Night	16% 7% 28% 35% 14%	617
June	1st to 10th	Night	8% 5% 26% 42% 18%	570
	11th to 20th	Night	10% 4 31% 42% 14%	570
	21st to end	Night	7% 5% 34% 39% 13% 1	570
July	1st to 10th	Night	5% 2 18% 44% 29% 2	555
	11th to 20th	Night	3 1 23% 49% 21% 2	552
	21st to end	Night	3 2 18% 51% 25% 1	624
August	1st to 10th	Night	8% 2 22% 41% 25% 1	567
	11th to 20th	Night	9% 3 19% 44% 23% 3	564
	21st to end	Night	9% 3 23% 40% 23% 3	627
September	1st to 10th	Night	9% 5% 21% 38% 24% 3	570
	11th to 20th	Night	11% 3 27% 38% 19% 1	570
	21st to end	Night	11% 6% 31% 34% 16% 2	576
October	1st to 10th	Night	15% 9% 33% 29% 13% 1	760
	11th to 20th	Night	17% 13% 37% 26% 7%	760
	21st to end	Night	20% 12% 33% 27% 8%	836
November	1st to 10th	Night	12% 14% 37% 30% 7%	850
	11th to 20th	Night	15% 16% 41% 22% 6%	950
	21st to end	Night	17% 12% 39% 25% 7% 1	950
December	1st to 10th	Night	15% 13% 42% 23% 7%	950
	11th to 20th	Night	16% 12% 38% 28% 5% 1	950
	21st to end	Night	20% 16% 37% 24% 4	1045

Page generated at 2024-11-03 01:11:26. Version ac07

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