Delta Rocky Crest Resort
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Delta Rocky Crest Resort clear sky chart from 2005-11-06 to 2025-10-04.

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	17% 11% 4 8% 5% 4 4 3 5% 6% 33%	127025
	Night	17% 13% 5% 9% 5% 4 4 3 5% 6% 30%	122336
Transparency	Day	51% 6% 11% 21% 10% 1	130592
	Night	55% 5% 11% 19% 10% 1	126858
Seeing	Day	23% 14% 31% 20% 8% 3	16194
	Night	24% 12% 28% 25% 10% 1	25132

By Month

Percentage Cloud Cover NE (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	13% 18% 10% 10% 4 4 3 3 4 5% 26%	3158
	11th to 20th	Day	10% 21% 9% 20% 7% 6% 5% 3 4 3 12%	3715
	21st to end	Day	12% 20% 9% 15% 6% 7% 4 3 3 4 17%	4466
February	1st to 10th	Day	13% 21% 7% 15% 7% 3 4 3 4 4 20%	1800
	11th to 20th	Day	13% 16% 6% 13% 6% 5% 3 3 4 6% 25%	1753
	21st to end	Day	15% 18% 6% 13% 6% 5% 4 3 4 4 22%	1518
March	1st to 10th	Day	19% 14% 4 10% 5% 4 4 2 3 5% 29%	4918
	11th to 20th	Day	12% 15% 6% 9% 6% 5% 5% 3 5% 7% 27%	4980
	21st to end	Day	18% 16% 6% 7% 4 3 3 3 4 4 31%	5465
April	1st to 10th	Day	21% 14% 4 6% 4 4 4 3 5% 6% 29%	2360
	11th to 20th	Day	22% 11% 3 5% 4 4 4 2 4 5% 36%	2505
	21st to end	Day	23% 11% 3 6% 3 3 4 3 4 5% 34%	2600
May	1st to 10th	Day	19% 9% 3 7% 4 4 4 4 5% 7% 34%	5952
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 5% 7% 41%	6318
	21st to end	Day	23% 8% 3 6% 4 4 4 3 5% 6% 36%	6949
June	1st to 10th	Day	19% 7% 2 6% 6% 4 4 3 5% 7% 36%	2851
	11th to 20th	Day	14% 6% 2 6% 6% 4 4 4 6% 8% 39%	3000
	21st to end	Day	20% 7% 2 6% 5% 4 4 3 6% 8% 34%	3000
July	1st to 10th	Day	16% 6% 2 6% 5% 4 5% 4 6% 9% 37%	6819
	11th to 20th	Day	13% 6% 2 6% 4 3 4 3 5% 7% 47%	6591
	21st to end	Day	9% 4 2 5% 4 4 4 4 6% 7% 51%	6619
August	1st to 10th	Day	13% 7% 3 6% 5% 5% 6% 4 6% 9% 37%	4234
	11th to 20th	Day	17% 6% 2 6% 4 4 4 4 6% 9% 37%	4174
	21st to end	Day	10% 4 2 5% 4 4 5% 5% 6% 8% 45%	4553
September	1st to 10th	Day	14% 6% 2 7% 4 4 4 4 6% 7% 41%	2400
	11th to 20th	Day	16% 6% 1 5% 3 4 4 3 6% 6% 46%	2272
	21st to end	Day	21% 8% 3 6% 5% 5% 4 3 5% 6% 36%	2167
October	1st to 10th	Day	21% 8% 3 7% 4 4 4 3 4 7% 34%	1930
	11th to 20th	Day	27% 11% 3 7% 4 5% 4 4 5% 7% 23%	1900
	21st to end	Day	30% 14% 3 8% 4 3 4 3 4 5% 21%	2076
November	1st to 10th	Day	21% 14% 4 7% 4 4 4 4 5% 7% 26%	1615
	11th to 20th	Day	20% 16% 4 9% 5% 5% 5% 4 5% 5% 22%	1600
	21st to end	Day	22% 22% 4 8% 6% 5% 4 3 4 5% 17%	1600
December	1st to 10th	Day	17% 25% 7% 10% 5% 5% 5% 4 4 5% 15%	2600
	11th to 20th	Day	19% 24% 6% 14% 4 3 3 2 3 4 18%	2986
	21st to end	Day	26% 19% 5% 13% 4 3 3 2 3 4 18%	3581
January	1st to 10th	Night	13% 18% 10% 13% 6% 5% 4 3 4 5% 20%	6808
	11th to 20th	Night	12% 18% 7% 20% 7% 6% 5% 4 4 4 13%	6137
	21st to end	Night	12% 19% 9% 14% 8% 6% 4 3 4 4 16%	6490
February	1st to 10th	Night	13% 19% 6% 12% 7% 5% 4 4 5% 5% 20%	2600
	11th to 20th	Night	13% 16% 7% 13% 6% 5% 4 3 5% 5% 24%	2533
	21st to end	Night	15% 18% 5% 11% 6% 5% 4 4 4 4 23%	2110
March	1st to 10th	Night	17% 13% 4 9% 5% 4 4 3 5% 6% 31%	4920
	11th to 20th	Night	11% 14% 6% 9% 5% 5% 5% 4 5% 7% 29%	4979
	21st to end	Night	21% 12% 4 7% 4 3 4 3 4 5% 33%	5467
April	1st to 10th	Night	21% 13% 3 8% 5% 3 4 3 4 6% 30%	2040
	11th to 20th	Night	19% 11% 3 8% 4 3 4 3 5% 5% 35%	1861
	21st to end	Night	21% 10% 3 8% 5% 5% 4 3 5% 6% 30%	1800
May	1st to 10th	Night	18% 7% 2 7% 5% 5% 4 4 6% 7% 35%	3973
	11th to 20th	Night	12% 7% 2 6% 5% 4 4 4 6% 7% 43%	3575
	21st to end	Night	18% 8% 2 6% 4 4 4 4 5% 7% 37%	3926
June	1st to 10th	Night	15% 8% 2 7% 4 5% 4 3 6% 8% 38%	1543
	11th to 20th	Night	14% 6% 2 5% 3 3 5% 3 7% 9% 43%	1400
	21st to end	Night	17% 7% 2 6% 4 4 3 4 6% 7% 40%	1400
July	1st to 10th	Night	15% 6% 3 6% 4 4 4 3 5% 8% 42%	3160
	11th to 20th	Night	15% 5% 2 5% 3 3 4 3 5% 6% 49%	3375
	21st to end	Night	10% 6% 2 5% 3 3 3 3 5% 7% 52%	4216
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 8% 46%	2915
	11th to 20th	Night	16% 6% 2 6% 3 4 4 3 4 7% 45%	2875
	21st to end	Night	15% 5% 2 4 3 3 4 3 5% 7% 50%	3311
September	1st to 10th	Night	12% 5% 2 6% 4 5% 4 3 6% 7% 47%	2000
	11th to 20th	Night	12% 5% 2 4 4 3 4 3 5% 8% 50%	2125
	21st to end	Night	19% 7% 2 6% 5% 4 4 3 4 6% 41%	2232
October	1st to 10th	Night	21% 7% 2 6% 4 4 5% 3 5% 6% 36%	2317
	11th to 20th	Night	25% 11% 3 8% 5% 4 4 4 4 6% 26%	2280
	21st to end	Night	27% 12% 4 8% 5% 3 3 3 4 5% 25%	2518
November	1st to 10th	Night	23% 13% 3 7% 4 4 4 2 4 6% 30%	2680
	11th to 20th	Night	18% 17% 5% 8% 5% 5% 4 3 6% 6% 24%	2800
	21st to end	Night	24% 19% 6% 9% 4 4 4 3 4 5% 17%	2800
December	1st to 10th	Night	18% 26% 7% 9% 4 4 3 3 5% 6% 14%	4580
	11th to 20th	Night	19% 22% 7% 16% 6% 4 4 2 3 4 13%	5208
	21st to end	Night	23% 21% 6% 13% 4 4 4 3 3 4 15%	7382

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	61% 4 7% 19% 8%	3159
	11th to 20th	Day	78% 3 5% 8% 5% 1	3747
	21st to end	Day	73% 5% 6% 9% 7% 1	4466
February	1st to 10th	Day	69% 4 7% 14% 4 1	1800
	11th to 20th	Day	61% 6% 9% 14% 9% 1	1762
	21st to end	Day	66% 5% 8% 15% 6%	1518
March	1st to 10th	Day	60% 4 11% 9% 14% 2	4921
	11th to 20th	Day	57% 5% 13% 16% 8% 2	4980
	21st to end	Day	55% 5% 8% 19% 11% 1	5465
April	1st to 10th	Day	57% 5% 9% 18% 10% 1	2360
	11th to 20th	Day	52% 5% 7% 23% 13% 1	2505
	21st to end	Day	52% 5% 9% 18% 13% 3	2600
May	1st to 10th	Day	48% 7% 10% 20% 9% 6%	5961
	11th to 20th	Day	43% 7% 12% 20% 17% 1	6322
	21st to end	Day	49% 5% 11% 19% 13% 3	6949
June	1st to 10th	Day	47% 7% 9% 23% 13% 1	2851
	11th to 20th	Day	42% 6% 11% 25% 15% 1	3000
	21st to end	Day	47% 6% 13% 21% 11% 1	3000
July	1st to 10th	Day	42% 6% 15% 26% 10% 1	6746
	11th to 20th	Day	37% 5% 12% 33% 13%	6510
	21st to end	Day	32% 5% 13% 34% 16%	6430
August	1st to 10th	Day	43% 6% 14% 26% 10% 1	4221
	11th to 20th	Day	42% 7% 15% 26% 8%	4213
	21st to end	Day	34% 7% 13% 35% 10%	4553
September	1st to 10th	Day	40% 7% 14% 27% 11% 1	2400
	11th to 20th	Day	38% 5% 15% 29% 12% 1	2272
	21st to end	Day	50% 6% 10% 24% 9%	2167
October	1st to 10th	Day	46% 5% 13% 24% 11% 1	3190
	11th to 20th	Day	50% 7% 14% 24% 6%	3140
	21st to end	Day	59% 5% 14% 17% 5%	3402
November	1st to 10th	Day	56% 7% 14% 18% 5%	1615
	11th to 20th	Day	64% 5% 12% 13% 5% 1	1600
	21st to end	Day	70% 7% 9% 11% 3 1	1600
December	1st to 10th	Day	72% 4 12% 9% 3	2600
	11th to 20th	Day	73% 3 7% 12% 5%	2986
	21st to end	Day	72% 3 5% 12% 7%	3581
January	1st to 10th	Night	67% 4 7% 14% 7%	6808
	11th to 20th	Night	74% 7% 6% 7% 6% 1	6180
	21st to end	Night	71% 6% 7% 8% 7% 1	6490
February	1st to 10th	Night	65% 6% 9% 15% 5% 1	2600
	11th to 20th	Night	62% 5% 10% 16% 7% 1	2535
	21st to end	Night	64% 5% 8% 15% 7% 1	2110
March	1st to 10th	Night	55% 5% 11% 13% 12% 4	4930
	11th to 20th	Night	54% 6% 15% 16% 8% 1	4980
	21st to end	Night	54% 5% 8% 19% 13% 2	5467
April	1st to 10th	Night	55% 5% 8% 19% 11% 2	2040
	11th to 20th	Night	50% 5% 7% 21% 15% 2	1861
	21st to end	Night	54% 5% 9% 15% 15% 2	1800
May	1st to 10th	Night	47% 6% 10% 21% 13% 4	3980
	11th to 20th	Night	38% 7% 11% 23% 19% 2	3576
	21st to end	Night	46% 5% 10% 23% 14% 1	3927
June	1st to 10th	Night	44% 6% 10% 23% 14% 2	1543
	11th to 20th	Night	36% 6% 12% 26% 19%	1400
	21st to end	Night	42% 6% 14% 24% 12% 1	1400
July	1st to 10th	Night	41% 5% 13% 27% 12% 2	3125
	11th to 20th	Night	37% 5% 11% 34% 13% 1	3333
	21st to end	Night	33% 4 9% 37% 17% 1	4091
August	1st to 10th	Night	37% 4 17% 25% 16% 1	2904
	11th to 20th	Night	39% 6% 18% 25% 11% 1	2902
	21st to end	Night	34% 5% 12% 37% 12% 1	3311
September	1st to 10th	Night	35% 8% 17% 26% 13% 1	2000
	11th to 20th	Night	33% 6% 15% 32% 13%	2125
	21st to end	Night	45% 5% 12% 27% 11%	2232
October	1st to 10th	Night	38% 5% 11% 28% 17%	3837
	11th to 20th	Night	49% 6% 15% 23% 7%	3779
	21st to end	Night	57% 5% 15% 16% 6%	4142
November	1st to 10th	Night	55% 5% 12% 21% 6%	2680
	11th to 20th	Night	59% 5% 14% 14% 6% 1	2800
	21st to end	Night	69% 5% 12% 11% 3	2800
December	1st to 10th	Night	71% 5% 13% 8% 3	4580
	11th to 20th	Night	76% 4 7% 9% 4	5208
	21st to end	Night	75% 4 6% 10% 5%	7382

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	21% 22% 39% 14% 4 1	200
	11th to 20th	Day	28% 20% 32% 16% 5%	247
	21st to end	Day	29% 15% 36% 16% 4	330
February	1st to 10th	Day	30% 26% 33% 7% 2 1	300
	11th to 20th	Day	24% 25% 40% 10% 1	300
	21st to end	Day	34% 27% 31% 8%	249
March	1st to 10th	Day	24% 21% 35% 15% 4	486
	11th to 20th	Day	23% 20% 37% 16% 4 1	500
	21st to end	Day	31% 16% 31% 15% 5% 1	550
April	1st to 10th	Day	29% 19% 30% 14% 8%	500
	11th to 20th	Day	36% 16% 23% 16% 8% 2	492
	21st to end	Day	31% 15% 35% 13% 6% 1	500
May	1st to 10th	Day	25% 12% 35% 18% 8% 3	503
	11th to 20th	Day	20% 16% 29% 22% 10% 3	527
	21st to end	Day	21% 13% 32% 21% 10% 2	573
June	1st to 10th	Day	20% 13% 34% 25% 7% 1	581
	11th to 20th	Day	16% 14% 32% 26% 9% 2	730
	21st to end	Day	23% 11% 36% 22% 7% 2	730
July	1st to 10th	Day	12% 9% 34% 29% 13% 2	721
	11th to 20th	Day	15% 11% 28% 29% 13% 4	619
	21st to end	Day	12% 8% 35% 29% 10% 6%	576
August	1st to 10th	Day	15% 5% 26% 33% 15% 7%	526
	11th to 20th	Day	18% 4 27% 27% 15% 9%	519
	21st to end	Day	15% 9% 30% 26% 14% 6%	583
September	1st to 10th	Day	16% 11% 28% 25% 13% 7%	530
	11th to 20th	Day	15% 6% 25% 26% 18% 9%	530
	21st to end	Day	20% 11% 23% 29% 13% 3	530
October	1st to 10th	Day	24% 16% 25% 20% 12% 3	502
	11th to 20th	Day	29% 18% 33% 14% 5% 1	490
	21st to end	Day	38% 16% 30% 14% 2	525
November	1st to 10th	Day	31% 20% 33% 15% 1	225
	11th to 20th	Day	25% 24% 38% 12% 2	200
	21st to end	Day	34% 18% 38% 9% 2 1	200
December	1st to 10th	Day	31% 21% 30% 16% 2 1	200
	11th to 20th	Day	39% 23% 24% 12% 2 1	200
	21st to end	Day	38% 19% 30% 9% 4 1	220
January	1st to 10th	Night	27% 17% 32% 20% 4 1	1000
	11th to 20th	Night	30% 16% 31% 19% 4 1	819
	21st to end	Night	21% 13% 36% 23% 8% 1	880
February	1st to 10th	Night	24% 18% 35% 20% 3	800
	11th to 20th	Night	22% 16% 35% 21% 6%	783
	21st to end	Night	23% 21% 30% 22% 4	660
March	1st to 10th	Night	21% 19% 33% 23% 4	800
	11th to 20th	Night	20% 18% 35% 23% 5% 1	800
	21st to end	Night	22% 12% 31% 25% 9% 1	880
April	1st to 10th	Night	28% 15% 30% 22% 5%	800
	11th to 20th	Night	25% 14% 27% 24% 9% 1	677
	21st to end	Night	25% 10% 30% 26% 8%	600
May	1st to 10th	Night	22% 7% 25% 34% 10% 1	572
	11th to 20th	Night	17% 8% 31% 33% 10% 1	394
	21st to end	Night	14% 6% 31% 34% 15%	433
June	1st to 10th	Night	20% 7% 28% 34% 11%	400
	11th to 20th	Night	17% 8% 26% 36% 13%	400
	21st to end	Night	21% 6% 23% 36% 13% 1	400
July	1st to 10th	Night	11% 4 21% 45% 17% 1	390
	11th to 20th	Night	14% 6% 23% 36% 21% 1	388
	21st to end	Night	11% 5% 25% 36% 22% 1	562
August	1st to 10th	Night	14% 5% 17% 37% 26% 2	597
	11th to 20th	Night	13% 5% 19% 37% 24% 3	594
	21st to end	Night	19% 5% 23% 30% 20% 2	709
September	1st to 10th	Night	14% 7% 27% 30% 19% 3	800
	11th to 20th	Night	14% 6% 23% 31% 22% 4	800
	21st to end	Night	22% 6% 21% 31% 17% 2	800
October	1st to 10th	Night	23% 10% 27% 27% 12% 1	773
	11th to 20th	Night	31% 12% 25% 23% 8% 1	760
	21st to end	Night	34% 14% 29% 19% 4	836
November	1st to 10th	Night	34% 10% 26% 22% 7% 1	780
	11th to 20th	Night	29% 16% 30% 19% 5%	800
	21st to end	Night	35% 14% 29% 18% 4	800
December	1st to 10th	Night	34% 18% 28% 15% 5%	800
	11th to 20th	Night	31% 18% 33% 14% 3 1	800
	21st to end	Night	33% 15% 30% 18% 4	1045

Page generated at 2025-10-01 01:39:05. Version ac07

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