Deer Ridge Lookout
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deer Ridge Lookout clear sky chart from 2005-11-06 to 2024-11-28.

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	12% 13% 3 7% 4 4 4 3 5% 6% 36%	105544
	Night	13% 16% 4 8% 4 4 4 3 5% 6% 34%	102528
Transparency	Day	49% 6% 12% 19% 10% 3	105303
	Night	52% 6% 13% 18% 9% 3	102414
Seeing	Day	22% 17% 27% 22% 11% 2	15144
	Night	20% 11% 21% 32% 16% 2	24269

By Month

Percentage Cloud Cover NW (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	14% 38% 11% 13% 4 3 3 3 3 3 5%	2347
	11th to 20th	Day	14% 24% 6% 10% 5% 3 4 3 4 5% 21%	2516
	21st to end	Day	22% 32% 7% 12% 5% 3 3 2 3 3 8%	2794
February	1st to 10th	Day	16% 28% 5% 10% 6% 3 4 3 4 5% 15%	1520
	11th to 20th	Day	12% 25% 7% 12% 7% 4 4 3 3 4 20%	1718
	21st to end	Day	13% 24% 7% 12% 6% 5% 3 3 3 5% 19%	1570
March	1st to 10th	Day	10% 23% 6% 10% 6% 5% 5% 4 5% 6% 21%	3138
	11th to 20th	Day	11% 17% 3 7% 3 3 3 2 3 5% 42%	3347
	21st to end	Day	16% 26% 5% 10% 6% 5% 4 3 4 4 16%	4031
April	1st to 10th	Day	16% 20% 4 9% 5% 5% 6% 4 6% 6% 20%	2280
	11th to 20th	Day	17% 16% 4 9% 5% 5% 5% 3 4 5% 26%	2385
	21st to end	Day	16% 14% 4 10% 6% 6% 5% 4 5% 6% 25%	2470
May	1st to 10th	Day	17% 13% 5% 10% 6% 5% 5% 3 4 5% 28%	4291
	11th to 20th	Day	10% 8% 3 9% 6% 7% 6% 5% 7% 8% 30%	4377
	21st to end	Day	16% 14% 4 10% 7% 6% 5% 4 6% 6% 20%	5161
June	1st to 10th	Day	21% 9% 3 7% 6% 5% 5% 3 5% 7% 29%	2850
	11th to 20th	Day	19% 9% 2 9% 7% 6% 6% 4 6% 6% 27%	2850
	21st to end	Day	10% 5% 2 5% 4 4 5% 4 6% 8% 46%	2850
July	1st to 10th	Day	3 3 1 4 3 3 3 3 4 5% 68%	4740
	11th to 20th	Day	3 2 1 2 2 2 3 2 4 5% 74%	4502
	21st to end	Day	3 3 1 3 3 2 4 3 5% 6% 68%	4790
August	1st to 10th	Day	4 3 1 3 3 3 5% 3 6% 8% 60%	4401
	11th to 20th	Day	5% 3 1 3 3 3 3 3 5% 7% 64%	4102
	21st to end	Day	7% 4 2 5% 4 4 4 3 6% 7% 55%	4413
September	1st to 10th	Day	7% 5% 2 5% 3 4 3 3 5% 7% 55%	2280
	11th to 20th	Day	11% 8% 2 7% 3 3 4 3 6% 8% 47%	2133
	21st to end	Day	14% 8% 2 6% 4 4 4 3 5% 8% 42%	2090
October	1st to 10th	Day	11% 6% 2 4 3 3 4 4 6% 8% 49%	3442
	11th to 20th	Day	16% 8% 1 6% 4 4 4 3 6% 8% 39%	2856
	21st to end	Day	21% 18% 4 6% 4 4 3 3 4 5% 26%	3101
November	1st to 10th	Day	25% 21% 4 9% 4 4 2 4 5% 5% 16%	1764
	11th to 20th	Day	21% 24% 4 10% 4 3 4 2 4 4 18%	1602
	21st to end	Day	16% 28% 6% 12% 6% 4 3 2 4 5% 14%	1379
December	1st to 10th	Day	16% 23% 7% 11% 6% 4 3 3 4 4 20%	1330
	11th to 20th	Day	19% 32% 7% 11% 4 3 3 3 4 3 10%	1682
	21st to end	Day	17% 25% 5% 12% 5% 5% 4 4 5% 5% 13%	2442
January	1st to 10th	Night	19% 36% 9% 11% 4 4 3 2 3 3 7%	4627
	11th to 20th	Night	15% 19% 6% 11% 5% 4 4 3 4 5% 23%	4382
	21st to end	Night	23% 34% 5% 12% 4 3 3 2 3 3 9%	4862
February	1st to 10th	Night	16% 25% 5% 9% 5% 4 4 3 4 5% 20%	2660
	11th to 20th	Night	15% 22% 5% 9% 4 4 4 4 5% 6% 23%	2345
	21st to end	Night	11% 25% 6% 9% 5% 4 4 2 5% 5% 25%	1884
March	1st to 10th	Night	10% 20% 6% 8% 5% 4 5% 4 4 6% 28%	3736
	11th to 20th	Night	12% 17% 3 6% 3 3 2 2 3 5% 44%	3631
	21st to end	Night	17% 18% 5% 11% 6% 5% 4 3 5% 5% 20%	3622
April	1st to 10th	Night	13% 14% 4 7% 3 4 4 4 6% 9% 31%	1900
	11th to 20th	Night	14% 12% 4 7% 5% 4 6% 4 4 5% 35%	1745
	21st to end	Night	12% 10% 4 9% 5% 5% 5% 4 6% 7% 33%	1710
May	1st to 10th	Night	12% 11% 3 10% 6% 6% 6% 5% 6% 6% 30%	2668
	11th to 20th	Night	8% 6% 2 7% 5% 4 5% 5% 7% 8% 43%	2499
	21st to end	Night	17% 10% 3 7% 5% 5% 5% 5% 6% 8% 27%	2414
June	1st to 10th	Night	16% 8% 2 7% 5% 4 4 4 5% 8% 38%	1330
	11th to 20th	Night	17% 6% 2 5% 5% 6% 7% 5% 6% 8% 32%	1330
	21st to end	Night	6% 3 2 5% 4 3 4 4 7% 8% 54%	1330
July	1st to 10th	Night	2 1 1 2 2 2 3 3 5% 6% 72%	2220
	11th to 20th	Night	2 1 1 2 2 2 3 2 3 4 78%	2441
	21st to end	Night	4 1 1 2 1 2 2 2 4 5% 77%	2762
August	1st to 10th	Night	4 3 1 3 2 2 3 3 5% 9% 65%	2529
	11th to 20th	Night	4 3 2 4 3 3 3 3 6% 8% 62%	2720
	21st to end	Night	5% 3 1 5% 4 3 4 4 5% 7% 60%	3242
September	1st to 10th	Night	4 3 1 5% 2 3 4 3 5% 6% 62%	1900
	11th to 20th	Night	8% 5% 2 6% 3 4 4 4 7% 8% 49%	2046
	21st to end	Night	13% 6% 2 4 3 2 3 3 6% 7% 50%	2090
October	1st to 10th	Night	9% 5% 2 4 3 3 4 3 5% 8% 55%	3535
	11th to 20th	Night	14% 8% 2 5% 3 3 3 4 6% 7% 46%	4071
	21st to end	Night	17% 13% 3 6% 4 3 3 3 5% 9% 33%	4457
November	1st to 10th	Night	23% 19% 4 6% 4 4 4 3 5% 6% 21%	2535
	11th to 20th	Night	20% 23% 4 8% 5% 4 4 3 5% 5% 20%	2775
	21st to end	Night	20% 24% 5% 10% 5% 4 3 3 3 4 19%	2956
December	1st to 10th	Night	18% 23% 6% 12% 6% 5% 3 2 3 4 18%	2850
	11th to 20th	Night	19% 27% 8% 10% 5% 4 4 3 4 4 11%	3510
	21st to end	Night	14% 25% 7% 13% 6% 5% 4 4 4 5% 12%	5214

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	84% 5% 6% 3 1	2347
	11th to 20th	Day	66% 5% 11% 10% 5% 4	2540
	21st to end	Day	82% 5% 7% 4 2	2794
February	1st to 10th	Day	73% 5% 9% 7% 4 2	1520
	11th to 20th	Day	72% 5% 9% 8% 5%	1727
	21st to end	Day	71% 6% 8% 10% 6%	1570
March	1st to 10th	Day	63% 6% 10% 13% 8%	3138
	11th to 20th	Day	49% 3 26% 21% 2	3348
	21st to end	Day	73% 5% 8% 10% 3	4031
April	1st to 10th	Day	66% 6% 13% 13% 2	2280
	11th to 20th	Day	61% 6% 12% 16% 4	2385
	21st to end	Day	61% 6% 13% 16% 3 1	2470
May	1st to 10th	Day	59% 4 11% 20% 5%	4291
	11th to 20th	Day	48% 7% 15% 24% 5%	4380
	21st to end	Day	62% 8% 13% 14% 3	5162
June	1st to 10th	Day	57% 5% 13% 18% 7%	2850
	11th to 20th	Day	58% 7% 12% 17% 6% 1	2850
	21st to end	Day	37% 6% 16% 28% 13% 1	2850
July	1st to 10th	Day	18% 6% 8% 28% 27% 12%	4666
	11th to 20th	Day	14% 3 7% 16% 32% 27%	4424
	21st to end	Day	16% 5% 8% 25% 30% 16%	4639
August	1st to 10th	Day	20% 5% 14% 31% 22% 7%	4384
	11th to 20th	Day	20% 4 14% 42% 18% 1	4142
	21st to end	Day	28% 6% 15% 32% 16% 1	4412
September	1st to 10th	Day	31% 4 12% 31% 17% 4	2280
	11th to 20th	Day	39% 4 14% 26% 15% 2	2133
	21st to end	Day	41% 6% 21% 21% 9% 1	2090
October	1st to 10th	Day	33% 5% 19% 35% 7%	3442
	11th to 20th	Day	42% 7% 19% 22% 10%	2856
	21st to end	Day	61% 6% 13% 13% 6%	3101
November	1st to 10th	Day	70% 8% 8% 10% 3	1764
	11th to 20th	Day	70% 7% 10% 7% 4 1	1602
	21st to end	Day	73% 5% 10% 8% 3	1379
December	1st to 10th	Day	70% 5% 9% 12% 3	1330
	11th to 20th	Day	80% 5% 8% 5% 2	1684
	21st to end	Day	71% 8% 10% 8% 3	2442
January	1st to 10th	Night	85% 3 5% 4 1	4627
	11th to 20th	Night	65% 4 9% 12% 6% 4	4420
	21st to end	Night	82% 4 6% 5% 2	4862
February	1st to 10th	Night	67% 6% 10% 10% 5% 2	2660
	11th to 20th	Night	63% 8% 11% 12% 5%	2346
	21st to end	Night	65% 4 11% 12% 7% 1	1884
March	1st to 10th	Night	58% 6% 14% 15% 8%	3736
	11th to 20th	Night	47% 4 22% 24% 3	3631
	21st to end	Night	66% 7% 10% 14% 3	3622
April	1st to 10th	Night	50% 9% 18% 17% 6%	1900
	11th to 20th	Night	52% 6% 14% 20% 9%	1745
	21st to end	Night	50% 7% 15% 21% 7% 1	1710
May	1st to 10th	Night	55% 6% 12% 21% 7%	2668
	11th to 20th	Night	37% 7% 16% 30% 9%	2499
	21st to end	Night	53% 7% 16% 20% 4	2414
June	1st to 10th	Night	46% 5% 16% 22% 9% 1	1330
	11th to 20th	Night	46% 8% 16% 20% 9% 1	1330
	21st to end	Night	28% 6% 18% 29% 18% 2	1330
July	1st to 10th	Night	13% 4 10% 32% 28% 12%	2185
	11th to 20th	Night	12% 3 8% 15% 28% 34%	2397
	21st to end	Night	12% 3 7% 26% 31% 21%	2674
August	1st to 10th	Night	18% 3 14% 31% 25% 10%	2521
	11th to 20th	Night	21% 5% 13% 38% 20% 3	2745
	21st to end	Night	23% 5% 16% 32% 22% 2	3242
September	1st to 10th	Night	24% 4 12% 31% 21% 7%	1900
	11th to 20th	Night	32% 7% 15% 28% 16% 3	2046
	21st to end	Night	35% 5% 22% 24% 12% 2	2090
October	1st to 10th	Night	29% 5% 20% 35% 9%	3535
	11th to 20th	Night	36% 9% 14% 25% 15%	4071
	21st to end	Night	50% 10% 16% 18% 6%	4457
November	1st to 10th	Night	65% 7% 12% 11% 3 1	2535
	11th to 20th	Night	67% 7% 11% 9% 5%	2775
	21st to end	Night	68% 6% 11% 11% 3	2956
December	1st to 10th	Night	73% 5% 8% 11% 4	2850
	11th to 20th	Night	77% 6% 11% 5% 2	3507
	21st to end	Night	74% 6% 11% 6% 3	5214

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% 18% 27% 19% 9% 1	180
	11th to 20th	Day	22% 20% 29% 18% 11%	180
	21st to end	Day	21% 25% 27% 20% 7% 2	198
February	1st to 10th	Day	28% 22% 33% 14% 3 1	180
	11th to 20th	Day	29% 21% 23% 19% 8%	346
	21st to end	Day	25% 21% 31% 18% 6%	382
March	1st to 10th	Day	32% 20% 25% 16% 6% 2	460
	11th to 20th	Day	26% 17% 22% 20% 13% 2	460
	21st to end	Day	32% 21% 23% 15% 7% 2	506
April	1st to 10th	Day	30% 21% 24% 18% 5% 1	460
	11th to 20th	Day	27% 23% 24% 16% 7% 2	452
	21st to end	Day	27% 18% 28% 17% 7% 3	460
May	1st to 10th	Day	24% 15% 27% 23% 7% 3	463
	11th to 20th	Day	22% 15% 27% 25% 8% 2	488
	21st to end	Day	24% 13% 20% 23% 16% 3	734
June	1st to 10th	Day	26% 15% 22% 23% 11% 3	680
	11th to 20th	Day	24% 19% 24% 20% 11% 2	680
	21st to end	Day	14% 14% 24% 25% 18% 5%	680
July	1st to 10th	Day	9% 12% 28% 31% 17% 3	671
	11th to 20th	Day	7% 20% 36% 22% 12% 3	537
	21st to end	Day	6% 15% 37% 26% 12% 3	531
August	1st to 10th	Day	8% 12% 35% 26% 15% 3	487
	11th to 20th	Day	6% 12% 34% 26% 16% 5%	477
	21st to end	Day	12% 16% 32% 24% 12% 4	539
September	1st to 10th	Day	16% 18% 25% 24% 14% 3	490
	11th to 20th	Day	17% 14% 29% 26% 12% 2	490
	21st to end	Day	24% 18% 27% 19% 11% 1	490
October	1st to 10th	Day	23% 15% 29% 20% 11% 2	490
	11th to 20th	Day	28% 15% 22% 21% 11% 4	314
	21st to end	Day	32% 18% 25% 18% 7% 2	330
November	1st to 10th	Day	36% 15% 20% 24% 6%	300
	11th to 20th	Day	35% 15% 25% 17% 7%	257
	21st to end	Day	30% 18% 23% 15% 12% 1	194
December	1st to 10th	Day	29% 19% 20% 18% 12% 2	180
	11th to 20th	Day	26% 21% 23% 22% 8% 1	180
	21st to end	Day	25% 14% 27% 22% 12% 1	198
January	1st to 10th	Night	31% 17% 23% 24% 6%	890
	11th to 20th	Night	24% 15% 25% 29% 8%	760
	21st to end	Night	19% 14% 28% 29% 9% 1	836
February	1st to 10th	Night	26% 13% 26% 28% 7% 1	760
	11th to 20th	Night	24% 11% 25% 29% 11%	744
	21st to end	Night	21% 14% 21% 29% 13% 1	628
March	1st to 10th	Night	23% 16% 20% 29% 12% 1	760
	11th to 20th	Night	23% 13% 18% 31% 14% 1	760
	21st to end	Night	23% 14% 21% 26% 14% 2	836
April	1st to 10th	Night	20% 11% 19% 31% 19% 1	760
	11th to 20th	Night	19% 14% 24% 29% 12% 2	617
	21st to end	Night	18% 11% 29% 30% 12% 1	570
May	1st to 10th	Night	17% 7% 21% 35% 18% 2	456
	11th to 20th	Night	13% 5% 20% 33% 27% 2	374
	21st to end	Night	20% 9% 18% 28% 23% 2	411
June	1st to 10th	Night	22% 7% 18% 29% 19% 4	380
	11th to 20th	Night	19% 7% 21% 33% 19% 2	380
	21st to end	Night	8% 6% 14% 44% 26% 2	380
July	1st to 10th	Night	5% 2 9% 44% 38% 1	370
	11th to 20th	Night	4 2 16% 49% 27% 2	368
	21st to end	Night	4 4 12% 46% 34% 1	416
August	1st to 10th	Night	4 3 13% 39% 36% 4	378
	11th to 20th	Night	5% 4 13% 37% 37% 4	509
	21st to end	Night	8% 4 17% 41% 27% 3	684
September	1st to 10th	Night	7% 4 19% 40% 24% 6%	760
	11th to 20th	Night	11% 6% 14% 33% 31% 5%	760
	21st to end	Night	16% 8% 15% 37% 20% 5%	760
October	1st to 10th	Night	20% 7% 15% 39% 18% 1	760
	11th to 20th	Night	21% 6% 16% 34% 20% 2	760
	21st to end	Night	25% 10% 22% 29% 12% 2	836
November	1st to 10th	Night	32% 12% 19% 31% 5%	780
	11th to 20th	Night	29% 17% 22% 25% 6% 1	895
	21st to end	Night	28% 12% 22% 28% 10%	986
December	1st to 10th	Night	23% 14% 25% 28% 10%	950
	11th to 20th	Night	24% 15% 29% 26% 5%	950
	21st to end	Night	26% 13% 29% 26% 5%	1045

Page generated at 2024-11-24 21:22:18. Version ac07

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