Deer Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deer Park 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	11% 8% 3 6% 4 4 4 3 5% 6% 44%	105155
	Night	13% 9% 3 7% 4 4 4 4 5% 6% 40%	102439
Transparency	Day	39% 7% 13% 21% 15% 6%	104923
	Night	43% 7% 12% 19% 13% 6%	102317
Seeing	Day	15% 11% 24% 27% 18% 5%	14818
	Night	18% 6% 17% 35% 22% 3	23926

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	22% 23% 6% 10% 5% 5% 4 3 5% 5% 12%	2539
	11th to 20th	Day	22% 15% 5% 9% 6% 6% 4 3 3 5% 23%	2516
	21st to end	Day	29% 21% 6% 9% 5% 4 4 2 3 4 12%	2794
February	1st to 10th	Day	22% 14% 4 10% 5% 5% 4 3 5% 6% 21%	1520
	11th to 20th	Day	15% 15% 5% 8% 5% 4 4 3 5% 6% 28%	1767
	21st to end	Day	16% 15% 5% 8% 6% 4 4 4 5% 5% 29%	1570
March	1st to 10th	Day	13% 13% 4 8% 5% 5% 5% 4 7% 7% 30%	3138
	11th to 20th	Day	11% 8% 3 6% 4 3 3 3 4 5% 50%	3263
	21st to end	Day	15% 13% 3 9% 7% 5% 6% 5% 5% 6% 25%	4134
April	1st to 10th	Day	15% 10% 4 8% 5% 6% 6% 5% 6% 7% 27%	2280
	11th to 20th	Day	12% 8% 3 7% 6% 5% 4 4 6% 6% 38%	2316
	21st to end	Day	10% 8% 2 8% 7% 6% 5% 4 7% 8% 35%	2470
May	1st to 10th	Day	9% 6% 3 7% 5% 5% 5% 5% 6% 8% 41%	4358
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 5% 7% 11% 44%	4377
	21st to end	Day	9% 7% 2 8% 6% 6% 6% 5% 7% 8% 34%	4859
June	1st to 10th	Day	16% 7% 2 6% 5% 4 4 3 5% 7% 41%	2850
	11th to 20th	Day	12% 6% 3 6% 5% 5% 5% 5% 6% 8% 39%	2850
	21st to end	Day	6% 4 2 5% 3 4 4 4 5% 6% 57%	2850
July	1st to 10th	Day	2 2 1 3 3 3 3 2 3 5% 74%	4468
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 3 79%	4420
	21st to end	Day	2 1 1 2 2 2 2 2 4 5% 77%	4790
August	1st to 10th	Day	3 2 1 3 2 2 3 2 4 7% 69%	4401
	11th to 20th	Day	3 3 1 3 2 3 3 3 5% 7% 67%	4159
	21st to end	Day	3 3 1 4 3 3 4 3 4 7% 63%	4256
September	1st to 10th	Day	5% 3 1 3 2 3 3 3 4 6% 67%	2280
	11th to 20th	Day	7% 4 2 4 4 4 4 4 6% 7% 53%	2179
	21st to end	Day	8% 4 2 6% 4 4 5% 4 6% 8% 49%	2090
October	1st to 10th	Day	8% 5% 2 4 4 3 4 3 4 8% 56%	3345
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 4 6% 8% 43%	2973
	21st to end	Day	18% 8% 2 7% 4 4 5% 4 5% 7% 36%	3101
November	1st to 10th	Day	25% 12% 3 7% 5% 3 4 3 4 6% 27%	1710
	11th to 20th	Day	22% 13% 4 9% 5% 4 4 3 4 5% 26%	1601
	21st to end	Day	20% 18% 5% 13% 5% 4 4 4 4 5% 19%	1380
December	1st to 10th	Day	20% 15% 7% 12% 6% 4 4 3 3 5% 20%	1330
	11th to 20th	Day	25% 24% 6% 11% 5% 5% 4 2 3 3 12%	1682
	21st to end	Day	20% 23% 5% 9% 5% 4 4 4 5% 5% 15%	2539
January	1st to 10th	Night	26% 19% 5% 9% 6% 5% 5% 3 4 4 13%	4406
	11th to 20th	Night	21% 15% 4 10% 5% 4 3 3 4 7% 25%	4382
	21st to end	Night	29% 23% 5% 8% 4 3 3 2 3 4 16%	4862
February	1st to 10th	Night	18% 17% 4 8% 5% 4 4 4 5% 6% 26%	2660
	11th to 20th	Night	15% 12% 4 8% 5% 5% 5% 5% 5% 5% 30%	2297
	21st to end	Night	12% 12% 3 9% 6% 5% 4 4 6% 6% 33%	1884
March	1st to 10th	Night	11% 11% 3 7% 5% 4 5% 5% 7% 7% 36%	3736
	11th to 20th	Night	12% 8% 2 5% 4 3 4 2 4 5% 53%	3716
	21st to end	Night	14% 10% 3 8% 6% 6% 6% 5% 7% 8% 26%	3503
April	1st to 10th	Night	11% 9% 3 6% 6% 5% 5% 4 6% 8% 36%	1900
	11th to 20th	Night	11% 9% 3 7% 6% 5% 4 4 4 6% 40%	1815
	21st to end	Night	10% 7% 3 7% 5% 6% 5% 5% 5% 7% 40%	1710
May	1st to 10th	Night	10% 6% 2 7% 5% 6% 6% 5% 7% 8% 37%	2589
	11th to 20th	Night	7% 4 2 5% 4 4 5% 4 6% 9% 51%	2516
	21st to end	Night	13% 6% 3 7% 5% 5% 5% 4 8% 8% 36%	2712
June	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 6% 9% 43%	1330
	11th to 20th	Night	10% 5% 3 5% 6% 5% 6% 4 7% 7% 42%	1330
	21st to end	Night	5% 5% 2 4 3 3 3 4 7% 7% 57%	1330
July	1st to 10th	Night	1 2 1 3 3 3 2 2 4 7% 72%	2473
	11th to 20th	Night	1 1 1 2 1 2 2 2 2 4 82%	2540
	21st to end	Night	1 1 1 2 1 1 2 2 3 5% 80%	2762
August	1st to 10th	Night	3 3 1 3 2 2 2 2 4 7% 72%	2529
	11th to 20th	Night	3 3 1 4 3 3 4 3 6% 6% 63%	2674
	21st to end	Night	3 2 1 5% 3 4 4 3 5% 7% 62%	3416
September	1st to 10th	Night	4 2 1 3 2 3 4 3 6% 7% 66%	1900
	11th to 20th	Night	7% 4 2 6% 4 4 4 4 6% 8% 52%	2000
	21st to end	Night	10% 5% 2 5% 3 3 5% 3 5% 7% 54%	2090
October	1st to 10th	Night	6% 3 1 4 3 3 3 3 6% 8% 60%	3631
	11th to 20th	Night	10% 5% 2 5% 3 4 4 4 6% 8% 49%	3958
	21st to end	Night	14% 6% 2 6% 4 5% 5% 4 5% 7% 41%	4457
November	1st to 10th	Night	22% 12% 3 7% 5% 4 4 4 6% 7% 28%	2469
	11th to 20th	Night	20% 11% 4 8% 5% 5% 5% 4 5% 6% 28%	2578
	21st to end	Night	21% 13% 3 8% 6% 4 4 4 5% 6% 26%	2778
December	1st to 10th	Night	18% 14% 6% 10% 6% 4 3 3 5% 5% 26%	2850
	11th to 20th	Night	25% 19% 6% 10% 5% 4 4 3 5% 5% 15%	3510
	21st to end	Night	21% 18% 5% 12% 6% 5% 4 4 4 5% 16%	5146

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	72% 11% 8% 7% 2	2539
	11th to 20th	Day	64% 7% 11% 12% 3 3	2540
	21st to end	Day	76% 8% 9% 5% 2	2794
February	1st to 10th	Day	64% 9% 13% 9% 4 1	1520
	11th to 20th	Day	56% 11% 13% 13% 7%	1776
	21st to end	Day	57% 9% 12% 14% 7% 1	1570
March	1st to 10th	Day	49% 9% 14% 18% 10% 1	3138
	11th to 20th	Day	36% 6% 20% 31% 5%	3263
	21st to end	Day	56% 11% 15% 12% 5%	4134
April	1st to 10th	Day	53% 8% 17% 17% 5% 1	2280
	11th to 20th	Day	44% 7% 19% 17% 11% 2	2316
	21st to end	Day	45% 8% 17% 20% 9% 2	2470
May	1st to 10th	Day	36% 9% 14% 28% 12% 1	4358
	11th to 20th	Day	29% 8% 17% 32% 13% 1	4380
	21st to end	Day	41% 10% 19% 23% 6% 1	4860
June	1st to 10th	Day	43% 6% 13% 22% 15% 2	2850
	11th to 20th	Day	39% 8% 14% 23% 12% 3	2850
	21st to end	Day	26% 6% 14% 28% 21% 5%	2850
July	1st to 10th	Day	13% 4 7% 17% 32% 26%	4399
	11th to 20th	Day	11% 2 6% 12% 28% 41%	4345
	21st to end	Day	11% 3 6% 20% 36% 24%	4639
August	1st to 10th	Day	16% 3 6% 23% 36% 15%	4384
	11th to 20th	Day	17% 4 9% 39% 25% 4	4201
	21st to end	Day	20% 5% 11% 33% 26% 4	4255
September	1st to 10th	Day	19% 5% 12% 29% 25% 10%	2280
	11th to 20th	Day	28% 8% 13% 24% 22% 4	2179
	21st to end	Day	31% 9% 18% 27% 11% 4	2090
October	1st to 10th	Day	28% 5% 15% 35% 16% 1	3345
	11th to 20th	Day	37% 8% 18% 24% 13%	2973
	21st to end	Day	47% 8% 16% 19% 9% 1	3101
November	1st to 10th	Day	59% 9% 14% 14% 4 1	1710
	11th to 20th	Day	61% 10% 11% 11% 4 2	1601
	21st to end	Day	66% 10% 11% 9% 3	1380
December	1st to 10th	Day	68% 7% 12% 10% 4	1330
	11th to 20th	Day	80% 7% 7% 5% 2	1684
	21st to end	Day	68% 9% 12% 7% 3	2539
January	1st to 10th	Night	72% 8% 9% 9% 2 1	4406
	11th to 20th	Night	59% 8% 13% 15% 3 2	4420
	21st to end	Night	72% 9% 10% 6% 2 1	4862
February	1st to 10th	Night	59% 9% 14% 12% 6% 1	2660
	11th to 20th	Night	53% 9% 17% 12% 8% 1	2299
	21st to end	Night	50% 8% 14% 17% 10% 1	1884
March	1st to 10th	Night	40% 9% 16% 24% 10% 1	3736
	11th to 20th	Night	35% 6% 18% 32% 10%	3717
	21st to end	Night	49% 11% 17% 18% 5%	3503
April	1st to 10th	Night	44% 8% 15% 23% 9% 1	1900
	11th to 20th	Night	43% 7% 12% 21% 15% 2	1815
	21st to end	Night	41% 8% 13% 22% 15% 2	1710
May	1st to 10th	Night	37% 8% 14% 25% 15% 1	2589
	11th to 20th	Night	25% 8% 14% 33% 19% 1	2516
	21st to end	Night	40% 10% 14% 24% 11%	2712
June	1st to 10th	Night	38% 7% 11% 21% 19% 4	1330
	11th to 20th	Night	37% 8% 14% 19% 17% 5%	1330
	21st to end	Night	25% 5% 11% 26% 25% 8%	1330
July	1st to 10th	Night	13% 3 6% 16% 29% 33%	2433
	11th to 20th	Night	8% 2 5% 12% 18% 54%	2492
	21st to end	Night	9% 2 3 17% 34% 36%	2674
August	1st to 10th	Night	14% 2 5% 18% 39% 22%	2521
	11th to 20th	Night	20% 4 6% 31% 30% 9%	2698
	21st to end	Night	20% 5% 11% 25% 29% 9%	3416
September	1st to 10th	Night	16% 5% 8% 27% 28% 14%	1900
	11th to 20th	Night	28% 6% 11% 22% 23% 9%	2000
	21st to end	Night	30% 6% 14% 28% 16% 6%	2090
October	1st to 10th	Night	23% 4 10% 42% 21%	3631
	11th to 20th	Night	33% 7% 16% 24% 20% 1	3958
	21st to end	Night	40% 8% 15% 28% 8% 2	4457
November	1st to 10th	Night	54% 10% 15% 15% 5% 1	2469
	11th to 20th	Night	57% 10% 14% 12% 5% 2	2578
	21st to end	Night	59% 9% 15% 12% 5%	2778
December	1st to 10th	Night	60% 9% 13% 15% 4	2850
	11th to 20th	Night	71% 11% 10% 6% 2	3507
	21st to end	Night	67% 11% 12% 7% 3	5146

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	32% 10% 19% 21% 13% 4	180
	11th to 20th	Day	32% 10% 18% 21% 13% 6%	180
	21st to end	Day	34% 7% 22% 23% 13% 2	198
February	1st to 10th	Day	26% 14% 30% 22% 6% 2	180
	11th to 20th	Day	25% 14% 25% 23% 11% 2	413
	21st to end	Day	20% 15% 26% 25% 13% 1	382
March	1st to 10th	Day	21% 17% 29% 21% 9% 3	460
	11th to 20th	Day	18% 14% 22% 23% 20% 3	460
	21st to end	Day	22% 17% 24% 24% 11% 2	506
April	1st to 10th	Day	20% 15% 27% 22% 11% 4	460
	11th to 20th	Day	18% 21% 26% 19% 12% 4	452
	21st to end	Day	11% 16% 28% 29% 14% 3	460
May	1st to 10th	Day	11% 11% 31% 28% 15% 4	463
	11th to 20th	Day	17% 10% 26% 25% 17% 6%	488
	21st to end	Day	13% 10% 23% 29% 18% 7%	549
June	1st to 10th	Day	17% 10% 23% 26% 20% 4	680
	11th to 20th	Day	13% 13% 30% 28% 13% 3	680
	21st to end	Day	5% 7% 25% 30% 27% 6%	680
July	1st to 10th	Day	3 7% 28% 33% 25% 3	521
	11th to 20th	Day	5% 8% 26% 36% 19% 7%	484
	21st to end	Day	3 5% 24% 37% 22% 8%	531
August	1st to 10th	Day	5% 6% 20% 34% 25% 9%	487
	11th to 20th	Day	4 4 21% 29% 30% 12%	477
	21st to end	Day	7% 9% 22% 27% 25% 10%	539
September	1st to 10th	Day	7% 5% 24% 29% 24% 11%	490
	11th to 20th	Day	8% 11% 23% 26% 24% 7%	490
	21st to end	Day	12% 12% 26% 26% 18% 7%	490
October	1st to 10th	Day	12% 9% 23% 29% 22% 6%	490
	11th to 20th	Day	16% 11% 17% 26% 21% 9%	379
	21st to end	Day	27% 8% 21% 29% 12% 3	330
November	1st to 10th	Day	32% 7% 18% 30% 12% 1	282
	11th to 20th	Day	32% 10% 17% 26% 13% 4	219
	21st to end	Day	29% 6% 18% 26% 18% 3	180
December	1st to 10th	Day	29% 8% 22% 23% 11% 6%	180
	11th to 20th	Day	32% 10% 22% 24% 10% 2	180
	21st to end	Day	32% 14% 18% 24% 11% 2	198
January	1st to 10th	Night	37% 7% 17% 25% 11% 2	760
	11th to 20th	Night	28% 8% 19% 29% 14% 3	760
	21st to end	Night	26% 5% 20% 32% 16% 1	836
February	1st to 10th	Night	25% 8% 22% 32% 12% 2	760
	11th to 20th	Night	22% 7% 21% 33% 15% 2	744
	21st to end	Night	18% 8% 21% 33% 18% 2	628
March	1st to 10th	Night	21% 8% 18% 33% 18% 2	760
	11th to 20th	Night	20% 7% 17% 34% 21% 1	760
	21st to end	Night	20% 6% 19% 38% 15% 2	836
April	1st to 10th	Night	15% 7% 18% 39% 20% 2	760
	11th to 20th	Night	14% 7% 24% 38% 15% 2	687
	21st to end	Night	13% 6% 24% 36% 20% 2	570
May	1st to 10th	Night	9% 6% 18% 38% 26% 2	416
	11th to 20th	Night	11% 5% 13% 30% 33% 7%	374
	21st to end	Night	13% 5% 17% 34% 27% 5%	411
June	1st to 10th	Night	12% 6% 15% 42% 23% 2	380
	11th to 20th	Night	11% 5% 23% 37% 22% 2	380
	21st to end	Night	8% 3 11% 47% 28% 4	380
July	1st to 10th	Night	4 2 9% 43% 40% 3	370
	11th to 20th	Night	2 2 14% 46% 35% 1	368
	21st to end	Night	1 1 8% 42% 44% 3	416
August	1st to 10th	Night	4 2 11% 37% 42% 5%	378
	11th to 20th	Night	3 3 9% 35% 42% 9%	475
	21st to end	Night	3 3 12% 38% 40% 3	780
September	1st to 10th	Night	5% 2 12% 41% 34% 6%	760
	11th to 20th	Night	7% 4 13% 32% 38% 7%	760
	21st to end	Night	11% 4 17% 35% 29% 5%	760
October	1st to 10th	Night	13% 4 15% 38% 28% 2	760
	11th to 20th	Night	14% 5% 15% 36% 26% 3	760
	21st to end	Night	20% 3 21% 37% 16% 3	836
November	1st to 10th	Night	27% 7% 17% 36% 13%	760
	11th to 20th	Night	26% 7% 21% 30% 15% 2	760
	21st to end	Night	27% 8% 14% 32% 17% 2	878
December	1st to 10th	Night	25% 6% 16% 35% 16% 2	950
	11th to 20th	Night	34% 6% 16% 32% 12%	950
	21st to end	Night	36% 7% 16% 31% 10%	1003

Page generated at 2024-11-02 23:11:13. Version ac07

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