Elkford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elkford clear sky chart from 2005-11-06 to 2025-01-07.

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% 10% 4 10% 6% 6% 6% 5% 6% 8% 34%	108766
	Night	3 9% 4 11% 7% 6% 6% 5% 6% 8% 34%	108823
Transparency	Day	47% 8% 15% 19% 10% 2	108521
	Night	47% 9% 15% 19% 8% 1	108714
Seeing	Day	18% 19% 30% 20% 9% 2	15404
	Night	12% 13% 33% 29% 11% 2	24623

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	1 7% 8% 25% 10% 8% 6% 5% 6% 8% 17%	2261
	11th to 20th	Day	1 8% 5% 11% 6% 8% 6% 5% 6% 10% 34%	2402
	21st to end	Day	3 11% 5% 10% 7% 7% 6% 5% 6% 10% 29%	2794
February	1st to 10th	Day	1 10% 3 10% 8% 8% 8% 6% 9% 9% 27%	1520
	11th to 20th	Day	1 11% 6% 15% 7% 7% 6% 6% 7% 8% 26%	1662
	21st to end	Day	1 10% 5% 16% 11% 8% 6% 6% 6% 8% 22%	1570
March	1st to 10th	Day	1 9% 5% 15% 9% 8% 5% 5% 5% 8% 31%	3138
	11th to 20th	Day	2 14% 6% 11% 6% 5% 5% 3 6% 7% 36%	3411
	21st to end	Day	2 22% 8% 18% 8% 6% 5% 4 5% 6% 16%	3941
April	1st to 10th	Day	6% 18% 6% 14% 7% 6% 6% 4 5% 7% 21%	2285
	11th to 20th	Day	5% 20% 6% 13% 6% 6% 5% 4 5% 7% 23%	2440
	21st to end	Day	9% 18% 5% 11% 5% 6% 5% 4 6% 7% 24%	2470
May	1st to 10th	Day	12% 23% 6% 10% 5% 4 4 4 5% 5% 23%	4265
	11th to 20th	Day	7% 12% 4 10% 7% 7% 7% 6% 8% 7% 25%	4616
	21st to end	Day	15% 15% 5% 12% 7% 6% 6% 4 6% 6% 18%	5161
June	1st to 10th	Day	15% 12% 4 10% 7% 5% 4 3 6% 7% 27%	2850
	11th to 20th	Day	16% 12% 4 11% 7% 6% 5% 5% 5% 6% 21%	2850
	21st to end	Day	9% 6% 2 9% 7% 5% 6% 5% 7% 9% 35%	2850
July	1st to 10th	Day	5% 4 2 6% 5% 5% 5% 4 6% 8% 49%	4740
	11th to 20th	Day	5% 3 1 5% 4 5% 5% 4 7% 9% 53%	4740
	21st to end	Day	3 3 2 5% 4 5% 4 4 6% 7% 58%	4831
August	1st to 10th	Day	7% 5% 2 6% 6% 5% 6% 5% 7% 8% 43%	4401
	11th to 20th	Day	7% 4 2 6% 4 5% 5% 5% 7% 8% 47%	4086
	21st to end	Day	7% 4 2 5% 5% 5% 5% 4 7% 7% 49%	4521
September	1st to 10th	Day	8% 8% 2 7% 5% 4 4 3 5% 8% 46%	2307
	11th to 20th	Day	9% 8% 2 7% 4 4 6% 4 6% 8% 41%	2100
	21st to end	Day	7% 9% 3 8% 5% 5% 4 4 6% 7% 42%	2090
October	1st to 10th	Day	5% 7% 2 6% 5% 5% 4 4 6% 7% 49%	3412
	11th to 20th	Day	4 6% 2 6% 5% 5% 6% 4 7% 9% 45%	2873
	21st to end	Day	4 8% 4 8% 6% 5% 6% 6% 7% 8% 38%	3101
November	1st to 10th	Day	5% 13% 4 12% 9% 5% 5% 6% 7% 7% 27%	1723
	11th to 20th	Day	2 10% 3 12% 7% 6% 6% 6% 9% 8% 31%	1525
	21st to end	Day	2 11% 4 10% 7% 6% 6% 4 7% 11% 32%	1400
December	1st to 10th	Day	1 6% 4 12% 7% 7% 8% 6% 8% 9% 31%	2290
	11th to 20th	Day	1 8% 4 15% 12% 10% 9% 6% 8% 8% 20%	2642
	21st to end	Day	1 10% 4 16% 9% 6% 7% 5% 7% 8% 27%	3498
January	1st to 10th	Night	1 10% 9% 23% 11% 8% 7% 5% 6% 6% 14%	4817
	11th to 20th	Night	7% 5% 12% 8% 8% 7% 7% 8% 9% 29%	4513
	21st to end	Night	4 16% 5% 12% 8% 6% 6% 4 7% 10% 21%	4862
February	1st to 10th	Night	2 8% 5% 13% 10% 9% 8% 5% 7% 9% 24%	2660
	11th to 20th	Night	1 9% 5% 14% 7% 7% 6% 5% 6% 9% 30%	2400
	21st to end	Night	1 8% 3 14% 9% 7% 6% 6% 7% 8% 29%	1884
March	1st to 10th	Night	1 8% 6% 14% 8% 7% 7% 5% 7% 11% 28%	3736
	11th to 20th	Night	2 15% 4 8% 5% 4 4 4 6% 9% 37%	3568
	21st to end	Night	2 21% 10% 15% 7% 5% 5% 4 5% 6% 20%	3710
April	1st to 10th	Night	4 13% 5% 8% 6% 5% 6% 5% 7% 9% 31%	1894
	11th to 20th	Night	4 13% 5% 10% 5% 5% 5% 4 6% 9% 34%	1691
	21st to end	Night	5% 12% 6% 11% 5% 6% 5% 4 5% 7% 34%	1710
May	1st to 10th	Night	8% 18% 6% 10% 5% 5% 4 4 5% 5% 30%	2685
	11th to 20th	Night	5% 8% 3 8% 5% 6% 6% 6% 8% 10% 35%	2277
	21st to end	Night	12% 15% 4 9% 5% 5% 5% 4 6% 7% 28%	2414
June	1st to 10th	Night	11% 9% 3 7% 6% 3 5% 5% 8% 8% 34%	1330
	11th to 20th	Night	16% 9% 3 9% 5% 5% 6% 5% 6% 7% 30%	1330
	21st to end	Night	7% 5% 2 6% 4 5% 4 5% 8% 7% 48%	1330
July	1st to 10th	Night	4 3 1 5% 4 4 4 4 5% 8% 57%	2220
	11th to 20th	Night	4 3 2 4 2 4 4 3 5% 7% 63%	2220
	21st to end	Night	2 2 1 3 2 3 3 3 5% 6% 70%	2719
August	1st to 10th	Night	7% 6% 2 6% 4 4 4 3 5% 7% 52%	2529
	11th to 20th	Night	5% 4 1 6% 4 5% 5% 4 5% 10% 50%	2751
	21st to end	Night	6% 4 2 4 3 4 5% 4 6% 10% 53%	3146
September	1st to 10th	Night	6% 4 2 5% 3 3 4 3 5% 9% 56%	1871
	11th to 20th	Night	8% 6% 2 6% 3 3 5% 4 5% 9% 49%	2080
	21st to end	Night	8% 6% 2 6% 4 4 5% 4 6% 9% 47%	2090
October	1st to 10th	Night	4 6% 2 5% 4 3 4 3 6% 10% 53%	3552
	11th to 20th	Night	3 6% 2 6% 4 4 4 4 6% 9% 53%	4053
	21st to end	Night	3 8% 3 9% 4 5% 6% 5% 8% 9% 39%	4457
November	1st to 10th	Night	4 12% 4 12% 8% 6% 6% 5% 7% 9% 26%	2555
	11th to 20th	Night	1 9% 5% 10% 8% 7% 8% 7% 7% 10% 29%	2871
	21st to end	Night	1 10% 4 11% 10% 8% 7% 5% 7% 9% 28%	3000
December	1st to 10th	Night	1 6% 4 13% 9% 8% 11% 8% 8% 8% 24%	4890
	11th to 20th	Night	1 8% 6% 19% 10% 10% 11% 6% 7% 7% 17%	5550
	21st to end	Night	1 9% 6% 16% 9% 9% 8% 6% 7% 9% 21%	7458

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	62% 14% 11% 7% 4 1	2261
	11th to 20th	Day	50% 7% 12% 13% 13% 4	2426
	21st to end	Day	51% 11% 19% 14% 4 1	2794
February	1st to 10th	Day	52% 10% 16% 13% 6% 2	1520
	11th to 20th	Day	55% 9% 16% 12% 6% 1	1671
	21st to end	Day	59% 8% 13% 13% 6% 1	1570
March	1st to 10th	Day	54% 7% 13% 13% 12% 1	3138
	11th to 20th	Day	50% 6% 22% 18% 4	3412
	21st to end	Day	68% 8% 10% 8% 6%	3941
April	1st to 10th	Day	63% 6% 16% 11% 4	2285
	11th to 20th	Day	62% 5% 14% 14% 4	2440
	21st to end	Day	60% 6% 15% 16% 2 1	2470
May	1st to 10th	Day	63% 6% 11% 17% 4	4265
	11th to 20th	Day	52% 10% 16% 18% 3	4620
	21st to end	Day	64% 10% 11% 11% 3	5162
June	1st to 10th	Day	59% 6% 14% 15% 6%	2850
	11th to 20th	Day	63% 6% 11% 13% 6% 1	2850
	21st to end	Day	44% 7% 17% 21% 11% 1	2850
July	1st to 10th	Day	31% 7% 11% 23% 25% 4	4666
	11th to 20th	Day	26% 7% 9% 29% 26% 3	4659
	21st to end	Day	25% 4 9% 25% 26% 11%	4678
August	1st to 10th	Day	35% 8% 14% 25% 15% 3	4384
	11th to 20th	Day	32% 8% 21% 29% 10%	4126
	21st to end	Day	31% 6% 20% 32% 10% 1	4520
September	1st to 10th	Day	36% 6% 15% 25% 16% 2	2307
	11th to 20th	Day	41% 6% 16% 25% 12% 1	2100
	21st to end	Day	42% 6% 18% 24% 9% 1	2090
October	1st to 10th	Day	34% 7% 19% 33% 7%	3412
	11th to 20th	Day	37% 8% 21% 22% 11% 1	2873
	21st to end	Day	42% 10% 20% 20% 8%	3101
November	1st to 10th	Day	57% 10% 14% 14% 5% 1	1723
	11th to 20th	Day	50% 10% 20% 14% 6% 1	1525
	21st to end	Day	49% 11% 17% 14% 7% 1	1400
December	1st to 10th	Day	49% 11% 18% 15% 5% 1	2290
	11th to 20th	Day	58% 14% 15% 10% 3	2644
	21st to end	Day	50% 10% 12% 16% 10% 2	3498
January	1st to 10th	Night	69% 12% 8% 7% 3 1	4817
	11th to 20th	Night	52% 8% 12% 10% 10% 8%	4551
	21st to end	Night	57% 14% 12% 11% 5% 1	4862
February	1st to 10th	Night	56% 8% 11% 14% 8% 2	2660
	11th to 20th	Night	53% 8% 15% 15% 8%	2401
	21st to end	Night	50% 8% 13% 19% 8% 1	1884
March	1st to 10th	Night	51% 11% 15% 13% 11%	3736
	11th to 20th	Night	44% 10% 22% 19% 4	3568
	21st to end	Night	63% 9% 13% 13% 3	3710
April	1st to 10th	Night	50% 9% 21% 14% 6%	1894
	11th to 20th	Night	47% 8% 18% 22% 4	1691
	21st to end	Night	50% 6% 16% 22% 4 1	1710
May	1st to 10th	Night	55% 6% 13% 23% 4	2685
	11th to 20th	Night	39% 11% 20% 25% 6%	2277
	21st to end	Night	55% 8% 16% 14% 7%	2414
June	1st to 10th	Night	46% 8% 20% 20% 6% 1	1330
	11th to 20th	Night	50% 8% 18% 17% 7% 1	1330
	21st to end	Night	32% 8% 20% 28% 11% 1	1330
July	1st to 10th	Night	24% 7% 16% 27% 22% 4	2185
	11th to 20th	Night	20% 6% 13% 32% 24% 5%	2178
	21st to end	Night	16% 4 10% 30% 27% 12%	2633
August	1st to 10th	Night	29% 8% 15% 28% 16% 3	2521
	11th to 20th	Night	29% 7% 25% 26% 12% 1	2777
	21st to end	Night	27% 6% 24% 33% 11% 1	3146
September	1st to 10th	Night	27% 5% 18% 33% 14% 3	1871
	11th to 20th	Night	34% 8% 16% 30% 11% 1	2080
	21st to end	Night	36% 8% 22% 22% 11% 1	2090
October	1st to 10th	Night	28% 8% 19% 33% 12%	3552
	11th to 20th	Night	29% 9% 20% 31% 10%	4053
	21st to end	Night	40% 11% 19% 25% 5%	4457
November	1st to 10th	Night	56% 10% 14% 13% 5% 1	2555
	11th to 20th	Night	52% 10% 14% 16% 7% 1	2871
	21st to end	Night	54% 9% 14% 14% 7% 1	3000
December	1st to 10th	Night	57% 11% 14% 12% 5% 1	4890
	11th to 20th	Night	65% 11% 10% 10% 4	5547
	21st to end	Night	56% 10% 13% 11% 7% 2	7458

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	15% 17% 36% 19% 8% 5%	192
	11th to 20th	Day	12% 16% 39% 26% 4 3	180
	21st to end	Day	12% 20% 47% 15% 5% 2	198
February	1st to 10th	Day	24% 16% 42% 12% 6%	180
	11th to 20th	Day	12% 19% 37% 25% 6% 1	279
	21st to end	Day	16% 23% 36% 20% 4 1	382
March	1st to 10th	Day	23% 27% 29% 14% 5% 2	460
	11th to 20th	Day	21% 22% 30% 19% 6% 3	460
	21st to end	Day	19% 25% 31% 18% 6% 2	506
April	1st to 10th	Day	21% 25% 31% 17% 5% 1	460
	11th to 20th	Day	22% 22% 33% 14% 7% 2	452
	21st to end	Day	24% 23% 31% 13% 6% 2	460
May	1st to 10th	Day	22% 21% 27% 17% 10% 3	463
	11th to 20th	Day	21% 12% 27% 22% 14% 4	623
	21st to end	Day	25% 15% 19% 25% 14% 2	734
June	1st to 10th	Day	23% 19% 27% 19% 10% 2	680
	11th to 20th	Day	25% 18% 26% 19% 9% 2	680
	21st to end	Day	14% 16% 27% 25% 14% 4	680
July	1st to 10th	Day	13% 16% 25% 26% 17% 4	671
	11th to 20th	Day	14% 18% 25% 26% 15% 3	668
	21st to end	Day	8% 19% 32% 24% 13% 3	559
August	1st to 10th	Day	13% 14% 32% 26% 11% 3	487
	11th to 20th	Day	10% 17% 30% 30% 9% 4	477
	21st to end	Day	14% 18% 33% 22% 10% 3	539
September	1st to 10th	Day	17% 21% 30% 18% 10% 3	490
	11th to 20th	Day	18% 18% 33% 21% 8% 3	490
	21st to end	Day	24% 26% 29% 15% 5% 1	490
October	1st to 10th	Day	19% 20% 30% 20% 8% 2	451
	11th to 20th	Day	22% 20% 27% 17% 11% 2	300
	21st to end	Day	25% 19% 30% 20% 5% 2	330
November	1st to 10th	Day	19% 23% 33% 18% 6% 1	300
	11th to 20th	Day	21% 22% 37% 15% 4 1	263
	21st to end	Day	17% 17% 38% 15% 10% 6%	200
December	1st to 10th	Day	14% 21% 34% 19% 8% 5%	200
	11th to 20th	Day	12% 21% 40% 21% 6% 1	200
	21st to end	Day	9% 12% 44% 24% 9% 2	220
January	1st to 10th	Night	13% 16% 43% 22% 6% 1	981
	11th to 20th	Night	9% 15% 48% 23% 5% 1	839
	21st to end	Night	8% 17% 42% 25% 6% 1	836
February	1st to 10th	Night	10% 13% 42% 24% 9% 2	760
	11th to 20th	Night	10% 12% 43% 28% 7%	744
	21st to end	Night	9% 14% 36% 30% 9% 2	628
March	1st to 10th	Night	8% 16% 41% 25% 9% 1	760
	11th to 20th	Night	12% 19% 29% 30% 9% 1	760
	21st to end	Night	11% 13% 33% 31% 11% 2	836
April	1st to 10th	Night	14% 15% 29% 32% 9% 2	754
	11th to 20th	Night	11% 18% 33% 26% 10% 2	563
	21st to end	Night	13% 16% 32% 29% 10% 1	570
May	1st to 10th	Night	15% 10% 27% 32% 15% 1	473
	11th to 20th	Night	12% 9% 18% 33% 23% 4	374
	21st to end	Night	22% 9% 18% 27% 21% 2	411
June	1st to 10th	Night	17% 8% 26% 32% 15% 2	380
	11th to 20th	Night	21% 9% 25% 29% 15% 1	380
	21st to end	Night	10% 10% 19% 37% 21% 2	380
July	1st to 10th	Night	8% 5% 18% 44% 25% 1	370
	11th to 20th	Night	7% 6% 22% 43% 22%	368
	21st to end	Night	5% 7% 16% 47% 24% 1	416
August	1st to 10th	Night	8% 5% 12% 41% 31% 2	378
	11th to 20th	Night	8% 6% 19% 40% 25% 2	528
	21st to end	Night	11% 11% 22% 36% 19% 1	627
September	1st to 10th	Night	10% 9% 23% 31% 22% 5%	731
	11th to 20th	Night	12% 8% 20% 35% 19% 5%	760
	21st to end	Night	15% 12% 31% 26% 13% 3	760
October	1st to 10th	Night	13% 12% 24% 35% 13% 2	760
	11th to 20th	Night	11% 16% 28% 32% 12% 1	760
	21st to end	Night	13% 16% 33% 30% 8% 1	836
November	1st to 10th	Night	17% 15% 37% 25% 6%	800
	11th to 20th	Night	16% 20% 38% 22% 4 1	1000
	21st to end	Night	11% 16% 40% 24% 8% 1	1000
December	1st to 10th	Night	10% 16% 39% 27% 7% 1	1000
	11th to 20th	Night	9% 17% 45% 25% 5% 1	1000
	21st to end	Night	8% 14% 46% 25% 7%	1100

Page generated at 2025-01-04 01:23:59. Version ac07

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