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 2024-01-17.

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	7% 10% 4 9% 8% 4 6% 6% 6% 8% 32%	74637
	Night	4 8% 4 9% 8% 4 6% 6% 7% 9% 35%	75200
Transparency	Day	50% 8% 15% 18% 8% 1	74328
	Night	47% 9% 16% 19% 9% 1	75027
Seeing	Day	18% 20% 30% 20% 9% 2	14112
	Night	12% 14% 33% 29% 11% 2	23389

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 8% 6% 12% 8% 6% 8% 7% 8% 11% 24%	1329
	11th to 20th	Day	1 7% 4 10% 8% 5% 7% 7% 7% 13% 32%	1426
	21st to end	Day	1 8% 4 9% 9% 5% 8% 7% 7% 11% 31%	1584
February	1st to 10th	Day	1 9% 3 9% 10% 5% 9% 8% 9% 10% 27%	1440
	11th to 20th	Day	1 9% 6% 14% 9% 5% 7% 7% 7% 9% 25%	1572
	21st to end	Day	2 7% 6% 14% 13% 6% 7% 7% 6% 9% 23%	1480
March	1st to 10th	Day	3 10% 6% 11% 10% 6% 8% 7% 6% 9% 26%	1800
	11th to 20th	Day	3 15% 6% 11% 8% 5% 6% 5% 6% 8% 27%	1927
	21st to end	Day	4 20% 8% 13% 9% 4 6% 6% 6% 7% 18%	2243
April	1st to 10th	Day	6% 16% 7% 13% 9% 5% 6% 5% 5% 7% 21%	2164
	11th to 20th	Day	6% 20% 7% 11% 8% 4 5% 5% 5% 7% 22%	2310
	21st to end	Day	10% 16% 6% 10% 6% 4 6% 5% 6% 7% 25%	2340
May	1st to 10th	Day	10% 19% 6% 9% 7% 3 5% 6% 6% 6% 24%	2430
	11th to 20th	Day	11% 13% 4 8% 7% 5% 5% 5% 6% 6% 29%	2604
	21st to end	Day	22% 12% 4 9% 7% 4 5% 5% 6% 6% 21%	2917
June	1st to 10th	Day	16% 11% 5% 9% 8% 4 5% 4 5% 6% 26%	2700
	11th to 20th	Day	17% 11% 5% 9% 8% 5% 6% 6% 5% 7% 20%	2700
	21st to end	Day	9% 6% 3 8% 8% 4 6% 6% 7% 9% 35%	2700
July	1st to 10th	Day	7% 5% 2 6% 7% 4 6% 6% 6% 9% 41%	2700
	11th to 20th	Day	8% 4 2 5% 6% 5% 6% 5% 7% 8% 44%	2700
	21st to end	Day	4 3 2 5% 5% 3 5% 5% 6% 8% 55%	2768
August	1st to 10th	Day	7% 5% 2 5% 7% 4 5% 6% 6% 7% 47%	2507
	11th to 20th	Day	8% 4 3 5% 3 3 5% 5% 6% 7% 51%	2333
	21st to end	Day	9% 4 2 5% 6% 3 5% 5% 7% 8% 46%	2574
September	1st to 10th	Day	9% 8% 2 6% 6% 3 4 4 5% 8% 45%	2186
	11th to 20th	Day	9% 8% 3 6% 5% 3 5% 5% 6% 8% 42%	1990
	21st to end	Day	8% 9% 3 7% 6% 4 4 6% 6% 7% 42%	1980
October	1st to 10th	Day	8% 11% 4 8% 8% 5% 5% 4 5% 6% 36%	1944
	11th to 20th	Day	5% 9% 4 7% 8% 4 7% 5% 6% 8% 38%	1638
	21st to end	Day	3 10% 5% 8% 7% 4 7% 7% 6% 9% 33%	1782
November	1st to 10th	Day	5% 12% 5% 11% 10% 5% 5% 7% 7% 8% 27%	1636
	11th to 20th	Day	2 8% 4 9% 8% 4 8% 7% 9% 9% 32%	1449
	21st to end	Day	2 9% 5% 9% 7% 4 6% 6% 7% 12% 33%	1330
December	1st to 10th	Day	1 8% 5% 10% 8% 5% 7% 6% 8% 11% 31%	1330
	11th to 20th	Day	1 10% 6% 12% 12% 6% 9% 7% 6% 8% 22%	1682
	21st to end	Day	1 11% 5% 10% 9% 4 6% 6% 7% 10% 30%	2442
January	1st to 10th	Night	1 9% 6% 14% 11% 7% 8% 7% 7% 8% 22%	2836
	11th to 20th	Night	1 7% 6% 11% 9% 5% 8% 7% 8% 11% 27%	2695
	21st to end	Night	1 6% 4 11% 9% 4 7% 7% 8% 11% 31%	2772
February	1st to 10th	Night	2 7% 6% 10% 12% 7% 8% 7% 6% 10% 25%	2520
	11th to 20th	Night	2 8% 6% 12% 9% 5% 7% 7% 6% 9% 29%	2270
	21st to end	Night	1 6% 5% 12% 11% 6% 6% 7% 7% 9% 30%	1776
March	1st to 10th	Night	1 8% 5% 10% 9% 7% 7% 7% 8% 11% 28%	2160
	11th to 20th	Night	3 12% 5% 8% 6% 4 6% 7% 8% 10% 33%	2032
	21st to end	Night	3 10% 6% 11% 8% 4 6% 6% 7% 9% 30%	2111
April	1st to 10th	Night	4 11% 5% 8% 7% 4 6% 6% 7% 10% 32%	1795
	11th to 20th	Night	4 13% 6% 9% 6% 4 5% 5% 6% 9% 34%	1601
	21st to end	Night	6% 11% 6% 10% 6% 4 5% 5% 5% 7% 35%	1620
May	1st to 10th	Night	7% 13% 5% 6% 7% 4 6% 6% 7% 8% 32%	1529
	11th to 20th	Night	8% 10% 3 5% 5% 3 5% 6% 7% 9% 39%	1289
	21st to end	Night	17% 10% 4 6% 4 4 6% 5% 6% 7% 31%	1358
June	1st to 10th	Night	11% 8% 3 7% 5% 3 4 7% 8% 9% 35%	1260
	11th to 20th	Night	17% 8% 3 7% 5% 3 6% 6% 6% 8% 30%	1260
	21st to end	Night	6% 5% 2 5% 5% 3 5% 6% 7% 8% 48%	1260
July	1st to 10th	Night	5% 4 1 3 5% 2 5% 5% 5% 9% 55%	1260
	11th to 20th	Night	3 4 2 3 3 3 4 5% 5% 8% 59%	1260
	21st to end	Night	3 3 2 3 4 2 3 4 5% 7% 64%	1547
August	1st to 10th	Night	6% 4 2 5% 4 3 4 5% 3 6% 59%	1432
	11th to 20th	Night	7% 2 1 4 3 3 4 6% 4 9% 57%	1568
	21st to end	Night	7% 5% 2 3 3 2 4 5% 5% 9% 54%	1782
September	1st to 10th	Night	6% 4 2 5% 4 2 3 4 5% 9% 55%	1772
	11th to 20th	Night	9% 6% 2 5% 4 2 4 5% 5% 8% 50%	1970
	21st to end	Night	8% 6% 2 5% 5% 3 6% 4 6% 9% 46%	1980
October	1st to 10th	Night	7% 8% 3 7% 6% 3 5% 4 4 8% 44%	2016
	11th to 20th	Night	4 8% 3 7% 6% 4 5% 5% 7% 10% 42%	2320
	21st to end	Night	3 10% 4 10% 6% 4 5% 5% 8% 9% 34%	2574
November	1st to 10th	Night	5% 11% 5% 10% 10% 4 6% 6% 8% 10% 26%	2424
	11th to 20th	Night	2 8% 5% 9% 8% 6% 8% 8% 6% 11% 30%	2727
	21st to end	Night	2 8% 6% 8% 11% 6% 8% 7% 7% 9% 29%	2850
December	1st to 10th	Night	2 8% 5% 11% 11% 5% 6% 7% 7% 10% 28%	2850
	11th to 20th	Night	1 9% 6% 14% 12% 7% 10% 8% 8% 8% 17%	3510
	21st to end	Night	1 8% 5% 12% 12% 6% 8% 7% 8% 10% 22%	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	55% 12% 16% 10% 5% 2	1329
	11th to 20th	Day	49% 10% 18% 15% 6% 2	1426
	21st to end	Day	51% 9% 17% 14% 8% 1	1584
February	1st to 10th	Day	52% 10% 17% 13% 7% 2	1440
	11th to 20th	Day	56% 9% 16% 13% 5% 1	1581
	21st to end	Day	58% 8% 14% 12% 7% 1	1480
March	1st to 10th	Day	57% 10% 16% 13% 5%	1800
	11th to 20th	Day	59% 7% 12% 16% 6%	1928
	21st to end	Day	66% 7% 15% 8% 4 1	2243
April	1st to 10th	Day	64% 7% 15% 11% 4	2164
	11th to 20th	Day	63% 5% 14% 13% 4	2310
	21st to end	Day	60% 6% 16% 15% 2 1	2340
May	1st to 10th	Day	60% 6% 16% 14% 3	2430
	11th to 20th	Day	55% 6% 16% 19% 4	2608
	21st to end	Day	63% 8% 12% 14% 3	2918
June	1st to 10th	Day	59% 6% 14% 15% 5%	2700
	11th to 20th	Day	64% 6% 12% 13% 5%	2700
	21st to end	Day	44% 7% 18% 20% 10% 1	2700
July	1st to 10th	Day	37% 8% 15% 25% 13% 2	2626
	11th to 20th	Day	35% 7% 12% 25% 18% 2	2619
	21st to end	Day	27% 5% 11% 31% 22% 3	2614
August	1st to 10th	Day	35% 7% 15% 26% 14% 4	2490
	11th to 20th	Day	31% 6% 19% 30% 14% 1	2333
	21st to end	Day	35% 6% 16% 28% 13% 2	2574
September	1st to 10th	Day	38% 6% 15% 24% 16% 2	2186
	11th to 20th	Day	41% 5% 16% 25% 13% 1	1990
	21st to end	Day	43% 6% 18% 23% 8% 1	1980
October	1st to 10th	Day	50% 7% 13% 22% 7% 1	1944
	11th to 20th	Day	45% 8% 18% 19% 9%	1638
	21st to end	Day	49% 10% 18% 17% 6% 1	1782
November	1st to 10th	Day	58% 10% 14% 13% 5% 1	1636
	11th to 20th	Day	48% 10% 21% 14% 6% 1	1449
	21st to end	Day	48% 12% 17% 15% 8% 1	1330
December	1st to 10th	Day	50% 10% 16% 15% 8% 2	1330
	11th to 20th	Day	57% 14% 13% 11% 5%	1684
	21st to end	Day	46% 11% 11% 17% 13% 3	2442
January	1st to 10th	Night	62% 10% 11% 10% 5% 2	2836
	11th to 20th	Night	53% 11% 14% 13% 6% 2	2695
	21st to end	Night	49% 11% 15% 14% 9% 1	2772
February	1st to 10th	Night	56% 8% 12% 14% 8% 2	2520
	11th to 20th	Night	54% 8% 16% 15% 7%	2271
	21st to end	Night	50% 8% 14% 19% 8% 2	1776
March	1st to 10th	Night	51% 11% 18% 13% 7%	2160
	11th to 20th	Night	47% 10% 18% 17% 7% 1	2032
	21st to end	Night	51% 10% 19% 15% 5% 1	2111
April	1st to 10th	Night	49% 9% 21% 14% 6%	1795
	11th to 20th	Night	48% 8% 18% 21% 5%	1601
	21st to end	Night	50% 6% 16% 22% 4 1	1620
May	1st to 10th	Night	48% 8% 20% 18% 6%	1529
	11th to 20th	Night	40% 8% 22% 25% 5% 1	1289
	21st to end	Night	53% 7% 18% 17% 5%	1358
June	1st to 10th	Night	45% 8% 20% 20% 6%	1260
	11th to 20th	Night	50% 8% 18% 17% 6%	1260
	21st to end	Night	32% 9% 21% 27% 11% 1	1260
July	1st to 10th	Night	26% 7% 21% 30% 13% 3	1225
	11th to 20th	Night	23% 7% 15% 29% 22% 3	1218
	21st to end	Night	20% 6% 14% 32% 24% 4	1461
August	1st to 10th	Night	28% 6% 15% 30% 17% 4	1424
	11th to 20th	Night	25% 6% 18% 35% 14% 1	1568
	21st to end	Night	27% 7% 15% 33% 17% 1	1782
September	1st to 10th	Night	27% 5% 18% 33% 13% 3	1772
	11th to 20th	Night	34% 8% 15% 30% 12% 2	1970
	21st to end	Night	37% 8% 22% 21% 11% 1	1980
October	1st to 10th	Night	41% 7% 15% 26% 10% 1	2016
	11th to 20th	Night	39% 10% 20% 22% 8% 1	2320
	21st to end	Night	48% 10% 16% 19% 7%	2574
November	1st to 10th	Night	55% 10% 14% 14% 5% 1	2424
	11th to 20th	Night	52% 10% 14% 16% 7% 1	2727
	21st to end	Night	53% 9% 14% 14% 8% 1	2850
December	1st to 10th	Night	54% 11% 13% 14% 8% 1	2850
	11th to 20th	Night	63% 13% 13% 8% 4	3507
	21st to end	Night	53% 12% 13% 11% 10% 2	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	16% 17% 36% 18% 8% 5%	180
	11th to 20th	Day	12% 16% 40% 25% 4 3	172
	21st to end	Day	13% 19% 47% 15% 5% 2	176
February	1st to 10th	Day	25% 18% 43% 10% 5%	160
	11th to 20th	Day	13% 18% 39% 25% 4	249
	21st to end	Day	13% 23% 37% 22% 4 1	346
March	1st to 10th	Day	23% 27% 29% 14% 5% 2	420
	11th to 20th	Day	22% 23% 28% 19% 5% 2	420
	21st to end	Day	19% 26% 31% 16% 6% 2	462
April	1st to 10th	Day	20% 24% 32% 19% 5% 1	420
	11th to 20th	Day	23% 23% 33% 13% 7% 2	412
	21st to end	Day	23% 24% 30% 14% 7% 2	420
May	1st to 10th	Day	21% 22% 27% 17% 10% 3	423
	11th to 20th	Day	21% 12% 26% 22% 14% 4	575
	21st to end	Day	25% 14% 19% 25% 14% 2	679
June	1st to 10th	Day	22% 19% 27% 20% 11% 2	630
	11th to 20th	Day	25% 19% 26% 20% 9% 2	630
	21st to end	Day	13% 16% 28% 25% 14% 4	630
July	1st to 10th	Day	13% 16% 26% 25% 17% 3	621
	11th to 20th	Day	15% 19% 25% 26% 13% 2	618
	21st to end	Day	8% 19% 32% 23% 13% 3	514
August	1st to 10th	Day	13% 15% 34% 25% 11% 2	447
	11th to 20th	Day	10% 18% 31% 29% 9% 3	437
	21st to end	Day	15% 17% 35% 22% 9% 3	495
September	1st to 10th	Day	18% 23% 31% 17% 8% 2	450
	11th to 20th	Day	18% 19% 33% 19% 8% 2	450
	21st to end	Day	25% 26% 28% 16% 5% 1	450
October	1st to 10th	Day	20% 21% 29% 19% 9% 3	414
	11th to 20th	Day	22% 21% 27% 17% 11% 2	270
	21st to end	Day	25% 20% 31% 18% 4 2	297
November	1st to 10th	Day	21% 23% 33% 18% 5% 1	270
	11th to 20th	Day	20% 22% 39% 15% 4	237
	21st to end	Day	17% 18% 37% 12% 10% 6%	180
December	1st to 10th	Day	16% 23% 33% 16% 8% 4	180
	11th to 20th	Day	12% 23% 40% 19% 5% 1	180
	21st to end	Day	10% 13% 43% 22% 10% 2	198
January	1st to 10th	Night	13% 17% 44% 20% 6% 1	950
	11th to 20th	Night	9% 15% 48% 22% 5% 1	827
	21st to end	Night	8% 18% 42% 25% 5% 1	792
February	1st to 10th	Night	11% 13% 43% 23% 8% 1	720
	11th to 20th	Night	11% 12% 43% 28% 6%	704
	21st to end	Night	7% 14% 37% 31% 10% 2	592
March	1st to 10th	Night	8% 16% 42% 24% 9% 1	720
	11th to 20th	Night	12% 19% 29% 29% 8% 2	720
	21st to end	Night	11% 13% 32% 30% 11% 2	792
April	1st to 10th	Night	12% 15% 29% 33% 10% 2	715
	11th to 20th	Night	11% 18% 33% 26% 10% 2	533
	21st to end	Night	12% 16% 32% 29% 10% 1	540
May	1st to 10th	Night	15% 9% 27% 33% 15% 1	449
	11th to 20th	Night	12% 10% 18% 33% 23% 4	354
	21st to end	Night	22% 9% 19% 28% 22% 2	389
June	1st to 10th	Night	17% 7% 26% 32% 16% 3	360
	11th to 20th	Night	21% 9% 25% 29% 15%	360
	21st to end	Night	10% 11% 19% 36% 22% 2	360
July	1st to 10th	Night	7% 5% 18% 45% 24% 1	350
	11th to 20th	Night	7% 7% 23% 43% 20%	348
	21st to end	Night	5% 7% 16% 47% 23% 2	394
August	1st to 10th	Night	8% 5% 13% 41% 32% 2	358
	11th to 20th	Night	8% 6% 19% 40% 25% 2	500
	21st to end	Night	11% 11% 23% 35% 19% 1	594
September	1st to 10th	Night	10% 10% 24% 31% 20% 5%	692
	11th to 20th	Night	13% 8% 21% 34% 20% 6%	720
	21st to end	Night	16% 12% 31% 26% 13% 3	720
October	1st to 10th	Night	14% 12% 23% 35% 14% 2	720
	11th to 20th	Night	11% 16% 29% 31% 12% 1	720
	21st to end	Night	13% 16% 34% 29% 7% 1	792
November	1st to 10th	Night	17% 15% 38% 23% 6%	759
	11th to 20th	Night	17% 19% 38% 21% 4 1	950
	21st to end	Night	12% 17% 41% 22% 7% 1	950
December	1st to 10th	Night	11% 17% 39% 25% 7% 1	950
	11th to 20th	Night	9% 17% 45% 24% 5% 1	950
	21st to end	Night	9% 14% 46% 25% 7%	1045

Page generated at 2024-01-14 07:55:02. Version ac07

Copyright 2024 Attilla Danko