Merrickville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Merrickville clear sky chart from 2005-11-06 to 2024-01-13.

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	18% 9% 4 7% 6% 3 5% 4 5% 6% 33%	74735
	Night	18% 10% 4 7% 6% 3 4 4 5% 6% 32%	74991
Transparency	Day	51% 6% 11% 19% 11% 1	74440
	Night	53% 6% 11% 19% 10% 1	74820
Seeing	Day	23% 17% 30% 19% 8% 3	13394
	Night	23% 14% 30% 24% 8% 1	22626

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	16% 19% 7% 9% 7% 3 5% 5% 4 4 21%	1517
	11th to 20th	Day	20% 15% 6% 10% 7% 4 4 3 3 4 24%	1456
	21st to end	Day	14% 14% 5% 11% 7% 5% 5% 5% 5% 5% 23%	1670
February	1st to 10th	Day	17% 14% 5% 10% 9% 4 5% 5% 4 5% 23%	1620
	11th to 20th	Day	14% 15% 6% 8% 7% 3 5% 4 4 5% 28%	1584
	21st to end	Day	20% 15% 6% 7% 8% 3 4 5% 4 4 23%	1480
March	1st to 10th	Day	16% 12% 6% 10% 6% 4 5% 4 3 5% 28%	1799
	11th to 20th	Day	18% 13% 4 7% 7% 4 4 4 4 6% 31%	1980
	21st to end	Day	20% 11% 3 6% 5% 2 3 3 4 5% 37%	2291
April	1st to 10th	Day	21% 11% 4 6% 6% 2 4 4 5% 5% 33%	2160
	11th to 20th	Day	21% 8% 3 6% 5% 3 4 4 4 5% 37%	2134
	21st to end	Day	24% 9% 3 7% 5% 3 4 3 5% 5% 32%	2260
May	1st to 10th	Day	19% 9% 3 6% 5% 3 5% 4 4 6% 35%	2520
	11th to 20th	Day	17% 7% 3 6% 5% 3 4 4 4 7% 40%	2478
	21st to end	Day	15% 6% 3 5% 5% 3 6% 5% 6% 7% 39%	2725
June	1st to 10th	Day	22% 8% 3 5% 6% 4 4 5% 6% 7% 30%	2520
	11th to 20th	Day	16% 6% 3 5% 6% 3 5% 5% 6% 8% 38%	2520
	21st to end	Day	19% 7% 3 6% 6% 4 5% 5% 6% 7% 32%	2520
July	1st to 10th	Day	12% 5% 3 5% 5% 3 5% 5% 6% 8% 42%	2520
	11th to 20th	Day	12% 6% 3 5% 5% 3 5% 6% 7% 8% 39%	2520
	21st to end	Day	11% 5% 2 6% 6% 4 6% 6% 8% 8% 38%	2744
August	1st to 10th	Day	12% 6% 2 7% 6% 4 5% 5% 5% 8% 39%	2453
	11th to 20th	Day	13% 6% 2 5% 5% 3 5% 5% 6% 9% 39%	2269
	21st to end	Day	14% 5% 2 5% 6% 3 5% 5% 5% 9% 40%	2376
September	1st to 10th	Day	14% 5% 3 5% 6% 4 5% 5% 5% 7% 41%	2160
	11th to 20th	Day	15% 5% 2 5% 5% 3 4 4 4 7% 46%	2160
	21st to end	Day	18% 6% 3 5% 4 3 5% 4 5% 7% 40%	1922
October	1st to 10th	Day	22% 7% 3 7% 5% 2 5% 3 4 6% 36%	1800
	11th to 20th	Day	22% 9% 3 7% 6% 3 5% 4 4 6% 29%	1800
	21st to end	Day	27% 10% 4 5% 6% 3 4 5% 5% 5% 27%	1846
November	1st to 10th	Day	16% 7% 3 6% 6% 4 6% 6% 6% 6% 33%	1671
	11th to 20th	Day	18% 12% 4 8% 7% 4 5% 4 4 6% 29%	1542
	21st to end	Day	22% 13% 5% 8% 8% 3 5% 4 5% 5% 22%	1520
December	1st to 10th	Day	25% 15% 5% 9% 7% 3 4 4 5% 5% 18%	1520
	11th to 20th	Day	22% 15% 5% 8% 7% 3 4 4 3 4 25%	1906
	21st to end	Day	27% 17% 6% 9% 6% 3 4 3 3 3 20%	2772
January	1st to 10th	Night	19% 15% 6% 12% 7% 4 5% 3 4 4 21%	2649
	11th to 20th	Night	20% 15% 5% 10% 8% 3 4 4 5% 5% 22%	2549
	21st to end	Night	14% 12% 6% 11% 8% 4 5% 4 4 5% 27%	2683
February	1st to 10th	Night	17% 15% 6% 11% 8% 4 5% 4 5% 5% 21%	2340
	11th to 20th	Night	15% 14% 5% 9% 7% 4 5% 4 3 5% 30%	2261
	21st to end	Night	17% 14% 5% 8% 7% 4 5% 3 4 4 29%	1776
March	1st to 10th	Night	17% 13% 5% 8% 7% 4 5% 4 3 5% 30%	2146
	11th to 20th	Night	18% 13% 5% 7% 6% 2 4 3 4 5% 34%	1979
	21st to end	Night	19% 9% 3 7% 5% 3 3 4 3 5% 38%	2064
April	1st to 10th	Night	21% 10% 5% 6% 5% 3 4 3 4 7% 33%	1800
	11th to 20th	Night	21% 7% 3 6% 6% 3 3 4 4 5% 37%	1775
	21st to end	Night	22% 10% 2 7% 5% 3 3 6% 4 5% 33%	1715
May	1st to 10th	Night	23% 7% 3 5% 5% 2 4 5% 5% 6% 36%	1440
	11th to 20th	Night	16% 7% 3 5% 5% 2 4 4 5% 6% 41%	1415
	21st to end	Night	13% 6% 3 5% 4 3 5% 4 5% 7% 46%	1550
June	1st to 10th	Night	18% 5% 4 6% 5% 3 5% 5% 6% 8% 34%	1440
	11th to 20th	Night	16% 6% 2 5% 4 2 5% 4 5% 8% 41%	1440
	21st to end	Night	16% 7% 3 5% 5% 3 6% 5% 5% 8% 36%	1440
July	1st to 10th	Night	9% 4 3 6% 6% 3 4 5% 5% 9% 46%	1440
	11th to 20th	Night	12% 4 3 5% 5% 3 5% 6% 6% 9% 43%	1440
	21st to end	Night	10% 4 2 5% 4 3 5% 7% 7% 8% 46%	1574
August	1st to 10th	Night	10% 6% 2 5% 6% 4 5% 5% 6% 8% 42%	1483
	11th to 20th	Night	11% 6% 3 7% 4 4 4 4 6% 8% 44%	1612
	21st to end	Night	13% 4 2 6% 5% 3 5% 4 6% 7% 45%	1980
September	1st to 10th	Night	13% 6% 2 6% 5% 3 4 5% 5% 5% 46%	1800
	11th to 20th	Night	15% 5% 2 4 4 2 3 4 5% 7% 50%	1800
	21st to end	Night	16% 6% 3 5% 5% 2 4 4 5% 6% 42%	2035
October	1st to 10th	Night	17% 7% 4 6% 5% 3 5% 5% 5% 7% 36%	2160
	11th to 20th	Night	21% 9% 3 6% 6% 3 4 4 6% 7% 32%	2160
	21st to end	Night	25% 9% 3 7% 5% 3 4 4 5% 6% 28%	2510
November	1st to 10th	Night	19% 10% 4 5% 5% 3 4 4 4 6% 36%	2407
	11th to 20th	Night	18% 10% 4 7% 6% 3 4 5% 4 5% 32%	2636
	21st to end	Night	22% 13% 4 8% 6% 4 4 4 4 6% 24%	2660
December	1st to 10th	Night	21% 17% 7% 10% 7% 4 4 4 4 4 19%	2660
	11th to 20th	Night	22% 15% 4 8% 6% 2 4 4 3 4 27%	3288
	21st to end	Night	31% 15% 4 10% 6% 3 3 4 3 4 17%	4884

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	67% 6% 10% 12% 6%	1518
	11th to 20th	Day	66% 5% 7% 11% 9% 1	1456
	21st to end	Day	63% 5% 11% 12% 8% 1	1670
February	1st to 10th	Day	64% 5% 8% 17% 4 2	1620
	11th to 20th	Day	59% 5% 10% 16% 9% 1	1593
	21st to end	Day	65% 6% 8% 11% 9% 1	1480
March	1st to 10th	Day	59% 4 11% 15% 10% 1	1802
	11th to 20th	Day	56% 4 11% 14% 12% 3	1980
	21st to end	Day	51% 4 7% 17% 14% 6%	2291
April	1st to 10th	Day	54% 5% 7% 19% 13% 3	2160
	11th to 20th	Day	50% 4 8% 19% 16% 2	2134
	21st to end	Day	55% 5% 8% 14% 14% 4	2260
May	1st to 10th	Day	50% 5% 9% 18% 15% 3	2520
	11th to 20th	Day	45% 5% 10% 22% 15% 2	2482
	21st to end	Day	43% 9% 12% 21% 13% 2	2725
June	1st to 10th	Day	52% 7% 10% 19% 12% 1	2520
	11th to 20th	Day	43% 7% 9% 25% 13% 2	2520
	21st to end	Day	50% 9% 11% 18% 11% 1	2520
July	1st to 10th	Day	37% 7% 12% 28% 15% 1	2450
	11th to 20th	Day	38% 9% 16% 27% 10%	2445
	21st to end	Day	41% 10% 15% 23% 10%	2591
August	1st to 10th	Day	43% 8% 14% 24% 10%	2439
	11th to 20th	Day	40% 8% 15% 25% 10% 1	2269
	21st to end	Day	40% 7% 14% 27% 12%	2376
September	1st to 10th	Day	40% 8% 13% 26% 13%	2160
	11th to 20th	Day	37% 7% 11% 30% 14%	2160
	21st to end	Day	43% 7% 14% 27% 9%	1922
October	1st to 10th	Day	51% 4 11% 22% 11%	1800
	11th to 20th	Day	55% 8% 13% 16% 7% 1	1800
	21st to end	Day	59% 7% 10% 15% 8% 1	1846
November	1st to 10th	Day	49% 7% 14% 21% 7% 1	1671
	11th to 20th	Day	56% 7% 11% 15% 10% 1	1542
	21st to end	Day	64% 7% 11% 11% 6%	1520
December	1st to 10th	Day	69% 6% 11% 10% 2 1	1520
	11th to 20th	Day	64% 5% 15% 12% 3	1906
	21st to end	Day	72% 4 8% 13% 4	2772
January	1st to 10th	Night	68% 6% 10% 12% 5%	2649
	11th to 20th	Night	66% 6% 10% 10% 7% 1	2549
	21st to end	Night	60% 5% 8% 16% 9% 1	2683
February	1st to 10th	Night	66% 5% 10% 13% 6% 1	2340
	11th to 20th	Night	59% 4 10% 19% 7%	2263
	21st to end	Night	60% 5% 8% 16% 10% 1	1776
March	1st to 10th	Night	58% 4 11% 15% 10% 1	2156
	11th to 20th	Night	54% 5% 10% 18% 11% 2	1980
	21st to end	Night	50% 4 8% 19% 16% 4	2064
April	1st to 10th	Night	53% 4 9% 20% 13% 2	1800
	11th to 20th	Night	50% 5% 8% 18% 17% 2	1775
	21st to end	Night	53% 5% 9% 15% 15% 3	1715
May	1st to 10th	Night	49% 6% 8% 17% 15% 5%	1440
	11th to 20th	Night	43% 6% 9% 22% 18% 3	1416
	21st to end	Night	37% 8% 15% 20% 16% 3	1551
June	1st to 10th	Night	48% 9% 12% 19% 11% 1	1440
	11th to 20th	Night	41% 7% 11% 21% 17% 2	1440
	21st to end	Night	45% 10% 11% 20% 13% 1	1440
July	1st to 10th	Night	35% 8% 11% 27% 18% 2	1400
	11th to 20th	Night	36% 7% 14% 30% 13%	1392
	21st to end	Night	34% 9% 16% 26% 14% 1	1486
August	1st to 10th	Night	38% 10% 15% 23% 13% 1	1473
	11th to 20th	Night	39% 7% 15% 26% 13% 1	1612
	21st to end	Night	37% 9% 13% 28% 13% 1	1980
September	1st to 10th	Night	39% 8% 11% 28% 14% 1	1800
	11th to 20th	Night	33% 7% 14% 34% 11% 1	1800
	21st to end	Night	41% 6% 11% 30% 11% 1	2035
October	1st to 10th	Night	48% 8% 9% 22% 13% 1	2160
	11th to 20th	Night	50% 7% 13% 20% 9%	2160
	21st to end	Night	57% 7% 13% 14% 9% 1	2510
November	1st to 10th	Night	49% 6% 14% 21% 10% 1	2407
	11th to 20th	Night	54% 6% 12% 17% 10% 1	2636
	21st to end	Night	61% 7% 12% 14% 5%	2660
December	1st to 10th	Night	69% 6% 10% 12% 3	2660
	11th to 20th	Night	62% 4 10% 16% 8% 1	3288
	21st to end	Night	72% 5% 8% 12% 3	4884

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	23% 24% 33% 14% 5%	180
	11th to 20th	Day	34% 18% 29% 15% 3 1	164
	21st to end	Day	23% 27% 31% 13% 6%	214
February	1st to 10th	Day	35% 29% 29% 7%	240
	11th to 20th	Day	31% 26% 37% 6%	251
	21st to end	Day	33% 20% 33% 13% 1	346
March	1st to 10th	Day	25% 21% 32% 17% 4	420
	11th to 20th	Day	29% 20% 35% 13% 3 1	420
	21st to end	Day	30% 22% 27% 14% 6% 1	462
April	1st to 10th	Day	31% 21% 28% 15% 5% 1	420
	11th to 20th	Day	32% 19% 24% 14% 8% 3	412
	21st to end	Day	31% 21% 28% 14% 5% 2	420
May	1st to 10th	Day	26% 19% 29% 17% 7% 2	423
	11th to 20th	Day	22% 18% 34% 18% 7% 2	447
	21st to end	Day	21% 16% 29% 22% 10% 1	485
June	1st to 10th	Day	24% 14% 33% 21% 7% 1	450
	11th to 20th	Day	16% 16% 33% 23% 10% 3	450
	21st to end	Day	20% 14% 33% 19% 10% 3	450
July	1st to 10th	Day	13% 8% 29% 34% 13% 3	445
	11th to 20th	Day	14% 13% 29% 28% 14% 3	444
	21st to end	Day	14% 8% 33% 32% 9% 3	488
August	1st to 10th	Day	15% 9% 27% 32% 13% 3	446
	11th to 20th	Day	16% 5% 28% 27% 17% 7%	439
	21st to end	Day	15% 13% 32% 21% 13% 7%	495
September	1st to 10th	Day	14% 13% 30% 23% 13% 7%	450
	11th to 20th	Day	15% 9% 27% 23% 14% 11%	450
	21st to end	Day	19% 13% 29% 22% 12% 5%	450
October	1st to 10th	Day	26% 15% 25% 17% 12% 5%	450
	11th to 20th	Day	26% 20% 30% 18% 5% 1	450
	21st to end	Day	34% 14% 27% 21% 4	428
November	1st to 10th	Day	27% 19% 28% 18% 6% 1	365
	11th to 20th	Day	24% 24% 32% 12% 6% 2	202
	21st to end	Day	29% 21% 35% 11% 4	180
December	1st to 10th	Day	33% 21% 32% 12% 2	180
	11th to 20th	Day	31% 30% 28% 9% 2 1	180
	21st to end	Day	35% 21% 29% 12% 2 1	198
January	1st to 10th	Night	27% 19% 33% 17% 4	760
	11th to 20th	Night	31% 18% 27% 20% 3 1	729
	21st to end	Night	21% 16% 34% 24% 4	792
February	1st to 10th	Night	26% 20% 34% 17% 3	720
	11th to 20th	Night	23% 18% 39% 16% 2	703
	21st to end	Night	25% 20% 33% 18% 4	592
March	1st to 10th	Night	25% 16% 33% 22% 3	720
	11th to 20th	Night	27% 21% 29% 19% 5%	720
	21st to end	Night	25% 16% 29% 24% 6% 1	792
April	1st to 10th	Night	27% 15% 31% 24% 3	720
	11th to 20th	Night	28% 16% 29% 19% 7%	711
	21st to end	Night	27% 14% 28% 23% 7%	635
May	1st to 10th	Night	26% 10% 26% 28% 9% 2	360
	11th to 20th	Night	19% 10% 38% 26% 7%	354
	21st to end	Night	15% 10% 38% 25% 12%	389
June	1st to 10th	Night	19% 8% 31% 35% 7% 1	360
	11th to 20th	Night	16% 11% 30% 31% 12% 1	360
	21st to end	Night	19% 6% 32% 28% 13%	360
July	1st to 10th	Night	8% 8% 31% 40% 13% 1	350
	11th to 20th	Night	14% 4 26% 41% 15% 1	348
	21st to end	Night	10% 4 32% 42% 12% 1	394
August	1st to 10th	Night	14% 4 26% 36% 19% 1	409
	11th to 20th	Night	12% 3 26% 35% 23% 2	548
	21st to end	Night	13% 8% 30% 31% 17% 2	792
September	1st to 10th	Night	16% 7% 30% 31% 15% 1	720
	11th to 20th	Night	18% 7% 24% 29% 19% 4	720
	21st to end	Night	18% 11% 25% 24% 20% 1	720
October	1st to 10th	Night	20% 13% 29% 22% 14% 2	720
	11th to 20th	Night	26% 13% 30% 22% 8%	720
	21st to end	Night	30% 14% 27% 24% 5%	792
November	1st to 10th	Night	26% 15% 30% 19% 9%	740
	11th to 20th	Night	25% 17% 31% 17% 9%	760
	21st to end	Night	31% 17% 27% 19% 6%	760
December	1st to 10th	Night	31% 18% 29% 18% 3	760
	11th to 20th	Night	29% 18% 31% 17% 4 1	760
	21st to end	Night	35% 16% 29% 18% 2	836

Page generated at 2024-01-10 01:25:00. Version ac07

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