Jock River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jock River Observatory 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	18% 9% 3 7% 6% 3 5% 5% 5% 6% 33%	74764
	Night	18% 10% 4 7% 6% 3 4 4 5% 6% 33%	75054
Transparency	Day	51% 5% 12% 21% 10% 1	74469
	Night	53% 4 11% 20% 10% 1	74883
Seeing	Day	22% 14% 30% 21% 10% 3	13379
	Night	23% 12% 30% 26% 9% 1	22605

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	17% 17% 6% 10% 8% 3 4 4 4 3 22%	1517
	11th to 20th	Day	19% 15% 6% 9% 7% 3 5% 4 4 4 24%	1488
	21st to end	Day	13% 13% 6% 9% 6% 4 6% 6% 6% 5% 25%	1652
February	1st to 10th	Day	15% 16% 5% 10% 7% 4 5% 5% 5% 5% 24%	1620
	11th to 20th	Day	14% 15% 5% 7% 7% 3 5% 4 5% 6% 29%	1583
	21st to end	Day	20% 14% 4 8% 7% 3 5% 5% 5% 5% 25%	1480
March	1st to 10th	Day	15% 12% 4 9% 7% 4 5% 5% 5% 5% 30%	1797
	11th to 20th	Day	17% 10% 4 8% 6% 4 5% 4 5% 6% 32%	1972
	21st to end	Day	20% 10% 3 6% 5% 2 3 4 4 5% 38%	2297
April	1st to 10th	Day	23% 10% 4 6% 5% 3 4 3 4 6% 32%	2160
	11th to 20th	Day	21% 8% 3 6% 5% 3 4 4 4 5% 37%	2134
	21st to end	Day	23% 10% 3 6% 5% 3 4 4 4 5% 33%	2277
May	1st to 10th	Day	21% 7% 3 6% 5% 3 5% 4 5% 7% 35%	2520
	11th to 20th	Day	17% 7% 3 5% 6% 3 4 5% 5% 7% 40%	2478
	21st to end	Day	16% 5% 3 5% 6% 4 5% 5% 6% 7% 38%	2725
June	1st to 10th	Day	22% 7% 3 6% 6% 3 6% 5% 5% 6% 30%	2520
	11th to 20th	Day	15% 6% 2 6% 5% 3 6% 6% 6% 8% 39%	2520
	21st to end	Day	18% 6% 4 6% 7% 3 6% 6% 5% 7% 32%	2520
July	1st to 10th	Day	12% 5% 2 5% 5% 4 5% 6% 6% 8% 42%	2520
	11th to 20th	Day	13% 5% 3 5% 5% 4 5% 6% 6% 9% 40%	2520
	21st to end	Day	11% 5% 3 5% 5% 4 6% 6% 7% 9% 39%	2744
August	1st to 10th	Day	12% 6% 2 6% 6% 4 5% 6% 5% 7% 40%	2472
	11th to 20th	Day	12% 6% 3 6% 5% 4 5% 5% 6% 8% 41%	2272
	21st to end	Day	14% 5% 2 6% 5% 3 5% 5% 6% 9% 41%	2376
September	1st to 10th	Day	14% 5% 2 5% 5% 3 4 6% 5% 8% 42%	2160
	11th to 20th	Day	14% 5% 2 5% 5% 2 4 4 5% 8% 46%	2158
	21st to end	Day	17% 6% 2 5% 5% 3 4 5% 5% 7% 40%	1926
October	1st to 10th	Day	22% 7% 3 5% 6% 3 5% 4 5% 7% 35%	1800
	11th to 20th	Day	22% 8% 3 7% 8% 4 5% 5% 6% 6% 28%	1800
	21st to end	Day	26% 10% 4 6% 5% 3 5% 4 4 5% 27%	1832
November	1st to 10th	Day	16% 9% 4 6% 5% 4 5% 5% 5% 7% 33%	1671
	11th to 20th	Day	20% 11% 4 8% 6% 4 4 4 4 6% 29%	1535
	21st to end	Day	21% 13% 4 8% 7% 5% 5% 5% 5% 6% 21%	1520
December	1st to 10th	Day	23% 14% 5% 10% 6% 5% 4 4 5% 5% 18%	1520
	11th to 20th	Day	22% 15% 4 9% 6% 4 5% 4 4 5% 24%	1906
	21st to end	Day	28% 15% 5% 11% 6% 3 3 3 3 3 20%	2772
January	1st to 10th	Night	18% 15% 7% 11% 6% 4 5% 5% 4 5% 19%	2649
	11th to 20th	Night	18% 16% 6% 10% 8% 3 5% 4 4 4 22%	2616
	21st to end	Night	13% 14% 6% 9% 7% 3 4 4 4 6% 30%	2701
February	1st to 10th	Night	15% 14% 5% 11% 7% 4 6% 5% 5% 5% 22%	2340
	11th to 20th	Night	14% 12% 6% 10% 7% 3 5% 5% 5% 4 29%	2262
	21st to end	Night	17% 14% 4 7% 7% 4 5% 5% 4 5% 30%	1776
March	1st to 10th	Night	17% 13% 5% 8% 7% 3 5% 4 4 4 30%	2150
	11th to 20th	Night	17% 12% 5% 6% 7% 3 3 3 4 5% 35%	1984
	21st to end	Night	19% 8% 4 6% 5% 3 4 3 4 4 39%	2058
April	1st to 10th	Night	22% 10% 3 6% 5% 3 4 4 4 6% 33%	1800
	11th to 20th	Night	19% 9% 3 6% 6% 3 4 4 4 5% 37%	1775
	21st to end	Night	23% 8% 3 6% 6% 3 4 4 5% 7% 33%	1697
May	1st to 10th	Night	22% 7% 2 4 4 3 4 5% 6% 6% 35%	1440
	11th to 20th	Night	18% 8% 3 5% 4 2 3 5% 4 7% 40%	1415
	21st to end	Night	13% 6% 3 4 5% 3 4 4 6% 7% 45%	1550
June	1st to 10th	Night	17% 6% 3 6% 7% 3 5% 5% 6% 8% 33%	1440
	11th to 20th	Night	16% 5% 2 6% 4 3 4 5% 5% 8% 42%	1440
	21st to end	Night	18% 6% 2 6% 6% 3 5% 4 5% 7% 36%	1440
July	1st to 10th	Night	11% 4 2 6% 5% 4 5% 4 5% 9% 46%	1440
	11th to 20th	Night	12% 5% 2 5% 5% 3 6% 5% 6% 9% 43%	1440
	21st to end	Night	10% 4 3 6% 6% 3 4 5% 6% 9% 44%	1574
August	1st to 10th	Night	9% 6% 3 6% 6% 3 3 6% 5% 9% 43%	1462
	11th to 20th	Night	11% 6% 2 5% 6% 3 4 5% 6% 8% 44%	1611
	21st to end	Night	12% 5% 2 5% 5% 3 4 4 6% 8% 45%	1980
September	1st to 10th	Night	12% 5% 3 6% 6% 3 4 4 5% 7% 46%	1800
	11th to 20th	Night	15% 4 2 5% 4 2 3 4 5% 8% 49%	1801
	21st to end	Night	16% 5% 3 6% 5% 4 3 3 4 7% 44%	2031
October	1st to 10th	Night	18% 7% 4 6% 4 3 4 4 6% 6% 37%	2160
	11th to 20th	Night	21% 10% 3 7% 6% 3 4 5% 4 6% 32%	2160
	21st to end	Night	24% 10% 4 7% 6% 3 4 4 5% 6% 28%	2522
November	1st to 10th	Night	20% 10% 4 6% 6% 2 3 3 4 6% 36%	2407
	11th to 20th	Night	18% 10% 4 7% 7% 4 4 4 5% 6% 31%	2641
	21st to end	Night	22% 12% 5% 8% 6% 4 4 4 5% 6% 25%	2660
December	1st to 10th	Night	21% 16% 5% 9% 8% 3 6% 5% 5% 5% 17%	2660
	11th to 20th	Night	23% 15% 5% 8% 6% 3 3 4 3 4 27%	3288
	21st to end	Night	31% 17% 4 9% 5% 3 3 4 3 3 18%	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	68% 4 9% 14% 5%	1518
	11th to 20th	Day	65% 3 9% 12% 10% 1	1488
	21st to end	Day	59% 6% 12% 14% 8% 1	1652
February	1st to 10th	Day	62% 4 9% 19% 4 2	1620
	11th to 20th	Day	57% 4 12% 18% 8% 1	1592
	21st to end	Day	61% 4 10% 15% 9% 1	1480
March	1st to 10th	Day	57% 4 11% 18% 10% 1	1800
	11th to 20th	Day	54% 4 12% 16% 11% 3	1972
	21st to end	Day	49% 4 9% 19% 14% 5%	2297
April	1st to 10th	Day	54% 4 6% 21% 12% 3	2160
	11th to 20th	Day	50% 3 7% 22% 15% 2	2134
	21st to end	Day	55% 3 8% 15% 14% 4	2277
May	1st to 10th	Day	49% 4 8% 20% 15% 4	2520
	11th to 20th	Day	45% 5% 9% 22% 16% 3	2482
	21st to end	Day	45% 5% 13% 21% 13% 2	2725
June	1st to 10th	Day	54% 5% 10% 19% 12% 1	2520
	11th to 20th	Day	43% 6% 12% 24% 13% 3	2520
	21st to end	Day	50% 6% 14% 20% 10% 1	2520
July	1st to 10th	Day	37% 6% 14% 27% 15% 1	2450
	11th to 20th	Day	39% 5% 16% 28% 11%	2445
	21st to end	Day	41% 7% 15% 26% 11%	2591
August	1st to 10th	Day	42% 7% 15% 26% 10%	2458
	11th to 20th	Day	41% 5% 17% 26% 10% 1	2272
	21st to end	Day	40% 5% 14% 28% 13% 1	2376
September	1st to 10th	Day	40% 6% 14% 29% 12%	2160
	11th to 20th	Day	37% 5% 12% 32% 13% 1	2158
	21st to end	Day	44% 5% 15% 27% 9%	1926
October	1st to 10th	Day	50% 5% 12% 23% 10% 1	1800
	11th to 20th	Day	56% 5% 15% 16% 6% 1	1800
	21st to end	Day	60% 4 12% 15% 8%	1832
November	1st to 10th	Day	49% 6% 15% 22% 7% 1	1671
	11th to 20th	Day	57% 4 13% 15% 9% 1	1535
	21st to end	Day	64% 5% 13% 11% 6%	1520
December	1st to 10th	Day	68% 6% 12% 11% 3 1	1520
	11th to 20th	Day	64% 5% 13% 14% 4	1906
	21st to end	Day	72% 3 7% 14% 3	2772
January	1st to 10th	Night	69% 4 10% 12% 5%	2649
	11th to 20th	Night	67% 4 9% 11% 8% 1	2616
	21st to end	Night	57% 4 9% 18% 11% 1	2701
February	1st to 10th	Night	64% 4 9% 16% 7% 1	2340
	11th to 20th	Night	58% 4 11% 19% 8% 1	2264
	21st to end	Night	57% 4 9% 18% 11% 1	1776
March	1st to 10th	Night	58% 3 10% 17% 11% 2	2160
	11th to 20th	Night	53% 3 10% 19% 12% 3	1985
	21st to end	Night	49% 3 7% 20% 16% 4	2058
April	1st to 10th	Night	53% 4 9% 18% 14% 2	1800
	11th to 20th	Night	50% 4 7% 22% 16% 1	1775
	21st to end	Night	52% 4 8% 17% 16% 4	1697
May	1st to 10th	Night	49% 5% 7% 20% 15% 5%	1440
	11th to 20th	Night	45% 4 7% 23% 19% 2	1416
	21st to end	Night	38% 5% 16% 21% 18% 2	1551
June	1st to 10th	Night	47% 7% 12% 22% 10% 1	1440
	11th to 20th	Night	41% 5% 12% 24% 17% 2	1440
	21st to end	Night	47% 6% 13% 20% 14% 1	1440
July	1st to 10th	Night	36% 6% 12% 28% 17% 2	1400
	11th to 20th	Night	37% 5% 13% 32% 13%	1392
	21st to end	Night	37% 6% 15% 27% 14%	1486
August	1st to 10th	Night	38% 7% 18% 24% 13% 1	1452
	11th to 20th	Night	38% 5% 16% 28% 12%	1611
	21st to end	Night	37% 4 17% 29% 12% 1	1980
September	1st to 10th	Night	39% 6% 11% 29% 15% 1	1800
	11th to 20th	Night	35% 4 14% 35% 10% 1	1801
	21st to end	Night	42% 5% 12% 31% 11%	2031
October	1st to 10th	Night	47% 5% 11% 23% 14% 1	2160
	11th to 20th	Night	54% 4 12% 21% 9%	2160
	21st to end	Night	58% 4 13% 16% 8%	2522
November	1st to 10th	Night	52% 3 14% 21% 9% 1	2407
	11th to 20th	Night	55% 4 12% 18% 9% 1	2641
	21st to end	Night	61% 4 13% 16% 5%	2660
December	1st to 10th	Night	68% 5% 9% 13% 4	2660
	11th to 20th	Night	63% 4 9% 16% 7% 1	3288
	21st to end	Night	72% 3 8% 13% 4	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% 21% 27% 25% 5%	180
	11th to 20th	Day	31% 16% 33% 15% 5% 1	172
	21st to end	Day	21% 21% 33% 18% 7%	206
February	1st to 10th	Day	35% 23% 33% 10%	240
	11th to 20th	Day	27% 26% 38% 10%	250
	21st to end	Day	30% 19% 32% 17% 2	346
March	1st to 10th	Day	25% 17% 35% 18% 6%	420
	11th to 20th	Day	28% 15% 34% 19% 4	420
	21st to end	Day	30% 19% 25% 16% 8% 1	462
April	1st to 10th	Day	29% 19% 30% 16% 5% 1	420
	11th to 20th	Day	30% 20% 21% 16% 11% 2	412
	21st to end	Day	34% 16% 28% 15% 7% 1	420
May	1st to 10th	Day	24% 15% 31% 21% 6% 3	423
	11th to 20th	Day	20% 16% 34% 20% 8% 3	447
	21st to end	Day	18% 15% 33% 23% 11% 1	485
June	1st to 10th	Day	26% 10% 31% 22% 9% 2	450
	11th to 20th	Day	17% 14% 30% 25% 11% 3	450
	21st to end	Day	20% 12% 29% 24% 12% 3	450
July	1st to 10th	Day	13% 6% 29% 31% 18% 3	445
	11th to 20th	Day	12% 8% 31% 29% 16% 4	444
	21st to end	Day	14% 7% 30% 31% 15% 4	488
August	1st to 10th	Day	14% 8% 27% 30% 18% 4	446
	11th to 20th	Day	13% 7% 24% 29% 18% 9%	439
	21st to end	Day	14% 10% 29% 26% 13% 8%	495
September	1st to 10th	Day	17% 10% 28% 20% 15% 9%	450
	11th to 20th	Day	14% 8% 26% 24% 18% 10%	450
	21st to end	Day	17% 10% 32% 20% 16% 5%	450
October	1st to 10th	Day	25% 14% 24% 21% 12% 5%	450
	11th to 20th	Day	26% 16% 29% 21% 6% 2	450
	21st to end	Day	32% 15% 26% 22% 5%	421
November	1st to 10th	Day	25% 16% 30% 19% 8% 1	365
	11th to 20th	Day	27% 18% 34% 14% 4 3	195
	21st to end	Day	28% 19% 33% 15% 4 1	180
December	1st to 10th	Day	29% 18% 35% 15% 3	180
	11th to 20th	Day	31% 24% 29% 13% 2 1	180
	21st to end	Day	32% 21% 32% 12% 3 1	198
January	1st to 10th	Night	25% 16% 34% 20% 4	760
	11th to 20th	Night	28% 17% 29% 21% 5%	748
	21st to end	Night	19% 13% 37% 26% 5% 1	792
February	1st to 10th	Night	25% 14% 37% 20% 4	720
	11th to 20th	Night	22% 16% 37% 20% 4	703
	21st to end	Night	24% 18% 30% 23% 4	592
March	1st to 10th	Night	24% 15% 36% 23% 3	720
	11th to 20th	Night	23% 19% 32% 20% 5%	720
	21st to end	Night	25% 14% 27% 25% 8% 1	792
April	1st to 10th	Night	27% 13% 30% 23% 6%	720
	11th to 20th	Night	24% 16% 28% 23% 8%	711
	21st to end	Night	27% 14% 28% 24% 7% 1	617
May	1st to 10th	Night	25% 9% 29% 27% 9% 1	360
	11th to 20th	Night	23% 10% 27% 31% 9%	354
	21st to end	Night	14% 6% 39% 27% 13%	389
June	1st to 10th	Night	19% 6% 31% 35% 8% 1	360
	11th to 20th	Night	18% 7% 27% 35% 12% 1	360
	21st to end	Night	20% 5% 32% 28% 14% 1	360
July	1st to 10th	Night	9% 7% 29% 41% 15%	350
	11th to 20th	Night	12% 4 25% 42% 16% 1	348
	21st to end	Night	10% 4 30% 40% 15% 2	394
August	1st to 10th	Night	12% 3 24% 39% 20% 1	388
	11th to 20th	Night	13% 3 21% 38% 23% 2	547
	21st to end	Night	14% 6% 27% 32% 20% 2	792
September	1st to 10th	Night	14% 7% 28% 33% 17% 1	720
	11th to 20th	Night	17% 6% 22% 31% 21% 3	720
	21st to end	Night	18% 8% 25% 26% 20% 2	720
October	1st to 10th	Night	21% 9% 28% 26% 15% 2	720
	11th to 20th	Night	26% 12% 29% 24% 8% 1	720
	21st to end	Night	27% 14% 27% 26% 6%	792
November	1st to 10th	Night	28% 13% 28% 23% 9% 1	740
	11th to 20th	Night	25% 16% 32% 17% 9% 1	760
	21st to end	Night	29% 16% 26% 22% 7%	760
December	1st to 10th	Night	31% 15% 29% 22% 4	760
	11th to 20th	Night	28% 16% 30% 19% 6% 1	760
	21st to end	Night	34% 13% 31% 18% 4	836

Page generated at 2024-01-14 09:55:00. Version ac07

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