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 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	17% 10% 3 8% 5% 5% 5% 4 5% 7% 33%	105183
	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 31%	103839
Transparency	Day	51% 5% 12% 22% 10% 1	108666
	Night	53% 5% 12% 20% 10% 1	108445
Seeing	Day	22% 14% 30% 21% 10% 3	14623
	Night	23% 12% 29% 26% 9% 1	23809

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% 16% 6% 11% 6% 5% 5% 4 5% 4 22%	2565
	11th to 20th	Day	15% 14% 6% 12% 7% 5% 6% 3 4 5% 23%	2520
	21st to end	Day	15% 16% 7% 12% 6% 6% 5% 4 5% 5% 18%	2882
February	1st to 10th	Day	14% 16% 4 12% 6% 5% 5% 4 5% 5% 25%	1710
	11th to 20th	Day	13% 16% 5% 9% 6% 4 4 3 5% 5% 29%	1673
	21st to end	Day	19% 14% 3 8% 6% 5% 4 4 5% 5% 26%	1570
March	1st to 10th	Day	20% 13% 3 9% 6% 5% 4 3 4 5% 27%	3116
	11th to 20th	Day	12% 15% 5% 10% 6% 5% 5% 3 5% 6% 29%	3472
	21st to end	Day	14% 9% 2 7% 5% 3 4 3 5% 6% 43%	4031
April	1st to 10th	Day	22% 11% 3 7% 5% 4 3 3 4 6% 32%	2280
	11th to 20th	Day	21% 10% 3 6% 4 4 4 3 4 5% 36%	2254
	21st to end	Day	23% 10% 2 7% 5% 4 4 3 4 5% 33%	2404
May	1st to 10th	Day	21% 7% 3 7% 4 5% 4 4 6% 7% 32%	4426
	11th to 20th	Day	18% 9% 3 8% 5% 4 5% 4 5% 7% 33%	4398
	21st to end	Day	15% 6% 2 7% 5% 5% 5% 4 6% 8% 38%	4837
June	1st to 10th	Day	22% 8% 2 7% 5% 5% 5% 4 5% 6% 30%	2660
	11th to 20th	Day	14% 7% 2 7% 5% 4 5% 5% 6% 7% 38%	2660
	21st to end	Day	19% 7% 3 7% 6% 5% 5% 4 6% 7% 32%	2660
July	1st to 10th	Day	12% 6% 2 7% 6% 5% 6% 5% 7% 9% 35%	4440
	11th to 20th	Day	13% 6% 2 5% 4 5% 5% 5% 7% 9% 39%	4440
	21st to end	Day	10% 6% 2 6% 4 4 5% 4 7% 9% 43%	4814
August	1st to 10th	Day	15% 7% 3 8% 5% 5% 5% 4 5% 8% 36%	4361
	11th to 20th	Day	16% 7% 2 6% 4 4 4 4 6% 8% 39%	3985
	21st to end	Day	15% 6% 2 6% 4 4 5% 4 7% 9% 39%	4180
September	1st to 10th	Day	14% 6% 2 6% 5% 4 4 4 5% 7% 43%	2280
	11th to 20th	Day	13% 5% 2 6% 5% 3 4 4 5% 8% 47%	2277
	21st to end	Day	17% 6% 2 6% 5% 4 4 4 5% 7% 40%	2033
October	1st to 10th	Day	21% 7% 2 6% 5% 4 4 3 5% 7% 35%	1900
	11th to 20th	Day	21% 8% 3 8% 7% 5% 4 4 6% 6% 29%	1900
	21st to end	Day	25% 11% 3 8% 4 4 5% 3 4 5% 28%	1933
November	1st to 10th	Day	16% 9% 3 7% 5% 5% 5% 4 6% 7% 33%	1761
	11th to 20th	Day	19% 12% 4 9% 6% 5% 4 3 4 6% 30%	1615
	21st to end	Day	21% 14% 4 8% 6% 6% 5% 4 5% 5% 21%	1600
December	1st to 10th	Day	21% 19% 6% 11% 5% 6% 4 4 5% 5% 15%	2600
	11th to 20th	Day	18% 15% 5% 12% 6% 5% 4 3 4 4 24%	2986
	21st to end	Day	23% 15% 5% 11% 6% 4 5% 3 3 4 21%	3960
January	1st to 10th	Night	18% 16% 7% 12% 5% 5% 4 3 4 5% 21%	4514
	11th to 20th	Night	13% 14% 6% 13% 8% 6% 5% 4 5% 5% 22%	4440
	21st to end	Night	18% 19% 6% 10% 5% 5% 3 3 4 5% 21%	4757
February	1st to 10th	Night	14% 16% 5% 11% 7% 6% 5% 4 5% 5% 23%	2470
	11th to 20th	Night	14% 13% 5% 11% 6% 5% 4 4 5% 4 29%	2392
	21st to end	Night	17% 14% 3 8% 6% 5% 5% 4 4 5% 29%	1884
March	1st to 10th	Night	21% 13% 4 8% 5% 4 4 3 4 4 32%	3724
	11th to 20th	Night	18% 16% 5% 9% 5% 4 3 3 5% 6% 27%	3484
	21st to end	Night	16% 10% 3 6% 4 4 4 3 5% 5% 40%	3600
April	1st to 10th	Night	21% 11% 3 7% 5% 4 4 4 4 6% 32%	1900
	11th to 20th	Night	19% 10% 2 7% 5% 4 4 3 4 5% 36%	1875
	21st to end	Night	23% 9% 3 7% 5% 4 4 2 5% 7% 33%	1791
May	1st to 10th	Night	20% 8% 3 7% 5% 5% 5% 5% 6% 7% 29%	2514
	11th to 20th	Night	19% 8% 3 6% 5% 4 4 4 5% 7% 34%	2495
	21st to end	Night	13% 7% 2 6% 4 4 5% 4 6% 8% 40%	2738
June	1st to 10th	Night	16% 7% 2 7% 6% 5% 6% 4 6% 8% 32%	1520
	11th to 20th	Night	16% 5% 3 7% 3 4 4 4 6% 8% 41%	1520
	21st to end	Night	20% 6% 2 6% 5% 4 4 4 6% 6% 35%	1520
July	1st to 10th	Night	11% 7% 3 10% 6% 6% 5% 4 5% 8% 35%	2520
	11th to 20th	Night	13% 5% 2 6% 4 4 5% 4 7% 8% 42%	2520
	21st to end	Night	11% 6% 2 7% 5% 4 4 4 5% 8% 43%	2739
August	1st to 10th	Night	12% 7% 2 8% 4 4 4 4 5% 8% 40%	2564
	11th to 20th	Night	13% 7% 3 6% 5% 4 5% 4 6% 7% 41%	2812
	21st to end	Night	12% 6% 2 7% 4 4 5% 4 6% 8% 42%	3476
September	1st to 10th	Night	12% 5% 2 7% 5% 4 4 3 5% 6% 47%	1900
	11th to 20th	Night	15% 4 2 6% 3 3 3 3 4 7% 50%	1902
	21st to end	Night	16% 6% 2 6% 5% 4 4 3 4 6% 44%	2144
October	1st to 10th	Night	17% 7% 3 7% 4 4 4 3 6% 6% 38%	2280
	11th to 20th	Night	20% 10% 3 8% 5% 4 4 4 4 6% 33%	2280
	21st to end	Night	23% 10% 4 8% 5% 5% 4 3 5% 6% 28%	2663
November	1st to 10th	Night	20% 11% 4 8% 5% 3 3 2 4 6% 35%	2537
	11th to 20th	Night	17% 11% 3 9% 6% 5% 4 3 5% 6% 31%	2780
	21st to end	Night	21% 14% 4 9% 5% 5% 4 3 5% 6% 24%	2800
December	1st to 10th	Night	19% 17% 5% 11% 6% 6% 5% 4 5% 6% 16%	4580
	11th to 20th	Night	23% 15% 4 10% 6% 4 4 3 3 4 25%	5208
	21st to end	Night	27% 17% 3 9% 4 4 4 3 4 4 20%	6996

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	65% 4 15% 10% 5% 1	2566
	11th to 20th	Day	64% 3 11% 13% 8%	2520
	21st to end	Day	69% 5% 12% 10% 5%	2882
February	1st to 10th	Day	61% 4 9% 20% 4 2	1710
	11th to 20th	Day	57% 4 11% 18% 8% 1	1682
	21st to end	Day	60% 4 11% 14% 10% 2	1570
March	1st to 10th	Day	60% 3 10% 18% 9% 1	3119
	11th to 20th	Day	56% 4 12% 16% 9% 2	3472
	21st to end	Day	43% 3 8% 26% 17% 3	4031
April	1st to 10th	Day	54% 4 6% 21% 12% 3	2280
	11th to 20th	Day	51% 3 7% 22% 15% 2	2254
	21st to end	Day	55% 3 8% 16% 14% 4	2404
May	1st to 10th	Day	51% 5% 10% 22% 10% 2	4440
	11th to 20th	Day	52% 4 13% 20% 10% 2	4402
	21st to end	Day	44% 4 12% 23% 15% 1	4837
June	1st to 10th	Day	54% 5% 10% 19% 12% 1	2660
	11th to 20th	Day	43% 6% 12% 24% 13% 2	2660
	21st to end	Day	50% 6% 14% 20% 10% 1	2660
July	1st to 10th	Day	41% 7% 15% 24% 12% 1	4370
	11th to 20th	Day	38% 6% 15% 31% 9%	4365
	21st to end	Day	36% 7% 13% 32% 11%	4661
August	1st to 10th	Day	46% 6% 15% 24% 9%	4347
	11th to 20th	Day	43% 6% 15% 28% 8%	4024
	21st to end	Day	40% 6% 16% 26% 12%	4180
September	1st to 10th	Day	39% 6% 14% 29% 12%	2280
	11th to 20th	Day	36% 5% 13% 32% 14% 1	2277
	21st to end	Day	43% 5% 15% 26% 10%	2033
October	1st to 10th	Day	47% 5% 12% 29% 7%	3160
	11th to 20th	Day	46% 5% 15% 25% 8%	3140
	21st to end	Day	49% 5% 17% 21% 7%	3158
November	1st to 10th	Day	49% 6% 15% 23% 7% 1	1761
	11th to 20th	Day	57% 4 13% 16% 9% 1	1615
	21st to end	Day	65% 5% 13% 10% 6%	1600
December	1st to 10th	Day	70% 6% 12% 10% 2	2600
	11th to 20th	Day	63% 6% 10% 15% 6%	2986
	21st to end	Day	68% 4 8% 16% 4	3960
January	1st to 10th	Night	67% 3 16% 11% 4	4514
	11th to 20th	Night	63% 5% 14% 12% 5%	4440
	21st to end	Night	67% 4 11% 11% 6% 1	4757
February	1st to 10th	Night	63% 4 10% 17% 7% 1	2470
	11th to 20th	Night	58% 4 11% 19% 8% 1	2394
	21st to end	Night	57% 4 9% 18% 11% 1	1884
March	1st to 10th	Night	56% 3 10% 20% 9% 2	3734
	11th to 20th	Night	59% 3 13% 15% 8% 1	3485
	21st to end	Night	45% 3 6% 24% 18% 3	3600
April	1st to 10th	Night	53% 4 9% 18% 14% 2	1900
	11th to 20th	Night	51% 4 7% 22% 15% 1	1875
	21st to end	Night	52% 3 8% 17% 16% 3	1791
May	1st to 10th	Night	54% 4 11% 19% 9% 3	2520
	11th to 20th	Night	50% 4 12% 22% 12% 1	2496
	21st to end	Night	42% 4 14% 21% 17% 1	2739
June	1st to 10th	Night	48% 7% 12% 22% 11% 1	1520
	11th to 20th	Night	40% 5% 12% 24% 17% 2	1520
	21st to end	Night	48% 6% 12% 19% 14% 1	1520
July	1st to 10th	Night	45% 8% 13% 19% 13% 1	2480
	11th to 20th	Night	38% 7% 13% 33% 8%	2472
	21st to end	Night	39% 7% 14% 25% 15%	2651
August	1st to 10th	Night	41% 7% 15% 25% 11% 1	2554
	11th to 20th	Night	41% 7% 16% 29% 7%	2839
	21st to end	Night	39% 6% 15% 26% 12% 2	3476
September	1st to 10th	Night	38% 5% 10% 30% 15% 1	1900
	11th to 20th	Night	34% 4 14% 36% 11% 1	1902
	21st to end	Night	42% 4 12% 30% 12%	2144
October	1st to 10th	Night	41% 5% 13% 29% 12%	3800
	11th to 20th	Night	45% 5% 15% 26% 9%	3779
	21st to end	Night	49% 6% 17% 21% 8%	4388
November	1st to 10th	Night	52% 4 14% 21% 9% 1	2537
	11th to 20th	Night	55% 4 12% 18% 10% 1	2780
	21st to end	Night	62% 4 13% 16% 5%	2800
December	1st to 10th	Night	68% 6% 12% 12% 3	4580
	11th to 20th	Night	64% 4 7% 14% 10% 1	5208
	21st to end	Night	68% 3 7% 13% 9%	6996

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% 19% 30% 23% 5%	192
	11th to 20th	Day	29% 17% 34% 14% 5% 1	180
	21st to end	Day	21% 20% 34% 19% 6%	231
February	1st to 10th	Day	31% 21% 33% 13% 1	270
	11th to 20th	Day	26% 26% 38% 10%	280
	21st to end	Day	29% 19% 32% 17% 2	382
March	1st to 10th	Day	25% 17% 35% 18% 5%	460
	11th to 20th	Day	27% 17% 34% 18% 4	460
	21st to end	Day	29% 21% 26% 15% 8% 1	506
April	1st to 10th	Day	30% 19% 30% 15% 5% 1	460
	11th to 20th	Day	31% 21% 22% 14% 10% 2	452
	21st to end	Day	34% 16% 28% 14% 7% 2	460
May	1st to 10th	Day	24% 15% 30% 22% 6% 2	463
	11th to 20th	Day	20% 16% 32% 21% 9% 3	487
	21st to end	Day	18% 16% 31% 24% 11% 1	529
June	1st to 10th	Day	26% 10% 30% 23% 10% 2	490
	11th to 20th	Day	17% 14% 31% 25% 11% 3	490
	21st to end	Day	21% 14% 29% 22% 11% 3	490
July	1st to 10th	Day	13% 7% 30% 30% 16% 3	485
	11th to 20th	Day	13% 8% 31% 29% 15% 4	484
	21st to end	Day	13% 7% 30% 31% 14% 4	532
August	1st to 10th	Day	15% 8% 26% 30% 17% 4	486
	11th to 20th	Day	14% 7% 23% 29% 17% 8%	479
	21st to end	Day	14% 9% 29% 27% 13% 8%	539
September	1st to 10th	Day	17% 10% 30% 20% 15% 8%	490
	11th to 20th	Day	13% 7% 25% 23% 19% 13%	490
	21st to end	Day	18% 10% 31% 21% 16% 5%	490
October	1st to 10th	Day	24% 14% 24% 21% 11% 5%	490
	11th to 20th	Day	25% 17% 30% 20% 7% 1	490
	21st to end	Day	31% 15% 27% 21% 5%	456
November	1st to 10th	Day	26% 16% 30% 18% 8% 1	395
	11th to 20th	Day	24% 20% 35% 14% 4 3	215
	21st to end	Day	31% 19% 32% 14% 4 1	200
December	1st to 10th	Day	30% 18% 32% 16% 5%	200
	11th to 20th	Day	32% 25% 28% 13% 3 1	200
	21st to end	Day	31% 20% 31% 14% 3 1	220
January	1st to 10th	Night	26% 15% 35% 20% 4	785
	11th to 20th	Night	27% 17% 29% 21% 5%	760
	21st to end	Night	20% 13% 36% 25% 5% 1	836
February	1st to 10th	Night	24% 14% 36% 22% 4	760
	11th to 20th	Night	22% 17% 37% 20% 4	743
	21st to end	Night	24% 19% 30% 23% 4	628
March	1st to 10th	Night	24% 15% 35% 23% 4	760
	11th to 20th	Night	23% 19% 32% 20% 5%	760
	21st to end	Night	25% 15% 27% 24% 8%	836
April	1st to 10th	Night	27% 13% 30% 23% 5%	760
	11th to 20th	Night	25% 17% 28% 23% 8%	751
	21st to end	Night	27% 14% 28% 24% 7% 1	651
May	1st to 10th	Night	24% 9% 29% 27% 9% 1	380
	11th to 20th	Night	23% 10% 27% 31% 10%	374
	21st to end	Night	14% 6% 40% 28% 13%	411
June	1st to 10th	Night	18% 6% 31% 36% 8% 1	380
	11th to 20th	Night	17% 8% 28% 35% 12% 1	380
	21st to end	Night	21% 7% 31% 27% 14% 1	380
July	1st to 10th	Night	9% 6% 29% 41% 14%	370
	11th to 20th	Night	13% 5% 25% 42% 15% 1	368
	21st to end	Night	10% 4 29% 40% 15% 2	416
August	1st to 10th	Night	13% 3 24% 40% 19%	410
	11th to 20th	Night	13% 3 21% 37% 23% 2	578
	21st to end	Night	13% 6% 27% 32% 20% 2	836
September	1st to 10th	Night	14% 7% 28% 34% 16% 1	760
	11th to 20th	Night	16% 6% 21% 31% 23% 3	760
	21st to end	Night	19% 8% 26% 26% 20% 2	760
October	1st to 10th	Night	20% 9% 29% 26% 15% 1	760
	11th to 20th	Night	25% 12% 29% 24% 8% 1	760
	21st to end	Night	27% 14% 27% 26% 6%	836
November	1st to 10th	Night	27% 14% 27% 23% 8% 1	780
	11th to 20th	Night	24% 16% 33% 17% 9% 1	800
	21st to end	Night	29% 17% 26% 21% 6%	800
December	1st to 10th	Night	30% 15% 29% 22% 4	800
	11th to 20th	Night	28% 16% 30% 19% 5% 1	800
	21st to end	Night	34% 13% 30% 19% 4	880

Page generated at 2025-01-04 03:23:58. Version ac07

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