Burnt Jacket Mountain Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burnt Jacket Mountain 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	16% 11% 4 9% 6% 5% 5% 4 5% 7% 30%	104528
	Night	16% 12% 4 10% 6% 5% 5% 4 5% 6% 28%	104566
Transparency	Day	51% 7% 11% 19% 10% 1	108026
	Night	52% 7% 11% 18% 10% 1	109145
Seeing	Day	25% 17% 30% 18% 8% 2	15737
	Night	24% 16% 28% 23% 8% 1	24213

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	10% 15% 6% 13% 9% 5% 5% 4 5% 6% 22%	2565
	11th to 20th	Day	11% 12% 7% 16% 10% 6% 5% 2 4 4 24%	2520
	21st to end	Day	11% 10% 5% 14% 8% 7% 6% 4 6% 6% 24%	2772
February	1st to 10th	Day	13% 14% 5% 11% 8% 7% 5% 4 5% 6% 21%	1652
	11th to 20th	Day	11% 13% 7% 13% 9% 6% 5% 3 4 5% 23%	1783
	21st to end	Day	11% 13% 4 11% 8% 7% 5% 4 5% 6% 26%	1570
March	1st to 10th	Day	17% 17% 5% 10% 6% 4 4 3 4 4 27%	3116
	11th to 20th	Day	15% 19% 5% 10% 6% 5% 4 3 4 5% 23%	3442
	21st to end	Day	19% 13% 5% 9% 5% 4 3 3 4 7% 28%	3874
April	1st to 10th	Day	17% 14% 3 9% 6% 5% 4 4 5% 5% 26%	2280
	11th to 20th	Day	17% 11% 3 7% 5% 4 5% 4 5% 6% 34%	2398
	21st to end	Day	19% 12% 4 8% 5% 4 4 3 4 6% 32%	2470
May	1st to 10th	Day	18% 10% 3 8% 6% 6% 6% 4 6% 6% 29%	4106
	11th to 20th	Day	19% 10% 3 8% 4 5% 6% 5% 6% 6% 27%	4224
	21st to end	Day	14% 8% 2 8% 6% 6% 5% 5% 6% 8% 31%	4987
June	1st to 10th	Day	24% 9% 2 6% 5% 5% 4 4 6% 8% 28%	2850
	11th to 20th	Day	18% 6% 3 7% 5% 5% 4 4 6% 7% 35%	2850
	21st to end	Day	19% 10% 3 9% 6% 4 4 4 6% 9% 26%	2850
July	1st to 10th	Day	13% 7% 3 8% 5% 5% 6% 5% 7% 9% 33%	4580
	11th to 20th	Day	13% 7% 2 8% 6% 5% 5% 4 6% 9% 36%	4440
	21st to end	Day	12% 8% 3 7% 5% 5% 5% 5% 6% 6% 37%	4814
August	1st to 10th	Day	16% 7% 3 8% 6% 6% 6% 5% 7% 8% 29%	4178
	11th to 20th	Day	15% 9% 4 9% 6% 6% 6% 4 6% 8% 27%	4045
	21st to end	Day	15% 8% 3 7% 4 4 5% 4 5% 7% 37%	4468
September	1st to 10th	Day	12% 7% 2 6% 4 4 4 4 6% 9% 42%	2225
	11th to 20th	Day	16% 6% 3 6% 3 3 3 3 4 6% 48%	2090
	21st to end	Day	16% 8% 3 7% 4 4 5% 4 6% 7% 37%	2090
October	1st to 10th	Day	16% 10% 3 7% 5% 4 4 3 4 8% 35%	2062
	11th to 20th	Day	17% 14% 3 8% 5% 4 5% 4 4 6% 30%	1823
	21st to end	Day	21% 16% 3 9% 4 4 4 3 4 5% 26%	1881
November	1st to 10th	Day	18% 13% 4 7% 5% 4 4 4 4 5% 31%	1761
	11th to 20th	Day	16% 16% 5% 10% 6% 3 4 4 5% 6% 25%	1773
	21st to end	Day	20% 14% 5% 11% 4 5% 4 4 5% 7% 22%	1575
December	1st to 10th	Day	15% 16% 6% 15% 8% 7% 5% 3 4 4 18%	2280
	11th to 20th	Day	16% 14% 5% 9% 5% 5% 4 3 5% 6% 28%	2618
	21st to end	Day	16% 14% 5% 11% 6% 5% 5% 4 5% 5% 24%	3516
January	1st to 10th	Night	12% 14% 6% 15% 9% 7% 5% 3 4 4 20%	4514
	11th to 20th	Night	12% 13% 5% 14% 11% 8% 6% 4 5% 5% 17%	4440
	21st to end	Night	11% 12% 5% 15% 9% 6% 6% 5% 5% 5% 21%	4884
February	1st to 10th	Night	11% 15% 5% 11% 7% 7% 6% 5% 5% 6% 23%	2527
	11th to 20th	Night	10% 13% 7% 11% 9% 7% 7% 4 4 6% 22%	2280
	21st to end	Night	13% 13% 4 10% 6% 7% 4 4 4 6% 29%	1884
March	1st to 10th	Night	22% 16% 4 9% 5% 4 5% 3 4 4 25%	3724
	11th to 20th	Night	13% 17% 7% 12% 6% 6% 5% 4 5% 4 22%	3517
	21st to end	Night	23% 14% 4 10% 5% 4 3 3 4 7% 24%	3754
April	1st to 10th	Night	20% 15% 5% 7% 4 3 3 4 5% 5% 30%	1900
	11th to 20th	Night	18% 11% 2 6% 5% 4 5% 3 5% 6% 34%	1730
	21st to end	Night	20% 11% 3 9% 4 4 5% 4 5% 5% 29%	1710
May	1st to 10th	Night	22% 11% 3 6% 4 5% 5% 4 6% 7% 28%	2834
	11th to 20th	Night	17% 10% 4 9% 6% 5% 6% 4 5% 7% 26%	2699
	21st to end	Night	15% 7% 2 6% 4 4 4 4 7% 9% 38%	2590
June	1st to 10th	Night	21% 10% 4 7% 5% 4 4 4 6% 6% 29%	1330
	11th to 20th	Night	17% 7% 2 6% 6% 4 5% 5% 5% 7% 36%	1330
	21st to end	Night	18% 10% 4 7% 5% 4 4 4 7% 7% 30%	1330
July	1st to 10th	Night	11% 8% 3 8% 5% 5% 6% 4 6% 7% 36%	2379
	11th to 20th	Night	17% 7% 3 7% 5% 4 4 4 6% 7% 37%	2520
	21st to end	Night	11% 9% 3 7% 5% 5% 5% 4 6% 7% 38%	2739
August	1st to 10th	Night	19% 8% 3 8% 5% 6% 5% 4 6% 6% 31%	2720
	11th to 20th	Night	13% 9% 4 9% 6% 7% 7% 3 6% 7% 29%	2782
	21st to end	Night	13% 8% 2 6% 5% 3 4 3 5% 7% 44%	3185
September	1st to 10th	Night	13% 6% 2 5% 3 3 4 4 5% 8% 47%	1953
	11th to 20th	Night	14% 5% 2 6% 4 4 3 3 5% 7% 46%	2090
	21st to end	Night	16% 8% 2 6% 5% 5% 4 4 5% 7% 39%	2090
October	1st to 10th	Night	16% 8% 3 7% 5% 5% 4 3 5% 6% 37%	2118
	11th to 20th	Night	18% 12% 3 7% 4 4 4 3 5% 6% 33%	2355
	21st to end	Night	22% 13% 4 8% 4 4 4 3 4 5% 27%	2717
November	1st to 10th	Night	18% 13% 4 9% 4 4 4 3 5% 6% 29%	2537
	11th to 20th	Night	15% 13% 6% 11% 5% 5% 4 3 4 6% 28%	2625
	21st to end	Night	17% 13% 5% 12% 6% 5% 5% 3 6% 6% 22%	2822
December	1st to 10th	Night	15% 13% 6% 20% 9% 7% 5% 4 4 4 13%	4910
	11th to 20th	Night	18% 14% 4 11% 8% 6% 5% 3 5% 5% 21%	5591
	21st to end	Night	17% 14% 5% 10% 6% 5% 4 3 4 4 27%	7456

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	56% 8% 11% 18% 6% 1	2566
	11th to 20th	Day	58% 10% 5% 18% 8% 1	2520
	21st to end	Day	58% 6% 10% 13% 12% 1	2772
February	1st to 10th	Day	61% 5% 7% 14% 10% 2	1652
	11th to 20th	Day	60% 6% 9% 14% 9% 1	1791
	21st to end	Day	57% 6% 8% 16% 9% 4	1570
March	1st to 10th	Day	61% 4 7% 12% 13% 3	3119
	11th to 20th	Day	60% 7% 9% 13% 10% 1	3442
	21st to end	Day	57% 5% 5% 16% 15% 3	3874
April	1st to 10th	Day	58% 5% 9% 15% 11% 3	2280
	11th to 20th	Day	51% 5% 9% 21% 14% 1	2398
	21st to end	Day	55% 4 8% 19% 11% 3	2470
May	1st to 10th	Day	53% 8% 10% 18% 10% 1	4120
	11th to 20th	Day	54% 7% 14% 17% 7% 1	4228
	21st to end	Day	47% 8% 13% 19% 14% 1	4987
June	1st to 10th	Day	54% 5% 13% 21% 7%	2850
	11th to 20th	Day	47% 6% 12% 21% 12% 1	2850
	21st to end	Day	55% 6% 12% 18% 8%	2850
July	1st to 10th	Day	43% 8% 18% 20% 10%	4510
	11th to 20th	Day	43% 8% 15% 28% 5%	4365
	21st to end	Day	46% 8% 11% 28% 8%	4661
August	1st to 10th	Day	49% 9% 15% 21% 5%	4164
	11th to 20th	Day	51% 8% 16% 20% 5%	4084
	21st to end	Day	43% 8% 13% 21% 14%	4468
September	1st to 10th	Day	37% 7% 15% 26% 14% 1	2225
	11th to 20th	Day	38% 4 12% 29% 15% 1	2090
	21st to end	Day	45% 6% 11% 25% 13% 1	2090
October	1st to 10th	Day	50% 9% 12% 19% 9%	3426
	11th to 20th	Day	50% 7% 11% 24% 9%	3000
	21st to end	Day	45% 6% 17% 19% 14%	3081
November	1st to 10th	Day	54% 6% 11% 18% 10% 1	1761
	11th to 20th	Day	55% 8% 9% 16% 10% 2	1773
	21st to end	Day	58% 6% 13% 18% 5%	1575
December	1st to 10th	Day	66% 8% 10% 10% 7%	2280
	11th to 20th	Day	51% 8% 11% 13% 14% 3	2618
	21st to end	Day	55% 8% 9% 14% 9% 4	3516
January	1st to 10th	Night	60% 9% 10% 15% 6%	4514
	11th to 20th	Night	59% 12% 9% 14% 6% 1	4440
	21st to end	Night	60% 7% 8% 14% 10% 1	4884
February	1st to 10th	Night	57% 7% 9% 16% 9% 2	2527
	11th to 20th	Night	55% 10% 9% 15% 10% 1	2283
	21st to end	Night	54% 7% 7% 18% 11% 3	1884
March	1st to 10th	Night	61% 5% 7% 16% 8% 3	3734
	11th to 20th	Night	59% 9% 11% 12% 9% 1	3518
	21st to end	Night	59% 5% 6% 18% 11% 1	3754
April	1st to 10th	Night	55% 4 7% 15% 16% 3	1900
	11th to 20th	Night	49% 6% 9% 22% 14% 2	1730
	21st to end	Night	54% 6% 8% 17% 11% 3	1710
May	1st to 10th	Night	52% 7% 15% 17% 8% 1	2840
	11th to 20th	Night	56% 6% 13% 18% 6% 1	2700
	21st to end	Night	40% 6% 19% 21% 13% 1	2591
June	1st to 10th	Night	54% 6% 12% 20% 8%	1330
	11th to 20th	Night	46% 6% 13% 22% 11% 2	1330
	21st to end	Night	52% 5% 15% 20% 9%	1330
July	1st to 10th	Night	44% 8% 16% 22% 10%	2339
	11th to 20th	Night	44% 7% 14% 29% 6%	2472
	21st to end	Night	42% 10% 14% 27% 8%	2651
August	1st to 10th	Night	52% 7% 14% 22% 4	2710
	11th to 20th	Night	51% 9% 15% 17% 8%	2809
	21st to end	Night	37% 10% 14% 23% 15% 1	3185
September	1st to 10th	Night	35% 6% 15% 30% 13% 1	1953
	11th to 20th	Night	37% 5% 13% 28% 16%	2090
	21st to end	Night	42% 6% 13% 26% 12% 1	2090
October	1st to 10th	Night	47% 9% 12% 21% 11%	3534
	11th to 20th	Night	43% 10% 10% 26% 10%	3904
	21st to end	Night	45% 6% 18% 19% 10% 1	4467
November	1st to 10th	Night	54% 5% 11% 20% 9% 1	2537
	11th to 20th	Night	53% 8% 9% 17% 11% 2	2625
	21st to end	Night	57% 8% 12% 15% 7%	2822
December	1st to 10th	Night	66% 11% 8% 12% 4	4910
	11th to 20th	Night	56% 8% 7% 15% 13% 1	5592
	21st to end	Night	56% 6% 10% 17% 10% 2	7456

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	32% 22% 32% 11% 3	192
	11th to 20th	Day	32% 28% 27% 9% 3 1	180
	21st to end	Day	25% 18% 40% 12% 5% 1	198
February	1st to 10th	Day	29% 22% 30% 16% 2 1	312
	11th to 20th	Day	27% 29% 33% 8% 2	424
	21st to end	Day	30% 20% 33% 14% 2	382
March	1st to 10th	Day	32% 20% 33% 13% 3	460
	11th to 20th	Day	28% 23% 30% 15% 4 1	460
	21st to end	Day	31% 20% 27% 14% 6% 1	506
April	1st to 10th	Day	34% 23% 23% 14% 6% 1	460
	11th to 20th	Day	30% 22% 27% 14% 6% 2	452
	21st to end	Day	31% 19% 32% 12% 5% 2	460
May	1st to 10th	Day	31% 16% 32% 15% 5% 1	463
	11th to 20th	Day	27% 14% 33% 18% 7% 1	487
	21st to end	Day	22% 18% 32% 20% 6% 1	614
June	1st to 10th	Day	28% 15% 30% 19% 8% 2	680
	11th to 20th	Day	22% 14% 30% 22% 11% 2	680
	21st to end	Day	24% 11% 31% 23% 9% 2	680
July	1st to 10th	Day	18% 11% 36% 22% 12% 1	573
	11th to 20th	Day	16% 11% 41% 20% 10% 2	484
	21st to end	Day	16% 10% 36% 27% 9% 2	532
August	1st to 10th	Day	18% 12% 28% 28% 12% 2	486
	11th to 20th	Day	17% 13% 25% 27% 15% 3	479
	21st to end	Day	19% 13% 27% 24% 14% 3	539
September	1st to 10th	Day	15% 14% 32% 22% 13% 4	490
	11th to 20th	Day	22% 12% 26% 18% 15% 7%	490
	21st to end	Day	19% 14% 29% 22% 10% 6%	490
October	1st to 10th	Day	20% 17% 29% 16% 13% 4	475
	11th to 20th	Day	29% 16% 29% 14% 9% 2	390
	21st to end	Day	33% 21% 25% 15% 5%	429
November	1st to 10th	Day	29% 19% 24% 21% 6% 1	395
	11th to 20th	Day	29% 25% 26% 15% 5% 1	400
	21st to end	Day	35% 21% 24% 15% 4 1	375
December	1st to 10th	Day	28% 23% 30% 18% 3	200
	11th to 20th	Day	37% 29% 23% 9% 3 1	200
	21st to end	Day	34% 21% 28% 13% 4 1	220
January	1st to 10th	Night	25% 25% 28% 20% 3	785
	11th to 20th	Night	27% 23% 29% 18% 4	760
	21st to end	Night	19% 24% 35% 18% 4	836
February	1st to 10th	Night	22% 25% 33% 18% 3	760
	11th to 20th	Night	22% 27% 32% 17% 2	743
	21st to end	Night	24% 21% 34% 18% 3	628
March	1st to 10th	Night	26% 19% 32% 20% 2	760
	11th to 20th	Night	24% 22% 27% 21% 6%	760
	21st to end	Night	26% 21% 25% 22% 6%	836
April	1st to 10th	Night	31% 18% 27% 21% 4	760
	11th to 20th	Night	24% 18% 28% 23% 8%	606
	21st to end	Night	30% 15% 28% 20% 8%	570
May	1st to 10th	Night	29% 11% 26% 27% 6% 1	570
	11th to 20th	Night	24% 13% 29% 25% 8% 1	500
	21st to end	Night	22% 9% 30% 29% 9%	411
June	1st to 10th	Night	24% 8% 27% 30% 8% 1	380
	11th to 20th	Night	18% 10% 24% 32% 15%	380
	21st to end	Night	23% 4 29% 33% 10% 1	380
July	1st to 10th	Night	16% 5% 27% 40% 11% 1	370
	11th to 20th	Night	18% 5% 23% 37% 17% 1	368
	21st to end	Night	17% 5% 25% 38% 14% 1	416
August	1st to 10th	Night	20% 6% 20% 38% 16% 1	501
	11th to 20th	Night	16% 10% 21% 34% 17% 1	562
	21st to end	Night	17% 7% 25% 32% 18% 2	662
September	1st to 10th	Night	14% 9% 28% 31% 16% 2	760
	11th to 20th	Night	18% 10% 22% 31% 17% 2	760
	21st to end	Night	21% 9% 28% 27% 13% 2	760
October	1st to 10th	Night	23% 11% 24% 27% 15% 1	760
	11th to 20th	Night	26% 16% 28% 20% 9% 2	760
	21st to end	Night	31% 18% 28% 19% 5%	836
November	1st to 10th	Night	27% 18% 26% 21% 8% 1	780
	11th to 20th	Night	26% 21% 25% 18% 8% 1	813
	21st to end	Night	28% 21% 26% 21% 4 1	900
December	1st to 10th	Night	29% 19% 31% 17% 4	900
	11th to 20th	Night	30% 21% 27% 17% 4 1	900
	21st to end	Night	30% 22% 28% 17% 3	980

Page generated at 2025-01-04 03:23:59. Version ac07

Copyright © 2025 Attilla Danko.