Burkes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burkes Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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% 8% 3 7% 5% 4 4 4 5% 7% 35%	101509
	Night	18% 9% 3 7% 4 4 4 4 5% 7% 35%	98578
Transparency	Day	46% 6% 12% 21% 12% 2	105034
	Night	47% 6% 13% 21% 12% 2	103143
Seeing	Day	24% 15% 31% 20% 8% 2	15675
	Night	23% 12% 32% 26% 7%	24204

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% 10% 2 6% 4 5% 4 4 5% 6% 38%	2517
	11th to 20th	Day	17% 7% 3 8% 6% 4 3 3 4 6% 40%	2520
	21st to end	Day	15% 11% 3 8% 5% 4 5% 4 5% 5% 34%	2772
February	1st to 10th	Day	18% 11% 2 6% 5% 4 5% 4 6% 5% 34%	1690
	11th to 20th	Day	12% 10% 5% 10% 5% 6% 4 4 5% 6% 34%	1794
	21st to end	Day	14% 11% 3 8% 5% 4 6% 5% 5% 5% 34%	1570
March	1st to 10th	Day	25% 13% 3 7% 5% 4 4 3 4 4 29%	3116
	11th to 20th	Day	19% 10% 3 7% 6% 5% 4 3 4 5% 33%	3464
	21st to end	Day	26% 9% 3 7% 4 3 3 3 6% 6% 30%	3847
April	1st to 10th	Day	22% 12% 4 7% 5% 4 3 2 5% 5% 32%	2280
	11th to 20th	Day	19% 8% 2 6% 5% 4 3 3 5% 8% 37%	2393
	21st to end	Day	23% 9% 3 7% 4 3 4 3 4 6% 34%	2470
May	1st to 10th	Day	21% 8% 3 7% 4 5% 5% 4 6% 7% 30%	4106
	11th to 20th	Day	19% 9% 3 8% 5% 5% 5% 4 5% 7% 30%	4134
	21st to end	Day	16% 5% 2 6% 5% 5% 5% 4 7% 9% 36%	4887
June	1st to 10th	Day	24% 8% 2 7% 4 4 4 4 6% 7% 30%	2850
	11th to 20th	Day	18% 8% 2 6% 4 4 5% 5% 6% 7% 36%	2850
	21st to end	Day	25% 7% 3 6% 5% 4 5% 4 6% 7% 29%	2850
July	1st to 10th	Day	14% 6% 2 6% 6% 5% 6% 5% 6% 9% 35%	4455
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 5% 7% 9% 36%	4440
	21st to end	Day	18% 7% 2 7% 5% 4 4 4 6% 7% 36%	4814
August	1st to 10th	Day	17% 6% 3 8% 5% 6% 5% 4 6% 9% 33%	4112
	11th to 20th	Day	17% 9% 3 7% 5% 4 5% 4 5% 8% 33%	4045
	21st to end	Day	12% 6% 2 6% 3 4 4 5% 6% 9% 43%	4446
September	1st to 10th	Day	10% 4 3 7% 5% 5% 4 4 5% 7% 47%	2214
	11th to 20th	Day	12% 6% 2 5% 3 3 4 3 5% 6% 51%	2090
	21st to end	Day	16% 6% 2 5% 4 4 4 3 6% 7% 42%	2090
October	1st to 10th	Day	19% 7% 2 7% 5% 4 4 3 5% 7% 38%	2063
	11th to 20th	Day	19% 7% 2 5% 4 4 4 3 5% 7% 39%	1845
	21st to end	Day	23% 10% 2 7% 4 4 4 3 4 5% 35%	1881
November	1st to 10th	Day	17% 6% 2 6% 4 4 5% 5% 5% 6% 40%	1761
	11th to 20th	Day	20% 7% 2 5% 3 4 4 4 6% 6% 39%	1800
	21st to end	Day	22% 8% 2 6% 3 4 3 3 3 6% 40%	1616
December	1st to 10th	Day	22% 10% 3 7% 4 5% 4 4 5% 5% 32%	1430
	11th to 20th	Day	22% 10% 3 5% 4 3 2 3 5% 5% 38%	1738
	21st to end	Day	25% 11% 2 6% 4 4 4 4 4 5% 30%	2559
January	1st to 10th	Night	14% 10% 3 7% 5% 5% 4 3 5% 6% 36%	4429
	11th to 20th	Night	13% 9% 4 9% 5% 5% 5% 4 5% 7% 33%	4440
	21st to end	Night	15% 12% 4 9% 5% 4 5% 4 4 6% 31%	4884
February	1st to 10th	Night	15% 10% 3 9% 6% 5% 5% 4 6% 7% 31%	2489
	11th to 20th	Night	13% 11% 4 8% 5% 4 5% 4 5% 6% 37%	2270
	21st to end	Night	15% 12% 3 7% 5% 5% 4 3 4 5% 37%	1884
March	1st to 10th	Night	28% 12% 3 5% 4 4 3 2 4 4 30%	3724
	11th to 20th	Night	16% 12% 3 7% 5% 5% 6% 5% 5% 7% 29%	3494
	21st to end	Night	26% 10% 2 7% 4 5% 4 3 6% 6% 27%	3768
April	1st to 10th	Night	23% 12% 3 5% 4 3 3 4 4 5% 34%	1900
	11th to 20th	Night	20% 6% 3 7% 5% 5% 4 3 6% 7% 35%	1735
	21st to end	Night	25% 10% 2 6% 3 4 4 3 4 6% 33%	1710
May	1st to 10th	Night	23% 8% 3 5% 4 3 4 4 6% 9% 31%	2834
	11th to 20th	Night	17% 8% 3 9% 6% 5% 5% 4 6% 9% 27%	2788
	21st to end	Night	15% 6% 3 7% 5% 3 4 4 6% 8% 39%	2686
June	1st to 10th	Night	20% 10% 2 7% 5% 4 4 4 6% 7% 30%	1330
	11th to 20th	Night	16% 7% 3 6% 5% 4 5% 3 6% 9% 38%	1330
	21st to end	Night	23% 8% 2 6% 4 5% 4 4 6% 8% 29%	1330
July	1st to 10th	Night	12% 6% 2 6% 5% 5% 6% 5% 8% 9% 34%	2487
	11th to 20th	Night	16% 7% 2 7% 5% 4 4 4 6% 8% 36%	2520
	21st to end	Night	14% 5% 2 5% 4 4 4 4 7% 9% 41%	2739
August	1st to 10th	Night	19% 7% 3 7% 6% 5% 5% 4 6% 7% 31%	2785
	11th to 20th	Night	16% 9% 2 7% 5% 5% 6% 4 6% 8% 32%	2782
	21st to end	Night	13% 6% 2 7% 4 3 4 3 6% 7% 45%	3206
September	1st to 10th	Night	13% 4 2 4 3 3 4 4 5% 8% 49%	1966
	11th to 20th	Night	16% 6% 2 5% 2 2 4 2 3 6% 52%	2090
	21st to end	Night	18% 6% 2 5% 4 3 4 3 4 7% 45%	2090
October	1st to 10th	Night	19% 7% 2 6% 4 4 5% 3 5% 6% 39%	2116
	11th to 20th	Night	18% 5% 2 6% 4 4 5% 4 5% 7% 40%	2332
	21st to end	Night	24% 10% 2 5% 4 4 4 3 5% 6% 34%	2717
November	1st to 10th	Night	17% 7% 2 7% 4 3 4 3 5% 6% 41%	2537
	11th to 20th	Night	18% 6% 2 6% 4 4 4 4 5% 8% 39%	2600
	21st to end	Night	17% 8% 2 6% 5% 4 4 3 6% 7% 37%	2780
December	1st to 10th	Night	22% 11% 3 7% 4 4 4 4 5% 5% 32%	2965
	11th to 20th	Night	23% 8% 3 5% 4 4 3 3 4 6% 37%	3681
	21st to end	Night	25% 11% 3 6% 3 3 4 3 4 5% 34%	5160

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	45% 5% 15% 23% 11% 1	2518
	11th to 20th	Day	44% 7% 12% 24% 11% 2	2520
	21st to end	Day	50% 5% 15% 16% 13% 1	2772
February	1st to 10th	Day	49% 5% 12% 19% 13% 2	1690
	11th to 20th	Day	50% 5% 11% 18% 13% 2	1803
	21st to end	Day	48% 6% 11% 19% 10% 5%	1570
March	1st to 10th	Day	59% 5% 8% 12% 13% 3	3119
	11th to 20th	Day	50% 7% 10% 19% 11% 3	3464
	21st to end	Day	53% 5% 7% 16% 16% 4	3847
April	1st to 10th	Day	54% 4 9% 16% 13% 5%	2280
	11th to 20th	Day	45% 6% 10% 22% 15% 2	2393
	21st to end	Day	51% 4 9% 18% 13% 4	2470
May	1st to 10th	Day	51% 8% 13% 17% 9% 2	4120
	11th to 20th	Day	50% 8% 15% 17% 9% 1	4138
	21st to end	Day	40% 9% 16% 19% 15% 1	4887
June	1st to 10th	Day	51% 7% 13% 20% 9% 1	2850
	11th to 20th	Day	45% 7% 12% 19% 15% 2	2850
	21st to end	Day	53% 7% 13% 16% 10% 1	2850
July	1st to 10th	Day	43% 7% 14% 24% 11%	4385
	11th to 20th	Day	41% 7% 15% 26% 10% 1	4365
	21st to end	Day	46% 6% 12% 22% 13% 1	4661
August	1st to 10th	Day	48% 6% 14% 25% 6%	4098
	11th to 20th	Day	47% 8% 16% 21% 8%	4084
	21st to end	Day	36% 6% 14% 26% 17% 1	4446
September	1st to 10th	Day	34% 7% 15% 26% 17% 1	2214
	11th to 20th	Day	33% 5% 10% 29% 20% 2	2090
	21st to end	Day	39% 6% 11% 28% 15% 1	2090
October	1st to 10th	Day	54% 5% 9% 20% 12% 1	3427
	11th to 20th	Day	37% 4 12% 29% 17% 1	3048
	21st to end	Day	38% 4 15% 22% 20% 2	3081
November	1st to 10th	Day	43% 6% 14% 22% 14% 2	1761
	11th to 20th	Day	43% 6% 11% 20% 17% 3	1800
	21st to end	Day	46% 4 16% 23% 10% 1	1616
December	1st to 10th	Day	53% 6% 11% 19% 10% 1	1430
	11th to 20th	Day	48% 5% 11% 19% 15% 3	1738
	21st to end	Day	56% 6% 9% 19% 8% 2	2559
January	1st to 10th	Night	46% 6% 14% 23% 9% 1	4429
	11th to 20th	Night	48% 8% 14% 17% 11% 3	4440
	21st to end	Night	53% 6% 10% 19% 12% 1	4884
February	1st to 10th	Night	51% 5% 12% 18% 11% 3	2489
	11th to 20th	Night	48% 5% 10% 20% 15% 2	2272
	21st to end	Night	49% 5% 10% 19% 14% 4	1884
March	1st to 10th	Night	58% 4 9% 15% 10% 4	3734
	11th to 20th	Night	50% 9% 14% 16% 10% 2	3495
	21st to end	Night	55% 5% 7% 16% 14% 2	3768
April	1st to 10th	Night	52% 5% 8% 17% 16% 3	1900
	11th to 20th	Night	46% 7% 9% 21% 16% 1	1735
	21st to end	Night	51% 6% 11% 15% 14% 3	1710
May	1st to 10th	Night	47% 7% 19% 17% 8% 1	2840
	11th to 20th	Night	50% 8% 16% 18% 7% 1	2789
	21st to end	Night	40% 8% 18% 21% 12% 1	2687
June	1st to 10th	Night	51% 6% 14% 19% 8% 1	1330
	11th to 20th	Night	43% 6% 15% 20% 13% 2	1330
	21st to end	Night	52% 7% 14% 17% 9% 2	1330
July	1st to 10th	Night	43% 7% 17% 21% 11%	2447
	11th to 20th	Night	44% 7% 14% 26% 9%	2472
	21st to end	Night	38% 8% 15% 26% 12% 1	2651
August	1st to 10th	Night	52% 8% 13% 21% 6%	2775
	11th to 20th	Night	47% 8% 16% 19% 9%	2809
	21st to end	Night	37% 6% 15% 23% 16% 2	3206
September	1st to 10th	Night	33% 7% 14% 30% 15% 1	1966
	11th to 20th	Night	35% 4 11% 30% 19% 1	2090
	21st to end	Night	41% 5% 11% 28% 14% 1	2090
October	1st to 10th	Night	44% 6% 14% 22% 13% 1	3532
	11th to 20th	Night	36% 5% 10% 29% 18% 1	3868
	21st to end	Night	40% 4 13% 27% 14% 2	4467
November	1st to 10th	Night	43% 6% 12% 24% 13% 1	2537
	11th to 20th	Night	43% 5% 11% 23% 16% 2	2600
	21st to end	Night	46% 5% 16% 19% 13% 2	2780
December	1st to 10th	Night	53% 5% 10% 20% 11% 1	2965
	11th to 20th	Night	49% 5% 10% 19% 16% 1	3682
	21st to end	Night	52% 5% 13% 18% 11% 1	5160

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	29% 16% 33% 17% 6%	180
	11th to 20th	Day	29% 23% 29% 13% 4 1	180
	21st to end	Day	20% 23% 33% 19% 4	198
February	1st to 10th	Day	30% 14% 31% 21% 3	350
	11th to 20th	Day	25% 25% 34% 14% 2	431
	21st to end	Day	23% 21% 33% 18% 4	382
March	1st to 10th	Day	30% 20% 32% 15% 3	460
	11th to 20th	Day	27% 21% 34% 14% 4 1	460
	21st to end	Day	30% 22% 26% 14% 6% 2	506
April	1st to 10th	Day	34% 22% 26% 13% 5% 1	460
	11th to 20th	Day	31% 24% 27% 12% 6% 1	452
	21st to end	Day	32% 20% 28% 14% 5% 1	460
May	1st to 10th	Day	32% 16% 32% 16% 4 1	463
	11th to 20th	Day	24% 18% 33% 17% 6% 1	487
	21st to end	Day	22% 17% 36% 18% 7%	553
June	1st to 10th	Day	26% 14% 32% 19% 8% 1	680
	11th to 20th	Day	21% 15% 27% 23% 12% 1	680
	21st to end	Day	27% 11% 28% 25% 8% 1	680
July	1st to 10th	Day	18% 12% 35% 26% 8% 1	500
	11th to 20th	Day	15% 9% 39% 24% 11% 3	484
	21st to end	Day	14% 8% 38% 27% 10% 3	532
August	1st to 10th	Day	14% 8% 35% 29% 12% 1	486
	11th to 20th	Day	18% 8% 29% 28% 14% 4	479
	21st to end	Day	17% 10% 33% 24% 12% 3	539
September	1st to 10th	Day	13% 11% 34% 25% 13% 4	490
	11th to 20th	Day	19% 10% 27% 24% 12% 8%	490
	21st to end	Day	17% 13% 29% 24% 11% 6%	490
October	1st to 10th	Day	21% 16% 24% 23% 13% 3	475
	11th to 20th	Day	26% 13% 29% 19% 10% 2	390
	21st to end	Day	31% 14% 29% 19% 5% 1	429
November	1st to 10th	Day	26% 14% 29% 21% 8% 1	395
	11th to 20th	Day	29% 15% 32% 19% 5% 1	400
	21st to end	Day	30% 17% 28% 20% 5%	400
December	1st to 10th	Day	27% 15% 36% 17% 5%	230
	11th to 20th	Day	34% 21% 33% 10% 3	200
	21st to end	Day	33% 18% 29% 14% 5%	204
January	1st to 10th	Night	22% 16% 34% 25% 3	760
	11th to 20th	Night	24% 17% 36% 20% 4	760
	21st to end	Night	17% 17% 39% 22% 4	836
February	1st to 10th	Night	22% 15% 34% 26% 4	760
	11th to 20th	Night	22% 18% 38% 19% 2	743
	21st to end	Night	21% 14% 36% 25% 3	628
March	1st to 10th	Night	26% 15% 35% 23% 1	760
	11th to 20th	Night	21% 18% 34% 21% 6%	760
	21st to end	Night	26% 15% 31% 22% 5%	836
April	1st to 10th	Night	30% 15% 32% 21% 3	760
	11th to 20th	Night	24% 15% 34% 22% 5%	611
	21st to end	Night	31% 13% 31% 21% 4	570
May	1st to 10th	Night	25% 12% 31% 27% 4	570
	11th to 20th	Night	23% 12% 37% 22% 5%	550
	21st to end	Night	20% 7% 34% 34% 5%	411
June	1st to 10th	Night	24% 8% 31% 31% 6%	380
	11th to 20th	Night	19% 4 28% 38% 10%	380
	21st to end	Night	26% 4 28% 37% 6%	380
July	1st to 10th	Night	18% 4 32% 37% 10%	370
	11th to 20th	Night	16% 3 27% 42% 13% 1	368
	21st to end	Night	16% 4 24% 43% 13%	416
August	1st to 10th	Night	14% 6% 28% 39% 13%	540
	11th to 20th	Night	16% 6% 26% 38% 13% 1	562
	21st to end	Night	16% 6% 26% 38% 13% 1	670
September	1st to 10th	Night	16% 5% 31% 35% 12% 1	760
	11th to 20th	Night	18% 6% 28% 30% 16% 3	760
	21st to end	Night	20% 8% 30% 28% 13% 1	760
October	1st to 10th	Night	21% 8% 27% 31% 13%	760
	11th to 20th	Night	22% 10% 29% 29% 9% 1	760
	21st to end	Night	29% 14% 30% 22% 5%	836
November	1st to 10th	Night	24% 11% 31% 26% 7% 1	780
	11th to 20th	Night	22% 15% 32% 23% 7% 1	800
	21st to end	Night	26% 17% 29% 23% 4	890
December	1st to 10th	Night	28% 12% 36% 19% 6%	900
	11th to 20th	Night	26% 16% 35% 21% 3	900
	21st to end	Night	29% 15% 32% 20% 3	917

Page generated at 2024-12-21 04:13:46. Version ac07

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