Whiskyjack Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Whiskyjack 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	16% 13% 4 10% 6% 5% 5% 4 5% 6% 26%	101567
	Night	15% 14% 5% 11% 7% 5% 5% 3 5% 5% 25%	98534
Transparency	Day	58% 6% 11% 17% 7% 1	105066
	Night	60% 6% 10% 16% 7% 1	103125
Seeing	Day	28% 20% 28% 16% 6% 2	15242
	Night	26% 18% 27% 21% 8% 1	24006

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	9% 17% 9% 16% 11% 8% 6% 3 4 4 12%	2517
	11th to 20th	Day	7% 13% 5% 24% 14% 8% 4 3 3 3 16%	2520
	21st to end	Day	10% 16% 8% 18% 6% 8% 4 3 4 4 19%	2772
February	1st to 10th	Day	10% 18% 7% 16% 11% 7% 5% 3 4 3 17%	1581
	11th to 20th	Day	9% 19% 9% 16% 9% 6% 5% 3 3 4 16%	1848
	21st to end	Day	9% 18% 4 14% 9% 8% 5% 3 5% 6% 19%	1570
March	1st to 10th	Day	18% 16% 5% 11% 7% 5% 4 3 4 4 23%	3116
	11th to 20th	Day	14% 22% 7% 15% 6% 5% 3 2 3 3 20%	3352
	21st to end	Day	15% 17% 6% 12% 5% 5% 3 3 4 4 27%	4001
April	1st to 10th	Day	18% 19% 5% 11% 6% 4 3 3 4 4 24%	2280
	11th to 20th	Day	14% 17% 4 8% 4 4 4 3 4 6% 31%	2342
	21st to end	Day	21% 17% 4 9% 4 3 4 3 4 5% 27%	2470
May	1st to 10th	Day	22% 12% 3 7% 6% 5% 5% 4 5% 6% 26%	4106
	11th to 20th	Day	20% 9% 3 8% 5% 6% 5% 4 5% 6% 28%	4352
	21st to end	Day	15% 7% 3 8% 6% 6% 6% 5% 7% 9% 29%	4837
June	1st to 10th	Day	27% 10% 3 6% 5% 4 5% 4 6% 6% 24%	2750
	11th to 20th	Day	18% 8% 3 6% 6% 5% 5% 5% 6% 8% 30%	2850
	21st to end	Day	22% 9% 3 9% 6% 6% 4 5% 6% 7% 25%	2745
July	1st to 10th	Day	13% 8% 2 8% 6% 6% 6% 4 8% 9% 30%	4440
	11th to 20th	Day	13% 7% 3 9% 5% 6% 6% 4 8% 9% 30%	4440
	21st to end	Day	15% 8% 3 8% 5% 5% 5% 4 5% 6% 36%	4814
August	1st to 10th	Day	17% 7% 3 9% 6% 6% 6% 5% 7% 8% 25%	4282
	11th to 20th	Day	16% 8% 4 9% 6% 6% 6% 5% 6% 8% 24%	4045
	21st to end	Day	17% 8% 2 7% 5% 4 5% 4 6% 7% 35%	4322
September	1st to 10th	Day	16% 8% 2 6% 4 4 4 4 5% 8% 38%	2275
	11th to 20th	Day	17% 8% 3 6% 4 4 3 4 5% 6% 42%	2090
	21st to end	Day	18% 8% 3 6% 5% 5% 4 4 6% 7% 34%	2090
October	1st to 10th	Day	18% 13% 3 7% 4 5% 4 4 6% 8% 28%	2090
	11th to 20th	Day	15% 17% 4 10% 6% 4 5% 3 6% 5% 26%	1778
	21st to end	Day	19% 22% 5% 9% 5% 4 3 3 4 5% 22%	1881
November	1st to 10th	Day	13% 18% 6% 9% 6% 5% 5% 3 4 4 27%	1761
	11th to 20th	Day	15% 18% 7% 12% 6% 4 4 3 5% 5% 22%	1800
	21st to end	Day	14% 18% 8% 12% 6% 5% 4 4 5% 6% 18%	1612
December	1st to 10th	Day	15% 23% 9% 16% 7% 4 3 2 3 3 14%	1400
	11th to 20th	Day	14% 17% 8% 12% 7% 5% 5% 3 4 4 21%	1738
	21st to end	Day	18% 21% 7% 15% 6% 4 4 3 4 3 16%	2700
January	1st to 10th	Night	11% 15% 8% 20% 12% 6% 6% 3 3 3 12%	4429
	11th to 20th	Night	9% 16% 7% 19% 14% 9% 6% 4 4 3 10%	4440
	21st to end	Night	10% 15% 9% 19% 8% 7% 5% 4 5% 4 14%	4884
February	1st to 10th	Night	9% 14% 7% 15% 11% 8% 6% 3 5% 5% 17%	2595
	11th to 20th	Night	8% 17% 8% 17% 10% 9% 4 3 4 4 17%	2218
	21st to end	Night	9% 16% 5% 13% 8% 6% 7% 3 4 5% 24%	1884
March	1st to 10th	Night	19% 19% 5% 9% 5% 4 5% 2 3 4 24%	3724
	11th to 20th	Night	13% 20% 8% 13% 6% 5% 4 3 4 3 21%	3607
	21st to end	Night	17% 16% 6% 12% 7% 4 3 2 4 4 25%	3629
April	1st to 10th	Night	18% 17% 4 9% 4 4 4 3 4 4 27%	1900
	11th to 20th	Night	18% 14% 4 7% 5% 4 5% 4 4 6% 31%	1787
	21st to end	Night	19% 15% 3 8% 4 3 5% 3 5% 6% 28%	1710
May	1st to 10th	Night	23% 11% 3 6% 4 4 5% 4 7% 7% 25%	2834
	11th to 20th	Night	18% 10% 2 9% 6% 5% 4 4 5% 6% 32%	2569
	21st to end	Night	18% 7% 2 6% 4 5% 4 4 7% 9% 34%	2738
June	1st to 10th	Night	25% 9% 3 7% 6% 4 3 3 4 7% 29%	1420
	11th to 20th	Night	16% 9% 3 7% 4 4 4 4 6% 8% 35%	1330
	21st to end	Night	17% 9% 4 7% 7% 4 5% 4 6% 6% 30%	1427
July	1st to 10th	Night	13% 7% 3 8% 7% 6% 6% 5% 6% 7% 32%	2520
	11th to 20th	Night	17% 7% 3 8% 6% 6% 4 4 7% 7% 32%	2520
	21st to end	Night	12% 8% 3 7% 5% 5% 6% 5% 6% 7% 38%	2739
August	1st to 10th	Night	20% 7% 4 8% 4 5% 5% 3 6% 6% 30%	2602
	11th to 20th	Night	14% 7% 3 10% 6% 6% 6% 6% 7% 8% 30%	2782
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 6% 40%	3332
September	1st to 10th	Night	15% 7% 2 7% 4 5% 4 3 5% 7% 42%	1905
	11th to 20th	Night	17% 7% 2 6% 4 3 4 3 5% 6% 44%	2090
	21st to end	Night	18% 8% 2 6% 3 3 4 3 5% 7% 41%	2090
October	1st to 10th	Night	17% 9% 3 7% 4 4 5% 4 6% 5% 34%	2090
	11th to 20th	Night	19% 15% 3 7% 5% 5% 4 4 5% 5% 29%	2399
	21st to end	Night	21% 17% 5% 8% 3 4 5% 4 5% 5% 24%	2717
November	1st to 10th	Night	17% 17% 6% 10% 6% 5% 4 3 5% 5% 25%	2537
	11th to 20th	Night	13% 16% 7% 12% 6% 4 4 4 5% 5% 25%	2600
	21st to end	Night	14% 17% 7% 14% 9% 5% 4 3 4 5% 19%	2780
December	1st to 10th	Night	15% 19% 8% 16% 10% 5% 4 4 5% 4 12%	3000
	11th to 20th	Night	13% 20% 7% 18% 7% 6% 4 3 4 4 14%	3681
	21st to end	Night	19% 18% 6% 13% 7% 4 4 3 3 4 19%	5025

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	76% 5% 9% 8% 2	2518
	11th to 20th	Day	76% 3 5% 12% 4 1	2520
	21st to end	Day	69% 6% 8% 8% 8% 2	2772
February	1st to 10th	Day	74% 3 5% 9% 8% 1	1581
	11th to 20th	Day	74% 3 7% 9% 6% 1	1857
	21st to end	Day	67% 4 8% 13% 6% 2	1570
March	1st to 10th	Day	66% 4 7% 12% 9% 2	3119
	11th to 20th	Day	71% 4 7% 10% 7% 1	3352
	21st to end	Day	61% 4 6% 14% 14% 2	4001
April	1st to 10th	Day	65% 3 8% 13% 8% 2	2280
	11th to 20th	Day	55% 4 8% 20% 12% 1	2342
	21st to end	Day	61% 4 8% 14% 10% 3	2470
May	1st to 10th	Day	59% 6% 10% 16% 8% 1	4120
	11th to 20th	Day	55% 9% 15% 15% 6% 1	4356
	21st to end	Day	48% 9% 12% 21% 10%	4837
June	1st to 10th	Day	58% 7% 9% 20% 5%	2750
	11th to 20th	Day	50% 7% 12% 21% 9% 1	2850
	21st to end	Day	58% 8% 10% 17% 6%	2745
July	1st to 10th	Day	46% 9% 15% 23% 7%	4370
	11th to 20th	Day	47% 9% 14% 26% 4	4365
	21st to end	Day	47% 7% 12% 27% 6%	4661
August	1st to 10th	Day	53% 8% 15% 19% 4	4268
	11th to 20th	Day	54% 9% 16% 16% 5%	4084
	21st to end	Day	46% 8% 14% 19% 12% 2	4322
September	1st to 10th	Day	44% 8% 13% 24% 11%	2275
	11th to 20th	Day	44% 5% 11% 26% 13% 1	2090
	21st to end	Day	48% 7% 12% 22% 10% 1	2090
October	1st to 10th	Day	52% 6% 14% 21% 7%	3480
	11th to 20th	Day	56% 5% 11% 22% 6%	2929
	21st to end	Day	54% 5% 14% 19% 8%	3081
November	1st to 10th	Day	61% 5% 9% 16% 8% 1	1761
	11th to 20th	Day	66% 5% 8% 13% 7% 2	1800
	21st to end	Day	69% 6% 10% 13% 3	1612
December	1st to 10th	Day	78% 4 6% 7% 5%	1400
	11th to 20th	Day	69% 4 6% 11% 10% 1	1738
	21st to end	Day	75% 4 6% 9% 6% 1	2700
January	1st to 10th	Night	78% 6% 6% 7% 2	4429
	11th to 20th	Night	80% 5% 5% 8% 2	4440
	21st to end	Night	73% 5% 7% 7% 5% 1	4884
February	1st to 10th	Night	69% 6% 7% 11% 7% 1	2595
	11th to 20th	Night	73% 4 8% 9% 5% 1	2220
	21st to end	Night	65% 5% 6% 14% 9% 1	1884
March	1st to 10th	Night	65% 4 8% 14% 6% 2	3734
	11th to 20th	Night	68% 6% 7% 11% 7% 1	3608
	21st to end	Night	64% 4 5% 14% 12% 2	3629
April	1st to 10th	Night	61% 4 7% 14% 12% 1	1900
	11th to 20th	Night	54% 6% 8% 19% 12% 1	1787
	21st to end	Night	57% 7% 9% 16% 10% 2	1710
May	1st to 10th	Night	55% 9% 14% 16% 7% 1	2840
	11th to 20th	Night	52% 8% 12% 21% 6% 1	2570
	21st to end	Night	45% 8% 16% 19% 12%	2739
June	1st to 10th	Night	57% 6% 11% 20% 6%	1420
	11th to 20th	Night	47% 7% 12% 22% 10% 1	1330
	21st to end	Night	53% 9% 11% 19% 8%	1427
July	1st to 10th	Night	48% 9% 16% 19% 8%	2480
	11th to 20th	Night	46% 11% 15% 23% 5%	2472
	21st to end	Night	44% 8% 16% 26% 5%	2651
August	1st to 10th	Night	53% 8% 15% 22% 3	2592
	11th to 20th	Night	48% 12% 17% 16% 5%	2809
	21st to end	Night	44% 8% 13% 21% 14% 1	3332
September	1st to 10th	Night	43% 7% 13% 26% 10%	1905
	11th to 20th	Night	42% 5% 14% 27% 11% 1	2090
	21st to end	Night	44% 8% 11% 25% 11% 1	2090
October	1st to 10th	Night	47% 8% 12% 22% 11%	3480
	11th to 20th	Night	55% 6% 10% 22% 7%	3987
	21st to end	Night	52% 7% 13% 18% 7% 2	4467
November	1st to 10th	Night	62% 5% 11% 15% 6% 1	2537
	11th to 20th	Night	62% 5% 10% 13% 8% 1	2600
	21st to end	Night	70% 6% 9% 11% 4	2780
December	1st to 10th	Night	76% 6% 7% 8% 3	3000
	11th to 20th	Night	76% 4 6% 8% 6%	3682
	21st to end	Night	70% 5% 8% 11% 6%	5025

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% 28% 31% 9% 1	180
	11th to 20th	Day	36% 24% 27% 12% 2 1	180
	21st to end	Day	25% 22% 36% 14% 2 1	198
February	1st to 10th	Day	33% 29% 28% 7% 2	241
	11th to 20th	Day	31% 31% 29% 7% 2	456
	21st to end	Day	34% 26% 25% 14% 2	382
March	1st to 10th	Day	31% 25% 29% 11% 4	460
	11th to 20th	Day	32% 27% 24% 13% 4	460
	21st to end	Day	34% 21% 25% 13% 7%	506
April	1st to 10th	Day	37% 22% 24% 11% 5%	460
	11th to 20th	Day	33% 24% 24% 12% 5% 2	452
	21st to end	Day	36% 21% 26% 11% 4 2	460
May	1st to 10th	Day	36% 17% 29% 13% 3 2	463
	11th to 20th	Day	25% 21% 29% 18% 7% 1	487
	21st to end	Day	21% 24% 34% 16% 4 1	529
June	1st to 10th	Day	34% 17% 28% 15% 6% 1	580
	11th to 20th	Day	23% 16% 27% 24% 9% 1	680
	21st to end	Day	26% 16% 32% 17% 8% 1	575
July	1st to 10th	Day	19% 15% 35% 23% 7% 1	485
	11th to 20th	Day	20% 16% 37% 18% 7% 2	484
	21st to end	Day	20% 13% 36% 25% 5% 2	532
August	1st to 10th	Day	19% 15% 31% 23% 11% 1	486
	11th to 20th	Day	19% 13% 29% 25% 10% 4	479
	21st to end	Day	23% 17% 24% 20% 12% 4	539
September	1st to 10th	Day	22% 15% 28% 20% 10% 3	490
	11th to 20th	Day	22% 11% 25% 21% 14% 8%	490
	21st to end	Day	21% 16% 25% 21% 12% 4	490
October	1st to 10th	Day	26% 16% 27% 16% 11% 4	490
	11th to 20th	Day	29% 19% 27% 15% 8% 2	403
	21st to end	Day	36% 22% 22% 15% 5%	429
November	1st to 10th	Day	33% 22% 25% 16% 3	395
	11th to 20th	Day	29% 23% 30% 12% 5% 2	400
	21st to end	Day	34% 25% 26% 11% 3 1	297
December	1st to 10th	Day	27% 28% 31% 13% 2	200
	11th to 20th	Day	38% 28% 26% 6% 4 1	200
	21st to end	Day	34% 32% 24% 8% 2	204
January	1st to 10th	Night	26% 28% 31% 13% 2	760
	11th to 20th	Night	25% 27% 29% 15% 3	760
	21st to end	Night	18% 27% 34% 17% 4 1	836
February	1st to 10th	Night	21% 28% 33% 15% 2	760
	11th to 20th	Night	25% 26% 32% 15% 2	743
	21st to end	Night	25% 22% 34% 16% 2	628
March	1st to 10th	Night	27% 21% 32% 18% 3	760
	11th to 20th	Night	27% 23% 28% 17% 4 1	760
	21st to end	Night	27% 21% 24% 21% 6% 1	836
April	1st to 10th	Night	33% 19% 26% 17% 5%	760
	11th to 20th	Night	27% 18% 26% 23% 6%	663
	21st to end	Night	30% 20% 27% 19% 4 1	570
May	1st to 10th	Night	29% 14% 29% 20% 7% 1	570
	11th to 20th	Night	21% 15% 30% 27% 7% 1	422
	21st to end	Night	23% 12% 30% 26% 8% 1	411
June	1st to 10th	Night	31% 7% 29% 24% 8% 1	380
	11th to 20th	Night	22% 7% 23% 33% 15%	380
	21st to end	Night	21% 9% 27% 32% 11%	380
July	1st to 10th	Night	17% 7% 29% 34% 11% 1	370
	11th to 20th	Night	17% 8% 25% 34% 14% 1	368
	21st to end	Night	19% 6% 19% 38% 16%	416
August	1st to 10th	Night	20% 4 19% 37% 18% 1	435
	11th to 20th	Night	17% 8% 23% 33% 18% 1	562
	21st to end	Night	19% 9% 24% 29% 17% 2	744
September	1st to 10th	Night	19% 9% 25% 32% 14% 1	760
	11th to 20th	Night	22% 8% 20% 28% 20% 2	760
	21st to end	Night	23% 10% 26% 23% 16% 2	760
October	1st to 10th	Night	23% 13% 23% 29% 12% 1	760
	11th to 20th	Night	30% 15% 23% 21% 9% 1	760
	21st to end	Night	33% 18% 27% 17% 4	836
November	1st to 10th	Night	33% 18% 24% 18% 5%	780
	11th to 20th	Night	27% 21% 28% 16% 8% 1	800
	21st to end	Night	28% 25% 27% 15% 4 1	840
December	1st to 10th	Night	29% 24% 29% 14% 4	900
	11th to 20th	Night	31% 25% 25% 14% 5% 1	900
	21st to end	Night	35% 23% 26% 14% 2	876

Page generated at 2024-12-21 04:13:50. Version ac07

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