Luckydog Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Luckydog Observatory clear sky chart from 2005-11-06 to 2026-07-31.

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	12% 8% 3 8% 5% 4 5% 4 6% 7% 38%	138933
	Night	12% 10% 4 9% 5% 4 4 4 5% 6% 37%	134437
Transparency	Day	43% 6% 12% 25% 13% 1	142459
	Night	45% 5% 12% 23% 14% 1	138988
Seeing	Day	18% 11% 30% 25% 13% 4	18355
	Night	18% 9% 30% 31% 11% 1	28164

By Month

Percentage Cloud Cover SE (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	7% 12% 7% 18% 8% 7% 5% 4 4 5% 22%	4691
	11th to 20th	Day	6% 12% 6% 12% 7% 4 6% 7% 9% 6% 24%	4710
	21st to end	Day	9% 13% 6% 10% 6% 4 5% 3 5% 6% 35%	5691
February	1st to 10th	Day	9% 13% 5% 9% 6% 4 5% 4 5% 7% 32%	1890
	11th to 20th	Day	12% 11% 5% 8% 5% 4 5% 4 5% 6% 36%	1870
	21st to end	Day	12% 11% 3 11% 6% 4 4 3 6% 6% 34%	1730
March	1st to 10th	Day	15% 8% 3 4 3 3 3 3 4 6% 48%	4671
	11th to 20th	Day	11% 6% 2 7% 4 4 5% 4 5% 9% 44%	5090
	21st to end	Day	24% 11% 3 8% 4 4 4 3 4 5% 30%	5852
April	1st to 10th	Day	18% 13% 3 7% 5% 4 4 4 5% 6% 31%	2520
	11th to 20th	Day	18% 12% 3 8% 4 4 4 4 5% 5% 32%	2494
	21st to end	Day	19% 10% 3 7% 5% 4 4 4 5% 7% 32%	2545
May	1st to 10th	Day	12% 6% 2 6% 4 5% 5% 4 7% 7% 42%	8147
	11th to 20th	Day	14% 6% 3 6% 4 4 4 4 5% 7% 43%	8222
	21st to end	Day	16% 7% 3 7% 5% 4 4 4 5% 7% 39%	9047
June	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 7% 9% 44%	2940
	11th to 20th	Day	13% 5% 2 6% 4 5% 5% 4 6% 9% 41%	2940
	21st to end	Day	12% 6% 3 7% 4 4 5% 4 6% 8% 39%	2940
July	1st to 10th	Day	9% 5% 2 7% 5% 5% 6% 4 8% 9% 41%	6500
	11th to 20th	Day	7% 5% 2 6% 4 4 4 4 6% 8% 50%	6500
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 5% 7% 9% 40%	7065
August	1st to 10th	Day	9% 6% 3 7% 5% 5% 6% 4 6% 8% 41%	4305
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 7% 44%	4109
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 46%	4312
September	1st to 10th	Day	14% 5% 2 5% 3 3 4 3 6% 8% 47%	2400
	11th to 20th	Day	11% 6% 2 7% 4 4 4 4 5% 9% 46%	2400
	21st to end	Day	13% 6% 2 6% 4 4 4 3 5% 7% 45%	2129
October	1st to 10th	Day	15% 7% 2 5% 3 3 4 4 4 6% 47%	2000
	11th to 20th	Day	18% 8% 3 7% 4 4 4 3 4 6% 39%	2000
	21st to end	Day	17% 11% 3 8% 3 3 4 3 4 5% 39%	2100
November	1st to 10th	Day	13% 9% 3 6% 4 4 4 4 5% 6% 42%	1852
	11th to 20th	Day	14% 13% 4 10% 5% 5% 4 2 4 6% 32%	1743
	21st to end	Day	12% 13% 3 9% 4 4 4 3 5% 5% 37%	1680
December	1st to 10th	Day	8% 10% 5% 13% 5% 7% 6% 4 5% 7% 32%	2690
	11th to 20th	Day	14% 14% 6% 11% 7% 6% 5% 4 5% 6% 21%	3088
	21st to end	Day	18% 22% 9% 15% 5% 4 4 3 4 4 14%	4070
January	1st to 10th	Night	8% 12% 6% 14% 8% 5% 4 4 5% 5% 28%	8232
	11th to 20th	Night	8% 14% 6% 14% 7% 6% 7% 6% 7% 6% 20%	8280
	21st to end	Night	8% 13% 6% 9% 6% 5% 5% 4 6% 6% 31%	8522
February	1st to 10th	Night	9% 13% 6% 11% 6% 6% 5% 4 4 5% 32%	2730
	11th to 20th	Night	10% 11% 4 8% 6% 5% 4 3 4 6% 40%	2635
	21st to end	Night	14% 10% 3 10% 6% 5% 4 3 4 5% 37%	2076
March	1st to 10th	Night	14% 9% 4 7% 4 3 3 3 5% 5% 43%	5446
	11th to 20th	Night	10% 9% 3 7% 4 4 4 3 5% 8% 44%	5090
	21st to end	Night	24% 12% 4 10% 5% 4 3 2 4 5% 28%	5318
April	1st to 10th	Night	16% 12% 4 7% 4 3 3 4 5% 5% 37%	2100
	11th to 20th	Night	19% 8% 3 6% 4 4 4 4 4 6% 38%	2075
	21st to end	Night	18% 10% 3 6% 4 4 4 3 5% 6% 36%	2072
May	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 6% 8% 45%	4733
	11th to 20th	Night	14% 6% 1 6% 4 4 4 3 5% 7% 46%	4670
	21st to end	Night	15% 8% 3 7% 5% 4 4 4 5% 6% 39%	5139
June	1st to 10th	Night	10% 5% 2 6% 4 4 5% 5% 5% 9% 45%	1680
	11th to 20th	Night	11% 6% 2 6% 5% 4 5% 4 6% 8% 44%	1680
	21st to end	Night	10% 6% 2 5% 4 4 4 3 6% 8% 49%	1680
July	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 6% 9% 44%	3698
	11th to 20th	Night	6% 6% 2 5% 3 4 4 3 6% 9% 52%	3697
	21st to end	Night	7% 5% 2 6% 4 4 4 4 6% 9% 48%	4027
August	1st to 10th	Night	9% 4 2 6% 4 4 5% 4 5% 7% 50%	2851
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 51%	2947
	21st to end	Night	10% 5% 2 5% 3 4 4 4 5% 7% 50%	3586
September	1st to 10th	Night	10% 4 2 5% 4 4 3 3 5% 7% 53%	2000
	11th to 20th	Night	12% 5% 1 5% 4 3 4 4 5% 7% 52%	2000
	21st to end	Night	9% 5% 2 5% 4 3 4 4 4 6% 55%	2247
October	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 5% 6% 51%	2400
	11th to 20th	Night	17% 8% 2 6% 4 4 4 3 5% 6% 42%	2400
	21st to end	Night	17% 10% 3 7% 4 3 4 3 6% 6% 37%	2739
November	1st to 10th	Night	14% 8% 3 6% 4 3 4 3 5% 5% 44%	2666
	11th to 20th	Night	14% 12% 5% 10% 6% 4 4 3 4 5% 33%	2872
	21st to end	Night	15% 12% 4 10% 5% 3 4 3 4 5% 35%	2940
December	1st to 10th	Night	7% 8% 4 10% 8% 6% 6% 4 5% 8% 34%	4720
	11th to 20th	Night	13% 17% 6% 12% 6% 4 4 3 5% 5% 24%	5339
	21st to end	Night	20% 17% 7% 15% 6% 4 4 3 4 4 16%	7150

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	64% 4 12% 14% 7%	4692
	11th to 20th	Day	53% 5% 10% 18% 14%	4710
	21st to end	Day	50% 5% 11% 24% 9%	5691
February	1st to 10th	Day	53% 4 13% 18% 11% 1	1890
	11th to 20th	Day	49% 5% 10% 25% 10% 1	1879
	21st to end	Day	51% 5% 11% 21% 10% 2	1730
March	1st to 10th	Day	38% 3 13% 28% 14% 4	4671
	11th to 20th	Day	37% 5% 14% 31% 12% 2	5090
	21st to end	Day	57% 5% 10% 16% 10% 2	5854
April	1st to 10th	Day	54% 5% 10% 20% 10% 1	2520
	11th to 20th	Day	53% 5% 10% 20% 10% 2	2494
	21st to end	Day	51% 6% 11% 20% 11% 1	2545
May	1st to 10th	Day	37% 6% 9% 27% 18% 2	8186
	11th to 20th	Day	39% 7% 10% 28% 15% 1	8226
	21st to end	Day	43% 6% 9% 26% 12% 3	9061
June	1st to 10th	Day	35% 6% 14% 28% 15% 2	2940
	11th to 20th	Day	40% 6% 14% 24% 16% 1	2940
	21st to end	Day	41% 6% 13% 25% 13% 2	2940
July	1st to 10th	Day	36% 9% 17% 30% 7% 1	6431
	11th to 20th	Day	30% 7% 15% 31% 16% 1	6425
	21st to end	Day	37% 9% 15% 22% 16% 1	6869
August	1st to 10th	Day	38% 7% 13% 29% 12% 1	4290
	11th to 20th	Day	36% 6% 12% 32% 12% 1	4148
	21st to end	Day	32% 7% 15% 31% 14% 1	4311
September	1st to 10th	Day	35% 5% 15% 27% 17% 1	2400
	11th to 20th	Day	36% 6% 14% 32% 12%	2400
	21st to end	Day	38% 5% 11% 30% 15% 1	2129
October	1st to 10th	Day	25% 4 6% 42% 23% 1	3260
	11th to 20th	Day	37% 5% 10% 25% 20% 2	3240
	21st to end	Day	42% 5% 11% 29% 12% 1	3377
November	1st to 10th	Day	42% 5% 13% 24% 14% 2	1852
	11th to 20th	Day	54% 4 10% 22% 10% 1	1743
	21st to end	Day	49% 5% 17% 22% 8%	1680
December	1st to 10th	Day	51% 6% 17% 18% 7% 1	2690
	11th to 20th	Day	61% 6% 12% 15% 5% 1	3085
	21st to end	Day	74% 4 7% 11% 3	4070
January	1st to 10th	Night	57% 5% 14% 18% 6%	8233
	11th to 20th	Night	61% 5% 10% 12% 12%	8280
	21st to end	Night	51% 5% 13% 20% 10%	8522
February	1st to 10th	Night	54% 3 12% 19% 11% 1	2730
	11th to 20th	Night	46% 5% 12% 25% 11% 1	2636
	21st to end	Night	49% 5% 11% 21% 11% 2	2076
March	1st to 10th	Night	43% 4 11% 25% 12% 5%	5446
	11th to 20th	Night	38% 5% 11% 29% 14% 3	5090
	21st to end	Night	60% 4 9% 17% 9% 1	5318
April	1st to 10th	Night	49% 4 9% 22% 14% 2	2100
	11th to 20th	Night	47% 5% 9% 20% 17% 3	2075
	21st to end	Night	48% 5% 10% 21% 14% 3	2072
May	1st to 10th	Night	36% 6% 8% 25% 24% 1	4757
	11th to 20th	Night	37% 6% 11% 22% 20% 4	4671
	21st to end	Night	44% 7% 9% 23% 15% 2	5149
June	1st to 10th	Night	35% 6% 13% 27% 17% 2	1680
	11th to 20th	Night	37% 7% 11% 22% 20% 2	1680
	21st to end	Night	33% 6% 16% 25% 16% 4	1680
July	1st to 10th	Night	34% 8% 16% 28% 12% 1	3660
	11th to 20th	Night	27% 6% 15% 34% 16% 1	3652
	21st to end	Night	30% 9% 18% 23% 19% 2	3912
August	1st to 10th	Night	32% 7% 13% 30% 18% 2	2842
	11th to 20th	Night	33% 6% 14% 30% 16% 1	2974
	21st to end	Night	32% 6% 14% 27% 17% 3	3586
September	1st to 10th	Night	31% 5% 10% 30% 24% 1	2000
	11th to 20th	Night	33% 5% 12% 33% 16% 1	2000
	21st to end	Night	30% 5% 10% 32% 22% 1	2247
October	1st to 10th	Night	25% 3 7% 35% 28% 2	3920
	11th to 20th	Night	30% 5% 11% 26% 26% 1	3899
	21st to end	Night	45% 4 9% 26% 15% 1	4412
November	1st to 10th	Night	41% 5% 13% 24% 16% 2	2666
	11th to 20th	Night	54% 4 11% 19% 10% 2	2872
	21st to end	Night	52% 4 12% 24% 8% 1	2940
December	1st to 10th	Night	47% 6% 19% 22% 6% 1	4720
	11th to 20th	Night	61% 6% 11% 15% 7%	5341
	21st to end	Night	72% 4 8% 11% 5%	7150

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	16% 13% 40% 20% 7% 3	330
	11th to 20th	Day	21% 17% 40% 18% 4 1	330
	21st to end	Day	22% 17% 36% 18% 6% 1	363
February	1st to 10th	Day	17% 20% 42% 14% 5% 1	330
	11th to 20th	Day	19% 23% 35% 18% 4 1	330
	21st to end	Day	21% 18% 44% 15% 2	273
March	1st to 10th	Day	21% 18% 40% 16% 4 1	330
	11th to 20th	Day	25% 17% 35% 17% 5% 2	330
	21st to end	Day	32% 13% 30% 18% 6% 1	477
April	1st to 10th	Day	31% 13% 34% 17% 5%	540
	11th to 20th	Day	27% 19% 25% 20% 8% 1	532
	21st to end	Day	26% 14% 30% 21% 8% 1	565
May	1st to 10th	Day	20% 14% 30% 25% 9% 2	753
	11th to 20th	Day	22% 11% 29% 25% 11% 3	775
	21st to end	Day	20% 7% 29% 25% 14% 5%	844
June	1st to 10th	Day	12% 7% 28% 32% 18% 4	780
	11th to 20th	Day	17% 7% 34% 25% 14% 2	780
	21st to end	Day	14% 8% 32% 28% 13% 4	780
July	1st to 10th	Day	9% 4 22% 29% 25% 11%	771
	11th to 20th	Day	8% 5% 26% 31% 20% 9%	768
	21st to end	Day	7% 4 25% 39% 18% 7%	845
August	1st to 10th	Day	8% 4 21% 34% 24% 9%	726
	11th to 20th	Day	15% 4 18% 29% 24% 10%	679
	21st to end	Day	11% 6% 23% 31% 21% 8%	583
September	1st to 10th	Day	16% 6% 23% 30% 19% 5%	530
	11th to 20th	Day	11% 5% 23% 37% 19% 5%	530
	21st to end	Day	17% 9% 28% 24% 18% 3	445
October	1st to 10th	Day	18% 12% 28% 26% 14% 2	330
	11th to 20th	Day	27% 15% 33% 19% 6%	330
	21st to end	Day	26% 15% 33% 19% 6% 1	363
November	1st to 10th	Day	18% 15% 40% 19% 5% 2	330
	11th to 20th	Day	22% 19% 34% 17% 7% 1	330
	21st to end	Day	23% 15% 38% 19% 4	330
December	1st to 10th	Day	19% 14% 42% 18% 7%	330
	11th to 20th	Day	23% 14% 39% 18% 5%	330
	21st to end	Day	28% 15% 38% 14% 3 1	363
January	1st to 10th	Night	15% 14% 34% 28% 8% 1	1050
	11th to 20th	Night	18% 14% 36% 26% 5%	1050
	21st to end	Night	20% 11% 35% 28% 5% 1	1155
February	1st to 10th	Night	16% 14% 35% 28% 6% 1	1050
	11th to 20th	Night	16% 13% 39% 25% 6%	1001
	21st to end	Night	20% 13% 36% 26% 4	692
March	1st to 10th	Night	21% 11% 37% 25% 5% 1	819
	11th to 20th	Night	20% 11% 33% 27% 8% 1	630
	21st to end	Night	25% 10% 30% 28% 7% 1	693
April	1st to 10th	Night	22% 14% 34% 25% 5%	630
	11th to 20th	Night	23% 11% 31% 27% 8%	623
	21st to end	Night	24% 7% 32% 28% 8% 1	630
May	1st to 10th	Night	21% 5% 32% 33% 8%	630
	11th to 20th	Night	21% 7% 27% 36% 9% 1	621
	21st to end	Night	16% 4 28% 38% 13% 1	683
June	1st to 10th	Night	13% 6% 26% 42% 14%	630
	11th to 20th	Night	14% 5% 28% 40% 13%	630
	21st to end	Night	14% 3 23% 43% 17% 1	630
July	1st to 10th	Night	9% 2 15% 41% 31% 3	615
	11th to 20th	Night	7% 3 20% 40% 27% 2	612
	21st to end	Night	7% 2 16% 49% 23% 3	687
August	1st to 10th	Night	7% 2 14% 48% 29% 2	597
	11th to 20th	Night	13% 2 13% 41% 26% 5%	594
	21st to end	Night	12% 2 17% 43% 23% 3	660
September	1st to 10th	Night	13% 3 21% 39% 20% 5%	600
	11th to 20th	Night	14% 4 20% 36% 23% 3	600
	21st to end	Night	12% 7% 25% 37% 18% 1	765
October	1st to 10th	Night	16% 6% 28% 32% 16% 2	800
	11th to 20th	Night	21% 11% 31% 28% 9% 1	800
	21st to end	Night	22% 10% 30% 30% 7% 1	880
November	1st to 10th	Night	19% 10% 34% 27% 9% 1	820
	11th to 20th	Night	20% 16% 34% 23% 6%	982
	21st to end	Night	22% 15% 32% 24% 7%	1050
December	1st to 10th	Night	19% 13% 38% 24% 6% 1	1050
	11th to 20th	Night	21% 14% 33% 24% 6% 1	1050
	21st to end	Night	27% 13% 30% 24% 5%	1155

Page generated at 2026-07-28 02:25:21. Version ac07

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