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 2025-03-27.

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	13% 9% 4 8% 5% 4 5% 4 5% 7% 37%	109224
	Night	12% 10% 4 9% 5% 4 4 4 5% 6% 37%	110340
Transparency	Day	45% 6% 12% 24% 12% 1	112794
	Night	46% 5% 11% 23% 14% 1	114910
Seeing	Day	18% 10% 30% 25% 13% 4	16368
	Night	18% 9% 30% 31% 11% 1	26428

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	6% 11% 7% 19% 8% 7% 5% 4 4 5% 24%	3617
	11th to 20th	Day	7% 11% 7% 11% 7% 5% 6% 8% 9% 6% 23%	3620
	21st to end	Day	11% 16% 7% 10% 5% 3 4 3 4 5% 33%	4395
February	1st to 10th	Day	10% 13% 5% 9% 6% 4 5% 5% 5% 7% 32%	1800
	11th to 20th	Day	12% 11% 5% 8% 5% 4 5% 4 5% 6% 35%	1779
	21st to end	Day	12% 11% 4 10% 6% 4 4 3 6% 6% 35%	1650
March	1st to 10th	Day	16% 8% 3 4 3 3 3 3 4 6% 47%	3283
	11th to 20th	Day	10% 7% 3 8% 5% 4 5% 4 5% 8% 43%	3590
	21st to end	Day	23% 12% 3 10% 4 4 4 3 4 5% 26%	4061
April	1st to 10th	Day	19% 13% 3 7% 5% 3 4 4 4 6% 31%	2280
	11th to 20th	Day	18% 13% 3 8% 4 4 3 4 5% 5% 33%	2254
	21st to end	Day	20% 10% 3 7% 5% 4 4 4 4 7% 32%	2303
May	1st to 10th	Day	18% 7% 3 7% 4 4 5% 4 6% 7% 36%	4362
	11th to 20th	Day	14% 6% 3 7% 4 4 5% 4 5% 7% 41%	4399
	21st to end	Day	17% 7% 2 7% 5% 4 4 4 6% 7% 37%	4824
June	1st to 10th	Day	12% 5% 2 6% 4 4 4 4 7% 9% 45%	2660
	11th to 20th	Day	12% 5% 2 6% 5% 5% 5% 4 6% 8% 42%	2660
	21st to end	Day	12% 6% 3 7% 5% 4 5% 4 6% 8% 40%	2660
July	1st to 10th	Day	11% 5% 2 7% 5% 5% 6% 5% 8% 9% 37%	4440
	11th to 20th	Day	5% 3 2 5% 4 4 5% 4 6% 9% 53%	4440
	21st to end	Day	7% 6% 3 7% 5% 5% 5% 5% 7% 9% 41%	4813
August	1st to 10th	Day	9% 6% 3 7% 5% 5% 6% 4 6% 8% 41%	4173
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 4 6% 7% 45%	3981
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 46%	4180
September	1st to 10th	Day	14% 6% 2 5% 3 3 4 3 5% 7% 47%	2280
	11th to 20th	Day	11% 6% 2 7% 3 4 3 4 4 8% 47%	2280
	21st to end	Day	13% 7% 2 6% 4 4 4 3 5% 7% 45%	2023
October	1st to 10th	Day	15% 7% 2 5% 4 3 4 4 4 7% 46%	1900
	11th to 20th	Day	18% 8% 3 6% 4 4 4 3 4 7% 39%	1900
	21st to end	Day	17% 11% 3 8% 3 3 4 3 4 5% 39%	1995
November	1st to 10th	Day	14% 9% 3 6% 4 4 4 4 5% 7% 42%	1762
	11th to 20th	Day	15% 13% 4 10% 5% 5% 4 2 4 6% 32%	1660
	21st to end	Day	13% 13% 3 9% 4 4 4 3 5% 6% 38%	1600
December	1st to 10th	Day	8% 9% 5% 12% 5% 7% 6% 4 5% 7% 33%	2610
	11th to 20th	Day	14% 14% 6% 11% 7% 6% 5% 4 5% 6% 21%	3008
	21st to end	Day	18% 21% 9% 15% 5% 4 4 3 4 4 14%	3982
January	1st to 10th	Night	7% 11% 7% 16% 8% 5% 5% 3 5% 5% 28%	6348
	11th to 20th	Night	10% 13% 6% 13% 6% 6% 6% 6% 9% 6% 20%	6360
	21st to end	Night	10% 15% 7% 9% 6% 5% 5% 3 5% 5% 30%	6582
February	1st to 10th	Night	9% 13% 6% 11% 6% 6% 5% 4 4 5% 33%	2600
	11th to 20th	Night	9% 11% 4 8% 6% 5% 4 3 4 6% 39%	2507
	21st to end	Night	14% 10% 3 9% 6% 5% 4 3 4 5% 36%	1980
March	1st to 10th	Night	14% 10% 3 6% 4 3 3 3 5% 6% 42%	3820
	11th to 20th	Night	10% 8% 2 7% 5% 5% 4 3 5% 8% 42%	3590
	21st to end	Night	25% 12% 4 10% 4 4 3 2 4 5% 28%	3707
April	1st to 10th	Night	16% 12% 3 7% 4 3 3 4 5% 5% 38%	1900
	11th to 20th	Night	19% 8% 2 6% 4 4 4 4 5% 6% 38%	1875
	21st to end	Night	18% 10% 3 6% 4 4 4 3 5% 5% 37%	1875
May	1st to 10th	Night	17% 7% 2 7% 5% 4 4 3 6% 8% 38%	2540
	11th to 20th	Night	12% 6% 2 6% 4 4 3 3 5% 7% 48%	2506
	21st to end	Night	13% 6% 2 5% 4 4 4 3 6% 7% 45%	2743
June	1st to 10th	Night	10% 5% 2 6% 4 4 5% 4 5% 9% 46%	1520
	11th to 20th	Night	11% 6% 2 6% 4 4 5% 4 6% 8% 45%	1520
	21st to end	Night	9% 6% 2 5% 4 4 4 3 6% 8% 49%	1520
July	1st to 10th	Night	11% 7% 2 7% 4 4 4 4 6% 8% 44%	2530
	11th to 20th	Night	4 3 1 5% 4 4 4 4 6% 10% 55%	2530
	21st to end	Night	6% 4 2 6% 5% 4 4 4 6% 9% 50%	2750
August	1st to 10th	Night	9% 4 2 6% 4 4 5% 4 5% 7% 50%	2763
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 51%	2855
	21st to end	Night	10% 5% 2 5% 3 4 4 4 5% 7% 50%	3476
September	1st to 10th	Night	10% 4 2 5% 4 4 3 3 5% 7% 53%	1900
	11th to 20th	Night	12% 5% 1 4 3 3 3 3 4 7% 53%	1900
	21st to end	Night	9% 5% 2 5% 4 4 4 4 4 6% 54%	2135
October	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 5% 6% 51%	2280
	11th to 20th	Night	16% 7% 2 6% 4 4 4 4 5% 6% 43%	2280
	21st to end	Night	17% 10% 3 7% 4 3 4 3 6% 6% 37%	2602
November	1st to 10th	Night	14% 8% 3 6% 4 3 4 4 5% 5% 44%	2536
	11th to 20th	Night	14% 12% 5% 10% 6% 4 4 3 4 5% 33%	2735
	21st to end	Night	16% 12% 4 9% 5% 3 4 3 4 5% 36%	2800
December	1st to 10th	Night	7% 8% 3 10% 8% 6% 6% 4 5% 8% 35%	4580
	11th to 20th	Night	13% 17% 6% 12% 6% 4 4 3 5% 5% 24%	5199
	21st to end	Night	20% 17% 7% 15% 6% 4 4 3 4 4 16%	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	62% 3 11% 17% 6%	3618
	11th to 20th	Day	54% 5% 10% 15% 16%	3620
	21st to end	Day	55% 4 13% 18% 10%	4395
February	1st to 10th	Day	53% 4 13% 18% 11% 1	1800
	11th to 20th	Day	50% 5% 10% 24% 10% 1	1788
	21st to end	Day	50% 5% 11% 21% 10% 2	1650
March	1st to 10th	Day	40% 4 11% 26% 16% 3	3283
	11th to 20th	Day	39% 5% 11% 32% 11% 2	3590
	21st to end	Day	60% 5% 11% 15% 8% 1	4061
April	1st to 10th	Day	54% 5% 10% 21% 10% 1	2280
	11th to 20th	Day	53% 4 9% 21% 11% 2	2254
	21st to end	Day	51% 6% 11% 19% 11% 1	2303
May	1st to 10th	Day	46% 6% 9% 23% 15% 1	4403
	11th to 20th	Day	41% 6% 9% 32% 10% 1	4403
	21st to end	Day	44% 7% 9% 24% 14% 2	4837
June	1st to 10th	Day	34% 6% 14% 28% 15% 2	2660
	11th to 20th	Day	39% 6% 14% 23% 17% 1	2660
	21st to end	Day	41% 6% 13% 26% 13% 2	2660
July	1st to 10th	Day	40% 9% 16% 26% 8% 1	4371
	11th to 20th	Day	26% 8% 16% 31% 18% 1	4365
	21st to end	Day	35% 9% 16% 21% 18% 1	4662
August	1st to 10th	Day	38% 7% 13% 29% 12% 1	4158
	11th to 20th	Day	36% 6% 12% 33% 13% 1	4020
	21st to end	Day	33% 7% 15% 30% 14% 1	4179
September	1st to 10th	Day	36% 5% 14% 26% 18% 1	2280
	11th to 20th	Day	36% 5% 13% 33% 13%	2280
	21st to end	Day	39% 5% 11% 30% 15% 1	2023
October	1st to 10th	Day	25% 4 6% 42% 23% 1	3160
	11th to 20th	Day	37% 5% 10% 25% 21% 2	3140
	21st to end	Day	42% 5% 11% 30% 12% 1	3272
November	1st to 10th	Day	42% 5% 13% 24% 13% 2	1762
	11th to 20th	Day	55% 4 10% 21% 10% 1	1660
	21st to end	Day	47% 5% 17% 22% 8% 1	1600
December	1st to 10th	Day	50% 6% 17% 19% 7% 1	2610
	11th to 20th	Day	62% 6% 12% 14% 5% 1	3005
	21st to end	Day	74% 4 7% 11% 3	3982
January	1st to 10th	Night	57% 5% 11% 20% 7% 1	6348
	11th to 20th	Night	59% 6% 10% 12% 13%	6360
	21st to end	Night	55% 5% 12% 18% 10% 1	6582
February	1st to 10th	Night	55% 3 12% 18% 11% 1	2600
	11th to 20th	Night	47% 5% 12% 24% 11% 1	2508
	21st to end	Night	50% 5% 11% 21% 12% 2	1980
March	1st to 10th	Night	43% 4 11% 27% 12% 3	3820
	11th to 20th	Night	39% 5% 9% 28% 16% 2	3590
	21st to end	Night	60% 4 7% 19% 8% 1	3707
April	1st to 10th	Night	48% 5% 9% 22% 14% 2	1900
	11th to 20th	Night	47% 5% 9% 20% 17% 3	1875
	21st to end	Night	48% 5% 10% 20% 14% 3	1875
May	1st to 10th	Night	44% 7% 9% 20% 20%	2564
	11th to 20th	Night	37% 5% 10% 25% 19% 3	2507
	21st to end	Night	36% 8% 10% 25% 19% 1	2751
June	1st to 10th	Night	35% 6% 13% 27% 18% 2	1520
	11th to 20th	Night	36% 7% 11% 23% 21% 2	1520
	21st to end	Night	32% 6% 16% 25% 17% 4	1520
July	1st to 10th	Night	37% 7% 16% 26% 12% 2	2490
	11th to 20th	Night	23% 6% 16% 36% 16% 2	2482
	21st to end	Night	28% 9% 17% 23% 21% 2	2662
August	1st to 10th	Night	33% 7% 12% 29% 18% 2	2754
	11th to 20th	Night	32% 5% 14% 31% 16% 1	2882
	21st to end	Night	33% 7% 14% 27% 17% 3	3476
September	1st to 10th	Night	32% 4 9% 30% 24% 1	1900
	11th to 20th	Night	32% 4 12% 34% 17% 1	1900
	21st to end	Night	31% 5% 10% 32% 21% 1	2135
October	1st to 10th	Night	25% 3 7% 36% 28% 2	3800
	11th to 20th	Night	30% 5% 11% 27% 26% 1	3779
	21st to end	Night	46% 4 9% 26% 15% 1	4275
November	1st to 10th	Night	42% 5% 12% 23% 16% 2	2536
	11th to 20th	Night	54% 4 11% 19% 10% 1	2735
	21st to end	Night	52% 4 13% 24% 8% 1	2800
December	1st to 10th	Night	46% 6% 19% 23% 6% 1	4580
	11th to 20th	Night	61% 5% 11% 15% 7%	5201
	21st to end	Night	72% 4 7% 11% 5%	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	16% 13% 39% 21% 8% 3	300
	11th to 20th	Day	21% 16% 40% 17% 4 1	300
	21st to end	Day	23% 16% 36% 18% 6% 1	330
February	1st to 10th	Day	17% 20% 42% 15% 5% 1	300
	11th to 20th	Day	19% 23% 34% 18% 4 1	300
	21st to end	Day	22% 18% 43% 15% 2	249
March	1st to 10th	Day	22% 18% 41% 14% 4 1	300
	11th to 20th	Day	24% 17% 34% 18% 6% 2	300
	21st to end	Day	32% 11% 29% 19% 7% 1	419
April	1st to 10th	Day	32% 10% 33% 18% 6%	460
	11th to 20th	Day	28% 17% 25% 21% 8% 1	452
	21st to end	Day	28% 13% 29% 22% 8% 1	483
May	1st to 10th	Day	22% 12% 31% 24% 9% 2	653
	11th to 20th	Day	21% 11% 28% 26% 11% 3	675
	21st to end	Day	20% 7% 29% 24% 15% 5%	734
June	1st to 10th	Day	12% 6% 28% 31% 19% 4	680
	11th to 20th	Day	16% 5% 33% 26% 16% 3	680
	21st to end	Day	14% 7% 31% 29% 14% 4	680
July	1st to 10th	Day	9% 3 21% 29% 25% 12%	671
	11th to 20th	Day	8% 4 27% 31% 20% 9%	668
	21st to end	Day	7% 4 25% 38% 19% 8%	739
August	1st to 10th	Day	8% 4 21% 35% 24% 9%	676
	11th to 20th	Day	15% 4 18% 29% 24% 10%	631
	21st to end	Day	12% 5% 23% 31% 20% 9%	539
September	1st to 10th	Day	17% 5% 23% 31% 19% 5%	490
	11th to 20th	Day	12% 5% 23% 35% 19% 5%	490
	21st to end	Day	18% 10% 28% 24% 17% 2	409
October	1st to 10th	Day	19% 13% 27% 25% 14% 2	300
	11th to 20th	Day	27% 14% 32% 20% 6%	300
	21st to end	Day	26% 16% 34% 17% 6% 1	330
November	1st to 10th	Day	19% 12% 41% 20% 6% 2	300
	11th to 20th	Day	22% 18% 35% 17% 7% 1	300
	21st to end	Day	23% 14% 39% 19% 4	300
December	1st to 10th	Day	18% 14% 43% 18% 7%	300
	11th to 20th	Day	23% 14% 38% 19% 6%	300
	21st to end	Day	29% 15% 36% 15% 3 1	330
January	1st to 10th	Night	15% 14% 34% 28% 8% 1	1000
	11th to 20th	Night	19% 13% 36% 27% 5% 1	1000
	21st to end	Night	21% 11% 34% 27% 5% 1	1100
February	1st to 10th	Night	17% 14% 34% 28% 6% 1	1000
	11th to 20th	Night	16% 13% 40% 25% 6%	953
	21st to end	Night	21% 13% 36% 26% 5%	660
March	1st to 10th	Night	21% 11% 37% 25% 5% 1	780
	11th to 20th	Night	18% 11% 34% 28% 8% 1	600
	21st to end	Night	25% 9% 29% 29% 8% 1	647
April	1st to 10th	Night	21% 14% 34% 26% 5%	570
	11th to 20th	Night	24% 10% 30% 28% 8%	563
	21st to end	Night	23% 7% 34% 28% 8% 1	570
May	1st to 10th	Night	23% 5% 32% 32% 7% 1	570
	11th to 20th	Night	20% 6% 27% 37% 9% 1	561
	21st to end	Night	16% 3 28% 38% 14% 2	617
June	1st to 10th	Night	13% 5% 26% 42% 14% 1	570
	11th to 20th	Night	14% 4 26% 42% 14%	570
	21st to end	Night	14% 3 23% 42% 17% 1	570
July	1st to 10th	Night	8% 2 16% 40% 31% 3	555
	11th to 20th	Night	8% 3 21% 41% 25% 3	552
	21st to end	Night	7% 1 16% 49% 25% 3	624
August	1st to 10th	Night	7% 2 14% 48% 29% 2	567
	11th to 20th	Night	13% 2 13% 41% 26% 5%	564
	21st to end	Night	12% 2 17% 44% 23% 3	627
September	1st to 10th	Night	13% 3 20% 40% 20% 5%	570
	11th to 20th	Night	14% 3 21% 36% 23% 3	570
	21st to end	Night	12% 7% 26% 37% 17% 1	727
October	1st to 10th	Night	17% 6% 27% 32% 16% 2	760
	11th to 20th	Night	21% 11% 31% 29% 9% 1	760
	21st to end	Night	22% 10% 31% 29% 7% 1	836
November	1st to 10th	Night	19% 10% 34% 27% 9% 1	780
	11th to 20th	Night	21% 16% 34% 23% 6%	935
	21st to end	Night	22% 14% 33% 24% 7%	1000
December	1st to 10th	Night	19% 12% 38% 24% 5% 1	1000
	11th to 20th	Night	22% 13% 34% 24% 7% 1	1000
	21st to end	Night	27% 13% 30% 24% 5%	1100

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