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 2024-02-25.

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	14% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	78383
	Night	13% 9% 4 7% 6% 3 4 4 5% 6% 37%	80970
Transparency	Day	47% 5% 12% 23% 11% 1	78083
	Night	48% 5% 11% 22% 12% 1	80790
Seeing	Day	18% 10% 29% 25% 13% 4	14883
	Night	18% 9% 30% 31% 11% 1	24961

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	8% 14% 10% 14% 8% 4 5% 4 4 5% 24%	2527
	11th to 20th	Day	10% 12% 4 11% 10% 4 5% 11% 7% 6% 20%	2530
	21st to end	Day	15% 19% 8% 11% 7% 3 3 3 4 5% 21%	3070
February	1st to 10th	Day	10% 12% 5% 8% 7% 3 5% 6% 5% 7% 32%	1710
	11th to 20th	Day	12% 10% 5% 8% 5% 3 5% 5% 5% 6% 35%	1687
	21st to end	Day	13% 11% 4 9% 8% 4 4 4 5% 5% 34%	1520
March	1st to 10th	Day	15% 11% 6% 6% 5% 3 4 4 4 7% 35%	1833
	11th to 20th	Day	12% 8% 5% 7% 5% 3 4 4 4 8% 38%	1980
	21st to end	Day	22% 9% 3 7% 5% 3 4 5% 5% 7% 30%	2275
April	1st to 10th	Day	18% 12% 5% 6% 6% 3 4 5% 5% 6% 31%	2160
	11th to 20th	Day	18% 12% 4 7% 5% 3 4 4 5% 6% 33%	2134
	21st to end	Day	20% 10% 4 6% 6% 2 5% 5% 4 7% 31%	2181
May	1st to 10th	Day	16% 8% 3 6% 6% 4 6% 6% 6% 8% 30%	2497
	11th to 20th	Day	16% 7% 3 6% 7% 4 5% 5% 5% 7% 34%	2479
	21st to end	Day	17% 6% 3 6% 6% 3 5% 5% 6% 8% 37%	2725
June	1st to 10th	Day	12% 5% 2 4 5% 3 4 5% 6% 9% 45%	2520
	11th to 20th	Day	12% 5% 2 5% 5% 3 5% 5% 5% 9% 43%	2520
	21st to end	Day	11% 6% 3 7% 5% 3 6% 5% 6% 9% 40%	2520
July	1st to 10th	Day	7% 4 1 5% 5% 3 5% 5% 7% 9% 49%	2520
	11th to 20th	Day	7% 4 2 6% 5% 3 5% 5% 6% 9% 47%	2520
	21st to end	Day	7% 4 3 4 5% 4 5% 6% 7% 10% 46%	2743
August	1st to 10th	Day	7% 4 2 6% 5% 4 6% 6% 7% 10% 43%	2369
	11th to 20th	Day	13% 6% 2 5% 5% 3 4 5% 7% 8% 44%	2269
	21st to end	Day	10% 5% 2 6% 5% 3 5% 4 6% 8% 47%	2376
September	1st to 10th	Day	15% 6% 2 4 4 2 4 4 5% 8% 46%	2160
	11th to 20th	Day	12% 5% 2 6% 5% 3 4 4 4 8% 47%	2160
	21st to end	Day	14% 6% 2 5% 4 3 5% 4 5% 7% 43%	1918
October	1st to 10th	Day	16% 7% 2 4 5% 2 4 5% 4 6% 44%	1800
	11th to 20th	Day	20% 8% 3 6% 4 3 4 4 4 7% 38%	1800
	21st to end	Day	18% 10% 4 7% 4 2 4 3 4 5% 38%	1890
November	1st to 10th	Day	13% 8% 4 5% 5% 3 4 5% 5% 7% 43%	1672
	11th to 20th	Day	16% 11% 5% 9% 7% 3 5% 3 4 6% 32%	1577
	21st to end	Day	13% 11% 3 7% 5% 3 3 4 5% 6% 40%	1520
December	1st to 10th	Day	15% 12% 5% 11% 5% 3 6% 5% 4 5% 29%	1520
	11th to 20th	Day	13% 12% 7% 8% 7% 3 6% 4 5% 7% 28%	1918
	21st to end	Day	19% 20% 9% 11% 6% 3 3 4 4 4 17%	2783
January	1st to 10th	Night	9% 13% 10% 13% 7% 4 4 4 4 5% 26%	4428
	11th to 20th	Night	11% 13% 7% 12% 8% 4 5% 6% 8% 5% 22%	4440
	21st to end	Night	14% 18% 9% 10% 7% 3 4 3 4 5% 23%	4596
February	1st to 10th	Night	9% 12% 6% 10% 7% 4 5% 5% 4 5% 33%	2470
	11th to 20th	Night	10% 9% 4 7% 7% 4 5% 4 4 6% 40%	2379
	21st to end	Night	15% 9% 4 8% 7% 3 5% 3 5% 5% 36%	1831
March	1st to 10th	Night	16% 11% 4 5% 5% 3 4 4 5% 6% 36%	2142
	11th to 20th	Night	13% 9% 3 6% 6% 4 5% 5% 5% 7% 38%	1980
	21st to end	Night	19% 11% 3 6% 6% 3 5% 3 5% 6% 32%	2080
April	1st to 10th	Night	16% 11% 4 6% 5% 3 3 5% 5% 5% 38%	1800
	11th to 20th	Night	20% 8% 3 5% 5% 3 4 5% 5% 6% 37%	1775
	21st to end	Night	18% 10% 3 5% 5% 4 4 4 5% 5% 36%	1777
May	1st to 10th	Night	20% 7% 3 5% 4 3 4 4 7% 8% 35%	1460
	11th to 20th	Night	16% 7% 3 5% 4 3 4 5% 5% 7% 41%	1416
	21st to end	Night	14% 5% 2 4 5% 3 4 4 7% 7% 46%	1551
June	1st to 10th	Night	10% 4 2 5% 5% 3 5% 5% 5% 9% 47%	1440
	11th to 20th	Night	11% 6% 2 5% 5% 3 4 5% 6% 8% 46%	1440
	21st to end	Night	8% 5% 2 4 4 3 4 4 6% 8% 51%	1440
July	1st to 10th	Night	5% 5% 1 4 4 3 3 4 6% 9% 54%	1440
	11th to 20th	Night	6% 4 1 4 4 3 4 4 6% 10% 54%	1440
	21st to end	Night	6% 2 2 3 4 3 4 4 6% 10% 54%	1575
August	1st to 10th	Night	6% 2 2 5% 5% 4 5% 6% 6% 9% 51%	1566
	11th to 20th	Night	11% 5% 2 4 5% 2 4 4 5% 7% 51%	1631
	21st to end	Night	10% 4 2 4 4 2 4 4 5% 7% 54%	1980
September	1st to 10th	Night	11% 4 2 4 5% 4 4 4 5% 7% 51%	1800
	11th to 20th	Night	13% 5% 2 4 4 2 3 4 4 7% 54%	1800
	21st to end	Night	10% 5% 3 4 4 3 4 5% 4 6% 53%	2021
October	1st to 10th	Night	14% 5% 2 4 4 3 3 4 4 7% 50%	2160
	11th to 20th	Night	18% 7% 2 5% 4 3 5% 4 5% 6% 41%	2160
	21st to end	Night	17% 10% 3 6% 5% 2 4 4 6% 6% 37%	2465
November	1st to 10th	Night	14% 7% 3 6% 5% 3 4 5% 5% 5% 45%	2406
	11th to 20th	Night	14% 11% 5% 9% 7% 3 5% 4 4 5% 33%	2598
	21st to end	Night	16% 10% 4 8% 5% 3 4 3 4 5% 37%	2660
December	1st to 10th	Night	12% 12% 5% 11% 8% 3 5% 5% 5% 6% 28%	2660
	11th to 20th	Night	14% 13% 5% 10% 7% 3 5% 5% 5% 6% 27%	3279
	21st to end	Night	21% 15% 6% 12% 7% 4 4 4 3 5% 19%	4884

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% 3 13% 13% 5%	2528
	11th to 20th	Day	60% 5% 10% 18% 6%	2530
	21st to end	Day	66% 3 12% 14% 4	3070
February	1st to 10th	Day	52% 4 14% 18% 11% 1	1710
	11th to 20th	Day	50% 5% 10% 24% 10% 1	1696
	21st to end	Day	52% 5% 10% 20% 11% 2	1520
March	1st to 10th	Day	51% 4 14% 21% 9% 1	1833
	11th to 20th	Day	46% 4 13% 22% 13% 2	1980
	21st to end	Day	54% 4 11% 21% 8% 1	2275
April	1st to 10th	Day	54% 5% 10% 20% 10% 1	2160
	11th to 20th	Day	53% 4 10% 21% 10% 2	2134
	21st to end	Day	52% 6% 11% 18% 11% 1	2181
May	1st to 10th	Day	50% 7% 12% 21% 9% 1	2497
	11th to 20th	Day	50% 6% 12% 21% 11% 1	2483
	21st to end	Day	45% 6% 10% 23% 14% 2	2725
June	1st to 10th	Day	35% 6% 15% 29% 14% 2	2520
	11th to 20th	Day	39% 6% 14% 24% 17% 1	2520
	21st to end	Day	40% 6% 13% 26% 13% 1	2520
July	1st to 10th	Day	31% 8% 15% 32% 13% 2	2451
	11th to 20th	Day	33% 7% 15% 26% 17% 2	2445
	21st to end	Day	31% 7% 17% 28% 14% 2	2591
August	1st to 10th	Day	34% 7% 14% 33% 11% 2	2354
	11th to 20th	Day	37% 7% 12% 30% 13% 1	2269
	21st to end	Day	35% 6% 11% 28% 17% 2	2376
September	1st to 10th	Day	37% 5% 14% 26% 17% 1	2160
	11th to 20th	Day	36% 5% 13% 33% 12%	2160
	21st to end	Day	40% 5% 11% 29% 14% 1	1918
October	1st to 10th	Day	41% 6% 9% 30% 13%	1800
	11th to 20th	Day	47% 4 12% 23% 13% 1	1800
	21st to end	Day	48% 5% 12% 22% 13% 1	1890
November	1st to 10th	Day	41% 5% 14% 24% 14% 2	1672
	11th to 20th	Day	55% 4 10% 20% 10% 1	1577
	21st to end	Day	46% 5% 18% 23% 8% 1	1520
December	1st to 10th	Day	57% 5% 13% 17% 8% 1	1520
	11th to 20th	Day	55% 6% 16% 15% 7% 1	1915
	21st to end	Day	71% 4 8% 13% 4	2783
January	1st to 10th	Night	60% 5% 10% 19% 6%	4428
	11th to 20th	Night	61% 4 11% 15% 9%	4440
	21st to end	Night	65% 4 9% 16% 5% 1	4596
February	1st to 10th	Night	55% 3 11% 19% 11% 2	2470
	11th to 20th	Night	46% 5% 12% 24% 12% 2	2380
	21st to end	Night	51% 5% 10% 21% 11% 2	1831
March	1st to 10th	Night	49% 5% 14% 21% 9% 1	2142
	11th to 20th	Night	45% 5% 12% 23% 13% 2	1980
	21st to end	Night	53% 4 10% 21% 10% 2	2080
April	1st to 10th	Night	48% 5% 9% 22% 15% 2	1800
	11th to 20th	Night	48% 5% 9% 19% 16% 3	1775
	21st to end	Night	49% 5% 11% 19% 14% 3	1777
May	1st to 10th	Night	46% 5% 11% 23% 14%	1460
	11th to 20th	Night	43% 5% 12% 24% 14% 1	1417
	21st to end	Night	37% 6% 12% 25% 18% 2	1552
June	1st to 10th	Night	35% 6% 13% 27% 18% 1	1440
	11th to 20th	Night	36% 7% 11% 23% 21% 2	1440
	21st to end	Night	30% 6% 17% 27% 16% 4	1440
July	1st to 10th	Night	26% 6% 14% 34% 18% 3	1400
	11th to 20th	Night	26% 6% 15% 32% 19% 3	1392
	21st to end	Night	24% 6% 18% 30% 17% 4	1487
August	1st to 10th	Night	27% 7% 15% 32% 16% 3	1557
	11th to 20th	Night	33% 5% 14% 30% 17% 2	1631
	21st to end	Night	30% 6% 13% 29% 17% 5%	1980
September	1st to 10th	Night	33% 5% 9% 28% 23% 1	1800
	11th to 20th	Night	32% 4 12% 34% 18% 1	1800
	21st to end	Night	32% 5% 10% 32% 20% 1	2021
October	1st to 10th	Night	35% 4 10% 31% 19% 2	2160
	11th to 20th	Night	43% 6% 11% 22% 18% 1	2160
	21st to end	Night	48% 5% 11% 22% 13% 1	2465
November	1st to 10th	Night	41% 5% 12% 23% 17% 2	2406
	11th to 20th	Night	55% 4 11% 19% 10% 1	2598
	21st to end	Night	51% 3 13% 24% 8% 1	2660
December	1st to 10th	Night	56% 4 12% 20% 7% 1	2660
	11th to 20th	Night	56% 6% 13% 18% 6% 1	3281
	21st to end	Night	69% 4 8% 13% 5%	4884

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	17% 13% 38% 21% 8% 3	270
	11th to 20th	Day	23% 14% 39% 18% 4 1	270
	21st to end	Day	24% 15% 35% 19% 7% 1	297
February	1st to 10th	Day	16% 20% 43% 15% 5% 1	270
	11th to 20th	Day	20% 24% 32% 19% 4 1	270
	21st to end	Day	23% 17% 40% 18% 2	210
March	1st to 10th	Day	22% 19% 38% 15% 5% 1	240
	11th to 20th	Day	23% 17% 34% 18% 7% 2	240
	21st to end	Day	33% 11% 28% 19% 8% 1	361
April	1st to 10th	Day	31% 10% 33% 19% 6%	420
	11th to 20th	Day	26% 18% 24% 22% 9% 1	412
	21st to end	Day	27% 12% 29% 22% 8% 1	441
May	1st to 10th	Day	22% 13% 32% 24% 8% 1	603
	11th to 20th	Day	22% 11% 28% 25% 11% 3	625
	21st to end	Day	20% 6% 29% 24% 16% 5%	679
June	1st to 10th	Day	11% 5% 28% 32% 20% 5%	630
	11th to 20th	Day	16% 5% 33% 27% 17% 3	630
	21st to end	Day	13% 6% 30% 30% 15% 5%	630
July	1st to 10th	Day	8% 2 21% 30% 26% 12%	621
	11th to 20th	Day	9% 4 28% 32% 20% 8%	618
	21st to end	Day	6% 4 25% 38% 19% 8%	684
August	1st to 10th	Day	8% 2 20% 36% 24% 9%	626
	11th to 20th	Day	16% 3 17% 29% 25% 11%	583
	21st to end	Day	13% 5% 22% 31% 20% 9%	495
September	1st to 10th	Day	18% 5% 22% 31% 18% 5%	450
	11th to 20th	Day	12% 5% 24% 34% 19% 6%	450
	21st to end	Day	19% 10% 29% 24% 17% 2	374
October	1st to 10th	Day	21% 12% 25% 25% 15% 3	270
	11th to 20th	Day	28% 15% 31% 20% 6%	270
	21st to end	Day	26% 17% 33% 17% 6% 1	297
November	1st to 10th	Day	17% 12% 42% 21% 6% 2	270
	11th to 20th	Day	21% 17% 35% 18% 7% 1	270
	21st to end	Day	23% 13% 39% 21% 5%	270
December	1st to 10th	Day	19% 12% 43% 19% 8%	270
	11th to 20th	Day	23% 12% 38% 20% 6%	270
	21st to end	Day	30% 15% 37% 14% 3	297
January	1st to 10th	Night	16% 14% 35% 27% 8% 1	950
	11th to 20th	Night	19% 12% 36% 27% 5% 1	950
	21st to end	Night	21% 11% 33% 28% 6% 1	1045
February	1st to 10th	Night	16% 14% 34% 29% 7% 1	950
	11th to 20th	Night	16% 12% 39% 26% 6%	905
	21st to end	Night	21% 14% 34% 26% 5%	611
March	1st to 10th	Night	22% 11% 36% 25% 6% 1	702
	11th to 20th	Night	19% 9% 33% 29% 8% 1	540
	21st to end	Night	24% 9% 28% 29% 8% 1	594
April	1st to 10th	Night	21% 14% 34% 26% 5%	540
	11th to 20th	Night	25% 10% 29% 28% 8%	533
	21st to end	Night	23% 7% 33% 28% 8% 1	540
May	1st to 10th	Night	23% 5% 32% 32% 7% 1	540
	11th to 20th	Night	21% 6% 26% 37% 9% 1	531
	21st to end	Night	16% 3 27% 38% 14% 2	584
June	1st to 10th	Night	12% 4 26% 42% 15% 1	540
	11th to 20th	Night	15% 4 25% 42% 15%	540
	21st to end	Night	13% 3 23% 43% 18% 1	540
July	1st to 10th	Night	8% 2 16% 39% 32% 3	525
	11th to 20th	Night	8% 3 20% 42% 25% 2	522
	21st to end	Night	7% 1 15% 49% 24% 3	591
August	1st to 10th	Night	7% 1 13% 48% 30% 2	537
	11th to 20th	Night	13% 2 13% 40% 27% 6%	534
	21st to end	Night	12% 2 18% 43% 23% 3	594
September	1st to 10th	Night	13% 3 19% 40% 19% 6%	540
	11th to 20th	Night	14% 3 22% 35% 22% 4	540
	21st to end	Night	13% 8% 27% 35% 16% 1	688
October	1st to 10th	Night	17% 7% 27% 31% 17% 2	720
	11th to 20th	Night	21% 11% 30% 29% 9% 1	720
	21st to end	Night	22% 10% 31% 30% 7% 1	792
November	1st to 10th	Night	18% 10% 35% 27% 10% 1	740
	11th to 20th	Night	20% 16% 34% 23% 7%	888
	21st to end	Night	22% 13% 33% 24% 7%	950
December	1st to 10th	Night	20% 12% 38% 24% 5% 1	950
	11th to 20th	Night	22% 12% 35% 24% 7% 1	950
	21st to end	Night	27% 13% 31% 24% 4	1045

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