Dogstar Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dogstar 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% 8% 4 7% 6% 4 5% 5% 5% 7% 35%	78799
	Night	14% 9% 3 6% 5% 3 5% 5% 5% 7% 39%	80509
Transparency	Day	45% 7% 11% 16% 16% 4	78522
	Night	42% 7% 12% 17% 17% 5%	80305
Seeing	Day	21% 12% 22% 22% 15% 8%	13983
	Night	19% 9% 20% 28% 19% 4	24145

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	15% 9% 4 5% 4 2 4 5% 6% 6% 40%	2836
	11th to 20th	Day	14% 9% 6% 7% 5% 3 4 4 4 4 43%	2840
	21st to end	Day	21% 11% 3 4 4 2 3 3 4 4 41%	3124
February	1st to 10th	Day	16% 10% 4 6% 5% 3 4 4 5% 6% 38%	1838
	11th to 20th	Day	18% 11% 4 6% 5% 3 3 3 4 6% 37%	1848
	21st to end	Day	20% 10% 3 6% 5% 3 4 4 4 6% 35%	1520
March	1st to 10th	Day	16% 7% 4 5% 4 2 4 5% 4 7% 42%	1904
	11th to 20th	Day	19% 10% 3 7% 5% 3 5% 5% 5% 6% 34%	1980
	21st to end	Day	16% 10% 5% 6% 5% 3 4 5% 5% 6% 34%	2178
April	1st to 10th	Day	12% 8% 3 5% 6% 3 5% 5% 6% 7% 41%	1980
	11th to 20th	Day	15% 9% 3 6% 5% 3 5% 5% 5% 6% 39%	2161
	21st to end	Day	14% 7% 3 5% 6% 3 5% 4 5% 7% 40%	2340
May	1st to 10th	Day	13% 9% 3 7% 6% 4 4 5% 5% 7% 37%	2340
	11th to 20th	Day	15% 9% 4 7% 7% 4 7% 6% 4 7% 30%	2301
	21st to end	Day	12% 7% 3 8% 7% 4 6% 7% 7% 9% 30%	2531
June	1st to 10th	Day	12% 9% 4 7% 8% 5% 7% 7% 7% 8% 27%	2340
	11th to 20th	Day	8% 6% 4 9% 7% 5% 9% 8% 8% 8% 29%	2340
	21st to end	Day	10% 7% 4 7% 8% 5% 7% 7% 7% 10% 29%	2340
July	1st to 10th	Day	11% 7% 4 11% 9% 5% 7% 8% 8% 9% 20%	2340
	11th to 20th	Day	12% 8% 4 9% 9% 5% 8% 8% 8% 8% 21%	2340
	21st to end	Day	10% 7% 5% 9% 8% 6% 8% 8% 7% 9% 23%	2547
August	1st to 10th	Day	11% 9% 4 9% 8% 6% 7% 8% 8% 8% 23%	2327
	11th to 20th	Day	14% 7% 4 9% 9% 6% 7% 7% 7% 9% 24%	2303
	21st to end	Day	13% 10% 4 9% 8% 4 7% 6% 7% 7% 25%	2358
September	1st to 10th	Day	12% 8% 4 8% 7% 4 7% 5% 6% 7% 31%	1980
	11th to 20th	Day	15% 8% 4 8% 8% 4 5% 5% 5% 8% 29%	1980
	21st to end	Day	13% 8% 3 6% 6% 5% 5% 5% 5% 6% 37%	1980
October	1st to 10th	Day	11% 6% 3 5% 5% 3 5% 4 5% 7% 46%	1980
	11th to 20th	Day	12% 7% 2 5% 4 2 3 4 4 6% 51%	1800
	21st to end	Day	13% 7% 1 4 4 2 3 4 4 6% 52%	1980
November	1st to 10th	Day	10% 6% 2 4 4 2 4 4 4 5% 55%	1736
	11th to 20th	Day	12% 7% 2 4 3 2 5% 4 4 7% 50%	1710
	21st to end	Day	13% 9% 2 6% 4 3 3 4 5% 6% 44%	1710
December	1st to 10th	Day	22% 9% 3 5% 4 3 4 5% 4 6% 35%	1710
	11th to 20th	Day	15% 8% 3 4 5% 3 4 5% 5% 5% 43%	2153
	21st to end	Day	15% 9% 5% 7% 6% 3 4 4 4 5% 39%	3124
January	1st to 10th	Night	15% 14% 5% 5% 4 2 3 3 4 5% 41%	4109
	11th to 20th	Night	17% 11% 3 6% 4 2 3 4 4 5% 42%	4120
	21st to end	Night	21% 16% 3 5% 4 2 3 3 3 4 36%	4532
February	1st to 10th	Night	13% 10% 4 6% 5% 4 4 4 4 7% 40%	2337
	11th to 20th	Night	19% 10% 4 6% 5% 2 4 4 4 5% 37%	2218
	21st to end	Night	20% 10% 5% 8% 5% 3 4 4 4 6% 32%	1831
March	1st to 10th	Night	13% 10% 4 6% 4 3 4 4 5% 5% 41%	2054
	11th to 20th	Night	18% 9% 3 6% 5% 3 4 5% 5% 8% 34%	1980
	21st to end	Night	14% 8% 5% 7% 7% 3 5% 4 6% 7% 35%	2178
April	1st to 10th	Night	13% 8% 3 5% 5% 3 5% 4 5% 7% 43%	1980
	11th to 20th	Night	12% 9% 3 4 4 2 4 4 6% 7% 44%	1762
	21st to end	Night	12% 6% 3 6% 5% 3 4 5% 4 7% 45%	1620
May	1st to 10th	Night	12% 9% 3 6% 5% 3 6% 5% 5% 7% 39%	1620
	11th to 20th	Night	12% 8% 3 6% 7% 4 5% 6% 6% 8% 35%	1592
	21st to end	Night	9% 7% 3 5% 7% 4 6% 6% 7% 9% 36%	1744
June	1st to 10th	Night	9% 7% 4 6% 6% 4 6% 6% 9% 12% 33%	1620
	11th to 20th	Night	6% 6% 2 5% 5% 3 7% 7% 8% 11% 40%	1620
	21st to end	Night	9% 6% 2 4 5% 3 6% 7% 9% 12% 37%	1620
July	1st to 10th	Night	10% 8% 3 7% 7% 4 7% 8% 8% 11% 28%	1620
	11th to 20th	Night	10% 6% 3 5% 6% 5% 7% 8% 10% 11% 29%	1620
	21st to end	Night	9% 6% 4 7% 7% 4 7% 7% 8% 10% 31%	1771
August	1st to 10th	Night	10% 6% 3 7% 7% 4 6% 7% 7% 11% 32%	1611
	11th to 20th	Night	11% 7% 2 8% 7% 4 6% 6% 6% 9% 34%	1598
	21st to end	Night	10% 7% 3 6% 6% 4 7% 6% 7% 11% 33%	1973
September	1st to 10th	Night	10% 7% 4 6% 6% 4 6% 6% 8% 8% 35%	1980
	11th to 20th	Night	13% 7% 3 8% 6% 3 5% 6% 6% 8% 35%	1980
	21st to end	Night	11% 8% 3 5% 5% 4 4 5% 5% 7% 44%	1980
October	1st to 10th	Night	13% 6% 2 4 5% 3 4 3 4 7% 48%	1980
	11th to 20th	Night	13% 7% 3 6% 5% 3 4 4 4 6% 46%	2160
	21st to end	Night	12% 8% 2 4 4 2 4 4 4 5% 51%	2376
November	1st to 10th	Night	12% 7% 2 4 4 2 4 4 5% 7% 49%	2339
	11th to 20th	Night	12% 9% 3 5% 5% 2 3 4 4 6% 47%	2470
	21st to end	Night	14% 9% 2 5% 4 3 5% 4 4 6% 44%	2470
December	1st to 10th	Night	20% 11% 4 6% 4 3 4 6% 4 5% 34%	2470
	11th to 20th	Night	13% 11% 4 7% 5% 2 4 3 4 5% 43%	3042
	21st to end	Night	15% 11% 7% 8% 5% 3 5% 5% 5% 8% 28%	4532

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	36% 6% 9% 15% 26% 7%	2837
	11th to 20th	Day	40% 8% 8% 12% 27% 6%	2840
	21st to end	Day	43% 2 10% 14% 23% 7%	3124
February	1st to 10th	Day	47% 5% 8% 17% 17% 6%	1838
	11th to 20th	Day	48% 4 6% 16% 19% 6%	1858
	21st to end	Day	49% 5% 8% 12% 18% 7%	1520
March	1st to 10th	Day	41% 4 8% 18% 21% 8%	1904
	11th to 20th	Day	50% 5% 9% 14% 16% 6%	1980
	21st to end	Day	50% 5% 11% 16% 14% 3	2178
April	1st to 10th	Day	41% 5% 11% 21% 18% 4	1980
	11th to 20th	Day	44% 5% 9% 16% 20% 5%	2161
	21st to end	Day	42% 6% 11% 24% 15% 2	2340
May	1st to 10th	Day	45% 7% 13% 19% 14% 3	2340
	11th to 20th	Day	53% 8% 11% 16% 10% 1	2305
	21st to end	Day	47% 10% 13% 19% 10% 1	2531
June	1st to 10th	Day	52% 10% 15% 17% 6% 1	2340
	11th to 20th	Day	46% 11% 17% 14% 10% 1	2340
	21st to end	Day	47% 11% 15% 17% 9% 2	2340
July	1st to 10th	Day	54% 13% 15% 13% 6%	2275
	11th to 20th	Day	54% 13% 17% 9% 7% 1	2271
	21st to end	Day	50% 13% 16% 14% 6% 1	2405
August	1st to 10th	Day	55% 11% 14% 16% 4	2314
	11th to 20th	Day	53% 11% 14% 14% 7% 1	2303
	21st to end	Day	54% 10% 13% 14% 7% 2	2358
September	1st to 10th	Day	49% 8% 11% 16% 12% 3	1980
	11th to 20th	Day	52% 6% 10% 16% 14% 2	1980
	21st to end	Day	46% 7% 11% 16% 15% 5%	1980
October	1st to 10th	Day	37% 7% 9% 18% 23% 6%	1980
	11th to 20th	Day	33% 5% 10% 21% 21% 10%	1800
	21st to end	Day	33% 4 8% 20% 23% 11%	1980
November	1st to 10th	Day	32% 4 8% 17% 28% 12%	1736
	11th to 20th	Day	34% 3 7% 20% 26% 10%	1710
	21st to end	Day	39% 4 7% 18% 25% 7%	1710
December	1st to 10th	Day	50% 4 7% 17% 15% 6%	1710
	11th to 20th	Day	40% 4 9% 13% 23% 11%	2150
	21st to end	Day	43% 4 13% 19% 18% 4	3124
January	1st to 10th	Night	41% 5% 9% 13% 25% 8%	4109
	11th to 20th	Night	42% 6% 6% 13% 24% 9%	4120
	21st to end	Night	47% 6% 9% 12% 20% 7%	4532
February	1st to 10th	Night	43% 4 11% 17% 19% 5%	2337
	11th to 20th	Night	48% 7% 6% 17% 18% 5%	2219
	21st to end	Night	52% 6% 8% 15% 15% 5%	1831
March	1st to 10th	Night	44% 6% 8% 15% 20% 8%	2054
	11th to 20th	Night	45% 6% 12% 19% 14% 4	1980
	21st to end	Night	48% 7% 10% 19% 14% 2	2178
April	1st to 10th	Night	39% 6% 12% 21% 21% 2	1980
	11th to 20th	Night	37% 6% 11% 21% 20% 5%	1762
	21st to end	Night	37% 8% 13% 26% 15% 1	1620
May	1st to 10th	Night	41% 8% 15% 23% 11% 2	1620
	11th to 20th	Night	45% 9% 16% 19% 10%	1593
	21st to end	Night	40% 10% 16% 25% 8% 1	1745
June	1st to 10th	Night	40% 14% 18% 20% 6% 1	1620
	11th to 20th	Night	33% 12% 25% 22% 7% 1	1620
	21st to end	Night	35% 14% 19% 20% 10% 3	1620
July	1st to 10th	Night	44% 14% 18% 16% 8%	1575
	11th to 20th	Night	40% 18% 23% 12% 5% 3	1566
	21st to end	Night	41% 14% 21% 17% 6% 1	1672
August	1st to 10th	Night	43% 15% 20% 17% 6%	1600
	11th to 20th	Night	45% 13% 17% 15% 10% 1	1598
	21st to end	Night	41% 11% 21% 18% 7% 2	1973
September	1st to 10th	Night	41% 13% 15% 18% 11% 2	1980
	11th to 20th	Night	46% 9% 12% 17% 15% 1	1980
	21st to end	Night	39% 8% 12% 20% 16% 4	1980
October	1st to 10th	Night	36% 6% 12% 19% 23% 5%	1980
	11th to 20th	Night	37% 5% 11% 20% 19% 7%	2160
	21st to end	Night	35% 4 8% 19% 25% 10%	2376
November	1st to 10th	Night	34% 5% 9% 20% 23% 9%	2339
	11th to 20th	Night	37% 5% 7% 16% 24% 11%	2470
	21st to end	Night	40% 4 7% 21% 21% 7%	2470
December	1st to 10th	Night	49% 6% 9% 15% 15% 7%	2470
	11th to 20th	Night	40% 5% 9% 13% 25% 8%	3044
	21st to end	Night	50% 5% 12% 15% 15% 3	4532

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	34% 21% 31% 13% 1	270
	11th to 20th	Day	38% 22% 21% 16% 3	270
	21st to end	Day	32% 28% 27% 10% 3	297
February	1st to 10th	Day	34% 20% 33% 10% 3	270
	11th to 20th	Day	46% 24% 23% 7%	270
	21st to end	Day	45% 28% 20% 6% 1	210
March	1st to 10th	Day	30% 17% 32% 14% 7% 1	344
	11th to 20th	Day	30% 24% 27% 14% 4 1	420
	21st to end	Day	27% 22% 26% 16% 6% 1	462
April	1st to 10th	Day	25% 16% 25% 23% 9% 1	420
	11th to 20th	Day	21% 22% 20% 23% 12% 2	412
	21st to end	Day	22% 13% 27% 21% 12% 4	420
May	1st to 10th	Day	20% 19% 28% 17% 11% 5%	423
	11th to 20th	Day	22% 10% 24% 23% 13% 8%	447
	21st to end	Day	15% 9% 19% 27% 16% 13%	485
June	1st to 10th	Day	17% 6% 20% 28% 18% 12%	450
	11th to 20th	Day	10% 6% 20% 24% 26% 14%	450
	21st to end	Day	14% 7% 26% 21% 18% 14%	450
July	1st to 10th	Day	12% 4 14% 27% 25% 17%	445
	11th to 20th	Day	12% 3 14% 27% 24% 20%	444
	21st to end	Day	11% 3 13% 26% 27% 20%	488
August	1st to 10th	Day	17% 6% 15% 23% 20% 19%	446
	11th to 20th	Day	14% 4 14% 26% 29% 13%	439
	21st to end	Day	15% 4 13% 23% 26% 20%	495
September	1st to 10th	Day	11% 4 15% 28% 28% 14%	450
	11th to 20th	Day	15% 5% 14% 28% 26% 12%	450
	21st to end	Day	16% 7% 18% 30% 23% 6%	450
October	1st to 10th	Day	19% 8% 19% 26% 19% 9%	450
	11th to 20th	Day	14% 14% 26% 27% 16% 4	450
	21st to end	Day	19% 13% 23% 29% 12% 3	495
November	1st to 10th	Day	18% 13% 28% 26% 13% 2	334
	11th to 20th	Day	23% 18% 31% 23% 5%	270
	21st to end	Day	19% 18% 36% 20% 6% 1	270
December	1st to 10th	Day	35% 18% 28% 15% 3	270
	11th to 20th	Day	27% 17% 31% 20% 4 1	270
	21st to end	Day	31% 18% 35% 13% 4	297
January	1st to 10th	Night	28% 13% 30% 24% 5%	760
	11th to 20th	Night	27% 16% 30% 21% 6%	760
	21st to end	Night	23% 14% 36% 24% 4	836
February	1st to 10th	Night	21% 13% 31% 31% 4	760
	11th to 20th	Night	31% 15% 32% 21% 1	743
	21st to end	Night	32% 18% 28% 20% 3	611
March	1st to 10th	Night	24% 14% 30% 26% 5%	720
	11th to 20th	Night	27% 15% 25% 24% 8% 2	720
	21st to end	Night	24% 12% 29% 25% 10%	792
April	1st to 10th	Night	23% 16% 25% 26% 10% 1	720
	11th to 20th	Night	20% 11% 24% 29% 14% 2	577
	21st to end	Night	16% 10% 21% 35% 17% 1	540
May	1st to 10th	Night	16% 9% 23% 31% 18% 2	540
	11th to 20th	Night	15% 7% 18% 32% 23% 4	531
	21st to end	Night	14% 3 12% 29% 34% 8%	584
June	1st to 10th	Night	12% 3 13% 33% 32% 7%	540
	11th to 20th	Night	9% 1 14% 29% 35% 12%	540
	21st to end	Night	11% 3 8% 32% 39% 7%	540
July	1st to 10th	Night	12% 2 8% 24% 45% 9%	525
	11th to 20th	Night	11% 2 7% 26% 41% 14%	522
	21st to end	Night	9% 2 6% 23% 47% 13%	591
August	1st to 10th	Night	13% 2 7% 26% 41% 11%	537
	11th to 20th	Night	12% 3 7% 29% 39% 10%	534
	21st to end	Night	13% 2 8% 25% 39% 13%	614
September	1st to 10th	Night	12% 3 10% 28% 38% 9%	720
	11th to 20th	Night	16% 3 12% 28% 31% 9%	720
	21st to end	Night	15% 5% 14% 34% 28% 4	720
October	1st to 10th	Night	17% 7% 17% 24% 26% 8%	720
	11th to 20th	Night	17% 9% 23% 30% 18% 3	720
	21st to end	Night	17% 10% 18% 36% 15% 3	792
November	1st to 10th	Night	16% 6% 20% 36% 18% 4	740
	11th to 20th	Night	20% 11% 23% 33% 11% 3	760
	21st to end	Night	21% 11% 21% 32% 14% 1	760
December	1st to 10th	Night	29% 11% 23% 29% 8%	760
	11th to 20th	Night	23% 11% 26% 31% 8% 1	760
	21st to end	Night	27% 12% 25% 31% 4	836

Page generated at 2024-02-22 06:05:47. Version ac07

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