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 2024-10-25.

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% 3 8% 5% 5% 5% 4 6% 7% 35%	100970
	Night	14% 9% 3 7% 4 4 4 4 5% 7% 38%	97792
Transparency	Day	45% 8% 12% 17% 15% 4	100783
	Night	42% 8% 13% 17% 15% 5%	97649
Seeing	Day	21% 13% 23% 22% 14% 7%	14949
	Night	19% 9% 21% 28% 19% 4	24979

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 6% 3 3 4 4 6% 6% 40%	2836
	11th to 20th	Day	14% 10% 5% 8% 4 4 4 3 3 4 42%	2840
	21st to end	Day	21% 11% 3 5% 3 3 3 2 4 4 41%	3124
February	1st to 10th	Day	16% 10% 4 7% 4 4 4 3 5% 5% 37%	1838
	11th to 20th	Day	17% 12% 3 6% 5% 3 2 3 4 6% 37%	1848
	21st to end	Day	20% 11% 2 7% 4 4 4 3 4 6% 35%	1570
March	1st to 10th	Day	23% 9% 3 5% 3 3 3 3 4 6% 38%	3308
	11th to 20th	Day	14% 8% 2 5% 3 3 3 3 4 4 49%	3480
	21st to end	Day	17% 9% 3 6% 4 4 4 4 5% 5% 37%	3815
April	1st to 10th	Day	12% 9% 3 6% 5% 4 4 5% 6% 7% 40%	2090
	11th to 20th	Day	14% 10% 3 7% 4 4 5% 4 5% 6% 39%	2284
	21st to end	Day	14% 7% 3 6% 5% 5% 4 3 5% 7% 40%	2470
May	1st to 10th	Day	16% 11% 3 8% 5% 5% 5% 4 5% 6% 32%	4082
	11th to 20th	Day	19% 10% 4 8% 5% 4 6% 4 5% 6% 28%	4081
	21st to end	Day	10% 7% 3 8% 5% 5% 5% 5% 7% 9% 35%	4476
June	1st to 10th	Day	12% 10% 3 9% 7% 7% 6% 5% 7% 7% 27%	2470
	11th to 20th	Day	8% 7% 3 10% 6% 7% 8% 6% 9% 8% 28%	2470
	21st to end	Day	10% 7% 3 7% 8% 6% 7% 6% 7% 9% 30%	2470
July	1st to 10th	Day	8% 6% 3 10% 8% 6% 7% 6% 8% 10% 29%	4120
	11th to 20th	Day	10% 8% 4 10% 7% 7% 7% 6% 8% 8% 26%	4120
	21st to end	Day	14% 10% 5% 14% 9% 9% 8% 5% 6% 7% 13%	4466
August	1st to 10th	Day	8% 8% 4 9% 7% 7% 7% 6% 8% 9% 26%	4104
	11th to 20th	Day	11% 6% 3 8% 6% 7% 7% 5% 8% 11% 29%	4044
	21st to end	Day	8% 7% 3 9% 6% 6% 6% 5% 7% 7% 36%	4134
September	1st to 10th	Day	11% 9% 4 9% 6% 6% 7% 5% 6% 7% 31%	2090
	11th to 20th	Day	15% 9% 4 10% 6% 6% 5% 4 6% 8% 29%	2090
	21st to end	Day	14% 8% 3 7% 5% 6% 5% 4 5% 6% 36%	2090
October	1st to 10th	Day	11% 6% 2 6% 4 5% 4 3 5% 7% 46%	2090
	11th to 20th	Day	11% 7% 2 5% 3 3 3 3 4 6% 53%	1900
	21st to end	Day	13% 7% 1 4 4 2 3 2 4 6% 53%	2027
November	1st to 10th	Day	10% 6% 2 4 3 3 4 4 5% 5% 54%	1736
	11th to 20th	Day	12% 7% 2 4 3 3 5% 3 5% 6% 50%	1710
	21st to end	Day	13% 9% 2 7% 4 3 4 3 5% 6% 44%	1710
December	1st to 10th	Day	22% 10% 3 5% 4 4 4 4 4 6% 35%	1710
	11th to 20th	Day	15% 9% 3 5% 4 3 4 4 5% 5% 43%	2153
	21st to end	Day	15% 9% 5% 8% 5% 4 4 3 4 5% 39%	3124
January	1st to 10th	Night	14% 14% 4 6% 3 3 3 2 4 5% 41%	4109
	11th to 20th	Night	17% 12% 3 6% 3 3 3 3 4 5% 42%	4120
	21st to end	Night	21% 16% 3 6% 3 3 3 2 3 4 36%	4532
February	1st to 10th	Night	13% 10% 3 6% 4 5% 4 4 5% 6% 39%	2337
	11th to 20th	Night	19% 12% 3 7% 4 4 4 3 4 5% 37%	2218
	21st to end	Night	20% 10% 4 8% 5% 4 4 4 5% 5% 32%	1884
March	1st to 10th	Night	21% 14% 3 8% 5% 4 4 3 5% 5% 28%	3543
	11th to 20th	Night	14% 7% 2 5% 4 4 4 4 5% 8% 44%	3480
	21st to end	Night	15% 8% 3 7% 5% 4 4 4 5% 7% 37%	3817
April	1st to 10th	Night	13% 9% 3 7% 4 4 5% 3 5% 6% 42%	2090
	11th to 20th	Night	12% 10% 3 5% 4 3 4 3 6% 7% 43%	1860
	21st to end	Night	11% 8% 3 7% 5% 4 4 3 5% 7% 45%	1710
May	1st to 10th	Night	17% 12% 3 8% 4 4 5% 3 5% 7% 31%	2813
	11th to 20th	Night	19% 10% 3 7% 5% 4 5% 3 5% 7% 31%	2812
	21st to end	Night	8% 7% 3 7% 6% 5% 6% 5% 8% 10% 36%	3079
June	1st to 10th	Night	10% 8% 3 7% 5% 5% 5% 6% 8% 11% 32%	1710
	11th to 20th	Night	6% 6% 2 6% 4 4 7% 5% 8% 11% 39%	1710
	21st to end	Night	9% 6% 2 5% 4 5% 6% 6% 9% 11% 37%	1710
July	1st to 10th	Night	9% 7% 2 8% 6% 6% 7% 6% 8% 12% 29%	2840
	11th to 20th	Night	10% 6% 3 6% 6% 6% 6% 6% 8% 10% 33%	2840
	21st to end	Night	17% 11% 4 10% 7% 7% 6% 5% 7% 8% 20%	3087
August	1st to 10th	Night	8% 6% 3 8% 6% 5% 7% 5% 8% 12% 32%	2825
	11th to 20th	Night	15% 7% 2 8% 5% 5% 5% 4 6% 9% 33%	2785
	21st to end	Night	8% 6% 2 5% 4 4 5% 4 7% 10% 45%	3483
September	1st to 10th	Night	10% 7% 3 8% 5% 6% 6% 5% 8% 8% 35%	2090
	11th to 20th	Night	12% 8% 3 9% 5% 5% 5% 4 6% 9% 34%	2090
	21st to end	Night	13% 8% 2 6% 4 5% 4 4 5% 7% 42%	2090
October	1st to 10th	Night	12% 6% 2 5% 4 4 4 3 5% 7% 48%	2090
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 4 6% 48%	2280
	21st to end	Night	12% 8% 1 4 3 3 4 3 4 5% 52%	2435
November	1st to 10th	Night	12% 7% 2 5% 4 4 3 4 5% 6% 49%	2339
	11th to 20th	Night	12% 10% 3 6% 4 3 3 3 4 6% 47%	2470
	21st to end	Night	14% 9% 2 6% 3 4 4 4 4 6% 43%	2470
December	1st to 10th	Night	19% 11% 4 6% 4 3 4 4 4 5% 34%	2470
	11th to 20th	Night	13% 12% 3 8% 4 3 3 3 4 5% 43%	3042
	21st to end	Night	14% 12% 6% 9% 5% 4 5% 4 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% 13% 18% 7%	1570
March	1st to 10th	Day	46% 4 7% 17% 17% 10%	3308
	11th to 20th	Day	37% 5% 7% 17% 22% 12%	3480
	21st to end	Day	47% 4 9% 22% 13% 4	3815
April	1st to 10th	Day	41% 6% 11% 20% 19% 5%	2090
	11th to 20th	Day	43% 5% 10% 17% 20% 5%	2284
	21st to end	Day	42% 6% 11% 24% 15% 2	2470
May	1st to 10th	Day	47% 10% 11% 19% 12% 2	4120
	11th to 20th	Day	51% 10% 10% 20% 9% 1	4085
	21st to end	Day	40% 11% 15% 19% 15% 1	4489
June	1st to 10th	Day	51% 10% 15% 17% 6% 1	2470
	11th to 20th	Day	45% 11% 17% 15% 10% 1	2470
	21st to end	Day	46% 11% 15% 16% 10% 2	2470
July	1st to 10th	Day	45% 14% 17% 17% 6%	4055
	11th to 20th	Day	50% 15% 19% 11% 4 1	4051
	21st to end	Day	66% 11% 10% 8% 4	4324
August	1st to 10th	Day	47% 13% 16% 20% 3	4091
	11th to 20th	Day	42% 12% 21% 13% 9% 3	4083
	21st to end	Day	42% 12% 12% 22% 10% 1	4134
September	1st to 10th	Day	48% 9% 11% 16% 13% 3	2090
	11th to 20th	Day	52% 6% 11% 16% 14% 2	2090
	21st to end	Day	46% 7% 12% 15% 14% 5%	2090
October	1st to 10th	Day	36% 7% 9% 18% 24% 7%	2090
	11th to 20th	Day	32% 4 10% 20% 21% 12%	1900
	21st to end	Day	33% 4 8% 20% 24% 11%	2027
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	51% 6% 8% 14% 15% 5%	1884
March	1st to 10th	Night	52% 6% 14% 11% 13% 5%	3543
	11th to 20th	Night	35% 6% 10% 22% 17% 10%	3480
	21st to end	Night	46% 5% 10% 20% 13% 6%	3817
April	1st to 10th	Night	39% 6% 12% 20% 20% 3	2090
	11th to 20th	Night	37% 6% 12% 20% 20% 5%	1860
	21st to end	Night	37% 8% 13% 26% 15% 1	1710
May	1st to 10th	Night	45% 12% 13% 21% 8% 1	2840
	11th to 20th	Night	46% 11% 16% 18% 8%	2813
	21st to end	Night	33% 15% 19% 25% 9%	3087
June	1st to 10th	Night	41% 14% 18% 19% 7% 1	1710
	11th to 20th	Night	33% 12% 25% 22% 7% 1	1710
	21st to end	Night	35% 14% 18% 20% 11% 3	1710
July	1st to 10th	Night	42% 16% 20% 17% 5%	2795
	11th to 20th	Night	39% 19% 25% 13% 3 1	2786
	21st to end	Night	58% 13% 15% 10% 3 1	2988
August	1st to 10th	Night	39% 15% 26% 16% 4	2814
	11th to 20th	Night	43% 13% 21% 13% 9% 1	2812
	21st to end	Night	31% 10% 21% 28% 9% 1	3483
September	1st to 10th	Night	41% 12% 15% 17% 12% 2	2090
	11th to 20th	Night	46% 9% 12% 18% 14% 1	2090
	21st to end	Night	40% 8% 13% 19% 15% 4	2090
October	1st to 10th	Night	35% 6% 12% 19% 24% 5%	2090
	11th to 20th	Night	36% 5% 11% 20% 19% 9%	2280
	21st to end	Night	34% 4 8% 19% 25% 10%	2435
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	46% 26% 21% 6% 1	225
March	1st to 10th	Day	32% 16% 31% 14% 7% 1	380
	11th to 20th	Day	29% 23% 28% 14% 4 1	460
	21st to end	Day	26% 24% 27% 16% 6% 1	506
April	1st to 10th	Day	27% 17% 25% 22% 8% 1	460
	11th to 20th	Day	22% 22% 21% 22% 11% 2	452
	21st to end	Day	22% 13% 29% 21% 12% 4	460
May	1st to 10th	Day	20% 20% 28% 17% 10% 5%	463
	11th to 20th	Day	22% 10% 24% 23% 13% 7%	487
	21st to end	Day	14% 10% 22% 27% 16% 12%	529
June	1st to 10th	Day	17% 7% 22% 28% 17% 11%	490
	11th to 20th	Day	9% 6% 22% 25% 25% 13%	490
	21st to end	Day	14% 7% 27% 21% 18% 13%	490
July	1st to 10th	Day	11% 4 15% 29% 24% 16%	485
	11th to 20th	Day	12% 4 14% 27% 23% 20%	484
	21st to end	Day	11% 5% 14% 26% 26% 19%	532
August	1st to 10th	Day	17% 6% 18% 23% 19% 17%	486
	11th to 20th	Day	13% 5% 17% 25% 27% 12%	479
	21st to end	Day	14% 4 13% 24% 26% 19%	539
September	1st to 10th	Day	10% 6% 16% 28% 27% 13%	490
	11th to 20th	Day	15% 6% 18% 27% 24% 11%	490
	21st to end	Day	18% 8% 19% 28% 22% 6%	490
October	1st to 10th	Day	18% 8% 21% 27% 18% 9%	490
	11th to 20th	Day	14% 14% 26% 27% 16% 3	490
	21st to end	Day	19% 13% 24% 29% 12% 3	514
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% 19% 3	628
March	1st to 10th	Night	25% 14% 30% 25% 5%	760
	11th to 20th	Night	26% 14% 26% 24% 8% 1	760
	21st to end	Night	24% 13% 30% 24% 9%	836
April	1st to 10th	Night	23% 16% 25% 25% 9% 1	760
	11th to 20th	Night	21% 11% 25% 29% 13% 2	609
	21st to end	Night	15% 11% 22% 35% 16% 1	570
May	1st to 10th	Night	16% 10% 23% 31% 18% 2	570
	11th to 20th	Night	15% 8% 18% 32% 22% 4	561
	21st to end	Night	14% 3 13% 30% 32% 7%	617
June	1st to 10th	Night	12% 4 14% 34% 31% 6%	570
	11th to 20th	Night	9% 1 14% 30% 34% 12%	570
	21st to end	Night	11% 3 9% 32% 38% 7%	570
July	1st to 10th	Night	12% 2 9% 24% 45% 9%	555
	11th to 20th	Night	10% 2 7% 25% 42% 13%	552
	21st to end	Night	9% 3 6% 23% 45% 12%	624
August	1st to 10th	Night	13% 2 9% 27% 39% 10%	567
	11th to 20th	Night	12% 4 9% 29% 38% 9%	564
	21st to end	Night	13% 2 8% 25% 39% 13%	649
September	1st to 10th	Night	12% 4 10% 29% 37% 9%	760
	11th to 20th	Night	16% 4 13% 28% 30% 8%	760
	21st to end	Night	17% 5% 13% 34% 27% 4	760
October	1st to 10th	Night	16% 7% 18% 25% 26% 8%	760
	11th to 20th	Night	16% 9% 24% 31% 18% 3	760
	21st to end	Night	17% 10% 18% 36% 16% 3	812
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 2024-10-22 20:20:59. Version ac07

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