HSV Stargazers Observation Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the HSV Stargazers Observation Site clear sky chart from 2005-11-06 to 2024-07-31.

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	14% 6% 2 6% 4 4 4 3 5% 7% 43%	89545
	Night	14% 6% 2 5% 3 3 3 3 5% 6% 49%	90288
Transparency	Day	40% 6% 10% 21% 18% 5%	89315
	Night	35% 5% 10% 22% 21% 6%	90122
Seeing	Day	17% 11% 25% 26% 18% 5%	14988
	Night	16% 10% 24% 29% 17% 2	24788

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	18% 8% 3 6% 4 3 3 2 4 5% 44%	2847
	11th to 20th	Day	13% 12% 3 6% 3 3 3 2 4 4 49%	2850
	21st to end	Day	25% 6% 2 4 3 2 2 2 3 4 47%	3135
February	1st to 10th	Day	22% 9% 3 5% 3 3 3 2 4 4 41%	1710
	11th to 20th	Day	18% 9% 2 6% 4 3 3 2 5% 5% 42%	1762
	21st to end	Day	23% 8% 3 7% 4 3 3 3 4 5% 37%	1660
March	1st to 10th	Day	23% 10% 3 6% 3 3 3 2 3 5% 38%	3436
	11th to 20th	Day	15% 7% 3 6% 4 4 4 3 4 6% 44%	3480
	21st to end	Day	17% 7% 3 6% 4 4 4 2 4 6% 42%	3814
April	1st to 10th	Day	15% 7% 2 5% 4 4 4 3 4 6% 45%	2251
	11th to 20th	Day	18% 6% 2 5% 4 4 4 2 4 6% 45%	2254
	21st to end	Day	17% 7% 2 7% 5% 4 4 3 5% 6% 41%	2280
May	1st to 10th	Day	20% 7% 2 7% 5% 4 4 3 4 7% 36%	3783
	11th to 20th	Day	14% 5% 2 6% 5% 5% 5% 4 5% 7% 42%	4082
	21st to end	Day	15% 7% 3 8% 6% 5% 6% 4 6% 7% 34%	4477
June	1st to 10th	Day	9% 6% 2 6% 6% 5% 5% 5% 6% 9% 41%	2470
	11th to 20th	Day	5% 4 2 6% 6% 6% 6% 5% 7% 9% 43%	2470
	21st to end	Day	5% 4 2 5% 5% 6% 6% 5% 8% 10% 46%	2470
July	1st to 10th	Day	6% 6% 2 7% 7% 7% 7% 6% 8% 10% 34%	2470
	11th to 20th	Day	7% 4 2 5% 6% 5% 5% 5% 7% 9% 46%	2470
	21st to end	Day	7% 5% 2 6% 5% 6% 6% 5% 9% 9% 38%	2678
August	1st to 10th	Day	6% 4 2 7% 6% 7% 6% 6% 8% 9% 38%	2328
	11th to 20th	Day	10% 6% 2 6% 5% 4 5% 5% 7% 9% 41%	2163
	21st to end	Day	8% 5% 2 6% 6% 6% 6% 5% 7% 9% 42%	2376
September	1st to 10th	Day	12% 5% 2 5% 4 4 5% 4 5% 7% 46%	2160
	11th to 20th	Day	15% 5% 2 5% 3 4 5% 4 5% 8% 44%	2122
	21st to end	Day	11% 4 2 4 3 4 4 3 5% 6% 54%	1895
October	1st to 10th	Day	9% 4 2 6% 4 3 4 2 5% 6% 56%	1800
	11th to 20th	Day	16% 5% 1 5% 3 3 2 2 4 6% 55%	1800
	21st to end	Day	18% 5% 2 4 3 3 3 3 3 5% 51%	1980
November	1st to 10th	Day	12% 5% 2 5% 3 2 3 3 3 5% 57%	1858
	11th to 20th	Day	12% 5% 2 4 3 2 2 2 5% 6% 55%	1900
	21st to end	Day	21% 7% 2 5% 4 2 3 2 3 5% 46%	1663
December	1st to 10th	Day	19% 6% 2 5% 3 3 3 3 4 6% 46%	1520
	11th to 20th	Day	15% 8% 3 7% 5% 3 4 3 5% 3 43%	1996
	21st to end	Day	16% 8% 3 7% 4 4 5% 4 5% 5% 38%	3135
January	1st to 10th	Night	16% 8% 2 6% 4 3 4 2 4 5% 45%	4108
	11th to 20th	Night	18% 6% 2 4 3 2 2 2 3 4 54%	4120
	21st to end	Night	24% 8% 2 3 2 2 2 2 3 4 47%	4532
February	1st to 10th	Night	21% 9% 3 5% 4 3 3 3 4 5% 42%	2470
	11th to 20th	Night	18% 7% 2 6% 4 4 3 3 4 5% 46%	2302
	21st to end	Night	20% 8% 2 4 3 3 3 3 3 5% 46%	1808
March	1st to 10th	Night	21% 9% 2 5% 3 3 3 3 5% 5% 41%	3419
	11th to 20th	Night	17% 7% 2 5% 3 3 3 2 4 5% 50%	3480
	21st to end	Night	13% 7% 3 6% 5% 4 4 3 5% 8% 42%	3817
April	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 5% 7% 50%	1929
	11th to 20th	Night	14% 4 2 5% 4 4 4 3 5% 6% 50%	1875
	21st to end	Night	13% 6% 2 5% 3 3 4 3 5% 7% 49%	1900
May	1st to 10th	Night	19% 7% 2 6% 4 4 3 4 5% 7% 38%	3109
	11th to 20th	Night	15% 7% 2 5% 4 4 4 4 5% 7% 44%	2823
	21st to end	Night	16% 7% 2 6% 4 4 4 4 5% 8% 41%	3090
June	1st to 10th	Night	6% 4 2 4 3 4 4 3 7% 10% 54%	1710
	11th to 20th	Night	4 3 2 5% 4 3 4 3 5% 9% 58%	1710
	21st to end	Night	4 3 1 3 3 3 4 4 6% 8% 61%	1710
July	1st to 10th	Night	5% 4 1 5% 4 5% 6% 5% 8% 12% 44%	1710
	11th to 20th	Night	3 3 1 4 3 4 4 4 8% 11% 54%	1710
	21st to end	Night	5% 2 1 4 4 5% 5% 5% 6% 11% 52%	1871
August	1st to 10th	Night	5% 3 2 4 4 4 4 5% 7% 12% 50%	1611
	11th to 20th	Night	7% 3 1 4 4 4 5% 4 6% 11% 51%	1737
	21st to end	Night	6% 4 1 5% 3 4 4 4 8% 8% 52%	1980
September	1st to 10th	Night	7% 4 1 5% 3 4 5% 4 6% 6% 58%	1800
	11th to 20th	Night	9% 5% 2 5% 3 3 4 4 5% 7% 52%	1833
	21st to end	Night	9% 3 1 4 3 3 3 4 5% 6% 60%	2046
October	1st to 10th	Night	9% 4 2 3 2 2 3 3 4 7% 60%	2160
	11th to 20th	Night	12% 4 1 5% 3 2 3 2 4 5% 59%	2160
	21st to end	Night	17% 5% 2 4 3 2 3 2 2 3 56%	2376
November	1st to 10th	Night	12% 4 2 4 3 3 3 2 4 5% 59%	2220
	11th to 20th	Night	11% 5% 1 4 4 3 3 3 4 6% 55%	2280
	21st to end	Night	15% 8% 2 5% 3 3 2 2 4 5% 51%	2506
December	1st to 10th	Night	18% 6% 2 5% 3 3 3 3 4 5% 47%	2660
	11th to 20th	Night	18% 6% 2 5% 4 4 3 3 3 4 48%	3184
	21st to end	Night	16% 7% 2 6% 4 4 4 3 4 5% 45%	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	45% 3 5% 22% 21% 4	2848
	11th to 20th	Day	40% 3 10% 22% 21% 3	2850
	21st to end	Day	43% 3 6% 18% 21% 9%	3135
February	1st to 10th	Day	48% 4 8% 19% 17% 4	1710
	11th to 20th	Day	45% 4 6% 20% 19% 6%	1771
	21st to end	Day	51% 4 6% 14% 17% 9%	1660
March	1st to 10th	Day	50% 4 7% 12% 18% 10%	3436
	11th to 20th	Day	41% 5% 8% 22% 18% 5%	3480
	21st to end	Day	45% 4 8% 21% 20% 1	3814
April	1st to 10th	Day	40% 5% 9% 21% 20% 5%	2251
	11th to 20th	Day	43% 4 8% 20% 19% 7%	2254
	21st to end	Day	43% 6% 9% 19% 19% 3	2280
May	1st to 10th	Day	47% 6% 10% 21% 13% 2	3818
	11th to 20th	Day	39% 9% 11% 25% 15% 1	4086
	21st to end	Day	47% 8% 12% 19% 10% 3	4489
June	1st to 10th	Day	37% 8% 13% 24% 15% 2	2470
	11th to 20th	Day	35% 8% 13% 24% 19% 2	2470
	21st to end	Day	30% 9% 13% 27% 19% 3	2470
July	1st to 10th	Day	37% 12% 15% 23% 12% 1	2406
	11th to 20th	Day	31% 9% 13% 27% 16% 3	2401
	21st to end	Day	36% 11% 16% 26% 11% 1	2537
August	1st to 10th	Day	36% 10% 17% 26% 10% 1	2314
	11th to 20th	Day	36% 9% 12% 24% 16% 2	2163
	21st to end	Day	35% 10% 14% 24% 13% 4	2376
September	1st to 10th	Day	37% 7% 10% 20% 19% 7%	2160
	11th to 20th	Day	36% 8% 11% 17% 22% 6%	2122
	21st to end	Day	30% 7% 8% 20% 26% 9%	1895
October	1st to 10th	Day	29% 5% 10% 21% 26% 9%	1800
	11th to 20th	Day	33% 3 6% 19% 28% 12%	1800
	21st to end	Day	37% 5% 6% 20% 22% 10%	1980
November	1st to 10th	Day	31% 3 8% 25% 24% 8%	1858
	11th to 20th	Day	31% 3 8% 19% 28% 10%	1900
	21st to end	Day	45% 2 5% 17% 25% 6%	1663
December	1st to 10th	Day	41% 4 9% 22% 18% 6%	1520
	11th to 20th	Day	45% 4 5% 18% 23% 6%	1993
	21st to end	Day	46% 5% 9% 16% 18% 6%	3135
January	1st to 10th	Night	42% 4 6% 18% 27% 3	4108
	11th to 20th	Night	36% 4 9% 22% 24% 6%	4120
	21st to end	Night	42% 4 9% 18% 23% 5%	4532
February	1st to 10th	Night	46% 4 7% 19% 17% 6%	2470
	11th to 20th	Night	43% 3 7% 20% 21% 6%	2303
	21st to end	Night	42% 3 8% 16% 22% 9%	1808
March	1st to 10th	Night	45% 5% 8% 13% 18% 11%	3419
	11th to 20th	Night	39% 4 7% 25% 18% 7%	3480
	21st to end	Night	40% 5% 9% 23% 21% 2	3817
April	1st to 10th	Night	34% 5% 9% 23% 20% 10%	1929
	11th to 20th	Night	35% 5% 8% 22% 21% 9%	1875
	21st to end	Night	34% 6% 11% 24% 21% 4	1900
May	1st to 10th	Night	45% 7% 10% 22% 13% 3	3139
	11th to 20th	Night	39% 7% 13% 27% 14% 1	2824
	21st to end	Night	41% 7% 14% 22% 13% 2	3099
June	1st to 10th	Night	25% 10% 14% 30% 19% 2	1710
	11th to 20th	Night	24% 5% 12% 33% 23% 3	1710
	21st to end	Night	20% 6% 13% 32% 24% 5%	1710
July	1st to 10th	Night	27% 11% 21% 25% 15% 1	1665
	11th to 20th	Night	20% 8% 19% 28% 21% 3	1656
	21st to end	Night	24% 10% 16% 32% 17% 1	1772
August	1st to 10th	Night	23% 8% 21% 32% 14% 1	1601
	11th to 20th	Night	26% 8% 15% 29% 19% 2	1737
	21st to end	Night	27% 9% 15% 27% 19% 3	1980
September	1st to 10th	Night	26% 7% 11% 25% 23% 8%	1800
	11th to 20th	Night	32% 8% 9% 20% 25% 7%	1833
	21st to end	Night	25% 5% 9% 22% 30% 10%	2046
October	1st to 10th	Night	25% 5% 11% 22% 25% 12%	2160
	11th to 20th	Night	29% 3 7% 17% 31% 13%	2160
	21st to end	Night	36% 4 5% 19% 25% 11%	2376
November	1st to 10th	Night	29% 4 7% 22% 26% 11%	2220
	11th to 20th	Night	31% 3 7% 21% 27% 11%	2280
	21st to end	Night	37% 4 7% 18% 27% 6%	2506
December	1st to 10th	Night	40% 5% 8% 18% 21% 7%	2660
	11th to 20th	Night	41% 3 5% 18% 25% 7%	3185
	21st to end	Night	41% 4 8% 22% 21% 4	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	29% 20% 31% 15% 5%	270
	11th to 20th	Day	31% 20% 35% 11% 1 1	270
	21st to end	Day	25% 25% 33% 12% 4	297
February	1st to 10th	Day	33% 19% 32% 12% 4	270
	11th to 20th	Day	31% 27% 30% 9% 2	270
	21st to end	Day	42% 23% 26% 8% 2	225
March	1st to 10th	Day	31% 17% 33% 15% 3	270
	11th to 20th	Day	33% 21% 33% 12% 1	270
	21st to end	Day	31% 25% 32% 10% 1	297
April	1st to 10th	Day	24% 22% 34% 14% 6%	431
	11th to 20th	Day	29% 16% 33% 16% 5% 1	452
	21st to end	Day	23% 19% 33% 17% 7% 2	460
May	1st to 10th	Day	24% 15% 32% 21% 7% 1	468
	11th to 20th	Day	17% 8% 32% 27% 13% 2	675
	21st to end	Day	11% 9% 29% 31% 16% 4	734
June	1st to 10th	Day	11% 6% 18% 34% 24% 7%	680
	11th to 20th	Day	7% 4 21% 38% 24% 7%	680
	21st to end	Day	4 4 24% 37% 23% 8%	680
July	1st to 10th	Day	6% 3 17% 34% 32% 8%	671
	11th to 20th	Day	6% 2 13% 37% 32% 10%	668
	21st to end	Day	7% 3 13% 33% 33% 11%	736
August	1st to 10th	Day	7% 1 15% 36% 31% 9%	626
	11th to 20th	Day	14% 2 9% 36% 31% 8%	477
	21st to end	Day	11% 1 7% 29% 37% 15%	495
September	1st to 10th	Day	11% 3 12% 27% 37% 10%	450
	11th to 20th	Day	11% 2 16% 26% 35% 10%	412
	21st to end	Day	14% 5% 17% 40% 20% 4	270
October	1st to 10th	Day	6% 7% 32% 33% 17% 4	270
	11th to 20th	Day	17% 13% 34% 24% 10% 2	270
	21st to end	Day	28% 15% 32% 18% 6% 1	297
November	1st to 10th	Day	18% 16% 32% 21% 11% 1	270
	11th to 20th	Day	16% 17% 40% 21% 4 2	270
	21st to end	Day	31% 16% 26% 21% 5% 1	270
December	1st to 10th	Day	26% 24% 27% 17% 7%	270
	11th to 20th	Day	26% 20% 30% 19% 5%	270
	21st to end	Day	29% 16% 40% 12% 2	297
January	1st to 10th	Night	24% 18% 29% 26% 4	950
	11th to 20th	Night	25% 19% 29% 22% 4	950
	21st to end	Night	23% 16% 33% 24% 4	1045
February	1st to 10th	Night	27% 17% 29% 23% 4	950
	11th to 20th	Night	24% 18% 36% 20% 2	828
	21st to end	Night	28% 20% 30% 19% 3	552
March	1st to 10th	Night	23% 11% 33% 28% 5%	570
	11th to 20th	Night	24% 14% 30% 27% 4	570
	21st to end	Night	19% 16% 32% 27% 6%	627
April	1st to 10th	Night	17% 17% 33% 26% 7%	570
	11th to 20th	Night	15% 15% 34% 25% 10% 1	563
	21st to end	Night	16% 13% 35% 26% 9%	570
May	1st to 10th	Night	15% 7% 31% 36% 11% 1	570
	11th to 20th	Night	15% 9% 26% 30% 17% 2	561
	21st to end	Night	10% 6% 25% 32% 23% 4	617
June	1st to 10th	Night	8% 2 15% 36% 35% 5%	570
	11th to 20th	Night	5% 2 14% 41% 34% 4	570
	21st to end	Night	5% 1 14% 39% 36% 6%	570
July	1st to 10th	Night	5% 1 12% 32% 43% 7%	555
	11th to 20th	Night	3 11% 34% 41% 10%	552
	21st to end	Night	6% 7% 35% 43% 9%	624
August	1st to 10th	Night	4 1 10% 37% 40% 7%	537
	11th to 20th	Night	9% 1 10% 36% 37% 6%	534
	21st to end	Night	8% 1 7% 32% 45% 7%	594
September	1st to 10th	Night	8% 2 8% 33% 42% 6%	540
	11th to 20th	Night	10% 2 14% 32% 39% 4	540
	21st to end	Night	10% 3 16% 31% 34% 5%	606
October	1st to 10th	Night	11% 3 18% 34% 29% 4	720
	11th to 20th	Night	14% 8% 26% 35% 17% 1	720
	21st to end	Night	21% 9% 27% 26% 16% 1	792
November	1st to 10th	Night	13% 10% 25% 34% 16% 2	740
	11th to 20th	Night	14% 11% 32% 31% 12%	760
	21st to end	Night	20% 15% 28% 24% 12%	826
December	1st to 10th	Night	24% 10% 31% 28% 7%	950
	11th to 20th	Night	25% 13% 27% 28% 7%	950
	21st to end	Night	24% 16% 28% 26% 6%	1045

Page generated at 2024-07-28 08:52:13. Version ac07

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