Star Hoppers Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Star Hoppers Observatory clear sky chart from 2005-11-06 to 2024-10-20.

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% 10% 4 8% 5% 5% 5% 4 5% 7% 33%	100786
	Night	14% 12% 4 8% 5% 4 4 3 5% 6% 34%	97877
Transparency	Day	48% 7% 12% 20% 11% 1	100583
	Night	49% 6% 12% 20% 11% 1	97751
Seeing	Day	18% 13% 29% 22% 13% 5%	15428
	Night	19% 10% 30% 28% 11% 1	25209

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	14% 21% 7% 13% 5% 5% 4 2 3 4 20%	2527
	11th to 20th	Day	15% 21% 7% 14% 9% 8% 4 3 4 4 12%	2530
	21st to end	Day	26% 22% 8% 11% 5% 4 3 2 3 3 14%	3007
February	1st to 10th	Day	13% 15% 6% 13% 9% 5% 5% 4 3 5% 21%	1710
	11th to 20th	Day	14% 15% 5% 13% 9% 6% 4 3 4 4 24%	1798
	21st to end	Day	12% 18% 6% 13% 6% 4 4 3 4 5% 25%	1570
March	1st to 10th	Day	16% 16% 5% 9% 5% 4 4 3 4 6% 28%	3176
	11th to 20th	Day	12% 12% 6% 10% 6% 5% 4 3 5% 7% 29%	3480
	21st to end	Day	18% 14% 4 9% 6% 4 4 3 4 5% 29%	3815
April	1st to 10th	Day	16% 13% 4 9% 6% 5% 4 3 5% 5% 30%	2228
	11th to 20th	Day	17% 12% 3 7% 4 4 4 4 6% 6% 35%	2402
	21st to end	Day	17% 8% 3 9% 5% 4 4 3 5% 7% 34%	2470
May	1st to 10th	Day	18% 9% 3 7% 4 4 5% 4 5% 6% 34%	4082
	11th to 20th	Day	16% 8% 3 6% 5% 4 5% 4 6% 9% 36%	4081
	21st to end	Day	11% 6% 3 6% 4 4 4 3 5% 9% 45%	4530
June	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 7% 8% 40%	2707
	11th to 20th	Day	10% 7% 2 7% 5% 4 5% 4 5% 9% 41%	2850
	21st to end	Day	12% 6% 2 6% 6% 6% 5% 5% 8% 10% 36%	2672
July	1st to 10th	Day	11% 6% 3 7% 5% 6% 5% 5% 8% 9% 36%	4440
	11th to 20th	Day	8% 5% 2 5% 4 4 5% 5% 7% 10% 47%	4440
	21st to end	Day	8% 5% 2 6% 6% 6% 6% 5% 7% 9% 40%	4597
August	1st to 10th	Day	12% 5% 2 6% 5% 6% 5% 5% 6% 8% 40%	4104
	11th to 20th	Day	11% 7% 2 6% 4 5% 5% 5% 7% 9% 39%	4044
	21st to end	Day	8% 6% 3 8% 5% 5% 6% 4 7% 9% 40%	4472
September	1st to 10th	Day	11% 7% 2 8% 5% 5% 5% 4 6% 8% 39%	2160
	11th to 20th	Day	10% 6% 2 5% 3 3 5% 3 7% 8% 47%	2090
	21st to end	Day	15% 7% 2 7% 4 4 6% 5% 6% 8% 35%	2090
October	1st to 10th	Day	13% 7% 3 7% 4 4 5% 3 5% 7% 41%	2045
	11th to 20th	Day	18% 11% 3 8% 5% 5% 5% 4 4 7% 31%	1890
	21st to end	Day	21% 13% 3 7% 5% 4 4 3 5% 7% 28%	1816
November	1st to 10th	Day	12% 10% 4 7% 6% 4 4 4 6% 7% 36%	1672
	11th to 20th	Day	14% 14% 5% 9% 5% 6% 4 4 5% 6% 29%	1710
	21st to end	Day	18% 15% 5% 8% 5% 5% 4 3 4 6% 27%	1615
December	1st to 10th	Day	14% 16% 8% 14% 7% 4 4 2 4 5% 22%	1520
	11th to 20th	Day	15% 17% 6% 11% 6% 4 5% 5% 5% 5% 22%	1713
	21st to end	Day	23% 24% 6% 14% 5% 3 3 3 4 4 11%	2733
January	1st to 10th	Night	15% 17% 7% 13% 5% 5% 4 3 4 4 22%	4428
	11th to 20th	Night	13% 18% 9% 15% 6% 7% 6% 4 4 4 14%	4440
	21st to end	Night	23% 17% 10% 11% 6% 4 4 3 3 4 16%	4651
February	1st to 10th	Night	16% 16% 5% 11% 7% 6% 5% 3 4 4 23%	2470
	11th to 20th	Night	12% 15% 6% 11% 8% 5% 4 3 5% 5% 26%	2266
	21st to end	Night	17% 14% 4 10% 5% 5% 4 3 5% 6% 27%	1884
March	1st to 10th	Night	15% 13% 4 9% 4 4 3 3 4 6% 34%	3677
	11th to 20th	Night	9% 10% 4 7% 5% 4 5% 4 5% 7% 41%	3480
	21st to end	Night	16% 10% 3 9% 5% 4 4 3 5% 5% 35%	3817
April	1st to 10th	Night	16% 13% 3 6% 5% 4 4 3 5% 6% 35%	1969
	11th to 20th	Night	18% 10% 3 6% 5% 4 3 3 6% 7% 36%	1725
	21st to end	Night	17% 8% 2 6% 4 4 4 3 6% 6% 38%	1710
May	1st to 10th	Night	15% 9% 3 6% 5% 4 3 4 6% 8% 37%	2813
	11th to 20th	Night	15% 7% 3 7% 4 3 3 3 5% 7% 43%	2812
	21st to end	Night	10% 6% 2 5% 5% 4 4 4 6% 7% 48%	3022
June	1st to 10th	Night	11% 6% 2 5% 4 3 4 3 6% 10% 46%	1463
	11th to 20th	Night	9% 6% 2 6% 4 4 4 5% 7% 8% 45%	1330
	21st to end	Night	10% 6% 2 6% 4 4 3 3 5% 9% 47%	1494
July	1st to 10th	Night	8% 5% 1 5% 4 4 4 5% 7% 10% 46%	2530
	11th to 20th	Night	10% 4 2 4 3 3 4 4 6% 7% 54%	2530
	21st to end	Night	5% 6% 2 5% 5% 5% 5% 5% 6% 10% 47%	2958
August	1st to 10th	Night	11% 5% 2 5% 4 4 4 3 6% 8% 47%	2825
	11th to 20th	Night	10% 7% 2 5% 3 4 5% 3 5% 8% 48%	2785
	21st to end	Night	7% 6% 3 7% 5% 4 4 3 5% 8% 49%	3180
September	1st to 10th	Night	10% 7% 2 6% 4 4 4 3 5% 7% 48%	2000
	11th to 20th	Night	10% 5% 2 4 4 3 4 3 5% 7% 54%	2090
	21st to end	Night	15% 8% 2 7% 4 3 5% 3 5% 7% 42%	2090
October	1st to 10th	Night	14% 7% 3 7% 4 4 3 3 4 6% 45%	2134
	11th to 20th	Night	19% 11% 3 8% 4 4 5% 3 5% 5% 34%	2275
	21st to end	Night	22% 12% 3 7% 5% 5% 5% 3 4 5% 30%	2538
November	1st to 10th	Night	14% 10% 3 6% 5% 4 4 3 5% 6% 41%	2406
	11th to 20th	Night	16% 12% 4 8% 5% 5% 5% 4 6% 6% 30%	2470
	21st to end	Night	20% 15% 4 8% 5% 4 4 3 4 6% 27%	2560
December	1st to 10th	Night	17% 18% 6% 11% 5% 5% 5% 3 4 6% 20%	2660
	11th to 20th	Night	14% 17% 6% 13% 6% 5% 4 4 5% 5% 22%	3479
	21st to end	Night	25% 25% 7% 11% 5% 3 3 3 3 4 12%	4916

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	66% 6% 10% 13% 4	2528
	11th to 20th	Day	75% 6% 11% 6% 3	2530
	21st to end	Day	77% 4 9% 7% 3 1	3007
February	1st to 10th	Day	63% 6% 9% 14% 7%	1710
	11th to 20th	Day	63% 4 9% 14% 9% 1	1808
	21st to end	Day	61% 5% 11% 14% 6% 2	1570
March	1st to 10th	Day	57% 6% 12% 19% 6%	3176
	11th to 20th	Day	52% 6% 14% 18% 8% 1	3480
	21st to end	Day	57% 6% 12% 14% 10% 2	3815
April	1st to 10th	Day	54% 5% 11% 19% 11%	2228
	11th to 20th	Day	48% 6% 12% 20% 12% 2	2402
	21st to end	Day	49% 6% 13% 17% 14% 1	2470
May	1st to 10th	Day	46% 7% 12% 21% 11% 2	4120
	11th to 20th	Day	42% 9% 14% 24% 9% 1	4085
	21st to end	Day	36% 7% 12% 18% 24% 4	4543
June	1st to 10th	Day	38% 7% 13% 26% 14% 2	2707
	11th to 20th	Day	39% 8% 12% 23% 16% 2	2850
	21st to end	Day	39% 9% 14% 22% 15% 1	2672
July	1st to 10th	Day	41% 9% 14% 19% 16% 2	4371
	11th to 20th	Day	29% 7% 14% 33% 15% 1	4365
	21st to end	Day	36% 9% 14% 18% 21% 2	4451
August	1st to 10th	Day	38% 9% 13% 23% 16% 1	4091
	11th to 20th	Day	37% 9% 11% 30% 11% 1	4083
	21st to end	Day	38% 8% 15% 26% 12% 1	4471
September	1st to 10th	Day	40% 8% 14% 24% 12% 2	2160
	11th to 20th	Day	32% 8% 14% 31% 14% 1	2090
	21st to end	Day	44% 7% 13% 23% 12%	2090
October	1st to 10th	Day	42% 6% 11% 25% 14% 1	2045
	11th to 20th	Day	51% 7% 13% 19% 9% 1	1890
	21st to end	Day	55% 6% 13% 17% 8%	1816
November	1st to 10th	Day	46% 6% 14% 22% 11% 1	1672
	11th to 20th	Day	55% 5% 13% 17% 8% 1	1710
	21st to end	Day	58% 5% 13% 16% 6% 1	1615
December	1st to 10th	Day	66% 4 11% 15% 3	1520
	11th to 20th	Day	62% 6% 14% 14% 4	1709
	21st to end	Day	78% 4 9% 6% 3	2733
January	1st to 10th	Night	64% 6% 11% 13% 5% 1	4428
	11th to 20th	Night	70% 7% 10% 8% 4	4440
	21st to end	Night	71% 5% 10% 11% 3	4651
February	1st to 10th	Night	64% 6% 10% 12% 7% 1	2470
	11th to 20th	Night	59% 5% 10% 17% 8%	2267
	21st to end	Night	57% 5% 12% 16% 8% 1	1884
March	1st to 10th	Night	50% 5% 13% 24% 7% 1	3677
	11th to 20th	Night	39% 6% 16% 20% 17% 1	3480
	21st to end	Night	49% 6% 12% 21% 11% 1	3817
April	1st to 10th	Night	49% 5% 10% 21% 13% 2	1969
	11th to 20th	Night	46% 6% 11% 17% 18% 2	1725
	21st to end	Night	45% 7% 11% 19% 16% 3	1710
May	1st to 10th	Night	44% 7% 12% 21% 13% 4	2840
	11th to 20th	Night	41% 6% 11% 28% 12% 2	2813
	21st to end	Night	34% 8% 12% 21% 20% 6%	3030
June	1st to 10th	Night	34% 6% 11% 29% 18% 2	1463
	11th to 20th	Night	34% 8% 14% 24% 19% 2	1330
	21st to end	Night	34% 7% 13% 26% 19% 1	1494
July	1st to 10th	Night	31% 6% 14% 27% 16% 6%	2490
	11th to 20th	Night	28% 7% 12% 31% 21% 1	2482
	21st to end	Night	30% 11% 17% 19% 22% 2	2864
August	1st to 10th	Night	34% 7% 14% 27% 16% 1	2814
	11th to 20th	Night	33% 7% 11% 36% 11% 2	2812
	21st to end	Night	34% 7% 12% 32% 14% 1	3180
September	1st to 10th	Night	34% 7% 13% 27% 17% 2	2000
	11th to 20th	Night	30% 6% 11% 29% 21% 2	2090
	21st to end	Night	41% 6% 12% 27% 14% 1	2090
October	1st to 10th	Night	39% 6% 10% 26% 18% 1	2134
	11th to 20th	Night	51% 6% 12% 19% 12% 1	2275
	21st to end	Night	55% 5% 11% 20% 8% 1	2538
November	1st to 10th	Night	43% 6% 11% 26% 14% 1	2406
	11th to 20th	Night	53% 7% 13% 18% 8% 1	2470
	21st to end	Night	57% 5% 13% 19% 6% 1	2560
December	1st to 10th	Night	66% 5% 10% 13% 5%	2660
	11th to 20th	Night	61% 7% 12% 13% 6% 1	3482
	21st to end	Night	77% 5% 10% 6% 2	4916

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	23% 19% 38% 14% 6%	270
	11th to 20th	Day	23% 16% 45% 14% 2 1	270
	21st to end	Day	31% 17% 30% 17% 4 1	297
February	1st to 10th	Day	26% 19% 37% 14% 2 1	270
	11th to 20th	Day	25% 21% 37% 15% 1	270
	21st to end	Day	28% 27% 34% 9% 2	225
March	1st to 10th	Day	25% 23% 37% 11% 4	300
	11th to 20th	Day	23% 14% 34% 22% 6% 1	460
	21st to end	Day	29% 14% 33% 19% 5% 1	506
April	1st to 10th	Day	20% 19% 33% 21% 7% 1	460
	11th to 20th	Day	27% 18% 32% 14% 5% 5%	452
	21st to end	Day	24% 14% 32% 19% 10% 2	460
May	1st to 10th	Day	24% 16% 27% 21% 11% 2	463
	11th to 20th	Day	18% 11% 30% 23% 12% 6%	487
	21st to end	Day	16% 8% 22% 29% 17% 7%	557
June	1st to 10th	Day	12% 10% 30% 29% 16% 4	680
	11th to 20th	Day	13% 10% 31% 26% 17% 4	680
	21st to end	Day	12% 9% 31% 29% 15% 5%	680
July	1st to 10th	Day	10% 6% 23% 30% 21% 10%	671
	11th to 20th	Day	11% 7% 28% 28% 19% 7%	668
	21st to end	Day	9% 5% 25% 31% 21% 9%	611
August	1st to 10th	Day	9% 6% 22% 26% 22% 14%	486
	11th to 20th	Day	14% 4 20% 28% 22% 12%	479
	21st to end	Day	11% 5% 23% 28% 21% 11%	539
September	1st to 10th	Day	13% 8% 24% 24% 20% 10%	490
	11th to 20th	Day	11% 4 21% 23% 28% 13%	490
	21st to end	Day	18% 14% 21% 23% 18% 7%	490
October	1st to 10th	Day	18% 11% 28% 20% 17% 6%	490
	11th to 20th	Day	21% 18% 27% 26% 7% 1	486
	21st to end	Day	30% 16% 36% 15% 2	331
November	1st to 10th	Day	19% 20% 36% 17% 6% 2	270
	11th to 20th	Day	21% 24% 33% 16% 6% 1	270
	21st to end	Day	27% 21% 37% 12% 3	225
December	1st to 10th	Day	27% 21% 32% 13% 7%	180
	11th to 20th	Day	23% 26% 41% 7% 2 1	180
	21st to end	Day	25% 28% 33% 13% 1	285
January	1st to 10th	Night	22% 16% 37% 20% 5% 1	950
	11th to 20th	Night	25% 15% 34% 22% 4 1	950
	21st to end	Night	20% 13% 35% 26% 5%	903
February	1st to 10th	Night	25% 13% 36% 23% 2	760
	11th to 20th	Night	22% 16% 35% 23% 4	743
	21st to end	Night	26% 17% 35% 19% 3	628
March	1st to 10th	Night	21% 14% 35% 23% 7%	760
	11th to 20th	Night	18% 15% 37% 24% 5% 1	760
	21st to end	Night	23% 12% 30% 27% 7% 1	836
April	1st to 10th	Night	20% 16% 37% 23% 4 1	639
	11th to 20th	Night	21% 13% 35% 22% 6% 2	563
	21st to end	Night	21% 10% 33% 29% 7%	570
May	1st to 10th	Night	19% 8% 32% 33% 7% 1	570
	11th to 20th	Night	21% 4 31% 33% 11% 1	561
	21st to end	Night	12% 4 26% 39% 18% 2	617
June	1st to 10th	Night	12% 6% 25% 44% 13%	513
	11th to 20th	Night	11% 5% 30% 42% 12%	380
	21st to end	Night	12% 5% 23% 42% 17% 1	544
July	1st to 10th	Night	10% 2 20% 39% 27% 3	555
	11th to 20th	Night	11% 2 22% 42% 20% 3	552
	21st to end	Night	5% 3 20% 49% 21% 2	624
August	1st to 10th	Night	9% 2 17% 43% 27% 2	567
	11th to 20th	Night	9% 2 21% 35% 28% 4	564
	21st to end	Night	10% 4 19% 36% 28% 3	627
September	1st to 10th	Night	12% 4 23% 34% 24% 4	670
	11th to 20th	Night	12% 4 18% 35% 26% 4	760
	21st to end	Night	17% 6% 23% 31% 19% 4	760
October	1st to 10th	Night	19% 7% 26% 29% 17% 1	760
	11th to 20th	Night	26% 13% 26% 26% 8% 1	759
	21st to end	Night	28% 12% 33% 23% 4	792
November	1st to 10th	Night	20% 13% 29% 27% 10% 1	740
	11th to 20th	Night	22% 17% 34% 20% 7% 1	760
	21st to end	Night	27% 13% 35% 20% 5%	760
December	1st to 10th	Night	23% 17% 35% 19% 5%	760
	11th to 20th	Night	22% 15% 40% 20% 3	907
	21st to end	Night	30% 14% 37% 17% 1	1045

Page generated at 2024-10-17 13:09:42. Version ac07

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