EyeScope Star Shack
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the EyeScope Star Shack clear sky chart from 2005-11-06 to 2024-11-02.

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% 11% 4 9% 5% 4 4 3 5% 6% 34%	101189
	Night	15% 14% 5% 11% 6% 4 4 3 4 5% 28%	97848
Transparency	Day	28% 48% 6% 12% 6%	100945
	Night	31% 49% 6% 9% 5%	97711
Seeing	Day	19% 13% 28% 25% 12% 3	15678
	Night	21% 11% 28% 28% 11% 1	25321

By Month

Percentage Cloud Cover NE (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	12% 26% 15% 22% 6% 4 3 1 2 2 5%	2527
	11th to 20th	Day	13% 19% 9% 22% 16% 8% 3 2 3 2 4	2530
	21st to end	Day	16% 23% 10% 17% 7% 6% 4 2 3 3 8%	2783
February	1st to 10th	Day	9% 19% 8% 15% 14% 8% 3 3 4 4 13%	1620
	11th to 20th	Day	13% 15% 7% 16% 9% 5% 5% 3 5% 3 19%	1826
	21st to end	Day	12% 16% 6% 13% 8% 5% 5% 3 4 4 23%	1570
March	1st to 10th	Day	13% 12% 4 7% 5% 4 4 4 5% 7% 35%	3118
	11th to 20th	Day	8% 14% 6% 12% 5% 5% 4 4 5% 6% 30%	3402
	21st to end	Day	15% 12% 8% 14% 6% 5% 4 3 4 5% 24%	3941
April	1st to 10th	Day	19% 13% 3 9% 4 4 4 3 4 6% 30%	2280
	11th to 20th	Day	20% 12% 4 6% 4 3 3 3 5% 5% 36%	2364
	21st to end	Day	15% 10% 4 8% 4 4 5% 4 5% 6% 35%	2470
May	1st to 10th	Day	14% 8% 2 6% 4 4 4 3 5% 7% 43%	4108
	11th to 20th	Day	10% 6% 3 6% 4 4 4 3 4 6% 47%	4237
	21st to end	Day	12% 6% 2 5% 4 4 4 4 6% 9% 44%	4837
June	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 6% 9% 44%	2817
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 9% 42%	2850
	21st to end	Day	15% 7% 2 5% 4 4 3 4 6% 8% 43%	2808
July	1st to 10th	Day	18% 8% 2 5% 3 3 4 3 5% 8% 42%	4440
	11th to 20th	Day	9% 4 2 4 3 4 4 3 6% 8% 54%	4440
	21st to end	Day	9% 5% 2 4 4 4 4 3 6% 9% 50%	4814
August	1st to 10th	Day	8% 6% 2 6% 5% 5% 5% 5% 7% 8% 44%	4247
	11th to 20th	Day	14% 5% 2 5% 3 3 4 3 5% 7% 48%	4044
	21st to end	Day	13% 6% 2 6% 4 4 4 3 5% 6% 46%	4377
September	1st to 10th	Day	15% 6% 2 5% 4 4 3 3 6% 7% 45%	2252
	11th to 20th	Day	14% 5% 2 6% 4 3 4 3 5% 7% 46%	2090
	21st to end	Day	18% 7% 3 5% 4 4 5% 3 6% 8% 37%	2090
October	1st to 10th	Day	20% 9% 3 7% 4 4 3 3 5% 8% 34%	2090
	11th to 20th	Day	25% 15% 5% 10% 5% 5% 4 3 3 5% 19%	1790
	21st to end	Day	24% 18% 4 9% 6% 6% 4 3 5% 5% 16%	1881
November	1st to 10th	Day	18% 20% 4 9% 4 4 3 3 4 6% 25%	1681
	11th to 20th	Day	14% 26% 8% 13% 6% 4 4 3 4 4 14%	1710
	21st to end	Day	18% 25% 9% 14% 5% 4 3 2 4 3 13%	1532
December	1st to 10th	Day	15% 27% 14% 17% 5% 4 3 2 3 3 8%	1330
	11th to 20th	Day	16% 24% 9% 18% 9% 6% 3 2 3 3 8%	1671
	21st to end	Day	20% 23% 10% 17% 7% 4 3 2 3 4 7%	2622
January	1st to 10th	Night	13% 24% 10% 23% 8% 4 3 2 2 3 9%	4428
	11th to 20th	Night	12% 18% 7% 25% 16% 6% 3 2 2 2 7%	4440
	21st to end	Night	16% 24% 9% 19% 8% 5% 4 2 3 3 7%	4884
February	1st to 10th	Night	11% 18% 7% 18% 13% 6% 4 2 3 3 13%	2559
	11th to 20th	Night	12% 15% 7% 16% 10% 6% 5% 3 4 5% 18%	2237
	21st to end	Night	14% 18% 6% 12% 6% 5% 5% 3 4 5% 21%	1884
March	1st to 10th	Night	16% 11% 4 6% 4 3 3 3 4 6% 41%	3722
	11th to 20th	Night	9% 16% 5% 10% 5% 4 4 4 5% 5% 34%	3557
	21st to end	Night	15% 11% 6% 11% 7% 5% 4 4 5% 6% 26%	3707
April	1st to 10th	Night	20% 12% 4 9% 5% 5% 5% 4 4 5% 28%	1900
	11th to 20th	Night	19% 10% 4 8% 5% 4 4 3 5% 5% 34%	1764
	21st to end	Night	17% 10% 3 7% 5% 3 4 3 5% 6% 35%	1710
May	1st to 10th	Night	16% 8% 2 8% 4 4 5% 4 5% 5% 39%	2833
	11th to 20th	Night	12% 9% 3 7% 5% 5% 5% 3 5% 6% 40%	2648
	21st to end	Night	18% 6% 3 5% 4 4 3 3 5% 7% 41%	2750
June	1st to 10th	Night	14% 7% 2 7% 6% 4 5% 3 5% 8% 40%	1359
	11th to 20th	Night	11% 6% 2 7% 5% 4 5% 4 6% 8% 41%	1330
	21st to end	Night	12% 7% 2 6% 5% 4 4 3 4 7% 45%	1365
July	1st to 10th	Night	14% 7% 2 7% 4 3 4 3 6% 7% 41%	2530
	11th to 20th	Night	8% 6% 2 6% 4 3 5% 4 6% 7% 51%	2530
	21st to end	Night	8% 6% 2 6% 4 4 4 4 6% 8% 48%	2750
August	1st to 10th	Night	11% 6% 3 7% 4 4 5% 3 5% 8% 42%	2671
	11th to 20th	Night	14% 5% 2 5% 3 4 3 3 5% 7% 48%	2785
	21st to end	Night	11% 6% 2 6% 4 4 4 4 5% 6% 47%	3276
September	1st to 10th	Night	13% 6% 3 6% 5% 4 4 3 5% 6% 47%	1909
	11th to 20th	Night	16% 6% 2 6% 3 3 3 3 5% 7% 44%	2090
	21st to end	Night	19% 6% 3 8% 4 5% 4 3 6% 7% 37%	2090
October	1st to 10th	Night	19% 10% 3 6% 4 4 4 3 5% 5% 37%	2090
	11th to 20th	Night	23% 14% 4 10% 5% 4 4 4 4 5% 23%	2384
	21st to end	Night	27% 16% 3 9% 5% 4 4 3 4 4 20%	2717
November	1st to 10th	Night	19% 19% 4 9% 5% 4 3 2 4 5% 25%	2420
	11th to 20th	Night	16% 25% 6% 12% 6% 4 4 3 3 4 16%	2470
	21st to end	Night	18% 26% 9% 13% 6% 4 3 3 3 3 12%	2643
December	1st to 10th	Night	15% 30% 10% 17% 6% 3 3 2 2 3 9%	2850
	11th to 20th	Night	15% 22% 9% 22% 7% 4 3 2 3 3 11%	3526
	21st to end	Night	22% 22% 10% 15% 6% 4 3 3 3 3 9%	5040

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	60% 36% 2 2 1	2528
	11th to 20th	Day	58% 37% 2 2 1	2530
	21st to end	Day	51% 41% 5% 2 1	2783
February	1st to 10th	Day	29% 65% 2 3 1	1620
	11th to 20th	Day	23% 64% 4 5% 4	1836
	21st to end	Day	22% 65% 4 6% 3	1570
March	1st to 10th	Day	29% 41% 8% 14% 7%	3120
	11th to 20th	Day	36% 41% 7% 12% 3 1	3402
	21st to end	Day	42% 41% 3 8% 5% 1	3941
April	1st to 10th	Day	22% 64% 3 8% 3	2280
	11th to 20th	Day	18% 65% 3 7% 6% 1	2364
	21st to end	Day	17% 65% 4 7% 7%	2470
May	1st to 10th	Day	24% 42% 6% 15% 13% 1	4120
	11th to 20th	Day	21% 40% 6% 22% 10%	4241
	21st to end	Day	23% 41% 7% 14% 14% 1	4837
June	1st to 10th	Day	15% 64% 4 10% 5% 1	2817
	11th to 20th	Day	16% 64% 5% 8% 5% 1	2850
	21st to end	Day	15% 63% 4 12% 5%	2808
July	1st to 10th	Day	31% 36% 10% 16% 6% 1	4371
	11th to 20th	Day	16% 37% 11% 27% 7% 1	4365
	21st to end	Day	19% 37% 8% 22% 13%	4662
August	1st to 10th	Day	22% 40% 8% 21% 9%	4232
	11th to 20th	Day	26% 38% 7% 22% 7%	4083
	21st to end	Day	27% 39% 9% 20% 5%	4376
September	1st to 10th	Day	18% 60% 6% 11% 5%	2252
	11th to 20th	Day	13% 60% 5% 14% 7% 1	2090
	21st to end	Day	16% 60% 6% 12% 5%	2090
October	1st to 10th	Day	23% 60% 3 10% 4	2090
	11th to 20th	Day	28% 60% 3 7% 2	1790
	21st to end	Day	32% 59% 3 4 2	1881
November	1st to 10th	Day	31% 57% 3 7% 2	1681
	11th to 20th	Day	31% 60% 4 3 1	1710
	21st to end	Day	34% 59% 3 3 1	1532
December	1st to 10th	Day	35% 58% 3 3 1	1330
	11th to 20th	Day	45% 50% 2 3 1	1671
	21st to end	Day	53% 37% 5% 2 2	2622
January	1st to 10th	Night	54% 37% 5% 4 1	4428
	11th to 20th	Night	55% 38% 3 2 1	4440
	21st to end	Night	53% 40% 4 2 1	4884
February	1st to 10th	Night	27% 65% 2 3 2 1	2559
	11th to 20th	Night	22% 64% 4 8% 2	2238
	21st to end	Night	21% 65% 4 6% 4	1884
March	1st to 10th	Night	27% 40% 11% 14% 7%	3733
	11th to 20th	Night	32% 41% 7% 15% 5%	3558
	21st to end	Night	37% 42% 6% 9% 5%	3707
April	1st to 10th	Night	22% 65% 2 6% 4 1	1900
	11th to 20th	Night	20% 65% 2 8% 3 2	1764
	21st to end	Night	19% 64% 3 7% 6% 1	1710
May	1st to 10th	Night	26% 42% 6% 13% 11% 2	2840
	11th to 20th	Night	24% 41% 5% 20% 9%	2649
	21st to end	Night	28% 40% 9% 11% 9% 3	2751
June	1st to 10th	Night	16% 65% 4 9% 6% 1	1359
	11th to 20th	Night	15% 65% 4 9% 5% 1	1330
	21st to end	Night	15% 63% 3 11% 7% 1	1365
July	1st to 10th	Night	30% 36% 10% 13% 8% 2	2490
	11th to 20th	Night	20% 39% 10% 20% 11% 1	2482
	21st to end	Night	21% 38% 9% 16% 15%	2662
August	1st to 10th	Night	27% 39% 9% 15% 9%	2662
	11th to 20th	Night	25% 38% 10% 20% 8%	2812
	21st to end	Night	22% 39% 9% 19% 10%	3276
September	1st to 10th	Night	15% 60% 7% 11% 7%	1909
	11th to 20th	Night	15% 60% 5% 12% 8%	2090
	21st to end	Night	19% 59% 7% 10% 5%	2090
October	1st to 10th	Night	23% 60% 4 9% 5%	2090
	11th to 20th	Night	25% 60% 4 8% 3	2384
	21st to end	Night	30% 58% 4 6% 2	2717
November	1st to 10th	Night	31% 58% 3 5% 2	2420
	11th to 20th	Night	29% 59% 5% 5% 2	2470
	21st to end	Night	33% 60% 4 2 1	2643
December	1st to 10th	Night	33% 59% 3 4	2850
	11th to 20th	Night	43% 49% 5% 2 1	3525
	21st to end	Night	51% 40% 5% 3 1	5040

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	21% 16% 40% 17% 5% 1	270
	11th to 20th	Day	23% 18% 36% 17% 4 1	270
	21st to end	Day	24% 15% 34% 21% 5%	297
February	1st to 10th	Day	21% 26% 35% 11% 5% 1	270
	11th to 20th	Day	18% 26% 35% 18% 3 1	270
	21st to end	Day	21% 26% 41% 11% 2	225
March	1st to 10th	Day	19% 23% 36% 19% 4	270
	11th to 20th	Day	20% 15% 34% 22% 9%	408
	21st to end	Day	27% 14% 27% 23% 8% 1	506
April	1st to 10th	Day	25% 13% 33% 20% 7% 2	460
	11th to 20th	Day	29% 16% 26% 17% 11% 1	452
	21st to end	Day	20% 15% 29% 23% 11% 2	460
May	1st to 10th	Day	21% 16% 28% 21% 12% 3	463
	11th to 20th	Day	15% 10% 35% 29% 8% 4	578
	21st to end	Day	14% 11% 27% 30% 15% 3	734
June	1st to 10th	Day	15% 9% 30% 30% 13% 2	680
	11th to 20th	Day	16% 8% 28% 32% 13% 3	680
	21st to end	Day	18% 7% 26% 31% 15% 3	680
July	1st to 10th	Day	10% 7% 26% 33% 18% 6%	671
	11th to 20th	Day	11% 8% 25% 34% 16% 6%	668
	21st to end	Day	11% 6% 25% 35% 19% 5%	739
August	1st to 10th	Day	10% 5% 23% 32% 22% 8%	578
	11th to 20th	Day	14% 5% 18% 34% 19% 10%	479
	21st to end	Day	18% 8% 19% 30% 19% 5%	539
September	1st to 10th	Day	16% 10% 24% 23% 20% 6%	490
	11th to 20th	Day	12% 7% 21% 30% 21% 8%	490
	21st to end	Day	17% 11% 20% 28% 18% 5%	490
October	1st to 10th	Day	24% 15% 26% 20% 14% 2	490
	11th to 20th	Day	30% 16% 28% 22% 3 1	376
	21st to end	Day	32% 17% 30% 16% 4 1	330
November	1st to 10th	Day	29% 15% 31% 18% 6%	273
	11th to 20th	Day	21% 25% 33% 17% 3	270
	21st to end	Day	25% 30% 28% 13% 4	210
December	1st to 10th	Day	31% 19% 30% 14% 5% 1	180
	11th to 20th	Day	24% 27% 34% 12% 2 1	180
	21st to end	Day	31% 28% 32% 8% 2 1	252
January	1st to 10th	Night	22% 17% 33% 21% 6% 1	950
	11th to 20th	Night	23% 17% 31% 23% 6%	950
	21st to end	Night	21% 12% 33% 27% 6%	1045
February	1st to 10th	Night	19% 17% 33% 24% 5% 1	849
	11th to 20th	Night	19% 17% 32% 26% 6%	743
	21st to end	Night	24% 15% 32% 24% 4	628
March	1st to 10th	Night	17% 10% 35% 27% 10% 1	760
	11th to 20th	Night	18% 12% 36% 28% 6%	760
	21st to end	Night	20% 9% 28% 33% 9% 1	777
April	1st to 10th	Night	25% 10% 30% 28% 6% 1	570
	11th to 20th	Night	24% 10% 29% 27% 10% 1	563
	21st to end	Night	20% 10% 28% 33% 9% 1	570
May	1st to 10th	Night	16% 7% 29% 36% 11% 1	570
	11th to 20th	Night	18% 7% 27% 37% 11% 1	561
	21st to end	Night	16% 5% 23% 36% 20% 1	617
June	1st to 10th	Night	16% 5% 26% 38% 15%	409
	11th to 20th	Night	11% 5% 24% 43% 17% 1	380
	21st to end	Night	14% 6% 23% 38% 18% 1	415
July	1st to 10th	Night	13% 3 18% 45% 19% 3	555
	11th to 20th	Night	11% 4 19% 38% 26% 3	552
	21st to end	Night	10% 2 21% 38% 27% 2	624
August	1st to 10th	Night	11% 3 18% 41% 26% 1	567
	11th to 20th	Night	11% 5% 15% 36% 30% 3	564
	21st to end	Night	17% 6% 17% 36% 22% 1	627
September	1st to 10th	Night	14% 4 23% 33% 22% 3	579
	11th to 20th	Night	18% 4 20% 32% 22% 3	760
	21st to end	Night	22% 7% 18% 33% 16% 3	760
October	1st to 10th	Night	23% 11% 23% 29% 13% 1	760
	11th to 20th	Night	31% 12% 26% 24% 7% 1	760
	21st to end	Night	34% 14% 25% 21% 5% 1	836
November	1st to 10th	Night	28% 14% 29% 21% 6% 1	745
	11th to 20th	Night	27% 18% 31% 20% 4	760
	21st to end	Night	30% 18% 30% 18% 4	810
December	1st to 10th	Night	26% 21% 32% 18% 3	950
	11th to 20th	Night	23% 21% 35% 16% 4 1	950
	21st to end	Night	30% 15% 34% 18% 3	1045

Page generated at 2024-10-30 01:22:55. Version ac07

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