Messier 110 Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Messier 110 Observatory clear sky chart from 2005-11-06 to 2024-11-12.

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	11% 6% 2 5% 4 4 4 3 5% 7% 49%	101342
	Night	11% 5% 2 5% 3 3 3 3 5% 7% 54%	97944
Transparency	Day	33% 6% 11% 25% 21% 5%	105033
	Night	30% 5% 10% 25% 23% 6%	102380
Seeing	Day	13% 9% 27% 29% 18% 4	15493
	Night	13% 10% 31% 32% 13% 1	25329

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	12% 9% 4 6% 4 4 3 3 4 6% 45%	2847
	11th to 20th	Day	10% 7% 2 5% 5% 3 3 3 5% 6% 52%	2850
	21st to end	Day	19% 13% 3 5% 2 2 2 2 3 4 45%	3135
February	1st to 10th	Day	14% 10% 3 7% 5% 2 3 3 4 5% 43%	1710
	11th to 20th	Day	13% 6% 2 6% 4 4 3 2 5% 6% 47%	1802
	21st to end	Day	15% 8% 2 5% 4 4 4 3 5% 5% 45%	1594
March	1st to 10th	Day	13% 6% 2 5% 3 2 3 2 3 5% 55%	3436
	11th to 20th	Day	11% 6% 2 4 3 3 3 3 5% 7% 53%	3480
	21st to end	Day	13% 9% 3 8% 5% 5% 4 4 5% 6% 37%	3814
April	1st to 10th	Day	10% 6% 3 5% 4 4 4 4 6% 7% 47%	2091
	11th to 20th	Day	14% 6% 2 5% 4 4 4 4 6% 7% 44%	2254
	21st to end	Day	18% 7% 2 7% 4 3 3 3 5% 5% 42%	2456
May	1st to 10th	Day	20% 9% 3 6% 4 4 3 3 4 5% 39%	4082
	11th to 20th	Day	10% 6% 3 7% 4 4 4 4 6% 7% 45%	4082
	21st to end	Day	14% 6% 2 7% 5% 5% 5% 4 6% 8% 38%	4477
June	1st to 10th	Day	5% 4 2 6% 5% 4 5% 5% 7% 9% 48%	2470
	11th to 20th	Day	8% 5% 2 5% 4 4 4 3 6% 8% 51%	2470
	21st to end	Day	5% 3 1 3 3 4 4 4 6% 7% 59%	2470
July	1st to 10th	Day	9% 5% 2 5% 5% 5% 4 5% 7% 8% 46%	4120
	11th to 20th	Day	6% 3 2 4 4 4 4 4 6% 9% 55%	4120
	21st to end	Day	6% 3 1 4 4 4 5% 4 7% 11% 51%	4465
August	1st to 10th	Day	5% 4 1 4 3 3 4 4 6% 9% 57%	4104
	11th to 20th	Day	7% 3 2 5% 4 4 4 5% 7% 9% 49%	4041
	21st to end	Day	5% 3 2 4 4 3 4 3 6% 9% 58%	4321
September	1st to 10th	Day	11% 4 1 5% 4 4 4 4 4 6% 54%	2126
	11th to 20th	Day	11% 6% 2 5% 3 4 4 4 7% 7% 49%	2090
	21st to end	Day	9% 4 1 4 3 4 4 3 5% 6% 58%	2090
October	1st to 10th	Day	9% 4 2 4 2 3 4 2 5% 7% 58%	1971
	11th to 20th	Day	11% 3 1 4 2 2 2 2 4 5% 63%	1900
	21st to end	Day	15% 5% 1 4 2 3 3 2 4 5% 55%	2090
November	1st to 10th	Day	11% 4 1 4 3 3 3 3 3 6% 59%	1949
	11th to 20th	Day	10% 5% 2 3 3 2 2 2 3 6% 61%	1719
	21st to end	Day	15% 7% 1 3 3 2 2 2 5% 5% 55%	1710
December	1st to 10th	Day	13% 7% 2 6% 3 4 3 3 3 6% 51%	1710
	11th to 20th	Day	14% 7% 3 7% 4 4 4 3 4 5% 46%	2161
	21st to end	Day	15% 13% 5% 7% 5% 4 4 4 5% 5% 33%	3135
January	1st to 10th	Night	11% 8% 2 7% 3 3 3 3 5% 6% 48%	4108
	11th to 20th	Night	8% 5% 2 6% 3 4 4 3 5% 7% 54%	4120
	21st to end	Night	21% 8% 2 4 2 2 3 2 3 4 47%	4532
February	1st to 10th	Night	14% 9% 2 6% 4 3 3 3 4 5% 46%	2470
	11th to 20th	Night	13% 7% 3 6% 3 3 2 2 4 6% 51%	2280
	21st to end	Night	13% 7% 2 5% 4 4 4 3 3 4 52%	1858
March	1st to 10th	Night	12% 7% 2 5% 3 3 3 3 5% 5% 52%	3419
	11th to 20th	Night	11% 4 2 4 2 3 2 3 5% 6% 59%	3480
	21st to end	Night	13% 6% 2 6% 4 4 4 3 5% 6% 47%	3817
April	1st to 10th	Night	11% 5% 2 4 4 3 3 3 5% 6% 55%	2086
	11th to 20th	Night	14% 5% 2 5% 3 2 3 2 6% 7% 50%	1875
	21st to end	Night	14% 7% 2 5% 4 3 3 2 4 5% 49%	1720
May	1st to 10th	Night	15% 8% 2 5% 4 4 3 3 5% 7% 44%	2823
	11th to 20th	Night	15% 6% 3 6% 3 4 3 3 5% 6% 46%	2823
	21st to end	Night	11% 5% 2 5% 3 3 4 4 7% 9% 48%	3090
June	1st to 10th	Night	5% 4 2 4 4 4 4 4 6% 8% 55%	1710
	11th to 20th	Night	4 3 2 3 3 3 4 4 7% 11% 55%	1710
	21st to end	Night	3 3 1 3 2 3 4 3 6% 9% 63%	1710
July	1st to 10th	Night	7% 4 2 4 4 4 4 4 6% 10% 51%	2850
	11th to 20th	Night	2 2 1 3 3 3 5% 3 5% 9% 64%	2850
	21st to end	Night	5% 3 1 4 3 3 4 3 5% 8% 60%	3098
August	1st to 10th	Night	3 2 1 3 3 3 3 4 7% 8% 62%	2836
	11th to 20th	Night	5% 3 2 5% 5% 5% 5% 4 6% 9% 52%	2798
	21st to end	Night	3 2 1 3 3 3 4 3 5% 8% 64%	3338
September	1st to 10th	Night	9% 5% 1 4 3 3 3 3 4 6% 60%	2050
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 7% 51%	2090
	21st to end	Night	8% 3 2 4 3 3 4 3 4 5% 61%	2090
October	1st to 10th	Night	7% 3 1 4 3 2 2 3 4 6% 62%	2188
	11th to 20th	Night	12% 4 1 3 2 2 3 2 4 5% 62%	2280
	21st to end	Night	14% 5% 2 4 3 3 3 2 3 4 58%	2508
November	1st to 10th	Night	10% 5% 1 3 2 2 3 3 4 5% 63%	2345
	11th to 20th	Night	10% 4 2 4 2 3 3 2 4 6% 59%	2484
	21st to end	Night	14% 5% 2 4 3 3 3 2 4 6% 54%	2470
December	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 4 6% 52%	2470
	11th to 20th	Night	12% 7% 3 6% 3 4 4 3 4 5% 50%	3036
	21st to end	Night	17% 9% 3 6% 4 3 3 3 4 6% 43%	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	42% 4 8% 24% 20% 2	2848
	11th to 20th	Day	33% 4 15% 26% 16% 5%	2850
	21st to end	Day	45% 3 7% 22% 21% 2	3135
February	1st to 10th	Day	44% 4 11% 22% 16% 4	1710
	11th to 20th	Day	39% 3 9% 27% 18% 4	1812
	21st to end	Day	41% 3 7% 22% 19% 8%	1594
March	1st to 10th	Day	33% 3 6% 22% 25% 10%	3436
	11th to 20th	Day	31% 6% 11% 27% 21% 4	3480
	21st to end	Day	47% 6% 9% 26% 10% 1	3814
April	1st to 10th	Day	34% 6% 11% 23% 19% 6%	2091
	11th to 20th	Day	38% 6% 11% 21% 16% 6%	2254
	21st to end	Day	44% 7% 9% 23% 17% 2	2456
May	1st to 10th	Day	48% 5% 7% 20% 16% 4	4120
	11th to 20th	Day	36% 9% 12% 23% 18% 1	4086
	21st to end	Day	43% 8% 13% 19% 14% 3	4489
June	1st to 10th	Day	30% 9% 15% 27% 16% 3	2470
	11th to 20th	Day	31% 6% 13% 28% 18% 3	2470
	21st to end	Day	22% 7% 14% 30% 22% 5%	2470
July	1st to 10th	Day	33% 8% 15% 25% 17% 3	4056
	11th to 20th	Day	25% 6% 10% 31% 24% 2	4051
	21st to end	Day	25% 8% 19% 32% 16% 1	4325
August	1st to 10th	Day	23% 6% 13% 27% 25% 6%	4090
	11th to 20th	Day	29% 8% 19% 25% 17% 2	4080
	21st to end	Day	23% 7% 13% 38% 15% 4	4320
September	1st to 10th	Day	32% 5% 10% 22% 22% 10%	2126
	11th to 20th	Day	33% 7% 12% 21% 22% 5%	2090
	21st to end	Day	28% 5% 8% 21% 30% 7%	2090
October	1st to 10th	Day	18% 4 8% 16% 41% 13%	3270
	11th to 20th	Day	15% 2 5% 23% 39% 16%	3140
	21st to end	Day	26% 3 7% 28% 29% 6%	3428
November	1st to 10th	Day	28% 4 6% 27% 26% 8%	1949
	11th to 20th	Day	27% 3 9% 28% 27% 7%	1719
	21st to end	Day	33% 3 9% 24% 26% 5%	1710
December	1st to 10th	Day	36% 5% 8% 30% 20% 2	1710
	11th to 20th	Day	41% 3 6% 23% 24% 3	2159
	21st to end	Day	52% 4 10% 20% 12% 2	3135
January	1st to 10th	Night	38% 3 9% 27% 19% 4	4108
	11th to 20th	Night	29% 7% 15% 23% 23% 3	4120
	21st to end	Night	42% 3 9% 21% 21% 3	4532
February	1st to 10th	Night	41% 4 11% 21% 19% 5%	2470
	11th to 20th	Night	37% 3 8% 27% 20% 6%	2280
	21st to end	Night	38% 3 7% 19% 22% 10%	1858
March	1st to 10th	Night	35% 4 8% 19% 21% 12%	3419
	11th to 20th	Night	27% 4 10% 32% 22% 5%	3480
	21st to end	Night	38% 5% 10% 31% 13% 2	3817
April	1st to 10th	Night	31% 4 11% 22% 23% 9%	2086
	11th to 20th	Night	34% 4 11% 23% 19% 9%	1875
	21st to end	Night	38% 5% 9% 24% 22% 3	1720
May	1st to 10th	Night	40% 6% 11% 18% 20% 4	2850
	11th to 20th	Night	38% 6% 11% 26% 16% 1	2824
	21st to end	Night	31% 6% 16% 24% 21% 2	3099
June	1st to 10th	Night	25% 8% 15% 30% 19% 3	1710
	11th to 20th	Night	22% 6% 14% 34% 20% 4	1710
	21st to end	Night	18% 6% 15% 30% 24% 7%	1710
July	1st to 10th	Night	27% 8% 16% 28% 17% 4	2805
	11th to 20th	Night	18% 5% 10% 35% 30% 3	2796
	21st to end	Night	22% 6% 15% 35% 21% 2	2999
August	1st to 10th	Night	17% 6% 14% 32% 25% 7%	2826
	11th to 20th	Night	27% 7% 16% 25% 21% 4	2825
	21st to end	Night	17% 7% 11% 41% 18% 5%	3338
September	1st to 10th	Night	27% 4 9% 25% 24% 11%	2050
	11th to 20th	Night	32% 6% 10% 20% 26% 6%	2090
	21st to end	Night	25% 4 8% 24% 31% 7%	2090
October	1st to 10th	Night	15% 3 7% 14% 40% 23%	3656
	11th to 20th	Night	19% 2 5% 19% 37% 18%	3779
	21st to end	Night	25% 4 7% 27% 28% 9%	4120
November	1st to 10th	Night	26% 3 8% 24% 29% 9%	2345
	11th to 20th	Night	28% 3 7% 25% 28% 8%	2484
	21st to end	Night	33% 4 7% 21% 28% 7%	2470
December	1st to 10th	Night	34% 4 10% 27% 20% 5%	2470
	11th to 20th	Night	37% 3 8% 21% 26% 4	3037
	21st to end	Night	43% 3 10% 22% 19% 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	20% 15% 34% 26% 6%	270
	11th to 20th	Day	23% 15% 42% 16% 3 1	270
	21st to end	Day	19% 15% 39% 21% 6%	297
February	1st to 10th	Day	22% 14% 40% 20% 3	270
	11th to 20th	Day	18% 19% 42% 19% 2	270
	21st to end	Day	25% 22% 39% 12% 3	225
March	1st to 10th	Day	17% 20% 39% 19% 5%	270
	11th to 20th	Day	20% 19% 40% 18% 3	270
	21st to end	Day	19% 25% 33% 18% 4	297
April	1st to 10th	Day	13% 22% 41% 18% 6%	271
	11th to 20th	Day	20% 16% 38% 21% 5%	452
	21st to end	Day	23% 18% 30% 20% 8% 1	636
May	1st to 10th	Day	17% 12% 38% 24% 7% 1	653
	11th to 20th	Day	16% 11% 31% 27% 12% 3	675
	21st to end	Day	16% 9% 31% 22% 16% 6%	734
June	1st to 10th	Day	6% 4 22% 37% 25% 5%	680
	11th to 20th	Day	7% 2 26% 39% 22% 4	680
	21st to end	Day	5% 2 23% 42% 24% 5%	680
July	1st to 10th	Day	8% 2 15% 31% 31% 13%	671
	11th to 20th	Day	3 2 13% 38% 36% 7%	668
	21st to end	Day	8% 1 9% 33% 36% 13%	739
August	1st to 10th	Day	6% 2 12% 44% 32% 5%	676
	11th to 20th	Day	8% 2 15% 36% 32% 7%	665
	21st to end	Day	6% 2 9% 34% 39% 10%	628
September	1st to 10th	Day	11% 3 9% 29% 35% 13%	336
	11th to 20th	Day	7% 1 16% 39% 29% 9%	300
	21st to end	Day	13% 4 21% 33% 23% 6%	300
October	1st to 10th	Day	8% 6% 28% 30% 22% 6%	300
	11th to 20th	Day	7% 12% 38% 29% 12% 1	300
	21st to end	Day	21% 13% 30% 26% 8% 2	330
November	1st to 10th	Day	15% 10% 40% 25% 8% 2	300
	11th to 20th	Day	14% 12% 38% 21% 12% 1	273
	21st to end	Day	21% 16% 35% 22% 5% 1	270
December	1st to 10th	Day	14% 14% 42% 20% 9% 1	270
	11th to 20th	Day	19% 14% 37% 22% 7% 1	270
	21st to end	Day	12% 24% 40% 19% 4	297
January	1st to 10th	Night	14% 14% 40% 27% 6%	950
	11th to 20th	Night	14% 16% 37% 27% 5%	950
	21st to end	Night	14% 16% 38% 28% 5%	1045
February	1st to 10th	Night	18% 15% 38% 25% 3	950
	11th to 20th	Night	17% 18% 36% 26% 3	805
	21st to end	Night	17% 17% 38% 25% 3	602
March	1st to 10th	Night	15% 13% 38% 31% 4	570
	11th to 20th	Night	20% 13% 38% 26% 4	570
	21st to end	Night	19% 13% 40% 23% 4	627
April	1st to 10th	Night	14% 16% 41% 25% 4	570
	11th to 20th	Night	18% 12% 39% 25% 6%	563
	21st to end	Night	17% 12% 39% 24% 7% 1	570
May	1st to 10th	Night	16% 8% 41% 29% 6%	570
	11th to 20th	Night	15% 8% 29% 33% 14% 1	561
	21st to end	Night	11% 5% 30% 35% 18% 2	617
June	1st to 10th	Night	7% 2 23% 42% 25% 1	570
	11th to 20th	Night	5% 3 28% 45% 18% 1	570
	21st to end	Night	4 1 26% 50% 19% 1	570
July	1st to 10th	Night	5% 1 16% 45% 31% 3	555
	11th to 20th	Night	3 1 13% 49% 31% 3	552
	21st to end	Night	6% 1 12% 42% 38% 2	624
August	1st to 10th	Night	3 2 14% 50% 30% 2	567
	11th to 20th	Night	5% 1 15% 44% 32% 3	564
	21st to end	Night	4 1 12% 40% 40% 3	627
September	1st to 10th	Night	10% 1 14% 42% 31% 1	570
	11th to 20th	Night	12% 2 19% 38% 26% 3	570
	21st to end	Night	10% 4 20% 39% 24% 3	570
October	1st to 10th	Night	8% 3 29% 36% 22% 3	668
	11th to 20th	Night	13% 8% 37% 31% 11% 1	760
	21st to end	Night	16% 13% 29% 31% 10% 1	836
November	1st to 10th	Night	12% 9% 38% 28% 12% 1	785
	11th to 20th	Night	13% 13% 35% 30% 9%	956
	21st to end	Night	17% 14% 32% 28% 9%	950
December	1st to 10th	Night	15% 15% 33% 30% 6% 1	950
	11th to 20th	Night	19% 12% 36% 27% 6%	950
	21st to end	Night	17% 16% 35% 28% 4	1045

Page generated at 2024-11-08 21:45:39. Version ac07

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