Morning Star Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Morning Star Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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	17% 12% 4 8% 5% 4 4 4 5% 7% 30%	101199
	Night	17% 13% 5% 9% 5% 4 4 3 5% 6% 31%	97793
Transparency	Day	51% 6% 11% 20% 10% 1	104843
	Night	53% 6% 11% 19% 10% 2	102288
Seeing	Day	26% 17% 25% 18% 10% 4	14768
	Night	25% 15% 22% 25% 11% 1	24351

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	17% 23% 9% 15% 4 3 3 2 3 4 17%	2713
	11th to 20th	Day	11% 21% 10% 18% 9% 4 3 2 3 3 15%	2840
	21st to end	Day	23% 19% 10% 13% 8% 4 3 2 3 3 13%	3124
February	1st to 10th	Day	16% 19% 7% 12% 9% 5% 3 3 3 4 20%	1710
	11th to 20th	Day	16% 16% 8% 13% 5% 4 4 3 4 6% 20%	1663
	21st to end	Day	19% 18% 5% 11% 6% 4 3 2 4 4 23%	1565
March	1st to 10th	Day	18% 14% 7% 8% 4 4 4 3 4 6% 29%	3435
	11th to 20th	Day	14% 15% 6% 12% 5% 5% 4 2 4 5% 28%	3480
	21st to end	Day	18% 13% 3 8% 4 4 4 3 4 6% 33%	3815
April	1st to 10th	Day	15% 17% 3 7% 5% 3 5% 3 5% 6% 29%	2232
	11th to 20th	Day	17% 14% 3 7% 4 4 3 3 5% 6% 33%	2254
	21st to end	Day	22% 11% 3 6% 4 4 5% 3 5% 6% 31%	2430
May	1st to 10th	Day	24% 10% 3 8% 5% 4 5% 4 5% 5% 27%	4082
	11th to 20th	Day	21% 9% 3 8% 6% 4 5% 3 6% 7% 28%	4130
	21st to end	Day	15% 6% 2 6% 4 5% 5% 5% 6% 9% 36%	4823
June	1st to 10th	Day	17% 7% 3 7% 5% 5% 5% 4 6% 8% 33%	2660
	11th to 20th	Day	16% 7% 3 6% 5% 6% 6% 5% 7% 9% 32%	2660
	21st to end	Day	16% 6% 2 6% 5% 5% 5% 5% 6% 10% 34%	2660
July	1st to 10th	Day	11% 6% 2 7% 5% 6% 5% 5% 7% 8% 39%	4440
	11th to 20th	Day	11% 7% 3 6% 5% 5% 6% 4 7% 10% 37%	4133
	21st to end	Day	14% 8% 3 8% 5% 5% 4 4 6% 7% 36%	4466
August	1st to 10th	Day	16% 9% 3 8% 5% 5% 5% 5% 7% 8% 28%	4104
	11th to 20th	Day	14% 6% 3 7% 5% 5% 6% 5% 6% 7% 35%	4044
	21st to end	Day	10% 5% 2 6% 4 5% 6% 5% 7% 10% 40%	4226
September	1st to 10th	Day	17% 6% 2 5% 5% 4 4 3 4 8% 42%	2280
	11th to 20th	Day	13% 6% 2 6% 5% 4 4 4 5% 7% 44%	2167
	21st to end	Day	22% 10% 4 7% 4 3 4 3 4 6% 33%	2047
October	1st to 10th	Day	18% 7% 2 5% 5% 4 4 3 6% 8% 38%	1900
	11th to 20th	Day	19% 10% 4 6% 5% 4 4 3 5% 5% 35%	1900
	21st to end	Day	22% 14% 3 6% 3 3 4 3 3 6% 33%	2090
November	1st to 10th	Day	13% 13% 3 6% 4 4 4 3 5% 7% 40%	1884
	11th to 20th	Day	15% 17% 5% 7% 5% 3 4 3 6% 6% 29%	1520
	21st to end	Day	19% 18% 8% 8% 4 4 4 2 5% 5% 23%	1520
December	1st to 10th	Day	19% 21% 10% 12% 5% 4 3 3 4 4 17%	1520
	11th to 20th	Day	18% 20% 8% 11% 4 3 3 3 5% 6% 19%	1910
	21st to end	Day	22% 24% 8% 10% 5% 3 3 2 4 4 15%	2772
January	1st to 10th	Night	13% 24% 9% 15% 5% 4 3 3 3 4 17%	4228
	11th to 20th	Night	14% 19% 9% 17% 5% 6% 4 3 4 3 15%	4120
	21st to end	Night	24% 18% 9% 11% 9% 3 2 2 3 3 15%	4532
February	1st to 10th	Night	16% 16% 7% 12% 6% 4 4 3 4 5% 23%	2470
	11th to 20th	Night	17% 16% 6% 13% 6% 5% 4 3 5% 4 22%	2403
	21st to end	Night	17% 16% 6% 13% 5% 4 4 3 4 4 24%	1884
March	1st to 10th	Night	21% 14% 4 7% 5% 3 3 3 4 6% 30%	3418
	11th to 20th	Night	14% 14% 9% 9% 5% 3 3 3 4 5% 30%	3480
	21st to end	Night	17% 12% 4 9% 4 4 3 2 4 5% 37%	3817
April	1st to 10th	Night	16% 16% 4 7% 5% 4 4 3 4 6% 31%	1948
	11th to 20th	Night	18% 11% 2 5% 4 5% 3 4 5% 7% 36%	1875
	21st to end	Night	17% 10% 3 7% 6% 4 5% 3 5% 6% 35%	1766
May	1st to 10th	Night	28% 10% 3 7% 4 5% 4 3 5% 6% 26%	2813
	11th to 20th	Night	19% 12% 3 8% 5% 4 4 3 5% 5% 32%	2759
	21st to end	Night	15% 8% 3 7% 4 4 4 5% 6% 9% 35%	2732
June	1st to 10th	Night	13% 7% 2 6% 5% 4 5% 4 6% 7% 42%	1520
	11th to 20th	Night	12% 6% 3 7% 4 4 6% 4 7% 10% 36%	1520
	21st to end	Night	14% 7% 2 4 4 5% 3 4 6% 11% 40%	1520
July	1st to 10th	Night	12% 7% 3 8% 5% 4 5% 4 6% 8% 37%	2520
	11th to 20th	Night	11% 6% 3 7% 4 5% 5% 4 6% 9% 41%	2822
	21st to end	Night	13% 9% 3 7% 5% 5% 4 5% 5% 6% 39%	3087
August	1st to 10th	Night	17% 8% 3 6% 4 5% 5% 4 6% 8% 34%	2825
	11th to 20th	Night	16% 7% 2 6% 5% 4 4 3 5% 6% 40%	2785
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 10% 46%	3398
September	1st to 10th	Night	15% 5% 2 5% 3 4 4 3 5% 7% 46%	1900
	11th to 20th	Night	11% 5% 2 4 3 3 4 3 5% 8% 51%	2009
	21st to end	Night	18% 8% 3 6% 4 4 4 3 5% 6% 38%	2133
October	1st to 10th	Night	18% 7% 2 6% 3 4 3 3 5% 7% 43%	2280
	11th to 20th	Night	19% 8% 2 5% 4 5% 4 3 5% 6% 38%	2280
	21st to end	Night	25% 11% 2 6% 3 3 4 3 4 6% 33%	2508
November	1st to 10th	Night	11% 12% 4 6% 4 4 4 3 5% 5% 42%	2292
	11th to 20th	Night	17% 16% 4 7% 5% 4 4 3 5% 5% 30%	2660
	21st to end	Night	18% 17% 5% 7% 5% 4 4 3 4 4 28%	2660
December	1st to 10th	Night	21% 21% 8% 12% 4 3 3 3 3 4 16%	2660
	11th to 20th	Night	19% 18% 8% 12% 6% 4 3 3 4 4 21%	3285
	21st to end	Night	21% 23% 8% 11% 6% 4 4 3 4 4 13%	4884

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	72% 6% 8% 11% 3 1	2714
	11th to 20th	Day	76% 3 7% 10% 3 1	2840
	21st to end	Day	78% 5% 6% 9% 2	3124
February	1st to 10th	Day	69% 4 8% 12% 6% 1	1710
	11th to 20th	Day	65% 6% 9% 13% 6%	1672
	21st to end	Day	64% 5% 10% 13% 7% 2	1565
March	1st to 10th	Day	55% 6% 11% 21% 6%	3435
	11th to 20th	Day	55% 7% 12% 20% 6% 1	3480
	21st to end	Day	51% 6% 12% 20% 10% 1	3815
April	1st to 10th	Day	54% 6% 11% 17% 10% 2	2232
	11th to 20th	Day	51% 5% 11% 16% 15% 2	2254
	21st to end	Day	53% 5% 11% 20% 9% 1	2430
May	1st to 10th	Day	58% 6% 9% 18% 8% 1	4120
	11th to 20th	Day	53% 8% 12% 18% 8% 1	4134
	21st to end	Day	41% 9% 16% 21% 11% 2	4837
June	1st to 10th	Day	47% 8% 11% 22% 10% 1	2660
	11th to 20th	Day	45% 8% 14% 20% 11% 1	2660
	21st to end	Day	44% 8% 12% 25% 11%	2660
July	1st to 10th	Day	41% 8% 12% 24% 13% 2	4370
	11th to 20th	Day	40% 7% 14% 25% 13%	4063
	21st to end	Day	46% 5% 9% 22% 16% 1	4324
August	1st to 10th	Day	50% 8% 15% 20% 7%	4091
	11th to 20th	Day	45% 7% 11% 27% 10%	4083
	21st to end	Day	36% 8% 14% 27% 13% 2	4226
September	1st to 10th	Day	41% 6% 11% 22% 16% 4	2280
	11th to 20th	Day	38% 6% 12% 27% 16% 1	2167
	21st to end	Day	51% 4 12% 20% 12% 1	2047
October	1st to 10th	Day	36% 6% 8% 30% 19% 1	3160
	11th to 20th	Day	45% 6% 11% 20% 11% 7%	3140
	21st to end	Day	38% 3 10% 29% 19% 1	3428
November	1st to 10th	Day	45% 5% 13% 18% 17% 3	1884
	11th to 20th	Day	55% 6% 10% 16% 10% 2	1520
	21st to end	Day	64% 4 11% 14% 7%	1520
December	1st to 10th	Day	72% 4 9% 10% 4	1520
	11th to 20th	Day	66% 5% 9% 16% 3	1906
	21st to end	Day	73% 5% 8% 11% 2	2772
January	1st to 10th	Night	71% 5% 7% 12% 4 1	4228
	11th to 20th	Night	73% 5% 10% 10% 2	4120
	21st to end	Night	76% 4 5% 12% 3 1	4532
February	1st to 10th	Night	64% 5% 9% 16% 6%	2470
	11th to 20th	Night	66% 5% 9% 14% 7%	2405
	21st to end	Night	63% 5% 9% 14% 8% 1	1884
March	1st to 10th	Night	55% 5% 12% 21% 6%	3418
	11th to 20th	Night	51% 10% 13% 20% 5% 1	3480
	21st to end	Night	48% 6% 11% 22% 13% 1	3817
April	1st to 10th	Night	54% 5% 10% 18% 12% 1	1948
	11th to 20th	Night	47% 6% 13% 17% 15% 2	1875
	21st to end	Night	48% 7% 10% 23% 10% 3	1766
May	1st to 10th	Night	58% 6% 9% 16% 9% 2	2840
	11th to 20th	Night	52% 9% 12% 18% 8% 1	2760
	21st to end	Night	41% 10% 15% 20% 10% 4	2739
June	1st to 10th	Night	40% 8% 11% 27% 13% 1	1520
	11th to 20th	Night	41% 9% 13% 25% 10% 2	1520
	21st to end	Night	38% 8% 14% 25% 14% 1	1520
July	1st to 10th	Night	43% 8% 11% 21% 13% 3	2480
	11th to 20th	Night	39% 6% 16% 24% 14% 1	2769
	21st to end	Night	44% 7% 10% 18% 19% 2	2988
August	1st to 10th	Night	47% 8% 15% 22% 8%	2814
	11th to 20th	Night	43% 6% 10% 29% 12% 1	2812
	21st to end	Night	33% 7% 15% 31% 12% 2	3398
September	1st to 10th	Night	37% 7% 10% 25% 18% 3	1900
	11th to 20th	Night	30% 7% 14% 28% 20% 1	2009
	21st to end	Night	46% 6% 12% 20% 15% 1	2133
October	1st to 10th	Night	37% 6% 9% 27% 20% 1	3800
	11th to 20th	Night	39% 4 10% 24% 13% 9%	3779
	21st to end	Night	39% 4 10% 26% 20% 1	4120
November	1st to 10th	Night	43% 5% 11% 20% 17% 4	2292
	11th to 20th	Night	56% 5% 9% 17% 11% 3	2660
	21st to end	Night	60% 5% 10% 18% 7% 1	2660
December	1st to 10th	Night	71% 4 9% 10% 4 1	2660
	11th to 20th	Night	68% 5% 8% 15% 4	3288
	21st to end	Night	73% 6% 9% 10% 2	4884

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	39% 28% 18% 9% 5% 1	236
	11th to 20th	Day	43% 29% 21% 4 2 1	270
	21st to end	Day	35% 29% 28% 6% 2	297
February	1st to 10th	Day	34% 28% 30% 7% 1	270
	11th to 20th	Day	46% 28% 20% 6%	270
	21st to end	Day	41% 27% 24% 7% 1	306
March	1st to 10th	Day	35% 25% 24% 13% 2	460
	11th to 20th	Day	35% 24% 25% 12% 4 1	460
	21st to end	Day	35% 23% 25% 13% 3 1	506
April	1st to 10th	Day	30% 25% 24% 15% 4 1	460
	11th to 20th	Day	26% 24% 26% 13% 8% 3	452
	21st to end	Day	31% 20% 25% 18% 5% 1	460
May	1st to 10th	Day	31% 19% 24% 16% 8% 2	463
	11th to 20th	Day	26% 16% 29% 17% 8% 3	487
	21st to end	Day	18% 14% 24% 24% 13% 6%	529
June	1st to 10th	Day	21% 14% 26% 24% 12% 3	490
	11th to 20th	Day	21% 14% 24% 21% 15% 5%	490
	21st to end	Day	20% 12% 29% 25% 11% 3	490
July	1st to 10th	Day	16% 8% 24% 24% 17% 11%	485
	11th to 20th	Day	12% 10% 29% 26% 16% 6%	484
	21st to end	Day	15% 10% 24% 28% 18% 5%	532
August	1st to 10th	Day	15% 10% 23% 26% 19% 7%	486
	11th to 20th	Day	20% 8% 23% 22% 18% 10%	479
	21st to end	Day	15% 7% 24% 27% 19% 9%	539
September	1st to 10th	Day	21% 9% 19% 24% 19% 9%	490
	11th to 20th	Day	15% 3 21% 29% 22% 9%	490
	21st to end	Day	29% 14% 23% 16% 14% 5%	490
October	1st to 10th	Day	22% 13% 23% 24% 15% 4	490
	11th to 20th	Day	27% 16% 27% 20% 9% 1	490
	21st to end	Day	33% 17% 27% 16% 7%	539
November	1st to 10th	Day	22% 19% 24% 23% 10% 2	460
	11th to 20th	Day	34% 24% 25% 12% 4 1	180
	21st to end	Day	32% 26% 29% 12% 1	180
December	1st to 10th	Day	38% 29% 21% 7% 3 1	180
	11th to 20th	Day	44% 19% 27% 8% 2	180
	21st to end	Day	39% 26% 24% 8% 3	198
January	1st to 10th	Night	32% 27% 24% 13% 4	760
	11th to 20th	Night	34% 24% 25% 14% 3	760
	21st to end	Night	31% 26% 27% 15% 1	836
February	1st to 10th	Night	32% 21% 27% 17% 2	760
	11th to 20th	Night	34% 29% 25% 11% 1	743
	21st to end	Night	35% 20% 26% 16% 2	628
March	1st to 10th	Night	29% 21% 27% 21% 2	760
	11th to 20th	Night	31% 23% 20% 19% 5% 1	760
	21st to end	Night	29% 21% 27% 18% 5% 1	836
April	1st to 10th	Night	28% 18% 28% 20% 5%	760
	11th to 20th	Night	25% 16% 26% 24% 9% 1	751
	21st to end	Night	22% 14% 27% 30% 6% 1	626
May	1st to 10th	Night	27% 10% 23% 30% 9% 1	570
	11th to 20th	Night	22% 11% 24% 33% 10%	534
	21st to end	Night	12% 8% 21% 32% 24% 3	411
June	1st to 10th	Night	14% 6% 22% 37% 19% 1	380
	11th to 20th	Night	14% 9% 19% 36% 20% 2	380
	21st to end	Night	15% 5% 24% 38% 18% 1	380
July	1st to 10th	Night	13% 4 18% 40% 23% 3	370
	11th to 20th	Night	11% 7% 16% 37% 25% 4	535
	21st to end	Night	14% 5% 14% 42% 23% 2	624
August	1st to 10th	Night	13% 4 12% 41% 28% 2	567
	11th to 20th	Night	15% 5% 11% 37% 28% 4	564
	21st to end	Night	14% 3 15% 37% 26% 4	784
September	1st to 10th	Night	16% 6% 16% 33% 24% 4	760
	11th to 20th	Night	13% 4 16% 34% 29% 4	760
	21st to end	Night	23% 9% 20% 26% 19% 3	760
October	1st to 10th	Night	22% 8% 19% 30% 20% 2	760
	11th to 20th	Night	25% 13% 25% 26% 9% 1	760
	21st to end	Night	31% 14% 24% 26% 5%	836
November	1st to 10th	Night	20% 12% 24% 33% 10% 1	760
	11th to 20th	Night	31% 18% 23% 21% 6% 1	760
	21st to end	Night	30% 20% 26% 19% 5% 1	760
December	1st to 10th	Night	38% 22% 20% 16% 3	760
	11th to 20th	Night	34% 23% 24% 18% 2	760
	21st to end	Night	32% 22% 26% 18% 1	836

Page generated at 2024-11-03 02:11:17. Version ac07

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