Melita
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Melita clear sky chart from 2005-11-06 to 2025-02-21.

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	10% 8% 3 8% 6% 5% 5% 4 6% 8% 37%	112169
	Night	8% 9% 3 9% 6% 5% 5% 4 6% 7% 36%	115220
Transparency	Day	45% 5% 16% 25% 9% 1	111902
	Night	46% 5% 15% 24% 9% 1	115077
Seeing	Day	13% 8% 29% 31% 15% 4	16534
	Night	14% 6% 31% 36% 12% 1	26674

By Month

Percentage Cloud Cover SW (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	5% 12% 6% 16% 11% 9% 7% 6% 8% 6% 15%	3286
	11th to 20th	Day	3 8% 4 12% 11% 10% 11% 8% 9% 7% 15%	3640
	21st to end	Day	6% 13% 6% 14% 8% 6% 4 3 5% 6% 31%	4004
February	1st to 10th	Day	9% 14% 5% 14% 8% 6% 6% 3 6% 6% 25%	1600
	11th to 20th	Day	6% 12% 4 9% 8% 8% 7% 5% 8% 9% 24%	1810
	21st to end	Day	7% 11% 4 12% 8% 6% 7% 5% 7% 8% 25%	1570
March	1st to 10th	Day	10% 14% 5% 12% 8% 5% 5% 5% 7% 7% 22%	3130
	11th to 20th	Day	6% 10% 6% 12% 8% 7% 6% 5% 6% 7% 27%	3342
	21st to end	Day	9% 11% 5% 12% 8% 6% 6% 4 6% 8% 24%	4023
April	1st to 10th	Day	9% 10% 3 7% 6% 4 4 4 6% 9% 39%	2280
	11th to 20th	Day	15% 12% 4 8% 5% 4 5% 4 6% 7% 31%	2393
	21st to end	Day	14% 9% 3 8% 6% 5% 4 4 5% 7% 36%	2470
May	1st to 10th	Day	20% 8% 2 7% 4 4 4 4 6% 7% 35%	4323
	11th to 20th	Day	18% 8% 3 6% 5% 5% 5% 5% 5% 7% 33%	4446
	21st to end	Day	17% 7% 2 6% 5% 4 4 3 6% 8% 38%	5173
June	1st to 10th	Day	13% 5% 2 6% 4 4 4 4 6% 8% 43%	2850
	11th to 20th	Day	15% 7% 3 6% 5% 4 4 5% 7% 8% 36%	2850
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 4 6% 9% 41%	2850
July	1st to 10th	Day	7% 4 2 5% 4 5% 6% 5% 7% 11% 45%	4750
	11th to 20th	Day	5% 4 2 5% 3 3 4 4 6% 9% 54%	4593
	21st to end	Day	4 3 1 4 4 3 4 5% 7% 10% 55%	4802
August	1st to 10th	Day	9% 5% 2 5% 3 4 5% 4 6% 9% 48%	4411
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 6% 9% 49%	4134
	21st to end	Day	9% 5% 2 6% 4 4 4 3 6% 8% 50%	4450
September	1st to 10th	Day	10% 5% 2 6% 3 3 4 3 5% 7% 53%	2280
	11th to 20th	Day	13% 6% 2 6% 4 4 3 3 5% 6% 48%	2133
	21st to end	Day	15% 6% 2 4 3 3 3 4 5% 7% 48%	2090
October	1st to 10th	Day	11% 7% 2 6% 4 4 4 3 5% 7% 49%	3409
	11th to 20th	Day	7% 8% 2 6% 4 3 4 3 6% 8% 50%	2832
	21st to end	Day	11% 10% 4 9% 3 4 4 3 5% 7% 39%	3091
November	1st to 10th	Day	15% 12% 4 9% 5% 4 3 4 5% 6% 32%	1763
	11th to 20th	Day	10% 16% 5% 12% 7% 4 4 3 5% 6% 28%	1560
	21st to end	Day	8% 15% 4 10% 7% 5% 6% 5% 6% 5% 29%	1400
December	1st to 10th	Day	5% 14% 6% 15% 10% 10% 7% 4 5% 5% 19%	2290
	11th to 20th	Day	10% 14% 5% 12% 8% 6% 7% 4 6% 10% 20%	2643
	21st to end	Day	5% 9% 5% 15% 6% 6% 7% 5% 5% 6% 31%	3498
January	1st to 10th	Night	5% 11% 5% 17% 10% 10% 7% 6% 6% 6% 17%	6677
	11th to 20th	Night	5% 8% 3 12% 10% 10% 9% 7% 8% 8% 20%	6340
	21st to end	Night	6% 12% 6% 15% 7% 6% 5% 4 6% 6% 26%	6974
February	1st to 10th	Night	9% 13% 5% 11% 7% 6% 6% 5% 6% 6% 26%	2800
	11th to 20th	Night	6% 10% 4 9% 9% 6% 5% 5% 6% 7% 32%	2494
	21st to end	Night	7% 11% 5% 10% 6% 5% 5% 4 6% 7% 35%	1884
March	1st to 10th	Night	9% 12% 5% 10% 6% 5% 5% 4 7% 7% 30%	3734
	11th to 20th	Night	6% 10% 3 8% 5% 4 5% 4 6% 8% 40%	3622
	21st to end	Night	6% 13% 6% 12% 6% 4 5% 3 6% 7% 31%	3615
April	1st to 10th	Night	5% 9% 3 8% 5% 4 5% 5% 6% 8% 43%	1900
	11th to 20th	Night	15% 11% 3 7% 5% 5% 5% 3 6% 6% 34%	1734
	21st to end	Night	14% 8% 2 8% 5% 4 5% 4 5% 7% 38%	1710
May	1st to 10th	Night	17% 8% 2 6% 5% 4 5% 4 5% 7% 37%	2643
	11th to 20th	Night	15% 6% 2 7% 6% 4 4 4 5% 7% 40%	2457
	21st to end	Night	14% 8% 3 7% 4 5% 4 3 6% 7% 40%	2414
June	1st to 10th	Night	15% 4 1 5% 4 4 4 4 7% 8% 44%	1330
	11th to 20th	Night	13% 5% 2 6% 5% 4 5% 4 6% 7% 42%	1330
	21st to end	Night	10% 4 1 5% 4 4 5% 5% 6% 9% 45%	1330
July	1st to 10th	Night	7% 3 1 5% 4 4 5% 5% 8% 12% 47%	2220
	11th to 20th	Night	7% 3 2 4 3 3 3 3 6% 8% 60%	2374
	21st to end	Night	4 3 1 4 3 4 4 4 6% 10% 56%	2761
August	1st to 10th	Night	7% 3 2 5% 4 3 4 4 7% 8% 55%	2528
	11th to 20th	Night	5% 3 2 6% 4 5% 4 3 7% 9% 52%	2704
	21st to end	Night	7% 3 1 5% 3 4 4 3 6% 8% 55%	3215
September	1st to 10th	Night	7% 4 2 5% 4 3 4 3 5% 7% 56%	1900
	11th to 20th	Night	12% 4 2 5% 3 3 3 4 6% 8% 49%	2047
	21st to end	Night	15% 7% 3 5% 4 4 3 3 4 7% 45%	2090
October	1st to 10th	Night	10% 7% 2 6% 3 3 3 3 4 6% 51%	3526
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 4 6% 7% 45%	4087
	21st to end	Night	9% 8% 2 7% 5% 4 5% 4 6% 7% 44%	4467
November	1st to 10th	Night	13% 11% 4 8% 5% 4 5% 4 5% 7% 35%	2535
	11th to 20th	Night	9% 12% 5% 12% 7% 5% 4 3 5% 6% 31%	2834
	21st to end	Night	8% 12% 4 11% 8% 5% 4 3 6% 6% 33%	3000
December	1st to 10th	Night	6% 13% 5% 12% 9% 7% 8% 6% 6% 7% 21%	4900
	11th to 20th	Night	9% 14% 4 10% 8% 6% 6% 4 5% 9% 23%	5564
	21st to end	Night	5% 9% 3 13% 8% 7% 8% 5% 6% 6% 29%	7480

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	64% 5% 13% 14% 4	3287
	11th to 20th	Day	63% 4 13% 14% 6%	3640
	21st to end	Day	56% 3 18% 18% 4	4004
February	1st to 10th	Day	60% 3 13% 16% 8% 1	1600
	11th to 20th	Day	54% 5% 13% 19% 9%	1819
	21st to end	Day	55% 4 16% 19% 5% 1	1570
March	1st to 10th	Day	59% 5% 14% 17% 5%	3130
	11th to 20th	Day	55% 4 18% 17% 5%	3342
	21st to end	Day	56% 6% 15% 17% 7%	4023
April	1st to 10th	Day	41% 3 17% 27% 11% 1	2280
	11th to 20th	Day	51% 4 13% 20% 11% 1	2396
	21st to end	Day	47% 5% 17% 23% 8%	2470
May	1st to 10th	Day	48% 4 16% 22% 10% 1	4323
	11th to 20th	Day	48% 4 13% 22% 12% 1	4450
	21st to end	Day	44% 5% 13% 29% 9%	5173
June	1st to 10th	Day	39% 4 21% 26% 9% 2	2850
	11th to 20th	Day	43% 6% 18% 23% 9% 1	2850
	21st to end	Day	39% 6% 20% 27% 7% 1	2850
July	1st to 10th	Day	31% 8% 27% 28% 6%	4676
	11th to 20th	Day	26% 5% 18% 41% 9% 1	4512
	21st to end	Day	23% 6% 23% 36% 12% 1	4651
August	1st to 10th	Day	32% 5% 17% 32% 13% 1	4396
	11th to 20th	Day	31% 5% 20% 36% 7%	4175
	21st to end	Day	32% 4 17% 37% 9%	4449
September	1st to 10th	Day	31% 4 16% 33% 15% 1	2280
	11th to 20th	Day	38% 4 19% 26% 12% 1	2133
	21st to end	Day	37% 3 14% 30% 14%	2090
October	1st to 10th	Day	37% 3 13% 34% 12% 1	3409
	11th to 20th	Day	32% 3 15% 39% 11%	2832
	21st to end	Day	45% 3 12% 29% 10%	3091
November	1st to 10th	Day	53% 4 16% 19% 7% 1	1763
	11th to 20th	Day	57% 4 16% 16% 7% 1	1560
	21st to end	Day	55% 7% 16% 17% 5%	1400
December	1st to 10th	Day	67% 4 14% 11% 4	2290
	11th to 20th	Day	60% 4 17% 16% 2	2640
	21st to end	Day	52% 4 10% 23% 9% 1	3498
January	1st to 10th	Night	66% 4 11% 16% 3	6677
	11th to 20th	Night	59% 3 15% 16% 6%	6340
	21st to end	Night	58% 6% 16% 17% 3	6974
February	1st to 10th	Night	56% 4 15% 17% 8%	2800
	11th to 20th	Night	48% 5% 14% 20% 12%	2495
	21st to end	Night	48% 3 15% 24% 11%	1884
March	1st to 10th	Night	50% 4 18% 22% 5%	3734
	11th to 20th	Night	40% 4 21% 28% 6%	3622
	21st to end	Night	52% 4 12% 25% 6%	3615
April	1st to 10th	Night	37% 5% 12% 28% 16% 3	1900
	11th to 20th	Night	51% 4 9% 22% 13% 1	1734
	21st to end	Night	46% 4 12% 25% 12% 2	1710
May	1st to 10th	Night	46% 4 12% 23% 14%	2643
	11th to 20th	Night	43% 4 12% 26% 14% 2	2458
	21st to end	Night	43% 4 14% 28% 10%	2414
June	1st to 10th	Night	36% 5% 16% 26% 14% 3	1330
	11th to 20th	Night	40% 5% 17% 24% 12% 2	1330
	21st to end	Night	33% 7% 20% 32% 8% 1	1330
July	1st to 10th	Night	29% 10% 26% 25% 9% 1	2185
	11th to 20th	Night	23% 5% 18% 41% 12% 1	2332
	21st to end	Night	24% 5% 21% 33% 16% 2	2674
August	1st to 10th	Night	26% 5% 19% 34% 14% 2	2520
	11th to 20th	Night	28% 5% 20% 37% 9% 1	2729
	21st to end	Night	27% 4 18% 36% 14% 1	3215
September	1st to 10th	Night	28% 4 12% 34% 20% 2	1900
	11th to 20th	Night	33% 4 18% 29% 15% 1	2047
	21st to end	Night	40% 4 12% 30% 13% 2	2090
October	1st to 10th	Night	35% 3 11% 34% 14% 4	3526
	11th to 20th	Night	38% 3 11% 35% 13% 1	4087
	21st to end	Night	40% 3 13% 34% 10%	4467
November	1st to 10th	Night	48% 5% 15% 22% 8% 2	2535
	11th to 20th	Night	53% 5% 16% 19% 6%	2834
	21st to end	Night	52% 5% 20% 18% 6%	3000
December	1st to 10th	Night	62% 6% 17% 11% 4	4900
	11th to 20th	Night	59% 4 18% 15% 3	5566
	21st to end	Night	52% 6% 11% 20% 10% 1	7480

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	10% 6% 33% 31% 15% 5%	300
	11th to 20th	Day	10% 8% 36% 33% 10% 2	300
	21st to end	Day	13% 8% 32% 33% 11% 2	330
February	1st to 10th	Day	13% 7% 35% 36% 9%	300
	11th to 20th	Day	8% 6% 36% 32% 13% 4	300
	21st to end	Day	4 6% 28% 44% 15% 3	225
March	1st to 10th	Day	11% 10% 36% 30% 10% 3	270
	11th to 20th	Day	11% 9% 31% 29% 17% 3	270
	21st to end	Day	15% 6% 31% 27% 18% 3	416
April	1st to 10th	Day	12% 11% 34% 32% 9% 3	460
	11th to 20th	Day	20% 8% 32% 27% 12% 1	594
	21st to end	Day	16% 8% 27% 32% 15% 2	650
May	1st to 10th	Day	14% 8% 30% 31% 13% 3	653
	11th to 20th	Day	18% 8% 26% 28% 16% 4	675
	21st to end	Day	18% 10% 22% 30% 16% 3	734
June	1st to 10th	Day	13% 10% 27% 29% 16% 5%	680
	11th to 20th	Day	16% 10% 30% 28% 12% 4	680
	21st to end	Day	11% 9% 23% 34% 19% 4	680
July	1st to 10th	Day	9% 4 22% 35% 22% 8%	671
	11th to 20th	Day	8% 6% 30% 32% 17% 7%	668
	21st to end	Day	4 3 28% 35% 22% 7%	739
August	1st to 10th	Day	10% 5% 22% 36% 21% 7%	676
	11th to 20th	Day	10% 6% 21% 28% 28% 7%	665
	21st to end	Day	11% 6% 25% 33% 20% 5%	705
September	1st to 10th	Day	10% 9% 34% 28% 14% 4	490
	11th to 20th	Day	17% 10% 26% 30% 15% 1	343
	21st to end	Day	23% 10% 29% 25% 13% 1	300
October	1st to 10th	Day	21% 8% 30% 24% 13% 3	300
	11th to 20th	Day	18% 12% 29% 28% 10% 3	300
	21st to end	Day	24% 5% 38% 24% 7% 3	330
November	1st to 10th	Day	25% 8% 25% 30% 10% 2	300
	11th to 20th	Day	17% 10% 38% 24% 9% 1	300
	21st to end	Day	14% 8% 37% 31% 8% 2	300
December	1st to 10th	Day	11% 8% 36% 29% 13% 2	300
	11th to 20th	Day	17% 8% 40% 27% 6% 2	300
	21st to end	Day	10% 4 35% 32% 14% 5%	330
January	1st to 10th	Night	11% 5% 36% 33% 13% 1	1000
	11th to 20th	Night	15% 7% 35% 35% 8% 1	1000
	21st to end	Night	12% 9% 35% 35% 9%	1100
February	1st to 10th	Night	15% 8% 31% 34% 12% 2	1000
	11th to 20th	Night	12% 6% 31% 37% 13% 2	889
	21st to end	Night	11% 5% 28% 39% 14% 2	628
March	1st to 10th	Night	15% 7% 32% 32% 13% 3	760
	11th to 20th	Night	10% 7% 34% 35% 13% 2	660
	21st to end	Night	13% 6% 30% 36% 13% 3	627
April	1st to 10th	Night	9% 7% 37% 36% 10% 1	570
	11th to 20th	Night	20% 6% 28% 37% 8% 1	563
	21st to end	Night	16% 6% 30% 34% 13% 1	570
May	1st to 10th	Night	16% 5% 28% 36% 14%	570
	11th to 20th	Night	16% 4 31% 36% 12%	561
	21st to end	Night	20% 6% 25% 37% 12% 1	617
June	1st to 10th	Night	15% 5% 31% 31% 17% 1	570
	11th to 20th	Night	16% 4 32% 35% 13% 1	570
	21st to end	Night	11% 4 26% 41% 17% 1	570
July	1st to 10th	Night	7% 3 19% 45% 25%	555
	11th to 20th	Night	7% 4 26% 46% 16% 1	552
	21st to end	Night	6% 3 23% 51% 16% 2	624
August	1st to 10th	Night	8% 4 22% 47% 18% 1	567
	11th to 20th	Night	7% 3 21% 43% 23% 3	564
	21st to end	Night	11% 3 29% 40% 16% 1	627
September	1st to 10th	Night	8% 5% 28% 38% 17% 3	570
	11th to 20th	Night	14% 5% 33% 36% 11% 1	570
	21st to end	Night	17% 6% 31% 32% 13% 1	570
October	1st to 10th	Night	17% 6% 32% 33% 11%	590
	11th to 20th	Night	19% 7% 29% 33% 10% 1	940
	21st to end	Night	17% 8% 32% 32% 10% 1	1045
November	1st to 10th	Night	18% 8% 34% 32% 7% 1	975
	11th to 20th	Night	15% 9% 35% 30% 9% 2	1000
	21st to end	Night	13% 9% 38% 32% 8%	1000
December	1st to 10th	Night	12% 7% 35% 32% 12% 2	1000
	11th to 20th	Night	16% 9% 32% 31% 10% 1	1000
	21st to end	Night	17% 4 31% 34% 12% 2	1100

Page generated at 2025-02-18 02:26:29. Version ac07

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