Minakakis Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Minakakis Observatory clear sky chart from 2005-11-06 to 2025-02-25.

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 9% 6% 5% 5% 4 6% 7% 32%	109169
	Night	13% 10% 3 8% 5% 5% 5% 4 6% 7% 34%	109468
Transparency	Day	47% 9% 14% 19% 10% 1	112809
	Night	46% 9% 13% 19% 11% 1	113992
Seeing	Day	18% 16% 30% 22% 10% 3	15004
	Night	18% 14% 32% 25% 10% 1	24305

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	10% 13% 6% 15% 6% 5% 5% 4 5% 6% 24%	3597
	11th to 20th	Day	9% 18% 7% 17% 9% 7% 5% 4 5% 5% 14%	3998
	21st to end	Day	17% 16% 6% 14% 7% 5% 5% 4 5% 5% 17%	4466
February	1st to 10th	Day	13% 15% 5% 12% 9% 6% 4 4 5% 6% 21%	1800
	11th to 20th	Day	11% 13% 5% 13% 8% 6% 5% 3 6% 6% 24%	1753
	21st to end	Day	17% 12% 5% 12% 7% 4 5% 3 5% 6% 25%	1512
March	1st to 10th	Day	18% 11% 5% 10% 6% 5% 5% 3 4 5% 29%	3432
	11th to 20th	Day	10% 13% 5% 9% 6% 6% 6% 4 5% 6% 30%	3480
	21st to end	Day	14% 10% 4 8% 5% 5% 5% 3 6% 6% 35%	3815
April	1st to 10th	Day	15% 12% 4 8% 6% 6% 5% 4 6% 7% 29%	2224
	11th to 20th	Day	17% 9% 3 7% 4 5% 4 4 5% 6% 36%	2351
	21st to end	Day	19% 9% 3 7% 6% 3 4 4 5% 6% 33%	2470
May	1st to 10th	Day	17% 8% 3 7% 4 4 4 4 6% 8% 34%	4108
	11th to 20th	Day	16% 8% 3 8% 5% 5% 6% 4 6% 7% 31%	4320
	21st to end	Day	10% 5% 2 5% 4 4 4 4 6% 8% 46%	4837
June	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 4 6% 8% 38%	2660
	11th to 20th	Day	10% 5% 3 6% 5% 4 5% 4 7% 9% 39%	2680
	21st to end	Day	12% 6% 2 6% 5% 4 5% 5% 7% 9% 39%	2850
July	1st to 10th	Day	9% 4 2 6% 5% 5% 6% 5% 8% 10% 40%	4582
	11th to 20th	Day	8% 4 2 5% 5% 4 5% 5% 8% 9% 44%	4412
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 7% 10% 42%	4466
August	1st to 10th	Day	16% 7% 2 6% 4 4 5% 4 6% 9% 37%	4104
	11th to 20th	Day	9% 6% 3 8% 6% 6% 6% 5% 8% 9% 34%	4044
	21st to end	Day	9% 6% 2 5% 4 5% 6% 4 8% 9% 42%	4382
September	1st to 10th	Day	11% 7% 2 6% 5% 5% 6% 4 6% 8% 41%	2280
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 5% 9% 45%	2138
	21st to end	Day	14% 6% 3 7% 6% 6% 5% 5% 7% 8% 34%	2069
October	1st to 10th	Day	18% 9% 3 7% 4 5% 5% 3 5% 7% 35%	1900
	11th to 20th	Day	18% 9% 3 9% 6% 5% 5% 3 5% 7% 30%	1900
	21st to end	Day	22% 11% 4 8% 6% 7% 5% 4 5% 6% 23%	2090
November	1st to 10th	Day	12% 10% 4 9% 6% 5% 5% 5% 7% 7% 31%	1703
	11th to 20th	Day	13% 11% 4 10% 7% 5% 6% 4 6% 8% 27%	1600
	21st to end	Day	16% 14% 5% 9% 7% 5% 6% 4 6% 6% 22%	1600
December	1st to 10th	Day	16% 17% 5% 12% 6% 7% 5% 4 6% 6% 14%	2600
	11th to 20th	Day	21% 17% 5% 8% 5% 5% 4 4 5% 6% 20%	2986
	21st to end	Day	26% 17% 7% 13% 5% 5% 4 3 4 4 12%	3960
January	1st to 10th	Night	13% 11% 4 11% 6% 6% 5% 4 5% 7% 28%	6349
	11th to 20th	Night	10% 12% 5% 14% 11% 7% 6% 4 6% 9% 15%	5882
	21st to end	Night	15% 11% 5% 12% 6% 6% 5% 4 6% 7% 22%	6490
February	1st to 10th	Night	13% 13% 3 10% 8% 6% 5% 4 6% 7% 25%	2600
	11th to 20th	Night	11% 12% 5% 11% 7% 6% 6% 4 5% 7% 27%	2533
	21st to end	Night	12% 11% 4 10% 7% 6% 5% 4 6% 7% 28%	2033
March	1st to 10th	Night	18% 8% 3 8% 5% 5% 5% 4 5% 7% 30%	3408
	11th to 20th	Night	11% 9% 4 7% 5% 4 5% 4 6% 7% 39%	3479
	21st to end	Night	15% 8% 3 6% 4 4 4 3 5% 5% 43%	3817
April	1st to 10th	Night	16% 10% 3 7% 5% 4 5% 4 6% 5% 33%	1955
	11th to 20th	Night	15% 8% 3 7% 5% 5% 4 4 6% 6% 38%	1795
	21st to end	Night	15% 9% 3 7% 5% 4 4 4 6% 7% 37%	1710
May	1st to 10th	Night	16% 8% 2 6% 5% 4 4 4 5% 6% 40%	2833
	11th to 20th	Night	15% 8% 3 7% 5% 5% 4 4 5% 7% 37%	2572
	21st to end	Night	9% 3 2 5% 4 4 4 4 6% 9% 51%	2738
June	1st to 10th	Night	11% 5% 2 6% 5% 5% 4 5% 7% 8% 43%	1520
	11th to 20th	Night	9% 5% 2 6% 5% 4 4 4 7% 9% 43%	1491
	21st to end	Night	10% 5% 3 6% 4 3 4 4 6% 8% 47%	1330
July	1st to 10th	Night	6% 5% 2 5% 4 4 5% 4 5% 9% 53%	2360
	11th to 20th	Night	10% 3 1 5% 4 3 4 3 6% 8% 52%	2544
	21st to end	Night	6% 4 2 5% 4 4 4 4 7% 8% 51%	3087
August	1st to 10th	Night	10% 5% 2 7% 4 4 4 3 6% 7% 46%	2825
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 5% 8% 49%	2785
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 6% 8% 47%	3241
September	1st to 10th	Night	9% 5% 2 6% 4 4 5% 4 6% 7% 48%	1900
	11th to 20th	Night	10% 6% 1 4 3 3 3 3 5% 7% 55%	2038
	21st to end	Night	14% 7% 3 7% 4 5% 5% 3 4 7% 41%	2110
October	1st to 10th	Night	16% 7% 2 8% 4 3 4 4 5% 7% 41%	2280
	11th to 20th	Night	16% 10% 3 7% 5% 6% 4 4 4 7% 36%	2280
	21st to end	Night	19% 9% 3 8% 5% 4 4 4 6% 7% 30%	2508
November	1st to 10th	Night	14% 8% 2 7% 5% 5% 5% 4 6% 7% 38%	2591
	11th to 20th	Night	13% 11% 3 7% 5% 6% 5% 5% 7% 7% 30%	2800
	21st to end	Night	17% 11% 3 9% 5% 4 5% 4 7% 8% 27%	2800
December	1st to 10th	Night	14% 14% 5% 12% 6% 6% 6% 5% 7% 7% 18%	4580
	11th to 20th	Night	15% 18% 4 9% 5% 5% 6% 5% 5% 6% 20%	5208
	21st to end	Night	23% 17% 7% 12% 5% 4 4 3 5% 5% 15%	6996

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	54% 11% 12% 11% 10% 1	3598
	11th to 20th	Day	69% 8% 10% 9% 4	4032
	21st to end	Day	66% 8% 11% 8% 6%	4466
February	1st to 10th	Day	62% 10% 10% 13% 3 1	1800
	11th to 20th	Day	59% 9% 11% 13% 6% 2	1762
	21st to end	Day	59% 8% 12% 13% 7% 1	1512
March	1st to 10th	Day	54% 10% 13% 15% 7% 1	3435
	11th to 20th	Day	49% 11% 14% 18% 7% 2	3480
	21st to end	Day	45% 10% 13% 20% 10% 2	3815
April	1st to 10th	Day	52% 8% 12% 17% 10% 1	2224
	11th to 20th	Day	47% 8% 12% 19% 13% 1	2351
	21st to end	Day	50% 8% 11% 17% 12% 2	2470
May	1st to 10th	Day	43% 10% 16% 17% 12% 2	4120
	11th to 20th	Day	47% 12% 15% 18% 7% 1	4324
	21st to end	Day	34% 9% 14% 21% 18% 4	4837
June	1st to 10th	Day	40% 10% 12% 22% 14% 2	2660
	11th to 20th	Day	38% 9% 15% 22% 15% 1	2680
	21st to end	Day	38% 10% 15% 23% 14%	2850
July	1st to 10th	Day	34% 8% 16% 24% 15% 2	4512
	11th to 20th	Day	30% 9% 16% 33% 11% 1	4337
	21st to end	Day	34% 10% 16% 22% 17% 1	4324
August	1st to 10th	Day	41% 8% 15% 22% 13% 1	4091
	11th to 20th	Day	40% 10% 17% 23% 9%	4083
	21st to end	Day	35% 9% 15% 32% 9% 1	4382
September	1st to 10th	Day	38% 10% 15% 26% 11% 1	2280
	11th to 20th	Day	34% 8% 15% 29% 14%	2138
	21st to end	Day	44% 10% 15% 22% 8%	2069
October	1st to 10th	Day	38% 9% 15% 25% 12% 1	3160
	11th to 20th	Day	40% 8% 15% 22% 15%	3140
	21st to end	Day	52% 8% 14% 19% 7%	3428
November	1st to 10th	Day	46% 10% 15% 20% 7% 1	1703
	11th to 20th	Day	52% 11% 16% 15% 7%	1600
	21st to end	Day	58% 11% 14% 13% 4	1600
December	1st to 10th	Day	66% 9% 14% 8% 3	2600
	11th to 20th	Day	62% 8% 12% 10% 7%	2986
	21st to end	Day	73% 9% 7% 6% 5%	3960
January	1st to 10th	Night	51% 11% 11% 19% 7%	6349
	11th to 20th	Night	61% 14% 10% 11% 4	5923
	21st to end	Night	56% 8% 13% 11% 10% 1	6490
February	1st to 10th	Night	56% 10% 13% 16% 5% 1	2600
	11th to 20th	Night	55% 8% 13% 16% 8%	2535
	21st to end	Night	53% 9% 14% 16% 7%	2033
March	1st to 10th	Night	48% 11% 15% 19% 6% 1	3418
	11th to 20th	Night	40% 10% 18% 20% 11% 2	3480
	21st to end	Night	40% 8% 10% 24% 16% 1	3817
April	1st to 10th	Night	50% 8% 9% 18% 13% 1	1955
	11th to 20th	Night	45% 7% 11% 20% 15% 2	1795
	21st to end	Night	45% 8% 12% 18% 15% 3	1710
May	1st to 10th	Night	42% 8% 14% 17% 15% 3	2840
	11th to 20th	Night	42% 12% 17% 18% 9% 2	2573
	21st to end	Night	27% 11% 14% 22% 23% 3	2739
June	1st to 10th	Night	36% 9% 13% 24% 17% 1	1520
	11th to 20th	Night	34% 7% 15% 23% 19% 2	1491
	21st to end	Night	35% 7% 14% 26% 16% 1	1330
July	1st to 10th	Night	27% 7% 16% 24% 22% 4	2321
	11th to 20th	Night	29% 6% 14% 32% 17% 1	2496
	21st to end	Night	29% 9% 15% 28% 17% 2	2988
August	1st to 10th	Night	36% 7% 13% 27% 15% 3	2814
	11th to 20th	Night	32% 8% 17% 30% 12% 1	2812
	21st to end	Night	32% 8% 14% 30% 14% 1	3241
September	1st to 10th	Night	32% 9% 15% 28% 14% 1	1900
	11th to 20th	Night	29% 7% 13% 32% 19% 1	2038
	21st to end	Night	42% 8% 12% 26% 11% 1	2110
October	1st to 10th	Night	31% 7% 10% 26% 24% 1	3800
	11th to 20th	Night	42% 7% 12% 23% 14%	3779
	21st to end	Night	40% 7% 16% 25% 11% 1	4120
November	1st to 10th	Night	43% 8% 15% 21% 12% 1	2591
	11th to 20th	Night	49% 11% 15% 16% 8% 1	2800
	21st to end	Night	52% 12% 18% 14% 4	2800
December	1st to 10th	Night	59% 12% 15% 11% 3	4580
	11th to 20th	Night	59% 10% 11% 12% 8%	5208
	21st to end	Night	69% 9% 10% 8% 4	6996

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	19% 27% 34% 16% 5% 1	200
	11th to 20th	Day	22% 31% 31% 12% 3	293
	21st to end	Day	24% 29% 32% 13% 3	330
February	1st to 10th	Day	22% 34% 32% 11% 2	300
	11th to 20th	Day	25% 30% 35% 9% 1	300
	21st to end	Day	35% 23% 35% 7%	237
March	1st to 10th	Day	23% 22% 33% 18% 5%	460
	11th to 20th	Day	20% 25% 35% 15% 4	460
	21st to end	Day	27% 18% 32% 16% 5% 1	506
April	1st to 10th	Day	19% 23% 37% 15% 6%	460
	11th to 20th	Day	29% 20% 28% 15% 6% 2	452
	21st to end	Day	25% 16% 35% 15% 7% 2	460
May	1st to 10th	Day	22% 15% 30% 20% 9% 4	463
	11th to 20th	Day	16% 13% 32% 24% 12% 3	487
	21st to end	Day	13% 10% 31% 26% 14% 5%	529
June	1st to 10th	Day	13% 15% 33% 27% 10% 2	490
	11th to 20th	Day	13% 12% 27% 31% 14% 2	510
	21st to end	Day	15% 10% 33% 30% 9% 3	680
July	1st to 10th	Day	9% 6% 29% 34% 19% 5%	575
	11th to 20th	Day	12% 8% 26% 29% 17% 8%	484
	21st to end	Day	8% 6% 30% 35% 16% 5%	532
August	1st to 10th	Day	11% 8% 24% 29% 19% 8%	486
	11th to 20th	Day	9% 6% 26% 27% 22% 10%	479
	21st to end	Day	13% 7% 24% 30% 17% 8%	539
September	1st to 10th	Day	13% 9% 26% 25% 18% 9%	490
	11th to 20th	Day	9% 8% 22% 25% 23% 13%	490
	21st to end	Day	17% 12% 27% 24% 15% 5%	490
October	1st to 10th	Day	21% 14% 28% 20% 13% 4	490
	11th to 20th	Day	20% 21% 32% 17% 8% 2	490
	21st to end	Day	27% 20% 29% 17% 6%	539
November	1st to 10th	Day	19% 27% 29% 18% 5% 1	283
	11th to 20th	Day	25% 28% 30% 12% 6% 1	200
	21st to end	Day	24% 23% 39% 13% 2	200
December	1st to 10th	Day	27% 28% 30% 14% 1	200
	11th to 20th	Day	32% 28% 28% 11% 2	200
	21st to end	Day	28% 25% 32% 12% 2 1	220
January	1st to 10th	Night	21% 24% 36% 15% 4 1	800
	11th to 20th	Night	24% 22% 32% 18% 3	800
	21st to end	Night	17% 18% 40% 20% 5%	880
February	1st to 10th	Night	20% 25% 36% 18% 2	800
	11th to 20th	Night	21% 21% 37% 17% 4	783
	21st to end	Night	19% 23% 36% 19% 3	647
March	1st to 10th	Night	20% 17% 38% 21% 4	760
	11th to 20th	Night	20% 20% 35% 20% 5%	760
	21st to end	Night	20% 15% 35% 23% 7%	836
April	1st to 10th	Night	23% 15% 36% 24% 3	760
	11th to 20th	Night	19% 15% 35% 22% 7% 2	671
	21st to end	Night	19% 11% 34% 25% 10%	570
May	1st to 10th	Night	17% 8% 32% 29% 12% 2	570
	11th to 20th	Night	16% 8% 31% 32% 13% 1	425
	21st to end	Night	11% 7% 28% 35% 18%	411
June	1st to 10th	Night	13% 7% 31% 36% 13% 1	380
	11th to 20th	Night	9% 8% 31% 37% 15% 1	380
	21st to end	Night	12% 5% 29% 38% 15%	380
July	1st to 10th	Night	6% 5% 24% 43% 22% 1	370
	11th to 20th	Night	10% 4 30% 36% 19% 2	379
	21st to end	Night	9% 3 25% 40% 20% 2	624
August	1st to 10th	Night	10% 2 22% 40% 24% 2	567
	11th to 20th	Night	7% 3 19% 41% 26% 3	564
	21st to end	Night	11% 4 28% 32% 24% 2	692
September	1st to 10th	Night	11% 8% 24% 33% 19% 5%	760
	11th to 20th	Night	12% 5% 24% 26% 26% 6%	760
	21st to end	Night	18% 9% 21% 29% 18% 4	760
October	1st to 10th	Night	18% 10% 29% 25% 16% 3	760
	11th to 20th	Night	20% 15% 31% 24% 8% 1	760
	21st to end	Night	24% 16% 32% 24% 4	836
November	1st to 10th	Night	21% 13% 32% 25% 9% 1	780
	11th to 20th	Night	18% 20% 34% 20% 7% 1	800
	21st to end	Night	23% 18% 34% 21% 4	800
December	1st to 10th	Night	26% 20% 35% 14% 5%	800
	11th to 20th	Night	23% 21% 39% 14% 3	800
	21st to end	Night	28% 20% 31% 19% 2	880

Page generated at 2025-02-22 06:51:33. Version ac07

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