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 2026-07-16.

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	13% 9% 4 8% 6% 5% 5% 4 6% 7% 33%	138755
	Night	13% 9% 4 8% 5% 5% 5% 4 6% 7% 34%	133868
Transparency	Day	46% 9% 13% 20% 11% 1	142352
	Night	46% 9% 13% 19% 12% 1	138360
Seeing	Day	18% 16% 30% 22% 10% 3	16871
	Night	18% 14% 32% 25% 10% 1	25971

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	13% 14% 6% 14% 6% 5% 6% 4 5% 6% 22%	4661
	11th to 20th	Day	9% 19% 9% 17% 9% 8% 5% 3 5% 5% 12%	5204
	21st to end	Day	14% 14% 5% 13% 8% 7% 6% 5% 5% 5% 17%	5780
February	1st to 10th	Day	13% 15% 5% 12% 9% 6% 4 4 5% 6% 22%	1890
	11th to 20th	Day	11% 13% 5% 13% 9% 6% 5% 3 6% 6% 24%	1843
	21st to end	Day	17% 12% 5% 11% 7% 4 5% 3 5% 6% 25%	1627
March	1st to 10th	Day	17% 10% 4 11% 6% 4 4 3 5% 5% 31%	5042
	11th to 20th	Day	11% 11% 5% 9% 5% 5% 5% 4 6% 8% 31%	5090
	21st to end	Day	15% 10% 4 9% 6% 5% 5% 3 5% 5% 33%	5586
April	1st to 10th	Day	15% 11% 4 8% 6% 6% 5% 4 6% 7% 29%	2458
	11th to 20th	Day	16% 10% 4 7% 5% 5% 4 3 5% 6% 35%	2601
	21st to end	Day	18% 9% 3 7% 6% 3 4 4 5% 6% 34%	2730
May	1st to 10th	Day	17% 8% 3 7% 5% 5% 4 4 5% 7% 34%	7642
	11th to 20th	Day	14% 8% 3 8% 5% 5% 5% 4 6% 7% 35%	8061
	21st to end	Day	16% 5% 2 5% 4 4 4 4 6% 7% 44%	9060
June	1st to 10th	Day	12% 6% 2 6% 5% 5% 5% 4 6% 8% 40%	2940
	11th to 20th	Day	10% 5% 3 7% 6% 5% 6% 5% 7% 9% 39%	2962
	21st to end	Day	13% 6% 2 6% 5% 4 5% 5% 7% 9% 39%	3150
July	1st to 10th	Day	8% 5% 2 6% 5% 5% 6% 5% 8% 10% 40%	6716
	11th to 20th	Day	7% 4 2 5% 5% 5% 6% 4 7% 10% 46%	6388
	21st to end	Day	7% 4 2 6% 4 5% 5% 4 7% 9% 47%	6424
August	1st to 10th	Day	15% 7% 2 6% 4 4 5% 4 6% 9% 38%	4234
	11th to 20th	Day	9% 6% 3 8% 6% 6% 6% 4 8% 9% 35%	4174
	21st to end	Day	9% 6% 2 5% 4 5% 6% 4 8% 9% 42%	4520
September	1st to 10th	Day	11% 7% 2 6% 5% 5% 6% 4 6% 8% 42%	2400
	11th to 20th	Day	10% 6% 2 6% 4 4 4 4 6% 9% 45%	2250
	21st to end	Day	14% 6% 2 7% 6% 6% 5% 5% 7% 8% 34%	2178
October	1st to 10th	Day	17% 8% 3 7% 4 5% 5% 3 6% 7% 37%	2000
	11th to 20th	Day	18% 9% 3 9% 6% 5% 5% 4 6% 7% 30%	2000
	21st to end	Day	21% 11% 4 8% 6% 7% 5% 4 6% 6% 23%	2200
November	1st to 10th	Day	12% 10% 4 8% 6% 5% 5% 5% 7% 7% 31%	1790
	11th to 20th	Day	12% 11% 4 10% 7% 5% 6% 4 6% 8% 27%	1680
	21st to end	Day	15% 14% 5% 10% 7% 5% 6% 4 6% 6% 21%	1680
December	1st to 10th	Day	16% 17% 6% 12% 6% 7% 5% 4 6% 6% 15%	2680
	11th to 20th	Day	20% 17% 5% 8% 6% 5% 4 4 5% 6% 20%	3066
	21st to end	Day	26% 17% 7% 13% 5% 5% 4 3 4 4 12%	4048
January	1st to 10th	Night	13% 12% 5% 11% 6% 6% 5% 4 5% 7% 27%	8234
	11th to 20th	Night	8% 15% 6% 14% 10% 7% 6% 5% 6% 8% 15%	7662
	21st to end	Night	12% 10% 5% 12% 8% 6% 5% 5% 6% 7% 23%	8401
February	1st to 10th	Night	12% 13% 3 10% 7% 6% 5% 4 6% 7% 27%	2730
	11th to 20th	Night	11% 11% 5% 11% 7% 6% 6% 4 5% 7% 27%	2663
	21st to end	Night	12% 12% 4 10% 7% 6% 5% 4 6% 7% 28%	2175
March	1st to 10th	Night	15% 8% 4 9% 4 5% 5% 4 6% 8% 32%	5018
	11th to 20th	Night	9% 8% 3 7% 5% 4 6% 4 7% 9% 38%	5089
	21st to end	Night	17% 9% 3 7% 4 4 4 3 5% 5% 40%	5588
April	1st to 10th	Night	16% 10% 3 8% 6% 4 5% 4 6% 6% 32%	2161
	11th to 20th	Night	15% 8% 3 8% 5% 5% 4 4 6% 6% 37%	1986
	21st to end	Night	14% 9% 3 7% 4 4 4 4 6% 7% 38%	1890
May	1st to 10th	Night	17% 8% 2 6% 5% 5% 5% 4 5% 6% 37%	5257
	11th to 20th	Night	14% 7% 2 7% 5% 5% 5% 4 5% 7% 39%	4784
	21st to end	Night	17% 4 2 5% 4 3 3 3 5% 7% 47%	5114
June	1st to 10th	Night	10% 5% 2 6% 5% 5% 4 5% 6% 8% 45%	1680
	11th to 20th	Night	9% 5% 2 6% 4 4 4 4 7% 9% 43%	1647
	21st to end	Night	9% 6% 3 6% 4 3 4 4 6% 8% 47%	1470
July	1st to 10th	Night	6% 5% 2 6% 4 4 5% 4 5% 9% 49%	3450
	11th to 20th	Night	9% 4 1 5% 4 4 4 3 6% 9% 51%	3678
	21st to end	Night	7% 4 2 5% 3 4 4 4 6% 8% 53%	4428
August	1st to 10th	Night	9% 5% 2 7% 4 4 4 3 6% 7% 47%	2915
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 5% 8% 49%	2875
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 6% 8% 48%	3344
September	1st to 10th	Night	8% 5% 2 6% 4 4 5% 4 6% 8% 49%	2000
	11th to 20th	Night	10% 5% 1 4 3 3 3 3 5% 7% 56%	2146
	21st to end	Night	15% 7% 3 7% 4 5% 5% 3 4 7% 41%	2221
October	1st to 10th	Night	15% 7% 2 7% 3 3 4 4 5% 7% 43%	2400
	11th to 20th	Night	16% 9% 3 7% 5% 6% 4 4 4 7% 36%	2400
	21st to end	Night	19% 9% 3 8% 5% 4 4 4 6% 7% 31%	2640
November	1st to 10th	Night	14% 8% 2 7% 5% 5% 5% 4 6% 6% 38%	2724
	11th to 20th	Night	13% 11% 3 7% 5% 6% 5% 5% 6% 7% 30%	2940
	21st to end	Night	16% 11% 3 9% 6% 4 5% 4 7% 8% 26%	2940
December	1st to 10th	Night	13% 14% 5% 12% 6% 6% 6% 5% 7% 7% 18%	4720
	11th to 20th	Night	15% 18% 4 9% 5% 5% 5% 5% 5% 6% 21%	5348
	21st to end	Night	23% 16% 7% 12% 5% 4 4 3 5% 5% 15%	7150

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	58% 10% 11% 11% 9% 1	4662
	11th to 20th	Day	71% 8% 9% 8% 4	5238
	21st to end	Day	64% 8% 11% 10% 6%	5780
February	1st to 10th	Day	62% 10% 10% 13% 4 1	1890
	11th to 20th	Day	59% 9% 11% 14% 6% 2	1852
	21st to end	Day	59% 7% 12% 14% 7% 1	1627
March	1st to 10th	Day	52% 8% 15% 13% 11% 1	5045
	11th to 20th	Day	47% 9% 17% 18% 6% 3	5090
	21st to end	Day	49% 9% 11% 19% 11% 1	5586
April	1st to 10th	Day	53% 7% 12% 17% 11% 1	2458
	11th to 20th	Day	48% 7% 11% 20% 12% 1	2601
	21st to end	Day	49% 8% 11% 18% 11% 2	2730
May	1st to 10th	Day	46% 8% 14% 18% 10% 4	7651
	11th to 20th	Day	44% 10% 13% 20% 13% 1	8065
	21st to end	Day	39% 7% 11% 26% 15% 2	9061
June	1st to 10th	Day	39% 10% 12% 22% 16% 1	2940
	11th to 20th	Day	38% 9% 15% 23% 14% 1	2962
	21st to end	Day	38% 10% 14% 23% 14%	3150
July	1st to 10th	Day	34% 8% 16% 25% 15% 2	6647
	11th to 20th	Day	29% 8% 15% 31% 16% 1	6313
	21st to end	Day	30% 9% 15% 28% 17% 1	6240
August	1st to 10th	Day	41% 8% 15% 22% 13% 1	4221
	11th to 20th	Day	40% 9% 17% 24% 9%	4213
	21st to end	Day	35% 9% 15% 32% 9% 1	4520
September	1st to 10th	Day	37% 10% 15% 26% 11% 1	2400
	11th to 20th	Day	34% 8% 15% 30% 13%	2250
	21st to end	Day	44% 10% 15% 22% 9%	2178
October	1st to 10th	Day	37% 9% 15% 26% 13% 1	3260
	11th to 20th	Day	40% 8% 15% 22% 15%	3240
	21st to end	Day	52% 8% 14% 19% 7%	3538
November	1st to 10th	Day	47% 10% 15% 20% 7% 1	1790
	11th to 20th	Day	51% 11% 15% 15% 7%	1680
	21st to end	Day	59% 10% 14% 13% 4	1680
December	1st to 10th	Day	66% 9% 13% 9% 3	2680
	11th to 20th	Day	62% 8% 12% 10% 7%	3066
	21st to end	Day	73% 9% 7% 6% 5%	4048
January	1st to 10th	Night	53% 10% 13% 17% 7%	8234
	11th to 20th	Night	61% 13% 9% 11% 5%	7703
	21st to end	Night	56% 8% 13% 13% 11%	8401
February	1st to 10th	Night	55% 9% 12% 17% 5% 1	2730
	11th to 20th	Night	55% 8% 13% 17% 8%	2665
	21st to end	Night	53% 9% 14% 16% 7%	2175
March	1st to 10th	Night	44% 10% 15% 17% 12% 2	5028
	11th to 20th	Night	38% 9% 20% 21% 10% 2	5090
	21st to end	Night	44% 7% 10% 20% 17% 2	5588
April	1st to 10th	Night	51% 8% 10% 17% 13% 1	2161
	11th to 20th	Night	46% 7% 11% 20% 15% 2	1986
	21st to end	Night	44% 8% 12% 19% 15% 2	1890
May	1st to 10th	Night	44% 8% 13% 15% 14% 5%	5264
	11th to 20th	Night	42% 10% 14% 19% 13% 2	4785
	21st to end	Night	37% 7% 12% 25% 18% 2	5115
June	1st to 10th	Night	34% 9% 12% 24% 19% 1	1680
	11th to 20th	Night	34% 7% 15% 23% 19% 2	1647
	21st to end	Night	36% 7% 14% 26% 16% 1	1470
July	1st to 10th	Night	30% 8% 16% 24% 20% 3	3411
	11th to 20th	Night	29% 7% 13% 29% 20% 2	3630
	21st to end	Night	29% 8% 13% 28% 21% 2	4297
August	1st to 10th	Night	35% 7% 13% 26% 15% 3	2904
	11th to 20th	Night	32% 7% 17% 30% 12% 1	2902
	21st to end	Night	32% 8% 14% 31% 14% 1	3344
September	1st to 10th	Night	31% 9% 16% 29% 14% 1	2000
	11th to 20th	Night	28% 7% 13% 33% 19% 1	2146
	21st to end	Night	42% 8% 12% 25% 12% 1	2221
October	1st to 10th	Night	31% 7% 10% 27% 24% 1	3920
	11th to 20th	Night	42% 7% 12% 24% 15%	3899
	21st to end	Night	40% 7% 16% 25% 11% 1	4252
November	1st to 10th	Night	43% 8% 15% 21% 12% 1	2724
	11th to 20th	Night	49% 11% 15% 16% 8% 1	2940
	21st to end	Night	52% 11% 18% 14% 4	2940
December	1st to 10th	Night	59% 12% 15% 12% 3	4720
	11th to 20th	Night	58% 10% 11% 12% 8%	5348
	21st to end	Night	69% 9% 10% 8% 4	7150

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% 26% 35% 15% 4	220
	11th to 20th	Day	23% 31% 31% 11% 3	322
	21st to end	Day	23% 28% 32% 13% 3	363
February	1st to 10th	Day	22% 32% 32% 11% 4	330
	11th to 20th	Day	25% 28% 35% 10% 1	330
	21st to end	Day	34% 23% 36% 8%	273
March	1st to 10th	Day	22% 21% 34% 17% 4	540
	11th to 20th	Day	22% 26% 33% 15% 4	540
	21st to end	Day	27% 20% 32% 16% 4 1	594
April	1st to 10th	Day	21% 23% 35% 15% 5%	540
	11th to 20th	Day	27% 22% 27% 16% 6% 2	532
	21st to end	Day	24% 15% 35% 16% 7% 2	540
May	1st to 10th	Day	22% 15% 31% 20% 8% 3	543
	11th to 20th	Day	16% 13% 34% 23% 11% 4	567
	21st to end	Day	15% 11% 31% 25% 12% 5%	617
June	1st to 10th	Day	12% 14% 34% 28% 10% 2	570
	11th to 20th	Day	13% 13% 31% 29% 13% 2	592
	21st to end	Day	15% 10% 32% 31% 10% 3	780
July	1st to 10th	Day	9% 6% 28% 34% 18% 5%	665
	11th to 20th	Day	11% 8% 26% 31% 17% 8%	544
	21st to end	Day	8% 6% 31% 35% 16% 5%	576
August	1st to 10th	Day	10% 8% 23% 30% 21% 8%	526
	11th to 20th	Day	9% 6% 26% 28% 22% 9%	519
	21st to end	Day	13% 8% 23% 30% 18% 8%	583
September	1st to 10th	Day	13% 9% 25% 24% 18% 10%	530
	11th to 20th	Day	8% 7% 21% 26% 24% 13%	530
	21st to end	Day	17% 12% 25% 25% 15% 5%	530
October	1st to 10th	Day	19% 14% 27% 21% 14% 5%	530
	11th to 20th	Day	20% 20% 34% 17% 7% 2	530
	21st to end	Day	27% 20% 29% 19% 6%	583
November	1st to 10th	Day	20% 27% 29% 18% 5% 1	310
	11th to 20th	Day	24% 29% 29% 12% 5% 1	220
	21st to end	Day	23% 25% 37% 14% 1	220
December	1st to 10th	Day	26% 28% 30% 15% 1	220
	11th to 20th	Day	30% 28% 29% 11% 1	220
	21st to end	Day	30% 26% 30% 12% 2 1	242
January	1st to 10th	Night	20% 24% 36% 15% 4	840
	11th to 20th	Night	24% 23% 32% 18% 3	840
	21st to end	Night	16% 19% 40% 19% 5%	924
February	1st to 10th	Night	19% 24% 36% 20% 2	840
	11th to 20th	Night	21% 21% 37% 18% 4	823
	21st to end	Night	20% 23% 36% 19% 3	692
March	1st to 10th	Night	20% 18% 37% 21% 4	840
	11th to 20th	Night	21% 20% 34% 21% 5%	840
	21st to end	Night	21% 15% 35% 23% 6%	924
April	1st to 10th	Night	23% 15% 36% 23% 3	840
	11th to 20th	Night	19% 15% 34% 23% 7% 1	742
	21st to end	Night	18% 11% 34% 27% 10%	630
May	1st to 10th	Night	17% 8% 33% 28% 12% 2	630
	11th to 20th	Night	16% 8% 32% 31% 12% 1	470
	21st to end	Night	12% 7% 29% 35% 16%	455
June	1st to 10th	Night	13% 6% 30% 36% 14%	420
	11th to 20th	Night	10% 8% 31% 37% 14%	420
	21st to end	Night	12% 5% 29% 41% 14%	420
July	1st to 10th	Night	6% 5% 23% 44% 22%	410
	11th to 20th	Night	10% 3 30% 37% 19% 1	410
	21st to end	Night	9% 3 25% 41% 20% 2	657
August	1st to 10th	Night	9% 2 21% 40% 26% 2	597
	11th to 20th	Night	8% 3 18% 41% 26% 3	594
	21st to end	Night	10% 4 27% 33% 23% 2	729
September	1st to 10th	Night	11% 8% 24% 33% 20% 5%	800
	11th to 20th	Night	11% 5% 23% 27% 27% 6%	800
	21st to end	Night	18% 9% 21% 30% 19% 4	800
October	1st to 10th	Night	17% 9% 29% 25% 17% 3	800
	11th to 20th	Night	21% 14% 31% 25% 8% 1	800
	21st to end	Night	24% 15% 32% 25% 4	880
November	1st to 10th	Night	21% 14% 31% 25% 9% 1	820
	11th to 20th	Night	18% 21% 34% 20% 7% 1	840
	21st to end	Night	23% 18% 34% 21% 4	840
December	1st to 10th	Night	26% 19% 35% 15% 4	840
	11th to 20th	Night	23% 21% 39% 14% 3	840
	21st to end	Night	28% 20% 31% 18% 2	924

Page generated at 2026-07-13 03:14:53. Version ac07

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