Mind's Eye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mind's Eye Observatory clear sky chart from 2005-11-06 to 2026-03-03.

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	7% 5% 2 7% 5% 6% 6% 5% 8% 10% 38%	130802
	Night	8% 6% 2 7% 5% 5% 5% 4 7% 9% 43%	130362
Transparency	Day	35% 11% 19% 20% 12% 3	134469
	Night	35% 10% 19% 21% 12% 4	134765
Seeing	Day	7% 4 17% 28% 26% 18%	17603
	Night	8% 3 16% 31% 31% 11%	27761

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	6% 5% 2 5% 4 4 4 3 5% 8% 54%	5258
	11th to 20th	Day	15% 10% 3 8% 5% 5% 5% 4 6% 8% 31%	5280
	21st to end	Day	15% 6% 2 6% 4 5% 5% 4 7% 7% 40%	5780
February	1st to 10th	Day	11% 5% 2 7% 5% 4 4 5% 6% 7% 45%	2084
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 6% 8% 51%	2108
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 7% 7% 49%	1903
March	1st to 10th	Day	6% 5% 2 8% 6% 6% 6% 4 7% 9% 41%	4957
	11th to 20th	Day	3 3 1 3 3 4 4 4 5% 8% 61%	4980
	21st to end	Day	8% 4 2 7% 5% 5% 6% 4 7% 9% 44%	5465
April	1st to 10th	Day	5% 4 2 6% 5% 5% 5% 5% 8% 9% 47%	2200
	11th to 20th	Day	8% 5% 2 7% 5% 4 6% 6% 8% 9% 41%	2284
	21st to end	Day	5% 4 1 6% 5% 6% 5% 5% 7% 10% 46%	2400
May	1st to 10th	Day	3 2 1 3 4 5% 6% 6% 8% 12% 51%	5405
	11th to 20th	Day	7% 5% 2 6% 5% 5% 5% 4 7% 10% 45%	5769
	21st to end	Day	5% 4 2 6% 5% 6% 6% 6% 8% 11% 42%	6433
June	1st to 10th	Day	11% 9% 4 10% 7% 8% 7% 6% 8% 10% 21%	2600
	11th to 20th	Day	6% 7% 3 8% 6% 7% 7% 7% 10% 12% 27%	2600
	21st to end	Day	8% 8% 3 8% 7% 7% 8% 6% 9% 12% 25%	2600
July	1st to 10th	Day	7% 6% 2 8% 7% 8% 8% 7% 10% 13% 26%	5900
	11th to 20th	Day	5% 5% 2 7% 6% 7% 7% 6% 10% 14% 31%	5900
	21st to end	Day	4 5% 2 7% 6% 6% 7% 6% 9% 14% 33%	6424
August	1st to 10th	Day	4 4 2 9% 8% 8% 9% 7% 10% 15% 24%	4234
	11th to 20th	Day	4 3 2 6% 5% 6% 8% 6% 9% 14% 35%	3890
	21st to end	Day	5% 5% 3 8% 7% 7% 9% 7% 11% 14% 24%	4065
September	1st to 10th	Day	7% 5% 3 9% 10% 9% 9% 7% 10% 10% 22%	2200
	11th to 20th	Day	10% 7% 2 9% 7% 7% 8% 7% 8% 10% 24%	2200
	21st to end	Day	9% 6% 3 9% 7% 8% 8% 7% 8% 10% 25%	2200
October	1st to 10th	Day	11% 7% 3 8% 6% 7% 6% 5% 8% 10% 29%	2105
	11th to 20th	Day	7% 6% 3 7% 5% 6% 6% 5% 8% 9% 39%	2000
	21st to end	Day	8% 6% 3 5% 5% 5% 5% 4 7% 9% 44%	2200
November	1st to 10th	Day	9% 5% 2 7% 5% 6% 7% 5% 7% 9% 39%	2057
	11th to 20th	Day	9% 7% 2 7% 6% 6% 5% 5% 6% 10% 38%	2100
	21st to end	Day	9% 6% 3 6% 5% 5% 5% 4 7% 9% 40%	2100
December	1st to 10th	Day	6% 5% 2 5% 4 4 4 4 6% 7% 53%	3093
	11th to 20th	Day	9% 7% 2 7% 5% 7% 7% 6% 8% 10% 33%	3463
	21st to end	Day	10% 6% 3 8% 7% 6% 7% 4 7% 8% 34%	4565
January	1st to 10th	Night	6% 3 2 5% 3 3 4 3 6% 8% 57%	7635
	11th to 20th	Night	13% 10% 4 9% 5% 5% 4 4 6% 7% 33%	7680
	21st to end	Night	13% 6% 2 6% 4 4 4 3 5% 6% 46%	8401
February	1st to 10th	Night	11% 5% 2 7% 3 4 3 3 6% 8% 49%	2530
	11th to 20th	Night	8% 4 2 5% 3 3 5% 4 6% 8% 52%	2395
	21st to end	Night	8% 4 2 4 4 3 4 3 6% 8% 55%	1903
March	1st to 10th	Night	7% 5% 2 7% 5% 4 5% 4 6% 8% 48%	4941
	11th to 20th	Night	4 3 1 3 2 3 4 4 7% 10% 58%	4980
	21st to end	Night	7% 5% 2 6% 4 4 5% 4 7% 8% 47%	5467
April	1st to 10th	Night	5% 3 1 4 4 4 4 4 5% 9% 56%	2200
	11th to 20th	Night	5% 4 1 5% 4 4 5% 4 7% 9% 51%	2065
	21st to end	Night	6% 4 2 5% 5% 4 5% 4 7% 8% 52%	2000
May	1st to 10th	Night	3 3 1 4 4 4 5% 4 8% 10% 54%	4490
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 7% 9% 47%	4138
	21st to end	Night	5% 4 2 7% 4 5% 5% 5% 8% 11% 44%	4421
June	1st to 10th	Night	9% 8% 3 8% 5% 6% 6% 6% 8% 11% 29%	1800
	11th to 20th	Night	6% 6% 2 7% 7% 7% 7% 6% 10% 12% 30%	1800
	21st to end	Night	6% 6% 3 7% 7% 5% 7% 5% 9% 11% 34%	1800
July	1st to 10th	Night	7% 7% 3 8% 6% 6% 6% 5% 9% 12% 32%	4058
	11th to 20th	Night	4 4 2 5% 5% 4 6% 6% 8% 14% 41%	4057
	21st to end	Night	3 4 2 7% 6% 5% 5% 4 8% 11% 45%	4427
August	1st to 10th	Night	3 5% 3 8% 6% 7% 6% 5% 8% 13% 36%	2915
	11th to 20th	Night	4 4 2 6% 5% 5% 6% 5% 8% 12% 42%	3125
	21st to end	Night	7% 6% 2 8% 6% 6% 7% 6% 10% 14% 29%	3813
September	1st to 10th	Night	6% 7% 3 9% 7% 7% 7% 7% 9% 12% 26%	2200
	11th to 20th	Night	9% 9% 3 9% 6% 7% 6% 5% 7% 10% 29%	2200
	21st to end	Night	9% 7% 3 10% 6% 6% 7% 5% 7% 10% 29%	2200
October	1st to 10th	Night	11% 8% 2 9% 5% 5% 5% 5% 7% 9% 34%	2293
	11th to 20th	Night	7% 6% 2 6% 5% 6% 5% 5% 7% 9% 43%	2400
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 7% 8% 45%	2640
November	1st to 10th	Night	9% 7% 2 6% 5% 5% 5% 4 7% 8% 42%	2461
	11th to 20th	Night	7% 6% 2 7% 5% 5% 5% 4 6% 8% 44%	2520
	21st to end	Night	10% 6% 2 6% 5% 4 5% 5% 7% 9% 42%	2520
December	1st to 10th	Night	6% 4 1 5% 4 3 4 4 5% 8% 56%	4302
	11th to 20th	Night	12% 7% 2 8% 5% 5% 5% 4 6% 8% 37%	4952
	21st to end	Night	10% 8% 3 8% 6% 5% 5% 4 6% 8% 36%	6633

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	28% 5% 11% 28% 23% 5%	5259
	11th to 20th	Day	49% 7% 10% 19% 12% 4	5280
	21st to end	Day	40% 7% 9% 24% 15% 5%	5780
February	1st to 10th	Day	35% 7% 12% 19% 20% 8%	2084
	11th to 20th	Day	27% 7% 15% 25% 19% 7%	2118
	21st to end	Day	30% 7% 12% 18% 25% 8%	1903
March	1st to 10th	Day	35% 11% 12% 18% 20% 3	4957
	11th to 20th	Day	19% 7% 13% 28% 20% 13%	4980
	21st to end	Day	33% 8% 12% 27% 15% 5%	5465
April	1st to 10th	Day	27% 11% 16% 25% 18% 4	2200
	11th to 20th	Day	34% 10% 14% 19% 18% 5%	2284
	21st to end	Day	29% 9% 13% 22% 24% 4	2400
May	1st to 10th	Day	19% 10% 24% 30% 14% 3	5437
	11th to 20th	Day	32% 10% 21% 24% 12%	5773
	21st to end	Day	29% 11% 21% 29% 10%	6447
June	1st to 10th	Day	51% 13% 20% 12% 3	2600
	11th to 20th	Day	41% 17% 23% 18% 2	2600
	21st to end	Day	44% 17% 24% 12% 3	2600
July	1st to 10th	Day	42% 16% 29% 11% 2	5835
	11th to 20th	Day	35% 15% 37% 11% 1	5831
	21st to end	Day	34% 15% 28% 23%	6240
August	1st to 10th	Day	40% 20% 29% 9% 1	4221
	11th to 20th	Day	30% 17% 29% 16% 8%	3927
	21st to end	Day	40% 19% 31% 8% 2	4065
September	1st to 10th	Day	48% 20% 19% 11% 2	2200
	11th to 20th	Day	46% 20% 20% 12% 2	2200
	21st to end	Day	47% 16% 16% 12% 8% 1	2200
October	1st to 10th	Day	50% 13% 19% 12% 5% 2	3430
	11th to 20th	Day	32% 9% 11% 25% 21% 3	3240
	21st to end	Day	29% 6% 12% 27% 22% 5%	3538
November	1st to 10th	Day	37% 9% 13% 18% 17% 6%	2057
	11th to 20th	Day	41% 8% 11% 19% 15% 7%	2100
	21st to end	Day	37% 8% 13% 21% 15% 6%	2100
December	1st to 10th	Day	28% 7% 20% 25% 13% 7%	3093
	11th to 20th	Day	43% 8% 13% 17% 15% 5%	3460
	21st to end	Day	43% 9% 13% 18% 13% 3	4565
January	1st to 10th	Night	25% 6% 13% 31% 18% 8%	7636
	11th to 20th	Night	48% 6% 12% 18% 11% 4	7680
	21st to end	Night	38% 6% 12% 25% 13% 7%	8401
February	1st to 10th	Night	32% 7% 13% 20% 18% 9%	2530
	11th to 20th	Night	27% 8% 13% 24% 21% 7%	2396
	21st to end	Night	27% 7% 15% 21% 24% 7%	1903
March	1st to 10th	Night	34% 8% 13% 21% 20% 5%	4941
	11th to 20th	Night	18% 8% 19% 27% 17% 12%	4980
	21st to end	Night	30% 8% 13% 26% 19% 3	5467
April	1st to 10th	Night	23% 8% 19% 28% 16% 6%	2200
	11th to 20th	Night	28% 9% 16% 22% 21% 5%	2065
	21st to end	Night	27% 8% 15% 25% 21% 4	2000
May	1st to 10th	Night	20% 10% 24% 30% 13% 3	4520
	11th to 20th	Night	30% 10% 21% 31% 8%	4139
	21st to end	Night	29% 11% 22% 30% 8%	4429
June	1st to 10th	Night	45% 13% 24% 15% 3	1800
	11th to 20th	Night	39% 16% 23% 18% 3	1800
	21st to end	Night	38% 17% 27% 16% 3	1800
July	1st to 10th	Night	42% 14% 28% 15% 1	4015
	11th to 20th	Night	29% 17% 43% 10%	4006
	21st to end	Night	30% 15% 29% 25% 2	4297
August	1st to 10th	Night	36% 17% 35% 11% 1	2904
	11th to 20th	Night	29% 15% 33% 14% 8%	3154
	21st to end	Night	40% 18% 32% 9% 1	3813
September	1st to 10th	Night	44% 20% 22% 12% 2	2200
	11th to 20th	Night	48% 15% 21% 13% 3	2200
	21st to end	Night	47% 15% 16% 13% 8% 1	2200
October	1st to 10th	Night	54% 12% 15% 11% 7% 1	3748
	11th to 20th	Night	34% 8% 12% 25% 18% 2	3899
	21st to end	Night	33% 7% 10% 25% 21% 5%	4252
November	1st to 10th	Night	37% 9% 14% 17% 16% 7%	2461
	11th to 20th	Night	37% 8% 13% 23% 14% 6%	2520
	21st to end	Night	37% 8% 14% 20% 17% 5%	2520
December	1st to 10th	Night	27% 7% 18% 31% 12% 5%	4302
	11th to 20th	Night	42% 8% 15% 16% 14% 6%	4954
	21st to end	Night	43% 9% 14% 18% 11% 5%	6633

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	7% 8% 37% 32% 14% 2	330
	11th to 20th	Day	8% 11% 36% 28% 13% 4	330
	21st to end	Day	13% 14% 37% 29% 6%	363
February	1st to 10th	Day	9% 8% 28% 34% 18% 4	330
	11th to 20th	Day	8% 5% 29% 36% 17% 4	390
	21st to end	Day	8% 5% 29% 34% 22% 3	446
March	1st to 10th	Day	3 8% 33% 41% 14% 1	508
	11th to 20th	Day	6% 6% 29% 36% 20% 3	500
	21st to end	Day	5% 4 31% 33% 21% 5%	550
April	1st to 10th	Day	4 4 32% 36% 19% 5%	500
	11th to 20th	Day	5% 6% 24% 38% 21% 5%	492
	21st to end	Day	5% 3 16% 42% 25% 9%	500
May	1st to 10th	Day	3 1 17% 38% 29% 11%	503
	11th to 20th	Day	9% 2 14% 30% 30% 14%	527
	21st to end	Day	8% 2 8% 24% 37% 22%	573
June	1st to 10th	Day	12% 2 9% 24% 30% 23%	530
	11th to 20th	Day	8% 2 5% 18% 32% 35%	530
	21st to end	Day	6% 2 4 14% 29% 45%	530
July	1st to 10th	Day	5% 2 4 11% 32% 46%	525
	11th to 20th	Day	5% 1 2 12% 36% 43%	524
	21st to end	Day	6% 1 2 20% 27% 44%	576
August	1st to 10th	Day	3 2 5% 13% 32% 45%	526
	11th to 20th	Day	3 1 2 9% 35% 49%	519
	21st to end	Day	8% 2 5% 19% 31% 35%	583
September	1st to 10th	Day	8% 3 3 17% 33% 38%	530
	11th to 20th	Day	8% 2 6% 21% 33% 29%	530
	21st to end	Day	9% 2 7% 24% 32% 26%	530
October	1st to 10th	Day	12% 4 10% 32% 32% 10%	530
	11th to 20th	Day	7% 4 15% 36% 27% 11%	530
	21st to end	Day	7% 3 20% 35% 28% 7%	583
November	1st to 10th	Day	11% 6% 18% 33% 25% 6%	535
	11th to 20th	Day	10% 6% 22% 36% 22% 4	540
	21st to end	Day	8% 3 21% 36% 27% 5%	540
December	1st to 10th	Day	5% 6% 28% 37% 19% 5%	377
	11th to 20th	Day	9% 6% 26% 38% 18% 4	330
	21st to end	Day	8% 6% 29% 35% 18% 4	363
January	1st to 10th	Night	10% 7% 25% 36% 20% 2	840
	11th to 20th	Night	9% 6% 29% 36% 17% 2	840
	21st to end	Night	10% 8% 30% 38% 13%	924
February	1st to 10th	Night	11% 6% 23% 39% 19% 1	840
	11th to 20th	Night	8% 5% 27% 41% 17% 1	823
	21st to end	Night	10% 3 22% 45% 20%	692
March	1st to 10th	Night	5% 6% 29% 44% 15% 1	809
	11th to 20th	Night	6% 3 23% 44% 21% 3	800
	21st to end	Night	6% 3 27% 41% 22% 1	880
April	1st to 10th	Night	5% 4 22% 46% 21% 2	800
	11th to 20th	Night	6% 4 20% 46% 24% 1	791
	21st to end	Night	6% 2 17% 46% 26% 3	800
May	1st to 10th	Night	6% 1 14% 47% 30% 3	800
	11th to 20th	Night	9% 2 12% 38% 33% 6%	645
	21st to end	Night	6% 1 8% 25% 46% 14%	650
June	1st to 10th	Night	11% 2 7% 24% 45% 12%	600
	11th to 20th	Night	8% 1 5% 15% 48% 23%	600
	21st to end	Night	5% 2 3 12% 46% 32%	600
July	1st to 10th	Night	7% 2 3 10% 45% 32%	585
	11th to 20th	Night	6% 1 3 8% 39% 44%	582
	21st to end	Night	5% 1 1 10% 45% 38%	657
August	1st to 10th	Night	3 1 5% 9% 46% 36%	597
	11th to 20th	Night	5% 1 2 9% 47% 36%	742
	21st to end	Night	9% 1 5% 16% 43% 26%	880
September	1st to 10th	Night	6% 2 6% 14% 45% 28%	800
	11th to 20th	Night	11% 2 5% 19% 41% 22%	800
	21st to end	Night	12% 3 6% 19% 42% 19%	800
October	1st to 10th	Night	13% 2 9% 31% 35% 9%	800
	11th to 20th	Night	8% 3 12% 30% 40% 8%	800
	21st to end	Night	10% 3 17% 33% 30% 7%	880
November	1st to 10th	Night	9% 4 19% 32% 31% 4	820
	11th to 20th	Night	9% 5% 19% 38% 27% 3	840
	21st to end	Night	10% 4 20% 39% 26% 2	840
December	1st to 10th	Night	8% 3 21% 38% 27% 3	840
	11th to 20th	Night	10% 5% 21% 37% 23% 4	840
	21st to end	Night	7% 5% 22% 38% 26% 2	924

Page generated at 2026-02-28 01:40:24. Version ac07

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