Kendrick Astro Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kendrick Astro 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	15% 9% 3 8% 5% 5% 5% 4 6% 7% 34%	138355
	Night	15% 9% 3 8% 5% 5% 5% 4 5% 7% 34%	134304
Transparency	Day	45% 8% 14% 21% 11% 1	141949
	Night	47% 8% 13% 19% 11% 1	138797
Seeing	Day	17% 10% 28% 27% 14% 4	16550
	Night	18% 9% 29% 29% 13% 1	25946

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	17% 10% 4 11% 6% 5% 5% 4 7% 7% 23%	4661
	11th to 20th	Day	10% 17% 8% 16% 8% 6% 5% 3 5% 5% 16%	5108
	21st to end	Day	15% 14% 5% 12% 6% 5% 5% 4 6% 6% 21%	5780
February	1st to 10th	Day	15% 14% 4 12% 7% 5% 5% 4 5% 6% 24%	1890
	11th to 20th	Day	12% 14% 6% 11% 7% 6% 5% 4 4 6% 25%	1843
	21st to end	Day	17% 13% 4 10% 6% 5% 5% 4 5% 6% 26%	1620
March	1st to 10th	Day	18% 9% 3 8% 5% 4 5% 4 5% 5% 33%	5042
	11th to 20th	Day	12% 12% 4 9% 5% 5% 5% 4 6% 8% 30%	5090
	21st to end	Day	18% 9% 3 8% 6% 5% 4 3 4 6% 33%	5586
April	1st to 10th	Day	17% 12% 3 8% 5% 5% 5% 4 5% 6% 30%	2478
	11th to 20th	Day	19% 10% 3 7% 5% 3 4 3 5% 6% 34%	2571
	21st to end	Day	20% 8% 2 8% 4 5% 5% 4 5% 6% 33%	2730
May	1st to 10th	Day	18% 8% 3 8% 5% 4 4 4 6% 7% 33%	7642
	11th to 20th	Day	14% 8% 3 7% 5% 5% 4 4 6% 8% 36%	8159
	21st to end	Day	18% 5% 2 5% 3 4 4 3 6% 7% 43%	9060
June	1st to 10th	Day	13% 6% 2 6% 6% 4 5% 4 7% 8% 40%	2940
	11th to 20th	Day	11% 5% 2 6% 5% 5% 5% 4 8% 9% 39%	2940
	21st to end	Day	12% 5% 2 6% 4 5% 5% 5% 7% 10% 40%	2940
July	1st to 10th	Day	9% 4 2 6% 5% 5% 5% 5% 7% 10% 41%	6500
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 7% 9% 48%	6430
	21st to end	Day	7% 4 2 6% 4 5% 5% 4 7% 9% 47%	6472
August	1st to 10th	Day	16% 7% 2 6% 4 4 5% 4 6% 8% 39%	4234
	11th to 20th	Day	10% 6% 3 7% 5% 6% 5% 4 8% 9% 37%	4174
	21st to end	Day	9% 6% 2 6% 4 4 5% 5% 6% 9% 45%	4488
September	1st to 10th	Day	13% 5% 2 6% 4 4 5% 4 6% 9% 43%	2400
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 3 6% 8% 48%	2281
	21st to end	Day	13% 6% 2 7% 6% 5% 5% 4 6% 9% 37%	2160
October	1st to 10th	Day	17% 8% 2 6% 4 4 4 3 6% 7% 38%	2000
	11th to 20th	Day	19% 8% 3 8% 6% 5% 5% 4 5% 7% 31%	2000
	21st to end	Day	23% 10% 3 8% 5% 6% 5% 4 7% 7% 22%	2200
November	1st to 10th	Day	15% 8% 4 8% 6% 4 5% 4 6% 8% 33%	1782
	11th to 20th	Day	15% 12% 3 9% 6% 5% 5% 6% 6% 8% 26%	1680
	21st to end	Day	19% 13% 4 9% 6% 5% 5% 3 7% 7% 22%	1680
December	1st to 10th	Day	19% 14% 4 10% 7% 6% 6% 4 6% 6% 18%	2680
	11th to 20th	Day	21% 15% 4 9% 5% 5% 4 4 6% 6% 22%	3066
	21st to end	Day	27% 15% 6% 11% 5% 5% 4 3 4 5% 15%	4048
January	1st to 10th	Night	14% 12% 4 10% 6% 6% 6% 5% 6% 7% 25%	8234
	11th to 20th	Night	12% 16% 5% 13% 9% 7% 6% 4 5% 5% 17%	7762
	21st to end	Night	14% 12% 5% 11% 7% 6% 6% 4 6% 6% 23%	8401
February	1st to 10th	Night	14% 14% 5% 9% 6% 5% 5% 3 5% 7% 26%	2730
	11th to 20th	Night	15% 14% 4 9% 7% 5% 4 5% 5% 6% 27%	2663
	21st to end	Night	14% 12% 4 10% 6% 5% 5% 3 6% 6% 29%	2181
March	1st to 10th	Night	17% 9% 4 8% 6% 5% 5% 4 5% 6% 31%	5018
	11th to 20th	Night	11% 8% 3 8% 5% 5% 5% 4 7% 8% 36%	5089
	21st to end	Night	21% 8% 3 6% 4 3 3 3 4 5% 39%	5588
April	1st to 10th	Night	18% 9% 3 7% 6% 4 4 3 5% 6% 32%	2140
	11th to 20th	Night	16% 9% 3 6% 5% 4 5% 3 5% 7% 37%	2015
	21st to end	Night	16% 7% 3 7% 4 4 4 5% 5% 7% 37%	1890
May	1st to 10th	Night	21% 8% 2 7% 5% 4 4 3 5% 6% 35%	5257
	11th to 20th	Night	15% 7% 3 7% 4 5% 5% 4 6% 8% 37%	4698
	21st to end	Night	18% 5% 2 5% 4 3 3 3 4 6% 45%	5114
June	1st to 10th	Night	13% 4 2 6% 4 5% 5% 3 6% 8% 44%	1680
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 5% 6% 10% 42%	1680
	21st to end	Night	11% 5% 3 6% 5% 4 4 4 6% 8% 43%	1680
July	1st to 10th	Night	7% 5% 2 6% 4 5% 5% 3 6% 9% 48%	3680
	11th to 20th	Night	10% 4 2 5% 3 4 4 3 6% 9% 50%	3640
	21st to end	Night	9% 4 2 4 4 3 4 3 7% 7% 53%	4376
August	1st to 10th	Night	10% 5% 2 6% 5% 5% 5% 3 6% 7% 46%	2915
	11th to 20th	Night	11% 4 1 6% 3 3 4 4 5% 8% 51%	2875
	21st to end	Night	10% 5% 2 5% 4 4 4 4 6% 8% 47%	3376
September	1st to 10th	Night	9% 5% 2 6% 3 4 5% 3 6% 8% 48%	2000
	11th to 20th	Night	9% 4 2 4 4 3 3 3 5% 6% 57%	2115
	21st to end	Night	15% 6% 3 6% 4 4 4 3 6% 7% 42%	2240
October	1st to 10th	Night	15% 7% 2 7% 4 3 4 4 5% 6% 42%	2400
	11th to 20th	Night	18% 9% 3 7% 5% 3 4 4 4 6% 36%	2400
	21st to end	Night	20% 9% 3 8% 4 5% 4 4 6% 6% 32%	2640
November	1st to 10th	Night	16% 8% 3 7% 5% 4 4 4 5% 7% 38%	2729
	11th to 20th	Night	16% 10% 4 8% 5% 5% 5% 4 6% 6% 32%	2940
	21st to end	Night	20% 11% 3 8% 5% 5% 5% 4 6% 7% 26%	2940
December	1st to 10th	Night	18% 13% 5% 10% 6% 6% 6% 5% 6% 6% 20%	4720
	11th to 20th	Night	17% 17% 4 9% 5% 5% 5% 4 6% 6% 23%	5348
	21st to end	Night	26% 14% 7% 10% 6% 4 4 4 4 5% 16%	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	54% 10% 16% 12% 8%	4662
	11th to 20th	Day	70% 6% 11% 9% 4	5142
	21st to end	Day	60% 6% 14% 12% 8%	5780
February	1st to 10th	Day	59% 8% 14% 15% 4 1	1890
	11th to 20th	Day	58% 8% 13% 14% 5% 1	1852
	21st to end	Day	56% 8% 15% 14% 6% 1	1620
March	1st to 10th	Day	49% 8% 15% 15% 12% 1	5045
	11th to 20th	Day	47% 8% 17% 18% 7% 2	5090
	21st to end	Day	48% 8% 12% 19% 11% 1	5586
April	1st to 10th	Day	52% 6% 12% 18% 10% 1	2478
	11th to 20th	Day	48% 6% 11% 21% 13% 1	2571
	21st to end	Day	48% 8% 11% 19% 11% 2	2730
May	1st to 10th	Day	46% 8% 15% 18% 11% 3	7651
	11th to 20th	Day	44% 9% 14% 19% 12% 1	8163
	21st to end	Day	39% 6% 11% 28% 14% 2	9061
June	1st to 10th	Day	39% 9% 13% 22% 16% 1	2940
	11th to 20th	Day	37% 9% 15% 24% 15% 1	2940
	21st to end	Day	36% 9% 15% 25% 14% 1	2940
July	1st to 10th	Day	34% 8% 17% 25% 15% 2	6430
	11th to 20th	Day	29% 7% 15% 32% 16% 1	6355
	21st to end	Day	30% 8% 15% 28% 18% 1	6286
August	1st to 10th	Day	41% 8% 15% 21% 15% 1	4221
	11th to 20th	Day	38% 9% 18% 24% 11% 1	4213
	21st to end	Day	32% 9% 15% 34% 10% 1	4488
September	1st to 10th	Day	36% 10% 15% 28% 11% 1	2400
	11th to 20th	Day	32% 7% 17% 29% 14% 1	2281
	21st to end	Day	41% 10% 15% 25% 9%	2160
October	1st to 10th	Day	34% 7% 17% 29% 13% 1	3260
	11th to 20th	Day	37% 6% 17% 26% 14%	3240
	21st to end	Day	50% 8% 15% 20% 6%	3538
November	1st to 10th	Day	47% 9% 15% 21% 8% 1	1782
	11th to 20th	Day	52% 9% 15% 15% 7%	1680
	21st to end	Day	58% 10% 16% 14% 3	1680
December	1st to 10th	Day	64% 8% 15% 9% 3	2680
	11th to 20th	Day	60% 9% 14% 10% 7%	3066
	21st to end	Day	69% 8% 10% 8% 5%	4048
January	1st to 10th	Night	53% 10% 15% 18% 4	8234
	11th to 20th	Night	65% 9% 12% 10% 4	7803
	21st to end	Night	58% 8% 13% 11% 10% 1	8401
February	1st to 10th	Night	56% 7% 14% 17% 4 1	2730
	11th to 20th	Night	56% 8% 13% 15% 7%	2665
	21st to end	Night	54% 7% 14% 17% 7%	2181
March	1st to 10th	Night	50% 8% 12% 17% 11% 2	5028
	11th to 20th	Night	40% 8% 20% 20% 10% 2	5090
	21st to end	Night	44% 6% 9% 21% 17% 2	5588
April	1st to 10th	Night	50% 6% 12% 18% 12% 2	2140
	11th to 20th	Night	47% 6% 10% 21% 14% 2	2015
	21st to end	Night	44% 7% 12% 20% 15% 2	1890
May	1st to 10th	Night	48% 7% 11% 15% 14% 4	5264
	11th to 20th	Night	44% 10% 13% 18% 14% 2	4699
	21st to end	Night	38% 6% 11% 25% 17% 2	5115
June	1st to 10th	Night	37% 7% 12% 24% 17% 3	1680
	11th to 20th	Night	35% 7% 13% 22% 20% 2	1680
	21st to end	Night	37% 7% 13% 24% 18% 1	1680
July	1st to 10th	Night	33% 6% 15% 24% 20% 2	3640
	11th to 20th	Night	30% 6% 14% 30% 18% 1	3592
	21st to end	Night	29% 7% 13% 28% 22% 1	4247
August	1st to 10th	Night	35% 7% 14% 27% 15% 2	2904
	11th to 20th	Night	32% 6% 16% 32% 12% 1	2902
	21st to end	Night	32% 8% 15% 31% 13% 1	3376
September	1st to 10th	Night	32% 8% 16% 28% 14% 1	2000
	11th to 20th	Night	28% 6% 14% 35% 17%	2115
	21st to end	Night	41% 8% 13% 26% 12% 1	2240
October	1st to 10th	Night	32% 7% 11% 26% 23% 1	3920
	11th to 20th	Night	41% 7% 15% 26% 11%	3899
	21st to end	Night	39% 7% 17% 26% 10% 1	4252
November	1st to 10th	Night	44% 7% 15% 22% 12% 1	2729
	11th to 20th	Night	49% 9% 15% 18% 9% 1	2940
	21st to end	Night	55% 9% 18% 14% 3	2940
December	1st to 10th	Night	60% 10% 15% 12% 3	4720
	11th to 20th	Night	60% 8% 11% 13% 7%	5348
	21st to end	Night	68% 9% 11% 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% 16% 34% 21% 7% 1	220
	11th to 20th	Day	23% 21% 34% 14% 7% 1	305
	21st to end	Day	24% 14% 34% 22% 6%	363
February	1st to 10th	Day	21% 17% 38% 19% 5%	330
	11th to 20th	Day	22% 17% 38% 20% 2	330
	21st to end	Day	24% 22% 30% 21% 2	294
March	1st to 10th	Day	19% 12% 39% 24% 6%	540
	11th to 20th	Day	19% 18% 32% 23% 7% 1	540
	21st to end	Day	25% 11% 32% 24% 6% 1	594
April	1st to 10th	Day	21% 15% 32% 25% 7%	540
	11th to 20th	Day	26% 11% 33% 20% 9% 3	532
	21st to end	Day	21% 10% 33% 25% 9% 2	540
May	1st to 10th	Day	17% 12% 29% 26% 12% 4	543
	11th to 20th	Day	15% 7% 27% 30% 16% 5%	567
	21st to end	Day	15% 6% 23% 31% 19% 6%	617
June	1st to 10th	Day	12% 6% 28% 35% 16% 3	570
	11th to 20th	Day	13% 7% 26% 32% 19% 2	570
	21st to end	Day	14% 6% 25% 32% 18% 4	570
July	1st to 10th	Day	8% 5% 19% 34% 26% 9%	565
	11th to 20th	Day	12% 4 20% 33% 22% 8%	544
	21st to end	Day	7% 3 20% 40% 23% 7%	576
August	1st to 10th	Day	10% 5% 18% 30% 26% 11%	526
	11th to 20th	Day	9% 5% 17% 33% 25% 12%	519
	21st to end	Day	10% 6% 19% 32% 22% 10%	583
September	1st to 10th	Day	13% 5% 21% 29% 22% 11%	530
	11th to 20th	Day	8% 4 17% 29% 27% 15%	530
	21st to end	Day	14% 5% 29% 28% 16% 8%	530
October	1st to 10th	Day	19% 9% 25% 25% 15% 7%	530
	11th to 20th	Day	18% 12% 35% 23% 9% 2	530
	21st to end	Day	26% 12% 30% 25% 7% 1	583
November	1st to 10th	Day	19% 16% 28% 26% 10% 1	317
	11th to 20th	Day	20% 20% 33% 20% 6% 1	220
	21st to end	Day	23% 16% 37% 20% 3	220
December	1st to 10th	Day	25% 16% 33% 20% 5%	220
	11th to 20th	Day	27% 22% 29% 18% 4	220
	21st to end	Day	28% 17% 35% 17% 2	242
January	1st to 10th	Night	22% 15% 38% 19% 5%	840
	11th to 20th	Night	27% 15% 32% 23% 4	840
	21st to end	Night	19% 11% 38% 25% 7%	924
February	1st to 10th	Night	20% 14% 40% 22% 3	840
	11th to 20th	Night	22% 13% 37% 24% 4	823
	21st to end	Night	20% 12% 41% 23% 4	692
March	1st to 10th	Night	18% 12% 37% 26% 7%	840
	11th to 20th	Night	20% 13% 35% 24% 6% 1	840
	21st to end	Night	21% 10% 30% 29% 9% 1	924
April	1st to 10th	Night	23% 9% 33% 29% 6%	840
	11th to 20th	Night	18% 10% 33% 28% 9% 2	771
	21st to end	Night	19% 8% 26% 34% 12%	630
May	1st to 10th	Night	18% 5% 27% 32% 16% 2	630
	11th to 20th	Night	15% 4 24% 40% 17%	435
	21st to end	Night	11% 5% 24% 36% 23% 2	455
June	1st to 10th	Night	13% 2 21% 44% 19% 1	420
	11th to 20th	Night	11% 4 26% 38% 20% 1	420
	21st to end	Night	10% 4 21% 43% 21%	420
July	1st to 10th	Night	6% 2 16% 47% 27% 2	410
	11th to 20th	Night	11% 3 19% 38% 26% 3	398
	21st to end	Night	9% 2 15% 46% 26% 3	631
August	1st to 10th	Night	9% 3 14% 40% 32% 3	597
	11th to 20th	Night	9% 2 15% 38% 32% 5%	594
	21st to end	Night	10% 2 20% 36% 28% 3	748
September	1st to 10th	Night	11% 5% 21% 33% 25% 6%	800
	11th to 20th	Night	11% 3 16% 31% 32% 6%	800
	21st to end	Night	17% 5% 21% 32% 21% 5%	800
October	1st to 10th	Night	17% 6% 25% 28% 21% 3	800
	11th to 20th	Night	20% 10% 31% 28% 11% 1	800
	21st to end	Night	23% 9% 32% 29% 6% 1	880
November	1st to 10th	Night	20% 10% 27% 30% 11% 1	820
	11th to 20th	Night	20% 11% 35% 24% 8% 2	840
	21st to end	Night	24% 11% 34% 24% 6%	840
December	1st to 10th	Night	27% 12% 34% 21% 5%	840
	11th to 20th	Night	22% 14% 41% 19% 4	840
	21st to end	Night	30% 12% 34% 22% 2	924

Page generated at 2026-07-13 03:14:54. Version ac07

Copyright © 2026 Attilla Danko.