Cat's Paw Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cat's Paw Observatory clear sky chart from 2005-11-06 to 2026-04-17.

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	18% 8% 2 6% 4 4 4 3 5% 7% 39%	131045
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 40%	131129
Transparency	Day	29% 38% 7% 14% 10% 2	134578
	Night	29% 36% 7% 14% 11% 2	135683
Seeing	Day	24% 18% 32% 17% 6% 2	16906
	Night	23% 15% 33% 23% 6%	25933

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	11% 9% 3 7% 4 4 4 3 5% 5% 45%	4661
	11th to 20th	Day	16% 9% 3 5% 3 3 3 2 4 4 47%	4650
	21st to end	Day	15% 9% 2 5% 3 4 3 3 4 5% 47%	5124
February	1st to 10th	Day	18% 8% 2 5% 5% 4 4 4 6% 7% 37%	2002
	11th to 20th	Day	14% 8% 2 6% 4 4 4 3 4 7% 42%	2048
	21st to end	Day	19% 10% 3 5% 4 3 4 3 5% 5% 39%	1730
March	1st to 10th	Day	23% 11% 2 6% 3 3 3 2 4 6% 37%	4576
	11th to 20th	Day	17% 9% 2 5% 4 4 4 4 5% 6% 41%	4889
	21st to end	Day	25% 9% 2 6% 4 4 4 3 5% 5% 32%	5901
April	1st to 10th	Day	21% 9% 3 6% 4 3 3 3 5% 7% 38%	2520
	11th to 20th	Day	18% 7% 2 6% 3 4 4 4 6% 6% 40%	2449
	21st to end	Day	21% 7% 2 6% 5% 4 3 3 5% 6% 39%	2600
May	1st to 10th	Day	29% 11% 3 7% 4 3 4 2 4 7% 26%	5886
	11th to 20th	Day	23% 9% 3 7% 4 4 4 3 5% 6% 33%	5895
	21st to end	Day	21% 6% 2 6% 4 4 5% 4 5% 7% 35%	6949
June	1st to 10th	Day	19% 6% 2 6% 4 5% 5% 5% 6% 8% 34%	2800
	11th to 20th	Day	17% 6% 2 6% 5% 5% 5% 4 6% 8% 37%	2800
	21st to end	Day	16% 6% 2 6% 4 4 5% 5% 6% 9% 38%	2800
July	1st to 10th	Day	18% 7% 2 6% 5% 4 5% 4 7% 9% 32%	6360
	11th to 20th	Day	13% 6% 2 6% 5% 6% 5% 5% 8% 11% 34%	6360
	21st to end	Day	17% 6% 2 6% 4 4 5% 4 5% 7% 40%	6926
August	1st to 10th	Day	17% 8% 3 8% 5% 4 6% 4 6% 8% 31%	4243
	11th to 20th	Day	12% 6% 3 7% 5% 6% 5% 5% 6% 8% 37%	4086
	21st to end	Day	7% 4 2 5% 5% 5% 6% 5% 7% 9% 46%	4312
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 5% 6% 44%	2390
	11th to 20th	Day	13% 6% 2 5% 2 4 3 2 5% 6% 51%	2200
	21st to end	Day	20% 6% 2 6% 4 4 4 3 4 6% 42%	2200
October	1st to 10th	Day	22% 7% 2 5% 3 2 4 2 4 5% 44%	2200
	11th to 20th	Day	17% 6% 2 4 3 4 3 3 4 7% 47%	1971
	21st to end	Day	18% 6% 3 5% 4 4 4 3 4 6% 43%	1980
November	1st to 10th	Day	16% 7% 2 5% 3 4 4 4 4 4 48%	1851
	11th to 20th	Day	18% 6% 1 5% 3 3 3 2 4 7% 47%	1890
	21st to end	Day	18% 7% 2 5% 4 3 3 3 4 6% 44%	1890
December	1st to 10th	Day	15% 9% 2 4 3 3 3 3 4 6% 48%	2792
	11th to 20th	Day	20% 6% 2 4 3 2 2 2 3 5% 49%	3066
	21st to end	Day	20% 10% 4 7% 4 3 3 3 4 4 39%	4048
January	1st to 10th	Night	15% 7% 2 5% 3 3 4 3 4 6% 49%	8234
	11th to 20th	Night	15% 10% 3 8% 4 4 3 3 4 4 40%	8235
	21st to end	Night	15% 9% 3 7% 4 5% 4 3 4 5% 41%	9057
February	1st to 10th	Night	16% 9% 3 7% 4 4 4 3 5% 6% 40%	2611
	11th to 20th	Night	17% 8% 3 5% 4 4 4 4 5% 5% 40%	2458
	21st to end	Night	19% 9% 2 6% 5% 3 4 3 4 5% 41%	2076
March	1st to 10th	Night	25% 8% 2 4 4 3 4 3 5% 6% 38%	5484
	11th to 20th	Night	18% 10% 3 6% 4 3 4 3 5% 5% 40%	5289
	21st to end	Night	25% 9% 3 5% 4 4 4 4 5% 4 33%	5270
April	1st to 10th	Night	21% 8% 3 6% 4 4 5% 3 4 7% 36%	2100
	11th to 20th	Night	19% 8% 3 5% 5% 4 4 3 5% 5% 38%	2031
	21st to end	Night	21% 7% 3 7% 4 4 4 4 3 5% 40%	1800
May	1st to 10th	Night	29% 9% 3 7% 4 4 4 3 5% 6% 26%	4054
	11th to 20th	Night	20% 9% 2 8% 5% 5% 5% 4 6% 7% 28%	4033
	21st to end	Night	21% 8% 3 7% 5% 5% 4 4 6% 7% 31%	3934
June	1st to 10th	Night	16% 8% 2 6% 5% 5% 4 4 5% 8% 36%	1600
	11th to 20th	Night	19% 7% 2 7% 4 4 4 4 4 8% 37%	1600
	21st to end	Night	16% 8% 2 6% 3 3 5% 3 7% 8% 39%	1600
July	1st to 10th	Night	18% 9% 3 6% 4 3 5% 4 5% 10% 33%	3600
	11th to 20th	Night	18% 8% 3 7% 4 4 4 4 6% 9% 34%	3600
	21st to end	Night	14% 8% 3 7% 4 4 4 3 5% 7% 41%	3926
August	1st to 10th	Night	23% 7% 2 6% 4 5% 5% 4 6% 7% 30%	2873
	11th to 20th	Night	10% 7% 3 8% 5% 6% 6% 5% 7% 7% 37%	2957
	21st to end	Night	9% 4 2 5% 3 3 4 3 5% 8% 55%	3586
September	1st to 10th	Night	13% 6% 3 6% 5% 4 4 4 6% 6% 43%	2008
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 4 6% 52%	2200
	21st to end	Night	20% 8% 3 6% 4 4 4 3 4 5% 41%	2200
October	1st to 10th	Night	20% 6% 2 6% 4 3 3 3 3 6% 44%	2200
	11th to 20th	Night	16% 5% 2 5% 3 3 3 3 4 8% 47%	2424
	21st to end	Night	19% 8% 2 6% 3 4 3 3 4 6% 41%	2860
November	1st to 10th	Night	14% 6% 2 5% 4 3 4 4 4 6% 48%	2667
	11th to 20th	Night	17% 7% 2 5% 4 3 3 3 4 5% 47%	2730
	21st to end	Night	16% 6% 2 5% 3 3 4 3 5% 7% 45%	2730
December	1st to 10th	Night	19% 8% 2 4 4 3 3 2 4 5% 47%	4604
	11th to 20th	Night	22% 9% 2 5% 3 3 3 3 4 5% 42%	5348
	21st to end	Night	18% 11% 4 6% 3 3 3 2 4 5% 40%	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	32% 22% 7% 20% 17% 3	4662
	11th to 20th	Day	32% 22% 6% 17% 16% 7%	4680
	21st to end	Day	33% 23% 8% 18% 18% 1	5124
February	1st to 10th	Day	19% 59% 7% 8% 6% 1	2002
	11th to 20th	Day	20% 58% 2 9% 9% 2	2057
	21st to end	Day	17% 59% 5% 11% 7% 1	1730
March	1st to 10th	Day	38% 29% 7% 8% 9% 10%	4579
	11th to 20th	Day	30% 30% 10% 21% 8% 1	4889
	21st to end	Day	42% 29% 4 11% 9% 5%	5901
April	1st to 10th	Day	22% 59% 3 7% 7% 2	2520
	11th to 20th	Day	16% 61% 4 8% 9% 1	2449
	21st to end	Day	19% 62% 3 8% 7% 2	2600
May	1st to 10th	Day	45% 32% 11% 9% 4	5897
	11th to 20th	Day	41% 31% 11% 11% 6% 1	5899
	21st to end	Day	37% 31% 7% 15% 10%	6949
June	1st to 10th	Day	17% 62% 4 9% 7%	2800
	11th to 20th	Day	16% 62% 5% 10% 6% 1	2800
	21st to end	Day	15% 61% 4 10% 9% 1	2800
July	1st to 10th	Day	36% 30% 9% 15% 10% 1	6290
	11th to 20th	Day	31% 30% 14% 17% 8% 1	6285
	21st to end	Day	32% 27% 8% 20% 13% 1	6728
August	1st to 10th	Day	34% 39% 9% 13% 4 1	4229
	11th to 20th	Day	27% 39% 9% 20% 6%	4125
	21st to end	Day	16% 40% 10% 20% 12% 1	4312
September	1st to 10th	Day	17% 58% 4 12% 9%	2390
	11th to 20th	Day	17% 57% 4 10% 11% 2	2200
	21st to end	Day	21% 57% 4 9% 8% 1	2200
October	1st to 10th	Day	23% 37% 6% 15% 15% 3	3590
	11th to 20th	Day	17% 36% 4 17% 23% 3	3174
	21st to end	Day	17% 36% 9% 20% 16% 2	3180
November	1st to 10th	Day	19% 54% 6% 10% 10% 1	1851
	11th to 20th	Day	17% 54% 4 9% 13% 3	1890
	21st to end	Day	18% 54% 4 15% 7% 2	1890
December	1st to 10th	Day	24% 35% 9% 21% 11%	2792
	11th to 20th	Day	27% 31% 9% 12% 15% 6%	3066
	21st to end	Day	37% 27% 5% 16% 11% 4	4048
January	1st to 10th	Night	29% 21% 8% 26% 14% 2	8234
	11th to 20th	Night	37% 21% 7% 16% 13% 5%	8280
	21st to end	Night	38% 23% 6% 14% 16% 4	9057
February	1st to 10th	Night	19% 59% 5% 9% 7% 1	2611
	11th to 20th	Night	18% 58% 3 8% 11% 2	2460
	21st to end	Night	20% 58% 3 9% 7% 2	2076
March	1st to 10th	Night	37% 29% 6% 10% 11% 6%	5494
	11th to 20th	Night	32% 30% 12% 14% 9% 2	5290
	21st to end	Night	41% 29% 3 7% 14% 5%	5270
April	1st to 10th	Night	23% 59% 3 7% 6% 2	2100
	11th to 20th	Night	18% 61% 5% 6% 8% 1	2031
	21st to end	Night	19% 62% 3 8% 7% 1	1800
May	1st to 10th	Night	43% 33% 10% 9% 4 1	4060
	11th to 20th	Night	42% 32% 10% 10% 4 1	4034
	21st to end	Night	39% 31% 9% 14% 6%	3935
June	1st to 10th	Night	17% 62% 4 9% 8%	1600
	11th to 20th	Night	17% 62% 4 10% 6%	1600
	21st to end	Night	14% 61% 5% 12% 7% 1	1600
July	1st to 10th	Night	36% 29% 8% 16% 11%	3560
	11th to 20th	Night	35% 29% 11% 16% 7% 1	3552
	21st to end	Night	32% 27% 8% 21% 12% 1	3809
August	1st to 10th	Night	37% 39% 7% 10% 6% 1	2863
	11th to 20th	Night	28% 41% 8% 18% 5%	2984
	21st to end	Night	14% 38% 12% 20% 17%	3586
September	1st to 10th	Night	17% 58% 5% 13% 7% 1	2008
	11th to 20th	Night	16% 57% 3 11% 11% 1	2200
	21st to end	Night	23% 57% 3 9% 7%	2200
October	1st to 10th	Night	24% 38% 7% 17% 11% 2	3590
	11th to 20th	Night	12% 35% 5% 18% 27% 3	3960
	21st to end	Night	18% 36% 7% 22% 16% 2	4610
November	1st to 10th	Night	19% 54% 5% 11% 9% 2	2667
	11th to 20th	Night	17% 54% 4 10% 13% 3	2730
	21st to end	Night	17% 55% 6% 15% 6% 2	2730
December	1st to 10th	Night	27% 34% 7% 21% 10%	4604
	11th to 20th	Night	33% 31% 9% 9% 16% 2	5348
	21st to end	Night	35% 27% 5% 16% 14% 3	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	30% 27% 26% 14% 3	220
	11th to 20th	Day	31% 28% 33% 6% 2	220
	21st to end	Day	29% 26% 33% 10% 1 1	242
February	1st to 10th	Day	31% 24% 31% 13% 1	472
	11th to 20th	Day	32% 28% 31% 7% 2	536
	21st to end	Day	30% 23% 34% 11% 3	446
March	1st to 10th	Day	32% 21% 32% 13% 2	540
	11th to 20th	Day	31% 26% 28% 11% 3 1	540
	21st to end	Day	32% 25% 30% 8% 4 2	594
April	1st to 10th	Day	35% 24% 26% 10% 4 1	540
	11th to 20th	Day	30% 25% 29% 12% 3 1	516
	21st to end	Day	29% 20% 30% 17% 2 2	500
May	1st to 10th	Day	33% 23% 29% 11% 3	503
	11th to 20th	Day	25% 18% 39% 13% 3 1	527
	21st to end	Day	21% 16% 35% 21% 5% 2	573
June	1st to 10th	Day	23% 14% 34% 21% 8% 1	530
	11th to 20th	Day	17% 19% 37% 21% 5% 1	530
	21st to end	Day	19% 13% 38% 22% 7% 1	530
July	1st to 10th	Day	19% 11% 31% 26% 11% 2	525
	11th to 20th	Day	17% 9% 32% 29% 12% 2	524
	21st to end	Day	14% 11% 39% 26% 9% 1	576
August	1st to 10th	Day	13% 11% 34% 30% 10% 3	526
	11th to 20th	Day	14% 9% 34% 29% 11% 3	519
	21st to end	Day	12% 11% 37% 23% 13% 5%	583
September	1st to 10th	Day	19% 12% 29% 23% 13% 4	530
	11th to 20th	Day	17% 12% 27% 25% 12% 7%	530
	21st to end	Day	24% 11% 34% 20% 7% 4	530
October	1st to 10th	Day	27% 12% 27% 19% 9% 5%	530
	11th to 20th	Day	21% 17% 33% 17% 10% 2	472
	21st to end	Day	26% 18% 30% 16% 7% 2	462
November	1st to 10th	Day	23% 17% 32% 17% 9% 2	425
	11th to 20th	Day	27% 22% 32% 14% 5%	430
	21st to end	Day	28% 23% 29% 14% 6%	430
December	1st to 10th	Day	25% 28% 31% 12% 5%	293
	11th to 20th	Day	35% 24% 32% 6% 2	220
	21st to end	Day	29% 24% 30% 13% 2 2	242
January	1st to 10th	Night	23% 20% 37% 17% 3	840
	11th to 20th	Night	31% 19% 33% 15% 2	840
	21st to end	Night	23% 22% 35% 17% 3	924
February	1st to 10th	Night	24% 19% 37% 19% 1	840
	11th to 20th	Night	27% 21% 36% 14% 1	823
	21st to end	Night	26% 22% 33% 17% 3	692
March	1st to 10th	Night	26% 19% 35% 17% 3	840
	11th to 20th	Night	23% 22% 35% 17% 3	840
	21st to end	Night	28% 20% 33% 16% 3	924
April	1st to 10th	Night	26% 21% 33% 17% 3	840
	11th to 20th	Night	24% 20% 35% 17% 4	811
	21st to end	Night	25% 18% 38% 17% 3	600
May	1st to 10th	Night	30% 15% 32% 20% 4	600
	11th to 20th	Night	22% 16% 38% 22% 3	592
	21st to end	Night	22% 8% 35% 29% 5%	441
June	1st to 10th	Night	17% 11% 34% 30% 9%	400
	11th to 20th	Night	21% 7% 37% 29% 6%	400
	21st to end	Night	19% 5% 36% 35% 5% 1	400
July	1st to 10th	Night	16% 4 32% 38% 9%	390
	11th to 20th	Night	16% 4 33% 37% 10% 1	388
	21st to end	Night	16% 4 32% 40% 8%	438
August	1st to 10th	Night	15% 5% 34% 36% 10%	568
	11th to 20th	Night	13% 5% 30% 39% 12% 1	638
	21st to end	Night	14% 6% 26% 36% 15% 2	880
September	1st to 10th	Night	17% 6% 30% 35% 11% 1	800
	11th to 20th	Night	17% 7% 28% 29% 16% 3	800
	21st to end	Night	25% 7% 27% 28% 11% 2	800
October	1st to 10th	Night	24% 11% 27% 25% 12% 2	800
	11th to 20th	Night	20% 11% 35% 23% 11% 1	800
	21st to end	Night	24% 15% 33% 21% 7%	880
November	1st to 10th	Night	20% 15% 32% 24% 9% 1	820
	11th to 20th	Night	23% 18% 35% 17% 6%	840
	21st to end	Night	23% 19% 32% 21% 4 1	840
December	1st to 10th	Night	26% 17% 35% 17% 5%	840
	11th to 20th	Night	29% 18% 32% 19% 2	840
	21st to end	Night	27% 19% 34% 18% 2	924

Page generated at 2026-04-14 02:44:25. Version ac07

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