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 2024-12-24.

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 4 5% 7% 38%	101602
	Night	18% 8% 3 6% 4 4 4 3 5% 6% 39%	98522
Transparency	Day	25% 47% 6% 12% 9% 1	105153
	Night	25% 47% 6% 12% 9% 1	103060
Seeing	Day	24% 18% 32% 18% 7% 2	15242
	Night	22% 14% 33% 23% 6% 1	24211

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	15% 9% 2 6% 4 3 4 3 4 4 46%	2517
	11th to 20th	Day	18% 8% 3 6% 4 4 4 3 4 4 40%	2520
	21st to end	Day	21% 13% 4 7% 3 3 3 3 4 5% 35%	2772
February	1st to 10th	Day	20% 8% 2 5% 5% 4 4 4 6% 6% 36%	1809
	11th to 20th	Day	14% 8% 2 6% 4 4 5% 3 4 7% 42%	1848
	21st to end	Day	20% 10% 3 5% 5% 3 4 3 5% 5% 37%	1570
March	1st to 10th	Day	26% 14% 3 7% 3 3 3 2 4 5% 31%	3116
	11th to 20th	Day	12% 6% 2 5% 4 5% 4 4 7% 7% 44%	3340
	21st to end	Day	23% 10% 2 6% 4 3 4 3 5% 5% 36%	4026
April	1st to 10th	Day	20% 9% 3 6% 4 3 3 3 5% 7% 37%	2280
	11th to 20th	Day	18% 7% 2 6% 3 4 5% 4 6% 6% 40%	2257
	21st to end	Day	21% 7% 2 6% 5% 3 3 3 5% 6% 38%	2470
May	1st to 10th	Day	26% 12% 3 7% 4 3 4 2 4 7% 29%	4106
	11th to 20th	Day	24% 9% 3 8% 4 4 4 3 5% 6% 32%	4101
	21st to end	Day	16% 5% 2 5% 4 4 4 3 5% 8% 44%	4837
June	1st to 10th	Day	19% 7% 2 5% 4 4 4 5% 6% 8% 34%	2660
	11th to 20th	Day	16% 6% 2 6% 5% 4 5% 4 6% 8% 37%	2660
	21st to end	Day	15% 6% 2 6% 4 4 5% 5% 6% 9% 37%	2660
July	1st to 10th	Day	14% 6% 2 6% 5% 5% 6% 5% 7% 9% 34%	4440
	11th to 20th	Day	15% 6% 2 5% 5% 5% 5% 4 7% 10% 36%	4440
	21st to end	Day	20% 8% 3 7% 5% 4 5% 4 6% 8% 32%	4814
August	1st to 10th	Day	18% 8% 3 8% 5% 4 6% 4 6% 8% 30%	4113
	11th to 20th	Day	13% 6% 3 7% 5% 5% 5% 5% 6% 8% 37%	3959
	21st to end	Day	8% 4 2 5% 5% 5% 6% 5% 7% 9% 46%	4180
September	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 5% 6% 45%	2271
	11th to 20th	Day	13% 6% 2 5% 2 4 3 2 5% 6% 51%	2090
	21st to end	Day	20% 6% 2 6% 3 4 4 3 4 6% 43%	2090
October	1st to 10th	Day	23% 8% 2 5% 3 3 4 2 4 5% 43%	2090
	11th to 20th	Day	16% 6% 2 4 3 4 3 3 4 7% 48%	1872
	21st to end	Day	18% 6% 2 5% 4 4 4 3 4 6% 43%	1881
November	1st to 10th	Day	16% 7% 2 5% 3 4 3 4 4 4 48%	1761
	11th to 20th	Day	19% 6% 1 4 3 3 3 2 4 7% 47%	1800
	21st to end	Day	18% 7% 2 5% 4 3 3 3 4 6% 44%	1800
December	1st to 10th	Day	20% 8% 2 5% 4 4 4 3 5% 6% 40%	1670
	11th to 20th	Day	21% 6% 2 5% 4 2 3 3 3 5% 45%	1986
	21st to end	Day	21% 10% 3 7% 4 3 4 3 5% 4 35%	2796
January	1st to 10th	Night	17% 7% 2 5% 3 3 3 2 4 6% 48%	4429
	11th to 20th	Night	16% 11% 4 8% 4 4 3 2 4 4 40%	4440
	21st to end	Night	22% 12% 4 8% 5% 4 4 3 3 4 31%	4884
February	1st to 10th	Night	17% 9% 3 7% 4 3 4 3 5% 5% 40%	2364
	11th to 20th	Night	17% 8% 3 6% 5% 4 3 4 5% 5% 40%	2218
	21st to end	Night	19% 9% 2 6% 4 3 4 3 4 5% 41%	1884
March	1st to 10th	Night	30% 10% 2 4 3 3 3 3 4 5% 33%	3724
	11th to 20th	Night	11% 9% 3 6% 5% 4 5% 4 6% 6% 43%	3618
	21st to end	Night	25% 8% 2 5% 4 4 4 4 5% 4 34%	3604
April	1st to 10th	Night	19% 8% 3 7% 4 4 5% 3 4 7% 37%	1900
	11th to 20th	Night	20% 8% 3 5% 5% 4 4 3 5% 6% 38%	1870
	21st to end	Night	21% 7% 3 7% 4 4 3 3 3 5% 40%	1710
May	1st to 10th	Night	25% 9% 4 8% 4 4 4 4 5% 6% 27%	2834
	11th to 20th	Night	24% 10% 2 8% 5% 5% 5% 3 6% 7% 25%	2813
	21st to end	Night	18% 6% 2 5% 4 4 4 4 6% 8% 38%	2746
June	1st to 10th	Night	16% 8% 2 6% 5% 5% 4 4 5% 8% 36%	1520
	11th to 20th	Night	18% 7% 2 7% 4 4 4 4 4 8% 38%	1520
	21st to end	Night	16% 8% 2 6% 3 3 5% 3 7% 8% 39%	1520
July	1st to 10th	Night	16% 7% 3 6% 4 4 6% 5% 6% 10% 32%	2520
	11th to 20th	Night	16% 7% 2 6% 4 4 4 4 6% 10% 37%	2520
	21st to end	Night	17% 10% 3 8% 5% 5% 4 4 6% 7% 31%	2739
August	1st to 10th	Night	23% 7% 2 6% 4 5% 6% 4 6% 7% 29%	2784
	11th to 20th	Night	10% 7% 3 8% 5% 6% 6% 5% 7% 7% 36%	2864
	21st to end	Night	9% 4 2 5% 3 3 4 3 5% 8% 55%	3476
September	1st to 10th	Night	14% 6% 3 6% 5% 4 4 4 6% 6% 43%	1907
	11th to 20th	Night	15% 6% 2 5% 4 3 3 3 3 6% 51%	2090
	21st to end	Night	19% 7% 3 6% 4 4 4 3 4 5% 41%	2090
October	1st to 10th	Night	21% 7% 2 6% 4 3 3 3 3 6% 41%	2090
	11th to 20th	Night	16% 5% 2 5% 3 3 3 4 4 7% 48%	2303
	21st to end	Night	20% 8% 2 7% 3 4 3 3 4 6% 40%	2717
November	1st to 10th	Night	14% 6% 2 6% 4 3 4 4 4 6% 48%	2537
	11th to 20th	Night	18% 7% 2 5% 4 3 3 2 4 5% 47%	2600
	21st to end	Night	16% 6% 2 5% 3 3 4 3 5% 7% 46%	2600
December	1st to 10th	Night	21% 7% 3 5% 4 3 3 3 5% 5% 40%	2726
	11th to 20th	Night	20% 8% 2 4 4 3 3 4 5% 6% 42%	3428
	21st to end	Night	20% 12% 3 7% 3 3 3 3 4 5% 35%	4933

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	26% 37% 5% 20% 10% 2	2518
	11th to 20th	Day	29% 39% 4 18% 8% 1	2520
	21st to end	Day	38% 41% 4 11% 5% 1	2772
February	1st to 10th	Day	17% 65% 6% 7% 4 1	1809
	11th to 20th	Day	17% 64% 2 7% 8% 2	1857
	21st to end	Day	15% 65% 4 9% 5% 1	1570
March	1st to 10th	Day	41% 41% 6% 6% 6% 2	3119
	11th to 20th	Day	18% 43% 10% 18% 10% 1	3340
	21st to end	Day	34% 40% 3 10% 8% 5%	4026
April	1st to 10th	Day	20% 65% 3 6% 5% 1	2280
	11th to 20th	Day	15% 66% 3 8% 8% 1	2257
	21st to end	Day	18% 65% 3 7% 6% 1	2470
May	1st to 10th	Day	37% 42% 9% 7% 5%	4120
	11th to 20th	Day	37% 41% 10% 8% 4	4105
	21st to end	Day	23% 42% 6% 15% 14% 1	4837
June	1st to 10th	Day	15% 65% 4 9% 6%	2660
	11th to 20th	Day	14% 65% 5% 10% 5% 1	2660
	21st to end	Day	14% 64% 4 9% 8%	2660
July	1st to 10th	Day	29% 40% 8% 13% 10% 1	4370
	11th to 20th	Day	27% 38% 11% 14% 9% 1	4365
	21st to end	Day	35% 37% 7% 11% 8% 1	4661
August	1st to 10th	Day	34% 40% 10% 12% 4	4099
	11th to 20th	Day	27% 40% 8% 20% 5%	3998
	21st to end	Day	16% 41% 10% 20% 12% 1	4180
September	1st to 10th	Day	15% 61% 4 11% 8%	2271
	11th to 20th	Day	16% 60% 4 9% 10% 2	2090
	21st to end	Day	19% 60% 3 9% 8% 1	2090
October	1st to 10th	Day	24% 38% 6% 15% 15% 3	3480
	11th to 20th	Day	16% 37% 3 17% 23% 3	3075
	21st to end	Day	16% 37% 9% 20% 16% 2	3081
November	1st to 10th	Day	18% 57% 6% 9% 9% 1	1761
	11th to 20th	Day	16% 57% 4 8% 13% 3	1800
	21st to end	Day	16% 57% 4 14% 6% 2	1800
December	1st to 10th	Day	21% 57% 5% 8% 9%	1670
	11th to 20th	Day	24% 46% 6% 8% 10% 6%	1986
	21st to end	Day	34% 38% 6% 15% 7%	2796
January	1st to 10th	Night	23% 37% 7% 23% 7% 3	4429
	11th to 20th	Night	29% 37% 7% 16% 8% 2	4440
	21st to end	Night	42% 40% 5% 8% 5% 1	4884
February	1st to 10th	Night	17% 65% 5% 7% 5% 1	2364
	11th to 20th	Night	16% 64% 3 6% 10% 2	2220
	21st to end	Night	17% 64% 3 8% 6% 2	1884
March	1st to 10th	Night	38% 41% 5% 9% 6% 2	3734
	11th to 20th	Night	20% 42% 11% 13% 12% 2	3619
	21st to end	Night	36% 41% 3 6% 10% 4	3604
April	1st to 10th	Night	20% 65% 3 6% 5% 1	1900
	11th to 20th	Night	15% 66% 5% 6% 7% 1	1870
	21st to end	Night	17% 65% 3 7% 6% 1	1710
May	1st to 10th	Night	35% 45% 8% 10% 2	2840
	11th to 20th	Night	40% 42% 9% 7% 2	2814
	21st to end	Night	25% 42% 9% 15% 8%	2747
June	1st to 10th	Night	15% 65% 4 9% 7%	1520
	11th to 20th	Night	15% 65% 4 10% 6%	1520
	21st to end	Night	13% 64% 5% 11% 6% 1	1520
July	1st to 10th	Night	31% 40% 7% 12% 10%	2480
	11th to 20th	Night	28% 39% 11% 15% 8%	2472
	21st to end	Night	35% 38% 7% 10% 10% 1	2651
August	1st to 10th	Night	37% 40% 7% 9% 5% 1	2774
	11th to 20th	Night	28% 42% 8% 17% 4	2891
	21st to end	Night	13% 39% 11% 20% 16%	3476
September	1st to 10th	Night	16% 60% 4 12% 7% 1	1907
	11th to 20th	Night	16% 60% 3 9% 11% 1	2090
	21st to end	Night	21% 60% 3 8% 7%	2090
October	1st to 10th	Night	25% 39% 8% 17% 10% 2	3480
	11th to 20th	Night	11% 36% 4 17% 28% 3	3839
	21st to end	Night	18% 37% 7% 21% 15% 2	4467
November	1st to 10th	Night	18% 57% 5% 10% 9% 2	2537
	11th to 20th	Night	17% 56% 4 9% 12% 3	2600
	21st to end	Night	16% 57% 5% 14% 6% 2	2600
December	1st to 10th	Night	22% 57% 5% 10% 7%	2726
	11th to 20th	Night	24% 47% 7% 9% 12% 2	3428
	21st to end	Night	34% 38% 5% 15% 8%	4933

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% 26% 26% 15% 3	180
	11th to 20th	Day	27% 28% 34% 7% 3	180
	21st to end	Day	24% 26% 35% 12% 2 1	198
February	1st to 10th	Day	33% 23% 31% 12% 2	399
	11th to 20th	Day	30% 30% 31% 7% 2	456
	21st to end	Day	31% 21% 34% 11% 3	382
March	1st to 10th	Day	31% 20% 33% 13% 2	460
	11th to 20th	Day	30% 26% 29% 11% 4 1	460
	21st to end	Day	29% 23% 32% 8% 5% 2	506
April	1st to 10th	Day	33% 23% 26% 11% 5% 1	460
	11th to 20th	Day	29% 25% 30% 13% 3 1	452
	21st to end	Day	28% 21% 29% 17% 2 2	460
May	1st to 10th	Day	33% 23% 29% 12% 3	463
	11th to 20th	Day	24% 17% 40% 14% 3 1	487
	21st to end	Day	19% 16% 35% 22% 5% 2	529
June	1st to 10th	Day	23% 14% 33% 21% 8% 1	490
	11th to 20th	Day	16% 19% 37% 21% 6% 1	490
	21st to end	Day	19% 13% 38% 22% 7% 1	490
July	1st to 10th	Day	18% 11% 31% 27% 12% 1	485
	11th to 20th	Day	18% 8% 32% 29% 11% 3	484
	21st to end	Day	15% 11% 38% 26% 9% 1	532
August	1st to 10th	Day	14% 10% 34% 30% 9% 2	486
	11th to 20th	Day	15% 9% 33% 29% 11% 3	479
	21st to end	Day	12% 10% 35% 24% 13% 5%	539
September	1st to 10th	Day	19% 11% 29% 23% 13% 4	490
	11th to 20th	Day	18% 12% 27% 24% 12% 7%	490
	21st to end	Day	24% 11% 34% 19% 7% 4	490
October	1st to 10th	Day	28% 12% 27% 19% 9% 5%	490
	11th to 20th	Day	20% 17% 33% 18% 10% 3	437
	21st to end	Day	25% 18% 30% 17% 7% 2	429
November	1st to 10th	Day	22% 16% 33% 17% 9% 2	395
	11th to 20th	Day	27% 21% 32% 15% 6%	400
	21st to end	Day	27% 22% 30% 15% 6% 1	400
December	1st to 10th	Day	24% 28% 31% 12% 5%	270
	11th to 20th	Day	34% 25% 33% 7% 2 1	200
	21st to end	Day	26% 24% 33% 12% 3 2	204
January	1st to 10th	Night	23% 19% 37% 18% 3	760
	11th to 20th	Night	30% 19% 35% 14% 2	760
	21st to end	Night	22% 22% 35% 17% 3	836
February	1st to 10th	Night	24% 19% 37% 19% 1	760
	11th to 20th	Night	26% 22% 37% 13% 1	743
	21st to end	Night	26% 21% 33% 16% 3	628
March	1st to 10th	Night	25% 18% 36% 17% 4	760
	11th to 20th	Night	21% 23% 36% 17% 3	760
	21st to end	Night	27% 19% 34% 16% 4	836
April	1st to 10th	Night	25% 20% 34% 18% 3	760
	11th to 20th	Night	23% 19% 35% 18% 4	746
	21st to end	Night	25% 18% 37% 17% 3	570
May	1st to 10th	Night	29% 14% 31% 20% 4	570
	11th to 20th	Night	23% 16% 37% 22% 2	562
	21st to end	Night	21% 7% 36% 29% 6%	419
June	1st to 10th	Night	17% 10% 33% 31% 9%	380
	11th to 20th	Night	21% 6% 37% 29% 6%	380
	21st to end	Night	19% 4 36% 34% 6% 1	380
July	1st to 10th	Night	16% 4 33% 38% 9%	370
	11th to 20th	Night	15% 4 33% 38% 9% 1	368
	21st to end	Night	16% 4 30% 41% 9%	416
August	1st to 10th	Night	15% 5% 34% 36% 9%	539
	11th to 20th	Night	13% 5% 30% 39% 12%	605
	21st to end	Night	15% 6% 25% 37% 16% 2	836
September	1st to 10th	Night	18% 6% 31% 34% 11% 1	760
	11th to 20th	Night	18% 7% 28% 28% 17% 3	760
	21st to end	Night	25% 7% 28% 27% 11% 2	760
October	1st to 10th	Night	25% 10% 26% 25% 12% 2	760
	11th to 20th	Night	19% 11% 35% 23% 12% 1	760
	21st to end	Night	24% 15% 33% 21% 7%	836
November	1st to 10th	Night	18% 15% 33% 24% 9% 1	780
	11th to 20th	Night	23% 18% 35% 18% 6%	800
	21st to end	Night	23% 20% 32% 21% 4 1	800
December	1st to 10th	Night	26% 17% 35% 17% 5%	800
	11th to 20th	Night	28% 18% 32% 20% 2	800
	21st to end	Night	26% 19% 35% 17% 2	851

Page generated at 2024-12-21 04:13:49. Version ac07

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