Cat's Eye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cat's Eye Observatory clear sky chart from 2005-11-06 to 2025-02-06.

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	10% 6% 2 5% 4 4 4 3 5% 7% 49%	109049
	Night	11% 6% 2 5% 3 3 3 3 5% 6% 53%	109444
Transparency	Day	32% 6% 10% 20% 20% 11%	112906
	Night	31% 5% 10% 20% 21% 13%	113714
Seeing	Day	12% 9% 25% 31% 19% 5%	15119
	Night	12% 9% 31% 35% 13% 1	25195

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	11% 8% 3 6% 2 3 3 3 3 4 54%	4077
	11th to 20th	Day	11% 7% 2 4 3 2 3 2 4 6% 56%	4080
	21st to end	Day	20% 6% 2 6% 3 2 3 2 3 6% 47%	4972
February	1st to 10th	Day	14% 6% 2 6% 4 3 3 2 4 5% 51%	1950
	11th to 20th	Day	14% 6% 2 5% 4 4 4 3 4 6% 48%	1849
	21st to end	Day	13% 7% 2 4 2 3 3 3 4 6% 52%	1570
March	1st to 10th	Day	14% 7% 3 6% 4 3 3 3 5% 6% 47%	3302
	11th to 20th	Day	16% 10% 3 8% 4 5% 5% 3 5% 5% 36%	3480
	21st to end	Day	10% 7% 2 6% 4 3 4 3 5% 7% 48%	3814
April	1st to 10th	Day	11% 7% 2 6% 4 4 4 4 5% 7% 46%	2090
	11th to 20th	Day	16% 6% 2 6% 4 3 4 3 5% 6% 46%	2173
	21st to end	Day	11% 7% 2 5% 6% 4 4 3 4 5% 49%	2362
May	1st to 10th	Day	18% 8% 3 6% 4 5% 4 4 6% 7% 37%	4082
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 5% 6% 45%	4082
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 8% 40%	4477
June	1st to 10th	Day	5% 4 2 5% 5% 4 5% 4 6% 9% 52%	2470
	11th to 20th	Day	5% 5% 2 5% 5% 4 4 4 7% 10% 50%	2470
	21st to end	Day	6% 4 2 5% 6% 5% 6% 5% 7% 9% 44%	2470
July	1st to 10th	Day	5% 5% 2 6% 5% 5% 6% 5% 6% 9% 47%	4120
	11th to 20th	Day	3 3 2 4 4 4 5% 4 6% 10% 55%	4120
	21st to end	Day	8% 5% 2 5% 5% 5% 6% 4 8% 9% 43%	4465
August	1st to 10th	Day	1 1 1 3 3 3 3 3 6% 9% 67%	3923
	11th to 20th	Day	4 2 1 3 3 4 4 4 5% 10% 60%	3726
	21st to end	Day	4 3 2 5% 5% 6% 6% 5% 7% 11% 47%	4101
September	1st to 10th	Day	9% 6% 3 8% 6% 5% 4 3 5% 6% 46%	2090
	11th to 20th	Day	9% 7% 2 8% 5% 5% 5% 4 6% 7% 43%	2090
	21st to end	Day	10% 3 2 5% 4 4 4 4 7% 7% 50%	2090
October	1st to 10th	Day	5% 4 2 5% 4 4 4 3 5% 7% 57%	2090
	11th to 20th	Day	11% 6% 2 4 4 3 3 3 5% 6% 54%	2022
	21st to end	Day	11% 5% 1 4 3 3 3 3 3 5% 59%	2090
November	1st to 10th	Day	13% 7% 2 5% 4 3 3 3 5% 5% 49%	1933
	11th to 20th	Day	8% 5% 1 5% 3 3 5% 3 5% 7% 54%	1800
	21st to end	Day	13% 7% 2 6% 4 3 4 2 3 6% 50%	1800
December	1st to 10th	Day	19% 10% 3 7% 3 3 2 2 4 4 42%	2940
	11th to 20th	Day	11% 9% 3 7% 4 3 4 3 5% 6% 45%	3391
	21st to end	Day	10% 6% 2 5% 3 2 2 2 3 4 61%	4488
January	1st to 10th	Night	13% 6% 2 6% 2 2 2 2 3 5% 55%	5888
	11th to 20th	Night	10% 3 2 3 2 2 2 2 4 6% 65%	5900
	21st to end	Night	25% 6% 2 5% 3 3 3 2 4 5% 43%	6048
February	1st to 10th	Night	13% 6% 2 6% 4 3 2 2 4 4 52%	2340
	11th to 20th	Night	14% 6% 2 6% 3 4 3 3 4 5% 51%	2218
	21st to end	Night	13% 8% 2 5% 4 3 3 3 4 6% 50%	1884
March	1st to 10th	Night	10% 9% 2 6% 4 4 4 3 5% 7% 46%	3554
	11th to 20th	Night	16% 11% 2 6% 5% 4 4 4 5% 5% 37%	3480
	21st to end	Night	10% 9% 2 6% 3 3 3 3 4 6% 49%	3817
April	1st to 10th	Night	8% 7% 2 6% 3 4 3 3 5% 6% 51%	2090
	11th to 20th	Night	13% 8% 2 5% 3 3 3 3 4 6% 48%	1951
	21st to end	Night	13% 7% 2 5% 4 3 3 3 4 6% 50%	1815
May	1st to 10th	Night	19% 12% 3 5% 3 2 2 3 4 6% 40%	2823
	11th to 20th	Night	10% 6% 3 5% 3 4 4 4 5% 7% 50%	2823
	21st to end	Night	11% 7% 2 4 3 4 4 4 6% 8% 47%	3090
June	1st to 10th	Night	3 4 2 3 3 2 4 3 7% 10% 60%	1710
	11th to 20th	Night	4 4 1 4 2 3 4 3 5% 8% 62%	1710
	21st to end	Night	5% 4 1 4 3 4 4 5% 7% 8% 55%	1710
July	1st to 10th	Night	4 4 1 4 4 4 4 4 6% 10% 55%	2850
	11th to 20th	Night	2 2 1 4 3 3 3 3 6% 9% 63%	2850
	21st to end	Night	6% 7% 2 6% 3 4 4 4 7% 10% 47%	3098
August	1st to 10th	Night	1 1 2 2 2 3 3 4 6% 76%	3012
	11th to 20th	Night	3 2 1 3 2 3 4 4 6% 10% 62%	3113
	21st to end	Night	3 5% 1 5% 3 3 4 4 7% 10% 54%	3549
September	1st to 10th	Night	8% 5% 2 5% 3 5% 4 3 5% 8% 51%	2090
	11th to 20th	Night	8% 7% 2 6% 4 4 5% 3 6% 8% 47%	2090
	21st to end	Night	7% 5% 2 4 4 3 5% 3 6% 8% 53%	2090
October	1st to 10th	Night	4 4 1 4 3 3 3 3 4 7% 64%	2090
	11th to 20th	Night	10% 5% 2 4 3 3 3 3 4 6% 56%	2137
	21st to end	Night	12% 6% 2 4 3 2 3 2 3 3 61%	2508
November	1st to 10th	Night	11% 6% 2 6% 3 3 2 2 3 6% 56%	2360
	11th to 20th	Night	8% 6% 1 5% 3 3 3 3 5% 6% 59%	2600
	21st to end	Night	14% 6% 2 5% 3 3 3 3 5% 6% 50%	2600
December	1st to 10th	Night	19% 8% 3 5% 3 4 4 3 4 5% 43%	4250
	11th to 20th	Night	15% 11% 2 5% 3 2 3 2 3 5% 48%	4816
	21st to end	Night	12% 7% 2 4 2 2 2 2 3 4 60%	6490

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% 5% 4 20% 23% 15%	4078
	11th to 20th	Day	30% 3 5% 16% 27% 19%	4080
	21st to end	Day	40% 3 5% 10% 27% 15%	4972
February	1st to 10th	Day	36% 4 7% 13% 21% 19%	1950
	11th to 20th	Day	37% 4 6% 18% 19% 16%	1859
	21st to end	Day	34% 4 7% 16% 22% 17%	1570
March	1st to 10th	Day	38% 5% 7% 13% 20% 16%	3302
	11th to 20th	Day	48% 8% 8% 10% 16% 10%	3480
	21st to end	Day	33% 7% 10% 16% 20% 15%	3814
April	1st to 10th	Day	37% 5% 9% 16% 18% 14%	2090
	11th to 20th	Day	39% 5% 8% 16% 20% 12%	2173
	21st to end	Day	38% 6% 6% 20% 19% 11%	2362
May	1st to 10th	Day	45% 8% 11% 13% 17% 7%	4120
	11th to 20th	Day	39% 6% 10% 16% 21% 9%	4086
	21st to end	Day	36% 10% 13% 26% 12% 4	4489
June	1st to 10th	Day	28% 7% 14% 27% 20% 4	2470
	11th to 20th	Day	29% 7% 13% 25% 21% 6%	2470
	21st to end	Day	34% 10% 12% 22% 18% 5%	2470
July	1st to 10th	Day	30% 8% 17% 37% 7%	4056
	11th to 20th	Day	22% 8% 16% 34% 17% 3	4051
	21st to end	Day	30% 9% 18% 29% 13% 1	4325
August	1st to 10th	Day	14% 5% 12% 38% 30% 1	3909
	11th to 20th	Day	19% 6% 22% 38% 13% 2	3762
	21st to end	Day	28% 11% 17% 24% 18% 2	4100
September	1st to 10th	Day	39% 7% 10% 19% 18% 9%	2090
	11th to 20th	Day	39% 7% 12% 18% 18% 6%	2090
	21st to end	Day	31% 7% 10% 20% 19% 13%	2090
October	1st to 10th	Day	16% 4 7% 11% 27% 36%	3480
	11th to 20th	Day	25% 4 6% 18% 24% 22%	3340
	21st to end	Day	23% 5% 6% 17% 37% 13%	3428
November	1st to 10th	Day	37% 5% 8% 17% 21% 12%	1933
	11th to 20th	Day	30% 5% 9% 16% 21% 19%	1800
	21st to end	Day	37% 4 5% 18% 22% 15%	1800
December	1st to 10th	Day	46% 3 6% 16% 19% 10%	2940
	11th to 20th	Day	38% 6% 8% 11% 23% 14%	3389
	21st to end	Day	28% 3 4 15% 27% 22%	4488
January	1st to 10th	Night	32% 3 5% 18% 26% 16%	5888
	11th to 20th	Night	22% 2 4 19% 28% 26%	5900
	21st to end	Night	44% 3 4 9% 21% 17%	6048
February	1st to 10th	Night	35% 4 8% 11% 22% 20%	2340
	11th to 20th	Night	35% 4 6% 17% 20% 17%	2218
	21st to end	Night	37% 4 6% 12% 22% 19%	1884
March	1st to 10th	Night	36% 6% 8% 14% 22% 13%	3554
	11th to 20th	Night	46% 8% 8% 12% 15% 11%	3480
	21st to end	Night	35% 6% 11% 16% 18% 15%	3817
April	1st to 10th	Night	34% 5% 10% 19% 16% 17%	2090
	11th to 20th	Night	38% 5% 9% 14% 18% 16%	1951
	21st to end	Night	36% 5% 9% 19% 21% 10%	1815
May	1st to 10th	Night	45% 6% 9% 17% 13% 10%	2850
	11th to 20th	Night	31% 8% 12% 21% 18% 10%	2824
	21st to end	Night	33% 8% 14% 28% 12% 5%	3099
June	1st to 10th	Night	18% 9% 16% 33% 21% 3	1710
	11th to 20th	Night	21% 6% 16% 29% 23% 6%	1710
	21st to end	Night	25% 7% 16% 29% 19% 5%	1710
July	1st to 10th	Night	22% 9% 23% 38% 7% 1	2805
	11th to 20th	Night	18% 8% 18% 36% 18% 2	2796
	21st to end	Night	30% 8% 23% 29% 10% 1	2999
August	1st to 10th	Night	11% 5% 14% 42% 28% 1	3002
	11th to 20th	Night	16% 7% 28% 35% 11% 2	3143
	21st to end	Night	23% 11% 20% 24% 19% 2	3549
September	1st to 10th	Night	31% 7% 13% 23% 18% 9%	2090
	11th to 20th	Night	34% 8% 15% 21% 16% 6%	2090
	21st to end	Night	28% 7% 11% 21% 18% 14%	2090
October	1st to 10th	Night	13% 3 9% 15% 22% 37%	3480
	11th to 20th	Night	22% 3 10% 16% 30% 20%	3545
	21st to end	Night	24% 4 5% 19% 33% 15%	4120
November	1st to 10th	Night	32% 4 8% 19% 22% 15%	2360
	11th to 20th	Night	27% 4 8% 21% 21% 19%	2600
	21st to end	Night	36% 4 8% 16% 20% 16%	2600
December	1st to 10th	Night	44% 4 7% 16% 17% 12%	4250
	11th to 20th	Night	40% 4 5% 12% 20% 19%	4817
	21st to end	Night	30% 3 4 16% 29% 18%	6490

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	18% 16% 41% 20% 4 1	300
	11th to 20th	Day	22% 15% 36% 20% 6% 1	300
	21st to end	Day	16% 20% 38% 21% 5%	330
February	1st to 10th	Day	24% 14% 34% 21% 7%	285
	11th to 20th	Day	23% 18% 40% 17% 2	270
	21st to end	Day	22% 20% 41% 15% 2	225
March	1st to 10th	Day	18% 20% 42% 18% 2	270
	11th to 20th	Day	19% 20% 36% 19% 6%	270
	21st to end	Day	16% 21% 43% 15% 3 1	297
April	1st to 10th	Day	16% 23% 41% 17% 3	270
	11th to 20th	Day	18% 21% 39% 18% 4	371
	21st to end	Day	14% 19% 42% 19% 6%	542
May	1st to 10th	Day	14% 14% 42% 26% 4	653
	11th to 20th	Day	18% 10% 33% 27% 10% 1	675
	21st to end	Day	14% 10% 31% 32% 12% 1	734
June	1st to 10th	Day	5% 3 23% 43% 23% 4	680
	11th to 20th	Day	7% 2 21% 51% 17% 3	680
	21st to end	Day	6% 2 14% 42% 29% 6%	680
July	1st to 10th	Day	5% 3 13% 38% 31% 10%	671
	11th to 20th	Day	3 1 7% 43% 38% 8%	668
	21st to end	Day	4 1 6% 42% 37% 10%	739
August	1st to 10th	Day	2 4 41% 40% 13%	573
	11th to 20th	Day	7% 3 5% 34% 38% 13%	477
	21st to end	Day	5% 2 7% 28% 43% 16%	499
September	1st to 10th	Day	10% 1 8% 28% 36% 17%	300
	11th to 20th	Day	6% 2 7% 32% 38% 16%	300
	21st to end	Day	12% 1 6% 33% 37% 11%	300
October	1st to 10th	Day	5% 2 15% 38% 32% 8%	300
	11th to 20th	Day	10% 5% 27% 35% 20% 3	300
	21st to end	Day	18% 15% 28% 23% 14% 2	330
November	1st to 10th	Day	21% 9% 29% 31% 8% 3	300
	11th to 20th	Day	17% 12% 30% 25% 10% 6%	300
	21st to end	Day	20% 18% 34% 19% 6% 3	300
December	1st to 10th	Day	17% 11% 34% 27% 8% 2	300
	11th to 20th	Day	17% 18% 36% 22% 7% 1	300
	21st to end	Day	15% 14% 37% 25% 8%	330
January	1st to 10th	Night	16% 11% 37% 29% 6% 1	1000
	11th to 20th	Night	16% 13% 37% 29% 5%	1000
	21st to end	Night	18% 12% 37% 27% 6%	905
February	1st to 10th	Night	19% 14% 37% 25% 5%	780
	11th to 20th	Night	17% 15% 42% 23% 2	744
	21st to end	Night	18% 17% 47% 17% 1	628
March	1st to 10th	Night	17% 16% 41% 25% 2	658
	11th to 20th	Night	17% 11% 40% 27% 4	570
	21st to end	Night	12% 15% 50% 21% 3	627
April	1st to 10th	Night	9% 15% 51% 22% 3	570
	11th to 20th	Night	16% 16% 44% 22% 2	563
	21st to end	Night	13% 12% 51% 19% 6%	570
May	1st to 10th	Night	13% 13% 45% 26% 3	570
	11th to 20th	Night	12% 8% 40% 32% 8% 1	561
	21st to end	Night	13% 8% 36% 33% 10%	617
June	1st to 10th	Night	3 2 28% 48% 18% 1	570
	11th to 20th	Night	5% 2 35% 47% 11%	570
	21st to end	Night	5% 3 18% 51% 21% 2	570
July	1st to 10th	Night	6% 2 12% 52% 26% 2	555
	11th to 20th	Night	3 1 11% 57% 26% 2	552
	21st to end	Night	3 1 9% 58% 26% 3	624
August	1st to 10th	Night	1 6% 60% 31% 3	567
	11th to 20th	Night	5% 1 7% 53% 31% 3	564
	21st to end	Night	4 1 9% 46% 35% 4	627
September	1st to 10th	Night	9% 1 11% 43% 32% 4	570
	11th to 20th	Night	11% 1 8% 44% 33% 2	570
	21st to end	Night	9% 1 14% 47% 27% 2	570
October	1st to 10th	Night	5% 2 17% 47% 27% 2	570
	11th to 20th	Night	11% 4 25% 43% 14% 2	617
	21st to end	Night	15% 9% 29% 29% 17% 1	836
November	1st to 10th	Night	13% 8% 27% 38% 13% 1	800
	11th to 20th	Night	10% 8% 34% 34% 13% 1	1000
	21st to end	Night	16% 11% 33% 30% 9% 1	1000
December	1st to 10th	Night	15% 11% 32% 35% 7% 1	1000
	11th to 20th	Night	20% 10% 35% 30% 6%	1000
	21st to end	Night	15% 11% 36% 31% 6%	1100

Page generated at 2025-02-03 02:05:52. Version ac07

Copyright © 2025 Attilla Danko.