Carvel Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Carvel Observatory clear sky chart from 2005-11-06 to 2026-09-14.

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	9% 9% 3 8% 5% 5% 5% 4 6% 8% 36%	155385
	Night	9% 10% 4 10% 6% 5% 5% 4 6% 8% 33%	144420
Transparency	Day	43% 7% 17% 24% 8% 1	155081
	Night	47% 7% 16% 21% 9% 1	144307
Seeing	Day	13% 7% 24% 31% 18% 6%	18427
	Night	14% 6% 28% 35% 16% 2	26690

By Month

Percentage Cloud Cover NW (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	7% 15% 5% 11% 7% 5% 5% 4 6% 8% 27%	4125
	11th to 20th	Day	4 7% 3 8% 7% 6% 6% 5% 7% 9% 38%	4119
	21st to end	Day	6% 12% 4 9% 6% 6% 6% 4 5% 8% 35%	4982
February	1st to 10th	Day	9% 12% 5% 11% 7% 7% 7% 4 7% 8% 23%	1680
	11th to 20th	Day	6% 12% 5% 12% 7% 6% 7% 4 6% 7% 28%	1756
	21st to end	Day	3 15% 5% 11% 9% 7% 6% 5% 7% 6% 25%	1648
March	1st to 10th	Day	4 11% 4 10% 7% 6% 5% 4 6% 10% 31%	4618
	11th to 20th	Day	6% 12% 4 10% 5% 4 4 4 6% 8% 37%	5008
	21st to end	Day	10% 15% 5% 14% 6% 6% 5% 4 6% 7% 23%	5773
April	1st to 10th	Day	8% 14% 3 9% 6% 5% 5% 5% 7% 8% 30%	2597
	11th to 20th	Day	11% 10% 4 8% 6% 6% 5% 5% 7% 8% 31%	2700
	21st to end	Day	10% 10% 4 9% 6% 6% 5% 4 6% 7% 33%	2734
May	1st to 10th	Day	10% 7% 2 7% 5% 5% 5% 4 6% 8% 40%	8571
	11th to 20th	Day	12% 10% 4 9% 6% 6% 6% 5% 7% 8% 26%	8755
	21st to end	Day	11% 6% 2 8% 6% 6% 6% 5% 7% 10% 34%	9649
June	1st to 10th	Day	17% 7% 3 7% 5% 5% 5% 4 6% 7% 32%	3150
	11th to 20th	Day	18% 8% 3 9% 7% 6% 7% 5% 6% 7% 24%	3334
	21st to end	Day	11% 6% 2 6% 4 5% 6% 4 7% 10% 38%	3360
July	1st to 10th	Day	8% 4 2 5% 4 5% 5% 5% 8% 10% 45%	9283
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 4 6% 8% 43%	8820
	21st to end	Day	10% 5% 2 5% 4 5% 5% 4 7% 9% 45%	9569
August	1st to 10th	Day	12% 6% 2 6% 4 5% 5% 5% 7% 9% 39%	6518
	11th to 20th	Day	11% 6% 2 6% 5% 5% 5% 5% 7% 9% 40%	6171
	21st to end	Day	8% 4 2 6% 4 4 5% 4 8% 9% 45%	6570
September	1st to 10th	Day	12% 7% 3 6% 4 4 4 3 6% 8% 43%	2642
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 5% 9% 43%	2250
	21st to end	Day	9% 7% 3 8% 5% 5% 5% 4 6% 9% 40%	2200
October	1st to 10th	Day	9% 9% 3 8% 5% 4 5% 4 5% 7% 41%	3425
	11th to 20th	Day	10% 12% 4 7% 4 4 5% 5% 6% 8% 35%	2932
	21st to end	Day	7% 12% 4 9% 5% 5% 5% 4 6% 7% 35%	3200
November	1st to 10th	Day	11% 17% 4 10% 6% 5% 5% 4 6% 7% 25%	1654
	11th to 20th	Day	7% 12% 5% 11% 6% 5% 4 4 5% 7% 33%	1475
	21st to end	Day	6% 11% 5% 15% 6% 6% 6% 4 6% 8% 27%	1470
December	1st to 10th	Day	10% 16% 6% 12% 6% 6% 6% 4 6% 7% 21%	2360
	11th to 20th	Day	8% 13% 5% 13% 8% 6% 6% 4 5% 8% 23%	2712
	21st to end	Day	3 8% 3 9% 5% 5% 5% 4 6% 9% 41%	3575
January	1st to 10th	Night	8% 14% 6% 14% 8% 6% 5% 3 5% 6% 24%	8768
	11th to 20th	Night	3 8% 4 10% 7% 6% 5% 5% 6% 7% 39%	8779
	21st to end	Night	7% 13% 4 10% 6% 4 5% 4 6% 8% 33%	9257
February	1st to 10th	Night	6% 13% 5% 13% 8% 7% 5% 4 6% 7% 27%	2940
	11th to 20th	Night	6% 12% 5% 11% 8% 7% 6% 6% 6% 6% 28%	2750
	21st to end	Night	5% 14% 5% 11% 7% 6% 6% 4 5% 8% 29%	2155
March	1st to 10th	Night	3 10% 5% 12% 8% 6% 5% 4 6% 9% 32%	5496
	11th to 20th	Night	5% 11% 4 11% 7% 6% 6% 5% 8% 8% 28%	5211
	21st to end	Night	11% 15% 6% 14% 6% 6% 5% 4 5% 5% 24%	5442
April	1st to 10th	Night	8% 10% 4 11% 7% 7% 6% 5% 7% 7% 29%	2022
	11th to 20th	Night	8% 12% 4 11% 7% 5% 6% 4 7% 7% 28%	1871
	21st to end	Night	12% 10% 4 9% 4 4 5% 4 6% 9% 34%	1884
May	1st to 10th	Night	13% 8% 3 7% 5% 5% 4 4 5% 7% 38%	4348
	11th to 20th	Night	12% 9% 4 11% 8% 7% 6% 5% 7% 7% 25%	4105
	21st to end	Night	11% 8% 2 7% 5% 5% 6% 4 6% 9% 37%	4522
June	1st to 10th	Night	18% 8% 3 9% 5% 5% 5% 5% 5% 7% 30%	1470
	11th to 20th	Night	16% 10% 4 9% 7% 7% 7% 6% 7% 8% 19%	1281
	21st to end	Night	12% 7% 2 7% 5% 6% 6% 5% 7% 9% 34%	1260
July	1st to 10th	Night	8% 5% 2 7% 4 5% 5% 4 7% 10% 43%	3660
	11th to 20th	Night	13% 6% 2 7% 5% 5% 6% 4 6% 9% 38%	4140
	21st to end	Night	12% 4 2 6% 4 4 4 4 6% 9% 45%	4499
August	1st to 10th	Night	15% 7% 3 7% 5% 5% 5% 4 6% 7% 35%	3629
	11th to 20th	Night	13% 7% 3 8% 5% 5% 6% 4 6% 8% 35%	3883
	21st to end	Night	11% 4 2 6% 4 5% 5% 4 6% 9% 44%	4578
September	1st to 10th	Night	12% 6% 2 7% 4 4 4 4 6% 8% 44%	1975
	11th to 20th	Night	11% 7% 3 5% 5% 4 4 5% 6% 8% 44%	2217
	21st to end	Night	11% 7% 3 6% 4 4 5% 4 6% 9% 41%	2200
October	1st to 10th	Night	9% 7% 3 8% 5% 5% 5% 5% 6% 8% 39%	3765
	11th to 20th	Night	9% 8% 3 8% 4 5% 5% 5% 6% 8% 38%	4216
	21st to end	Night	7% 10% 4 9% 6% 5% 6% 4 6% 8% 35%	4600
November	1st to 10th	Night	13% 15% 6% 10% 6% 5% 4 3 5% 7% 26%	2843
	11th to 20th	Night	8% 13% 6% 11% 6% 6% 5% 4 6% 7% 28%	3141
	21st to end	Night	7% 13% 5% 11% 7% 7% 5% 4 6% 7% 28%	3150
December	1st to 10th	Night	10% 18% 5% 11% 6% 5% 5% 4 5% 6% 24%	5040
	11th to 20th	Night	9% 16% 6% 12% 7% 6% 6% 4 5% 7% 22%	5700
	21st to end	Night	3 9% 4 10% 6% 5% 5% 4 6% 7% 41%	7623

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	55% 4 13% 15% 12% 1	4125
	11th to 20th	Day	41% 5% 16% 17% 20% 2	4140
	21st to end	Day	48% 6% 20% 23% 4	4983
February	1st to 10th	Day	57% 5% 14% 14% 8% 1	1680
	11th to 20th	Day	53% 7% 13% 18% 9%	1764
	21st to end	Day	55% 7% 13% 18% 7% 1	1648
March	1st to 10th	Day	47% 6% 17% 20% 10%	4618
	11th to 20th	Day	44% 6% 14% 24% 11%	5009
	21st to end	Day	58% 7% 9% 18% 8% 1	5773
April	1st to 10th	Day	48% 9% 16% 20% 7% 1	2597
	11th to 20th	Day	48% 7% 14% 21% 9%	2700
	21st to end	Day	49% 6% 14% 22% 8% 2	2734
May	1st to 10th	Day	41% 5% 11% 28% 14% 1	8571
	11th to 20th	Day	51% 8% 12% 24% 6%	8759
	21st to end	Day	42% 8% 20% 23% 6% 1	9650
June	1st to 10th	Day	48% 6% 15% 21% 8% 1	3150
	11th to 20th	Day	56% 8% 15% 15% 5%	3334
	21st to end	Day	39% 9% 22% 24% 5% 1	3360
July	1st to 10th	Day	31% 8% 22% 29% 8% 1	9206
	11th to 20th	Day	37% 7% 18% 27% 10% 1	8739
	21st to end	Day	33% 8% 23% 26% 10%	9362
August	1st to 10th	Day	39% 8% 23% 28% 2	6500
	11th to 20th	Day	36% 9% 22% 28% 5%	6213
	21st to end	Day	31% 8% 25% 31% 5%	6569
September	1st to 10th	Day	39% 7% 20% 26% 7% 2	2642
	11th to 20th	Day	38% 6% 18% 30% 8%	2250
	21st to end	Day	39% 6% 18% 26% 9% 2	2200
October	1st to 10th	Day	41% 7% 23% 23% 6%	3425
	11th to 20th	Day	45% 6% 14% 25% 10%	2932
	21st to end	Day	46% 6% 18% 25% 5%	3200
November	1st to 10th	Day	56% 6% 15% 16% 6% 1	1654
	11th to 20th	Day	50% 6% 17% 19% 8%	1475
	21st to end	Day	53% 7% 15% 17% 6% 1	1470
December	1st to 10th	Day	61% 7% 16% 11% 5% 1	2360
	11th to 20th	Day	58% 7% 15% 14% 5%	2714
	21st to end	Day	38% 5% 13% 28% 14% 2	3575
January	1st to 10th	Night	60% 4 11% 13% 10% 1	8769
	11th to 20th	Night	43% 5% 16% 18% 16% 2	8820
	21st to end	Night	49% 5% 20% 19% 7%	9257
February	1st to 10th	Night	56% 5% 12% 18% 8% 1	2940
	11th to 20th	Night	53% 7% 13% 15% 11% 1	2752
	21st to end	Night	52% 6% 11% 21% 10% 1	2155
March	1st to 10th	Night	47% 6% 17% 22% 9%	5496
	11th to 20th	Night	48% 7% 16% 19% 10%	5211
	21st to end	Night	59% 7% 9% 18% 7%	5442
April	1st to 10th	Night	51% 8% 12% 19% 9% 1	2022
	11th to 20th	Night	52% 7% 12% 18% 9% 2	1871
	21st to end	Night	46% 7% 13% 22% 12% 1	1884
May	1st to 10th	Night	43% 6% 9% 25% 15% 2	4345
	11th to 20th	Night	53% 9% 12% 20% 7%	4105
	21st to end	Night	42% 7% 21% 23% 7% 1	4526
June	1st to 10th	Night	52% 7% 12% 19% 9% 1	1470
	11th to 20th	Night	59% 9% 15% 14% 3	1281
	21st to end	Night	42% 11% 20% 22% 4 1	1260
July	1st to 10th	Night	34% 8% 23% 24% 11%	3628
	11th to 20th	Night	40% 8% 17% 26% 7% 1	4098
	21st to end	Night	34% 8% 23% 27% 7% 1	4401
August	1st to 10th	Night	46% 7% 20% 25% 1	3622
	11th to 20th	Night	44% 9% 20% 22% 5%	3907
	21st to end	Night	34% 7% 22% 30% 6%	4578
September	1st to 10th	Night	37% 7% 18% 25% 11% 2	1975
	11th to 20th	Night	38% 6% 16% 28% 10% 2	2217
	21st to end	Night	38% 7% 16% 25% 13% 2	2200
October	1st to 10th	Night	41% 7% 20% 25% 7%	3765
	11th to 20th	Night	41% 7% 14% 29% 8%	4216
	21st to end	Night	44% 7% 21% 23% 5%	4600
November	1st to 10th	Night	58% 6% 10% 19% 7% 1	2843
	11th to 20th	Night	54% 7% 13% 19% 7% 1	3141
	21st to end	Night	53% 6% 15% 19% 6% 2	3150
December	1st to 10th	Night	60% 7% 14% 14% 5% 1	5040
	11th to 20th	Night	60% 6% 15% 13% 5%	5697
	21st to end	Night	41% 5% 14% 25% 14% 2	7623

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	10% 5% 31% 30% 20% 4	220
	11th to 20th	Day	12% 10% 27% 30% 14% 7%	220
	21st to end	Day	14% 9% 29% 26% 17% 5%	242
February	1st to 10th	Day	14% 6% 30% 35% 13% 3	220
	11th to 20th	Day	12% 5% 35% 31% 15% 2	282
	21st to end	Day	9% 7% 35% 30% 13% 6%	364
March	1st to 10th	Day	14% 8% 27% 31% 18% 2	540
	11th to 20th	Day	10% 6% 33% 32% 14% 5%	540
	21st to end	Day	14% 9% 27% 30% 16% 4	594
April	1st to 10th	Day	10% 14% 31% 28% 13% 3	540
	11th to 20th	Day	14% 11% 24% 28% 17% 6%	532
	21st to end	Day	15% 10% 27% 26% 17% 5%	540
May	1st to 10th	Day	14% 10% 23% 33% 16% 4	674
	11th to 20th	Day	12% 7% 22% 36% 18% 6%	775
	21st to end	Day	16% 6% 21% 32% 19% 7%	844
June	1st to 10th	Day	18% 11% 23% 30% 13% 4	780
	11th to 20th	Day	20% 7% 22% 25% 21% 6%	964
	21st to end	Day	13% 4 19% 31% 24% 9%	990
July	1st to 10th	Day	11% 4 19% 36% 21% 8%	932
	11th to 20th	Day	11% 4 21% 32% 23% 9%	768
	21st to end	Day	10% 6% 16% 30% 27% 11%	849
August	1st to 10th	Day	10% 5% 17% 30% 23% 14%	605
	11th to 20th	Day	9% 5% 24% 32% 23% 7%	557
	21st to end	Day	13% 6% 16% 29% 25% 11%	627
September	1st to 10th	Day	15% 7% 25% 28% 17% 8%	570
	11th to 20th	Day	16% 6% 20% 30% 21% 7%	543
	21st to end	Day	11% 11% 31% 28% 14% 5%	530
October	1st to 10th	Day	14% 6% 25% 34% 16% 5%	437
	11th to 20th	Day	15% 8% 29% 26% 16% 5%	330
	21st to end	Day	13% 15% 34% 25% 10% 3	363
November	1st to 10th	Day	19% 5% 34% 28% 12% 2	330
	11th to 20th	Day	12% 6% 38% 29% 13% 2	223
	21st to end	Day	7% 8% 30% 39% 10% 6%	220
December	1st to 10th	Day	14% 7% 30% 33% 10% 5%	220
	11th to 20th	Day	10% 12% 32% 29% 15% 2	220
	21st to end	Day	9% 5% 23% 36% 22% 6%	242
January	1st to 10th	Night	13% 6% 32% 34% 14% 2	1050
	11th to 20th	Night	11% 10% 31% 34% 12% 2	1050
	21st to end	Night	14% 11% 33% 29% 11% 1	1018
February	1st to 10th	Night	10% 9% 26% 35% 18% 3	840
	11th to 20th	Night	11% 6% 32% 36% 14% 1	824
	21st to end	Night	9% 5% 29% 35% 17% 4	692
March	1st to 10th	Night	9% 5% 31% 36% 17% 2	840
	11th to 20th	Night	12% 5% 30% 36% 15% 2	840
	21st to end	Night	15% 5% 25% 38% 14% 3	924
April	1st to 10th	Night	12% 9% 26% 38% 14% 2	762
	11th to 20th	Night	14% 9% 29% 33% 14% 1	623
	21st to end	Night	16% 7% 26% 37% 14%	624
May	1st to 10th	Night	16% 5% 25% 39% 13% 2	420
	11th to 20th	Night	13% 4 26% 37% 19% 1	414
	21st to end	Night	19% 6% 20% 37% 16% 2	455
June	1st to 10th	Night	20% 7% 26% 31% 14% 1	420
	11th to 20th	Night	20% 5% 21% 33% 20% 2	420
	21st to end	Night	14% 5% 17% 38% 24% 2	420
July	1st to 10th	Night	14% 4 14% 46% 22% 1	410
	11th to 20th	Night	13% 5% 18% 42% 20% 2	408
	21st to end	Night	13% 2 18% 38% 26% 2	460
August	1st to 10th	Night	12% 6% 16% 33% 29% 4	418
	11th to 20th	Night	12% 4 17% 37% 28% 2	505
	21st to end	Night	13% 3 19% 40% 24% 1	693
September	1st to 10th	Night	15% 3 18% 40% 22% 2	715
	11th to 20th	Night	14% 4 18% 42% 20% 2	812
	21st to end	Night	14% 6% 29% 35% 15% 2	800
October	1st to 10th	Night	16% 4 26% 37% 16% 1	800
	11th to 20th	Night	13% 6% 33% 32% 15% 2	800
	21st to end	Night	13% 8% 32% 32% 13% 1	880
November	1st to 10th	Night	21% 7% 29% 32% 10% 2	998
	11th to 20th	Night	13% 8% 35% 30% 12% 2	1050
	21st to end	Night	12% 5% 36% 36% 10% 2	1050
December	1st to 10th	Night	15% 8% 32% 31% 13% 2	1050
	11th to 20th	Night	13% 6% 32% 33% 14% 1	1050
	21st to end	Night	12% 5% 28% 36% 16% 3	1155

Page generated at 2026-09-11 02:11:54. Version ac07

Copyright © 2026 Attilla Danko.