Greencastle
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Greencastle clear sky chart from 2005-11-06 to 2024-08-30.

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	14% 9% 3 7% 5% 4 4 4 5% 8% 37%	95538
	Night	15% 10% 4 7% 4 4 4 3 5% 6% 38%	93504
Transparency	Day	45% 7% 12% 22% 13% 2	95294
	Night	46% 6% 11% 21% 14% 2	93355
Seeing	Day	17% 11% 27% 24% 16% 6%	15356
	Night	18% 9% 28% 29% 14% 1	25154

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	14% 16% 8% 11% 4 4 5% 4 4 6% 24%	2527
	11th to 20th	Day	16% 11% 6% 12% 7% 6% 6% 6% 6% 5% 19%	2530
	21st to end	Day	26% 20% 6% 9% 4 3 2 2 4 5% 18%	2893
February	1st to 10th	Day	17% 13% 6% 9% 6% 4 4 3 5% 5% 29%	1900
	11th to 20th	Day	15% 11% 4 11% 5% 5% 4 3 5% 6% 31%	1848
	21st to end	Day	16% 15% 5% 9% 4 3 3 3 5% 5% 32%	1570
March	1st to 10th	Day	22% 18% 3 7% 4 3 2 2 4 4 31%	3120
	11th to 20th	Day	13% 9% 3 6% 4 3 4 3 5% 7% 44%	3308
	21st to end	Day	16% 10% 4 8% 5% 5% 5% 4 5% 7% 31%	4068
April	1st to 10th	Day	14% 12% 3 7% 5% 3 3 3 5% 8% 36%	2280
	11th to 20th	Day	17% 9% 2 6% 4 4 4 4 5% 6% 39%	2254
	21st to end	Day	20% 7% 2 7% 4 4 4 3 5% 7% 35%	2399
May	1st to 10th	Day	18% 10% 3 8% 5% 5% 5% 4 6% 9% 28%	4082
	11th to 20th	Day	20% 7% 2 6% 4 4 4 4 4 7% 38%	4081
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 5% 6% 9% 40%	4664
June	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 5% 5% 8% 43%	2660
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 7% 9% 45%	2660
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 4 7% 9% 42%	2660
July	1st to 10th	Day	13% 6% 2 7% 4 4 5% 4 6% 10% 38%	4440
	11th to 20th	Day	6% 4 2 5% 4 5% 5% 5% 8% 12% 44%	4440
	21st to end	Day	10% 7% 2 7% 5% 4 6% 5% 7% 10% 35%	4756
August	1st to 10th	Day	8% 5% 2 5% 4 5% 5% 4 8% 11% 44%	2457
	11th to 20th	Day	10% 5% 2 6% 5% 5% 6% 4 8% 9% 41%	2268
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 6% 9% 51%	2485
September	1st to 10th	Day	12% 7% 2 5% 4 4 5% 3 5% 8% 44%	2160
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 7% 8% 47%	1980
	21st to end	Day	11% 4 2 5% 4 4 5% 3 5% 7% 50%	1980
October	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 7% 48%	1980
	11th to 20th	Day	15% 7% 2 7% 4 4 5% 3 5% 6% 42%	1831
	21st to end	Day	19% 9% 2 9% 4 4 4 4 4 6% 36%	1782
November	1st to 10th	Day	10% 7% 2 5% 4 4 4 3 6% 6% 50%	1672
	11th to 20th	Day	17% 10% 3 8% 5% 4 4 2 4 6% 38%	1710
	21st to end	Day	18% 10% 3 8% 4 4 4 3 4 5% 36%	1710
December	1st to 10th	Day	18% 15% 4 9% 5% 4 4 3 4 5% 31%	1682
	11th to 20th	Day	15% 15% 7% 9% 5% 4 4 3 3 5% 29%	1918
	21st to end	Day	21% 21% 8% 11% 5% 3 3 3 4 5% 17%	2783
January	1st to 10th	Night	17% 15% 8% 12% 5% 3 4 3 4 5% 25%	4428
	11th to 20th	Night	13% 18% 6% 14% 7% 5% 5% 4 4 4 20%	4440
	21st to end	Night	26% 17% 7% 8% 4 3 3 2 3 4 22%	4756
February	1st to 10th	Night	19% 12% 5% 10% 5% 4 3 3 4 5% 28%	2280
	11th to 20th	Night	14% 11% 4 9% 5% 4 5% 3 5% 7% 33%	2218
	21st to end	Night	19% 13% 4 8% 4 3 3 3 5% 5% 32%	1884
March	1st to 10th	Night	21% 17% 3 5% 3 3 3 2 4 5% 33%	3733
	11th to 20th	Night	13% 6% 3 6% 4 4 4 3 4 6% 47%	3650
	21st to end	Night	18% 8% 3 7% 4 4 4 3 4 6% 37%	3579
April	1st to 10th	Night	13% 10% 3 6% 4 4 4 3 6% 7% 39%	1900
	11th to 20th	Night	18% 8% 2 5% 4 3 3 3 5% 7% 41%	1875
	21st to end	Night	16% 9% 3 7% 4 4 5% 4 6% 5% 37%	1781
May	1st to 10th	Night	18% 11% 3 7% 5% 5% 4 3 5% 7% 30%	2813
	11th to 20th	Night	19% 7% 3 5% 4 4 3 4 5% 7% 41%	2812
	21st to end	Night	11% 5% 2 7% 4 4 4 4 6% 8% 44%	2881
June	1st to 10th	Night	9% 6% 3 7% 3 3 3 3 6% 8% 49%	1520
	11th to 20th	Night	8% 6% 2 6% 4 4 3 4 5% 8% 49%	1520
	21st to end	Night	6% 5% 2 5% 5% 4 5% 4 8% 11% 45%	1520
July	1st to 10th	Night	10% 5% 2 6% 3 4 4 3 6% 10% 48%	2530
	11th to 20th	Night	6% 4 2 4 3 3 4 5% 6% 9% 55%	2530
	21st to end	Night	8% 8% 3 7% 4 4 5% 4 7% 10% 40%	2801
August	1st to 10th	Night	6% 4 2 6% 4 4 5% 4 6% 9% 50%	1701
	11th to 20th	Night	6% 4 2 6% 4 5% 5% 5% 6% 9% 49%	1849
	21st to end	Night	6% 4 2 5% 3 4 3 3 5% 9% 57%	2080
September	1st to 10th	Night	11% 6% 3 5% 3 4 4 4 5% 7% 48%	1800
	11th to 20th	Night	7% 5% 1 4 3 3 4 3 6% 8% 55%	1961
	21st to end	Night	12% 4 2 5% 3 3 4 3 6% 7% 51%	1980
October	1st to 10th	Night	9% 3 3 5% 4 4 4 4 5% 6% 53%	1980
	11th to 20th	Night	17% 7% 2 5% 3 3 3 2 4 6% 47%	2124
	21st to end	Night	18% 10% 3 5% 4 3 4 3 4 6% 39%	2574
November	1st to 10th	Night	10% 7% 3 4 4 3 4 3 5% 6% 50%	2406
	11th to 20th	Night	13% 10% 3 7% 4 4 4 3 5% 7% 41%	2470
	21st to end	Night	19% 13% 4 7% 4 3 3 3 4 4 35%	2470
December	1st to 10th	Night	17% 12% 5% 9% 6% 4 3 3 5% 6% 30%	2495
	11th to 20th	Night	17% 13% 5% 9% 4 3 4 3 5% 5% 32%	3279
	21st to end	Night	23% 19% 7% 10% 5% 4 4 3 3 4 18%	4884

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	59% 6% 9% 20% 6%	2528
	11th to 20th	Day	63% 5% 14% 11% 6%	2530
	21st to end	Day	69% 4 9% 14% 3 1	2893
February	1st to 10th	Day	57% 5% 10% 17% 9% 2	1900
	11th to 20th	Day	54% 5% 11% 20% 9% 1	1858
	21st to end	Day	53% 5% 10% 21% 9% 2	1570
March	1st to 10th	Day	57% 4 7% 17% 12% 2	3120
	11th to 20th	Day	38% 7% 12% 29% 13% 1	3308
	21st to end	Day	50% 9% 14% 22% 5% 1	4068
April	1st to 10th	Day	46% 8% 11% 20% 15% 1	2280
	11th to 20th	Day	45% 6% 9% 25% 10% 4	2254
	21st to end	Day	48% 7% 11% 21% 10% 3	2399
May	1st to 10th	Day	49% 9% 15% 21% 6%	4120
	11th to 20th	Day	45% 8% 12% 25% 9%	4085
	21st to end	Day	37% 10% 12% 19% 19% 2	4677
June	1st to 10th	Day	37% 8% 12% 24% 15% 4	2660
	11th to 20th	Day	33% 8% 12% 23% 21% 3	2660
	21st to end	Day	37% 8% 16% 19% 17% 4	2660
July	1st to 10th	Day	41% 6% 12% 25% 14% 2	4371
	11th to 20th	Day	30% 8% 15% 28% 17% 1	4365
	21st to end	Day	41% 9% 15% 19% 14% 2	4606
August	1st to 10th	Day	31% 9% 15% 28% 14% 2	2444
	11th to 20th	Day	36% 9% 14% 25% 15% 1	2268
	21st to end	Day	28% 8% 14% 26% 17% 7%	2485
September	1st to 10th	Day	36% 8% 12% 24% 16% 4	2160
	11th to 20th	Day	33% 7% 12% 24% 21% 3	1980
	21st to end	Day	32% 7% 11% 25% 23% 3	1980
October	1st to 10th	Day	35% 6% 11% 25% 20% 3	1980
	11th to 20th	Day	41% 6% 10% 23% 20% 1	1831
	21st to end	Day	49% 5% 10% 22% 13% 1	1782
November	1st to 10th	Day	34% 4 14% 26% 17% 5%	1672
	11th to 20th	Day	48% 4 9% 21% 15% 4	1710
	21st to end	Day	50% 4 11% 21% 13% 1	1710
December	1st to 10th	Day	57% 5% 10% 18% 10%	1682
	11th to 20th	Day	57% 5% 7% 22% 7% 1	1915
	21st to end	Day	69% 5% 10% 10% 5%	2783
January	1st to 10th	Night	60% 7% 11% 15% 7%	4428
	11th to 20th	Night	66% 5% 9% 13% 6%	4440
	21st to end	Night	66% 4 8% 14% 8%	4756
February	1st to 10th	Night	58% 4 12% 17% 8% 1	2280
	11th to 20th	Night	51% 6% 11% 18% 13% 1	2219
	21st to end	Night	54% 5% 10% 19% 11% 2	1884
March	1st to 10th	Night	55% 4 8% 22% 10% 2	3733
	11th to 20th	Night	37% 7% 10% 23% 22% 2	3650
	21st to end	Night	46% 7% 12% 26% 8% 1	3579
April	1st to 10th	Night	43% 7% 11% 24% 14% 2	1900
	11th to 20th	Night	43% 5% 10% 20% 16% 5%	1875
	21st to end	Night	46% 7% 10% 20% 13% 4	1781
May	1st to 10th	Night	50% 11% 12% 19% 7% 1	2840
	11th to 20th	Night	41% 8% 14% 27% 10%	2813
	21st to end	Night	35% 9% 13% 21% 18% 4	2889
June	1st to 10th	Night	33% 7% 11% 26% 20% 4	1520
	11th to 20th	Night	31% 7% 12% 23% 21% 6%	1520
	21st to end	Night	31% 9% 16% 21% 19% 4	1520
July	1st to 10th	Night	33% 7% 11% 27% 19% 4	2490
	11th to 20th	Night	24% 7% 14% 31% 23% 2	2482
	21st to end	Night	38% 7% 15% 21% 15% 4	2712
August	1st to 10th	Night	29% 8% 14% 28% 18% 2	1690
	11th to 20th	Night	29% 8% 15% 26% 20% 2	1849
	21st to end	Night	25% 6% 14% 27% 21% 7%	2080
September	1st to 10th	Night	34% 8% 13% 23% 18% 6%	1800
	11th to 20th	Night	26% 6% 12% 26% 25% 4	1961
	21st to end	Night	32% 8% 10% 23% 23% 5%	1980
October	1st to 10th	Night	30% 6% 12% 24% 23% 4	1980
	11th to 20th	Night	40% 4 7% 25% 21% 3	2124
	21st to end	Night	46% 4 10% 21% 16% 3	2574
November	1st to 10th	Night	35% 6% 10% 24% 21% 4	2406
	11th to 20th	Night	42% 4 10% 24% 16% 3	2470
	21st to end	Night	52% 4 9% 22% 12% 1	2470
December	1st to 10th	Night	55% 5% 10% 19% 10% 1	2495
	11th to 20th	Night	51% 7% 11% 18% 13% 1	3281
	21st to end	Night	70% 6% 8% 10% 6% 1	4884

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	24% 17% 33% 19% 6%	270
	11th to 20th	Day	26% 20% 34% 17% 1 1	270
	21st to end	Day	27% 20% 32% 18% 2 1	297
February	1st to 10th	Day	26% 19% 37% 16% 3	270
	11th to 20th	Day	25% 24% 32% 14% 5%	270
	21st to end	Day	31% 15% 39% 12% 3	225
March	1st to 10th	Day	24% 25% 34% 14% 3	270
	11th to 20th	Day	26% 20% 34% 14% 5% 1	353
	21st to end	Day	29% 19% 31% 15% 6%	506
April	1st to 10th	Day	20% 18% 32% 20% 8% 1	460
	11th to 20th	Day	22% 17% 30% 19% 10% 2	452
	21st to end	Day	26% 17% 30% 18% 7% 2	460
May	1st to 10th	Day	19% 17% 30% 22% 9% 3	463
	11th to 20th	Day	20% 9% 29% 24% 13% 6%	487
	21st to end	Day	11% 7% 28% 27% 18% 9%	639
June	1st to 10th	Day	12% 6% 26% 32% 18% 5%	680
	11th to 20th	Day	12% 4 25% 35% 20% 5%	680
	21st to end	Day	12% 6% 30% 25% 20% 7%	680
July	1st to 10th	Day	10% 3 19% 27% 25% 16%	671
	11th to 20th	Day	6% 5% 22% 31% 25% 12%	668
	21st to end	Day	11% 3 16% 32% 29% 9%	706
August	1st to 10th	Day	10% 4 14% 27% 31% 14%	486
	11th to 20th	Day	14% 4 19% 30% 24% 10%	479
	21st to end	Day	6% 2 14% 32% 31% 15%	532
September	1st to 10th	Day	11% 4 17% 30% 28% 10%	450
	11th to 20th	Day	10% 2 15% 27% 32% 14%	450
	21st to end	Day	12% 10% 22% 23% 24% 9%	450
October	1st to 10th	Day	11% 7% 28% 32% 17% 5%	450
	11th to 20th	Day	14% 17% 33% 25% 10% 1	338
	21st to end	Day	29% 16% 34% 21% 1	297
November	1st to 10th	Day	12% 19% 29% 24% 13% 3	270
	11th to 20th	Day	23% 19% 31% 18% 9% 1	270
	21st to end	Day	24% 14% 37% 21% 3	270
December	1st to 10th	Day	17% 26% 34% 17% 4 1	270
	11th to 20th	Day	23% 15% 40% 15% 6% 1	270
	21st to end	Day	31% 18% 33% 15% 3	297
January	1st to 10th	Night	22% 16% 34% 24% 4	950
	11th to 20th	Night	24% 16% 37% 19% 4	950
	21st to end	Night	22% 15% 36% 24% 3	1022
February	1st to 10th	Night	25% 12% 37% 25% 2	760
	11th to 20th	Night	20% 15% 38% 24% 2	743
	21st to end	Night	26% 14% 38% 20% 3	628
March	1st to 10th	Night	25% 14% 34% 23% 4	760
	11th to 20th	Night	21% 13% 37% 23% 5% 1	760
	21st to end	Night	25% 8% 35% 27% 5% 1	701
April	1st to 10th	Night	18% 12% 35% 28% 7%	570
	11th to 20th	Night	20% 12% 29% 27% 10%	563
	21st to end	Night	21% 10% 36% 26% 7% 1	570
May	1st to 10th	Night	19% 8% 35% 29% 10%	570
	11th to 20th	Night	17% 5% 24% 34% 16% 3	561
	21st to end	Night	10% 4 24% 39% 22% 2	617
June	1st to 10th	Night	10% 4 23% 41% 21% 1	570
	11th to 20th	Night	10% 3 21% 44% 21% 1	570
	21st to end	Night	8% 3 22% 39% 26% 2	570
July	1st to 10th	Night	10% 2 10% 39% 32% 6%	555
	11th to 20th	Night	6% 4 15% 37% 34% 4	552
	21st to end	Night	7% 3 11% 45% 31% 3	624
August	1st to 10th	Night	8% 2 11% 41% 34% 4	567
	11th to 20th	Night	7% 3 12% 42% 33% 4	564
	21st to end	Night	7% 2 12% 30% 42% 6%	624
September	1st to 10th	Night	12% 4 14% 37% 30% 4	540
	11th to 20th	Night	10% 3 14% 36% 34% 4	701
	21st to end	Night	12% 7% 19% 33% 26% 3	720
October	1st to 10th	Night	10% 4 25% 34% 22% 4	720
	11th to 20th	Night	19% 12% 26% 29% 13% 1	720
	21st to end	Night	23% 12% 33% 26% 6% 1	792
November	1st to 10th	Night	16% 8% 35% 30% 11% 1	740
	11th to 20th	Night	17% 15% 31% 28% 9%	760
	21st to end	Night	24% 13% 30% 26% 7%	760
December	1st to 10th	Night	23% 12% 38% 21% 5%	785
	11th to 20th	Night	24% 10% 34% 25% 6% 1	950
	21st to end	Night	31% 13% 32% 19% 4	1045

Page generated at 2024-08-27 09:49:41. Version ac07

Copyright © 2024 Attilla Danko.