YCAS Stewartstown Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the YCAS Stewartstown Observing Site clear sky chart from 2005-11-06 to 2024-02-10.

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% 6% 3 5% 5% 3 5% 5% 6% 8% 40%	78287
	Night	15% 6% 3 5% 5% 3 4 4 5% 7% 43%	80670
Transparency	Day	42% 5% 12% 24% 15% 3	77995
	Night	41% 5% 11% 24% 16% 3	80481
Seeing	Day	19% 11% 27% 23% 14% 5%	13879
	Night	18% 10% 30% 29% 12% 1	23433

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	15% 6% 2 4 4 2 5% 4 6% 6% 45%	2517
	11th to 20th	Day	14% 9% 4 8% 7% 4 4 4 4 5% 36%	2758
	21st to end	Day	18% 10% 3 7% 6% 4 5% 4 5% 5% 34%	3124
February	1st to 10th	Day	14% 8% 3 5% 6% 3 4 5% 6% 8% 38%	1701
	11th to 20th	Day	15% 8% 2 5% 5% 3 5% 5% 6% 7% 39%	1641
	21st to end	Day	19% 9% 3 6% 5% 2 4 4 5% 5% 37%	1480
March	1st to 10th	Day	13% 5% 2 5% 5% 4 5% 3 4 6% 47%	1894
	11th to 20th	Day	15% 7% 2 5% 5% 3 4 5% 6% 8% 39%	1980
	21st to end	Day	18% 8% 3 6% 5% 4 4 4 5% 6% 38%	2241
April	1st to 10th	Day	13% 8% 3 6% 4 4 5% 5% 5% 7% 39%	2160
	11th to 20th	Day	14% 5% 3 5% 5% 3 4 5% 6% 7% 44%	2134
	21st to end	Day	18% 5% 2 5% 5% 3 4 4 5% 8% 40%	2160
May	1st to 10th	Day	17% 7% 3 5% 6% 3 5% 5% 6% 8% 36%	2293
	11th to 20th	Day	20% 7% 3 5% 5% 3 5% 5% 5% 7% 35%	2478
	21st to end	Day	14% 5% 2 5% 6% 3 4 4 7% 9% 39%	2725
June	1st to 10th	Day	13% 5% 2 5% 5% 4 5% 6% 7% 10% 38%	2520
	11th to 20th	Day	13% 6% 3 5% 5% 3 5% 5% 7% 9% 38%	2520
	21st to end	Day	11% 3 2 5% 6% 3 5% 5% 7% 10% 43%	2520
July	1st to 10th	Day	10% 4 3 5% 6% 4 5% 6% 8% 10% 40%	2520
	11th to 20th	Day	7% 3 2 5% 5% 4 6% 7% 8% 11% 43%	2520
	21st to end	Day	9% 6% 2 6% 7% 4 6% 6% 7% 10% 37%	2576
August	1st to 10th	Day	9% 5% 2 6% 7% 4 6% 6% 7% 8% 38%	2327
	11th to 20th	Day	10% 5% 3 6% 6% 5% 6% 6% 7% 8% 39%	2196
	21st to end	Day	13% 5% 2 5% 5% 3 5% 6% 6% 8% 41%	2376
September	1st to 10th	Day	15% 6% 2 5% 5% 3 5% 4 4 6% 44%	2160
	11th to 20th	Day	13% 5% 2 5% 4 3 4 4 5% 8% 48%	2160
	21st to end	Day	18% 6% 3 5% 5% 3 5% 5% 4 7% 40%	1913
October	1st to 10th	Day	18% 6% 2 4 5% 2 4 4 5% 7% 44%	1800
	11th to 20th	Day	17% 6% 3 4 4 2 4 4 5% 6% 46%	1800
	21st to end	Day	16% 6% 2 6% 4 2 4 4 6% 6% 44%	1980
November	1st to 10th	Day	12% 6% 2 4 3 3 3 3 5% 8% 50%	1695
	11th to 20th	Day	17% 4 2 4 3 2 4 5% 4 5% 48%	1696
	21st to end	Day	15% 6% 3 4 4 3 5% 4 4 7% 44%	1520
December	1st to 10th	Day	16% 8% 3 5% 6% 3 4 4 5% 8% 37%	1520
	11th to 20th	Day	17% 7% 3 4 5% 2 5% 5% 6% 7% 39%	1910
	21st to end	Day	17% 8% 3 6% 6% 4 5% 6% 5% 7% 35%	2772
January	1st to 10th	Night	14% 7% 3 6% 5% 3 5% 5% 5% 8% 40%	4429
	11th to 20th	Night	18% 8% 3 5% 4 2 3 3 4 6% 43%	4184
	21st to end	Night	20% 10% 3 5% 4 2 3 4 4 6% 38%	4532
February	1st to 10th	Night	16% 8% 3 6% 5% 3 4 4 6% 6% 41%	2464
	11th to 20th	Night	17% 7% 3 6% 5% 3 4 4 5% 6% 40%	2204
	21st to end	Night	17% 7% 3 7% 5% 3 5% 4 5% 5% 40%	1776
March	1st to 10th	Night	13% 5% 2 4 5% 2 4 5% 5% 7% 47%	2064
	11th to 20th	Night	16% 7% 3 5% 5% 3 4 5% 5% 5% 43%	1980
	21st to end	Night	17% 8% 3 6% 4 3 3 3 5% 6% 42%	2114
April	1st to 10th	Night	15% 7% 3 6% 6% 3 4 4 6% 7% 39%	1800
	11th to 20th	Night	14% 5% 2 5% 5% 3 5% 4 6% 8% 43%	1775
	21st to end	Night	19% 8% 2 5% 4 2 4 4 4 6% 43%	1800
May	1st to 10th	Night	17% 6% 3 6% 6% 2 4 4 5% 7% 38%	1679
	11th to 20th	Night	17% 8% 3 7% 4 2 4 4 5% 8% 38%	1415
	21st to end	Night	13% 6% 2 5% 5% 3 5% 5% 6% 9% 41%	1550
June	1st to 10th	Night	13% 4 2 6% 4 3 4 5% 6% 8% 46%	1440
	11th to 20th	Night	11% 6% 2 5% 5% 4 5% 6% 7% 9% 40%	1440
	21st to end	Night	10% 4 3 3 5% 3 6% 6% 6% 10% 44%	1440
July	1st to 10th	Night	9% 5% 3 7% 7% 4 6% 6% 7% 8% 39%	1440
	11th to 20th	Night	6% 4 1 6% 5% 3 6% 6% 7% 9% 48%	1440
	21st to end	Night	8% 4 3 4 5% 4 5% 5% 7% 9% 46%	1740
August	1st to 10th	Night	10% 4 2 5% 5% 3 6% 6% 8% 10% 42%	1611
	11th to 20th	Night	11% 6% 3 6% 6% 4 7% 6% 5% 7% 41%	1687
	21st to end	Night	13% 5% 2 5% 4 3 5% 5% 6% 8% 44%	1980
September	1st to 10th	Night	14% 6% 2 6% 4 2 3 3 6% 7% 46%	1800
	11th to 20th	Night	11% 5% 2 4 3 2 4 3 4 7% 54%	1800
	21st to end	Night	17% 7% 2 5% 5% 3 4 4 4 6% 43%	2042
October	1st to 10th	Night	20% 6% 2 5% 3 2 3 4 5% 5% 44%	2160
	11th to 20th	Night	15% 5% 2 4 4 2 4 4 5% 6% 49%	2160
	21st to end	Night	17% 5% 2 4 4 2 4 4 4 6% 47%	2376
November	1st to 10th	Night	11% 5% 2 4 4 2 4 4 5% 6% 53%	2380
	11th to 20th	Night	15% 7% 2 5% 4 2 4 4 4 7% 47%	2479
	21st to end	Night	13% 4 2 5% 5% 3 4 4 6% 7% 46%	2660
December	1st to 10th	Night	16% 8% 2 6% 6% 4 5% 5% 5% 7% 38%	2660
	11th to 20th	Night	17% 6% 2 5% 5% 3 5% 4 5% 7% 42%	3285
	21st to end	Night	16% 7% 3 6% 6% 3 5% 5% 6% 8% 34%	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	40% 4 12% 28% 12% 4	2518
	11th to 20th	Day	51% 3 10% 19% 14% 3	2758
	21st to end	Day	52% 5% 10% 24% 9% 1	3124
February	1st to 10th	Day	43% 5% 14% 25% 12% 2	1701
	11th to 20th	Day	44% 5% 10% 26% 13% 2	1650
	21st to end	Day	49% 3 9% 21% 13% 4	1480
March	1st to 10th	Day	40% 3 12% 28% 15% 2	1894
	11th to 20th	Day	43% 4 11% 20% 18% 5%	1980
	21st to end	Day	47% 5% 7% 21% 16% 3	2241
April	1st to 10th	Day	43% 5% 11% 19% 17% 4	2160
	11th to 20th	Day	39% 6% 11% 23% 17% 5%	2134
	21st to end	Day	43% 5% 10% 21% 18% 3	2160
May	1st to 10th	Day	45% 6% 10% 22% 14% 3	2293
	11th to 20th	Day	47% 6% 12% 20% 13% 2	2482
	21st to end	Day	40% 7% 16% 23% 12% 2	2725
June	1st to 10th	Day	40% 7% 13% 24% 15% 1	2520
	11th to 20th	Day	41% 7% 13% 23% 12% 2	2520
	21st to end	Day	35% 7% 15% 27% 15% 1	2520
July	1st to 10th	Day	39% 8% 12% 22% 16% 3	2450
	11th to 20th	Day	32% 7% 16% 28% 16% 2	2445
	21st to end	Day	40% 8% 12% 23% 15% 2	2432
August	1st to 10th	Day	41% 8% 12% 25% 13%	2314
	11th to 20th	Day	40% 7% 13% 22% 16% 2	2196
	21st to end	Day	38% 7% 13% 25% 14% 4	2376
September	1st to 10th	Day	41% 5% 11% 20% 18% 4	2160
	11th to 20th	Day	35% 4 9% 27% 21% 4	2160
	21st to end	Day	44% 4 9% 21% 20% 3	1913
October	1st to 10th	Day	41% 4 11% 26% 16% 2	1800
	11th to 20th	Day	40% 4 11% 23% 20% 2	1800
	21st to end	Day	41% 4 9% 26% 18% 2	1980
November	1st to 10th	Day	34% 3 13% 26% 19% 4	1695
	11th to 20th	Day	38% 4 10% 25% 20% 3	1696
	21st to end	Day	41% 4 11% 30% 12% 2	1520
December	1st to 10th	Day	47% 5% 14% 22% 12% 1	1520
	11th to 20th	Day	43% 5% 10% 31% 10% 1	1906
	21st to end	Day	49% 5% 14% 21% 11% 1	2772
January	1st to 10th	Night	42% 5% 10% 28% 12% 3	4429
	11th to 20th	Night	44% 4 12% 25% 14% 2	4184
	21st to end	Night	48% 4 7% 28% 11% 2	4532
February	1st to 10th	Night	44% 4 13% 25% 12% 2	2464
	11th to 20th	Night	45% 4 9% 21% 18% 3	2206
	21st to end	Night	46% 4 9% 21% 16% 4	1776
March	1st to 10th	Night	36% 5% 11% 26% 19% 2	2064
	11th to 20th	Night	43% 5% 10% 22% 16% 4	1980
	21st to end	Night	44% 4 10% 21% 17% 5%	2114
April	1st to 10th	Night	45% 4 10% 19% 18% 4	1800
	11th to 20th	Night	39% 4 11% 21% 20% 5%	1775
	21st to end	Night	42% 5% 9% 22% 17% 5%	1800
May	1st to 10th	Night	45% 6% 10% 21% 15% 4	1679
	11th to 20th	Night	45% 6% 13% 15% 19% 2	1416
	21st to end	Night	39% 8% 17% 21% 13% 3	1551
June	1st to 10th	Night	35% 8% 11% 26% 18% 2	1440
	11th to 20th	Night	40% 6% 16% 21% 15% 1	1440
	21st to end	Night	34% 7% 13% 28% 16% 2	1440
July	1st to 10th	Night	42% 7% 16% 20% 13% 3	1400
	11th to 20th	Night	31% 8% 16% 26% 17% 2	1392
	21st to end	Night	33% 7% 18% 22% 19% 1	1643
August	1st to 10th	Night	35% 8% 16% 26% 14% 1	1600
	11th to 20th	Night	41% 7% 13% 21% 16% 2	1687
	21st to end	Night	37% 6% 14% 22% 16% 4	1980
September	1st to 10th	Night	39% 4 13% 21% 19% 4	1800
	11th to 20th	Night	31% 4 11% 26% 25% 4	1800
	21st to end	Night	42% 5% 8% 21% 21% 3	2042
October	1st to 10th	Night	43% 4 12% 23% 17% 2	2160
	11th to 20th	Night	36% 4 9% 30% 18% 2	2160
	21st to end	Night	38% 4 9% 27% 19% 2	2376
November	1st to 10th	Night	33% 4 10% 27% 21% 5%	2380
	11th to 20th	Night	40% 3 8% 24% 19% 5%	2479
	21st to end	Night	37% 4 12% 28% 17% 2	2660
December	1st to 10th	Night	47% 5% 11% 23% 13% 1	2660
	11th to 20th	Night	42% 5% 12% 23% 16% 3	3288
	21st to end	Night	47% 6% 13% 22% 11% 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% 25% 32% 14% 3 1	180
	11th to 20th	Day	33% 20% 31% 14% 2	249
	21st to end	Day	22% 24% 38% 10% 6% 1	297
February	1st to 10th	Day	24% 19% 39% 14% 4	267
	11th to 20th	Day	29% 21% 40% 9% 1	308
	21st to end	Day	32% 16% 34% 16% 2	346
March	1st to 10th	Day	22% 21% 32% 23% 3	420
	11th to 20th	Day	22% 20% 35% 17% 4 2	420
	21st to end	Day	25% 17% 33% 18% 6% 1	462
April	1st to 10th	Day	22% 15% 37% 18% 6% 1	420
	11th to 20th	Day	19% 16% 29% 21% 10% 5%	412
	21st to end	Day	26% 14% 32% 19% 7% 2	420
May	1st to 10th	Day	25% 16% 26% 20% 10% 3	423
	11th to 20th	Day	21% 11% 29% 23% 12% 3	447
	21st to end	Day	19% 4 21% 27% 20% 9%	485
June	1st to 10th	Day	15% 9% 28% 25% 16% 6%	450
	11th to 20th	Day	17% 6% 26% 27% 17% 6%	450
	21st to end	Day	14% 4 23% 34% 17% 8%	450
July	1st to 10th	Day	14% 2 16% 29% 27% 13%	445
	11th to 20th	Day	5% 3 18% 33% 30% 11%	444
	21st to end	Day	12% 5% 20% 33% 23% 7%	488
August	1st to 10th	Day	12% 3 21% 28% 26% 10%	446
	11th to 20th	Day	12% 3 15% 32% 26% 12%	439
	21st to end	Day	11% 4 19% 30% 21% 14%	495
September	1st to 10th	Day	20% 4 19% 20% 23% 14%	450
	11th to 20th	Day	14% 5% 18% 27% 24% 12%	450
	21st to end	Day	23% 8% 22% 27% 14% 6%	450
October	1st to 10th	Day	21% 7% 22% 23% 18% 8%	450
	11th to 20th	Day	18% 11% 28% 26% 14% 3	450
	21st to end	Day	18% 11% 37% 24% 8% 2	495
November	1st to 10th	Day	17% 10% 30% 28% 12% 3	377
	11th to 20th	Day	19% 17% 31% 22% 10% 1	356
	21st to end	Day	23% 20% 33% 18% 7%	180
December	1st to 10th	Day	24% 17% 39% 14% 3 2	180
	11th to 20th	Day	28% 18% 33% 13% 7%	180
	21st to end	Day	21% 18% 36% 16% 8%	198
January	1st to 10th	Night	18% 15% 43% 20% 3	760
	11th to 20th	Night	23% 16% 32% 25% 3	760
	21st to end	Night	18% 15% 45% 21% 2	836
February	1st to 10th	Night	20% 15% 37% 26% 2	759
	11th to 20th	Night	22% 20% 39% 18% 1	703
	21st to end	Night	23% 19% 38% 18% 2	592
March	1st to 10th	Night	19% 16% 39% 23% 4	720
	11th to 20th	Night	22% 14% 36% 22% 6%	720
	21st to end	Night	21% 11% 40% 22% 6%	792
April	1st to 10th	Night	21% 16% 39% 19% 5%	720
	11th to 20th	Night	18% 10% 35% 28% 9%	711
	21st to end	Night	24% 10% 31% 27% 8%	720
May	1st to 10th	Night	21% 8% 29% 31% 10% 1	599
	11th to 20th	Night	19% 6% 31% 34% 10% 1	354
	21st to end	Night	16% 3 19% 40% 20% 1	389
June	1st to 10th	Night	14% 1 24% 39% 20% 1	360
	11th to 20th	Night	13% 3 23% 45% 16% 1	360
	21st to end	Night	11% 2 20% 50% 17%	360
July	1st to 10th	Night	11% 2 17% 40% 27% 3	350
	11th to 20th	Night	7% 1 14% 44% 31% 3	348
	21st to end	Night	11% 2 15% 44% 24% 3	560
August	1st to 10th	Night	11% 2 10% 48% 27% 2	537
	11th to 20th	Night	12% 2 14% 39% 29% 3	623
	21st to end	Night	14% 1 13% 40% 28% 4	792
September	1st to 10th	Night	15% 3 19% 34% 25% 4	720
	11th to 20th	Night	14% 3 14% 36% 27% 5%	720
	21st to end	Night	20% 4 21% 33% 21% 2	720
October	1st to 10th	Night	22% 5% 20% 28% 19% 5%	720
	11th to 20th	Night	18% 9% 27% 33% 13%	720
	21st to end	Night	21% 8% 34% 26% 12%	792
November	1st to 10th	Night	14% 6% 35% 34% 11% 1	740
	11th to 20th	Night	19% 13% 32% 27% 8% 1	760
	21st to end	Night	16% 15% 34% 28% 7%	760
December	1st to 10th	Night	22% 14% 36% 21% 6% 1	760
	11th to 20th	Night	18% 14% 40% 23% 5%	760
	21st to end	Night	20% 14% 36% 28% 2	836

Page generated at 2024-02-07 06:11:59. Version ac07

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