Stephenville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stephenville clear sky chart from 2005-11-06 to 2025-01-07.

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	23% 14% 5% 11% 6% 4 4 3 4 5% 21%	104839
	Night	22% 16% 6% 14% 6% 4 4 3 4 5% 18%	104356
Transparency	Day	37% 45% 7% 8% 2	108278
	Night	40% 43% 6% 8% 2	109022
Seeing	Day	32% 15% 26% 18% 8% 2	18116
	Night	31% 14% 24% 23% 8% 1	25300

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	13% 20% 10% 27% 13% 4 3 2 2 2 5%	2574
	11th to 20th	Day	19% 24% 8% 23% 7% 5% 2 2 3 2 5%	2530
	21st to end	Day	10% 18% 9% 26% 12% 7% 4 2 2 3 8%	2783
February	1st to 10th	Day	19% 17% 6% 22% 14% 7% 3 3 3 2 5%	1567
	11th to 20th	Day	18% 19% 7% 17% 13% 6% 3 3 3 2 10%	1705
	21st to end	Day	14% 16% 7% 16% 13% 8% 4 2 4 4 12%	1570
March	1st to 10th	Day	17% 15% 4 13% 8% 7% 4 3 4 5% 20%	3114
	11th to 20th	Day	20% 23% 8% 16% 7% 6% 4 3 3 2 9%	3271
	21st to end	Day	24% 18% 7% 12% 5% 3 2 2 4 5% 18%	4167
April	1st to 10th	Day	23% 19% 7% 12% 5% 4 4 2 4 5% 16%	2280
	11th to 20th	Day	20% 13% 3 9% 4 4 4 3 5% 6% 29%	2282
	21st to end	Day	26% 11% 5% 6% 4 4 4 3 4 4 30%	2527
May	1st to 10th	Day	22% 12% 4 8% 5% 4 4 3 4 5% 28%	4425
	11th to 20th	Day	17% 11% 3 7% 4 5% 4 3 5% 7% 33%	4398
	21st to end	Day	31% 10% 3 6% 4 4 4 3 4 6% 24%	4836
June	1st to 10th	Day	28% 10% 3 7% 4 4 4 4 5% 7% 23%	2810
	11th to 20th	Day	23% 7% 3 7% 4 3 4 5% 6% 8% 32%	2850
	21st to end	Day	30% 11% 2 6% 4 4 3 3 4 6% 26%	2833
July	1st to 10th	Day	29% 13% 3 7% 4 4 4 3 4 6% 22%	4440
	11th to 20th	Day	30% 12% 3 6% 4 4 4 3 4 5% 25%	4440
	21st to end	Day	23% 7% 2 5% 3 3 3 3 5% 7% 37%	4815
August	1st to 10th	Day	27% 8% 3 7% 4 4 4 4 5% 7% 27%	4424
	11th to 20th	Day	24% 8% 3 6% 3 4 4 3 5% 6% 36%	4269
	21st to end	Day	21% 7% 2 7% 5% 4 5% 4 5% 8% 33%	4190
September	1st to 10th	Day	24% 8% 3 6% 5% 4 4 3 6% 7% 30%	2280
	11th to 20th	Day	27% 9% 3 7% 5% 3 4 3 5% 6% 26%	2205
	21st to end	Day	29% 10% 3 7% 4 4 4 4 6% 6% 24%	2090
October	1st to 10th	Day	25% 11% 3 7% 3 4 4 4 5% 7% 27%	1945
	11th to 20th	Day	29% 13% 4 8% 4 5% 3 3 5% 6% 20%	1809
	21st to end	Day	28% 19% 5% 10% 4 3 3 3 4 5% 16%	1881
November	1st to 10th	Day	30% 22% 5% 9% 6% 4 4 3 4 3 10%	1760
	11th to 20th	Day	28% 22% 7% 9% 5% 4 3 3 3 4 12%	1605
	21st to end	Day	23% 26% 10% 13% 5% 4 3 3 3 3 6%	1511
December	1st to 10th	Day	15% 26% 9% 19% 5% 5% 4 4 3 3 7%	2290
	11th to 20th	Day	28% 22% 10% 18% 5% 3 3 2 2 3 4	2628
	21st to end	Day	20% 20% 9% 22% 7% 3 2 2 2 4 8%	3735
January	1st to 10th	Night	13% 18% 11% 29% 12% 4 3 1 1 2 5%	4514
	11th to 20th	Night	18% 21% 7% 26% 8% 5% 3 2 3 2 4	4440
	21st to end	Night	11% 15% 9% 24% 9% 9% 4 2 4 4 10%	4884
February	1st to 10th	Night	17% 18% 6% 24% 15% 7% 2 1 2 2 5%	2609
	11th to 20th	Night	16% 19% 8% 19% 11% 6% 4 2 3 3 8%	2361
	21st to end	Night	13% 17% 7% 18% 11% 6% 3 3 3 3 16%	1884
March	1st to 10th	Night	16% 14% 5% 14% 10% 5% 4 3 4 5% 20%	3726
	11th to 20th	Night	15% 24% 8% 18% 8% 5% 4 3 3 3 10%	3685
	21st to end	Night	24% 19% 5% 11% 5% 3 3 2 3 6% 17%	3465
April	1st to 10th	Night	23% 18% 7% 12% 4 3 4 2 4 5% 17%	1900
	11th to 20th	Night	19% 16% 5% 9% 5% 4 4 3 4 6% 27%	1847
	21st to end	Night	20% 13% 6% 8% 4 5% 4 3 5% 6% 26%	1650
May	1st to 10th	Night	25% 11% 4 7% 5% 4 3 3 5% 8% 25%	2525
	11th to 20th	Night	20% 9% 3 6% 4 4 4 4 5% 7% 34%	2506
	21st to end	Night	32% 9% 3 5% 3 3 4 2 5% 7% 26%	2749
June	1st to 10th	Night	31% 11% 4 8% 4 3 4 3 5% 6% 22%	1368
	11th to 20th	Night	22% 10% 2 6% 3 4 5% 3 6% 7% 32%	1330
	21st to end	Night	27% 10% 3 8% 5% 4 5% 4 5% 6% 22%	1341
July	1st to 10th	Night	29% 15% 4 8% 5% 4 4 3 3 6% 19%	2530
	11th to 20th	Night	29% 15% 4 6% 4 4 4 3 4 6% 21%	2530
	21st to end	Night	23% 7% 2 5% 3 3 3 3 4 6% 41%	2750
August	1st to 10th	Night	21% 9% 3 7% 5% 4 5% 4 6% 8% 29%	2516
	11th to 20th	Night	24% 10% 3 6% 5% 4 4 3 4 5% 33%	2568
	21st to end	Night	22% 7% 3 6% 4 4 4 4 4 6% 35%	3462
September	1st to 10th	Night	26% 8% 3 6% 4 5% 4 3 6% 7% 30%	1900
	11th to 20th	Night	30% 9% 2 5% 3 4 4 3 5% 6% 28%	1975
	21st to end	Night	27% 10% 3 7% 4 3 4 2 4 6% 29%	2090
October	1st to 10th	Night	24% 10% 3 7% 4 4 4 4 6% 7% 28%	2232
	11th to 20th	Night	29% 13% 4 9% 4 4 4 3 4 5% 21%	2370
	21st to end	Night	28% 16% 5% 9% 4 4 3 3 4 6% 18%	2717
November	1st to 10th	Night	27% 20% 5% 11% 5% 4 4 4 4 4 12%	2538
	11th to 20th	Night	29% 22% 6% 11% 5% 4 3 2 4 3 11%	2790
	21st to end	Night	25% 25% 8% 13% 6% 4 4 2 3 3 7%	2885
December	1st to 10th	Night	17% 24% 9% 20% 7% 5% 4 3 3 4 6%	4900
	11th to 20th	Night	30% 19% 9% 18% 5% 3 2 1 2 3 8%	5581
	21st to end	Night	18% 20% 10% 21% 6% 4 3 2 3 3 11%	7238

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	57% 36% 4 3	2575
	11th to 20th	Day	58% 36% 2 3 1	2530
	21st to end	Day	49% 41% 2 3 3 2	2783
February	1st to 10th	Day	30% 64% 2 3 1	1567
	11th to 20th	Day	29% 63% 2 4 1	1713
	21st to end	Day	29% 64% 1 4 1	1570
March	1st to 10th	Day	38% 40% 6% 8% 8%	3118
	11th to 20th	Day	56% 38% 3 2 1	3271
	21st to end	Day	45% 39% 2 11% 2	4167
April	1st to 10th	Day	26% 64% 2 4 3	2280
	11th to 20th	Day	20% 65% 3 6% 5%	2282
	21st to end	Day	25% 65% 3 4 2 1	2527
May	1st to 10th	Day	40% 39% 7% 12% 1	4440
	11th to 20th	Day	31% 39% 14% 13% 3	4402
	21st to end	Day	40% 39% 9% 9% 3	4836
June	1st to 10th	Day	21% 65% 6% 7% 2	2810
	11th to 20th	Day	20% 65% 5% 8% 3	2850
	21st to end	Day	23% 63% 4 7% 3	2833
July	1st to 10th	Day	46% 36% 6% 9% 3	4370
	11th to 20th	Day	43% 37% 9% 10% 1	4364
	21st to end	Day	28% 37% 18% 15% 2	4662
August	1st to 10th	Day	38% 37% 11% 12% 1	4410
	11th to 20th	Day	30% 38% 12% 14% 6% 1	4311
	21st to end	Day	30% 39% 13% 16% 3	4190
September	1st to 10th	Day	21% 60% 5% 9% 5%	2280
	11th to 20th	Day	26% 60% 6% 6% 1	2205
	21st to end	Day	21% 60% 6% 10% 3	2090
October	1st to 10th	Day	34% 38% 8% 16% 4	3231
	11th to 20th	Day	40% 41% 11% 5% 3	2991
	21st to end	Day	40% 39% 9% 10% 2	3092
November	1st to 10th	Day	36% 56% 3 4 1	1760
	11th to 20th	Day	36% 56% 3 4 1	1605
	21st to end	Day	38% 56% 3 2 1	1511
December	1st to 10th	Day	49% 38% 8% 4 1	2290
	11th to 20th	Day	61% 32% 5% 2	2627
	21st to end	Day	60% 26% 6% 7%	3735
January	1st to 10th	Night	58% 35% 2 4 1	4514
	11th to 20th	Night	57% 37% 3 3 1	4440
	21st to end	Night	47% 38% 3 4 6% 2	4884
February	1st to 10th	Night	32% 64% 1 2 1	2609
	11th to 20th	Night	31% 63% 3 3	2364
	21st to end	Night	28% 64% 2 4 2	1884
March	1st to 10th	Night	39% 40% 4 11% 5%	3735
	11th to 20th	Night	55% 39% 2 3 1	3686
	21st to end	Night	45% 39% 3 10% 3	3465
April	1st to 10th	Night	26% 64% 3 5% 2	1900
	11th to 20th	Night	21% 65% 4 6% 4	1847
	21st to end	Night	25% 64% 5% 4 1	1650
May	1st to 10th	Night	38% 39% 9% 13% 1	2530
	11th to 20th	Night	29% 39% 12% 17% 4	2507
	21st to end	Night	38% 39% 8% 13% 1	2750
June	1st to 10th	Night	22% 65% 3 8% 2	1368
	11th to 20th	Night	21% 65% 3 9% 2	1330
	21st to end	Night	23% 64% 3 6% 3	1341
July	1st to 10th	Night	51% 36% 5% 5% 3 1	2491
	11th to 20th	Night	48% 36% 8% 7% 1	2482
	21st to end	Night	26% 36% 14% 20% 3	2663
August	1st to 10th	Night	36% 38% 12% 14% 1	2505
	11th to 20th	Night	34% 39% 12% 9% 4 2	2592
	21st to end	Night	31% 39% 14% 14% 3	3461
September	1st to 10th	Night	20% 60% 6% 10% 4	1900
	11th to 20th	Night	25% 59% 7% 7% 2	1975
	21st to end	Night	21% 59% 7% 9% 3	2090
October	1st to 10th	Night	28% 37% 11% 19% 5%	3726
	11th to 20th	Night	38% 38% 11% 11% 2	3932
	21st to end	Night	40% 38% 11% 10% 1	4467
November	1st to 10th	Night	35% 55% 3 5% 1	2538
	11th to 20th	Night	37% 56% 4 3 1	2790
	21st to end	Night	38% 56% 3 3	2885
December	1st to 10th	Night	51% 37% 6% 5% 1	4900
	11th to 20th	Night	56% 32% 7% 5% 1	5583
	21st to end	Night	59% 26% 6% 9% 1	7238

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	29% 26% 28% 12% 3 1	388
	11th to 20th	Day	32% 22% 27% 15% 4 2	370
	21st to end	Day	26% 20% 29% 19% 5%	407
February	1st to 10th	Day	32% 24% 26% 10% 6% 1	370
	11th to 20th	Day	30% 25% 28% 11% 4 1	366
	21st to end	Day	26% 21% 31% 13% 5% 3	307
March	1st to 10th	Day	24% 23% 32% 16% 4 2	370
	11th to 20th	Day	34% 18% 22% 14% 9% 3	397
	21st to end	Day	34% 19% 25% 14% 7% 2	506
April	1st to 10th	Day	35% 21% 28% 12% 3	460
	11th to 20th	Day	28% 16% 29% 17% 9% 1	480
	21st to end	Day	32% 12% 27% 22% 5% 2	650
May	1st to 10th	Day	34% 13% 23% 20% 7% 3	653
	11th to 20th	Day	28% 11% 24% 23% 11% 2	674
	21st to end	Day	34% 12% 30% 17% 5% 2	735
June	1st to 10th	Day	34% 8% 26% 21% 10% 2	680
	11th to 20th	Day	28% 10% 25% 25% 10% 2	680
	21st to end	Day	34% 11% 23% 19% 9% 3	680
July	1st to 10th	Day	32% 7% 26% 21% 11% 2	670
	11th to 20th	Day	32% 10% 23% 22% 13%	668
	21st to end	Day	33% 8% 24% 22% 12% 1	740
August	1st to 10th	Day	27% 9% 24% 26% 12% 2	675
	11th to 20th	Day	28% 8% 24% 27% 10% 2	667
	21st to end	Day	27% 11% 29% 21% 11% 2	549
September	1st to 10th	Day	26% 14% 30% 23% 6% 2	490
	11th to 20th	Day	33% 14% 31% 16% 6% 1	450
	21st to end	Day	34% 14% 26% 18% 6% 2	390
October	1st to 10th	Day	29% 18% 28% 17% 7% 2	390
	11th to 20th	Day	36% 15% 22% 15% 10% 2	390
	21st to end	Day	39% 18% 18% 18% 6% 1	429
November	1st to 10th	Day	42% 22% 22% 11% 4	395
	11th to 20th	Day	42% 16% 20% 14% 7% 2	400
	21st to end	Day	42% 20% 24% 12% 3	400
December	1st to 10th	Day	36% 20% 26% 12% 6% 1	400
	11th to 20th	Day	38% 21% 28% 12% 1 1	400
	21st to end	Day	29% 22% 23% 17% 8% 1	440
January	1st to 10th	Night	32% 24% 26% 15% 4	881
	11th to 20th	Night	31% 24% 27% 14% 3 1	850
	21st to end	Night	24% 18% 32% 21% 5%	935
February	1st to 10th	Night	29% 22% 27% 16% 5%	826
	11th to 20th	Night	27% 22% 31% 15% 4 1	743
	21st to end	Night	22% 16% 30% 20% 9% 3	628
March	1st to 10th	Night	24% 22% 29% 19% 5% 1	760
	11th to 20th	Night	24% 17% 24% 25% 8% 1	755
	21st to end	Night	29% 14% 27% 21% 8% 1	627
April	1st to 10th	Night	35% 13% 26% 19% 6%	570
	11th to 20th	Night	26% 14% 24% 28% 8% 1	564
	21st to end	Night	28% 12% 24% 27% 8% 1	570
May	1st to 10th	Night	30% 7% 20% 30% 11% 2	570
	11th to 20th	Night	30% 6% 20% 30% 12% 2	562
	21st to end	Night	33% 8% 21% 29% 8% 1	616
June	1st to 10th	Night	36% 6% 21% 27% 9% 1	570
	11th to 20th	Night	25% 7% 20% 35% 12% 1	570
	21st to end	Night	29% 6% 21% 30% 12% 1	570
July	1st to 10th	Night	33% 8% 18% 28% 14% 1	556
	11th to 20th	Night	28% 6% 18% 35% 12%	552
	21st to end	Night	33% 5% 15% 34% 13%	623
August	1st to 10th	Night	25% 7% 16% 36% 15% 1	568
	11th to 20th	Night	28% 7% 21% 29% 14% 1	562
	21st to end	Night	27% 6% 21% 29% 16% 1	627
September	1st to 10th	Night	28% 11% 22% 28% 10% 1	570
	11th to 20th	Night	34% 8% 24% 28% 7%	570
	21st to end	Night	29% 11% 30% 22% 7% 1	570
October	1st to 10th	Night	29% 11% 26% 27% 6%	712
	11th to 20th	Night	36% 13% 18% 25% 8% 1	807
	21st to end	Night	37% 15% 22% 20% 5%	946
November	1st to 10th	Night	39% 18% 23% 17% 4	880
	11th to 20th	Night	41% 13% 23% 16% 6% 1	900
	21st to end	Night	40% 18% 22% 17% 3	900
December	1st to 10th	Night	33% 21% 22% 17% 6%	900
	11th to 20th	Night	36% 23% 26% 14% 2	900
	21st to end	Night	27% 21% 27% 19% 6% 1	990

Page generated at 2025-01-04 04:24:04. Version ac07

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