Saint Stephen
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saint Stephen clear sky chart from 2005-11-06 to 2025-02-21.

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	19% 9% 3 7% 4 4 4 3 5% 7% 35%	108213
	Night	19% 9% 3 7% 4 4 4 3 5% 6% 35%	110432
Transparency	Day	49% 4 11% 22% 13% 2	111774
	Night	49% 3 11% 23% 12% 2	115037
Seeing	Day	25% 17% 31% 19% 6% 1	16457
	Night	25% 14% 31% 23% 6%	24663

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	14% 13% 4 8% 6% 5% 5% 4 5% 6% 30%	3289
	11th to 20th	Day	14% 12% 3 9% 5% 3 3 3 4 5% 39%	3570
	21st to end	Day	12% 9% 3 9% 5% 5% 4 4 5% 6% 39%	4233
February	1st to 10th	Day	17% 12% 4 8% 5% 6% 4 3 5% 6% 32%	1800
	11th to 20th	Day	15% 12% 3 8% 5% 5% 5% 3 5% 6% 34%	1763
	21st to end	Day	12% 13% 2 7% 5% 4 4 4 5% 7% 37%	1570
March	1st to 10th	Day	25% 12% 3 7% 4 4 3 3 4 5% 30%	3238
	11th to 20th	Day	19% 15% 4 7% 6% 5% 4 3 5% 6% 25%	3480
	21st to end	Day	27% 11% 5% 7% 4 3 4 3 5% 5% 25%	3816
April	1st to 10th	Day	22% 13% 3 8% 4 3 3 3 4 6% 29%	2222
	11th to 20th	Day	21% 9% 2 6% 4 3 4 2 5% 6% 37%	2442
	21st to end	Day	24% 9% 2 6% 4 4 3 4 5% 5% 35%	2470
May	1st to 10th	Day	22% 9% 2 7% 5% 4 4 3 5% 8% 31%	4106
	11th to 20th	Day	18% 8% 3 7% 4 4 5% 4 5% 7% 35%	4166
	21st to end	Day	18% 8% 2 6% 4 5% 5% 4 6% 9% 34%	5017
June	1st to 10th	Day	24% 8% 3 8% 4 5% 4 3 5% 6% 29%	2850
	11th to 20th	Day	21% 8% 2 6% 4 3 3 4 5% 7% 38%	2850
	21st to end	Day	27% 7% 3 7% 5% 4 4 3 5% 6% 27%	2850
July	1st to 10th	Day	16% 6% 2 6% 6% 5% 5% 4 7% 8% 33%	4760
	11th to 20th	Day	20% 7% 2 5% 4 4 5% 4 7% 9% 34%	4578
	21st to end	Day	19% 6% 2 6% 5% 4 5% 5% 6% 7% 35%	4625
August	1st to 10th	Day	22% 8% 3 7% 5% 5% 4 3 5% 7% 32%	4105
	11th to 20th	Day	17% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	4045
	21st to end	Day	12% 5% 2 5% 4 4 5% 5% 7% 8% 44%	4532
September	1st to 10th	Day	13% 4 1 5% 5% 4 3 2 4 7% 51%	2228
	11th to 20th	Day	17% 6% 2 5% 3 3 3 3 4 5% 49%	2090
	21st to end	Day	19% 7% 2 5% 2 3 3 2 4 6% 45%	2090
October	1st to 10th	Day	19% 7% 2 6% 5% 4 4 3 5% 7% 39%	1971
	11th to 20th	Day	21% 6% 2 5% 5% 4 4 3 4 7% 39%	1900
	21st to end	Day	21% 8% 3 6% 6% 4 4 3 4 5% 35%	1940
November	1st to 10th	Day	21% 7% 3 6% 3 4 4 4 5% 4 39%	1761
	11th to 20th	Day	21% 6% 2 6% 4 4 3 3 5% 7% 39%	1612
	21st to end	Day	21% 10% 3 7% 4 4 4 3 5% 5% 34%	1600
December	1st to 10th	Day	22% 10% 2 5% 3 3 4 4 6% 8% 33%	2550
	11th to 20th	Day	23% 9% 3 7% 4 4 3 2 3 4 38%	2618
	21st to end	Day	22% 10% 3 5% 3 4 4 3 5% 5% 35%	3476
January	1st to 10th	Night	13% 11% 4 9% 5% 5% 5% 4 6% 7% 31%	6655
	11th to 20th	Night	16% 10% 3 9% 5% 5% 4 3 5% 6% 34%	6315
	21st to end	Night	10% 10% 4 7% 4 4 4 4 5% 6% 41%	6720
February	1st to 10th	Night	16% 11% 3 6% 5% 4 5% 4 6% 6% 32%	2600
	11th to 20th	Night	15% 11% 3 9% 6% 4 5% 3 6% 5% 32%	2519
	21st to end	Night	16% 11% 3 6% 6% 5% 4 3 4 5% 37%	1885
March	1st to 10th	Night	26% 14% 3 6% 4 5% 4 2 3 4 28%	3602
	11th to 20th	Night	19% 15% 3 8% 5% 5% 5% 4 5% 6% 25%	3479
	21st to end	Night	31% 8% 2 6% 5% 4 4 4 4 5% 27%	3816
April	1st to 10th	Night	24% 12% 2 6% 5% 4 3 3 3 4 33%	1956
	11th to 20th	Night	24% 9% 3 5% 3 4 5% 2 5% 5% 34%	1688
	21st to end	Night	26% 8% 2 6% 4 4 4 3 5% 6% 31%	1710
May	1st to 10th	Night	23% 7% 3 6% 3 3 4 4 5% 6% 37%	2834
	11th to 20th	Night	19% 8% 2 7% 6% 5% 6% 5% 6% 7% 30%	2727
	21st to end	Night	17% 8% 3 6% 5% 4 5% 4 5% 8% 35%	2598
June	1st to 10th	Night	26% 7% 2 6% 4 4 5% 4 5% 7% 28%	1330
	11th to 20th	Night	18% 7% 3 6% 5% 4 4 4 6% 7% 35%	1330
	21st to end	Night	27% 7% 2 6% 5% 4 4 3 4 7% 29%	1330
July	1st to 10th	Night	16% 7% 3 6% 6% 5% 6% 6% 7% 9% 31%	2210
	11th to 20th	Night	21% 7% 2 6% 4 4 5% 4 7% 9% 32%	2382
	21st to end	Night	19% 7% 2 6% 4 4 4 4 7% 8% 36%	2894
August	1st to 10th	Night	22% 10% 4 7% 5% 5% 4 3 5% 6% 30%	2825
	11th to 20th	Night	15% 9% 3 8% 6% 4 5% 4 6% 8% 33%	2782
	21st to end	Night	11% 6% 2 6% 4 4 5% 3 5% 8% 47%	3124
September	1st to 10th	Night	16% 5% 2 4 5% 4 3 3 5% 7% 47%	1945
	11th to 20th	Night	17% 6% 2 4 2 3 3 3 5% 5% 49%	2090
	21st to end	Night	20% 6% 2 5% 3 3 3 2 5% 7% 45%	2090
October	1st to 10th	Night	20% 6% 2 5% 3 4 4 3 5% 7% 41%	2209
	11th to 20th	Night	19% 7% 3 6% 4 3 3 3 5% 6% 41%	2280
	21st to end	Night	24% 8% 3 6% 4 4 3 3 4 6% 36%	2655
November	1st to 10th	Night	20% 7% 2 6% 4 4 4 4 5% 6% 39%	2537
	11th to 20th	Night	20% 7% 3 6% 4 4 4 3 5% 6% 38%	2786
	21st to end	Night	21% 8% 2 7% 4 4 4 4 5% 7% 35%	2800
December	1st to 10th	Night	18% 9% 3 7% 4 3 4 3 5% 6% 38%	4636
	11th to 20th	Night	23% 9% 2 5% 3 4 4 3 4 4 38%	5591
	21st to end	Night	22% 11% 3 7% 3 4 4 3 4 5% 34%	7502

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	54% 2 13% 23% 7%	3290
	11th to 20th	Day	49% 3 10% 26% 10% 2	3600
	21st to end	Day	47% 2 10% 18% 20% 4	4233
February	1st to 10th	Day	54% 3 10% 18% 13% 2	1800
	11th to 20th	Day	52% 3 11% 19% 13% 2	1771
	21st to end	Day	47% 4 10% 24% 11% 5%	1570
March	1st to 10th	Day	58% 2 8% 17% 11% 4	3242
	11th to 20th	Day	59% 4 9% 15% 11% 2	3480
	21st to end	Day	61% 3 4 16% 13% 2	3816
April	1st to 10th	Day	56% 4 8% 15% 14% 3	2222
	11th to 20th	Day	48% 4 8% 23% 15% 2	2442
	21st to end	Day	50% 4 7% 20% 15% 5%	2470
May	1st to 10th	Day	53% 3 11% 22% 9% 1	4120
	11th to 20th	Day	50% 3 13% 24% 8% 2	4170
	21st to end	Day	47% 4 15% 19% 14% 1	5017
June	1st to 10th	Day	55% 4 11% 19% 11% 1	2850
	11th to 20th	Day	46% 4 11% 21% 16% 2	2850
	21st to end	Day	57% 4 10% 16% 11% 1	2850
July	1st to 10th	Day	47% 5% 13% 22% 12% 1	4685
	11th to 20th	Day	46% 5% 14% 24% 10% 1	4498
	21st to end	Day	46% 6% 13% 24% 10% 1	4478
August	1st to 10th	Day	52% 5% 11% 23% 8%	4092
	11th to 20th	Day	50% 5% 15% 21% 9%	4084
	21st to end	Day	34% 5% 13% 28% 20% 1	4532
September	1st to 10th	Day	34% 4 11% 31% 19% 1	2228
	11th to 20th	Day	37% 4 9% 27% 20% 4	2090
	21st to end	Day	42% 3 8% 29% 17% 1	2090
October	1st to 10th	Day	50% 4 11% 25% 10%	3270
	11th to 20th	Day	39% 3 10% 34% 14%	3140
	21st to end	Day	37% 3 16% 25% 18% 1	3177
November	1st to 10th	Day	48% 4 11% 22% 15% 1	1761
	11th to 20th	Day	44% 4 12% 21% 16% 2	1612
	21st to end	Day	52% 4 13% 22% 8% 1	1600
December	1st to 10th	Day	48% 4 15% 23% 10%	2550
	11th to 20th	Day	53% 3 11% 17% 12% 5%	2618
	21st to end	Day	51% 4 11% 19% 13% 3	3476
January	1st to 10th	Night	52% 2 11% 26% 7% 1	6655
	11th to 20th	Night	51% 4 11% 24% 9% 1	6360
	21st to end	Night	44% 2 9% 23% 18% 4	6720
February	1st to 10th	Night	51% 3 11% 19% 13% 2	2600
	11th to 20th	Night	53% 4 8% 19% 13% 2	2522
	21st to end	Night	50% 2 9% 20% 15% 3	1885
March	1st to 10th	Night	62% 2 7% 15% 12% 2	3611
	11th to 20th	Night	59% 3 11% 16% 10% 2	3480
	21st to end	Night	60% 3 6% 17% 12% 2	3816
April	1st to 10th	Night	55% 4 6% 16% 14% 4	1956
	11th to 20th	Night	51% 3 8% 20% 16% 2	1688
	21st to end	Night	54% 3 8% 17% 15% 3	1710
May	1st to 10th	Night	48% 3 18% 21% 9% 1	2840
	11th to 20th	Night	53% 4 16% 20% 7% 1	2728
	21st to end	Night	48% 4 17% 23% 9% 1	2599
June	1st to 10th	Night	55% 5% 10% 22% 8% 1	1330
	11th to 20th	Night	48% 4 11% 24% 11% 2	1330
	21st to end	Night	57% 4 10% 19% 8% 3	1330
July	1st to 10th	Night	48% 5% 15% 20% 11%	2175
	11th to 20th	Night	48% 5% 16% 24% 8%	2339
	21st to end	Night	46% 5% 13% 22% 13% 1	2802
August	1st to 10th	Night	55% 5% 12% 19% 8%	2813
	11th to 20th	Night	47% 5% 16% 23% 9%	2809
	21st to end	Night	34% 5% 14% 27% 18% 2	3124
September	1st to 10th	Night	38% 4 11% 31% 15% 1	1945
	11th to 20th	Night	37% 3 12% 27% 19% 2	2090
	21st to end	Night	40% 3 9% 31% 16% 1	2090
October	1st to 10th	Night	46% 3 11% 28% 12% 1	3690
	11th to 20th	Night	37% 2 10% 30% 20%	3779
	21st to end	Night	43% 2 12% 27% 14% 2	4368
November	1st to 10th	Night	45% 4 13% 24% 13% 1	2537
	11th to 20th	Night	47% 4 10% 23% 15% 2	2786
	21st to end	Night	49% 5% 13% 21% 10% 1	2800
December	1st to 10th	Night	47% 3 11% 29% 10%	4636
	11th to 20th	Night	49% 3 10% 21% 15% 2	5592
	21st to end	Night	53% 3 10% 19% 13% 2	7502

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	30% 23% 32% 14% 2 1	200
	11th to 20th	Day	32% 25% 30% 10% 2 1	200
	21st to end	Day	23% 22% 33% 19% 4	337
February	1st to 10th	Day	28% 24% 29% 16% 3	400
	11th to 20th	Day	25% 28% 35% 10% 2	401
	21st to end	Day	26% 24% 30% 16% 3	382
March	1st to 10th	Day	29% 25% 31% 13% 3	460
	11th to 20th	Day	25% 25% 32% 12% 5% 1	460
	21st to end	Day	32% 23% 26% 12% 5% 2	506
April	1st to 10th	Day	34% 23% 28% 10% 2 2	460
	11th to 20th	Day	31% 22% 30% 13% 3	452
	21st to end	Day	30% 20% 33% 13% 3 1	460
May	1st to 10th	Day	30% 19% 31% 16% 3	463
	11th to 20th	Day	23% 20% 32% 19% 4 1	533
	21st to end	Day	26% 17% 32% 18% 7% 1	735
June	1st to 10th	Day	27% 16% 31% 19% 5% 1	680
	11th to 20th	Day	23% 14% 31% 22% 8% 2	680
	21st to end	Day	33% 9% 31% 19% 8% 1	680
July	1st to 10th	Day	22% 9% 34% 25% 9% 1	670
	11th to 20th	Day	21% 8% 34% 25% 10% 2	565
	21st to end	Day	19% 9% 36% 28% 6% 1	532
August	1st to 10th	Day	18% 9% 34% 28% 10% 1	486
	11th to 20th	Day	19% 8% 33% 27% 10% 2	479
	21st to end	Day	19% 11% 31% 27% 10% 3	539
September	1st to 10th	Day	14% 12% 36% 28% 8% 1	490
	11th to 20th	Day	24% 12% 28% 20% 12% 4	490
	21st to end	Day	19% 16% 31% 22% 8% 4	490
October	1st to 10th	Day	19% 16% 29% 23% 10% 3	427
	11th to 20th	Day	24% 17% 28% 19% 10% 2	390
	21st to end	Day	27% 17% 33% 17% 5%	429
November	1st to 10th	Day	28% 18% 27% 20% 5% 2	395
	11th to 20th	Day	27% 25% 28% 15% 6% 1	400
	21st to end	Day	31% 21% 26% 18% 3 1	400
December	1st to 10th	Day	31% 19% 30% 15% 5%	366
	11th to 20th	Day	37% 28% 24% 9% 3	200
	21st to end	Day	30% 28% 26% 11% 4	220
January	1st to 10th	Night	26% 22% 29% 20% 3	868
	11th to 20th	Night	28% 19% 30% 20% 3	800
	21st to end	Night	17% 25% 37% 17% 4	880
February	1st to 10th	Night	26% 19% 31% 20% 4	800
	11th to 20th	Night	25% 26% 30% 16% 2 1	783
	21st to end	Night	24% 21% 32% 19% 4	629
March	1st to 10th	Night	26% 20% 34% 19% 2	760
	11th to 20th	Night	25% 17% 32% 21% 5%	760
	21st to end	Night	27% 16% 32% 19% 5%	836
April	1st to 10th	Night	33% 17% 32% 15% 3	713
	11th to 20th	Night	28% 16% 33% 18% 4	564
	21st to end	Night	32% 11% 33% 18% 6%	570
May	1st to 10th	Night	26% 12% 32% 24% 5%	570
	11th to 20th	Night	28% 12% 32% 23% 6%	562
	21st to end	Night	22% 11% 37% 25% 5% 1	530
June	1st to 10th	Night	29% 6% 32% 28% 5% 1	380
	11th to 20th	Night	23% 7% 33% 28% 9% 1	380
	21st to end	Night	29% 3 30% 32% 6%	380
July	1st to 10th	Night	19% 4 40% 29% 8%	370
	11th to 20th	Night	22% 6% 25% 35% 11%	368
	21st to end	Night	21% 3 31% 34% 10%	508
August	1st to 10th	Night	19% 5% 30% 36% 10%	568
	11th to 20th	Night	20% 4 28% 35% 12%	562
	21st to end	Night	16% 7% 28% 35% 13% 1	627
September	1st to 10th	Night	18% 4 37% 28% 12% 1	655
	11th to 20th	Night	21% 8% 28% 28% 13% 2	760
	21st to end	Night	21% 9% 29% 27% 13% 1	760
October	1st to 10th	Night	23% 7% 28% 29% 12%	760
	11th to 20th	Night	22% 12% 32% 22% 11% 1	760
	21st to end	Night	27% 17% 30% 21% 6%	836
November	1st to 10th	Night	26% 14% 30% 22% 6% 1	780
	11th to 20th	Night	26% 18% 28% 21% 7% 1	894
	21st to end	Night	30% 18% 28% 19% 5%	900
December	1st to 10th	Night	32% 15% 31% 19% 4	900
	11th to 20th	Night	29% 23% 29% 15% 3	900
	21st to end	Night	30% 22% 28% 16% 4	990

Page generated at 2025-02-18 04:26:29. Version ac07

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