Transit Dreams North
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Transit Dreams North clear sky chart from 2005-11-06 to 2026-04-02.

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	18% 13% 5% 10% 5% 4 4 3 5% 6% 27%	131592
	Night	17% 16% 5% 11% 6% 4 4 3 4 5% 24%	130190
Transparency	Day	56% 6% 11% 17% 9% 1	135186
	Night	61% 6% 10% 15% 8% 1	134682
Seeing	Day	27% 18% 28% 17% 8% 2	16255
	Night	27% 16% 27% 21% 8% 1	25808

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	15% 26% 10% 23% 7% 3 2 2 2 2 8%	4661
	11th to 20th	Day	9% 26% 13% 22% 10% 6% 3 2 3 2 5%	5126
	21st to end	Day	14% 16% 7% 19% 10% 11% 7% 3 3 3 7%	5780
February	1st to 10th	Day	16% 22% 7% 17% 8% 5% 4 3 3 3 12%	1890
	11th to 20th	Day	13% 20% 9% 18% 8% 4 4 3 3 4 14%	1843
	21st to end	Day	18% 20% 6% 13% 7% 4 4 3 5% 5% 16%	1643
March	1st to 10th	Day	16% 16% 8% 12% 5% 4 3 2 3 5% 25%	5042
	11th to 20th	Day	12% 19% 7% 8% 3 4 4 3 4 6% 29%	5090
	21st to end	Day	21% 17% 5% 9% 4 3 3 3 4 5% 25%	5586
April	1st to 10th	Day	20% 18% 4 7% 5% 3 4 3 4 5% 28%	2396
	11th to 20th	Day	19% 15% 2 7% 4 4 3 3 4 7% 32%	2375
	21st to end	Day	21% 13% 3 6% 4 4 4 3 4 5% 33%	2600
May	1st to 10th	Day	27% 9% 3 7% 5% 4 4 3 5% 6% 27%	5888
	11th to 20th	Day	20% 9% 3 8% 5% 5% 5% 4 5% 7% 29%	6272
	21st to end	Day	24% 8% 2 5% 4 4 4 4 5% 7% 34%	6949
June	1st to 10th	Day	19% 7% 2 6% 4 5% 5% 4 5% 7% 36%	2800
	11th to 20th	Day	16% 6% 3 5% 4 6% 5% 5% 7% 9% 35%	2800
	21st to end	Day	17% 7% 2 5% 4 4 5% 4 6% 8% 39%	2800
July	1st to 10th	Day	13% 5% 2 6% 4 4 5% 4 5% 10% 42%	6360
	11th to 20th	Day	15% 6% 3 7% 5% 4 4 4 6% 8% 39%	6360
	21st to end	Day	13% 5% 2 6% 4 4 4 4 6% 8% 43%	6453
August	1st to 10th	Day	18% 6% 3 6% 4 4 4 4 6% 8% 37%	4234
	11th to 20th	Day	17% 6% 2 8% 5% 5% 6% 5% 7% 9% 28%	4174
	21st to end	Day	15% 5% 2 5% 4 4 4 4 6% 9% 41%	4411
September	1st to 10th	Day	17% 7% 2 6% 4 4 4 4 6% 8% 38%	2400
	11th to 20th	Day	15% 6% 2 5% 4 4 4 4 6% 8% 43%	2325
	21st to end	Day	18% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	2130
October	1st to 10th	Day	24% 8% 3 6% 3 4 3 4 6% 7% 33%	2000
	11th to 20th	Day	25% 12% 4 9% 4 4 4 3 4 5% 28%	2000
	21st to end	Day	30% 16% 3 8% 5% 4 3 3 4 5% 21%	2200
November	1st to 10th	Day	20% 16% 4 8% 4 4 4 3 4 5% 27%	1850
	11th to 20th	Day	16% 25% 4 9% 4 4 3 3 5% 5% 21%	1680
	21st to end	Day	21% 28% 6% 9% 5% 4 4 3 3 4 15%	1680
December	1st to 10th	Day	19% 32% 12% 12% 4 3 3 2 2 3 7%	2680
	11th to 20th	Day	20% 24% 7% 19% 5% 3 2 2 3 4 11%	3066
	21st to end	Day	20% 27% 7% 11% 7% 4 3 2 3 3 12%	4048
January	1st to 10th	Night	15% 26% 10% 24% 7% 3 2 2 3 2 7%	8234
	11th to 20th	Night	10% 24% 12% 25% 11% 5% 3 2 2 2 4	7741
	21st to end	Night	14% 18% 8% 18% 9% 10% 5% 3 3 3 9%	8401
February	1st to 10th	Night	17% 22% 7% 17% 8% 5% 3 2 3 3 13%	2730
	11th to 20th	Night	16% 17% 8% 18% 7% 5% 4 3 4 5% 14%	2663
	21st to end	Night	18% 18% 6% 17% 6% 4 4 3 4 5% 15%	2160
March	1st to 10th	Night	18% 16% 5% 10% 7% 4 3 2 4 5% 24%	5018
	11th to 20th	Night	16% 18% 4 8% 4 3 3 3 4 6% 30%	5089
	21st to end	Night	17% 15% 6% 10% 4 4 4 2 4 5% 29%	5588
April	1st to 10th	Night	21% 16% 4 7% 4 4 3 2 4 5% 28%	2027
	11th to 20th	Night	21% 12% 3 7% 4 3 3 4 4 6% 33%	1975
	21st to end	Night	19% 10% 4 6% 5% 4 5% 3 4 7% 33%	1815
May	1st to 10th	Night	27% 12% 3 7% 5% 4 4 3 4 5% 27%	4053
	11th to 20th	Night	17% 8% 2 6% 5% 4 5% 4 6% 7% 34%	3607
	21st to end	Night	24% 8% 2 6% 3 3 3 3 6% 7% 35%	3926
June	1st to 10th	Night	15% 7% 3 7% 6% 6% 4 5% 6% 7% 36%	1600
	11th to 20th	Night	13% 7% 2 7% 5% 4 5% 4 6% 7% 39%	1600
	21st to end	Night	16% 7% 2 6% 5% 4 4 4 6% 7% 39%	1600
July	1st to 10th	Night	15% 6% 2 7% 4 4 4 3 6% 9% 40%	3600
	11th to 20th	Night	14% 6% 2 6% 4 4 4 4 6% 7% 42%	3600
	21st to end	Night	12% 6% 2 5% 4 4 4 4 5% 7% 47%	4382
August	1st to 10th	Night	13% 8% 3 7% 4 4 4 4 7% 8% 38%	2915
	11th to 20th	Night	20% 7% 3 7% 4 5% 4 4 5% 6% 34%	2875
	21st to end	Night	12% 5% 2 6% 4 4 5% 4 6% 8% 43%	3452
September	1st to 10th	Night	17% 6% 2 5% 4 3 4 3 5% 7% 43%	2000
	11th to 20th	Night	14% 5% 2 4 3 3 4 3 5% 6% 49%	2071
	21st to end	Night	20% 9% 2 6% 4 4 4 3 5% 8% 34%	2268
October	1st to 10th	Night	19% 7% 3 6% 3 5% 4 3 6% 5% 38%	2400
	11th to 20th	Night	25% 12% 3 6% 5% 4 4 3 4 6% 28%	2400
	21st to end	Night	30% 12% 3 7% 4 4 3 4 5% 5% 24%	2640
November	1st to 10th	Night	20% 15% 3 8% 4 3 4 2 4 5% 32%	2662
	11th to 20th	Night	18% 21% 4 9% 5% 4 4 3 4 5% 22%	2940
	21st to end	Night	20% 24% 7% 10% 5% 4 4 3 3 5% 16%	2940
December	1st to 10th	Night	18% 31% 11% 13% 5% 3 3 2 3 3 7%	4720
	11th to 20th	Night	19% 28% 8% 15% 5% 3 3 2 3 3 10%	5348
	21st to end	Night	21% 26% 7% 12% 6% 4 3 3 3 4 11%	7150

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	85% 3 4 5% 2	4662
	11th to 20th	Day	86% 4 5% 3 2	5160
	21st to end	Day	82% 5% 7% 4 1	5780
February	1st to 10th	Day	78% 4 7% 8% 2	1890
	11th to 20th	Day	75% 5% 7% 10% 3	1852
	21st to end	Day	70% 5% 10% 11% 4 1	1643
March	1st to 10th	Day	62% 5% 12% 16% 5%	5045
	11th to 20th	Day	55% 6% 17% 14% 6% 1	5090
	21st to end	Day	61% 6% 6% 18% 8% 1	5586
April	1st to 10th	Day	59% 5% 11% 15% 10%	2396
	11th to 20th	Day	52% 6% 10% 20% 10% 2	2375
	21st to end	Day	55% 6% 9% 16% 13% 1	2600
May	1st to 10th	Day	57% 6% 10% 16% 8% 3	5897
	11th to 20th	Day	52% 8% 10% 18% 11% 1	6276
	21st to end	Day	49% 7% 12% 19% 11% 2	6949
June	1st to 10th	Day	46% 7% 12% 19% 14% 1	2800
	11th to 20th	Day	44% 9% 13% 21% 12%	2800
	21st to end	Day	43% 8% 13% 23% 13% 1	2800
July	1st to 10th	Day	38% 8% 13% 26% 15% 1	6290
	11th to 20th	Day	41% 8% 14% 21% 16%	6285
	21st to end	Day	38% 8% 12% 26% 16%	6268
August	1st to 10th	Day	44% 8% 14% 22% 12%	4221
	11th to 20th	Day	47% 11% 15% 20% 6%	4213
	21st to end	Day	38% 9% 12% 30% 10% 1	4411
September	1st to 10th	Day	44% 7% 12% 25% 12% 1	2400
	11th to 20th	Day	38% 7% 12% 28% 14% 1	2325
	21st to end	Day	51% 7% 12% 19% 10% 1	2130
October	1st to 10th	Day	43% 7% 13% 23% 12% 1	3260
	11th to 20th	Day	50% 5% 15% 16% 12% 3	3240
	21st to end	Day	51% 6% 15% 20% 8% 1	3538
November	1st to 10th	Day	58% 6% 9% 17% 8% 2	1850
	11th to 20th	Day	64% 5% 11% 13% 5% 2	1680
	21st to end	Day	74% 5% 9% 9% 4	1680
December	1st to 10th	Day	84% 4 5% 5% 1	2680
	11th to 20th	Day	78% 5% 9% 7% 2	3066
	21st to end	Day	77% 5% 9% 6% 3	4048
January	1st to 10th	Night	84% 5% 5% 4 2	8234
	11th to 20th	Night	87% 4 5% 2 1	7782
	21st to end	Night	80% 5% 8% 6% 2	8401
February	1st to 10th	Night	77% 5% 7% 8% 3	2730
	11th to 20th	Night	73% 5% 8% 10% 3	2665
	21st to end	Night	71% 5% 9% 9% 5%	2160
March	1st to 10th	Night	62% 6% 10% 15% 6% 1	5028
	11th to 20th	Night	54% 6% 13% 18% 6% 3	5090
	21st to end	Night	55% 8% 8% 16% 11% 2	5588
April	1st to 10th	Night	59% 5% 9% 17% 9% 1	2027
	11th to 20th	Night	52% 5% 11% 18% 12% 2	1975
	21st to end	Night	51% 6% 10% 18% 13% 2	1815
May	1st to 10th	Night	60% 5% 7% 14% 9% 5%	4060
	11th to 20th	Night	47% 9% 13% 21% 10% 1	3608
	21st to end	Night	48% 6% 11% 20% 12% 2	3927
June	1st to 10th	Night	43% 9% 12% 21% 13% 2	1600
	11th to 20th	Night	42% 8% 12% 22% 15% 1	1600
	21st to end	Night	42% 8% 14% 22% 13% 2	1600
July	1st to 10th	Night	40% 6% 13% 24% 15% 1	3560
	11th to 20th	Night	38% 8% 15% 23% 15% 1	3552
	21st to end	Night	35% 7% 14% 23% 19% 2	4252
August	1st to 10th	Night	40% 8% 15% 26% 10% 1	2904
	11th to 20th	Night	48% 8% 13% 22% 8%	2902
	21st to end	Night	35% 8% 15% 30% 11% 1	3452
September	1st to 10th	Night	39% 7% 13% 26% 13% 2	2000
	11th to 20th	Night	35% 6% 13% 28% 17% 1	2071
	21st to end	Night	48% 7% 12% 20% 11% 1	2268
October	1st to 10th	Night	42% 7% 11% 22% 16% 1	3920
	11th to 20th	Night	51% 5% 12% 16% 13% 2	3899
	21st to end	Night	48% 5% 16% 21% 9% 1	4252
November	1st to 10th	Night	55% 5% 9% 19% 9% 2	2662
	11th to 20th	Night	64% 6% 10% 12% 6% 2	2940
	21st to end	Night	71% 7% 10% 9% 3	2940
December	1st to 10th	Night	82% 5% 7% 4 1	4720
	11th to 20th	Night	80% 5% 7% 6% 2	5348
	21st to end	Night	77% 6% 7% 7% 3	7150

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	33% 32% 23% 7% 3 1	220
	11th to 20th	Day	39% 34% 18% 6% 2	308
	21st to end	Day	35% 27% 26% 9% 3	363
February	1st to 10th	Day	39% 26% 25% 9% 1	330
	11th to 20th	Day	37% 30% 27% 5%	330
	21st to end	Day	43% 24% 28% 5%	344
March	1st to 10th	Day	34% 22% 29% 12% 3	540
	11th to 20th	Day	35% 23% 30% 9% 2 1	540
	21st to end	Day	36% 22% 26% 13% 4	594
April	1st to 10th	Day	35% 21% 28% 11% 4	504
	11th to 20th	Day	36% 22% 22% 11% 7% 2	492
	21st to end	Day	31% 18% 30% 16% 3 1	500
May	1st to 10th	Day	33% 16% 28% 16% 5% 2	503
	11th to 20th	Day	24% 15% 29% 22% 8% 1	527
	21st to end	Day	22% 13% 29% 22% 10% 4	573
June	1st to 10th	Day	21% 17% 35% 19% 7% 1	530
	11th to 20th	Day	18% 16% 29% 25% 10% 1	530
	21st to end	Day	21% 14% 36% 20% 8% 1	530
July	1st to 10th	Day	13% 11% 32% 26% 16% 3	525
	11th to 20th	Day	14% 12% 31% 26% 13% 4	524
	21st to end	Day	15% 9% 34% 27% 12% 3	576
August	1st to 10th	Day	14% 9% 26% 29% 16% 5%	526
	11th to 20th	Day	16% 10% 28% 26% 17% 4	519
	21st to end	Day	17% 9% 31% 25% 13% 5%	583
September	1st to 10th	Day	18% 13% 25% 23% 16% 5%	530
	11th to 20th	Day	13% 8% 22% 28% 21% 8%	530
	21st to end	Day	19% 21% 25% 21% 11% 4	530
October	1st to 10th	Day	23% 13% 27% 19% 14% 3	530
	11th to 20th	Day	32% 18% 28% 15% 5% 1	530
	21st to end	Day	40% 18% 25% 14% 3	583
November	1st to 10th	Day	33% 20% 27% 13% 5% 1	389
	11th to 20th	Day	45% 19% 24% 10% 3 1	220
	21st to end	Day	44% 27% 23% 6% 1	220
December	1st to 10th	Day	44% 24% 23% 7% 3	220
	11th to 20th	Day	45% 23% 24% 9%	220
	21st to end	Day	40% 26% 25% 6% 2	242
January	1st to 10th	Night	35% 26% 26% 10% 3	840
	11th to 20th	Night	37% 27% 24% 10% 2	840
	21st to end	Night	29% 25% 30% 13% 3	924
February	1st to 10th	Night	32% 25% 27% 14% 2	840
	11th to 20th	Night	31% 25% 31% 11% 1	823
	21st to end	Night	35% 24% 28% 13% 1	692
March	1st to 10th	Night	30% 19% 31% 15% 4	840
	11th to 20th	Night	33% 21% 27% 15% 4	840
	21st to end	Night	29% 17% 32% 15% 6% 1	924
April	1st to 10th	Night	31% 17% 30% 19% 2	805
	11th to 20th	Night	30% 15% 27% 20% 6% 1	791
	21st to end	Night	25% 11% 32% 26% 6%	615
May	1st to 10th	Night	27% 10% 23% 30% 9% 1	600
	11th to 20th	Night	15% 8% 34% 36% 7%	413
	21st to end	Night	18% 9% 26% 32% 13% 1	433
June	1st to 10th	Night	16% 8% 32% 32% 11% 1	400
	11th to 20th	Night	16% 10% 27% 37% 9%	400
	21st to end	Night	18% 8% 33% 33% 10%	400
July	1st to 10th	Night	12% 6% 23% 42% 16% 2	390
	11th to 20th	Night	13% 6% 28% 36% 17% 1	388
	21st to end	Night	14% 4 27% 36% 17% 1	637
August	1st to 10th	Night	12% 5% 20% 41% 20% 2	597
	11th to 20th	Night	12% 7% 22% 33% 24% 2	594
	21st to end	Night	14% 7% 25% 32% 21% 2	798
September	1st to 10th	Night	19% 9% 23% 29% 17% 3	800
	11th to 20th	Night	15% 7% 21% 29% 27% 3	800
	21st to end	Night	23% 11% 22% 27% 14% 3	800
October	1st to 10th	Night	22% 11% 27% 23% 15% 1	800
	11th to 20th	Night	31% 17% 25% 20% 6% 1	800
	21st to end	Night	37% 16% 27% 17% 3	880
November	1st to 10th	Night	30% 16% 28% 19% 6% 1	820
	11th to 20th	Night	34% 20% 28% 13% 5% 1	840
	21st to end	Night	36% 23% 26% 11% 4	840
December	1st to 10th	Night	40% 26% 19% 11% 4	840
	11th to 20th	Night	38% 25% 25% 11% 2	840
	21st to end	Night	38% 24% 26% 10% 1	924

Page generated at 2026-03-30 02:18:38. Version ac07

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