TamyMartOffgrid
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TamyMartOffgrid clear sky chart from 2005-11-06 to 2024-11-10.

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	17% 10% 3 8% 5% 5% 4 3 5% 7% 32%	101626
	Night	17% 12% 4 9% 5% 4 4 3 5% 6% 31%	97500
Transparency	Day	28% 47% 7% 13% 5%	105122
	Night	29% 47% 7% 11% 5%	102093
Seeing	Day	23% 16% 30% 20% 8% 2	14451
	Night	22% 13% 29% 25% 9% 1	23547

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% 20% 6% 11% 7% 5% 4 3 4 3 21%	2517
	11th to 20th	Day	14% 14% 6% 15% 7% 6% 4 3 4 5% 20%	2520
	21st to end	Day	13% 17% 8% 14% 8% 6% 5% 3 4 5% 18%	2914
February	1st to 10th	Day	13% 16% 5% 12% 8% 5% 4 4 5% 5% 23%	1710
	11th to 20th	Day	12% 16% 6% 11% 6% 5% 4 3 5% 6% 27%	1663
	21st to end	Day	18% 14% 4 9% 5% 5% 4 4 6% 5% 25%	1549
March	1st to 10th	Day	20% 16% 4 9% 5% 4 4 3 3 6% 26%	3166
	11th to 20th	Day	11% 17% 6% 12% 6% 5% 4 3 4 5% 26%	3480
	21st to end	Day	14% 8% 3 7% 6% 4 3 3 5% 6% 42%	3996
April	1st to 10th	Day	22% 13% 3 7% 5% 4 4 3 4 5% 30%	2280
	11th to 20th	Day	22% 11% 3 6% 5% 4 3 3 4 5% 35%	2254
	21st to end	Day	23% 10% 3 8% 5% 4 4 3 3 5% 32%	2431
May	1st to 10th	Day	21% 9% 3 7% 5% 5% 4 4 6% 7% 31%	4426
	11th to 20th	Day	17% 9% 3 8% 5% 4 4 3 5% 8% 34%	4398
	21st to end	Day	17% 7% 2 7% 5% 5% 5% 4 6% 7% 37%	4837
June	1st to 10th	Day	22% 8% 3 8% 5% 4 5% 4 5% 7% 29%	2660
	11th to 20th	Day	16% 6% 3 6% 5% 4 5% 4 6% 7% 38%	2660
	21st to end	Day	18% 8% 2 7% 5% 5% 5% 5% 6% 6% 32%	2660
July	1st to 10th	Day	12% 6% 3 8% 5% 5% 5% 5% 7% 10% 34%	4440
	11th to 20th	Day	14% 5% 2 6% 5% 4 5% 4 7% 8% 40%	4440
	21st to end	Day	12% 5% 2 6% 4 4 4 3 6% 8% 46%	4814
August	1st to 10th	Day	14% 6% 3 7% 6% 6% 6% 4 6% 8% 34%	4310
	11th to 20th	Day	17% 6% 2 6% 4 5% 4 4 7% 8% 36%	4030
	21st to end	Day	13% 5% 2 6% 4 5% 5% 4 7% 10% 39%	4180
September	1st to 10th	Day	15% 5% 2 6% 4 4 4 3 7% 6% 42%	2280
	11th to 20th	Day	13% 5% 2 7% 4 4 4 4 5% 7% 45%	2280
	21st to end	Day	18% 6% 2 7% 5% 3 4 3 5% 7% 39%	2015
October	1st to 10th	Day	22% 7% 3 6% 5% 4 5% 3 5% 6% 35%	1900
	11th to 20th	Day	24% 10% 3 7% 6% 4 5% 3 4 6% 27%	1900
	21st to end	Day	26% 10% 3 7% 5% 5% 4 2 4 6% 27%	1954
November	1st to 10th	Day	16% 10% 3 6% 5% 4 5% 5% 5% 7% 34%	1724
	11th to 20th	Day	20% 14% 5% 9% 5% 5% 4 3 5% 5% 25%	1520
	21st to end	Day	22% 16% 4 11% 6% 5% 6% 3 3 5% 19%	1520
December	1st to 10th	Day	20% 20% 7% 10% 6% 5% 4 3 4 5% 15%	1520
	11th to 20th	Day	20% 15% 4 11% 6% 4 4 3 4 5% 24%	1906
	21st to end	Day	26% 21% 5% 12% 3 4 3 2 2 3 18%	2772
January	1st to 10th	Night	17% 19% 7% 13% 6% 5% 4 3 4 5% 19%	4429
	11th to 20th	Night	12% 14% 5% 14% 7% 5% 5% 4 5% 6% 23%	4440
	21st to end	Night	14% 19% 6% 12% 8% 6% 5% 3 4 4 20%	4727
February	1st to 10th	Night	13% 14% 6% 13% 7% 6% 5% 3 5% 6% 23%	2470
	11th to 20th	Night	12% 16% 5% 12% 6% 4 4 3 4 5% 29%	2403
	21st to end	Night	16% 13% 4 10% 7% 4 4 4 4 6% 27%	1903
March	1st to 10th	Night	20% 13% 4 8% 5% 4 4 3 3 4 32%	3672
	11th to 20th	Night	15% 17% 5% 11% 6% 4 4 3 5% 6% 24%	3479
	21st to end	Night	14% 10% 4 8% 5% 4 4 3 4 6% 40%	3636
April	1st to 10th	Night	21% 12% 4 7% 4 4 4 3 4 6% 31%	1900
	11th to 20th	Night	19% 10% 3 7% 5% 4 5% 3 4 6% 35%	1875
	21st to end	Night	21% 10% 3 7% 4 4 4 3 4 6% 32%	1767
May	1st to 10th	Night	20% 10% 3 7% 4 4 5% 3 6% 6% 31%	2514
	11th to 20th	Night	20% 8% 3 6% 4 4 5% 4 5% 6% 34%	2495
	21st to end	Night	15% 7% 2 7% 5% 5% 5% 4 6% 7% 38%	2738
June	1st to 10th	Night	17% 7% 2 7% 5% 5% 4 4 7% 8% 33%	1520
	11th to 20th	Night	13% 7% 3 5% 4 4 4 4 6% 7% 42%	1520
	21st to end	Night	18% 7% 3 5% 4 5% 5% 4 5% 8% 36%	1520
July	1st to 10th	Night	13% 6% 2 8% 6% 5% 6% 4 6% 8% 36%	2520
	11th to 20th	Night	14% 6% 2 7% 4 4 4 4 6% 7% 42%	2520
	21st to end	Night	11% 5% 2 5% 4 4 5% 4 6% 8% 45%	2739
August	1st to 10th	Night	13% 6% 3 7% 4 5% 5% 4 6% 8% 40%	2615
	11th to 20th	Night	15% 7% 2 6% 5% 3 4 4 6% 7% 40%	2785
	21st to end	Night	15% 5% 2 6% 4 4 5% 4 5% 7% 43%	3444
September	1st to 10th	Night	11% 5% 3 6% 4 4 4 4 5% 6% 47%	1900
	11th to 20th	Night	15% 5% 1 4 3 3 4 3 5% 7% 49%	1900
	21st to end	Night	18% 8% 2 7% 4 4 3 3 4 6% 43%	2160
October	1st to 10th	Night	19% 8% 2 5% 4 4 4 3 4 6% 40%	2280
	11th to 20th	Night	21% 8% 3 8% 6% 5% 5% 3 4 6% 31%	2280
	21st to end	Night	22% 12% 3 9% 4 5% 4 3 5% 6% 27%	2642
November	1st to 10th	Night	18% 12% 3 6% 5% 4 4 3 6% 6% 32%	2555
	11th to 20th	Night	20% 12% 4 8% 5% 6% 4 4 4 5% 27%	2660
	21st to end	Night	21% 15% 4 10% 5% 4 4 3 5% 6% 22%	2660
December	1st to 10th	Night	20% 19% 6% 10% 6% 4 5% 4 5% 4 17%	2660
	11th to 20th	Night	22% 16% 5% 10% 5% 4 3 2 4 4 25%	3288
	21st to end	Night	28% 19% 5% 12% 4 4 3 2 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	44% 38% 9% 4 5%	2518
	11th to 20th	Day	43% 37% 8% 9% 3	2520
	21st to end	Day	47% 40% 6% 5% 1	2914
February	1st to 10th	Day	24% 65% 2 6% 2 1	1710
	11th to 20th	Day	21% 64% 3 7% 5%	1672
	21st to end	Day	21% 65% 4 3 5% 2	1549
March	1st to 10th	Day	39% 40% 5% 9% 6%	3169
	11th to 20th	Day	36% 41% 6% 9% 6% 2	3480
	21st to end	Day	24% 40% 5% 18% 12% 1	3996
April	1st to 10th	Day	21% 65% 3 5% 5% 1	2280
	11th to 20th	Day	20% 65% 1 8% 5% 1	2254
	21st to end	Day	20% 65% 3 6% 6%	2431
May	1st to 10th	Day	32% 42% 5% 15% 5%	4440
	11th to 20th	Day	31% 41% 10% 14% 4	4402
	21st to end	Day	30% 40% 7% 13% 9%	4837
June	1st to 10th	Day	18% 64% 3 9% 4	2660
	11th to 20th	Day	16% 65% 4 8% 5% 1	2660
	21st to end	Day	17% 64% 4 10% 4	2660
July	1st to 10th	Day	29% 38% 10% 16% 7%	4370
	11th to 20th	Day	25% 37% 10% 24% 4	4365
	21st to end	Day	22% 37% 10% 25% 7%	4661
August	1st to 10th	Day	31% 38% 10% 15% 5%	4296
	11th to 20th	Day	30% 38% 9% 18% 4	4069
	21st to end	Day	24% 39% 12% 18% 7%	4180
September	1st to 10th	Day	17% 61% 6% 11% 5%	2280
	11th to 20th	Day	14% 60% 5% 15% 6%	2280
	21st to end	Day	14% 60% 7% 12% 7%	2015
October	1st to 10th	Day	32% 38% 7% 20% 3	3160
	11th to 20th	Day	27% 38% 10% 18% 6%	3140
	21st to end	Day	32% 38% 13% 14% 3	3192
November	1st to 10th	Day	27% 57% 5% 8% 2	1724
	11th to 20th	Day	24% 60% 5% 8% 2 1	1520
	21st to end	Day	28% 60% 4 3 4	1520
December	1st to 10th	Day	30% 60% 3 5% 2	1520
	11th to 20th	Day	34% 49% 8% 6% 4	1906
	21st to end	Day	49% 37% 2 10% 2	2772
January	1st to 10th	Night	44% 37% 11% 6% 2	4429
	11th to 20th	Night	39% 38% 12% 9% 2	4440
	21st to end	Night	48% 39% 7% 4 2	4727
February	1st to 10th	Night	22% 65% 4 6% 3	2470
	11th to 20th	Night	20% 64% 2 9% 4	2405
	21st to end	Night	20% 65% 4 6% 6%	1903
March	1st to 10th	Night	34% 41% 6% 12% 6% 1	3682
	11th to 20th	Night	39% 41% 7% 8% 4 1	3480
	21st to end	Night	26% 43% 4 15% 10% 3	3636
April	1st to 10th	Night	19% 65% 3 7% 4 1	1900
	11th to 20th	Night	18% 65% 3 8% 6% 1	1875
	21st to end	Night	19% 65% 3 6% 7% 1	1767
May	1st to 10th	Night	34% 42% 7% 13% 4	2520
	11th to 20th	Night	32% 42% 8% 13% 4	2496
	21st to end	Night	30% 41% 7% 13% 9% 1	2739
June	1st to 10th	Night	15% 66% 4 11% 4 1	1520
	11th to 20th	Night	13% 66% 3 9% 8%	1520
	21st to end	Night	17% 64% 4 9% 6%	1520
July	1st to 10th	Night	34% 38% 9% 10% 9%	2480
	11th to 20th	Night	27% 37% 10% 22% 4	2472
	21st to end	Night	23% 38% 10% 21% 8%	2651
August	1st to 10th	Night	27% 39% 9% 18% 8%	2605
	11th to 20th	Night	30% 39% 10% 19% 3	2812
	21st to end	Night	25% 38% 10% 16% 8% 2	3444
September	1st to 10th	Night	13% 61% 6% 14% 6%	1900
	11th to 20th	Night	13% 61% 5% 16% 5% 1	1900
	21st to end	Night	15% 60% 5% 13% 7%	2160
October	1st to 10th	Night	23% 37% 10% 21% 9%	3800
	11th to 20th	Night	26% 38% 12% 18% 6%	3779
	21st to end	Night	32% 38% 12% 12% 6%	4354
November	1st to 10th	Night	27% 57% 7% 7% 3	2555
	11th to 20th	Night	24% 60% 5% 8% 3	2660
	21st to end	Night	25% 61% 5% 6% 3	2660
December	1st to 10th	Night	28% 61% 4 5% 2	2660
	11th to 20th	Night	34% 49% 4 9% 4	3288
	21st to end	Night	49% 36% 3 8% 3	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	22% 23% 33% 19% 3	180
	11th to 20th	Day	25% 18% 38% 16% 3 1	180
	21st to end	Day	22% 21% 33% 20% 5%	240
February	1st to 10th	Day	29% 26% 30% 12% 3	270
	11th to 20th	Day	28% 27% 37% 7% 1	270
	21st to end	Day	32% 23% 30% 13% 2	361
March	1st to 10th	Day	27% 19% 35% 14% 5%	460
	11th to 20th	Day	26% 21% 34% 15% 3 1	460
	21st to end	Day	30% 21% 29% 14% 5% 1	506
April	1st to 10th	Day	32% 22% 25% 15% 5% 1	460
	11th to 20th	Day	35% 19% 21% 14% 9% 2	452
	21st to end	Day	30% 21% 29% 13% 6% 1	460
May	1st to 10th	Day	28% 14% 32% 16% 6% 3	463
	11th to 20th	Day	20% 18% 31% 21% 8% 3	487
	21st to end	Day	21% 18% 31% 20% 9% 2	529
June	1st to 10th	Day	24% 14% 31% 21% 8% 1	490
	11th to 20th	Day	18% 15% 31% 23% 10% 3	490
	21st to end	Day	22% 14% 31% 22% 10% 2	490
July	1st to 10th	Day	12% 8% 32% 34% 11% 3	485
	11th to 20th	Day	14% 10% 34% 26% 13% 3	484
	21st to end	Day	13% 9% 32% 29% 12% 3	532
August	1st to 10th	Day	14% 9% 28% 30% 14% 4	486
	11th to 20th	Day	16% 7% 23% 32% 14% 7%	479
	21st to end	Day	16% 11% 29% 25% 14% 5%	539
September	1st to 10th	Day	18% 11% 31% 21% 14% 6%	490
	11th to 20th	Day	13% 10% 23% 23% 20% 9%	490
	21st to end	Day	19% 13% 27% 22% 12% 6%	490
October	1st to 10th	Day	25% 15% 25% 21% 11% 3	490
	11th to 20th	Day	29% 19% 29% 16% 7% 1	490
	21st to end	Day	30% 19% 28% 19% 4	466
November	1st to 10th	Day	27% 17% 31% 18% 6% 1	364
	11th to 20th	Day	29% 23% 31% 13% 3 1	180
	21st to end	Day	29% 23% 33% 11% 3 1	180
December	1st to 10th	Day	32% 13% 39% 13% 3	180
	11th to 20th	Day	31% 24% 35% 9% 1 1	180
	21st to end	Day	33% 18% 36% 10% 2 1	198
January	1st to 10th	Night	27% 14% 35% 20% 3	760
	11th to 20th	Night	28% 18% 28% 20% 5%	760
	21st to end	Night	19% 15% 38% 23% 6%	836
February	1st to 10th	Night	20% 19% 35% 22% 3	760
	11th to 20th	Night	22% 19% 37% 19% 3	743
	21st to end	Night	23% 20% 29% 23% 5%	628
March	1st to 10th	Night	25% 16% 33% 22% 4	760
	11th to 20th	Night	23% 19% 33% 19% 6%	760
	21st to end	Night	22% 18% 33% 19% 7%	836
April	1st to 10th	Night	28% 14% 30% 23% 5%	760
	11th to 20th	Night	24% 19% 29% 20% 7% 1	751
	21st to end	Night	26% 16% 28% 24% 6%	627
May	1st to 10th	Night	24% 8% 29% 28% 9% 1	380
	11th to 20th	Night	25% 9% 27% 30% 9%	374
	21st to end	Night	15% 9% 37% 27% 12%	411
June	1st to 10th	Night	18% 9% 29% 36% 7%	380
	11th to 20th	Night	16% 7% 29% 33% 14% 1	380
	21st to end	Night	19% 7% 27% 33% 14%	380
July	1st to 10th	Night	10% 4 29% 41% 15% 1	370
	11th to 20th	Night	12% 5% 23% 43% 17% 1	368
	21st to end	Night	11% 5% 25% 44% 13% 1	416
August	1st to 10th	Night	12% 5% 23% 39% 21%	435
	11th to 20th	Night	12% 4 20% 37% 23% 3	564
	21st to end	Night	14% 7% 25% 34% 18% 2	817
September	1st to 10th	Night	13% 8% 28% 31% 18% 1	760
	11th to 20th	Night	16% 7% 23% 28% 22% 3	760
	21st to end	Night	21% 9% 25% 26% 18% 2	760
October	1st to 10th	Night	23% 12% 26% 23% 15% 1	760
	11th to 20th	Night	26% 13% 29% 24% 7% 1	760
	21st to end	Night	26% 16% 30% 24% 4	836
November	1st to 10th	Night	25% 16% 27% 25% 7% 1	779
	11th to 20th	Night	26% 16% 32% 15% 9%	760
	21st to end	Night	31% 17% 26% 21% 5%	760
December	1st to 10th	Night	30% 18% 31% 18% 3	760
	11th to 20th	Night	28% 17% 30% 19% 5% 1	760
	21st to end	Night	34% 17% 30% 16% 4	836

Page generated at 2024-11-07 06:55:50. Version ac07

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