Tatlock Quarry Outlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tatlock Quarry Outlook clear sky chart from 2005-11-06 to 2026-03-03.

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	15% 11% 4 9% 5% 5% 5% 4 5% 6% 32%	131339
	Night	15% 12% 4 9% 6% 5% 5% 3 5% 6% 31%	129815
Transparency	Day	51% 6% 12% 20% 10% 1	134830
	Night	52% 6% 12% 19% 10% 1	134411
Seeing	Day	23% 16% 31% 19% 8% 2	16012
	Night	22% 15% 31% 23% 8% 1	25292

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	11% 17% 5% 12% 8% 7% 6% 4 5% 6% 20%	4661
	11th to 20th	Day	11% 20% 7% 14% 8% 6% 4 3 4 4 19%	4650
	21st to end	Day	9% 16% 7% 16% 8% 8% 6% 3 4 4 18%	5499
February	1st to 10th	Day	13% 15% 4 14% 7% 5% 4 3 5% 5% 24%	1890
	11th to 20th	Day	11% 15% 5% 11% 6% 6% 4 4 5% 5% 27%	1843
	21st to end	Day	18% 14% 4 10% 7% 6% 5% 4 4 4 24%	1704
March	1st to 10th	Day	17% 15% 5% 11% 6% 4 4 3 4 6% 26%	4588
	11th to 20th	Day	10% 13% 4 9% 6% 6% 5% 4 6% 6% 30%	4980
	21st to end	Day	15% 13% 4 8% 5% 4 3 3 4 4 38%	5694
April	1st to 10th	Day	20% 13% 3 8% 4 4 4 3 4 6% 32%	2400
	11th to 20th	Day	21% 11% 3 7% 3 3 4 3 4 4 36%	2374
	21st to end	Day	21% 11% 3 7% 5% 4 4 3 4 5% 32%	2533
May	1st to 10th	Day	23% 10% 3 7% 5% 4 4 3 5% 6% 28%	6346
	11th to 20th	Day	15% 9% 4 9% 5% 5% 4 4 6% 7% 32%	6318
	21st to end	Day	20% 8% 3 7% 4 5% 4 4 6% 6% 34%	6949
June	1st to 10th	Day	19% 9% 3 8% 5% 5% 5% 4 6% 6% 31%	2800
	11th to 20th	Day	13% 6% 2 7% 5% 5% 5% 5% 6% 7% 38%	2800
	21st to end	Day	17% 6% 3 7% 5% 5% 5% 4 6% 7% 33%	2800
July	1st to 10th	Day	13% 6% 3 8% 6% 5% 5% 5% 6% 9% 35%	6360
	11th to 20th	Day	10% 5% 2 7% 5% 5% 5% 4 7% 8% 43%	6360
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 6% 10% 46%	6926
August	1st to 10th	Day	14% 8% 3 7% 5% 4 5% 4 6% 7% 37%	4402
	11th to 20th	Day	17% 6% 2 6% 4 4 5% 4 5% 9% 37%	4174
	21st to end	Day	12% 6% 2 6% 4 4 5% 5% 6% 10% 40%	4312
September	1st to 10th	Day	14% 5% 2 6% 5% 5% 5% 4 5% 8% 41%	2400
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 6% 8% 47%	2400
	21st to end	Day	17% 7% 2 6% 5% 5% 5% 2 5% 7% 39%	2120
October	1st to 10th	Day	19% 8% 3 7% 5% 5% 4 3 5% 6% 37%	2000
	11th to 20th	Day	20% 10% 3 8% 5% 5% 5% 3 6% 6% 30%	2000
	21st to end	Day	25% 11% 3 8% 5% 4 5% 3 5% 6% 26%	2077
November	1st to 10th	Day	15% 10% 3 8% 6% 4 4 4 6% 6% 33%	1825
	11th to 20th	Day	16% 13% 4 10% 4 6% 5% 3 4 6% 28%	1680
	21st to end	Day	20% 15% 5% 11% 7% 5% 4 3 5% 5% 20%	1680
December	1st to 10th	Day	20% 19% 6% 12% 7% 5% 4 3 4 5% 14%	2680
	11th to 20th	Day	15% 17% 6% 12% 6% 5% 4 3 3 4 24%	3066
	21st to end	Day	22% 17% 5% 14% 5% 4 3 2 3 4 20%	4048
January	1st to 10th	Night	12% 16% 8% 14% 8% 5% 4 4 5% 5% 19%	8234
	11th to 20th	Night	11% 16% 6% 15% 9% 6% 5% 3 5% 5% 19%	8235
	21st to end	Night	11% 15% 6% 12% 7% 8% 5% 4 5% 5% 22%	8681
February	1st to 10th	Night	11% 16% 6% 11% 7% 5% 4 4 5% 5% 24%	2730
	11th to 20th	Night	12% 12% 6% 11% 7% 5% 5% 3 5% 6% 29%	2663
	21st to end	Night	13% 13% 4 10% 7% 5% 5% 4 5% 5% 28%	2101
March	1st to 10th	Night	20% 14% 4 10% 5% 4 4 3 3 4 29%	5279
	11th to 20th	Night	10% 13% 4 8% 5% 5% 5% 5% 7% 8% 30%	4979
	21st to end	Night	17% 11% 4 9% 5% 5% 4 3 5% 6% 33%	5238
April	1st to 10th	Night	19% 11% 4 9% 4 4 3 2 4 7% 33%	2000
	11th to 20th	Night	19% 9% 3 7% 5% 4 4 3 4 5% 37%	1975
	21st to end	Night	20% 11% 3 7% 5% 4 5% 3 4 6% 33%	1882
May	1st to 10th	Night	23% 10% 3 7% 4 5% 5% 4 5% 6% 28%	3594
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 3 6% 7% 42%	3575
	21st to end	Night	18% 9% 3 7% 4 4 5% 3 5% 8% 34%	3926
June	1st to 10th	Night	15% 7% 3 6% 5% 6% 5% 5% 6% 7% 36%	1600
	11th to 20th	Night	12% 7% 2 8% 4 4 4 4 5% 7% 43%	1600
	21st to end	Night	16% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	1600
July	1st to 10th	Night	11% 7% 3 8% 6% 5% 6% 5% 7% 8% 36%	3600
	11th to 20th	Night	12% 5% 2 6% 4 5% 4 4 5% 8% 46%	3600
	21st to end	Night	8% 5% 2 6% 5% 5% 4 4 6% 7% 48%	3926
August	1st to 10th	Night	10% 6% 2 7% 5% 4 5% 4 7% 8% 42%	2743
	11th to 20th	Night	13% 6% 2 6% 4 5% 4 3 5% 7% 44%	2875
	21st to end	Night	11% 5% 2 6% 5% 5% 5% 3 6% 8% 44%	3553
September	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 6% 6% 47%	2000
	11th to 20th	Night	13% 5% 2 4 3 4 4 3 5% 6% 51%	2000
	21st to end	Night	16% 7% 3 7% 3 4 3 3 5% 6% 43%	2278
October	1st to 10th	Night	17% 9% 2 6% 4 4 3 3 5% 6% 40%	2400
	11th to 20th	Night	19% 9% 3 9% 5% 4 4 4 6% 8% 31%	2400
	21st to end	Night	20% 10% 4 8% 5% 4 4 3 5% 7% 30%	2761
November	1st to 10th	Night	16% 11% 3 8% 4 4 5% 3 4 5% 35%	2689
	11th to 20th	Night	16% 12% 4 8% 6% 4 5% 4 5% 6% 30%	2940
	21st to end	Night	19% 15% 5% 10% 6% 3 4 4 5% 6% 23%	2940
December	1st to 10th	Night	18% 17% 5% 12% 6% 5% 6% 5% 5% 6% 16%	4720
	11th to 20th	Night	20% 15% 6% 11% 5% 5% 4 3 3 4 25%	5348
	21st to end	Night	25% 17% 4 12% 5% 4 3 3 4 3 20%	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	63% 6% 13% 12% 5% 1	4662
	11th to 20th	Day	68% 5% 9% 9% 9%	4680
	21st to end	Day	68% 5% 8% 10% 8% 1	5499
February	1st to 10th	Day	62% 5% 8% 18% 6% 1	1890
	11th to 20th	Day	58% 4 11% 17% 9% 1	1852
	21st to end	Day	62% 4 10% 12% 10% 1	1704
March	1st to 10th	Day	59% 5% 9% 12% 13% 3	4591
	11th to 20th	Day	51% 7% 15% 15% 10% 2	4980
	21st to end	Day	49% 4 6% 19% 19% 3	5694
April	1st to 10th	Day	54% 5% 6% 19% 13% 3	2400
	11th to 20th	Day	51% 5% 7% 19% 16% 2	2374
	21st to end	Day	54% 4 8% 16% 14% 4	2533
May	1st to 10th	Day	55% 6% 9% 18% 10% 2	6357
	11th to 20th	Day	49% 7% 12% 18% 12% 1	6322
	21st to end	Day	48% 6% 12% 21% 11% 1	6949
June	1st to 10th	Day	52% 6% 9% 19% 12% 1	2800
	11th to 20th	Day	42% 7% 11% 25% 13% 2	2800
	21st to end	Day	48% 7% 12% 21% 11% 1	2800
July	1st to 10th	Day	43% 7% 14% 25% 10%	6290
	11th to 20th	Day	34% 8% 14% 28% 15%	6285
	21st to end	Day	32% 7% 14% 36% 11%	6728
August	1st to 10th	Day	45% 7% 15% 24% 10%	4388
	11th to 20th	Day	42% 6% 15% 28% 9% 1	4213
	21st to end	Day	37% 7% 15% 30% 10% 1	4312
September	1st to 10th	Day	39% 7% 14% 29% 11%	2400
	11th to 20th	Day	34% 7% 14% 31% 15%	2400
	21st to end	Day	45% 6% 13% 26% 10%	2120
October	1st to 10th	Day	44% 6% 11% 31% 8%	3260
	11th to 20th	Day	45% 5% 14% 22% 12% 1	3240
	21st to end	Day	50% 6% 17% 21% 6% 1	3328
November	1st to 10th	Day	50% 5% 15% 23% 7% 1	1825
	11th to 20th	Day	56% 6% 12% 16% 9% 1	1680
	21st to end	Day	66% 5% 12% 10% 7% 1	1680
December	1st to 10th	Day	71% 7% 12% 8% 2	2680
	11th to 20th	Day	64% 6% 10% 13% 7%	3066
	21st to end	Day	69% 4 8% 14% 5%	4048
January	1st to 10th	Night	65% 5% 11% 12% 5% 1	8234
	11th to 20th	Night	66% 5% 10% 12% 6%	8280
	21st to end	Night	62% 5% 8% 13% 11% 1	8681
February	1st to 10th	Night	60% 5% 11% 18% 6% 1	2730
	11th to 20th	Night	57% 5% 10% 19% 8% 1	2665
	21st to end	Night	56% 6% 10% 18% 10% 1	2101
March	1st to 10th	Night	60% 4 7% 16% 10% 3	5289
	11th to 20th	Night	49% 7% 18% 16% 8% 2	4980
	21st to end	Night	49% 6% 8% 22% 12% 2	5238
April	1st to 10th	Night	53% 5% 8% 19% 14% 3	2000
	11th to 20th	Night	50% 4 7% 21% 16% 1	1975
	21st to end	Night	52% 5% 7% 17% 16% 3	1882
May	1st to 10th	Night	55% 7% 9% 18% 8% 3	3600
	11th to 20th	Night	40% 7% 14% 21% 15% 2	3576
	21st to end	Night	47% 7% 14% 17% 15% 1	3927
June	1st to 10th	Night	45% 8% 12% 23% 12% 1	1600
	11th to 20th	Night	39% 7% 12% 24% 17% 2	1600
	21st to end	Night	46% 8% 12% 21% 13% 1	1600
July	1st to 10th	Night	42% 8% 16% 19% 14% 1	3560
	11th to 20th	Night	35% 7% 13% 31% 13%	3552
	21st to end	Night	33% 7% 13% 32% 14%	3809
August	1st to 10th	Night	38% 7% 15% 26% 13% 1	2733
	11th to 20th	Night	38% 6% 16% 30% 9% 1	2902
	21st to end	Night	36% 8% 17% 27% 12% 1	3553
September	1st to 10th	Night	35% 6% 13% 31% 14% 1	2000
	11th to 20th	Night	32% 6% 13% 36% 11% 1	2000
	21st to end	Night	42% 6% 12% 30% 11% 1	2278
October	1st to 10th	Night	37% 6% 13% 30% 14%	3920
	11th to 20th	Night	41% 7% 17% 24% 10%	3899
	21st to end	Night	47% 7% 17% 22% 8%	4460
November	1st to 10th	Night	50% 6% 13% 21% 9% 1	2689
	11th to 20th	Night	54% 5% 12% 19% 9% 1	2940
	21st to end	Night	60% 6% 12% 16% 5%	2940
December	1st to 10th	Night	66% 7% 13% 11% 2	4720
	11th to 20th	Night	63% 5% 8% 14% 10% 1	5348
	21st to end	Night	69% 4 6% 12% 9%	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	23% 20% 39% 15% 3	220
	11th to 20th	Day	32% 21% 34% 10% 4	220
	21st to end	Day	23% 22% 37% 15% 4	311
February	1st to 10th	Day	29% 25% 31% 12% 2	330
	11th to 20th	Day	27% 28% 38% 7% 1	330
	21st to end	Day	31% 22% 35% 10% 1	420
March	1st to 10th	Day	28% 21% 34% 14% 4	508
	11th to 20th	Day	30% 17% 36% 14% 3 1	500
	21st to end	Day	33% 21% 28% 12% 5% 1	550
April	1st to 10th	Day	31% 22% 30% 11% 5% 1	500
	11th to 20th	Day	35% 20% 21% 15% 7% 2	492
	21st to end	Day	30% 21% 30% 11% 6% 1	500
May	1st to 10th	Day	26% 16% 33% 17% 6% 2	503
	11th to 20th	Day	18% 17% 37% 19% 7% 2	527
	21st to end	Day	20% 14% 35% 19% 10% 3	573
June	1st to 10th	Day	23% 14% 34% 21% 8% 1	530
	11th to 20th	Day	15% 14% 36% 22% 10% 2	530
	21st to end	Day	20% 15% 33% 21% 10% 2	530
July	1st to 10th	Day	12% 10% 31% 32% 13% 3	525
	11th to 20th	Day	12% 10% 33% 29% 12% 4	524
	21st to end	Day	14% 10% 34% 29% 10% 4	576
August	1st to 10th	Day	14% 7% 29% 33% 13% 4	526
	11th to 20th	Day	13% 7% 30% 28% 16% 5%	519
	21st to end	Day	15% 11% 31% 26% 12% 6%	583
September	1st to 10th	Day	14% 15% 28% 25% 11% 7%	530
	11th to 20th	Day	12% 10% 25% 24% 19% 11%	530
	21st to end	Day	19% 13% 30% 20% 12% 5%	530
October	1st to 10th	Day	24% 15% 26% 22% 10% 4	530
	11th to 20th	Day	26% 21% 31% 16% 5% 1	530
	21st to end	Day	32% 16% 30% 18% 3 1	514
November	1st to 10th	Day	28% 19% 30% 16% 6% 1	399
	11th to 20th	Day	28% 21% 31% 13% 5% 1	220
	21st to end	Day	31% 25% 32% 8% 3	220
December	1st to 10th	Day	30% 19% 36% 12% 3	220
	11th to 20th	Day	33% 27% 28% 9% 3	220
	21st to end	Day	34% 19% 27% 16% 2 1	242
January	1st to 10th	Night	25% 21% 34% 17% 3	840
	11th to 20th	Night	28% 19% 30% 18% 5% 1	840
	21st to end	Night	20% 16% 36% 23% 5%	924
February	1st to 10th	Night	21% 21% 34% 20% 3	840
	11th to 20th	Night	20% 20% 41% 16% 3	823
	21st to end	Night	23% 23% 31% 20% 3	692
March	1st to 10th	Night	25% 18% 33% 19% 4	809
	11th to 20th	Night	23% 20% 33% 19% 4 1	800
	21st to end	Night	24% 16% 31% 22% 6%	880
April	1st to 10th	Night	28% 15% 32% 21% 4	800
	11th to 20th	Night	26% 18% 29% 19% 7%	791
	21st to end	Night	26% 14% 30% 22% 7% 1	682
May	1st to 10th	Night	22% 12% 29% 26% 11% 1	400
	11th to 20th	Night	18% 11% 35% 27% 8% 1	394
	21st to end	Night	13% 11% 35% 28% 12%	433
June	1st to 10th	Night	16% 10% 34% 32% 9%	400
	11th to 20th	Night	14% 12% 32% 30% 12% 1	400
	21st to end	Night	19% 8% 31% 31% 12%	400
July	1st to 10th	Night	7% 9% 32% 38% 13% 1	390
	11th to 20th	Night	11% 6% 27% 44% 11% 1	388
	21st to end	Night	9% 5% 30% 43% 12% 1	438
August	1st to 10th	Night	10% 6% 26% 40% 19%	490
	11th to 20th	Night	12% 4 25% 36% 21% 3	594
	21st to end	Night	13% 8% 30% 30% 17% 2	860
September	1st to 10th	Night	13% 9% 31% 29% 17% 2	800
	11th to 20th	Night	15% 6% 23% 30% 23% 4	800
	21st to end	Night	19% 10% 27% 23% 20% 2	800
October	1st to 10th	Night	22% 12% 26% 24% 15% 2	800
	11th to 20th	Night	25% 15% 31% 22% 7% 1	800
	21st to end	Night	26% 17% 29% 23% 5%	880
November	1st to 10th	Night	25% 18% 29% 22% 6%	820
	11th to 20th	Night	24% 18% 33% 16% 8% 1	840
	21st to end	Night	31% 18% 27% 18% 5%	840
December	1st to 10th	Night	30% 16% 33% 17% 3	840
	11th to 20th	Night	29% 18% 31% 18% 3	840
	21st to end	Night	35% 16% 28% 18% 3	924

Page generated at 2026-02-28 01:40:26. Version ac07

Copyright © 2026 Attilla Danko.