Turtle Rock Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Turtle Rock Observatory clear sky chart from 2005-11-06 to 2024-11-02.

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	14% 9% 3 7% 5% 5% 5% 4 6% 7% 35%	101169
	Night	15% 9% 3 7% 5% 4 4 4 5% 7% 37%	97752
Transparency	Day	48% 5% 11% 21% 13% 2	100982
	Night	47% 4 11% 21% 14% 2	97609
Seeing	Day	21% 12% 21% 23% 16% 7%	15070
	Night	19% 10% 19% 31% 18% 2	25123

By Month

Percentage Cloud Cover SE (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	17% 14% 7% 11% 5% 3 3 3 4 6% 28%	2836
	11th to 20th	Day	16% 18% 8% 11% 8% 3 4 3 3 3 23%	2840
	21st to end	Day	16% 18% 5% 9% 5% 4 4 3 3 4 29%	3124
February	1st to 10th	Day	17% 13% 4 9% 5% 4 5% 3 5% 5% 31%	1715
	11th to 20th	Day	21% 13% 4 10% 4 4 3 3 4 4 30%	1848
	21st to end	Day	22% 12% 4 8% 4 3 3 3 5% 5% 32%	1570
March	1st to 10th	Day	20% 13% 4 6% 4 3 4 3 4 6% 34%	3395
	11th to 20th	Day	13% 8% 3 7% 4 3 4 3 4 6% 45%	3480
	21st to end	Day	17% 10% 3 6% 4 4 4 3 5% 6% 37%	3815
April	1st to 10th	Day	14% 8% 3 6% 5% 5% 5% 4 5% 7% 38%	2090
	11th to 20th	Day	15% 8% 2 6% 5% 4 4 4 5% 6% 41%	2296
	21st to end	Day	16% 8% 3 6% 6% 5% 4 4 4 6% 37%	2470
May	1st to 10th	Day	20% 9% 4 8% 6% 5% 5% 4 5% 6% 27%	4082
	11th to 20th	Day	18% 8% 3 9% 6% 5% 5% 5% 6% 6% 29%	4081
	21st to end	Day	10% 6% 3 7% 5% 5% 6% 5% 8% 10% 34%	4476
June	1st to 10th	Day	11% 7% 3 7% 6% 5% 5% 5% 8% 10% 35%	2470
	11th to 20th	Day	9% 6% 2 8% 7% 7% 6% 6% 7% 9% 34%	2470
	21st to end	Day	10% 6% 2 8% 6% 5% 5% 5% 8% 9% 35%	2470
July	1st to 10th	Day	7% 5% 2 6% 5% 6% 7% 6% 9% 11% 36%	4120
	11th to 20th	Day	11% 7% 3 7% 5% 4 6% 5% 8% 9% 36%	4120
	21st to end	Day	18% 9% 3 10% 7% 7% 7% 5% 6% 8% 20%	4466
August	1st to 10th	Day	11% 7% 3 9% 7% 6% 6% 5% 9% 11% 27%	4104
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 4 8% 10% 34%	4044
	21st to end	Day	6% 4 1 4 4 4 4 4 6% 9% 54%	4318
September	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 5% 7% 8% 41%	2090
	11th to 20th	Day	13% 7% 3 7% 4 4 5% 4 7% 7% 39%	2090
	21st to end	Day	15% 6% 3 7% 5% 5% 5% 4 6% 8% 38%	2090
October	1st to 10th	Day	14% 6% 2 5% 4 4 4 3 5% 6% 48%	2015
	11th to 20th	Day	15% 7% 2 5% 3 4 4 3 4 5% 49%	1900
	21st to end	Day	16% 8% 2 5% 4 4 3 3 4 6% 45%	2090
November	1st to 10th	Day	12% 7% 2 5% 3 3 3 3 4 6% 50%	1787
	11th to 20th	Day	11% 11% 2 6% 4 4 5% 3 5% 7% 42%	1710
	21st to end	Day	15% 9% 3 6% 4 4 3 3 5% 6% 42%	1710
December	1st to 10th	Day	20% 14% 4 9% 4 4 3 3 4 6% 30%	1710
	11th to 20th	Day	17% 14% 3 8% 3 3 3 4 6% 7% 32%	2153
	21st to end	Day	16% 15% 7% 9% 5% 5% 5% 4 6% 5% 24%	3124
January	1st to 10th	Night	18% 17% 7% 10% 5% 4 4 3 4 4 25%	4109
	11th to 20th	Night	19% 12% 4 9% 5% 4 4 3 4 4 32%	4120
	21st to end	Night	20% 12% 4 8% 5% 4 4 3 4 5% 29%	4532
February	1st to 10th	Night	16% 11% 4 8% 5% 4 4 3 5% 6% 34%	2461
	11th to 20th	Night	20% 12% 4 8% 5% 4 4 3 5% 4 30%	2218
	21st to end	Night	21% 13% 3 8% 5% 4 3 3 4 6% 30%	1884
March	1st to 10th	Night	22% 13% 3 7% 4 3 4 3 3 5% 32%	3457
	11th to 20th	Night	14% 7% 4 6% 4 3 4 3 5% 6% 45%	3480
	21st to end	Night	14% 7% 2 6% 4 4 5% 4 5% 7% 42%	3817
April	1st to 10th	Night	13% 9% 3 8% 4 3 5% 4 5% 7% 38%	2090
	11th to 20th	Night	14% 9% 2 5% 4 4 5% 4 6% 6% 41%	1845
	21st to end	Night	14% 8% 2 6% 5% 5% 5% 4 4 6% 42%	1710
May	1st to 10th	Night	18% 10% 3 8% 5% 5% 5% 3 5% 7% 30%	2813
	11th to 20th	Night	17% 10% 3 8% 5% 4 4 4 5% 8% 32%	2812
	21st to end	Night	10% 7% 3 7% 5% 5% 6% 4 7% 10% 35%	3079
June	1st to 10th	Night	10% 5% 2 7% 4 4 5% 5% 7% 11% 39%	1710
	11th to 20th	Night	6% 5% 3 6% 6% 6% 5% 6% 6% 10% 41%	1710
	21st to end	Night	9% 6% 2 7% 5% 5% 5% 4 6% 11% 39%	1710
July	1st to 10th	Night	10% 5% 2 6% 5% 5% 6% 6% 9% 11% 35%	2840
	11th to 20th	Night	11% 5% 3 6% 4 5% 4 4 7% 12% 40%	2840
	21st to end	Night	15% 10% 4 12% 6% 6% 5% 5% 6% 8% 23%	3087
August	1st to 10th	Night	12% 7% 3 8% 5% 5% 5% 5% 8% 11% 31%	2825
	11th to 20th	Night	12% 7% 3 7% 5% 5% 5% 5% 7% 8% 36%	2785
	21st to end	Night	5% 4 2 4 3 4 4 4 6% 9% 54%	3302
September	1st to 10th	Night	12% 7% 2 7% 4 5% 4 3 4 7% 44%	2090
	11th to 20th	Night	13% 7% 3 7% 4 4 4 3 5% 7% 44%	2090
	21st to end	Night	14% 7% 2 6% 4 5% 3 3 5% 7% 45%	2090
October	1st to 10th	Night	14% 6% 1 6% 4 4 3 3 4 6% 49%	2163
	11th to 20th	Night	15% 7% 2 4 4 3 3 3 5% 5% 49%	2280
	21st to end	Night	15% 7% 2 5% 4 3 3 2 5% 6% 47%	2508
November	1st to 10th	Night	13% 7% 3 5% 3 3 3 3 4 5% 51%	2311
	11th to 20th	Night	14% 9% 3 6% 4 3 4 3 4 7% 44%	2470
	21st to end	Night	13% 10% 2 6% 4 4 3 3 5% 5% 44%	2470
December	1st to 10th	Night	19% 13% 4 9% 5% 4 3 3 4 6% 29%	2470
	11th to 20th	Night	17% 13% 4 10% 4 4 4 3 4 5% 33%	3042
	21st to end	Night	16% 16% 7% 9% 5% 5% 5% 3 5% 8% 23%	4532

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	60% 3 5% 16% 13% 3	2837
	11th to 20th	Day	68% 3 4 14% 10% 1	2840
	21st to end	Day	62% 2 5% 15% 15% 1	3124
February	1st to 10th	Day	56% 3 7% 18% 14% 1	1715
	11th to 20th	Day	59% 3 6% 17% 14% 2	1858
	21st to end	Day	55% 2 8% 15% 16% 4	1570
March	1st to 10th	Day	54% 2 7% 19% 15% 4	3395
	11th to 20th	Day	43% 3 7% 26% 17% 4	3480
	21st to end	Day	49% 3 7% 26% 14% 2	3815
April	1st to 10th	Day	46% 3 10% 23% 15% 3	2090
	11th to 20th	Day	44% 3 8% 22% 19% 4	2296
	21st to end	Day	49% 3 11% 23% 11% 2	2470
May	1st to 10th	Day	57% 4 11% 19% 9% 1	4120
	11th to 20th	Day	56% 4 10% 24% 6% 1	4085
	21st to end	Day	43% 6% 14% 24% 11% 2	4489
June	1st to 10th	Day	42% 7% 16% 21% 13% 1	2470
	11th to 20th	Day	43% 9% 14% 18% 13% 2	2470
	21st to end	Day	43% 7% 14% 20% 16% 1	2470
July	1st to 10th	Day	38% 10% 21% 18% 11% 1	4055
	11th to 20th	Day	41% 7% 18% 25% 7% 1	4051
	21st to end	Day	61% 7% 10% 15% 7%	4324
August	1st to 10th	Day	46% 9% 18% 20% 7%	4091
	11th to 20th	Day	40% 8% 16% 24% 9% 2	4083
	21st to end	Day	27% 5% 20% 33% 14% 1	4318
September	1st to 10th	Day	38% 7% 13% 22% 15% 6%	2090
	11th to 20th	Day	42% 7% 9% 23% 17% 2	2090
	21st to end	Day	45% 5% 10% 21% 16% 3	2090
October	1st to 10th	Day	38% 3 8% 24% 21% 6%	2015
	11th to 20th	Day	39% 3 8% 26% 19% 6%	1900
	21st to end	Day	42% 3 6% 26% 17% 6%	2090
November	1st to 10th	Day	36% 3 7% 21% 28% 5%	1787
	11th to 20th	Day	41% 3 7% 22% 21% 6%	1710
	21st to end	Day	45% 3 7% 21% 19% 4	1710
December	1st to 10th	Day	58% 3 8% 18% 11% 2	1710
	11th to 20th	Day	51% 3 8% 16% 18% 3	2150
	21st to end	Day	62% 2 6% 21% 8% 1	3124
January	1st to 10th	Night	65% 2 5% 14% 12% 2	4109
	11th to 20th	Night	58% 3 5% 15% 17% 2	4120
	21st to end	Night	59% 3 7% 17% 14% 1	4532
February	1st to 10th	Night	51% 3 10% 20% 14% 2	2461
	11th to 20th	Night	58% 3 6% 18% 11% 4	2219
	21st to end	Night	57% 3 7% 18% 11% 4	1884
March	1st to 10th	Night	57% 2 6% 19% 14% 2	3457
	11th to 20th	Night	41% 3 9% 26% 16% 6%	3480
	21st to end	Night	43% 3 9% 26% 17% 2	3817
April	1st to 10th	Night	44% 5% 10% 22% 15% 3	2090
	11th to 20th	Night	42% 5% 9% 21% 18% 5%	1845
	21st to end	Night	45% 4 11% 26% 12% 1	1710
May	1st to 10th	Night	55% 5% 11% 21% 8% 1	2840
	11th to 20th	Night	51% 5% 12% 25% 6% 1	2813
	21st to end	Night	43% 6% 14% 24% 10% 2	3087
June	1st to 10th	Night	38% 8% 18% 20% 14% 1	1710
	11th to 20th	Night	36% 8% 21% 22% 12% 2	1710
	21st to end	Night	39% 9% 15% 22% 13% 3	1710
July	1st to 10th	Night	40% 10% 20% 20% 10% 1	2795
	11th to 20th	Night	35% 8% 23% 26% 6% 2	2786
	21st to end	Night	57% 9% 12% 17% 5%	2988
August	1st to 10th	Night	44% 9% 19% 22% 6%	2814
	11th to 20th	Night	42% 8% 17% 23% 9%	2812
	21st to end	Night	25% 6% 18% 36% 13% 1	3302
September	1st to 10th	Night	41% 6% 13% 21% 16% 4	2090
	11th to 20th	Night	39% 6% 12% 23% 19% 1	2090
	21st to end	Night	40% 5% 10% 25% 18% 2	2090
October	1st to 10th	Night	37% 4 8% 23% 22% 5%	2163
	11th to 20th	Night	39% 3 8% 26% 20% 4	2280
	21st to end	Night	40% 3 5% 25% 21% 6%	2508
November	1st to 10th	Night	37% 3 8% 21% 24% 6%	2311
	11th to 20th	Night	42% 3 7% 19% 23% 6%	2470
	21st to end	Night	42% 3 7% 25% 19% 3	2470
December	1st to 10th	Night	58% 3 8% 18% 11% 2	2470
	11th to 20th	Night	55% 3 7% 17% 15% 3	3044
	21st to end	Night	62% 3 8% 15% 11% 1	4532

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% 30% 26% 11% 3 1	270
	11th to 20th	Day	38% 24% 27% 10% 1	270
	21st to end	Day	34% 26% 26% 12% 3	297
February	1st to 10th	Day	31% 19% 33% 11% 5%	270
	11th to 20th	Day	43% 26% 23% 8% 1	270
	21st to end	Day	41% 23% 26% 8% 1	225
March	1st to 10th	Day	25% 21% 26% 21% 6% 2	431
	11th to 20th	Day	27% 23% 27% 18% 3 1	460
	21st to end	Day	30% 19% 23% 20% 7% 1	506
April	1st to 10th	Day	28% 17% 24% 19% 10% 2	460
	11th to 20th	Day	21% 18% 28% 19% 12% 3	452
	21st to end	Day	26% 14% 25% 21% 11% 4	460
May	1st to 10th	Day	25% 16% 26% 19% 9% 5%	463
	11th to 20th	Day	19% 10% 23% 24% 15% 8%	487
	21st to end	Day	16% 8% 21% 22% 20% 13%	529
June	1st to 10th	Day	13% 6% 21% 30% 21% 9%	490
	11th to 20th	Day	10% 6% 20% 28% 25% 11%	490
	21st to end	Day	13% 8% 24% 23% 23% 8%	490
July	1st to 10th	Day	14% 5% 13% 25% 26% 16%	485
	11th to 20th	Day	13% 4 13% 32% 25% 13%	484
	21st to end	Day	15% 6% 13% 30% 25% 11%	532
August	1st to 10th	Day	14% 6% 17% 25% 24% 15%	486
	11th to 20th	Day	15% 4 14% 29% 23% 15%	479
	21st to end	Day	12% 2 10% 27% 29% 20%	539
September	1st to 10th	Day	12% 3 14% 27% 30% 14%	490
	11th to 20th	Day	15% 6% 11% 24% 30% 14%	490
	21st to end	Day	19% 8% 18% 27% 20% 7%	490
October	1st to 10th	Day	18% 5% 19% 29% 23% 7%	490
	11th to 20th	Day	17% 15% 19% 25% 19% 4	490
	21st to end	Day	20% 12% 22% 27% 15% 4	539
November	1st to 10th	Day	18% 12% 25% 27% 14% 4	379
	11th to 20th	Day	20% 21% 28% 21% 8% 1	270
	21st to end	Day	18% 20% 36% 19% 6% 1	270
December	1st to 10th	Day	31% 18% 31% 16% 3	270
	11th to 20th	Day	27% 20% 27% 18% 8%	270
	21st to end	Day	31% 18% 29% 15% 6% 1	297
January	1st to 10th	Night	26% 19% 27% 25% 4	760
	11th to 20th	Night	29% 16% 27% 24% 4	760
	21st to end	Night	22% 19% 32% 24% 2	836
February	1st to 10th	Night	23% 16% 29% 30% 3	760
	11th to 20th	Night	30% 21% 28% 20% 1	743
	21st to end	Night	30% 18% 28% 22% 1	628
March	1st to 10th	Night	24% 14% 29% 27% 6%	760
	11th to 20th	Night	25% 16% 26% 26% 7%	760
	21st to end	Night	19% 13% 30% 29% 8%	836
April	1st to 10th	Night	20% 16% 27% 29% 9%	760
	11th to 20th	Night	19% 14% 24% 31% 12% 1	680
	21st to end	Night	16% 8% 25% 39% 11% 2	570
May	1st to 10th	Night	17% 11% 22% 34% 15% 2	570
	11th to 20th	Night	17% 7% 17% 35% 22% 2	561
	21st to end	Night	11% 4 13% 34% 33% 6%	617
June	1st to 10th	Night	10% 4 10% 41% 29% 5%	570
	11th to 20th	Night	8% 2 12% 36% 36% 6%	570
	21st to end	Night	12% 2 10% 38% 35% 3	570
July	1st to 10th	Night	14% 3 7% 34% 38% 4	555
	11th to 20th	Night	14% 2 3 32% 42% 7%	552
	21st to end	Night	11% 3 7% 36% 34% 9%	624
August	1st to 10th	Night	13% 2 7% 32% 42% 4	567
	11th to 20th	Night	15% 2 6% 34% 37% 6%	564
	21st to end	Night	12% 3 4 30% 43% 8%	693
September	1st to 10th	Night	13% 4 8% 33% 37% 5%	760
	11th to 20th	Night	16% 4 9% 30% 35% 5%	760
	21st to end	Night	15% 5% 15% 34% 28% 2	760
October	1st to 10th	Night	18% 4 14% 30% 28% 5%	760
	11th to 20th	Night	19% 8% 20% 34% 18% 1	760
	21st to end	Night	20% 11% 17% 36% 15% 1	836
November	1st to 10th	Night	17% 9% 17% 39% 16% 2	745
	11th to 20th	Night	19% 12% 22% 36% 10% 1	760
	21st to end	Night	19% 11% 26% 33% 10% 1	760
December	1st to 10th	Night	28% 13% 26% 27% 6%	760
	11th to 20th	Night	24% 14% 25% 31% 5% 1	760
	21st to end	Night	27% 13% 24% 31% 5%	836

Page generated at 2024-10-30 01:22:55. Version ac07

Copyright © 2024 Attilla Danko.