Blackbird State Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blackbird State Forest clear sky chart from 2005-11-05 to 2017-03-14.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
38%
14606
21%
45182
12%
14571
49%
14571
26%
28166

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
27%
718
22%
2497
10%
716
43%
716
19%
1543
January16th to endNight
22%
768
22%
2496
8%
768
41%
768
22%
1562
February1st to 15thNight
20%
703
19%
2263
6%
701
37%
701
21%
1421
February16th to endNight
21%
631
26%
1893
8%
631
43%
631
23%
1177
March1st to 15thNight
27%
716
21%
2062
9%
716
41%
716
26%
1302
March16th to endNight
27%
704
22%
1873
10%
704
37%
704
27%
1236
April1st to 15thNight
26%
658
20%
1646
5%
658
34%
658
28%
1103
April16th to endNight
37%
660
20%
1650
7%
660
43%
660
30%
1083
May1st to 15thNight
38%
499
18%
1489
10%
499
44%
499
23%
997
May16th to endNight
52%
342
16%
1369
15%
342
57%
342
22%
812
June1st to 15thNight
52%
330
18%
1320
18%
330
60%
330
22%
783
June16th to endNight
61%
330
15%
1320
19%
330
64%
330
28%
733
July1st to 15thNight
58%
310
14%
1240
16%
310
61%
310
21%
761
July16th to endNight
66%
417
16%
1369
16%
389
70%
389
30%
790
August1st to 15thNight
69%
531
19%
1511
14%
528
70%
528
33%
941
August16th to endNight
63%
700
18%
1750
10%
700
65%
700
35%
1138
September1st to 15thNight
57%
660
27%
1650
15%
660
61%
660
35%
1075
September16th to endNight
54%
657
24%
1781
19%
657
58%
657
32%
1140
October1st to 15thNight
48%
660
23%
1980
20%
660
55%
660
27%
1238
October16th to endNight
38%
704
28%
2123
17%
704
53%
704
31%
1235
November1st to 15thNight
37%
700
24%
2277
14%
700
51%
700
27%
1361
November16th to endNight
32%
720
22%
2415
12%
720
46%
720
22%
1472
December1st to 15thNight
27%
720
19%
2520
9%
720
41%
720
19%
1591
December16th to endNight
25%
768
23%
2688
8%
768
43%
768
20%
1672

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 ForecastData
Points
Cloud CoverDay
13%5%2442445%7%43%
45526
Night
14%5%2442445%7%43%
45360
Cloud CoverDay
13%5%2442445%7%43%
45536
Night
14%5%2442445%7%43%
45365
TransparencyDay
38%412%24%16%2
45222
Night
39%411%23%17%3
45182
SeeingDay
16%8%24%24%18%7%
5014
Night
17%8%28%30%13%1
14610

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
14%6%24425%45%6%43%
1440
16th to endDay
15%7%24423446%44%
1728
February1st to 15thDay
15%6%2442445%6%42%
1596
16th to endDay
12%8%26%5%24347%42%
1580
March1st to 15thDay
14%6%24424447%45%
1856
16th to endDay
17%5%2442445%5%43%
1999
April1st to 15thDay
15%5%24425%346%44%
1972
16th to endDay
13%424323447%46%
1980
May1st to 15thDay
16%6%244345%5%7%38%
2140
16th to endDay
12%4235%35%5%6%9%42%
2394
June1st to 15thDay
11%5%24435%6%7%10%38%
2310
16th to endDay
10%423425%46%9%45%
2310
July1st to 15thDay
8%5%245%35%6%7%9%42%
2310
16th to endDay
43245%46%6%10%11%39%
2388
August1st to 15thDay
9%5%25%4345%6%10%41%
2096
16th to endDay
10%4245%3447%9%43%
2100
September1st to 15thDay
12%42442446%8%44%
1980
16th to endDay
15%5%26%5%25%446%41%
1848
October1st to 15thDay
17%5%13423346%46%
1650
16th to endDay
16%424423335%48%
1749
November1st to 15thDay
16%414424446%46%
1581
16th to endDay
15%5%24324347%45%
1543
December1st to 15thDay
15%5%25%42445%6%42%
1440
16th to endDay
17%6%25%43435%6%40%
1536
January1st to 15thNight
17%5%25%42445%6%42%
2497
16th to endNight
16%7%24424446%42%
2496
February1st to 15thNight
15%7%245%2445%5%42%
2262
16th to endNight
15%6%2432435%5%46%
1893
March1st to 15thNight
16%5%23323348%44%
2050
16th to endNight
15%6%35%5%23345%43%
1873
April1st to 15thNight
15%6%24434447%42%
1646
16th to endNight
17%5%13324347%45%
1650
May1st to 15thNight
16%7%26%41445%7%38%
1489
16th to endNight
12%5%345%2446%9%40%
1367
June1st to 15thNight
12%6%26%42445%8%42%
1320
16th to endNight
8%5%245%2446%10%44%
1320
July1st to 15thNight
7%426%6%36%7%7%9%37%
1320
16th to endNight
5%335%436%5%5%12%42%
1471
August1st to 15thNight
8%4235%36%6%5%9%44%
1522
16th to endNight
11%5%24425%5%6%8%44%
1750
September1st to 15thNight
12%5%235%23446%47%
1650
16th to endNight
13%6%2442435%7%44%
1781
October1st to 15thNight
17%5%2441435%5%45%
1980
16th to endNight
15%413313346%51%
2123
November1st to 15thNight
14%6%24323345%49%
2277
16th to endNight
15%6%24425%45%6%42%
2415
December1st to 15thNight
17%5%25%5%2445%7%38%
2520
16th to endNight
17%424325%45%7%41%
2688

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
13%6%25%4145%46%44%
1440
16th to endDay
16%6%24323446%44%
1728
February1st to 15thDay
15%6%25%4245%46%43%
1596
16th to endDay
12%7%35%5%34437%42%
1580
March1st to 15thDay
14%6%24424445%45%
1867
16th to endDay
17%5%2442445%5%43%
1998
April1st to 15thDay
14%5%24424446%45%
1972
16th to endDay
14%424423447%47%
1980
May1st to 15thDay
16%5%244345%5%7%38%
2140
16th to endDay
12%4245%346%5%10%42%
2394
June1st to 15thDay
11%5%24425%5%7%9%39%
2310
16th to endDay
10%424425%46%9%45%
2310
July1st to 15thDay
8%425%5%35%5%6%10%41%
2310
16th to endDay
5%3245%46%6%9%11%39%
2388
August1st to 15thDay
10%5%25%4345%6%10%41%
2096
16th to endDay
10%4245%3446%9%43%
2100
September1st to 15thDay
12%5%1442446%7%44%
1980
16th to endDay
15%5%26%4245%46%41%
1848
October1st to 15thDay
17%5%2332335%6%46%
1650
16th to endDay
16%5%15%323345%49%
1749
November1st to 15thDay
17%414324446%46%
1581
16th to endDay
15%5%15%324347%45%
1543
December1st to 15thDay
15%5%25%42445%6%42%
1440
16th to endDay
18%6%25%434346%40%
1536
January1st to 15thNight
16%5%25%42445%6%42%
2497
16th to endNight
17%6%24324445%43%
2496
February1st to 15thNight
15%7%24424445%43%
2255
16th to endNight
15%5%24324345%46%
1893
March1st to 15thNight
16%6%23324347%45%
2062
16th to endNight
15%6%35%433345%43%
1873
April1st to 15thNight
16%5%24435%45%6%42%
1646
16th to endNight
18%5%13334346%46%
1650
May1st to 15thNight
18%6%35%424448%38%
1489
16th to endNight
12%5%35%5%2447%8%41%
1367
June1st to 15thNight
11%5%35%5%2445%8%42%
1320
16th to endNight
8%5%344235%6%10%44%
1320
July1st to 15thNight
7%427%5%37%7%8%9%37%
1320
16th to endNight
5%335%426%5%6%11%43%
1471
August1st to 15thNight
8%4145%26%6%6%9%44%
1522
16th to endNight
11%5%245%246%6%7%44%
1750
September1st to 15thNight
12%5%24433347%47%
1650
16th to endNight
13%6%15%33345%7%44%
1781
October1st to 15thNight
16%6%235%13346%45%
1980
16th to endNight
16%313323345%51%
2123
November1st to 15thNight
14%6%25%313345%49%
2277
16th to endNight
15%5%2442445%6%43%
2415
December1st to 15thNight
18%5%26%43345%7%38%
2520
16th to endNight
17%5%2433445%6%41%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
39%415%22%13%4
1441
16th to endDay
40%311%25%15%3
1728
February1st to 15thDay
41%412%26%13%2
1599
16th to endDay
42%310%27%13%2
1580
March1st to 15thDay
39%411%24%17%2
1867
16th to endDay
42%310%21%18%3
1999
April1st to 15thDay
40%310%24%16%5%
1972
16th to endDay
36%410%18%23%6%
1980
May1st to 15thDay
42%6%13%21%14%1
2140
16th to endDay
36%6%16%25%14%1
2398
June1st to 15thDay
37%7%14%26%12%1
2310
16th to endDay
33%5%15%23%19%1
2310
July1st to 15thDay
36%6%12%24%16%3
2161
16th to endDay
31%7%16%27%14%2
2227
August1st to 15thDay
36%6%12%26%16%1
2083
16th to endDay
35%5%13%23%17%4
2100
September1st to 15thDay
36%5%12%22%20%2
1980
16th to endDay
42%47%19%23%1
1848
October1st to 15thDay
38%311%27%17%2
1650
16th to endDay
38%27%28%20%2
1749
November1st to 15thDay
38%410%24%19%3
1581
16th to endDay
39%310%27%15%3
1543
December1st to 15thDay
40%415%24%11%2
1440
16th to endDay
44%412%24%13%1
1536
January1st to 15thNight
41%410%21%17%3
2497
16th to endNight
41%310%26%16%1
2496
February1st to 15thNight
42%311%24%15%2
2263
16th to endNight
39%39%23%20%3
1893
March1st to 15thNight
40%312%25%16%2
2062
16th to endNight
42%210%22%18%2
1873
April1st to 15thNight
41%310%19%19%4
1646
16th to endNight
39%47%19%22%7%
1650
May1st to 15thNight
44%5%10%20%16%2
1489
16th to endNight
39%6%15%19%15%3
1369
June1st to 15thNight
39%6%14%22%16%1
1320
16th to endNight
33%6%15%25%17%2
1320
July1st to 15thNight
39%7%16%19%12%3
1240
16th to endNight
31%8%15%27%14%1
1369
August1st to 15thNight
33%8%14%23%18%1
1511
16th to endNight
36%5%12%22%20%2
1750
September1st to 15thNight
36%5%9%24%21%3
1650
16th to endNight
38%47%21%23%4
1781
October1st to 15thNight
40%410%24%18%3
1980
16th to endNight
34%39%29%19%3
2123
November1st to 15thNight
38%39%22%18%7%
2277
16th to endNight
40%310%24%17%2
2415
December1st to 15thNight
44%311%24%14%1
2520
16th to endNight
42%412%23%14%2
2688

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
16%29%31%11%9%1
61
16th to endDay
25%28%32%10%4
96
February1st to 15thDay
20%24%39%13%1
113
16th to endDay
14%15%43%22%3
239
March1st to 15thDay
15%19%29%28%7%
264
16th to endDay
20%11%37%18%8%4
224
April1st to 15thDay
19%11%33%20%11%2
210
16th to endDay
18%8%26%21%19%6%
210
May1st to 15thDay
30%7%25%17%14%5%
228
16th to endDay
16%416%25%26%10%
267
June1st to 15thDay
15%7%21%29%18%8%
255
16th to endDay
12%322%28%26%5%
255
July1st to 15thDay
11%117%30%30%8%
245
16th to endDay
6%113%33%33%11%
270
August1st to 15thDay
12%113%27%32%13%
253
16th to endDay
9%7%33%29%20%
268
September1st to 15thDay
14%216%21%25%19%
255
16th to endDay
22%314%27%17%15%
254
October1st to 15thDay
20%5%21%25%20%7%
255
16th to endDay
14%8%31%29%14%1
270
November1st to 15thDay
17%10%27%24%17%3
235
16th to endDay
16%15%33%17%15%
163
December1st to 15thDay
15%25%25%23%8%3
60
16th to endDay
34%15%31%15%3
64
January1st to 15thNight
18%16%33%26%5%
720
16th to endNight
21%12%38%25%1
768
February1st to 15thNight
18%15%39%23%1
704
16th to endNight
19%18%36%22%3
631
March1st to 15thNight
19%13%35%26%4
716
16th to endNight
18%10%37%24%8%1
704
April1st to 15thNight
19%13%36%25%5%
658
16th to endNight
19%9%29%29%12%
660
May1st to 15thNight
21%6%27%33%10%
499
16th to endNight
13%420%43%17%
343
June1st to 15thNight
13%322%43%16%
330
16th to endNight
9%317%50%18%
330
July1st to 15thNight
10%217%41%28%
310
16th to endNight
4213%47%28%3
417
August1st to 15thNight
10%9%47%29%2
531
16th to endNight
13%111%35%33%4
700
September1st to 15thNight
15%217%33%27%3
660
16th to endNight
17%216%35%25%3
657
October1st to 15thNight
20%419%35%17%3
660
16th to endNight
18%9%30%28%12%
704
November1st to 15thNight
17%8%31%27%13%2
700
16th to endNight
16%12%29%29%10%
720
December1st to 15thNight
22%11%32%22%10%1
720
16th to endNight
19%12%38%25%4
768
Page generated at 2017-03-15 11:32:38. Version ac04

Copyright 2017 A. Danko


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