Bootland Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bootland Farm clear sky chart from 2005-11-06 to 2024-03-18.

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
28%
22814
13%
80981
8%
22727
35%
22727
14%
58371

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 10thNight
12%
753
6%
4413
2%
737
18%
737
4%
3432
January11th to 20thNight
18%
755
7%
4399
3%
740
24%
740
4%
3300
January21st to endNight
19%
829
7%
4707
6%
814
28%
814
6%
3792
February1st to 10thNight
15%
760
10%
2470
3%
760
22%
760
10%
1908
February11th to 20thNight
16%
742
13%
2405
4%
740
28%
740
12%
1778
February21st to endNight
22%
628
13%
1911
6%
628
32%
628
14%
1413
March1st to 10thNight
18%
760
14%
2241
7%
760
27%
760
14%
1678
March11th to 20thNight
20%
752
15%
2068
7%
752
29%
752
17%
1506
March21st to endNight
26%
792
20%
2088
8%
792
34%
792
20%
1478
April1st to 10thNight
21%
720
15%
1800
5%
720
26%
720
18%
1327
April11th to 20thNight
25%
711
17%
1775
6%
711
32%
711
20%
1282
April21st to endNight
27%
601
16%
1681
6%
601
35%
601
18%
1243
May1st to 10thNight
33%
360
17%
1440
14%
360
43%
360
17%
939
May11th to 20thNight
31%
354
21%
1416
15%
354
47%
354
18%
875
May21st to endNight
37%
389
14%
1551
12%
388
49%
388
23%
913
June1st to 10thNight
35%
360
10%
1440
8%
360
44%
360
16%
925
June11th to 20thNight
39%
360
13%
1440
17%
360
48%
360
21%
856
June21st to endNight
41%
360
10%
1440
12%
360
48%
360
17%
929
July1st to 10thNight
48%
350
14%
1400
17%
350
57%
350
26%
790
July11th to 20thNight
50%
348
16%
1392
22%
348
56%
348
25%
811
July21st to endNight
51%
394
15%
1486
15%
372
57%
372
24%
870
August1st to 10thNight
50%
431
16%
1495
13%
429
56%
429
24%
921
August11th to 20thNight
53%
534
18%
1598
12%
534
58%
534
31%
996
August21st to endNight
46%
769
18%
1957
8%
769
50%
769
31%
1292
September1st to 10thNight
45%
720
16%
1800
6%
720
48%
720
31%
1198
September11th to 20thNight
50%
720
21%
1800
13%
720
54%
720
34%
1170
September21st to endNight
43%
720
20%
2048
15%
720
47%
720
26%
1367
October1st to 10thNight
34%
720
17%
2160
11%
720
42%
720
20%
1473
October11th to 20thNight
24%
720
13%
2160
7%
720
33%
720
15%
1607
October21st to endNight
23%
792
13%
2490
6%
792
31%
792
13%
1877
November1st to 10thNight
26%
740
15%
2435
10%
740
35%
740
16%
1697
November11th to 20thNight
20%
760
14%
2660
9%
760
29%
760
12%
1929
November21st to endNight
19%
760
9%
2660
4%
760
25%
760
9%
2070
December1st to 10thNight
15%
760
7%
2660
4%
760
20%
760
7%
2181
December11th to 20thNight
15%
760
10%
3246
5%
759
23%
759
7%
2498
December21st to endNight
12%
830
5%
4849
2%
817
18%
817
4%
4050

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
17%10%47%6%35%45%6%32%
78497
Night
17%11%48%6%35%45%6%31%
81289
TransparencyDay
52%7%11%19%10%1
78202
Night
53%7%12%18%9%1
81118
SeeingDay
22%16%31%20%9%3
13526
Night
22%14%30%24%9%1
22840

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 10thDay
15%15%6%10%10%45%45%422%
2517
11th to 20thDay
13%15%6%13%10%45%45%5%21%
2520
21st to endDay
15%19%7%13%8%5%5%33418%
2944
February1st to 10thDay
14%14%5%12%8%45%45%5%23%
1710
11th to 20thDay
11%14%7%9%8%44446%28%
1663
21st to endDay
19%11%48%7%45%5%45%26%
1542
March1st to 10thDay
17%11%6%9%7%35%445%29%
1933
11th to 20thDay
15%12%48%8%45%5%45%30%
2058
21st to endDay
18%10%36%6%34345%37%
2268
April1st to 10thDay
23%12%36%5%3445%5%32%
2160
11th to 20thDay
21%9%36%43444438%
2134
21st to endDay
22%9%47%5%25%346%32%
2294
May1st to 10thDay
21%8%37%5%34446%35%
2520
11th to 20thDay
17%7%46%5%3445%6%39%
2478
21st to endDay
16%6%36%6%35%5%6%7%38%
2725
June1st to 10thDay
20%8%46%5%45%5%5%6%32%
2520
11th to 20thDay
15%5%26%5%35%5%6%7%40%
2520
21st to endDay
18%6%36%5%46%6%7%8%32%
2520
July1st to 10thDay
10%6%25%5%36%6%7%9%39%
2520
11th to 20thDay
11%5%36%5%45%5%8%8%39%
2520
21st to endDay
12%425%5%36%6%7%10%39%
2744
August1st to 10thDay
11%6%36%7%45%6%7%7%40%
2431
11th to 20thDay
12%6%26%7%45%5%5%7%40%
2303
21st to endDay
14%5%35%5%35%5%7%9%39%
2381
September1st to 10thDay
14%6%25%6%4446%7%42%
2160
11th to 20thDay
14%5%25%5%35%45%7%45%
2160
21st to endDay
17%6%35%5%3446%7%40%
1910
October1st to 10thDay
20%8%37%5%445%45%35%
1800
11th to 20thDay
22%9%46%6%45%5%5%7%27%
1800
21st to endDay
27%11%37%6%34446%26%
1865
November1st to 10thDay
15%10%46%6%35%5%5%6%36%
1639
11th to 20thDay
18%11%5%8%6%45%5%5%6%28%
1520
21st to endDay
21%13%5%9%7%45%5%46%21%
1520
December1st to 10thDay
22%18%6%12%7%345%45%15%
1520
11th to 20thDay
20%15%48%6%45%45%426%
1906
21st to endDay
28%16%6%12%5%3322319%
2772
January1st to 10thNight
16%17%9%11%8%44445%19%
4429
11th to 20thNight
12%13%5%13%9%5%6%5%5%5%23%
4440
21st to endNight
16%19%6%9%8%5%5%43420%
4710
February1st to 10thNight
13%14%6%10%9%46%5%47%23%
2470
11th to 20thNight
13%12%6%10%8%35%346%29%
2403
21st to endNight
16%11%5%9%7%35%5%6%5%29%
1911
March1st to 10thNight
17%14%47%7%35%34430%
2231
11th to 20thNight
16%12%6%8%5%3435%6%33%
2067
21st to endNight
17%8%37%6%3445%6%38%
2088
April1st to 10thNight
21%9%37%6%345%45%34%
1800
11th to 20thNight
20%9%36%5%34445%37%
1775
21st to endNight
21%10%37%6%44345%33%
1681
May1st to 10thNight
21%7%35%5%3445%6%37%
1440
11th to 20thNight
19%7%34434447%41%
1415
21st to endNight
13%5%25%5%345%5%7%45%
1550
June1st to 10thNight
16%6%36%6%36%6%7%8%34%
1440
11th to 20thNight
13%6%35%6%2446%7%44%
1440
21st to endNight
16%6%25%6%346%6%8%38%
1440
July1st to 10thNight
9%6%25%5%35%6%5%7%47%
1440
11th to 20thNight
11%5%25%6%335%6%9%43%
1440
21st to endNight
10%425%6%45%5%7%9%43%
1574
August1st to 10thNight
10%5%26%7%345%6%11%42%
1505
11th to 20thNight
9%5%25%6%35%5%5%8%47%
1598
21st to endNight
12%5%25%5%25%46%8%45%
1957
September1st to 10thNight
12%5%26%5%345%5%7%46%
1800
11th to 20thNight
15%5%235%34446%49%
1800
21st to endNight
17%5%25%5%3445%6%43%
2048
October1st to 10thNight
18%7%36%5%345%46%38%
2160
11th to 20thNight
21%9%36%5%46%5%5%6%30%
2160
21st to endNight
23%11%46%6%35%45%7%27%
2490
November1st to 10thNight
19%10%36%5%3445%6%35%
2435
11th to 20thNight
18%11%47%7%35%5%5%6%29%
2660
21st to endNight
21%13%5%10%6%3445%5%23%
2660
December1st to 10thNight
21%17%6%9%7%45%5%45%17%
2660
11th to 20thNight
21%15%5%9%7%3444426%
3288
21st to endNight
30%17%6%10%5%3433317%
4884

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 10thDay
62%10%12%9%6%
2518
11th to 20thDay
64%7%9%12%6%1
2520
21st to endDay
70%7%8%9%5%1
2944
February1st to 10thDay
64%5%9%16%5%1
1710
11th to 20thDay
57%5%13%15%9%1
1672
21st to endDay
59%6%10%13%10%2
1542
March1st to 10thDay
57%5%10%16%10%1
1936
11th to 20thDay
55%5%11%15%12%2
2058
21st to endDay
50%5%7%18%14%6%
2268
April1st to 10thDay
54%47%18%12%3
2160
11th to 20thDay
49%6%7%22%15%2
2134
21st to endDay
55%48%14%15%4
2294
May1st to 10thDay
50%5%8%18%15%3
2520
11th to 20thDay
45%6%9%21%17%2
2482
21st to endDay
45%7%12%20%13%3
2725
June1st to 10thDay
52%7%10%19%11%1
2520
11th to 20thDay
42%7%11%23%13%3
2520
21st to endDay
48%8%13%20%11%1
2520
July1st to 10thDay
37%8%12%27%15%1
2450
11th to 20thDay
38%9%15%25%12%
2445
21st to endDay
39%10%15%27%10%
2591
August1st to 10thDay
41%10%15%24%11%
2417
11th to 20thDay
42%9%14%26%8%1
2303
21st to endDay
40%8%15%25%11%1
2381
September1st to 10thDay
40%8%13%28%11%
2160
11th to 20thDay
38%7%12%30%13%1
2160
21st to endDay
44%8%14%26%9%
1910
October1st to 10thDay
50%7%10%22%10%1
1800
11th to 20thDay
56%8%14%16%6%1
1800
21st to endDay
59%6%12%15%6%1
1865
November1st to 10thDay
48%7%15%23%6%1
1639
11th to 20thDay
56%7%13%14%8%1
1520
21st to endDay
64%7%12%9%6%1
1520
December1st to 10thDay
70%7%11%9%31
1520
11th to 20thDay
61%7%13%13%6%
1906
21st to endDay
74%37%13%3
2772
January1st to 10thNight
65%8%14%10%3
4429
11th to 20thNight
62%8%14%12%4
4440
21st to endNight
68%6%9%10%6%
4710
February1st to 10thNight
61%6%10%15%6%1
2470
11th to 20thNight
57%6%10%19%7%1
2405
21st to endNight
55%6%11%18%9%1
1911
March1st to 10thNight
57%5%11%16%10%1
2241
11th to 20thNight
53%5%11%18%11%2
2068
21st to endNight
48%5%8%20%14%4
2088
April1st to 10thNight
52%5%9%18%14%2
1800
11th to 20thNight
49%5%8%22%14%2
1775
21st to endNight
54%5%6%16%16%3
1681
May1st to 10thNight
48%6%7%20%15%5%
1440
11th to 20thNight
43%6%9%23%16%3
1416
21st to endNight
36%8%15%20%19%2
1551
June1st to 10thNight
44%9%13%23%10%1
1440
11th to 20thNight
39%7%11%23%18%2
1440
21st to endNight
42%10%15%19%13%1
1440
July1st to 10thNight
34%8%14%25%17%3
1400
11th to 20thNight
36%7%13%30%14%
1392
21st to endNight
35%9%16%27%13%
1486
August1st to 10thNight
36%10%17%23%13%1
1495
11th to 20thNight
34%8%17%29%11%1
1598
21st to endNight
36%8%16%29%11%1
1957
September1st to 10thNight
37%8%12%27%14%1
1800
11th to 20thNight
35%6%14%33%10%1
1800
21st to endNight
42%6%12%31%9%
2048
October1st to 10thNight
47%6%11%21%14%
2160
11th to 20thNight
53%8%12%19%8%
2160
21st to endNight
56%7%14%15%8%
2490
November1st to 10thNight
50%6%14%20%9%
2435
11th to 20thNight
55%7%12%17%8%1
2660
21st to endNight
62%6%13%14%4
2660
December1st to 10thNight
69%6%11%12%3
2660
11th to 20thNight
63%5%9%15%7%1
3288
21st to endNight
73%5%6%12%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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
22%22%33%19%4
180
11th to 20thDay
29%18%36%11%5%
180
21st to endDay
22%19%37%18%4
249
February1st to 10thDay
28%27%31%11%3
270
11th to 20thDay
28%27%39%5%1
270
21st to endDay
31%23%33%12%1
354
March1st to 10thDay
27%19%35%15%3
460
11th to 20thDay
25%20%34%17%31
449
21st to endDay
32%20%27%15%5%
462
April1st to 10thDay
30%20%30%13%6%
420
11th to 20thDay
31%21%20%17%9%2
412
21st to endDay
29%19%32%13%6%1
420
May1st to 10thDay
27%15%29%19%8%2
423
11th to 20thDay
20%17%32%21%7%3
447
21st to endDay
20%16%32%20%10%3
485
June1st to 10thDay
25%13%32%20%8%1
450
11th to 20thDay
18%15%30%23%11%3
450
21st to endDay
17%14%33%22%12%2
450
July1st to 10thDay
10%8%29%34%14%4
445
11th to 20thDay
11%9%33%27%16%4
444
21st to endDay
14%9%33%29%12%3
488
August1st to 10thDay
13%6%31%30%14%5%
446
11th to 20thDay
13%7%27%31%16%7%
439
21st to endDay
14%12%28%25%14%7%
495
September1st to 10thDay
14%10%31%22%14%8%
450
11th to 20thDay
13%12%25%24%17%8%
450
21st to endDay
18%14%30%19%14%6%
450
October1st to 10thDay
24%16%24%21%11%4
450
11th to 20thDay
24%22%30%17%5%2
450
21st to endDay
30%21%26%19%41
437
November1st to 10thDay
24%20%30%19%7%1
333
11th to 20thDay
24%23%34%12%42
180
21st to endDay
29%27%31%9%31
180
December1st to 10thDay
29%21%36%12%2
180
11th to 20thDay
33%23%33%8%21
180
21st to endDay
29%24%32%11%41
198
January1st to 10thNight
25%17%37%18%3
760
11th to 20thNight
26%20%28%20%5%
760
21st to endNight
19%15%37%24%4
836
February1st to 10thNight
21%18%37%21%3
760
11th to 20thNight
19%19%39%19%3
743
21st to endNight
24%20%29%23%4
628
March1st to 10thNight
24%17%34%21%3
760
11th to 20thNight
24%20%32%18%6%1
752
21st to endNight
22%16%31%23%8%
792
April1st to 10thNight
27%16%30%23%5%
720
11th to 20thNight
24%20%28%20%8%
711
21st to endNight
26%14%28%23%8%1
601
May1st to 10thNight
23%9%29%26%11%1
360
11th to 20thNight
22%10%33%28%7%1
354
21st to endNight
14%7%37%29%12%1
389
June1st to 10thNight
16%8%33%34%8%
360
11th to 20thNight
15%9%30%33%12%1
360
21st to endNight
18%9%25%34%14%
360
July1st to 10thNight
7%8%28%41%15%1
350
11th to 20thNight
11%5%27%42%15%1
348
21st to endNight
10%5%27%44%13%2
394
August1st to 10thNight
10%7%23%40%19%1
431
11th to 20thNight
11%225%36%22%3
534
21st to endNight
13%8%27%34%17%2
769
September1st to 10thNight
14%7%28%30%18%2
720
11th to 20thNight
17%7%22%31%20%3
720
21st to endNight
18%10%24%25%20%2
720
October1st to 10thNight
23%12%26%24%14%1
720
11th to 20thNight
24%16%31%20%9%1
720
21st to endNight
27%17%28%23%5%
792
November1st to 10thNight
26%14%28%25%7%
740
11th to 20thNight
24%18%33%15%9%1
760
21st to endNight
30%18%26%20%6%
760
December1st to 10thNight
30%18%32%17%3
760
11th to 20thNight
27%19%32%18%41
760
21st to endNight
32%16%31%17%3
836
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