Catoctin Mountain Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Catoctin Mountain Park clear sky chart from 2005-11-05 to 2018-03-21.

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
40%
15915
20%
49242
12%
15876
49%
15876
24%
31559

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
22%
777
19%
2628
8%
776
37%
776
17%
1706
January16th to endNight
21%
832
21%
2704
8%
832
39%
832
20%
1743
February1st to 15thNight
24%
763
17%
2482
6%
761
39%
761
17%
1610
February16th to endNight
19%
683
19%
2097
5%
683
36%
683
18%
1397
March1st to 15thNight
27%
780
21%
2161
10%
780
39%
780
23%
1456
March16th to endNight
25%
792
21%
2160
9%
792
36%
792
24%
1447
April1st to 15thNight
28%
718
16%
1796
5%
718
35%
718
25%
1257
April16th to endNight
40%
720
18%
1800
7%
720
45%
720
30%
1205
May1st to 15thNight
41%
524
17%
1604
12%
524
46%
524
22%
1097
May16th to endNight
52%
374
18%
1497
18%
374
58%
374
20%
918
June1st to 15thNight
55%
360
18%
1440
20%
360
61%
360
24%
827
June16th to endNight
61%
360
18%
1440
19%
360
67%
360
25%
818
July1st to 15thNight
58%
340
12%
1360
16%
340
60%
340
17%
861
July16th to endNight
72%
541
16%
1572
14%
508
75%
508
34%
920
August1st to 15thNight
70%
539
18%
1609
15%
536
70%
536
31%
996
August16th to endNight
68%
735
22%
1881
15%
735
69%
735
35%
1202
September1st to 15thNight
58%
720
25%
1800
14%
720
62%
720
35%
1165
September16th to endNight
56%
717
25%
1983
21%
717
59%
717
31%
1283
October1st to 15thNight
47%
720
22%
2160
18%
720
54%
720
25%
1415
October16th to endNight
39%
768
28%
2304
18%
768
54%
768
31%
1366
November1st to 15thNight
41%
760
23%
2414
17%
760
51%
760
27%
1465
November16th to endNight
33%
780
21%
2708
13%
780
46%
780
20%
1665
December1st to 15thNight
27%
780
15%
2730
6%
780
40%
780
15%
1838
December16th to endNight
25%
832
18%
2912
6%
832
39%
832
18%
1902

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
14%6%25%5%35%5%5%7%38%
49595
Night
13%6%25%5%3445%7%41%
49424
Cloud CoverDay
14%5%25%5%35%5%5%7%39%
49605
Night
14%5%2442445%7%42%
49428
TransparencyDay
42%7%12%21%14%2
49295
Night
39%7%11%23%15%2
49242
SeeingDay
18%10%22%23%18%7%
6207
Night
17%9%27%30%13%1
15920

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
13%6%47%6%35%447%36%
1637
16th to endDay
13%11%35%5%2445%7%35%
1872
February1st to 15thDay
14%9%36%7%35%5%46%34%
1710
16th to endDay
15%7%36%5%25%445%37%
1662
March1st to 15thDay
14%8%26%435%336%40%
2114
16th to endDay
16%8%36%6%1445%6%36%
2190
April1st to 15thDay
14%6%36%5%2445%7%39%
2152
16th to endDay
17%6%35%424346%41%
2163
May1st to 15thDay
18%6%25%5%25%6%6%7%33%
2352
16th to endDay
15%7%36%5%245%5%6%37%
2618
June1st to 15thDay
12%4245%35%5%7%10%38%
2520
16th to endDay
11%4245%35%5%6%9%41%
2520
July1st to 15thDay
10%426%6%36%6%6%8%38%
2520
16th to endDay
7%426%6%37%6%7%10%35%
2486
August1st to 15thDay
11%5%26%5%46%6%7%9%33%
2340
16th to endDay
11%5%25%4245%6%8%41%
2308
September1st to 15thDay
16%413434446%44%
2160
16th to endDay
13%5%25%5%25%45%7%40%
1974
October1st to 15thDay
17%5%2342435%6%44%
1800
16th to endDay
13%5%15%3245%47%45%
1920
November1st to 15thDay
13%6%2442335%7%43%
1774
16th to endDay
17%6%25%5%23446%41%
1579
December1st to 15thDay
16%6%36%435%6%5%7%33%
1560
16th to endDay
15%7%27%5%35%5%5%7%34%
1664
January1st to 15thNight
15%7%35%5%245%6%7%36%
2628
16th to endNight
14%7%35%5%2445%6%39%
2704
February1st to 15thNight
13%7%36%4345%6%7%37%
2480
16th to endNight
14%7%36%5%345%5%6%36%
2097
March1st to 15thNight
15%6%35%435%446%40%
2149
16th to endNight
16%6%25%5%2445%6%41%
2160
April1st to 15thNight
13%7%36%5%35%46%7%37%
1796
16th to endNight
15%6%2442346%7%42%
1800
May1st to 15thNight
18%6%25%5%2445%8%36%
1604
16th to endNight
11%7%35%5%2445%8%42%
1495
June1st to 15thNight
10%4245%2446%9%45%
1440
16th to endNight
9%3245%345%6%9%44%
1440
July1st to 15thNight
10%5%246%46%5%5%9%39%
1440
16th to endNight
5%324335%6%6%11%46%
1679
August1st to 15thNight
8%425%5%25%5%6%8%45%
1620
16th to endNight
10%42343445%9%46%
1881
September1st to 15thNight
12%5%145%2346%7%47%
1800
16th to endNight
14%414435%436%46%
1983
October1st to 15thNight
16%5%24434446%43%
2160
16th to endNight
14%5%14323347%48%
2304
November1st to 15thNight
12%6%35%42335%5%46%
2414
16th to endNight
15%5%2443445%7%41%
2708
December1st to 15thNight
15%7%35%7%35%5%5%6%34%
2730
16th to endNight
15%7%25%4246%6%7%36%
2912

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%37%6%36%447%37%
1637
16th to endDay
13%10%45%435%35%8%37%
1872
February1st to 15thDay
13%7%36%6%446%46%35%
1710
16th to endDay
14%7%36%5%35%35%5%38%
1662
March1st to 15thDay
13%7%345%45%346%41%
2125
16th to endDay
17%7%35%5%2345%5%38%
2189
April1st to 15thDay
14%5%25%5%3435%7%39%
2152
16th to endDay
17%6%24423446%41%
2163
May1st to 15thDay
18%6%245%35%6%6%8%33%
2352
16th to endDay
16%6%35%5%245%5%7%37%
2618
June1st to 15thDay
13%3235%25%5%8%10%39%
2520
16th to endDay
12%3245%35%5%6%9%41%
2520
July1st to 15thDay
10%5%25%6%36%6%6%8%38%
2520
16th to endDay
7%5%25%5%47%7%6%10%36%
2486
August1st to 15thDay
11%5%25%6%46%6%7%9%35%
2340
16th to endDay
12%5%35%4245%6%9%40%
2308
September1st to 15thDay
16%5%1432445%7%44%
2160
16th to endDay
16%5%245%3445%7%40%
1974
October1st to 15thDay
20%5%12423446%44%
1800
16th to endDay
14%425%4245%46%45%
1920
November1st to 15thDay
13%5%2433445%7%44%
1774
16th to endDay
17%5%25%5%2345%6%41%
1579
December1st to 15thDay
16%5%35%5%35%5%6%7%35%
1560
16th to endDay
15%5%27%5%25%5%5%7%36%
1664
January1st to 15thNight
15%6%25%4245%5%7%39%
2628
16th to endNight
14%7%36%424346%41%
2704
February1st to 15thNight
13%6%35%42446%7%39%
2473
16th to endNight
14%7%15%6%25%5%5%7%37%
2097
March1st to 15thNight
15%6%24435%45%5%42%
2161
16th to endNight
16%5%25%424447%41%
2160
April1st to 15thNight
12%7%35%435%46%7%38%
1796
16th to endNight
16%6%2342445%7%42%
1800
May1st to 15thNight
20%6%14433447%37%
1603
16th to endNight
12%6%25%5%2445%7%42%
1495
June1st to 15thNight
11%4244245%6%8%45%
1440
16th to endNight
9%3145%245%7%10%44%
1440
July1st to 15thNight
10%425%6%36%6%5%9%39%
1440
16th to endNight
6%324335%6%7%11%46%
1679
August1st to 15thNight
8%426%435%5%5%8%45%
1620
16th to endNight
11%4134245%6%8%47%
1881
September1st to 15thNight
12%4244235%5%7%48%
1800
16th to endNight
15%5%13424436%47%
1983
October1st to 15thNight
19%5%14424435%43%
2160
16th to endNight
14%413322446%50%
2304
November1st to 15thNight
11%7%24323445%48%
2414
16th to endNight
15%42443446%6%42%
2708
December1st to 15thNight
15%6%35%6%35%6%46%36%
2730
16th to endNight
15%5%25%5%245%6%8%38%
2912

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
45%5%13%21%12%2
1638
16th to endDay
45%5%13%21%10%2
1872
February1st to 15thDay
47%7%11%20%10%1
1712
16th to endDay
45%6%13%22%10%1
1662
March1st to 15thDay
43%6%11%21%15%1
2125
16th to endDay
46%6%11%18%14%2
2190
April1st to 15thDay
43%5%11%19%16%2
2152
16th to endDay
42%5%8%19%19%4
2163
May1st to 15thDay
45%7%12%19%13%1
2352
16th to endDay
45%7%12%20%12%1
2622
June1st to 15thDay
37%10%13%23%14%
2520
16th to endDay
36%9%14%23%14%1
2520
July1st to 15thDay
40%10%12%19%14%3
2371
16th to endDay
38%8%14%22%14%2
2330
August1st to 15thDay
42%8%14%19%14%
2327
16th to endDay
37%6%13%25%13%2
2308
September1st to 15thDay
38%5%12%19%21%2
2160
16th to endDay
41%5%8%21%19%2
1974
October1st to 15thDay
41%5%10%24%16%2
1800
16th to endDay
37%5%11%27%18%
1920
November1st to 15thDay
38%5%14%19%16%5%
1774
16th to endDay
41%5%11%27%12%1
1579
December1st to 15thDay
45%8%14%21%9%1
1560
16th to endDay
45%7%13%21%11%
1664
January1st to 15thNight
43%7%12%20%13%3
2628
16th to endNight
42%5%11%27%11%1
2704
February1st to 15thNight
42%7%13%22%13%1
2482
16th to endNight
43%6%11%22%14%1
2097
March1st to 15thNight
41%7%10%26%12%1
2161
16th to endNight
42%5%11%21%16%2
2160
April1st to 15thNight
42%7%11%19%15%2
1796
16th to endNight
39%411%20%17%6%
1800
May1st to 15thNight
46%6%8%21%14%2
1604
16th to endNight
40%7%13%21%14%2
1497
June1st to 15thNight
34%8%12%27%16%
1440
16th to endNight
33%8%13%24%17%2
1440
July1st to 15thNight
41%10%12%19%12%3
1360
16th to endNight
29%8%18%23%17%2
1572
August1st to 15thNight
35%7%14%23%17%1
1609
16th to endNight
33%7%12%24%19%3
1881
September1st to 15thNight
34%7%12%20%22%3
1800
16th to endNight
38%5%8%23%20%3
1983
October1st to 15thNight
42%5%8%22%18%2
2160
16th to endNight
33%5%9%29%19%1
2304
November1st to 15thNight
36%5%9%24%17%6%
2414
16th to endNight
39%6%10%22%17%2
2708
December1st to 15thNight
47%7%11%21%10%1
2730
16th to endNight
42%9%15%21%10%1
2912

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
20%34%26%11%6%
110
16th to endDay
23%25%36%12%2
144
February1st to 15thDay
22%28%40%8%
135
16th to endDay
27%16%34%19%2
243
March1st to 15thDay
19%22%25%26%6%
330
16th to endDay
23%12%31%22%7%2
311
April1st to 15thDay
18%16%25%24%13%2
270
16th to endDay
23%7%24%18%18%7%
270
May1st to 15thDay
28%16%20%16%13%5%
288
16th to endDay
22%6%17%22%23%7%
331
June1st to 15thDay
16%5%21%25%22%7%
315
16th to endDay
14%424%27%22%6%
315
July1st to 15thDay
15%322%25%24%8%
305
16th to endDay
7%211%30%30%16%
326
August1st to 15thDay
14%16%23%29%15%
313
16th to endDay
12%8%29%28%20%
332
September1st to 15thDay
15%418%17%26%17%
315
16th to endDay
21%211%25%24%14%
314
October1st to 15thDay
23%5%13%29%21%7%
315
16th to endDay
12%13%29%27%15%2
336
November1st to 15thDay
18%9%20%31%18%1
294
16th to endDay
21%20%25%20%10%2
109
December1st to 15thDay
17%30%25%15%7%3
90
16th to endDay
21%17%38%16%5%
96
January1st to 15thNight
20%16%36%23%3
780
16th to endNight
19%14%39%25%1
832
February1st to 15thNight
18%17%34%27%1
764
16th to endNight
21%19%35%21%1
683
March1st to 15thNight
20%13%34%26%4
780
16th to endNight
19%13%37%23%6%1
792
April1st to 15thNight
17%14%36%26%4
718
16th to endNight
20%8%26%30%13%
720
May1st to 15thNight
24%6%21%32%14%
524
16th to endNight
16%319%37%21%1
375
June1st to 15thNight
11%122%36%25%1
360
16th to endNight
9%118%48%20%1
360
July1st to 15thNight
13%117%41%25%1
340
16th to endNight
6%112%42%32%4
541
August1st to 15thNight
11%8%46%30%2
539
16th to endNight
13%110%39%30%4
735
September1st to 15thNight
14%218%32%29%2
720
16th to endNight
19%116%28%30%3
717
October1st to 15thNight
22%320%28%21%2
720
16th to endNight
17%8%32%29%11%
768
November1st to 15thNight
15%8%29%34%11%1
760
16th to endNight
18%15%28%28%8%
780
December1st to 15thNight
19%13%32%25%7%
780
16th to endNight
20%10%39%27%3
832
Page generated at 2018-03-22 11:34:24. Version ac04

Copyright 2018 A. Danko


Catoctin Mountain Park Clear Sky Chart |Charts Home