11/28/2022
Chimney Rock Lunatic
Since the dawn of humanity, people have been fascinated by the motion of the sun, moon, stars, and other celestial objects. One naturally occurring observatory of the moon is at Chimney Rock National Monument (near Pagosa Springs in southwest Colorado). Only in recent decades have archeologists discovered that the moon can be seen rising between the pinnacles at Chimney Rock. It is now believed that this phenomenon is a major reason the ancient Pueblo people constructed such an extensive complex of buildings at this site.
MLS (Major Lunar Standstill):
The path of the moon across the night sky varies over time. The variation in the moon’s path is due to: the plane of the orbit is tilted relative to the Earth’s equator, the moon’s orbit is elliptical, the moon’s orbit precesses. As a result of these factors, the path of the moon across the sky varies every day. At times the moon follows a more northerly path and at times it is more southerly. It takes around 18.6 years for a full cycle from north to south and back. The 3 – 4 years out of the 18.6 year cycle when the path is more to the north is called the Major Lunar Standstill. Some also refer to the period of southerly path as an MLS as well. Some refer to the southerly period as the Minor Lunar Standstill.
PGMR (Pinnacle Gap Moon Rise):
For a few dozen times in each MLS, the moon rises between the pinnacles at Chimney Rock (as seen from the ground near the pinnacles). I have taken it upon myself to name this Pinnacle Gap Moon Rise (PGMR) events. Many people conflate MLS with PGMR. To me, this is like confusing Christmas with winter. Please feel free to adopt my term “PGMR”.
During the MLS, PGMR events occur throughout the year. PGMR events occur at all phases of the moon from new moon (0% illuminated) to full moon (100% illuminated).
Viewing PGMR:
Chimney Rock National Monument is closed to vehicles from January 1 to April 30. If CR receives early snow, it may close in December. During this time, visitors can hike in from outside the monument grounds. Chimney Rock and the visitor center is open to the public from May 16 to September 30. During this period, the Chimney Rock Interpretive Association (CRIA – a mostly volunteer group) offers a variety of tours. CRIA will probably offer their official CRIA – MLS tours for a dozen or so PGMR events. When CRIA offers an official tour, visitors will need to purchase tickets from CRIA. For other PGMR events, visitors are on their own. CRIA has yet to announce dates for their official tours. My best guess is CRIA will offer tours for PGMRs that occur: May 15 – Sept 30, that occur at night, when the moon is near full illumination, when moon path is furthest north. It seems that CRIA / USFS will not make public information on PGMR events that are separate from CRIA tours.
Using the graph (profile profile photo) and the tables below, you can determine when you might want to visit CR to observe a PGMR. The photo was taken from the ground in the area where visitors can view the pinnacles. The horizontal lines show the elevation. The diagonal lines show the moon path for various moon rise azimuth angles. The graph was calibrated by taking pictures of the moon when it was close to the pinnacles and comparing it to calculations of moon position using Stellarium (free software for viewing position of celestial objects). Using Stellarium, the bottom of the pinnacle gap is about 2.6 degrees above the horizon. Using a surveyor’s theodolite, the bottom of the gap is 2.15 degrees above the horizon. The difference in bottom of pinnacle gap between Stellarium and a theodolite could be due to: parallax (Stellarium may be measuring angles from center of Earth), refraction (bending of light by Earth’s atmosphere which changes apparent position of moon and stars), or other factors beyond my knowledge.
Drone PGMR Observations:
Since the bottom of the pinnacle gap is uphill from the observation area, it is possible to use a very tall ladder, very long selfie stick, drone, etc. to view PGMR events that could not otherwise be viewed from ground level. The squiggly line below the gap in the photo shows where the pinnacle gap would appear to an observer that was elevated enough to bring the bottom of the gap to even with the horizon.
I believe that drone use is currently prohibited on federal lands without a special permit. I expect it will be a lengthy process to get a special permit at Chimney Rock. Plan accordingly.
The table below shows moonrise azimuth for some additional dates.
PGMR Visible From Ground
Year Month Month Day Time Stellarium Moon Rise Azimuth Illum
2023 Mar 03 1 12:35 54.6 76%
2023 Mar 03 28 11:26 54.3 50%
2023 Apr 04 24 09:16 54.6 23%
2023 Apr 04 25 10:08 54.5 33%
2023 May 05 22 07:58 54.3 11%
2023 Jun 6 18 05:50 54.5 1%
2023 Jul 7 16 04:38 54.5 1%
2023 Aug 8 12 02:33 54.2 12%
2023 Sep 09 8 00:27 54.0 34%
2023 Sep 09 9 01:22 54.5 25%
2023 Oct 10 4 22:19 54.2 71%
2023 Oct 10 5 23:13 54.0 61%
2023 Nov 11 1 21:00 53.7 85%
2023 Nov 11 2 21:58 54.7 77%
2023 Nov 11 28 17:47 54.3 99%
2023 Nov 11 29 18:43 54.2 96%
2023 Dec 12 26 16:31 54.1 99%
2024 Jan 01 22 14:24 53.9 94%
2024 Jan 01 23 15:21 54.5 98%
2024 Feb 02 18 12:20 54.0 75%
2024 Feb 02 19 13:14 53.9 83%
2024 Mar 03 16 11:14 54.3 49%
2024 Mar 03 17 12:08 53.5 59%
2024 Apr 04 13 09:57 53.5 32%
2024 Apr 04 14 10:56 54.1 43%
2024 May 05 10 07:43 54.2 10%
2024 May 05 11 08:41 53.7 17%
2024 Jun 06 7 06:25 53.7 2%
2024 Jun 06 8 07:26 54.5 7%
2024 Jul 7 4 04:14 54.0 2%
2024 Jul 7 5 05:12 54.0 0%
2024 Jul 07 31 02:08 54.5 15%
2024 Aug 08 1 03:03 53.7 8%
2024 Aug 08 28 00:58 53.4 27%
2024 Aug 08 29 01:57 54.1 18%
2024 Sep 09 23 22:52 53.6 64%
2024 Sep 09 24 23:50 53.5 53%
2024 Oct 10 20 20:41 54.4 88%
2024 Oct 10 21 21:38 53.4 79%
2024 Nov 11 17 18:21 53.6 97%
2024 Nov 11 18 19:24 54.0 91%
2024 Dec 12 14 16:03 54.7 100%
2024 Dec 12 15 17:03 53.7 99%
2025 Jan 01 11 14:47 53.7 96%
2025 Jan 01 12 15:50 54.3 99%
2025 Feb 02 7 12:39 53.9 79%
2025 Feb 02 8 13:39 53.6 88%
2025 Mar 03 6 10:35 54.3 54%
2025 Mar 03 7 11:32 53.3 65%
2025 Apr 04 3 10:24 53.4 38%
2025 Apr 04 4 11:27 54.1 50%
2025 Apr 4 30 08:10 54.1 14%
2025 May 05 1 09:13 53.6 23%
2025 May 5 28 06:53 53.7 5%
2025 May 5 29 08:01 54.7 11%
2025 Jun 6 24 04:34 54.3 1%
2025 Jun 6 25 05:38 54.0 0%
2025 Jul 7 22 03:21 53.7 6%
2025 Aug 08 18 01:12 53.6 24%
2025 Aug 08 19 02:15 54.1 15%
2025 Sep 09 13 23:07 53.9 61%
2025 Sep 09 15 00:08 53.5 37%
2025 Oct 10 11 22:00 53.5 75%
2025 Nov 11 7 18:45 54.1 95%
2025 Nov 11 8 19:51 54.3 88%
2025 Dec 12 5 17:28 53.9 100%
2026 Jan 01 1 15:04 54.3 98%
2026 Jan 01 2 16:12 54.5 99%
2026 Jan 01 29 13:51 53.8 90%
2026 Feb 02 25 11:41 53.7 68%
2026 Feb 02 26 12:46 54.6 79%
2026 Mar 03 24 10:36 54.0 41%
2026 Mar 03 25 11:39 54.1 53%
2026 Apr 04 21 09:29 54.0 27%
2026 May 5 18 07:13 54.3 7%
2026 Jun 6 15 05:58 54.5 1%
2026 Jul 7 12 03:35 54.3 4%
2026 Aug 08 9 02:24 54.3 13%
2026 Sep 09 5 00:13 54.2 36%
2026 Oct 10 1 22:08 54.4 73%
2027 Jan 01 19 14:04 54.7 92%
PGMR Visible From Elevated Position
Year Month Month Day Time Stellarium Moon Rise Azimuth Illum
2023 Jan 01 5 15:54 55.0 99%
2023 Jan 01 6 16:47 55.6 100%
2023 Feb 02 1 13:50 55.0 89%
2023 Feb 02 2 14:41 55.1 94%
2023 Feb 2 27 11:01 55.6 57%
2023 Feb 02 28 11:45 55.2 67%
2023 Mar 3 2 13:30 56.0 84%
2023 Mar 03 27 10:37 55.7 40%
2023 Mar 03 29 12:20 55.0 60%
2023 Apr 4 26 11:06 56.2 42%
2023 May 05 21 07:07 55.3 5%
2023 May 05 23 08:54 55.3 18%
2023 Jun 6 17 05:02 56.3 0%
2023 Jun 6 19 06:44 54.8 3%
2023 Jul 7 15 03:46 54.9 4%
2023 Jul 7 17 05:35 56.1 0%
2023 Aug 08 11 01:43 55.1 20%
2023 Aug 8 13 03:28 55.2 7%
2023 Sep 09 6 23:39 55.6 54%
2023 Oct 10 3 21:32 56.7 80%
2023 Oct 10 7 00:11 55.7 40%
2023 Oct 10 31 20:08 55.1 92%
2023 Nov 11 27 16:58 56.7 99%
2023 Nov 11 30 19:44 56.2 90%
2023 Dec 12 25 15:38 54.9 99%
2023 Dec 12 27 17:30 55.3 100%
2024 Jan 01 21 13:34 55.6 88%
2024 Feb 2 17 11:32 56.2 65%
2024 Feb 2 20 14:14 55.9 90%
2024 Mar 03 18 13:06 54.9 69%
2024 Apr 04 12 09:04 55.4 22%
2024 Apr 4 15 11:58 56.7 53%
2024 May 05 12 09:43 55.4 26%
2024 Jun 6 6 05:31 55.4 0%
2024 Jul 7 3 03:24 56.7 6%
2024 Jul 7 6 06:16 56.2 1%
2024 Aug 8 2 04:04 55.0 3%
2024 Aug 08 27 00:05 54.9 37%
2024 Sep 9 22 22:00 56.0 75%
2024 Sep 9 26 00:53 55.9 32%
2024 Oct 10 22 22:42 54.9 69%
2024 Nov 11 16 17:26 56.1 100%
2024 Dec 12 16 18:10 55.4 99%
2025 Jan 01 10 13:53 55.7 91%
2025 Feb 2 6 11:49 56.6 70%
2025 Feb 2 9 14:44 55.8 94%
2025 Mar 03 8 12:36 54.8 76%
2025 Apr 04 2 09:28 55.4 27%
2025 May 5 2 10:21 56.0 34%
2025 May 5 27 05:54 55.6 1%
2025 Jun 6 26 06:49 56.6 3%
2025 Jul 07 21 02:22 55.1 13%
2025 Jul 7 23 04:29 55.0 2%
2025 Aug 8 17 00:18 55.9 35%
2025 Sep 9 16 01:15 55.8 27%
2025 Oct 10 10 21:00 54.9 85%
2025 Oct 10 12 23:06 55.0 64%
2025 Nov 11 6 17:47 56.7 99%
2025 Dec 12 4 16:24 55.2 99%
2025 Dec 12 6 18:40 55.8 97%
2026 Jan 01 28 12:49 54.8 82%
2026 Jan 01 30 15:01 55.8 96%
2026 Feb 02 24 10:44 55.6 56%
2026 Mar 3 23 09:42 56.7 30%
2026 Apr 04 20 08:27 55.0 17%
2026 Apr 4 22 10:39 56.0 38%
2026 May 5 17 06:13 56.7 2%
2026 May 05 19 08:22 55.2 14%
2026 Jun 6 14 04:52 55.1 0%
2026 Jul 7 11 02:36 56.6 11%
2026 Jul 7 13 04:45 55.3 1%
2026 Aug 08 8 01:20 54.8 22%
2026 Sep 09 3 23:15 55.4 60%
2026 Sep 09 6 01:20 55.5 25%
2026 Sep 9 30 21:12 56.6 83%
2026 Oct 10 2 23:12 55.0 62%
2026 Oct 10 28 20:00 55.2 93%
2026 Oct 10 29 21:03 54.8 86%
2026 Nov 11 24 16:45 56.3 99%
2026 Nov 11 25 17:46 54.8 99%
2026 Nov 11 26 18:57 56.2 95%
2026 Dec 12 22 15:23 55.3 99%
2026 Dec 12 23 16:30 55.2 99%
2027 Jan 1 18 13:04 56.4 84%
2027 Jan 1 20 15:15 56.1 98%
2027 Feb 02 15 11:49 55.0 70%
2027 Feb 02 16 12:52 55.0 80%
2027 Mar 03 14 10:44 55.8 43%
2027 Mar 03 15 11:43 54.8 55%
2027 Mar 3 16 12:50 56.6 66%
2027 Apr 4 10 08:42 56.7 18%
2027 Apr 04 11 09:38 55.1 28%
2027 Apr 4 12 10:43 56.0 40%
2027 May 5 8 07:29 55.7 8%
2027 May 05 9 08:33 55.8 16%
2027 Jun 6 4 05:15 56.5 0%
2027 Jun 6 5 06:16 55.5 2%
2027 Jul 7 2 03:55 55.7 3%
2027 Jul 7 3 05:02 56.0 0%
2027 Jul 7 29 01:39 56.3 20%
2027 Jul 7 30 02:39 55.3 11%
2027 Aug 08 26 00:24 55.5 34%
2027 Aug 8 27 01:28 56.1 23%
2027 Sep 9 21 22:19 56.1 71%
2027 Sep 09 22 23:18 55.8 60%
2027 Oct 10 19 21:13 56.0 84%
2027 Nov 11 15 18:05 56.2 98%
2027 Dec 12 13 16:52 56.4 100%
2028 Jan 1 9 14:30 56.2 95%
2028 Feb 2 5 12:13 56.7 74%
2028 Feb 2 6 13:12 56.3 84%
2028 Mar 3 4 10:59 56.3 58%
