OPOD - Moonbows, County Donegal

Last updated on September 16, 2023

OPOD - Moonbows: A Spectacular Phenomenon in County Donegal

Moonbows, also known as lunar rainbows, are a breathtaking atmospheric optical phenomenon that occurs when the moonlight is refracted and reflected by water droplets in the air. While rainbow arcs are typically formed by sunlight, moonbows are created by the light of the moon. In this article, we delve into the mesmerizing moonbows captured by photographer Peter O'Toole in County Donegal, Ireland, and explore the factors that contribute to witnessing this ethereal display of nature.

Peter O'Toole had the privilege of capturing his first moonbow images in Glenveagh Park, Donegal, where the combination of excellent dark skies and frequent showers made it an ideal location for spotting this elusive phenomenon. The moonbow appeared as ghostly phantoms of white 180-degree arcs of refracted light, creating a surreal and enchanting sight. Although the colors were not visible to the naked eye, they were beautifully captured in O'Toole's photographs.

In some of the shots taken by O'Toole, faint secondary bows can also be observed. These secondary bows appear as additional, more delicate arcs of light outside the primary moonbow. The presence of a darker sky known as Alexander's dark band between the two bows enhances the visibility of the outer secondary rainbow.

To increase your chances of witnessing a moonbow, here are some tips to keep in mind:

1. Choose the right location: Look for locales with a combination of frequent short showers and clouds interspersed with clear skies. While County Donegal in Ireland, the Western Highlands of Scotland, Hawaii, and Patagonia are known to be good locations for moonbow sightings, they are not the only places where this phenomenon can occur.

2. Seek dark skies: To fully appreciate the beauty of a moonbow, it is essential to find a location away from the light pollution of cities. The absence of artificial light allows the moonbow's ethereal glow to stand out against the night sky.

3. Consider the moon's position: Moonbows are most visible when the moon is less than 40 degrees high in the sky. Pay attention to the moon's phase and position to plan your moonbow hunting excursion accordingly.

4. A full moon is not essential: While a full moon can enhance the visibility of a moonbow, it is not a prerequisite. Moonbows can be observed even when the moon is not at its fullest phase. So, don't be discouraged if you can't time your visit during a full moon.

5. Timing is crucial: Moonbows are best spotted after twilight has ended, but they can still be visible during late twilight. Wait until the sky has darkened sufficiently to increase your chances of witnessing this ethereal phenomenon.

6. Rain opposite the moon: For a moonbow to form, there must be rain opposite the moon. The raindrops act as prisms, refracting and reflecting the moonlight to create the beautiful arc of light. Keep an eye on the weather forecast and plan your moonbow expedition when rain showers are expected.

7. Be patient and prepared: Spotting a moonbow requires patience and perseverance. Prepare yourself for wet conditions, as getting close to rain showers means you might get caught in them. Dress appropriately and bring protective gear to ensure you can fully enjoy the experience.

Moonbows are truly a sight to behold, captivating both photographers and nature enthusiasts alike. They serve as a reminder of the beauty and complexity of our atmosphere and the interplay between light and water droplets suspended in the air. So, if you find yourself in a location with the right conditions, take the opportunity to witness this magical phenomenon firsthand.

Lunar Primary & Secondary Bows

Peter O'Toole's first moonbow images from County Donegal, Ireland. 6th October '11 with the moon 11.2 days old - two days past first quarter. ©Peter O'Toole, shown with permission

The outer secondary rainbow is faintly visible with the darker sky of Alexanders dark band between the two bows.

"Here are my first Moonbow shots! I took them in Glenveagh Park, Donegal where there are excellent dark skies and a lot of showers feeding down from the hills across the boglands. It wasn't long before I spotted my first moonbow a truly amazing sight, just couldn't believe my eyes to what i was seeing - ghostly phantoms of white 180 degree arcs of refracted light, The colours were invisible to my eyes but evident in the photos. I have also attached monochrome versions .lowest image. to show what moonbow really look like to the naked vision although there have been reports of bow colours being seen. Also visible in some of the shots are very faint secondary bows.

Taken 23.30- 00.00hrs BST on 6th October with Pentax K-x, 18-55 zoom Lens kit set at 18mm, F/3.5, ISO1600 for 10 secs."

To best catch a moonbow:

(1) find a locale with frequent short showers and clouds interspersed with clear skies. Ireland, the Western Highlands of Scotland, Hawaii and Patagonia are good but not exclusive locations.

(2) Find dark skies away from city light pollution.

(3) The moon must be less than 40 degrees high.

(4) A full moon is good but it is not essential (see the moonbow challenge).

(5) Twilight should be over but they can be spotted during late twilight.

(6) There must be rain opposite the moon and the raindrops must be moonlit.

(7) Be patient and prepared to get wet!

Note: this article has been automatically converted from the old site and may not appear as intended. You can find the original article here.

Reference Atmospheric Optics

If you use any of the definitions, information, or data presented on Atmospheric Optics, please copy the link or reference below to properly credit us as the reference source. Thank you!