How to mount anchor light to this...

[OS2Dude]

Catalina Yachts uses a tube with a notch on the side and a flat plat on top. You could make your own version where the notched side of the tube bolts to the side of the mast.

[Sindbaad]

While you are at it, insert a photocell at the mast top between the light and the power supply. Together with an LED bulb you are never worried about having the light on when it is dark and off when it gets light. I turn the light on when I anchor the first night and never worry about it.

[deltaten]

I picked up a small, all around mastop fixture and a Marineland all around hi-intensity LED. Fixed up monel wire "basket", added loops top and bottom and rigged 50' of 18 GA wire paired with sufficient 550 cord as downhaul.
Hook on the spare halyard, hoist to mid-point, cleat off downhaul and plug into cigarette lighter fixture.
Done!

[VIKINGBEAR]

I use same principle as deltaten in hoisting the anchor light, except I was lucky to buy a 15 LED “LULU KAUKAUA” anchor light from Bebi Electronics in Fiji Islands. It has a light Sensing Switch: Sun down-light on, Sun up-light off.
Draws only <0.090 amps but is probably the brightest anchor light in any anchorages.
www.Bebi-electronics.com

[deltaten]

From memory... the Bebi was great; but someone hadda complain and gottem in trouble...gone! Guess 'cause it wasn't "approved" ?!..... by the Big Mfgrs

Oh, and BTW....
My day-shape is hung the same way. Could be used same time if I'd be staying anchored thru/past 24 hrs. Simply a pc of black PVC signboard cut into 12" circles and slotted to fit together. A bit of 550 to fasten. at top and provide hangin loop and loop at bottom...voila'

[Icarus]

Originally Posted by cyrano138

I'm new to anchor lights, mast-related repairs in general. Most of the anchor lights I've found look like they need to be mounted to a flat surface. Does anybody know of one designed to mount to this masthead cap? This is what I have.

Why would anyone mount an anchor light 18m or so above sea level?
I have a small light mounted on the aft rail, which partly illuminates the boat...easy to see from a distance and in case the bulb blows easy to replace.