Good outdoor through beam sensor

[skydivewags]

I am looking for a good through beam sensor that will work outdoors. I would like to keep it on the cheap. I found the following sensors and they work but at the 8' distance I need they are very hard to align and keep aligned.

https://www.allelectronics.com/item/osu-1130/span-style-color-ff0000-strong-reduced/strong/span-br-through-beam-photo-electric-sensor-pair/1.html

This is to track a dog going through a "gate". I have two sensors to try to catch all heights of the dogs. I looked at some light curtains but the cost is a bit high and I am not sure if they will work outdoors or not. If they will be easier to align and more robust, I might splurge on a light curtain.

This is for a timed event, so I need to know when the dog goes through the gate, motion sensors will not be accurate enough as the dogs will be close to the gate before going through it.

Thanks for any help!

[artag]

Are single-ended sensors easier to align ? They work with a passive retroreflector / corner reflector so all the alignment is internal to the sensor.

[skydivewags]

Well, a retro-reflective sensor eliminates half of the devices you have to adjust, so, I would say you are right.  The only sensor I have like that doesn't have the range I need.  It seems like the beam would have to travel twice the distance with that type of sensor, so that would have an affect.