Focus/Distance Question

[sloch24]

I'm a new member of the forum. I thought I'd get that out of the way first.

I am in need of a laser that will produce a small dot at just over 1000'. It doesn't have to be powerful, just visual.

I own 5 acres of land, and I have mounted 3" PVC posts at the corners of my property. These 4 points are marking the surveyor pins. I would like to mark the property in 200' increments along the 1038' sides and use these stakes to measure off of.

I could do this at dusk or at night if need be, I just need to find something that won't produce a fist sized dot at 1038'

Is there a moderately priced or inexpensive laser that can do this? I don't want to get into a lot of money, but with todays technology I assume that there is something that will work for what I need.

I know nothing about the different colors or wavelengths. So I am definitely a newbie. I welcome all suggestions and criticism.


Thanks in advance!

 

[diachi]

I'm a new member of the forum. I thought I'd get that out of the way first.

I am in need of a laser that will produce a small dot at just over 1000'. It doesn't have to be powerful, just visual.

I own 5 acres of land, and I have mounted 3" PVC posts at the corners of my property. These 4 points are marking the surveyor pins. I would like to mark the property in 200' increments along the 1038' sides and use these stakes to measure off of.

I could do this at dusk or at night if need be, I just need to find something that won't produce a fist sized dot at 1038'

Is there a moderately priced or inexpensive laser that can do this? I don't want to get into a lot of money, but with todays technology I assume that there is something that will work for what I need.

I know nothing about the different colors or wavelengths. So I am definitely a newbie. I welcome all suggestions and criticism.


Thanks in advance!

How small of a dot do you need roughly - can you give us a rough number? :yh:

 

[sloch24]

I guess I didn't really think about how small. What are my options?

Is there a table or chart somewhere that shows what size at what length that I could look at? I've googled it a couple of times but haven't found anything that is helpful. Maybe I'm looking in the wrong place.

Ideally, it would be the same at 1000ft as it would at 10ft, but I'm open to a little bit of measuring error. I guess I don't need it to be exact, but accurate to within a few inches across 1000' would be nice if possible to do inexpensively.

 

[steve001]

I guess I didn't really think about how small. What are my options?

Is there a table or chart somewhere that shows what size at what length that I could look at? I've googled it a couple of times but haven't found anything that is helpful. Maybe I'm looking in the wrong place.

Ideally, it would be the same at 1000ft as it would at 10ft, but I'm open to a little bit of measuring error. I guess I don't need it to be exact, but accurate to within a few inches across 1000' would be nice if possible to do inexpensively.

Ain't gonna happen without custom optics or a laser custom made with custom optics. It's possible to do though. The way is to use long positive focal length lenses. A laser built using a 5mw green laser module plus appropriate optics I think could do it. For reference Google mining laser levels.

 

[sloch24]

I guess my question is: At 1000', what is the capability of a non-expensive laser? Am I looking at a dot of 2", 1'? I imagine I could still measure from the center of the dot no matter how large it is.

I know nothing about these things and was hoping someone could give me a little advice as to what is available, and what to look for.

I can put up a target at the far end and measure from the center of the dot, then do the same at midpoint (and everywhere else along the line that I want to measure.

This would still be an accurate measurement, right?

Thanks for the replies so far. Remember, I'm a newb, so please have patience with my ignorance.

 

[diachi]

I guess my question is: At 1000', what is the capability of a non-expensive laser? Am I looking at a dot of 2", 1'? I imagine I could still measure from the center of the dot no matter how large it is.

With a non-expensive DPSS laser you're looking at probably >1ft diameter at 300m.

Numbers used: Distance 300m, Divergence 1mRad, initial beam diameter 2mm. Those are sort of average numbers for a cheap DPSS laser - they may be a little better but more likely somewhat worse.

Now what you can do is throw in a beam expander (Basically a telescope), that'll increase the initial beam diameter by a given multiplication and reduce the divergence by the same factor.

So say you use a 3x beam expander with the numbers above; you'll have an initial beam of 6mm with a divergence of 0.3333.....mRad and a spot of ~100mm at 300m - roughly anyway, allowing for margins of error of course. If you bring that up to 10x then you'd have a spot roughly 50mm in diameter at 300m.

Again, that's making some assumptions - your mileage may vary. And of course, extra components add cost.

So best case - you're looking at ~50mm - likely more. Not to mention the slightest wobble at the laser end will have the target end bouncing all over the place - you'll need a good solid surface for the laser.

 

[GSS]

I would at least for the moment buy a couple cheap ebay pointers at $4 or $5 a pop or even cheaper. Then go on from what you see they do. Get a green and a red to see which color shows up best on the land. They will most likely be rated at 5mw but 90% of the time are way stronger. This way you get an idea of what they can and can't do, then be able to explain what might be missing.

 

[sloch24]

Thanks for the replies.

I was hoping for a little better out of a cheap laser. Now I know. It sounds doable with the optics described, but I was looking for a quick and dirty way to do what I need to do in the next week or so.

I may play around later, but at this point I think I'm probably going to hold off on the idea of using a laser to mark positions.

Thanks again to everyone who responded for the information, that's just what I was looking for but couldn't seem to find online.

 

[steve001]

Thanks for the replies.

I was hoping for a little better out of a cheap laser. Now I know. It sounds doable with the optics described, but I was looking for a quick and dirty way to do what I need to do in the next week or so.

I may play around later, but at this point I think I'm probably going to hold off on the idea of using a laser to mark positions.

Thanks again to everyone who responded for the information, that's just what I was looking for but couldn't seem to find online.

This might work. The divergence can be adjusted down to 0.05 mrads. That's low. 50mW ND50 Long Distance Laser Designator, Green Laser Designator ? HighLasers

 

[sloch24]

Thanks for the link. I'll have to look into it.