I'm not sure. AFAIK this hasn't been attempted in LPF, so all we have is some basic math/science and speculation. IMHO the biggest unknown is how much of the beam 10 miles of air will scatter/absorb (it probably won't work with any available handheld if there's fog or very polluted air).
Good luck and don't forget to keep us updated.
BTW I just tried various lasers with the furthest target I have (~350m) and the best results were with the 520nm 30mW and the 650nm 200mW (on my sig). The 650nm was slightly better, actually, but that might be because our eyes have an easier time focusing on red at long distances. Either way those reds are very cheap on chinese websites, so you might as well give it a shot!
The 1.5W 462nm gave pretty bad results as expected, despite it's higher visibility compared to the 445nm's.
Those specs are usually not accurate (that's the reason for the <) - I think the PL520 is, at the very worst, close to 1mrad. I'm not sure of the divergence of the PLP520-B1, but it's multimode (bad sign).
Agreed with the rest of your post
We are going to try to choose the best days that we can, and may have to repeat the test a few times. Unless the scattering is severe, we will at the very least be able to determine if it passes the convexity. Even better, if the weather allows, we can measure the height difference between point A and B.
The most important part of the test would be the measurement of curvature in real time. At ~10 cm above water level or so, light should not travel the full ~10 mile distance of the lake (with atmospheric refraction accounted for), and should NOT be seen by the helper standing on point B.
If there were a third observer viewing the beam perpendicularly, they would be able to see the laser elongate toward point B of the shore as the tripod rises above water level (regardless of scattering/refraction, the beam should "grow")
I was thinking a pl520 or a lpc 826. the divergence is great on the lpc 826, but I didnt know if a 300mW expanded 660nm would be bright enough. I agree the red seems a bit better than the 520 single mode when it comes to divergence.
I have been able to clearly see the dot of my lpc 826 @ 1 mile with no expander, so maybe a 10X expander could work to give a small dot @ 10 miles.
good news is this is one of the cheapest lasers around, bad news is I've never seen one with a BE, but I'm sure it could be done.
perhaps a custom host builder could make a focus adapter that accomodates say a jetlasers BE
Sounds great, do you know who to ask?
Worst case scenario, I'll have to mod the B.E. myself (if it's within my capability)
I think 30-50mW is way to weak to punch through 10 miles of sea level atmosphere and make a dot on something even with excellent divergence and a beam expander but perhaps I am wrong.
This guy is talking 10 miles ---52,800 ft ---- 16,000 meters
Well, there is another lake that is ~4.5 miles but I would need permission to access the other side of the shore, and at this time of year it gets flooded (marsh)
There is a 12.1 miler too, but that's reserved for doing last or with one of the lab style lasers
My best bet is the ~7.5 mile lake, and I can reduce the distance down if necessary. What I may end up doing is 3.5 miles one day, 5 miles the next, and finally the full length
Then I can try doing the 12.1 miler once I've covered those distances
I want to order a laser ASAP so I'll probably make my decision by tomorrow or Weds. at the latest.
Best case somebody can do a B.E. mod, USA preferably but international is fine. I have the funds available right now in an approved PP acc. with 300+ 100% pos. feedback on eBay, so I can make a purchase anytime
Thank you all,
