Help for Botswana guide star gazing

[henrysaunt03]

Hello experts,

I travelled to Botswana in May 2016 and discovered green laser pointers for star gazing! My guide has since contacted me and asked if I could replace his laser, as his stopped working. His English is limited and he could not tell me the brand or strength of the one he had.

I researched through this forum and ordered a 5mw through Optotronics. It was not strong enough to reach the stars, so I spoke with the owner and he recommended that I get a 30mw. So I exchanged the 5mw for a 30mw. I just tested the 30mw last night and it didn't reach the stars either. (I live in Maine with very little light pollution, btw.)

I am looking for advice. I really want to help my Botswana friend and get him a pointer that will help him do his job! It's a lot of money for me at this point (I'm about $100 in) and I don't know what to do. Your thoughts are very much appreciated!!
Thanks,
Amy

 

[diachi]

What do you mean by "Didn't reach the stars"? Do you mean it doesn't have a visible beam?

 

[NightExplorer96]

What do you mean by "Didn't reach the stars"? Do you mean it doesn't have a visible beam?

I think that's what he mean, as "technically"laser light will reach the stars but would be very diffused at that point If that's what's you mean OP, 50mW of 532nm is what is generally recommended for beginning star pointing. :yh:

-Alex

 

[diachi]

I think that's what he mean, as "technically"laser light will reach the stars but would be very diffused at that point If that's what's you mean OP, 50mW of 532nm is what is generally recommended for beginning star pointing. :yh:

-Alex

I agree, 50mW is a good starting point, but 30mW should still be plenty visible though...

Not to mention it seems that all those >5mW Optotronics pens are usually making more power than advertised.

 

[henrysaunt03]

Yes, by "not reaching the stars" I meant you cannot see the green dot in the sky. (It was a clear night with little light pollution.) In Botswana, it was like pointing on a chalkboard. He easily pointed to stars for us.

I see on the Optotonics web site a 55mw, 75mw and 100mw...

Would there be a downside to getting a 75mw, other than the expense? I'm concerned about sending the 30 back and finding the 55 doesn't meet my needs...then being back in this same situation.

And the one I have was labeled 30mw but the handwritten testing note says it tested at 35.

Again, thanks for your thoughts.
Amy

 

[diachi]

Yes, by "not reaching the stars" I meant you cannot see the green dot in the sky. (It was a clear night with little light pollution.) In Botswana, it was like pointing on a chalkboard. He easily pointed to stars for us.

I see on the Optotonics web site a 55mw, 75mw and 100mw...

Would there be a downside to getting a 75mw, other than the expense? I'm concerned about sending the 30 back and finding the 55 doesn't meet my needs...then being back in this same situation.

And the one I have was labeled 30mw but the handwritten testing note says it tested at 35.

Again, thanks for your thoughts.
Amy

Please clarify - you can't see the beam or you can't see the dot? There's a difference.

Beam:

(Much more power than 30mW I'd say )

Dot:

You won't be able to see the dot in the sky because there's nothing for it to terminate on. You *should* be able to see the beam at might though.

First we should figure out why your 30mW isn't doing what you want (it should be...) before moving up in power.

 

[Jhop]

You can get a 40 or 80 mw 532 pointer from sanwu from under 20$ (before shipping). Check it out https://www.sanwulasers.org/product/304green

 

[henrysaunt03]

Ok, I tested it again last night. It gives me a thin beam that I can see for a few yards (I don't really know how far). The dot part is what I am looking for. I was amazed in Botswana when my guide had this pointer and it truly did give a dot. He pointed at and circled various stars to show us what he was talking about. It really was like looking at a chalkboard. I didn't understand how it worked because as diachi says, there is nothing for the beam to terminate on. But the dot was there. And that type of pointer is what I would like to send my friend.

Your expertise is appreciated.
Amy

 

[diachi]

Ok, I tested it again last night. It gives me a thin beam that I can see for a few yards (I don't really know how far). The dot part is what I am looking for. I was amazed in Botswana when my guide had this pointer and it truly did give a dot. He pointed at and circled various stars to show us what he was talking about. It really was like looking at a chalkboard. I didn't understand how it worked because as diachi says, there is nothing for the beam to terminate on. But the dot was there. And that type of pointer is what I would like to send my friend.

Your expertise is appreciated.
Amy

The beam should be visible for hundreds of feet - from the ground it should look like it goes all the way to the star - that's how it generally works for pointing out stars with a laser beam.

There must have been some low, thin fog or some such in Botswana. Thin enough that you could still see the stars but thick enough that it could produce a "dot" when shining the laser on it. You need something to terminate on to see the dot - unless you're doing guide stars with 10s (100s?) of thousands of dollars worth of 589nm lasers...