450nm for astronomy pointing?

[svdr]

Hi, I am an astronomer, and I like usig lasers for pointing my telescope at night.

So, I used a 5mW green (beam visibility is OK for me) BUT the greenies allways die from cold temps because they are DPSS. I can use greenies only in summer.

After that, I went with a 300mW red. Left that one also, even at 300mW, beam visibility isn't great. However, they don't suffer the cold.

Now I am thinking about a 80mW 450nm. Beam visibilty should equal a 5mW greenie, or be even slightly brighter. As they are also SS, temperature should not be an issue.

Any experience or thoughts on this?

I think about the OSRAM PL450B 450nm 80mW diode. What driver should I need? (would maybe run it at 100mW) I also Prefer using AA or AAA batteries.

 

[Coby]

I have used my 2000mW 445nm before to to star pointing, it'll work, you just have to focus it to infinite very good so the beam stays as small as possible.

 

[nugget]

Hello, sorry just wanted to know what is focusing to infinity?

 

[Coby]

Focus to infinite means you point your laser to a far away object (a wall 100m further for example) and then you start focussing the beam (using the focus-wheel thingy at the front of the laser) until the dot you see on the wall is the smallest possible.

You'll notice that at first the dot will be very large but by focussing it gets smaller. By doing this on a far away object you "focus to infinite" providing the tightest beam you can get.

 

[Jubathoph]

my 80 me pl450 is very visible at night

 

[svdr]

my 80 me pl450 is very visible at night

That sounds like very good news to me! Jubathoph, can you compare it to the beam of a 5mW green?

Coby, I see that you're also from B, and Blord also. Any chance that we can discuss further on this in our native language? (assuming you are Flemish)(aucun problème si tu es Francophone)

That 2000mW must be waaaayy bright in the sky. I have an old homeboosted 30mW 532nm and even that one is far too bright for pointing stars and deepsky objects.

 

[TheReddish]

Hmm assuming, your eyes and my eyes are close. A conservatively driven PL450b would be around 150mw. At 150mw indoors the 5mw green is 2.55% less bright than the 150mw 450nm. Outside at night, I do not have the hard data but the 450nm at 150mw "should be around" 3.25x brighter than the 5mw 532 due to our eyes adapting to darkness.

 

[Blord]

Do you really need a blue pointer for astronomy ? Green laser are much more visible than blue at lower power. Get cheap ND1 filter. Cut a piece out and stick it in front of your 30mW laser. It will make your laser 3mW green.

 

[svdr]

Do you really need a blue pointer for astronomy ? Green laser are much more visible than blue at lower power. Get cheap ND1 filter.

I know. I am currently using a 5mW green. But as I wrote above, green DPSS lasers tend to 'die' when exposed at near freezing temperatures, because the optical train in the module shrinks out of collimation. Every year, it's the same pain when winter arrives and nighttemperatures drop. You see, we're talking about a fixed mounted laser on a large telescope that is outside for several hours. The laser itself is in *exact* collimation with the field of the telescope, so I cannot quickly take it off and put it in my pocket for warming up. The point is to put laser on, move telescope so that the beam reaches the desired point in the sky, shut laser off and look at the desired sky object.

A 'regular' solid state laser doesn't suffer this cold sensitivity. My 300mW red is great at below freezing, but I don't like the beam visibility. It's just no bright enough. I feel also objected shining a 300mW device in the sky (even though nobody sees it).

Since the arrival of the PL450B, my problem -and that of many amateur astronomers in cold climates with me- may come to an end.

@ TheReddish : I would run it at 80mW instead of 150. An 80mW 450nm beam should about equal the beam brightness of a 5mW 532 (I think...).

 

[Blord]

I have soon a 60mW 450nm blue laser for sale. The build is ready but I didn't made the ad yet. The diode is the Osram single mode 450nm LD so the beam is nice and tight.

You could also consider the 110mW 638nm Mitsubishi single mode diode. It has almost the same visibility as the 300mW 660nm red but at much lower power.

 

[svdr]

Very tempting. What's the price? Are these things stil pot regulated so that I can tweak it at my personal need? You know, make it a little bit dimmer or brighter?

 

[svdr]

PM sent

 

[Moistenator]

Very tempting. What's the price? Are these things stil pot regulated so that I can tweak it at my personal need? You know, make it a little bit dimmer or brighter?

Don't turn it up too much!:thinking: