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Opinions on laser pointers as finders?


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Hi everyone.

I'm in the process of building a briefcase dobsonian from an OTA I acquired recently. In the interests of portability and room in the aluminium case I''m using, I hope to use an inexpensive 5mw green laser pointer from Ebay as the only finder on this scope.

I've trialled this configuration on my other Dob using velcro, and I've come across a few issues. I was wondering about other people's experiences in using laser pointers as finders, and any caveates I should be aware of.

My issues that I've seen so far:

1. The cold makes this pointer stop putting out green light.

2. There can be problems trying to align the pointer unless you are using a proper laser pointer bracket.

3. It's not a good idea to use this when the house you're staying in is in the flight path for the local regional airport..

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I think they're perfectly OK. I have the Celestron laser and it works nicely. That said, a Telrad and /or a finder complement it too. The chances of an aeroplane flying through the beam are very low and in any case we 'laser finding' astronomers are pretty responsible as a group and dont go waving the things around gratuitously like gormless teenagers.

I find that I need to heat it with an eyepiece heater and that even then it can sometimes get going slowly.

Recommended.

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Thanks for the feedback.

My other option for a finder is going to be a Quickfinder red-dot finder for twilight and daytime use, as this is small enough and light enough for my requirements.

I'll start another thread to follow the briefcase scope build.

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Thanks for the feedback.

My other option for a finder is going to be a Quickfinder red-dot finder for twilight and daytime use, as this is small enough and light enough for my requirements.

I'll start another thread to follow the briefcase scope build.

The Quckfinder is excellent. It's really effective, lightweight and clips on and off in a moment so very suitable for a highly portable scope. It probably weighs less than a laser pointer in it's mount does and I fancy is a bit more accurate.

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I live right next door (and i mean right next door) to an International Airport. I'd never consider using a laser pointer. The Rigel Quick Finder and Rigel MRF are at the top of my list. Currently i'm using the billy basic Skywatcher RDF, which i actually quite like using.

Russ

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Surely a standard laser pointer also doesn't have a visible beam, you wll only see the beam if there are imperfections in the air that pick it up or dense moisture. i have a few lasers myself but i think they may be a bit big lol This is what i do in my spare time and i need to use a haze machine to make the beams 'show'

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I've used a laser as a finder

very useful it was in my old obs where room was a little tight as it meant I did not have to get right behind the scope to see the beam

They are a tool and like all tools if used properly are safe

Steve

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Surely a standard laser pointer also doesn't have a visible beam, you wll only see the beam if there are imperfections in the air that pick it up or dense moisture. i have a few lasers myself but i think they may be a bit big lol This is what i do in my spare time and i need to use a haze machine to make the beams 'show'

You will see a green laser easy enough once it is dark if you are behind it, which is where you will be if you use at as a finder. They are also fun ( in a responsible way :)) to play with, I mean, use in the dark when its snowing!

Allan

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Thanks for all the feedback!

The pointer I recieved is a 5Mw 532nm unit of class IIIa, and the beam is *very* visible at night, up to 1km by naked eye and about 2km with a pair of binoculars. I could see the reflection from a motorway sign easily from 3km away (2m wide beam at that distance) - note: the cars would not have been able to see the beam as the roadway is behind an embankment - I'm not being silly with it.

It's weird seeing the beam reach into the cloudbase and clearly illuminate the cloud at a height of about 1000ft. It can be clearly seen from the side as well when I got a friend to go down the road a bit and point it straight up.

During the day, I can see the spot on sunlit tarmac at about 50 m.

Somethign to be responsible with I think.

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Wonder what one of my 150mw jobbies would do if I got it outside! Animations on clouds sounds like fun lol

Careful there isnt a picture of a bat on it..... you never know.....

Allan

Edited by alfingido
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Curiously, perhaps, laser pointers do not seem to disturb imagers as much as you might think. I had a guest who, when I asked what he was shooting, said NGC whatsit whatsit over there - and pointed at it with his laser. Then he said Ah, Doh, Curses and Drat, etc. But it did not show on his image. Interesting. Likewise, if trying to guide a Dob user with a laser you really do have to be pretty much on axis with them, so to speak, for the beam to show.

As I have said before, a great trick is to squirt your laser through your finder to see where you are pointing. Since I have an abominable neck affliction this simple technique spares me a lot of miserable grovelling when star aligning our mounts.

Olly

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I was thinking of having a laser light to guide my scope. Then I sat down and REALLY thought it through.

It comes down to ONE issue.

How much of a complete prat the local police/constables are.

If they've got a mad on then you can COUNT on spending the night in a lock-up. And depending on the mood of the local prosecutor's office you could very well be looking at a jail term.

Now before everyone gets hasty I should point out that I personally know of two fathers and sons who ended up getting charged AND CONVICTED not just for interfering with the safe operation of an airplane BUT AS TERRORISTS!!! Both sets recieved suspended sentences but are on probation for 5 years and ANY mis-step can send them directly to prison without trial of any kind.

Ditch the laser pointer... it's not worth gambling your freedom on.

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Hi Olly,

I had never thought of firing a laser THROUGH a finder - must try it next time there is a clear sky. I too have a (major) neck affliction and have recently changed my kit accordingly - see below. The biggest problem I have with my laser is that it suffers, more than I do, with the cold, so I have to keep the laser plus bracket in my pocket to keep it warm. Both inconvenient and uncomfortable!

Best wishes from all at WPAOG

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Get a laser mount from ScopeStuff in the US, fits a standard Synta base. To combat the power fade in the cold, just loosen the top screws on the mount and take the pointer out and keep it in your pocket, pop it back in to use it, the bottom 4 screws will ensure it's pointing in the right direction.

I use mine with a 9x50 Right angle finder as my finders of choice. You can mount them side by side with an adapter from scopestuff... need to design the scope balance to take this into consideration.

I bet I have more overhead plane trouble than most and I just make 110% sure I can't hear or see any planes. The beam is only visible to those close to it.

A very useful tool, use with care and there'll be no trouble.

PEterW

PS I would love to see how sensitive imagers would be to a laser pointer nearby (5m away and used for fractions of a second at a time, which is all I ever need). If it causes a problem I'd be more than happy to use another finder.

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Thanks to WPOAG for the good wishes. I am baffled by this 'not working in the cold' theme because up here in the mountains we get minus 15 quite often in winter and mine works fine all the time. (Galaxy Products one.)

Olly

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Good laser finders will last many hours in the cold, and by good I mean ones with beam output regulation built in to keep the beam at a constant brightness. The cheaper lasers that are often found on eBay, and indeed some of the not so cheap ones sold by astro dealers can't stand the cold at all.

Generally you have to go to a proper laser supplier to get the good ones.

John

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Good laser finders will last many hours in the cold, and by good I mean ones with beam output regulation built in to keep the beam at a constant brightness. The cheaper lasers that are often found on eBay, and indeed some of the not so cheap ones sold by astro dealers can't stand the cold at all.

Generally you have to go to a proper laser supplier to get the good ones.

John

Sorry but even the best dont last in the cold.

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I think there's maybe a little misunderstanding in some of the notes above.

Yes, I too find that mine works perfectly in the cold.

Simply wrap an eyepiece heater around it and that will (a) keep the battery warmer and (:headbang: heat the lasing head of the pointer. Even if i have not heated the finder, it will generally start as a weak red spot but in a few moments comes to life as a nice clear green line. The beam is completely invisible off axis unless its raining, snowing or foggy. I think we can agree that these are not the conditions in which any of us ever remove the cover of our telescopes. In all of this, I'm assuming that no one is using anything more powerful than the 5mW offerings from the likes of Celestron. The more powerful ones are probably unnecesary and unsuited to amateur astronomy.

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