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1.25" Laser Collimator


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Cloudy Nights laser

After purchasing my first reflector in about six years (a 10î f/5.6 Discovery), I started looking around for devices that could aid in accurate collimation; wringing out the optimum performance of this scopeís optics.  With other scopes in the past, I had used everything from a film canister with a pinhole poked in it, to the excellent set of Tectron collimating tools.   I decided to look into the current generation of laser collimators as most are advertised and touted as being the ìbe-all, end-allî of reflector collimation.  Buy one of these, all the descriptions said, and your collimation will be quick and accurately set every time.

I decided on a ìmiddle of the roadî unit, not wanting to go too cheap, but not wanting to spend nearly what my telescope cost in the first place until I could get some idea if I even liked using one of these lasers.  I chose this model, available through many retailers, for the following reasons. 

  1. It was relatively cheap, anywhere from $50 to $70 retail. 
  2. At least with a smaller scope like mine, one can remain at the rear of the tube and make adjustments, while watching the results of these adjustments on the laserís target grid.
  3. The final selling point for me was that the laser was adjustable: if you dropped it and it got out of kilter, you could realign it.

When the unit arrived, I was impressed with its heft and overall appearance.  It is made from machined aluminum and is a nice-looking unit.  The device turns on and off via a setscrew: turn the screw in and it turns on the laser.  Screw it back out and it turns it off.  In the center of the unit is a cutout where one can see the laser coming out.  Around this hole is a white ìtargetî with a grid pointed on it.  In theory, if your telescopeís collimation is pretty close to ìon,î the returning laser dot should appear somewhere on this grid, then you simply use the primary adjustments to move the beam until it disappears back into the same hole it came out of.  Thatís the gist of it as explained in all the catalogs, but thereís more to it than that.

INSTRUCTIONS AND USE

The instructions that came with my unit were a bit vague.  If youíve never collimated a reflector with your ìnaked eye,î these instructions wonít make this process much more clear and, as stated in the instructions, this ìrough alignmentî procedure must be performed before the laser can be used, unless youíre lucky and your scope is pretty close in the first place.  If you donít know how to align your focuser and diagonal, these instructions wonít help you any, especially if you throw in the ìoffset diagonalî factor that a lot of scopes, especially faster ones, seem to have.   If youíre not comfortable with performing a visual adjustment of your secondary and making sure your focuser is square, these instructions wonít help any, so you might want to read up on that procedure while waiting for your laser to arrive.  

If youíre lucky enough to put the unit in your focuser and have the returning beam appear on the target grid, the rest is easy.  You simply make adjustments to the primary mirror and watch the dot.  Itís handy to be able to see the dot, because you can see how each adjustment you make affects the movement of the dot on the target grid; no back-and-forth to see the results of each adjustment, no wondering which way to turn which wing nut to get the beam to go here or there.

PROS OF THE UNIT

Thatís the big pro to this unit: the ability to remain at the rear of the telescope while making adjustments and seeing those adjustments occur in ìreal time.î  Another nice feature is that you have access to the laser unit inside the housing itself.  You can screw off a cap at the rear and the laser is visible, held by setscrews used to adjust it.  More on that to follow.  The reason itís nice to have access to the laser is that the laser is just a standard ìgas station laserî used in all kinds of devices from crude pointers to cat toys.  If this laser every stops working, it would be possible, with enough searching, to find one to replace it.  It would just have to be roughly the same dimensions with a side on/off switch that the housing thumbscrew would activate when turned it.  I even talked to one gentlemen who went to a nearby gas station and went through their assortment of novelty lasers then picked the one with the smallest, tightest dot and took it home and replaced the one that came with the unit. 


CONS OF THE UNIT

Thatís about where the pros end.   I needed to save some space for the cons, and Iíll start with the biggest one first.  The barrel on the unit that fits into the focuser is machined too small.  As a result, the unit flops around in the focuser and is so loose you can actually feel and hear it making a ìthunkî sound if you move the top of it back and forth with your finger.  Now, I must say, my instrument doesnít have the finest focuser on the market, but itís not a bad one, either.  Itís a nice, heavy metal 1.25î rack and pinion unit that I would imagine can be found on thousands of telescopes across the country, a focuser a lot of these laser units will be likely to encounter when being used.    I tried this laser unit in other focusers and other 1.25î diagonals and adapters and the fit was the same in all of them:  way too loose.   If I just happened to get a bad unit, then quality control is an issue. 

As a result of this loose fit, when the unit is installed in the focuser, even a slight touch on one end can send the beam dancing back and forth across the diagonal Ωî inch or more.  Tightening the focuser set screw just causes the unit to pivot to one side.  I opted for letting the unit rest in the diagonal without tightening the set screw, and I used cellophane tape to ìshimî the unit so it fit snugly into the focuser.   One shouldnít have to resort to wrapping tape around the barrel to get this unit to fit properly into the focuser.  It should either be machine to a tighter tolerance, or the barrel that fits into the focuser should be made much longer to help eliminate slop and make sure itís square in the focuser.  Thereís not much point in moving your diagonal and secondary by hundredths of an inch to make sure theyíre square, then using this unit that doesnít fit squarely in the focuser tube.   Until you can get this unit to fit perfectly square in the focuser, the accuracy of the laser beam isnít even a factor: youíre wasting your time.  Which brings me to my second big con:

The laser in this unit is adjustable, and the maker even supplies an Allen wrench to adjust the three setscrews that hold the laser in the housing, just as you would align a finder in a ring using setscrews.  The instructions state that you should remove the cap so you can see if the laser unit is centered in the housing and states ìyour eye can make this judgement quite accurately.î  Frankly put, I donít believe this.  The proper way to make sure the alignment on any laser collimator is good is to place the unit in one (preferably two) v-shaped blocks, point it at a wall a distance away, then rotate the entire unit and see if the beam remains in one spot, or moves around in a circle.  If the laser is square, the dot will remain in one place.  If the beam is ìoff to one sideî in the housing, when you rotate the unit, the dot will travel in a circle on a wall.   There is simply no way you can ìeyeballî the unit in the housing and tell if it is square with the housing.   This unit could be tracing a circular pattern an inch in diameter 10 feet away and youíd never be able to tell itís that far off by looking at the laser sitting in the housing.  Mine was, anyway.  Once you find out your alignment is off, itís a pretty simple matter to adjust it to where it should be.


SUMMARY


For the price, this unit serves a function in the reflector-owning community and is not a bad deal.  It is a useful tool that, with a little research and practice, can be made into an effective collimation aid, but I feel that the ads and catalog descriptions for this product are misleading and a lot of people could either be disappointed with it, or could be doing more harm than good to their telescope by using it and the instructions as supplied and theyíd never know it.

Like I said, if youíve never done a ìnaked eyeî collimation of your focuser and secondary at a minimum, you should do some research on this tricky subject before you decided to buy one of these laser units.  Chances are, if you have a telescope from a reputable manufacturer and youíre sure nobody has ìtinkeredî with it, your focuser and secondary are probably set right and any adjustments you make might do more harm than good.   I was lucky and mine were fine and, remember, unless something really bad happens to your telescope, this secondary/focuser alignment will only need to be done once.   If you have no idea how to rough-collimate your mirrors and you put the laser unit in and you donítí get a return beam on the target grid, you might not know what to do next.  I would highly recommend a lot of pre-purchase research on collimating ìthe old-fashioned wayî and focuser/secondary adjustments in particular.

Since youíre wasting your time with the unit and possibly making things worse if the unit isnít properly collimated itself, I would also highly recommend doing some research and learning how to make and use v-blocks to make sure the laser unit is properly aligned.  A ìv-blockî is nothing more than a v-shaped jig the unit can rest in, touching on the sides but not the bottom.  Nothing fancy machined to thousands of an inch here, you can make them out of wood.  I used aluminum stock.  

The final obstacle to overcome is the loose fit of the unit in the focuser.  I used cellophane tape.  If you had a two-inch focuser, you could probably find some way to get the unit shimmed in a 2î-1/25î adapter and just leave it there all the time and slip the whole thing into your focuser.  Unless you can get the unit to fit snugly and squarely in your focuser, youíre wasting your time with it.  I tried several types of tape from metal foil to basic cellophane tape and the cellophane worked for me.

If youíre willing to deal with these fixes,  this unit could earn a place of honor in your eyepiece case.  Every time you take your scope out,  itís a simple matter to slip the laser in and basically within a minute or two, you can make sure your optics are perfectly aligned.   Iím careful with the laser, but still v-block it once a month or so to make sure itís holding its collimation:  itís kind of fun to do anyway.  

In the end, my recommendations?   This unit is a step above the basic non-adjustable lasers, but falls far short of the premium laser collimators on the market.  If youíre a tinkerer on a budget such as myself, not afraid to move things around inside the telescope, or just donít want to spend hundreds of dollars on a top-notch laser collimator, this laser could work for you.  If youíre a beginner and the idea of shimming the focuser barrel of the laser, v-blocking it and moving all the mirrors in your scope intimidates you, I would not recommend using one of these units.   The best question to ask yourself would be, ìIf that laser dot doesnít show up anywhere on that target grid, what would I do next?î

If you want a ìplug and playî laser you wonít have any doubts about, I would go with the general Internet advice and say, ìIf youíre going to buy a laser, buy a good one.î  These units can range from $200-500 and up, but are machined to high tolerances and would probably last a lifetime with proper care.

If you want to go the route I did, rest assured that there are literally thousands of people who will give you all the advice you need about laser collimators and making and using v-blocks and other collimation techniques and aspects of these devices.   After all, what else is there to do on a cloudy night?  Playing with laser beams in the basement is always cool as far as Iím concerned.




 




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