First Collimation - Newbie

[Langy]

I’ve had my scope now for about 6-8 weeks and always had the collimation thought in my mind. Now I dare say like all newbies the thought of twiddling with scope mirrors is not an initial welcoming thought. After watching several YouTube videos on the subject I had decided that the Cheshire would be my preferred option, however for some reason I ended up buying the Laser, must have been the gadget side of me making the final decision.

Now the Laser collimator has to be collimated to make sure that you get accurate readings. To do this you need a nice stable base to sit it on and rotate. Not sure how I got the idea but I had decided on what I would use and raided my sons bedroom for his lego box. With just using a few bricks I ended up with this.

The important thing is to make sure that there are two points on the collimator that allows a balanced point to rotate it in a perfect circle. Initially I had the laser warning label in the way on one surface so I just moved it to somewhere else.

I sat the collimator on a window sill in my lounge and pointed it to the other end. Fortunately my lounge is around 6M long. Rotating the collimator I noticed that it produced a circle of 40mm meaning that it was out by about 20mm over the 6M. The adjustment screws were hidden under some rubber sealant which I managed to mostly prize off. When I got through it a 2mm allen seemed to fit even though I still couldn’t see the screws. With some adjustments I just couldn’t get it any better, far worse if anything. In the end I managed to get it back to the 20mm I initially had and left it at that.

Now anyone who has the Astromaster 130EQ and have tried to collimate it will know that it doesn’t have a centre spot on the primary. I’ve watched a couple of videos on cleaning and centre spotting the mirror. If collimation was frightening for a newbie I’m sure you can imagine our thoughts on taking out the primary to stick on a centre spot. When I spoke to Alan at Skies Unlimited where I purchased the collimator he said that in my case he had in the past made a paper template with a centre spot and lower it onto the mirror with a bamboo cane and some blue tack to weigh it down. Not keen on the bamboo cane I had another idea. Using PhotoShop I created an initial document 5mm wide at 300 dpi and created a circle with a black border. Then increasing the canvas size up to 130mm left the circle in the centre and then on a new layer created another circle with the border again at 130mm. Printed and cut out I then used three 1M lengths of string and some sellotape to stick to my template as below.

Being paper and not card it can easily be slotted between the spider arms that holds the secondary mirror. Now for something that really shouldn’t be done when collimating a reflector. To get the paper down into position using my method you have to have the scope pointing straight up, not advised as objects can fall straight onto the primary. It only took a couple of minutes and my template was in place and I now had a centre spot hovering over the primary.

I had left the focusing tube at the point of focus for my 20mm EP as this would be the better distance for where most focusing happens. Before I placed the collimator into the focusing tube I made sure that the two tightening thumb screws were flush with the inside, then they could be tightened equally so that the collimator fitted more centrally. Surprised, when I fitted the collimator into the focusing tube it was already quite a tight fit, meaning that minor turns of the thumb screws were required to hold it in place.

Looking down at my template I could see that the laser was only about 5mm outside of the circle. With some very minor adjustment of the secondary mirror I soon had it in the centre as below.

Next onto the Primary setting and that was just out of centre. Now I may be wrong but I thought that you had to loosen the thumb screws as these were the locking screws on the base. I couldn’t budge these by hand and wasn’t going to get some mole grips on them just yet. Armed with a screwdriver I tried the screws next to them and with a gentle turn could see the primary alignment moving. With a couple of minor adjustments all was aligned. 

Now I may not have done it the way most people would, but I think that I now have a collimated scope within the best degree of what I can currently achieve. With the collimator being 20mm out over 6M that drops down to a possible 2mm out on my 650mm focal length, not sure if that doubles for the primary or not.

[Pyrodave]

The first time is always nerve racking, It gets easier every time you do it . I recently Flocked my scope so had to remove everything from the tube. I wasn't looking forward to doing it, but it all went back easily, and I didn't have any spare parts at the end (Bonus) even managed to square up the focuser .

It actually seemed easier doing everything from scratch .

[gbarnett]

I've got the same laser collimator (- different scope though - 200P dob). I do think it's harder to collimate the laser than the actual scope. It's just a matter of trial & error and keep fiddling until you've got it as good as you can - I've not got mine perfect either. I could probably whittle away a good hour or so trying to fine tune it - at least it's something to do on cloudy nights  - and at least once the laser's collimated it should stay that way unless it's dropped. I think that's why people prefer Cheshire collimators as there's less hassle. Nice V block!

[Langy]

I've got the same laser collimator (- different scope though - 200P dob). I do think it's harder to collimate the laser than the actual scope. It's just a matter of trial & error and keep fiddling until you've got it as good as you can - I've not got mine perfect either. I could probably whittle away a good hour or so trying to fine tune it - at least it's something to do on cloudy nights  - and at least once the laser's collimated it should stay that way unless it's dropped. I think that's why people prefer Cheshire collimators as there's less hassle. Nice V block!

Yes I think if I can get the holes properly cleared to see the adjustment screws like will be far easier. With only being 20mm out over 6M I thought was reasonable. I'm sure there are many other factors within the scope itself that can create a greater error.

Thanks the Lego was by far better than anything I could have made. The laser sits in there a treat and rotates around. I did wonder if I was going to have to tape the plate down on the window-sill, but it didn't move as you rotated the laser.

[wolfpaw]

I've got the same laser collimator (- different scope though - 200P dob). I do think it's harder to collimate the laser than the actual scope. It's just a matter of trial & error and keep fiddling until you've got it as good as you can - I've not got mine perfect either. I could probably whittle away a good hour or so trying to fine tune it - at least it's something to do on cloudy nights  - and at least once the laser's collimated it should stay that way unless it's dropped. I think that's why people prefer Cheshire collimators as there's less hassle. Nice V block!

It doesn't matter how well-collimated the laser is if it doesn't sit accurately within the focuser. I found that the laser never went into the focuser exactly the same the way twice, no matter how much tape I put around it to try and take out the miniscule amount of slack.

[wookie1965]

I had the exact same laser and it was out tried and tried to adjust it no luck, after i had used it on my scope when i put a Cheshire in could see how far it was out  the laser in now in the bin and im sticking to the Cheshire. Saying that if the laser has worked for you and your get good views great enjoy your scope while the weather holds.

[Physicist13]

Like the lego!

any collimation like this is only to get the overall collimation close...not perfect. If you want it better then you really need to collimate using a star and an eyepiece...get nice circular se of airey rings. But like all this sort of thing, remember not to let it spoil your fun time! How fussed are you really if its a bit out? With a Newt you'll also get Coma error unless a corrector is in the optical path and this is more likely to be more severe than the collimation error effect...unless its way off..which is why a "rough" check using a laser is useful before viewing/imaging.

P

[Langy]

I know I'm limited with my scope but I'm just trying to make sure I can get the best out of it.

Collimation can obviously be an issue with a reflector, so I thought that if I could make sure it is reasonably close then it all adds to that point of where I want to be.