Colimator project

[oshb5]

Hi all iv just got a SCT my first and im a bit lost about collimating it also i have not got it on a dovetail yet so have no mount that can track a star to do the collimation. also no false star so was looking at teh laser collimators and the only one that looks like it can do a SCT is the Hotech But wow what a price around £300 This got my brain cogs turning over. Anyway this is what i done so far and where i am at teh moment with it

Its not finished yet but you can get where im headed. I need to wire it up These parts are winging their way to me as i type. The lasers iv fitted is a crosshair one to the center and single point ones at the other 3 points round the outer ring. I just need a way to make sure hey are at right angles to the back board (possibly the same sort of set up as the collimation screws them selves on each of the laser module We will se when I get round to testing it) and finally a way to aligne this to the SCT as shown in the Hotech video I think a Cg3 should work as a quick fix. If it does i can then make a proper smaller pan tilt unit and fit it to the bottom.

Any comments?

Regs Andy

[CGolder]

Hello andy, looks impressive, my only comment would be that star collimation on a sct is so easy it makes using lasers a bit silly :-) ofc u need a star to do that

Sent from my ZTE-RACER using Tapatalk

[ixalon]

Hi Andy

Great minds think alike. I started building one of these last week too. I usually collimate using a star and luckily my SCT holds it well, but since seeing is rarely good enough to see the diffraction rings clearly and building astro stuff (and especially stuff with lasers) is so much fun, I thought I'd give it a try considering how cheap laser modules are these days

To ensure the lasers are all parallel (i.e. collimated themselves) I'm drilling 12mm holes (the diameter of the modules) though 6mm sheet aluminium with a drill press to ensure they're all perpendicular to the surface. I've also got holders (http://odicforce.com/shop/article_OFL207/Alloy-Module-Holder_Heatsink-(12mm).html?shop_param=cid%3D25%26aid%3DOFL207%26) which I can bolt to the back. Hopefully that will be enough, if not then, I can drill the holes a little larger, use rubber grommets, and place 3 blocks with thumbscrews around each laser to nudge their angle slightly (as you suggested).

The other important bit is the mirror that goes in the focuser. It's important this is perpendicular too (see the problems people often have with cheap laser collimators that don't sit flat and centred). I've copped out of building one of those so I've asked the wonderful chaps at FLO to import a hotech self-centering 2" mirror for me.

I'll post some pics when I've got it built. Good luck!

Edit: My plan for attaching to a tripod is to drill a hole in the back and tap a 1/4"-20 thread, so I can attach a quick release plate. The whole thing is pretty light, so it shouldn't budge once screwed down.

[oshb5]

Mine is 4mm plastic board with strengthening rib on the back. The holes are made with a miller a 12mm end mill was plunged through so they are at right angles. I also have a lathe so the laser module carriers are made out of 1 1/2 delrin machined down to 1 1/4. Not sure why I machined them to 1 1/4 force of habit I suppose making astro stuff and drilled to match the laser module outer diameter the cross-hair central one was fine as it was 9 mm the smaller 3 where a bit of a funny size just under 4mm so drilled it 4mm and tried to get them central but have now ordered some 9mm lasers to replace these. So all carriers will be the same. Iv made the flange 12mm where if fits through the board and fits flat to the back of the board . if the laser fitted snug in the mounts then they would be spot on but they dont hence the need to adjust them . Im thinking of fitting three adjustment screws just like the collimation ones in each laser carrier to do the adjusting. i have a mirror copy of the board and will set it up across the room and provided the lasers hit the same spots on the copy of the board they will be right. As for the mirror I thought about ordering a proper 2" Hotech one but was unsure where to get one from.. So I have a friend who owns a glass workshop so got him to cut me a 2" mirror to fit a SCT screw on cap i made 2"x 24 tpi. The mirror then sits on the rear cell so should be in the right place the only thing I did wondered was Is it a plain flat mirror that fits into the back for reflecting or is it concave or convex one only time will tell? This is my only worry. But as you are ordering one from FLO i will possibly do the same.. Also thinking of making the tilt and turn as cannot find a cheap Cg3 at the moment

If it works then i will get some aliminium plate and also make some carriers out of aluminium I have plenty of bar aluminium but its plate I have not got. How much was your piece of plate? But I will try this to make sure it works first. Its cost so little to date.

Andy

P.S. iStuff alwas feels better when you have made it im not sure weather thats because you have made it yourself or its the money you have save LOL

[ixalon]

I got the plate from these guys http://stores.ebay.co.uk/Aluminium-Droitwich for £13.90 - probably could have got it cheaper from a local source but this saved the hassle.

I'm not sure at all about the mirror - another reason I've ordered one.

I've printed a matching target and can take it down the bottom of the garden (roughly 20m away) to check the alignment (if aligned at that distance, should be fine at 2-4x the scope's focal length).

[ixalon]

How are you getting on with building your collimator oshb5?

The tightly fitting holes in the aluminum sheet were not enough to ensure alignment between the laser diodes, so I need to rethink my plan a little...

[oshb5]

Hi

Iv had the same problem. So iv been thinking If you make the laser module holders a bit longer so they stick through the plate Then you put a circlip on the end which sticks through. Then like on the secondary mirror put 3 collimation screws so you can adjust the laser alignment How about that?

Andy