Arrghhh, Collimation

[Kit-Fox]

So put my Omni XLT 150 to rights collimation wise today.

arrrghhhh! I can see why people really dont like doing it, thought I was gonna end breaking everything. Thanks to Astro Baby's Guide which was a good read and the search function I think I managed to get it all sorted.

It does get easier to do doesnt it?

&

Will I have have to it properly often? By that I mean both mirrors?

[GazOC]

Unless it gets a good knock you can usually get away with giving the primary a little tweak to get things right.

[Kit-Fox]

Well from what I did I'd say the primary wasnt bad. The secondary was well out however, got that all sorted but really didnt like the experience, made everything feel just a little too fragile for my liking.

Just using the celestron collicap atm, followed a combination of its instructions & the general advice from Astro Baby's guide. Thinking I might need to get myself one of the cheshire like ones though, really strained my eyes using the collicap

[Doc]

I used just the collicap for a while, but then bought a laser collimator and using both of them collimation is alot easier.

[661-pete]

I don't do it very often: certainly not every time I have the 'scope out - but then that's not very often anyway. In a sequence of four imaging nights, I tweaked a bit after the first night and then left alone. It seems that, contrary to some reviews and opinions, the OO mechanics are quite stable: they 'stay put' in this respect.

I found that, even before the last tweak, the amount of out-of-collimation of the scope itself was very slight, in fact it was outweighed by the amount of out-of-collimation of the laser collimator itself. The laser has tiny adjustment screws but I'm afraid to touch them for fear of making things worse. So I compensate by twisting the laser around. Problem is, if the beam hits the paper ring instead of the primary surface, I don't get a proper reflection. Any comments on this?

[glennbech]

A Laser and a cheshire in combination works for me. I use the laser to adjust my secondary so that it hits the the center point on the primary. I then use the cheshire when adjusting the primary.

I found that the return beam on the laser was too unreliable on my baader laser collimator. Just wiggeling it a bit in the EP holder made the return beam move all over the place.

My pain when collmating is the low quality allen screws, that on my model of the SW explorer 200 cannot be fitted with bobs knobs... According to bob himself. But that is another story.....

[aussi skywatcher]

Hi. I too have an issue with the collimation screws on my Skywatcher 8". I have replaced them all (inc the grub screws) with stainless steel allen screws, much better than phillips head screws. For the actual adjustment screws I have used a 3mm thick "washer" to cover the countersunk screw hole and for the locking screws I have left them 5mm longer than the adjusting screws so that they are easily identified in the dark or low light. If you are lucky you can get allen screws with a ribbed edge around the head and this enables them to be used like "Bobs Knobs". Just be careful when fitting the adjusting screws that you dont make them too long or you will hit the mirror back with them.

Cheers Aussi skywatcher:)

[MidnightSun]

Like was said, the laser seems to work great for me and unless you really bump it around, the secondary shouldn't need much work at all. I lug my scope outside about 20 ft. nightly, and have adjusted the sec. once in 4 yrs. Unless you take it for a car ride, it shouldn't need much of a tweaking from time to time...

[The Warthog]

I have a C6N, which uses a push-pull system to adjust the collimation. I have been thinking that if I got some little coil springs, I could put them on the 'pull' screws, and use the push screws as 'holder' screws, and collimate like anyone else does, instead of messing around with two screws for each position on the back of the mirror cell. Has anyone actually done this?

[acey]

A 150mm scope will need collimating only rarely - and only do it if a star test shows the scope to be out of collimation. As the primary gets bigger and heavier (and as f-ratio gets shorter), collimation is necessary more often. With an 8-inch I did it ever few weeks or months, now with a 12-inch I do it every time I use it.

The secondary on any solid tube scope will rarely need adjusting, though on my Flextube (or on any truss tube) it's another task that's necessary every time.

I use a laser for secondary and Cheshire for primary and it all takes a few minutes, plus a moment longer to re-align the finder (which you always have to do after collimating).

With the 8-inch, for a long time I just used a collimation cap. I bought a Cheshire so I could learn to use it ahead of buying the 12-inch. But I immediately wished I'd bought it sooner - the Cheshire makes things so much easier. If the secondary is rarely to be adjusted, then a laser isn't necessary at all - the Cheshire is cheaper, simpler to use, and more accurate.

Andrew

[Kit-Fox]

Well since doing it the scope has been moved aroudn a fair bit from inside the house to outside & has retained its collimation really well

Just happy its keeping it, hated the experience (eyestrain) with the colli cap, meh something to keep in mind for any future purchasing decisions.

Thanks for the replies & advice folks much appreciated