How's my collimation?

[teoulennon]

Hey there,

I've been a lurker for a few years now and am excited to finally join!

I've collimated my Orion xt8 for the first time this morning using the supplied eyepiece.

What do you guys think? Any suggestions?

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[Uranium235]

Looks alright to me (assuming its an f5)

Edit: though it is difficult to tell if the secondary is centred.

[teoulennon]

Thanks for the input Uranium, what makes it difficult to tell about the secondary?

Any suggestions?

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[ronl]

Looks like it is close enough for observing, just needs a tweak to the right of the 

secondary.

[Dave In Vermont]

Agreed with roni. But if an F/5, the entire picture of where the image is will be off. But the center of the dark-circle with the crosshairs is notably still of a bit. You want to bring the black-circle and the airy-ring inside into the exact center.

It's a pain with fast Newtonian's - but will be easy after you get it right this time.

Clear & Sharp Skies,

Dave

[dweller25]

Thats looking OK, now fine tune on a star and you are good to go.......

[coulthamst]

I agree with Dave in Vermont's assessment

[teoulennon]

Thanks for the suggestions guys, much appreciated!

I probably made it more complicated than necessary but it was frustrating enough to get me to order a laser collimator!

[Charic]

Thanks for the suggestions guys, much appreciated!

I probably made it more complicated than necessary but it was frustrating enough to get me to order a laser collimator!

A Cheshire Sight tube would offer more benefits and probably be more accurate in setting up the secondary mirror.  I've used a Collimation cap, (very easy to use )  then the laser, has its inaccuracy problems, (most do, the laser itself needs to be precisely collimated and needs to fit the focuser 100% without  any slop, every time to get guaranteed results ?) then the Cheshire arrived, possibly the most accurate method. The Laser is best used for final quick adjustment to the primary mirror by using a Barlow-Laser combination. 

[teoulennon]

Thanks charic, I'll have to look into the Cheshire sight tube.

I've seen them online, but have never thought much of them bc I always just hear about lasers.

The secondary mirror was such a pain to adjust to me.

I'd like to get the most out if my equipment so whatever it takes I'll try!

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[Charic]

I paid £23 for my Cheshire, same place on-line as the BST Starguiders - There were two versions, LONG or SHORT. I chose the longer version.  If I withdraw the Cheshire slightly from the focuser tube, it acts like the shorter version? It just affects the  view when adjusting, and depending on the size/length of your focuser assembly?  I preferred the tighter view -longer version for my 200P Skyliner. I still use the Laser, out in the field, so to speak,  but only with a Barlow lens. A laser through a Barlow lens illuminates the  primary mirror surface, causing the centre spot to cast a shadow over the angled face of the Laser face plate. Its quicker and easier to align the shadow around the centre hole in the face of the Laser than trying to get the laser spot "inside the hole" ......get the Laser spot inside the hole, then touch the Laser body, it may move due to the sloppiness of the fitting, the Laser spot is back outside the hole again, this just causes frustration. If you centre the reflection around the hole, its about as good as the telescope will get. Touch the laser body again, still sloppy  maybe? but the shadow still encircles the hole in the Laser faceplate, about as good as it will get, considering the tightness of  fit......satisfaction........ and job done!

The laser alone should be ok, after all, its a Laser! But Lasers would be best if they were reliable! My 'Next Generation laser' has three inset grub screws, akin in layout to those found on a Newtonian secondary mirror. Adjust one, then the next until alignment is achieved. Alignment is achieved when, "If you rotate the Laser body in a horizontal jig with the laser spot on a distant wall -  when you rotate the Laser body the spot on the wall remains in position, WITHOUT  describing an elliptical or any other off-set feature? The Laser spot must remain central with out ANY off-axis movement. It must look static in position, while your rotating the laser body. Get this right and the laser is good. get it wrong, or it arrives wrong, there lies the problem?

With the Cheshire alone, yes its still possible to have a sloppy fit within the focuser (even  eyepieces suffer the same sloppiness due to tolerances, I'm not just picking on Lasers) but no batteries required, no additional tests, and  no adjustments to the laser beam, removing those adjuster grommets may/could  affect your warranty? On my Laser, two of the three grub screws seem to work ok? One just rotates and never seems to tighten, although looking inside, all looks fine? I've looked inside twice now, as my Laser's battery cap/switch unit has a mind of its own? and unless certain contacts remain in place, the on/off can be temperamental, but I like to know the ins and outs of how things work, and  I'm quite prepared  and more than happy to carry out my own fixes to overcome certain issues.

You can spend little or loads, but with a laser, they all have the same basic feature set. Some may adjust or are easier to adjust, some are not. The simple collimation cap is the most easiest to use, but you will always doubt yourself?  I bought the laser to overcome this, but reliability and set-up were an issue at first. I trust the Laser now using the   Barlow method, but that leaves my secondary mirror adjustments out of the equation.

The Cheshire fits the bill, it us used for the whole set-up from start to finish, and once mastered (collimating) its a quick and painless issue for me. 

[Uranium235]

Its worth using a cheshire/sight tube before doing anything. That will tell you whether your secondary is properly centred and whether it needs and rotation (always the hardest part). After that I use the laser, but to ensure a repeatable connection I use a threaded M48 connection to attach the collimation devices to the focuser.

Honestly, I was complete duffer when I first started with collimation (and may still be!...lol). But over time you learn the little oddities that your telescope may have, like learning which part of the focuser or spider relates to a corner or dodgy artefact in your images.