Thrown away my duff Skywatcher laser collimator

[Grunthos]

I bought a 250mm Dobo 6 or 7 weeks ago (and a laser collimator).

Had a few "teething problems" getting my head round visualising collimation procedures but finally got the hang of it (thanks to much advice on SGL btw).

However, I never could seem to get a decent, spot on collimation.

Finally got round to checking the collimation of my Skywatcher laser collimator today. It was well off! (e.g. described a circle of approx. diameter 50-60mm when projecting onto wall at 4meter range).

Decided to collimate the collimator and that is where the troubles began. The skywatcher adjustment screws are covered by a rubbery/plastic substance that is very difficult to remove. The allen screws for adjustment do virtually nothing.

I've spent almost 2 hours trying to get this equipment to align with no joy. Gave up in disgust.

Have decided to give into the dark side and ordered a Cheshire collimator.

Between that, my drilled 35mm film canister, two coloured bits of paper and Mk1 eyeball I hope to be collimating like a pro in the not too distant future (KISS?).

(Might buy another laser collimator in future to do the "barlowed laser" thing but it's going to need to be an easily collimated one - Antares? with a decent price attached).

[Moonshane]

the alignment of a laser becomes irrelevant if you use a barlow so you can probably use the one you have if you rescue it.

[Grunthos]

the alignment of a laser becomes irrelevant if you use a barlow so you can probably use the one you have if you rescue it.

Thanks for that. Might as well get some sort of use out of it.

[ollypenrice]

My Telescope House Astro Engineering laser has adjustment screws that work well. I make vee blocks by banging two pairs of 6 inch nails into a bit of planed timber. The vee is formed by the nails crossing. Dead simple and dead accurate since a vee is a vee is a vee...

Olly

[jam1e1]

Mine had that rubbery stuff on way, could try using a heated paperclip to burn it out or sharp thin knife to poke it out, managed to get to screws in the end on mine

[Dodge]

the alignment of a laser becomes irrelevant if you use a barlow so you can probably use the one you have if you rescue it.

Doesn't the laser need to be collimated to align the secondary though?

[Moonshane]

Doesn't the laser need to be collimated to align the secondary though?

yes it would but you would not use a barlow (or a misaligned laser) for that.

[Charic]

.........The Barlow  should only be used  in stage 3 to align the Primary mirror. Stage 1 being the central alignment of the secondary mirror to the focuser. stage 2 aligning the secondary mirror to the Primary mirror using the laser. Stage 3,  Barlowed laser to adjust the primary.

By Barlowing the laser beam, it becomes diffused, so instead of seeing a returned laser spot  image on the Barlow target, you get a reflection of the centre marking (doughnut) on the target, which then encircles the centre hole in/on the Barlow target showing correct alignment.

It makes for easier adjustment, rather than trying to chase a red laser spot into the hole. 

The Barlow also needs to be collimated. A simple jig to hold the Barlow, and the fine adjustment of the  3 "hidden screws" on the Barlow . YouTube for more info.