Amazon laser collimation gizmo. Quick review

[GasGiant]

Just a quick note to those maybe deciding on a laser collimator.

I purchased this 

https://www.amazon.co.uk/dp/B07J5WBG4K?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

Yesterday and it duly arrived this morning. I popped it on my engineers V block to test if it was true and it was bob on. No deflection in the light spot as I rotated it.

I have been collimating my Dob with a cheshire and thought I was pretty accurate with it !! doh, nope. Fitting the laser I could see that It was out by quite a lot!  Not sure how much ' out by quite a lot' affects viewing experience though. 😂

I adjusted both the secondary and primary within a couple of minutes. So easy !!   

The acid test of course is when we have a clear spot enough to look at something ! 

I would recommend this. 

[Orange Smartie]

Thanks for sharing this. Is the collimator itself collimatable? If it did arrive out of alignment, would you be able to tweak it?

Pete

[GasGiant]

No and yes

So around the barrel near the top are 3 equally distanced dips. This I believe is where the setting screws are for the laser. These have been filled in with a soft rubber type substance.  I would imagine during manufacture  the laser is set and the screws covered over.

Potentially you could dig out that rubber and set the screw ?

Edited September 12 by GasGiant

[Clarkey]

3 hours ago, Orange Smartie said:

Is the collimator itself collimatable

Yes, you can remove the cover and collimate the laser. I have the same cheap version, and it was quite a way off. Just remove the gunk with a small screwdriver.

[bosun21]

The laser can be dead centre on the primary mirror mark yet still be miles out of collimation. I found it essential to correctly position the secondary mirror in relation to the focuser draw tube. I use a Concenter(centre) for this task. Once done the laser is ideal for collimation checks before each observing session.

[Mr Spock]

8 hours ago, GasGiant said:

Not sure how much ' out by quite a lot' affects viewing experience though.

A lot! It needs to be spot on to be sharp. The more it's out, the fuzzier everything gets.

[John]

Thanks for that feedback.

I have one of those that came with a 10 inch dob that I bought 2nd hand recently. My example seems to need a bit of collimation though - tested in a similar way to yours, the beam at around 3 metres described a 50mm (approx) circle as I turned the collimator around. Mine needs adjustment !

 

[GasGiant]

Worked a treat.  Was up at 3, looked at Jupiter.  Boom. Spot on  🫡

[Earthserpent]

Thanks for an honest review - I think these collimator gizmos are most susceptible to cheap manufacturing 

[PeterStudz]

The only way I know of making sure collimation is spot on is to do a star test. 

[GasGiant]

24 minutes ago, PeterStudz said:

The only way I know of making sure collimation is spot on is to do a star test. 

How is that performed?

Im not sure I can get better. Everything looks round and sharp 🤔 but sometimes atmospheric conditions will play tricks on you ?

[John]

1 hour ago, PeterStudz said:

The only way I know of making sure collimation is spot on is to do a star test. 

Yep, that's my "acid test" as well.

I tend to find my cheshire more accurate than my lasers when I star test the scope. 

How to star test a telescope | BBC Sky at Night Magazine 

[Mr Spock]

Other methods of collimation work just fine, however, for a long tube, in the dark, you can't beat a laser.
Here's my guide:

 

[GasGiant]

I understand there are two main trains of thought when it comes to collimation.  Cheshire-laser, and it appears there are definitely two camps 😃

 

How more accurate can you get that a thin line of light?   With a Cheshire it seems to me there are more variables to go wrong when lining everything up! 🤔

[Mr Spock]

I can't answer for others, but I find a Cheshire difficult to use. What I have found when I follow the procedure I posted is, my scope is collimated so well, it passes a star test without further intervention.

I t's a great advantage to be up and running in seconds with as little fiddling as possible. Observing time, not fiddle time!

[Ardsley Astro]

I think my laser collimator is the same one but it was definitely out of collimation. I did have a Cheshire but its weird one that wont slide all the way down the focuser tube. So ordered a SVBONY Cheshire yesterday on Amazon and it arrived the same day. Low and behold the Secondary was way too far towards the primary mirror. So pulled that back and got everything squared away. Now out of interest I wondered what the out of collimation laser would show. What I found was if I rotated it in the focuser tube it form form a small circle on the primary mirror. Now I don't have a jig to put it into to try and adjust it but I thought smeg it and dug out the rubber to get to the adjustment screws. Then made an adjustment and rotated it 360 degrees in the focuser again, watching what it did on the primary mirror. Rinsed and repeated until no matter what the rotation of the laser collimator the laser always landed on the same spot on the primary mirror.

Now have I done something stupid here or is that good enough to collimate the laser.

 

[Tiny Clanger]

I have an identical laser, dug out the goo to get to the screws, collimated it, but it still shifted in the focuser tube as the tube racked in or out, or if the screws holding the laser in place were differently set, or if a butterfly flapped it's wings in Brazil ...

Found the cure is to use the excellent, simple, barlowed laser technique explained here:

https://www.tomhole.com/wp-content/uploads/2020/12/blaser.pdf

[Captain Scarlet]

Barlowed laser is the method I use. Unfortunately almost all methods assume and require that the centre-spot of the primary is in fact at the centre of the mirror. For every mirror I have owned, this has not been the case, one grossly so (in an otherwise 1/10 wave-specified mirror!). In such cases all methods except the star test guarantee mis-collimation. Even with the star test, by centring the shadow of the secondary, you risk “collimating out the offset”, also ensuring mis-collimation. Owing to all this, I believe many if not most Newtonians are always out of collimation and that this is a big contributor to Newtonians’ poorer reputation than refractors.

Cheers, Magnus

[CraigT82]

2 hours ago, Captain Scarlet said:

Barlowed laser is the method I use. Unfortunately almost all methods assume and require that the centre-spot of the primary is in fact at the centre of the mirror. For every mirror I have owned, this has not been the case, one grossly so (in an otherwise 1/10 wave-specified mirror!). In such cases all methods except the star test guarantee mis-collimation. Even with the star test, by centring the shadow of the secondary, you risk “collimating out the offset”, also ensuring mis-collimation. Owing to all this, I believe many if not most Newtonians are always out of collimation and that this is a big contributor to Newtonians’ poorer reputation than refractors.

Cheers, Magnus

Indeed! The only truly perfect method of primary collimation is the examination of an in focus star and its first diffraction ring - looking for evenness of illumination of the first ring, and if uneven, moving the star using the primary collimation screws so that the star moves in the direction of the brightest part of the ring.