Barlowed laser

[bosun21]

I have just started using the Barlowed laser method for collimation on my 8” Dobsonian. This is the first times that my Cheshire and laser agree every time. Before when using just the laser there was always a discrepancy when checking with the Cheshire. Are most folks using the Barlowed laser method?

 

[wookie1965]

Most cheap lasers need collimating themselves that's probably why your laser and Cheshire did not correspond. 

The barlowed method is a good collimation for longer reflectors so you don't need to stretch your arms down to tweak the primary. 

Nothing beats a good Cheshire/sight tube IMHO. 

 

[bosun21]

2 hours ago, wookie1965 said:

Most cheap lasers need collimating themselves that's probably why your laser and Cheshire did not correspond. 

The barlowed method is a good collimation for longer reflectors so you don't need to stretch your arms down to tweak the primary. 

Nothing beats a good Cheshire/sight tube IMHO. 

 

My laser is a hotech and I checked the collimation with an engineers v block and it’s good at 5m. I think it’s that with the compression clamp in my focuser i never re site the laser the exact  same way twice. I’m in the process of fitting a click lock, so that should be better. I agree with you that the Cheshire is my main tool, although I like a final check on site and in the dark the Barlowed laser is great. I must be doing it right as my star tests are good and at the end of the day that’s the important part 

 

[wookie1965]

Get a self centering adapter 2" to 1.25" never go wrong with that.

https://www.altairastro.com/altair-2-inch---125-inch-self-centering-eyepiece-adapter-211-p.asp

[Mr Spock]

I fixed the post for you 

[Spile]

My goto tools are the Cheshire eyepiece and sight tube combination tool for the secondary (secondary and primary) and cap (primary).

[bosun21]

22 minutes ago, Spile said:

My goto tools are the Cheshire eyepiece and sight tube combination tool for the secondary (secondary and primary) and cap (primary).

That’s what I use as well, although I use the laser on site after arriving and setting up. It’s much easier and quicker in the dark 

[Stardaze]

I’ve been using a barlowed laser of late but the it’s still slightly out against the Cheshire. Very marginal though. 

[John]

I use all three methods but mostly a simple cheshire eyepiece. I'm most confident about the cheshire because post adjustment star tests seem to demonstrate that this device gets it right.

My secondary mirrors rarely seem to need adjusting. Usually it is just a tweak to the primary tilt that is required.

Edited December 19, 2021 by John

[bosun21]

Same with me. I had to initially adjust my secondary mirror before first light and haven’t had to since. That’s where the Barlowed laser comes into play as all that’s ever required is a tweak to the primary.

[Stu]

I’ve never used a barlowed laser, though it does seem a popular method. I use a Concenter for the secondary and a Hotech laser for the primary. I confess I’ve never checked the collimation on the laser but the results are good so I reckon it must be fine. With the Hotech you don’t use the focuser locking screws, it has its own self centring mechanism.

[Pixies]

The only times I have tried to barlow a laser was using the cheap single lens barlows that come with starter scopes (I have amassed a few). With these ones - and I'm sure you know the ones I mean - the laser light reflects straight back from the first uncoated surface and lights up the target so brightly that you can't make out anything else.

[wimvb]

I use a barlowed laser to collimate my skywatcher 190MN. The secondary has a center mark which I can see projected on the primary. I align this with the mark on the primary, and both back on the laser's disk. I also check that the secondary mark is centered in the focuser.