Laser check??

[bosun21]

When I use my 8” Dobsonian for a night of stargazing I use a sack barrow to wheel it about 150 meters to my nice dark grassy park. I always wonder if my collimation has gone off whilst wheeling it there. I use a long smooth Cheshire and collimation cap to collimate it frequently. I was thinking about buying a laser to collimate the primary in situ. I would use the Barlowed method. Does anyone else employ some sort of check after transporting their telescope?. Thanks 

[Pixies]

I use a long Cheshire to collimate the dob. But I have a cheap shorty Cheshire that I use if it's just a quick check and simple adjustment of the primary "in the field". 

Just stick it in and hold the red led torch up to the side port. You can quickly see if the eye hole is within the doughnut. Like an annular ring.

[ONIKKINEN]

I have never used my telescope without first transporting it in a car, so i always assume it has been bumped around. But turns out most of the time the collimation is unchanged or ever so slightly off i doubt it would be noticeable. I do checking with a laser, as i think thats an instant way to see if collimation has changed. I don't think a laser on its own is a good enough collimator since you cant easily see the shape of your secondary, but once good collimation is achieved its a good tool to check quickly. Usually if i do remember to check collimation and end up needing to adjust, its tiny adjustments only, like at best 1/10th of a turn in some direction.

[Louis D]

I just leave a Rigel Aline in the 2" to 1.25" adapter during transport.  I point the scope at a bright light or light wall (or use a flashlight shining into the tube) and look to see that the center mark ring is centered around the peephole reflection.

[bosun21]

1 hour ago, ONIKKINEN said:

I have never used my telescope without first transporting it in a car, so i always assume it has been bumped around. But turns out most of the time the collimation is unchanged or ever so slightly off i doubt it would be noticeable. I do checking with a laser, as i think thats an instant way to see if collimation has changed. I don't think a laser on its own is a good enough collimator since you cant easily see the shape of your secondary, but once good collimation is achieved its a good tool to check quickly. Usually if i do remember to check collimation and end up needing to adjust, its tiny adjustments only, like at best 1/10th of a turn in some direction.

Thanks for your reply and it’s mainly the primary mirror that I was concerned about. So I will ponder over either a laser or just take along one of my collimation caps 

[bosun21]

1 hour ago, Louis D said:

I just leave a Rigel Aline in the 2" to 1.25" adapter during transport.  I point the scope at a bright light or light wall (or use a flashlight shining into the tube) and look to see that the center mark ring is centered around the peephole reflection.

Yes that’s what I reckon as well. If everything is looking good under the cap then you aren’t far off 

[bosun21]

1 hour ago, ONIKKINEN said:

I have never used my telescope without first transporting it in a car, so i always assume it has been bumped around. But turns out most of the time the collimation is unchanged or ever so slightly off i doubt it would be noticeable. I do checking with a laser, as i think thats an instant way to see if collimation has changed. I don't think a laser on its own is a good enough collimator since you cant easily see the shape of your secondary, but once good collimation is achieved its a good tool to check quickly. Usually if i do remember to check collimation and end up needing to adjust, its tiny adjustments only, like at best 1/10th of a turn in some direction.

Thanks for your reply and my secondary is as good as I can possibly get it. It’s dead centre in my focuser and concentric. Like you say the laser is convenient for checking the primary.

[wookie1965]

As Pixies said just shine a red torch into the the Cheshire from the side takes seconds.

[Pixies]

3 hours ago, wookie1965 said:

As Pixies said just shine a red torch into the the Cheshire from the side takes seconds.

Yep. A Cheshire rather than a collimation cap, means you can check the primary collimation using a torch in the dark. But if you are happy that your laser is collimated OK, it's perfectly fine to use it to check the primary. In fact, if you need to make an adjustment, it is easier than a Cheshire, as you don't need 4 feet long arms!

Actually, my old shorty Cheshire has the crosshairs removed - it's just acting as a side-lit collimation cap. If I want to align the secondary, I'll use the long Cheshire.

[wookie1965]

10 minutes ago, Pixies said:

Yep. A Cheshire rather than a collimation cap, means you can check the primary collimation using a torch in the dark. But if you are happy that your laser is collimated OK, it's perfectly fine to use it to check the primary. In fact, if you need to make an adjustment, it is easier than a Cheshire, as you don't need 4 feet long arms!

Actually, my old shorty Cheshire has the crosshairs removed - it's just acting as a side-lit collimation cap. If I want to align the secondary, I'll use the long Cheshire.

Yes a Barlowed laser is easier then you can use any laser whether that is collimated or not. Then you can check with the Cheshire just to be sure. 

[Spile]

I will never check my secondary or primary alignment in the dark. My 200P keeps both secondary and primary aligned very well so I check them once a week with a Cheshire eyepiece and sight tube combination tool once a week and tweak as needed.

[bomberbaz]

I think if I was starting out afresh I would be using howie glatter gear, never heard anything bad about it. I believe the lasers hold collimation extremely well and are very versatile plus extremely accurate.

Howie Glatter | First Light Optics

However the  HG laser and any accessories are quite costly and when I bought my gear I didn't have the funds so bought a Hotech collimator laser. Slight problem with this is it doesn't hold perfect collimation itself and so needs collimating itself occasionally.  

I did this today and couldn't quite make a perfect laser collimation, I had a donut with a diameter of about 5mm at a range of 12 feet/3.6M. 

IMHO this is going to give you a pretty good collimation. However I do double check this (light permitting) with a concenter eyepiece and a standard cheshire for good measure.

Back to the start, if I had to start again, the HG route would be my preferred option. 

[bosun21]

On 26/10/2021 at 10:10, Pixies said:

Yep. A Cheshire rather than a collimation cap, means you can check the primary collimation using a torch in the dark. But if you are happy that your laser is collimated OK, it's perfectly fine to use it to check the primary. In fact, if you need to make an adjustment, it is easier than a Cheshire, as you don't need 4 feet long arms!

Actually, my old shorty Cheshire has the crosshairs removed - it's just acting as a side-lit collimation cap. If I want to align the secondary, I'll use the long Cheshire.

Thanks for your reply and I’ve been using my Cheshire before I went out and the Barlowed laser in situ. I have only got my red headlamp atm, so I’ll pick myself up a red torch and retire the laser method. Thanks 

[Pixies]

1 minute ago, bosun21 said:

Thanks for your reply and I’ve been using my Cheshire before I went out and the Barlowed laser in situ. I have only got my red headlamp atm, so I’ll pick myself up a red torch and retire the laser method. Thanks 

I said 'torch' - I was referring to my red headlamp hand-held!

If the barlowed laser works for you, you don't  have to retire it. It'll make things easier to adjust in situ.

[bosun21]

49 minutes ago, bomberbaz said:

I think if I was starting out afresh I would be using howie glatter gear, never heard anything bad about it. I believe the lasers hold collimation extremely well and are very versatile plus extremely accurate.

Howie Glatter | First Light Optics

However the  HG laser and any accessories are quite costly and when I bought my gear I didn't have the funds so bought a Hotech collimator laser. Slight problem with this is it doesn't hold perfect collimation itself and so needs collimating itself occasionally.  

I did this today and couldn't quite make a perfect laser collimation, I had a donut with a diameter of about 5mm at a range of 12 feet/3.6M. 

IMHO this is going to give you a pretty good collimation. However I do double check this (light permitting) with a concenter eyepiece and a standard cheshire for good measure.

Back to the start, if I had to start again, the HG route would be my preferred option. 

Yes I did consider the HG route but was put off by the price of something that up to then. I didn’t know if it worked well. The collimation of the lasers are a constant worry of are they or aren’t they?. This is why I only trust them when employed with a Barlow. Thanks 

[johninderby]

The Hotech laser is perfectly collimated and stays that way but not cheap but still a good buy when you consider how good it is. The crosshair beam makes colimating easier than the simple red dot type.

[bomberbaz]

7 hours ago, bosun21 said:

Yes I did consider the HG route but was put off by the price of something that up to then. I didn’t know if it worked well. The collimation of the lasers are a constant worry of are they or aren’t they?. This is why I only trust them when employed with a Barlow. Thanks 

read the blurb about the HG lasers, the guy throws them several times to shock them to see if they hold collimation, if they do then they pass. For me that is why I would get one now if starting out.

TBH this thread is making me reconsider buying one of them again!

@johninderby "The Hotech laser is perfectly collimated and stays that way but not cheap but still a good buy when you consider how good it is. The crosshair beam makes colimating easier than the simple red dot type."

Trouble is they don't though. Mine may be an old one but collimation has slipped and although a 5mm donut at 3500mm isn't too bad, it is still there and I would prefer it to not be!

Edited October 29, 2021 by bomberbaz

[johninderby]

Had two of the Hotech and both were perfect and never lost colimation so I can only say what I found.

[bomberbaz]

52 minutes ago, johninderby said:

Had two of the Hotech and both were perfect and never lost colimation so I can only say what I found.

Just reread my post John, didn't mean my reply to sound negative if it came across as such, so sorry if indeed  it did but like you was just giving my own point of view. 🙂

[johninderby]

9 minutes ago, bomberbaz said:

Just reread my post John, didn't mean my reply to sound negative if it came across as such, so sorry if indeed  it did but like you was just giving my own point of view. 🙂

No problem.👍🏻

You can’t do any more than pass on your own experiences.

[Stu]

I’ve always assumed my Hotech is spot on, although I’ve never actually checked it! It gives star test results which I’m happy with so seems ok.

[JeremyS]

I originally used a cheap Chinese device, commonly available from many outlets. Was nowhere near collimated 

Moved on to a Hotech and never looked back.

[Louis D]

I've been using the 1990s version of the AstroSystems laser collimator that was both 1.25" and 2" compatible.  It seems to have held its collimation just fine over the years.