collimation tool advice

[DAT]

Hello there, I am still struggling with collimation but getting very close, I think...As soo as I can, I will take up someone's kind offer of an in person tutorial.

For the time being, my cap and Chesire sight tube will certainly be good enough but was wandering whether someone could recommend a good laser that I can buy in the UK. I have been suggested everything from Glatter to Baader, Astrsystems and Ho-tech. All have pros and cons from price, to availability in the UK and so on. I am thinking of a laser to collimate in the dark and eventually to be more precise.

Also, what do people think about a Concentre. Would that help for the secondary? I have posted on CN and had some advice already and as usual there is a wealth of information coming my way. Am interested in an SGL slant on the matter.

I am in no rush to make a purchase as I have everything I need to get the job done now.

Thanks in advance

[apaulo]

I  purchased a concentre 1-2 years ago, my honest opinion of it is, very over priced . Yes it done a job, once  when needed. To collimate in the dark, just shine a red torch down the scope and use the cheshire.

[Mr Spock]

I use a concentre (concenter - US) for the secondary. Once you have the secondary in the right position, you don't need to adjust it again. So I suppose value for money is low, but I found mine invaluable.

I have a guide for laser collimation here: 

I do my 12" in the dark and it takes seconds. Plus with a laser you have the advantage of adjusting the primary from a distance.

[PeterC65]

I find that a laser collimator is the best tool for aligning the primary and secondary. The secondary alignment rarely needs adjusting but the primary alignment needs it regularly.

For adjusting the position of the secondary (along and across the axis of the scope, and its rotation) and I use a Cheshire eyepiece. But that only needs doing once.

The laser collimator I use is this one. It was correctly collimated itself from new and makes alignment of the primary and secondary easy in daylight and in the dark, although in the dark I do need to use a torch to be able to see the centre mark on the primary. I use it in 2" focusers with a standard 2" to 1.25" adapter as the one that comes with the collimator is plastic.

What I like about this laser collimator, compared with say the Baader, is that the laser target on the collimator is at 45° so you can orientate it so that you can see where the laser dot falls on the target from the primary end of the scope, allowing you to stan at the end and make the necessary adjustments.

 

[woldsman]

If the concenter rings align with the secondary disc and are sharply focussed, the tool helps with secondary mirror collimation. However, unlike OCAL and similar camera based software (which display the rings on a screen), you have to go from collimation screws to eyepiece. On my Newtonian the concenter rings are also a bit fuzzy. This could be because it is f5 but it’s the faster scopes that need the most precision. I bought a concenter preowned and agree the price tag for new is a bit steep. They do come up fairly regularly though.

[Ratlet]

I bought a cheap yi webcam (had it already to be fair) and with a wrap of craft foam it fits perfectly in the 2" focuser.  This let me do my secondary position as you can get software to overlay circles on the live image.

Positioning the secondary is something that needs doing/check infrequently so it works for me as it's cheap.

After that it's the laser.  I got a cheap one of Amazon.  Just need to check the collimation or the laser every so often and all is good.  Takes seconds to check the collimation at night.

[PeterStudz]

What size Newtonian do you have? A laser might be more useful for a large Dob but for my Skywatcher 8” and little 4.5” (travel, grab-and-go) I’ve never thought that I needed a laser. I have a good cheshire collimating eyepiece plus collimation cap (basically a cap with a hole in).

Once the secondary has been done it really doesn’t need to be touched unless I’ve cleaned the mirrors. Occasionally I need to give the primary a tweak and here the “cap with the hole in” does the job. Never needed to adjust anything in the dark. When I’ve taken the 8” Dob in the car I’ve been surprised to see that the collimation didn’t shift at all. But if it did it would really have just been the primary. 

When I took the 4.5” abroad which involved a 1.5 hours car journey, 4hr flight, 2 hours in a taxi, dragging the case/telescope over cobbled streets plus a ferry journey by sea, I was very surprised to find that collimation had not shifted one bit. In fact I was a bit disappointed as I’d taken by collimation tools with me and was ready for collimation action. Instead I settled down for a beer.

Personally I wouldn’t rush out and buy anything until you find out what works best for you. 

Edited April 3 by PeterStudz

[RT65CB-SWL]

Though I do not own a ‘Newtonian’ or ‘Dobosnian’ reflector telescope, (I have two catadioptrics and two refractors), at the time of writing/posting, I have and use the following collimating tools in my accessories case/tool box.

• Baader mk. lll
• Hotech SCA
• Hubble Optics 5-star artificial star
• two 1.25” collimatation eyepiece caps
• a 2” Concenter
• Tectron collimation set [comprises of: 1x sight tube, 1x ‘Cheshire’ eyepiece, 1x collimatation eyepiece cap

I have used ‘cheap’ laser collimators. Some do need collimating before use, where as the two I now own did not.

Of all the tools listed above, a collimation eyepiece cap is the cheapest. Alternatively you can make one from a milk bottle top. You just need to drill a small hole of about 1-1.5mm in the centre of it.

 

[PeterC65]

I use my laser collimator with a 6" and 8" Newtonian. What I really like about it is that I can watch the laser dot move into the right position while at the same time adjusting the primary or secondary screws. I don't need to stretch to look through a Cheshire / collimation cap, or worse, go back and forth between the Cheshire / collimation cap and the adjustment screws. I suppose camera based collimation systems are popular for the same reason.

I haven't replaced my secondar adjusters with Bob's Knobs but I suppose this would make it easier to adjust the position of the secondary, allowing you to feel for the right knob and adjust it while looking through the Cheshire / collimation cap.

 

[PeterStudz]

I have replaced my secondary screws with “Bobs Knobs” - well some cheaper thumb screws -  and also did the milk bottle modification. This does make adjusting the secondary so much easier. But you don’t do it that often so it’s hard to say if it’s worth it for you. I had to take my 8” Dob apart so it was a quick, simple and cheap thing to do at the same time. 

[DAT]

Thank you, a nice selection of opinions  and advice. I think given I have a Chesire, a concentre would perhaps be overkill although as someone has pointed out, it would be even better to try and see what works.  Not sure about the laser either, as I have an 8" dob some seem to think this is not necessary, I think I would like to improve with what I have and then perhaps think about what would help to be more precise. I understand this is not strictly necessary but I enjoy the challenge of getting things just right

(I have an 8" stellalyra f5.9 dob)

[wookie1965]

6 hours ago, PeterC65 said:

I find that a laser collimator is the best tool for aligning the primary and secondary. The secondary alignment rarely needs adjusting but the primary alignment needs it regularly.

For adjusting the position of the secondary (along and across the axis of the scope, and its rotation) and I use a Cheshire eyepiece. But that only needs doing once.

The laser collimator I use is this one. It was correctly collimated itself from new and makes alignment of the primary and secondary easy in daylight and in the dark, although in the dark I do need to use a torch to be able to see the centre mark on the primary. I use it in 2" focusers with a standard 2" to 1.25" adapter as the one that comes with the collimator is plastic.

What I like about this laser collimator, compared with say the Baader, is that the laser target on the collimator is at 45° so you can orientate it so that you can see where the laser dot falls on the target from the primary end of the scope, allowing you to stan at the end and make the necessary adjustments.

 

Check that laser I have had two and both were out worth checking.

[wookie1965]

1 hour ago, PeterStudz said:

I have replaced my secondary screws with “Bobs Knobs” - well some cheaper thumb screws -  and also did the milk bottle modification. This does make adjusting the secondary so much easier. But you don’t do it that often so it’s hard to say if it’s worth it for you. I had to take my 8” Dob apart so it was a quick, simple and cheap thing to do at the same time. 

Did you put a 1mm washer in front of the holder then the milk bottle washer then the mirror?

[PeterC65]

21 minutes ago, wookie1965 said:

Check that laser I have had two and both were out worth checking.

I have and it's fine.

Some people don't seem to like laser collimators and I don't understand why. Mostly you just need to check and adjust the primary alignment, sometimes the secondary alignment, and only once (unless you drop the scope) do you need to adjust the secondary position.

 

[bosun21]

I am also a fan of the Concentre(Concenter) for an accurate alignment of the secondary mirror. Once properly aligned it shouldn't need to be adjusted again unless the telescope has been roughly handled. I also rate my 2" Hotech laser highly as it eliminates any movement of the laser inside the focuser. I can also position the laser on the primary mirror spot in the dark without having to use a torch as when the laser is on the centre spot it becomes a clear cross making the process both quick and accurate. The primary mirror reflection also becomes a cross ensuring accuracy. The most important aspect to me is that it is repeatable. I can collimate then remove and replace the laser and still be collimated. For peace of mind I also check against a cap and cheshire which always correspond with each other. I find that when planetary imaging I check the collimation every session as its vitally important.

[PeterStudz]

29 minutes ago, wookie1965 said:

Did you put a 1mm washer in front of the holder then the milk bottle washer then the mirror?

There are various suggested options of milk bottle washer, metal washer just a couple of milk bottle washers etc. I initial tried a 1mm washer + milk bottle washer but for my secondary I was short of space - the gap was small. So I went with two milk bottle washers like this. It has worked well since I did it roughly 2 years ago now. 
 

Link to article…

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=136801

Edited April 3 by PeterStudz

[PeterStudz]

18 minutes ago, bosun21 said:

I find that when planetary imaging I check the collimation every session as its vitally important.

I check collimation before every session whatever I’m doing. I leave the “cap with a hole” on the focuser as a dust cap (small bit of masking tape over the hole). As I’m familiar with it, just by looking down the cap, I can immediately see if the telescope is collimated or not. 

[wookie1965]

13 minutes ago, PeterC65 said:

I have and it's fine.

Some people don't seem to like laser collimators and I don't understand why. Mostly you just need to check and adjust the primary alignment, sometimes the secondary alignment, and only once (unless you drop the scope) do you need to adjust the secondary position.

 

Yes as long as the secondary is in the right place like you said wont need to touch it just a tweak of the primary. First laser like yours went in the bin it would not collimate I would get it doing a 2mm circle at 26ft then try it on the scope and it was miles out was not holding collimation. bought a second one that needed collimating got that doing a 2mm circle at 26ft away gave that to the bloke who bought my 8" reflector.

[bosun21]

2 minutes ago, PeterStudz said:

I check collimation before every session whatever I’m doing. I leave the “cap with a hole” on the focuser as a dust cap (small bit of masking tape over the hole). As I’m familiar with it, just by looking down the cap, I can immediately see if the telescope is collimated or not. 

Yes I also check collimation before every session now that I think about it. I can then be sure that it's the seeing conditions that are the limiting factor on a particular night.

[wookie1965]

28 minutes ago, PeterStudz said:

There are various suggested options of milk bottle washer, metal washer just a couple of milk bottle washers etc. I initial tried a 1mm washer + milk bottle washer but for my secondary I was short of space - the gap was small. So I went with two milk bottle washers like this. It has worked well since I did it roughly 2 years ago now. 
 

Link to article…

https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=136801 392.83 kB · 443 downloads

I did the 1mm washer as when I took the secondary out of my 8" it had divots in, I sanded it down but put the washer there anyway. Did that with the 10" as well bloke who bought it said all the mods I had done were great. I should never have sold that 8". 

[DAT]

With regards to some of the collimation tools mentioned, if one has a 2" focuser and a good 2" to 1.25" reducer, does it matter whether one uses say a 1.25" or 2" laser or concentre?