# Laser Collimator For Dobsonian vs Newtonian

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Will a laser collimator like the Gosky 1.25 Metal Laser Collimator, https://www.amazon.com/gp/product/B01M4IVUYG/ref=crt_ewc_title_dp_1?ie=UTF8&psc=1&smid=AHQ6VCR020F8X, work for a dobsonian even though it says it's for a newtonian?

A Dob is a Newtonian, so yes it will work. Strictly speaking the Dob bit is the mount, but it's nearly always a newtonian that's mounted.

## A step by step guide to Collimation

If like me you own some sort of reflector telescope, whether this be a Newtonian, Dobsonian, Ritchey Chretien or as I have a Hyperboloid Astrograph then you’ll know that there is a very strong importance on collimation, the faster the optics the more critical collimation becomes, especially for imaging. After recently removing the rear mirror assembly for cleaning, as well as changing from the QHY183M to the QHY268C-PH amongst onther stuff in the imaging train, I wanted to share my experience and knowledge around collimation. Let’s start off with the details on what I use

## Laser Collimator For Dobsonian vs Newtonian - Astronomy

A couple of questions: First, did you use the whole Cheshire collimation tool set (including the auto collimator) or just the Cheshire tool? Did you also use the sight tube (I don't understand everything in this yet so if the question seems stupid it probably is)?

Also, Zhumell has a deluxe collimator. Would it be any better than the one included with the scope, do you think?

I don't currently have an autocollimator, but the Cheshire I have is a sight-tube/Cheshire combo tool. It functions both as a sight tube and as a Cheshire, so I can use the same tool to do everthing from centering the secondary to aligning the primary with one tool.

As far as the Zhumell deluxe laser, I'm sure it might be a little nicer, but the inherent problem with a laser collimator is that it needs to be collimated, just as the scope needs to be collimated. Putting the laser in a Barlow will diffuse the beam, which can be quite useful. By placing a paper target on the Barlow, you can center the shadow of the center dot on that target. Then you know that you are perfectly collimated, as this is not dependent on the laser's collimation.

Hope this helps. Once I get a hold of a Barlow, I'm going to do a write-up on Barlowed laser collimation.

DO you have a recommendation as to where to buy the collimation tool set from? I'm looking at getting an order turned in so I can really see!

I got mine at the Cloudy Nights Classifieds section. This item at telescopes.com is similar to my Cheshire eyepiece.

Your headline would have been more accurate if it had said: Why Not to Simply Rely on a Laser Collimator.

Perhaps a good follow-up post would be how to collimate your laser collimator. Assuming it has a round body, this is fairly straightforward.

Clamp a piece of angle iron or aluminum in place and lay the collimator in it (pointing at a wall). Now roll the collimator (rotating it in place 360 degrees). If perfectly collimated, the laser should stay at the same point on the wall. If it travels in a circle, it is out of collimation.

Good laser collimators can themselves be collimated. I have an Orion Lasermate Deluxe. I'm told the collimation screws are under a self-adhesive label.

You bring up a good point, cheekygeek, as most laser collimators do have a means to collimate them. I've been meaning to make such a jig, but school lately has been hectic!

On my Zhumell laser, the collimation screws are set into the body, inside some little holes. If I remember correctly, they are allen screws.

Anyways, another way to collimate a laser is to actually put it in the telescope, and adjust your secondary WAY out of whack, so that the laser beam misses the secondary entirely on the return trip and exits the objective. Then your telescope has become the jig, and you can get a decent collimation of the laser in this manner. If I get time this weekend, I'll do a write-up of the process for future use.

I had the same mechanical slop problem with my 10" LightBridge using the LaserMate collimator until I found a company solves the slop problem with their new SCA technology. I went ahead and bought the SCA laser collimator last week, and the laser works like a charm.

## What about Laser Collimators?

### Best for more advanced users: Orion 12″ XT12i

Almost everyone who buys a Dobsonian as a beginner gets one without a computer. That’s fine for general observing for newcomers to the hobby. Once you have been doing this a while and want to find more and more difficult targets you may need two things a larger aperture telescope and a computer. This is the best Dobsonian for solving those problems.

The Orion Intelliscope push to system is the best Dobsonian electronics package and bridges the gap between full manual with no computer to a full go-to system. It tells you where to push and then confirms you are on the target once you get there. Not only does that make finding objects easier, but substantially faster. Besides, one of the things that makes the best Dobsonian for you is if you will use it. Being able to find targets quickly absolutely makes some people more likely to use their telescope and therefore, makes it the best Dobsonian for them.

Another excellent use for the computer on a dob is for outreach. Set it up, align it, and take requests on what people want to see. With a 12″ aperture there is virtually nothing you can’t see, assuming it is up. This is probably the absolute best Dobsonian for outreach.

This is much like the xt8 as far as reliability and simplicity is concerned. Orion also added a much nicer finder and improved substantially on the base. Overall this the best Dobsonian for any user if it is in your budget.

### Best for advanced users who need portability: Orion 12″ XX12i

This little guy is on the best Dobsonian list because it will allow you all the capabilities of the standard 12″ Intelliscope Dobsonian telescope with the added benefit of being far easier to transport, even in a small car. It also has an upgraded focuser but not quite as nice a finder when compared to the standard 12″ Intelliscope.

To really make the portability work, Orion even makes a set of padded cases, the Orion 15094 Case Set, that each piece goes into. While there are other cases for telescopes, and some for dobs, these Orion cases are the best Dobsonian cases out there. This makes it one of the best Dobsonians to carry out to the dark site.

The base on this and the standard Intelliscope are the same, making the tube the only difference. The components of the truss tube variant seem to be made of heavier gauge metal making it not only stiffer, but a lot nicer to work with. Everything seems amazingly stable.

As with most truss tube setups, you will want to make sure you get the shroud that fits it and Orion makes a specific 15097 Light Shroud for this model and it really is the best Dobsinain shroud you can get for it.

If you need portability, a reasonable price, push to capabilities, and excellent views, this is the best Dobsonian for you.

### Best top of the line mass-produced: Orion 14″ XX14g

Most of the portability of the 12″ truss tube with more seeing power and a full go to computer system, this guy will provide amazing images of any target you choose to point it at and still not give you a hernia trying to get it out to the field.

If you want the best views you can get while still staying portable in a mass-produced telescope, this is the best Dobsonian for you.

One of the advantages of the 14″ over the 12″ is that the base also collapses. This makes it as easy to transport than the 12″ model, just a little different.

This telescope also has the full goto controller that they use with their EQ mounts. In my opinion, this is the absolute best Dobsonian GOTO package available from any manufacturer.

Off and on Orion, as well as other manufacturers, have produced larger models than this 14″. They did not make this list because they are not always in production or lack some of the features of the XX14g. They also tend to get exponentially harder to transport once you get over this 14″ model. Unless you drive a full-sized SUV or don’t mind putting a telescope in the back of a pickup, this is about as large as you want to go.

## Collimation Tools: What You Need and What You Don’t

Aligning the optics of your reflector telescope is crucial for optimal performance — all the more so if you have a telescope with a focal ratio of f/5 or less. A good tool can make the difference between successful collimation, and an exercise in frustration that encourages you to settle for “good enough.” But selecting the right tool can be more confusing than actually using it. On-line discussions offer a bewildering array of opinions and experiences — some of which posted by people who make and sell the products they (naturally enough) recommend. So what do you really need to collimate your scope?

Here is a rundown of the various collimation tools commonly available, and their relative strengths and weaknesses. My evaluations are based on several decades of making and using reflector telescopes. All the devices discussed below can produce satisfactory collimation. What generally distinguishes one from another is not accuracy, but rather, ease of use and cost.

Option #1: No Tools

Yes, it is possible to collimate your reflector without any tools. It’s called the “star test.” The detailed ins and outs of this method are beyond the scope of this article, but essentially you centre a bright star in the eyepiece, throw it out of focus, and note where the shadow of the secondary mirror is positioned within the expanded disk of light. It should be centred. The test becomes progressively more sensitive the nearer you get to focus. Regardless of what other collimation method you use, the star test is the final arbiter of optical alignment. If it looks right in the star test, it is right.

Best features: You can do it without spending a single dollar. No centre dot is needed on the primary mirror.
Worst features: The method takes some experience and isn’t the best choice for absolute beginners. It’s also usually more time consuming than other methods and requires a star (or point-source light). It’s also not the best way to ensure the secondary mirror is correctly placed.
Ease of use: For the highest accuracy you’ll need a night of good, steady seeing. Experience will make the method more reliable and effective.

Option #2: Collimation Cap

A simple, inexpensive collimation cap.

Possibly your telescope came with one of these. Orion Telescopes supplies them with their reflectors, as do some other manufacturers. The device is simply a plastic cap with a small hole in its centre and a reflective underside. If your telescope didn’t come with one, you can make one with an old plastic film canister. For 90% of the collimation I do, this is the tool that I use. The only time I usually need something more is when I’m assembling a scope from scratch.

Best features: Cheap and effective.
Worst features: Not the best tool for aligning the secondary mirror (though it can be done). Requires the centre of the primary mirror to be marked.
Accuracy: Very accurate if your mirror’s centre dot is correctly positioned.
Ease of Use: Very easy to use.

Option #3: Cheshire Eyepiece

This combination tool from Orion is a Cheshire eyepiece and sight tube in one.

Not an “eyepiece” in the usual sense of the word, a Cheshire is a sight tube with a small hole at the top that you look through, and a shiny surface tilted at 45° and aimed at a large hole in the side of the tube. The version Orion (and others) sell also has a set of cross-hairs at the bottom of the tube for aligning the secondary mirror. This “all-in-one” collimation tool is excellent. Indeed, if you have one of these, you need nothing else.

Best features: One tool that does it all. Relatively inexpensive.
Worst features: In the dark you’ll probably need a red flashlight to illuminate the shiny surface of the collimation eyepiece. Requires a centre-dotted primary mirror.
Accuracy: Very accurate if your mirror’s centre dot is correctly positioned.
Ease of use: Easy to use.

Option #4: Laser Collimator

A laser collimator tool for 1¼” focusers.

Laser collimators have been around for many years now and seem to be especially attractive to those who equate lasers with precision. Unfortunately, it’s been my experience that beginners all too often end up de-collimating their scopes when using one of these. Why? The Achilles heel of the laser collimator is that its accuracy depends on how carefully you’ve adjusted your scope’s secondary mirror — a procedure that is far more difficult than it is important to image quality. In other words, if your scope’s secondary mirror isn’t set correctly, you can actually achieve a “pass” by putting your primary mirror out of alignment — a situation that can have disastrous consequences when it comes to image quality. That said, I have a laser collimator and find it a useful tool for adjusting the tilt of the secondary mirror. I don’t recommend it for adjusting the primary, however.

Best features: Can be used in the dark. Useful for adjusting the secondary mirror.
Worst features: Can lead to miscollimation. Batteries required. Expensive relative to benefits. Requires centre of primary to be marked.
Accuracy: Potentially accurate if used correctly. Accuracy dependent on mechanical alignment of the laser within its housing and how the device seats in the focuser. Accuracy highly dependent on positioning of the secondary mirror.
Ease of use: Relatively difficult to use successfully.

Option #5: Barlowed Laser

These views show the target for a Barlowed laser setup. The images show the telescope nearly collimated (top) and fully collimated (bottom).

The Barlowed laser is the newest approach in the collimation game. Most people heard about it the first time when Nils Olof Carlin’s article appeared in the January 2003 issue of Sky & Telescope (page 121). As editor of the telescope-making department, I had the privilege of working with Nils to bring this to the pages of the magazine. Essentially the setup consists of an ordinary laser collimator used in conjunction with a Barlow fitted with a target attached in front of the lens. You can also purchase Barlowed lasers from commercial sources such as Howie Glatter and Kendrick Astro Equipment. Unlike a plain laser, the Barlowed version works very well and avoids the pitfalls of the former. This is my favourite method for collimating in the dark.

Best feature: Works well in the dark.
Worst features: Can be relatively expensive. Requires the centre of the primary mirror be marked.
Accuracy. Very accurate.
Ease of use: Very easy.

Recommendations

The five options described above cover those most commonly available and frequently used. With varying ease, all of them can help you accurately collimate scopes — even those with fast (under f/5) focal ratios. There are other tools and systems, but mostly they are either variations of those covered here, or devices that increase the complexity of the operation without a corresponding improvement in accuracy.

For most people, a simple collimation cap is fine. The Barlowed laser is also a good option, especially if you already have a Barlow lens in your eyepiece box. If you do most of your collimation in the dark when you arrive at an observing site, this is the way to go. Nearly as convenient and useful is the Cheshire eyepiece. The important thing to remember is that you don’t have to get a bunch of tools — one chosen with care is all you need. Take the time to learn how to use it well and you won’t need another.

I’m purely a visual observer and mostly use scopes that are shade over f/4. For collimation I use either a Cheshire or laser to position the secondary mirror (something that rarely needs adjustment) and a simple collimation cap for tweaking the primary. That’s it. My scopes are always perfectly aligned, something I can quickly verify with a star test. Collimation rarely takes me more than a minute and most nights all I do is check to see that everything is okay since I last used my scope. There’s really no reason to spend any more time on it than that.

If you want to read more about collimation, I can recommend Nils Olof Carlin’s excellent piece, Some Collimation Myths and Misunderstandings That article should fill in most of the gaps arising from the brevity of this overview.

## 114 Newtonian or 6" dobsonian?

• topic starter

This is my first post ever on the net so here goes! We are trying to find a scope to buy my father for Christmas. He is not new to astronomy but hasn't owned a scope before. We are in Wellington, NZ and the selection of scopes isn't that great here. I have done quite a bit of research over the net but the exercise of choosing one of many scopes is rather dauting! Due to price limitations and what is available here (too expensive to import) we have got it down to the Konus or AstroNZ (Auckland Astronomical Society retail arm) 114 Newtonian or the AstroNZ 6" or 8" dobsonian. Can anyone advise on whuch would be best for a beginner? Someone told me that the dobs are not that easy to track with etc and the Konusmotor 114 comes with a tracking motor. Also he will want to be able to take photos and we want something that will be good for planets and deep sky viewing. We can only afford around $650NZ (I think this is about$350US). Would a refractor be better? Any advice would be greatly appreciated ASAP as we don't have much time left to buy something before Christmas.

### #2 imjeffp

2. Me? I'd look for a 6" newtonian on a GEM, like this one. The extra aperture vs. the 114 is a good thing, and the GEM with the addition of a drive motor will track the sky for you. And if you ignored #1, you could use a webcam with acceptable results on the GEM.

### #3 kiwisailor

Take a look on Trademe, there have been a couple of 6" & 8" dobs for sale lately- stay away from the short tube newts (one currently for sale). The small EQ mounts are pretty shakey, the 8" dob would be the best for viewing, your dad could take some snaps of the moon, but for serious photography, you are talking serious money.

### #4 Guest_**DONOTDELETE**_*

• topic starter

### #5 Scott Beith

First thing: Welcome to Cloudy Nights .

An 8" Dob will show you so much more than the 4.5" that you would be amazed. Forget astrophotography for a while - a minimal setup will cost big . Even though I use refractors, I would suggest an 8" Dob in a heartbeat for a first scope. It will bring enjoyment for years.
If you chose an EQ mounted scope - go for a 6" f/5.

To all of you who know me - yes that hurt to say it.

### #6 kiwisailor

The 8" with the laser collimator would be a good call, make sure your dad signs up to Cloudy Nights and he'll get plenty of bang for the bucks

¼°per minute, and the typical high power (250×) eypiece will have a Field Of View around ½°. You don't really want to watch a planet from edge to edge, as typically the best quality image will be away from the edges. Kind of a long winded way of explaining the benefits of tracking with an Equatorial mount.

Also in favor of the Dobsonian. He could use the Dob for a couple of years and save up (or you could) for an Equatorial mount to put the same Newtonian on. Makes your Christmas shopping easier in the next year or two.

### #8 Guest_**DONOTDELETE**_*

• topic starter

### #9 Guest_**DONOTDELETE**_*

• topic starter

### #11 Scott Beith

Most people find tracking a Dob easy.

I unfortunately am not one of them - 99% have no problem.

I am also a Slobbering Refractor Freak, so the advice I give will be adjusted to the needs of your Father - not necessarily my needs.

Aperture and ease of use is a great combo for a beginner - and the 8" Dob offers both.

### #12 Mitrovarr

The general advice given is to get the largest scope you can afford and can carry, and there's a good reason for it. A 8" scope is noticably better than a 6", and a 6" is noticably better than a 4.5". A 8" scope just blows away a 4.5" scope, there's no comparison.

The aperture difference matters most with regard to diffuse and planetary nebulae, galaxies, and globular clusters. Planets will look a lot better in a larger scope, but only when conditions are right. Open clusters generally look good in anything.

The difference really is impressive, an 8" telescope can get partial or total resolution on about half the messier globulars, a 6" can only get resolution on some of the brighter and looser ones, and a 4.5" is hard pressed to resolve any but the brightest and easiest (you guys are lucky down there, with 47 Tucanae and Omega Centauri.) The 8" will show all the messier planetary nebulae quite well and many others as well, the 6" will show the messiers (some faintly) and a few others, and the 4.5" will only bring in the showpieces, and then dimly.

With regard to astrophotography, I wouldn't let it influence your decision. There isn't anything that 350 can buy that is suitable for long-exposure through-the-scope astrophotography. Any telescope, even a dobsonian, can be used for eyepiece projection photography of the planets. The only kind of photography a telescope like the Konusmotor can do that a dobsonian can't is piggyback astrophotography, where the camera is mounted on the back of the telescope for a long-exposure wide-field images of the sky. Tracking with a dobsonian is not really a big deal, except at very high power when looking at the planets. Even then, you have to consider that the dobsonians can handle much higher power, because of the aperture. Plus, a new user will have to figure how to align the equatorial mount, which is kind of a pain. Cheap equatorian mounts also usually aren't as stable as cheap dobsonians. The only time I really miss tracking is when I'm observing in a group and other people are looking through the scope. ## Cheshire eyepiece vs. laser collimator? Both are good, but both take some practice and understanding of each's limitations. You can get very close with a Cheshire eyepiece, and the price is lower. I also think a Cheshire works better for the alignment of the secondary. At least it's less prone to errors caused by miscollimation of the tool itself. For the alignment of the primary, a Barlowed laser makes the job pretty easy. ### #3 lamplight ### #4 obin robinson I have both. I use both. I should say though I use the laser MUCH more often. ### #5 csrlice12 ### #6 *skyguy* ### #7 csrlice12 Not really, I just turned 60 and use the Glatter exclusively. Did a lot of research first though buy once, spend once. but the Cheshire will give you just as good results for a lot less price. It's just a bit more involved to use, but does a fantastic job. Remember, us old farts are from the "Star Wars/Star Trek" Generation. Lasers are cool! Those two guys using their green lasers as light sabers and making deep breathing sounds. look at their ages next time. ### #8 Feidb ### #9 bigstormgirl If you're over 50 . a Cheshire. If your under 50 . a laser. It's a generation thing! ### #10 FoggyEyes Cheshire: When you initially put the scope together or major problem like dropping the OTA and it rolled down the hill. This gets the secondary dead on and everything well lined up. Laser: All other times for fine tuning the collimation, you can also point out the OTA rolling down the hill. ### #11 csrlice12 ### #12 SkyGibbon ### #13 Muleya ### #14 Tim D ### #15 Jarrod Both. Cheshire for getting the secondary centered in the tube and for getting the initial secondary tilt. Then the laser for fine-tuning the secondary. Then add a barlow to the laser to do the primary. I then like to check a final time with the cheshire to get visual confirmation that everything looks perfectly aligned because if there is an issue with laser centering/parallelization, it should show up here. A good laser is more accurate, and is quicker and easier to use. The cheshire is more foolproof. ### #16 CeleNoptic ### #17 DaveG ### #18 Diana N Well, not clear why to use both? If your laser collimator holds its alignment well and it's more convenient than why to bother with the Cheshire? ### #19 Diana N How about a3 plastic cap with a reflective inside?

A reflective interior? My, my aren't we getting fancy .

(Says another old fart who's a graduate from the Kodak Film Can School of Collimation.)

### #20 CeleNoptic

I use both, for the reasons already stated.

Stated where? Here I can see mostly statements like the Cheshire for the secondary, the laser for the primary without clear reasoning.

Because the first step in collimation is getting the secondary holder properly positioned under the focuser, and the laser collimator can't help with that.

### #23 Vic Menard

Exactly! That was one of the first videos I downloaded after I got my Dob a year and a half ago. I'm puzzled why laser collimator can't help with the positioning of the secondary mirror . I've been using laser collimator only .

"Positioning" or placement of the secondary mirror is accomplished by aligning three circles:
the bottom edge of the focuser or sight tube,
the actual edge of the secondary mirror, and
the reflected edge of the primary mirror.

When the secondary mirror tilt is adjusted to aim the laser beam at the primary mirror center spot, the focuser axis is being collimated. Adjusting the primary mirror to cause the beam to return on itself back to the laser emitter provides a coarse primary mirror axial alignment.

Secondary mirror placement is usually assessed before the focuser axial alignment. The two alignments interact and change each other, so to achieve optimal alignment, the two alignments are repeated systematically reducing residual errors of both.

If the secondary mirror placement isn't assessed as part of the axial alignment procedures, it's quite possible that a significant secondary mirror placement error can be propagated over time, potentially impacting image performance.

### #24 CeleNoptic

Secondary mirror placement is usually assessed before the focuser axial alignment. The two alignments interact and change each other, so to achieve optimal alignment, the two alignments are repeated systematically reducing residual errors of both.

Vic, thanks for the detailed explanation. Now it's clear what is the duty of the cheshire .

( after checking that the laser beam is not exiting out the front)

### #25 tezster

I have a potentially silly question - everyone always warns about a laser collimator potentially being miscollimated itself, but I've never heard of the same thing said about passive tools i.e. Cheshire/sight tubes.

Does this mean that all cheshire and/or sight tubes, no matter what they cost or who produces them, are 100% accurate? Is there something inherent in their design and production that makes them so easy to make?