Collimating a Skywatcher 10 inch collapsible dobsonian

[Mountain_Wanderer]

Hi guys,

I'm interested in getting the Skywatcher 10 inch collapsible dobsonian as my first telescope.

Just need to know how difficult it is to collimate these beasts. I need to get collimation spot on due to the focal ratio of 4.7. What would be the best device to use? I'd prefer a device that doesn't need electricity to use.

And, how exactly do you collimate? Can you do this in complete darkness or do you need to have a light shining in the tube/eyepiece? Also, does collimation usually require tweaking of all the components, or do you usually only need to tweak the secondary mirror or eyepiece but rarely the primary mirror?

Just curious too about whether you need to let the primary mirror cool down before you can collimate? Or can you collimate straight away?

Would a newbie like me be able to learn collimation rather quickly or can it be a pitfall and so would a solid tube be the better option?

Thanks guys.

[that_guy (Tony)]

Collimating is easy with a collimating tool, like one of them laser collimators... people gets all stressed about how hard collimating is...but its real easy and you can easily do it with the right tools... also, you might wanna change the philip screws for the secondary collimation to a bobs knob.. they make things a lot easier.. i doont have them cos im cheap.. also, you can get a fan for your primary but you wont need to cool your scope to collimate.

just me 2 cents worth
tony

[Colin_Fraser]

I have a 10" dob and was worried about collimation as well.
That's until I bought a Hotech laser collimator.
Read the instructions and it took all of 5 minutes to get it collimated just right. It's easy. http://www.youtube.com/watch?v=ME-CB...e=channel_page

[5ash (Philip)]

My experience with Laser collimators indicates to me that cheap ones are a waste of time. Most of the cheaper ones can be rotated in the eyepiece holder to reveal the spots position changing on the primaries surface.This is due to poor alignment of the collimator in the focuser and /or poor alignment of the laser diode in the body of the collimator. The Hotech one mentioned above certainly makes an attempt to assure alignment in the focuser.The only way to test the collimators accuracy quickly would be to collimate with it , remove it and then replace it , if its accurate the spot should be where it was.So try before you buy might be the way to go.When i had a Schmidt Newtonian i collimated roughly with a hotech collimator and fine tuned using a cheshire eyepiece .
philip

[Visionoz (Bill)]

Hi Jowel (Name?)

Check this out - may help you to understand how to collimate:
http://www.andysshotglass.com/Collimating.html

HTH
Cheers
Bill

[qld]

Originally Posted by Visionoz

Hi Jowel (Name?)

Check this out - may help you to understand how to collimate:
http://www.andysshotglass.com/Collimating.html

HTH
Cheers
Bill

hi J
theSKYWATCHER FOCUSER is why it is difficult to collimate with any of the quality BARLOWED laser collimators,as the focuser( A VERY LOUSY STANDARD SKYWATCHER FOCUSER)drawtube is very long and you can not see the image on the barlow lense ,the solution is to have the eyepiece adaptor head reduced by turning it on lathe.down to 1/8 thichness.Once you can see the barlow the collimation is dead easy,you can also change the focuser to a low profile type.i have done both and use a astrosystems laser barlowed collimator.the spider vanes on the secondary are a bit light on and flex when collimating the secondary mirror,just take care not to over tighten the screws(these too you can replace with hex alen head bolt s...cheaper than bobs knobs)
otherwise its a good little scope

[bmitchell82 (Brendan)]

Ive never had a issue collimating my 10" with the Astrosystems barlow laser nor the hotech nor cheshire they all work just the level of accuracy differes. Although i now have cats eye equipment it is extremely accurate to micron accuracy for a start a reasonable laser that has been collimated will suffice for the beginner and will be far easier to understand whats happening for a start.

[Mountain_Wanderer]

Thanks fellas for all this advice.

I'm just wondering whether or not I buy a solid tube or collapsible, will I still need to collimate every time before I use it. Do solid tubes still require collimation before use? In that case, if I know I'm gonna be stuck with collimation no matter what, then I might as well get a collapsible version.

I've read that cheshire collimators are much more accurate, but it's hard to adjust the primary mirror and look in the eyepiece at the same time and so you need another person to help out by looking in the eyepiece. Can collimation with a cheshire be done with 1 person only, despite this issue?

[Stu Ward]

I have a solid Dobsonian, and now i have become very used to collimating I do so every time i take the scope out.

Its a quick 2 minute job, half the time i do not need to adjust, but after i have checked I can be comfortable in the fact that the optics are giving their best !!

It really is very easy once you get the hang of it

Stu

[Liz]

Originally Posted by Stu Ward

I have a solid Dobsonian, and now i have become very used to collimating I do so every time i take the scope out.

Its a quick 2 minute job, half the time i do not need to adjust, but after i have checked I can be comfortable in the fact that the optics are giving their best !!

It really is very easy once you get the hang of it

Stu

Thats what you need to do Jowell - once in the habit, its quick and easy.
Ah, in saying that, I collimate .... rarely. I have the 10" collapsible, and they dont seem to need it as much, but I probably need to do it more often than what what I do.

[NGC2264 (Gordon)]

Jowel,

I have the sky watcher 10" collapsible dobsonian and I love it - a great first telescope in my opinion. I went with the collapsible because I didn't have enough room for the solid tube either in storage or carting it around. For me the collapsible was the way to go. Of course you realise that once you get the 10", six months later you'll wish you got the 12"

In terms of collimation I have both the laser collimator and a Cheshire cross-hair piece collimator. You'll hear people say laser collimators aren't as accurate as cheshire collimators. And then you'll find the old school folk who say that the only way to really collimate a telescope is by doing it on a star without any device.

A laser collimator is fine so long as the laser itself is collimated. The easy way to determine this is to put it into the eyepiece holder and rotate it around. Watch the dot on the primary mirror and see if the dot moves around. If it stays in the same spot then the laser collimator is good. if it moves around then you have a problem with your device and it needs to be adjusted.

One advantage of a laser collimator over a Cheshire is that when you are out in the dark viewing and you need to collimate your scope, Cheshire is useless and the laser is what you need unless you know how to collimate it using a star. I got my laser collimator from York Optical and it was just fine.

In collimating the 10" collapsible I found that trying to adjust the secondary mirror was really hard work. The screws were really hard to turn. Thankfully I have never really had to do it. Adjusting the primary mirror was actually the easiest part of the process.

As with everything to do with astronomy, you've just got to dive in and do it. The more times you do it, the more confortable you will about doing it.

[WadeH (Wade)]

Hi Jowel,

Originally just the thought of collimating scared the proverbial out of me but I bought an Orion Cheshire collimator and read the very good Skywatcher manual and off I went. Patience and perseverance is the name of the game here. In very little time I found it easy and only takes me a few minutes (daytime of course).
I surpose that one factor of influence could be do you want the scope for visual or astrophotography. Visual is more forgiving.
Also, I would recomend forgeting about the locking screws as I found that they just warp the mirror out of collimation when they are tightened and that the scope doesnt need them anyhow.
As for how often, I have only collimated once in the past year and that includes three car trips! Just treat the scope gentlly and well padded in transport.

[pjwdesigngm (Paul)]

Hi, pjwdesigngm in Sterling Heights, Michigan USA

I own a Skywatcher 10" collapsible DOB, and I have spent much of my time in collimation of this scope because the eyepiece tube and secondary were not aligned from the manufacturer, also the primary spot was not centered. Once I had resolved the issues above, collimation was quite easy, even for one person. I did purchase Bob's knobs for the secondary for ease of adjusting. The most important thing you must remember is that a laser collimator will only assure you that one spot is aligned on the optical path. A cheshire eyepiece will get your primary aligned to the optical path as if you were looking at a flat mirror (even though the primary is curved). Remember, the optical path needs to be correct (looking through eyepiece tube without an eyepiece and seeing secondary centered and circular in shape) and the center of the primary in the center of the secondary (check the center spot on the primary to make sure it is in the center, mine was 5mm off). If your mirrors are aligned correctly the laser will hit the center spot and the cheshire would prove that your primary is square to the optical path.
I hope this helps, I am still a newbie as far as observing goes, but I am pretty confident about my collimation. I will probably flock this scope and build a shroud for it to increase contrast, also looking at making it a tracking DOB.
Clear Skies, Paul

[Mountain_Wanderer]

Thanks for this advice guys and gals.

What scares me about a collapsible is that if I transport it to a dark site, and then extend the tube and set up the scope, I will only be able to collimate it in the dark using a laser and not a cheshire.

A cheshire can only be used when you have light in the day. Sure, witha solid tube you can collimate in the day before you set off on a trip to a dark site. But with a collapsible you need to collimate on the spot in the dark. How did people collimate collapsible dobs in the dark before lasers were invented?

[Mountain_Wanderer]

Hey all,

Would it be possible to collimate with a cheshire in the dark at the observing point? You would need some sort of light though. How about attaching a small light at the top of the tube to light up the tube? Would this allow you to collimate with a cheshire in the dark?

Jowel

[Jeeps (Sam)]

I bought a 10" Skywatcher collapsible early this year. I have a saxon laser collimator and have found it easy to deal with. I can usually collimate within 5 minutes in the dark. I only collimate every 3 or 4 times i take the scope outside, i collapse it everytime, and even then it's usually just a 10 second adjustment to the primary.

You can go overboard with collimation, it doesn't have to be EXACTLY perfect

cheers

[Liz]

I found this helpful .... though truthfully, i still havent collimated my scope.

http://www.youtube.com/watch?v=yd3mjOr8rc0