Collimation of newtonian (Skywatcher 200p)

[coxy322]

Hello.

My 200P has not been collimated since new, I can only assume that it was collimated prior to purchase (so said the shop adviser on collection...).

Its been used several times now and I need to think about my first Collimation attempt... Although I have no tool to do this (ie: Laser or Cheshire).

So, my questions are:

1) Is it worth buying a tool - threads on here suggest that Lasers are not so good as they are cracked up to be and Cheshire tools also get a mixed review on here.

2) If I do not use any specific tool, is the film-canister method reliable and easy? Are there any links to a good instruction set on how to achieve this? The instructions that came with the scope are a little difficult to understand and given my first attempt I want to get it right!

Observing seems ok, I cannot notice too much being wrong with my scope, although I am pretty sure that collimation will be out as the scope has been in and out of the shed many times now!

3) Final question - my scope has no base, the locking screws and mirror screws are exposed underneath and the scope sits on these when stored in the shed. Am I running the risk of knocking out the mirror alignment by not having a suitable base to home it on!?

[Astro Imp]

Although this guide users a Cheshire you may like to look at Astro Baby's guide.

HTH

[IvanT]

I found using a laser on my 200p very hit and miss. Conversely, since switching to using a Cheshire I've had no problems.

Sent from my iPhone using Tapatalk

[angusb1]

This is a very good guide I found on using a Cheshire to collimate, the priciples are really well-explained and apply equally to using other methods

John Reed Home Page Collimation - Cheshire

I've also found the barlowed laser method here very useful

http://www.astromart.com/articles/article.asp?article_id=827

then finish off with a star test

[Stephen]

1) YES! The 200P will most likely need collimating every time you use it for best results. If you aren't sure about collimating a laser, get a Cheshire for fool proof use

2) The film canister method does not allow you to fully collimate both mirrors, you need the canister in addition to the Cheshire.

3) See point 1) It's going to need collimating each time as simply moving it can knock it out.

Once you get it all set up, collimating should be a 5 minute max task each time you set the scope up (once it's cooled down.)

[rightguard]

my 200p has no base either, however the screws dont poke out. so if you're knocking the screws then its likely to knock it out abit.

hardest part for me is reaching the damn screws! being a short-ish man at 5'8, my arms just wont reach the third screw! makes it very tedious indeed, having to keep switching from looking to screwing.

headaches everytime because of that.

[coxy322]

my 200p has no base either, however the screws dont poke out. so if you're knocking the screws then its likely to knock it out abit.

My screws do poke out - the scope actually sits on the locking screws! Anybody know what sort of base is good - can I buy or should I make my own out of polystyrene etc??

Why are collimation tools not handed out with the scope on purchase - if the process is so important for getting a good experience with the scope?! Slightly annoying..

So if the Cheshire is the recommended option, who can recommend a decent model?

[Muphrid]

hardest part for me is reaching the damn screws! being a short-ish man at 5'8, my arms just wont reach the third screw! makes it very tedious indeed, having to keep switching from looking to screwing.

headaches everytime because of that.

Using the laser collimator means that it is possible to adjust the screws because you can see what the laser beam is doing while standing at the back of the scope (or at least you can with the collimator that I have used)

[coxy322]

Thanks for the responses so far - great stuff...

Have had a quick read of the Astro-Baby site and picked out this bit:

"Note: Some scopes require the secondary mirror to be offset from the centre of the tube. This in itself raises questions. Some telescopes will have the secondary offset on its holder in which case the centre of the vanes should be centred to the tube while other manufacturers will opt for the vanes centre point being off centre. The offset on most scopes will be in millimetres and wont affect collimation by much. You should check whether your telescope requires offsetting with the manufacturer or supplier. If you cannot get an answer assume that the mirror holder is to be central to the telescope tube."

So, anybody know how this applies to the SkyWatcher 200p (BD model). ?

[rightguard]

My screws do poke out - the scope actually sits on the locking screws! Anybody know what sort of base is good - can I buy or should I make my own out of polystyrene etc??

Why are collimation tools not handed out with the scope on purchase - if the process is so important for getting a good experience with the scope?! Slightly annoying..

So if the Cheshire is the recommended option, who can recommend a decent model?

my old 150 was like that - no base and long screws poking out. come to think of it i dont think it was ever much of a problem collimation wise, just be sure that all screws including the locking nuts are snuggly tightened.

polystyrene base sounds liek a good idea tho, just make sure its stable

cheshires are pretty much the same. can buy them from flo, scopesnskies, and many other places.

agreed they should be given out with the scope, even if the price is added on top - it should come as a package

[rightguard]

Using the laser collimator means that it is possible to adjust the screws because you can see what the laser beam is doing while standing at the back of the scope (or at least you can with the collimator that I have used)

are they any good? ive heard people moan about them, but id like one if i can adjust the screws easier! how much are they?

[Antx]

I use the 200p and will do a collimation check on each outing

I have used a laser from the outset and have been very happy with it.

I love the fact that you can concentrate on primary mirror adjustment without having to reach round from the eyepiece.

I rarely have to correct the secondry mirror but will tweak the primary on every other session, especially if I have had to do a trip in the car (just enough knocks to upset things)

I found that the laser made the whole process so quick and easy; I have ended up checking/tweaking as a habit:icon_salut:

[Stephen]

Thanks for the responses so far - great stuff...

Have had a quick read of the Astro-Baby site and picked out this bit:

"Note: Some scopes require the secondary mirror to be offset from the centre of the tube. This in itself raises questions. Some telescopes will have the secondary offset on its holder in which case the centre of the vanes should be centred to the tube while other manufacturers will opt for the vanes centre point being off centre. The offset on most scopes will be in millimetres and wont affect collimation by much. You should check whether your telescope requires offsetting with the manufacturer or supplier. If you cannot get an answer assume that the mirror holder is to be central to the telescope tube."

So, anybody know how this applies to the SkyWatcher 200p (BD model). ?

The scope in astro babys guide is in fact a 200P IIRC? Just follow the pictures

[angusb1]

are they any good? ive heard people moan about them, but id like one if i can adjust the screws easier! how much are they?

Yes they are very good if you use them with the barlowed method because then you don't have to worry about the collimator itself being collimated. If you don't use a barlow you need to make sure the laser is "straight" or collimated first.

[pritc]

Yes they are very good if you use them with the barlowed method because then you don't have to worry about the collimator itself being collimated. If you don't use a barlow you need to make sure the laser is "straight" or collimated first.

I always use the 'Barlowed method' to collimate my 200P.

You do not have to worry about collimating the laser.

Wayne

[Moonshane]

my 200p has no base either, however the screws dont poke out. so if you're knocking the screws then its likely to knock it out abit.

hardest part for me is reaching the damn screws! being a short-ish man at 5'8, my arms just wont reach the third screw! makes it very tedious indeed, having to keep switching from looking to screwing.

headaches everytime because of that.

if you are talking about the primary adjusters then you only need to move two of them. the third will rarely if ever need to be touched.

just adjust the two nearest to you (i.e. that you can reach).

[Moonshane]

My screws do poke out - the scope actually sits on the locking screws! Anybody know what sort of base is good - can I buy or should I make my own out of polystyrene etc??

So if the Cheshire is the recommended option, who can recommend a decent model?

the locking screws are a waste of time and if I had your scope, I'd remove them to be honest.

Most Cheshire/sight tubes are the same, except the Astro-Engineering (blue ones) which are really awful. the cheap one from FLO is perfectly fine.

http://www.firstlightoptics.com/collimation/cheshire-collimating-eyepiece.html and will last 'forever'.

[Paulb3098]

Hi

With a set of "bobs knobs" and a laser it takes only two mins to collimate. No more fiddling with allen keys in the dark.

Paul

Newtonian Knobs

[todd8137]

the locking screws are a waste of time and if I had your scope, I'd remove them to be honest.

Most Cheshire/sight tubes are the same, except the Astro-Engineering (blue ones) which are really awful. the cheap one from FLO is perfectly fine.

First Light Optics - Cheshire Collimating Eyepiece and will last 'forever'.

i use the blue one it works fine for me a mate brought a laser one round i did it first with the "blue one" and it was the same ?

[Moonshane]

maybe I just got a bad one. it was extremely shiny inside and I could make no sense of what I saw.

[johninderby]

There are good laser colimators and there are cheap laser colimators, but not really any good cheap ones. I use the Hotech and it is so easy to use and dead accurate every time. Now that I've been using the Hotech for a while there's no way I'd ever want to go back to a Chesire.

Unless you are willing to spend a fair bit on a top quality laser though a Cheshire is the next best alternative as it's cheap and it works. However Chesires can also suffer from problems. The main one being that the crosshairs may not be centred in the tube. Also some people can't focus on the crosshairs properly. I have seen a Chesire that had an extendable tube with the crosshairs in it that let you adjust for this but can't remember who made it.

John

[rightguard]

i had trouble getting the cheshire crosshairs centered - there was play wheni insertedit intot he focusser, it wasnt a snug fit

[umadog]

You need a tool. A cheshire/sight-tube tool is good bet if you don't want to spend too much. If you're worried about quality then buy the tools from Catseye. They're precision machined and won't have any slop in the focuser. The film canister is still a tool, it's just a coarsely-made tool.

As others have said, avoid cheap lasers. There's nothing magic about collimating with a laser--it doesn't do anything fundamentally different. You will be measuring the same stuff with both a Cheshire and a laser. The exception being that you can use the sight-tube to round the secondary. You can't use a laser to round the secondary.

[Andyfx]

Personally I use both a Hotech and Cheshire and collimation is a breeze on my 200P.

[umadog]

The barlowed laser method is the preferred laser technique for adjusting the primary. For adjusting the secondary, the laser still needs to be collimated. Collimation is not so critical for this alignment, however.

Here are some links to websites discussing collimation:http://www.physiol.ox.ac.uk/~raac/collimationLinks.shtml