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Skywatcher collimation worries

Swedeman2013

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Swedeman2013

Swedeman2013

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I bought a used 200p collapsible Skywatcher months ago and have enjoyed a summer of gazing however I've noticed images are less sharp now, no doubt the scope needs collimation, I've carried it in and out the house dozens of times. I've read countless articles about tools to buy and how to get started, yet the task seems dizzying with so many opposite ideas about the values of lasers and such.im wondering if its best to bring it to our nearest astronomy store and let the experts help me choose the right equipment and techniques. It's a common problem but any advice would help here, thanks.

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Avocette

Avocette

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OK - in an ideal world (money not too restricted) make a collimation cap using an old 35mm plastic film canister (or buy one for about £5 in UK) to check/set up the secondary mirror position, then use a laser collimator to finely adjust the secondary mirror angle (make the laser hit the primary centre spot) and then use the laser together with a Barlow lens to set up the primary mirror.

After that check it's all good with a 'collimating eyepiece' (Cheshire with sight tube and crossed wires).

Some people can make all the adjustments with just the collimating eyepiece and you might be one of them!

The Barlow lens laser combination gets rid of errors in the accuracy of the laser, but you can test and adjust the laser collimator itself by making a small test rig.

Just out of curiosity, what do the primary mirror adjusters look like on your 200p flextube (crosshead screws to adjust and Allen screws to lock, or two types of knurled chromium knobs)?

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Scott

Scott

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I pretty much use Avocette's method and to be honest, I can't think of an easier method (well not one that works anyway :) ). although the first two steps take a little while to sort, they really only need doing the once with just a check after that (unless the secondary gets bumped)  after that, it's only really a tweak of the primary adjusting screws (1 or 2 minutes at the most). We all start off thinking collimation is a daunting task and end up wondering why :D.

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bingevader

bingevader

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It is daunting at first, but as you have already said, it does get considerably easier with experience.

I use a film canister and a Cheshire and to be honest, if done regularly, it doesn't need much tweaking. Frankly, I'm uncollimating (sp?) and then re-collimating my 'scope each time I do it! But some people do suggest a Laser collimator is easier.

There's no simple way, it's a process that needs to be followed step by step, but follow a guide like Laurie61 has suggested and you'll be fine.

Just allow yourself plenty of time and take that time to understand each step as you go.

Cheers

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Charic

Charic

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Swedeman2013.... the first reply, Laurie61 is the way to go, at no expense, and Avocette mentions how to use the laser. The focuser dust cap from your scope can be your collimation cap, but it needs a 1mm hole in it (this hole in the cap is simply to align your eyesight right down the middle of the focus tube, its possible to align without it, as in the initial positioning of the secondary mirror, but without the 1mm pinhole, your eyesight could be off-axis/centre)and  when you finish collimation a bit of tape to cover hole in the cap when back in use as a dust cap.That will save you  £5!  I followed the Astro-Baby instructions, you cant really go wrong. (I needed a white piece of paper on the inside of the cap to see the reflection of the centre spot from the primary mirror whilst shining a bright light down the tube, or nice bright skylight will work [ Im using a 200P Newt/Dob] The paper also needs the 1mm hole!). Once the spot/ring is centred over the peephole that your looking through, all is good. Im new to all this, but learning so fast. My scope is perfect at present? the resolution of what I see up there is great! The draw back for me at present is that two of us set up the collimation (me viewing through the cap, Son adjusting the primary mirror. A laser would resolve this issue, but follow that guide. youll be ok.

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Nuno

Nuno

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Hi Swedeman2013 :)

Just one off-topic question. Where did you buy a an 8" SW collapsable scope?

I was searching and I thought that they stoped making the 8" version of the SW flex tube.

Sorry for not being able to help on your topic question, I dont own a telescope yet to know how the cullimation works :(

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Nuno

Nuno

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Thanks for the tip Swedeman2013 :)

I am deciding if  I go to an 8" without flex tube or 10" with flex tube (as first scope) but it in my case I think I will go to the 8" SW standard.. I see very good reviews about the scope :)

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Avocette

Avocette

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Avocette, it has screws and Allen screws . Again, I'd like the simplest way to fine tune my scope and learn how to do it faster each time. It seems daunting now but I know it will get better with more experience.

In my 200p I found the fine adjustments with the original screws crushing neoprene O rings very difficult to carry out. So I replaced the screws and Allen screws with Bob's Knobs but after experimenting with my own springs, I explained to Bob the problems I was having and he added some Bob's Springs in place of the O rings, and some appropriately longer Knobs. Making adjustments is now much easier and consistent, although a small drawback is that the Knobs protrude from the back of the tube end casting so the tube must be laid horizontally on something soft like a sofa or bed when separated from the base.

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mareprah

mareprah

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Haven't read the whole topic, but I'd just like to say smthing about laser - If you'll buy one, be sure to buy the one that can be collimated as well! Made that mistake, don't want the same one for you...Not that mine is far off, but still, a little adjustment would be welcome...

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John

John

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I'd likw to try Barlow collimation on mine. My Barlow doesnt have a filter thread. Anyone help with naming  a cheapy make that has a filter thread I could use.

You don't need one with a filter thread. The laser collimator goes in the barlow which then goes in the scope. The effect of the barlow is to spread the laser beam out so that it, ideally, more than covers the central spot / ring on the primary mirror. Once you have this you can collimate the primary using the shadow of the primary central spot / ring that should show on the diagonal "window" in the laser collimator. You need good batteries in the laser collimator to ensure a strong beam and the shadow of the spot / ring can be a little indistinct in bright light.

Before all of the above, you need to make sure the tilt of the secondary is good which you can use the un-barlowed laser collimator to sort out. 

As mareprah says, it's worth getting a laser collimator that can be collimated itself as they are often out of whack which makes the whole excercise rather futile !

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Charic

Charic

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mareprah.......I contacted a retailer this week with that question, apparently the adjusters  on their version are concealed under the label and silicone inserts, a small pick/knife gets access. Not sure what model you have, but its a possibility they may be there?

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Gomtuu

Gomtuu

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Just my two penn'orth:

Laser collimators work well, but only if the laser itself is properly collimated and there is no wobble in the focusser.

The laser + barlow technique simply uses the laser as a projector beam to image the centre mark of the primary, so it doesn't have to be accurate or wobble-free. Of course, if the primary doesn't have a centre mark, it won't work.

I personally use a cheshire, then a barlowed laser for the fine tuning of the primary. I've never needed to adjust the secondary since I first collimated it - as somebody above said, unless you bump it... and then you'd have to give a a big bump at that...

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  • 1 month later...
Swedeman2013

Swedeman2013

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An update; it seems many of my collimation problems turned out to be fogging issues! I'm finding out these bigger tubes need more time to chill out as autumn has arrived. Once cooled my Skywatcher is tack sharp without ever putting a screwdriver to it! Clear skies!

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Gomtuu

Gomtuu

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Haven't read the whole topic, but I'd just like to say smthing about laser - If you'll buy one, be sure to buy the one that can be collimated as well! Made that mistake, don't want the same one for you...Not that mine is far off, but still, a little adjustment would be welcome...

Even the ones that don't appear to have collimation screws usually do. There are three small circular depressions around the laser collimator where they have simply plugged the screw holes with black silicone (one of them sometimes has a sticky label over it).

If you scrape out the silicone, you should find three small allen screws.

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