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Primary Mirror (Skywatcher Skyliner 200P) - Collimation

mrjonathanbrown

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RichM63

RichM63

Posted
Posted

Phew Jonathon, what a performance, I feel your pain.

I wouldn't fancy faffing about with tiny allen keys and screw drivers on a freezing dark night.

If you do go to an Astro shop, a quick giggle reveals, Merchant City Cameras on Parnie St as Skywatcher dealers see if they can change your allen/philips screws over to user friendly thumb screws, much easier to use if they are suitable for a Skyliner.

Rich

post-34135-0-58825900-1399627616_thumb.j

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oldpink

oldpink

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Merchant City Cameras is a small shop with a couple of scopes in the window, I think they are just a reseller rather than a specialist telescope dealers

last time I went in to look for a Barlow he didn't have any and only a couple of standard eye pieces, not sure if they could help you out
as they are primarily a camera shop

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radiostationx

radiostationx

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Hi guys,

I have a 200p skylines, the Phillips (mirror adjusting screw) size m5 x 20mm, 25mm will do but metric m5 is the thread style and pitch.

These are known as stainless countersunk set screws/ machine Screws.

Normally they will come with either 3mm hex head or Phillips no2.

Lots of engineering suppliers do these.

You can get knurled head stainless thumbscrews m5 also.

The little hard to see Allen things provide the lock by pushing the mirror plate upwards towards the open end of the scope.this locks the mirror cell in place by push pull on the screws in each pair.

These little fellas are known as stainless grub screws, m5 thread again for the 200p with length of 25mm, 30mm will do.

Also these are available from engineering suppliers.

I only know this as I chewed up the head of one of my mirror adjusters, they are very soft chinese ss.

The mirror holder is made from aluminium.

Replaced with a2 stainless with hex head, never a prob since.

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wookie1965

wookie1965

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When i first did my scope i was exactly like you pulling my hair out, the thing to do is sit down have a brew and read through what you need to do i have used astrobabys but this one which shows the steps alot easier get yourself the coloured card it makes things much easier. Once you have done your secondary you will never have to touch this again unless  you drop or knock your scope.

http://www.schlatter.org/Dad/Astronomy/collimate.htm

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RichM63

RichM63

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Don't give up. When I bought my second hand 200P the PO had moved just about every screw he could have even down to mucking up the spider position. I'll post you a pic or two in a mo'.

Just take your time, maybe have Dion's collimation videos running and hit pause whilst you check against your scope.

A couple of bits of coloured card, bright light, a point and shoot, and download Al's Collimation Aid to overlay concentric circles over your image will get you to be very accurate in next to no time.

Before, note the North/South, West/East differences.

post-34135-0-89962300-1399649602_thumb.j

After + overlay of collimation aid.

post-34135-0-27483800-1399649683_thumb.j

A good and informative collimation thread can be found here.

But as a kind person pointed out to me when I started measuring pixels, seek medical help. ;)

Best of luck,

Rich

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bingevader

bingevader

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Once you've mastered collimating the 2°, the 1° is much more straight forward.

Just take your time and take it a step at a time and you'll be fine.

It can be daunting at first. Try to get your head round why you are doing each particular step and then once it clicks, it does become much easier.

Honest.  :smiley:

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Floater

Floater

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Okay, here goes. I'm a beginner and hesitate to offer any advice - but I've been through your trauma.

My 150P came with a set of tools, like yours I guess, and I almost burst myself trying to figure out why the Allen (repeat Allen!) key wouldn't 'bite'. It's because the supplied key is the wrong size. It fits the secondary mirror adjustment screws but does NOT fit the primary mirror locking screws. (Shame on Skywatcher.) From what I read above you've now got an Allen key that does fit. That's a big step forward.

Collimating is not as daunting as it first appears and you WILL get there. I know everyone says that - but they only say that 'cos it's true. However, the next big step forward for you will be replacing those ridiculously difficult screws that are in your 'scope with Bob's Knobs screws. Trust me, these will lessen the furrows in your brow. As I wrote earlier, I've bin there!

Keep posting. People with more experience than I can dream of are here to help you.

And if my little bit of input has helped I'll be tickled pink ...

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Charic

Charic

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Ok....as you say your scope is so messed up, lets start at the beginning.........The secondary mirror needs the three Alan bolts fully loosened (anticlockwise) you can take one right out if you want, just to see how long it is? Your secondary is out of adjustment anyway, so it wont hurt to look and learn (will give you more confidence too) then screw the Philips bolt all the way in (clockwise) supporting the mirror stub by passing your hand through the spider assembly. (also note that the telescope should be level/ish, so that you don’t drop anything directly onto the primary mirror.

By screwing the bolt clockwise, this draws the secondary mirror towards you (and away from the primary mirror) or if you look through the focuser, the mirror will be to the left of the focuser on-axis with the telescopes tube.

At this point turn the three secondary Alan bolts until they just touch the secondary mirror assembly ( screw the Alan bolts back in until they stop turning, but not tight (just touching)) This is the base line for the secondary mirror. Now by supporting the secondary mirror (as before ) with one hand (don’t touch the face of the mirror) you unscrew the secondary mirror bolt. You unscrew this bolt until the mirror appears to be central between the right and left hand sides of the focuser tube (or Cheshire) the top and bottom sides will take care of them selves. Depending on how much movement the mirror needs I would unscrew the secondary bolt maybe 4 times, then re-tighten the Alan bolts. This keeps the secondary mirror straight ( technically not tilted-yet?). Once your happy with the central position of the secondary mirror, you will now rotate the mirror along its axis, again without touching the face of the mirror. As you view this motion through the focuser tube, the mirror will look fully circular in appearance, and then elliptical as you rotate further. Your object here is to get that mirror looking as perfectly circular as is possible. Once that is achieved, the 3rd stage is to adjust the tilt of the secondary mirror, This is achieved my tightening or loosening each Alan bolt in tiny increments, until you can just see the three mirror clips around the primary mirror housing, by viewing through the focuser at the secondary mirror. You may not see all of the clip/s, just the slightest amount possible, but you should see a bit of each of them. Once that is done, the secondary mirror is set-up.

You now sit at the focuser (after a cuppa?) and have your partner undo (loosen) the primary mirror Alan bolts far enough to allow her/him to screw in the primary mirror adjusters until just tensioned, no more, then turn back by about a 1/4 or 1/2 turn. This gives a bit of play and allows the tension (rubber) washers to function (there is an upgrade to this part of the telescope, but your not ready for that just yet?) now get your partner to start adjusting the primary mirror adjusters (pick anyone to start with) and just make tiny adjustments again. You at this stage should be looking into the focuser, through your Cheshire, or collimation cap, and say stop when the centre spot from the primary mirror aligns with the centre of the Cheshire and the reflection of your eye. you will adjust each Philips adjuster in-turn or randomly until the mirror is aligned.  You'll know what I mean when you see it.

Once everything is aligned, gently, I said GENTLY tighten the Alan bolts on the primary, just enough to lock, without shifting the mirror. it doesn't take much to knock the mirror, in which case, you just repeat the primary adjustments again.

If you look on the web, you see that the coloured sheets of paper I mentioned in the PM blocks the reflections from the primary mirror, and aids with sighting the secondary mirror much easier. some folk are confused as to what they should actually look at, and should disregard the rest.

If you don’t succeed from using this text, any on-line guide, or our arranged telephone call, I will be passing your area next Week. Would take no more than 1 hour. 5 Mins to adjust, 10 mins for a Brew and 45 Mins telling you what I just did to collimate your scope. You'll be teaching others before you know it?

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radiostationx

radiostationx

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If you don’t succeed from using this text, any on-line guide, or our arranged telephone call, I will be passing your area next Week. Would take no more than 1 hour. 5 Mins to adjust, 10 mins for a Brew and 45 Mins telling you what I just did to collimate your scope. You'll be teaching others before you know it?

In the spirit of SGL... It doesnt get any better than that for a newbie who is stuck...Well dome Charic.

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RichM63

RichM63

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Yup as per wookie, cept on the 200P the distances from the edge of the OTA to the rim of the secondary holder will more like 100mm.

If you can follow the guide you will not go wrong.

From post #62 in the above thread is where I reset the spider (no point in me reposting)

Post up a down the focuser pic, complete with 2 bits of coloured paper then we can all have a look see, and may be give you direction pointers.

Cheers,

Rich

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Charic

Charic

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radiostationx.......many thanks....... I`d also just like to  say sorry to oldpink &  tinker1947 for jumping so quickly into a private message with mrjonathanbrown but the OP said," more likely an issue for the Skyliner 200P", and to be honest I had exactly the same issue, in which case Skywatcher had supplied an Alan key that was far too small, it just didn't fit? I was wanting mrjohn...to remove the Alan bolts completely to ensure they were not sat in a threadbare hole, and/or to prove that the Alan key fitted correctly. That could'nt be done if were giving differing answers, so despite your interest to help, I could'nt persuade him to remove anything, if others were trying to prevent that. I've just spoken by phone and Im glad to say, it just looks like a Star test is all that's needed now. So exciting!

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mrjonathanbrown

mrjonathanbrown

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So my understanding right now is that the secondary mirror is offset only by a few millimetres - what should my measurements be reading for each direction - The spider vanes have been adjusted (not sure by how much- someone touched them!! now I'm trying to re-fix it) 

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Charic

Charic

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Just the mirror or the Spider?

You know how some people use a collimation cap with a centre hole? Why not go big daddy style!

If you were to create a small hole 'Dead-Centre" in the OTA dust cap, between the two raised aperture cap features, and big enough to see the secondary mirror adjuster screw, you could leave  the dust cap in place and peep through the hole, and if the '+' (cross) on the Philips adjuster is centred to the hole, then the Spider will be dead centre to the OTA (OpticalTubeAssembly) If its not dead centre, then grabbing two of the spider adjusters at the same time (opposing each other) and  turn them both at the same time and direction , either away from you or towards you (looking from the front of the telescope - it makes sense when you turn the adjusters, if you turn them both away, at the same time, one will tighten while the other loosens) the spider will move either side of centre. Do this with the other two adjusters at the same time until the spider id central.

Note though, that unless "someone" has already adjusted the Spider, or the unit is second hand, Its unlikely that the spider needs any adjustment at all.

Some will also note that you have just holed a dust cap. You could cut a CD case and apply it to the inside of the dust cap ( to maintain dust protection) but still allowing visual inspection,and if you make a 'cross' with some fuse wire, you'll create an extra aiming reticule to help align that bolt?

There is a feature that describes "off-set " secondary mirror collimation, but that's not required to be set manually for a Skyliner!

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mrjonathanbrown

mrjonathanbrown

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Does the skyliner require the the mirror holder to be dead centre yeah? I thought there was suppose a slight off-set positioning thats why I'm all confused lol - Because I assume it would be easy to centre just use a measuring tape.. but if there is suppose to be a slight off-centreing how do I work that out - I can't find any information on the manual on the factory position of the mirror holder. Your idea is brilliant btw if being the case Its suppose to be centre that would be brilliant and an easy task. It just threw me a little when I read somewhere the mirror holder is suppose to be slightly off-centre by a few millimetres. @Charic top stuff btw! appreciating all the help

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bingevader

bingevader

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The mirror is off-set from its holder in the factory when it is assembled. So for you, all you need worry about is getting the holder centred by adjusting the spider vanes equally with your measuring tape.  :smiley:

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