Struggling with skywatcher secondary mirror

[peterpixel]

I have just acquired a second hand skywatcher 1309 EQ2 scope and decided to check collimation, not because there is a problem, but because I thought I should know how its done.

I am using a well collimated laser but I cannot adjust the secondary mirror at all. The screw in the centre is so tight I cannot shift it and when I look down the 3 adjustment holes I cannot see anything to adjust - no allen key holes - nothing.

Can someone shed some light on whats going on here. I have stuck a paper reinforcemet ring onto the centre of the primary mirror but cannot get the laser spot to move into it (although its not far off)!

Thanks

[wookie1965]

To turn the centre screw you must back up the 3 adjustment screws first. 

To be honest if it's good don't mess with it the secondary will not need moving unless the scope is dropped or severely banged. 

Edited July 6, 2021 by wookie1965

[Alan64]

7 hours ago, peterpixel said:

I have just acquired a second hand skywatcher 1309 EQ2 scope and decided to check collimation, not because there is a problem, but because I thought I should know how its done.

I am using a well collimated laser but I cannot adjust the secondary mirror at all. The screw in the centre is so tight I cannot shift it and when I look down the 3 adjustment holes I cannot see anything to adjust - no allen key holes - nothing.

Can someone shed some light on whats going on here. I have stuck a paper reinforcemet ring onto the centre of the primary mirror but cannot get the laser spot to move into it (although its not far off)!

Thanks

That 130/900 Newtonian is a rather nice instrument.  The secondary-hub, the spider-vanes and the cowling are all in one piece.  This is the cowling from my Celestron 127/1000, which is the same as your own...

Are those three screws missing?

[Spile]

Can you take a photo through a cap or ideally a Cheshire Sight Tube combination tool and post it here?

As Woodkie1965 said, you need to (slightly) loosen each outer bolt before attempting to loosen the centre screw.

Edited July 7, 2021 by Spile

[peterpixel]

6 hours ago, Alan64 said:

That 130/900 Newtonian is a rather nice instrument.  The secondary-hub, the spider-vanes and the cowling are all in one piece.  This is the cowling from my Celestron 127/1000, which is the same as your own...

Are those three screws missing?

Yes, no screws, just holes!

[Soligor Rob]

First thoughts are there threads in the holes? if so then the grub screws are simply missing.

2nd you might be able to just centre the laser if it's only a little way off by moving the secondary by hand, worth a try.

Edited July 7, 2021 by Soligor Rob
more info

[peterpixel]

6 minutes ago, Spile said:

Can you take a photo through a cap or ideally a Cheshire Sight Tube combination tool and post it here?

As Woodkie1965 said, you need to (slightly) loosen each outer bolt before attempting to loosen the centre screw.

There are no screws to loosen.

[CraigT82]

1 hour ago, peterpixel said:

There are no screws to loosen.

You will need to find three screws to go in those holes. The secondary tilt is adjusted using them and if they are not there that's a bit of an issue! I guess the central screw has just been tightened down hard so that the secondary holder is butted right up against the central boss? 

What is the view like through the focuser is the secondary mirror obviously misaligned? 

[peterpixel]

41 minutes ago, CraigT82 said:

You will need to find three screws to go in those holes. The secondary tilt is adjusted using them and if they are not there that's a bit of an issue! I guess the central screw has just been tightened down hard so that the secondary holder is butted right up against the central boss? 

What is the view like through the focuser is the secondary mirror obviously misaligned? 

No its not obviously misaligned. I have found 3 bolts that seem to match the thread but they just screw in and dont seem to do anything as the secondary is so tightly fixed against the boss as you suggest. Is it worth taking the spider out and trying to get the central screw out as I dont want to push too hard while its in the scope??? WD40?

[Tiny Clanger]

If it's not obviously misaligned, I'd leave it as it is. This quote explains the role of the secondary :

"It’s important to remember though that even though adjusting the secondary is the most involved part of the process, it’s also the least important. So long as you can see the whole primary reflected in the secondary, you’ll be fine. And you won’t have to mess with it very often either. Indeed, I’ve gone years without having to touch the secondary mirror in some of my telescopes. Just remember it’s just a flat piece of glass with no optical power — all it does is divert light from the primary mirror out the side of the tube."

That's from this page https://garyseronik.com/a-beginners-guide-to-collimation/  which I found was, for me,  the clearest explanation out there on the subject.

Heather

[wookie1965]

I suspect that the secondary will not be under the focuser as it is screwed up so tight, I collimated a scope very similar to this on Sunday. 

Owner told me the views were soft and he had used a laser when I put my Cheshire in the secondary was too far towards the front of the OTA. 

I think you are going have to take the front off and don't spray wd40 put it on a rag and put it around the screw. 

I would try different screwdrivers or bits until you find a tight fit if you feel it slipping stop try a different one. 

Failing that may have to use a hacksaw cut the slot longer and use a slotted screwdriver to remove that screw. 

I wish I was closer so I could come and help. 

[wulfrun]

The central screw-head looks rather chewed up and it appears to be recessed. I would certainly try to avoid doing anything first, see if you can get it acceptably in collimation.

If it does need to be moved, I'd remove the vane assembly and carefully and slowly drill the head off the screw (if a screwdriver won't give enough purchase). The vane assembly looks like a casting so I'd avoid any major strain on it, it'll probably crack relatively easily. You'd need to wrap the mirror up and be thorough with cleaning up afterwards. Pretty drastic, last-resort stuff!

I would not recommend WD40 for much beyond gate hinges etc, it's definitely not the best for freeing stubborn threads. Plus-Gas or similar work far better, as does diesel fuel. I'd also get some heat into the central part where the screw is too (heat-gun). There's a fair risk to the secondary mirror though with any of the above, you need to tread carefully.

Edited July 7, 2021 by wulfrun
added info

[Tiny Clanger]

17 hours ago, peterpixel said:

I have just acquired a second hand skywatcher 1309 EQ2 scope and decided to check collimation, not because there is a problem, but because I thought I should know how its done.

If there's no problem ...

[Alan64]

4 hours ago, peterpixel said:

Yes, no screws, just holes!

Your local hardware should have those.  Take the telescope with you, introduce them to your sample of the master's industry.  They'll get a kick out of that, and should be delighted to help.  This is how the assembly is constructed.  There's the centre-screw and its spring, and the three adjustment-screws; simple...    

If I'm not mistaken, all of those screws are M3.  The centre-screw, however, may, I say may, be an M4.

However, for the three adjustment screws, get the socket-head type instead of the Phillips; for example...

That way, you can turn the screws with the thumb and forefinger to adjust, then a hex-key to tighten.

Learn, know, and master the secondary-assembly of your Newtonian; its faults and foibles, its twists and turns, and you'll be golden.

[Soligor Rob]

Please don't use WD40, it's not a lubricant, the clue is in the name WD = Water Displacement, the 40 refers to how many times it was changed until the got it right.

IF you want to use a lubricant of anything, door locks, rust preventative etc etc then get yourself some ACF50.

 

[Tiny Clanger]

20 minutes ago, Soligor Rob said:

Please don't use WD40, it's not a lubricant, the clue is in the name WD = Water Displacement, the 40 refers to how many times it was changed until the got it right.

IF you want to use a lubricant of anything, door locks, rust preventative etc etc then get yourself some ACF50.

 

WD40 is really great for getting sticky labels off things though

[peterpixel]

On 07/07/2021 at 12:13, peterpixel said:

No its not obviously misaligned. I have found 3 bolts that seem to match the thread but they just screw in and dont seem to do anything as the secondary is so tightly fixed against the boss as you suggest. Is it worth taking the spider out and trying to get the central screw out as I dont want to push too hard while its in the scope??? WD40?

I have just used a collomation cap and everything looks to be well aligned now I have put a doughnut on the primary. Just cannot understand why would they put the main secondary screw on so tight, just hope it never goes out of collimation 🙄.

Thanks to all who replied

[Spile]

Take a photo through the focuser. Ideally through a cap (see diagram) or even better using a sight tube (also in diagram)

 

 

[peterpixel]

44 minutes ago, Spile said:

Take a photo through the focuser. Ideally through a cap (see diagram) or even better using a sight tube (also in diagram)

 

Not sure I was straight on with the camera but this is as good as I can get

 

 

[Alan64]

2 hours ago, peterpixel said:

Not sure I was straight on with the camera but this is as good as I can get

 

I can see the three primary clips, evenly ; good.  However, there in the centre, the larger, fatter circle needs to be directly over the smaller, thin one.

As it sits, it's okay for low-power observations, as a great many are out of the box, out the gate, but not so good for the higher and highest powers of which a 130mm aperture is capable.

Your 130/900 is configured, designed, for medium-to-high powers, but the collimation is going to have to be spot on for sharp, pleasing images at those powers.

It is at the higher and highest powers where "Wow!" and "Look at that!" are exclaimed aloud.

[Spile]

Here is my take...

The clips are all visible, the primary reflection (red) is circular and concentric with the focus tube (blue).

A piece of coloured paper behind the focus tube would make it easier to see the outline of the secondary - as you can see I use yellow paper. From what I can tell,  the axis runs 10.30 - 4.30 with the primary mirror at 4.30.

The red arrow shows the primary tilt correction required.

 

[peterpixel]

great, many thanks, will ahve a go

Cheers,

Peter