What's wrong with this picture?

[MortonH]

This is the view down the tube of my Newt after collimation.

Anyone see anything not quite right?

[Atmos]

Me thinks your secondary needs a repositioning :)

[MortonH]

Yes, except it's a new scope and I don't even know if such an adjustment is possible.

[Saturnine]

It seems that the focuser is on the wrong position for the diagonal, you may need to cut another hole in the tube at 90 deg. to align them correctly. Seriously , is the diagonal way off centre in its holder, even allowing for collimation offset.

Jeff

[MortonH]

That's how it looks to me, as if it's been attached way off-centre. First time I stuck the laser collimator in the red dot was almost off the edge of the primary. I was able to get the dot where it should be after a LOT of adjustment but the secondary just looks wrong.

Seems like a warranty return is required.

[Saturnine]

Doesn't matter who the retailer was / is, do they actually open the box and have a look down the tube and understand what they see, before they send it out or you pick it up.

[Atmos]

Loosen the three hex bolts and then partially unscrew the centre screw, probably only need one rotation. From there you can rotate the secondary around, tighten that screw and then you'll have to re-collimate from there.

I had to do it on my dob ages ago after I was playing around with it, only took a few minutes to fix.

[MortonH]

Ah, so it is possible. Problem is that the central screw was so tight it stripped when I tried to loosen it. I hate the fact that they use cheap soft screws in these things.

I already had a conversation with Saxon today before making a second attempt to fix it. Guess I'll be talking to them again tomorrow.

[MortonH]

I bought it from Astro Pete's in Brisbane because his price was way better than elsewhere. Since I'm in Sydney it was shipped direct from the warehouse in Melbourne to reduce the shipping cost.

So nobody has had a look at it since it was assembled and boxed up in China.

[RobF]

Just back off the main centre screw (or all of the 3 adjusting screws), rotate, then re-collimate should do it?

Eventually you'll want to slack it right off to start from scratch, so why not now.

[MortonH]

Fortunately there was enough left of the centre screw thread to loosen it with a flat head screwdriver. It now looks fine.

Thanks for all the help. :thumbsup:

[Atmos]

Glad it's all fixed (bar the screw) :)

[RobF]

All that's needed now is some clear sky :)

[traveller]

Morton, I always follow these instructions
https://starizona.com/acb/basics/using_collimating_newt.aspx
Cheers
Bo

[MortonH]

Thanks. That's the best explanation I've seen.

[MortonH]

Saxon called me today to check up on progress (quite impressed with their customer care). They're sending me a new central screw so I can replace mine before it gets stripped completely.

In a way I'm glad this happened as I now have a much better understanding of how the secondary mirror system works.

[mental4astro]

Sure it's the steel bolt that's stripped and not the aluminium spider hub?

[MortonH]

Yes. The "star" on the Phillips screw head is clearly mangled.

[mental4astro]

Ok, the head of the bolt is stripped.

Before you go too much more with changing the bolt, put a little WD40 under the bolt head, and a little time for the oil to seep in. It will help loosen the threads and ease any damage that may have occurred. I'm talking a drop of the stuff, not a squirt from the can. If all you have is a can of the stuff, spray some onto a bit of plastic, or some other surface, and pick up the liquid from the material that's pooled. Any excess on the hub can be cleaned up when you remove the bolt & secondary mirror. You won't be putting on so much that it will coat everything! Just a drop. Dry lubricants won't seep down the threads where you need it.

[MortonH]

Thanks Alex!

[Allan]

The other thing you might want to check Morton are you spider vains. They don't look very parallel to me. The way I check is to grab a piece of cotton and hold it on either side of the tube where the vains attach to the tube. If the vains don't run exactly in line with the cotton across the whole diameter you will end up with 8 diffraction spikes instead of 4.

[RobF]

Allan is right - the entire secondary assembly looks to be rotated with the vanes not converging at a single point - in the 3rd pic at least....

[AG Hybrid]

Looks like the price was way better for a reason. The spider veins dont even converge on the secondary properly. You didn't say what kind of scope it was?

[MortonH]

The spider vanes are now parallel but they seem to be offset on either side of centre by design. Can't remember if my previous scope was the same.

This one is a Saxon but it's the same as the Skywatcher model, both made by Synta to same spec.

I tried it out the other night and it seemed ok but the seeing was poor so I didn't use high enough power to notice any issue with the diffraction spikes. I'll check again when I can.

[raymo]

The spider vanes do converge correctly. The secondary holder has been
rotated by someone trying to loosen the centre screw. When the holder is back in its correct position the bottom two mirror adjusting screws will be
parallel to the vanes that are horizontal in the picture.
raymo

[MortonH]

Thanks Raymo. Will check that out later.

[MortonH]

Ok, so here are current pics after the adjustments of the other night. The secondary may not be perfectly positioned as I'm waiting for the replacement central bolt and then I'll do it more carefully.

However, I'm concerned with the comments about the spider vanes not converging to a single point. As you can see from the pics, there are four flat areas around the circular holder where the vanes attach. The vanes are screwed in and there is no way for them to move relative to the holder, nor does the holder itself rotate, so if the bottom two collimation screws aren't parallel with the vanes it must have been made that way.

None of the vanes seem to point directly at the centre of the hub. However I'm not sure if that matters? Do scopes with curved vanes meet in the middle? So isn't the important thing that they're parallel?

Just tested it on Canopus and there are two very close, parallel sets of diffraction spikes.

So are you saying the holes to attach the vanes to the secondary holder are in the wrong place?

[raymo]

You don't have a problem Morton, I have seen this many times over the
years. As I said, the secondary holder has been twisted to the left by someone trying to loosen the central screw. If you look carefully at your last picture you will see that none of the vanes is perpendicular to the
secondary holder. The top vane for instance leans to the left.
If you put two Allen keys in the bottom two mirror adjusting screws, [the horizontal ones]hold them in place with one hand, and put a screwdriver or something similar between them, and turn the secondary holder to the right until the vanes are at perfect right angles to each other. You will probably have to do it several times, as the vanes will try to spring back a bit from the position you stop in. Shouldn't take you more than a few minutes. As I said before, the bottom two screws should end up parallel to the horizontal vanes.
raymo

[MortonH]

Hmm, I'll need to be feeling brave to do that!

By the way, I used the scope tonight for several hours and it performed well. The diffraction spikes weren't an issue on Jupiter which showed good detail and contrast in average seeing conditions. Deep sky stuff was as good as it gets from my location.

So there's nothing badly wrong with the scope as it is. But when I get the new central screw I'll have a good look at sorting it out properly. What could possibly go wrong? :lol:

[raymo]

I'd happily do it for you, but you are 2,490 kays away. You'll find it quite
easy, all you're doing is the opposite of what caused the issue in the first place. You can alternatively remove, straighten, and refit the vanes one at a time. Just make sure that the foot of each vane that its two securing screws fit through is at exactly 90* to the rest of the vane.
Remember to have the tube pretty much horizontal, so no screws or tools can fall onto the primary mirror.
raymo