Modifying my TS SuperNewt Primary Mirror

[Catanonia]

As you will be aware, I have been having some collimation and perhaps optics pinching issues with the TS SuperNewt F2.8

After some discussions with Tim and Blinky (thanks gents) I took the whole lot apart again and had a look.

My mirror clips were tight !!!!! My 1st ever newtonian and I didn't know better. So the chances are that as the mirror reshaped due to reaching temperature it distorted slightly giving the problems.

So I have now loosened them off enough to just fit a business card underneath. But doing this introduced the old problem of mirror flop on the primary. Easy to see, with the clamps "loose" and the mirror "floating" you could move it a few mm each way and so it was obvious that in the tube as it rotated from horizontal to vertical it too would shift a few mm due to gravity and the weight of the primary. You can see the mirror clips spacing in the second picture.

I didn't want to go down the silicone route just yet so I wanted a better fix.

I noticed that the mirror is held in place with 3 cork inserts at 120 degrees apart. These were not quite thick enough to prevent movement. This is the simple problem, the mirror was not held firm enough in the assemble.

So taking that business card, I cut some pieces and on all three contact points with the cork spacing, slotted and taped in a piece of the said business card.

Perfect fit and the mirror is now rock stable

Hopefully this will help a few of the problems and allow the mirror to "float" and shape correctly.

Now to re collimate and move the scope around and check it holds well.

Fingers crossed, a very very simple fix.

Some piccies of the job completed

Don't worry about the mirror state, it was washed and dried nicely before being put back in. I must have the most cleaned primary in the world by now, 3 times after a few weeks :D Seems silly not to give it a wash and blow whilst it is out especially when it got rained on the other night

[Catanonia]

Well just finished collimation and testing.

Getting really used to the Cats Eye collimation kit now, once you get the hang of it, it is really really nice and simple.

Got collimation within 5 mins

Locked everything down, focuser etc and collimated with Cats Eye and checked it a few times.

Then tighted up locking nuts, and with focuser tightened with the Cats Eye kit in so nothing could move, chucked the scope around the air simulating rapid scope movements in all directions.

Put the scope back on the bench, and it was perfectly collimated still according to the Cats Eye

I did worry to start with as I forgot the lock the focuser and the 1st time the swing around was enough to budge the amazing steeltrack my a nads nadger and the Cats Eye showed this clearly.

SO RESULT Looks like my simple bodge job to the primary has worked

[Moonshane]

sounds like you'll fit in well with us newt owners - modding already after a few days of ownership

[Catanonia]

sounds like you'll fit in well with us newt owners - modding already after a few days of ownership

LOL, the missus just sighs when I take a £1800 scope and start to strip it on day 1 :D:D

[Tim]

That should help. You could always keep an eye out for some thin cork shims for a more permanent fix.

One other thing that might be worth considering would be blacking that ground edge on the mirror. You'll need nerves of steel!!! You can do it with a permanent marker, which is better than nothing, but matt black paint is better. Or else you can cut out a round mask just to hide that outer edge and have it sit just in front of the mirror.

The reason is, anything which can reflect light, will, and that bright edge will have unwanted photons bouncing all over the place. Its a tedious procedure, and one which I haven't yet dared to do permanently on my 10" newt (I have made a mask for it) but is one of the things you can do to refine an image even more.

Here's a link, which includes tips, pics and method.

Top Ten Ways of Improving Newtonian Telescope Optics

Tim

[Moonshane]

yeah but she doesn't know the price is all in the dip they make in the centre of the primary does she?

[Catanonia]

That should help. You could always keep an eye out for some thin cork shims for a more permanent fix.

One other thing that might be worth considering would be blacking that ground edge on the mirror. You'll need nerves of steel!!! You can do it with a permanent marker, which is better than nothing, but matt black paint is better. Or else you can cut out a round mask just to hide that outer edge and have it sit just in front of the mirror.

The reason is, anything which can reflect light, will, and that bright edge will have unwanted photons bouncing all over the place. Its a tedious procedure, and one which I haven't yet dared to do permanently on my 10" newt (I have made a mask for it) but is one of the things you can do to refine an image even more.

Here's a link, which includes tips, pics and method.

Top Ten Ways of Improving Newtonian Telescope Optics

Tim

LOL Not a chance mate am I taking a pernament ink marker to that mirror :D:D

[blinky]

Hmmm...... im sure that when i loosened the clips then tightened the collimation screws all it did was pull the mirror clips tight again! I am going to see how i get on with the scope and may yet end up removing my silicone but i think i need to experiment with collimation more beforr removing all that silicone - i cant believe silicone would stop a big mirror like ours from moving!

i think my collimation is still the root of my probs and the silicone is better than it was

Sent from my Scroll Excel using Tapatalk

[Catanonia]

Hmmm...... im sure that when i loosened the clips then tightened the collimation screws all it did was pull the mirror clips tight again! I am going to see how i get on with the scope and may yet end up removing my silicone but i think i need to experiment with collimation more beforr removing all that silicone - i cant believe silicone would stop a big mirror like ours from moving!

i think my collimation is still the root of my probs and the silicone is better than it was

Sent from my Scroll Excel using Tapatalk

Collimation is the key with these fast scopes @ F4 says me after 2 weeks of experience LOL Mine shows up worse as I have a corrector / reducer down to F2.8 and so even small errors show up.

Such things as pinching of optics will become evident.

One thing I have noticed with my collimation is that if I do it by sight using a Cheshire and or a laser, the Cats Eye shows on F4 it is normally massively off, by quite a degree. Once I correct with the Cats Eye, the Cheshire looks the same as before, but of course it is properly collimated. It is all down to the small accuracies that you cannot see in a Cheshire.

The theory makes sense with the floating mirror. It needs space to expand and contract it's shape smoothly. If you hold it down with a load of silicon, this could cause pinching / shaping problems as some parts of the mirror will not be able to expand at the same rates as the others. Pinching in certain spots.

The method I have used seems to be much simplier and sits with the design of the scope, just refining the tolerences a bit more with the shimming.

All that said, I haven't tried it out yet, so everthing I have said could be BS.

If I were you Craig, I would concentrate on the collimation and get that as close as you can with a Cheshire and star test. If you still get the issue with say 10 second subs (to eliminate guiding problems) then I would look at the silicon. Looking at your pictures, you did use a lot of silicon.

Where do you life Craig, I am in Cheshire Sandbach and would be more than happy to meet up at yours or mine with my Cats Eye kit to have a play. It won't be perfect as you don't have the Cats Eye donut, I am guessing the normal one, but we can get alot closer with it.

Also are you totally sure your donut is central. Mine direct from factory was easily 2 - 3 mm out.

[blinky]

I live in Edinburgh so a meet is kind of out the question - thanks for the offer though!

I am about to post a thread of my own rather than interfere with your thread anymore!

[Catanonia]

I live in Edinburgh so a meet is kind of out the question - thanks for the offer though!

I am about to post a thread of my own rather than interfere with your thread anymore!

No worries mate. I visit Glasgow and Scotland every few months, so might not be impossible as long as you buy the beer

[Catanonia]

yeah but she doesn't know the price is all in the dip they make in the centre of the primary does she?

Arhhh, so that is why that marble rolled to the centre of it

[Catanonia]

Ok next jobs when I get this newt sorted.

1. Blacken the secondary

2. Blacken or mask the primary.

3. Flock ??????

Unsure whether flocking is necessary as it is a carbon tube and fairly black already.