Captain Scarlet

19 minutes ago, Simon128D said:

The hostel were we do all the observing is fully booked I am sorry to tell you. I got booked into a B&B just down the road from there.

At the very worst I'm 2.5 hours drive away in Baltimore, I'll get there one way or another! My neighbour will know plenty of people who live much closer so I'm sure it won't come to the full drive.

1 hour ago, Simon128D said:

... I am also booked in for Skelligs star party, not sure if you'll be going to that but if so then you'll see me there and I will have this scope with me.

Thanks for the reminder. I've just made an enquiry. Hopefully they'll have space, and hopefully I'll be able to meet some other Ireland-based astronomers. My big dob might even be ready by then!

Magnus

Wow what a read! Well worth the mirror-hassle I hope. Did the B&B landlord show any interest to have a look through?

Magnus

54 minutes ago, Stu said:

The tape was not a problem at all, until I wanted to clean the mirror, then it was a tight pain, leaving stickiness all over the cell which I had to clean up.

Yes this is a worry for me too. The residues of silicone especially on the sides add friction when dry and might reduce friction when wet,  making misjudging grasping it all the easier. Will have to be extremely careful.

11 hours ago, jetstream said:

Magnus, years ago I purchased an 8" f3.8 OOUK and it arrived in the same way with respect to the mirror cell and had massive astigmatism. It gets better- after removing the silicone the mirror was too thick to be properly supported with the nylon tips... if supported properly the mirror was pushed up into the "L" clips that retain the mirror. This also added big restraint on the glass.

Make sure you have enough room to support the mirror properly while maintaining a bit of room to the clips.

I posted this years ago with pictures.

I did put it the top half back together again before putting it into its travel-capsule, and it fits in fine with enough clearance to allow it to all work as it should. I'll demonstrate in a few days when I resume the build.

I do plan on a couple of modifications though. I'll grind off the "hook-over" bits of the restraining clips: they're far too big for their job and will introduce quite large needless diffraction artifacts. I'll replace them with a much thinner (from the point of view of the light-path) arrangement, perhaps such as Obsession suggest for their big dobs. And if I'm only ever going to use it on an alt-az mount, I might fashion a sling between a pair of those side-posts to spread the load more evenly. It won't make too much difference on a mirror as small as this but everything counts and it's all practise for my impending 20" dob build for which such an arrangement is truly necessary.

1 hour ago, markse68 said:

... I have found that i need to set a reasonable gap between the side mirror supports and mirror as the aluminium cell contracts in the cold and pinches the mirror otherwise. ...

My calculations might be wrong but on an initial lookup Aluminium's expansion coefficient (dL/L = 23e-6 per K) suggests that a, say, 160mm length will contract by 1/270th of a millimeter per degree change in temperature. Or for 10 degrees change, that's 1/27th of a mm. I can't believe that's enough to noticeably pinch from the standard suggested "paper-thin" gap unless the nylon side-grubs have already been tightened onto the mirror? (Which I used to do myself before someone asked me innocently why all my stars were triangular )

Cheers, Magnus

11 minutes ago, davidc135 said:

Captain Scarlet.

Do you think that the mirror deserves its 1/10 wave rating?  David

That I couldn’t say, but I have no reason to think otherwise. The zygo report for it certainly supports the 1/10-ness. I also have an OO 300mm 1/10 mirror which I bought new a couple of years ago and it star-tested beautifully one night of good seeing and stable temperature, and gave a brief view of Mars of amazing clarity. It is after all “what they do” so I’d be reasonably confident the mirror is as claimed.

However the proof of the pudding is in the, er, observing, so once I’ve got it properly installed again I’ll report back.

M

2 minutes ago, Stu said:

… Will you be changing your SGL name? 😉

John DobKenzie just wouldn’t sound right 😃

55 minutes ago, Dave scutt said:

The carbon tube looks so nice can't wait to see pictures of it finished 

Ironically length for length the carbon tube is heavier than the alu one: it’s lined with 6mm of hardfoam on the inside to make it extremely stiff. Not such a long drive for you to come and see it in person?

M

Some months ago I bought, from a member here, an Orion Optics VX8 1/10-wave-upgraded scope, originally made in June 2017. I am about to transport it from the UK to Ireland, where a new Helmerichs carbon tube awaits. Over the past couple of days I’ve dismantled it to fit into a suitcase for air-transport. The mirror-cell itself proved useful as a way of holding the primary mirror, with the front-clips handily providing clearance above the mirror surface. The two end-caps for the main tube also combined to make a convenient capsule to keep everything protected against any airline-manhandling.

Deconstructed, ready for "suitcasing up", surrounded by shock-absorbing clothes. Spot the clever way I've protected the secondary

Carbon tube awaits:

However, in the process of dismantling, I came across a fair number of things worthy of note. Things which perhaps explain why the seller sold such a nominally lovely scope, and of which the original manufacturer ought to be ashamed.

The first thing to prepare it for transportation was to remove the primary mirror and cell from the OTA. I’ve always rather liked the look of the smaller Orion cells. They comprise a 9-point whiffle-tree design with a well-engineered look about them. I discovered that, although the cell is indeed nice, the way it had been installed into this telescope was anything but.

-    The primary mirror was silicone-glued to the three “floating” triangles, such that many of the nylon pads on which the mirror was supposed to be supported weren’t even touching the mirror.

-    There was more silicone on the sides gluing the mirror to each of the three edge-supports, and in all cases it had by no means been sparingly applied.

-    There was tape wrapped all around the edge of the mirror OVER the side-supports.

-    On the main support base of the cell, there are three lugs with threaded holes to receive big bolts through the side of the tube, providing the means of securing the whole cell to the OTA. These main bolts were finger-tight only, and the smaller bolts securing the lugs to the cell-base were rattling loose.

-    In other words, within the cell as a whole, the things supposed to be loose and free-floating were glued to death, and the things supposed to be tight were loose!

-    The scope is sold as a 200mm f/4.5 scope with a nominal focal length of 900mm. The sticker on the side of the mirror states FL 870.9mm. The difference is enough to seriously alter the position of any holes you might want to drill in a virgin tube. (But actually this suits me, as this will serve part of its duty as a wide-ish field scope). I’m going to have to measure the focal length properly myself before making holes, as I’m not trusting the sticker. It does explain why I had to remove a spacer to achieve focus though.

-    Perhaps most egregiously, if that were possible, the centre “doughnut” on the main mirror I measured to be 3mm away from the true centre of the mirror. Even by eye I could tell it wasn’t quite in the centre. This makes the scope, to an unsuspecting owner, guaranteed to be miscollimated by no small degree! Using normal collimating techniques, a 3mm error at the mirror translates into a 6mm error back at the eyepiece, which means that the eyepiece centre-field will be looking at a spot fully 6mm away from the coma-free part of the image. This explained why I was seeing coma even after several attempts at collimation.

There are other problems with design rather than construction with this scope.

-    Obviously, the supplied tube being thin aluminium, it’s quite flexible, so a long or heavy eyepiece-stack causes droop. This was why I ordered the carbon tube in the first place.

-    Every single one of the fittings is posi-drive. I would have thought Hex or Torx would be more appropriate for something as modern as 2017? Perhaps I am wrong here.

-    The end-rings for the main tube, which help keep it round, wrap inwards over the tube-end causing the clear aperture at the front end to be exactly 200mm. In other words, 800mm or so in front of the mirror, the aperture is still the same as the mirror itself, clipping all off-axis rays and reducing illumination for anything other than the very centre-point of the image.

I feel so sorry for whoever has owned this scope before me, especially the person who bought it new. I can imagine the anticipation and excitement buying a scope with such a lovely mirror and cell, followed by terribly disappointing performance: a scope requiring remedial attention well beyond what a normal buyer of even a premium scope would expect to do; and providing horrid views of the sky. So far I’ve had to completely dismantle the cell to its constituent parts to remove all the silicone. I’ll have to soak off the centre-spot and place one actually in the centre: not too difficult to do but certainly not expected.

Pictures below with some annotation. And I’ll add more to the thread to document its journey into the carbon tube and subsequently to comment on its hopefully stellar performance.

Cheers, Magnus

***

Silicone everywhere. Whoever did this looks as though they were in a hurry:

Just in case the silicone isn't enough to hold the mirror rock solid:

some nylon-tip supports not even touching the mirror:

OTA attachment lug rattling loose:

Silicone and tape as much removed as possible:

Pic showing actual centre of the mirror (the little cross), vs the doughnut:

 Wry nice read. Well done finally getting back out there.

Magnus

Very nice Dave and jealous! I’m in the UK at the moment in Bortle 8 so have missed the run of moon-down fine weather in Ireland grrrr. Back in a few days bringing the cloud with me no doubt! 😄

Magnus

On 25/03/2022 at 09:03, Nyctimene said:

… and I rewarded myself with an excellent B.Nardini Grappa Riserva (60° proof). …

What does that translate to in terms of _true_ Field of View 🙃?

Seriously though very interesting and added to my next session!

Cheers, Magnus

You’ll start off by instinctively thinking to yourself “dammit a streak of cloud, how annoying”. And then realize it’s not cloud but the MW. In all seriousness.

Enjoy it, Magnus

My filter collection increases, thanks to FLO and funded by the sale of my Skymax 150: A UHC filter. Will go nicely with my Oiii to fit inside the extended eyecups of some of my binoculars.

Nice read. Just had a very short session tonight myself with the VX8 and I can confirm that although transparency is much much better tonight than it has been the last week, M51 is still invisible from here (not far from your old house) 🤣! Another thing that’s been missing until tonight: dew. Possibly not unconnected.

M 

Wow that's definitely going to be worth getting up for, thanks! It's going to be quite a show, with Jupiter, Venus, Mars, Neptune and Saturn all close by to boot!

Magnus

All set up ready for a clear night.

… when I realized on going out to observe that all my power supplies for this mount are in Ireland. And I’m in London. 🤦‍♂️.

Transparency is the worst I’ve ever seen it here. Nominally clear but I can’t even discern Pherkad, just by Kochab, so probably not too much of a lost session. And my brightness reading ought to be around 19; it’s in fact 18.4.

Magnus.

I have a scope for sale in the classifieds section, and I initially offered it for sale "courier-included". Delivered, it's garnered some interest. But I've had to change to "collection only" for the time being because I can't find a service that hasn't got such a thing (fragile, telescope, glass/mirrored etc) on its restricted list.

Can anyone suggest a service I can use, UK to UK (it's near London despite my sig-location).

Thanks, Magnus

I've re-acquainted myself with my LZOS 105, which has been in the UK while I've been in Ireland. Now I'm back in the UK for a few days, it's been outside all day and all I can say is WOW. The quick views I've just had of Sigma Orionis, including quite easily the more difficult C star, at about 72x (Delite 18.2 and Celestron Ultima Barlow) totally remind me of the first time I looked through @Stu's Tak a few years ago. Completely mesmerising. Although I love the view of star-fields through a biggish newt, mainly because you can see so many, there is something indefinably beautiful about the refractor view. Stunning. More tonight after dinner I hope.

I feel your frustration. I ordered a high-spec mirror from a certain well-known uk mirror maker and it arrived with a couple of deep scratches, in response to which they directed me to the small print. Grrr.

I also received a bigger mirror from a much better-reputation uk mirror maker and yes it did have a bit of packaging/insulation dust on it. But after a sloosh of water all that dust disappeared and it is pristine.

if I were you, I’d rinse your mirror and hopefully all will be good.

Magnus

A few months ago I bought GrumpyMartian's VX8, but it had a Losmandy dovetail on its rings. and the only saddles I have here where I am in the UK for a couple of weeks are all Vixen. Therefore ... an adapter, courtesy of RVO, to avoid having to really tediously de-dovetail my LZOS and re-screw it onto the VX8's holes.

Flex in the tube at different altitudes? My SW 200p was terrible in that respect and I don’t expect my own VX8 to be any different. If I put my glatter laser in, the spot moves as I change altitude. That’s why I got a carbon tube. Tomorrow I’m returning to the UK for a fortnight where my VX8 currently resides so I’ll give it another test.

For me tonight, one of those nights of such terrible seeing you debate whether to sell off the piece of rubbish you happen to be looking through...

I have 3 2” diagonals, a Baader, a Revelation and an OEM Skywatcher one. In the past I measured and noted the Baader and the Revelation to be each 107mm. The external extension on the SW can be seen to be the same length as the Revelation one, so my assumption would be that it too is 107mm.

If I get a moment later today I’ll test that theory on a scope for par-focality with an actual eyepiece

Cheers Magnus

17 minutes ago, PeterW said:

Sounds great, but worried about what beasties might eat you if you fell off that little ladder in the dark… your “Michelin man” suit would probably save you! 
 

Peter

I understand the Capercaillies are pretty ferocious up there!