Captain Scarlet

Mark d’you reckon it’s viable commercially? Looks as if it might be to me. I for one would definitely be a buyer. M

Haha I was wondering if anybody would notice that bodge! Well spotted. One of the unanticipated difficulties from the extra ota tube thickness. I’ll probably use the existing OO rings and add the required distance with some slightly longer hinges from the local hardware store … it’s all pretty crudely put together as it is.

Thank you. The view is much of the reason we moved here. The other is the darkness. By coincidence after a long dry spell (in sunset terms) this vista presented itself just this evening...

Over the last few weeks I've been gradually morphing an Orion Optics VX8 1/10 from the sorry state of affairs it was when I bought it, to a state of loveliness, in both form and function. To look at, the original VX8 scope was fine: newish, clean, no scuffs etc. It was only on close inspection that some serious problems became apparent, to the extent that it was essentially uncollimatable, and therefore horrid to look through. These problems were no fault of the SGL member who sold it to me, though it may well have been some of the reason he sold it. The as-sold OO VX8 has design flaws and in the case of this copy, production flaws too. I've tried to fix all these. I've transformed it into what it should be, and some. It's now a beauty to look at and, I hope, to look through. Though I haven't yet had a chance aside from doing the collimation. But I have checked that my design work worked: I reached focus just where I hoped it would be, 70mm from the outside of the tube. Phew! The main problems I fixed were: - The centre-spot on the primary was 3mm (!!) from the true centre of the mirror. It was this that made it virtually impossible to collimate or get a decent view. I removed the old spot and installed a new one, properly centred. Now the 1/10-wave spec can do its thing. - A new Klaus Helmerichs carbon tube. The original VX8 tube is Aluminium and thin, therefore not rigid. Any significant eyepiece-train load would cause "droop" and collimation-shift. The new tube is extremely stiff, I can't shift collimation with even a hard pull on an eyepiece. - The VX8 has end-rings to try to keep the tube round at each end. To keep them stiff, these rings wrap over across and into the open end of the tube, leaving a resulting clear aperture at the front of the tube of exactly 200mm, i.e. the same as the primary mirror 871mm away. This means that only the precisely on-axis spot receives the full 200mm. Anything off-axis gets vignetted by the end-ring. The new tube has no such "wrap-over". - The OO cell is actually a lovely mirror cell, and I would certainly buy one new. But in the factory during assembly all its moving parts and more besides get slathered in gobs of silicone glue. Why on earth? The whole point of the cell is exactly its moving parts. Anyway, I removed all that nasty stuff, plus the sticky-tape untidily wrapped around the edge of the primary, so the cell can now support the mirror in the way it's designed to. The first image below shows everything neatly arranged, ready for assembly. Easy final step, right? Wrong. The extra 6mm tube-thickness presented me with a good few difficulties, some anticipated but some not. Luckily I did find ways around the unanticipated ones. Neat and Tidy and ready for assembly: The extra tube thickness meant that the spider wasn't quite wide enough. Luckily I had enough M4 nuts lying around that I could insert between the boss and the spider-arms, giving some crucial extra width: The lovely rear cell: Some pictures of general loveliness: And finally, it joins its bigger sibling (a 300mm OO 1/10 mirror with Helmerichs tube): Thanks for drooling, Magnus

Mercury! Thanks for the reminder. It's higher now for us at 51 degrees N than it has been for some time, until end April. M

West Cork yes indeed! Setting up only the refractor on the ayo just outside the house took ages because I would stop and stand and gawp between trips. Magnus

Tonight satisfying and frustrating at the same time. Satisfying because it was a lovely clear night with the Moon not due up until 0055. Satisfying because seeing was the best I think I've ever experienced (star-testing Polaris showed crisp perfectly stable rings both sides of focus at max mag for the scope I had: 217x with 0.48mm EP). Satisfying because it was the second darkest night I have ever measured here, in 5 years. 21.97 on my SQM-L. It was fascinating to see it get darker as countryside lights went out, and then get "brighter" as Luna started to approach Moonrise. Satisfying because the transparency was superb: the MacGillicuddy Reeks 60km distant were very sharply defined before sunset, always a good indicator. Some supposedly clear evenings you can't see them at all. Frustrating because, lovely session though it was, I HAD THE WRONG SCOPE OUT! I'd put out my 105mm LZOS for a very short wide-field session as I had early errands next day. It turned into a longer session, damn the early start, I wasn't going to miss skies like this even with the wrong scope. I dearly wish I'd got my 12" out. The whole session worthy of a separate report over the next day or so I think, but I had far and away the cleanest best view of Epsilon Lyrae, the Double Double, I've ever had bar none. By no means the most difficult target I know, but still a good indicator. Cheers, Magnus

OK I’m TRYING to get on with this, but I have some difficulties… … HE thinks he’s helping

Does Mrs Stu know you have this much time on your hands? 😁 M

I plucked up the courage actually to perform the centre-spot placement today. I initially intended to use the template to mark a marker-pen spot, and with tweezers place the centre-spot over it. But I found my hand wasn't perfectly still enough to be certain of getting the initial spot in the right place. So I adopted a different strategy. I taped the triangular spot to my template in just the right place using a piece of low-tack masking tape. I removed the adhesive backing from the centre-spot. I placed two strips of multiple-layer flocking paper, one on each side of it to give clearance, to ensure that when I laid the whole thing onto the mirror, it wouldn't stick until I was happy with the positioning and pressed it down. It worked first time. The spot I also made from black flocking paper, in my never-ending quest to remove any source of bright scattered light from my tubes (i.e. from a white spot). Success! Whereas before the spot was fully 3mm from the true centre of the mirror, almost on the paper of the donut, now I've measured it to be 0.2mm from the centre. I reckon I'll not get it better than that. Cheers, Magnus. Pics below preparing the press-on template: Laid in place and ready to press down: Finished result (central dot marks the true mirror centre in the last pic):

First Light in Ireland for my LZOS 105, I’ve been dying to try it for years actually with my Nagler 31 for 21x nearly 4 degs FoV in dark (-ish given Luna) skies. Lovely quick tour of a few favourites including double cluster, Alnilam S, Pleiades, Polaris A/B and half-split the double-double with the Delos 6. 4 Trapezium stars were detectable with the N31 too which surprised me. Observing chair certainly helped there. As mentioned in the Lunar observing thread X and V were seen, and a random occultation, around 2225, it just snuffed out, I think it was that well-known star TYC 1903-0472-1 😂

Me too with all three aforementioned, first time noting them also. First Irish Light for my LZOS 105. Magnus

Those who noticed my recent “Deconstructing, Fixing and Upgrading a used OO VX8” thread may recall that one of the problems I identified with the scope, with the mirror itself, was that the centre-spot “donut” was manifestly not in the centre. This makes the scope essentially uncollimatable, or guaranteed to mis-collimate. The method I used to establish this was to take a DSLR photograph of the mirror, face-on, with a reasonably long focal-length camera lens and the picture centred around the centre of the mirror. In Photoshop I then chose three arbitrary roughly-equally-spaced points around the edge and noted their pixel-coordinates. I used a formula to determine from those coordinates, the pixel-coordinates of the true centre of the mirror. I’ve since worked out a less involved way of checking this, which can be used both to check the centred-ness of a spot already in place, AND to place a new spot centrally when the time comes. A common suggestion is to trace a circle on a piece of paper or card, fold it over a couple of times, and where the folds meet, there is your centre. That’s fine, but my new method lends itself better to using graph paper, with no need to try to cut accurate circles or curves. It turns out that a 3-4-5 triangle has a couple of really nice properties: one, it’s a right-angled triangle so its corners can be trivially marked on right-angled graph paper. And second, the centre of the circle that passes through the three points of the triangle has nice round-number coordinates too. So a triangle that has the coordinates (0,0), (0,3) & (4,0) will have the centre of the circle at (2.0,1.5). All extremely easy to scale up, no nasty pi-related fractions of millimetres to try to judge, rather easy to mark directly onto graph-paper and cut out, and possible to check and re-attach a centre-ring without removing the mirror from its clips, as the 3-4-5 will fit inside them, as shown. In case anyone likes this and plans to use it, I’ve added a little table below with the triangle-and-centre coordinates of some common mirror-diameters, plus a picture of my own in action. If you look closely at the hole I made in the centre, you can see just how far out my own spot is! Cheers, Magnus

Happy Birthday. We of course will need to see any astro-related presents! Magnus

When it does come time to clean it though, bear in mind that what’s on the mirror is no ordinary dust, it’s very fine _sand_ and needs extreme care to clean it without leaving scratches

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.

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

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.

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. 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

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

John DobKenzie just wouldn’t sound right 😃

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