Captain Scarlet

Christ you said expensive but I wasn’t expecting that! £45 ish for 100ml. But I’m still tempted.

M

On 13/02/2022 at 12:04, Alan White said:

I have the top left one by Roger N Clark, a brilliant book in my view.

Totally agree. His sketches are a superb independent view of what you should expect from an 8” scope in a dark sky. And this book, the appendices, was the inspiration for me to write my own planisphere/skyview software. Not to mention his analysis of the sensitivity etc of the human eye. Really very good. But quite expensive/difficult to get hold of lately…

Magnus

Courtesy of @Alan White and brought back to Ireland today: my first ever Takahashi objets:

Propeller nicely on show…

Those of you who’ve been following the DIY Thread et al may have noticed that I’ve spent the last 2-3 months re-tubing a 2017 Orion Optics VX8 1/10 Newtonian into a Klaus Helmerichs carbon tube. It had a lot of problems, and with most of them addressed I assembled and rough-collimated it a couple of days ago. Last night clouds dutifully disappeared, as of course they always do when a scope is good and ready, so Lady Luck decreed that clear skies were the order of the, er, night.

I took it out to cool quite early and noticed during the evening that dew was forming, which has been unusually absent from all my previous sessions this year as far as I remember. This would be interesting, as one of the features of the tube I ordered was a 1025mm length, i.e. very long for a 200mm f/4.3. In other words, a large built-in dew shield! We would see during the evening if that worked (it did!).

Another design feature I’d built in was an aggressively short out-focus distance of only 70mm. The height of my Baader Diamond Steeltrack outside the tube is 63mm at minimum, so not much to spare! In the event, not quite enough (with the Paracorr2) for some of my eyepieces, predictably the longer ones and especially the Nagler 31. I had to confine myself to Delos 10mm (100x) and shorter for the session. There was very little in it, though, I reckoned a few millimetres extra height would do it. I spent today, the day after, calibrating my relative focal distances for all my eyepieces and it turns out I need only 4mm more to accommodate my whole set, including N31. There’s more than that left in the quite long collimation-bolts on the OO cell so I can use them to push the primary further up the tube to push my focal plane a smidgin further out. Though I might also drill an extra set of cell-holding holes 20mm further up to give me lots of options.

Anyway, to the session itself. I’d cobbled together a not-very-exotic list just before it got dark enough, and rattled through them. In the event, there was a milky sheen of high cloud throughout the night, mostly transparent enough to see through but occasionally forcing me to find another part of the sky. By about 1am, it had clouded over completely. Apparently around 11pm there was a huge fireball over Cork: I was certainly outside and in full flow but I must have been looking West. I missed it.

Earlier, just after 9pm I finally this year got around to looking for Mercury, and found it easily enough, through my Kowa TSN-883 spotting scope at 60x. The 45% phase was obvious. Always a treat to see that planet.

Back to the OH200, as I’ve named the scope formerly known as VX8. In-the-field collimation required no further adjustments to anything after what I’d done inside, so in went the Nagler 31. And out it came again straight away, for reasons described above, and I stayed with 100x or higher for the session. The overall impression, compared to when I last looked through this scope as a necessarily-grossly-miscollimated VX8, was one of joy and beauty, no more nasty coma! I’m very happy with it now, with only a few tweaks left to do.

First up was the Leo Triplet, only because I’d written it down first. All three, M66, M65 and NGC 3628 were easily on show. I was surprised, actually. I last observed these a month or so ago with my 300mm and in my dark skies they were of course impressive. I was expecting them, especially NGC 3628, to be visible but spoiled by my experience at 300mm. Not so, they were very satisfying to look at. I couldn’t get all three in one view, of course, but next time with the extra out-focus, I shall!

Anticipating a wide-field experience with the relatively short focal length of this scope I had M44, Praesepe or Beehive on my list. 100x magnification notwithstanding, it was still a very nice view, the trio of triplet stars at the centre all in view. Beautiful pinpoints.

I haven’t looked at M13 since last year, and knowing that globular clusters respond very well to larger aperture, I was expecting an underwhelming sight even here in an 8”. M13 was pretty much the first thing I looked at when I got my very first scope a few years ago in mag 21.8 country. That scope was my Skymax 180, i.e. 7” scope also with c. 33% obstruction, and I recall I was, if truth be told, a little disappointed then. I’d previously seen M13 through a friend’s Mak 127 from London as a dim homogeneous smudge and had been expecting Wow through the 180 in dark skies. I recall it was merely a brighter homogeneous smudge. So I was expecting similar last night, and was very pleasantly surprised to see a dense cluster of actual stars all the way to the centre. It was impressive, and I was extremely pleased. I’m starting to really like this 8” newt.

Next on my list I had the Cat’s Eye Nebula. I typed in NGC 6543 to my Nexus DSC handset, pushed-to to the region, and saw nothing. I looked at the Nexus’ information on NGC 6543 and it told me it was the Snail Nebula. I assumed I’d typed the numbers wrong and the Snail Nebula was some indistinct AP object far beyond visual, and moved on. In fact they are one and the same. I’d only roughly aligned to start with and should have slewed around to find the Cat’s Eye: I’m familiar with it and it should have been easy. It was obviously just out of my FoV.

Iota Cancri, a competitor to Albireo by all accounts as a blue/yellow double, was next. I found it easily enough, but was barely able to detect the colours, but really nothing special, certainly no competition to Albireo or its superior, Almach. A little puzzled, I looked up to see I was looking through cloud! No wonder. And it didn’t seem to be about to disappear. Next!

I went to M52, also cloud-underwhelming. Next!

Nearly finally, I chose what seemed the only unobscured patch of sky remaining, near Vega, and chose Epsilon Lyrae again, which looked so amazing recently through my 4” LZOS. This view was similarly crisp and clean, even at only 100x. But it was NE-windy by now and I only got brief still spells between gusts.

Finally of all, I went to Izar and confirmed that this scope performs well. Easily split.

It would have been nice to try to see some of the Ursa Major objects, M51, M81/2 and the other more difficult ones all of which I’ve had incredible views of with my 300mm, but they were all basically straight up, in the dob “alt-az hole”

So, all in all, I’m very happy with this scope, with a good few improvements to come. Not least replacing the 63mm secondary (CO 31.5%) with a 50mm one (CO 25%) which ought to make a noticeable difference. And as you can see from the final “put-away” pic, dew happened! But no effect on anything inside the tube.

Cheers, Magnus

Just saw Mercury first time this year. 60x with the Kowa 88 spotting scope. Very definite 45% phase going on…

Hopefully more to come later for First Light with my finished 8”:

Magnus

On 24/04/2022 at 22:39, markse68 said:

… Are you planning to trim down the mirror clips on the OO cell? The previous owner of mine had chopped them off really short so they only catch the bevel which works fine if you adjust the nylon grub screws so the mirror can’t move sideways and clear them.

Mark

Yes I have a number of things I still want to do. One of them is just what you say: to grind off the excessive diffraction-contributing overhang of the mirror-clips and replace them with the minimum necessary to stop the mirror from falling forward when inverted.

Also the secondary is bigger than I want. 63mm, i.e. 31.5% CO. I’m strictly visual so I’ll be getting a 50mm secondary at some point.

M

Bracknell not far from Wokingham, which is where @Stu used to live … he’d be a very good person to guide you as to local spots 

And welcome to SGL,

Magnus

I went to the hardware shop today and got some hinges. @Roy Challen. A little drilling of a few extra holes later, my rings work as they should, no bungees in sight! A little black paint tomorrow and nobody would be any the wiser!

Ready for First Light, whenever that may be…

1 hour ago, ONIKKINEN said:

Nice and shiny tube, looks very nice!

Curious as to what this bit is though, ventilation hole for the fan on the cell to pull air from in front of the mirror or just some placeholder thing?

Haha that was the other thing I thought I'd wait until someone else noticed before talking about it! You suggest it might be "ventilation hole for the fan on the cell to pull air from in front of the mirror". Well, yes it is, er, sort of, by default though.

There are two explanations:

1. I'd designed the whole thing to the nth degree, worked out where I needed all the holes etc etc. I measured and measured and checked and checked before drilling all the small holes: spider-holder holes, mirror-cell attachment holes, finder-bracket holes, and the single pilot hole to act as a guide for my 80mm hole-cutter for the big focus-tube hole. I have to say, I drill very nice holes with great accuracy, working up from 1mm hand-held spotting-indentation, drilling then all the way up to the required size. Very careful. Finally I got my 80mm hole-cutter, run backwards of course for easier cutting without catching, lovely smooth and also a good job. Lovely lovely. 10 seconds later I realized that I'd used one of the spider-holes as my pilot hole, not the focus-hole pilot hole.  ........................................... Oh God. Oh my God. You can imagine the stream and volume of swear-words as I strode around the house holding my head in my hands. How could I be so BLOODY STUPID!

2. In the design phase, I had given a lot of thought to the thermal management of closed Newtonian tubes, especially extremely well-insulated ones like this with its epoxy-carbonfibre skin and 5mm hardfoam inner liner. I had genuinely been mulling about creating a focsuer-sized ventilation hole near the primary mirror. But in the end I decided to "go conventional" to begin with , and decide later.

This stupid mistake made my decision for me. Once I'd calmed down, I realized I could simply turn the tube back to front and start again. Which I did, being very careful second time to use the correct pilot hole! Hence the makeshift "hatch-cover". If you look carefully at the images, you'll see various random "unused" holes and bits of tape covering holes, the collateral damage of my idiocy.

You also say "nice shiny tube". It is, of course, it's beautiful, but more to the point it's extremely stiff, more so than I was expecting. Exerting some serious force to the laser when in the focus tube, I could not get the spot to move. Very pleased and well worth the wait for Klaus Helmerich.

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

56 minutes ago, Roy Challen said:

Err, you will be getting some proper tube rings for this won't you?😀

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.

3 hours ago, Greymouser said:

Excellent job. Yes I am jealous of the lovely scopes, your skill, but most importantly that view from your window!

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

1 hour ago, Kon said:

I just finished observing Mercury for the first time through my telescope! Awful seeing but so satisfying to bag it. Between the disco ball colours and wind, i managed to make some of its phase, looked like 3/4 full, give or take with the seeing. I have now managed to see all planets in our solar system! Super excited. I managed some imaging so i will see if can pull anything out of them.

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

12 hours ago, F15Rules said:

Wow!! 21.97 sqm??

I'm betting you're in West Cork at the moment then...not Middlesex!!😂😂

Amazing sky that must have been👍..

Dave

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