Fo_Cuss

Thanks for that link fozzy :) Sourcing supplies in France is always very difficult. As it stands, I will be trying Black 3.0 ... because I've researched it, and ordered the product. We will see how it goes. If it is a fail, then I will resort to traditional methods 🌝

Belt & Braces - Best Laid Plans Solving Resonance (again) Having got to grips with resonance, I moved on ... but the brain keeps working in the background. The solution it came up with, was 'felt washers'. It seemed hard to disagree, even though the scope does not now resonante to any great extent. However, this is now, and the scope isn't finished. Consequently, it does appear to be a sensible course of action to further separate the scope from the 'U' bracket ... and fortuitously add some damping to the clamp assembly. Felt seems to be the most likely candidate for this task. Having said that ... it is just theory; though sound enough to locate and purchase the washers. Evidently, what I needed were 'fishing rod spool, clutch washers' (who would have thought it?) 25mm x 8.5mm x 1mm The idea is that these will be soaked in a light grease, and placed either side of the scope tube, between it and the U bracket ... allowing smooth rotation, whilst providing damping. I bought them from Dave in Manchester. You maybe know him ... he runs Trafford Tackle Repairs and has an ebay site purpldsere ... a friendly helpful chap - the sort that you like to do business with. Scope Expansion The chimney flues were looking great, until I contacted the trader ... not in stock, don't know when.... Worse; nobody seemed to stock this kit. ... and finding a 100mm to 60mm reducer, is like finding rocking horse droppings My search finally fell upon custom car exhaust tips. ... and out of that lot, I found this : It obviously need a lot of working. The outlet end is rolled, and I will surely be forced to hone out both ends, to accept the 61.5mm scope tube, and the 100mm extension tube. Talking of 100mm Extension Tube I think that I am going to initially try a plastic downpipe. Nobody seems to have the short length stainless, and I can get it in plastic just down the road for €5 (2m). I need to examine it; but only 250mm (or so) is needed. It should be rigid enough, and of course, it can be reinforced. To be honest ... just getting a tube that will fit, is my main objective ... the rest will then fall into place. Lens Mounting Shoulder I was looking at 100mm internal circlips, but by now I was suffering 'spending fatigue' (typically a male condition) ... I'll get over it Once I have everything in my hands, an adjustable shoulder will present itself ... and with the laser calibrator, all will be well. So the die is almost cast. Money has fled from my account, in all directions. Updates to follow 🌝

From what I can gather (from the charts)... Black 3.0 is substantially superior to Krylon. I note that absorption varies between 94% and 95%. However, without the test report, the results are meaningless. The YouTube videos show that, if the paint is not properly applied, the results will not be ideal. Did the testers correctly create the coating? Typically the answer depends upon who was paying for the test 😉

Looks interesting, but I couldn't find the link to the experiment - tried loads of search terms. Do you have the link?

Thanks John, for that advice and link I may need it. However, I'm very tempted to try Stuart Semple's Black 3.0 It's not that I'm looking to cut corners. If the paint can absorb 99% of light ... it may be as good as gets. ... and there are further considerations. I want to black the edges of the lenses ... therefore I anyway need a suitable paint. The scope is to be a refractor. Hopefully, this will mean that all the light entering the lens, will be directed to the focal point. ... this presuming that the lens shroud has been appropriately flocked. It will be a great experiment ... and has potential to form the basis for a genuine video review of the paint (much needed). Also, it will add to the knowledge base for other DIY scope builders that follow. Let's see how it goes. We can but try 🌝

Flocking the modern way - will it work? I'd talked earlier about looking into a paint solution, thinking that the ultra black would cost an arm and a leg... In fact, this is not the case. Yes, the nanotube black is way out of budget, but there have been other developments. A British Artist (Anish Kapoor) developed an ultra black acrylic paint, but refused to share it with the community. This caused outrage around the world (presumably, all publicity is good publicity). Another British artist (Stuart Semple) set about creating his own version - Black. ... available to everyone in the world except Anish Kapoor - hahahahaha! Through feedback and further development Black 2.0 was released. This absorbs around 96% of light, and costs £12 for 150ml covering a claimed 2m x 2m. (a very reasonable price - no different to consumer grade black bases) Apparently, this is a usable paint, self-priming, with a stable surface. Black 3.0 followed (currently Black 3.2) - £15 for 150ml This absorbs around 99% of light. It requires a primer, and the surface finish scratches easily. Application The good news is that both versions can be thinned with water. In fact, multiple thin coats produce the blackest finish. A matched primer can be purchased, though Black 2.0 is stated to be excellent, ensuring that only a small quantity of Black 3.0 will then be needed. Otherwise, any acrylic primer can be used - presumably, the darker the better. What this should mean, is that a solution could be swilled around tubes, multiple times. Far easier than struggling with sticky backed material. Also, it can be used for lens edges - simply painted on. It should mean that everything that requires blacking, can be blacked. YouTube Reviews They are almost all appalling. I can't get my head around why you would buy a hight tech paint, and not read the instructions ... and if you were producing a review video, it surely would be a must. But no! All but one, simply squeezed a glob out, didn't add water, didn't prime the surface ... and then complained about it. I finally found one, that primed the object with Black 2.0, and finished it with Black 3.0 (a beta version). It's worth a look. He does an interesting test, wherby you cannot tell which way the object is rotating. ... and the finish is exceptionally black. It doesn't stand up to laser light, but my guess is that it will be perfect for our needs. I intend to buy it 🌝 Tubing Update Managed to get into town today, to check out flue component availability. Very limited - nothing anywhere near what I need. On the bright side; I was able to get a feel of stainless flues. Very nice and light. There were some ferrous steel examples, that were extremely heavy, by comparison. Overall, the trip was worth it, as it confirmed that stainless steel flues should be ideal for a scope 🌝

Solved - Lock Shaft, Vertical Axis, Resonance Lock Shaft The shaft slides through a rotating lock. As the front of the scope rises, the shaft angle changes, and the lock rotates ... the screw acts as the axel, rotating in a hole in the U bracket. The problem was that the bracket metal is too thin, and the hole too large, and it's spinning on a couple of screw threads. Even after I had replaced the nut with a nylon lock nut, the screw axel had way too much play. ... and the turning force from the shaft, is always going to be one sided; causing the lock to waggle around. This would cause the shaft to bind. Rubbish! There should have been turned a short spigot (then the screw thread) with a sliding fit into the hole in the U bracket. It's less of a problem when a component is freely rotating (like the scope) ... but with the shaft pushing and pulling ... no chance! I had no option but to fit a sleeve over the screw thread, and enlarge the hole to fit. I ended up cutting down an old biro pen: This was a right pain in the neck, but with the help of a butane torch, and reducing the thread diameter, I got it on. Brilliant! The lock is now forced to rotate concentrically, regardless of the unbalanced force from the shaft. Smooth 😎 Vertical Axis - The Horror The shaft was tapered, but the bore wasn't ... and the top diameter of the taper was slopping around in the bore. It's only hope was that the U bracket shoulder could clamp down on the top face of the tripod ... but the clamp assembly was a failure - the design prevented any clamping action. Consequently, I broke off the clamp limiter (central plastic spigot), allowing me to pull the U bracket down onto the top face of the tripod. I packed the bore with PTFE and thick grease ... and by some strange good fortune, the clamp screw spins, without unscrewing itself (what!) The scope rotates beautifully now ✌️ Scope Resonance With the horizontal axis scope screws (up and down) loose, resonance had been effectively eliminated. However, I wanted some clamping pressure on the scope ... enough to allow it to glide, and to hold it (when in position). I discovered the problem. The U bracket was too wide. When the clamp srews were tightened, the U bracket became highly strung under compression. This was the root cause of the resonance. I fitted 3 washers to the side opposite the lock shaft, and 1 washer on the lock shaft side of the scope: This arrangement created a better alignment of the lock shaft. Hahaha ... it maxed out the lock shaft function 😀 It also transformed the scope movement action. The scope now glides up and down, at the slightest pressure - zero jerking at start of movement - Wow! ... and when the pressure is removed, it stops in position. It's ...... Victory! 🌝

Thanks John ... yes, that is true. I think that the point being made by Mike, was that the scopes of that era were much longer than of today. Having said that, I note your advice that my scope length would fall into the usable category for these type of eyepieces

Actually ... the next step was to reflect. It's always a good move, when carrying out a project. it's all too easy to press on regardless. The concept of 'make a decision and stick to it' can easily end up with a wrong path being chosen. ... particularly when in a fog 😉 The eyepiece thread is producing good information ... more to come perhaps. I took some time off, to re-examine the resonance question? The fundamentals seem to be solidifying. It appears that the key problem areas are: Horizontal & Vertical Axis The horizontal axis is via the two lock screws, through the 'U' mount, into the scope tube. Screwed tight, the resonance period increases. Learning this, was the breakthrough in understanding that the core problem revolved (ouch) around the axis 😀 Of course, it's obvious once you know (typical)! The solution lies with the semi-loose lock shaft - connected from the tube horizontal centre line to the 'U' bracket (below the centre line). Yes, locking the shaft helps. However; by unscrewing the tube horizontal lock screws, the scope has close to zero 'horizontal axial resonance' ! Nice! What is happening here? At first glance, you might think that, by locking the H axis, this would improve rigidity (locking the triangle). However, for resonance, it is different. If a tube was lying on the floor... If you pushed it; it would simply move (it wouldn't vibrate) If it was fixed in the middle, it would swing one way, then reverse, then reverse again - the undulations getting ever smaller. The reverberations would continue for a very long time, because the energy of one swing, is mostly conserved by the metal spring. ... a bit like a pendulum. Why not pivot around the lock shaft screw? Ive fitted an 'O' ring to the screw The scope is resting on the lock screw threads In both cases, the enrgy is not conserved. Hence, when the scope is tapped ... it vibrates for only a few milliseconds. How to apply this knowledge? The ideal would be (I think), to fit a second lock shaft on the opposite side of the tube, towards the rear of the scope ... using different geometry. (If a second lock shaft was fitted in mirror image to the first, we would simply create a new pivot point around the 'U' screws) A second lock shaft might provide an additional benefit... The two lock shafts could be left almost loose, to allow free flowing movement of the scope. Whether this development is required, is another matter, because the lockshaft itself, needs further development. It is simply too crude. The shaft doesn't slide without jerking. I have some ideas on how to solve this problem....

Thanks again Mike. Yes, I see the logic. Those eyepiece designs were created in a distant era. All this information helps fill the gaps

Thanks for that input Mike BTW I like the sig "Many look, few observe". To that, I think that I would add "and reflect". RE the long F ratios I had thought that F11 was towards the long side, but when I calculate 700/60 I see that = F11.6 So by choosing a larger lens (93mm) ... even though the scope will be extended an additional 300mm, the focal ratio actually drops. Are you aware of the fundamentals (concerning effect on the eyepiece), or was your statement based upon experience? I'm guessing that the light angle (from horizontal) is too large for the lens design. Presumably, a longer focal length would bring the light angle into the spec of the KSON Super Abbe Orthoscopics? The 'blurb' never discusses such matters. (In every field, the blurb never does) ... it leaves the new entrant with lots of basic questions; like: My starter scope has a 60mm lens, rated at f700mm. Yet 700mm measurement is only achieved with the focus tube fully extended. Is that because it was primarily designed for use with a 45 deg mirror? Is the focal length derived from perfectly parallel light? By that, I mean: An object at 10km is not producing parallel light. Neither is the moon. The sun is said to produce parallel light ... but clearly, distant stars more so. What isn't definitively clear to me, is the focal length at each of the 4 instances for any given lens. The lens has an ability to bend light. Logically therefore, for closer objects (the light spreading outwards), the point of focus must be a greater distance than with parallel light. I saw this, when testing the scope on an object at 10km. The kellner type lens had to be extended outwards from the housing (focus wound out to the max). Yet with the 45 deg mirror in place, the focus tube had to be wound in. It is obviously simple maths, but you know ... it's only simple when you have grasped the fundamentals 🤪 Why bother with the fundamentals? Well if you have seen my DIY thread... You'll know that I am modding the starter scope, and extending it by 300mm. However; maybe I should extend it 330mm ... but maybe that would be good for inverted viewing, but not with the 45 deg mirror. ... and what about fitting a full horizontal & vertical flipper unit ... how might that effect the extension length choice? These minefields are prepared for us to walk on ... and usually it goes BOOM (without foreknowledge) ⚠️

Merlin66, Ah! That explains the SLR adapter contraptions that I fell across, during research. It is something that I will look into. My own method was to fabricate an eyepiece diameter tube, permanently fixed to a smart phone spare back; aligned centrally. I had trialled a 'bought' bracket, but it was useless. My design was perfect for the job. It allowed instant changes of the eyepiece - simply push in and mount. Perfect alignment every time. Not the most aesthetically pleasing design. Rather; 'function over form' Great for when with one's son, as both get to see what is going on. ... and of course, images can be recorded by simply clapping one's hands (no vibrations). My guess is that the moving mirror in an SLR might not be so forgiving. No doubt this is why there are simple chip based systems. I saw one, but didn't pursue it. I need to find it again, and look deeper.

Thanks for those calming words From what you say ... 'going with the long focal length' was the right move RE the exit pupil and eye relief (is this AKA back focus?) When testing the scope in its original format (with kellner lenses)... I found that digital viewing produced the same image that my eye saw, only that it was a far more relaxing experience. Further; as light fell, the camera software auto adjusted, and produced viewable images that by eye, could not be seen. The only problem was that the camera lens had to be too close to the exit pupil, slightly cropping the circle. For this reason, I was less concerned about the small exit pupils of the Abbe and Possl. However, I do need to research the back focus distance. If all eyepieces will work fine ... I can select one with a suitable eye relief distance

The scope spec is firming up to be d93/f1000. I'll either use flocking material or create a trillion indentations in the surfaces (with peening machine), and use matt barbeque paint. A laser calibrator is on the aquisition list. Consequently, everything should ultimately be at 'best possible'. I will likely need some guidance on the doublet air gap. Other than that ... with trembling anticipation... May I ask for views on suitable eyepieces? I've read a few of the threads on this forum. It seems that many eyepieces fall short of expectations. Also, Ive noted that people have talked about the effect of long focal lengths on specific designs. Either way, I have an initial list, made up from what seems available at reasonable cost. I intend to carry out both terrestrial, and extra-terrestrial viewing. Perhaps these different fields require different eyepieces? *** TMB/Burgess Planetary II I've read the 'touchy subject' thread. I understand the issues, but I'm not in any position to take sides. The design seems to offer a 'free lunch', with remarkable 58 deg viewing. However, I've read reviews on this forum, talking of ghosting, and scattered light. My intention is to blacken the scope internals as much as is possible - perhaps this will be enough? Kson Super Abbe 4 lenses - apparently popular for over a hundred years. Celestron 1.25" Omni Plossl 4 lenses - apparently popular for a longer period than the Abbe. In the same Omni range, Celestron offer a 2x Barlow (2 lens). *** They all purport to be good lenses. The Celestron range is cheaper, but hey, they might be just fine. Are any of them good for both day and night viewing, or should I be looking for specific day and night eyepieces? ... and which eyepieces are better suited to a 93/1000 refractor scope?

I'm just now speccing the design. It looks like it will be an airgapped doublet 93/1000, with , as yet undecided eyepieces. I'm just now heading over to the eyepiece forum, to learn why every eyepiece on my interested list, is rubbish 😀

Lenses, Calibration, Tube Upsizing, Flocking Eyepieces I've added Celestron Omni Plossl eyepieces and 2x Barlow, to the consideration list. The Barlow is 2 lens, and the eyepieces 4 lens. I note SGL has an eyepiece forum (that I will be using). I've already perused it, and found it fairly horrifying 😲 ... expensive eyepieces branded as 'useless' 😁 Doublet The starter scope objective lens assembly was dismantled, to reveal two 'loose' lenses, held in place by a plastic threaded cylinder. Neither of the lenses were coated. They were airgapped by 3 small strips of tape, at the perimeter of one of the lenses. Upon examining the images of the available glued lenses; I could see no evidence of any airgapping method. From this, I presume that they are not airgapped. Research indicates that an air gap improves focus ... leading me away from selecting glued lenses. ... though perhaps they are better aligned for eccentricity, as I note that each lens is always marked at the edge. Does anyone have any knowledge of this? If this is the case; with the starter lenses being installed loose ... this may be another reason for the scope's poor focussing (with the lack of coatings). A laser calibrator is available. Perhaps this will be a required item, if focus is to be maximised? The annoying aspect of the objective lens, is that the simple plastic 'lens enclosure' is priced around €18 - the same price as the laser calibrator!!! I guess it is their high profit item. Tube Upsizing This went very well ... ebay to the rescue, for rapid viewing of what is available. It looks like the best bet will be stainless steel flue adapters. They offer many options, but critically, 60mm/80mm and 60mm/100mm are available. Of course; they match the spacer tubing ... meaning that the correct focal length can be achieved. The key feature is that the 60mm end goes inside the 60mm tube ... and the large end goes outside the tube. This should work perfectly; though an additional perimeter spacer will be required for a 93mm D lens. A 100mm D lens would be ideal, but they all seem to be 104mm or 106mm Flue adapters might sound a bizarre choice for a telescope ... and further, they are not swaged or spun. Instead, they are welded. However, they will be machine made, so effectively concentric enough. Ha! That laser calibrator is looking more and more like a required purchase At this moment in time, I believe that 60mm/100mm is the best option. This would accomodate a 93mm objective lens, with wiggle room for calibration. I don't know how I will mount the lens (yet). Something will surely fall out in the wash 😉 Flocking The material that I've seen, is glue backed. ... so likely to be a very messy job. €8 gets 0.5 m long x 0.7 m wide about 0.5 mm thick This is when that new ultra black paint would come in handy. I'll look into it, but I expect it to cost at least an arm and a leg. I do have some matt black barbeque spray paint. Does anyone have any experience of this as an alternative to material flocking? Next step, is to visit the local hardware stores, to see if they have the flue gear in stock. Having the kit in hand, is always useful. Oh yes ... and try to finalise the eyepiece strategy

Made some progress, and better understand the doublet type lens. Objective Lens The two types readily available are glued and airgapped. At around €40 delivered (plus risk of taxes), I've found a 93/800 glued and a 80/900 airgapped with mounting ring - both multi-coated. I have yet to draw out the angles, and look for tubing; but I presume that a suitable arrangement can be found. My understanding is that greater focal length is beneficial, but perhaps more so the lens diameter. Also perhaps; the air gapped lenses might provide better focus of all light beams. Does anyone have an opinion on the 93/800 glued vs 80/900 airgapped? Eyepieces The eyepieces produced a good deal of researching ... many of the links coming to SGL :) They range from €6 upwards. The 3 types that I concentrated on was in the €35 - €45 bracket Burgess €35 Kson Super Abbe €40 TMB €45 All are multi-coated. Both the Burgess and the TMB, are housed in TMB Planetary II enclosures. I note that this is a touchy subject (as reported here on SGL) I have no idea what the difference is ... perhaps just the name. The blurb for the Kson Super Abbe sounded great (as per usual), but some reviews suggested otherwise on SGL. However, that was back in 2011 ... perhaps the manufacturing techniques have improved. I note that both TMB types have a standard final lens diameter (and extendable eyeguard) - FOV 60 deg ... whereas the Kson final lens, reduces in diameter - FOV 30 deg - 50 deg Without knowing anything more ... the Burgess seems to be a reasonable bet. I'm wondering if the Burgess will also be okay for terrestrial spotting. Their web page mentions 'light scatter'. Does anyone have experience with the TMB type eyepieces? Anyway, the project has gained direction. I need to now make strides with the tubing, and the focus angle. :)

Thanks for the welcome guys. I'm up for building a telescope, but I think that I'll avoid the hand grinding for the moment Rick 🤫

Hello everyone I'm a new member, looking for some fundamental advice on gaining 'focus'. I have a starter telescope 60/700 with 4, 9, 12, 20 mm Kellner type eyepieces. It's okay (read rubbish), as it provides plenty of learning potential - it having major viewing issues that might otherwise have been masked (if it had been built to a higher specification). Plus, there are no concerns over 'messing it up' - a liberating concept 🤨 The project To gain a telescope that will focus. Here's a very brief outline of where I'm currently at: Tripod It has a telescopic tripod with a 'U' bracket azimuth mount. The first thing that I learned, was that the system resonance could be dramatically reduced, by not tightening the central horizontal axis mount shaft. An O ring was fitted to the sloppy vertical axis lock shaft, and a plastic pad installed to the lock screw faces. Then all the joints and lock faces were lubricated with silicone grease. From a user perspective, the tripod was born again. However, the horizontal axis lock screw was a beautiful fail. When locked, the whole system resonated when touched. Leaving the shaft to run free, solved the issue. Resonance now only occurs in the telescope, and this, only for around 1.5 seconds. It was a big lesson. I'd noted one user (with a balanced EQ mount) talking about stabilisation taking a few seconds (after each touch). I came to the conclusion, that the tripod and mount would ideally need to be heavy and rigid. This drove home the concept of 'the gulf' between upgrades - perhaps applicable to all aspects of a telescope. In my mind, I figured ... don't expect a 'fancy tripod and mount' to solve the problem - it would need to be an expensive 'fancy tripod and mount'. I'm thinking of adding weight, to further absorb the resonance. Also, a PTFE washer might be of benefit. Telescope Single lens. The manual has no reference to it being Achromatic, but my guess is that all scopes are now sold with this type of bonded lens. The image circumference is blue when viewed. The manual states that the eyepieces are kellner type. The focus tube slides in a plastic housing, on PTFE strips. The rack is chromed plastic. The pinion is spring loaded brass. Tensioned up, it has no lag. The adjuster rotary knob is too small - I intend to increase its diameter, to gain finer adjustment. ... however... The view is not sharp, regardless of position. Solutions (advice required) My concern, about buying a better scope, is that the jump in quality might not be worth the money. The Celestron 90/1000 is available for around £140 delivered. A bigger aperture, and longer focal length, might dramatically improve the problem. However, I watched a review video of the Astromaster 70/900, and the images were barely any better. I'm guessing that the lens is the same, only bigger. The 90/1000 is surely better still, but, as a consequence, I'm thinking that the solution lies with: Superior lens - perhaps the same crystal, but coated. Two lenses (doublet) Superior eyepiece The problem is 'lack of specifications', and lack of lens suppliers. - every telescope site that I visited, listed every component that you could desire, except lenses. I guess that everybody goes directly to China - I can do that. Superior eyepieces are interesting, because @ 1.25" they are standard, so a good investment regardless. The questions are : Will a superior eyepiece solve the focus problem? What coatings should I specify, for new lenses? Is doublet the way forward? Regarding my current tube I'm thinking that I could simply add tubing, to build the diameter (for a larger lens and focal length). I'd then have to add counterbalance weights (or move the mounting screws). The doublet lenses, and superior eyepiece would probably cost less than £140, and I'd have a far superior scope compared to the single lens Astromaster - maybe

It's that time of year, when the skies are overcast. Perhaps the next best thing to using a telescope, is talking about telescopes ... at least, that's what I'm hoping 😁 Fo