Hello all, I'm looking for a company (or person) who could make a custom threaded adaptor, essentially a step down T2 with an unusual thread on one side - M53x0.75mm male to T2 male. Any leads that anyone is aware of? I have found a company in the Europe area but outside of the EU. The adaptor plus shipping is about 45eur so will end up being closer to 60-65eur once you add the import charges and tax etc., which is quite a lot of money for a small adaptor!

I have a bunch of notifications for saved searches on specific astro gear (mainly 0.965" EPs) for that well known auction site, and there is someone based in an EU country whose items often show up in my searches. Whilst they are often harder to get hold of items, most of these things have been listed at vastly increased prices (200 eur for a late production era CZJ Huygens anyone?). Many of them do not sell and yet keep getting relisted either at the same price or occasionally reduced but still inflated. I'm not sure I really get the logic.

Saw the above while having a browse through Ebay seeing what was on offer for a new member who wants a starter scope with a budget of 300 UK quid... AND went OoooHHHH. Quite a bargain with the Losmandy G11 mount. Just a 'little' drive down to Italy 🙂 https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=losmandy+g11&_sacat=0&LH_TitleDesc=0&_odkw=losmandy+G8 If anyone is interested in a C11 at 33% of the price I would take the Losmandy @ 67%... The only problem being.. The item offered has a 99.99% chance of being a total SCAM 🙂

I think that is going to come down to experimentation. We always had an ammeter in circuit so once you know what works it is easy to repeat. I would not expect aluminium wire to glow before producing a vapour in vacuum. It may start to sag, though. One other thought that has occurred to me is that aluminium oxidises in air to form a thin layer of Al2O3. You won't want any oxygen in there when it vapourises, so will need to clean the wire immediately prior to use and not touch it with your hands. Lots to think about.

@Mandy D so far so good with the peripheral bits and pieces. As to the method- I assume that once the rig is 'glued' together the general idea would be to start the variac at a low voltage (any suggestions as to how low) then slowly increase it until the aluminium wire begins to vapourise?? I came across someone within the Ice in Space forum, Oz based, that aluminises via home edition. Trying to join their network to ask a few questions. Alas, so far the application seems to be in limbo. Possibly because Oz regards CZR as containing spies for the Kremlin 😞

@AlentejoSkies in case you hadn't seen

Yes, that looks like it might well work.

Hello folks, If any of you are around in Berlin next weekend I will be visiting the Lange Nacht der Astronomie (LNDA) at Tempelhofer Feld, and taking a scope with me. Would love to say Hi to any SGL members who are also visiting. https://www.planetarium.berlin/en/lnda

This one is a little closer! Should have looked a little closer at the specs of the previous one 😞 Comes from running around in a daze looking for the base plate for the bell jar 😞

The Variac seems properly specified and should work well for this application.

The specification seems messed up. A power rating of 100 W with a 230 V secondary rated at 24 A? I get 5520 VA for that, then add on the other secondary ... That is 100 VA, which must be the 100 W they specify. The weight is given as 1000 kg, which is clearly incorrect, yet 1000 g would be nowhere near heavy enough for the ratings as calculated above. Have you seen a photograph of this thing in which the size is clearly discernible? I'd be cautious about parting with the money for this.

As to a variac. Has the item as shown below qualify?? I am certainly becoming far more interested (thanks to you Mandy) within the field of aluminising than waiting for a clear sky to trip over something or other on a dark night! A wonderful new 'hobby' 🙂 The sky's the limit! A gold plated telescope mirror!!!

Mandy, you are a 'fairy godmother'! Cannot express how much I appreciate your advise! OK to practicalities... Would the toroid as appears below be sufficient?

Yes, that is exactly what we are looking at - low voltage, high current. The high current will ohmically heat the aluminium to close to melting point and because it is in a vacuum, the aluminium will boil off it's surface to produce the vapour we need and then deposit itself on everything (literally, everything!) in the chamber. Have a look at the photo. Note, I have secured the ends of the winding to the adjacent turns with cable ties. The blue wire is 6mm². Apply the rated voltage to the primary (presumably 230 V) and measure the voltage across the new secondary. Divide this by the number of times the wire passes through the centre of the core (6 in my photo) and that will give you a turns per volt figure that you can use to determine your required secondary turns. Obviously, the voltage will fall a bit under load, but the Variac allows you to adjust it, so don't worry too much about that. You can safely increase the primary voltage by about 10% or so above rated. 6mm² should be OK for up to about 60A or so for the short period you need to run this. You will need short, heavy cables to the aluminium wire in the chamber to minimise volt drop.

Ooooh. Now let me attempt to work the above out 🙂 as experience with electricity only runs to making a few valve/tube amplifiers and other simple projects! (I shall leave out the wiring projects that might bring consternation to the supply companies... and other interfering authorities). Thus- Wind turns of insulated copper wire as an additional secondary coil around an existing toroidal tfmr whose primary is fed from the output of a variac connected to the mains? Have I got that part right? The 'extra' secondary is then connected to the aluminium wire to slowly vaporise it.... A low voltage high amp supply I assume. Due to your expertise, this thread (to me) is becoming fascinating 🙂

I'm not sure you want to go with either approach with aluminium dust, other than as a fun experiment, but I would seriously try to get a suitable transformer rather than using mains. Two possible approaches I would consider for vapourising aluminium: The first one is similar to the way we did it in the semiconductor lab, but you won't have access to a thick tungsten wire coil, so you might consider experimenting with a short length of heater coil from an old fan heater. This is usually a nichrome wire and if you put a length of aluminium MIG welding wire or similar down the centre of it and slowly(!) increase the current using a low voltage transformer supplied by a Variac it may work. I'm not sure whether you will get any impurities in the aluminium vapour - most likely you will - but it may work OK. The second method is to heat the aluminium directly using an electric current. If you slowly increase the current, using the above method, and keep the temperature of the wire below melting point it will vapourise aluminium from the surface of the metal and eventually, before the wire burns right through, coat everything in the chamber with a thin layer of aluminium. This method should result in lower impurities. The biggest problem, for the second method, is getting a suitable power supply and what I would do is buy or salvage a suitable size toroidal transformer, say 200 VA or so and wrap a few turns of thick insulated wire through the core, over the existing secondary and feed it from a variac. I'm not sure how much power you will need or what voltage, but a bit of experimentation should resolve this issue. Ordinary PVC insulated flex will do, as long as you don't let it get too hot. For the fan heater coil, you should be able to run this from a variable d.c. power supply, but you will need one that can supply up to about 4 amps or so. Obviously, these are only ideas and you will have to consider all aspects of safety, yourself.

Mandy, your Hired! My only experience with a smallish vacuum pump has been to evacuate air conditioning units, and in conjunction with a 150mm bell jar to 'rip' the air from high temperature silicon rubber to be used for lead/tin/cadmium castings. Kicking myself a bit as left a huge old electric welder within Australia, the transformer would have been ideal to vaporise aluminium. Hmm maybe the 240v mains would suffice!! 🙂 Just a couple of wires placed within a small pile of aluminium dust, maybe flick the RCD's but no real danger. At sometime or other will experiment with small secondaries that would fit within the bell jar. I much prefer making optics rather than using the finished article. Especially within Europe where the skies are 'miserable'... 😞 Your input/replies are much appreciated. 🙂

Good luck, if you try it! I was vac depositing gold onto semiconductors. We put pure gold wire inside the coils of a heavy tungsten wire filament and the prepared semiconductors on the bottom plate, then put a glass bell jar over it and used vaseline for the seal. First stage vaccing was done with a two stage Edwards mechanical vacuum pump. Second stage was a diffusion pump, which took a very long time to get down to the hard vacuum necessary so we left it overnight. In the morning I passed a current of about 30 amps through the filament and vapourised the gold, which covered absolutely everything in the chamber. Then air was allowed back in and we could lift the bell jar and remove our items. It's not the simplest process to get right, but it works well. Admittedly, I've no experience with telescope mirrors, but one of my physics lecturers did a lot of them using the same process. I hope this helps if you decide to give it a try. You will certainly have fun. I know I did.

Thanks @Stu and @Grant! Really appreciate you doing this 🙂

Yep, after some discussions downstairs, Grant has kindly setup a European Buy/Sell section. Hope you guys find it useful, and you can run the club in parallel for any discussions just of European relevance, or whatever you chose. Enjoy 👍 Stu

Actually, this might be a moot point; I've just noticed this exciting development in the classifieds section of the main forum:

Hello all, So according to the mods and forum rules, we must use the normal classifieds section for any sales, which makes sense. That said, as it's a bit difficult to know that an ad is from an EU member, I had two thoughts on how we might make it a bit easier: 1. Mark in the title that it is an EU sale/wanted 2. Link to that post in a 'Notifications' thread here, which members who wish to be notified can follow It's an extra step, but this way anyone who does want to notify our little group can do so easily. To ensure that we don't spam anyone or break any rules, we would obviously need to be fairly strict about what can be posted in that thread - just links to classifieds and a simple message such as 'New for sale post' , 'New wanted post", and no buying or selling direct in the thread. Assuming that this isn't an issue with the code of conduct, does this make sense? How do we feel about it? Would love to hear feedback (even if you think it's a stupid idea 🙂) or other ideas. Thanks!

Oohh arrrh- appreciate the suggestions, however, they are thwart with problems. One being, my Czech is limited to about 50-100 words! Thus communications would be somewhat difficult, especially within technical fields... 😞 in anycase not sure if I would like the experimentation which most likely would need several attempts necessitating travels to Prague or Brno. The principle is simple enough, its implementation might require a certain degree of prior experience. However, your reply has me thinking and I will certainly look into a DIY rig to aluminise mirrors! After all it's just a matter of 'exploding' some aluminium dust/wool within a vacuum chamber 🙂 So long as I can experiment at leisure, in my own time... Why not 🙂 Then again, silvering is a relatively simple process, simply avoid the silver azide catastrophe (it happened once in the distant past).... I thank you for the response and suggestions 🙂

I wonder if it is worth giving the semiconductor physics or engineering departments in the universities of your country a call to see if they would put it through their vacuum deposition chambers. I recall when I was in the semiconductor lab at Sheffield that we had quite a large chamber which would take a modest mirror. Perhaps one of the grad students would be happy to do it for you at a local uni.

Not exactly keen to visit the UK 🙂 I may need to travel to Australia early 2023, if so will take the mirrors with me and get it done there. The mirrors are still only 99% figured thus may make another secondary for a Gregorian focus. Silvering them is no real problem, I'm just getting a bit lazy in my old age 🙂