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Michele Scotti

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Everything posted by Michele Scotti

  1. Michele Scotti
    Interestingly silver spraying is avaialbe as a kit in the US (https://angelgilding.com/silver-on-glass/spray-silver.html) and a collaboration started with some ATMs - I'd say they're almost done in proving the enhanced durability of the process + antiaging agent. My understanding is that this is modern approach to Silvering where: there is no hazard it's "easy" for ATMs durability is similar to Aluminium - or at least not as bad as 1y refresh needed- it's in general cheaper than Aluminium - at least for my personal project Would you be able to have a look at the chemical kit? I've got the info below from the data sheets from Angel Gild website. As far as I get it: preparation with "Tin for Silver Concentrate", spraying simultaneously "Sensitizer for 2-Part Silver Solution" + "2-Part Spray Silver Reducer" Tin for Silver Concentrate SnCl2·2H2O Stannous chloride dihydrate 1 - 5 Weight % 2-Part Spray Silver Solution Silver nitrate AgNO3 10 - 25 weight-% Ammonium hydroxide (Ammonia solution 25%) NH4OH 5 - 10 weight-% 2-Part Spray Silver Reducer – C3030 Sodium hydroxide 10 - 25 weight-% Ammonium hydroxide 1336-21-6 1 - 3 weight-% *The exact percentage (concentration) of composition has been withheld as a trade secret.
  2. Michele Scotti
    Hi Nigel, is the process you're familiar with an 'immersion' type? Also, out of curiosity, where the fulminate can generate from? Btw, I need to fetch the list of chemicals involved in this process and post it here
  3. Michele Scotti
    I'm talking about Silvering -as an alternative to Aluminizing-. Specifically spraying Silvering Can't see the use of Nitric Acid in this process
  4. Michele Scotti
    I posted on the specific thread for the 800mm mirror but I guess it went unnoticed. Also I've searched for similar topic on this forum and found out only something from 2013. Anyway - I'd like to go with Silvering (+anti-tarnishing agent). There is a big piece of work that has been done by a group in the US. https://sites.google.com/site/spraysilveringtelescopemirrors/home This is the quite interesting spraying process:: https://youtu.be/2noVRDWppII?t=312 I've contacted the company that sells the kit of chemicals (in the USA) -and that collaborated with the ATM team- but the very interesting price of ca. 130$ for a complete set was brutally met with a 250$ shipping cost mainly due to Hazardous Fees. I wonder if anybody on this side of the pond have ever had some experience with that - looking for some advice. Silver Nitrate in a pretty pure form doesn't break the bank by the look of it.
  5. Michele Scotti
    That blade is the scariest this in the garage! I was surprised when I watched the video - I usually wear heavy gloves and goggles. Safety first! 😬
  6. Michele Scotti
    I was in two minds if this is going on the mirror thread or here on the project. Anyway.... Sub-frame and whiffle-tree almost completed.The frame came up pretty light as it’s all Aluminium yet sturdy – there’s a couple of details left to sort out but so far so good. Here is the sub-frame along with the H-frame. Whiffle-tree awaiting the nylon-covered bearings Here is the video of the build:
  7. Michele Scotti
    CAD is updated now with the collimation subframe and whiffle tree at 45deg +/-20deg Getting on with the work on actual parts too.
  8. Michele Scotti
    Pads for polishing prepared on a full tool - we'll give it a go MOT
  9. Michele Scotti
    As we are getting in the polishing phase I start to consider the coating. Aluminazing is out for few reasons but chiefly: cost and the peril of shipping. back and forth. I'd like to go with Silvering (+anti-tarnishing agent). There is a big piece of work that has been done by a group in the US. https://sites.google.com/site/spraysilveringtelescopemirrors/home I've contacted the company that sells the chemicals -and that collaborated with the ATM team- but the very interesting price of ca. 130$ for a complete set was brutally met with a 250$ shipping cost mainly due to Hazardous Fees. I wonder if anybody on this side of the pond have ever had some experience with that - looking for some advice. Silver Nitrate in a pretty pure form doesn't break the bank by the look of it.
  10. Michele Scotti
    Yeah somehow the link is not working. Here it is again: Yes, it's a quantitative measurement to assess the structural soundness of the telescope - this is a major design parameter when engineering big telescopes like VLT, E-ELT etc... It's not self-explaining but you can measure the wobbling of the structure which is basically what you are experiencing at the eyepiece when touching the focuser or moving the scope or if there's a gust of wind. The reaction of the telescope it's embedded in its intimate construction parameters. You can place the phone vertically where you have the "24" engraved with double-side tape or even with a clamp -just firm enough not to let it move. The idea being that scope and phone moves together. As an external The X axis for the app will be left-right so hit the structure from a side - like the side of the focuser board- with an hammer. Of course doesn't need to be hard at all - you'll see with the sensitivity of the app. Glad that you're interested - speak later
  11. Michele Scotti
    Fount it! I tried on a old-ish Android I have and it works. https://play.google.com/store/apps/details?id=de.bremen.btm.movalyzer&hl=it&gl=US Sorry to pester but if you could do that it's would be of great help
  12. Michele Scotti
    Oh damn! Didn't consider that it's only on IOS. Thanks for looking into that anyway
  13. Michele Scotti
    Hi, as it seems you have a well built big aperture scope -btw congrats!- may I ask you to take a measurement of its natural frequency? It is one of the key aspect of the mechanical performance of a telescope and would definitely help me to benchmark our project. I loosely described it here you have a nice flat area over the focuser where it would be easy to clamp your phone and run AnaHerz - it takes 2min. Kalispera! Michele
  14. Michele Scotti
    Some time ago I introduced the H-frame being a thin Aluminum bonded structure at the bottom of the mirror box. Here is a pic of the item: Bonding was a purposeful choice to stay in line with the spirit of the project i.e. a build that is approachable by as many people as possible that may do not have access to or be skillful with welding. It goes without saying that if you can weld, by all means you should go with that. Now bonding, especially with Aluminum makes people itchy. And for a good reason. The oxide layer can impair a good adhesion with catastrophic results - conversely if taken care of it can yield outstanding performances. Key here is that eppoxy is applied just after the surface is roughed up with sandpaper so that Oxygen doesn't virtually have time to cause harm. Not that is strictly needed, as Aluminium oxidation is not instantaneous although certainly faster than the more obvious ferrous reaction. What I came up with is a specific, unscientific, uncontrolled stress test. The result is ongoing: as of now 6cm^2 (ca. 1in^2) could take 25kg (60lbs) for 2 months.
  15. Michele Scotti
    That's Planewave direct drive specification - 10 ticks/arcsec. Maybe it works with less but they kind of set the standard in case the DD is coupled directly to the axis.
  16. Michele Scotti
    Hi John, you're right the stroke is dead center and the tool I think sub-radius - like 45% of the diameter. We tried a full tool but the friction was way too high. The main grinding was done with a CNC diamond tool. I'm definitely not an expert in making mirrors - I've only done few , long time ago. For sure I'll ask about your consideration and come back to you. Btw I've cobble up another video - not advisable if you're seasick ;D https://www.youtube.com/watch?v=w4HIsp1-zXw
  17. Michele Scotti
    Work continues with #800grit: Aiming at #1000 then #1500 to prepare a pitch lap and check if we have something that resambles a sphere.
  18. Michele Scotti
    I saw this several times and it is saved in my favorite yt folder. Did you try to use any water or was it messy? This is another good example: https://www.youtube.com/watch?v=eRdr86gXBLI Although it started like this....: https://www.youtube.com/watch?v=lonAulU-kWA
  19. Michele Scotti
    On with #200 grit... Cheers
  20. Michele Scotti
    An update on the mirror side of the project as a part of the club has been working on the mirror for a few months now. The bulk of the material has been ground off at a machine shop that works on granite. Subsequently, the hogging was done with a half tool to smooth everything out with #80 grit. You "may" notice that the route we took is the ....most impervious...but cheaper and readily available. Also not very recommendable which is a flat 25mm float glass. All in all, I'd consider this a practice run for the part of the team who works on the mirror - we'll gain some experience. Since we are not expencing to reach lambda/4 we are still exploring some alternative solution for a potential 2nd mirror. I'm getting more and more convinced that everything taken into consideration a 25mm thick float (?) slumped meniscus is the way to go. The big deal is that it looks pretty hard to find a suitable place in Europe to slump the glass - it's probabaly me not looking hard enough. Currently we are looking at 2800mm FL
  21. Michele Scotti
    Well done - much of satisfaction when things turn for the best. Would you be able to make another video just like those before to check what it's fixed and what are the residual contributions. Btw is now the motor/worm assembly fixed solidly and not sprung anymore, right?
  22. Michele Scotti
    The SiTech controller accepts 5v pulses as 'telescope encoder' so that gives an easy way to directly wire industrial encoders to it. In the last few months I managed to salvage parts of a Renishaw encoding system - now 'obsolete'. I suppose they are coming from some CNC machinery. Here I'm testing one of the 3 read-heads which has a 1micron resolution although the final system needs 0.1micron resolution. This equals ca. 30 pulses each arcsecond - hopefully it should be plenty for tracking accuracy. This is a very crude test just to see if the salvaged hardware is working properly. The grating ruler is 1000mm long and is intended for the trunnion outer diameter to sort out the Altitude position. The next step is to test the two RGH22 read-heads with 0.1micron resolution. If you're curious I'm using a DSO138 oscilloscope kit - first time for me working on such an instrument but it was quite straightforward after a couple of tutorials. It's like 20$/£/Euros but I mean...it works for me. I opened a thread on encoders some time ago - I'm planning to add some findigns there for whom is interested to adapt this type of encoders to their scope.
  23. Michele Scotti
    Hi Rusted, sorry I missed some of the last messages. Did you identify the source of the substantial wheel movement as per your vid here: https://youtu.be/bWKQBCOkrNw?t=14 ? Also, I recall you ordered angular bearings - were you able to instal them? Did you notice any improvement?
  24. Michele Scotti
    Hi Huw, can you explain this sketch? Apologies if it's explained somehre else but couldn't find anything.
  25. Michele Scotti
    If the camera is on a tripod on the floor what I see is that the wheel is moving away from the wormgear assembly. I almost have the fealing that the entire RA shaft is pushed around by the reaction on the teeth. On the video from the right side you clearly see that the housing and the mounitng plate experience small deflection. From the 'front view' video instead the deflection of the wormgear assy is more pronounced. I'm a bit baffled - would you agree with the observation? For peace of mind I'd take a vid from the left side too and another one where you can check whether the main RA shaft and its housing are moving relatively to the main pier. Angular bearings are a good decision - you nee to have a strategy to pre-load them though. It should be feasible with the housing you have though by adding a small plate.
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