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About barkis

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    Carlisle Cumbria

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  1. Chris, those three smoothing grades were used by the Science Master at Trinity School in the City. There was an Active Mirror making Group, who were active for a long period, and Although my only link with the School, was with our Astro. Society Chairman, who was a Physics master at the School. It was he who supplied me with this material, together with 3 spare 6" blanks. All that was left after the Mirror Making Group ended their projects. I have prepared those three, together with a quantity of Aluminium Oxide 400, and a larger quantity of 400 Carbo. Waiting to be boxed and dispatched. I've no doubt about these products, but If you feel you don't wish to risk them, then that's OK. I can understand your head spinning a bit with all the Posts you have had to digest., and some trepidation might be starting to creep in. I'll let you decide yourself before I parcel these up.
  2. And If anyone finds the thief, please SHOOT. The Low Life needs sending to the Unhappy Hunting Ground.
  3. Hi Chris. I am busy preparing the grades for transporting now. I have had to go up Town with the Good Lady this afternoon, domestic chores you know, no way to escape them I'm afraid. I will be sending 400 Carbo. my favourite smoother, I love the satin finish on that one. Of course that is not fine enough to start the polishing stage. There is some 400 Alux too, which might give it a more sheeny look, you can use that or not, depends on how you see the surface under an Eyepiece. Always good to check all over for any pits too large for 400 to remove. An unlikely scenario that though. The earlier smoothing powders are marked in Numbers, (225 is the 1st. Smoothing) (175 is the 2nd Smoothing) ( 125 is the 3rd. Smoothing.) That should take you down to where you can start the polishing stage. The containers are clearly marked with the order of use, so you can't go wrong. You should always thoroughly clean up, yourself, and the work area right after completing each grinding stage. I'm sure you know that, but a gentle reminder does no harm. I can send you some 80 Grit, which I use in my Sand Blaster Cabinet. It isn't a Carborundum grit, but I used it to hog out a 6" f4 blank years ago. It breaks down quicker than Carbo. but it should get you to where you need to be. Use it sparingly so it doesn't sludge up too much. Use Chordal Strokes initially, that will concentrate the grinding more in the centre of the mirror, As you near the depth, widen the strokes to 1/3rd W strokes. You could move down to 125 Grit to get you nearer the target, move down to 225, then 400. You can start fine grinding then. DON'T FORGET THE CLEANUPS AFTER EACH GRIT SIZE PRIOR TO CHANGEOVER. . What size and f/ratio have you decided on Chris. ? let me know please. Would you like me to include NE. Howard's book in the parcel too. It is not as In depth as Texeraux's book, but very capable of doing the job for you.
  4. The Barlow, as already explained above, Artificially Doubles the Native Focal Length of your telescope. So, If your scope is f11 using a x2 Barlow Increase it to f22. A nice number for Lunar Imaging, without the need to include an eyepiece into the Optical Train. I've never been an avid fan of the Barlow lens, perhaps because I never owned a good quality one. Like eyepieces, there are good ones, and there are bad ones, Many a good telescope can suffer badly from using inferior quality Eyepieces, and additional lenses, whether a Negative one (Barlow), or Positive ones, (Focal Reducers).
  5. OK Chris. If you are going ahead with this. PM me your home Address, and I'll post this stuff off to you. I'm going to remove the contents from the Glass bottles to reduce weight, I will carefully transfer them into Plastic containers suitably labelled. And don't worry, I will be careful to avoid contamination. I will handle the finer ones, and lead up to the rest one by one .
  6. Having read through the thread, I see there is ls lots of input from folks, which is good. There is a chance of some confusion creeping in to your mind. I don't want to seem critical, it is great that some willing help is flowing in, which was expected really. Everybody wants to help. You need to take a step back, and re think what you wish to do I thought the price for the kit was a bit over the top. Have a look at Damian's post, regarding the possibility of obtaining blanks from another source. The rest of what's needed is obtainable from many places, so have a rethink on that price again, personally I wouldn't commit to that, but It's your project, and you mustn't be too influenced by us telling you this and that, helpful as it is. You said yourself you could almost buy a 200mm Dob. for that price, and as much as I appreciate you wanting to make your own, you have to be sensible about it too.. There is no rush to do it. Time is on your side. I'm sure somebody somewhere has blanks of various sizes they don't need. You could do a want Ad. you might get lucky.
  7. Chris, I've had a good look and the only grade I can find is a quantity of 400 Carborundum. You are welcome to it If you want it. There are some Jars that came from a local School Science department years ago. The Physics Teacher was a member of Border Astronomical Society, and he passed them on to me when the making of Mirrors ceased there. They are labelled (1st Smoothing 225. ) ( 2nd, Smoothing 175) (3rd. Smoothing 125). There is a good quantity in each container.. Yours If you want them.
  8. I might have some 100 grit, 120 is a bit slower, but it would mean less hard work removing the 80 pits would leave behind.
  9. Chris, I will have a look in my Store cupboard where I kept most of my Tubs and bottles of Grits, Alux, and I know I have Jeweller's Rouge, which is a very red, polishing agent, so called because it was used for polishing by Jewel profession. Mind you it stains very badly, and your wife will be very upset if you get it on anywhere but the job you are doing . Perhaps Cerium Oxide would be a better option for you. Hold fire on your ordering until I establish what I do have, it may save you some money, as I won't want anything for it. My mirror days are over, although I was tempted very much as I followed Damian's progress. Common sense prevailed though, and I won't return to the grind . You will need a water spray container to keep the grits lubed. Cheap enough at a Garden Centre Shop. To take a tip out of Nigel's post, you could reinforce your 19mm tool blank with some of thosetiny square tiles that some folks use in Bathroom or wash areas. They will give the tool added grinding power too. Just a thought.
  10. Mirrors have been created in all manner of places. A shed is a luxury compared to some strange abodes .
  11. Galaxies are a class of objects among many others in the Universe. Other being star Clusters, Globular, and Open Clusters, Planetary Nebula, Double Stars too, very rewarding subject to pursue. Galaxies are fine, but please don't neglect all the other goodies up there .
  12. Shed would be the place I reckon Chris. I did my first mirror in my Shed, but one careless episode spurred me into being a lot more careful than I had been. Whilst melting pitch on a portable Hot Plate, I left it unattended, and went indoors for a reason I don't recall. After a while, the wife who fortunately was looking out of the Kitchen window yelled at me. There are flames and black smoke pouring out of the shed. I had forgot IO had left the plate switched on, and the gasses from the then boiling pitch, had ignited. Fortunately, most of the damage was due to smoke and soot, and a couple of hours work sorted that. But, it focused my mind I tell you . Later I got myself a 45 gallon oil drum for a work top. I fitted a plywood section across the top of the drum, to which I attached three cleats to hold the disc in situ, but free enough to facilitate rotating it occasionally. The disc could be either the mirror, or the grinding/ polishing tool. Sometimes it is necessary to alternate them during both grinding and polishing stages. Also, I drilled holes either side of the plywood support piece, to enable the sludge created to be washed down into the drum. That way, everything could be kept clean. Contamination from previous grit particles, is to be stringently avoided, I used plastic sheet to cover the barrel top, prior to moving to the next fine grinding stage. The above isn't mandatory, but I found it a good way to do the work. Later, when I had my Garage built, I made a machine to to the hard work, and made provision for it to make it random, as a ritual stroke process is to be avoided if possible. The figuring had to be by hands though, the machine was not sophisticated enough for that job.
  13. There are pitfalls with Pitch laps Chris, too soft, or too hard, either can have detrimental effect on the mirror, but It's a subject to cover when you are up and running, If we fill your mind with too much Info. too early, it will just confuse. How and where do you propose to carry out you work on the mirror? Shed, Garage, or any other enclosure?
  14. Another sad loss. That list of prominent figures who have passed on, is getting ever longer. Gives one the shivers, but we all have to make way for others to take our place. I hope the History and Achievements of all those involved in the Moon Adventures, are forever remembered, the Excitement of those times was something else.
  15. I agree the with above post, Afocal photography has It's uses, but not for stars. Lunar and Planetary work an benefit from it.