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About Astrobits

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  1. Astrobits

    DIY newt with raspberry pi and camera

    I assume that you will be making a classical Newtonian with a secondary mirror and focusser. If that is correct then an 8"f/6 will fit into a 48" long tube easily. When I made 8" f/6 mirrors they were all installed in 48" long tubes. Nigel
  2. Astrobits

    Adjustable tension pivot bolts

    Try googleing "pivot bolts" Nigel
  3. Astrobits

    Best Astronomer. 𝕃𝕆𝕃

    I always associate BEST with a good English breakfast............Bacon,Egg,Sausage,Tomato Ill get me coat now. Nigel
  4. As title, close approach 14/15 May. Possibly as bright as mag 11ish. Info here: http://earthsky.org/space/lost-asteroid-to-pass-closely-may-15 Nigel
  5. Astrobits

    Heads up: Nova in Perseus

    The variable V392 has gone into a Nova outburst, currently at mag 7 ( it's normally around mag 16-17 ). Easy binocular target. Location: R.A. 04 43 21.38 Decl. +47 21 25.9 . charts available from the AAVSO using V392. Nigel
  6. Astrobits

    Very small DIY erecting monocular

    Have you considered irpoyser.co.uk for surplus optics? A bit more expensive on list prices but with no tariffs etc. might be useful. Nigel
  7. Astrobits

    Dragon Astro 12" Dob

    I had my ally tubes powder coated with a matte black finish. Not perfectly matte black but not shiny so less reflection than a shiny finish. Nigel
  8. Astrobits

    130pds mirror.

    It certainly looks a bit on the thin side but as Peter Drew implies shining a light onto the mirror reveals stuff that doesn't affect the operation of the telescope for normal use. To re-coat the 5" primary only VCSM charge £32 +£6 p&p. and you will not see any change in performance. Leave it alone. Nigel
  9. Astrobits

    Odd 'Scope

    As the seller is "Jessica's Antiques" in Huddersfield perhaps someone who is in the vicinity could have a look at it in the shop. I am too far away unfortunately. Nigel
  10. Astrobits

    Odd 'Scope

    In one of the pics there is something on the opposite side of the scope to the second focusser. Could this be a finder arrangement? Nigel
  11. Astrobits

    Market treasure?

    Ian Poyser used to live in Rochester, Kent before he moved to Wales. Nigel
  12. Not negative at all, I was just merely pointing out that filters that perform the required function have been available for some time. The new one is just an improved version which will suit more light polluted skies. Regarding price, Image Optics started selling the filters to my spec for around £50. I was retailing them for less than that. Can't see them on their web site now. Nigel
  13. Those were just two that I pulled up from my files. 20+ years ago I commissioned a company in Essex ( Image Optics/Galvoptics ) to produce some LP/Nebula filters to my specification. ( I am sure that they could have done any specification had they been asked ). When I used these in the dark skies of Norfolk there was no advantage to the narrowest transmission filter over the broader one. In the more light polluted skies elsewhere then the narrowest transmission filter did perform better than the wider one. If you have a lot of light pollution then maybe line filters would be even better than the one you mentioned. I also agree with Louise that you might need to give different exposures to the two wavelengths which could not be done with that particular filter. Nigel
  14. A number of filters transmit both O111 and Ha and have been available for years. Most also transmit some longer IR which can be cut with a second suitable filter. For example: Though I must say that the filter referred to is very neatly done. Nigel
  15. Astrobits

    The 8.75" f/6.7 Mirror Grind

    When you make up the test apparatus is up to you. Personally, I don't test until I am satisfied that all the pits have been polished out. The best way to check for pits is to examine the surface with a 10x loupe ( 25mm eyepiece ). I used a light box with a sheet of black paper/card on top from which holes had been cut. The mirror is put face up on this. Examine the area just into the dark edge and the pits stand out as bright specks. The first test that I do when starting figuring is to examine a pinhole image with the 10x loupe in and out of focus. This is a very quick check for astigmatism. Thereafter I use a knife edge for the normal Foucault set up. Moving the knife edge either side of focus gives the same info to me as a single edge of a Ronchi grating hence I have never owned or used a Ronchi grating. When I am getting nearer to the parabola I include a null test ( Dall Null ) which I find is much easier than using Foucault or Ronchi tests. There is info on using a the basic Foucault on the internet to finish mirrors. Nigel

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