Tuesday, January 18, 2011

Exquisite 60mm home-made long focus refractor


On behalf of Silviu aka ''zoth'',amateur astronomer in Bucharest,Romania.
The instrument was first described in November 2010 on ''60mmtelescopeclub'',a great yahoogroup dedicated to small telescope astronomy.
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I'm going to tell you the story of a ''new under the stars'' peculiar 60mm refractor.The story started 38 years ago when Silviu at age 12 fall in love with the stary heaven.At that time a 60mm refractor seem to him a huge telescope and it was only a dream,unachievable dream.
Things changed a lot over the years and after owning and building more telescopes, Silviu,already an acomplished ATM-er,saw an opportunity in 2009 to make his dream come true.He designed a 60x840mm classic Fraunhofer objective ,using BK7 and F2 glass.But then he had to face the reality of optical shops who are using tools with pre-determined radii.So Silviu had to adapt his project and re- optimise keeping the eyes on the goal:making of an exquisite small refractor objective.The end result is the actual 60x828mm lens,with a spacing of 0.09mm,anti-reflection coated with a multi-layer broad band AR coating.The non-colimatable Aluminium cell is also designed by Silviu.Like the home-made 1.25 inch and 60mm travel sliding focuser ,the body being made of Aluminium and the steel draw-tube having two internal steps.The tube of the refractor is a re-used Al tube wich housed a 60x900mm lens of ''Alcor'' brand and have two baffles while another two baffles are in the draw-tube of the focuser. OTA have a length of 750mm and weight 1.4 kilograms.
The refractor is riding a TS-AZ Teleskop Service mounting.
The refractor was finished Sunday,fourteenths of November, but the first light happened in September.Oculars used for the first light was PL 17mm/48x;Ortho 9mm/92x;ortho7mm/118x;ortho6mm/138x.The Moon images was gorgeous,no traces of chromatic aberation,similar to Silviu's 80mm ED,very good definition,crisp images,fine details,awesome contrast.One thing noticed by Silviu was that while at 138x the lower light made Moon observation more comfortable,there where no aditional details compared to 118x.Anyway,no trace discerned of any haze due to CA or spherical aberation.
On Jupiter,at 92x,very clean images,again no haze due to aberations,the NEB very clear but hints of some structure and of more belts toward the Northern Pole.Siviu pushed in the 7mm ortho for 118x and he noticed ,very pleased ,festoons in NEB and confirmation of more jovian belts ,much less conspicious and without further details.
One galilean satelite was very close to jovian limb.
In his letter about the first light,Silviu is stating that he made observations of Jupiter through many instruments and from many locations but this was the best Jovian images ever.Not even his 5 inch Mak,very dear to him,did not offered such exquisit images.His conclusion is this:folowing his childhood dream to build a long focus small achromatic refractor was more than worthwhile and is a winner on planetary details.
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Description made by me,Mircea, according to details and pictures from Silviu.I will add here only the logo created by Robert Little for the ''60mmtelescopeclub'':