Building a telescope.

[chrisjose1913]

Hello I am looking at building a telescope soon. Ideally a 4/5 inch refractor. I am having an issue finding a cheap objective lens for the project. It seems achromatic lens cost a fair amount. any suggestions ? I am on a low budget so may be asking the impossible.  

[triton1]

I did toy about this before I bought mine but I was going to go the reflector route as the parts were cheaper and more readily available for example on astro boot there's a mirror for £25 and secondary for less 5inch I think also easier to construct.Does it need to be a frac?

[NGC 1502]

Hello I am looking at building a telescope soon. Ideally a 4/5 inch refractor. I am having an issue finding a cheap objective lens for the project. It seems achromatic lens cost a fair amount. any suggestions ? I am on a low budget so may be asking the impossible.

 

You will also need a tube, focuser, finder, mount etc. Could use Astroboot as suggested in post #2, or there's Astrobuysell http://www.astrobuysell.com/uk/ for a complete scope ( depending on budget ) although there's no denying the satisfaction of a successful DIY build.

Whatever route you take, hope it goes well, Ed.

[chrisjose1913]

Thanks both helpful. I would rather go down the route of building a refractor. So ideally I need a cheap solution for a objective lens but also reducing the limit the effects of chromatic and spherical aberration that single lenses cause. 

[Pompey Monkey]

Thanks both helpful. I would rather go down the route of building a refractor. So ideally I need a cheap solution for a objective lens but also reducing the limit the effects of chromatic and spherical aberration that single lenses cause. 

The holy grail doesn't come cheap.

The Startravel 120 http://www.firstlightoptics.com/startravel/skywatcher-startravel-120-az3.html (or equivalent), will get you very close to what you want at a small fraction of what it would cost to build one yourself.

'Scopes of this aperture and quality were reserved for the very, very, well off when I was a kid. And I'm not 50 yet!

[Joseki]

Building a decent scope isn't the cheap option anymore.  However I'm sure there would be a lot of satisfaction in doing it - especially if you ended up with something superior to the standard scopes (you could always try grinding you own lens).  I think the cheapest option might be to buy a complete scope 2nd hand and just keep the lens.  - but then of course you might as well just give the tube a new paint job and upgrade the focuser.

.. but it could be an interesting project to try, see this link  http://amasci.com/amateur/teles.html

there are plenty of convex lenses on ebay.  - quality is going to be the issue though and even they aren't free.  I've seen projection lenses mentioned as optics for diy scopes, e.g. http://www.jonsinger.org/jossresearch/tjiirrs/012.html

btw there's a scratched skywatcher startravel 4" refractor on astro boot for £85 which might make a good donor scope.  http://www.astroboot.co.uk/AstroBoot

[mcolbert]

as John suggested eBay has some interesting options.  Check a possibility;  

http://www.ebay.de/itm/projection-lens-f-4-400-mm-104mm-diameter-130mm-long-new-old-stock-/301391829368?hash=item462c5a5978

michael

[ronin]

Could try Surplus Shed, they are a US company, SShed.

Just looked as there is/was something odd about getting the right items displayed, and there still is.

Link is to the front page, on the left is a catagory selection list, IGNORE the Lens Finder option.

Go the the top bit of the list that says Catagories, click on it and scroll down to Telescopes (not Telephones as I have just done), pick that and you get 3 pages of objectives they have selected as bits suitable for telescope building.

Presently not many lens are there but there are a few.

Also you can select Achromats from the same pick list and a faur number of achromats are displayed, as the sizes are assorted you will have to pick through the displayed items. I would expect it to be the Telescope Lens and the items that Lens Finder selects from. However from looking previously it may not - not sure that Lens Finder works 100% right.

[Ian123]

Found this..https://diy.org/skills/astronomer/challenges/354/make-a-telescope

I think this scope would even push Televue for optic quality 

[Dazzyt66]

Or if you wanted a fixer upper there is a 4.5inch Skywatcher tube and mirror for a tenner on AstroBoot....

Dazzyt

FirstScope (soon to be Skyliner 200p)

[mcolbert]

surplus shed is a good call by ronin.  I have purchased from them before and they are friendly and efficient.  Like many sites it's a matter of regularly visiting to see what's available.

michael