My low-cost, lightweight 80mm short-tube refractor

Wanna make a scope? Or better still, grind a mirror yourself. Or, you have some good tips in making a really useful accessory? This is the place to show what your hands can do...
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Hardwarezone
 
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Favourite scope: maksutov

My low-cost, lightweight 80mm short-tube refractor

Postby Hardwarezone » Thu Dec 19, 2013 10:59 pm

The lens is cemented, multicoated , green coating on the front, purple on the back. A little flaw on front coating near the middle.

darkened lens edge
added 3 baffles
internal 1/4" mounting nut to camera tripod
lens cell made from plastic cookie jar, epoxy ,7 layers of crafting foam as spacers
tube body and focuser from 106mm wide body shampoo bottle, focuser tube from 60mm fish oil bottle and 48mm pvc pipe
eyepiece is taken from old binoculars , kellner design, focal length and afov unknown
entire scope can be open for washing when it accumulate fungus


total weight is 550grams, materials expenditure less than $40
crafted with simple tools
clear aperture may be 76mm only due to my rough workmanship
the carbon fibre style vinyl sticker sheet didn't work out as I hope, makes the scope look uninviting and less fun

Image

Image

Image

stuff required
$2 daiso A+B epoxy , curing time is stated 10minutes but 1 day is needed for it to turn really hard and brittle
$2 daiso double sided black foam tape 1mm thick 30mm wide 3m long
$3.20 popular A4 size black crafting foam 2mm thick 10 sheet (usage is 5 sheets +1 for short dewshield)
$2.30 popular Staedtler lumocolor black permanent marker
$3 black vinyl sticker sheet 4 square feet (usage 2sq feet , bought online)

big and small scissors, gas stove, iron nail, plyer , plastic cutter, hand saw , plastic bags , toothpick , lego parts, hotglue , scotchtape

*update June 2014*
There is a visible film on the objective lens. Most probably fungus. My estimate was 8 months and this new data of 6 months is close.
Can be washed away with tap water and dishwashing detergent, this method is not recommended for more expensive scopes as it can cause micro-scratches on the coating.

Image

internal crafting foam baffle and polyester felt , both bought from popular bookstore
Image
Last edited by Hardwarezone on Tue Jun 10, 2014 6:26 pm, edited 3 times in total.

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Gary
 
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Joined: Tue Sep 30, 2003 7:06 am
Location: Toa Payoh

Re: low cost, lightweight 80mm short-tube refractor

Postby Gary » Sat Dec 21, 2013 12:21 am

Cool! Thanks for sharing your research and DIY. Do let us know how it performs under the clear sky!
http://www.astro.sg
email: gary[at]astro.sg
twitter: @astrosg


"The importance of a telescope is not how big it is, how well made it is.
It is how many people, less fortunate than you, got to look through it."
-- John Dobson.

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Airconvent
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Re: My low-cost, lightweight 80mm short-tube refractor

Postby Airconvent » Sat Dec 21, 2013 12:02 pm

Nice touch hardwarezone! The "lego" brick on top is meant to receive a future finder? Or decorative assessory?
Since the eyepiece comes from an old Bino, looks like you can make 2, built a frame so it can transform between "telescope mode" and "bino mode" :)
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Hardwarezone
 
Posts: 247
Joined: Fri May 17, 2013 2:50 am
Favourite scope: maksutov

Re: low cost, lightweight 80mm short-tube refractor

Postby Hardwarezone » Sun Dec 22, 2013 4:44 pm

Gary wrote:Cool! Thanks for sharing your research and DIY. Do let us know how it performs under the clear sky!

Tried to view Orion's Belt overhead this morning 1:10am to 2:10am in Johor, nice view with 100+ stars in eyepiece. move around slightly would be 200+ stars.
Orion's sword have less visible stars, did a sketch and counted 46 stars. Nebulosity doesn't look significantly bigger than 90mak.
The eyepiece TFOV frames 3 stars of the Belt just nice with a little bit extra. Need more tweaking because it slides out at high angle.
Can Focus to sufficiently pinpoint without distracting aberrations as long the focuser and eyepiece doesn't sag.
Day time view CA is visible on dark/pale contrasting surface like windows or flying birds.

Airconvent wrote:Nice touch hardwarezone! The "lego" brick on top is meant to receive a future finder? Or decorative assessory?
Since the eyepiece comes from an old Bino, looks like you can make 2, built a frame so it can transform between "telescope mode" and "bino mode" :)

I use 6 lego technic pieces for the pin and hole connection to secure the "cookie jar lens cell" with smaller diameter into the bigger diameter "shampoo bottle tube body", adding 1mm black foam tape to make up the small gap and eliminate wriggle.
Easy to assemble if need to open for wash or repair.

The other eyepiece is in a 48mm straight-through PVC tube with the original bino objective.
Did that to experiment image clarity improvement by removing the prism system and adding baffle.
Read about these tips & tricks on the internet but really need to see with my own eyes to experience the difference each step can bring.

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Gary
 
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Joined: Tue Sep 30, 2003 7:06 am
Location: Toa Payoh

Re: My low-cost, lightweight 80mm short-tube refractor

Postby Gary » Tue Dec 24, 2013 3:33 pm

Good stuff! 100+ stars in a single FOV is always a good thing! Missing Johor already. Will be back there more frequently in 2014. :)
http://www.astro.sg
email: gary[at]astro.sg
twitter: @astrosg


"The importance of a telescope is not how big it is, how well made it is.
It is how many people, less fortunate than you, got to look through it."
-- John Dobson.


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