16 inch Dob project under way

[Daniel-K]

thats correct Nigel and your spot on with the sleeks we thought we had a huge scratch but washed it all down it vanished were enjoying doing this mirror once its finished i think i would like to do a 12 or a 10. were looking at source's now for all the bits for the assembly of the scope, next week i would like to have a go at the upper truss

[Astrobits]

Sleeks don't vanish with washing. You probably only had a left-over bit of polishing agent. Once you have FULLY polished the mirror you are about halfway through the job

Nigel

[Daniel-K]

with looking at making the upper truss next week am i right in thinking the diameter should be slightly larger than the mirror about 18"?

[Astrobits]

!8" will do it nicely. Assuming an F/5 mirror, the field of view of a 25/100 eyepiece will be about 1.2 degrees and the tube will give a clear field of about 1.4 degrees

[Daniel-K]

very good i will be getting 15mm ply on friday with barry (joiner + silent partner ) and have a go at the upper truss and base box

[Daniel-K]

heres a picture of the wood and pfte that arrived yesterday

[Astrobits]

Just a quick note on safety with the PTFE. Use a craft knife to cut it. Avoid using a saw as this leads to much swarf. If this swarf gets burnt ( eg in cigarettes ) it can lead to unpleasant side effects with Flu like symptoms so take great care with all the bits of PTFE you generate. I used to work in ICI's Plastics Research Labs and my wife worked in their PTFE Tech Service so we are well aware of this phenomenon.

Nigel

[Daniel-K]

the mirror box is built ( no pics forgot my camera ) we have routed (by we i mean barry) the top truss and are having a octagon shape. tomorrow we will be routing out the altitude bearings and making the rocker box. then its just a case of fitting it all together

[Daniel-K]

so yesterday and today was very productive barry set to work (at last) doing what he does best.yesterday we got the mirror box knocked up fairly easy.today was a case of routing out the crescent shaped alt bearings from the 40mm ply and cutting out the holes to save some weight. we have cut all the pieces for the base box but they still need holes cutting out to match the rest of the scope, a job for tomorrow maybe.but it looks good and the ptfe teflon is doing its job feels nice and smooth.progress at last! there was a bit of going on but thats what barrys there for.

[estwing]

comin' on nicely now...

[wurzelmike]

really interesting thread, I'm sure you're almost there

[Daniel-K]

i left barry with the material do do the upper truss we scraped the octagon look and went for classic circles. have to say hes rather good with that router, its coming along nicely now, i will take some better pictures at the weekend and a more detailed description as right now im in the obs freezing on a imaging run oh by the way the upper truss is not attached to those thats just to give an idea of what it will look like

[estwing]

starting to come together now..WOW whats that about F2?

[3ggman]

Its going to be a monster. Very nice work, I look forward to seeing it finished.

[8kids]

Is that a heineken bottle top I see, I assume that's to give us some idea of scale?

[swamp thing]

Looking real good Dan, what's that, 1" ply you've used on the UTA?

[Chris]

Wow! thats looking amazing Dan very inspirational stuff, I've really enjoyed reading this thread.

Do you think my wife would kill me if I tried hogging out a 10-12" miirror indoors?

[Daniel-K]

Wow! thats looking amazing Dan very inspirational stuff, I've really enjoyed reading this thread.

Do you think my wife would kill me if I tried hogging out a 10-12" miirror indoors?

yea !! lol i got moaned at even doing it in the garage! theres a nice 10inch mirror set on astro boot would make a great project for a dob, i bought the same set last year to make a ultra light dob but never got round to it so so i sold the mirror

[Joseki]

That's some nice looking routing!

One techie question though - if those bearings are going in that position - at the bottom of the box, presumably to allow for a much lower rocker box - how's it going to balance? Just looking at the pictures it seems that there's nothing to balance the torque from the upper truss. If you've got a copy of Kriege & Berry I mean like their figure 7.3.

[Daniel-K]

Looking real good Dan, what's that, 1" ply you've used on the UTA?

its 40mm left over from the floor in my obsy planning on boring out some holes in the circles to save weight and to match the rest of the scope, it will also give us a good fixing point for the spider. which we are yet to come up with an idea

[Daniel-K]

That's some nice looking routing!

One techie question though - if those bearings are going in that position - at the bottom of the box, presumably to allow for a much lower rocker box - how's it going to balance? Just looking at the pictures it seems that there's nothing to balance the torque from the upper truss. If you've got a copy of Kriege & Berry I mean like their figure 7.3.

were doing this just by feel with no books or anything. we hope the weight of the upper truss will help with the balance but its not a big issue if it doesnt at first theres always a way around it like making a secondary holder more dense to add a bit of weight trail and error i say

[swamp thing]

40mm blimey I was way out

Are you looking to build a short UTA similar to the mock up in the pics then?

[Daniel-K]

40mm blimey I was way out

Are you looking to build a short UTA similar to the mock up in the pics then?

ideal yes. do we know why?no lol not quite sure how were going to attach them but i need to do some digging and get the ali truss poles orderd and then have mess around coming up with something the looks good and easy to assemble in the field

[Chris]

yea !! lol i got moaned at even doing it in the garage! theres a nice 10inch mirror set on astro boot would make a great project for a dob, i bought the same set last year to make a ultra light dob but never got round to it so so i sold the mirror

Thanks for the heads up:), Astroboot was down for a while I didn't realise it was back up and running, that mirror set is a great buy, too good to turn down!

[Daniel-K]

Thanks for the heads up:), Astroboot was down for a while I didn't realise it was back up and running, that mirror set is a great buy, too good to turn down!

add £100 on top you for materials and you have a 10inch dob