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rebuilding the dob coulter oddsey 8

garethmob

By garethmob
in DIY Astronomer

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garethmob

garethmob

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well after a few disapointing non sales of my dob im considering rebuilding it to make it more "modern.

first question though. is it worth it it is a F4.5 which is pretty impressive as the 200p is F6? what would that mean will only green eyepeices work good in it?

so i'll split it down now to what i beleive the scope is made of with the possiable idea for replacement

sonotube

focuser

primary mirror

secondary mirror

on base

under rotation wood

plastic peice (its some type of plastic thats very "sliky" for rotation (EDIT apparently its nylon is this still good?)

the 2 sides and a type of plastic "chair bottem?"

also i think the circlular arms on the tube to base

im going to attempt to do this as cheap as possiable but it is a very very very very long term project as i beleive the scope is worth saving

so with the ideas above

where can i get a sonotube from i will measure it later as it is a funky F4.5

heres some specs i found on it so i guess i have everything there

https://sites.google.com/site/coulterodyssey/home/specs

is there any way i can see if the mirror is working perfect enough? iv looked through with a few of my eyepeices and the image is very very good, but the focuser is "origional" drain pipe design :)

also what would be a good focuser, a decent but cheap focuser i wouldnt use it for AP what so ever thats what my astrotracs gonna be for:)

thanks for any help i get guys it will take a very long time to do this so i wont be updating this post that often! but i will try my best!!

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garethmob

garethmob

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ok i had this reply back from essex tubes

Thanks for the enquiry. We offer a standard brown kraft 254mm diameter x 6mm thick tube for this particular use at a cost of £35 + VAT.

We would be unable to match the below specs I'm afraid.

Regards

um thats thinner than the one i have any suggestions also anythin on the above with worth it?

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JamesF

JamesF

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You're only talking about a 1m length of tube, perhaps not even that long. Isn't it less than 800mm between the primary and secondary? I'd have thought it stood a reasonable chance of being sufficiently stiff over that sort of length. The only other thing that springs to mind immediately is aircon ducting, but that's probably far more awkward to work with.

James

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garethmob

garethmob

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I'm afraid I don't know. Those were the options I was thinking about for a dob of my own.

James

I think the problem ivgot is I'm bring a little specific in what I want. That tube should be good and work but I'd like thickness a bit more as it holds the focuser better. On the coulter there isn't any handles (that could change) so I pick it up by right hand under the runner and left hand tube and it has plenty of ridgeity there. Also through some mirracal collimating stays the same it dosent move with the slightest bang like the bushnell used to.

Does any one know the benefit of a f4.5 dob over a f6?

Sent from my iPhone using Tapatalk

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garethmob

garethmob

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i got it off a guy on asbas a few weeks ago only had chance to open it up

it looks nice but im a little worried luckly he gave me a few extra sheets than i ordered (2X12" and some small strips) i tried to bend one to fit on the side bearing and it snapped :) any ideas shane?

i'll have to get some turtle wax what should i use as friction, i have milk cartens gliders..

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Moonshane

Moonshane

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sorry Gaz, missed this query. maybe try heating it with a hairdryer to get it to bend to shape and it should then glue ok?

other option is make larger bearings and then you won't have to bend as much - again I'd use evostik impact adhesive.

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garethmob

garethmob

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no worries shane:) that warming up and bending seems a good idea! at present the bearing on the alt is chair gliders on the base with a plastic like material on the rings, im tempted to leave it, see if it needs doing after iv done the base. i ran into a problem i forgot i needed to drill into the bottem of the sheet for the screw so its on hold now :)

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garethmob

garethmob

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well.... base is done! very smooth! used tripple wax as i couldnt find turtle in my asda, drilled hole, and changed the bottem teflon disks with chair gliders, only snag is the gliders are quite big so i cant tighten the middle bolt much but its fine

fitted new focuser and ran into 2 problems, first, the secondary needs to be moved down a tiny bit now but i left the garage to a dark sight to test before i noticed.

next the major one, i need more in focus, i think its just the 2" to 1.25 adapter is fairly tall so its prob that which does it. going to try the megrez one but i dont think it will work. any ideas what i can do. i had to make a fairly large hole on the tube to get the 300p focuser on there already :(

my next plans is pot rivit a square of metal onto the tube for the wixey and gemred to live.

then it will be a new base for the mirror to live on, with eaiser collimation section

and a new secondary and secondary holder!

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Moonshane

Moonshane

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well.... base is done! very smooth! used tripple wax as i couldnt find turtle in my asda, drilled hole, and changed the bottem teflon disks with chair gliders, only snag is the gliders are quite big so i cant tighten the middle bolt much but its fine

fitted new focuser and ran into 2 problems, first, the secondary needs to be moved down a tiny bit now but i left the garage to a dark sight to test before i noticed.

next the major one, i need more in focus, i think its just the 2" to 1.25 adapter is fairly tall so its prob that which does it. going to try the megrez one but i dont think it will work. any ideas what i can do. i had to make a fairly large hole on the tube to get the 300p focuser on there already :)

my next plans is pot rivit a square of metal onto the tube for the wixey and gemred to live.

then it will be a new base for the mirror to live on, with eaiser collimation section

and a new secondary and secondary holder!

sounds like progress! just buy a longer bolt for the central pivot - I bet it's a standard size.

presumably the secondary can be adjusted in the spider to allow a little movement down the tube?

a requirement for more in focus is annoying. a few options. is it just a matter of a few mm? check this by taking out the adapter and hand holding the eyepiece in the focuser to check where the focus point is. measure how far down the top end of the silver nosepiece is and that's your required in focus (obviously do this for your most inwardly focusing eyepiece). if so then you can buy low profile 2-1.25 adapters that add only 1-2mm to the focuser - might be enough.

another option is to try a light pollution filter if you have one. this often brings in the focus point a bit.

finally (and I think the more likely solution), you might have to move the mirror up the tube a little (by a bit more than the amount established above) by drilling new holes and moving up or by cutting off a short section of the tube and drilling new holes.

none of the above is difficult. just take your time and use a template to set the points for the holes.

good luck (and welcome to the ever changing picture that is dobsonian modification! :()

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