10" dob mods

[GazK]

I've had my skywatcher flextube 10" dob for a few months now, long enough to know its strengths and weakness and to be bold enough to make a few mods. Here they are - hopefully this might inspire others to get stuck in.

1. Where to store the tension handles?

I store my dob in a tight space in the garage - it's not wide enough to leave the handles on, and in any case I want to leave them off for maximum grab-no-go readiness. So I got some large dia pipe clips from the local DIY and bolted them to the side of the rocker box:

2. Replace the stock finder with a telrad

I couldn't get on with the supplied finder, the position was poor and the reversal of image did my head in. So off it came and a telrad fitted instead. This has worked a treat and combined with a low power EP I haven't missed a magnified finder image yet:

PS If you're gonna do this, DONT do what I did and forget about the backing plate when you unscrew the finder riser. The sound of a steel plate dropping onto my mirror cap wrecked my nerves for the rest of the day!

3. Homemade dew heater for the telrad

Using the idea put forward by M110 here:http://stargazerslounge.com/diy-astronomer/80544-simple-telrad-dew-heater.html

I added a dew heater - I slightly modded the original plan, using a separate circuit driven by an extra pair of AAs and feeding 3 resistors in paralell - I couldnt get hold of a single resistor with a high enough maximum power.

4. Magnetic counterweight

My new Baader Hyperion was unbalancing the scope at low altitudes - and the tension handle is a last resort in these cases.

Using bcfcciderhead's magnetic car sign idea - http://stargazerslounge.com/beginners-help-advice/124986-common-dob-balance-issue-fixed.html - I extended the thought train. I sawed down an old pair of ally drop handlebars I had in the spares box, using the central 25mm dia section. Then I cut, drilled and tapped M6 a short section of 10mm steel bar to make a tee nut. This was force fitted into slots cut into the ally tube and epoxied in place. The whole lot was then screwed on to the M6 stud on the magnetic plate. Then a couple of 0.5kg exercise weights - 99p ea from the local fitness place - were added to finish off. No excuse for not buying big glass now! PS thats glow-in-the-dark tape added to the top.

5. Replace focuser tension grub screw

I wanted a tool-free way to adjust focuser tension, so a piece of M6 threaded bar, a wing nut and a normal nut were epoxied together like so:

Make sure the bolt is long enough to clear the locking thumbnut.

6. Secondary collimation screws

Now I'm sure bob's knob's are the bees knees, but $20 and a transatlantic journey seemed a tad disproportionate to the size of the problem. So some stainless steel M4 threaded bar was procured for £2 off ebay - we don't want any rust on this one - and a wingnut and normal nut epoxied together:

The wingnuts all stay behind the secondary shadow at all times.

7. Well... can you guess?

This last one is a work in progress:

Can you tell what it is yet? A further clue is in this Video, and my wife is holding up the completion of the build. Answers to the usual address...