Recovering an Ebay TSO

[RLWP]

I have just been scaring myself with the price of bigger mounts 

That home-built Dobsonian mount is looking very attractive...

Thanks for the comment about the thread, it's nice to get feedback

Richard

[RLWP]

Where was I? Oh yes

Collimation screws for the primary mirror:

The little nut is to lock the adjuster

It's a bit - erm - agricultural

Now, this primary mirror. It was sitting on a bit of flimsy foam, the hole in the mirror mount was filled with a plastic disk.

I have some large, 3mm thick rubber washers. Would it be OK to stand the mirror on those?

Do I glue the plastic disk back in, or do I allow the OTA to ventilate through it, or what?

Richard

[RLWP]

I'm a sucker for a good bit of theory: http://www.skyandtelescope.com/wp-content/uploads/Adler-NewtThermal.pdf

So, I've cut a hole for a fan, and drilled five exit holes:

The 'legs' are part of the tube, bent up then back flat to carry the fan.

High tech anti-vibration material:

Yes, it's bits of inner tube, which we will be seeing again later

Likewise, very sophisticated fan retainers:

Finally, to tidy it up, a skirt:

Yes, it's a strip of inner tube held on with a very large cable tie.

It may be made from stuff that was lying around, I'm pretty pleased with that

That's the OTA ventilation sorted, I've decided to leave the back of the mirror carrier open

Richard

[RLWP]

Those dribbles of yellow paint in the tube needed sorting out, so - reach down the tube with a brush full of blackboard paint or flock it? Ten quid with Wilko later*...

The end rings are out at the moment, making life easier. I marked a line 12mm into the tube at the secondary end:

I didn't fancy wrestling big sheets of sticky stuff into the tube, so I cut the sheet to length, then into 150mm sheets:

I got help to fit them, aligning the first one along the seam in the roller steel tube. The rest were butted up against the first one. The last strip was cut a bit narrower, I worked out the width with a bit of scrap backing:

Notice the superior 'blackness' of the flock on the left. I flocked right over the tube joint and onto the first strip. Cut out for the various holes and - oooh, it's very black in there

The mirror:

I don't know where these rubber washers came from, they seem ideal to sit the mirror onto. I also cut a piece out of a car inner tube and stretched it around the mirror, which makes it a perfect fit into the carrier. Sometimes, things just work

I cut a centre dot out of white sticky tape:

It's 1mm smaller than my collimator tube and I've coloured in three triangles, one for each adjuster. I'll put a coloured mark by each collimation screw corresponding to each triangle. Maybe that will help

Richard

*Ordering online with Wilko was an extremely simple operation. I take perverse pleasure in buying astronomy kit from a cheap'n'cheerful supermarket chain. This is the stuff I used, I needed two rolls for my 8" scope: http://www.wilko.com/sticky-back-plastic/d-c-fix-original-deco-self-adhesive-film-velour-black-348-0005/invt/0309578

[happy-kat]

What a great read.

[RLWP]

What a great read.

Thank you, much appreciated

I'm not sure why I have been putting this step off. Anyway, mirror clips:

They are from some left-over aluminium sheet I had around, hence the paint spots. I did, however, spend actual money on the 5mm screws from B&Q. I cut them short to make sure they didn't screw into the side of the mirror:

And the mounted mirror, cushioned with - you guessed it - bicycle inner tube:

I'm soon going to have to clean that mirror and see if the OTA collimates properly. Ooo-errr. After that, a mount

Richard

[RLWP]

Well, while I work out how to fit the focuser to the Fullerscope, I thought I'd finish this one off

The Konus, collimated and on the Fullerscope Mk III mount:

The Konus looks big on the mount, off the mount the Fuller dwarfs the Konus...

It seems to be cloudy here tonight

Richard

[Stub Mandrel]

Brilliant bit of 'coarse engineering'!

Has the scope's performance rewarded your patience and ingenuity?

[RLWP]

MORE: Whoops, I forgot

Thank you Astrobaby for your collimation guide. That, together with a large diameter dot made the job very easy

Richard

[RLWP]

Brilliant bit of 'coarse engineering'!

Has the scope's performance rewarded your patience and ingenuity?

Well, the top of the tree the other side of the road seen through our front window looks fairly spectacular....

Otherwise, I'm waiting for the weather

Richard

[RLWP]

FIRST LIGHT

Of course, I did it all wrong. After a very pleasant birthday dinner my son carried the mount out, I took out the scope. I roughly levelled the base, pointed it sort of North with the RA at 51 degrees ish.

No stars. Well, a few - I could just make out the Summer Triangle, so I could only just find Albireio. Why not

Good news, with a 25mm eyepiece I get a good separation. Even better, I can finally make out the difference in colour. But, I got a nasty flare on one side of the image. Very disappointing .

With few stars around, I was left with Mizar. Again, a nice separation, nasty flare, then clouds. So I gave up

Today, I checked the collimation, and the primary was out. I have adjusted it.

When will it hurry up and go dark!

Richard

[Stub Mandrel]

Maybe if we all face east and blow very, very hard?

[RLWP]

I must photograph my home made collimator, you'll love it

Richard

[RLWP]

QUICK REPORT

It's better. Bright stars produce a pronounced coma, work to be done there. I don't have the fan running yet either. On the other hand - wow, there's lots of bright little stars out there around Cassiopea!

Things to do:

get the scope balance right

make a slip ring

sort a power supply for the fan

redo the collimation

make sure the eyepieces are clean

align the finderscope properly

work out why the finderscope doesn't focus properly

Things are improving!

Richard

[dasilvor]

What a superb read and thank you for posting.

Good luck with the finishing touches.

Cheers

Dave

[RLWP]

What a superb read and thank you for posting.

Good luck with the finishing touches.

Cheers

Dave

Thank you Dave, it's nice to get responses to what I have written. Otherwise it's a bit like shouting into the void

I have ordered a variable power supply for the fan

Richard

[happy-kat]

I read every update :-)

[damnut]

Hi Richard,

What a great read, should inspire someone on a budget to see what can be achieved. Congrats.

[ollypenrice]

Shouting into the void? Is there anywhere else to shout? 

This is a great thread. Many thanks and keep at it! (I'm full of good ideas for other people...)

Olly

[RLWP]

So, armed with a length of aluminium channel section and a big jubilee clip (both from B&Q) I made a slip ring:

It was a bit of a challenge to bend into a circle, I should really have found a better sized disk to form around. Anyway, the hinge:

and the fastener:

I must replace that round headed screw in the clamp ring

Now I can rotate the 'scope in the clamp rings without upsetting the balance

Richard

[Stub Mandrel]

You sir, and an 'A-class' bodger! Bending channel like that is a major challenge.

[RLWP]

Naw - you just bend it. Then you bend it back a bit, kink it, swear a lot, flatten the sides, curse, sweat, push it around, drop it, kick it around the workshop in frustration, cut the ends off and there you are!

Richard

[RLWP]

Having fitted the Revelation focuser I rushed out last night to see what I could see. No collimation, no fan, no plan..

Cor, there's a lot more stars up there than I thought! I can see a great many more than with the ol' Prinz scope. I think I'm getting a wider field of view too

The collimation is still out, I can't get nice pinpoint stars. I have cured one of the issues though. The flare I was getting on bright stars appears to be down to my dirty glasses. I should have gone to Specsavers...

The focuser needs packing out from the tube:

If you look carefully, the eyepiece is only just in the focuser, and the 2" to 1 1/4" adapter is also pulled partly out. I'm going to make up some spacers to go between the focuser and the tube

The fan is wired up:

I bought a cheap power supply from Ebay: http://www.ebay.co.uk/itm/Mercury-661-400-Energy-Efficient-Switch-Mode-Power-Supply-600mA-Variable-Output-/400957999763?

It has multiple end fittings. More importantly, it has a variable output. The fan will run at anything from 4.5 to 12V, so I'm going to start with it down at 4.5. The eddy currents on the face of the mirror are going to be pretty weak, so a small forced draught will disturb them

Richard