Ongoing Mods on my Orion Optics UK 6" f11 Planetary Dobsonian

[Moonshane]

I am planning a few standard mods to my newly acquired slow newt which I bought at a bargain price and I'll use this thread to update from time to time the work I have done to this scope to improve its use and results.

As with my other 12" dob, I had some planned improvements before I even got it! The first was a simple one, the addition of a red dot finder. I had a Rigel Quikfinder from a now sold refractor, which being quite light and having a small footprint suited this scope very well so I fitted the base with car number plate double sided foam and that was that. Mod 1 sorted.

The next mod was also a simple one. I took out the secondary and used a magic marker to black out the sides. This should prevent any stray light hitting the sides of the mirror and bouncing around near the focuser. The idea is that this increases contrast. Refitted the mirror after checking the 'equality' of the spider vanes and that's it, Mod 2 done.

Mod 3. was really what resulted in me doing Mod 2. I bought a replacement dual speed Crayford focuser (used of course!!) as this makes the critical focus on planets and lunar detail so much easier. I had to drill four new holes in the OTA as the spacings were not the same but with careful placement and checking, double checking etc, this was a straight forward job. I removed the mirrors of course for this and it was then I discovered that they were better grade than I thought. I assumed that they were standard coatings and with 1/4PV figure but when I removed the cell, I saw a HILUX sticker and 1/6PV engraved into the side of the primary - result! I had to shim the focuser up a little with some plastic strips scavenged from somewhere and I sanded these with fine paper to make them matt black. These hold the focuser off the OTA just enough and this is a good way to fit a focuser not designed for 6" mirrors tubes but their larger cousins - no new base required and it works really well. Mod 3. completed but I need at least a 50mm extension tube which I had already.

Mod 4. was also a simple one. The scope is an absolute nightmare to balance as it has such a long tube and a light mirror; with the Quikfinder and a 6x30mm RACI finder fitted only my 11mm plossl could be used without literally handholding the OTA. In an attempt to correct this and on the advice of Ron (Barkis) another SGL member, I took out the Teflon blocks in the mount and replaced them with a line of self adhesive felt around the whole of the 'bearing' where the rings sit. This worked quite well but alas was not enough friction to hold the scope any more than before. Mod 4. completed but not as I'd hoped.

Mod 5. This was again a simple one and thanks to John (Jahmanson) another SGL member who was selling some knurled nuts, I managed to replace the lock nutson the scope and this makes for much easier, tool free collimation. Mod 5. done. I intend to replace the secondary adjusters eventually but as the secondary is so small (just 25mm across the narrowest point) it's hard to find something with a small enough head - no doubt I'll make my own eventually.

Mod 6. As the felt was not cutting it I have passed some materials across to a mate's mate who is going to drill and tap some 10mm x 30mm aluminium bar and make a proper friction brake but I am so desperate to make better use of the scope on Jupiter (which is currently giving a great show most nights) that when I came across a coat hook in the shed, I decided to make a temporary replacement. I straightened it and drilled some holes and then fitted it to the scope with a piece of teflon rod on the end of a 6mm bolt acting as the brake. This works really well but was just not enough for my heavier eyepieces. I then had an idea for Mod 7. which makes use of another Astroboot item that I knew would come in handy some day.

This was one of the 80mm x 5mm washers that appear from time to time and I had 'in stock'. I used some velcro strips and fixed it to the end of the OTA on the metal end cap. Although this is not that heavy, combined with the friction brake, I can now even use my 13mm Ethos and a borrowed 20mm Nagler with no balancing issues at all!! Success at last. I may buy a smaller one so it fits better (or as an additional one) and will also eventually replace the temp. friction brake for the better more stiff one which will work a lot better I suspect.

This is all the mods for now but I have planned, a full OTA flock and insulation, a tiny 4cm fan (on the way from Hong Kong) and a dew / stray light shield.

The first and second of these will be challenging in a five foot x six inch tube but we all like a challenge eh?

cheers

Shane

pics to follow

[Moonshane]

some more pics

[Rusty Strings]

Looking good Shane, keep us posted on the planetary views, a long FL 6" newt is on my wish list.

[Moonshane]

cheers John

the views should improve greatly for my now the OTA is not being shaken by me hand holding it!! here's my initial thoughts http://stargazerslounge.com/equipment-reviews/112331-orion-optics-uk-6-f11-dobsonian-review.html

I have to say that the views are so full of contrast compared with the 12" dob, which is no slouch either. it takes a surprisingly long time to cool though (well over an hour) and hence my next mod will be a small 4cm fan which I hope will fit inside between the end cap and the cell sucking air in through the small hole in the middle of the cap and pushing it up and out of the focuser. this should bring it down to maybe 30 mins and also if run while observing, steady the tube currents too.

[callisto]

Watching this thread with great interest Shane, as i am going to make similar mods to my dob .

cheers,

Mark

[Moonshane]

cheers Mark - glad you liked it. now I am starting this thread, I'll try and do step by step pics. dobs rule!

[Moonshane]

well, my fan arrived in one piece from Hong Kong via ebay all for the princely sum of 99p. It works too - confirmed by a quick test.

I bought this specific one as it was the slimmest I could find and I also wanted one that was small and would not produce as many vibrations as a larger unit. plus it has to suck air in through a hole only 10mm in diameter. I will fix it with velcro and this should further reduce the vibrations.

as you can see, at 4cm diameter it's a little cutie and should fit in between the end cap and the cell of my 6" dob.

[callisto]

Wow, thats a teenie weenie thing, watching with envious eyes

Mark.

p.s. how long did it take to arrive Shane.

[Moonshane]

not bad actually about a week.

if you have a little more of a gap behind the cap then I'd get maybe a 6-8m fan for yours. this will be plenty for mine.

[callisto]

Yeh, that might do the trick.

[Moonshane]

the main thing to check is thickness - it's really tight in mine as they squeezed every single millimetre of focal length out of the OTA. the mirror cell therefore sits literally right at the bottom of the tube.

[perrin6]

I might black-out the back of my secondary as part is open to the light, might do the edges too now (although they are aluminized).

RE: last photo. You could call your scopes 'Laurel' & 'Hardy'

Alan

[callisto]

What site did you get the fan from shane.

Mark

[Moonshane]

it was off ebay DC 12V 2 Pin Brushless Cool Cooler Fan For VGA Graphics on eBay (end time 24-Oct-10 12:43:15 BST) but there's plenty of suppliers and if you can get a slightly fatter one you will probably get one a bit quicker?

Maplins also do decent ones. mines been running for a while in the larger dob.

[callisto]

Cheers for that

[Moonshane]

I might black-out the back of my secondary as part is open to the light, might do the edges too now (although they are aluminized).

RE: last photo. You could call your scopes 'Laurel' & 'Hardy'

Alan

I reckon this is a good improvement. it really is noticeable when you look down the focuser tube for collimation.

ha ha Laurel and Hardy - my faves! this might stick !

[Moonshane]

I have to say that the photo of the two dobs together sums up the advantages of dobs in general and OO dobs in partic when it comes to how little floor space they take up!

[Moonshane]

Well my fan is in but it's really quite wimpy BUT I can feel airflow on my cheek even at half pace. The 12v setting is more 'powerful' but creates a surprising amount of vibration. It will be fine for cooling but for observing I'll reduce the voltage as I do for my larger dob.

The installation went quite smoothly really although I always end up swearing when soldering.

Here's some pics and a description of how it went:

1) Remove mirror - simple job - done in a couple of minutes - make sure you have the tube close to a wall / fence to prevent it flipping up as you remove the weight.

2) Remove the back plate. On my scope the collimation bolts come through a metal plate and therefore you have to take the nuts off to remove the plate for drilling etc. The mirror clips keep the surface of the primary off the table enough to be safe (assuming it's not got any crumbs on etc!!), watch out for the spring tension!!

3) Make up the wires. I used an old table lamp wire and stripped the outer casing. I then soldered the connector on the end and added some heat shrink tubing and a grommet where it passes through the end cap.

4) As I was doing this anyway I decided to make a more permanent solution for my little counterweight idea and drilled a hole for a 6mm bolt and used my 'spare' knurled nut for this. Looks a lot neater I think, and will also cover the smaller version which I may get to make it look a bit better still.

5) Holes drilled for the above and for the fan, I then fitted the wires through and soldered these to the ones from the fan itself. Ensure you slip some heat shrink on beforehand to cover the wire joins. I used a cable tie to hold them together and to prevent the wires being pulled out too much if I trip on the wires in the dark etc.

6) Now it's just a simple case of some velcro tabs on the fan corners (make sure you test it to ensure a) it all works and that the air blows the right way) and then stick it down.

7) Fit the mirror back together and then reinsert into the scope. Collimate and you are ready to go!

some pics below and more to follow

Cheers

Shane

[Moonshane]

more pics

[Moonshane]

last pics

[Moonshane]

some missed pics!

[callisto]

Great to see the pics Shane, hope everything went smoothly

I have flocked my scope today and cleaned the primary and secondary mirrors all went good.

I have also added the knurled nuts to the base for easy collmation, looks much better. I have ordered a 60mm fan for £1.17 so that should do the trick.

Mark.

[russ]

wow that is real impressive work Shane. Some seriously good modding going on there. And some ideas for our OO 150 F5

[Rusty Strings]

Good work. I surprised by the size of those mirror clips.

[Moonshane]

yeah I thought they were a bit large myself. I may try trimming them at some point.