Bresser Messier AR152s refurbish and repair

[badhex]

So, I've started repairs on my newly received but used and damaged Bresser Messier Ar-152s. For anyone interested in how I acquired it the backstory is here: http://stargazerslounge.com/topic/221349-bresser-messier-ar152s-cracked-objective-lens-collimationretaining-ring/

The short version is that I expected the objective cell lug to be broken off, but the rest of the damage (including the chip in the objective!) was news to me.

Things completed so far for this refurb are as follows:

Objective Lens Cell

- Replace chrome collimation bolts with black matte bolts

- Epoxy/pin lens cell collimation lug

- Remove objective lenses

Focuser Assembly

- Remove and replace sheared bolts

- Epoxy crack in outer rim

OTA

- Glue crack in plastic under dew shield

Here are a few pictures of the scope as it was when received - the initial and obvious damage most which was not revealed to me by the seller:

   

First step was to do the easy stuff. I grabbed the collimation bolts just before leaving for work, I have a wicked source for any kind of bolt you can imagine - Clerkenwell Screws in central London - and had a thought that maybe the missing bolts holding the focuser and tube together were the same size. At this point I found another problem - the bolts were actually sheared off inside the focuser assembly - eek:

After spending all day worrying about having to remove sheared bolts (The tool shops near me had damaged bolt removers which would do the job, but at a cost of £27 for a set of four!) I found that the bolts were actually loose enough that with a bit of care, a sharp knife and a small screwdriver I managed to work them out with no damage to the internal thread!

Next up was a quick superglue job on the crack inside the dew shield fitting. Not a load bearing or structural part so happy enough with Loctite to do the job, may repaint over later but it's not inside the tube so reflection should not be an issue:

Now for the more worrying bits - removing the objectives from the cell. I had trouble previously attempting to remove the retaining ring and had looked for a lens spanner to fit 152mm - unfortunately I was not willing to spend £50 on something I would use only twice so I improvised. Behold, my low tech custom lens spanner!

Once the retaining ring was carefully removed you can immediately see the scope (ahem) of the damage, and possible previous attempts to disassemble the cell. The inside of the cell itself was essentially covered with fine ground glass I think the only thing that saved the objectives from being scratched in between were the 3 tiny foil spacers between the two objectives:

And finally the objectives and the offending piece of broken glass.

After I'd washed down the cell, retaining ring and lug, I dried everything off and then mixed up some JB Weld steel epoxy. I am assured by what I have read that this stuff is amazing and hopefully plenty strong enough for my needs. I used a little on the crack in the focuser assembly, smoothed over and excess wiped away. Again it's not a structural part so with a touch of paint hopefully this will be good as new.

Finally I applied the JB weld to the broken lug and reattached, holding in place for 10 mins or so to hopefully get a good strong join. Pinning was not really possible as the clearance even for 3mm rod was too tight for my repair skills, although if I think the join is not strong enough I may reinforce with some thin metal sheeting.

Although it's clear that the threads are a touch misaligned, I've run a screw driver tip and scalpel between the thread to ensure they are a close as possible, and I may need to do some minor filing once fully cured. Hopefully, this should not present an issue - even if I need to file them back a bit around the join 98% of the cell threads are absolutely fine.

My next step will be to test  the strength of the join, and clean up the objectives ready for reassembly. At the moment, there are some tiny shards of glass  around the objectives plus a smeared spot of what looks like oil of some kind which was between the two, so I'm thinking that a thorough but careful rinse will be the first port of call.

Can anyone recommend if fairy or another detergent is a bad idea? Also, how to dry the cells? I don't really want to rub them with anything for fear of damaging them or the coating, but fear that leaving them to air dry will leave stains or spots. Hairdryer on cold (i.e. no heat at all, just blowing air) maybe?

Thanks all, sorry about the long post but hope you have enjoyed my repair pics. Will add updates when there are some!

[John]

You are doing some great work there !

I've cleaned objective lenses with the Baader Wonder Fluid applied with their micro fibre cloth and they have come up like new. Make sure you blow all the debris / glass dust off the lens surfaces before applying the cloth / fluid though.

Keep a note of the positioning of the foil spacers as they should go back where they were. Ideally the lens elements should be put back in the same relative positions they were in - there are sometimes index marks on the sides of the lenses to help you do this.

[badhex]

Thanks John

I seem to remember that the bottom element has a mark on the side, presumably this matches up to a mark on the top - and would they only have to be in the same positions relative to each other and not the cell?

Unfortunately the two elements were freely moving about in the cell so they were likely not aligned, and two of the foil spacers were pretty much floating about. I'm pretty lucky that they were there at all given the lack of care someone has shown. I think there was one remaining one in its correct place, and I believe they are equally spaced so I'll hopefully be able to use snakeyJ's pictures for reference.

Baader wonder fluid it is then!

[LeeB]

keep going, I clean my lenses as mirrors using mild soap solution and distilled water flush.and hair drier on cold., it beggars belief what some people do to scopes, they almost seem to want to damage them. Are you blackening the chip or stopping down, I have done both in the past and while not as pretty blacking just the chip works fine.

[badhex]

Hi Lee, thanks

Don't really want to stop the lens down so will black out for now - if it doesn't work out maybe I will resort to stopping down but would like to keep as wide as poss (even though I know it won't make that much difference shaving 3 mm aperture off)

Thanks

Joe

[LeeB]

excellent, be careful cleaning , remove the dust/glass dust with a running tap and soften your fingers in the soap solution for 10 mins, I always find the lightest touch with pre soaked fingers removes even the stubborn stuff without damage. if yopu still get any streaks use baader fluid and a clean cloth after the clean.

[philj]

Nice work, did you index the objective before splitting? To make sure they go back the same, the front element needs to go back the correct way round and usually but not always in the same aligmnent with the rear element. The foils only need to be equidistance at 120 degrees it doesnt matter if they have been shifted. If you replace a foil make sure its the same thickness as the others to avoid ghosting.

[John]

Thanks John

I seem to remember that the bottom element has a mark on the side, presumably this matches up to a mark on the top - and would they only have to be in the same positions relative to each other and not the cell?........

No problem. Yes, it's relative to each other rather than the cell - which is what Phil is talking about above. You are going to need to re-collimate anyway after this lot so the lens orientation in the cell won't matter.

Also, as Phil says, the air space between the lenses is important and needs to be just the right distance. If possible it's best to re-use the original foil spacers to ensure it stays the same.

[LeeB]

I have never had issues, with spacing , I use tiny squares of good quality ali foil , it is more important that they are all the same. you could mic the thickness if unsure.

[philj]

On my 4" f15 I used a Mr Kipling individual apple pie foil cup. I cut 3 new spacers and they worked a treat.

Mr Kipling makes exceedingly good spacers :-)

[badhex]

Haha excellent! Good old Mr. Kipling. No pie eating will be required however as I have the original spacers

I figured it would be just the elements being relative to each other, having had a look it appears there are marks on them to allow to easy alignment.

Additionally, from what I can see the chip does not appear to extend over the bottom lip of the cell so I suspect it's not smell much difference if any.

Thanks all

[cotterless45]

Ha ! Good old Mr. Kipling ! We also found that the pound shop does exceptionally fine solar film caps for 90mm refractors !

Well done with this scope revival. Many would have flinched and walked away. Following this re birth,

Nick.

[michael.h.f.wilkinson]

Awesome work! The damage to that scope was quite horrific

[badhex]

Thanks all. A quick check last night of the collimation lug repair seems sound but I guess I will have to wait and see. I'm awaiting delivery of some Baader wonder fluid but will give the objectives a gentle water pre-wash this weekend.

@Phil regards your above statement about alignment with the rear elements, no clue how I'd do this, no alignment marks on the rear elements without dismantling the cell (I guess) and given that's one of the few bits that's not broken I don't really want to do that!!!

[philj]

Hi Joe if you have alignment marks then you should be ok just get them matching. The front element is often matched to the rear by rotation. My 80mm towa was awful when I first got it but once I rotated the front element in relation to the rear in small stages, testing after each rotation it was transformed. I did this whilst viewing Jupiter at about 80x. Initial views I could get the major belts but no detail, I rotated apprix 10 degree and the views improved each time.

[badhex]

Ah, thanks Phil I thought you might be talking about matching with the rear elements in the focuser assembly, this being a petzval type design. The front and rear elements in the main objective cell are marked so should be good...

[F15Rules]

This is just brilliant stuff Joe and I take my hat off to you .

I think the seller should hang his head in shame at selling you a scope in that state without advising you of all the damage.

But the lens damage does not seem  bad and the chip in particular won't, I feel, be visible at all. I had a scope years ago with a much worse chip which extended about 15mm into an 80mm lens. I painted it over with flat matt black paint: it didn't look pretty but you couldn't tell from the views that there was any damage. Yours looks much less severe and the effects should be negligible: much more important will be the re-assembly and aligning of the two lens elements, but you have had some great advice from the guys here already and more to come, I'm sure, if you need it.

This will be one First Light report that will really be worth waiting for...Respect!!

Dave

[Jim Steele]

Fantastic work. What had the seller done to it for it too be in such bad shape?

Good luck with it - hope you get it sorted

[badhex]

Wow, thanks you guys! Extremely appreciative that you have all taken the time to read this stuff! This is why I love SGL!

Maybe I learnt my tenacity from waiting for dark skies in London

[nightfisher]

Joe, your doing a superb job on a poorly refractor, re the lens chip, i had an Antares 4" f15 with a ppretty bad clamshell chip about the size of a 5p coin, to be honest i never blacked it out and under the night sky it was invisible, even viewing a full moon it showed no artifacts

[badhex]

So I've now completed the initial water wash of the objective elements. Look much better without all that crud on them! You can also see the alignment marks in the picture below.

There are a few small stubborn water marks but I suspect all will be okay after a round of baader wonder fluid. There are also two - small and barely detectable - scratches in the coating between the two elements which I think happened while the objectives were freely moving about in the cell (so any time before I got it really) but I don't think they will be an issue, I could only just see them when looking from a low angle with light filling the objective.

I did a test assemble also, just without fitting the retaining ring - I think I need some of those fancy cotton gloves to stop finger marks on the lens edge like I'm handling the Elgin Marbles or something!

[cotterless45]

That looks superb !

Nick.

[cotterless45]

I don't know what folk get up to. I bought a small achro, looks like the chap tried to clean the edge of the objective with a Brillo pad stick. I've also got a zoom ep, so curiously cleaned that when observing anything bright , there's loads of little flecks in the fov !

I don't really mind rescuing gear.

The very worst was a Vixen 102 on a Super Polaris mount. The Synta green was grubby brown and the ota was full of curious white deposits. I thought he'd been keeping a rat in it ! The focuser grease had set hard !

Good luck to all rescuers out there !

Nick.

[badhex]

Thanks Nick. Yes, it is odd. I have a feeling that someone basically dropped this down the stairs or similar - there was a lot of damage, but I do like a challenge! There's also a satisfying feeling to be had knowing that you have put in work to get something up to standard, and I've always enjoyed fixing things!

Good luck indeed to other rescuers

[badhex]

Also, there's a chance to possibly make a few improvements along the way, like replacing those silly chrome collimation bolts and flocking the dew shield. I may also replace the finder shoe to a more standard fitting, I don't have the original finder and they appear hard to come by.