AE of Luton Mount refurb questions

[skybadger]

Hi all

I am renovating an old Astro Equipment of Luton Class C mount in my garage, have been for two years now.

The purpose of this is to place the mount in the observatory as the big load-bearing mount to replace the Vixen GP/DDX that is there currently.

What's been taking the time is working out how to drive it. It came to me with a seized synchronous motor in RA for tracking and a chunky dec motor with double worm gearing. I took these off - I wanted goto!

I was originally going to take my Skysensor motors off my GP/DX and put them on this, fitting replacement iOptrons on the GPDX

as that would become my portable mount.But I could never find a way within the confines of the space I had on the mount that would let me mount them.

Eventually I found a way, bought another Skysensor, made some mounts and have finally got the motors mounted.

There are some pictures.. followed by some questions I need help on...

This one shows the mount fully assembled (no motors) with the 10.5" skeleton tube newtonian on it.

For the telescope I disassembled the tube, re-balanced it, fitted tube stoppers and gave it a clean. Nothing much really.

The focuser-carry plate I machined to put a Moonlight crayford focuser on. The carry plate had originally mounted a thick single arm for the spider but been removed before it came to me,

so I made a round spider by beating Ally sheet around a cylinder and folding the ends to bolt to the carry-plate. It works quite well barring the obvious silly mistake.

I also dropped the secondary while doing this so its got a great big chip missing, meaning I'll have to re-make the carrier since it's epoxied on and put a new mirror on that.

There are some ronchigrams of the primary . Its hard to photograph through the foucault tester but I think the mirror is showing turned down edge - I'd like to get expert opinion on that ?

The dec motor shows a lot of grease on the worm since I was using gear lapping compound to get a good fit.

The RA motor has very little space due to the the swinging dec axis so had to be squeezed in, hence the cutout on the motor frame. I haven't lapped this since the fit seems quite good and the worm was in good condition.

Overall comments on the AE Luton telescope ?

The mount is very heavy cast iron and very smooth moving on its clutches but it lacks the ability to easily alter the altitude of the RA axis by fine amounts. Polar aligning is not going to be trivial.

The other thing that concerns me is that access to the worm bracket mount screws is very hard, especially now I've put the motors on.

The telescope mounting plate at the end of the dec axle I'm going to replace with a bolt-on shaft hub to carry other telescopes too.

I have used the scope without the motors to observe to check collimation and optical quality and I think the optics are quite good but I can't tell too well until I fix that secondary.

Since the tube uses 1" tubing, as a light shroud I just used blackout curtain and camping pole clips to hold it there.

Now finally to the purpose of the post - I need some help. I am looking for ways of compressing those springs on the mount axles, they put the pressure on the clutches and manually isn't enough.

I could also do with some mirror-making opinion on the ronchigrams - they're the first ones I have taken and making sure I have understood them would be useful.

Last but not least - anyone got one of these and measured the PE/errors on the worms ?

Thanks for any help

regards

Mike

[davew]

Hi Mike,

I'll not give an expert opinion on the mirror but will direct you to - Telescope Test Page

This next bit is taken roughly from what I've read.

One way round it until you get the mirror checked out properly is to make a mask slightly smaller than the mirror ie. if the mirror size is 300mm make a mask 295mm ( ish) and set it a mm or two above the surface. Look first with the mask in place then take it away and look again. If the view is much worse without the mask, try a few different sizes until you get it right.

Hope that helps.

Dave.

[Doc]

What a scope I would love this so much, you are one lucky man...

[runoffshed]

Great scope. Regarding the springs, I am trying to see how they are held in compression at present - do they press against a sleeve or something? (and the clutch at the other end) If so, is it not possible to make a spacer / sleeve to compress the spring further or am I missing something (I'm sure I am). A bearing of the correct diameter would also make a good spacer. Failing that, you could fit wedges between the coils of the springs - not very neat, I know.

I am certainly no expert but the ronchi does appear to show a turned edge. However, am I correct in thinking that AE were Jim Hysom and his brother? If so, Jim Hysom was certainly a very fine mirror maker and it would be surprising to find one of his mirrors with an edge like that. ( I think he did the optics and his brother the tubes/mounts etc...

Good luck with the project.

John

[Peter Drew]

Hello Skybadger. I had a close professional association with AE Luton when I was in the astro business. It is highly unlikely that the optics will be any other than good as AE prided themselves on their optical quality and I certainly never had any problems with all the ones I used. Their gearing was made by a third party and enjoyed a good reputation for accuracy. Their clutching arrangement often gave problems, either too much or too little friction with a tendency to be a bit "sticky". It is possible to make an adjustable improvement by replacing the supplied collar below the spring with a flanged one that can be grubscrewed to the shaft, then with a thick washer placed between the collar and the spring, three adjusting srews set at 120 degrees in the flange, will provide extra compression effort on the spring.

[skybadger]

Thanks Peter.

Your adjustable spacer idea is a good one.

The issue is that the spring at one end rests against a thrust washer against the plumber block so that the axle can revolve. The other end is held compressed by the shaft clamp. Pushing the shaft clamp to compress the spring can only be done so far without tools I don't have. The compression pulls the shaft end down tight onto the clutch, hence Peters suggestion of an adjustable spacer to control the clutch drag. I'm replacing the stock steel clamps with side-sprung one-piece stainless to prevent marring the shaft with grub screws. Makes it a beggar to get out of the shaft bearing blocks.

Thanks

Mike

[runoffshed]

HI Mike, just a bit more on Jim Hysom.

I have a 12" Newtonian which I purchased second hand in about 1993. It was made by a well known British manufacturer but the mirror turned out to have a very severe turned turn edge. I had heard of Jim Hysom as a very fine mirror maker who took a real pride in his optics, and at the time he was still working - as Hytel optics, I think - so I sent it off to him and he corrected the mirror using a sub-diameter tool for, what I thought, was a very reasonable cost. That's why I think, like Peter, that he would be very unlikely to let a mirror with a turned edge leave the factory .... if it has got a bad edge I suppose it may not be one of their mirrors. I don't know if Jim Hysom is still working but you could always try and track him down and get his opinion. Are there any markings on the mirror back?

Good luck and keep us updated on progress please.

John

[Mark Stuckey]

Hello As I have a lot of information regarding A.E telescopes, as well as the booking out (finished optics) if you can give me the information on the bottom or maybe side of the primary mirror i should be able to give you as to when this was made by who and who had tested it as welkl as there results, I have all the standard models here that i have restored upto the 14 inch cassigrain models.Mark

[skybadger]

Hi Mark

That would be great - I'll check tonight. Cheers

Mike

[Mr Spock]

Sigh... back in the 70's I used to drool over pictures of these in the BAA journal. Something like an 8" on a B-Type mount was about £1200... For someone on £50 a week it was stuff you could only dream of.

There's an observatory not too far from me which had a 14" on a cross axis mount. The observatory is still there, don't know about the scope.

[skybadger]

I now have the mirror spec - it says 'Terry Wickett 4019' on the back of the mirror.

I have just spent the last hour balancing the scope and attempting to adjust the springs. The dec one is easier - I just sit aside the dec axle and heave the dec weight along the axle, gives a good compression but sore nads..

The RA one I am making a variable spacer out of brass and steel, basically a pair of threaded collars that screw into each other to vary the compression.

Mark - have you a technique for comporessing these springs ? ANy phogtos of your renovated collection ?

Cheers

Mike

[twicko]

The AE telescope you are refurbishing was mine from new in about 1973 to early 80's when I sold it to a colleague who had become interested in astronomy and who used it for several years and then sold it on,possibly to you.

If you want to talk about the 'scope I am often on Skype and I can always contact my colleague to see if he has other info.

I joined the forum today on getting an email from my son who was stuck for access to his work so did a Google on my name and came up with your post!

Best wishes Terry

[Steve D]

Hi guys, newbie here.

I have inherited off my father who passed away last Friday one of the said AE 10" Newts with the standard GEM. Long story short, he had the mirrors re-aluminised by Orion optics about 15 years ago but never fitted them (I visited today to look over his other old scopes and they were sitll in the original packing). The tube (skeleton) is still resting on it's side in his hobby/junk room and the mount (which I repainted years ago) is in the pantry. I remember having the same clutch quandry as Skybadger, ie how to reset it. First I measured carefully the distance between the top of the spring to the bottom (where the collett with the grub screw is) then stripped the lot for paint. The way I got the correct compression when re-assembling was to use three large U-clamps at 120 degrees and just slowly turned (worked a treat). So now I find myself faced with a total refurb to bring this grand old lady back to life. If any of you guys have any pic's of thier scopes I would be most gratefull, needless to say I will post a full album as soon as work starts.

Many thanks.....Steve.

[bugtraq69]

Hi, I'm another newbie. I've got 2 AE mounts and 8.5-inch OTAs that need varying amounts of TLC. Ideally I'd like to refurb preferably to concours condition, but having trouble tracing what the original paint job would have looked like. I've looked for old catalogs but nothing found so far.

So far I have white primer, mid-blue overcoat, a ***kload of flaking grey Hammerite (on one) OTA/mount and flaking brown Hammerite (on the other), followed by various tube castings and pipes in matt black and the most disgusting shade of matt brown (old red primer?) you could possibly think of.

2nd question - I've got a Vixen GP/DX, how easy would it be to put the OTA on this mount whilst I'm working on an AE one? Seems to be within tolerances weight-wise, just not sure how to attach it without doing a bodge job.

Can anyone help on either point?

Thanks

peat

[A Walker]

Hi there,

Those Hammerite colours are likely to be original (or close to it). I did hear or read somewhere that AE only used Hammerite colours. Apparently the grey/siler was a very common colour used on their tubes. Could the Matt Brown be similar to the hammerite brown on the tube of my scope (see image)? I have seen this colour on several scopes in original condition from 1972 or there abouts. I do have

I do have copies of an old cataloge or two if anyone interested in AE scopes wants a copy please send me a PM with your email address and I can send them though. The file sizes are too large to attach.

Great to hear more of these beautiful old scopes are seeing the light of the night sky!

Regards

Andrew

[skybadger]

I haven't seen some of these responses and happened to come back across this post. thanks everyone.

The mount is now in the observatory and working fine. I eventually took the plunge and regreased with thick rocol cutting grease and the pe is now very smooth. I couldn;t find anything in the spec to say that it was anything but a tenacious grease.

I also solved the altitude adjustment issue by fitting a strip of pallet banding along the circumference of the RA head sector , fixed to the head at one end of the sector and to a plate via a thrust washer and m8 screw at the other. Unlock the secotr for adjustment, take the slack on the banding and tighten the screw to  adjust. Works lovely. All I need now is a means of adjustment in azimuth.

Right now I am usng using wooden blocks and a light hammer to adjust in azimuth. not the preferred way.

Mike

[ChrisLX200]

I haven't seen some of these responses and happened to come back across this post. thanks everyone.

The mount is now in the observatory and working fine. I eventually took the plunge and regreased with thick rocol cutting grease and the pe is now very smooth. I couldn;t find anything in the spec to say that it was anything but a tenacious grease.

I also solved the altitude adjustment issue by fitting a strip of pallet banding along the circumference of the RA head sector , fixed to the head at one end of the sector and to a plate via a thrust washer and m8 screw at the other. Unlock the secotr for adjustment, take the slack on the banding and tighten the screw to  adjust. Works lovely. All I need now is a means of adjustment in azimuth.

Right now I am usng using wooden blocks and a light hammer to adjust in azimuth. not the preferred way.

Mike

I loved the pics of the old AE mount, years ago I used to drool over the photos of those in their catalogue (which I still have somewhere). The mounts just looked so  - well engineered and robust in comparison to their competitors of the day (Fullerscopes for example). I used to dream about the Dall-Kirkham cassegrain on a C-mount

ChrisH

[roduni]

I am refurbishing an AE Luton 10" reflecter that has been around he world with me. I have retired and am now living in the Southern Hemisphere.

I am wondering how to convert the  220v-240v/50Hz motor; Drives for Southern Hemisphere must operate in reverse to the Northern Hemisphere of course.
I have had to relace the 1" eyepieces with 1.25" and had forgot about the motor problem. Do I simplly reverse the worm gear?

I will solve the problem eventually but any suggestions to speed up the process will be greatly apprecisted.

[skybadger]

This is an old topic now but... the motor will need to be reversed on the worm - either by replacing with one which turns the opposite drection ( in teh case of an ac syncro motor) or by moving the motor to the other end of the shaft, reversing the motor direction that way.

Or replace the whole motor with a stepper/dc motor and belt system for forward and reverse control. 

Good luck

Mike

 

[skybadger]

It's funny how topics seem to never die.

I'm adding more here since things have taken a new turn . It seems that while the mount can take the weight, the drive can't. First one RA motor developed a tick and refused to slew w-e and then the spare I replaced it with has developed a jerk. It will slew with accuracy but not track without jerking every 7-12seconds or so. I suspect in both cases damage to the internal spur gears. 

So I need to replace the motors with something more to use that will fit in the enclosed volume and remain skysensor compatible.

Since the original motors were tsukasa  tg35l brushed DC motors, and I can configure an integer output gearbox ratio on the controller, I need a DC motor with a 400ppr incremental encoder, 44mm diameter or less body and 10kgcm or so torque to drive a 30kg load through a 360 tooth worm. The current final output gearbox is 35:1. 

Any ideas of sources?