280mm grab and go scope

[Hedworx]

Ok the '280mm grab and go' title may have been a little misleading, congratulations for having a look anyway.

I have been very fortunate to be able to acquire this exquisite scope, my new 280mm refractor.

It is an APM-LZOS 280mm f10, air spaced apochromatic triplet

Only two of these lens cells were made in this size, this being number 2 of 2. The mechanics were fabricated by the famed Matthias Wirth from APM telescopes, I cannot express how incredible this instrument presents in every way.

The scope has two configurations, a straight tube if you have the space and a large enough peir and dome, or a folded setup which uses an optical flat secondary. The folded mode takes the overall length down to a 'manageable' 2.5m which is most likely the only way I will be able to wield such a monster.

My first priority will be to build a manual alt-az dobsonian style base to get me up and running manually to use as a visual planet killer. I have plans to mount it on an ASA DDM100 later this year, the pier and the like will no doubt be a mammoth task to engineer and build.

I dare say I will keep updates here as they happen if you would like to follow the journey as I go.

All going to plan I can mount the 180 Lzos as a finder scope.. maybe put a 2.7 APM barlow in there and I can double up on planetary cameras. 180 for RGB as colour and the 280 for IR perhaps.

[croweater]

Hi Luke. You rightfully look very proud standing next to your amazing new scope. Yes, please keep any updates coming.
Cheers, Richard

[Crater101]

A monster alright, but a worthwhile one. Looking forward to seeing how you set it all up. Keep us posted!

[EpickCrom]

Holy cow Luke:eyepop:

Please post a first light observing report once you get your new monster refractor up and running, I'm sure the views will be incredible :eyepop::eyepop:

[anj026]

Crikey thats awesome. If you haven't met Joshua Bunn (Albany) then I suggest you make contact as he will be able to help.

[Peter Ward]

Wow. An 11 inch refractor. Very impressive.
It will be interesting to see how you mount the beast.

Congrats!

[Leo.G]

Are you sure that isn't the gun turret off a war ship?
That is certainly one big telescope, it will be interesting to see what you do for a mount, it would be quite the undertaking.
Is the rotational inertia going to be an issue?
It doesn't look lightweight.
Sorry, same words as Peter above, not copied, my exact though too.

A head with 100Kg capacity, that answers my own thought as to "I bet it's heavy".

[Pierre_C]

Just wow.

:astron:

[TrevorW]

I think you need a bigger observatory :)

[Joshua Bunn]

Hey Andy,
Yeah, Luke and I have known each other for some time. We're working on the rollout pier for the DDM100 and this 280mm refractor. It will be lots of fun!

[Nikolas]

You need one of these (https://cdn.prod.website-files.com/617bfbfccfd67c8d5ae89950/646b5a59e64bbafaa346ba32_Hydraulic% 20truck%20cranes.jpg) to mount that thing!

[Bobbyoutback]

Congratulations Luke ''
Looks fantastic ' I'm Super impressed :eyepop: :)

Bobby

[anj026]

That's fantastic. I wish you both great success and it certainly sounds like fun to me.

[OzEclipse]

Hi Luke,
Amazing project. I can’t figure out how a 280mm f10 that has a 2800mm focal length so how does it end up with a 2.5m tube in a folded configuration?

Surely it’s more like 1.5m folded?

Good luck
Joe

[Hedworx]

The folded section would take about 900mm of the length of the straight tube I would say. There is only one mirror in this scope as opposed to the other folded designs with the 'N' or 'Z' shape. The dew shield is massive though at 500mm long, should be quite effective I would say. I should upload some more pictures with measurements I guess.

[Hedworx]

At over 50kg in it's naked state it sure will need some good engineering to work well. I don't think I will ever be able to use it as a straight tube... How would that even work haha, a skyscraper as a pier?

[Leo.G]

That's not something I'd like to be setting up and taking down every night. I struggle with a 14Kg refractor.
It's not I can't lift that weight, it's just how awkward it gets.
Yes, I do understand it's something that gets set up on a pier and mount and left in place, even I'm not that silly.

[Hedworx]

Added some more pics for those who are interested.

[Hedworx]

I need to make a dob-style alt-az base for this monster to get me up and running before I can mount it on the yet-to-arrive DDM100. I was thinking I could machine down these aluminium car wheels to be trunions for the dob-style base, it would save having to buy 25mm plate ali and the criss-cross spoke pattern might look kinda cool. Any thoughts?

The attached pics are a dob-base for a 228mm Lzos in Europe somewhere

[Hedworx]

I am making some progress on the manual alt-az dobsonian style base for this huge refractor.

I have fabricated a steel frame with three lockable wheels to which I have mounted a 800mm circle of laminated chipboard from an old shop display. I know it is not the best material to use but I had it laying around. It is 30mm thick and laminated on both sides with a smooth laminex style finish.

I have painted the edges with 2k epoxy with some black pigment in there to make it look nicer, should stop any water ingress and prevent swelling.

The two base boards are joined by a lazy-susan bearing and I have three hdpe pads in there as well. It isn't tpfe but they say it is almost as good, again.. what I had laying around.

I have made a start on getting the altitude trunions underway by cutting up some old Jeep wheels that I had gathering spiders in the backyard.

It is all a bit agricultural and some would be right to say it is sacrilege to mount such a fine instrument on a hap-hazard dob base like this, I agree... This is only a temporary measure to get the scope under the skies. Please dont bring out the pitchforks.

[Saturnine]

What a fantastic project and as far as the dob style mount, it is amazing what can be utilized from stuff just laying around. Keep the updates coming.

[Hedworx]

Will do, thanks for the encouragement. I had figured nobody was interested as the post hadn't gained much attention haha, talking to myself I thought.

I am not sure if this post should be in the ATM/DIY forum or not but I will keep posting my progress.

[Leo.G]

Coming along nicely, cut with a cut off wheel?
A plasma cutter would have been a lot easier but of course that's dependant on having access to one.
I have one in the shed and it's a pain dragging a compressor out to use it so I mostly use a grinder (see lazy). The plasma cutters are however fast and clean with minimal grind clean up.

[Hedworx]

I burnt through a bunch of grinder discs until I ran out, turns out the hardware store has grinder discs specially for Ali, that made a world of difference.

[Tinderboxsky]

Following with great interest.

I am a big fan of re-purposing items. Makes perfect sense when the mount is a temporary solution.

[Leo.G]

Yes, the regualr grinding/cutting wheels fill with swarf and can no longer maintain a grinding surface (same thing happens to files, keep a good wire brush handy to clear the teeth).
There are also better branded quality wheels than cheaper ones too (not suggesting you used cheap wheels).
It would have taken a while hand cutting the rims?

[Hedworx]

Got a fair bit done on the altitude trunions, machined flat and profiled ready for the next step. The chuck on the lathe was gripping the inside of the wheel so didn't have much gripping power...

This resulted in some lathe chatter on the outside edges as the harmonics of these were ringing like a bell. I am actually very happy with the chatter effect on the front side.

Next step is to machine out the center 5 stud holes and have one larger, better looking hole, then mounting them to the tube rings.





Angle grinder with the right discs worked well once I finally bought some ali ones. It only took ages with regular steel discs as I had to keep changing them haha

[Leo.G]

That chatter gives the rims a rather unique finish, they look great.
What's the swing (over the bed) on the lathe?
It's a big machine. It wouldn't be the easiest turning job gripping the inner edges.

Saying that a local engineer is selling a turret lathe, the thing is 30 feet long or thereabouts (I forget) and he said he's had offers of $2,000. It comes with $40K+ worth of chucks and tooling, I'm going to need a bigger garden shed. My cheap Chinese thing I have cost me a lot more than $2K (currently up around $8K with tooling and compound table and vice for accompanying milling machine).

[Hedworx]

Mockup of my cannon wheels, I mean... altitude trunions. They look pretty good for rough start, still plenty of finishing work to do to get the final look a lot nicer.

Now that I have the trunions sized and mocked up I can get the measurements to make the rest of the Dob base.

Overall length is around 2300mm and very top heavy. I need to have the rocker box extraordinarily tall as the weight is all in the lens. It will be a very odd looking scope for those who are used to the bottom heavy nature of most Dobsonians.

[Leo.G]

Wow, I was thinking you had 5 stud tube rings.
You mentioned boring the centres, what diameter hole are you going for in your calculations?
Too close to the spokes will weaken the overall design.
Would you be better going to a hub design you bolt the already stud holes to the hub for overall strength (unless they have been machined down to a flat surface).
I guess you are trying to maintain strength while keeping mass down?

Still, it's an impressive machining job and no easy undertaking I'd assume?
My lathe wouldn't even do mini minor rims, 300mm swing over bed but 700mm between centres.
Sadly I studied fitting and machining as an aside to fabrication engineering along with hydraulics and pneumatics back in the late 90s and still had a lathe for maybe 10 years later that but had to get rid of it during an emergency move into emergency accommodation. (Cert 2 in each I think, Cert 3 in fab engineering, arc, MIG, Tig, Oxy and fabrication design and loadings, I honestly don't remember which certificate for the 3 nights per week for 2 years for machining and hyd/pneu and have no idea where my paperwork is, I have no need of the qualifications, I can't work anyway.

We now have our own little Chinese thing in a garden shed up the back yard which came as a kit with a bolt on milling machine but I didn't like that idea because it's very restricted functionality so I bought a nice compound table ($1,000) (ForestWest have some nice gear for good prices) and a good vice and had my engineer friend drill and tap the cast bed of the compound table (I hate tapping cast iron, don't mind welding it when I have the correct blow torch handy for pre and post heating (and an oven for the rods) but I hate tapping the stuff. He did a great job on it but now I have to weld up a table/stand for the machine and I'm confused with my dimensions. I was going to make it the full travel length of the compound table but that's not really necessary and I save a lot of materials with a more compact size. I have 40x40 SHS, 4mm wall thickness and I have some 50mm (or 75, I forget) c channel with a 6mm flange and I was going to put that across to mount the compound table and mill. The more rigid the build is the better the milling finishes.
My main problem is getting the steel to bend a swarf/coolant tray because I'd like to add a recirculating pump to the coolant and eventually convert it to a CNC unit. No trailer or ute and delivery of a 1200x2400mm sheet is rather expensive.

That takes brains and money, I'm short of one and thin on the other, lol.
I really need to get it done soon. The lathe weighs 300 KG (small unit) and is standing firm on a stand I welded up (thankfully, I over engineer everything for strength, part of formerly being a forklift technician and car hoist specialist/technician over the years).


It's going to be a very interesting build when you get it all finished!

[Hedworx]

The reason for machining out the centres into one larger hole was purely for aesthetics, one hole will make it look less like a car rim that has been recycled. The large hole will cut out all the 5 smaller holes completely and leave the entire spoke design, there is plenty of meat left on the bone and the strength will not be affected I wouldn't think. Centre hole will be about 160mm in diameter.

[Leo.G]

They are going to look very nice and very likely original.

[AstroViking]

To paraphrase Paul Hogan...

"That's not a telescope.... THIS is a telescope."

I can't wait to see just how huge this machine is going to be.

[Hedworx]

I still underestimate the size of this thing!!!

Rocker box is coming along nicely, took the lens cell out of the tube to be able to lift it up into the bearing races, it is still so heavy... a real struggle by myself even with no lens.

Mocked up some panels with the tube in place and all held together by clamps, started the fabrication process and am pleased with the results so far.

[Leo.G]

WOW, is the lens the counterbalance?
You need a forklift or decent overhead crane for handling.
It's looking amazing!

[Hedworx]

Lens cell weighs about 27kg, so it balances where the rings are currently. I have a bit of room to move the tube up or down to achieve final balance once fabrication is done and assembly is complete

[Leo.G]

It's a mammoth undertaking but I'm sure it's going to be very rewarding when it's all finished. There's something very satisfying in knowing you do these things yourself and something to be said of your engineering skills and workmanship, it's all looking very professional.
I take my hat off to you sir!

[Hedworx]

Almost done with the fabrication part of the build, still plenty of smaller finishing touches to clean up. Overall though it is coming along quite nicely, might even see first light this week.

[anj026]

That's awesome Luke. Thanks for sharing the story and pictures.

[Leo.G]

That looks amazing Luke!

[Hedworx]

And of course it is cold, wet and raining!!!

[Leo.G]

Oh, I thought the rim centre was going to be a bearing point but I just realised the bolts to the brackets. It's still an amazing looking set up!
Do the rims roll in any particular material to protect the timber?
Looking back it looks like a strip of mild steel but I'm both blind and stupid!

Probably nothing this sort of weight (I don't have a working crane) but I've often used the yellow tongue from flooring to act as a bearing/sliding surface which removes risk of wear and is easily gotten and replaced.

Do you have a permanent smooth concrete area to roll it out on?
Sorry, I always over design everything and I'd have to have a lead base so it was counterbalanced at all times, that or outriggers. Then again, I have a sloping, uneven yard and struggle to roll a welder on a stand without it rolling off (40Kg MIG welder).

[Hedworx]

Just outside the garage door there is a hardstand area where I do my imaging and observing from. I wouldn't want to wheel it much further than that haha, the thing weighs a lot.

The trunions sit on HDPE pads (2 per side) the pads are 10mm thick and seem to ride pretty well. The hdpe might not be quite as slick as tpfe but it feels pretty acceptable to me, I might put a bit of soap on the trunions to try make the movement an little slicker. It isn't that it is sticky now, just the scope being so heavy makes the movement a one hand job instead of one finger job, oh the travesty.

Overall I am very pleased with the build. Only drawbacks at this stage is the insane top-heavy nature of a tall mount like this, one must be very careful when moving it and moving around it. It does also seem to take a second or two to settle as the moment arm is so long, I guess any sufficiently long instrument suffers with that same problem.

[Leo.G]

I think bearings or teflon (sorry, PTFE) grease on the pads would make movement easier but you need that bit of resistance if you want any chance of sighting any target I would imagine, unless motors and gears were involved. I'm guessing once that weight starts swinging it takes some stopping?
The resistance stops the unit running away from you when adjusting the RA.




Hence my mention of outriggers or heavy lead base. It's good you have a decent area to roll it though, that makes it much safer with the design and the height probably couldn't have been avoided with the length of the scope itself?

The build is extremely impressive!
Were I to own my own place and I had something extremely heavy I could leave on a more permanent mount but required moving to my viewing area and I had a decent concrete area to move it around I'd go rails. But my son is an absolute train buff (or was) and there would be a driven rail system designed whether I wanted it or not and, I'd go with it.

[Hedworx]

Thanks for the feedback Leo

Indeed, I concur. A more permanent installation is the endgame. This dob style base is only meant to be a temporary solution until I can mount it on an eq mount. The ASA DDM100 is in the pipeline but will be a few months away at the very least.
For a temporary solution this base serves a purpose and it seems to be sufficient for the time being. Ultimately a permanent pier setup is the goal but that will be a work in progress and span the foreseeable future.

[Leo.G]

For a temporary solution what you have done is beyond impressive!
Is that Ply you've used or particle board/MDF?
I couldn't see in the images, if particle board/MFD basic PVC wood glue is great to seal it to weather proof/make it weather resistant for dewy nights. If ply that is of minimal importance but the PVA glue is still good on edges. It can be mixed with water and painted on with a brush and dries clear.
I have no idea why I'm telling you this, with what you've just built I'm sure you know.

[Hedworx]

Haha yeah all good, it is 26mm chipboard with laminate on both sides, from an old stock stand shop fitting from a bookshop. The edges have been painted with 2k epoxy resin mixed with black pigment, as are all the glue joins along with a healthy amount of biscuits for good measure. Recycle what you have was the name of this build... so I used what I had laying around and built the mount for $0.

[Hedworx]

Ok... I am not an incredible story teller nor am I able to embellish details to keep one on the edge of their seat as I regale my experiences. I have never written an observing report either so I have no idea of the format or what things to talk about. Having said that I am sure there are some who would be eager to know what this scope is like so I shall try my best, here goes.

Let me first preface this evening with the weather report... dismal would be fitting. I had just finished a 12 hour shift but I am extremely keen to try this thing out, the cold, wind and incessant
sucker holes wouldn't get count me out tonight.

I have to move the scope out of the garage onto a carpark area made from that old pea-gravel bituminised stuff, even though a few short metres is all that is required it is painstakingly nerve-racking wheeling this thing around. The 60kg tube mounted so high is precarious to say the least, traversing small bumps feels like driving a monster truck over a pile of wrecked cars. It takes agonising minutes to move into place, the scope must be tilted up and down to clear various low-hanging obstructions like the garage door, roof rafters etc... this thing is big.

Once in place the wheels are locked, I make sure they are all facing outwards to maximise the footprint as much as possible. The movement is actually incredibly smooth, I am very surprised I was able to build it right the first time and have it move with the perfect amount of stiction. Although the movement is sensational, the settle time... well not so much. The moment arm on this tube is huge, and being such a heavy scope it really is under-mounted in it's current form, a 3 second settle time I would say. I doubt there would be a solution for this short of fabricating a 200kg steel base somehow. The 2800mm focal length is quite long, objects move through the field of view quite quickly so you need to constantly bump the scope, then wait the settle time and bump again, not ideal.

I only observed for around 30 mins to get a feel for the scope. I am using one of Denis Levatic's incredible bino viewers and a set of Docter/Noblex 12.5mm eyepieces. If you were ever on the fence about binoviewers I thoroughly recommend you seek out Denis and purchase some... they are simply the best.

The sucker holes were so bad that I would find a target, get focused and then get whited out, try again somewhere else. I was eventually able to dial the focus, get both eyepieces focussed in the same spot and try to find some stuff. Being f10 it was noticeably dimmer than my 16" f5 dob, some targets were much more difficult to find but I guess it is pointless comparing the two as they are vastly different instruments.

I have to say though, this lens cell is incredible, the stars are as sharp as a tack. As round as one could hope for across the field, no discernable colour fringing, no colour aberrations whatsoever, no spherical aberrations, no coma, nothing, it is literally perfect. I was able to clearly see the stars change shape and size based on seeing conditions, whether an appropriate cool down time would have changed this I don't know, most likely.

I viewed a few targets very briefly, fighting through the clouds and inclement weather was a struggle. This scope really will be a planetary and double star beast, Rigel and Acrux both split so much you
could park a bus in-between them. I don't know much about double stars or how those two pairs sit on the proximity scale but it was no challenge even in the slightest to discern the two pairs.
Omega Centauri looked sensational but dim, I could see the atmospheric turbulence much more noticeably on the globular cluster. The whole thing was wobbling like a desert mirage because of the field of view was full to the brim with stars. It only just fits in at 224X... I probably should have tried some lower power eyepieces first.

Ergonomically the scope is very cool, I have the folded tube slightly off center to the scopes main axis. This means I can move the binos either side of the tube axis and get many different angles to suit your head placement regardless of altitude. I think this feature will really shine once the scope is equatorially mounted, I cant wait. Only downside to being able to move the bino so much is that it changes the way you perceive movement, up is left, right down... then you go the other side, left is down, down is right etc, no easily learnt pattern as the mirrors are always in a different spot.

Well that is my first impressions, thanks for sticking with me. Hopefully I can get better at observing reports in the future instead of where I am now. "Stars are little white dots and round"
(please note the pic attached with the clear skies was not tonight, in no way shape or form was the weather that good)

[Leo.G]

Much respect Luke, proficient with timber and metal. Not many people can do that, I've had experience and training with both to a higher level with metal.

I was wondering about the rolling it in and out and did mention something. Here's a probably stupid question, I'm full of them (or was it full of it, I don't remember), could you put some sort of slip on outriggers with small casters/wheels which wouldn't have to actually roll on the ground?
Much like a lazy axle on a truck, if the unthinkable was to happen an extra measure of security whilst moving the unit and easily released and removed once in position?
A double timber V set-up which easily removes but gives extra protection in both axis while rolling the unit across the yard , any tilt and the wheel offers immediate support.

They could slip into some c brackets and be locked in place with a t bar threaded bolt (welded T across the top), it would be an extra minute or two to fit them and remove them again so you don't trip in the dark but give a lot of peace of mind and be reasonably simple to do,
Or a set of set in place rails done with 5mmx25 flat and joined with welded angle across between the rails so the angle gave a wide footprint, dyna-bolted down with welded flat bar (cut angle) on outer edges of flat, it's a lot of work, much like a mini rail, they use flat and box section for rails, even 3mm flat because it's easy to radius if necessary but that only works if you have one place to place the unit till you get your pier and mount. The wheels could be turned out of large-ish pulleys off washing machines or dryers. Damn, if you were closer I'd be offering to be over there welding it all up for you and setting the rails on or in the concrete, I'm beyond intrigued!
I have a set of relocatable rails I made with some 2" angle screwed to some old 4x2 timbers, it helps me get my heavy compressor up and down the steps at the shed and has been used for multiple other purposes. It also served to assist getting the 300+Kg lathe off a box trailer and into a shed before lifting the lathe with an engine crane onto it's stand I welded up. I rolled it down the rails on some pipe (aha, now I remember where my round 50mm 7075 aluminium went.


Welded flat between two lengths of 2" angle gives you a flat surface with minimal frictional resistance for the casters to roll in safely at minimal cost.



I was wondering about the moment with such a long tube and had mentioned a lead weight at the base.
Still, it must be the most AMAZING experience when it's in operation and very satisfying to think you did it all yourself. You deserve a lot of credit for what you have achieved.