Widefield Triple Imaging Rig

[Gina]

Mounted stepper motor.

[Gina]

Some fairly small design changes have resulted in reprinting the parts.  I had only printed parts for one imaging module so not too much wasted filament.  As usual with experimental projects, some design changes result from assembling the constituent parts.

I have decided to connect the three plates that make up each module with 6mm studding with the modules bolted together with 4mm nuts and bolts in flanges on the two outer end plates.  This should produce a solid turret imaging system.  The guiding system will be separate as incorporating it into the turret seemed too complicated (though there is always a possiblilty of a mark 2 turret triple imaging system).  Also, I'm working at maximum print size with the UP! printer.  Once I get my bigger experimental 3D printer operational I shall be able to make bigger objects.

Here are the designs.

Camera End Support Plate

Focus Motor Mounting Plate

Lens Hood End Support Plate

[Davey-T]

Looking good Gina, do you think you'll have it working for the winter nights ?

Dave

[Gina]

Thank you Dave

I shall have the second 460EX camera by the end of the month and I'm hoping that I shall be ready to try it out by then.  I have the studding and nuts on order for expected delivery early next week.  It's virtually impossible to say when I will have it ready for imaging, I'm afraid.

At the moment, I'm planning to use two 460EXs and one 314L+ though there is the possibility that I shall have sold both 314L+ cameras by the end of the month and might be limited to two cameras.  OTOH there is a faint possibility that I might have acquired a third 460EX as is my ultimate aim.

[Gina]

Two parts of one imaging module printed the third is in progress.

[Gina]

Third plate finished - supports camera end on the adapter from lens to camera.

[Gina]

Waiting for the studding now, though I could probably make the adapter for the camera and filter.

[Gina]

I'm certainly looking forward to trying a proper triple imaging rig with matched optics and cameras.  I've been asked about a triple imaging rig with telescopes   3 MN190s would definitely be too much but the Esprit 80ED is quite small and light - that would be a practical possibility   Rather expensive though but what a lovely thought   ATM I have two Evostar 80EDs but they are a fair bit heavier than the Esprit and decidedly inferior (but cheap).

[DIYASTRO]

Gina,

that is all looking very promising! Look forward to seeing the 'new rig' in finished format.

I too have dreamt of a multi imaging scope system, similar to my multi camera rigs but using three 12" reflectors with a 6" refractor as guidescope in the centre with lots of smaller camera modules that I know you have seen from my previous posts dotted in between!

I dream... just one massive fork mounted multiscope in a nice dome! Graig ( Blinky) talked about this some years ago, just need to win the lotto first!

Looking forward to seeing your camera system up and running.

Kind regards

Boyd

[Gina]

Thank you Boyd

While I wait for the 6mm threaded rods I'm looking at the overal mounting and rotational drive for the turret.  The pitch circle of the turret gear is 200mm (about 8") ie. nearly as big in diameter as my MN190.  My original idea was to mount the turret on 6 spur gears on 3 axles on some sort of framework.  The front has to have a 200mm diameter clear space to allow rotation without anything obscuring the view, making a central axle impractical.  I don't think a central axle supported from one end only would be stiff enough even with a largish tube.

It would be possible to support the back end with a central support though so I'm now thinking of using a central axle supported at the rear of the turret and to use 3 spur gears at the front.  One could be driven either manually or with a stepper motor and the others as idlers just to provide support.  Unfortunately the turret supports are too big for 3D printing - at least I think so.  Individual brackets and gear supports could be printed though.

Here's the turret and one of the three support pinions/gears as seen from the front.

[Gina]

I've just popped out and got the 460EX to see how everything will go together.  The weight and length lead me to think I may need more support.

Here is a photo of a 200mm lens and 460EX supported in roughly the positions they will take up.  There is a gap where the adapter will go in the photo as I haven't made one yet .

This is going to be one hefty imager when it's finished    Maybe I should have gone for smaller lenses first   I shall need to buy a few more lenses as I only have two of some focal lengths.  I'll have to see how the FOVs work out for the various combos.

BTW I shall definitely be having three 460EX mono cameras for this setup - the funds will be available

[DIYASTRO]

Gina,

I have tried this idea of using gears as some kind of 'bearing / drive' system.

It does work but... the tolerance is so small to avoid the friction/opposing gear lock when reversing is amazingly small!

With the gears that you have cut on your m/c I would think that they will 'lock' at some point in the revolution. You may be lucky, and find a sweet point... but since you appear to have the same type of gear system at each end, ( if I understand your construction correctly) the tolerance is just so small.

I have built similar systems and had to revert to bearings at each end with an independent drive.

None the less, its always worth a try, but I think you may find that greater accuracy may be achieved with plates and bearings at each end with a distinct separate drive.

Kind regards

Boyd

[Gina]

Yes, I think you could be right there Boyd - thank you for your input

I was originally thinking of having the same gear system at each end but I'm tending to move away from that now.  I was looking at a ball bearing earlier this evening and thinking that maybe three ball bearings and a plain rim on the turret may be more accurate and easier to make free of unwanted movement as the rig moved in RA.  I might go for three ball bearings supporting the front and a central axle at the back with a separate rotation drive.

Another change is that the original design allowed for a 314L+ camera rather than all 460EXs.  Now that I am definitely going for the three 460s I can move the individual imaging units closer together.  Also, if I go for ball bearing rather than gears for support I can save the width of the teeth - I would like to be able to print support plates that take all three imaging units at once.  This is currently not possible with the UP! printer though it would be with my experimental printer when I get it working.

[Gina]

If I were to go for narrower lenses the separation would be limited by the diameter of the 460s and I could just squeeze the 3 in 1 disc onto the print bed of the UP! I think.  Just trying it now

[Gina]

The printer struggled a bit with that and even at the limit of the printer there is not much "meat" in the plastic for the strength required.  So a full 3 in 1 printed plastic support is not on with this printer.  Back to segments then.  Anyway, I really want to use the three 200mm lenses as I have them already.  I am on the lookout for a third 105mm Takumar to match my other two but they seem as rare as hens teeth!

Definitely yet another new design on the books   Closer together and with a smooth rim also accomodating a central axle for rear support.

[Gina]

Here are photos of the 3 200mm lenses squeezed into the 3 in 1 front turret plate.  Well not quite actually - one of the lenses is a Vivitar f3.5 rather than the Asahi SMC Takumar f4 of the other two and it's slightly wider.  The Taks are without their lens hoods which TBH I don't think are needed for this application unless there's a moon shining into them.  An overall hood for the three could be made up to go on the front of the turret.

The central axle has been reclaimed from my experimental 3D ptinter, an unwanted component from the original Velleman kit.  The lenses need to be a few millimetres further apart but on a smaller pitch circle than the earlier design.  I believe we're heading in the right direction

[DIYASTRO]

Gina,

Looking good!

Don't know if you would be interested but there is a 200mm Asahi Tak f5.6 for £69 at Ffords Photographic. just in case you want to keep them all identical!

Regards

Boyd

[Gina]

Thank you Boyd   But a 200mm f5.6 would not be identical to an f4.  I'll see how the Vivitar goes and maybe look out for a Tak f4 on ebay if results are not good.  However, I think this was one of my old lenses that I used with the Pentax Spotmatic 35mm film SLR camera umpteen years and gave first rate results   And I have used it with my earlier widefield rig with good results

I have worked out a design for the front turret lens support plate that I can print in two parts rather than three.  By careful wangling of the join between the two pieces I have managed to just barely fit each part onto the print bed

[DIYASTRO]

Gina,

That looks like it should work well.

Sorry about the lens, thought you where using f5.6s'

They also have 3 135mm f3,5s' at £25-29 each!

just to tempt you that is!

Regards

Boyd

[Gina]

Both parts printed and glued together with acetone.  I have made no allowance for the standard oversize printing of 0.1mm so these parts are actually 0.2mm out as can be seen in the centre hole.  This has just been a test printed thinner than the final.  I shall now adjust the boundary between the two parts to allow for that 0.1mm overprint and increase thickness to the final 6mm.  Also holes are needed to take the connecting rods that connect this plate to the others.

[Gina]

Gina,

That looks like it should work well.

Sorry about the lens, thought you where using f5.6s'

They also have 3 135mm f3,5s' at £25-29 each!

just to tempt you that is!

Regards

Boyd

Thanks Boyd   There are lots of 135mm f3.5 lenses on ebay.  The two 135mm ones I have are f2.8 - somewhat rarer.  The 105mm ones are also 2.8 and I have two 55mm f1.8 one was my standard film camera lens.  Plenty of 55mm f1.8 and even f1.2 available.  Now that is a good photon collector!

[Gina]

Lenses fitted into front support plate.

[Gina]

The two lens part fitted to the print bed.

[Gina]

Been working out the focus motor mounting plates.  Not so easy with the lenses much closer together.  But I think I'm winning

[Gina]

And the other plate.  The focus sleeve of the lens is much bigger than the rest so there's very little "meat" left in the plastic between them, in fact none at a couple of points.