Peter Drew

Yes, you can use a 50mm aperture refractor or larger.  The larger refractor will probably be a better telescope but it will still operate only as a 50mm.      🙂 

Are you sure that it is the blocking filter that needs replacing?  It's usually the ITF filter, the one that is fitted before the blocking filter that fails and needs replacing.      🙂

Could cable management have anything to do with the problem?        🙂

Referring back to the original photo there is probably another clutch between the motor and the worm shaft, this is to protect the motor should something restrict the rotation of the wormwheel.  It is the bushing next to the motor output.  There are two rows of grub screws forming the connection, one set possibly fixed to the motor shaft and the other connecting the worm shaft with some facility for slippage in the event of a problem.  If this is the case it is another area for unwanted drive variation.      🙂 

It probably needs at least some grease as the clutch has to be able to slip in the event of something impeding the rotation.  The "trick" is to adjust the slippage torque to avoid slippage in normal use but also to avoid locking up.  Try tightening the nut a small amount.     🙂    

If the brass worm is turning then the wormwheel must also be turning which points to clutch slip as already diagnosed.      🙂

Give it a good sanding down and then a coat of silver-grey Hammerite.   Available as a spray can     🙂      

I'm afraid this is indicative of a de-contacted etalon, the etalon plates are held together by molecular fusion and cannot easily be re-contacted other than by the manufacturer.     ☹️ 

I was given one of these to "play" with some years ago, it is a "Bird-Jones" type.  It actually looked quite well made and finished but the performance was pretty sub par.  After faffing about with the collimation for ages I managed to get a fairly decent image out of it, good enough to please a complete beginner but not worth spending any extra money on it.  Quite a bargain for free.     🙂 

I fitted an AM5 to the top of a "Todmorden" pier by spacing with a ring cut from a 5" diameter 1/4" wall thickness tube between the bottom of the mount and a plate on top of the pier.  The 3/8 screwed rod pulling it all together would take some shifting to accidentally rotate the 5" ring.     😀 

Learning to collimate at F4 will be the least of your AP problems.      🙂

1 hour ago, YogSothoth said:

Probably means we’ve upset some sort of astronomical deity 🤣

Yes, that will teach us to not scoff at Astrology.     🙃

Google Mel Bartels for further insight.       🙂

To make any headway with this proposition you would have to consider an ultra-lightweight primary mirror.      🙂

Very difficult to assess a repair potential without having the tripod to hand.  High grade aluminium doesn't usually snap like that so it's probably the usual "pot" metal casting.

"Super Zenith's" are not a premium binocular and are unlikely to have a sophisticated collimation facility and probably not an economic professional repair.  To continue a DIY attempt, first undo the cross head screw from the centre of the eyepiece bridge then withdraw the complete assembly including the eyepieces.  Next, remove the rear covers of the prism covers.  Then replace the eyepiece assembly without the prism covers, this will give you access to any prism adjustment whilst being able to see the effect of any adjustment.  Prisms are usually held in place by metal straps, loosening these a little allows the prism to be nudged into better alignment.  Beware these straps are spring loaded and if relieved too far can spring off never to be seen again!         🙂

There are a couple of simple things you can try first.  The barrels that contain the objectives can usually be unscrewed, if so swap them over as this usually makes things better or worse.  If better, leave them swapped, next, slightly unscrew one of the barrels and note whether the improvement continues, if not, screw it up again and try the same on the other one.  If all this fails you will have to open them up and examine the setting of the prisms.      🙂

Be aware of he difference between a 1/6 wave mirror surface and a 1/6 wavefront at the eyepiece. A 1/6 wave mirror will present at best a 1'3 wavefront image at the eyepiece.  On this basis, a 1/8 wave mirror would be preferable to achieve the 1'4 wavefront at the eyepiece to satisfy the Rayleigh criterion for a diffraction limited Newtonian telescope.       🙂

Can't see the chips!    🙂

I have too many telescopes that I rarely get the chance to use, some of which are the dream ones of others which makes me feel undeserving.  After a struggle, I think a DS Lunt60 would be a useful addition as a G&G.    🙂

I think Ed has done Seestar a favour, it's become a "hot" topic.      🙂

Hello Ash.

You most certainly can!  Stellarium (and other planetarium apps) can provide you with everything you need for wheelchair observing including information text.  If you can connect to a large screen it is most impressive.  If this poor weather continues much longer we will all be doing the same!       🙂

I've still got five 8's, one 12 and two 16's.     🙂

I think I would call this a sleeve nut.  It would be intended to adjust end float on the worm shaft, not backlash.       🙂

+1    🙂