Swarf in my RASA 11 :(

[symmetal]

Having had my new RASA 11 for three weeks now and still no weather to try it out I've been tidying up the attachments to the top dovetail bar and fixing a carrying handle to it. I was going to drill mounting holes in the bar so removed it, though I ended up using losmandy clamps to hold everything so didn't need to drill the dovetail bar.

However, when unscrewing the front two dovetail mounting screws they it felt like they were grinding and they came undone after unscrewing only about 2 to 3 mm so very little of the screw is actually engaged with the scope body. 😲 It seems the bar front screws screw into a plate mounted below the scope front metal assembly piece and not into the front metal piece directly which just has drilled holes. The screws are only just long enough to reach the plate and it looks like the screws themselves were used to create the thread on the plate as the end few mm show significant wear. Here's a picture of the plate viewed from inside from a topic on CN detailing disassembly of the RASA 11 V2

Here are the screws from mine showing how much engages with the plate. I think the thread at the top of the plate is worn on one side as only about 2 turns actually feels it's engaging with the plate.

The rear dovetail mounting screws are fine as the scope rear metal assembly is actually threaded rather than just being a hole so around 5 or 6 mm of thread engages with the dovetail screw which unscrews fine with no grinding.

Another odd feature is the rear screws are 10-24 UNC 1" while the front screws are 10-32 UNF 1".

The result is swarf falling inside the scope when the front screws were removed and replaced as shown here with most lying on the assembly holing the front lens assembly with some falling to the bottom of the scope.

I'e ordered some replacement 10-32 UNF 1" screws from Kay's Fasteners on ebay as well as some 1 1/4" screws which should hopefully give a chance of a more reliable grip. I've been wondering how to possibly remove the swarf without removing the front corrector plate which will invalidate the guarantee and upset the collimation. I thought about trying some tiny neodymium magnets you can buy on Amazon for a few pounds. You can get some 1 x 2mm and others 3 x 3mm which will drop through the dovetail screw holes which are around 4.6mm in diameter. I don't want to have the scope sent away for cleaning as this is already the fourth RASA I've had. I'm assuming the mounting plate is made of steel and not aluminium. Being fairly thin I would hope it's steel.

I can contact Celestron to see what they suggest. Perhaps the whole front black assembly, can be removed from the white tube via the mounting screws which avoids removing the corrector plate on its own.

I don't think that removing a dovetail plate should be cause for invalidating a guarantee though, and they should be removeable without metal bits falling into the scope. 😬

Anybody think magnets on a bit of wire may help. Have to ensure the magnet doesn't fall off the wire, though if it did, it could be used as a loose swarf collector as it rolls around inside the scope. 😊

When the scope is on the mount and tilted on its side the whole weight of the scope is dependant on the engagement of a few mm of four relatively small screws, smaller than M5, while things attached to the dovetail bars use M6 or 1/4" screws. 🤔. The handle I fitted is attached with M6 screws which seems overkill in comparison.

Alan

[scotty38]

That's not good but are you sure that swarf's not aluminium?

[symmetal]

43 minutes ago, scotty38 said:

That's not good but are you sure that swarf's not aluminium?

It's possible, though the plate the dovetail screws screw into is fairly thin, around 3mm at most it looks like, so I was hoping it's steel. I've ordered some neodymium magnets anyway, 3 x 2mm and 3 x 0.5mm which arrive tomorrow so we'll find out. 😉 I'll try drilling a hole through one with a PCB drill hopefully without it shattering first. Drilling underwater avoids the magnet getting too hot and losing its magnetism as well. Fingers crossed. 😊

If they aren't magnetic, at least being metal shavings they should eventually end up rolling around the inside of the tube and not get onto the mirror or corrector plate as long as I don't tilt the scope while they are on the lens housing as they are at the moment. A fine modelling paint brush may reach them.

Alan

[The Lazy Astronomer]

That seems like an incredibly poor piece of engineering... Good one Celestron!

I'd probably still get in contact with retailer to be honest - for the significant monetary outlay of that scope, l really would expect better quality (on the plus side, maybe the fact that the mounting points are so poor means Celestron have spent all their money on the optics).

Have you checked to see that the threads on the plate haven't been stripped or otherwise damaged in such a way such that they won't accept a bolt? 

[david_taurus83]

If any of it is steel then you risk the magnet just popping off the wire and attaching to the inside of the tube or attaches itself the part the swarf is resting on!

[symmetal]

1 minute ago, The Lazy Astronomer said:

That seems like an incredibly poor piece of engineering... Good one Celestron!

I'd probably still get in contact with retailer to be honest - for the significant monetary outlay of that scope, l really would expect better quality (on the plus side, maybe the fact that the mounting points are so poor means Celestron have spent all their money on the optics).

Have you checked to see that the threads on the plate haven't been stripped or otherwise damaged in such a way such that they won't accept a bolt? 

Yes, I'll let FLO know about this thread tomorrow, (no pun intended) and see what they say. The threads on the plate appear OK as with the bolts cleaned up and no dovetail to limit the travel they screw in quite nicely with no further grinding, but there's no telling how much good thread is left. New bolts, hopefully arriving tomorrow should give a firmer grip, and if the 1 1/4" inch ones don't protrude into the light path, which I don't think they will should ensure that the full plate thread is at least being used.

The CN topic I linked to in the last post does say to expect for swarf when removing the dovetail so this seems to be standard. Using UNF on the front pair of screws compared to UNC, like the rear doesn't seem a good choice as the volume of metal between the threads is reduced. There don't seem to be reports of RASA 11s falling off mounts though, so this seems to be just sufficient to hold the scope. 😬

Alan

[symmetal]

18 minutes ago, david_taurus83 said:

If any of it is steel then you risk the magnet just popping off the wire and attaching to the inside of the tube or attaches itself the part the swarf is resting on!

There is no real strength required in the lens assembly holder and to save weight, I'd hope they used aluminium for that. The smaller magnets of 3 x 0.5mm have a pull strength of 80g so shouldn't be too strong, compared to 270g for the 3 x 2mm magnets. I'll bend the wire back on itslf and solder it once threaded through the magnet so it shouldn't pop off.

The tube must be aluminium as it isn't magnetic at all. I tested the outside areas with a magnet and found that stainless steel is only slightly magnetic compared to 'normal' steel. Zinc plated bolts and stainless steel bolts show this quite dramatically. The original black bolts used on the dovetail are only slightly magnetic so possibly stainless. Kays Fasteneners black coated screws are classed as high tensile steel which is generally stronger than stainless steel.

Alan

[symmetal]

Another option is a length of stiff tubing around 4mm OD, like ABS, brass etc, and attach it to a vacuum cleaner to suck the swarf out. I could even try 3D printing some square tubing which may work. 🙂

Alan

[FLO]

Hi @symmetal, sorry to hear your telescope needs cleaning. 

I see you received it less than a month ago. I see you have also contacted my colleague.

I am confident he, with Celestron, will find a solution for you but please can I ask you - from here onwards - to contact us before disassembling or modifying any part of your RASA-11 🙂 

Steve 

[symmetal]

36 minutes ago, FLO said:

I am confident he, with Celestron, will find a solution for you but please can I ask you - from here onwards - to contact us before disassembling or modifying any part of your RASA-11 🙂 

Thanks Steve. Though I would say that dovetail bars are intended to be removed and refitted by the user, and I've had no issue doing this with any other scope. The RASA 8s I had before had the separate top bar fitted by me in each case, as they don't come with a top bar, and they came on and off easily without dropping swarf into the scope. 

The magnets have arrived though I may wait for some thin stiff tubing to arrive tomorrow as I think sucking the swarf out is the better option, if possible. I'm currently 3D printing some tubing which may do the job, so it's likely it won't need to be cleaned after all.

Alan

[Stuart1971]

40 minutes ago, symmetal said:

Thanks Steve. Though I would say that dovetail bars are intended to be removed and refitted by the user, and I've had no issue doing this with any other scope. The RASA 8s I had before had the separate top bar fitted by me in each case, as they don't come with a top bar, and they came on and off easily without dropping swarf into the scope. 

The magnets have arrived though I may wait for some thin stiff tubing to arrive tomorrow as I think sucking the swarf out is the better option, if possible. I'm currently 3D printing some tubing which may do the job, so it's likely it won't need to be cleaned after all.

Alan

A perfectly obvious case of poor workmanship from the manufacturer, as if you have not had enough issues…..🙁

I was going to suggest a small tube and then sucking it out, I have done this through the back of my Meade SCT, due to the same issue, but mine was self inflicted due to cross threading a screw, but it worked a treat….mine was aluminium..

good luck sorting it out….👍🏻

[symmetal]

2 hours ago, Stuart1971 said:

A perfectly obvious case of poor workmanship from the manufacturer, as if you have not had enough issues…..🙁

I was going to suggest a small tube and then sucking it out, I have done this through the back of my Meade SCT, due to the same issue, but mine was self inflicted due to cross threading a screw, but it worked a treat….mine was aluminium..

good luck sorting it out….👍🏻

Thanks @Stuart1971, My first 3d printed tube worked a treat and removed all the swarf sitting on the lens assembly casing. However running the screws through again caused more swarf to fall. I then used the new 10 UNF 1" screws that arrived today and they have a much more positive feel to them when screwing them in which is good. While one went through nicely the other was stiffer and caused even more swarf to fall as it cleared out the thread again. This was the one where the original screw end was clearly worn where it had cut its own thread. Just printing a longer tube which hopefully will reach the bottom of the scope tube where some swarf accumulated too.

Hopefully I'll reach a stage where the screws can be inserted and removed without more swarf tumbling out.

Alan 

[ollypenrice]

All of this is a shame and if FLO/Celestron will help you out, then I'd follow Steve FLO's advice and await instruction.

On the other hand, removing the corrector of a Schmidt is ludicrously easy, the thing being to mark the orientation of the corrector in the tube using a bit of tape or a marker. I just cleaned my Meade ACF this morning, taking out and replacing the plate. Sure, the collimation of the RASA will probably be affected because anything affects it at F2!  But it will probably need collimating anyway.  Some arrive collimated, others don't.  Ours did need it.

In any event, relax, it's no big deal.

Olly

[symmetal]

Lens assembly casing is clean again, but had no luck clearing the swarf on the bottom. I tried using long lengths of heatshrink tubing which reached down there but there was no way to manipulate it properly and by luck, picked up 1 piece in 30 mins of trying. I did move the magnet around on the outside of the tube and the swarf wasn't attracted to it so it's probably aluminium. If it was steel there likely wouldn't be so much of it. Here's the swarf left in the bottom of the tube. They are out of focus so the specks appears larger than they are.

They should hopefully spend their lives rolling around the tube edge and work their way to the rear when the scope points vertically without settling on the mirror. It's a pity there aren't any access panels in the scope tube which would make life easier for dealing with issues like this.

Alan

[symmetal]

4 minutes ago, ollypenrice said:

All of this is a shame and if FLO/Celestron will help you out, then I'd follow Steve FLO's advice and await instruction.

On the other hand, removing the corrector of a Schmidt is ludicrously easy, the thing being to mark the orientation of the corrector in the tube using a bit of tape or a marker. I just cleaned my Meade ACF this morning, taking out and replacing the plate. Sure, the collimation of the RASA will probably be affected because anything affects it at F2!  But it will probably need collimating anyway.  Some arrive collimated, others don't.  Ours did need it.

In any event, relax, it's no big deal.

Olly

Thanks @ollypenrice. I have already replaced the front ring that clamps the corrector with the Celestron heated dew ring as per Celestron's instructions, having the scope pointing vertically on the mount, and you then reveal the grub screws around the edge pushing against the corrector plate to keep it in place. I wouldn't want to remove it at the moment, as it's still under guarantee, at least not without Flo's and Celestron's say so, but as you say it looks relatively easy to do.

Alan

[Stuart1971]

1 hour ago, symmetal said:

Lens assembly casing is clean again, but had no luck clearing the swarf on the bottom. I tried using long lengths of heatshrink tubing which reached down there but there was no way to manipulate it properly and by luck, picked up 1 piece in 30 mins of trying. I did move the magnet around on the outside of the tube and the swarf wasn't attracted to it so it's probably aluminium. If it was steel there likely wouldn't be so much of it. Here's the swarf left in the bottom of the tube. They are out of focus so the specks appears larger than they are.

They should hopefully spend their lives rolling around the tube edge and work their way to the rear when the scope points vertically without settling on the mirror. It's a pity there aren't any access panels in the scope tube which would make life easier for dealing with issues like this.

Alan

Why can’t you go in through the the focus tube at other end, or am I missing something about these scopes that are different….?

[symmetal]

12 minutes ago, Stuart1971 said:

Why can’t you go in through the the focus tube at other end, or am I missing something about these scopes that are different….?

There is no focus tube access from the rear like an SCT, and the rear is sealed as shown here.

Focusing is only by moving the primary mirror. The camera mounts on to the front of the corrector plate as can be seen in the first couple of photos posted. 🙂 A quad lens assembly is mounted on the rear of the corrector plate to correct the light entering the camera. This lens asembly housing was what was collecting the bulk of the swarf.

Alan