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Royal Astro 4" f10 Newt rebuild...

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#1 Kokatha man

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Posted 26 January 2020 - 04:34 AM

I thought I'd stop posting the images of the little RA Newt in the "What did you do to your scope..." thread as it becomes clear that it might actually get "first light" in a week or so - I'm hoping by Feb 2nd (Moon at First Quarter) but I have no intention of racing too fast or jinxing myself with that or any other deadline..! lol.gif

 

The first few postings will concentrate upon the scope itself, but the restoration of the GEM pier mount will follow on from this & I thought it good to chronicle a lot of what I've done contained within a single thread: many thanks once again to CharlieB for giving me several very essential parts such as the RA worm & fittings & the Dec clamping casting etc...& for a lot of images & dimensions of other mount parts I will have fabricated, as they would be virtually impossible to find anywhere.

 

Upon reflection this little scope has had a rough life in some ways, the tube was badly scored for some unfathomable reason, the c/weight & bar were lost & a poor substitute arrangement was stuck on: the primary mirror was scratched but fortunately these were only coating scratches & scuffs...re-coated the surface is as one would think it originally looked! smile.gif

 

And of course the broken casting as well as a substitute RA worm assembly.

 

There were some dents in the ota as well & the paint was of course very bad but I have managed to fix the tube up with 5 coats of "prime & paint" - finding some very fine wet & dry worked wonders at the finish on a thick paint-coat  by attending to some blemishes while I was cutting & polishing the topcoat without going below the paint-job.

 

 

But it is now starting to look like it was meant to! wink.gif

 

RoyalAstroAssembling#1.jpg

 

The clam-shell clamp you see is from another old junk find unit refurbished - I can affix a dovetail bar to this one so that the ota will get first light before the GEM is finished...although I have arranged for my friend Dennis to fabricate the remaining necessary mount parts in the next week or 2 after I send the drawings to him in the next few days...

 

Still finding oddities with thread types where those holding the end-castings onto the ota are 1/8" types although the Japanese did mix BSF/Whitworth with their metric threads...not to mention that weird JIS 0.9 pitch metric set in the primary cell!

 

I did replace the British threads of the 4 focuser-to-tube screws because although I don't know what the originals were, those in it when I got the scope were simple slot-heads, despite nearly everything else I've come across being phillips heads.

 

I replaced them with stainless c/sunk phillips head screws which I think look much better...to me slot-heads often signify cheap gear - which I believe the RA is most definitely not! smile.gif Maybe they were replacements...confused1.gif

 

I'm still deciding upon what I will do re the focuser - I've now fixed the issue I first had on re-assembling - it is now very smooth & light by some extremely fine & careful drum-sanding of the 3 red fibre strips inside the focuser body waytogo.gif  but I might discard (or rather, keep in the box) the screw-on spring-tube attachment that allows you to slip an ep in...by lining the fitting that one normally sees at the outer end of these types of drawtubes that has a pinch-screw - I won't drill & tap a pinch-screw even though that would be fairly easy to do...rather line the inside of this fitting so that an ep can slide in & out with good grip.

 

The diameter in this is slightly larger than those normally found so a pinch-screw would be less ideal here anyway imo: I want to do something with this aspect as I have realised that with the spring-tube screw-on attachment for ep fitting, the focus-position would require little racking out of the focuser draw-tube...I want to image with this scope & I have found that with these classic Japanese refractors getting enough in-focus can be an issue - but removing the extension that the spring-tube attachment creates should make in-focus much easier for imaging. smile.gif

 

So it'll be a felt of even some hard but smooth liner in the draw-tube fitting (minus the spring-tube) & this way any ep or camera nose-piece will slip that much further into the draw-tube.

 

Tomorrow I'll take a break &/or centre-spot the primary mirror & do some touch-up of flat black just inside the ota as well as on the nuts & screws that are internally visible - at 70 I found hand cutting & polishing even this little ota - plus all the fiddly bits - was well enough for one day! lol.gif

 

But at least now it is starting to look like a scope again..! smile.gif


Edited by Kokatha man, 26 January 2020 - 05:28 AM.

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#2 Kokatha man

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Posted 26 January 2020 - 08:02 PM

Today will be my "take it easy" day - I tend to get a bit manic when I start something & Pattie is always telling me that I don't know when to switch off - like in this thread I started probably lol.gif but as it is a bit of a soliloquy on what I'm doing & thinking I figure that's ok! wink.gif

 

I'll clean up some of the mess from rabbiting through packets of screws etc & dismantling & packing away the old Topic 4.5" f900mm Newt I've had many years that looks worse than the RA did when I got it...this isn't what I got the clam-shell clamp from that has been refurbished & on the RA tube you can see in the pikky in the first post - that's from a rubbish dump find...the 4.5" Topic I've had since 1970/71 whence it fell over & that clam-shell bracket ( a casting) broke causing me to stick it in a box of junk - for some reason I've carted it around ever since.

 

But I've made up my mind to strip the coating (very bad) off the Topic (I've gallons of ferric from being an artist) & turn it into a Solar scope after reading Dave Groski's article here: http://www.considine...groski/wlnewt/ 

 

I even have an old Herschel Wedge from the Yamamoto/SYW so I guess it might then qualify as a "Classic Solar scope"..! lol.gif

 

Back to the Royal Astro 4" Newt, here is a pikky of the little spring-tube that holds the ep that I spoke of in the first post above...it screws onto the fitting that screws into the chrome barrel drawtube.

 

RoyalAstro-epFittingIdea.jpg

 

If I can pare back the section indicated (there appears to be plenty of "meat" to do so) then I can insert the spring-tube from the inside end of that fitting: the result being that it will look to all intents just as it would without the spring-tube but having the ability to simply slip the ep - or a camera - straight into the fitting!  (which would make attaining sufficient back-focus much easier!)

 

A spot of flat black touching up & that's it for this project today. smile.gif

 


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#3 GUS.K

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Posted 26 January 2020 - 09:12 PM

Hi, thanks for sharing your rebuild progress.

Ivan



#4 Kokatha man

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Posted 26 January 2020 - 09:51 PM

Thanks Gus! I realised that I had not taken many pikkies at all of the scope & mount in the condition I bought it in Melbourne 2 years ago now...actually my eldest son Rafe purchased it for me after I asked him to have a look at it - the seller was what is known these days as a "flipper" although we always used to call them "wheelers & dealers" in the old days..! lol.gif

 

Here are a couple of the tube & one of the primary mirror...I was concerned but it turned out the scratches etc on it were only in the coating - the glass & figure beneath were AOK. smile.gif

 

Not sure what to do about the finder - it is a very nice little focusable unit using a Swift microscope ep as I'm led to believe: I have given this element a paint job etc but I know that finding an original here in Oz is nigh impossible...& I am leaning towards a nice little RACI unit as a far more sensible alternative. (made to conform to the rest of the scope if I go that way...)

 

RoyalAstroTubeDentOriginalCondition#1.jpg

 

RoyalAstroTubeDentOriginalCondition#2.jpg

 

RoyalAstroTubeDentOriginalCondition#3.jpg

 

RoyalAstroTubeDentOriginalCondition#4.jpg

 

 


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#5 Kokatha man

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Posted 27 January 2020 - 07:53 PM

Got up this morning & finished off painting the "fiddly bits" of the secondary holder/spider assembly & primary clips etc after touching up inside the ota as well as the primary cell yesterday...if I do any more today it'll be either the secondary mirror & spider installation, or centre-spotting (paper donut) the primary mirror.

 

Yesterday I solved the riddle of why flat black paint seemed to be getting everywhere on my bench etc - the bottom of this small but very old can had given out & paint was oozing out slowly...hammered the lid back on, turned it upside down & put it in a plastic bag 'cos there's still an inch or so of paint still in it - waste not, want not! lol.gif

 

More pikkies when both mirrors are installed. wink.gif

 

As something I'm doing alongside some of this I stripped the very tarnished coating off the old Topic 4.5" Newt...I note from an I.D. tag I saw on the internet that (some of?) these Topics had their origin as Towa scopes, which might tie in with my thinking Tasco was also involved. (if that's correct)

 

As said somewhere above I'm hoping to turn this old scope I've had since about 1971 into a solar scope by using un-coated mirrors & a Herschel wedge as per Dave G's article on said...

 

Not sure how good the optics are but I thought "why not?" The little sunspot yesterday & the start of a new cycle has me thinking it might be a worthwhile project. smile.gif


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#6 Senex Bibax

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Posted 28 January 2020 - 07:38 AM

If you turn it into a solar telescope, are you going to remove that silver warning sticker? lol.gif  Belated Happy Australia Day BTW. I'd have cracked open a cold Cooper's myself if I could get it in Canada.



#7 steve t

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Posted 28 January 2020 - 08:18 AM

This is a bit of a stretch, but you may be pleasantly surprised by the mirrors in this scope. I've been playing with a couple of 100x1000 mirrors and, so far they've looked very good. You may want to just get the primary and secondary recoated with modern coatings. You could end up with a very nice little scope.

Steve T


Edited by steve t, 28 January 2020 - 08:30 AM.


#8 Kokatha man

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Posted 28 January 2020 - 08:38 PM

If you turn it into a solar telescope, are you going to remove that silver warning sticker? lol.gif  Belated Happy Australia Day BTW. I'd have cracked open a cold Cooper's myself if I could get it in Canada.

The sticker was on the Royal Astro's ota - it was looking very daggy so I sanded it off during the tube prepping for painting...I do have a Cooper's occasionally as it is our local ale - although usually the light one nowadays as a diabetic who tries to look after himself. smile.gif

 

This is a bit of a stretch, but you may be pleasantly surprised by the mirrors in this scope. I've been playing with a couple of 100x1000 mirrors and, so far they've looked very good. You may want to just get the primary and secondary recoated with modern coatings. You could end up with a very nice little scope.

Steve T

Steve, the Topic is a 4.5"/900mm scope - the Royal Astro is the 100/1000mm one that I've had the optics re-coated on & am restoring: the Topic was either "use it as something or junk it" material so I decided upon the solar scope idea.

 

When I had the Royal Astro's mirrors re-coated just before Xmas I was in the last job lot done by the only telescope mirror re-coater in all of Oz bigshock.gif - he was having hassles with renting premises & being about 75 decided to call it quits...someone might take over his extensive equipment but the only other way folks get mirrors re-coated is to send them to someone who waits until he has a sufficient number & takes them to somewhere like Singapore...

 

I don't really need another non-specialised scope as well as the RA but in any case I purchased one of Sheldon's 100/1000mm Carton spherical mirrors when I was unsure if the RA's primary was only scratched on the coating (see image above) or deeper into the glass surface - but that turned out ok...so I do have a new 100/1000mm spherical mirror which by all accounts are considered very good - I stripped the Topic mirror but I wouldn't strip a brand-new Carton..! grin.gif


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#9 steve t

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Posted 28 January 2020 - 08:59 PM

Steve, the Topic is a 4.5"/900mm scope - the Royal Astro is the 100/1000mm one that I've had the optics re-coated on & am restoring: the Topic was either "use it as something or junk it" material so I decided upon the solar scope idea.

 

When I had the Royal Astro's mirrors re-coated just before Xmas I was in the last job lot done by the only telescope mirror re-coater in all of Oz bigshock.gif - he was having hassles with renting premises & being about 75 decided to call it quits...someone might take over his extensive equipment but the only other way folks get mirrors re-coated is to send them to someone who waits until he has a sufficient number & takes them to somewhere like Singapore...

 

I don't really need another non-specialised scope as well as the RA but in any case I purchased one of Sheldon's 100/1000mm Carton spherical mirrors when I was unsure if the RA's primary was only scratched on the coating (see image above) or deeper into the glass surface - but that turned out ok...so I do have a new 100/1000mm spherical mirror which by all accounts are considered very good - I stripped the Topic mirror but I wouldn't strip a brand-new Carton..! grin.gif

My mistake, got confused on which scope was whichsmile.gif 

 

Steve T



#10 CharlieB

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Posted 28 January 2020 - 10:54 PM

The sticker was on the Royal Astro's ota - it was looking very daggy so I sanded it off during the tube prepping for painting...I do have a Cooper's occasionally as it is our local ale - although usually the light one nowadays as a diabetic who tries to look after himself. smile.gif

 

Steve, the Topic is a 4.5"/900mm scope - the Royal Astro is the 100/1000mm one that I've had the optics re-coated on & am restoring: the Topic was either "use it as something or junk it" material so I decided upon the solar scope idea.

 

When I had the Royal Astro's mirrors re-coated just before Xmas I was in the last job lot done by the only telescope mirror re-coater in all of Oz bigshock.gif - he was having hassles with renting premises & being about 75 decided to call it quits...someone might take over his extensive equipment but the only other way folks get mirrors re-coated is to send them to someone who waits until he has a sufficient number & takes them to somewhere like Singapore...

 

I don't really need another non-specialised scope as well as the RA but in any case I purchased one of Sheldon's 100/1000mm Carton spherical mirrors when I was unsure if the RA's primary was only scratched on the coating (see image above) or deeper into the glass surface - but that turned out ok...so I do have a new 100/1000mm spherical mirror which by all accounts are considered very good - I stripped the Topic mirror but I wouldn't strip a brand-new Carton..! grin.gif

I'm pretty sure Astro Optical used Carton mirrors.  I think I got the last of Sheldon's 4" parabolic mirrors as a failsafe for my LN4-E.  But at f/10, the spherical ones are diffraction limited.


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#11 Kokatha man

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Posted 29 January 2020 - 05:18 AM

My mistake, got confused on which scope was whichsmile.gif

 

Steve T

Easily done with my writing style Steve..! lol.gif

 

I'm pretty sure Astro Optical used Carton mirrors.  I think I got the last of Sheldon's 4" parabolic mirrors as a failsafe for my LN4-E.  But at f/10, the spherical ones are diffraction limited.

Well, if you didn't someone else did get the last parabolic mirror Charlie..! smile.gif I knew if the figure on the spherical ones that Sheldon was selling were good there'd be nothing wrong with them & I hear that several people have spoken very highly of these spherical ones: I suppose I should have waited - or stripped the coating off my original mirror like I've just done with the Topic's - but I didn't & also knew it would probably be quite some time before I got around to doing the restoration...I didn't want to find out down the track if I needed a new mirror & Sheldon's supply had ran out.

 

Very fortunate that I rang the re-coater in Taree in NSW just as he was compiling his final job lot of orders before he closed shop for good..! Looks like he's done a top job of an enhanced coating plus the overcoat! waytogo.gif

 

I bit the bullet & pulled out some of my old jeweller's tools to complete the reversing of the sprung-tube ep holder that screws into the fitting on the end of the drawtube.

 

RoyalAstro-ModifiedDrawtubeFittingAspects.jpg

 

Here you can see where I pared down a section of the end-fitting...next image shows how it normally goes together plus the new slot I had to make because the original spring-tube's slot was constrained within the end-fitting & this brass tube needs to be able to expand to accept & grip any ep's etc...the last (rhs) image shows it re-assembled back-to-front in the manner I wanted to arrange these parts.

 

RoyalAstro-EPinModifiedDrawtubeFitting.jpg

 

The last 2 images show a 0.965" ep slid in & pushed right home in the rhs pikky: this I believe will give superior centring & negate any issues with enough out-focus, especially for a camera! Also with the modified 0.965" barlow I'm making as a site tube/cheshire. (more later! wink.gif )

 

I had to shorten the back screw that secures the draw-tube's rack to said - I couldn't remove it to reduce its length as the thread is far too fine so I resorted to shortening it by using a very fine jeweller's saw bade inserted into the drawtube to cut it* - apart from being back-to-front you wouldn't have any real reason to not think this is how it was meant to be imho. wink.gif

 

*ps: cutting it in situ means that the thread at the cut will be cleaned if I unscrew this tiny screw, allowing me to re-insert it again if the need ever arose - taking it out & cutting it would've been fraught with the risk that it would've been nigh-impossible to re-screw it back in! wink.gif


Edited by Kokatha man, 29 January 2020 - 06:04 AM.

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#12 steve t

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Posted 29 January 2020 - 08:45 AM

I'm pretty sure Astro Optical used Carton mirrors.  I think I got the last of Sheldon's 4" parabolic mirrors as a failsafe for my LN4-E.  But at f/10, the spherical ones are diffraction limited.

Check over on the ATM forum, there is some test data on the 100mm (4") x 1000mm Carton mirrors.

Steve T



#13 Bomber Bob

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Posted 29 January 2020 - 09:19 AM

I'm pretty sure Astro Optical used Carton mirrors.  I think I got the last of Sheldon's 4" parabolic mirrors as a failsafe for my LN4-E.  But at f/10, the spherical ones are diffraction limited.

I wouldn't be surprised that Mizar used Carton mirrors in the P-100.  I'll go through my photos & see if the edge had any markings that might help ID the real maker.



#14 Kokatha man

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Posted 29 January 2020 - 06:00 PM

Check over on the ATM forum, there is some test data on the 100mm (4") x 1000mm Carton mirrors.

Steve T

I'm presuming these are the tests Dale Eason did of your mirrors Steve..?

 

I really don't know what I'll end up doing with my brand new Carton 100/1000mm mirror tbh - atm I'm trying to get the RA fully-functional & that includes the mount, even if it is only to stand it on in the living room! :lol:

 

Very warm here in South Oz today, around 110F so whatever I do on the RA it'll be indoors in aircon comfort! ;)


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#15 steve t

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Posted 29 January 2020 - 07:15 PM

I'm presuming these are the tests Dale Eason did of your mirrors Steve..?

 

I really don't know what I'll end up doing with my brand new Carton 100/1000mm mirror tbh - atm I'm trying to get the RA fully-functional & that includes the mount, even if it is only to stand it on in the living room! lol.gif

 

Very warm here in South Oz today, around 110F so whatever I do on the RA it'll be indoors in aircon comfort! wink.gif

 

Yes,

 

I bought the mirrors, several years ago for an outreach that didn't happen, and they've been stored in a box since then. For a winter project I decided to build a small grab & go scope around one of them. Dale kindly offered to test them and those are his test results.

 

I've been stuck indoors lately with just the opposite problem. Winter in SW Ohio has been cold, damp, and cloudymad.gif  

 

We've been hearing about the fires in Australia and hope every thing is okay with you and your family.

 

Steve T 



#16 Kokatha man

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Posted 31 January 2020 - 04:06 AM

We've been lucky as far as fires go Steve - not the same for other places in South Australia nor the Eastern States however... frown.gif

 

Slowly advancing, cloudy weather for the next few days & nights so the Feb. 2nd target for "First Light" is immaterial...the First Quarter Moon will be invisible but I'm doing a bit of extra research/experimentation as I get towards the finish of the scope itself.

 

Here's the finder bracket re-painted wrinkle-black with the adjustment screws wire-brushed to rejuvenate them. (brass bristle-brush...use a glove on the hand holding them btw...! lol.gif )

 

The top (larger) one is obviously non-original (comes from a more modern alignment screw bracket imo) & also had no locking ring but I managed to find something in my box of trinkets to cut down & use as a reasonable substitute...as the top screw the larger size still maintains some sort of symmetry...

 

RoyalAstroFinderBracket.jpg

 

The little finder that came with the scope isn't original either as far as I know & I think it was CharlieB who said it was a Swift microscope ep...well, I knew it was "Swift" 'cos it says that lol.gif but he also said they can be quite decent ep's: it has a single pointed "spike" for a x-hair & the view through it is quite outstanding for so small an objective, with the ep having the benefit of being focus-able also...if I can't have an original (& here in Oz that's probably a wish too far) then I want to keep it as it has some provenance with this scope, even if it's not original kit...but I am thinking of converting the objective etc to RA because I can get quite severe neck problems & peering through a straight-through on a Newt is not my preferred option...but that can wait atm. wink.gif

 

RoyalAstroFinderScope.jpg

 

RoyalAstroFinderScopeSpike.jpg

 

 

As you can see in the pikky below I've also put the re-coated secondary back in its holder & re-assembled the spider - as Charlie reminded me a washer cut from a plastic milk carton is a good idea so I did so, allowing me to "spin" the mirror during initial aligning of things...

 

 

RoyalAstroSecondary&SpiderAssembly.jpg

 

 

RoyalAstroSecondary&SpiderAssembly-Rear.jpg

 

I'm still working out what to do with sitting the primary mirror in its cell - originally it had a packing of several layers of thick paper/card to the thickness of roughly 4.2mm...the mirror rests on this on a 10mm wide flange in the cell & today I purchased some self-adhesive, round felt stick-on tabs which are the right thickness but I'll have to see if I can punch them down to less that 10mm diameter to sit the primary mirror on - I don't want the back of the cell blocked off as it will cool better open like most modern Newts...even if it is only a small mirror: they ought to make a good support base as a ring of them stuck to that cell flange: probably also a little strip of self-adhesive felt under the relevant portion of each mirror clip in place of the existing 3 little strips of card or plastic, none of which is of the same material. wink.gif

 

Anyway, it is rolling along & tomorrow I'll probably centre-spot the primary with a paper donut & after that it will be the full re-assembling of the scope. smile.gif

 

EDIT: it just occurred to me that the purpose of the milk-carton washer is to allow the holder to spin while the adjustment screws stay stationary - oh well, I can get things back-to-front at times & the situation is easily remedied..! blush.gif  rofl2.gif bigblush.gif foreheadslap.gif

Remedied - & post altered to stop the inevitable cursory reader from telling me about it without seeing the "EDIT"..! :lol:


Edited by Kokatha man, 31 January 2020 - 04:27 AM.


#17 dave brock

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Posted 31 January 2020 - 06:59 AM

When I had the Royal Astro's mirrors re-coated just before Xmas I was in the last job lot done by the only telescope mirror re-coater in all of Oz bigshock.gif - he was having hassles with renting premises & being about 75 decided to call it quits...


Is Palmway Optical (Wayne Sainty) no more?

#18 Kokatha man

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Posted 31 January 2020 - 06:41 PM

I haven't made any inquiries since Wayne sent my mirrors back just before Xmas Dave - as said when I rang him to get them done he explained that he was having trouble with the lease of his premises...whether that meant he had to get out 'cos they wanted to hike the rent or whatever I don't know, but he felt at his age (& I was surprised to find out he was in his mid-70's) it was too much trouble to relocate.

 

He did say that he was negotiating the sale of his equipment to someone who wanted to keep the business operating but I don't know anymore than that - it'd certainly be a blow for anyone who needed a re-coat service & I know he was held in high regard. :(



#19 Kokatha man

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Posted 31 January 2020 - 09:53 PM

...edging nearer to completing the refurbishing of the scope aspect...hoping to give my friend Dennis a template for the missing casting at the bottom of the Dec element as well as plans for the new c/weight bar next week. fingerscrossed.gif

 

Cleaned the little finder's cement doublet objective, found the right o-ring & installed it in the bracket...adjusters appear to give plenty of responsive/reactive control over the finder's movements. smile.gif

 

Installed the secondary & spider managing to find suitable-sized stainless 316 washers where the knurled, spider-rod end-adjustment nuts are on the outside of the ota that were missing when I received it...as I said earlier, this old Royal Astro has seen a bit of life with tinkerings that have only become fully-apparent as I re-assemble everything.

 

 

RoyalAstroAssemble#1.jpg

 

RoyalAstroAssemble#1a.jpg

 

 

Atm I'm either going to simply cut some adhesive-backed 19mm felt disks that are the right height into half-circles with scissors, or go & buy a 10mm punch...the available smaller felt disks are much thinner/less height so I don't have the choice of straight-off-the-shelf ones...either way I think they should make a good support for the primary & allow the back of the mirror to be open for optimum cooling.

 

I tried a little experiment - successful! grin.gif - to lighten the focuser action a tad more by emulating the r&p units that have a split-spring strip that bears down on the focuser shafts either side of the pinion gear under the plate - that arrangement allows the amount of mesh or pressure on the rack from the pinion to be dependant on the spring's tension more so than just the tightness of the 2 screws that hold the little cover plate cut-outs down on the pinion shafts: in most cases this setup without the spring-strip only results in an either/or situation where fully-tightening those 2 screws (the intended operational mode) causes everything to be too stiff...or (usually) when loosening them off slightly there is too much slack between rack & pinion...well, in those I've played with, I've found this to be the case. wink.gif

 

I could cut a split-spring strip from hard brass but it is a fiddly job, so I have tried the reverse-action approach by inserting small, light springs under the plate, held in place by the 2 screws running through them into their thread-holes.

 

The rationale behind this is that when tightened until the springs still have a small amount of compression left in them there is still an amount of "ride" in the plate - or control on the tension applied to the shafts by the little cut-outs in the plate.

 

In normal circumstances I find these mechanisms are too stiff if you tighten the screws fully anyway...& these springs in situ certainly gives a much better, lighter & smoother focuser-action with no apparent rack/pinion slop - a clear success imho! waytogo.gif whistling.gif

 

RoyalAstroFocuserExperiment#1.jpg

 

Getting excited now even if it has been bucketing down last night - certainly a relief for those on Kangaroo Island which was burnt-out for around half of its' 1700 sq. miles recently...& hopefully brings respite to those in the Eastern States as this unexpected tropical feed from Northern Oz makes it way down south! fingerscrossed.gif bow.gif

 

 


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#20 Kokatha man

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Posted 01 February 2020 - 03:29 AM

I bit the bullet & centre-spotted the Royal Astro's primary mirror just now: carefully made a paper mask with an ever-so-slightly oversized circular cut-out for the small paper reinforcing donuts that Pattie found an old roll of in her stationary supplies...about to peel one off & you wouldn't believe it - the donut holes themselves were patently off-centre  in the paper donuts..!!! bigshock.gif mad.gif

 

Unwound a fair length of the donut tape till I found a couple that looked ok & checked them with my calipers then went ahead with the spotting...making a final cross-checking with a steel rule from multiple diameters: if it is out it'd be no more than a hair's breadth at most & I satisfied myself thinking how many of the factory-applied mirror donut holes were actually dead-true - & how accurately they were applied to the precise centres of the mirrors also... wink.gif

 

That's now out of the way - incidentally the RA primary is 104.5mm in diameter for an effective aperture of 103mm after the small bevel is taken into account.

 

I've decided to use a complete ring of the 19mm adhesive-backed felt disks, each cut in half to sit on the 10mm flange that supports the primary in the cell - I did have a 10mm punch but even half a 19mm disk is about 1.5x the area of a 10mm disk (π37 Vs π25) & I really don't expect these small mirrors to sag or distort under their own weight supported like this! wink.gif

 

RoyalAstroPrimaryCentre-spotted.jpg


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#21 Kokatha man

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Posted 01 February 2020 - 07:57 PM

I've sent this info as a PM to our resident RA Newt expert (CharlieB) but thought I'd post it out of interest here also: below (left hand side) is a pikky of one of the Royal Astro's threaded spider-rod ends looking at it from inside the ota.....the other is the setup on the budget Topic 4.5" f/l=900mm Newt that I'm turning into a solar scope as per Dave Groski's procedure.

 

RoyalAstroSecondary_Spider-InsideFixture.jpg                                             TOPIC-Secondary_Spider-InsideFixture.jpg

 

I'm hoping that Charlie can set me right but you should be able to see that the RA's knurled nut (left image) is longer & protrudes further into the ota than the Topic's arrangement on the right...

 

I am either missing these parts (I didn't receive them as part of the scope when I got it) or else that is all there is - to my mind this isn't the most secure method of holding the spider ends in the ota grooves whereas the Topic - a budget scope - has a much more secure setup with that knurled locking nut locking the spider-rod on the inside of the ota also. (with an enlarged recess to accept where the main knurled nut protrudes into the tube)

 

Whilst I don't wish to cannibalise parts from the Topic, the threads are identical & I will if that arrangement is preferable (which is certainly appears to be!) - if the RA had something similar it is still a puzzle because any inside locking "nut" would need to be longer/larger than that on the Topic & risk interfering with the light path. (possibly)

 

The Topic's parts would clean up nicely btw... wink.gif



#22 Kokatha man

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Posted 02 February 2020 - 01:48 AM

Charlie has confirmed the fact that there are no more parts to the Royal Astro spider-rod ends, giving his method of ensuring that there is little chance of movement by making sure they are positioned one end of the ota grooves or the other. waytogo.gif

 

Nevertheless I have decided upon using the better setup of the Topic's spider fixtures - I thought about these Topics a little more where I had previously described them as a "budget" scope...but in looking back they were $70Aus when there was a fixed exchange rate in Oz...according to one source $70Aus is worth $840Aus in today's money...probably slightly over the "official minimum weekly wage" here today.

 

That probably put it a bit above a "budget" pricing but then again a telescope would be considered a "luxury" good in some ways...

 

Bit another bullet & cut the 19mm adhesive-backed felt tabs to just over half size & placed one every 30° around the lip/flange for the primary in its cell: this meant almost edge-to-edge so plenty of support. smile.gif

 

I then cut out small A4 copy paper tabs of paper & inserted them under each mirror clip & screwed these up...then adjusted the 3 tiny grubscrews that centred the primary in its cell - resisting the desire to use a feeler gauge down the sides of the cell to ensure it was absolutely centred in the cell. (probably a 1000 reasons why that might not be necessary but I thought I'd re-assemble the scope's optics & align everything first before needing to look at this type of adjustment...)

 

I judged that everything was sitting snug with no pressure from the clips, but with the primary secure in the cell....again a star-test will tell me if I have that right but it did seem as if the replacing of the thick paper wadding with the felt tabs brought the mirror to an identical height re the clips...

 

RoyalAstroPrimaryFittedinCell.jpg

 

RoyalAstroPrimaryFittedinCell-REAR.jpg

 

 


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#23 Terra Nova

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Posted 02 February 2020 - 12:15 PM

It’s looking great! waytogo.gif



#24 Kokatha man

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Posted 02 February 2020 - 05:26 PM

Thanks Terra - today I'm feeling my age after some late-Sunday tidying up of the front yard in anticipation of the workmen putting up a new solar array on our roof today. :lol:

 

But I still hope to tinker around & check Charlie's notes to perhaps make up the cardboard template for my mate Dennis to make the missing casting from on one of his lathes...wrinkle-blacked it should look pretty much like the real par! ;) 



#25 Kokatha man

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Posted 04 February 2020 - 08:11 AM

...a bit of a lazy day as far as progressing the RA scope but I did polish up some of the chrome turn-key screws on some c/weights & made up the (rough) sketch for Dennis for the missing c/weight shaft & casting below the DEC casting...I'll take it down to him tomorrow.

 

Pretty rough even by my standards but I think it'll give Dennis enough information - I'll let him use a tiny bit of artistic license to work it out & I'll finish any rough/sharp corners he might leave...but with a good coat of wrinkle-black I think it'll be fairly difficult to distinguish it from an original aspect...experts excepted of course..! lol.gif

 

RoyalAstroCounterweightTop&BarPlan#2.png

 

 

 

 


Edited by Kokatha man, 04 February 2020 - 08:15 AM.



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