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Zhumell Z100 100mm f/4 Newtonian


Alan64

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I had acquired this kit round Christmas, 2016....

kit2.jpg.5d007e64d7a8c0d0697ede9bec44f61f.jpg

It is practically identical to the Sky-Watcher "Heritage" 100P, and to where, quite likely, both were manufactured in the same factory overseas...

http://www.firstlightoptics.com/user/products/sw_heritage_100p.jpg

The Orion(of California) "SkyScanner" 100mm is actually more closely identical to the "Heritage" 100P.  Hence, I look upon my own as the "dark horse" among the three.  Incidentally, I chose this one due to its more traditional focusser placement; albeit due to its special price at the time of US$89.99/£73.16 in addition.  It came with these two eyepieces, which differ slightly from those bundled with the other two...

oculars4.jpg.98e6ef6e2cda48e915e310e16ddd3f43.jpg

The outside of the telescope can use a little work, but it's where the light enters and travels along that concerns me the most...

objective2.jpg.214a7cb9f5f5d882865323166fb260a2.jpg

My, isn't that nice 'n' shiny?  In addition, it has those three, wonderful, thick, plastic spider-stalks...

Edited by Alan64
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010417-10mm.jpg.15d5ddd5ac190cf4b0fd35f4bf21b500.jpg

...that through the bundled 10mm Kellner.  I see a ghost, there in the centre of the Moon; a Moon ghost.  I don't like Moon ghosts, or ghosts of any sort, or flares.  I owe to that image my driving desire to make this telescope the best that it can ever be.  On the other hand, via my Vixen NPL 30mm Plossl, at 13x, the view's lovely...

011217-30mm.jpg.a65badea06da0126adbf1c281546e029.jpg

I did have the galaxy in Andromeda primarily in mind when I considered getting this telescope, and for a lowest power possible.  I didn't want an 80mm f/5 achromat(identical focal-length), as I already have an 80mm f/6.  

A few months later, in April 2017, I began to disassemble the telescope, and by renovating its wonky, plastic focusser.  I got most of the wonkiness out, but it will require further tweaking before I may declare it done.  Later, I removed the telescope's fixed dovetail-bar, and purchased a pair of tube-rings...

65793176_tuberings8b.jpg.7ba98392022f9da76e7fa38eae92f707.jpg

Almost $50 those rings had cost, and seemingly proprietary; "Antares" branded.  But now I can twirl it round and about, upon this tripod-type mount and that.  What do I not do for my telescopes.

But the very first thing that I did was to centre-spot the primary-mirror, as I was most curious as to how accurate the collimation was upon arrival, especially with the telescope's fixed, non-adjustable primary-cell...

7.jpg.563f83b0f34f9a7d4cd541a0eebc7b4f.jpg

The secondary-scene, before...

1712706017_orig.collimation2.jpg.f5f3ba8a6e8c1d2add742bb5e4c33921.jpg

...and after...

011417d.jpg.f9619cd61f8260a87bf7781e5101fb5d.jpg

Well, would you look at that.  It was bang-on all the while.

Edited by Alan64
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A hole was drilled at each end of the splint. for epoxy to flow into, and for securing further; every little bit helps...

splint15b.jpg.a3d47f77534d287713fdb91b80c1af56.jpg

There at the left, that's the "claw" of the splint.

Test fitting...

1403548358_testfitting.jpg.c72290b461741242617168bfa7aac608.jpg

The splint and its support were then epoxied into place with J-B Weld...

241381056_Itisdone!.jpg.09d8bc5a2bcc06826ae7cac101d4232e.jpg

All surfaces to be joined, as usual, were scored.  Note how the "claw" of the splint disappeared into the hub...

packing2.jpg.0b405c280a233d9b822076a99f7e17f0.jpg

The hub's well there for the favoured stalk was primed with a coating of plain epoxy, then epoxy infused with dust of rosewood was packed in all round and about the "claw" of the splint.  Hence, that shan't be popping loose and out anytime soon.

Edited by Alan64
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Can't neglect the plastic-stalk, as it needs bolstering as well where it joins the frame...

1742095769_stalksupport4b.jpg.17ec29d92d1f94a1e864a45b75279a89.jpg

1674898500_stalksupport5b.jpg.d79821ce9846813072c84e2bb658a77c.jpg

Where the stalk joins the hub, I installed a U-shaped bronze rod...

1493829223_bronzerod2.jpg.bfdd40e43630b31c126ab6f930ddbf77.jpg

You can see it there peeking out at you, and that to strengthen that union further.

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The aluminum-splint and the plastic-stalk must be made as one.  For the next step, I made a small rule, or straight-edge rather...

1570848112_miniruler2.jpg.7056509d65a00210865edecf0bd07107.jpg

I then marked each side of the plastic stalk, ground them out flush with the aluminum-splint, and scored the depressions...

163957895_bronzeplates4.jpg.37dc90800ad61ed195b94ff5e080d42c.jpg

Bronze plates; and custom clamping-pads of maple, hard-felt and wax-paper, which ensure that the plates lay perfectly flat......

1277943924_plateclamps.jpg.ca87c013a0a6c537b4371f9799802c2b.jpg

The plates were epoxied into place, and clamped until the epoxy cured.  Here, the removal of the clamping-pads...

1662994429_bronzeplates5.jpg.2d1d343d4a28859365eba4c13dad1b3b.jpg

...then the wax-paper...

276269634_bronzeplates7.jpg.a27b712d7a5ff2d5ee2c1af317db508c.jpg

757073481_bronzeplates8.jpg.08bf92ab98d5614ba90bfc1fd89bc1ec.jpg

The stalk and splint are now as one.

Edited by Alan64
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I had made the depressions for the plates a little too deep, so I then floated both with more epoxy...

float.jpg.8cbb1d558a43a60c50ea583088675e00.jpg

The favoured stalk in toto, completed...

1055234532_bronzeplates10.jpg.a3d2bd76a65e923f98ca9d046dab37b3.jpg

A silhouette...

silhouette2.jpg.b1004c5b16a7387cf0b4bea974f7348a.jpg

Note how the favoured stalk overall had narrowed as the modification progressed; the thinner, the better.

The other two were then cut out...

cowling2.jpg.727159b2bf00786f1631904a37678e9c.jpg

In the end, I do have one of the hub's set-screw holes aligned with the focusser...

cowling3b.jpg.9db538107ca6ba4f5670a6cde4b461df.jpg

...and just as it should be...

corrected2b.jpg.b592b69945a8fddf576edf694df49355.jpg

Edited by Alan64
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The cowling was placed over the primary cell, and to check for clearance...

958035550_allclear.jpg.999b9e7ca7db34d06946cc6f8348bd05.jpg

...all clear, and with no blocking of the primary-mirror.

Ah, but I can't blacken the cowling quite yet, for after I had removed the other stalks, the lone stalk is rigid, but the frame flexes a bit when the stalk is wiggled.  Now, when inserted into the optical-tube, it's more rigid.  Still, that's not quite good enough. 

Fortune has indeed favoured the foolish, as two of the three mounting holes of the cowling flank the lone stalk...

holes.jpg.906f0c53da8104ebbbabcde5f755f801.jpg

Bracing the frame from both sides of the stalk to just past those holes should increase the rigidity of the stalk considerably more.

aluminum2.jpg.0783d94a0b1c168b404fea622074b10a.jpg

aluminum3.jpg.e2eb99a77a7391fd67db395e0591c3be.jpg

Two strips of 1/32"-thick aluminum, veneer if you will, 11mm and 14mm in widths, and for these...

1109919035_framestiffeners.jpg.d34194aea68215353462c0d605dab948.jpg

...and scored on the opposite side...

498232763_framestiffeners2.jpg.76655233a09c7b0a5d7d94b22cb6eff3.jpg

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This, a rare image of an epoxying operation in action, and made possible by the slow curing-rate of same...

1176825548_J-BWeld5.jpg.17348cc025e0019356af0755a1e9791b.jpg

Incidentally, I braced the the third mounting-hole area opposite the stalk in addition.

I had to scrounge round the house for clothes-pins, eighteen to be exact...

917309090_framestiffeners4.jpg.af851a177a7c7396a68a62b7b87eb194.jpg

I had let that set whilst I went out for a spell, and when I returned home I removed the pins and secured the cowling onto the optical-tube for the final curing of the epoxy...

149213712_framestiffeners5.jpg.aebb841d37608abecbd70c02d1717873.jpg

That did the trick.  The stalk is now immovable.

Edited by Alan64
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The final washing of the cowling...

372246596_finalwash.jpg.f72cc7da03ff615b88b054ee06f6d8fc.jpg

The cowling was then masked...

masking.jpg.47405cab9a1a092a6d1c22c3c8fcdd6b.jpg

...primed...

primed.jpg.383bd039054128289ee52413cd39147a.jpg

...and painted front and back with chalkboard-black...

cowling7.jpg.16085db20b0e541e6812467aa6e846aa.jpg

cowling10.jpg.4a04e0bde9dc6fe248b74c2355b7e45a.jpg

cowling9.jpg.1c40b39f2e4c1d9b533534374707c7ec.jpg

...lovely.

All the additions are still clear of the edge round the primary-mirror...

671235440_allclear3.jpg.5cf18f9ed0423b15c44e54674867e937.jpg

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What of the secondary-mirror, and an integral part of the cowling?  I'll tell you what of it.  Just have a look...

1471743443_mirror-stalkposition4.jpg.93d62f8c0586ac89962b5847c9add2cf.jpg

At left, that wonky rotational-position speaks for itself.  At right, I wasn't certain at the time if the off-setting of the mirror in relation to the stalk was correct, and for an f/4 Newtonian.  It turned out that it wasn't.  The mirror was originally secured with double-sided foam-tape; was, that is...

1588307919_secondarymirror3.jpg.a5c68ab953610812ca7efabc83fc262a.jpg

This is an absolutely wonderful resource for situations like this...

http://www.deepskywatch.com/Articles/replace-offset-collimate-secondary.html

I never cared for mathematics, yet despite that combined with what few blond hairs I have left, I was able to understand it.  In the end, it required a distance of 9.15mm from the edge of the primary end of the secondary-mirror to the edge of its stalk.

I used aquarium-safe silicone as the adhesive...

sealant-adhesive3.jpg.898c88ed801e35195e6f798a9826e0b3.jpg

I applied the silicone as shown here...

2006321297_mirror-stalkposition8c.jpg.485e8d15ba97706a2abd2d927d0ee584.jpg

...and used round toothpicks for spacing...

curing.jpg.405139523f10518c45a5e579f9b739e5.jpg

I took that shot from about three feet away.  I tried to get closer, but it shouted out, "Don't touch me!"  So I backed away, slowly.

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The secondary-mirror and its stalk, before and after...

1778311703_mirror-stalkposition9.jpg.ff7091cbc2bd481717799c8159c3bc46.jpg

Note the now-correct off-setting at right.

1798512009_mirror-stalkposition8d.jpg.5aef134ac90a95548236e2eef281b838.jpg

Incidentally, I had epoxied a white-nylon washer on the back of the stalk, and for the new set-bolts to bear against; and as opposed to the "milk jug" solution.

The side of the hub round is black-anodised, but since it will be obscured by the secondary-mirror and -hub, I won't be blackening or flocking it.  However, I did blacken the secondary-mirror itself...  

1452735203_secondarymirror7.jpg.5f729f5146a16b0a3a97509cadeca8a7.jpg

Glamour shots...

1919978466_secondarymirror9.jpg.ce0f571ab0eb1cf8111df8def6ca05ef.jpg

1423706703_secondarymirror8.jpg.8f432f79309cb0ca7cb88d2b0f33d17f.jpg

617607185_cowling-mirror.jpg.1b82952a399196af2e0c4b3a7e0af085.jpg

The cowling, in toto, is completed.

Oh, these are the new set-screws, or bolts rather...

set-bolts.jpg.8494fca00371542bbe6dd01e5ee4243b.jpg

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Then turning back to the optical-tube, I had this to remedy.  All along, I wanted whichever finder to be closer to the focusser, and so as not to have to crane my neck as far over to look through it...

920174266_finder-baseholes.jpg.8470751287d1827764d0547e4c6d5519.jpg

1.  ...the original holes for the inadequate post-screws.

2.  ...where I got the "bright" idea, back in 2017, to position a Vexen-type finder-base there.

3.  ...yes, you guessed right, the final location for the finder-base.

Four holes to fill, not to mention the two larger ones where the dovetail-bar was once fixed.  But first I needed to back them with thin aluminum sheet.  I used 5-minute epoxy for this operation...

filling2.jpg.1cf65a5e15273178535b110ea3bd02d2.jpg

filling.jpg.e046f1707d5ac8a6b4a94b4087f891cb.jpg

filling3.jpg.d4c36d344215e5caea9fbe9436b72d3c.jpg

Where the dovetail-bar was once attached...

1074610696_filling5-dovetailbar.jpg.965218a09d1ac296b1722babd65e8590.jpg

Edited by Alan64
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On the outside of the optical-tube, the holes were filled with J-B Weld epoxy...

filling8.jpg.d056d7660d672cd6dcbeb02ab4cd950b.jpg

filling7.jpg.a6b137b46750d23a9da5d881e740df64.jpg

Those look like witches' hats.

All six fillings were then sanded down flush...

filling10.jpg.1f57b0ed89f3499d3a96d06d35cb3495.jpg

filling9.jpg.4189bfe9625a6ac76b4b68dd34c32b1c.jpg

All six will be painted over with gloss-black when the time comes.  There are some scratches to paint as well.  Now, the main goal is to seal said areas, not to make them invisible, as they most certainly will not be afterwards.

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As of this posting. this is where I'm at now, today, and at the back of the primary-mirror's cell...

1004929123_primarycell.jpg.87ad4c75e1f3301c81d611f213c5eaa1.jpg

It's 5:30 in the morning here.  Later today I will going out to pick up a pre-ordered hot-knife kit from a local crafts supply house.

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First, I described a line in the center, to test, then I began to cut...

1589978013_cellcutting.jpg.6d1ea8e14c5924fe5e2f16f0c7027615.jpg

The hot-knife did not cut through the plastic like butter.  Quite the contrary, as I had to go over the lines, over and over; gruelling, tedious work.  In the end...

750674313_cellcutting2.jpg.7e99326bb5a5e0b1ab84095d9dffe7f0.jpg

There's a piece of that infernal foam-tape peeking through.  

40652508_cellcutting3.jpg.082dc704e6221ee89cf37103ba23e880.jpg

849229810_cellcutting4.jpg.68f496c63355f7ee2eb28f87c0890daa.jpg

Using a snap-off knife, I slid it through and under each piece of tape, and until the primary-mirror was at long last freed from its prison...

1180515468_cellcutting5.jpg.e218a343068ca278923d13fe5d1ecaf2.jpg

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Immediately after freeing the mirror, I cleaned it, wrapped it in gift-tissue, then squirrelled it away for safe-keeping...

2076037011_primarymirror.jpg.48cbb0996c674fb68f1e6ee2c94e5102.jpg

314386204_primarymirror2.jpg.1eadd0991e83211b6818a7e0914d1dc9.jpg

The opening of the cell was then roughed out...

614116046_primarycell2.jpg.501bdc988e1d97427d96a4146aea7912.jpg

Last night, the cell's opening was evened out, sanded and steel-wooled smooth, then polished; whilst the interior was rough-sanded for the matte-blackening...

562990308_primarycell4.jpg.6590eeb7a767dbd58ce7888793e6d3ae.jpg

Why, it looks as though it arrived that way from the factory, yet did not.  Would that it had.

Pinched, distorted, the mirror will no longer be.  It shall "breathe", acclimate, and as nature intended.

837334482_hotknife11.jpg.8ec1e9472eabc0107b26ee6a73865ef0.jpg

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I thought it a wee bit odd that there were eleven, recessed, circular molding-marks within the cell...

1563208330_primarycell5.jpg.72b42e471f7e94a9407b6f61ddec0620.jpg

In any event, that got me thinking as to how many globs of silicone shall the mirror rest upon in the end; three, six, or eight?  What about five?  I haven't decided upon that yet, obviously.

With that mid-section removed, the cell doesn't flex in the least.  This plastic is rather hard.  I was going to epoxy an aluminum ring at the bottom, to perhaps strengthen the cell further, but then my silicone contains acetic acid which will corrode aluminum over time.  I think I'll bypass the use of aluminum in this instance.

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I cannot and will not rely upon the threaded plastic mounting-holes of the primary-cell, nor upon those of the cowling, either.  Zinc-plated nuts will be epoxied onto the inside instead...

746443449_primarymirror3.thumb.jpg.58e15212222bd43638b0153a8516c3ee.jpg

However, at the nuts' present thickness, the primary-mirror will not seat into place.  I was hoping they'd clear, but now I know that they'll have to be ground down thinner into jack-nuts.  I've been there, and done that, before...

jack-nuts.jpg.2e73e8040624d31c858f4826c7bfd72a.jpg

The same may have to be done for those of the cowling, but only if they threaten to jut into the light-path.  All six stainless-steel screws will need careful measuring and then cut; joy, joy, joy, lucky me.

I do wonder if others wonder why I am going to all of this trouble for this inexpensive, entry-level telescope.  The answer is quite simple...  

When completed, I will have the reflective and therefore apochromatic equivalent of a Synta ST80 achromat.

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1218365170_jacknuts3.jpg.ff52094a9d6bca776360e995ceafea5e.jpg

The mirror now clears the nuts.

Those nuts will be J-B Weld-ed into position., then blackened along with the rest.

In preparation for the nuts to be epoxied and later blackened, their surfaces all over must be roughened, with at least 80-grit paper, or diamond-filed as in this instance...

873830963_jacknuts4.jpg.d1d698b7ea68f50c202cd45b08599ade.jpg

1904094042_jacknuts4b.jpg.f6d3f25feb63d2b080d5188c249c7f3a.jpg

Such will ensure that the nuts will not pop off in future, particularly when under pressure and torqued.

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