Telekit progress

[Vermin]

I'm finding this quite easy going so far.

I've got the main components glued together as can be seen below. The mirror box is only dry fitted in this photo but is glued now:

http://www.webclot.com/scope/images/DSCF0002.JPG

Still plenty to do including lots of sanding and routing.

The mirror cell is this weekends planned work.

[Striker]

Yes but what is it.......kidding..

[ballaratdragons]

Thanks for the update Tom, looking good.

Certainly looks like a big task.

Did you end up making any templates before gluing? and were you able to get the aluminium rod?

[Vermin]

No need for the aluminium tube, I don't know how he did it, but a sheet metal worker mate from work managed to repair the crushed tubes to like new condition. A talented man.

I did not make templates, the kit is not a great design IMO, it's much lager than it has to be.

I had another setback tonight:

I'd been trying to make some sort of symmetrical arrangement of the mirror cell for over half an hour. I used a drafting triangle to draw an equilateral triangle through the collimation bolt holes to assist with alignment of the cross bars but this did not help.

I took the pieces apart again and noted there are 2 sets of different sized floatation pads! This coupled with a hole spacing error on one of the crossbars (~ 1/8" different from the rest) makes it impossible.

Just sent off another email to Astrosystems. If they say anything other than "replacement parts are on the way" I will not be a happy chappy.

I have a mirror cell I built a couple of years ago (see the for sale forum), I may just end up using it yet.


.

[iceman]

Looking nice Tom, shame yuo're still having issues though.

Can't wait to see it when it's all together.

[Vermin]

Well I did not get the response I was hopeing for:

"the bottom line is this cell, with some variations in dimension, will perform flawlessly in supporting your mirror. There is a good article written by a Japanese engineer about wavefront error vs support points and he shows that optically, a 9 point cell would be sufficient for a 16" It is in the Sky and Telescope for November 1994. And last, I have almost a match to your scope with my 16" f/4.6 with a 1.6" thick mirror and similar variation in the cell pad placement. When you see the central star of the Ring Nebula, mottling on the surface of Io, and detail withing the festoons on Jupiter you know the construction is well within needed tolerances.
Last, I wanted to relate a time last year when I observed two nights with with what I and others that used my telescope considered premium views, only to come home, remove the mirror for cleaning and find one of the flotation pads had broken loose from the orientation ring and had rotated 30 degrees.
It had been that way all weekend from the dust imprint on the back from the flotation points."

Personally I think it's an excuse for yet more shoddy workmanship.

Anyone else care to comment on this?

[ving]

glad to see some progress :)
seems like one thing after another though! :mad:

[janoskiss]

Just "smoke & mirrors" Vermin. Very poor service! Maybe your mirror cell will be allright for the job, but you wouldn't be happy if a few wheelnuts were missing on a new car, even if all the engineers in the world agreed that three per wheel are more than enough. And what about the resale value! How are you gonna explain to a prospective buyer that it just looks bad but it works just fine! Give them hell Vermin! Don't let them get off so easy.

I have online access to back issues of S&T through uni, and there is no article in the Nov 1994 issue by some "Japanese engineer" about mirror cells. They must mean this one about finite element modelling of mirror plate deformation:

Toshimi Taki, "Mirror support: 3 or 9 points?", Sky and Telescope. Cambridge: Sep 1994. Vol. 88, Iss. 3; p. 84 (4 pages).

There is one real problem with the study. It assumes that the mirror lays flat and the weight of the mirror is spread uniformly across its surface area. So the results can only apply when you're looking at the zenith. There's a followup article with more data tabulated here:

Toshimi Taki, "More thoughts on mirror-cell design", Sky and Telescope. Cambridge: Apr 1996. Vol. 91, Iss. 4; p. 75 (3 pages)

PM me if you want copies of the articles.

[Vermin]

Well I read the articles (thanks Steve) and found an old email from Mark where he did suggest a 9 pt cell would be adequate, so it looks like the current 18pt cell with small asymmetries will do the job.

I like your other arguments Steve, I can't be bothered trying to push the point though. I just want to get this scope finished and start observing again.

I'm taking the week before Easter off to really get stuck into it.

[Dave47tuc]

Keep working Tom:D

The end result will be:eyepop:

Good luck.

[rumples riot]

Looking good Vermin, nice work so far, all the components look put together well.

Just noticed that I am on 999.

[Vermin]

Spent a while trying to get the filter slide / focuser board to line up on the secondary cage tonight. Then realised that Astrosystems had drilled two pilot holes in the wrong place.

:doh:

I guess I should expect this sort of thing by now.

Should be easy to fix.

[janoskiss]

Geez, it's going from bad to worse. I can send you some scrap plywood if you want to start over :P

Seriously though ... Best wishes. Hope it all works out in the end, and all 200+ of us can come and visit to look thru yer massive scope. :whistle:

[ballaratdragons]

Geez Tom,

Did they do anything right?

[Vermin]

Another one: Mirror cover handle screws were too long, had to grind them down or they would have punched right through the cover.

Most of these problems are little things, and none of them insurmountable, but the list is growing:

Shipping damage to truss poles, mirror cell back, mirror box sides, secondary cage cover.
Wrong ground board foot supplied.
Lower truss clamp block split almost in half.
Lower truss clamp blocks not square
Poor accuracy of mirror cell components.
Altitude bearing extension inner radius wrong diameter.
Secondary cage struts too long.
Filter slide mounting pilot holes wrong.
Mirror cover handle screws too long.
Azimuth brake too short.

[ballaratdragons]

Yes Tom, they sound like small things, but so many of them.

It's not good at all for a company. If it was built by a mate down the road you could excuse some mistakes, but a company to have that many problems on one item. Not good advertising for them is it!

Imagine the heart-ache and problems if the kit was purchased by someone with no carpentry skills at all.!!!!!!

[Vermin]

Yeah this kit could be so much better if they just took a bit more care in the packing and inspection of parts.

I hope it's going to be worth the effort. I'm really worried about how well it's going to balance and how smooth the bearings are going to be. This should all have been easy to calculate in the design phase, but I'm not filled with confidence in them at the moment.

Time will tell... should be ready for a first light by the end of this month (would have been sooner but I've just gotten over a nasty case of the flu).

[ballaratdragons]

Even if it turns out that the balance is wrong and the action is not smooth, you'll fix it! I can tell you are the type of person who will make it work even better than the original.

[Vermin]

Well I doubt I'll turn it into expensive firewood, just depends how fed up I get :)

Don't you ever sleep?

[ballaratdragons]

Yeah, going to bed now as I am making heaps of mistakes on this computer from tiredness. Catch you soon.

Good luck with the firewood . . . oops, I mean 'scope'.

[acropolite]

:work: Nice work Tom, keep the photos and reports coming. I'm sure that despite the problems the final result will be awesome. After seeing your efforts, a couple of us here in Lonny are thinking of building truss dobs, hopefully scratch built if it's not too ambitious. Maybe when you've finished you could document and get mike to put in the "how to" pages...... Can anyone recommend a good book and or plans for a truss dob??

[Vermin]

The one and only book to get (I have a copy if you would like to borrow it):

http://www.globaldialog.com/~obsessiontscp/Book.html

If you are have trouble finding good quality ply sheets, I can help.

I also have a 16" mirror cell and some other bits for sale (see the sale/trade forum).

There are a couple of online how-to pages that cover the construction process of the Telekit already:

http://www.waningmoonii.com/Astrosystems%20Telekits.htm
http://mpgf.net/buildit.htm

If size is a concern I would not recommend the Telekit (I could fit an 18" mirror in my 16" Telekit mirror box if I used a Kriege/Berry style mirror cell).

Also had another couple of setbacks, the lower truss blocks are not square and I'm waiting for another set to be shipped out, and the azimuth brake is too short (I've made it higher with an additional furniture pad on the underside).

Apparently Astrosystems have had to fire one of their junior staff who was responsible for making these and many more mistakes.

[acropolite]

Thanks Tom, I'll order a copy of that book; it's quite cheap. I'll study up a bit and work out what bits I'm capable of building then if it's OK, pick your brains for more info when I'm better informed. Unfortunately the junior thing is all too prevalent these days; inexperience, overconfidence and no pride in their work.

[Vermin]

I pulled my finger out this weekend and got back into working on my scope after a long break.

I finished off the lower truss blocks by cutting some new bases and gluing them together.

I spent a while positioning and gluing the lower truss blocks and filling all voids and imperfections with wood putty ready for final sanding.

Tonight I did a dry assembly (no bearing surfaces) to determine the best focuser position.

The first thing I noticed was the size of the assembled scope. It's huge! See attached photo.

The second thing was how concentric the scope is. When positioned vertically and rotated through 360° the edge of the secondary cage did not deviate from a mark on the ceiling. and the gap between the mirror box and rocker was constant when moved in altitude (the boxes are square). YAY! The hours of careful attention to accuracy have paid off.

The third and final thing is that I prefer the focuser on the right side of the scope (looking from the front). I'm going to make a post surveying this preference for Dob owners, just out of interest.

Just a bit of assembly to go, but a lot of finishing sanding and varnishing/painting too.


I'm feeling much more happy about how this scope is going now.

[Vermin]

Here's a better pic:

[slice of heaven]

Looking good Vermin. Good to see a real telescope progressing.

The pic really gives some scale to how big it is. Not much clearance of the ceiling.

Slice

[Astroman]

Thats quite an impressive piece of scientific equipment. Can just see it wizzing around the night sky picking out all those faint fuzzies.

[bytor666]

yea....if you put the focuser on the right side of the scope it will be in just the right position. The ways it is on now it looks way too low.
---------------------------------
Mark
12" gso scope

[acropolite]

Truly a thing of beauty Tom, are you going to polish the woodwork? :D

[ving]

and then when you are done you will have to buy a ladder :P

look in very good!

[ballaratdragons]

I would be scared of it tipping over Tom. How do they counter for the off-centre of gravity?

[Vermin]

It should be perfectly balanced on the Alt bearings when fully assembled Ken, so the centre of gravity is over the base.

Phil, I've got sand paper down to 400 grit, and enough Wattyl satin varnish for 3 coats (last coat by spray can). The first coat is 50/50 varnish and thinners for better penetration.

Going step ladder hunting this weekend.

[Starkler]

Its looking very nice there :thumbsup:
If you start feeling symptoms of Tonys disease please let me know :)

[stringscope]

Yup, you will need a ladder alright!! Looks fantastic Vermin!!

Was the filter slide part of the standard kit?

Cheers.

[[1ponders]]

Now that is a serious scope. Awesome Tom. Have the jitters and twitches started yet, wanting to just sneak it outside for a quick peek? ;)

[Vermin]

Yep filter slide included Ian, and yes can't wait for first light!

[slice of heaven]

Hows the progress Tom??
Had first light yet???

[elusiver]

i was actually going through the show us your rig thread yesterday and thinking the same thing? FILL US IN!! WE WANT DETAILS!! :P :D ;)

i think he doesn't want to tell us how awesome it is on fear that 400 IISers showing up at his door wanting to take a peek! ;) :P :D

el :)

[seeker372011]

well, come on fill us in... :)

[iceman]

You know, I was just thinking about Tom over the last couple of days.. haven't seen him around here in *ages*. It's been over 6 weeks since he's last logged in.

Anyone know where he's gone?

[Vermin]

He went to work in Fiji (and to work on the less exotic King Island) for a while! :)

I have been very busy with work and family commitments but have been able to do a bit of work here and there on my Telekit, one or two more coats of varnish and it will be ready to assemble. I'll post some photos as soon as time allows.

I had to clear the ServoCAT tracking computer and motors through customs yesterday.

Unfortunately it looks like I'm flying back to King Island next week, so now I maybe finished by the end of next month.

Good to hear I was missed!

Cheers,

Tom.

PS: Got some aurora photos last night:
http://www.webclot.com/photos/Aurora%2025th%20August%202005/index.html

[slice of heaven]

What!!!!! Servocat too!!!!
I'd love to see that beastie swinging around on its own. :thumbsup:
Any progress is good progress, keep at it and post some pics when you can.

[[1ponders]]

WB Ver :) Nice aurora shots mate. Lucky bugger, but you can have the cold :P

[Vermin]

Oh so close. Just need a longer ALT drive cable (it's in the post) and the cloud to bleep off so I can have a go at first light.

[janoskiss]

Wow! It's been a long time coming, but it looks like it's going to be worth it! :thumbsup:

[Starkler]

I hope this isnt a rude question, but I'm interested to know what this project has cost you for the scope kit, optics, freight & taxes etc, not incl the servocat bits.

Im interested in getting a truss dob of around this size.

[Vermin]

Hehe you're telling me Steve. But I can see the light at the end of the tunnel (scope) now.

Geoff, not rude at all, though I'll have to dig out the receipts and right now I'm off to install a phone kit in my car, I'll see what I can tally up later on tonight.

[stringscope]

It looks magnificent Tom. I am looking forward to a first light report. After the TV101, 16" should "blow your sox off"!

Cheers,

[Vermin]

I'm hoping so Ian.

Starkler all prices in Aussi dollars:

Deep Sky Optics NSW 16" F5 $3000 + $200 shipping

2.6" Secondary and holder, $180 + $40 shipping

Telekit, spider, encoder mounting hardware and ALT bearing extension $1967

Feathertouch focuser $367

Customs Agent and import fees $483

Notes:

1) Telekit shipping is to first airport in the country only, you still have to pay local shipping (I seem to have lost this invoice)

3) ALT bearing extension only required if fitting a ServoCAT goto.

3) The Telekit is big. A lot bigger than an obsession or clone. This is due to having the truss fasteners on the inside of the mirror box.

[Vermin]

:party2:FINISHED!!!:party2:

Lovely clear night tonight (despite the Moon) so I managed to trim the truss poles on my scope.

Of course it did not all go to plan; I had to trim quite a bit from the poles (over 130mm) and as I peeled back the black heatshrink I noticed that one of the poles was joined with a wooden dowel!!

I paid for a kit of new parts, not cobbled together factory leftovers. Needless to say I was a bit peeved. especially as I had to cut through the dowel with a saw, stuffing up the nice neat tube cutter job I had done on the pole.

Nasty email to Astrosystems tomorrow.

Now for the good news.

The Moon through my Denk Bino was astounding, I'd still be there gawking with my mouth open now except I have to go to work tomorrow.

Jupiter showed spectacular detail, Io's disc was clearly visible against the planet, an 81A filter made a slight improvement in detail.

I did have considerable trouble merging the Bino view of Jupiter for some reason, this was not a problem on extended objects like Eta Carina or Omega Cent, both of which looked a little washed out due to the Moon and severe light pollution - but still captivating. Can't wait to get to a dark site.

Because of the extremely limited view from my front yard I did not align the ArgoNavis, but slewing with the ServoCAT was faultless, maybe a slight adjustment needed on the mid range speed is needed - as it was a bit fast and too close to the flat out slew speed.

I only did a rough collimation but noticed something odd when star testing:

Diffraction rings were concentric, but inside focus the rings were slight horizontal ellipses, outside focus they changed to slight vertical ellipses (or maybe vice versa, I can't remember). Any ideas what would cause this?

[syzygy]

Pinched optics somewhere (check the flat) or astigmatism.

[Starkler]

Yep astigmatism most likely caused by a pinched secondary.

[Vermin]

Thanks guys I'll check it out tonight if this weather holds up.

[wavelandscott]

Congrats on getting it all together...Hope you get some great views soon!

[Miaplacidus]

Congratulations, Tom. Looking forward to your first observing report with that monster.

What sort of filter to you use to dull the glare from the moon?

Good luck,

Brian.

[Vermin]

No filter on the binoviewer at the moment as it pokes through the filter slide. I may unscrew the light green filter from the slide and screw it onto the bino OCS, as that seemed to be the best option when cyclopsing with my other EPs.

Brian, you'll soon be able to have a look at one of the AST's Friday meetings, as I am going to rejoin the society to gain access to the site at Mt Canopus.

Cheers for the well wishes.

[Miaplacidus]

Looking forward to that, Tom!

[ausastronomer]

Tom,

If you have used a high grade commercial secondary mirror and holder such as a Protostar, Novak or Antares and haven't overtightened the secondary retainer then it may not be the secondary. What secondary and holder have you used ?

I am not familiar with the Telekit Primary Mirror cell nor am I aware of the thickness ratio of your primary. A Full thickness mirror is 1/6 and if your mirror is thinner than this it needs to be properly supported. Primary sag will also induce astigmatism. Make sure that all flotation points on the mirror cell are sitting squarely and bearing properly on the primary mirror.

CS-John B

[Vermin]

The culprit was a pinched secondary, as soon as I loosened off the holder the astigmatism disappeared.

Unfortunately just as I confirmed this and was refining the collimation the cloud rolled in calling a halt to this evenings viewing, looks like it's here to stay until Saturday at the least :(

[Starkler]

Do I win a prize :D

Glad that you got it sorted :thumbsup:

[Vermin]

You win a chocolate chip Internet cookie. :)

I put all my gadgets through their paces tonight, and after a quick bit of fussing about with backlash settings, slew rates and directions I got the ServoCAT running real sweet.

Even with my limited view from the front yard severely restricting the choice of alignment stars (difference in AZ between the two stars was only ~30°, and one star's ALT was in the atmospheric refraction band of less than 20°) the Argo Navis got every object I slewed to inside a 13mm Nagler EP (0.5° FOV).

Using Cartes du Ciel to tell the ServoCAT where to go after clicking around the sky was impressive.

Using Astroplanner to slew to a list of bright NGC objects (my yard is very light polluted) in order of azimuth was downright cheating. It was so effortless to find things I felt guilty! The seeing was terrible compared to the last few nights though.

Astroplanner did crash (floating point divide by zero error) when I tried to map my horizon. I had just mapped the whole horizon and when I hit "OK" it crashed loosing the lot. I'll try this again another night.

Now that I have everything tested and am familiar with the set-up process (set-up time ~35min, tear down time ~20 min), I can't wait to get out somewhere really dark.

Oh boy am I tired though. Bed time now.

EDIT: I managed to merge the image of Jupiter in my Denkmeier Binoviewer too. The problem is that if any diopter adjustment is made to the left ep the holder sags slightly. This is not a problem for extended objects but makes viewing planets very difficult for me. Fortunately I can get by focusing on the left ep then only adjusting the right diopter. According to Russ at Denkmeier the diopter adjustment just needs a bit more grease.Not worth sending it back though as my workaround is adequate.

[Miaplacidus]

Well done, Tom. You've made all of us green as lime jelly. A lot of sleepless nights ahead, I suspect.

About 10 of us from AST met up at a dark site in Lauderdale last night (thanks for the hospitality, Graham!). Lovely dark site. You would have loved it. As it was, I had the Megrez on your Panoramic mount, now complete with the Argo Navis, and it worked a treat as a smart finder for all the bigger guns without GOTO, as they could all follow the green laser to the DSOs that I could just barely see through the 80mm. Sombrero was magic.

Cheers,

Brian.

[Vermin]

Sounds like a top night. Any chance we could make it 11 people next time? I still have to perfect getting my scope in and out of the car though.

I had the same idea with the green laser goto slave, but the other way around:

1) Green laser on Goto Dob

2) TV101 on non goto GM8 mount slews to laser point (to invisible fuzzies) for long exposure photography.

[Miaplacidus]

Sure thing. The more the merrier as far as I'm concerned. (Wouldn't it be simpler to put encoders on the GM8?)

[Vermin]

Yep, but I can't afford 'em at the moment.