Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Dismantled my old (formatube based) OTA several months ago and been buying new hardware to go into the upgraded OTA.
My new components :
* ditched my old cellulose based Formatube (was getting very used looking and was pretty heavy) , will be using an offcut of white plastic stormwater pipe (316mm OD , 6mm wall thickness) that I got for nix from a friendly local plumber who told me I could have it when one of the local shopping mall’s carparks were “improved and reorganized” , he tossed in the big refuse bin and I asked if I have it , pays to be upfront ….
* new custom made 2" low profile crayford focusor to replace my old 2" Lumicon low profile helical focusor
* new AstroSystems spider and secondary holder to replace my old home made units (binned them)
* new Orion Optical (UK) mirror cell to replace my old home made silastic on plywood homemade mirror cell (ditched it), had to get modified side clamps made as the originals from Orion didn't fit my mirror , and a bit of final modification using my new Dremel and a cutting disk to make some "adjustments" to give a nice (not overly tight fit on the mirror's camfered edges) .... was very a very fiddlely process !!!
I wanted a Novak RQ Mirror Cell but he’s retired and his gear is now scarce as hens’ teeth.
* had my old Nova Optical 2.6” (1/10 wave) secondary recoated with very high reflectivity Broadband Dielectric coating with ultra high transmission TiO2 protective coating (should be considerable improvement over my SiO2 overcoated Aluminium that it originally came with).
* replaced my old home made tube rings with a custom made Orion Optical tube clamp rings complete with dovetail and blocks and compression clamps – was made to my specs --- very nice , even powder coated and felt lined so it wont scratch the tube
* My old Nova Optical 10” mirror has some blemishes on the SiO2 protected Aluminium coating , hoping these will come with some detergent and demin water, failing that I’ll buy some isopropyl alcohol , if that fails , then it’s off to be recoated …. Crossing fingers .
* bought some self adhesive flocking material from Proto Star (reviews are it’s the best around).
Rebuilding the OTA Stage 1 : Prep of tube offcut
The offcut was not cut very neatly or even squarely, but it is about 4” longer all up than I need for my telescope .
Calcs indicate that I can get away with a tube length of 1253mm for pure visual use .
Other min tube lengths I’ve calc’d are 1238mm for prime focus to my 40D via my Baader MFCC only with the focusor fully racked in , and 1216mm for prime focus to my 40D via my Lumicon 2” Esyguider and Lumicon 2” (0x) Coma Corrector – Field Flattener (CCFF) lens and the focusor fully racked in.
.
It makes sense to arrange my OTA with the mirror cell positioned to give focus with my Lumicon 2” Esyguider and CCFF in place with the focusor set for summer condition (focus with the drawtube a few mm out from fully racked in , and to acquire a 1” or 2” long 2” diam extension tube for those problem eyepieces that need a bit more focusor travel when using my Tele Vue Coma Corrector (which will modify my focal length a bit) or when I resort to using Barlow lenses to get a bit more magnification .
This makes more sense than moving the mirror cell position when switching from visual to prime focus imaging via the Baader MFCC or via the Lumicon CCFF and Esyguider.
I have none the less come up with design of mechanical system based on 3 bolts and a sliding arrangement (channel)to reproduceably adjust the mirror cell to focusor distance that I can implement if I decide the use of extension tubes for visual work introduces too much vigetting of the image. Nice to have a fall back position , however , each time the mirror cell location is changed the optical train will need to be recollimated (using my AstroSystems Laserbeam).
Squaring up the ends of the tube and trimming it:
I was hoping I might be able to pay someone with a complete workshop to do this, but the only local company who deals with plastic and plastic fabrication told me my tube is about 50mm too big in diameter for their plastic machining equipment (a special bandsaw and lathe) so there was nothing for it but to figure out how to do this with my own gear at home.
Arrangement used to square up the tube ends and cut off surplus material is as follows -
I set up my tube horizontally on top of two builder’s work horses (I know these are the same height so this made the tube properly horizontal , the work horses were positioned against the legs of my work bench in my garage (which is now in a clean and clutter free work area as result my recent spring cleanup) and I used a nice straight offcut of 2”x4” pine clamped with G-Clamps to the timber toppieces of the work horses to stop the tube from migrating as I turned it by hand when marking it up with a fine permanent marker and when it came to cutting the tube.
My 1m long straightedge with spirit levels together with my engineers’ bevel square (also with a builtin spirit level) provided assurance that the timber stop and work horses’ provided a horizontal base /
I then used the straight edge to gauge the perpendicular from the vertical side of the timber top-piece on the work horse arranged adjacent to end of the tube with an overlap of not more than 20mm (this is approximately how out of square the worse end of the tube is …. Based on measurements with a builders’ tape measure.
The bevel square was used to keep my guide line perpendicular (by eye against it) as I incrementally rotated the tube to add small extensions to the cutting guide line , I continued this process until the tube had rotated through 360 degrees and I was pleased when the lines joined.
I then arranged the tube to ensure my Dremel with a cutting wheel attachment didn’t throw most the dust on cutting the plastic straight into my face , I donned my safety googles and proceeded to carefully cut off the surplus plastic from the marked up end of the tube , slowly hand rotating the tube and taking carefully gaugbed cuts , easy does it was the order of business to ensure proper control of the cut while carefully following the marked line.
This marking up and cutting process on one end of the tube took the better part of 90 minutes , including thinking out the problem, setting up the “jig” , marking up , cutting and smoothing by lightly touching up with the same cutting tool to remove sharp edges.
Still a very dusty process - my arms and hands and the Dremel wound up heavily coated in plastic sawdust none-the-less.
More to follow :
Edited by Ian Robinson (08/22/09 09:46 AM)
|
Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1572
Loc: Fort Worth TX
|
|
Sounds good, but Universal WorldWide ATM Statute 18.50439.5b requires >>PICTURES<< ya know. Our attention span is not as long as your post 
Mike
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Quote:
Sounds good, but Universal WorldWide ATM Statute 18.50439.5b requires >>PICTURES<< ya know. Our attention span is not as long as your post
Mike
Will take some pictures as I progress this then , was a bit too focused on the process to do so this avo before I lost sun light.
|
Achernar
Postmaster
Reged: 02/25/06
Posts: 5025
Loc: Mobile, Alabama, USA
|
|
You know, you could make your 10-inch into a very compact truss-tube. I may do that at some point with my 10-inch Discovery Dob if the tube and base get dogeared. Do include some pictures, we'd be interested to see how your project is going.
Taras
--------------------
15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Quote:
You know, you could make your 10-inch into a very compact truss-tube. I may do that at some point with my 10-inch Discovery Dob if the tube and base get dogeared. Do include some pictures, we'd be interested to see how your project is going.
Taras
I did concider converting to a properly designed truss tube but decided it was too much bother and not enough gain.
I also have concerns about tube stiffness if it's a truss.
One day I'll upgrade my apeture (I'm thinking in terms of a 14.5 - 15" f4 or f3.5 as I think this will be about big as my New Atlux will "happliy" handle for imaging , I will likely do this as truss tube). THere will be enough gain then if I use a aluminium grade in the structure with high strength , high rigidity - but I'll have to learn how to weld aluminium else fabrication will be EXPENSIVE.
I also concidered using a rolled sheet of aluminium in my OTA but the this worked out expensive and my calcs showed it was not much lighter than than my plastic storm water pipe.
I also consider making a fibre glass tube , but it's a lot of bother making a proper template and the materials are toxic , and I a fibreglass tube with sufficient stiffness and rigidity would be heavier.
Looked into making a carbon fibre tube, but I was put off by the toxic materials involved , but a good template is also needed ,though carbon fibre will produce a light , rigid and stiff and tough tube - an option maybe for my next step up in aperture.
Edited by Ian Robinson (08/22/09 10:27 AM)
|
Achernar
Postmaster
Reged: 02/25/06
Posts: 5025
Loc: Mobile, Alabama, USA
|
|
Making an 10-inch Obsession style is a lot of trouble, but there is another way to make a smaller truss-tube Dob, namely join the tubing with brackets made from aluminum angle. You can then attach the combined poles and brackets to the mirror box and the upper cage. No welding required for anything since you can use a sheet of plywood as the "tailgate" for the primary mirror. Way easier than cutting, drilling, tapping, fitting and welding tubular steel as I have done for my 15-inch that is under way.
As for learning to weld, you will want a 230-volt MIG welder if you plan to weld aluminum, or a AC/DC stick welder. You cannot stick weld aluminum with an AC-only SMAW or stick welder as they're called in the trade. If you have access to a TIG welder, that is the best method to weld aluminum, especially thin aluminum. When molten aluminum does not glow, it turns into a shiny but still very hot liquid that is at least 1,300 degrees Fahrenheit. You must clean the metal thoroughly to weld aluminum, especially with the MIG and TIG process. There is no flux to bind to impurities and you must weld in a draft free area to prevent wind from blowing away the shielding gas. The arc is very intense and the noise is very loud compared to welding steel, and before trying to learn aluminum, practice on mild steel scrap first if you never did any welding.
Be careful while welding, the potential for electric shock, explosions, fire and burns are a constant hazard. Keep a fire extinguisher handy, and a first aid kit isn't a bad idea too. Safety glasses are a must when cutting or grinding, I can tell you all about what it's like getting metal taken out of your eye. It's not fun. The fumes can also be very harmful, even deadly if inhaled, so do this in an area with good ventilation free of flammables. And do not cut into anything or weld anything that ever held anything flammable, it could explode and a number of welders have died this way. I'm not trying to scare you off from welding, but be careful. It's a good thing to know how to do, because you can repair a lot of things around your house, or even your vehicles.
Last of all, build or get a metal table to do your welding and cutting on. You need a set of tools for welding that includes sqaures, a tape measure, files, hammers, clamps and a good visor and pair of gloves. Old woolen or cotton clothes and closed, leather shoes are a must. Do not tuck your pants into your shoes or boots, slag can slide right down to your feet and you will never forget the sensation of your feet on fire. Starching your clothes helps deflect slag and sparks. The arc is a hazard to the eyes of nearby people or animals, so you want to prevent them from getting their eyes scorched when you're welding. Keeping an extra visor handy is a good thing in case someone else has to be near you. And if someone is near you, warn them before starting a weld so they can look away.
Taras
--------------------
15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
Edited by Achernar (08/22/09 07:18 PM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Yep, I know welding is hazardous, spent over 15 years working at a steel works as a chemist then an engineer and I often managed projects involving the need to weld , but always had specialist welder tradesmen to call on to the actual welding to my or others' specs , never learn to weld myself but often directly supervised welders and witnessed them at work .... wish I'd taken the time to do some hands-on practical welding tech courses or the guys had shown me "the tricks of their trade" .
I'll stick with my current plan for my 10" OTA upgrade as I've all the stuff for that now and I don't want to start over again .
When I do my upgrade from 10" to 14'5 - 15" I'll likely do that as an all aluminium non-Obsession style surrier truss tube.
I don't particularly like Obsession / Starsplitter style scopes and I have very big reservations about 2 , 3 and 4 pole split tubes.
Edited by Ian Robinson (08/23/09 01:27 AM)
|
Achernar
Postmaster
Reged: 02/25/06
Posts: 5025
Loc: Mobile, Alabama, USA
|
|
I stand corrected. I know a couple of people who tried welding and quickly decided it was better for them to let someone else do it for them. I wouldn't have taken up welding without taking the courses first because the high pressure tanks and flying metal gave me the willies.
Taras
--------------------
15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Quote:
I stand corrected. I know a couple of people who tried welding and quickly decided it was better for them to let someone else do it for them. I wouldn't have taken up welding without taking the courses first because the high pressure tanks and flying metal gave me the willies.
Taras
Not in my department or one of my projects , but we had a welder killed in a vapour ignition when someone stuffed up and failed to purge with nitrogen a naptha recieving vessel that needed a repair to a cracked section of dished end.
My scope is not going to be used (much) in dob style, will be mounted up pretty-much permanently on my New Atlux which will be sitting atop my steel pier (when I get my ROR shed built), until then it'll be tripod mounted .
I'll probably make a Berry style plywood rockerbox for the 10" OTA for those nights I want to whip out the scope for some visual use and not have to bother with dragging out the Atlux and tripod (is bloody heavy !!!) or muck about with polar aligning. Got some left over precut telfon and Ebony Star laminate that I bought many years ago from CrazyEd and have never used.
Had the prodical son visiting yesterday so no progress from the other day.
Plan on squaring up the other end of the tube and cutting to my desired length , as well as cutting the focusor hole and giving the inside of the tube a sand with some sand-paper on a cork block to roughen it up a bit so the ProtoStar self adhesive flocking paper will get a good grip.
I may or may not have the time before I loose sunlight in the garage to flock it today (I've never run power permanetly to the garage , so if I want light in there at night time , it's the car's beams, or my miners' lamp, or I run a builders' outdoor extension cord from my underhouse power socket to the shed and plug in the old kitchen fluoro tube style light that's attached to the rafters.
Edited by Ian Robinson (08/23/09 10:27 PM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
OK , put the spirit levels back on the tube ends and found them a max of 6mm out of square (which was enough to bother me) - so used a different method to redo my cutting guide lines .
This time used my spirit level mtr-stick straight edge to get the vertical against the feeler rod on my venier calipers (placed on the inside bottom of the tune (adjustng the probe to get a vertical when squaring up against the top of the top - did this several times, rotating the tube about 20degs between checks and making the required correction on the top of the tube for each check).
I then reverted to using my bevel square (has a spirit level built in) to extend the cutting line between the marks.
When finished ,and recut using my Dremel minicutting wheel (EZ409) attachment, I wound up with my tube having tolerably squared ends (+/- 2mm).
Smoothing the end finishes and edges and tube-ends - I used my Dremel with the 120 grit grinding disk (#432).
Now pretty pleased with the ends .
Referring to my OTA design to get my focusor location, the centrepoint which was marked (8" from the end of the tube) , and the radiused base plate from my crayford focusor provided the template for my hole.
Cutting the hole for the focusor was achieved using a Dremel 1/8" cutting bit (# 351) - had to be very careful as this tool cuts through the plastic like a hot knife through butter and it would be really easy to go off-the-line or cut myself with it.
Finished off the hole made with the Dremel 120 grit grinding disk (#432).
Ensured the draw tube was able to move through the focusor hole.
Holes for the securing screws (or bolts) to hold the focusor in place were drilled with the Dremel 1/8" cutting bit (# 351) (since it was handy !).
Now ready to mark and drill the holes for the screws that will secure the spider and the mirror cell to the tube PRIOR TO FLOCKING - tomorrow.
Will then flock the tube prior to installing the hardware inside the tune - first star-light in a day or two - if my mirror cleans up OK with detergent and demin water rinse.
QUESTION : is it worth roughing up the inside surface of the stormwater pipe based OTA prior to installing the ProtoStar self adhesive flocking paper ?
(The adhesive is unlikely to be absorbed by the polished and currently smooth surface of the tube - so adhesion should be very good cf cellulose and timber based tubes.)
Edited by Ian Robinson (08/25/09 11:07 AM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
UPdate :
sorted the placement of the Orion Optical mirror cell and predrilled the holes (as precisely as I could to centre the mirror cell as closely as possible to the OTA cenrreline , turned out being a long job (jost to drill 6 holes , 3 to effect proper placement for astrograph mode1 (with Esyguider + coma corrector + camera attached) and 3 higher up the tube for astrograph mode2 (with MFCC + camera attached)).
Plenty of measurements with my vernier calipers to get the exact calculated positions of tube bolts (has provision for 6 , but will use 3 to get the cell centred before bolting through the tube).
My bevel square (I can set it give any length from 0 - 300mm from the rightangle edge , slides and is lockable) proved very handy once I'd determined the distance for the holes from the bottom of the tube.
I found it handy to elongate the holes to allow a little extra circumferential adjustment - checked the murror cell bolts in the tube and found it did, and only 3 x M6 pancake head bolts provide a very solid hold when tighted by screwdriver,
Ready to flock the tube tomorrow. I wont be using any extra glue as once I dust off the interior of the tube it will be very smooth and Protostar say the flocking sheets really grip this type of surface extremely well.
I'd forgotten how time consuming it is assembling newtonian OTA .... I don't plan to go through this again for a long time .
Edited by Ian Robinson (08/28/09 05:06 AM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Update :
Checked the bolt holes for the mirror cell and spider were positioned spot-on , after doing the wrap a big sheet of paper around the ends of the tube trick .... wish I'd thought of that ....
Turned out the ends of the tube were pretty close to spot on square and straight , just needed a little tweaking with the Dremel grinding wheel to remove a mm or 2 of excess material and smooth it all off with VERY LIGHT touches.... the Dremel grinding wheel will take plastic away super fast if you are not gentle.
The spider bolt holes turned out spot on +/- 1mm. 
The mirror cell bolt holes turned out dead on with < 1mm.
Flocking turned out being a long hot job in the garage this afternoon ..
.. the thermometer was showing 32 degrees Celsius when I got around to starting this job (and it's still winter here !!!) .. 
.. a very warm breeze blowing in the open door was very warm too ..
..
That self adhesive Protostar flocking material is superduper sticky stuff ..
..
the first bit I cut off the roll was a desaster, I was too ambitious with the size of sheet and it stuck to itself and to the inside of the tube in crinkledly way and I had to prettymuch destroy that bit of flocking material to get it off the tube and apart (so it went in the waste bucket).
Good thing I bought 30% more Protostar self adhesive flocking material than I needed ... ay !!!
Turned out to be easier to use offcuts of flocking not wider than 250mm x the width of the roll and to not be very fastidious about using a straight edge to cut each piece perfectly straignt (which is what I planned on doing until I discovered how sticky the stuff was and found out how awkward it was lining up the edges perfectly when you can't reach far enough into the tube with the arm to line it up and smooth it down .... so I decided to overlap adjacent sheets of flock rather than lining up the sheets edge to edge.
My trusty old 1m straight edge / spirit level turned out being the perfect tool to press down and smooth out the flocking material when it was attached to the tube's interior (the rounded edges where great and didn't damage the flock as much as a handy offcut of 80mm x 8mm aluminium bar did (it also was a bit too corroded and powery (been hanging about in the garage for many years looking for a use - and it left a residue on the flock which luckily came off OK).
I opted to overlap the sheets by about 50mm along the edges .... flocking sheets stick to each other like crazy !!!
All the trimmings from the overhanging bits (cut off with the Stanley Knife from the ends of flocking at the bottom and business end of the tube werr handy for flocking around and in the slightly oversized hole for the focusor and to "hide" the 4 brass bolts and nuts that hold the focusor to the tube.
I don't think I'll need to glue around the end edges of the flocking as it seems to stuck pretty good .... if I do I'll probably used some 5 minute Araldite and paint it on with small artists brush , that's good stuff ..
.. just not sure how it'll react with the plastic tube so I'll test it out on a bit of offcut that I'm using to make an new luderick burley scooper / tosser (a bit of 2" plastic pipe with 45deg caffered end on short bit of timber dowel) , if it that works and I don't wind up having the plastic disintegrate or turn to goo I'll be good to go.
Looks pretty black inside the tube , and flocking looks very great !!! . 
In the fading light at dusk the inside of the tube was as dark as inside a coal mine (I've been down a coal mine when I did a confined space and mine rescue 4 day training course when I was working so I know how dark it is down there) .... should be great for high contrast viewing and imaging.
Photos pending ....
Next job .... clean the primary .
Then fit the secondary to spider , the mirror to cell and laser collimate.
All my countrymen should be prepared for a long spell of overcast nights / or for the drought to break from Monday or Tuesday night as I plan on using the rebuilt OTA and my Atlux for field testing then .... So my appologies are offered in advance ...
Edited by Ian Robinson (08/29/09 10:38 PM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Some of my design calcs and how I modded the Orion Optical mirror cell side clamps to fit my mirror.
see http://www.iceinspace.com.au/forum/showpost.php?p=485799&postcount=3
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Update :
Stains on mirror cleaned up OK with dilute dish detergent soaked surgical 5x5cm cotton surgical absorbant pads and multiple rinses (warm dilute detergent) using a left over syringes (the community nurses used these to wash my surgical wounds out with sterile saline).
The tap water rinses using another left over syringe ensured no detergent residue was left on the surface.
When the water was beading nicely I knew all the detergent residue had been rinsed off.
Then immediately following the tap water rinse , I did not allow the mirror to dry , I rinsed thoroughly with demin water, again from left over syringe.
Wife has been told not to go near the sink until the mirror has been removed , currently standing with the back edge on the dishtowel on the draining area of the sink , leaning with the mirror back against the window sill.
Running the A/C to warm the air and get it circulating in order to get the mirror totally dry so my wife can do her things in time to see her shows tonight. Glared at me when I told her to wait 30 - 60 minutes for the mirror to dry .... she didn't like that idea at all ....
A few very small scratches from handling the mirror and from the old mirror cell about the edge , have to look close to see these so I am not terribly worried about them as I don't think they have any noticeable effect on the images I will see or record.
I did notice when I looked over the mirror with a hand magnifying glass that there lots of very small pin holes in the aluminium coating .... I don't think they have a noticeable effect but .... there are lot of them.
Mirror will be ready to go into the cell tomorrow .
Will take those pictures tomorrow before I install the mirrors .... that's a promise folks .
Additional notes : while my wife was watching Dancing with the Stars I checked the state of my tube's flocking (been 24 hr) and was very cool tonight - so I figured it was worth checking on a JIC basis .
Noticed some bubbles trapped (some about 2" long x 1" wide) under the flocking material and noted that some of the flocking material looked a bit loose (not coming away from the tube or drooping .
The tube is currently on two builder's workhorses - and orientated horizontally , it wont be ordinarily be stored between uses in this orientation until I build my ROR shed (that will be parked position) but will be stored standing up with mirror facing to the zenith with a bit end cap over the top of the tube.
So I have gotten busy this evening pressing it as hard ar I can by hand to the tune when I can reach the flocking to ensure good contact , and using some pressure applied the 1" wide straight edge on on my 1m straightedge/spirit level and giving the areas of flocking I can't reach with my arms as good a press down as I can , after I used the stanley knife make small cuts in the flocking material where there are obvious bubbles (spotted these bu shining my miners' lamp down the tube and as close to he surface as possible (the bubbles and rinkles (there are some small rinkles too) are highlited by their shadows. The cuts made it possible to press the flocking onto the tube surface and allowed the trapped air to escape doing the rub / press down process.
May be worthwhile letting the flocked tube settle and checking once a day over a few days (rotating the tube a bit between checks and giving flock that is starting to look the least bit loose or droopy another good pressdown) before I complete the OTA assembly but installing my optics and collimating.
In a few days I should be more confident of good contact and adhesion of the flocking material with the tube , and the tube will have had a chance to thermally cycle a few times from very cold / humid air conditions at night to warm and sunny in the day ..
.. if there's any problems with adhesion it should become apparent , -- if there is I can take steps and glue flock that wont adhere with a stronger paint on or spray on adhesive before I install my optics.
Will keep you guys posted on how things develop over the next few days or so.
Next tube I flock I'll be smarter and I'll get hold of nice bit of straight 50mm diam steel pipe or 10kg length of steel round bar (maybe 20mm diam ??) about 1m long whose ends I'll caffer and I'll use this to press the self adhesive flocking down in rolling manner rather than rubbing while pressing it down with a straightedge - it'll be easier and less wear and tear on the flocking). Wish I'd thought of this before I started flocking.
Edited by Ian Robinson (08/30/09 12:52 PM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Update :
I'm now satisfied that the ProtoStar SAF is not likely to have large part of it delaminate or force a OTA disassembly to reglue it.
Ready to move on to the optics installation phase and collimating. 
QUESTION :
Do any of you more experienced ATMers put any of fluffy stuff behind your secondaries (inside the secondary holder) ?
Mine came from AstroSystems full of fluffy sfuff and I am wondering if it's worth packing it behind the secondary .
Edited by Ian Robinson (09/08/09 04:01 AM)
|
Achernar
Postmaster
Reged: 02/25/06
Posts: 5025
Loc: Mobile, Alabama, USA
|
|
Polyester batting works pretty well, and it won't be food for mold and mildew.
Taras
--------------------
15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Taras , I think that may be what came packed inside the secondary holder.
I'll use the stuff AstroSystems provided.
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
OTA ready for me to install optics , sec-holder and mirror cell.
The Protostar self adhesive flock has stuck pretty well to the PVC tube and needed minimal additional glueing with Craft Glue = mostly glued as a preemptive measure JIC. Is pretty dark inside the tube with the flock attached.
Edited by Ian Robinson (09/10/09 11:07 AM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
Here is another aspect view : Meet "The Beast" .... the big red Pajero go anywhere fun machine.
Nice colour ... eh .
Edited by Ian Robinson (09/10/09 11:23 AM)
|
Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1165
Loc: Gateshead.NSW Nth Coast,Austra...
|
|
And another view : the beauty of my 2" custom made crayford is that I can adjust the racked in height above the tube by about 10mm from a minimum height of 51mm and then lock in that height ... will be handy for tuning the OTA for either of my astrograph modes .
Got 3 hot days forecast (Friday - Sunday) so I'll hold off installing my optics until after then to give the flocking a final static test.
Back to the CG5 handpaddle repair maybe, or maybe back to modding the steel peir (some arc welding), or maybe I'll get the rod and reel down and disappear for a day of two of fishing .
Edited by Ian Robinson (09/10/09 11:21 AM)
|
|
8 registered and 5 anonymous users are browsing this forum.
Moderator: Don W, Mike I. Jones
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 977
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 