Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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So despite good advice to the contrary I decided to try out a 1.25" focuser on my Tasco 11TE-5 4.5" newtonian figuring I can use a 0.965 insert and 0.965 lenses for observing while being able to pop in a webcam or DSLR for a bit of fun experimentation. Before anyone worries my intention is to *not* put any more holes in the tube then already exist and to save all the original hardware so the tube can be put back to it's original configuration exactly as it was.
First step of course was to remove the 0.965 focuser and see what I could find. I was very happy to see that the hole in the tube was actually designed for a 1.25" focuser, so no mods needed!
I was a lot less happy to see, now that the focuser and finder scope where removed, that the tube was bent/distorted in a number of ways around the mount points for both objects. This bending was not obvious when the hardware was attached, but is with a clean tube. I am guessing that these will make it hard to get a really good collimation as the focuser tube will be slightly out of true.
Do any of you have recomendations on how to fix this sort of damage?? 
Attached here (and the next couple posts) is the tube with focuser/finder attached, the tube without, and a couple attempts to show the distortions.
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Tube w/o focuser and finder. You can see some of the distortion by looking at the highlights on the tube.
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Looking down the tube to show the distortion/damage. The tube is pushed in slightly on both top and bottom of the location of the focuser mount base. It is also pushed in quite a bit on the lower section of finder mount base, and pulled out at the top of the finder's mount base.
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Closeup on the damage
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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And since I am flooding this thread with images anyway....
Here is the focuser I will be using. It is mostly cheap plastic, but is none the less a close visual match to the look of the original focuser. I will putting new holes into the focuser to match the existing mount holes in the tube, NOT putting new holes in the tube to match the existing holes on the focuser.. The new focuser has more travel both in and out so I have no issues reaching focus (I tested focus by "securing" the new focuser to the tube with elastic bands and looking at Jupiter and the Moon - worked fine  ).
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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mikey cee
Post Laureate
Reged: 01/18/07
Posts: 3531
Loc: bellevue ne.
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Falcon....If that were my scope I'd do two things. With sharp dents and creases I'd definitely go with glazing compound. Not Bondo. Secondly I'd put the finder bracket on facing the original direction. If cost wasn't a factor you could take it to a real body shop....not a metal butcher like some are. They might do cheaper than you think. Doesn't hurt toask.  Mike
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7x35 and 10x50 sears tower binocs, 3" f/10 edmunds reflector, 2.4" f/11.7 manon refractor, 6" f/8 jaegers refractor, "The 8 Ball" 8" f/13.3 brandt refractor, 3" f/15.8 sans&streiffe refractor, 3.1" f/15 selsi refractor(towa 339), 2.4" f/15 sears refractor, selsi 30x30mm spyglass, criterion 5-draw 25x45x75x spyglass(1957), 4.25" f/14.8 tasco 20te.
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Quote:
Secondly I'd put the finder bracket on facing the original direction.
wah? is that officially backwards then? It is how it has always been since I got the scope! 
Quote:
With sharp dents and creases I'd definitely go with glazing compound. Not Bondo
The cosmetics are not my primary concern right now. I am more concerned that a distorted tube will result in the focuser tube being out of true with the secondary resulting in the focal plane being slightly tilted. This is probably a non-issue for eyepieces but I do intend to experiment with imaging using the scope, and that *is* an issue for a camera.
When it comes time for cosmetic work there is more to do then just these creases... But that is for later. 
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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mikey cee
Post Laureate
Reged: 01/18/07
Posts: 3531
Loc: bellevue ne.
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Check all of the Tasco and Towa brands. Your bracket is officially backward...but then some folks do turn them 180°. Mike
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7x35 and 10x50 sears tower binocs, 3" f/10 edmunds reflector, 2.4" f/11.7 manon refractor, 6" f/8 jaegers refractor, "The 8 Ball" 8" f/13.3 brandt refractor, 3" f/15.8 sans&streiffe refractor, 3.1" f/15 selsi refractor(towa 339), 2.4" f/15 sears refractor, selsi 30x30mm spyglass, criterion 5-draw 25x45x75x spyglass(1957), 4.25" f/14.8 tasco 20te.
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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heh - well judging by the crease in the tube it has obviously been backwards for quite some time!
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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grendel
sage
Reged: 04/12/09
Posts: 250
Loc: Canterbury, Kent, UK
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I have a modern skywatcher that had much the same issues when I took the cheap plastic focuser with a plastic rack on the drawtube off (the rack had disintegrated- surprise surprise) and figured the main cause was with picking the scope up using the focuser as a handle, I have now fitted a decent old meade metal focuser and the scope is much sturdier, since the new focuser totally covered the area mangled by the old one I didnt do a lot to rectify the dents, but you do have to take the secondary out and laser the new focuser to a mark opposite in the tube (carefully measured and spotted) to get the focuser square in the tube, before trying to start thinking about colimation, then of course you have to remember that the focuser isnt a convenient handle (I know that this was probably caused by a previous owner, but we all get a little forgetful even now)
Grendel
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droid
rocketman
Reged: 08/29/04
Posts: 4047
Loc: ohio
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Sean: hey as long as the dents are covered by the focuser and finder bases, I wouldnt worry about it.Of course Im very tolerant of looks so long it works well.
On the other hand the finder bracket has apparently been mounted backwards for a while ,but if you can work with it, thats all that matters.
You've motivated me to find a 1.25 focuser for my 11-T 4.5 inch 
Ill follow this thread.
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12 inch Truss Reflector "John"
102mm Celestron C102HD
Tasco 7TE5 60mm Classic
Tasco 9TE5 60mm Classic
Celestron Ultima 2000 SCT
Remains of an 8 inch dob
Celestron Comet catcher(orange tube)
1960 Edscorp Space Conquerer 6inch f/8
10x50 Bushnell Binoculars.
11T 4.5 inch Tasco reflector Lunograsso?
60mm Telescope Club
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Doug76
Postmaster
Reged: 12/05/07
Posts: 5574
Loc: SE Louisiana, future Texan
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Yeah, the dents and such may be more cosmetic, and may not have changed the scopes' optical orientation at all.
And the finder bracket is backwards, but some prefer that positioning. Your choice really.
Were it me, and I really thought I had a problem, I'd remove everything from the tube, and lightly strike it from the inside with a rubber mallet to ease out some of the dents, then I'd repaint it, and remount everything. But that's just me.
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Doug
Truckstop Astronomer
The Universe, the light of God, in all it's majesty
6 achro refractors, 50mm-150mm
1 apo refractor, 90mm
1 SCT, 8 inch
UO Abbe Volcano Tops
Faworski Ortho's
Panoptic 24mm
Carton 100mm f/13 under construction 
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deSitter
Carpal Tunnel
Reged: 12/09/04
Posts: 2928
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A thought is to mount a turnbuckle between two form-fitted wood slabs that are made to fit the inside diameter of the tube - and just see what happens. The turnbuckle would need to be properly seated in each slab so as to distribute the force on the back of it - so you'd need to use sort sort of back plate on the wood pieces or maybe a threaded threaded insert. The final result would be to just push the tube back into place.
There is an astronomy surplus vendor who has things like Tasco tubes without optics - can't place his name though. Maybe someone knows. I bought a 6x30 finder objective from him.
ah here we go - Donald Rothman's Astro Parts Outlet
http://astronomy-mall.com/astro.parts.outlet/
-drl
Edited by deSitter (10/13/09 11:26 PM)
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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deSitter
That would be nice to have. A spare tube would allow mods to be made without fear of damaging the setup as a whole.
The outward-clamp/turnbuckle idea is interesting. I fear that the rolled seam edge of the sheet metal the tube is made out of would start to stretch/open before the tube would regain it's proper shape though...
Speaking of finders.... I took apart the stock finder to clean the lenses - there was more dust on them then glass in them - and found an amazingly small field block ring just behind the objective. Small that is in that the hole that let light through was tiny. I removed it, CONSIDERABLY brightening the view, but when I used it at night I found bright starts had *enormous* purple rings... I am guessing that the ring helped eliminate those? If so, should it have been right behind the objective as it was or should it have been closer to the eyepiece?
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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|
Quote:
take the secondary out and laser the new focuser to a mark opposite in the tube (carefully measured and spotted) to get the focuser square in the tube
Ahh yes, one of those suggestions that I fell dense for not thinking of in the first place....
Quote:
then of course you have to remember that the focuser isnt a convenient handle
I can tell you that I *myself* never used either the focuser or the finder as a handle, but then it has been transported back and forth to a few places and I am at minimum the 3rd and possibly 4th owner for this scope, so how knows what has occurred during it's lifetime!
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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droid: Well unless I can fix the crease created by the finder's base I suspect it will not even mount correctly to the tube in it's "correct" configuration... so it may indeed keep pointing that way!
As to doing a 1.25" mod to your own scope - this right here is the focuser I ordered myself. As I said the base and tube/rack itself are plastic (but do not look bad) and the travel both in and out is SLIGHTLY more then the stock focuser. It is not in any way an upgrade in terms of mechanics/performance, just in the ability to use 1.25" accessories or 0.965 eyepieces at my whim. I JUST got in today a set of 3 1.25" eyepieces and a camera adaptor so I will be able report on if any issues crop up reaching focus.... as soon as the weather clears.
It seems that the new scope curse can take effect even for slightly-modified scopes - so long as you need clear skys to test with!
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Doug - That matches somewhat what I was considering - in reverse. I was thinking that if I removed the secondary spider and the black rim ring I could perhaps get a large diameter pipe or a carved wood block to act as anvil that the tube can be slipped over. Then the tube can be hit with said rubber mallet from the outside. Gently.
If hitting anything with a mallet can ever be said to be gentle
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
|
deSitter
Carpal Tunnel
Reged: 12/09/04
Posts: 2928
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Quote:
deSitter
That would be nice to have. A spare tube would allow mods to be made without fear of damaging the setup as a whole.
The outward-clamp/turnbuckle idea is interesting. I fear that the rolled seam edge of the sheet metal the tube is made out of would start to stretch/open before the tube would regain it's proper shape though...
Speaking of finders.... I took apart the stock finder to clean the lenses - there was more dust on them then glass in them - and found an amazingly small field block ring just behind the objective. Small that is in that the hole that let light through was tiny. I removed it, CONSIDERABLY brightening the view, but when I used it at night I found bright starts had *enormous* purple rings... I am guessing that the ring helped eliminate those? If so, should it have been right behind the objective as it was or should it have been closer to the eyepiece?
I had a Meade 6x30 finder with the same baffle which caused considerable vignetting. The objective was grossly astigmatic and this baffle smoothed it over by stopping down the objective to 24mm or so - so I found another objective that works without a "baffle".
-drl
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Well I just picked up a red-dot finder, and hope to soon have some sort of guide scope as well, so perhaps I can simply not use the original finder.... It my usage it has never pointed in the right place anyway (the tube distortion probably has something to do with that)
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
|
grendel
sage
Reged: 04/12/09
Posts: 250
Loc: Canterbury, Kent, UK
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how about 2 blocks of wood shaped to the size of the tube, drill a hole through the middle and place them inside and outside at the focuser hole, throw a threaded rod through the hole (passing therough the focuser hole) then tighten some nuts on the threaded rod to slowly pull the tube back to shape.
Grendel
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