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Question about 1960s Tasco 11TE-5

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#1 tbar23

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Posted 27 September 2021 - 07:50 PM

Hi all - complete noob here. My father just brought me his 1960s Tasco 11TE-5 900mm telescope. We got it assembled and had a few hours of clear skies last night. We easily saw Jupiter’s moons and a tiny Saturn (with rings) using the H20mm eyepiece. We had absolutely no luck with the Barlow (2x?) or the H6mm. Both the H6mm and either eyepiece with the Barlow looked very, very blurry no matter how hard we tried to focus.

Note - we did zero testing / inspection of anything. This telescope probably hasn’t been used in at least 40 years. Other than aligning the finderscope, we did nothing other than pointing it skyward.

Looking down inside the tube, I’m pretty sure the primary mirror needs cleaning. In addition, I’m quite sure I could use some better eyepieces - which I’m assuming requires a 0.965 to 1.25” eyepiece adapter.

I haven’t investigated what a good thorough revitalization will cost, but I’m wondering if it is worth it. Should I just put the money towards a new(er) telescope??

How much performance can you get out of one of these Tascos?


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#2 BillShakes

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Posted 28 September 2021 - 04:36 PM

Hi - Welcome to Cloudy Nights.  The Tasco 11TE is a fun scope and, with a little TLC can give you great views.  

 

It likely needs to be collimated - aligning the primary and secondary mirrors so they are all on the same optical axis.  A bit tedious for a beginner but once complete, it shouldn't need to be done very often.  Search for "how to collimate a newtonian telescope".   Others may chime in here with links to good resources.  Once collimated, you should get usable views from the H6mm eyepiece.

 

Do some additional research before cleaning your mirrors - should be done carefully so as to avoid damage.  Again, a search for "how to clean a telescope mirror" should get you started.  

 

As for eyepieces, you should stay with .965 with this scope.  An adaptor for 1.25 will put the eyepieces too far from the focal point and will not come to focus, at least not without major surgery.  Throw out the Barlow.  Check out the Telescope Warehouse for a selection of decent, new .965 EPs to get started.  They are out of stock, but when available, these will get the most from your scope - Anteres Plossls at OPT corp.

 

The 114mm (4") 11TE can show you plenty - close double stars, the majority of the Messier catalog, nice planetary views, etc.  Its a real scope and a great one to learn with.  Some time stiffening the mount will help too.  Good luck and clear skies.


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#3 Bomber Bob

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Posted 28 September 2021 - 05:56 PM

Here's a quick reference on Newtonian Reflector collimation:

 

0 - Reflector Collimation Guide 1.jpg 0 - Reflector Collimation Guide 2.jpg

 

Mirror Cleaning:

 

- On the bottom of your scope, there should be 3 Philips-head screws near the edge of the back plate that hold the mirror cell to the tube frame.  First Time, I'd rest the scope on a bed, remove the 2 lowest screws first, then the top / highest screw.  The cell should fall backwards.

- Rest the cell on the bed, and you'll see 3 clips that hold the mirror in place.  Each clip should have 2 tiny Philips-head screws.  Carefully remove these, and put them in a pile / container with the other screws.  Each clip should have a felt and/or thin rubber pad that presses against the mirror.  You can wipe these with a paper towel if they're dirty.

- Clips removed, lift the mirror free of the cell, touching / holding ONLY the uncoated edges, and/or the uncoated back.

- IF the mirror is just dusty, place a soft rag beside the sink, and rinse the coated surface under the tap.  If there's gunk stuck to the coated surface after the rinse, spray the gunked spots with Windex, 409, etc., let it sit for a couple of minutes, then rise again.  409 is great a loosening grease-type gunk without scrubbing.  But, if there's still spots, use a CLEAN finger + more cleaner, and GENTLY rub the spot, then rinse.  Still gunked?  Take 3 Kleenex tissues -- or better yet, Lens Tissues -- rolled into a small ball, and use that with cleaner to gently scrub those spots.  That should remove all but the most stubborn gunk.  (Here at The Swamp, I get speckles of pine tree sap occasionally that is tough to remove!)

- After the final rinse, I stand the mirror on its edge on a soft rag or stacked paper towels, and let the water drain off.  I use another clean ball of tissues to nudge straggler drops down & off.  Then, I lay the mirror flat on the rag, and let it air dry.

- Once the mirror is completely dryI do my final polishing by exhaling on the coated surface; then, using another clean tissue ball, I start in the center, and very gently use small circles to move out to the edges.  Little to no pressure on the tissue ball.

 

While the cell & such is apart, I remove dust / dirt from the insides of the tube.  I check the small mirror (the secondary mirror), and if it's dusty, I use a Puffer Bulb to remove the dust.  If it needs more, and your hand is small enough, you can gently rub it with another tissue ball.  Most of the time, the secondary won't need to be dis-assembled to clean it.


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#4 tbar23

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Posted 28 September 2021 - 07:37 PM

Thanks to you both. I was just reading about collimation which reminded me to check on this post. Interesting to read your opinion regarding 0.965” eyepieces @BillShakes. How central NH are you? I’m just a few miles south of the NH/MA border (in MA).

@Bomber Bob - thanks for the visuals. I take it that some kind of cross-hair insert is required to find the required adjustments? 



#5 ccwemyss

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Posted 28 September 2021 - 08:01 PM

The diagram is showing the view through a Cheshire collimating eyepiece. It's a tube with a sight hole that looks through a hole in a 45 degree-angled plate with a set of crosshairs at the end of the tube. The plate is open to the side so that you can shine a light in on it. It then reflects in the mirror, with the crosshair in-between. That lets you see them reflected in the mirror, and keeps your eye centered, so you can adjust the mirrors until everything looks centered. The CN sponsor has them for $35 (although they are currently out of stock):

 

https://www.astronom...ating-tool.html

 

One thing about the Antares 0.965 eyepieces at OPT is that they are 1.25" eyepieces with a step-down barrel. The barrel is interchangeable with the other Antares Plossl eyepieces, so if you can only get one size in 0.965, and others in 1.25, you can swap barrels. Classic 0.965 eyepieces show up here on the classifieds fairly often. There's a thread about classic eyepieces that looks at the many different makes and models. 

 

Chip W. 


Edited by ccwemyss, 28 September 2021 - 08:01 PM.

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#6 Tenacious

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Posted 28 September 2021 - 08:24 PM

I've had 3 of these - usually good optics. 

 

+1 about staying with 0.965 size EPs.  Converting to 1.25" format involves some hidden perils and likely major surgery depending on the dimensions of the replacement 1.25" focuser.   We use the 0.965" Antares with ours.  

 

I haven't seen a 0.965" Cheshire on the market for a long time.  I made a simple one - not hard.


Edited by Tenacious, 28 September 2021 - 08:45 PM.


#7 tbar23

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Posted 28 September 2021 - 09:27 PM

Thanks. @Tenacious - would love to know the basics of how you built your 0.965” Cheshire.

 

So I did some quick reading on collimating. Given that I have no equipment, I simply looked down the focus tube and things appeared to be in reasonable shape. Despite some rain today, it looked like clouds were passing. I found Polaris and using the star collimating approach, I thought things looked remarkably good with a nice centered shadows when slightly out-of-focus.

Next I turned to Jupiter - everything looked pretty sharp with the 20mm EP. I switched to the 6mm EP and managed to get a reasonable image. Not nearly as crisp as the 20mm, but not bad.

I then moved to Saturn. Again, crisp image with 20mm (though Saturn is awfully small), and a less crisp but seemed to be better than the other night Saturn image with the 6mm.

Finally, I returned to my quest for M31 using the 20mm. Multiple times I found a “smudge”, but it just didn’t seem to be big enough to be M31!

I’ll get some sterile cotton balls and maybe give primary mirror cleaning a try. I’ll also keep an eye out for those CN sponsor EPs for 0.965.

Thanks, again, to all.



#8 tbar23

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Posted 29 September 2021 - 06:56 PM

Update: spent some more time collimating today. Finally pulled the primary cell out - looks pretty grimy, yes?

gallery_382566_17826_729874.jpeg



#9 Tenacious

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Posted 29 September 2021 - 08:09 PM

Yep, that's dirty!

 

do you have the kkkkkind of compass for drawng circles?

 

Im traveling and using an awful keyboard - be back at myy desk tomorrrow.



#10 tbar23

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Posted 29 September 2021 - 08:58 PM

I’ll need to take a look. I used to, but I can’t think of where I stashed it. I just realized that I reassembled stuff without marking the center of the primary. That was probably a mistake. Not terribly tough to disassemble though.



#11 Tenacious

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Posted 30 September 2021 - 08:32 PM

Back home.

 

So I guess you have seen the method of drawing a circle the size of your mirror and then another on the same center-point the size of a paper reinforcement ring?  If you cut out both circles, you have a template for placing the paper reinforcement ring accurately in the center of your primary.  I think you can see a pic of a "doughnut" in Bomber Bob's 2nd illustration in post #3.

 

Home-made cheshire: maybe temporarily disassemble that barlow mentioned in post #1?  You would have to make disks to define the axis of the barlow.  Maybe the top made from card stock and the bottom from clear plastic?

 

This is the one I made for our 11TE-5.

 

Collimator1.JPG

 

Collimator2.JPG

 

 



#12 Tenacious

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Posted 30 September 2021 - 09:03 PM

Did you try that 2 X barlow with the 20mm EP on Jupiter or Saturn?  Like a 10mm EP (90x magnification).  I'm not advocating for that barlow, just a test.

 

If we didn't already have the Antares set, I would be tempted by the 0.965" versions of the RKEs (no longer available?), at least the 28mm and 8mm.  Might take a while to find, though.


Edited by Tenacious, 30 September 2021 - 09:06 PM.


#13 tbar23

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Posted 01 October 2021 - 06:16 AM

Thanks @Tenacious ... so your homebrew design is more a collimation cap than a Cheshire, right? You're basically just making sure that your eye gets centered down the focal tube when collimating?

I haven't read up on the donut stencil for placing the reinforcement ring on my primary, but I'll go looking for it.

Re Barlow - no, I haven't returned to the Barlow. I need to look at it, again, but it seemed pretty hazy to me. I wonder if it is dirty or deteriorated plastic or ??

I'm not finding any 0.965" to purchase right now. However, I still have some cleaning / fine tuning to do before moving on.

 

Thanks for the advice.



#14 ccwemyss

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Posted 01 October 2021 - 08:51 AM

There's a 0.965 Unitron 7mm Symach on AM.

 

https://astromart.co...cular-excellent

 

Chip W. 



#15 Tenacious

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Posted 01 October 2021 - 10:43 AM

Cheshire might be a brand-name - clever design anyway.  With the peep-hole at the top and cross-hairs at the bottom, one can consistently get back to the same optical axis after each mirror tweak.  The 45 window on the side can help illuminate the secondary but also illuminate the backside of the peep-hole - helping you identify your own eye as it looks through the system and is reflected back.  I usually use a flashlight with mine.  Sadly, I don't recall seeing these in 0.965" size, but maybe they are out there.

 

I can collimate well with the home-brew (Yes, technically a collimation cap).  These devices (home-brew, Cheshire, or even laser) can get collimation pretty close.  The final step should always be pointing the scope at Polaris at high magnification, defocusing, and tweaking the primary for concentricity.

 

It's amusing how these scopes are always supplied 4mm EPs - a magnification that is seldom practical in our atmosphere, even if the EP were of high quality.  For solar system targets, 7mm to 12mm EPs will be a sweet spot.  For medium and low power targets (a 11TE-5 will show lots of these under a dark sky), longer focal length EPs work great.  I've even had pleasing views through a 42mm at large open clusters.


Edited by Tenacious, 01 October 2021 - 10:44 PM.


#16 yeldahtron

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Posted 02 October 2021 - 10:57 AM

Hi all - complete noob here. My father just brought me his 1960s Tasco 11TE-5 900mm telescope. We got it assembled and had a few hours of clear skies last night. We easily saw Jupiter’s moons and a tiny Saturn (with rings) using the H20mm eyepiece.

The 11TE-5 was the second scope I owned (early 70s).  Great views of the planets and the moon, even when using the stock, horrible Huygens eyepieces.  I had it when I lived in downtown Toronto (real downtown, near the parliament buildings and the ROM), so light pollution prevents me from commenting on performance with DSOs (other than the brightest ones, such as M42 -- always magnificent!), but it was a decent scope. Although the primary is spherical, f/8 means it should be well-enough corrected to continue to throw-up good views.

 

Given your scope is quite old now, is it time to resurface the mirrors?  What are 50+ year-old coatings like?

 

The scope should be capable of throwing up great views, if only you can find better-quality 0.965" EPs than those provided.


Edited by yeldahtron, 02 October 2021 - 11:01 AM.


#17 tbar23

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Posted 03 October 2021 - 10:13 AM

Thank you for all of the responses. I had a friend make me a Cheshire-like 3D printed Collimator - hoping to try it out soon. I’m also investigating that 7mm EP on AM.
Question about upgraded finderscope (or improving the stock one).
I find it difficult to see anything but the brightest objects through the original finder. I have also had trouble really dialing in the alignment of the finder. Any advice on either issue?

#18 yeldahtron

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Posted 03 October 2021 - 10:20 AM

I find it difficult to see anything but the brightest objects through the original finder. I have also had trouble really dialing in the alignment of the finder. Any advice on either issue?

If your vintage of 11TE-5 was the same as mine, the stock finder was a useless, single lens, incredibly stopped-down (by means of an internal plastic baffle that dropped the effective aperture to about 1/4") piece of junk.  I made a new finder for my scope out of an old 10x50 binocular and bought the required rings for it.  However, if you can find a stock focuser from the early 60s, like the one I had on my 9TE 60 mm refractor -- that had a ~1" aperture that was a glued achromat.  It performed well enough to be a finder, but from a practical perspective, something larger (6x30 or better) would be more useful.  However, if you are trying to preserve the look, the older version of the finder would make a nice addition to your classic scope.



#19 tbar23

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Posted 05 October 2021 - 08:33 PM

A few updates. Despite the lousy single lens stopped-down 5x24 finder, I did manage to improve its alignment. With improved alignment and a clean(er) primary, I was able to get some nice images of Jupiter and Saturn tonight - despite clouds - and even got pretty good viewing through the Barlow.

The near-zero eye relief makes the Huygen EPs really tough to use (and virtually impossible to photograph through with my iPhone), but enjoyed the 90x magnification tonight.

I also spent some time learning more about my equatorial mount, but it was too cloudy in the north to get a Polaris alignment done.

That said, can someone tell me about the two different markings on the RA ring? I see that the 0s are aligned and then they run up through 24/0 in opposite directions. Is this because the proper RA reading depends on which side of the mount the tube is on?

So let’s say I’m looking for M31, and I’ve got alt and azimuth set properly so that Polaris is well aligned.

Now I line up something like Mirach. Stellarium tells me that Mirach, from my location, is at 35.75* (roughly) declination, so I make sure that my Dec pointer is lined up with ~35.75*.

Stellarium also tells me that RA is ~1h11m. So I adjust my RA dial to line up with ~1h11m, but which of the two rings do I use??

Once I’ve got that down, I use Stellarium to figure out where to set things for M31 (~41.4* Dec and ~44m RA).

That’s it, right?

The big question I have is around which of those two RA markings to use.

 

And still searching for some 0.965” EPs …



#20 yeldahtron

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Posted 06 October 2021 - 08:44 AM

www.cloudynights.com/gallery/album/8277-tasco-11t-manual/ has a copy of the manual that tells how to use the setting circles

#21 tbar23

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Posted 06 October 2021 - 12:38 PM

www.cloudynights.com/gallery/album/8277-tasco-11t-manual/ has a copy of the manual that tells how to use the setting circles

Yeah, I’ve read the Use of the Setting Circles section a few times, but I don’t completely follow it. I really threw in the towel on steps 6 thru 8. On my mount, there is absolutely no way the moving indexes can be pointed to 6-6 and 6-18 if the fixed index is at 0-0 and the counter-weight bar is horizontal.

0-0 and 12-0, yes, but definitely not 90* with respect to that.

 

I do need to re-read the double index system again. I’m also assuming that something like Stellarium will tell me sidereal time, but I need to figure out where to look.

Oops, it actually looks like I should read the Position From a Guide Star section.

 

More reading to do …



#22 yeldahtron

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Posted 06 October 2021 - 02:19 PM

You might find that the setting circles are not sufficiently accurate on that mount to be useful.  I roughly polar aligned my mount so the scope axes would slew through RA and Dec, but I found the pointing accuracy of the setting circles to be wanting -- especially with the narrow field of view of the scope EPs.  I stuck to star-hopping.



#23 tbar23

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Posted 08 October 2021 - 05:38 PM

Sticking with the original thread subject of “Questions about 1960s Tasco 11TE-5” - I wanted to re-visit the finderscope. I may upgrade it at some point, but right now I’m looking to solve a problem with regards to the three adjustment set screws. They do not seem to hold the finderscope in place very well (it is VERY easy to bump the finder out of alignment even when set screws are tightened), nor do they all for very good adjustment.

Does anyone have recommendations on ways to improve the rigidity of the finder mounting and/or easy of alignment adjustment?

It seems like some kind of ramped or cambered piece on the set screw would help tremendously, but I’m not sure that would fit.

 

Advice welcome on both improving the stock finder and/or suggestions on upgrading.

 

Thanks!



#24 ccwemyss

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Posted 08 October 2021 - 11:18 PM

It sounds like yours is loose at the end opposite the thumb screws. Some of the 3-screw brackets had an O-ring at the front. Others had three tiny set-screws that need a jewelers screwdriver to adjust.

 

Chip W. 



#25 tbar23

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Posted 09 October 2021 - 05:27 PM

Thanks, Chip. Where in MA are you? I'm in Andover.

 

I tried a 1/16" thick o-ring, but even that is too thick. I ordered a 1mm thick o-ring (27mm OD / 25mm ID) and we'll see how that works. However, as a low-tech stop gap, I wrapped a thin line of tape around part of the finder to eliminate play at the front. I just did an alignment, and we'll see how well it lasts!




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