44 replies to this topic

[CharlieB]

I was given what appears to be a Tasco 4TVE by a very kind and generous CN'er.  Because of the type of optics (variable power erecting zoom), I decided to do a conversion to a standard refractor.  The objective is quite good and the auxiliary lenses in the variable power optics degrade the image quality by a fair amount.  After I applied some muscle with a pair of strap wrenches, I got the dew shield and objective cell removed.  They were on there awfully tight.  After I cleaned the cemented objective, I ran a DPAC test on it.  Here is the Ronchigram:

 

 

It compares quite well with my 40mm Royal R-42.

 

 

The biggest problem with converting these types of scopes is the focusing mechanics.  Because of the design of these variable power setups, the native focal length of the objective is considerably shorter than the combined objective/variable power combo.  I had to shorten the tube by about 6.25" to reach focus with a diagonal.

 

Unfortunately, the original eyepiece threads onto the focuser tube and it's an oddball size.  Attaching a standard .965" diagonal was a challenge.  

 

 

I discovered that a thin-wall .965" barrel give a very solid press fit onto the focuser draw tube.

 

 

 

So far, so good.  The next step was to take a standard .965" diagonal and use the eyepiece receiving end to fit onto the now-expanded draw tube.

 

 

The last piece of the puzzle was to unthread the other end of the diagonal that would normally be inserted into a draw tube and locate another eyepiece receiver from a different diagonal that has the same threads.  As you can see in the previous photo, I found a split ring one that works just fine.

 

While testing the setup, it was obvious that the draw tube wasn't blackened, so I flocked it and now it's an excellent little scope.

 

Now, it's time to strip it all back down for a repaint.

[Michael Covington]

Very interesting!   I still have my 4VTE (from 1968) and have not done much to restore it.  I like the long eye relief from the variable eyepiece.

[CharlieB]

I have a number of small scopes that have variable eyepieces, but they are designed to fit into standard .965" draw tubes.  The problem with many of these (and the one in the 4VTE) is that those tiny optical components get quite dirty or attacked by fungus over the years and that makes it almost impossible to clean them well and get clear views through them.

 

[Garyth64]

Looks good Charlie!

 

I did similar thing to my 4 VTE.  I cut part of it off, and made sleeve to hold a 1-1/2" section of a drawtube.  The drawtube is threaded for a 1-1/4" VB.

It's only a push-pull focuser, but it works.

 

I can either use it straight thru:

 

 

Or with a diagonal:

 

 

The metal rings on the tube are what is found on a Sears 6339a 40mm finder.  They fit on perfectly.

 

This finder can be used with the finder brackets that are on the Sears, or other brackets.

 

(excuse the feet in the photos)

Edited by Garyth64, 03 July 2020 - 06:58 PM.

[Bomber Bob]

For my 4VTE conversion, I cut off about 6" of the tube, removed all that internal terrestrial lens stuff, and had a .965" diagonal that threaded on to the VTE's tiny manual draw-tube:

 

 

Now, to make it pretty, too.

[CharlieB]

I painted the objective cell, dew shield and focuser today.  I decided on a metalflake dark blue.  The metalflake doesn't show up that well in the photos, but it looks nice.  The OTA is going to be silver Hammertone, a'la Bushnell.  Hammertone is a finicky paint and sometimes turns out nice and sometimes not.

 

 

The chrome on the focuser cleaned up nicely with some Turtle Chrome Polish

 

[CharlieB]

Here's the finished product.  The Hammertone came out acceptably well, not great.  Now, I have to set it aside for a few weeks to let the paint cure.  That's the hardest part.

 

 

[deepwoods1]

Looks beautiful! 

[Bomber Bob]

I painted the objective cell, dew shield and focuser today.  I decided on a metalflake dark blue.  The metalflake doesn't show up that well in the photos, but it looks nice.  The OTA is going to be silver Hammertone, a'la Bushnell.  Hammertone is a finicky paint and sometimes turns out nice and sometimes not.

 

IMG_0555 - Edited.jpg

 

The chrome on the focuser cleaned up nicely with some Turtle Chrome Polish

 

IMG_0556 - Edited.jpg

Excellent restore!  Now... you got me thinking... Since the 4348 & 4VTE have their labels, I was gonna go with their original black & white colors; but, if I do get a 30mm, and think of these 3 as a small frac set... I like the Meade Blue + hammered light gray on my TN5...  Or, since they ride on the olive green (?) KDS, coordinate them with it.

[CharlieB]

It was a quick, fun restore.  With the quality of the objective, it was worth the effort.  The views are very good and surprisingly bright.  The single baffle was knocked out of place when I received it and it was severely restricting throughput (along with the terrestrial optics).  At some point, I may remove the baffle and flock the tube.  

[GreyDay]

The objective is quite good and the auxiliary lenses in the variable power optics degrade the image quality by a fair amount

The biggest problem with converting these types of scopes is the focusing mechanics.  Because of the design of these variable power setups, the native focal length of the objective is considerable shorter than the combined objective/variable power combo.  I had to shorten the tube by about 6.25" to reach focus with a diagonal.

Great topic Charlie   A heads up for anyone taking on the same project.

 

I have several versions of the 40mm Kenko objective telescopes. One consideration before cutting is that they dont all have the same focal length, the fixed magnification scopes have slightly longer focal length.

 

As you rightly say the variable power optics are truly awful and degrade the objectives performance considerably. I experimented with my first 40mm using a Celestron 40TT OTA, the Celestron came with a single lens objective which i replaced with the Kenko cemented doublet and was pleasantly surprised by how capable the Kenko lenses really are!

 

After playing around with the Celestron OTA i found the fixed mag scope's objective wouldn't come to focus as the OTA was too short, it appears that all the 4VTE copies with "pull out" magnification draw tube are the same focal length. Other variants that have rotary mag adjustment are shorter and fixed mag are longer.

[oldmanastro]

Here's the finished product.  The Hammertone came out acceptably well, not great.  Now, I have to set it aside for a few weeks to let the paint cure.  That's the hardest part.

 

IMG_0564 - Edited.jpg

 

IMG_0567 - Edited.jpg

Superb restoration job. That hammertone looks great. The gray is quite similar to the one used by Sears in some of their telescopes from the 60s. 

 

Guido

[CharlieB]

The 6339-A Sears gray and black is a great color combo.  

 

The rattle can Hammertone just doesn't ever seem give the same texture that the old Bushnell's had  I was at an old hardware store a few weeks ago and they had a quart can of Hammertone gray for brushing or spraying.  I may go back to get it.

[Garyth64]

I agree.

 

Edited by Garyth64, 04 July 2020 - 09:30 PM.

[CharlieB]

Last photo.  The completed scope resting atop a Unitron 40mm mount.  On terrestrial objects, the scope is very close in views to the Royal Astro 40mm.  Haven't had a chance to test it at night.

 

 

[deepwoods1]

Wow! That looks great! 

[CharlieB]

I thought you might like that.

[GreyDay]

I was given what appears to be a Tasco 4TVE

Hi Charlie, just to start the mystery scope hunt i thought i should mention that your scope hasn't the same objective cell as all other Kenko or 4VTE models? the focuser wheels are different too!

 

maybe an early model or just a rebrand like so many others?

[CharlieB]

This scope does have the Circle K mark on the bottom of the pinion cover.  I'll do some research on other scopes like this and see what I come up with.  Perhaps it is an older model.

[CharlieB]

It is in an early 1960s Kenko catalog at Galukuma's web site, listed on page as model KT- 4, 15x-45x.  It's difficult to see much detail, but it looks like the same scope.

[GreyDay]

This scope does have the Circle K mark on the bottom of the pinion cover.

Good to know, all of mine have the circle K somewhere on them. The DPAC you posted earlier is really encouraging maybe those that don't consider a 40mm as worth the effort, could at least see use for them as guiders or finders

 

I've never understood how people say "you won't see anything with only 40/50mm", everyone knows 40 or 50mm bino's are a great way to start in astronomy!  Add to that Sky & Telescopes pocket sky atlas is limited to mag 7.6 yet a 40mm scope can do mag 9 under clear skies! some people really do under estimate these scopes

[CharlieB]

You can see a great deal with a 40 or 50mm scope.  Certainly not as much as a larger scope, but if you've seen all there is to see in a small scope, you've been around a very long time.  

[Vesper818]

Of course I wandered back in here looking for ideas....

Charlie, what a little treasury of mods and variations of the 4vte! 

A serious need for small scope rehab therapy had me looking on eBay again, and this overworked cutie was mine for the offer of 20 plus shipping!
It is a Tasco, but the labeling, and the heavy, more antiquated cell has me wondering if it was a pre-4vte version of the terrestrial 40mm. The mount speaks of a serious student doing the best with what they had. The Ota is screwed into the rail on the bottom. Objective looks nice though, and overall condition allows for guilt free customizing.

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[Vesper818]

I love your blue flake, and may swipe it for the tube color, as this will be a night viewing compliment to my solar set up Tasconado vte...
The focuser has the circle k (kenko?).

This mount could prove useful!

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[deSitter]

That is an amazingly good Ronchigram for a cemented lens. Nice work!

 

-drl