Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Barska 30070-225 Starwatcher: Anatomy & Renovation

  • Please log in to reply
28 replies to this topic

#1 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 20 January 2020 - 05:40 AM

...a 70mm f/4.3 achromat...

 

achromat8b.jpg

 

There are a few other brands of this refractor, generic brands, sold on eBay and elsewhere, but this Barska is the most costly, and for a whopping $50 from B&H Photo of New York.  For one, I didn't want to risk getting a plastic doublet.  At less than $50, wouldn't that be possible?  Certainly not impossible, so I went with the "best".  Also, I didn't want to risk getting a .965" focusser, and that aspect was rather difficult to discern among the images of the generics.  As it turns out, I chose well.

 

This wee tyke will serve two purposes: as a wonderfully diminutive grab 'n' go; yet also, secondarily, as a RACI finder-scope, I hope, and for my 127mm f/15 Maksutov.  

 

First, I removed the focusser...

 

focusser.jpg

 

The visual-back, at 1.25", leaves a lot to be desired...

 

visual back.jpg

 

I then had access to this...

 

mounting interface.jpg

 

...the highly-proprietary mounting-interface which is now history.  It will not be re-installed, although I might have use for its screws and nuts for something or other some day.


  • KevH and skysoldier173abn like this

#2 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 20 January 2020 - 07:15 AM

The dew-shield is friction-fitted onto the objective-cell; no surprise there...

 

dew shield.jpg

 

The optical-tube, and with the objective-cell still attached; stumpy little thing...

 

OTA.jpg

 

I have tube-rings for it, and courtesy of my Celestron "AstroMaster" 70mm f/13 achromat which has an even worse focusser, the worst on the planet actually...

 

tube rings.jpg

 

I'll probably use the Meade electric-blue bar that I have instead, and space the rings more closely for this one.

 

Why is the cell still attached to the tube?  Because it's glued on... scared.gif

 

doublet cell.jpg

 

...and if that wasn't enough, the cell is not exactly squared to the tube...

 

off-kilter.jpg

 

Fortunately, the glue is not of the cyanoacrylate species.  It is very much like rubber-cement rather.  Still, with just my hands, I couldn't pull nor twist it off.  I'll have to investigate that further, for off it must come.


  • KevH, AndresEsteban and skysoldier173abn like this

#3 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 20 January 2020 - 07:34 AM

Do I really want this baffle...

 

baffle.jpg

 

I could go ahead and pop it out, and flock it from fore to aft, just like one of Unk Al's.

 

Would the view be vignetted with any of my eyepieces?  I can test that beforehand.

 

The air-spaced, glass(!), crown-and-flint doublet...

 

doublet2.jpg

 

It appears that only one of the sides of the flint-element is coated, and with nothing on either side of the crown; criminy...

 

doublet.jpg

 

Note the spacer there on the left.  It is very much like those found within the Towa achromats of that bygone era.  It's awfully rough though, nothing like that type of spacer of the olden days, therefore I might replace it with three aluminum-foil spacers.

 

doublet3.jpg

 

I think we know what's going to happen to those later on.


  • KevH and AndresEsteban like this

#4 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 20 January 2020 - 08:20 AM

cell removal.jpg

 

That wasn't too difficult.  Now to figure out how to secure it later.


  • KevH likes this

#5 erin

erin

    Viking 1

  • *****
  • Posts: 843
  • Joined: 27 Jan 2018
  • Loc: MA

Posted 20 January 2020 - 09:13 AM

Thanks Sky Muse. This is cool to see!


  • Sky Muse likes this

#6 AndresEsteban

AndresEsteban

    Ranger 4

  • -----
  • Posts: 338
  • Joined: 28 Nov 2013
  • Loc: Rio de Janeiro, Brazil

Posted 21 January 2020 - 10:54 AM

I have a very much the same scope, a Toya 70 mm f/4.3. Nedded lot of modding to leave as an excellent scope for low power, let's say 30-40x .
1) I found it has a lot of chromatic aberration (as expected) but got better after repalcing the doublet spacer plastic ring for 3 hard cardboard paper spacers.
2) Remove all baffles, the one inside the OTA and the ones iside the drawtube of the focuser.
3) Shorten the focuser in order to reduce vignetting! (Need to raytrace to 1.25" eps. thus a 27mm focal diameter plane.
4) Flocking is mandatory, inside the OTA and inside the focuser drawtube.

After all these modifications I found it's a very capable low power scope! I've checked it against an Orion 80 mm f/5 short achormat and I must confess i was impressed by the amazing difference in qualty image between my modded Toya and the Orion. The Toya beated the Orion by long margin, either in definition, contrast and color rendering!
 

 
 
 
2019 01 12 CARJ pier Maua   Cópia

 

IMG 0023   Cópia


2019 01 12 CARJ pier Maua07

 

 
IMG 0022
 
Toya 70 mm f/4.2 with TMB 6 mm eyepiece - 50x
 
Toya 30070


If you wish you may download my paper with all the modifications done on this little but great scope (text in Portuguese but lot of illustrations):

https://mega.nz/#!4U...j5T3wbTK2IKmGYQ

Clear skies for us all!
Andy

  • eros312, Sky Muse and skysoldier173abn like this

#7 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 22 January 2020 - 06:11 AM

 

I have a very much the same scope, a Toya 70 mm f/4.3. Nedded lot of modding to leave as an excellent scope for low power, let's say 30-40x .
1) I found it has a lot of chromatic aberration (as expected) but got better after repalcing the doublet spacer plastic ring for 3 hard cardboard paper spacers.
2) Remove all baffles, the one inside the OTA and the ones iside the drawtube of the focuser.
3) Shorten the focuser in order to reduce vignetting! (Need to raytrace to 1.25" eps. thus a 27mm focal diameter plane.
4) Flocking is mandatory, inside the OTA and inside the focuser drawtube.

After all these modifications I found it's a very capable low power scope! I've checked it against an Orion 80 mm f/5 short achormat and I must confess i was impressed by the amazing difference in qualty image between my modded Toya and the Orion. The Toya beated the Orion by long margin, either in definition, contrast and color rendering!


If you wish you may download my paper with all the modifications done on this little but great scope (text in Portuguese but lot of illustrations):

https://mega.nz/#!4U...j5T3wbTK2IKmGYQ

Clear skies for us all!
Andy

Thank you Andres.  Yes, I discovered the baffle in the draw-tube earlier this morning, and yes, since I had removed the main baffle, that one must be removed as well, so I thought at the time.

 

I don't flock my draw-tubes, except that of my "Bird Jones".

 

Thank you again.


Edited by Sky Muse, 22 January 2020 - 07:35 AM.

  • AndresEsteban likes this

#8 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 22 January 2020 - 06:42 AM

As I had suspected, the reason the objective-cell would not fully seat onto the optical-tube was due to the paint...

 

aluminum.jpg

 

Whilst in the middle of removing the paint, I began to suspect something else, so I grabbed a horse-shoe type magnet.  After I had stripped the paint, then sanded and polished the bare surface, I got another type of magnet out...

 

neodymium.jpg

 

                whee.gif

 

 

...a neodymium.  We all know how grabby those are.  The optical-tube is of aluminum, therefore no need to worry about rust, as that bare area will remain bare.

 

The objective cell not only fully seats, but I can also rotate it quite easily...

 

aluminum2.jpg

 

What's this?

 

main baffle.jpg

 

Well, we know what happened to that, historically.

 

Prior to removing the paint, I fitted the focusser onto the tube, unsecured, and popped in my new GSO 32mm "Super Plossl"...

 

GSO 32mm Plossl7.jpg

 

...and then, I tapped the baffle out.


  • AndresEsteban likes this

#9 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 22 January 2020 - 12:02 PM

The baffle of the draw-tube of this refractor is part of a sleeve that seems to be glued into the tube.  I've ground out the baffle, but now I've got to figure out a way to eliminate the sleeve...

 

draw-tube baffle.jpg

 

gaah.gif



#10 AndresEsteban

AndresEsteban

    Ranger 4

  • -----
  • Posts: 338
  • Joined: 28 Nov 2013
  • Loc: Rio de Janeiro, Brazil

Posted 23 January 2020 - 12:10 AM

Thank you Andres.  Yes, I discovered the baffle in the draw-tube earlier this morning, and yes, since I had removed the main baffle, that one must be removed as well, so I thought at the time.

 

I don't flock my draw-tubes, except that of my "Bird Jones".

 

Thank you again.

Why not flocking? It improves contrast a lot and prevents refletions over the wall! I have all my refractors and drawtubes flocked!!!

Clear skies
Andy

 



#11 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 23 January 2020 - 01:14 AM

Why not flocking? It improves contrast a lot and prevents refletions over the wall! I have all my refractors and drawtubes flocked!!!

Clear skies
Andy

 

I flocked that of another plastic draw-tube, but only because the end of the tube was fitted with a lens-cell...

 

doublet11.jpg

 

Otherwise, I prefer the openings at the ends of my draw-tubes to be sharply defined.  I do use a deeper shade of matte-black paint for those.  This is the focusser of my Meade 90mm f/10 achromat...

 

focusser3b.jpg

 

My camera had a difficult time taking that image.  I had to brighten it afterwards even, in order to show some detail.  It's practically dead to light, utterly even.  I was astounded afterwards, and upon the sight of the Trapezium and its environs at a medium-high power, per its aperture.  The contrast rivalled that of my lone apochromat, if not having surpassed it.  I say that as I haven't worked on it, although it could use some treatment.  

 

I flock wherever I can, primarily.  Where I cannot, it gets the rattle-can. 


  • AndresEsteban likes this

#12 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 26 January 2020 - 09:25 AM

Oh dear, my thread was on the second page, and on its way to oblivion.  That won't do.

 

As I've been informed by a fellow member, this telescope, as it arrives, operates as a 30mm f/10, which is why I wasn't seeing any false-colour during the day.  The main baffle is out now, and I've ground out the baffle of the drawtube and reduced its sleeve to near nil...

 

draw-tube baffle3.jpg

 

draw-tube baffle2b.jpg

 

Now, you can still see a smidgen of the sleeve, but it's not thicker there at the top as it may seem.  The sleeve is now more or less flush with the rest of the tube.

 

The next step will be to reassemble the telescope, bring my Tele Vue 40mm Plossl to focus upon a star, straight-through, and then with my star-prism and -mirror diagonals, and mark the three positions for reducing the length of the draw-tube.  I will then choose the most viable of the three.

 

But that's going to have to wait until I get a clear night.  Earlier, the radar showed that practically the entire U.S. was under fluffy, puffy clouds.  Drat!



#13 Simon B

Simon B

    Apollo

  • *****
  • Posts: 1,165
  • Joined: 16 Jan 2017
  • Loc: BC, Canada

Posted 27 January 2020 - 06:43 AM

popcorn.gif


  • Sky Muse likes this

#14 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 30 January 2020 - 11:04 AM

I think that I had a window through this cloud-cover a couple of nights ago, but I missed it; that is, if there ever was one.  All I need is a clear shot at Polaris for an hour or so.  Is that a lot to ask?



#15 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 01 February 2020 - 11:30 AM

Tonight, the sky should be clear.  Within the focusser's housing, the extended portion of the run for the draw-tube...

 

focusser housing.jpg

 

...needs to be trimmed back...

 

focusser housing5.jpg

 

focusser housing3.jpg

 

focusser housing2.jpg

 

Before and after...

 

focusser housing4.jpg

 

That will help in getting the maximum aperture, and the most light, out of this thing; at least 60mm's worth, if not a teensy bit more.

 

focusser housing7.jpg


  • AndresEsteban likes this

#16 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 01 February 2020 - 06:51 PM

I have to decide upon this...

 

draw-tube extent.jpg

 

Forget allowing the 40mm to determine the length of the draw-tube.  If I focus a 32mm, and the tip of the drawtube is cut flush with the sleeve, as shown there in the image, then if I insert a 4mm the tip of the draw-tube will progress inward and diminish the aperture further.  Of course, if I cut the tube per the 4mm, I might not be able to rack outward enough to bring the 32mm into focus.

 

I may not be able to determine the final length of the draw-tube in one night.  I'm going to have to try several combinations, and with barlows included.


  • AndresEsteban likes this

#17 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 01 February 2020 - 10:26 PM

Tonight has been clear as a proverbial bell; but I just know it won't last.

 

The following measurements were taken between these two points, and whilst making use of the Moon...

 

measure here.jpg

 

Celestron star-prism: 32mm Plossl = 27mm

Barska star-mirror: 32mm = 7.5mm scared.gif

 

For kicks and giggles, I tested the Celestron 4mm SR from my "Bird Jones" kit...

 

Celestron star-prism: 4mm = 28mm  faint.gif

4mm w/Antares 2x-barlow, simulated 2mm = 17mm 

 

It wasn't all that sharp at 150x.bawling.gif  But then, I haven't properly spaced the lens-elements yet, and with proper spacers; also, the atmosphere might've played its nefarious part in that outcome.

 

Barska star-mirror: 4mm = 11.5mm

4mm w/Antares 2x-barlow, simulated 2mm = 3.5mm  whew.gif

 

Aside from that, it will be the 32mm that will determine the final length of the draw-tube(or will it?), but I will also need to test with my 12mm and 20mm eyepieces.  I also need to find that Explore Scientific star-mirror diagonal that came with my Maksutov...  

 

I just don't trust this Barska star-mirror, and I'm not about to buy one, either.

 

 


  • AndresEsteban likes this

#18 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 03 February 2020 - 04:58 PM

Last night was wonderful: in the 60s, and clear.  The Moon was up, so I used it again.  You would think that the Moon, and a star, would focus at different points, being that the Moon is so much closer to the Earth, but nope. lol.gif

 

I found my Explore Scientific star-mirror.  It was attached to my Antares 80mm f/6 achromat, and both within a cabinet.  But it's not better than that of the Barska kit, not at all.  Oh well...

 

I tried both the star-prism and the star-mirror with different eyepiece-barlow combinations once again, and they all came to focus.  All of the eyepieces required more travel outward when using the star-prism.  In that this telescope might serve as a finder-scope someday, I inserted my GSO 90° Amici/erect-image, and popped the 32mm Plossl into that.  The chromed portion of the draw-tube jutted out 11.5mm in that instance. 

 

However, in that the 32mm with the star-mirror focusses at 10.5mm, I'm thinking about cutting the tube down to a final length of 10mm plus the length of the run inside the focusser's housing, and let the chips fall where they may.



#19 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 09 February 2020 - 04:58 AM

10mm plus the length of the run within the focusser's housing(53mm) = 63mm.

 

First, I used my mini-hacksaw and cut the tube down to where it would fit under the chuck of my mini drill-press...

 

drawtube2.jpg

 

If you look closely, you can see the nick I had made for the final cut.

 

I then described a line round with a diamond-wheel.  I didn't want to cut it completely through, as the wheel spun too fast, at the lowest speed of the press, which would melt the plastic and "glue" it back together otherwise...

 

drawtube4.jpg

 

I then finished the cut with a jeweller's saw; perfect...

 

drawtube3.jpg

 

The Moon was out, a super one if I'm not mistaken, but I only caught brief glimpses as the clouds rolled over it constantly, and as I hand-held the wee achromat with the 32mm Plossl and the ES star-mirror diagonal inserted.  The view was very nice, but since the Moon was full I couldn't really compare it to past testings.  Of course the Moon seemed brighter, and with a yellow rim on one side and a blue-purple rim on the other.  

 

In any event, it won't be cut down further.  This little achromat is rather nifty.  I like it a lot, and I haven't even blackened and flocked it yet.

 

I would hate to put good money into a basic, GSO star-mirror diagonal, about $30, but I feel that I should for this one at least.  We'll see.  The image looked great through the 32mm.  Of course that's only at 9.4x.


Edited by Sky Muse, 09 February 2020 - 05:00 AM.

  • eros312, AndresEsteban and erin like this

#20 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 11 February 2020 - 01:46 AM

As it turned out, without an eyepiece in place, and with the draw-tube drawn out to where my 32mm Plossl comes to focus with a star-mirror diagonal, I and the camera can see the entire lens, and part of the inside of the OTA even...

 

70mm aperture.jpg

 

70mm aperture2.jpg

 

                                                          whee.gif

 

The doublet's spacer is difficult to see, yet marked. 

 

With the draw-tube shoved all the way inward, I can still see the doublet, but none of the OTA.  

 

So, it appears that I will have the full 70mm of aperture at my disposal, after all; although I've yet to measure the doublet at this point.

 

Keep in mind that that ended up by pure chance, and blind luck.


Edited by Sky Muse, 11 February 2020 - 02:39 AM.


#21 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 14 February 2020 - 12:21 AM

The bearings for the draw-tube within the focusser's housing consists of nothing more than these molded ridges...

 

bearings.jpg

 

They measure 0.020" in thickness, according to my digital-calipre.  However, the draw-tube wobbles within its run nonetheless.  

 

I will need to remove three of the ridges, as indicated, carefully, and then lay down 0.020"-thick PTFE strips for the bearings at those three points.  With however many layers of aluminum-foil tape required for the substrate, and the thickness of the clear double-sided tape used to affix the PTFE strips, the slop will be eliminated, yet the draw-tube will rack in and out easily.


  • AndresEsteban likes this

#22 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 15 February 2020 - 09:40 PM

The three ridges of the run for the draw-tube have been extirpated...

 

draw-tube run.jpg

 

I used an 80-grit sanding-drum on a Dremel tool to remove the ridges.  I then used 320-grit wrapped around a copper "dowel" to smooth them out.  After washing and drying, I then "painted" over the runs with 100% acetone, which smoothed the surfaces out to a glossy finish.  I then went over that with #0000 steel-wool, washed and dried again, then applied a final coat of acetone.

 

I don't think the remaining four ridges will interfere, but if they do I can sand them down a bit, but without eliminating them.


Edited by Sky Muse, 15 February 2020 - 09:42 PM.

  • AndresEsteban likes this

#23 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 17 February 2020 - 10:13 PM

I went ahead and ground down the remaining four ridges of the run, but only enough so as not to interfere with the new bearings for the draw-tube, and of PTFE(Teflon)...

 

PTFE.jpg

 

That's the thickest I have, and at 0.020", although I may go down to 0.015" and build up the substrate as needed.  I do have a roll of self-adhesive 0.030", but I've never been able to use it for these telescopes, as it's too thick.  In addition, the self-adhesive type doesn't quite allow for the freedom in adjusting the final thickness.  It, too, has double-sided tape applied to it, granted a bit more tenacious, but the Scotch double-sided tape is more than adequate, and allows that extra measure of versatility.  I've read of at least one fellow member who has suggested the self-adhesive type of PTFE, and from a supplier or two, and I winced upon the event.


  • AndresEsteban likes this

#24 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 17 February 2020 - 10:38 PM

This boils the posterior...

 

pinion-shaft bearings.jpg

 

Those plastic grooves are trying to pass themselves off as bearing surfaces for the pinion-gear's shaft.  That won't do, but what to do about it?  I've got a good idea.  But lets see how it turns out.

 

Asidedly, I saw stars earlier this evening, but no more.


  • AndresEsteban likes this

#25 Sky Muse

Sky Muse

    Cosmos

  • *****
  • topic starter
  • Posts: 7,665
  • Joined: 26 Oct 2012
  • Loc: Mid-South, U.S.

Posted 21 February 2020 - 10:08 AM

The bearings for the pinion-shaft were made of bronze, and formed with a drill-bit the same diameter as the shaft, with the help of my drill-press vise and wood...

 

pinion-shaft bearings2.jpg

 

Of course, the pinion-shaft is now elevated somewhat, and away from the rack.  That's not good, therefore I will need to wrap sandpaper around the drill-bit and sand down the two plastic grooves a little to compensate, but not too much.

 

 


  • AndresEsteban likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics