7055 replies to this topic

[TonyStar]

I neatly packaged the OnStep electronics and 3D printed a custom case for it. It took me a few failed prints to sort out all the design errors, tolerances are pretty tight, it fits like a glove!

 

Edited by TonyStar, 22 May 2017 - 11:38 AM.

[Pinbout]

Put some wood together

 

[musicengin]

Glued some more pieces together, cut some more pieces, and made a list of what next.  There could be pictures but I'm not a mobile phone user and I forgot to take the camera...

[roscoe]

no hurry, we'll all still be here tomorrow.....

[musicengin]

Thanks!

 

When I get it further along I'll definitely take pictures.  I'm not very good at negotiating the sense of people looking over my shoulder, even when they aren't; it makes for even more "no, maybe I should do it that other way..." coming from the endless inner debate.  But I had so much fun at Stellafane last summer with my first scope, that feeling is moving this scope along now.

 

I cut three more little parts out before work, they'll help stabilize the mirror cell collimation bolts.

[Mike Lynch]

Well, for those who may not know about this procedure, I managed (actually yesterday) to complete my build of a Surplus Shed 80mm f/400 scope for watching the August solar eclipse by flipping the lens elements around in the lens cell, making sure to keep the pencil marks on the two elements lined up.

 

A number of others who have built scopes from the SS 80mm and 127mm achromats have found this necessary to get decent views through their ATM scopes.

 

Before I flipped the lens elements, I was getting strange aberrations and uneven focus across the FOV.

 

After the procedure, I actually get very nice terrestiral and celestial views for such an inexpensive build!

 

Hope this may help some of you who run into this!

 

Clear skies....PLEASE!!

[jtsenghas]

Before I flipped the lens elements, I was getting strange aberrations and uneven focus across the FOV.

After the procedure, I actually get very nice terrestiral and celestial views for such an inexpensive build!

Hope this may help some of you who run into this!

Yes, in the case of the SS 127 mm achromat this isn't an error as much as an expectation by the maker on which direction the lens cell would be used. The more convex outermost surface of the lens assembly should face the sky.

[Mike Lynch]

Good point, J. T.!

 

Guess I should just say that ya gotta make sure the lens assembly is facing the correct direction... which isn't necessarily the way I (and others) intuitively believe the cell should be facing.  

[Benach]

Yesterday: with a fellow optical engineer made the calculations for the custom AR coatings of my telescope. Still a bit in awe of how interesting this is.

[member010719]

I have a 60x260mm lens from the flea market.

I'm making a  wide field RFT with it.

I firts tested the lens in a mock-up rig and image was quite good and accepted powers up to 40x-50x.

Made some work on the small OTA and when I put back the lens ,the image were horrible.

What happened was at first test , by mistake , I put the lens in his ''normal'' position.

Reading a bit showed that objectives with ''flint first or flint avant'' were made and used since the times of Dollonds.

 

Ziridava

[member010719]

I had a problem , I'm over it.

For the spider of the 8'' F/6 Dobsonian I had the central hub.

The arms of the spider are fastened to the tube via U screws.

My problem was the lack of U screws ,actually U screw with straight arms.

I found only with rounded arm between the threaded ones , not good for my purpose.

Here we see the similar spider for the 125mm F/4.5 reflector ,also in construction.

 

 

In the last weeks which passed from Easter ,I was not procrastinating but doing works like staining wood , adjusting some small parts , cutting members for an eyepiece shelf ,glueing the adaptor for HC-2 focuser.

And meditating on a solution to my problem.

 

 

 

 

This week I come up with this solution.

 

Grinding flat oposite sides of flat  slotted head screws , make a clamp of the same 0.5mm  galvanized steel sheet used for spider arms.

 

 

I haven't found very short rivets for thin sheets.

Modify  4mm rivets because three layers of 0.5mm sheet are less than 2mm tick.

 

 

Make pilot holes , final holes , bend the clamps ,prepare for riveting.

 

 

Do the riveting.

The end of the spider arm should sit inside the slot in the heads of the screws.

This reduce wobble of the screws , dont't allow screws to rotate and is helpful to stiffnes.

 

 

 

This was just an experiment to check fezability,now I will do the real thing.

But the way is paved.

 

Ziridava

 

 

Edited by ziridava, 31 May 2017 - 10:46 AM.

[drneilmb]

Preparing for a future mirror grinding project, noodling around a Foucault tester, I wanted to use a screw with a printed dial rather than a mechanical dial indicator, so I needed some code to make dials with arbitrary numbers of divisions and labels.
 


 

 

  #!/usr/bin/env python

  """Create vector graphics for dials."""

  from math import pi

  import gizeh


  RADIUS = 500
  surf = gizeh.Surface(width=2*RADIUS, height=2*RADIUS)
  CENTER = [RADIUS, RADIUS]


  def draw_dial(surf, n=100, major_ticks=5,
                tick_width=10, tick_length=50,
                major_tick_factor=1.5,
                font_size=100):

      def _minor_tick():
          return gizeh.rectangle(tick_width, tick_length,
                                 xy=[CENTER[0],0],
                                 fill=(0,0,0)).translate([0,tick_length/2])

      def _major_tick():
          return gizeh.rectangle(tick_width, tick_length*major_tick_factor,
                                 xy=[CENTER[0],0],
                                 fill=(0,0,0)).translate([0,tick_length/2*major_tick_factor])

      for i in range(n):
          if i % major_ticks == 0:
              tick = _major_tick()
              label = gizeh.text('{}'.format(i), 'Helvetica', font_size,
                                 v_align='top')
          else:
              tick = _minor_tick()
              label = None
          tick.rotate(2*pi*i/n, center=CENTER).draw(surf)
          if label is not None:
              label.rotate(pi) \
                  .translate([CENTER[0], 1.1*tick_length*major_tick_factor]) \
                  .rotate(2*pi*i/n, center=CENTER).draw(surf)

[Jeff Dunn]

Neat! Thanks for sharing this!

[member010719]

Neil

 

Future grinding ?

That sound great.

On the dials I believe you need  to show the centers  because you will need to make holes.

 

Mircea

[musicengin]

I wrote some notes on what I want to do this weekend so I can stay on track and get a lot done, I hope.

[jnanof]

Made a 2" pipe mount for my 6" Newt, 6" classic cass, and hopefully my 8" newt. Will be starting a new thread with more details.

 

http://imgur.com/a/2OOcS

 

 

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[Stardust Dave]

Trivial DIY project ,went to collimate the 4.25" Bushnell 78-2010 in my sig.
Images became suddenly horrible.

Doing a star test , the secondary shadow was swapping sides inside and outside of focus.

Confused me.  Everytime I touched the alllen screws on the secondary the pattern was shifting and a lot.

Then realized the issue was the corrector place and outing ring with secondary ,was coming off in my hand.

Literally falling off.

 Life as a "ball scope" well , its rolled and bounced out of its saddle ,off a tripod ,around a car -you name it.  

 

So the 3 screws that held the "corrector" and assembly to the tube, the tube had cracked and broke at the screw holes.

Had to epoxy the sides of tube on the seams , re square the corrector cell on the ragged edge of thin plastic tube,shimmed the secondary with a flat washer and milk jug washer.

 

Drilled holes in the corrector cell lower on the ring where the tube is thicker.

Put all back together ,collimated inside.

Low res pic to hide the extra screw holes and epoxy work 

Tested on Moon and Jupiter . Stars look good as its going to get.

For a junk grab n go scope. About 2 hours effort.

Saved from having to toss in the bin.

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Edited by Stardust Dave, 02 June 2017 - 01:04 PM.

[Pinbout]

Re-melted some corny lead casts to bricks for counterweights.

 

[DivisionByZero]

I got done sizing and painting a pair of light/dew shields for my main scope and my autoguider.  I've had a few imaging nights cut very short because my autoguider started dewing up very quickly.  The autoguider is a home-made PVC-scope with a surplus achromat lens (50mm dia, ~f/5).  I only had a short PVC fitting in front of the lens extending about 3/4".  It was not keeping the dew off and I would just lose my guide stars.  I needed also to make a more effective light shield for my main scope, though I thought my flocking improvements helped already with that, I figured: why not?

 

The shields are sheet metal (steel) and I think they were galvanized but it's been so long since I bought the metal, I can't quite remember.  I got Rustoleum white and black to do the outside and insides of the metal so it looks nice.  Even though the Rustoleum matte black is supposed to be matte black, it's fairly reflective.  For my imaging scope I'll end up flocking the tube with velvet, I think.  Probably the black is ok with my guide scope as I have some baffles inside the OTA already.  I don't own a resistance welder (really wish I did!) so I joined the tube with some 6-32 machine screws.

 

These two shields will attach to the OTAs via the slots at the bottom of the shield.  I've included the PVC fitting for the autoguider to show the attachment scheme.  The holes are drilled and tapped to take a 6-32 which is what you see in the PVC fitting.  The shields slip over the end and then a set of nuts can fix it down and keep it in place.  

 

Parts for some home-made heat straps and PWM controls have been ordered and are on the way.

 

[member010719]

Tuesday ,while working on the third arm of the spider for the 8 inch Dobsonian , I had an incident.

The 4mm drill bit  (of course made there )   broke , the  hand drill  slip and it hit my finger.

Now I have eleven finger nails.

For a few days my ATM-er authorisation was  suspended by the highest authority of our house hold....

 

But the Valkyries of ATM don't  dump a loyal worshiper !

 

 

Today I was visited by my friend Gabor and received as gift this excelent mirror of 100,5mm x 498mm and  Strehl 0.965.

 

 

So , more ATM work in the view !

 

Ziridava

 

[jtsenghas]

Well, it didn't happen today, but Tuesday we presented a lending telescope to our local library after I did a presentation of the history of this program since Marc Stowbridge did this first in New Hampshire in 2008. More on this here. 

[member010719]

I got this far with the spider for my 8'' F/6 ''Circus Canon''.

I was at riveting the third arm when the highest authority call me to dinner.

Just dare to be late after the nail multiplication  incident !

 

 

Ziridava

[CCD-Freak]

I got this far with the spider for my 8'' F/6 ''Circus Canon''.

I was at riveting the third arm when the highest authority call me to dinner.

Just dare to be late after the nail multiplication  incident !

 

 

 

Ziridava

Nicely done!  Your spider looks very rugged.

What are you using for the hub of your spider?  

I have a 10" f 10.5 mirror and I have been thinking of building a scope much like yours.

 

John

CCD-Freak

WD5IKX

[Bill Schneider]

I got this far with the spider for my 8'' F/6 ''Circus Canon''.

I was at riveting the third arm when the highest authority call me to dinner.

Just dare to be late after the nail multiplication  incident !

 

 

 

Ziridava

Just wondering (and maybe I'm missing something) - if it is a tube dob, how are you going to fish it down into the tube to align the extended screws with the holes? Won't it be too big to go into the tube?

Edited by Bill Schneider, 11 June 2017 - 02:52 PM.

[Pinbout]

Playing around with anneal alum and squishing it

 

 

https://www.youtube....h?v=D97ie6Kiccs

 

 

Edited by Pinbout, 12 June 2017 - 08:16 AM.