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

MIPS

  • Please log in to reply
24 replies to this topic

#1 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 30 July 2016 - 08:48 PM

This thread is going to take a look at "Mitch's Innovative Paracorr System" or MIPS.

 

To set the stage, I am building a trio of telescopes under similar telescope architecture. The 13"-er has completed design

and it's time to start fabricating stuff. Along the way I came up with a small myriad of alterations o telescope architecture

that should make telescopes stiffer, lighter, and higher performing. Tonight's episode is called MIPS.

 

The F/3 design point is very close to a "take no prisoners" in that everything must be played towards the middle. At F/3

you don't really have an option of larger secondary mirrors (CO), pretty much the smallest mirror that fully illuminates the central

image is "best". Given that the secondary has very little if any play with respect to offset and longitudinal position, one must

place the eyepiece and the Paracorr II at the best possible locations. Given the small secondary one does not have the freedom

of placing the bottom of the paracorr completely outside of the light columns which will ultimately reach focus.The best we can

do is to keep the Paracorr II outside of the planetary light columns.

 

With the above in mind, I took the liberty of drawing up what the upper assembly of my 13"-er would look like using a SIPS

(from Starlight Instruments). I did not go to the trouble of drawing it to perfect accuracy as this design point is for illustrations

only. 

 

SIPS1.jpg

 

Here we can see the secondary reflecting the converging light cones towards Newtonian focus just inside the outer edge of the 

secondary ring. The Paracorr II corrects the coma and creates a second focus plane some 47mm further outwards (the

Paracorr focus). If an eyepiece is placed so the the focal point of the EP is placed at Paracorr II focus the the image will be

in sharp and stargazing can commence.

 

I have estimated that the center of mass of the EP, focuser, SPIS body, and Paracorr is at the point with the downward pointing

red arrow (labeled Weight). It follows that the cantilever distance is that from this Center of Mass (weight:green) and the Base Plate.

The larger the cantilever distance the greater the torque moment is on the base plate, and the greater the forces into the tube wall.

 

I also notice that where I want to articulate the truss loads into the upper assemble is significantly outside that of where the base

plate wants to be positioned (so the poles to not vignette the light columns). You can see faint landing points for these truss loads

around the upper assembly ring.

 

Mitch's Innovative Paracorr System solves both of these problems simultaneously. The cantilever distance is vastly reduced

lowering the torque on the base plate, and at the same time, the truss loads are directed directly into the tube wall from the 

upper assembly rings; finally, the strength of the mounting to the tube wall is vastly improved with the second base (MIPS) plate.

 

MIPS.jpg

 

The Paracorr II, the secondary, the focuser, and the Eyepiece have not moved! The tube wall has moved outward, and a

second base plate (MIPS) that goes inside of the focuser base plate has been threaded with the same threads that  Paracorr II

uses to attach itself to its Tunable Top!

 

The first point of worry is how does one tune the Paracorr? To this, the last few mm of adjustment is performed with the threads

in the MIPS Plate, the rest of the adjustment is performed with the collimation bolts.

 

This system is not a retrofit for already existing telescopes, but a way for telescope under construction to become stiffer in

taking the truss loads into the upper assembly and stiffer in holding the optics on the optical axis at Paracorr focus.

 

Discuss!


  • Neptune and Bill Schneider like this

#2 Oberon

Oberon

    Soyuz

  • -----
  • Posts: 3,913
  • Joined: 24 Feb 2013
  • Loc: Hunter Valley NSW Australia

Posted 30 July 2016 - 10:12 PM

Agree. Another advantage is improved shielding.

Alternatively, for a truly super stiff UTA, keep the inner tube as well as the outer.

#3 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 31 July 2016 - 01:58 PM

Alternatively, for a truly super stiff UTA, keep the inner tube as well as the outer.

 

I am not sure how this would  help, as the truss loads are articulated directly into the CoG of the UTA and pointing directly at the outer tube wall.

 

UTAside01.JPG

 

So there should be negligible bending moments on the lower ring.


  • Neptune likes this

#4 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:32 PM

Ok, it's been a long-ish time and the plans have changed somewhat, but I have completed the first MIPS implementation.

 

The first picture shows the inner barrel of the paracorr 2 tunable top removed from the Paracorr 2.

 

MIPS02.JPG


  • Neptune likes this

#5 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:34 PM

The second picture shows a clever innovation.

 

MIPS03.JPG

 

Here, the outer barrel of the tunable top is unscrewed from the Paracorr 2 optics and then turned upside down, and screwed back on the same threads. This, now, provides a nice body to grab the paracorr 2 optics.



#6 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:39 PM

A tube was turned and bored to fit the outsides of the Paracorr barrel housing.

 

MIPS05.JPG

 

A brass thumb screw was turned down so that its nose just fit the focus position cam in the Paracorr 2 barrel housing. The edges of the thread are cut flat to press on the barrel cam to lock the P2 optics in place.

 

2 holes are drilled into the tube 0.030 so that set screws can hold the tube firmly but gently. You can see the dimple just under the threaded hole of the locking device.


  • Neptune, Pierre Lemay and brave_ulysses like this

#7 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:45 PM

A base plate was machined:

 

MIPS08.JPG

 

The plate started out as 9" by 4" by 1" (6061T6) aluminum. 

 

A hole was bored large enough that the P2 and outer barrel would pass through the center. Then 2 lands were cut inside the bore, one to fit the Focuser, the other to fit the Paracorr 2 adapter tube.

 

The front side was faced down 1/2" and the back side was faced down 1/4" leaving 1/4" place hanging off the bored hole.

 

The plate was "light weighted" by milling large triangles out and by milling a concentric slot centered on the bored hole in the center.

 

Finally, some 4-40 set screws were drilled and tapped to hold the focuser and the P2 Tube.


Edited by MitchAlsup, 07 November 2018 - 05:46 PM.

  • gregj888 and Neptune like this

#8 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:46 PM

A side view of the plate

 

MIPS09.JPG



#9 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:47 PM

Here is a picture of the assembled MIPS base plate with the P2 as far in as possible:

 

MIPS07.JPG


Edited by MitchAlsup, 07 November 2018 - 05:48 PM.

  • Neptune and brave_ulysses like this

#10 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:49 PM

Here is a picture of the Pe out as far as possible:

 

MIPS06.JPG



#11 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:51 PM

In order to focus the Paracorr, I machined a focus screen holder:

 

MIPS10.JPG

 

From the ledge of the flange at the top to the front lens of the P2 optics is 52mm.

 

The small ring holds to focus "screen". The screen is simply scotch tape.



#12 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:52 PM

The insides were cut at a taper that accepts a F/3.45 light cone from the P2 optics:

 

MIPS11.JPG



#13 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 05:55 PM

The wide end of  the taper fits snuggle on the threads holding the front lens element on the P2 optics.

 

MIPS12.JPG

The focuser tube outside is 1.998,5" to fit easily in a standard 2" focuser.



#14 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 07 November 2018 - 06:00 PM

So, this is what I came up with.

 

I was unwilling to let go of the necessity of inserting the P2 from the inside of the upper assembly.

 

I originally wanted to make a threaded hole that would fit the P2s outer threads, but threading into a blind hole with only 1mm of depth is above my pay grade. So, I though and fretted until I realized threads go both ways

and that one can turn the outer barrel around and use it for the focusing device--as it already has a cam machined accurately into it.

 

This also means the P2 holder weights in under an oz, the base place is maybe a shade heavier than a square plate, but having 6 holes and fitting the entire length of the upper assembly's tube, stiffens the whole upper end.

 

Finally, the goal of low cantilevered weight is realized.



#15 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 08 November 2018 - 05:37 PM

Here is a picture of MIPS attached to the upper assembly:

 

MIPS22.JPG



#16 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 08 November 2018 - 05:38 PM

From the side:

 

MIPS25.JPG



#17 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 08 November 2018 - 05:39 PM

And from the inside:

 

MIPS26.JPG

 

The plate part extends from the bottom of the tube to the top of the tube.


  • Neptune and brave_ulysses like this

#18 Oberon

Oberon

    Soyuz

  • -----
  • Posts: 3,913
  • Joined: 24 Feb 2013
  • Loc: Hunter Valley NSW Australia

Posted 09 November 2018 - 07:16 AM

I must confess I haven’t quite absorbed it, but it looks wonderful, like a hell of a lot of thought and careful machining has gone into it. bow.gif


  • PrestonE likes this

#19 Pierre Lemay

Pierre Lemay

    Surveyor 1

  • *****
  • Posts: 1,655
  • Joined: 30 Jan 2008
  • Loc: Montréal, Canada

Posted 09 November 2018 - 12:51 PM

I agree with Jonathan. Wonderful, clever work and carefull attention to details. You're onto something.



#20 s800

s800

    Explorer 1

  • -----
  • Posts: 95
  • Joined: 19 Mar 2008
  • Loc: Wisconsin

Posted 16 November 2018 - 04:13 PM

This concept addresses a limitation that many of us have looked at and not found a great solution for- well done.



#21 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 16 November 2018 - 08:20 PM

This concept addresses a limitation that many of us have looked at and not found a great solution for- well done.

I thought about the problem for at least 2 years (after SIPS) before coming up with the initial plan of attack.

Then it took a bit over a year to execute to fruition; with several machining road blocks in the way.



#22 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 14 October 2019 - 06:00 PM

More of this telescope build can now be found over at:: https://www.hobby-ma...ld.65805/page-2


  • Neptune, Mike Lockwood and brave_ulysses like this

#23 Spartinix

Spartinix

    Viking 1

  • *****
  • Posts: 829
  • Joined: 25 Apr 2017
  • Loc: Crete, Greece

Posted 15 October 2019 - 01:15 AM

Whoa. Very nice work!

#24 ckh

ckh

    Vanguard

  • -----
  • Posts: 2,000
  • Joined: 21 Feb 2015
  • Loc: Arizona

Posted 16 October 2019 - 02:12 PM

Really, really nice and innovative as well. Congrats!



#25 MitchAlsup

MitchAlsup

    Fly Me to the Moon

  • -----
  • topic starter
  • Posts: 6,078
  • Joined: 31 Aug 2009

Posted 16 October 2019 - 04:46 PM

I achieved first <day>light this afternoon.

 

I collimated as best I could in my shop:: the laser hits secondary, hits primary, then hits same spot on secondary and re-enters the laser.

 

I inserted the P2 and used a 21E. I can achieve focus for objects less than 200-feet away but not farther. I spent the afternoon bobbing the truss poles to push the focal plane farther into the scope. The last 1/2" of focus can be adjusted in the length of the poles themselves.

 

Almost ready..............


  • ad701xx, Neptune and happylimpet like 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