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Topics - John Pierce

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1
Equipment Discussions / acquired a celestron ci700 (losmandy g11)
« on: March 23, 2017, 02:04:02 PM »
so I just acquired a rather nice CI700 equatorial mount, this was a celestron branded 'cheapened' version of the Losmandy G11...   its a beast.  has alt and dec slo-mo motors but no goto.









I initially was thinking of using it for unguided piggyback as I don't really have a suitable scope for it, but now I'm wondering if I couldn't rebuild my Coulter 10" F/4.5 ... use one of Mark's Astrogoods alloy tubes, a better focuser than I now have, shorten up the tube enough that I can achieve focus with my DSLR (the secondary on the coulter is huge).  I have already replaced the coulter's primary mirror cell with one of Mark's creations, and the secondary spider with a curved vane spider from 1800destiny. 

http://www.astrogoods.com/atmparts.shtml

am I nuts for thinking this is a good idea?   the mount is rated for 60 lbs of instruments, 100 lbs total.   Celestron sold it with  C11 and C14 telescopes on it :-O


2
TAC Visual / Solar Binocs!
« on: March 01, 2017, 08:13:04 PM »


those are 100mm binoculars, with the 14mm eyepieces, they are 42X

thats V0.1 ...   the yellow frames were 3D printed and not quite dimensionally accurate, so I need to do some tweaking.  I have some felt strips I'm going to add to the top and bottom so they fit more securely.    The ThousandOaks solar film wrinkled a bit when I taped it down, so I need to lift the tape, and trim the edges just a bit, then tape it down again.   Finally, I want to cover in black gaffers tape to reduce glare from the yellow plastic.    I might move the solar film to the front when I trim it.


3
TAC Visual / Eclipse Glasses for uber Nerds...
« on: March 01, 2017, 06:25:22 PM »


thats a pair of Hobart welding goggles, retrofitted with shade 14 50mm lenses (they come with shade 5 which is far too light for sun viewing).

coming soon, my optician said they can cut me my Rx onto 50mm circular plastic, and index mark them so I install them correctly :)   this should be good :)

actually, since taking that selfie, I've also shortened the bridge so they fit tighter to my nose and are parallel and not walleyed like in the pic.

and after the eclipse, I guess I could wear them to burning man!

4
Forum stuff / fixed a dns registration problem!
« on: February 01, 2017, 10:31:01 PM »
I found and fixed a dns registraiton problem for the observers.org domain, so access to this forum should be much more reliable.   It was causing erratic DNS not found errors before.

5
Annual Star Parties / GSSP 2017!
« on: January 22, 2017, 09:54:02 PM »
Coming Soon, GSSP 2017!    June 21-25, 2017, at Frosty Acres Ranch

http://goldenstatestarparty.org

6
Equipment Discussions / solar finder ideas...
« on: January 20, 2017, 08:08:18 PM »
so thinking of the upcoming eclipse, I'm planning on making a safe solar filter for the club's 100mm binocular, which has 25x and 40x eyepieces....

It will need a sun finder, I'm thinking a brass tube, maybe 1/2" diameter and 4-6" long, with a translucent disc 1-2" in diameter superglued to the back... center the shadow of the tube on the disc as seen from behind, perfect.     this disc/screen probably should have a nice sharp black dot right in the middle

Whatcha guys think? 

I can use this mount I made for a laser pointer... 




the binos look like this, they are 45 degree, and take standard 1.25" eyepieces as long as they aren't too fat.   The 40X eyepieces are 14mm ES 82 deg. wide, similar to a Nagler, so the actual field of view is 2 degrees.



I'm thinking of finding some suitable cardboard, and taking a strip thats 6" x the outside circumference of the binoculars body, and using that as a template to cut a end piece, with 2 4" holes and thousand oaks solar film, assembled with gaffers tape :)      this should slip on and off the binos, if its too loose, I could always use wide blue painters tape to secure it.

7
TAC Astro Classifieds / For Sale: 24" Dobson
« on: January 02, 2017, 03:36:01 PM »
this is from a third party, I'm just posting this here for y'all to see.  please contact Greg per the PDF...



Dear Astronomer,
I am writing to inform you of a unique telescope that is now available. After over a decade of service, the Robert Ferguson Observatory has retired a 24" Dobsonian (to make room for a new 40".) The 24 has delivered amazing views of the universe to literally tens of thousands of people and is fully capable of continuing its mission for many more years to come. It just needs a new home.

For Sale: 24 Inch Dobsonian Reflector:
Riverside Telescope Makers Conference Merit Award, First Place 1993.
Al Nagler remarked, "the best image of M13" he had ever observed.
John Dobson recommended, "take that telescope to every State Park for public viewing."
During the Hale-Bopp appearance, the 24" became a nightly exhibit at the Berkeley Hall of Science.
Installed at the Robert Ferguson Observatory in Sugarloaf Ridge State Park (CA), in 2005.

Objective: 24", f/4.5, 1/12 wave, 4.5" thick, made by master mirror grinder Dave Verossa.
  • 9 point mirror cell
  • 2" focuser.
  • Equipped with the Orion Sky Wizard 3.
  • Finder #1 - 8" f/4.5 reflector with a 2" focuser and 40mm EP.
  • Finder #2 - 90mm refractor.
  • Finder #3 - Telrad.
  • Equipped with fans and thermocouple for rapid mirror cooling.
  • EP:
  • Tele Vue Naglar 13mm
  • Tele Vue Naglar 20mm Type 2
  • Tele Vue 32mm Wide Field
  • Orion Ultrascan 40mm multicoated
  • University Pretoria 28mm multicoated
  • Optica b/c Er. 20mm
  • Optica b/c Er. 25mm
  • Filters:
  • 2" Variable Polarizer
  • 2" Polarizer
  • 2" O III
The telescope is currently dismantled and in storage near Santa Rosa CA.
$8500.00 or best offer

see the attached PDF for photos and contact information.

8
Equipment Discussions / homemade truss dobson collimator
« on: November 07, 2016, 04:51:21 PM »
I recently acquired a 17.5" Discovery Truss Dobsonian...   Naturally, this requires collimation each time you assemble it.    The first step of secondary collimation is easy enough, I have a decent quality laser... but the primary mirror collimation is a pain with my peep sight cheshire equivalent... I've read about barlowed lasers in the past, and recently found out about Howie Blatter's "The Blug", but didn't want to spend the $75 or whatever on one.   

Hey, look here, I've got an old(!) Orion variable barlow, the kind you slide the lens up/down the tube to go from 2X to 3X...  its fully multicoated... so I remove the lens slide element from the tube, measure it, and use OpenSCAD to build a Blug clone that will hold this barlow...  My friend 3D printed it for me last night, and it works great.

 



I was going to put an o-ring in the groove around the part that goes into the back end of the focuser, but its such a snug fit as-is, I think I'll leave that out.

here's the SCAD file that generates it...

$fn=200;

inch=25.4;    // mm per inch

scale([inch,inch,inch])
{
  difference()
  {
    union(){
        translate([0,0,-3])cylinder(h=3,d=2.3); // main cylinder
        translate([0,0,0])cylinder(h=.2,d=1.98);   // 2" insert fudged to 1.98 for tolerance
        translate([0,0,.2])cylinder(h=.1,d=1.90); // groove for 2" OD 3/32" thick O-ring
        translate([0,0,.3])cylinder(h=.15,d=1.98); // rest of 2" insert
        translate([0,0,.45])cylinder(h=.05,d1=1.98,d2=1.93); // bevel
    }
   
    union(){
        translate([0,0,-.75])cylinder(h=1.26,d=1.175);   // barlow inset, fudged for tolerance
        translate([0,0,-3.0])cylinder(h=3.5,d=.2);      // laser hole
    }

    translate([1.25,0,-3]) rotate([0,45,0])cube(3.5,true);      // 45 degree truncate
  }
}

9
Equipment Discussions / counterbalancing a truss dob?
« on: October 21, 2016, 12:16:57 AM »
anyone have any ideas for how I add weight to the bottom of this?



I need to take a closeup of the bottom, next time I have it setup I'll do that.

anyways, it balances fine now with a telrad and one or another of my Explore Scientific 1.25" eyepieces...  but if I add my 9x50 erect finder, its way nose heavy.   I suppose I could move the finder shoe down to the side of the base box, hah!

10
Equipment Discussions / Wheelbarrow Handles on a Dob ...
« on: October 20, 2016, 11:45:19 PM »
so I recently bought Matt T's 17.5" Discovery truss scope...  main box is 75 lbs, quite a load to load in and out, and not easy at all to do a proper squat stand from ground level due to its size/shape.   Obvious solution is to add wheels and barrow handles, but it took me the better part of a week to cogitate different ways of doing this, and coming up with something simple enough that I could pull it off successfully, armed only with hand tools and a cordless drill ...

tuesday, I hit the hardware store during my lunch break, and got a couple wheels, a pair of wheelbarrow handles, and some hardware....   yesterday evening, I finished the build, using 3/8" t-nuts on the inside of the mirror box, and 3/8 x 3" bolts to secure the handles to the box.   I have some knobs coming that will snap onto the bolt heads so I won't need to use a wrench to run them in/out.



I have a pair of folding motorcycle ramps, put those on the back of my Tacoma 4x4 and I can run this up and down the ramps quite easily, and the 10" wheels easily run over terrain.

11
I have a hard shell drum case, roadie grade, that is like 28" in diameter and 22" deep, it could hold the top assembly of a fairly large dobson.   

Its a Hume & Berg Enduro case, just like this http://www.humesandberg.com/product_detail.php?product=730 
really sturdy, with 3 handles and 3 straps holding the lid on.   in Drum land, this is for a 24x18 bass drum, these sell for like $200+

I paid $75 for it sight unseen (my brother picked it up), but its way too big for my needs.    The drummer my brother got it from used it on a national tour, so its scuffed on the outside...

12
(thread split from an OR where mccarthymark mentions a "Springsonan")

any pictures of this 'springsonian' scope?

13
New Subscribers and Beginners: Start Here / Under the Milky Way
« on: September 27, 2016, 11:21:38 PM »
stumbled onto this amusing Australian tv series, apparently it ran across Australia earlier this year.

the whole thing is on youtube, https://www.youtube.com/playlist?list=PLJLn8vIAKEr-slN8lPq4iCIpkVSMo2qZ2

Under the Milky Way is a 6 part (28 min each) Australian TV comedy/drama about an astronomical observatory in Coonabarabran NSW, thats being shut down because a fancy new larger observatory has opened nearby.     The whole thing was filmed on location at Siding Springs and Coonabarabran.




14
Annual Star Parties / Calstar for 2 + RV space
« on: September 16, 2016, 11:54:12 PM »
Personal stuff has come up, I can't make calstar this year after all.

we paid for 2 people plus a RV space (power and water hookup), so ....  I'll happily pass this whole package on for some part of what we paid ($115 total, $35 per person, plus $50 for the RV space), make an offer.

15
Observing Intents / SCAC at Yosemite
« on: August 12, 2016, 09:31:20 PM »
Santa Cruz Astronomy Club's annual outing to Glacier Pt Yosemite.   members only.

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