University Lowbrow Astronomers

First Light of the “PK-457”.

by Mark S Deprest
Printed in Reflections: December, 2008.

PK-457, Photo#1

(Insert theme from 2001: A Space Odyssey)

From out of the foggy, darkest, all the way from Norman, OK via Dayton, OH it appeared with lots of warning in the driveway of John Causland! (Insert fanfare) The “PK-457”!!

The Mirror

After waiting TWENTY agonizing, grey, overcast days my latest acquisition, an 18” f/4.5 Truss Tube Dobsonian Reflector received “first-light” on November 22nd! The scope, now known and the PK-457, was originally built by Pete Kron of Norman, OK. Pete works for Astronomics and back in the late 1990’s he made number of “larger aperture” scopes in the Dave Kriege truss tube Dobsonian style. As you might have already figured out the “PK” is for Pete Kron and the “457” is the aperture in millimeters. The original buyer / owner of the PK-457 was Al Roberts of Dayton, OH and he is the gentleman that I purchased the scope from. The primary mirror is a Pegasus Optics mirror and according to the accompanying documentation is 1/10 wave-front P-V, with a Strehl ratio of 0.9604. (These are very good numbers) Al Roberts added a drive system to the scope and enjoyed it for 10 years. However, Al wanted something a little more portable, so he moved from “big Dobs” to SCT’s and put his Pete Kron 18” up for sale on Astromart. The timing, size, and price were all right and that’s when I entered the picture. There was just one issue I hadn’t saved up all the money I needed to cover cost of the scope. I have to say that I have the greatest wife in the whole world she supplied the balance as an early Christmas / Birthday present! So on November 2, 2008 Terri and I made the drive down to Dayton, OH to pay for and pick up the PK-457, which just fit into the back of my Saturn Vue. (My wife was a little worried about that at first, but I knew it would fit nicely! Well, I hoped it would.)

PK-457, Photo #2

Okay, so now I own an 18” f/4.5 telescope that; I can barely lift up into my car, that it just fits into and although I helped take it apart for transport to its new home, I hadn’t set it up yet. I had to wait until the next weekend before I got a chance to set it up for the first time. I spent some time working on it that weekend trying to determine all the things I want to do to it. You know all the little things that make the scope user friendly to you. Also, I wanted to test the drive system, as I was unfamiliar with it and the way it works. I made a few small improvements and cleaned up all the bearings so that everything moved nice and smooth. Now I was ready for a clear night and first light of the “PK-457”!!

Tech 200 DOB Driver II System

Saturday, November 22nd looked like it was going to be at least clear enough to some testing of the optics and drive system. I have mentioned the drive system a couple of times now and I should probably tell you a little about it. The Tech 2000 DOB Driver II system is unique in that it does not require any kind of alignment. That’s right, no two star, one star, or polar alignment of any kind. The system doesn’t need to know what time it is or where it is, you only need to center your object, put it in “Track” mode and as the object begins to drift out of the field of view, simply re-center the object and the system learns how much to continuously move each axis to keep that area of the sky centered in your field of view! Once the system knows this you don’t have to do anything else... the object stays centered! If you are using higher powers you may need to make some very fine corrections and the system then learns and is even that much more precise. The DD2 system can be used to track Planets, Moon, Sun, or Comets! How cool is that?!?! The DD2 system uses a motor powered friction wheel on the ground board for the azimuth drive and a motor powered belt and pulley wheel for the altitude drive. The system has internal encoders, so there is no need for any addition digital encoders to install on either axis. Both the altitude and azimuth motors have manual releases so that the scope can be used with or without the DD2. Because there are no additional encoders to install the DD2 system is less than $1000.00 to install on any Dobsonian scope. I was very anxious to try this system out and see if it really does what it says it does. I should add that the DD2 system does have the ability to use ASCOM and therefore allows you to computerize your scope and make it a true “GOTO” scope.

Mark at the telescope

I had hoped to do my first light at Peach Mt. but as the temperature dropped and the skies looked like they might be marginal at best, John Causland’s driveway seemed like a better place to set-up. That way if any mechanical issues came up I could go into John’s garage and work on fixing them, plus as the temperature looked like it might drop into the Teens, the ability to warm up in John’s house was very appealing. So as the sun was setting I began to set up the PK-457 in the driveway of John Causland (known to ACNO as the Causland Causeway). Although John was not going to be home until after 8:00pm, he told me to make myself at home (John is a very good friend!). As I finished the PK-457’s assembly (only the 4th time for me), I needed to align the Telrad Finder and Altair was well placed in the southwestern sky, so I centered it in the eyepiece and then adjusted the Telrad Finder so that Altair was centered in the middle of the smallest circle. I then put the DD2 into “Track” mode and made the necessary centering corrections and “Presto” the scope began to track Altair! Very cool! I kept Altair centered for over 15 minutes in both low (74x) and higher (182x) powers, that made Altair part of the PK-457’s “First-Light” night. The next object seen through the scope was M57 and its 14.8 magnitude central star which was actually fairly easy to pick out (extra aperture is good, extra aperture is wise!). After spending the next 20 minutes or so admiring the Ring Nebula, the clouds and haziness began to increase a bit in that area of the sky, so I used the “Pan” mode of the DD2 system to slew the scope over to a clearer patch of sky that just happened to be where M31 and company lived. By this time of night (7:30pm) M31 was almost 75 degrees above the horizon, this meant I could no longer stand on ground and reach the eyepiece, but one step up was all I’d need. I like the fact that I don’t have to climb multiple steps up a ladder to reach zenith. Okay, back to M31 and environs which in the University Optic’s 32mm MK-80 eyepiece just fits into the 65 arc minute FOV that it provides. I should probably mention something about the quality of the views the PK-457 was showing... does the word “eye-gasmic” help? After spend the next 45 minutes studying the intricacies of the Andromeda Galaxy and its two companions I decided to give the DD2 system a bit of a work out. So I began to slew it around to M15 which meant turning in azimuth almost 180 degrees and that when I found the first issue... I had a spot on the bottom of the rocker box that rubbed against the ground board and caused the drive motor to stall out. This was going to need fixing but for the time being I could disengage the azimuth drive and manually move the scope to my target. Once past the spot the scope moved freely and I re-engaged the azimuth drive and started tracking again. I was beginning to get some frost build-up on the exposed surfaces, this coupled with the fact that scope was out of balance because of the heavy eyepieces and the Televue Paracorr I was using made the UTA (upper tube assembly) want to nose dive. And now the altitude belt was beginning to slip (issue number 2), but this could be easily fixed with some counter-weight on the mirror box.

PK-457, Detail of Base

It was now about 8:30pm and Yasu & Yumi had shown up and John finally came home, so we all spent some time setting up scopes for Yasu and Yumi and John brought out the “61” a.k.a. his 24” Starmaster scope. After about thirty minutes Yumi was getting cold and decided to go in and make some tea for John and Yasu. I on the other hand I had noticed that the area of sky that was home to a Comet (that I had not seen yet) was now well above John’s roof and was very clear. So as the three of them went in to warm up, I went about the task of hunting down my 71st comet. After about fifteen minutes of searching an area of sky that contained very few visible reference stars, I found it! Comet C/2006 OF2 (Broughton) at 11.2 magnitude was surprisingly bright, with a very noticeable curved fan shaped tail that extended 5 to 8 arc minutes. I let out a loud whistle to announce my success to the trio warming themselves in the comfort of John’s kitchen and after a few minutes they all came down and verified my find! I personally can’t think of a better way for me to experience “First-Light” in any scope than with a comet! I do so love my comets! We spent the next couple of hours exploring Auriga’s clusters and ended the night with an incredible view of the Orion Nebula, just before mid-night.

John was cold and tired, Yasu and Yumi were also getting cold, so I began disassembling the PK-457 and packing up my frost covered gear, but all the while I kept a satisfied smile on my face. I am very pleased with my new scope, and the next time you see me at Peach Mt. it will be in the company of the “PK-457” I hope its very soon, I want to gather more star light in my eyes!

The PK-457 in John's Driveway

Photo Credits

All photos on this page taken by Mark Deprest.

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Copyright © 2013, the University Lowbrow Astronomers. (The University Lowbrow Astronomers are an amateur astronomy club based in Ann Arbor, Michigan).
This page originally appeared in Reflections of the University Lowbrow Astronomers (the club newsletter).
This page revised Sunday, March 9, 2014 4:30 PM.
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