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Can’t leave well enough alone – drilling holes in my Obsession


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Can’t leave well enough alone – drilling holes in my Obsession

By Chris Casebolt

Everyone has his or her own reasons for loving astronomy.  There’s the vastness, the beauty, the nature, the perspective, and the wonder.  For me, it’s the outreach – especially to kids.  Hearing that first “wow!” makes all the money, logistics, desperate memorization of facts and figures, and time I invest into the hobby worth it.  I also get to repeat my ridiculous introduction over and over:  “I’m an amateur astronomer – that’s French for ‘idiot with a telescope.’”

But that’s the external love.  On the inside, I’m a gadget freak.  And not just any old gadget – I like ones that are “elegant” (aesthetically designed, efficiently functional, and manufactured and assembled with craftsmanship).  Luckily such gadgets, accessories, and other add-ons are not hard to find in our hobby.  All it takes are some good conversations at star parties, thorough surfing of Cloudy Nights, and enough good deeds in the bank so you can smile at your spouse when another package arrives at the door.

I’ve noticed that most articles and reviews here on Cloudy Nights contain some sort of personal experience and equipment history.  Mine’s pretty brief – I’m still a developing rookie.  I started out 10 years ago while living in Minnesota by reading Terrence Dickenson’s Nightwatch and jumped in with an entry-level Celestron refractor on a stable but manual equatorial mount.  Got to a dark sky site once with it and found the Ring Nebula (M57).  A bit frustrated with hunting around using a non-intuitive eq mount, I embraced my laziness and moved to a Celestron CPC925 when I moved to Colorado.  I enjoyed the GPS, goto, and plenty of opportunities for upgrades.  I added a focuser, an improved finder scope, a binoviewer, and a counterweight kit.  I had lots of fun observing with it – and it was a heck of a fun scope to share at outreach programs.  Always fun to hear the crowd “ooos” and “aahhs” as it slewed rapidly from object to object.  Through observing mostly through the Milky Way star fields from Cygnus down to Sagittarius during the Summer, I found that I’m mostly a wide field viewer.  The TeleVue Panoptic 41mm is still my favorite eyepiece.  That insight lead me to a TeleVue NP101is, that I had mounted on an iOptron MiniTower Pro.  (And yes, I realize the “is” stands for “imaging system” – but I bought it for visual use given its fabulous optics and beefy, precise focuser.)  The apochromat gave me exquisite views – razor sharp across the field – but, a bit dim (of course, it’s a 4”).  Enter aperture fever.

The Obsession Telescopes web site has been a favorite of mine for years – I imagine Dave’s web page hit counts on the 22” UC and 25” Classic pages reflect the dreams of most of the community – especially the visually-biased.  (Thankfully for my budget, I seem to be immune from the imaging bug.)  In 2010, just 8 weeks before the Okie-Tex star party, I sent Dave Kriege an email asking if he could have an 18” classic ready and delivered to me in Oklahoma.  He said he did – so I ordered the scope.  I found it too tough to reach deep at the time of purchase to add ServoCAT to the 18”, so I downshifted and had Dave install the hi-res encoders and an Argo Navis DSC.  It’s a lot of fun to have a new Obsession delivered to you at a fantastic dark sky site by the man himself.  After some quick instructions and a rough collimation, I spent first light cruising the amazing beauty of the Veil Nebula for hours.  Talk about big “O” – observation through an Obsession with an O-III.

Most of 2011 passed and all I had to show for it gadget-wise was a whole fishing tackle box full of collimation tools.  It seems like lots of folks like Howie Glatter’s lasers and TuBlug, and lots of other folks like Jim Fry’s Catseye passive tools.  So I got both.   However, on the scope itself the push-to method just wasn’t cutting it – so I thought it was about time to “pimp my ride.”  Clearly I wanted to add the ServoCAT (and wow, my timing was right for the new Gen 3!) – but I wondered what elseI could add to my photon vacuum?  After shifting through another of my favorite web sites – Charlie Starks’ Markless Astronomics – I had my answer:  let’s try everything!

My first custom install onto my scope was the “Spider Wiring Kit” (SWK).  Great instructions, quality materials, and a bit of a challenge to install well (getting the wire perfectly across the top of the spider vane).  It works great and it’s nice not having to worry about a 9 volt battery dangling over my primary.  I really like how it allows me to just forget about the secondary mirror.

The wiring kit heading into the secondary mirror cell

The termination of the SWK into a RCA jack at the top of the OTA

Charlie’s web site pointed me over to Astrocrumb and their Filter Slide.  I typically use three 2” filters – a neutral density filter for moon and Jupiter, a UHC, and an O-III.  Astrocrumb’s slide holds all 3 securely and the movement is smooth with a perceptible “click” for each filter.  I had the “Omega Dew Terminator” (ODT) added to the slide, and also ordered a case to hold the slide and my filters.  I had a bit of trouble installing the slide brackets to the inside of my upper tube assembly – the best position for them placed them just a bit over the nuts securing my Feathertouch focuser.  I simply drilled out a bit of a crescent into the brackets allowing them to clear the nuts.  Bingo.  The Filter Slide obviously makes switching filters a snap, but I do get a bit of reflected light interfering with the view by having the filter separated from my eyepiece (only really noticeable on the darkest of nights).

Drilling into the Filter Slide mounts (with masking tape for paint at the ready)

The Filter Slide installed

Living in Colorado, dew is seldom an issue.  But, with the SWK and ODT now installed on my UTA, I ordered a “Big Dob Dew Buster” (BDDB) dew controller from Ron Keating – and Markless’s BDDB bracket.  The controller is solidly built, with an intuitive set-and-forget knob for temp control.  The bracket installed easily with great instructions and a drilling template from Markless.  My biggest bonehead move:  installing Velcro on the back of the bracket (double holding it to the UTA tube material along with two screws into the top ring), probably unnecessary and probably impossible to ever remove without messing up the material.  The BDDB itself gets Velcro and straps to secure it to the bracket.  This turns out to be pretty much a permanent installation that I don’t fuss with.  The BDDB also provides many more temperature-controlled ports, and direct 12v ports for further accessory expansion on the OTA.

The BDDB and bracket installed on the OTA

The BDDB’s power comes in from the bottom, with plenty of ports on both sides

Getting power up to the BDDB was easy using the Markless UTA power system.  This kit provides a clean install package, with a long RCA-to-RCA wire to run up a truss pole, a pass-through to the rocker box, and inside the rocker box – a fused RCA-to-RCA cable.  Velcro tie wraps are also provided to secure the wire to a truss pole.  Works great.  (I am kind of bummed that Charlie discontinued his powered truss tube kit – which I always thought was very cool, along the lines of the Spider Wiring Kit, using the scope itself as a conductor.  On the other hand, that installation looked a bit scary to do for a rookie like me, so the UTA power system is a safer bet anyway.)

The UTA power system’s provided pass-through port for the rocker box

After this slew of accessories as a warm up, I moved on to the installation of the ServoCAT.  This is the one installation that in hindsight I should have had done by the pros.  It’s straightforward, but I’m sure experience helps a ton.  Good instructions and an included and very useful install video helped me a bunch.  If you think you want to do this install yourself, I encourage you to really think about it.  If you think you’re going to save money, go to the hardware store and count how many $40+ forstner drill bits you’re going to buy!  I spent a lot of money on tools specific for this installation – which is always fun to do, but it doesn’t save money.  Along with the ServoCAT, I purchased the powered ground board option.  Not content to just leave that alone, I also added the Markless heavy duty cable and connector.

Here’s the Markless Astronomics heavy duty cable connector installed on the Stellar CAT powered ground board (the included microphone-type connector is visible inside the foot)

The toughest part of the ServoCAT installation is getting the central pivot pole exactly perpendicular to the rocker box.  I used a drill guide.  I was super careful, but I still ended up a couple of degrees off, and spent an entire weekend tweaking it so I could maintain the wonderfully smooth Obession-standard azimuth motion I had before the installation.  I finally got there, but only by adding a large square of Teflon to the center around the pivot pole (between the ground board and rocker box).  The ServoCAT’s motor boxes are actually the easiest part of the installation, although getting the Spring tension screw on the azimuth engage/disengage lever inside the rocker box is tricky since it’s a tight squeeze for fingers.  I also had some trouble attaching the altitude cable to the altitude bearing – I sheared off a screw going into the aluminum bearing so had to squeeze another hole into a very tight spot.  I dodged a couple of bullets and got the installation completed.

To run power to all of these upgrades was my next challenge.  ServoCAT comes with a power box, but sure enough Markless Astronomics has a cool upgrade:  the RCPM (remote controlled power module).  It’s a power box that sits inside the rocker box, with a control cable that runs to a control box on the DSC stalk.  Flip one switch at the start of your observing session inside the box (when you’re collimating), and then you can stand up and enjoy your evening – all of the accessory power can be controlled from the remote on the stalk.  That’s slick.

The RCPM’s control box mounted to the DSC stalk – great extra features of a main power switch and an LED light switch

The control box with the perspective of the Argo Navis and ServoCAT control boxes mounted to the top of the DSC stalk

The power cables and drive motors all snake around inside the rocker box.  Charlie’s RCPM and DSC stalk kits include spolit loom to clean up the wiring.

The inside of my rocker box with the RCPM and the ServoCAT’s azimuth drive motor and gear box (and the wiring for the UTA cable) – not the prettiest wiring job, and I’m sure Charlie will groan when he sees this picture!

The last upgrade was the Markless DSC stalk.  Again, Charlie supplied a complete, clean installation kit with great instructions.  It’s a nice upgrade to have the ServoCAT controller and my Argo Navis right next to each other on the stalk.  I also love having all the wires inside the stalk and out of the way.

Here’s the DSC stalk – and peeking behind it you can see the Markless Astronomics altitude cable stop attached to the mirror box

The side view – note how I used Velcro to hold both the wired ServoCAT control pad, and the matching-in-size remote handpad control box directly underneath the wired pad – slick!

For the business end of the heavy duty battery cable, I purchased the fabulous battery box by Markless Astronomics.  Just add a battery – note the cabling, the fuse, and the external connections available.  I power my Obsession and my iOptron from the same battery box, and I have an additional 12v plug for the eyepiece dew heaters inside my Wood Wonders eyepiece box.  Werker deep cycle 35 amp hour battery (not included, of course) easily lasts an entire weekend powering everything.

3 power connections on the outside of the box

Battery connections – with fuse – inside the box

Here’s the whole set up of accessories – pictured at the 2012 Texas Star Party.  A great set of toys!

Conclusion:  As mentioned, the array of accessories available to us in our hobby is just great.  The quality of materials, instructions, and install kits from both StellerCAT and Markless Astronomics was top-notch.  While the Obession 18” is certainly a fabulous scope “as is” – the upgrades I’ve added provide convenience and utility – especially for outreach programs.  My only small criticism would be the “alphabet soup” product naming convention Markless uses for its products:  BDDB, RCPM, HDBC, SWK, etc.

For a sense of scale, here’s the installation parts all laid out in their organized bags provided by the manufacturers:

ServoCAT installation kit

Markless Astronomics accessories / installation kits

Thanks all for reading, and clear skies!

- Chris (cjcyeti)




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