Markless™ Astronomics

Accessories for Big and not-so-Big Dobs

  1. Field Battery Box Kit by Markless™ Astronomics
  2. Basic Power Kit by Markless™ Astronomics
  3. Heavy Duty Battery Cable Kit by Markless™ Astronomics
  4. UTA Power System by Markless™ Astronomics
  5. UTA Power Cable by Markless™ Astronomics
  6. Typical Power System for a Truss Tube Dob Telescope



Field Battery™ Pack Kit (FBK-U1).

Here's an economical way to construct your own 30 AH 12 VDC battery pack for the field.   This kit consists of a wired Battery Box which is sized to contain a U1 size battery to connect to your telescope's 12 VDC power cord or cable.   The battery shown in the above photograph is a Werker, Model WKDC12-33J, 33 AH, 12 VDC battery and is NOT included in the kit.   Another battery which fits the battery box is the Xtreme U1 Deep Cycle Battery - Model SLIU1DC.   It is 31 AH, 12 VDC.   Check with Batteries Plus in you locality or online for both batteries.

This is a nice size for telescope use!   A U1 30 AH deep cycle battery weighs only about 25 lbs., much less than typical automotive-sized deep cycle marine batteries, and is about half the size of a typical car or deep cycle battery.  The box internal dimensions are 8 x 5 1/4 x 7 1/2 (inches).

Get this kit and supply your own battery and charger for a lot less than most self contained 30 AH battery packs that have more features than you probably really need or can use.   To complete the battery pack you are going to need a charger capable of charging at a rate that is not too great for the battery, but high enough that it does not take two days to charge.   A charger that seems to fit the bill is the Schumacher SC-600A.  It is a "smart charger" and has three different initial charging rates: 6 - 4 - 2 amps.   I think that the 6-amp rate is too high, but the 4 and 2 amp rates should be fine.   Do a search and read about it on line.   I found them at Walmart for ~ $29.

NOTICE!   This is a kit.   The user is responsible for its final assembly, setup, and use of all components in a safe manner.   Markless Astronomics is not responsible for the proper connection, use, and/or maintenance of your battery and/or charger.

There are several FBK-U1 kit models available.   Here are the Introductory Prices:

  • FBK-U1-APP       ..... $40.00   Comes with Anderson Power Pole SB-50 connector.   Mates with Markless Heavy Duty Battery Cable (HDBC) [click here].
  • FBK-U1-AUTO   ..... $42.00   Comes with a dual Auto Accessory Socket (Auto).   Mates with ServoCAT PGB power cable.
  • FBK-U1-BOTH   ..... $68.00   Comes with both APP and Auto connectors.
  • Optional Voltmeter ..... $20.00   Installed in lid with on-off switch, measures 2.5 to 30 volts; check your battery voltage under load.

  • Write for Shipping and Packaging costs and include your shipping address.   Please email for S&H to AK, HI, PR, and ROW.


    Also available are FBK-24 and FBK-27.   FBK-24 utilizes a Group 24 box.   FBK-27 utilizes a Group 27 box.   Please add $8 additonal to the prices to cover the larger battery box.

    This kit is great for use with any big Dob having a Powered Ground Board.   It also is great for tripod supported telescopes requiring 12 VDC.

    Each box is fused with a 10 ampere in-line fuse that lies across the top of the battery for easy access.

    Email me at cs(at)marklessastronomics dot com to order.   North Carolina residents, please add 7.25% sales tax.

    Charles Starks, Charlotte, NC




    Basic Power™ Wiring Kit for Dobs (BW1).

    Do you have a big Dob with an on-board 12VDC battery that needs wiring?   This kit may be for you.

    The kit (BW1) includes:

  • Markless Battery Bracket (click here to see details)
  • Markless Fused battery cable (FB1)

    The Battery Bracket can hold a battery that is up to 2.6” thick. That means typically, it can hold a 7.5 or 10.5 AH 12 VDC sealed battery.   Write me for a link to batteries of that size.

    The fused battery cable is made from heavy duty #16 zip cord, Anderson PowerPole connectors, aluminum mounting bracket, Faston T2 terminals, in-line fuse, and gold-plated RCA Phono plug.   The Powerpole connectors ensure that you do not have to exercise the fragile terminals on your battery.   If your battery requires ring terminals to connect to it, that can be accommodated.   The length of the cable is user determined, however I can assist you in determining its length.

    The Basic Wiring kit (BW1) is priced at $48 plus $7 shipping and handling via USPS Priority Mail.   North Carolina residents, please add 7.25% sales tax.  

    Recently, Mike from Washington installed the BWK, FCS1, and DB4S2 on his Obsession 15 Classic, and wrote of his experiences...


    Just wanted to let you know all of my electronic gear arrived and I was able get it mounted and running on my OTA. It was certainly worth every penny to have something that is well designed and works well. I could have spend hours sifting through electronic stores and not have come up with anything nearly as functional. In the near future I plan to get power to my UTA-I know where to look for what I will need.


    Other Markless accessories (not included in the BW1 Kit) that may be of interest (click on links below to see product and pricing).

  • Fan Connection & Switch Kit (FCS1 or FC2S1)
  • Power Disti-Bar (DB5/f) with fused jack for Argo Navis Power
  • Markless 4-foot RCA Phono cable to connect the DB5 to the base of a DSC Stalk
  • Markless 3-foot Phono cable for FCS1 connection to DB5.
  • Spider Wiring Kit (SWK)
  • Powered Truss System (PTS) (for Obsessions only)
  • DSC Stalk II

    Email me at cs(at)marklessastronomics dot com to order.

    Charles Starks, Charlotte, NC




    Markless Heavy Duty Battery Cable for PGB equipped Dobs

    features Anderson Power Pole connectors, #8 AWG copper wire for the main cable, and a much lower total resistance than a #18 gauge cable.   Anderson Power Pole connectors have been used with amateur radio operators’ equipment for many years and are a mainstay.   They are polarized, snap together, and form very secure, low resistance connections.

    There are three major parts to the package:

  • A 13-foot long main cable, (MC-13),
  • A short #10 AWG load cable for the powered ground board (PGB), (LC-18), and
  • A short #10 AWG source cable for your DC power source, SC-18.

    The purpose of the cable is not to boost the current carrying ability of the battery cable (which it does, but isn’t needed), rather it is to reduce the resistance and accompanying voltage drop of the telescope’s input battery cable when used with high current devices.

    All electrical wiring has a voltage drop equal to the current flowing in it multiplied by the total resistance of the wire.   The resistance of the wire is a factor of the metal used, its diameter, its length, its temperature, and the frequency of the signal on it.   In this case, the “signal” is direct current (12 volts DC).   All things considered, #8 AWG wire has 1/10th of the resistance of #18 AWG wire and, consequently, 1/10th of the voltage drop.

    The Heavy Duty Battery Cable typically runs from a 12 volt DC power source (e.g., a large battery) to your telescope’s Powered Ground Board.   It connects in parallel to your existing XLR connection wiring.   You do not remove the XLR wiring from the telescope, or disturb it.   See the accompanying photograph.   Once the HD Battery Cable system is installed, it is used in lieu of the XLR wiring, which is still present and can be used as a backup system.

    Who should get this kit?

  • Do you run a laptop from your telescope’s external power source through a DC-DC converter?
  • Do you have a ServoCAT installed?
  • Do you have multiple fans?
  • Do you have at least two dew heaters running?
  • Do you want a cool-looking, heavy duty battery cable?

    If you answered ‘yes’ to several of these questions, especially the first one and last one, you could benefit from the Heavy Duty Battery Cable.   Here’s why. Most DC-DC converters are designed to shut down if the input voltage to them falls below 11 volts.   Your 12 volt DC battery starts out at about 12.8 volts when fully charged.   After just an hour or two, the voltage may drop as low as 12.4 or even 12.2 volts.   When your telescope is running full tilt and a laptop is accessing its hard disk drive, the total current from the battery can reach as high as 4 to 7 amps.   The typical resistance of a #18 AWG copper wire power cable is close to 0.2 ohm. When coupled with other resistances in the power circuit (connectors, power pick-up devices, and other wiring) the total resistance easily approaches half an ohm, or more.   The total voltage drop across the total resistance can be as much as 2 to 3.5 volts.   Simple math tells you that the voltage seen at the load can drop below 11 volts and your DC-DC converter will cut out.   Prior to installing a Heavy Duty Battery Cable on my telescope, I experienced permanent failure of a DC-DC converter which had repeatedly cycled on and off.   Depending upon your brand of laptop, you may also hear an annoying “bee-boop” each time the converter cycles off and on.

    You may experience frequent variations in cooling fan speed as evidenced by the changing pitch of the fans when the voltage falls and rises due to the varying current flowing through the power cable.   The Heavy Duty Battery Cable cannot completely eliminate that condition due to other resistances in the power circuit, but it can help reduce it.

    As always, only the best materials have gone into this Markless Astronomics product.   The HD cable is made of tough materials and the cable itself easily can withstand trampling at star parties and the like.

    Other terminations and lengths of the Source Cable (SC-18) are available for your 12 VDC power source.   Contact me for assistance or to order: cs(at)marklessastronomics dot com

    Price: $90 plus $10 S&H, includes one each: MC-13, LC-18, and SC-18.   Can be added to any ground board equipped with the Powered Ground Board (PGB) option from StellarCAT.

    Additional cables:

  • LC-18 $20 plus $6 S&H
  • SC-18 $20 plus $6 S&H

    North Carolina residents, please add 7.25% sales tax.

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    Markless UTA Power System

    Introducing a UTA power system especially for the Obsession classic telescope and other big Dobs.   This system has two cables.   One goes inside the rocker box. The other goes outside the rocker box and up to the UTA. They are connected together with a feed through RCA coupler mounted on the front transom of a classic rocker box (RB). The system typically would connect the Power Rail of a ServoCAT system or a Markless Astronomics Distribution Bar to a dew heater controller on the UTA, such as the Big Dob Dew Buster.   See the accompanying photo for details. Write for a wire routing drawing.


  • Two cables, black twin cord, #16 gauge wire, Gold plated RCA plug on each end, covered with heat shrink tubing.
  •       Inside RB Cable, with In-line AGC 5 amp fuse and fuse holder
  •       Outside UTA Cable (non fused)
  • Feed through RCA Phono Coupler and mounting bracket

  • Price $55 plus $6 S&H, depending upon location.   North Carolina residents, please add 7.25% sales tax.   Please email me to order. cs(at)marklessastronomics dot com.

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    Markless UTA Power Cable

    Introducing a UTA power cable especially for the Obsession Ultra Compact (UC).   This cable typically would connect the Power Rail of a ServoCAT system to a dew heater controller on the UTA, such as the Big Dob Dew Buster   See the accompanying photos for details.


  • Black twin cord, #16 gauge wire, 8 ft.
  • Gold plated RCA plug on each end, covered with heat shrink tubing
  • In-line AGC 10 amp fuse and fuse holder

  • Price $26 plus $6 S&H.   North Carolina residents, please add 7.25% sales tax.   Please email me to order. cs(at)marklessastronomics dot com.

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    Great Astro Links to other fine products and ideas:

    Astrocrumb Filter Slides - a "MUST HAVE" accessory for your Big Dob. Roger builds 'em RIGHT!

    Obsession® Telescopes - by Dave Kriege - Heirloom Grade Telescopes for the discriminating astronomer



    Copyright 2003-2015, by Charles Starks, Charlotte, NC, All Rights Reserved

    Updated: 10:31 PM 04/21/2015