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Build Your Own EV Telescope Focuser

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What is a "Build-Your-Own" EV Focuser?

The Event Horizon Focuser (EV) is completely modular allowing us to offer customers a custom model where you can pick and choose which options are desired.  You can choose one of our six regular models (EV-1n, EV-1c, EV-2n, EV-2c, EV-3n or EV3c) which have a fixed design or you can design your own custom EV focuser which we will build to order.  If you were to exactly match one of the six regular models when picking options, the cost would be slightly higher since the build-your-own version is more costly for us to produce.  However, you have complete flexibility in creating a focuser that fits your needs and desires.  Just follow the steps below to create the codes for your special-order focuser.

"Build-Your-Own" JMI Event Horizon 2" Focuser

Print this page in landscape mode.
Select your options one-by-one in the steps below.
See the Focuser Comparison Chart for EV focuser specifications not mentioned here.
Standard focusers can be found on our Event Horizon Focuser page.
Place your order using the custom code generated using this page.
Add any other accessories you wish to purchase from the Event Horizon Focuser or Focuser Accessories Pages.

Select a code in the chart below to see a picture of that part.  For example, if you select "20" in the Drawtube section, you will see a picture of the 2.0" length drawtube.

To purchase a "Build-Your-Own" EV focuser using the Shopping Cart, select ONE "Buy Now" link for each OPTION.  In effect, you will be inserting ONE line in your shopping cart for each OPTION as if you were writing in a code for each box.  This page is NOT for buying individual parts.  You must select something for each option.





Available Codes with Descriptions

Standard Modular Body



  B = Specifies the "Build-Your-Own" Custom Version of the Event Horizon 2" Focuser



N = Newtonian or Generic (mounts on a surface from flat up to a radius >= 7.25")
C = Standard Cassegrain (mounts on standard 2" diameter Cassegrain threads)
L = Large-Format Cassegrain (mounts on 3.25" diameter Cassegrain threads)



20 = 2.0" Drawtube Length
25 = 2.5" Drawtube Length
30 = 3.0" Drawtube Length
46 = 4.6" Drawtube Length
57 = 5.75" Drawtube Length
Please see the chart below for more related spec's,
such as drawtube travel.



D = Dual Speed with Dial Indicator (0.064" and 0.58" of Travel per Revolution of Knob)
S = Single Speed (0.58" of Travel per Revolution of Knob)
Pusher Bearing



P = Pusher Bearing (extra pressure on the drive shaft/drawtube for 8 lbs lifting power)
Q = No Pusher Bearing (the focuser will only lift 5 pounds without the pusher bearing)



R = Rubber-Gripped Gold
A = Knurled-Aluminum Black (not available with dual-speed drive)



M = Motor (motor control using a hand unit or computer)
K = Manual (manual control using the knobs)
First Output Adapter



E = 1.25" Eyepiece Adapter
T = 1.25" Eyepiece Adapter with T-Threads
H = SCT Threaded Output Adapter (duplicates standard 2" diameter SCT threads)
Z = None
Second Output Adapter



E = 1.25" Eyepiece Adapter
T = 1.25" Eyepiece Adapter with T-Threads
H = SCT Threaded Output Adapter (duplicates standard 2" diameter SCT threads)
Z = None

* 4.6" Drawtube recommended for Lunt LS60T H-alpha Solar Scope and 5.75" Drawtube recommended for Explorer Scientific (ver 1 & 2)


You should end up with a 11-character code that includes all the options you have chosen.  This code should be entered as the description of your focuser.  For example, a custom EV focuser with the following options:

Newtonian (Generic) Base
3.0" Drawtube Length
Dual Speed Drive with Dial Indicator
Pusher Bearing Included
Rubber-Grip Knobs
1.25" Eyepiece and T-Thread Adapter

will have the following custom code:










and would have the following:

Part Number:  EVB  (will be the same for all "Build-Your-Own focusers)
Product Description Code:  BN30DIPRMTZ  (will vary according to the options you choose)

Model Number   Part Number   Description
EV-B EVB Build-Your-Own EV Focuser Code BN30DPRMTZ

Please specify a separate part number (as you normally would) for any other accessories such as:

Backup Plates

EV-LS Upgrade
EV-75 Upgrade
EV-VMC Upgrade
Extension Tube
Digital Readout (DRO)

Before you complete your order, please double check your codes!

We hope you enjoyed designing a special focuser just for YOU!  You will receive a fully assembled built-to-order focuser based on your custom specifications.

Drawtube Specifications
  Newtonian (Generic) Base Cassegrain Base**
2.0" 3.0" 2.4" 0.60" 0.2" 3.0" 2.4" 0.6" 0.0"
2.5" 3.5" 2.29" 1.21" 0.81" 3.5" 2.9" 0.6" 0.0"
3.0" 4.0" 2.19" 1.81" 1.41" 4.0" 3.4" 0.6" 0.0"
4.6" 5.6" 2.19" 3.41" 3.01" 5.6' 5.0" 0.6" 0.0"
5.75" 6.75" 2.19" 4.56" 4.16" 6.75" 6.15" 0.6" 0.0"

* Penetration is measured from the lowest point of the base and will be correct for flat-surface mounting.
If using the base on a curved surface, the penetration measurement will be longer (see picture below).

** The standard drawtube length for Cassegrain telescopes is 2.0".  Longer drawtubes increase the maximum
extension and minimum height but do not increase drawtube travel and cannot penetrate inside the telescope
when using the standard Cassegrain base.  The large-format and extra-large-format bases will allow penetration.

Option Codes Listed Alphabetically

##  =  Drawtube Length (various)
A  =  Knurled-Aluminum (black) Drive Knobs
B  =  Specifies the "Build-Your-Own" Model (EV-B)
C  =  Cassegrain Base (standard 2" diameter thread
D  =  Dual-Speed Drive
E  =  Eyepiece Adapter (1.25")
H  =  SCT Threaded Output Adapter ("to Hang SCT accessories on the back of the focuser")
K  =  Manual Control using Knobs (no motor)
L  =  Large-Format Cassegrain Base (3" diameter threads)
M  =  Motorized (includes hand unit)
N  =  Newtonian (Generic) Base
P  =  Pusher Bearing
Q  =  No Pusher Bearing ("Quit pushing")
R  =  Rubber-Gripped (gold) Knobs
S  =  Single-Speed Drive
T  =  T-thread and Eyepiece Adapter
X  =  EXtra-Large-Format Cassegrain Base (4" diameter threads)  OBSOLETE
Z  =  No Adapter (Zero)