Van Slyke Cover Article.e$S:Layout 1 - Astronomy Technology Today

BFO in its heyday. A variety of portable scopes were used 

to view many celestial objects at once during evening 

sky tours and for portable deployment at schools, etc. 

By Paul B. Van Slyke 

What Came Before 

When asked to write this article, I was 

hesitant because I’ve always believed that a low 

profile was in the best interest of my business 

and a quality product sells itself, without all the 

hype. That may sound counter-productive, 

from a capitalist perspective, and deserves further 

explanation. Perhaps a future article will 

include more about VSI products and my 

unique philosophy. 

I decided to accept ATT’s offer of this 

space because of two subjects I’ve been passionate 

about all my life: amateur telescope 

making and encouraging informed pro-space 

citizens. Applied properly, the former can be 

an exponential catalyst for the latter. The VSI 

website contains a slightly dated, but still topical 

article written about two decades ago and 

titled Why Space, for those who might share 

my adamant views on this astronomical subject 

(www.observatory.org/whyspace.htm). 

Many years ago, the “premier” astronomy 

magazine asked me for an article on the Black 

Forest Observatory (BFO). In my youthful exuberance 

(and ignorance), I jumped at the 

offer. To make a long story short, they sat on 

the article and never published it. Evidently, 

my viewpoint had a slant they considered inappropriate 

or simply did not support. I will 

not speculate on their agenda, but know that 

every person/organization has one, whether 

they know it or not. 

The following is not the identical unpublished 

article from long ago, but it does touch 

on the subjects others were [then] afraid to 

publish, and may still be? Unfortunately, the 

more things change, the more they stay the 

same, so I must [still] offer an abridged version 

with a more subtle persuasion. Before I tell the 

revised version of the story, an overview of 

BFO’s construction and equipment is provided, 

because that is what BFO was, and ATT 

is all about - telescopes and the associated 

equipment. 

The Facility 

Colorado’s largest observatory existed 

from 1986 to 2001. BFO, with its 18-foot 

dome and 30-inch Cassegrain, was not created 

for research. It was established to create a byproduct, 

[what I call] pro-space citizens. It was 

cut short by my need to eat and maintain a 

roof over my head - BFO was a non-profit in 

all aspects, especially for me. All I received 

from the endeavor was a giant honkin’ telescope 

which, in itself, could not sustain my existence. 

Thus, BFO finally gave way to the 

for-profit business, Van Slyke Instruments 

(VSI), but that is another story for another 

time. However, in its “heyday,” tens of thousands 

of people experienced the night sky during 

BFO’s short 15-year tenure. 

Although BFO was somewhat antiquated 

Astronomy TECHNOLOGY TODAY 33

BLACK FOREST OBSERVATORY 

BFO's warmroom/control center. 

by today’s standards, it did have all the expected 

“pomp and glitter” of Star Wars, Stargate, 

and all the sci-fi genre that people have 

come to expect from a [then] fairly sophisticated 

facility. To be honest, most of those rack 

mounts, monitors, oscilloscopes, microfiche 

rear projectors (Palomar Sky Survey, etc.), joysticks, 

lights, gauges and switches were nothing 

but “eye candy” for the public, emulating the 

vacuity of the Stargate stage sets. However, 

much of that seemingly superfluous equipment 

did actually serve a practical function in 

the operation of the facility. Our three desktop 

computers each contributed significantly, 

although only one of them actually controlled 

the positioning of the dome and telescope. The 

remaining two were for general reference, sky 

charts, etc. 

This story is also about the rambling and 

reminiscent memories of what has become a 

literal dinosaur - the Amateur Telescope Maker 

(ATM): that miniscule minority who would 

rather build a telescope than look, or image 

Get Yours 

Today! 

through it. The mainstream amateur astronomy 

community no longer designs and builds 

its telescopes from society’s discards, as it once 

did. The typical amateur today buys a go-to 

mount, a tube assembly and a CCD camera. 

We attach the mount to the floor of a suitable 

structure, the tube assembly to the mount, and 

insert a CCD camera in the hole in the back of 

the scope, enjoy a long gloat period, and flaunt 

our images to the world. How many of today’s 

amateur astronomer actually built that scope? 

Instead, a few very expensive parts are assembled. 

The ATM is dead. Long live the ATM. 

But I am not here to evaluate today’s amateur 

astronomer. With apologies to those who, like 

me, produce those high quality and relatively 

expensive parts, I am here, in part, to try and 

rejuvenate the wonderful hobby of telescope 

making by reflecting (pun intended) on my 

story of what was, and could be again. 

If you have no interest in building a telescope, 

the following will only be of passing curiosity. 

Hopefully it will be an interesting 

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the best, strongest, most 

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“read,” if nothing else. However, if you would 

like to build a telescope from the ground up, 

and would really enjoy more than a modicum 

of satisfaction from this accomplishment, you 

may help to reignite that dying spark known as 

the ATM. Of course, if you really want to purchase 

your Meade/Celestron/etc. telescope and 

just look through it for all eternity, at all eternity, 

I’ve no objection. We truly need amateur 

astronomers to support the community of 

businesses and people, yours truly included, 

who try to make a living from the mechanically 

challenged or disinterested. 

The Observatory 

Large commercial domes are expensive! 

That said, building your own from scratch, 

while a daunting task, can save much of your 

bankroll for the scope. You may say, “A rolloff-roof 

is simple, easy and adequate.” True, 

but it’s not as publicly acceptable or consistent 

with expectations as a domed observatory. People 

expect Mount Palomar, the Keck Twins, or 

better when they come to experience your observatory. 

Nothing less will satisfy! Comments 

from those who visited BFO ranged from, 

“This isn’t the Mount Palomar I expected…” 

to, “I was expecting a hut in the woods, and 

this is a real domed observatory. Impressive!” 

The dome was built by “world renown” 

mirror maker, Alan Raycraft, with very little 

[occasional] help from me. The base ring and 

ribs were formed from 1/2-inch plywood cut 

into circular hemispheres, by hand, using a jigsaw. 

The sectional flats were glued together, 

using construction adhesive, to form a rigid 

continuous frame structure. Yeah, I know what 

you’re thinking, “That’s a lot of time and tedious 

work!” But, remember what I suggested 

before, “It’s not the effort, it’s the continuing 

journey.” 

The gores were cut from 1/8-inch tempered 

Masonite, screwed and glued to the 

skeleton frame using construction adhesive. A 

conventional center split, bi-directional shutter 

was selected and built to take advantage of esthetics 

- a timeless symmetrical design. Long 

aluminum C-channel sections were built into 

the dome and dolly-type wheels were attached 

to the two shutter sections to provide easy 

34 Astronomy TECHNOLOGY TODAY


Alan Raycraft and Paul Van Slyke building the skeleton frame for 

BFO’s 18-foot dome. 

Local astronomy club members help move the dome from its construction 

site to the observatory (looking like a giant white, multilegged bug). 

opening and closing. 

The dome was lifted onto the square base 

structure with a large construction crane. Sixteen 

6-inch diameter metal wheels were attached 

to the square building. Two of the 

wheels were used in tandem, creating railroadtype 

wheel sets. In other words, two of the 

wheels were mounted on a central seesaw 

pivot, like a flotation arm, that applies even 

pressure between two of the wheels on the 

dome’s lower base ring. There is a materials 

conflict that must be noted. Metal wheels 

make it much easier to rotate the dome, but 

the metal wheels will eventually shred the plywood 

base ring. Using hard rubber wheels will 

make it much harder to rotate the dome, but 

the plywood laminate will not shred. My best 

solution was to have an 18-foot diameter, sectional 

sheet metal base ring made at a local 

sheet metal shop and attach it to the bottom of 

the dome’s base ring using wood or sheet metal 

screws. Use at least an 8 gage (1/8-inch thickness) 

sheet metal or the sheet metal will also 

eventually shred. 

After initial installation, the dome was rotated, 

by hand, using a long rope with many 

“volunteers” attached to the end. Watching 

them rotate the dome reminded me of the 

Egyptian slaves moving those massive stones 

with simple ropes and brute force…with appropriate 

music - possibly the March of the 

Slaves by Tchaikovsky. Usually I was the 

marcher, not the watcher. Eventually the dome 

rotation was motorized along with the shutters. 

A box-like bracket plate was used to 

mount the 1/2-HP reversible AC motor, a 

50:1 worm-gear reducer and a chain and 

sprocket turning a shaft, with a golf cart tire 

attached to the end and pressing against the 

dome’s lower base ring. I know it doesn’t sound 

like it would apply enough force/torque to rotate 

the dome, but it worked flawlessly for 15 

years with very little maintenance, even in 

heavy snow and ice conditions. The shutters 

were also motorized using two gear reduced 

Bodine AC reversible motors and an independent 

cable/pulley at each end of the shutters. 

If the shutter’s cables ever slipped, the 

motors could be individually reversed to resync 

the shutters. 

The Telescope 

I do not consider pushing your own glass 

a prerequisite to earning the title of ATM. 

Some may disagree. Mirror making, especially 

a large one, is a singular art requiring a tenacious 

disposition and the patience of a monk 

on a crusade. I have the utmost respect and admiration 

for the ATM who not only builds his 

telescope from scratch, but also grinds his own 



Spider and motorized secondary hub. 

mirror. However, building your own telescope, 

less the optics, requires enough skill to keep 

most of us, including myself, busy for a very 

long time. 

I personally believe that a telescope should 

not be built out of wood. Wood is for furniture. 

I’m going to get a lot of flack for this 

comment, but I think there is a lot of repressed 

support for this philosophy. I’ve built more telescopes 

in my life than I can remember, and 

they have all been metal. No Dobs and no 

alt/az mounts, because they could not track. 

Of course, nowadays many Dobs and alt/az 

RA axis with 20-inch Byers drive and 

3-motor drives. 

mounts track well via computer control. 

All my ATM telescopes were reverse engineered 

from society’s discards. Yes, all of 

them were metal, but they were fabricated 

from scrap metal - a shaft here, a tube there, 

etc. I would slow down when passing an old 

culvert lying beside the road - a possible telescope 

pier or tube? I’d spend all day at a local 

scrap metal yard, mind racing with endless 

possibilities. That was fun to me. I know, get a 

life! Do you need a fancy machining facility to 

shape these discarded metal structures to your 

needs? No, but a simple metal lathe and a 

Dec axis with 12-inch Mathis drive and 

3-motor drives. 

welder helps. However, my early telescope fabricating 

tools consisted largely of a bunch of 

files, hacksaw, and a hand drill. 

BFO’s 30-inch, f/9 Dall-Kirkham 

Cassegrain optics were fabricated, to my specifications, 

at a commercial facility in Utah. The 

30-inch, f/3 primary mirror was mounted in 

an 18-point flotation cell and the 12-inch secondary 

mirror was mounted in a spider assembly 

that provided a full 3 feet of back focus 

range with the push of a button. To clarify, 

moving the motorized secondary in or out 

from the primary changed back focus by a 



The dome rotation motor and mechanisms. 

The 30-inch Cassegrain primary and secondary mirrors before 

installation in the tube assembly. 

ratio of approximately 6 to 1. One inch of distance 

separation related to 6 inches of back 

focus change. Of course, this is a "rule-ofthumb" 

ratio. The primary mirror cell was 

heavy die-spring loaded and collimation was 

achieved by turning three large hand wheels. 

The helical, non-rotating motorized spider was 

stepper motor controlled and both were fabricated, 

from scratch, at my machine facility. 

The scope's visual back, which also doubled 

as the flotation system for the primary 

mirror, had a motorized 3-inch rack and pinion/Crayford 

custom designed focuser docked 

to it, providing a [front/rear] dual focusing capability. 

It was actually the prototype for a future 

focuser that would be called the VSI Super 

Power Focuser (SPF) - an R&P/Crayford hybrid. 

This early design finally gave way to a 

pure Crayford design that many of you may 

remember as the Monster Focuser, now also 

discontinued. 

I believe that a versatile scope should have 

secondary mirror [primary] 

focusing with a 

large secondary focuser 

docked to the visual 

back. In other words, a 

scope with only one focusing 

capability loses a 

lot of functionality, especially 

if you do visual 

and imaging with the 

same telescope. A significant 

change in back 

focus, say shortening 

your imaging train 

profile to accommodate 

a shorter 

visual/eyepiece profile, 

is much more convenient 

when you have 

dual focusing capability. 

The 3-foot diameter 

tube assembly was 

rolled from a 1/8-inch 

thick anodized aluminum 

sheet and simply 

held together at the 

seam using sheet metal 

screws. An internal ribbing structure served a 

dual purpose: providing structural stability and 

internal light baffling. Two stability trusses 

were attached to the front of the tube cradle 

and extended to the front of the tube assembly. 

Many ATMs build a telescope without considering 

the importance of primary mirror and 

tube internal diameter clearance. Even a truss 

tube can be affected by these parameters. I use 

another "rule of thumb" measurement for determining 

this clearance, which is 12 to 1. If 

you have a 12-inch diameter primary mirror, 

you need 1-inch of tube clearance between 

your mirror and your tube. A 36-inch scope 

would require 3 inches around its tube. These 

clearances are minimum - any less and tube 

currents will radiate into your parallel incoming 

light cone and deteriorate imaging quality. 

I've always preferred German equatorial 

mounts, but only if they are permanently 

mounted - counterweights can be heavy to 

transport. Except for the occasional mechanical 

flip-flop (crossing the meridian), an equatorial 

has no physical obstructions to deter 

pointing around the North Celestial Pole 

(NCP). Concerning fork mounted scopes, to 

me it is a "non-issue" to even consider it necessary 

to allow an imaging train to clear between 

your forks. I get this concern from so 

many people/clients who consider this an important 

factor that, when building an imaging 

train, they sacrifice much more important considerations 

just so the scope can point to the 

NCP unobstructed by the fork. Why? There 

are so few NCP celestial objects that would 

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The dome was loaded on the flatbed trailer before it was destroyed 

on I-25. Also shown is the crane that lifted the dome off the building. 

cause this conflict, that to even consider it a 

problem is obsessive-compulsive at best. 

The BFO mount, from the ground up, 

started with a reinforced concrete isolation 

platform, 3 feet in diameter and set about 5 

feet into the ground. A 3-foot diameter cardboard 

Sonotube worked great. A 4-inch 

ABS/PVC conduit was installed down the center 

and through the sidewall of the cardboard 

tube going to the warm-room. I found an old 

14-inch cast-iron sewer pipe about 4 feet long 

with a [12-bolt pattern] flange on one end for 

the pier, and it was free, discarded in a construction 

site. The wall thickness was a more 

than adequate 3/4 of an inch. 

The German equatorial mount was designed 

and created at a machine shop facility to 

which I was assigned at the time and primarily 

from pieces found in the scrap metal yard 

of that facility. The RA shaft was machined 

from a 3.5-inch diameter, solid steel shaft, fitted 

with 6-inch radial ball-bearings. The Dec 

shaft was a salvaged stainless steel control rod 

drive that was originally destined for a nuclear 

power plant, but was rejected. It was not radio 

active - important point! 

The RA shaft was equipped with a 20- 

inch Byers gear with a stainless steel worm and 

the Dec shaft was equipped with a 12-inch 

Mathis drive. The 12-inch Mathis drive was a 

little undersized, but, as noted before, when 

you are scrounging for parts, they are not always 

a perfect fit for the application. The 

worms were connected 

to three independent 

motor drive systems: a 

synchronous motor for 

simple tracking, a pair 

of stepper motors for 

tracking and variable 

speed slow motion 

control for pushbutton 

centering of objects in 

the field of view, and a 

pair of matched DC 

servo motors with 

tachometer feedback 

and closed-loop digital 

IC velocity controllers 

with ramping that provided 

tracking, slow motion and fast slewing 

with 5 inch-pounds of torque from 3 to 5000 

rpm. All three motor systems were mechanically 

connected via cog pulleys and belts to a 

common shaft that drove the worm gears in 

both axes. The stepper motor and the DC 

servo motor shafts rotated freely when off, and 

the synchronous motor had an automatic 

built-in magnetic clutch that disengaged the 

motor shaft when not running, so there were 

no motor engaging conflicts along the common 

motor shaft. When possible, I have always 

preferred to build redundant versatility 

into my scopes. 

Scope movement and positioning were 

available from a hand paddle at the scope, a 

joystick controller platform in the warm-room, 

or by computer. All three motor control systems 

were available at each control station - 

again, redundant versatility. The acronym for 

the computer control positioning and dome 

sync was “OTIS” (Observatory Telescope Interface 

System). A friend and I wrote the program 

in Basic Pro v4. After many code 

changes, we finally achieved a final operating 

version and compiled the open code. It worked 

well for years, but the software and hardware 

interface was built as a one-off proprietary system 

that was specifically designed for the DC 

servo motors and controllers that I acquired at 

a local electronics surplus store. These hardware 

motor controllers were surprisingly adequate, 

considering they were never actually 

designed to be computer interfaced in the first 

place. 

The End of BFO 

BFO’s 30-inch scope and 18-foot dome 

were sold, long after Van Slyke Instruments 

had become a viable business. I eventually decided 

that I am only one person and VSI alone 

had become a virtual 3-man operation: me, 

myself and I. It was difficult to make a decision 

to liquidate an effort that consumed 15 

years of my life. What really helped me accept 

the loss was my mental and physical condition 

at the time. I was totally exhausted from years 

of trying to maintain both businesses myself. 

At the time, the end of BFO was a relief. 

The scope was sold, dismantled and carefully 

packed in the buyer's truck. It is becoming 

operational again at a much better location 

at an elevation of over 9000 feet on the west 

side of Pikes Peak, still in Colorado. The dome 

was a different story. When the dome was 

lifted off the observatory building, it was split 

in two half hemispheres (it was designed that 

way) and loaded on a flatbed semi-trailer for 

its journey south. On its way down I-25, the 

dome sections caught a good head wind and 

[both] were launched off the back of the semi, 

tumbling down the middle of the freeway. 

Needless to say, they were demolished. Small 

pieces of dome were scattered along the highway 

for miles. The highway patrol was not 

happy with the mess either. Luckily, the dome 

was insured and no one injured. 

Of course the big hole in the center of the 

remaining building was a problem, so I had a 

framing crew build a pitched truss roof on the 

structure making the building whole again. 

My wife and I installed a nice drop ceiling, 

with lighting, and the old BFO is once again 

a viable structure supporting VSI. The lower 

building structure is now VSI's new office, 

shipping and receiving, storage and product 

warehouse. 

BFO's Educational 

Space Mission 

To return to our opening commentary 

and space, BFO's educational mission was to 

encourage pro-space citizens - to promote 



After BFO. VSI's new office, etc. 

space exploration by sharing a sense of personal 

connection to space. Our sky tours were offered 

to all, from school children to senior 

groups. We also traveled to schools with telescopes 

offering daytime solar programs and 

provided accredited in-service courses to K-12 

teachers with hands-on telescope experience. I 

even taught astronomy at the University 

of Colorado under an honorary teaching 

position. 

Initially, my most difficult challenge was 

how to overcome cloudy nights at the observatory. 

Eventually, I found an effective strategy 

for parting the clouds, both day and night. 

Was it divine intervention? No, just practical 

application and some techno-magic. Scheduled 

sessions were never weather dependent 

after this epiphany: I simply installed a small 2- 

inch monitor at the focus point of the eyepiece, 

and connected it to the 30-inch 

telescope like a regular eyepiece. At first, I 

didn’t think the plan would work, as children 

are not easily excited or impressed. We didn’t 

try to fool them into thinking it was the real 

thing in real time, but visitors were able to step 

up to the eyepiece, look “through the telescope,” 

and see whatever the computer wanted 

them to see. Turned out, everyone loved the 

idea. Even though they knew it wasn’t “real,” it 

provided a hands-on and engaging experience. 

The above, and other observatory “magic,” was 

designed to provide the sense of connection to 

space necessary to creating those pro-space citizens, 

not from sci-fi special effects magic, but 

from real magic - the catalyst created from 

knowledge and truth. 

The extended “space mission” of BFO 

was to provide a meaningful context for public 

consideration of issues relating to our connection 

with space (again, see Why Space for 

more) - for consideration of such questions as: 

Did our government mistake the wishes of 

[now] almost two generations of planet earth 

dwellers? Oh, we returned to space, but why 

did we need to return to anything? Why did 

we ever leave in the first place? After Apollo, 

the shuttle was developed, but its initial charter 

was to deploy dozens of military spy satellites 

to orbit before NASA could even begin to 

do any pure science and to develop space. Was 

NASA’s peaceful, scientific development of 

space deferred by the military? After all, the 

military had their own independent rocket 

program and could put spy satellites into orbit 

all day long. Was it governmental “bean 

counter” strategy that forestalled human exploration 

of space? Were our representatives, 

from both parties, appropriately considering 

our long-term space interests? And finally, did 

we needlessly spend over a billion NASA dollars 

just to find out that the space plane wouldn’t 

work? Is our Constellation space program 

going “back to the future” simply by readopting 

Apollo-like applications? Obviously, I have 

definite opinions on these matters, but offer 

these questions to better explain the range of 

bigger-than-Earth issues BFO was designed to 

encourage the consideration of, regardless of 

individual conclusions reached. 

My rhetorical questions are meant to be 

constructive, not to criticize or “point fingers” 

at anyone or any single organization. Nor are 

they intended as partisan. I simply maintain 

that, as a species, we can’t afford many more 

30-year delays in our space efforts. We may 

outgrow our home planet before it happens, 

but most of us who study astronomy know 

that the habitable “lifespan” of this planet is finite. 

However, the universe is, by comparison, 

infinite, with every star potentially orbited by 

habitable planets - there are enough extra-solar 

rocks out there for each of us to have our own, 

if we’ll only go. Think large! Is this the appropriate 

“place” for this discussion? Probably not. 

But, I hope I am talking to a receptive choir? 

If you own a telescope, you have all the tools 

you need to encourage in others a meaningful 

and real connection to the cosmos - especially 

when you create those tools with your own 

two hands. “The planet is in your galaxy.” 

As always, thanks for your continued 

support! 

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