"The Mod Squad"

Modification list

As good as the scope was when I got it, as with any Richberg scope, there are a number of things I wanted to tweak and modify.

Many of these changes had to be done with the mirror removed, since they required work on the mirror box or rocker box.  This was a "non-trivial" undertaking, since this is a 70 pound chunk of glass that fits pretty snugly in its cell.  I wonder if this is the first time the mirror has been out of its cell since 1995???  I cleaned the mirror when I had it out (a long garden hose rinse, followed by distilled water rinse and blotting with surgical cotton balls), and verified that it was in fact not in dire need of recoating, despite the fact that the current coatings are over 10 years old.  For the week that the mirror was out of the scope, I stored it in its shipping box (see below)

  "Shipping in the "Age of Innocence" -- it seems hard to believe in this age of using multiple layers of 3" insulation foam to package our mirrors, but this large and extremely heavy package made it safely at least from California (QSP Coaters) to Pat Rochford in Alabama, and may have gone to and from Pegasus Optics as well.  The box has a scant 1" of moderate density styrofoam on the bottom, and four layers of thick cardboard-- without any foam-- on the top!  I'm not even sure I'd use this as an inner box these days.  Possibly shipping wasn't as automated and rough in 1995, but I doubt it, since I had a desktop computer destroyed the year before in a coast-to-coast shipment. 

1.  "Fail safe" latch cord to keep the assembled scope from falling out of the rocker box during transport

This was my first mod-- a "dead man" rope clipped from the mirror box to the rocker box to avoid any possibility --however slim-- of the 'scope structure falling out of the base when I wheel it into and out of the garage fully assembled.  (It doesn't appear to be needed, but better safe than sorry is my motto!)

2.  Mounting larger pneumatic wheels and longer handles to replace the small hard plastic wheels previously used on the scope.  I opted for wheels with an 8" hub and ~13" outer diameter.  These should be plenty large enough for rolling the scope around on the ground, and will make it easier than the 6" hubbed wheels on Natasha when it comes to pushing this scope up the ramps and into my van.  (Every little bit helps when you're pushing 250 pounds uphill!)

I purchased another set of wheelbarrow handles and overlapped them with the current set, making each handle a full 80" long-- more than is standard for this size, but the longer handles increase my leverage.  I also mounted the wheels high enough that the scope can be used on level ground without removing them. (The previous version-- the rigid lawnmower wheels-- had so little ground clearance that observing with the handles attached was nearly impossible.) 

Note that I angled the handles down towards the rear of the scope; this allows me to get the lift the rear of the scope relatively high (to depress the front for moving the assembled scope into my garage) without having to lift the handles above my waist, and also gives me a reasonably strong position for leverage in heaving the scope up the ramps into my van.

3.  This view also shows an early (pole not yet cut to size) version of the base I made to let me affix the laptop/accessory tray I'd made for "Natasha" to this scope.  I opted to attach this to one of the barrow handles rather than drill into the scope.  I find an on-board tray indispensable for placing eyepieces, observing notebook, etc. on even if I am not planning to use a laptop that session.  As with Natasha, this tray can be easily lifted off the pole (and is for wheeling the scope into the garage) or rotated to differing positions during use.

4.  Modifying the ramps that came with the scope, to make them effectively wider and to make the rails along the outer edges higher to keep the scope from falling off halfway up or down.   I obsessed more over getting this right than anything else, since all of the other issues are at the end of the day minor performance issues, but getting the scope off-track when taking it out of the car would likely result in it falling 2 feet to the ground-- a true disaster!  My design philosophy was to try to come up with something virtually foolproof, since I would conceivably be faced with loading the scope into the van some night at 0300 in near-zero temperatures and when exhausted after a lengthy observing session. 

The biggest risk was actually faced in the process of unloading the scope, not in loading it.  I created a wooden template (see photo below) that can be used to set the spacing of the ramps top and bottom, and if I ensure that the wheels are lined up before pushing the scope up the ramp, the side rails I made will keep it on track.

However, when unloading the scope the mirror/rocker box combination is large enough that I can't see the wheels, making the very real risk that I could pull the scope out of the van sufficiently off-track to send it toppling to the ground.  I played around with making wooden "chutes" and "guides" to center the wheels on the ramp head if it was off-course, but any that were large enough to work were large enough to catch on the scope when it was being lowered, too. 

"I get by with a little help from my friends"  I was still playing around with various schemes, wheeling the bare rocker box into and out of the van, when a neighbor came over to chat.  He first suggested bringing a mirror to help me see the wheels-- which I mentally pooh-poohed-- but then quickly amended his idea to that of trying to use the van's rear-view mirror for this purpose.  By trial and error I found a position that would in fact allow me to see one of the ramp tops-- the left one-- and wrote the exact directions on how to set the mirror to this location onto my spacing template (see above).  I'd still rather have someone around to eyeball this before I "take the plunge" and pull the scope out of the van, but at least now I've got a way to do it solo as needed.

I removed the low (~3/4") ridges Pat had put on the top outer edges of each ramp; not only were these useless with the larger wheels, but taking them off made the ramps nearly 2" wider.  I put side boards on the outside of each rail, and set the template's spacing to a width that means that the scope cannot run off the inner edge of one ramp even if it is rubbing against the outer edge of the opposing ramp. 

The ramps-- you can see an early version of the "mini ramps" used at the top to ease unloading the scope

Another view of the ramps and scope

Just fits! The ramps have a scant few inches of clearance behind the van's rear door.

5.  Mounting a finder scope -- the Tuthill Super-80mm previously housed on Natasha-- to supplement the Telrad, since the previous owner had removed Pat's original finder.  This was done, and aligned coaxially with the Telrad. I've always been partial to 80mm finders... here' a scope that's actually large enough to warrant having one as its' finder!

6.  Flocking the mirror box and secondary cage with Protostar paper, since the original surfaces were somewhat dirty and don't seem as black and non-reflective as they can be. (In fact, they are somewhat shiny.)  I used nearly six 20" x 30" sheets of Protostar paper on all of the various surfaces of Brutus

The pre-flocked mirror box             Box with bottom side flocked.

Secondary cage with some flocking applied to interior opposite focuser

As with Natasha, I found that a thin strip of flocking paper affixed to the part of the truss tube facing the interior of the scope cuts any glare from the tubes.  In this image, you can also see the flocking paper applied around the rim of the mirror box.

7.  Adding a "Cat's Eye" reflective triangle to the primary mirror so that I can use the Cat's Eye Cheshire collimator and Infinity autocollimator.  I opted to leave the paper hole reinforcement ring Pat had in place as well, since it was stuck on securely and gave good alignment results.  ("If it ain't broke, don't fix it!")

8.  Labeling the upper cage/truss tube mounting hardware to facilitate setup and consistent collimation.  A trivial tweak.  In theory these Obsession-style upper connectors should be able to be mounted permanently on the secondary cage, but in practice this won't work in this case.

9.  Adding fans to the mirror box to supplement the two rear-mounted 50mm fans.  This entail adding four side/corner-mounted 80mm low vibration fans to break up the boundary layer, mounting each on closed cell foam and securing it by elastic cords to boards I mounted in each corner of the rocker box.  I used some spare Protostar flocking paper to cover the wiring and labels on each fan, and used some of the paper --stuck to itself-- to make baffles  on the top and sides to prevent the air from re-circulating and reducing the efficiency of the fan.  (Bryan Greer talks about this at http://www.fpi-protostar.com/bgreer/miscpages/fanselect.htm). 

I opted not to replace the two small rear mounted fans for a number of reasons: 

a) my replacements-- 120mm "Panaflo's"-- turned out to be higher in vibrational intensity than I'd expected,

b) putting a larger "footprint" of fans in the back would reduce the amount of light baffling I could apply to the rear of the mirror box,

c) tying into Pat Rochford's setup allowed me to run the side fans automatically and to control the rear ones by the toggle switch he had installed.

d) adding larger fans probably wouldn't make any difference in cooling the mirror, since blowing air on one face of a 70 lb piece of glass is not likely to be very effective at cooling it.  Better to just realize the mirror will remain warmer than the ambient temperature and deal it by continuously "washing" away the boundary layer as it forms.

Fan on left has been flocked, one on right has not               Making "baffles" out of folded over flocking paper

A safety modification-- putting reflective tape on the electrical cord and scope handles.

10.  Making larger collimation knobs to increase precision and accuracy when collimating.  The larger the diameter of a circle (or star, in this case), the finer the rotational movements possible. 

11. Adding a baffle at the back of the mirror cell to block the ubiquitous light pollution in my sidewalk observing site from entering the light path.  This was a sheet of black foam core board, attached to the rocker box with velcro.

This shows both the rear baffles and larger collimation knobs

12.  A 10" off-axis mask

By masking the secondary mirror and spider vanes with black foam core board, I can make this 24" f/4 scope into an unobstructed aperture 10"/f9.6 scope.  I look forward to playing around with this-- it should be a real "refractor killer" for planetary observing!  I'll experiment with each of the four unobstructed quadrants to see which gives the best views.  (I understand that mirror figure varies enough that one portion of the parabola might be the "sweet spot" for this application.)

  Update:  I tested the off-axis aperture mask, and was rewarded with my sharpest and cleanest split ever of the "E" and "F" stars in the Trapezium of M-42.  Mars also showed more observable detail than it had for a full two months prior.  See the 12 Jan. 2006 entry of 2005 Mars Observations for more detail.  (Later Update:  other nights have yielded more ambiguous results.  Sometimes "more light is better" even when the seeing is not that good and you'd expect a sub-aperture mask to excel.  Very interesting...)

13.  Making a more convenient way of getting "half steps" on a stepstool or stepladder

I toyed around with how I might modify my existing stepladders to add 'half steps' between the existing ones to deal with those times when the first step is too low but standing on the second one requires the observer to crouch a bit.  I eventually decided that, since I already had two step ladders that differed slightly in riser height, I could accentuate this by cutting one of them down to make them fully a half-step out of synch.  The one on the left below has been modified-- notice how its first two steps bisect the lower step of the battered old ladder on the right in height.  That means that I now have good alternation of height between the lower two steps of each ladder--which is all the lift I need to see through the eyepiece at zenith.  (I'll probably buy a standard 4 step ladder so that those shorter than 6 foot can use the scope at all viewing angles.) 

I've always believed in putting anything I could find onto the bottom of my step ladders to increase the size of the footprint and minimize the tendency of the legs to sink into soft ground.  The large wooden pads on the ladder on the right work wonderfully for this, but going to a similar scheme on the other ladder would prevent it from being folded closed.  In the vein of 'waste not, want not' I therefore took the stubs I had cut off of each leg and mounted them sideways onto each leg, taking care not to prevent the ladder from closing.  Not perfect, but it should help considerably in keeping the legs from sinking into the soil.

The modified stepladder  Close up of the feet       And it can still be folded closed!

14.  Using my Sky Commander "Flash 4" model Digital Setting Circle unit.

The unit had 4000 tick encoders installed; I did not purchase the DSC controller that came with it, preferring to use my nearly new Sky Commander.  I have had abysmal luck getting the unit to work-- there appear to be "issues" with the altitude encoder.  The azimuth encoder appears to be permanently affixed (a plate is welded to the bottom of the ground board), so replacing it would be "iffy".   Laying the DSC flat on its back results in putting the display at an angle that is difficult to see from the eyepiece, nor does the unit "stand up" at a good viewing angle if laid on its side.  I therefore made a wedge of wood and put clear caulk on it to make it grip the 'scope accessory tray.  It holds the DSC at a good viewing angle.

"Sky Commander" on my homemade wedge to optimize the viewing angle

Maintenance items done:

Graphite everywhere: While the weight bearing surfaces were unloaded, I put powdered graphite on the Teflon pads for both altitude and azimuth motion.  I also beveled the edges slightly on the altitude Teflon pads to reduce stiction.

Truss tube bag:  Now that the truss tubes have black velvet sections that I'd like to preserve in their pristine condition, keeping the tubes clean when the scope is transported became an issue.  Fortunately, tubes fit-- more or less-- in the Astrosystems bag I had purchased for Natasha's tubes and only used once.

"Unplanned" modifications/repairs that arose during overhaul

Realigning mirror triangles.  When I removed the primary, I noticed that one of the triangles of the mirror cell had detached from the plastic retaining ring that holds all six triangles in position.  (see image below and left)  This meant that the cell was not providing uniform support, even though I was still impressed by the image quality.  I used a T-square and ruler to align all six triangles afresh, and taped them down (see image at right) prior to re-gluing the plastic retaining ring.  (As an aside, I find it funny how many people are obsessive about eking out an extra 1/100th of a wavefront accuracy when using PLOP to design a mirror cell-- only to assemble the components in a cavalier fashion that degrades the cell accuracy well below a non-PLOP optimized one!) 

Replacing set screws controlling truss tube height.  The original design featured short wood screws drilled within each split wooden block to ensure that each truss tube could only be inserted to a specific depth.  The problem was that these screws had loosened up-- allowing some of the tubes to drop farther-- and one screw was missing entirely when I got the scope.  I initially planned only to replace the screws with thicker and longer ones, but then hit on the idea of putting a 1/4" hex nut on each screw head to make a positive stop for the tube end.  Each nut was aligned with angle of its truss tube end before being tightened.  If the originals lasted a full decade, this upgrade should hold until the wooden parts of the scope have weathered into uselessness!

Original droopy set screw                Beefer hex nut-backed replacement version]

Pending mods:

An overstock Lycra-nylon shroud from Astrosystems is on order.  The stretchier material will be easier to put on the assembled scope in the field, and I may install both shrouds for home use to deal with the rays from my local streetlight.

A "face cooler" mirror box lid featuring four high speed 120mm fans to pre-cool the primary's face prior to observing.  This separate cover will be put on the mirror prior to dark at star parties where the scope has sat in the sun all day and heated up considerably.  I will put high efficiency furnace filter material over the intake side of each fan to avoid "sandblasting" the mirror.

An overstock secondary cage storage bag from Astrosystems is also on order.  This will allow for safe transportation of the secondary cage (wouldn't want to marr the flocking paper lining), and will probably be large enough to accommodate the off-axis mask and "face cooler" mirror  box lid as well.  (I plan to keep these two accessories in the bag when the scope is set up at home, to keep them clean and easily found.)

A state of the art telescope cover for use at star parties.  I've opted to get one made of NASA-designed reflective materials http://www.telegizmos.com/ rather than another waterproofed nylon one, to keep the scope cooler at the Winter Star Party and any regional ones I may go to in the summertime.  At home the scope will probably be covered with plastic sheeting instead, since it is easier to get on and off and cheaper to replace if it rips. <g>

"Optional" mods that may be done at a later date

adding a nylon set screw to the focuser, if it will hold the Nagler 31/Paracorr combination or loaded binoviewers adequately.  I'd rather not marr the the barrels if I don't have to.

Reversing the upper cage (focuser, finder, Telrad, handle) to accommodate a right-handed vice left-handed observer. Update:  I've decided to hold off on this for now; I'm getting used to operating things 'backwards', and have come to see the rationale for Pat's decision to set things up this way.  Adding a second handle (actually a large oak drawer knob) on the opposite side of the lower cage ring from the current one lets me use my right hand for fine tracking motions, as I've always done.

an upper cage ring (straight out of Kriege & Berry) to facilitate one-man set up of the scope in the field by allowing the upper cage to be mounted when the scope is at a more comfortable altitude than the vertical.

a Powered Ground Board?  Is there one of these in Brutus' future?  I don't know-- it would be useful, but I don't want to repeat the lengthy Natasha power saga...

replacing the nylon webbing mirror cell sling with a "Teflon on Teflon tape" coated steel strap as is used on "Natasha"?  While I'm intellectually convinced that this would yield tighter collimation over the course of a viewing session, especially under humid conditions, "if it ain't broke don't fix it" is a worthy motto.  Especially when dealing with a 70 pound piece of glass!  

having the primary mirror recoated, possibly with an enhanced coating.  Even moving from fresh standard coatings to enhanced would increase the light grasp of the 'scope by as much as ~7%, which is not a trivial increase with a mirror of this size.  While they look intact, I am sure that the current coatings are well below the nominal 89% reflectivity of a standard coating, so what would a fresh set of coatings gain me-- 20%, 30% extra light-- or more?  (I found a detailed professional observatory study that concluded the minimum reflectivity loss for aluminum coatings was 2.5% per year-- but it was unclear whether these were over-coated mirrors, what the climatic conditions were etc.)   Anyone have an educated guess on how well 10 year old coatings perform in the humid East Coast conditions?  The downside is the risk of shipping the mirror, and the non-trivial cost of having a mirror of this size recoated ($500 and up-- well up, in the case of good quality enhanced coatings). Update:  since the mirror had to be removed to allow all of these modifications to occur, I decided to give it a good wash instead.  John Hudek said that if it was as reflective as I described, it wasn't in need of coating yet.  (This is quite a statement coming from someone who stood to make money on re-coating it!  I'll remember this when it does eventually need re-coating.)

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Again, as tweaks go, virtually all of these changes are more in the nature of customizing the scope to my observing style and preferences than "fixing it", reflecting the fact that this is already a great scope that provides impressive views.  The only "must do" mods were upgrading the wheels and the ramps, which were needed to allow the scope to be safely and readily transported to darker skies.