Making_a_Berry_Mount

A few of the guys in ASEM started an email thread about the woeful status of Christmas Department store telescopes...flimsy mounts, substandard tripods, poor finders, plastic eyepieces, and such.  Even if the optics were good, the problems with the rest of the kit were so bad, a beginner would have trouble finding and viewing anything.  After a few nights of frustration the new telescope would be relegated to either the closet or Craig's List.  We end up seeing some of these telescopes either at a Beginner's Meeting or at Broemmelsiek Park, particularly on a Friday night at one of our Public Viewing Sessions.  Many of the telescopes look "astronomical"...equatorial mounts, eyepiece trays, and finder scope, but down deep there are problems.  Most of the time we're happy to talk with the owner and take the time to help them get the scope set up and working, but deep in our hearts we know it is really time wasted.  Even at it's best, the scope isn't really ever able to perform well. 

Problems include:

Our email thread ended up suggesting a variety of remedies:

• Establishing a "suggested" list of things to look for or avoid when buying a  "Department Store" telescope and post it online.

• Examining some of the modest price telescopes that are available online and make specific recommendations for purchase based on the available funds.

• Having "workshop" days where the public is invited to build there own scope from parts that we suggest and quite possibly provide.

• Having "workshop" days where we help build things that can improve the normal "Department Store" telescope and make it more sturdy & user friendly.

• Developing a list that would suggest what could be typically seen, what to expect to see in the eyepiece, when to look for it, and how to find it.

• Shaky tripod, legs bent out when extended

• EQ-1 mount that requires polar alignment (difficult for beginners)

• knobs are hard to turn and bang into focuser

• takes .965" eyepieces rather than 1.25" standard

• dim finder scope

Before you get too excited about building and viewing it might be wise to visit a web page that Astronomics, the dealer that sponsors the CloudyNights forum, put together called  PERFORMANCE – WHAT CAN YOU EXPECT TO SEE IN A TELESCOPE?  The page does an excellent job detailing what can be seen with telescopes of various apertures and types.   The page covers solar system objects, stars, and deep sky objects.

Stealing a bit of the contents of Astronomic's table shows that the typical Department Store 60-70mm refractor or small reflector will show  "the larger globular star clusters, some of the brighter nebula, virtually all of the Messier objects from a dark sky site (although with relatively little detail visible in many of them) ."  I'll point out that there are not very many dark sky sites in Eastern Missouri.

If your goal is viewing from your driveway with a bright street light only ten feet away and seeing hundreds of deep sky objects with a 60mm Department Store telescope, nothing will help other than spending money on a better scope. 

If your goal is to improve the stability, aiming, and ease of use then building a Berry Style mount might help  significantly.

Berry style mount, home made tripod, red dot finder

It is not a Department Store telescope, but it isn't a wallet breaker either.

The Berry style mount will also work well on a Newtonian.

While searching online for various answers to the above, I stumbled across a 1997 article by Dave Trott called How to Redeem a Department Store Telescope that was originally published in Astronomy Magazine.  Dave pointed out that frequently the optics on a Department Store telescope really aren't too bad and with some pretty simple woodworking skills, a stable platform can be built.  While I don't really have a Department Store scope, I do have a pretty cheap 90mm doublet refractor that I usually use on an iOptron MiniTower Alt/AZ mount.  It works well, but does take about 15 minutes to get set up, leveled, powered and running.  There is a lot to pack and unpack when I drive out to my normal viewing site at Brommelsiek Park.  I thought, "what the heck, the mount might make it grab-n'-go" so I banged together one of Dave's suggested Berry mounts and a tripod.    I was more than impressed.  It  provides a very stable platform, is very fast to both set up and locate objects, took only a short time to construct, and was relatively cheap to build (assuming you have access to the tools).

Berry style mount, home made tripod, red dot finder and 90mm f/6.1 refractor

note the height adjustment on the right tripod leg

You can find Dave's Astronomy article including directions buried as a PDF in the link to his site above.  I'll admit that I made a number of changes.  First, Dave's mount is made of plywood.  I opted to make mine out of pine 1x3"s and 1x4"s.  My reason...less cutting in case we wanted to offer public building sessions.  Dave's plywood mount would require a table saw, my version requires only a chop saw.  Yes, hardwood would have been more solid and prettier, but pine was cheaper and the mount doesn't carry too much weight.  My second modification is related to how the cradle and rocker boxes mate.  The traditional method if for the cradle to drop and rest into either semi-circular or cutouts.  The traditional method gives a drop-in/lift-out mounted optical tube.  I opted for circles because I didn't want the cradle & rocker to come apart if bumped in the dark at a public viewing session.  So far the mount is smooth and the telescope stays in position when balanced correctly on the PVC pipe and felt pads.  If would be fairly easy to add a ALT tightening nut and bolt by putting a split in the upright above the PVC fitting(s).

My third modification was to add a cheap ($10) red dot finder to the rod that squeezes the optical tube in the cradle box.  The "zero power" red dot finder is much easier to use and sight than the typical 5x22 finder or bulls eye that comes with many new scopes.

In making the mount, the only critical dimension is the diameter of your optical tube.  If you cut the wood undersized you won't be able to mount the optical tube.  If you over cut, you'll be able to shim to size (with patience).  I mention this because my plan is to be able to shim other scopes to my mount, since most Department Store scopes are less than my 90mm OTA. 

A side view of the Berry mount showing the side of the rocker box.  The front part of the box has a hole at the bottom to attach to the tripod and holds ankle weights for counterbalance.  A 1/4"x20 threaded rod runs vertically from the bottom of the box to a tripod stretcher.  There is a "milk bottle" bearing between the box and the 4" round top of the tripod.  Washers and wing nuts on the top and bottom of the rod control the tension.  Azimuth rotation is smooth and easy.

You can see the PVC fittings best in this view.  The hole for the PVC fitting is oversized and lined with felt furniture glides.

If the telescope is well balanced fore-aft, the declination axis holds well.  Poor balance will cause one end of the scope to rise/fall when not held.

It is possible to make paper setting circles for both axis.

A back view of the mount showing how the three sided cradle box holds the telescope.  A 1/4"x20 threaded rod is used to pinch the telescope in place and hold a red dot finder.  The width of this cradle box is the only critical dimension in making the mount.  The inside of the cradle should be just slightly wider than your telescope AND felt used to line the box.  Too narrow and the scope won't fit.  Too wide and there may be too much play.

It is possible to shim the inside of the sides so that other optical tubes can be used.

Fore/aft balance on the scope is done by loosening the wing nuts on the 1/4"x20 rod and moving the telescope in and out.  

 The reason it is called a Berry mount is that it was popularized by Richard Berry in has book Build Your Own Telescope.