PolarAlign

Make a cheater bar for the Paramount altitude adjustment ring

What you need to know:

• The thread size for the threaded flat is 1/4-20
• Hole depth 0.28in or 7.2mm
  
• Maximum length of bar to avoid hitting the side plates is just over 2 inches. 

Buy:

• 1/4-20  2 inch hex head bolt
• 1/4-20 nut
• permanent or high strength thread locker fluid
  
• nitrile or rubber O-ring  ID 7/32 OD 11/32 section 1/16 inch
  

Thread the nut on the bolt, apply thread locker, allow to cure, remove excess thread locker from bolt, place O-ring  over exposed threads and move up to the nut.

I suggest stainless steel for metal parts. 

Make sure the bolt doesn't bottom in the threaded hole to avoid marring the finish in the bottom of the hole.

If you cannot measure the 7.2mm, you can estimate with a nut and a washer.  The standard 1/4-20 nut is 5.5mm thick.  Stacking a washer on the nut will put you at 6.75mm.  The nut with two washers is 7.84mm which is too deep.  

Make your own SBIG desiccant caps

What you need to know

The thread size is an M10, 1.25 pitch

You'll need

1. a flat washer with a hole large enough to allow the threaded portion of the desiccant plug to pass through it and sized so the O-ring seals against the flat surface. It needs to be thin enough so the threads on the desiccant plug engage the threads in the nut.
2. an M10 1.25mm hex nut
3. a flat disk to seal the bottom of the nut.  A dime works.
   
4. silicone aquarium adhesive or epoxy
5. Not needed but handy is an M10 1.25 pitch hex head bolt.  Use it to clamp the washer to the nut and to keep the washer aligned with the nut while the adhesive cures.  

Make your own astronomy lantern

Note: This is the first version of this lantern.  An improved version is described in detail on the Ideal Astronomy Lantern  page.

This lantern generates a wide swath of red light, good for setting up, and a much brighter red light that will illuminate a road or an entire camp site. On low in a tent, you'll have enough light but not bright enough to annoy others.  The light lights up an area rather than a focused beam like a flashlight.

What you need to know

Automobile LED tail lights/brake lights contain two circuits, one for the tail light and another much brighter for the brake light.

You'll need

1. A rear tail light/stop light. These are available from Harbor Freight Tools for $15-20 depending if you hit a sale.  Item 93263
   
2. Eight 1.5 volt dry cells in  give 12 volts when arranged in series (arranged nose to tail so each positive pole contacts the next cell's negative pole). Radio Shack has the holder, about $2
3. A single pole double throw switch will allow you to wire the light so flipping the switch one way will send current to one circuit, flipping the other way will send current to the other circuit. Radio Shack.
4. A small plywood box is easy to build that will hold eight AA batteries, the switch, the light in the front, and a handle on the top.

The batteries will last a very long time.  It'll be relatively rarely you'll need to open the box to replace batteries, so you can use wood screws to make one of the panels removable.  This is much easier than trying to make any other type of removable cover.

Mount the switch so it flips vertically.  Up should be the bright setting, middle is off, down is low.  If you mount the switch so it flips horizontally, it is easy to turn on the bright light instead of the dim one.  AlsoThis thing on high is bright enough to make you unpopular with astronomers.  When carried aimed at the ground on low, it's a very nice light. It'll light your path without annoying others.  When leaving an astronomy area, it can be put on the hood of the car and on bright, will light up the road until you get far enough away for white light.

Note: If you make this lantern, make the battery box complete all the way around the battery holder.  If made the way this one is pictured, a hard knock will dislodge one or two of the batteries from the holder and the light won't work until the top of the lantern is taken off and the batteries are pushed back into the holder.

Make a flats box for a small refractor from a piece of sewer pipe

I've fabricated a flat box from a piece of sewer pipe.  Sewer pipe is very light... doesn't need to contain pressure.  Anyway I had some from when I installed my shop vacuum system.  I was looking at a left over piece and I found the flared end fits perfectly on my Megrez 80 dew shield. 

I cut a 9.5" piece from the flared end so I got the flare and about 6" of nonflared pipe. 

Next I cut a 1" piece of nonflared from the remaining pipe so I now have he 9.5" pipe and a 1" ring.

Next I glued copy paper to each side of the ring.  After the glue dried I trimmed off the excess with a razor blade.  Now I've got the pipe and a thing that looks like a 4" drum 1" thick. The ring fits perfectly into the flared end of the pipe.

Next I used a plastic single serving cereal container (Kellogg's Frosted Flakes).  I removed the paint from the container with some acetone.  The large end of the cereal container fits perfectly into the nonflared pipe.  On the smaller end of the cereal container I put 3 cable ties.  These were connected end to end so I had a large ring.  Next I snugged up each cable tie so the heads were equidistant around the small end of the cereal container.  There's a molded in ring perfect for the cable ties.  I left the ends of the ties long.  Now the springy ends of the cable ties keep the smaller end of the cereal container centered in the tube.  The cereal container goes into the nonflared end of the pipe so the larger end of the container rests against the drum.

Next I cut down a CD so it is the same diameter as the outside of the nonflared end of the pipe.  I glued a 12 volt LED white light (automotive) to the center of the CD, drilled a hole in the CD near the edge then glued in a RCA jack.  The light faces in, the jack faces out. I soldered the light wires to the jack and glued the CD to the nonflared end of the tube.  Next I painted the outside of the tube black.

Now I can put the tube on the end of the telescope, hook up an RCA patch cable from my dew heater controller (12v output) to the end of the tube and get my flats.  The flats are perfect.

Make a front counterweight for the Paramount

The Paramount can carry impressive amounts of weight.  With a small telescope and a camera on the Paramount ME, though, it can remain unbalanced.   An 80mm telescope is short.  The camera needs to extend over the back end of the Versa-Plate. Even with the Versa-Plate moved to it's most forward position, there's insufficient weight in the front to balance the DEC axis.  There needs to be an easy way to add weight to the front of the plate and a way to adjust that weight.

Solution:

I used materials I had on hand.

A second dovetail plate was made.  The end of an approximately 10 pound cylinder of steel was drilled with a #7 drill and tapped with a 1/4-20 thread.  A 1/4" hole was drilled in the dovetail plate  near one end.  The steel cylinder was bolted to the dovetail plate. The end of the dovetail plate was trimmed to match the radius of the steel cylinder in order to minimize edges.  The sharp ends of the cylinder and the dovetail bar were blunted with a file. I've countersunk the hex head cap screw so the top of the plate is flush.

The weighted dovetail plate is inserted into the Versaplate from the front.  The weight can be adjusted by sliding the dovetail plate in the Versaplate and is fixed in place by the Paramount's front dovetail knob.  The following picture is for illustration.  I plan to finish the metal surfaces then black powdercoat.

As long as the weighted dovetail plate is short enough not to hit the the dovetail plate holding the telescope, the weight can be adjusted inward until either the dovetail plates meet or the weight contacts the front of the Versaplate.  Moving the telescope plate and the weight dovetail allows perfect balance.

Light Box for photographic flats

We've had cloudy skies for over 2 weeks now.  I went out this evening thinking it would be clear, we've had blue skies all day.  Clouds again, not a star in the sky.  I spent the evening making a flats box for the new telescope.

With astrophotography, good flat field exposures are crucial.   They are used to correct for  imperfections in the equipment such as vignetting, dust on filters, dust on the CCD, etc.  The goal is an absolutely evenly illuminated field.  This illuminated field can be photographed and any deviation from even illumination is due to the telescope, the filters, or the camera.  The flat field photographs can be used to correct the same abnormalities in the other pictures taken through the telescope.

The design

The design is similar in concept to the "sewer pipe" flats box described above.  That box yielded excellent flats.  This design doesn't rely on  finding a pipe that happens to fit on the end of the telescope.  This one is more attractive, and lighter.  Multiple disks of white copy paper are widely spaced to evenly diffuse the light.  12 Volt power conveniently comes from a jack on a dew heater.

The result

It's the silver cylinder.

The list

1. An old LED flashlight
2. Aluminum flashing (Home Depot or Lowes)
   
3. Thin 2" aluminum tape (auto store)
4. Cereal cup, single serving, plastic (Kellog's Frosted Flakes cup used here)
5. 5 needlecraft hoops, used to hold fabric for cross stitching (6 inch used here, Hobby Lobby, $0.79 each)
6. Wire with an RCA jack (stereo hook up cable, one end cut off)
7. Strong contact cement (Ace Hardware, "Industrial contact cement")
8. 4 sheet metal screws
9. 220 or 330 Ohm 1/2 watt resistor (Radio Shack)
10. Bubble wrap
    

The build

It has a single serving cereal cup in the base.  That cup is screwed to a disk of  thin aluminum and held with a wooden hoop and thin foil tape.  Inside the cup is an LED array (8 LEDs) taken from a cheap flashlight.  The array is soldered to a 330 Ohm resistor and attached to a wire with an RCA plug on the other end.   The resistor lets me power it with 12 volts from my dew heater instead of the 4.5 volts that came from the flashlight batteries.  I wrapped the array in bubble wrap to partially diffuse the light and to  hold it in the middle of the cup.  The array is pointed at the bottom of the cup. I contact cemented a disk of paper to the top of the cup to diffuse light.

The outside cylinder is made from thin aluminum flashing.  It's thin enough to cut with scissors or a paper cutter.  I used several 6 inch wooden needlecraft hoops to hold the flat aluminum in a cylinder, the aluminum is thin enough to be held between the inner and outer rings of  the hoops.  The aluminum was cut so there was 1 inch of overlap when it was rolled into a 6 inch cylinder.  With the aluminum held in the hoops,  I pop riveted the overlapping aluminum.  The wire for the light is brought out through a hole drilled in the overlapped aluminum.  I used just the inside rings of 3 of the hoops. I cemented them to the inside of the aluminum cylinder with "industrial contact cement" from Ace hardware. To each ring, I contact cemented a disk of copy paper, to act a diffuser.  The final two wooden rings are cemented near the opening and covered with a 2 inch strip of green felt.  The felt was turned over the end to cover the raw edge .  The whole thing slides on the end of the telescope.

It looks heavy but it is extremely light, it weighs less than 6 ounces.  It took about 3 hours including a trip to Hobby Lobby for the $0.79 wooden hoops. I had the aluminum, the rivets, the cup, the paper, and the tape so total cost was under $5.  This is a nice project for a cloudy evening. 

I plan to use the box for LRGB flats as well as narrow band flats.  The spectrum of the LED's may not be ideal for narrow band flat images.  Still any light in the narrow bands may be enough, so it will be interesting to test.  If the current white LEDs don't work for narrow band, I'll explore adding colored LEDs.  Incandescent bulbs can be used and will produce broad spectrum light but I'd rather go with the cooler and more reliable LEDs if possible.

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