Scopes and Other Stuff

New gear. I recently acquired a new Optec electronic focuser. It is so smooth and there is not any image shift. The downside, 62mm had to be trimmed off of the telescope's tube so that I could reach focus.

The scope has been mounted on a Losmandy G11. This makes for a significant jump in telescope performance. The old Celestron Super Polaris was at its limit and the new mount is such an improvement. The backlash in Declination is reduced by a huge margin and the tracking is much better.

OK, this might be a bit extreme, but when you want lots of stereo power for Mars, nothing beats lots of focal length. One 2.5x barlow and a 1.4x relay lens made for a stunning high power view of the red planet.

This shot shows the new guide scope configuration for our 13cm f8. Three wooden rings have been cut and mounted to the scope. The top element contains an 82.5mm f8.5 doublet. The centre element acts as a baffle and the lowest element holds a guiding eyepiece or our ST4. The whole unit adds very little extra weight to the scope. It allows me to use a focal reducer, field flattener that makes the scope an f5.6. It was impossible to off-axis guide before at this ratio.

Here is the guide scope in its component parts. Left, the objective in its cell. Middle, the central baffle. To the right is the focus assembly. To focus, loosen the wing nut and adjust until it is a bit inside focus and then move the tube in and out of the eyepiece holder. When focus is set once, it can be marked, left and forgotten.

This photo shows the modifications that I have had made to our ST4 to make it easier to use. The central disk shaped object is a shutter from a microscope camera. It is then threaded onto a brass fitting that slides into the eyepiece holder, shown here with a cable release attached. The shutter is a really big help when it comes to making dark frames, given that every time a new exposure length is needed, a new dark frame is needed, this simple addition is a blessing. The shutter goes down to 1/125 of a second, which makes it useful for solar system stuff too.

These pictures are close ups of the simple modifications that have been made to our Tel Rad here shown atop our 13cm f8 Astro-Physics refractor. A two watt, 100 ohm resistor has been carefully fitted underneath the window. At 12 volts, this produces 1.4 watts of heat, more than enough to keep the optics clear of frost or dew. An internal regulator also picks off the 12 volts to run the reticle and charge the internal Ni-Cad batteries. For a telescope of this aperture, the Tel Rad is the only needed finder as the main scope can be used with a 60mm eyepiece to give a 2.3 degree field as well as performing with ease at powers exceeding 20x per centimetre.

Much like a Tel Rad, the Rigel Quickfinder is a useful finder, especially where a small footprint is desired. While I slightly prefer the Tel Rad, there are cases where the Quickfinder is a better choice. Of course, it also has to be kept dew free. Here you can see where I have added two 120 ohm resistors wired in series under the finder window. An RCA jack on the front provides 12 volts. In this case, I have also put in an LM317 to regulate the voltage for the reticule, thus bypassing the need for the internal lithium battery.

I used to have just a rotary head attached to a 1/4 20 bolt running out the top of the rings that hold the scope in place. However, it took me a while to clue into the fact that the long star images were being caused by differential flexure. The cure for this problem was to build a bracket to hold our camera and lens securely to the telescope. This bracket uses a spare cradle ring and the existing spot to hold a camera swivel on the rings that hold the scope in place. The camera and the lens are attached to the bracket and the end of the lens is also supported. This got rid of the flexure problem.

This is a shot of our scope set up for eyepiece projection. On the bottom of the scope in the lower left is the OM-1 camera, next up the chain is a Vivitar 2X tele-converter and then a Meade variable eyepiece projection adapter. The scope sits on a Celestron Super Polaris mount with custom dual axis drives. This all sits on a phone pole that runs through the walls of the house to the bedrock below. (No bathroom is complete in our house unless it has a phone pole running through it.)

It is hard to see in the shot showing the whole scope, two up, but in this shot, I have detailed the counterweight end of the telescope. There is a metric threaded hole in the end of the shaft for the counter weight so I tapped a rod with 6mm-1.00 thread on one end and 1/4-20 on the other. Then I put a ball socket on the end to attach to a camera. I can piggy back (is that the right phrase?) a camera body on the bottom end of the scope now. This means that with a camera at prime focus on the main scope, a camera mounted on the scope and one on the counterweight, I can have three cameras going at once.

Here is our barndoor mount. It uses a 12 volt stepper motor from a disk drive to turn the shaft at one rpm. The controller has a switch to select from fast forward and sidereal rate. In the fast speed, the motor winds the door up and then in sidereal rate, the platform drops down to match the movement of the sky. I was lucky enough to find a surplus 3-9x 40mm rifle scope which is attached to the polar axis and centred on the axis of rotation. This makes it easy to do polar aligns, something that must be done between each movement of the camera. Surprisingly good results can be had from this platform, especially on EPH1600 slide film.

This shot shows an external view of our rooftop Observatory, with the doors open. The hops are Haulertaer and Cascade.

This view gives you an idea what the interior of the Observatory looks like. The pier really freed up the floor space. Just behind the ocular end of the scope is the trapdoor to the bedroom below. I originally intended to drywall the inside walls, but I found the stud space to be too valuable, so I put in shelves all the way around instead. Binoculars, eyepieces and camera lenses fit nicely on these narrow shelves. Instead of dimmers, I employed variacs for low light levels. They are infinitely variable, so the lights can be barely on for when some light is necessary. I plan to carpet the floor, someday, a softer surface to catch wayward oculars. The chimney is not in service any longer.

This picture details the pier. These Barry Mount isolation blocks are used to isolate the pier from the house. At the bottom end, the phone pole sits on a hockey puck. At the floor of the Observatory level, the four mounts keep down the transfer of vibrations from the house. Each metal disk is actually three parts, two metal cups with a neoprene shock absorber in the middle. This works very well isolating the scope from all but the worst door slams and washer spins. Fortunately, I do not have to do much laundry over clear nights...

Above is an image of our "studio". Here I am duplicating negatives to create slides on SO279 Vericolor film. The reflector holds a 250 watt photoflood lamp, then comes the negative holder in the slide duplicator attached to our OM-2, backed with our Verimagni finder. Unfortunately, the OM-2 only goes down to ISO12 and the film is approximately an ISO6 and times must be manually selected. (The OM-2 is remarkably good at picking the correct exposure for duplication work.) On the right (stage left) is our light box. The unit holds bulbs that give the same colour temperature as our slide scanner. This helps me judge the colours on our monitor with respect to the original image.

A detail of the homemade slide box. I found the 8X Nikon loupe to be a good compromise between cost and optical quality.

This composite shot above shows the stages of construction of an easy to build pier from wood and two scope mounts that we have built using this idea. Try to get below your frost line and have as much wood below as above for the pier height. The upper left shot shows how the four pieces fit together, the narrow side against the corner of the wide side of a piece of 2*4 pressure treated lumber. The fourth piece completes the square pier. I have given a talk to numerous clubs across the country and it is gratifying to get email from people who have copied this idea either in the field or in their observatory. I used a post hole digger to dig a hole as deeply as possible, lowered in the pier and poured concrete to keep it in place. I then filled the interior with sand. If you do not have any soil depth, try the method below.

This is an image of our old Manuel Mount. I stole this idea from Larry Manuel, a simple and easy way to mount a refractor. Basically this amounts to being a Dobsonian mount for a scope that has the eyepiece at the right end. The steep legged tripod is set in concrete on the bedrock under the shallow soil. The azimuth table is two pieces of plywood with three Teflon blocks on it. The rocker box has a piece of Formica underneath to slide smoothly on the Teflon. Missing from this photo is a separate dowel arm that came off the back of the scope. This made pointing the scope a breeze. Also missing are the binoculars that mounted off the altitude bearing. This provided a wide field, correctly oriented set of finder scopes at a nice height for observing.

Here is a more detailed view of the rocker box. Teflon mounted inside the altitude housing provides a slippery surface for the two plumbing pipe pieces that form the altitude bearing. A pair of yokes went over the top of the bearing to provide enough stiction for stable pointing and allow for slight changes in balance brought on by ocular changes. The battery serves two purposes. It counter balances the scope across the azimuth table and provides power for all of the dew heaters. A solar batter charger kept it topped up. This tripod is not in regular service anymore, yet it has weathered well for over a decade. Larry called this mount the Mount of Gibraltar.

Finally, what we do with extra dew heaters around here. Believe me, at -25C, an extra 15 watts of heat makes a difference to your hot chocolate...

For more information send mail to Mark Kaye at: mark.kaye@sympatico.ca

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