Friday, May 29, 2009

Scope Finished!

I assembled the painted parts this evening to finish the scope. There are some tweaks to do, but nothing major. The movement is somewhat stiff, so I want to add some SailKote to the bearings to get the stiffness out. The stiction is just right though, I am just not used to the stiff movements. I will be receiving my right angle finder tomorrow. I bought a dew controller and will be recieving the dew heaters this week. It is coming along nicely!

Monday, May 25, 2009

Star Hopping with a finderscope

On of my favorite activities when observing is star hopping. Having a star chart and a telescope is a simple and intimate way to observe the heavens. No computers, no setting circles, but starting from a known star, and working your way to your goal. Some can do it with dead reckoning, i.e., pointing their scope to an area of the sky and getting close. I can do that somewhat, but it can be frustrating and a pain in the neck (literally) to be constantly looking through a Telrad or red dot finder towards the sky. It would be nice to have a right angle finder to save your sore neck.

With the ballscope, I pretty much gave up on having that ability and thought I was doomed to a bad neck. Today, however, I was able to put a finder bracket on the scope. When the scope was a ballscope, the weight was just too much to put on the bottom to counter the effect of the extra weight on top. With the new configuration, I have the flexibility of adding a nice finderscope.

I cannot wait to get this thing under dark skies!!!

Saturday, May 23, 2009

The new scope at Perkins tonight

I brought the scope up to Perkins this evening for her grand appearance. She still looks rough (i.e., no paint) but she provided some great views of the sky to the delight of the folks there. There are still some balancing issues. Top to bottom is balanced just right, but front to back is still off. There is too much weight on the back. I lashed some brass stock that I borrowed to the front of the mirror box and that balanced it out right.

Before I left, I wired up the fans to a battery and switch. The fans were on all evening and kept the mirror at ambient temperature. The fans do not introduce any vibrations at the eyepiece which is good. That way, I can leave the running all night to fight dew and temperature changes.

The motion is nice and smooth. Stiction is not an issue. It takes a little more force to move it than I would like (it is not bad or objectionable). It reminds me of my observing buddy's Teeter scope, which is a great scope. But it is still not my old Obsession's smoothness. I am going to put some SailKote on it to see if that brings that smoothness back.

I am really please at how this scope has turned out. It sure is a pleasure to use and I cannot wait to try it under a dark sky.

Friday, May 22, 2009

Scope Assembly Completed and First Light

Last night I finished the 12.5" scope and got to use it under the stars. The first thing I noticed was the scope was just about perfectly balanced! Just a tad top heavy, but nothing that cannot be fixed with some small counterweights. The other thing is that it is so much lighter than the ballscope. The ballscope had a bunch of weight in it to balance it out. It was a real pain!

Here is a closeup of the back of the mirror cell. It is an open design to allow for better cooling. Fans will be blowing from the opposite side across the mirror. This will keep dew down and disrupt the boundary layer.

Here are the two 2" fans that will be blowing across the mirror. The opening above them is for the control panel (for the fans).

Here are collimation bolts. The 4 holes are for ventilation and for a possible 3rd fan in the future.

I got to observe with it last night looking at Saturn and M81 and M82. The scope moves so much better now. The azimuth stiction is just right. The altitude stiction is also nice, but takes more pressure to move the scope. It still moves smooth though. I used pocket holes for all joinery, although I think in the future I will probably use something different. Filling the holes with the plugs was messy. Plus, this forces me to have to paint it instead of using a stain.

I hope to build a 16" scope next and this scope was a prototype of sorts. I am also thinking about remaking the 8" to be a similar design. I think I am addicted to making telescopes. hehehehe

Thursday, May 21, 2009

Rocker box almost completed

Yesterday I just about completed the rocker box. I have a few more pieces of wood to cut, some laminate to place, and I should be done. I hope to have first light this evening. I chipped some of the laminate on the bearings trying to round it over, that was a mistake. It still works, but it just looks bad. Oh well. I may take the laminate off and get some more and apply it.

The real test came tonight when I placed the mirror box into the rocker box. A perfect fit! 1/8" clearance between the rocker box and the mirror box. And 1" of clearance on the bottom corner of the mirror box and the top of the rocker box, like I planned it, heheheh.

I hope to slap a coat of primer on after first light, then paint the first coat of black paint on the puppy tomorrow morning, then the final coat tomorrow evening. I hope to bring it to Perkins Observatory Friday night for her first outing.

Wednesday, May 20, 2009

Mirror Box Finished

This evening I finished and glued together the mirror box. It should be ready for painting tomorrow. I also attached the Ebony star strips to the bearings. Getting closer to being finished!!

Thursday, May 14, 2009

Mirror Cell Finished!

I finished the mirror cell and tested out with the mirror. It is a perfect fit!

The mirror sling bolts can be adjusted up and down to allow for the sling to be centered on the edge of the mirror. They are locked down by tightening the two bolts to compress the mirror sling loop. The sling is a 3/32" galvanized steel cable that has a vinyl coating. I plan to put some velcro on the bottom of the mirror to keep the cable from slipping. The collimation bolts appear to move smoothly enough. I may take the T-Nuts out and put some epoxy in there to keep the permanently mounted.

The scope is slowly coming together. I plan to cut the sides and the dowels to the appropriate length this weekend to get the right height on the mirror box. I want to keep it the same as when it was in the ballscope so that I don't have to recut truss tubes.

I hope to have enough time and wood to go ahead and get the rocker box and groundboard done so that I can focus on painting next week and get this out the door for new moon!!

I got a good feeling that this will turn out ok.

Wednesday, May 13, 2009

More work on the Mirror Cell

Cutting holes.. adding T-Nuts in preparation for the collimation bolts which should arrive tomorrow. Trying to decide on if I want to use springs with the collimation bolts.

Tuesday, May 12, 2009

12.5" Mirror Cell Partially Done

I am mostly done with the mirror cell. I got the cable sling and retaining pins done. Just need the collimation bolts attached to the mirror pads and some more holes drilled (for venting and the back mirror fan) and I will be done! I am hoping that I finish all of the cutting this weekend and dedicate next week for painting.

Tuesday, May 5, 2009

Parts of mirror box are done

I cut the parts for the mirror cell and mirror box this evening. They turned out better than I expected. I think I may have enough wood left to finish the whole thing off.

Monday, May 4, 2009

Bearings Done

I finished cutting out the bearings tonight. They turned out really well. Tomorrow I hope to get part of the mirror box cut out and maybe a dry assembly. The new scope is taking shape!

Friday, May 1, 2009

12.5" Scope Redesign

"A scope you make is never really done"

Ron Ravneberg warned me. That phrase echoes in my mind as I stay up late thinking about ways to improve my telescope. Every path I go down leads me to the same conclusion: time to try something new. The two telescopes that I have made are both based on a sphere as the interface between the mount and the telescope. This is a design that MAG1 Instruments and Edmund Scientific used for their commercial telescopes. While I really like this design, the limitations of it are hard to design around and every time I conquer a new challenge, another one is staring me in the face. Now, it is not the challenge that is frustrating me, but the cost involved to overcome that challenge. The money that I have spent on improving my ballscopes could have allowed me to purchase all of the items I really want on a telescope (like a Moonlight Focuser, anti-dew, right angle finder, etc.)

The current challenge is that the ball thickness is just not thick enough and the ball gets out of shape from some of weight of the scope (and also the stress involved in my technique of using pressure and friction to keep the mirror cell in place). This manifests itself at the eyepieces by the telescope rocking in certain orientations (about 30 degrees away from zenith). There are also alot of vibrations being enhanced by this (I may be barking up the wrong tree here on that one, but it is all I got to go on at the moment).

So I made a hard decision to start a new design based on good old two axis dobsonian mechanics. Originally, I was going to purchase either a Telekit from Astrosystems or a kit from, and those are some great kits. But what fun is it to build someone else's design? Not fun at all! (Plus, I just don't have the money).

The current secondary ring is just fine. In fact, I love the look of a single ring: nice and minimalistic. The struts are also fine (good job Moonlite on such a great product). So I will be reusing the secondary ring and struts. No need to redo those. I am on the second version of the secondary ring and it is pretty light.

The bottom end will be a hybrid type of mirror box of sorts. Part of it will be a ring and the other part a box. The mirror box will be opened to allow for cooling (an idea I borrowed from 18" bearings for a nice smooth action, and I will probably paint it black with some type of fleck paint on some parts to give it some character.

Here are some preliminary designs I came up with in Google Sketchup.