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2/09/2013

Updates to my 14" Dobstuff with 14 inch Zambuto

Well, tomorrow I am going to upload my sketches and post them. Last Saturday I and a few friends, Mat, Jeff, Josh and a new friend and a friend of Jeff went to the Pit n Pole location (for the last time during the fall, winter or early spring).  Our equipment frosted up and you can see that on my friend's Mat mirror after he got home (he left the mirror uncovered on the drive home and it still frosted right up!).


So, until summer when that site doesn't have any dew issues, we won't be returning there.  There are some other sites that are closer and don't have this problem so if we want a close site, we will be going there.  That observing night for me was 2 hours of getting the scope set up, and remembering what worked and what didn't.  I found that night I really had a balance issue for the scope.  So today, I took the scope over to Mat's house for an ATM session and we worked on the balance issues and a few more things.

One of the things I've noticed when using my new Dobstuff 14" Dob, is that at Zenith it was just a little taller than I am (I'm 6 foot) so I had to get on my tippy toes in order to view. Since the scope has a balance issue with too much weight on the upper OTA, and I wanted to lower it a little, today we drew two new identical holes where the bearings are connected to the mirror cell.  Here is a picture.


This hold had a slight split that I have since filed in and will cover with stain so it matches the wood.  This had an amazing affect on the balance of the scope, giving a really good new center of balance. After this Mat put on some counter weight with magnets and large washers strewn together and for the vast majority of travel in azimuth the scope was great. Down low and up near zenith the scope was still out of balance. This was with a Telrad, a 9x50 RACI, a Paracorr Type 1 with the white lettering, and a 30mm Explore Scientific 82 degree eyepiece in the Moonlight focuser.  This is the heaviest set up I would ever use.  At this point we had  put a 1 1/4 lb round weight on that right foot and held in place for now by the rubber foot that fits snug there.  The result was using that and then using the adjustable sliding counter weight on the far left strut, we achieve a perfect balance for the above set up and for any combination of my eyepieces. We tried the TeleVue 27mm Panoptic, the Pentax XW eyepieces and all worked wonderfully.  This means that any eyepiece I have in my collection will work with the Paracorr Type I on this scope with the scope being balanced from down low to zenith.  YES!!!!! Thanks Mat, Josh and Jeff for your help on this. We also put the Telrad and the 9x50 Finder together on the same Strut and this combination worked extremely well.  I'll post a picture next time I put the scope together.

One item I found well checking the balance is that the Formica on the bearings were connected with a tack, but they weren't glued down with contact cement. My friend Mat made his 16 inch dob 15 years ago and he glued and tacked his Formica down and after 8 plus years he removed the tacks as the glued Formica hasn't come loose at all.  When the weather warms here in April we will glue the Formica down on my dob as well.   This will stop the small popping sound I get as I move the scope up and down in azimuth.

Once this was done, we also moved the front Teflon on the bearings up so that the azimuth and altitude motions matched.  This was the final adaptation we did to the scope.  At this time the scope is in balance and the motions which are buttery smooth, matching in their silky smoothness (azimuth was probably just a touch too smooth vs altitude). Here you can see the Teflon that we moved forward, and the former hole.





If you get a DobStuff Dob and like me, you get the String Telescope version to hold your collimation, you'll find that the end of the strings are sharp and very pokey.  I LOVE the strings and how they help to keep the scope in collimation. I don't like how the ends begin to fray and the wires stab me as I attach them to the scope. So we found today a very simple fix.  Mat in his shop/garage where we do our ATMing also bikes (he is an avid biker) and had a slew of brake kimps that are used on bikes to krimp down the braking wires so they don't flay and stab.  So after Josh and Mat had put the ends back together they were able to put the ends into the brake kimps and after krimping them, the ends are fixed and no longer will stab me or anyone helping me put the strings on.  Here's a picture of the ends put inside the brake kimp before being krimped.




Here are both ends after being put in and krimped down.  YES! No more stabbing (it really does hurt!).



So since its new moon, snowing the state of Utah and cloudy in the entire state, instead of observing, my scope is now up and running and I won't need to spend time in the field setting up and adjusting.  I love my scope and like any new scope, it needed a few tweeks which are now done.

1 comment:

  1. Anonymous2/12/2013

    Glad we were able to help modify your telescope. It really is working well now.

    The pieces we added to the end of the cable to keep them from fraying are simply called "brake cable ends". If anyone else wants to add them, they should be sure to get BRAKE cable ends, not SHIFTER cable ends, as the shifter cable ends are too small for this job. Simply slide them over the cable and crimp with a crimping tool, or just pliers.

    Mat

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