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23.5" f/3.6 Dob

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#401 jtsenghas

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Posted 03 September 2020 - 07:54 PM

You're still making more steps forward than back, and learning to proceed more cautiously.  Hang in there. It's just another ATM life lesson. 


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#402 tommm

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Posted 03 September 2020 - 10:29 PM

Accidentally destroyed the rocker sides while attempting to fix a problem with the curves and now I have to make new ones. Sighs

Yeah, that stuff happens sometimes. You fix it and move on.


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#403 a__l

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Posted 03 September 2020 - 11:51 PM

Yeah, that stuff happens sometimes. You fix it and move on.

well yes post №374

 

There is another good saying. Listen to more experienced comrades.


Edited by a__l, 04 September 2020 - 12:46 AM.


#404 tommm

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Posted 04 September 2020 - 11:03 AM

I think you have forgotten what you were like when you were young a__I.


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#405 cuzimthedad

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Posted 04 September 2020 - 01:23 PM

One of the greatest learning techniques available is to do and correct our mistakes for the better. Makes the next go around a lot smoother and a better product. Keep that "Can do" spirit going!


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#406 Augustus

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Posted 13 September 2020 - 10:41 AM

Haven't gotten anything done lately - not really enthusiastic about working in the still-presently-hot garage, plus I have been working on upgrades to the 14.7", observing with the 14.7", doing outreach, college applications, and trying to get a job. 

 

I did however run all the calculations to make sure that the taller UTA wouldn't tip the scope over, which I was a bit concerned about, and I bought Lycra for the shroud. Also have been working on figuring out storage for this thing once it's done; since my garage is spider-infested and dusty I'm thinking of making an insulated cabinet in the corner of it to keep this scope, the 14.7", and most of my other gear in.

 

I would like to thank everyone for the support and well-wishes on this project; there have been times when I've considered just quitting altogether. It is a tremendous undertaking for anyone to build one of these, especially someone like me with only minimal experience in woodworking, metalworking and project management with a rather low budget to boot. I don't want to make a mockery of myself with this scope like I did with the 16" and 20.5".


Edited by Augustus, 13 September 2020 - 10:45 AM.

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#407 stargazer193857

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Posted 13 September 2020 - 12:20 PM

Accidentally destroyed the rocker sides while attempting to fix a problem with the curves and now I have to make new ones. Sighs


I read the Orion nebula looks amazing in big aperture and 21mm Ethos. Looks like M51 might have to be seen next year when the smoke clears.

#408 tommm

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Posted 13 September 2020 - 12:27 PM

I don't think you made a mockery of yourself. Got a little too hurried perhaps...give yourself a break, you are still young, most of us have close to half a century of experience on you.



#409 grzesznypl

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Posted 13 September 2020 - 12:39 PM

I don't think you made a mockery of yourself. Got a little too hurried perhaps...give yourself a break, you are still young, most of us have close to half a century of experience on you.

Agree, take a break, reassess your project, and restart by getting rid of spiders first grin.gif grin.gif 
But seriously, it sometimes helps to focus on something else, recover mentally and get back to the project with new enthusiasm and energy. Take your time, there are many decades of astronomy ahead of you.



#410 BradFran

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Posted 13 September 2020 - 05:24 PM

Don't stress telescope making so much... especially on a schedule. Enjoy observing as much as you can. There will always be a cloudy day to get something done on the scope. Clear nights are much more important. Besides, it seems to me the more you mess up, the better your telescopes get. I see nothing much to be ashamed of and a lot to be proud of. Most people don't make their mistakes public so that others can learn from them.


Edited by BradFran, 13 September 2020 - 05:25 PM.

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#411 stargazer193857

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Posted 13 September 2020 - 05:26 PM

Always have one of your two scopes working. Don't take both apart at the same time.
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#412 Augustus

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Posted 16 September 2020 - 11:28 PM

Today I started working again - albeit in a rather small way - by obtaining and testing some Harbor Freight loading ramps. I have gone to several Harbor Freight stores and had been unable to find them, and happened to pass by the one in Orange and they had the last set of ramps still in stock! I made some basic measurements to assess the loading angles and clearance I'll have with the finished LTA and rocker box, and found no issues other than that the starting angle is a bit steep, which is a little worrisome (but probably unavoidable).



#413 jtsenghas

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Posted 17 September 2020 - 05:55 AM

...and found no issues other than that the starting angle is a bit steep, which is a little worrisome (but probably unavoidable).

If it's enough of a concern, you can make wedge blocks slightly lower for angle than the current ramp inclination for the bottoms of the ramps to engage in, effectively lengthening the ramps in use.  On soft ground these may in fact work better than ramps alone. 


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#414 Augustus

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Posted 01 October 2020 - 03:35 PM

Work has fully resumed on the scope as of today. I am beginning to trace out the aluminum floatation supports to cut.

 

I have upsized the secondary mirror to 4.7" to avoid vignetting with a 25mm ES100 should I decide to purchase one, and upgraded to a heavier-duty AstroSystems spider. The UTA is of course ballooning in weight from this change plus the increased height, but I think I'll be okay.... worst case is I move the bearings up a little. 

 

The focuser board is going to be 1/4" aluminum with C-channels to brace it at the top and bottom. This allows me to get the focuser as close as possible to the secondary for maximum field illumination. 


Edited by Augustus, 01 October 2020 - 03:43 PM.


#415 Augustus

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Posted 19 October 2020 - 05:17 PM

Mirror box, rocker bottom, ground board, and UTA rings have been painted. I thought the mismatching varnish and plywood edges were ugly.

 

mbpainted2s.jpg



#416 Augustus

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Posted 19 October 2020 - 06:49 PM

Stacked height (with knobs removed) allowing for clearance between mirror box and base is 30.5". I think I can trim an inch or two off the UTA struts though; we'll see. Not a huge problem if I can't.

 

IMG_7123.jpeg

 

I might repaint the outward facing side of the bearings.

 

 


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#417 kb58

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Posted 20 October 2020 - 02:50 PM

Just remember that perfect is the enemy of good enough.


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#418 a__l

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Posted 20 October 2020 - 07:06 PM

It is better to cover the wood with a good varnish. Excluding the top of the mirror box. During operation, scratches occur, they are less noticeable than on any paint. But for this you must have a good wood and good work, you cannot hide flaws under varnish.

 

Always use a primer before painting the top of the mirror box with black.


Edited by a__l, 20 October 2020 - 07:26 PM.

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#419 Augustus

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Posted 20 October 2020 - 07:27 PM

It is better to cover the wood with a good varnish. Excluding the top of the mirror box. During operation, scratches occur, they are less noticeable than on any paint. But for this you must have a good wood and good work, you cannot hide flaws under varnish.


You’re right. I used plywood for the mirror box that looked ugly, and accidentally oversanded a small portion of a UTA ring and the mirror box.

Given the choice between needing to touch up paint occasionally and rebuilding the entire structure with the hope that I don’t mess anything up or get weird mismatching color tones with the varnish again, I’ll take the former. Plus, bright flashy colors look cool.

#420 Oberon

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Posted 21 October 2020 - 01:53 AM

Wood is attractive when well finished but as you’ve doubtless now discovered it can be a real challenge to get to that “well finished” look. I don’t blame you for painting...but I dare say you’ll discover in time that....well, paint can be attractive when well finished but can also be a real challenge to get that “well finished” look!!!

 

Keep at it grasshopper! waytogo.gif



#421 Pinbout

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Posted 21 October 2020 - 07:01 AM

The best finish, especially for outdoor, is catalyze poly. Not easy to apply cause it flashes... when spraying it can look bumpy but all of the sudden poof its very smooth. If you shoot till it’s smooth you’ll get runs. 


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#422 Augustus

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Posted 21 October 2020 - 08:14 AM

Wood is attractive when well finished but as you’ve doubtless now discovered it can be a real challenge to get to that “well finished” look. I don’t blame you for painting...but I dare say you’ll discover in time that....well, paint can be attractive when well finished but can also be a real challenge to get that “well finished” look!!!

Keep at it grasshopper! waytogo.gif


I’m no stranger to good finishes but the surface area of the parts of this scope are HUGE. That’s the main issue.

#423 Augustus

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Posted 21 October 2020 - 03:01 PM

Cut the poles and installed the pole brackets. Weird to think that the scope will be another 2-3" taller than it is now once it's on the actual rocker sides.

 

otacompletes.jpg

 

Remaining tasks before first light:

  • Build and paint new rocker sides
  • Cut floatation triangles and attach to bars
  • Install focuser board
  • Install spider/secondary
  • Make wheelbarrow handles
  • Install primary mirror

Edited by Augustus, 21 October 2020 - 03:01 PM.

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#424 Jack Day

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Posted 21 October 2020 - 04:49 PM

Zane,

 

I like the Blue an Black together!  Are you going to do anything fun for a knob on the center of the mirror cover?

 

-Jack


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#425 Augustus

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Posted 21 October 2020 - 08:55 PM

When I initially assembled this thing I got really freaked out about balance. The center of the bearings looks REALLY low. In reality the cut-off crescent shape throws you off by quite a bit. Here, I'll even show my work:

 

UTA: 19 lbs x ~60" from CoG = 1140 inch-pounds

  • ~8 lbs bare UTA w/focuser
  • ~5 lbs spider + secondary
  • Telrad + eyepiece + Paracorr: 5 lbs

Poles: 10 lbs x ~20" from CoG to center of poles = 200 inch-pounds

 

Mirror box: 109 lbs with CoM at 16" from CoG = 1744 inch-pounds

 

I'm probably underestimating the UTA weight a little and I'm not counting a shroud. Let's throw the shroud into the equation. At worst it's 5 pounds when soaked with dew, and the CoM of it is at the center of the poles or about 20" from CoG: 100 more inch-pounds.

 

This means there is roughly 300 inch-pounds of margin or enough to shove another 5 pounds on the UTA, aka enough margin that even if I'm an utter idiot the scope won't tip over.

 

Zane,

 

I like the Blue an Black together!  Are you going to do anything fun for a knob on the center of the mirror cover?

 

-Jack

Thank you! I just swapped that gold handle for a silver one that matches the hardware on the rest of the scope. Blue + gold is not my favorite.

 

I had a nice handle that I lost track of. Nothing too crazy.


Edited by Augustus, 21 October 2020 - 10:26 PM.



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