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Shop-built Evolution 6 wedge - did I do it right?

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#1 PLShutterbug

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Posted 20 September 2020 - 09:29 PM

Want first opinions, if you please. I decided to build my own wedge for my Evolution 6. Not sure if this is a prototype, or will last. I think tonight will be my first night in almost two weeks with clear weather, so I will take it out and play some.

 

Did I get it right?

 

As far as polar alignment ... in my photo, I want to point the leveling bubble on my tripod north, right? That will point the telescope straight south if it is aligned along that line.

 

I live at N47°55', W122°41'. I built in latitude adjustment from 30-60°, and 10° of side-to-side adjustment each way after the wedge is attached to my tripod (you can see that adjustment in the close-up detail).

 

Do I raise the wedge up to my latitude (the wedge puts the base of the mount at ~48°), or do I lower the wedge down from 90° by my latitude (the wedge puts the base of the mount at 42°)? I have read a couple of threads here where the wording doesn't seem clear.

 

Let me know what you think. Appreciate any comments. Thanks!

Attached Thumbnails

  • Finished wedge - wide view - JPG30.jpg
  • Finished wedge - closeup - JPG30.jpg
  • Finished wedge - tripod and base - JPG30.jpg

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#2 JohnBear

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Posted 20 September 2020 - 11:26 PM

That's my kind of hobby project! Looks like a vey nice design. most people just build a wood wedge for a fixed location, so they usually aren't adjustable. It looks plenty sturdy, and should last for a long long time.

 

My only question is why do you want a wedge for a computerized Evolution Alt/Az mount? Is if for a special purpose like AP?  

 

To polar align the scope on the wedge. The scope should be pointed straight up on the Evo mount. Then raise the wedge up so the scope and wedge is pointed North and straight at Polaris as seen thru the eyepiece. Also, make sure the base of the wedge is as level as possible at the start. 

 

Setup this way the  the Az base of the Evo mount will rotate on an axis perpendicular to the the Northern pole, and thus can easily track objects in the sky as the Earth rotates (with no Alt motor tracking needed). Just be sure the EVO is setup of this (EQ Mode I believe).

 

I hope you find this helpful. And I do like how you built the edge! 


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#3 PLShutterbug

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Posted 21 September 2020 - 01:14 AM

That's my kind of hobby project! Looks like a vey nice design. most people just build a wood wedge for a fixed location, so they usually aren't adjustable. It looks plenty sturdy, and should last for a long long time.

 

My only question is why do you want a wedge for a computerized Evolution Alt/Az mount? Is if for a special purpose like AP?  

 

To polar align the scope on the wedge. The scope should be pointed straight up on the Evo mount. Then raise the wedge up so the scope and wedge is pointed North and straight at Polaris as seen thru the eyepiece. Also, make sure the base of the wedge is as level as possible at the start. 

 

Setup this way the  the Az base of the Evo mount will rotate on an axis perpendicular to the the Northern pole, and thus can easily track objects in the sky as the Earth rotates (with no Alt motor tracking needed). Just be sure the EVO is setup of this (EQ Mode I believe).

 

I hope you find this helpful. And I do like how you built the edge! 

Thanks, JohnBear. It's not finished yet. I haven't rounded the tripod mount, the wedge base or the mount base yet, and I haven't sanded anything and obviously haven't varnished it yet. I wanted to make sure it worked before going through that effort.

 

Why did I build it? I want to learn astrophotography and I decided not to fork out $350 for the Celestron wedge. Everyone here says to buy an HEQ5 or EQ6-Pro at least, so I decided to do this part on the cheap. Besides, I really enjoy woodworking and this provided another opportunity to learn more about precision craftsmanship.

 

I will play with this while I save my pennies and decide whether this really is the hobby for me. If I decide yes then I'll take that $350 and put it towards the right equipment for the task.

 

I use SkyPortal on my iPhone to connect to the scope WiFi. Its instructions for alignment are different from yours.

 

First, I pointed the bubble level on the tripod to north. Note that I built the wedge so this level remains visible; that way I don't have to put a level on the wedge. 

 

Second, SkyPortal told me to align the mount's markings, position the scope level with the mount (not with the tripod), and make sure it was pointed straight south. This jibes with their instructions and illustrations I've read online. The mount points towards Polaris; the scope points south towards the celestial equator. Then I was to tap an Enter button.

 

Then the alignment. SkyPortal asked me to locate an object in the eastern sky and choose GoTo to let the scope go find it. It sort-of did, and then SkyPortal told me to use the on-screen arrows to center the object in the eyepiece and hit Align. I did. SkyPortal asked me to find a second object in the eastern sky and repeat that exercise. Then it asked for an object in the western sky and I did. Unlike the Alt/Az 3-star alignment procedure, SkyPortal kept allowing me to add more and more objects to the alignment until I tapped Done. Then I could get pretty easily to objects. I still needed to center them after a GoTo but I could then tap Align and that increased accuracy.

 

As I had read before, using the wedge caused the scope to end up in some weird orientations. When it pointed to Polaris the star diagonal was right on top of the center of the mount base. I kept having to rotate the diagonal so I could see things. But I sort-of expected this.

 

Then I decided to test the alignment by doing a few images. I went to my car to grab my camera and discovered I had left my Nikon F to Z adapter at home. ~!#$!^& So scratch that idea for tonight.

 

Regardless, I think this was a successful night. The wedge worked, and the alignment process was almost as easy as SkyPortal's three-star Alt-Az alignment.


Edited by PLShutterbug, 21 September 2020 - 01:16 AM.

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#4 trigger

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Posted 21 September 2020 - 04:33 AM

Looks legit!



#5 deansjc

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Posted 21 September 2020 - 09:25 AM

Well done.  I also made a prototype that works fine and I just kept using it.  Yours and mine differ a bit, but they do the same thing.  Here are my comments based on what I could see:

 

Your center of gravity looks perilously off and may cause you a problem.  It's a lot to have crash to the ground.  That creates a design problem.  The larger of the Celestron wedges has the ability to slide forward and back which is a great feature, but hard to emulate.  I would trade off the convenience of having the three hold downs fully accessible - which is nice but needed only for a short time during setup, by moving the hinge toward you.  Check for balance by lifting a single leg at a time and check for "resistance".  Or, I'm just guessing here based on the picture, put the heavy side over a leg and not the space between legs.  That should be safer.

 

If you will do your PA by un-snugging the hold downs and manually moving the wedge with full, gear, it will be very difficult to nail it.  Do you have a threaded adjustment?  Being able to do fine adjustments will be the difference in your PA success or lack thereof.

 

Sandy's PA advice is good, but challenging.  You will have a considerable amount of stress on the setup when pointing at the NCP.  Learn where that is relative to Polaris and you will get much better PA.  When you then point south, you may lose some precision in your PA since the COG can change.  You might wish to use StarSense and its ASPA routine to avoid that aspect.

 

'Glad to hear you will round and sand the wedge.  You'd be surprised how those sharp corners can be found in the dark :-)

 

DM me if you would like to see my setup.  My PA is about 1" - 3" and I can do 40-60 second images with no trailing.  It could be longer, but the SE mount is not top of line.  Your mount is more capable.

 

You'll get a lot of advice to give up the wedge.  Many struggle with it, very freely share their woes, or just want a superior solution.  Stick with it and you may be very pleased with your results.



#6 enigma-2

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Posted 21 September 2020 - 12:33 PM

I found a free android app named "just a compass" works perfectly to align due north. I put the cellphone on top of my Celestron, and move the scope to 0° north. Gets close enough as the Earth's magnet deviation in my area is minimal.

#7 Slimtannor

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Posted 21 September 2020 - 01:17 PM

I believe the center of the RA clutch should be right over the center of the tripod base. You could accomplish this by making your base plate a little longer. Also, the whole thing should be aligned with one of the legs, as to put most of the weight on one leg, so it doesn't topple over.

 

I will be making the same setup out of aluminum this fall, for my 8" Evo.

 

Good job. 

 

You might find this helpful.     https://www.celestro...nt-with-a-wedge


Edited by Slimtannor, 21 September 2020 - 01:28 PM.


#8 PLShutterbug

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Posted 21 September 2020 - 01:31 PM

I found a free android app named "just a compass" works perfectly to align due north. I put the cellphone on top of my Celestron, and move the scope to 0° north. Gets close enough as the Earth's magnet deviation in my area is minimal.

My iPhone has a compass app you can switch from True to magnetic north. I think that should work, right?


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#9 JamesDuffey

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Posted 21 September 2020 - 02:18 PM

That is what I use on the iphone to align to true north; an app called Compass? With this and the level function, I can blind align when Polaris is not visible-good enough for an hour or more of visual tracking.  

My iPhone has a compass app you can switch from True to magnetic north. I think that should work, right?


Edited by JamesDuffey, 21 September 2020 - 02:30 PM.


#10 PLShutterbug

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Posted 21 September 2020 - 09:12 PM

Based on advice here I've moved the hinge back almost 4-1/2". Now the center of the azimuth clutch knob is right on top of the center of the tripod, yet I can still manipulate all three of the left/right polar orientation adjusting knobs.

 

The original hinge position put 5 pounds 9 ounces (2.5Kg) weight on the back leg of the tripod (the one under the level), and both other legs errored out on my 10 pound-maximum scale. So over twice the weight on the "front" two legs than the back, so I agree it was somewhat perilous.

 

The new hinge positions is: back: Err (>10#); right-front: 10# 1oz; left-front: Err. Much better balance.

 

This does mean I have to round at least the tripod mounting plate, as the triangular section that locks the latitude adjustment now hits that plate if it is not exactly aligned at 0°.

 

Too cloudy to see anything tonight and early meetings until Friday means I won't be able to test it under the stars for a few days. I'll report back.

 

Attached Thumbnails

  • Wedge II Wide JPG30.jpg
  • Wedge II Detail JPG30.jpg


#11 speedster

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Posted 22 September 2020 - 12:04 AM

Great job.  To put the center of Gravity over the tripod, your first hinge location was right.  Compare it to the Celestron version:

 

1447758194_IMG_555064.jpg



#12 PLShutterbug

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Posted 22 September 2020 - 12:17 AM

I actually pulled that image into Visio and drew lines indicating the mount height. The hinge is about halfway between those two bolts to the right and third under the hinge.

 

My second location is closer to the image than my first. The weight comparison shows it is better balanced at the new location.



#13 deansjc

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Posted 22 September 2020 - 03:26 PM

I guess there  is some debate on where the COG actually is, as opposed to the consensus that the COG should be over the center of the tripod :-)  My only suggestion is to do the "feel test" by tilting the whole set up - carefully - onto just two legs and sense the push-back until it feels the same regardless of which way you tilt the rig.  It won't be precise, but will give you a very good sense.  I expect that the COG moves when you point north vs. south also, unless you have a well balanced OTA.  If you have an AP rig, you may have pushed the tube a fair way forward to accommodate your camera for zenith.

 

I could be wrong, but I believe that the Celestron wedge can be slide a few inches back and forth to accommodate different configurations.  I use an SE mount, which could be different of course, but my "sweet spot" is 2" in the direction of North.  I also have a leg aligned toward north.  It seems "just right".

 

You'll see hopefully in the picture here that I modeled my "prototype" off the Celestron mount, using pivots and not a hinge.  It works fine this way too.

 

 

Attached Thumbnails

  • Capture.JPG


#14 PLShutterbug

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Posted 22 September 2020 - 06:52 PM

I guess there  is some debate on where the COG actually is, as opposed to the consensus that the COG should be over the center of the tripod :-)  My only suggestion is to do the "feel test" by tilting the whole set up - carefully - onto just two legs and sense the push-back until it feels the same regardless of which way you tilt the rig.  It won't be precise, but will give you a very good sense.  I expect that the COG moves when you point north vs. south also, unless you have a well balanced OTA.  If you have an AP rig, you may have pushed the tube a fair way forward to accommodate your camera for zenith.

 

I could be wrong, but I believe that the Celestron wedge can be slide a few inches back and forth to accommodate different configurations.  I use an SE mount, which could be different of course, but my "sweet spot" is 2" in the direction of North.  I also have a leg aligned toward north.  It seems "just right".

 

You'll see hopefully in the picture here that I modeled my "prototype" off the Celestron mount, using pivots and not a hinge.  It works fine this way too.

Nice looking box. 
 

As I wrote above, I didn’t just lift and estimate. I used a 10# max. scale (most accurate I have for this weight range) and measured the force on each foot. With the hinge in the original position I had over twice as much force on each “front” foot. At the new one they are roughly similar. So I’m going to leave things as they are.

 

Yes, the Celestron wedge does allow forward/backward movement. I know my latitude so don’t need that sophisticated a setup. More important to me was ability to adjust latitude and east/west positioning relatively precisely.

 

Cloudy today so likely no chance to test. I will work on it again Thursday night.




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