TheSkySearchers

Plan: Build this DIY wedge for my ~ 5 lb Mak to sit on.

Qptions

• a. Just center everything and hope for the best.

• b. Try to estimate an offset to mounting holes so the center of mass of the scope is roughly over the vertical axis through the tripod.

• c. Try to include a counter weight attachment point so I can balance it after the fact.

Any thoughts, insights, tips, tricks, chemically induced metaphors are welcome.

i think you're over thinking this wedge idea 2 kg is nothing . is your mak on an alt az mount ? do you a have link or an image ?

GCoyote wrote: ↑Fri Aug 14, 2020 1:09 pm Plan: Build this DIY wedge for my ~ 5 lb Mak to sit on.






chemically induced metaphors are welcome.

hahahah

yobbo89 wrote: ↑Fri Aug 14, 2020 5:57 pm i think you're over thinking this wedge idea 2 kg is nothing . is your mak on an alt az mount ? do you a have link or an image ?

The mount was $25 bucks so I'm not out much if it falls off the deck. I want to practice on this easy one out before I try to mount anything heavier or more complicate.

Because the Mak is so short, the weight is pretty far back.

The design was intended to hold a Celestron SLT or GT Alt-Az mount. If you plan on using a different Alt-Az mount then you may need to adjust the placement of the hole that attaches the wedge to your tripod so your mount's CG is roughly centered over the tripod. Exact positioning is not really needed.
From the picture, you can see that for the SLT/GT you to place the tripod attachment hole 1 1/4" from the hinge line.


Cheers,
JT
BTW, it was my article and my design that you are building. If you have any questions, don't hesitate to ask. jt

Mount the scope and mount on the wedge. Then slide a dowel under the base plate of the wedge and move it north or south until the whole contraption balances. Mark the location of the dowel. That is (directly below) the centre of mass.

That's how I balanced my wedged C-90:

Thanks for that tip Kathy.

That is exactly how I balance my side-by-side AP set up before it gets mounted into the CEM60 saddle.

Cheers,
JT

KathyNS wrote: ↑Fri Aug 14, 2020 10:55 pm Mount the scope and mount on the wedge. Then slide a dowel under the base plate of the wedge and move it north or south until the whole contraption balances. Mark the location of the dowel. That is (directly below) the centre of mass.

That's how I balanced my wedged C-90:

Excellent, that's what I need to know!

JayTee wrote: ↑Fri Aug 14, 2020 10:23 pm The design was intended to hold a Celestron SLT or GT Alt-Az mount. If you plan on using a different Alt-Az mount then you may need to adjust the placement of the hole that attaches the wedge to your tripod so your mount's CG is roughly centered over the tripod. Exact positioning is not really needed.
From the picture, you can see that for the SLT/GT you to place the tripod attachment hole 1 1/4" from the hinge line.


Cheers,
JT
BTW, it was my article and my design that you are building. If you have any questions, don't hesitate to ask. jt

I was wondering why it looked familiar but I got it from AF.net and the rest of post is no longer available. It looks very simple and clean which is why I went with this one. I'll let you know if I have more questions.

Thanks everyone!

Here's the whole article with build instructions. I pulled from AF over to here, early on.
viewtopic.php?f=24&t=3129

BTW, I use a turnbuckle where the spings are for holding the correct latitude, the altitude adjustment lock. I found it made this wedge just a bit more solid for heavier loads on the mount.

Cheers,
JT

I have a good bit of composite decking material leftover from the last upgrade. It's more stable in the humidity than wood and very easy to work.

Please post pictures as you progress in your build. I am very interested in how things turn out for you.

Cheers,
JT

JayTee wrote: ↑Sat Aug 15, 2020 9:48 am Please post pictures as you progress in your build. I am very interested in how things turn out for you.

Cheers,
JT

Well I was half way through my last project before the the thought to take some pics hit me. I still have to get the hardware for this job and it would be much better if I could do it out on the patio so I need the weather to not suck so much.

I've got most of the hardware and started cutting the main bits of wood.

Question: I have an extra 3x finder scope I don't use. Any reason I can't mount it to one edge of the wedge plate to make polar alignment easier?

GCoyote wrote: ↑Sat Oct 17, 2020 12:46 am I've got most of the hardware and started cutting the main bits of wood.

Question: I have an extra 3x finder scope I don't use. Any reason I can't mount it to one edge of the wedge plate to make polar alignment easier?

Go for it! Good luck with the build.

Starting with JT's plans, I scrounged through my extensive collection of spare parts and leftovers.

I substituted composite decking material for the wooden parts:
+ Does not change shape with changes in humidity
+ Does not require protective paint or coating
- Noticeably heavier than typical woods
- Butt ugly
In place of the 3/4" dowel for the pivot I use a 1/2" polymer roller I stripped from some defunct appliance. Very strong and stable with little rolling friction.
Instead of making attachment points for the dowel, I used 1/2" conduit clamps. Fewer parts, no gluing.
Since my observing locations only vary by about 3 degrees in latitude, I swapped out the 7" 5/16 threaded rod for a 5" hex bolt of the same size.
So far so good. Add some spring tension and try setting it for my latitude.
Now to try putting a scope on it ... oops. A little butt heavy.
So to get the scope upright and get it to balance, I added a 90 degree adapter and a counter-weight.
Now to find the balance point. (Thanks for the tip Kathy!)
For the tripod adapter and low friction pad, I used ordinary furniture sliders and the side from some household cleaning product.
Last minute addition was a two axis bubble level. (Not shown)

So there you have, "The Mark I"

I was cleaning up for the night and happened to look up to see Mars smiling back at me despite a forecast for 46% cloud cover.

So I took the Mark I out on the patio and set it up by flashlight.
Levelling - Approximate
Polar Alignment - Approximate
Results - A little iffy.

Because I did not have a chance to test it out beforehand, I had all sorts of issues.

1. The adapter does not lock to the tripod so my polar alignment isn't locked in either. Need to figure out something for that.

2. The total weight made my one available tripod more than a bit 'bouncy'. It took a number of seconds to damp down after each adjustment.

3. I'm getting too much backlash when I try to track along the RA. Playing with the tension between the mount and the wedge did not eliminate it. I might have to try some different bearing materials and alternative counter weights to get it to track smoothly.

4. It turned out the scope and all attachments blocked the peep hole I'd made for polar alignment. I may have to mount that finder scope after all.

I have much heavier studio tripod but It needs some mods to accept astro gear. That will be another project.

Bottom line: I was having so much fun playing with my astro gear I forgot to finish my beer!

I have replaced the springs that secure the mount plate at the correct Latitude with a turnbuckle. This is a much more secure setup than relying on high tension springs.

Cheers,
JT

JayTee wrote: ↑Mon Oct 26, 2020 12:17 am I have replaced the springs that secure the mount plate at the correct Latitude with a turnbuckle. This is a much more secure setup than relying on high tension springs.

Cheers,
JT

Interesting idea. I'm sure I have one lying around somewhere. That might reduce the wobble a bit in the bargain.

ps. Already ordered some parts for a the heavier tripod.

Still doing upgrades.

I moved the bubble level a bit to make it easier to access the screws, countersunk some screws for a better fit, re-drilled the indentation under the wedge to give the latitude adjustment a more stable seat, and changed the springs for a turnbuckle as suggested.

Picking up some parts tomorrow for more modifications.