TEC 140 photos / dimensions

[Jonk]

I'm in the middle of drawing up the modifications required for my bigger pier for the Mesu MK2 mount, and I'd like some help from anyone with a TEC 140 please.

If possible, could you share some photos of it, with a camera / FW fitted, at full focuser travel, dew shield fully extended, on a mount with the scope in reasonable balance in the rings please?

I'd like to know the tube length with dew shield fully extended, focuser length fully extended and the overall length in mm too please.

I'm guessing the length of the bent part of the pier, and although I am highly unlikely to point it due N and let it rotate and hit the pier, I'd rather not have the possibility of it doing so!

I do appreciate I could slide it forwards and add counterweights, but I'd rather not do this if I can help it.

I currently have a QSI 683, but 'may' get an Atik 460 or similar, however the TEC 140 purchase is a long way down the road but I'd like to measure twice and cut once.

This is my current 'estimate' based on some photos I've seen - I've drawn the scope tube at 1m in length and placed a 'block' on the end to represent a camera.

Long term, I plan to have 2 x Star 71s and the TEC as a permanent set up.

 

 

[Jonk]

I've looked at some photos online and made an educated guess on the length / position in the rings.

This has let me improve the guesswork but still would really like someone to measure theirs in situ please, as I'm nearly ready to start asking local machine shops for prices and want to get this right first time.

Who has a TEC 140... @ollypenrice @kirkster501 @gnomus?

It's also an excuse to improve the 3d modelling and rendering!

Thanks.

   

[andrew s]

Sorry can't directly help, but as well as length you need to consider the center of mass.

I have had to place a scope based on dimensions to fit in the observatory but then used steel and lead counterweights to make it balance.

Regards Andrew 

[Jonk]

The centre of mass of the pier (theoretically) is shown as:

So it's very close to the middle.

It's also lower than half the height due to the base having more material.

A straight pier with wedge would be pretty much the same so I don't think this is an issue.

The only other potential issue I can think of is the upper angle / weld - this may need to be reinforced somehow as I can't help thinking it could peel off if not welded properly!

[andrew s]

I intended the balance point of the telescope .

Regards Andrew 

[Jonk]

Ah I see - yes that is something I need to know to ensure I have enough clearance. I'd rather not have to add weights due to lack of 'reach'.

[Davey-T]

On 29/07/2019 at 15:51, Jonk said:

Long term, I plan to have 2 x Star 71s and the TEC as a permanent set up.

Like this then 

 

You may need to make these as well to get them all aligned with each other and orthogonal to the mount.

Dave

 

 

Edited July 31, 2019 by Davey-T

[ollypenrice]

Your drawing is pretty good! We run a dual TEC140 here, one side with an Atik 460, EFW2 and TEC field flattener. I make the length 1245 mm, so 10mm more than your drawing. You need to allow for the cables to exit the rear of the camera on top of that.

Olly

[Graham Darke]

Here's a picture of mine. Measured 127cm from the front of the dew shield to the back of my camera with the focused fully racked out. That isn't of course the focus position for this camera (DSLR). 

[Jonk]

4 hours ago, Davey-T said:

Like this then 

You may need to make these as well to get them all aligned with each other and orthogonal to the mount.

Yes, that's it!

I haven't looked at alignment yet, but I suspect I will come calling for your ideas if i choose to make something, or I'll just buy the commercially made ones.

3 hours ago, ollypenrice said:

Your drawing is pretty good! We run a dual TEC140 here, one side with an Atik 460, EFW2 and TEC field flattener. I make the length 1245 mm, so 10mm more than your drawing. You need to allow for the cables to exit the rear of the camera on top of that. 

Thanks, I do enjoy CAD and am constantly tinkering and adjusting drawings like this. Very valuable information you've provided, so thanks.

I only hope my efforts reward me in the coming years with some good results!

2 hours ago, Graham Darke said:

Here's a picture of mine. Measured 127cm from the front of the dew shield to the back of my camera with the focused fully racked out.

Again, very valuable information - thanks very much.

I'll have to adjust the pier to suit, as I'm probably too close for comfort, but there's not a lot in it, a couple of inches at most.

[Jonk]

Some quick adjustments and I think I'm probably about there.

I'll get the drawings to the local metal shops and hopefully a favourable price and quick turnaround will happen.

Thanks for the help all, wish me luck!

[kirkster501]

Sorry I am only just back online after being away for two weeks.  Did you get what you needed?  Any measurements you need?

[StarryEyed]

If you used SOLIDWORKS did you run a vibration analysis?

what's the wall thickness?

what type and size weld? weld type?

what's the weight?

these greatly effects the cost and meeting and inherent stiffness you might have planned for.

big plates by the way. I know plate is cheap but.....

Always ask why it's so expensive.

Edited August 4, 2019 by StarryEyed

[Jonk]

On 04/08/2019 at 10:43, kirkster501 said:

Any measurements you need?

Possibly, but for this purpose I have the worst case from 2 others (the maximum length mainly).

I would ask to see where the scope sits in the rings for balance without any additional counterweights, but it would depend on your camera etc. to be accurate.

21 hours ago, StarryEyed said:

f you used SOLIDWORKS did you run a vibration analysis?

what's the wall thickness?

what type and size weld? weld type?

what's the weight?

these greatly effects the cost and meeting and inherent stiffness you might have planned for.

big plates by the way. I know plate is cheap but.....

Always ask why it's so expensive.

No, I've used Autodesk Fusion, as I already use it at work for modelling things for 3D printing. The idea behind this was not to design a product, it was to come up with an easy / affordable way to modify what I already had.

If the Mesu 200 MK2 wasn't ready, or I didn't know about it, I would've probably already ordered a MK1 (if still available) and left it at that. As it is, I want to take the opportunity to make the best of what I have, hence the modifications.

I can run analysis in Fusion, mass loads, vibrations, temperature, bending etc but for the small parts we make as one offs, these analyses are not often needed, so I haven't learnt how to use these tools properly.

From my limited design experience, I can see that the upper weld would be the most potential weak spot, but 1 properly welded 10mm thick pipe should be more than enough for say 150kg (max) on top, even at an angle. It is unlikely that I'll ever get near to 100kg so I should be ok - I have asked others for advice on this and whether any additional support is needed there, which won't affect the scope rotating around the RA axis.

The mass of the pier once complete, assuming the analysis is correct and I have done it correctly will not be far off 200kg! The current pier is around 100kg. It's a big heavy beast but I want to do this once and once only.

There are a few machine shops around me and people at work have offered to help, so I should be able to get this done within a reasonable price.

[StarryEyed]

Bolted to existing base with slots to allow a little direction.

polar axis tube sits in a cradle less stress.the connection between the tubes is a standard structurally and for welds. one change of direction one welded connection less chance of getting it wrong. less vibration less like half a tuning fork !

add bolted plates as a counter balance to keep the cog over the base. you can vary the load. none of the bolted plates have to be circular. plate is cheap cuting square plate is cheapest.

lower to the ground lower cog. easier access. smaller bracing plates smaller foot print.

 

Edited August 6, 2019 by StarryEyed

[kirkster501]

You'll do well to balance three telescopes.  I could not get this to work in my set up, to balance in all orientations.  I wanted to get my Meade 14" (lunar/planetary/visual), TEC140 (small scale AP) and FSQ85 (wide field AP) simultaneously mounted.  Hours and hours of fiddling and I could not get it to balance so the FSQ has been sacrificed off of the permanent set up and I just have the Meade and the TEC140 permanently mounted.  The Meade simply has to be permanently mounted,  it is far too heavy to keep taking off the mount.

I am going to try again at some point with a saddle arrangment like the one Davey-T has.  I did not try three side-by-side, I tried Meade and the FSQ atop the Tec140.  No way, Jose.....

[Jonk]

What I'll try to do is mount all 3 on a flat plate, bolted directly to the mount - no dovetails required.

Something like this I can get for £0:

As the large scope will be central, and a Star 71 will be on each side, the balance L-R should be straightforwards, or at least I hope it will be!

The cameras and focusers will be the same and the guide scope will probably be central, so if anything is out of balance that way, I'll have to add a moveable weight.

Forwards / backwards should be achievable by sliding the central scope.

Worst case, I'll have to add small weights, but this may be the lesser of 2 evils.

[kirkster501]

Balance in one plane is trivial.  Balance in multiple planes is much more difficult.  Not impossible but difficult.  For example, you could get it all balanced east of the meridian and then after the flip it is unbalanced.   You compromise to get it to balance both sides and then when pointing to the zenith you become unbalanced again...  aaaagggghhhh!!!!!  

You might need to develop some counterweight system that you can attach to the sheet with the holes.

[Jonk]

6 minutes ago, kirkster501 said:

For example, you could get it all balanced east of the meridian and then after the flip it is unbalanced.

Aha that's one good thing about a bent knee pier, no flip!

I know it will be tough, but if it was easy it probably wouldn't be as interesting.

No one does astronomy because it's easy.... do they?!

[Davey-T]

You need to make sure any adjusters don't foul the plate, a thicker , narrower one may be better.

Dave

[Jonk]

True, this plate hasn't been chosen yet, it's all in my head at the moment.

The method of scope alignment hasn't been decided on yet either... all future stuff, I have to get the pier done first!

[Davey-T]

1 hour ago, Jonk said:

True, this plate hasn't been chosen yet, it's all in my head at the moment.

The method of scope alignment hasn't been decided on yet either... all future stuff, I have to get the pier done first!

Could you speed it up please, I want to see your Mesu up and running before contemplating trying to fit one on my Meade wedge and I'm not getting any younger 😂

Dave

[Jonk]

Some of us have to go to work....!

I aim to have the pier done in the next month or so, then I'll be looking at ordering the mount and 'might' be able to get one from this current batch, else it will be early in the new year.

Whilst I wait for delivery, the dome can go up and I can start the internal work.

[kirkster501]

1 hour ago, Jonk said:

Some of us have to go to work....!

I aim to have the pier done in the next month or so, then I'll be looking at ordering the mount and 'might' be able to get one from this current batch, else it will be early in the new year.

Whilst I wait for delivery, the dome can go up and I can start the internal work.

Go for a TEC 160 if you  can.  The TEC140 is so good that you wish you would have done.....

[Jonk]

You know I did think about it, and would find a way to afford it but I doubt we have the skies to warrant the extra resolution it offers over the 140.

Don't tempt me!