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This stuff makes me nervous!

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#1 Murff

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Posted 28 July 2020 - 12:01 AM

This is my first refractor, and first German eq mount.  A long time ago I had a 10" Meade SCT on the normal mount with a wedge.

The whole rail mount, with just 2 screw pushing it sideways... make me soooo nervous!  I was just out testing the new set up, and I found myself checking those 2 knobs like every 30 seconds, especially when the scope was looking almost straight up.  I feel like I wish there was some safety device in place.  I'm sure it's just me being new, but that's a lot of $$ hanging by those 2 screws!


Edited by Murff, 28 July 2020 - 12:02 AM.

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#2 Goldengirl52

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Posted 28 July 2020 - 12:07 AM

This is my first refractor, and first German eq mount.  A long time ago I had a 10" Meade SCT on the normal mount with a wedge.

The whole rail mount, with just 2 screw pushing it sideways... make me soooo nervous!  I was just out testing the new set up, and I found myself checking those 2 knobs like every 30 seconds, especially when the scope was looking almost straight up.  I feel like I wish there was some safety device in place.  I'm sure it's just me being new, but that's a lot of $$ hanging by those 2 screws!

Ohmygosh, you're in Rogue River!!  I lived in Wimer years ago, and also right on the Rogue at one time in a cabin!  Talk about stars in those dark skies!!

 

Someone will get on here that knows about your scope and help calm your nerves I'm sure.  I'm brand new, just a few weeks ;)


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#3 Murff

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Posted 28 July 2020 - 12:09 AM

Lol, I put Rogue River, but I live out in Wimer, Queens Branch :)

It's a small world...


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#4 Sleep Deprived

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Posted 28 July 2020 - 12:11 AM

I agree with you 100%, but I think that's just the way it is.  I know I am nervous for exactly the same reason!



#5 RichA

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Posted 28 July 2020 - 12:12 AM

This is my first refractor, and first German eq mount.  A long time ago I had a 10" Meade SCT on the normal mount with a wedge.

The whole rail mount, with just 2 screw pushing it sideways... make me soooo nervous!  I was just out testing the new set up, and I found myself checking those 2 knobs like every 30 seconds, especially when the scope was looking almost straight up.  I feel like I wish there was some safety device in place.  I'm sure it's just me being new, but that's a lot of $$ hanging by those 2 screws!

1 x 1/4-20 bolt can hold over 1000lbs.  5 threads into 6061 aluminum is more.


Edited by RichA, 28 July 2020 - 12:14 AM.

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#6 Goldengirl52

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Posted 28 July 2020 - 12:14 AM

Lol, I put Rogue River, but I live out in Wimer, Queens Branch smile.gif

It's a small world...

It sure is and looking up makes it look even smaller, lol!!  I know Queens Branch for sure.  I went to Evans Valley school in 4 grade and part of 5th.  That was where I was the day Kennedy was shot.  I can't remember my teachers name now.  I just came in from viewing the moon tonight with 2 of my neighbors, and it was gorgeous.  I don't have my new scope yet, but we are using a very old Pentax.  Amazing, I'd never seen the craters of the moon with my own eyes ;)


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#7 M44

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Posted 28 July 2020 - 12:22 AM

I usually have an extra screw on the dovetail plate(objective side) as a stopper in case of accidental loosening.


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#8 Murff

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Posted 28 July 2020 - 12:36 AM

I usually have an extra screw on the dovetail plate(objective side) as a stopper in case of accidental loosening.

 

Ohh, that's a great idea!

 



#9 sg6

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Posted 28 July 2020 - 02:46 AM

I usually have an extra screw on the dovetail plate(objective side) as a stopper in case of accidental loosening.

I agree a good idea. Had not thought of it but the dovetail seems pretty secure anyway even when moving around. But a smallish extra screw does make sense and is both easy and inexpensive.

 

Looking at mine I may want an extra hole made as the present ones are just arranged wrong. But no worries there, easy enough to get one done.



#10 213Cobra

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Posted 28 July 2020 - 03:14 AM

Relax. I've been at this close to 60 years. In all the time that delta plates have existed, I've never had a scope fall away from its mount. The binding force of two quarter/twenty bolts against the aggregated contact area of the female and male delta plates is overkill for the mass of any telescope you are going to install on the mount. If you forget to tighten bolts, that's on you but you won't. Even securing one is going to keep your gear investment sufficiently safe.

 

Phil


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#11 noisejammer

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Posted 28 July 2020 - 06:31 AM

I strongly recommend the safety screw. Better, install one at each end.

 

I do tighten things but one day my TOA - which was held by an A-P DOVE08 - slipped all the way to the screw. It's next stop would have been the concrete floor of my balcony. And tears. Lots and lots of tears. smile.gif

 

I never really confirmed the cause for the slip but I suspect temperature changes coupled with a heavy load and a poor clamping knob design. Nevertheless, I removed that saddle the same day and I didn't observe until I'd replaced it.


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#12 gnowellsct

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Posted 28 July 2020 - 07:01 AM

This is my first refractor, and first German eq mount. A long time ago I had a 10" Meade SCT on the normal mount with a wedge.

The whole rail mount, with just 2 screw pushing it sideways... make me soooo nervous! I was just out testing the new set up, and I found myself checking those 2 knobs like every 30 seconds, especially when the scope was looking almost straight up. I feel like I wish there was some safety device in place. I'm sure it's just me being new, but that's a lot of $$ hanging by those 2 screws!


I don't know if it'll make you feel better but it's a design that is used by the top engineers and manufacturers in the business. This includes astro-physics, Losmandy, and vixen telescopes.

I know that the Altaz fork mount May feel normal to you but some of us have been using German equatorials since the 1960s. It's the fork mounts that seem weird.

And who would want a fork mount that is basically usable with only one telescope? I use half a dozen different telescopes on my three mounts. I switch them and mix them up.

As a final point you should know that even in the altaz configurations these days the rail secured by a screw is commonplace. For example in the Celestron SE and Evo designs the telescope is rail mounted. That's because more than one telescope is sold with each mount. And the great thing about it is if you get one of these mounts for example for a C8 You can use it with a 4-in refractor.

#13 gnowellsct

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Posted 28 July 2020 - 07:14 AM

I strongly recommend the safety screw. Better, install one at each end.

I do tighten things but one day my TOA - which was held by an A-P DOVE08 - slipped all the way to the screw. It's next stop would have been the concrete floor of my balcony. And tears. Lots and lots of tears. smile.gif

I never really confirmed the cause for the slip but I suspect temperature changes coupled with a heavy load and a poor clamping knob design. Nevertheless, I removed that saddle the same day and I didn't observe until I'd replaced it.

Generally speaking the issue hereis not following the same logic that is used when you tighten the lug nuts of a car wheel. When you tighten the lug nuts of a car wheel it is best to go down to moderately tight then use a star pattern Will you skip the immediately adjacent lug nuts and go to the one across from the one you just tightened.

When all the lug nuts have been moderately tightened you can then finish the job. I note that if you're doing it right you will use a torque wrench so you don't over tighten on the final step. If you just cramp things down as hard as you can by jumping on the lug wrench and such stuff you may succeed in warping your rotors.

But I digress. When you have two clamps on the dovetail if you just tighten one as tightly as you can because you're paranoid and then tighten the other one as tightly as you can, it can lead to the odd situation where the exaggerated pressure on the first clamp may make you think that the second clamp is tight when in fact it isn't. That's because you can't move the dovetail that last 32nd or 64th of an inch against the pressure of the first clamp. The result is an incomplete clamping which can lead to the consequences you describe.

The best way to avoid these surprises is tighten the first clamp just enough to provide moderate pressure while you tighten the second clamp. That one should also be moderate pressure. Then tighten the first clamp all the way down and then tighten the second clamp of the way down. It's just a version of what you do when you have lug nuts or any multi-screw system that has to be tightened down.

The ergonomics of handle design is important in this process and you are right that knobs which are too small aren't very helpful. Knobs which are too big present their own problem.

I won't go so far as to say it is the best possible system but it is a widely used system that allows a person to have one or two mounts and be able to use a large number of telescopes with them. So nearly as I can see the industry trend is toward an expansion of dovetail use. The DM6 discmount for example is a side mounted altaz rail type system. And as I indicated in a previous post Celestron has moved to this system for the SE and Evo lines which is kind of cool because now you buy a 6-in SCT with go to and if you want put a 4-in refractor on the mount and take the SCT off. Or vice versa. Vixen, l o s m a n d y, and astro-physics have been using the system for decades.

They are manufacturers who want their mounts to accept as many different telescopes as possible in order to widen the market. It has the interesting effect of encouraging people to own multiple telescopes all of which can be well mounted.

Edited by gnowellsct, 28 July 2020 - 07:22 AM.


#14 MirkoV69

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Posted 28 July 2020 - 08:25 AM

Some plates are designed with recessed screw seats but the screws do protrude a few millimiters in order to prevent accidental fall of scope in case of incorrect tightening. Otherwise just use one additional screw on the other side of the Losmandy just for peace of mind.

 

Mirko



#15 noisejammer

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Posted 28 July 2020 - 11:35 AM

... But I digress. When you have two clamps on the dovetail if you just tighten one as tightly as you can because you're paranoid and then tighten the other one as tightly as you can, it can lead to the odd situation where the exaggerated pressure on the first clamp may make you think that the second clamp is tight when in fact it isn't. ...

The ergonomics of handle design is important in this process and you are right that knobs which are too small aren't very helpful. Knobs which are too big present their own problem. ...

An interesting idea and possibly true, however I've always been a snug it up then tighten kind of user. To my mind, the knobs are more likely to be related to the problem because it's difficult to grip them in Toronto's cold.

 

Having used one for years, I find Tom's design of the DM6 saddle to be excellent. The floating nature of the jaws and their large surface area results in a good fit and reliable contact even if the dovetail is slightly misaligned. Since it slipped, the AP saddle is forever off my most-loved-gear list.



#16 daquad

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Posted 29 July 2020 - 06:58 PM

I always place the dovetail with rings attached first, making sure the rig is secured.  Then I place the scope in the rings and tighten them to the tube.  I've never had a problem with slippage doing it this way.  I use a Losmandy D-style plate for my mounts;  Vixen -style plates are trickier and require more diligence in set up, but the same general procedure should apply for secure holding of your OTA.  

 

However, for me anything over 4" short focus doublet should use a Losmandy-style dovetail.

 

Dom Q.



#17 helpwanted

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Posted 30 July 2020 - 05:12 PM

I put a bolt through an opening in the dovetail, then rest it on the clamp part... then balance the scope with eyepieces and diagonal in their focused position by moving the tube up and down in the holder. So now when I put the scope into the dovetail clam, I just rest it on the bolt and I know my balance is perfect once the scope is fully equipped... and that same bolt acts as a stop if anything slips.



#18 Jon Isaacs

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Posted 30 July 2020 - 08:58 PM

My own thinking/experience is that the bolt is very secure. Slipping and dropping come from improper installation, nearly always the result of trying to mount the scope at night, in the dark.

 

Either do it inside where you can see or use plenty of light so you can really see what you're doing.

 

Jon


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#19 RichA

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Posted 30 July 2020 - 09:16 PM

I strongly recommend the safety screw. Better, install one at each end.

 

I do tighten things but one day my TOA - which was held by an A-P DOVE08 - slipped all the way to the screw. It's next stop would have been the concrete floor of my balcony. And tears. Lots and lots of tears. smile.gif

 

I never really confirmed the cause for the slip but I suspect temperature changes coupled with a heavy load and a poor clamping knob design. Nevertheless, I removed that saddle the same day and I didn't observe until I'd replaced it.

Clamping mechanism might be better than the rounded heads of screws.  Like this, or other systems:

 

https://aliexpress.r...earchweb201603_



#20 Nippon

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Posted 31 July 2020 - 01:14 AM

Any dovetail a Losmandy D or a Vixen style is an accident waiting to happen without safety stop screws. If you are using a D dovetail in a dual D/V saddle make sure your stop screw sticks down enough to catch. Usually it takes an allen head cap screw along with 3 or 4 washers. Without those washers the dovetail will just sail right off the mount. Allen head cap screws are pretty square topped even if the dovetail tries to rise as it slides back, and it will, it is not going to get past the bolt. And as Jon said above have light on what your doing. I use a head lamp that has a very bright white light, a dimmer white light, and a nice red light. I observed with a guy back in the day that had an SP C80 and for those who are old you know that the SP mount used taps that the flat base of the tube rings bolted to. This guy would just sit his scope on the tabs while he went and got the thumb bolts. Usually the SP's attachment bolts were captive but he had removed the little C clips for some reason. Amazingly his scope never fell but it made me cringe every time. Also cringe worthy is all the photos I see on CN of scopes on their mounts with no counterweight, sometimes without even the counterweight shaft. A scope doesn't have to fall to the ground to get messed up. 




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