A general/conversational topic for discussion

[davekelley]

I hope this isn't out of place on here.  I have always wondered so I thought I'd put it to the forum.......whydo many large Maks even up to 150mm, feature the dovetail bar on the side edge of the ota, when surely it makes 100% more sense to place this on the underside, in terms of balance and just common sense really it seems a bit nutty hanging the ots from one side of the mount and tripos when clearly it should be atop and central to the whole setup?  Just seems so daft.

Any thoughts or explanations anybody?

[Mr niall]

Well there’s two points to consider; the first is - it depends on the Mak. Many come in a package with a mount and the position of the dovetail is relative to what works best with the type of mount. Relatively speaking even a 6 inch Mak is fairly compact so it’s not a massive issue generally.

The second thing I would say to consider is the fact that they’re rotatable so you can mount them however you like! You might need to adjust the mounting for the RDF but that’s it. So if you want to mount it differently it’s never a big deal. 

[johninderby]

You will find that pretty well all maks sold as seperate OTAs have the dovetail bar on the “bottom” as you described it.

It’s only those OTAs that come with some mounts that have them on the “side”

 

[Stu1smartcookie]

I had the same issue recently with a Celestron 102 .. it was set up to use on the right hand side of the mount … it proved to be a bit of a pain trying to mount it on other mounts … I suppose the answer is to buy a set rings .. then you can svivel the scope around . 

Edited August 8, 2021 by Stu1smartcookie

[SMF]

Definitely tube rings, id rather they came with them as standard. I’ve got the SkyMax 150 and the fixed position dovetail is a right royal pain on an EQ5. The finder scope becomes unusable without contortionists skills. Currently on the look out for a set to fit 182mm OD.

[doublevodka]

Purely down to manufacturer convenience, everyone you see with a short dovetail bolted to the side will have been supplied on a altaz mount designed to connect to that side, it's cheaper for them to use two bolts than a set of rings

Personally I agree they should all have rings as it would make them more versatile, but manufacturers would rather sell you more kit 😉

[doublevodka]

15 hours ago, SMF said:

Definitely tube rings, id rather they came with them as standard. I’ve got the SkyMax 150 and the fixed position dovetail is a right royal pain on an EQ5. The finder scope becomes unusable without contortionists skills. Currently on the look out for a set to fit 182mm OD.

https://www.firstlightoptics.com/tube-rings/skywatcher-telescope-tube-rings.html

 

Or on the astro buy and sell things on facebook there are some guys doing 3d printed ones depending on what you are after

[SMF]

1 hour ago, doublevodka said:

https://www.firstlightoptics.com/tube-rings/skywatcher-telescope-tube-rings.html

 

Or on the astro buy and sell things on facebook there are some guys doing 3d printed ones depending on what you are after

Thanks, the 182mm were out of stock yesterday. Ordering now.  

[Louis D]

Exactly why would it make more sense to mount a scope on top rather than on the side of the mount?  On an alt-az setup, you'd have to counterbalance a scope on top to keep it from turning the whole mount turtle at high altitudes, adding unnecessary weight to a grab and go rig.  Mounting it on the side allows it to be balanced front to rear at any altitude without any additional weights.  Here's my dual mount grab and go setup with a Mak side mounted on one side:

[Zermelo]

There really is no intrinsic "top" or "side" on an instrument that is symmetrical about its axis. I presume we're talking about the positioning of the dovetail with respect to the finder shoe (which for convenience we would prefer to be no lower than the eyepiece, when in use).

As an example, the Skymax 127 comes in two versions, with the shoe in different positions.

If you buy it as a package with a single-arm alt-az mount like the AZ GTI, you get this:

If you're looking from the eyepiece end of the OTA, the finder shoe is about 120 degrees anticlockwise from the dovetail.

But if you buy the OTA on its own, you get this:

where the shoe is offset about 120 degrees clockwise from the dovetail. If you put this is an AZ goto mount you might get the finder positioned lower than the eyepiece. Some goto mounts (including the AZ GTI) can be flashed so that you can operate with the OTA reversed, if needed. Or you can do what I did, and substitute a RACI finder that can just be turned upwards to match the eyepiece.

With an EQ goto mount, the eyepiece often ends up in odd positions in any case, so OTA rings are probably the way to go.

[RT65CB-SWL]

On 08/08/2021 at 17:06, davekelley said:

I hope this isn't out of place on here.  I have always wondered so I thought I'd put it to the forum.......whydo many large Maks even up to 150mm, feature the dovetail bar on the side edge of the ota, when surely it makes 100% more sense to place this on the underside, in terms of balance and just common sense really it seems a bit nutty hanging the ots from one side of the mount and tripos when clearly it should be atop and central to the whole setup?  Just seems so daft.

Any thoughts or explanations anybody?

You think that is bad!

 

Spare a thought for 'us' ETX90/105/125 users... there is no provision whatsoever for attaching a dovetail...

...bar if you remove the plastic flip mirror housing/visual back and replace it with a 'third-party' backplate...
hence the reason for the Jubilee/hose rings on mine!

Edited August 10, 2021 by Philip R