Equatorial Platform Mounts for Dobs

[WakeyTiger]

Can't find much on here about these - has anybody got one (bought, or self-built). Also, they are certainly much cheaper than the EQ6 mount I would need to convert my 200P dob (1200mm) - obviously you can't track for as long as a GOTO EQ mount, but other than that limitation, are they good value for money compared to a full EQ6 conversion?

Thanks folks, and clear skies!

Matt.

[ronin]

What I see advertised as Equitorial mounts for a Dob seem to be a motorised base that rotates in a plane via motors.

That is not an equitorial mount as in EQ5, HEQ5, EQ6 etc.

In effect you have much as present but don't have to nudge it as often. I suspect the catch is in the wording Equitorial "Platform".

If the intention is AP then the an EQ mount as in HEQ5, EQ6 is what is required.

[JamesF]

I think what you're talking about is often called a "wedge". It's a platform (motorised or otherwise) that allows the base of the dob to be tilted so it's in the same plane as the celestial equator. In turn that means to track an object you only need move the dob in the az plane and can leave alt alone.

From an imaging point of view, the target stays where you want it, but you do still get field rotation, which isn't an issue with an EQ mount. Field rotation probably isn't an issue for planetary imaging as there are programs that can "derotate" the images, but for DSO imaging it limits the sub length because with long exposures you'll get star trails.

James

[WakeyTiger]

Thanks for the comments guys, appreciated.

I think AP might be a goal pretty soon, I'm doing some planetary imaging with the dob as it stands, but it sounds like an EQ6 conversion is needed - and a platform would not be a good substitute in the long term.

[Parus major]

I'll make it easier for you. I own a lowly 150PL and had dreams of AP so I bought a EQ6 and it's seriously the best thing I've bought, rock solid and I haven't went down AP yet! It's like having a new telescope since the solidity adds to image quality.

[WakeyTiger]

Thanks for all the advice... Some great info here :-)

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[Saleratus]

Some of the information in this thread is inaccurate.

With an equatorial platform, you do NOT get field rotation. Your dob rests on the platform, and the whole platform moves with the rotation of the sky, just as a German Equatorial Mount would.

I have two equatorial platforms and love them. Why? Because they are simple and elegant--a true complement to the simplicity and elegance of a dob. Once you set the platform on it's tracking run, you aim and move your dob just as you always would, only when you take your hand off it, it's tracking. The ease of this is especially wonderful for a visual observer. The platform itself is something you just bung on the ground (pointed at the pole star) and start using. Setup takes about 1/10th the time of a GEM.

So what are the drawbacks? First, you have to reset them (and repoint your telescope) every hour or so. But this is pretty easy.

Second, they are made for a specific latitude (within a range of about 6 degrees or so), so you can't travel too far away from home with them. I have two platforms because I have two observing locations at very different latitudes.

Third, if you want to do astrophotography with an EQ platform, you have to get a more sophisticated one that can be guided in two axes. Most of the platforms you will see advertised for sale or as DIY projects only track on one axis. You probably don't want to build a two-axes platform yourself, but the guy who can do it for you--and who is widely considered the master of EQ platforms is Tom Osypowski in California. You can learn a lot from his site:

Equatorial Platforms: Home Page

I have no connection with him aside from being a very satisfied customer.

People don't know much about EQ platforms because they are a custom item made for a certain latitude. Thus the big companies aren't out there promoting them. However, don't take this general lack of knowledge in the amateur astro community as a vote against them--they really are wonderful at what they do.

[TonySpektr]

There's a very enthusiastic yahoo group for equatorial platforms.

I was going to build one but then the opportunity for a pier and a secondhand eq6 at a decent price came along

[Moonshane]

What Saleratus said! I made my own EQP for my 6" f11 dob (a planetary/doubles special) as this is very 'wobbly' when moved (nudging) being such a long tube/focal length. using this means I can track at high mags (the more accurate you align the longer the tracking) for several (10-15) minutes and even longer if accurately aligned (I usually cannot be bothered).

Here's my thread http://stargazerslounge.com/diy-astronomer/127311-equatorial-platform-dobsonian-telescopes.html (I go on a bit) and the (almost) finished article http://stargazerslounge.com/diy-astronomer/127311-equatorial-platform-dobsonian-telescopes.html it cost me about £100 max and some time; it's no Osypowski nut it works and it's mine!

I have to say though if you want to image them buy the right GEM mount - a 'proper' EQP to allow this would cost nearly as much as the right sort of mount anyway and you can always mount your dob OTA on the mount if required.

[WakeyTiger]

Some great reading here - many thanks to everyone who has posted here, really appreciated

Matt.

[WakeyTiger]

Shane, just spent most of the evening reading and understanding your thread...very well done sir! :beer:

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[ollypenrice]

It is important to distinguish between an equatorial platform and a wedge because they are not at all the same thing. I'm at Lat 44 and if I put a Dob on a wedge at that angle it would fall off!

For AP go for an NEQ6, quite honestly.

Olly

[Moonshane]

totally agree Olly. with both points, even though I thing my EQP is great for visual I'd not consider it an imaging rig. if you want an EQP to image properly you have to pay virtualy the price of an EQ6 anyway.