TRACKING PLATFORM FOR DOBSONIANS

[yoda]

Hi all a mate has just phoned about this U.K. Astronomy Buy & Sell has anybody used them before.

I have been wanting to get tracking for my dob but I don't want to get rid of my 10'' dob.

[NickK]

For proposed equatorial tracking it seems rather alt-azimuth to me..

[yoda]

If it dose what it says it will be a revilation for dob owners.

[swamp thing]

Hi Andy

They're supposed to work very well although admittedly i have not used one myself.

Personally i would make my own rather than spend that kind of money.

There are a few sites on the web that explain how to build one.

Regards Steve

[yoda]

Hi steve like I sed to Dave you have't seen my D,I,Y. LOL

[swamp thing]

Hi steve like I sed to Dave you have't seen my D,I,Y. LOL

That good huh?

Regards Steve

[JamesM]

Although I don't personally own one, I do observe with someone who uses it and from what I can tell, they're too expensive for what they are and are time limited in their tracking. He levels up the 'platform' in the desired direction but after about twenty minutes the tracking comes to the end of its cycle and so in order to maintain the object's observation, the platform has to be pointed in a new direction to begin all over again. Doing this in the dark is a pain as you have to ensure everything is still level when it's in the revised new position. The speed at which you track has to be 'determined' by adjustment which is itself a bit of a fiddle because the adjustment screw is small and there are no presets for different objects (observing the Moon). This system could benefit from having a larger control knob so that could at least get the speed finely adjusted.

In my opinion if it was a lot cheaper then it might have its uses but as a dobsonian owner, you expect to move the scope along with the object and so one of the virtues of this type of scope is the ease by which you can arrive, set and go - this product attempts to defeat this virtue.

James

[Skylook123]

The price seems similar to some similar products in the USA. The fundamental concept is that the device is designed to a latitude. When set up, it intends to track through 15 degrees of arc, to follow the sky for one hour (+/- 7.5 degrees from level). More than this is very difficult due to the center of gravity of the telescope assembly exceeding the footprint of the tacking platform and causing a tip over. So, if it works as designed, after one hour of tracking it needs to be stopped and reset to the opposite end of the travel and started again. Sky Commader DSCs have a feature that turns off the clock and allows use of a platform with the telescope.

There is at least one kit manufacturer that will sell the electronics and essential metal parts, and give instructions for constructing a platform. TL Systems (Sorry, no URL handy at the moment) is the company, and I built one of his setups in 1998 for a 10" dobsonian and it worked quite well. I believe the cost was 180$US at the time. Other than mounting a newtonian on a GEM instead of a Dob style mount, building or purchasing one of these typse of accessories is useful for high power viewing or imaging. Other options like motor drives in the azimuth and elevation axes such as ServoCat can serve the purpose, but they have field rotation eliminated by one of these tracking platforms. Myself, I found it tedious to set up, and bulky to transport and now with an 18", the platform would be highly impractical for my purposes. My home built did do wonders, however, for planet viewing.

[Mamsoth]

Hi yoda, I've got one (from that company to). The customer service is absolutely fantastic and the rig is fairly well made (although it does look a little rough around the edges compared to some of the ones in the US). Make sure you've got a very flat place to observe from and if you're going to be doing any AP make sure you observe on a solid surface. The feet do sink into softer ground and throw off polar alignment.

Matt

[yoda]

Thank's alot guys for your input.

Hi Matt how long tracking do you get from yours befor you have to restart again.

[JAO]

I don't know about these specific platforms but for dob users this sort of device allows the dob to track for up to an hour depending on what make you go for. I use a Tom Osypowski Platform which permits 60 minutes tracking and fine adjustment in Dec as well as RA.

Equatorial Platforms: Home Page

Whilst some dob owners use them for photography many use them for visual work in order to use high powers. I have one for when the conditions permit high power observing which I must confess is relatively rare.

There are several members of this forum who are in the process of making their own platforms

[Mamsoth]

It runs for an hour after which it hits a little shut off switch that automatically turns the motor off, you hear a sort of a click. The manual says try to reset the platform before it reaches the full hour but I think this is just so it doesn't take you by suprise when it stops rather than being for any mechanical reasons.

[yoda]

Thank's matey JAO.

[sweatysock]

A question just popped into my newbie head - and who better to answer it than you chaps ! An Equatorial Platform seems to work fine with a Dobsonian mount, but would it also work with a Alt-Az ?

I've got a Nexstar 8SE, and the only option I had previously looked at for long exposures photography would be buying a Wedge for the mount - and they are not cheap.

With the tripod legs splayed but not extended, I'd imagine it takes up a similar area to a large Dob base.... So with a bit of woodwork and a perhaps some weights suspended from the eyepiece tray to lower the center of gravity, do you think this would work ?

[JAO]

In theory yes it would work for an altaz mount but in practice it would not.

Dobs tend to have reasonably low centre of gravity which means when the platform is nearing its maximum travel and the scope base is tilted at quite an angle, it remains stable. With a scope on a tripod even with weights and the tripod at a lower position there would be a real possibility of the instrument falling over.

In reality a Wedge of some sort would be much more practical and probably cheaper.

[Peter Drew]

Actually in practice, an alt azimuth SCT would just sit on its base on the top board of the eq platform, however, being as this would give a very low eyepiece position, the platform would have to be placed on something like a pier. IMO, equatorial platforms are best suited to Newtonians 18" or larger where a suitably large, stable, tracking mount of conventional design would be much more expensive or difficult for the average DIY enthusiast to undertake.