Will a dual axis motor drive track objects?

[hurst]

I already own a 200p and an EQ5 mount but would like to get into astrophotography. Once set on a specific target, will the dual axis motor drive track it? GoTo is way out of my price range at the minute.

Thanks!

[Matt Scunthorpe]

Yes it will track it, how accurately depends on how accurate you have polar aligned the mount. But its not difficult yo get it pretty close.

Knly the RA is needed to track if money is tight. I only have RA motor on mine, dont really need to touch dec apart from lining up

[nephilim]

If your interested in AP then you should take a look at this http://stargazerslounge.com/topic/133187-guiding-conversion-project-for-200p-and-eq5/ its all to do with a diy conversion of the motor drive for the EQ5 to accept an st4 port for auto guiding, essential for long exposures. Its a long thread but for a setup thats not suited to AP the results will amaze you. I'm getting the 200p/EQ5 with motor drive on Friday to do exactly that. On a tight budget its a great way to do it. Good luck.

Steve

[Andymac79]

It really all depends on exposure time, your 200p will magnify errors aswell as targets. The EQ5 with a 200 is a tough gig for imaging, If you do it pay very close attention to the balance of the scope, be prepared to throw away a good chunk of your subs, I do and I only have a 400g camera...

[WaveSoarer]

I agree with Matt. I have the dual axis motors and I've used mine for astrophotography. You need to make sure that the mount is accurately polar aligned and you've balanced the telescope as best you can. With an SLR at prime focus I've used 120 second exposures with the stars still pretty sharp. The batteries were also running a bit low and I expect that the exposure time could have been extended quite a bit more.

I'm fairly pleased with the results I've had and you can stack lots of subs in software such as Deep Sky Stacker. You can certainly get a chance to extend your observational astronomy and get a chance to get some more detail in faint DSOs which otherwise just appear as fuzzy blobs. If you have the funds you can give it a go and you'll enjoy it. You'll certainly learn a lot. A Bahtinov mask is also a must for focusing. I bought one from FLO but you could always make your own.

[Andymac79]

If you are going to buy motors then get both, RA and DEC, there isnt much price diff and if you start guiding you will need the DEC motor for sure.

[WaveSoarer]

Incidentally, it's really easy to mount an SLR onto the 200p. All you need is a T-ring for the camera itself. You then just unscrew the 1.25" EP adapter and the T-ring screws on to the 2" adapter holder (this is held on to the focuser by the two thumb screws set 120 degrees apart which look like bigger versions of the thumb screws which hold the 1.25" EPs in place). There are a few links on here about how you do it. This will put the camera at prime focus. The as supplied 2x barlow lens actually screws directly on to the T-ring and this can then be inserted into the 1.25" holder just like any of your eyepieces. You can focus the SLR this way though the magnification is larger and there will be fewer photons per pixel for a given exposure time.

If you're interested in planets then you could use a modified webcam and there are loads of links on SGL about how to do this. I have an xbox webcam which is cheap but doesn't produce as good a final result as alternatives (which are either more expensive or impossible to get as they're not manufactured anymore).

[LukeSkywatcher]

I think you only need a single RA axis motor to track and image...........but get a dual axis setup as its cheap enough.

[stem1989]

it will track but accuracy is the key, spend a long time perfecting polar alignment, it must be bang on or as near as dammit. Guiding (you will need an st4 mod which can be cheap second hand) will most certainly improve your results, but depending on your magnification & polar alignment you should be able to get 30secs-1min subs, you will have to do a trial and error to begin with and work out how long your longest exposure time is going to be.

Steve

[ollypenrice]

In naive theory you only need to have the RA driven. Forget naive theory!! (Unless you are not guiding, in which case the dec motor clearly does nothing at all and you don't need it.) But if you are guiding then you won't get real guiding accuracy till you guide on both. It is a bad idea to base any guiding decisions on what seems logical at first glance. When you are trying to get the incredible accuracy required to track with sub pixel precision you enter a world in which the devil is in the detail. 1) Dec has backlash in the gears. 2) There is always polar misalignment. 3) The refractive index of the atmosphere varies with elevation above the horizon. Only an autoguider can correct for these. (OK, millionaire mounts have miniscule backlash and sky pointing models to vary the guide speed to allow for variable atmospheric refraction but most of us choose the cheaper option of autoguiding.)

Olly

[hurst]

Thanks for all your replies, still a bit confused!

I have seen this http://www.bristolcameras.co.uk/p-skywatcher-r-a-motor-drive-for-eq5-mount-20462-.htm

and this http://www.365astronomy.com/skywatcher-dualaxis-motor-drive-for-eq5-w-multispeed-handset-p-1943.html?zenid=0b601c172ce9e5a93ea95d8a1c0307ab

Im assuming the first one only tracks on one axis, is that correct? Again any help appreciated!

[WaveSoarer]

Hurst,

The RA motor drive (first link) will allow you to do tracking while the duak axis drive (second link) allows you to do tracking and some fine adjust on DEC and RA via the buttons on the handset. Actually, I expect that the RA motor drive will allow fint tuning of position in RA also via the buttons on its box too. There is a mod for the dual axis hand set which does allow guidng to be used but, as Olly has suggested, there are limits to how accurate this would be considering back-lash in the gears (particularly for DEC) with the dual axis motors on the EQ5 mount. There is a long thread on SGL all about this and excellent results can be achieved.

I only use tracking with the dual axis system and it works a bit like this. Once you've manually lined up on an object, with the fine DEC and RA adjust controls on the mount itself, you tighten the clutches for the motor gears (they work via friction and they are quite neat solution). With the gears engaged the handest is switched on by selecting N (for Northern hemisphere) on the handset and the RA axis motor immediatelt starts tracking. You can now centre the object in the field of view by pressing the RA (left and right hand buttons) or DEC (top and bottom buttons). The RA continues to track when you're doing the fine tuning. The switch on the top right of the handset controls the slewing speed for the fine adjustment (8x, 4x and 2x). I usualy leave it on 8x unless I'm using high magnification. That's pretty much it.

With just the single motor for RA then the you'd need to do any fine adjustment to DEC with only the mount's manual fine adjust control but that's hardly a great difficulty. I hope this helps.

Dave

[Andymac79]

Yes the first is single motor and second is both the motors, see Ollys post above for details. The dual kit is more cost effective in the long run if you will need the DEC motor at any time

[hurst]

Thanks for your help. I fitted the motors this afternoon.

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