Guiding ...... Help!

[Woolleson]

Hi.

After a month of being very happy with my SW 150P on a EQ3-2, I've got hooked on imaging, only planets at present but really want to do DSO's.

One thing that newbies should be made fully aware of, the night sky moves quick ..... Like lightening! With this i find keeping objects centralised, frustrating

So on to the question, now I realise a RA is the basic (read the very good "every photon counts") requirement. But looking around there is so many other "guiding systems".

For not only viewing but tracking what are my options, is a RA or RA/Dec all I need? Or would an off the shelf guiding system (don't really want to go DIY) like synguider be a better option?

*edit* One thing in my current location (I.e back garden) I'm positioned so though at present get good views of the skies from east to south I'm obstructed in the north and some west. With that Polaris in not easily seen, so that may have to be taken into account.

Any feedback would welcome

[Capricorn]

You are talking about a set of motors, this will allow tracking.

For guiding you need goto, the system has to be told where to goto by the guide scope and software.

Putting motors on the mount will be about £80-100. With motors you will need to accurately polar align the mount, when done you could track fairly accurately for, I think, 2-3 minutes.

With a guide system you can track/follow for 20-30 minutes.

I suspect it is not worth putting a goto on an EQ3-2 (cost), so a set of motors is probably the most feasible.

[Tinker1947]

The other problem that could arise, would be the extra weight of a guiding system on you present mount...

[Merlin66]

IMHO I'd at least consider adding an RA motor....

This, after some polar alignment, would allow the mount to track your target object and give you more observing time.....

[Woolleson]

Thanks, what's the issue with a goto on the mount?

I understand it is fine for adding a dslr, know its happy with a webcam. Would it be to unsteady or to much weight for the drives?

Longer tracking would be good, 3 mins seems a little short

[Freddie]

Tracking is simply adding a drive that will move mount at a set speed. Guiding fixes on a guide star and sends signals to the mount to ensure the guide star is kept in the same position. GOTO is not related to these things but allows you to tell the mount what you want it to point at and then will move to that object. Makes finding things easier.

[ollypenrice]

For guiding you need goto, the system has to be told where to goto by the guide scope and software.

Sorry but no, this is quite incorrect. GoTo and autoguiding are entirely unconnected. An autoguider corrects the tracking using a feedback loop from a separate camera: when the selected 'guide star' moves erroneously on the guide camera's chip that movement is reported to the PC which sends a correction to the mount to put it back where it was. Imagers want to keep the tracking error on their imaging camera within a single pixel so that it will be invisible. That is a very, very high standard of accuracy.

The accuracy needed depends mostly on focal length (but also on pixel size.) Three minutes at short telescope focal lengths requires autoguiding, though if you throw away many of your exposures you may end up with some that are error free. Even with an expensive (£5K) mount I autoguide even with the shortest telescope focal length I have. It's a fact of imaging life, but you can dip your toes in the water without it.

Olly

ollypenrice's Photos

[Woolleson]

Thanks for the in-depth replies.

Just to get my head around it, there is no need for a goto system. A RA drive will let me follow an object but only in one plane for about 3 mins.

An auto guider is a control method for both RA and DEC motorization via a camera mounted to a scope that locks onto a star and the computer then alters the motors to suit.

Sound about right?

If so and assuming my mount (take it that is both the tripod and eq head) can take the weight of a DSLR/webcam and a guider scope and cam (would a standard finder scope do?) would the option be a dual drive and auto tracking setup?

The auto guider sounds just what I'm after, does anyone have some recommendations?

Thanks again

[Capricorn]

Olly, do simple RA+Dec motors have feed back, or can they be controlled via the guide camera input to speed them up, slow them down or in general move them.

I was not aware that 2 simple motors were able to be this sophisticated.

[ollypenrice]

If you want a system that really works you need an HEQ5 and autoguider as a minimum. Lesser systems will work up to a point. This assumes that you stick to a reasonable focal length and scope weight. People always talk about weight but it is really only about a third of the equation along with size (for attracting wind), length (polar inertia) and focal length (tracking accuracy.) A good autoguider is a second hand old style CCD like the Meade DSI and a finder-guider or ST80.

Capricorn, the accuracy with which stepper motors respond to the autoguider depends on the fineness or coarseness of their steps. The HEQ5 beats the basic EQ5 in this respect. In theory it should be possible not to guide in Dec. In reality I always find that it is necessary, at least in one direction. The motors do need an autoguider to provide the feedback. Direct Drive mounts can have encoders on their shafts which correct them against an accurate clock but they are very expensive (decent sporsts car) and not all that likely to work as yet.

Olly

[ncjunk]

Olly, do simple RA+Dec motors have feed back, or can they be controlled via the guide camera input to speed them up, slow them down or in general move them.

I was not aware that 2 simple motors were able to be this sophisticated.

We've just been slightly confusing things earlier in the thread. Take the eq6 as an example it comes in two types syntrek and goto. Syntrek has the motors and control board, which controls our steppers for us via a basic hand controller, for moving the mount and tracking BUT has no goto. This mount can be connected to and auto guided via the control board either using the serial port or guide port. We connect a camera to a pc and run software to determine the error and feed it back to the mount. The goto version is exactly the same except it has a more complicated hand controller which contains a database of objects and can send the control board to the correct locations.

You may get an even simpler type of mount that just runs the motors at sidereel rate and nothing more (no control board). If you have that then no it can't be auto guided without some additional control or interface.

No idea what we have here but you can't just connect two motors and auto guide...but also goto isn't a requirement either.

[rocketandroll]

You have the basic theory sorted... so...

As has been suggested... in practical terms, you really have two options....

1: add RA motor to your EQ3 and stick with just a DSLR and lens for widefield stuff or a small scope and stick to short exposures. With a 150P on a motorised EQ3-2 (a friend of mine did this) you should get 30 - 40 second subs fairly easily... which with a modded camera at 800ISO+ will actually give you quite a lot you can do. A shorter focal length scope like a WO ZS70 or a fast 80mm ED would give you slightly longer subs, maybe a minute or slightly more. To get 3 minutes+ you would have to be using a 100mm lens or similar and have some seriously good polar alignment.

2: Go the 'serious' route and assume you'll want to be guiding sooner or later... buy a HEQ5 or NEQ6 (the goto would be nice but the Syntrek would do, as discussed) a dual saddle or extra scope rings, and ST80 to use as your guide scope and a QHY5 or even better a Lodestar guide camera, get an old laptop, install EQmod and PHD and away you go.

It should be noted... you say Polaris is hard to see from your location... for imaging of ANY kind you MUST be able to align the mount on Polaris before you start... no Polaris visible in Polarscope... no tracking OR guiding.

Actually, that's not 100% true as I know there are mounts that can Polar align without seeing Polaris... but the majority of options open to you DO need to see it to work.

Ben

[1981suede]

If you can't see Polaris but you can see south and east/west then you can use a technique called drift alignment. Give it a google - here is a good thread http://stargazerslounge.com/beginners-help-advice/135269-polar-alignment.html

[themos]

We can now say that you can autoguide with any EQ mount in the Skywatcher series: EQ1, EQ2, EQ3-2, EQ5, HEQ5, EQ6.

The main difference is the weight that each can carry and still track reliably. At one end of the scale, my EQ1 will work with a 135mm lens for 8 minutes exposure (at 8" per pixel). At the other, my EQ6 can do 10minutes with a Meade 2000mm f/10 SCT (at 0.5" per pixel) on a good night.

[Woolleson]

Thanks for all the time and effort you have put into this, very much appreciated.

I have been off looking at some of the options and have a few, sorry, questions.......... I'll stick them in the quote as red text.

You have the basic theory sorted... so...

As has been suggested... in practical terms, you really have two options....

1: add RA motor to your EQ3 and stick with just a DSLR and lens for wide field stuff or a small scope and stick to short exposures.

With this I assume you mean just use my DSLR either mounted on the tripod with a dovetail or the tripod screw on the OTA, giving me pictures of wide vistas, I have 50 - 300mm (plus a 1.5xTC) on my 20D & 40D. But this would not allow me to photograph DSO's

With a 150P on a motorised EQ3-2 (a friend of mine did this) you should get 30 - 40 second subs fairly easily... which with a modded camera at 800ISO+ will actually give you quite a lot you can do.

This sounds what I'm after, my mount to be motorised and get long enough exposures to DSO's. I assume by modded cam you mean a DSLR with the IR filter removed?

A shorter focal length scope like a WO ZS70 or a fast 80mm ED would give you slightly longer subs, maybe a minute or slightly more. To get 3 minutes+ you would have to be using a 100mm lens or similar and have some seriously good polar alignment.

This seems a good option too, I would use a cam (would my SPC900 do for this or would it have to be a Meade DSI like Olly suggested)on the WO ZS70, assuming then this would link back to software on my PC and then back to the motor drives. One other option I found while looking for guide cams/scopes was off axis guides. This seems an inexpensive (both weight and monetary wise) way of doing it. Are these any good? Being able to just attach my DSLR and SPC 900 via the focuser seems a win win. Plus is it right you can get flexure from adding another scope?

2: Go the 'serious' route and assume you'll want to be guiding sooner or later... buy a HEQ5 or NEQ6 (the goto would be nice but the Syntrek would do, as discussed) a dual saddle or extra scope rings, and ST80 to use as your guide scope and a QHY5 or even better a Lodestar guide camera, get an old laptop, install EQmod and PHD and away you go.

This could be my future path, but at the moment and being new to the hobby I'd like to stick with what I have modded and see how it goes; money is not the real issue here (well not all of it). My part of the world has very few clear skies and I'd kick myself if all that equipment is stored for weeks on end not being used. If I love and get to a point where my talent exceeds my equipment then yes I will opt for this.

It should be noted... you say Polaris is hard to see from your location... for imaging of ANY kind you MUST be able to align the mount on Polaris before you start... no Polaris visible in Polar scope... no tracking OR guiding.

I realise this, I'll probably cut down some trees or move to a dark site so can get around this, thanks for the link suede, very good and I will try that next.

Actually, that's not 100% true as I know there are mounts that can Polar align without seeing Polaris... but the majority of options open to you DO need to see it to work.

So if I was to splash some cash tomorrow, would the following work?

My unmodded Canon DSLR attached via this Meade LX Series Off Axis Guider | Telescope Accessories | Rother Valley Optics my SPC900 as the guide cam or First Light Optics - William Optics Zenithstar ZS70 2012 with my SPC900

Some guiding software, any recommendations here?

Motor drives like this: First Light Optics - Dual-Axis D.C. Motor Drive for EQ5

Would that give me a simple but usable setup?

But somehow as I’m finding in this hobby the answer is no, LOL

Thanks again for all your inputs, I’ve only quoted this post as I thought it would be easier to repost my questions, I’ve taken on board all you have said and read over many times till my little brain ached !!!!

Ben