Autoguiding as GoTo?

[Robert Anstruther]

Hi,

I'm currently trying to decide my new setup and in particular the mount. I haven't done Autoguiding before and not too familiar with it. I am a little confused about something.

Can Autoguiding be a replacement for the/a GoTo system? e.g. Can you also use 'GoTo' functions after alignment as well as guiding/tracking?

If I purcahsed the Losmandy GM-8 mount, can I plug my laptop directly into it and Autoguide or do I need also the Gemini GoTo system? If so, why?

I have read (from shoestring astronomy) about various adapters for the GM-8 for autoguiding but I don't really understand it! Is this adapter replacing the Gemini box in favour of a laptop and software?

The Shoestring Astronomy Store - Products

Sorry for all the questions but I've been reading all day I can't find an exact answer to my question.

[barkis]

I think it is safe to say that Auto guiding and Goto are really two separate entities. Autoguiding is achieved by employing a second telescope equipped with a Guide camera, of which there are various types. In addition, you need software to control the guiding via the information from the guide camera. Goto is a database of targets contained within the Hand controller of the mount that is used with your main telescope. In addition, if you use a planetary programme such as Stellarium (Free) or Starry Night, then you can select a target from within the programme, and slew the scope to that target.

There are numerous avenues open to you, as to which mount, guide camera, software, and of course computer required, usually a Laptop.

More information will come your way I'm certain. The Losmandy G8 mount will be a great mount to do all the things you need.

Anything specific you want to know, just ask.

Ron.

[barkis]

Robert, perhaps I need to clarify that Autoguiding is really only required for very accurate tracking during astrophotography.

I presume that taking images of deep sky objects is your aim.

Autoguiding does not need to be active in order to use the Goto capability of the mount. It is all done via the hand controller supplied. Neither is a computer required, if you are happy to just use the controller database objects.

Ron.

[Robert Anstruther]

Thanks for the reply Ron.

My aim would be to do DSO AP. I thought that GoTo and Autoguiding would be the same entity. If you can track objects (autoguiding) and have a database of these objects positions (GoTo) then you could mix these and get rid of the need of the hand controller and do all of it via the laptop. The only need for the hand controller after this would be if you wanted to use GoTo when you don't have your laptop or limited power supply.

e.g. Align Scope > GoTo 'M101' > Autoguide 'M101' > GoTo 'M51' > Autoguide 'M51'

I guess I am just wondering if there is a need to buy a GoTo system with my mount, or if I could do without it and use my laptop with software as the 'hand controller'. Then use the autoguiding for the tracking of the objects.

[Merlin66]

Can't speak for the GM8 ( but I do believe it needs the Gemini system to achieve GOTO capabilities)

A laptop can drive the scope via a serial/ Shoestring adaptor cable which is usually attached to the hand controller and allows programs like Stellarium/ TheSky/ CdC to send control signals to the mount (and get positional feedback). This allows you to click on an object and get the scope to move to that object. ( GOTO)

When you're there, autoguiding can be invoked via ANOTHER connection to the mounting. This can be controlled via the PC ( separate program ie PHD) when the guide camera is connected ( normally USB) to the PC and a subsequent cable ( either directly from the camera or from the computer) to the guide socket (ST-4) on the mount.

So it's a two stage process; move the scope to the object and then use the guide camera signals to make "minor corrections" during the imaging session.

All it all it means connecting:

PC to handcontroller ( Serial/ GOTO)

PC to Guide camera (USB)

Camera / PC to mounting ( USB)

Image Camera to PC (USB??)

Hope this helps......

[barkis]

Well Robert, you may have heard of a programme called EQMOD, which can allow scope control without the hand controller.

It uses ASCOM Protocol, but I'm not certain whether it is compatible with the Losmandy mount. If I was to guess, I would say at the present time no, but maybe sometime in the near future.

Shoestring Astronomy supply the device that allows conversion of the RS232 to USB. The device is known as EQDIR.

I have just recently gone that route myself, and still in the familiarisation stage, so someone with more experience would advise you better.

The Skywatcher EQ6Pro mount are the most popular users of Eqmod at present.

You are correct in the goto/ tracking marriage of course, dispensing with the hand controller, and using a laptop is basically substituting one computer for another. The laptop processor will calculate the number of steps the stepper motors need to take in both Right ascension and Declination, to get from one point in the sky to another.

Ron.

[SteveL]

I think you are confused about what autoguiding is.

A Goto mount will slew the mount to specified co-ordinate in the sky, and then the mount should track at sidereal rate across the sky from there on.

Autoguiding, on the other hand, is something that is used to elimimate any cause of the object moving in the field of view. Causes can be poor polar alignment, a breeze moving the OTA, PEC errors in the mount, differential flexure between imaging OTA and guiding OTA, and a few others. While taking long exposure images, the mount is tracking at sidereal rate, but the autoguiding is making tiny little adjustments to the mounts location to keep the target still. This is done by using a second camera (and usually a second OTA) to take repeated short exposures of the sky, and looking for movement (usually tracking on a singke selected star). As the star moves around, the audoguiding is just nudging the mount so the star stays in its original position.

[ollypenrice]

Anybody tried a GM8?

Olly

[Robert Anstruther]

Hi Steve,

I'm trying to figure out a way to cost cut The Gemini GoTo system is £1500, I thougt maybe the GoTo could be done via the autoguiding system, if it could track why couldn't it 'goto' as well with the right info. Or if there was a software and cable replacement for the hand controller. It would be alot cheaper for me to take that road if it existed as I would only need a guide camera/software & cable. It also would kill 2 birds with 1 stone, GoTo and Autoguiding, rather than the expensive route of a camera and the Gemini kit.

[SteveL]

There are two kinds of autoguiding as well..

one is via the old and original ST-4 socket, which just sends 1 or 2 commands to the mount at a time (RA+/RA-/DEC+/DEC-). These are simple "switch on/switch off" commands, and have no understanding of slewing a mount to a certain location. Its just up/down/left/right

The other way to send autoguiding commands is via the ASCOM mount driver, which you connect your PC/Laptop to the mount or handset. It sends serial commands to the mount, which in turn moves the mount by the required amount.

So, the short version is that autoguiding is in no way an alternative for GOTO....

[Robert Anstruther]

Ok thanks for all the information. Time to rethink!

[Psychobilly]

GOTO gets you there (or there abouts) .... AUTOGUIDING keep you there... both are possible with an "Ascom" link to the mount... but normally using different apps...

Peter....

[Reggie]

I've not had experience of the losmandy mount, I'm sure for that money its got to be good, looking at the gemini system that also costs a lot, do you need a mount that expensive?

Have you looked at the skywatcher HEQ5/HEQ6 Pro mounts? They come either with a handset with goto and autoguiding port, or you can buy them without the handset saving around £160 and spend £20-40 on a cable and connect it to a PC and use EQmod software (FREE ) and get superb goto control/accuracy/pec via a PC. Worth a look as they are quality mounts that produce good results, excellent price and options, EQmod is worth its weight in gold alone

[ollypenrice]

I think maybe I was thinking along the same lines as Reggie. When I sounded out the forum on the G11 there were some owners saying 'Aye' and some saying 'Nay.' The other mount in a similar price bracket to the G8 is the new version of the Vixen Sphinx. I have seen a few of those down here and their owners were all happy. The unguided periodic error is better than the EQ6 but with a guider running I don't know how much dfference there is.

The motors on the G8 have the look of an afterthought to me and seem to get in the way at times. It's quite an old design.

Olly.

[Merlin66]

Robert,

For the GOTO function, you need motor drives on both axis and POSITIONAL FEEDBACK to the controller.

Many mounts can drive in both axis ( with no GOTO capability) and can still be "Autoguided" through the ST4 port.

GOTO unfortunately is more complex.

[omneferuss]

Yes! the BIG difference is that GoTo has a motor-controller that knows where the scope is pointed....

You can autoguide with plain dumb motors, the camera and software merely watching the guidestar and saying "a lil up.. woah for a sec, now down a lil, faster... steady" and so on... just as you would be doing with the slomo's at the EP.

Hope this helps Oh! and another thing is 'slew rate'...GoTo motors can typically slew at up to 800x tracking rate, whereas dumb motors might only manage 8x.. your target would have set before you got to it

Robert,

For the GOTO function, you need motor drives on both axis and POSITIONAL FEEDBACK to the controller.

Many mounts can drive in both axis ( with no GOTO capability) and can still be "Autoguided" through the ST4 port.

GOTO unfortunately is more complex.

[Robert Anstruther]

Thanks again for all the info, in reference to the suggested EQ5/6 mount. I will probably go for this now as I can't afford the Losmandy setup (for the mount and goto). I was just weighing up my options. One thing I don't want to do is regret any purchases, my girlfriend and I are buying a house soon so I am not going to get any new kit for a while!

[Reggie]

Good luck with the house I'm sure you won't be disappointed with a HEQ5/6 Pro mount, as previously mentioned, EQMod is a very useful tool.