Autoguiding

[EA2007]

Afternoon,

Few questions:

1) This might sound stupid but.....when autoguiding, can the guidecam be pointed at a star quite far away from the object intended to be imaged. For example when viewing something quite remote from bright stars (such as M81) can a star such as Dubhe?

Just I was reading somewhere that using a webcam for autoguiding can cause issues as you need a fairly bright star for it to pick up.

2) Can anyone advise on software for autoguiding for use with a webcam and also list a fairly simple way of connecting it all up i.e. what cables one would need etc.

Many thanks.

[simon84]

If your using guide scope rings then yes you have a fair amount of sky that you can aim your guide scope at.

As for software I've just been playing with PHD Guiding which seems very simple to use.

I'm not really sure how to go about guiding with a webcam though as I've never tried it.

[lukebl]

You shouldn't neeed to look too far for a suitable guide star. My basic webcam can usually guide on a star of 5th or 6th magnitude, so you shouldn't need anything as bright as Dubhe. What camera will you be using as a guide cam?

I use PHD too. Apart from a few teething problems (user incompetence!) it works fine.

And you'll need patience and practice!

[shaunster]

Phd works better with a dim star anyway, using a really bright one and you will get poor guiding in most cases

[EA2007]

Thanks : )

I have an old webcam hidden somewhere, its not that good, but then again I haven't tried it yet. I have heard the Philips SPC900NC is the most popular one to go for?

Have to see about attaching it to the viewfinder scope. I would use the smaller6x30 that came with my C8 Schmidt, but then remembered I have a larger 9x50 viewfinder scope that came with my 8inch Newt. so that should give better results / magnification yeah?

[Dave Smith]

You will need a USB lead from the camera to your laptop (usually provided) and something like Shoestring astronomy GPUSB box and connector between the laptop and mount.

Shoestring Astronomy GPUSB for auto-guiding.

I also use PHD and have had no problems other than "user incompetence".

Dave

[Merlin66]

Although you can use a finder for guiding, a longer focal length say 400mm or so is better.

The ST80 is a popular guide scope.

The get the webcam to "talk" to the mounting, you need to mount the webcam to the guide scope ( a 1.25" nosepiece), connect it to a computer which is also running PHD guide software.

You then need a suitable cable connection from the computer to the ST-4 guide port on your mount. I use a ShoeString adaptor cable for this job.

[themos]

I've read that the further away the guide star is from your imaging "window", the more you will suffer from "field rotation" in your image as a result of polar alignment error.

Details and formulae at

http://celestialwonders.com/articles/polaralignment/PolarAlignmentAccuracy.pdf

Extract:

For example, with the parameters: alignment error = 10 arc minutes, field rotation = 9 microns,

exposure time = 15 minutes, focal length = 655 mm, target = 35 degrees, the calculated

maximum guide star angle is 3.38 degrees.

On the question of cables+software: You obviously need the camera cable connected to your laptop so that the laptop can "see" the frames as a video stream. Then you need some way of controlling your mount from the laptop. Do you use EQMOD already? If so, you're done.

[brantuk]

Yeah - I allways thought that the idea is to guide on a star "nearer" the object for better tracking accuracy.

[EA2007]

Thanks for the replies,

I have found the webcam and installed it, its a Labtec Notebook webcam, the software I have downloaded from the labtec site seems to give quite a few options for enhancing brightness and gain.

Shall have to try it sometime when the sky clears out, looking south of our house at the moment shows a massive grey storm cloud :s. Still need to find a good way of attaching it to the viewfinder scope, but I'll have a play with it.

As for 'themos' and the EQ Mod, no I haven't used it, I don't really know what it is....

[themos]

EQMOD is an ASCOM Telescope driver for your EQ6 mount. It allows lots of astro programs to control your mount.

The driver accesses the logic board of the EQ6 directly so you need to buy a suitable cable (or make one from components you buy).

[EA2007]

Okay, i think i downloaded it correctly.

I have two cables that came with the EQ6 Pro. one is a DB9 cable that goes from the SynScan handset to the mount and the other cable is light grey and has one end featuring an old 'dial-up' style telephone connection and the other a female 9-pin connector, presumably this is a RS232 connection.

Question is, I have no such output on my PC or laptop for a RS232 with 9-pin female connector and likewise how does one go about hooking it all up.

I have seen various diagrams, some go direct from the PC to the autoguider port, some go from the PC to the handset then down the DB9 cable to the mount.....i'm a little confused, diagrams would be appreciated.

[themos]

You downloaded what?

Your second cable is, I think, meant to plug in to your ST-4 autoguider port of the EQ6 but I really don't know.

None of your existing cables are good for EQMOD operation. You need something like Cables, Leads and Controllers - HitecAstro EQDIR adapter (the one on the left, for the EQ6). And a standard USB cable to connect that gizmo to your laptop.

[themos]

BTW, with EQMOD you won't use the ST-4 autoguider port of the EQ6. EQMOD supports guiding in a different way but you don't have to worry about it as most guiding software (PHD for instance) know how to do it through ASCOM (and EQMOD is an ASCOM driver).

[Merlin66]

To connect a DB9 serial plug to your computer you'll need a USB to Serial adaptor. They come in different types unfortunately and some work better than others. I use a KEYSPAN adaptor which works with all my software and hardware.

[EA2007]

I downloaded EQASCOM driver.

I did used to have a RS232 to USB converter, but sold it with my last scope.

Why don't they just make it easy and allow a simple USB direct link to either the mount or the handset?

Or better still, have a built in guidescope and ccd with the main scope/mount, that would be far easier!

[EA2007]

also, can you not use a direct link from a COM port on your PC to the autoguide port on the mount? i.e. by using an ethernet 'cat-5' cable?

It seems a bit daft that both connections are 'ethernet' style yet have to presumably be routed via pin connectors such as the RS232.....maybe I'm missing something here.

[themos]

I downloaded EQASCOM driver.

That wouldn't work unless you have downloaded the ASCOM Platform. Follow the instructions on

Download Center

After installing, please apply the Platform 5.5 Update!

Why don't they just make it easy and allow a simple USB direct link to either the mount or the handset?

Synta don't make Windows software for the mount so there would be no point. EQMOD is a third-party effort and they had to find out how the handset controls the EQ6 board so that they could fake that with an ad-hoc cable from the laptop.

Or better still, have a built in guidescope and ccd with the main scope/mount, that would be far easier!

I suppose Synta could officially support an ASCOM driver for their mount and sell a cable for it.

It seems a bit daft that both connections are 'ethernet' style yet have to presumably be routed via pin connectors such as the RS232.....maybe I'm missing something here.

I agree, I found the use of the RJ connector confusing. BTW, RS232 is a protocol, not a connector type, sorry for the pedantry.