Guiding techniques.

Last night I had a go at trying to get my canon 300d, 5" mak, eq6 mount and dslr focus to all work together. Easier said than done!! In the end I got all of the tecnology to play ball but my first 5 minute exposure on M51 clearly showed me that I need to employ guiding, (and probably buy a better mount too). Thinking about the options I considered the following.

Mounting a guidescope with an illuminated reticle eyepiece.

Advantages: Easy to set up. Dont need to connect ot all to the laptop introducing more technology to go wrong, also cheap.

Disadvantages: Long periods manually guiding

Mounting a guidescope with a webcam and an interface to the laptop.

Advantages: No manual guiding.
Disadvantages: More technology in the loop, longer setup.

Using a radial guider:

Advantages: No flexure to worry about. Quick setup.
Disadvantages: Manual guiding. May be difficult with my mak-cass.

It would seem the guys doing the red hot stuff use autoguiding. However the simplicity of the other options appeals to me. Have you guys any6 opinions/suggestions/other options.

Thanks,

Hello Dave,
One option is to upgrade the EQ6. There is a upgrade available with a computerized hand paddle and new motors. This SkyScan upgrade also includes an autoguide port for imaging. I do not know all the details, or how much it would cost for you fellas, but it is something to consider.

I've known about this for awhile, but rumors or a new version held me back from pulling the trigger. Information can be found here ...
www.skywatchertelescope.net/

SometimesKen

Hi Ken,

Thanks for the feedback. I am aware of the skyscan and am seriously considering this. What I forgot to mention is that I have already replaced the default eq6 drives with a setup from AWR tecnology

dspace.dial.pipex.com/awr.tech/system5.htm

This has an autoguider input in the form of a 9 pin din which accepts input from a serial port. I have the pinout so that I can build a cable to make it work with guidedog. I also replaced the thrust washers at each end of the worms on each axis. This elimates all of the slop which was evident before the upgrade. What I need to research before going down the skyscan route is whether the guiding will be more accurate than my AWR drive. Certainly the goto feature would be useful primarily for putting an object on the CCD saving me hunting for it.

Behind all of this I'm really thinking that if I want do decent imaging I'm eventually gonna have to bite the bullet and get hold of something like a losmandy gm11 at the minumum. I just wanna eqhaust the eq6 possibilities first tho.

Dave, all I have is a Celestron C8 with it's alt/az mount, I too need some serious guiding equipment, a guidescope is out of the question no matter what it's weight is, an sct does not track well with even a small amount of weight on top of it, I do all manual at the moment, with is certainly not easy Imaging at long focal lengths piggyback or otherwise is a non runner.

I think you should keep it simple, but if you well capable of using the laptop and all that goes with it , then I supose go for an autoguider, that way it sould be straight forward when imaging.

Keith..

Hi Dave, as I'm sure you are aware, guiding commands a book of at least 100 pages

You've certainly spent time thinking this one through and have your options set out.

I think you're right to steer clear of manual guiding - this will probably end up driving you nuts. Albeit the cheapest option...

For any kind of accurate guiding you need:
1. A good mount
2. Good gears/motors
3. Superb polar alignment

If you have these, you'll get away with about 5 minutes unguided operation (even with Periodic Error Correction PEC software).

Guided operation can be done in a number of ways. You can buy a CCD camera with an imaging chip and a guiding chip (eg SBIG), you can buy a Starlight express CCD camera that uses software techniques to image and guide with the same chip or you can buy a separate (cheap) guiding CCD. Not sure if a webcam would fit the bill here).

If you're going for a CCD imager/DSLR and a seperate guiding chip, you'll need two scopes lashed together rigidly.

The guiding CCD estimates where the guide star is and if it moves, it sends command(s) to the mount to adjust. BUt this all depends how good your mount is. The Losmandy G11 is a good budget mount and can guide successfully. Limitations are carrying weight, backlash and periodic error. The last two are quite high in the G11 compared to the high-end mounts but than can be reduced to a significant level. The EQ6 - I've no idea how good it is.

Possibly the best option is choose a guiding solution, try it out on the EQ6 whilst awaiting delivery of a G11.

I dunno if that answers any of your questions. The webcam almost certainly is out for deep sky - you'll never get a guide star bright enough to register on the CMOS chip.

Cheers

Dave McD

Hi,
Like Keith, I'm not fond of using a guide scope, especially on a SCT/MAK. The primary mirror can slop around and the guide scopes knows nothing about it, hence you end up with bad tracking anyway!!

I receintly bough an offaxis guider, they work grand on bigger scopes, but I dont know about smaller ones as you can end up blocking the fov.

Avoid the meade and celestron off axis guiders (so I read on the web), you see them alot on astromart and they cant give them away, they are difficult to use. Lumicon do good offaxis guiders.
Autoguiders work well, I'm going to try and do it manually first and see how it works out. If it proves very difficult, I'll get an autoguider.

Keep in mind that with a better mount, you probabily will still need some tracking correction.