Autoguiding with Guidedog

[Nico]

Could anyone provide help in relation to the following:

1. Can I autoguide with the webcam attached to an off axis guider, or must I use an attached telescope to the main instrument as suggested in traffic relating to Guidedog?

2. I believe all thats required to connect the PC to the scope when running Guidedog is an RS232 cable, is this the case?


Cheers.

Nico:confused:

[seeker372011]

Firstly, welcome to the forum, Nico.


in response to question 1., I dont see why not. All guidedog needs is a star image on lock on.


as afar as 2 is concerned I think the answer depends on your mount.

In my case my cable plugs into my handcontroller not the mount-even though there is a autoguider port in the mount. (I use a Celestron CG5 mount)

I believe that If I were to plug into the mount I would need a relay box..

Maybe if you let us know which mount you use someone can advise you better

[[1ponders]]

Hi Nico. With your lx200 your should be able to use either the RS232 port beside your handcontroller port or the autoguide port. I would suggest using the one next to the handcontroller port as you will already be connected to that if you are using software rather than the handcontroller to drive your scope.

And yes you can use an OAG. The hardest part of using one is finding a suitable star to guide on as you are limited to just the edge of your field of view. Much more difficult I found than using an OAG manually/visually

[robin]

Hi Nico, I find using an off axis guider ends up in hairpulling frustration!So much so that like many of the other people on tis forum, Im getting a separate guidescope to mount on top of my LX200.Its just trying to get a decent star to guide on.The edge of field stars are always bloated & fainter with an OAG

[[1ponders]]

Sorry Nico, I confused you with Nick. He has the LX200. What are you using?

[Nico]

Appologies, I'm using a Celestron 9.25 with focal reducer and canon 20D. Thanks for the feedback, it seems as though autoguiding through an OAG using guidedog may prove very difficult.

The problem that I'm faced with, as I'm sure most have experienced, is inaccurate polar alignment. I'm quite new to astrophotography and have realised that even though my polar alignment is quite good, photos in excess of 1 min show blurring as a result of tracking errors. I've found that obtaining fairly presise alignment can be achieved with consecutive exposures and moving the mount. Drifts in the wrong direction are clearly visible.

I discovered that there was quite a bit of Dec backlash so I fixed that by adjusting the worm gear mesh which resulted in backlash being very small. The same was done to the RA; however, initial backlash was not as great as was present in the Dec axis.

Should I consider a more upmarket autoguider, such as SBIGXXXX ?

[[1ponders]]

While I've not used Guidedog (I use K3CCDTools V2) you may be able to use Guidedog to assist in your polar alignment. If not download K3 V2 (its fully functional for a month or 30 uses, I can't remember which) and check out the Drift Explorer function. IMHO its brilliant for getting your polar alignment spot on!! Takes a bit of practice but its a great all round program. You can autoguide, polar align, planetary capture with webcam, process planetary captured images (not as easily processed as Registax but when working right (I'm a bit hit and miss with it) IMO produces a better final unprocessed image than registax).

Oh and if your celestron has PPec (permanent periodic error correction) you can use the autoguiding function to dtrive your ppec training which will help immensely when you want to take shorter images (say up to three minutes or so) without autoguiding. If you can get your PPEC really well trained and your polar alignment spot on then you may not need to autoguide at all for shots maybe up to three minutes.

Have a think about it

PS a dedicated astronomical CCD will be much more sensitive than a ToUcam for autoguiding so you could use fainter stars with the OAG.

[seeker372011]

Nico:

are you using the CG5 Mount? If so around 30 to 45 seconds seems to be about what people get without tracking errors even when polar aligned.

with autoguiding however this improves out of sight.

I use Guidedog-guidescope, not an OAG-with my CG5-and with halfway decent polar alignment I can get upto 20 minutes exposures with no trailing on my Canon 300D-and no field rotation. Havent tried for longer exposures who knows may be possible.


PS You can use GuideDog for help in polar alignment as well..just look at your dX and dY numbers after locking on to a star and that will tell you how your tracking is going

[[1ponders]]

Just to give you a comparison K3 V2 uses a graphical representation as well as numerical imformation to gauge your drift. The downside to K3, you have to pay for it. About $45 - $50 US. IMHO worth every cent at twice the price.

[gbeal]

Let me echo what Paul said about K3. I am a miserable sod (even Paul said so), and I tried IRIS for a while simply out of tightness.
I ended up paying for K3, and haven't looked back.
I too have tried the OAG method, and like almost all the others decided that a separate guidescope was the ticket.
The best purchase though was a decent set of guidescope rings, in my case a aset of Losmandy DR125's.

[gbeal]

Paul,
the K3 shot you posted, is this an average sort of example? I normally have my graph set at the max, and get +/- 1 in a neat saw tooth line, with the odd deviation.

[[1ponders]]

Nah Gary it was just a copy from the instruction manual for an example to demonstrate the graphical interface. Nothing special about it. Though I am interested in the K and Q settings in the demo though. I've never tried settings like that. My Q settings are normally 2 -3 times my K settings. Though the scale is the same for what I use. I've also just started to use sub-pixel guiding. Made one hell of a difference to my guiding accuracy

[gbeal]

Whew, thats OK then. I too am unsure, but seem to have the numbers sorted, whatever they are, and don't dare change them.

[[1ponders]]

do you use the sub-pixel guiding option?

[Robby]

Hi Paul,
I have never used the sub-pixel option... You've got me curious.. I'll have to give it ago.
Rob