Autoguiding with Gemini problems. Any ideas. - Page 2

[1ponders] (Paul) · #21 14-06-2008, 12:23 PM

Your setup is exactly how it was setup. Laptop and Gemini on different powersouces (different circuits even), Shoestring adapter into the laptop, shoestring cable going from adapter to gemini autoguider port, ToUcam plugged into USB Hub into laptop running PHD. PHD recognises camera and runs, Phd recognises GPUSB np and I can get a box around a nice bright star. Click on callibration and star don't move ;(

JohnG (John) · #22 14-06-2008, 12:33 PM

Well, ya got me

.

The only thing I can think of is what I said before, try increasing the Calbration Time, I know I have to use around 12 seconds, the old tale, the shorter the F/L the longer the Calibration Time.

Other than that I am out of ideas.

Cheers

[1ponders] (Paul) · #23 14-06-2008, 12:37 PM

How do you adjust the Calibration time? The program itself selected about 50 or so "steps"

JohnG (John) · #24 14-06-2008, 12:43 PM

Open up PHD, click on the Brain icon, in Calibration Steps, change the setting from the default (50m/s) up to around 2500, that should give you a fairly close number to what your after.

Cheers

[1ponders] (Paul) · #25 14-06-2008, 12:49 PM

Ok, it's already on 500. The camera had a focal reducer in train that reduced the native focal length of the scope from 2850mm to around 1200-1400mm so the 500 setting should have been more than enough. I use much less than that with my ED80 on my Digital Drive at home.

It seems that the signal just wasn't getting to the controller for some reason, or the autoguider port on the controller is playing up.

[1ponders] (Paul) · #26 14-06-2008, 12:52 PM

btw we tried to use the Hand Controller port as well.

Uhm that wasn't too successful. The mount went zooming across the sky out of control

JohnG (John) · #27 14-06-2008, 12:57 PM

Yep, had that happen

, an awful lot of button presses later I managed to stop it from wiping out a servo and motor, frightened the crap out of me

.

I think I would be still be inclined to try the higher calibration steps, there might be a fair bit of backlash in the system, once that is eliminated I would be suspecting the Autoguider Port, other than that,

, I think everything is exhausted.

Cheers

JohnG (John) · #28 14-06-2008, 01:07 PM

Try this sequence:

Turn on your Computer then the Gemini, startup your guide camera and make sure everything other than the guide cable being plugged into the Gemini is running, then plug the guide cable in.

I have to use this sequence to plug the ST4K in otherwise the mount slews out of control.

If that dosen't work, try plugging the guide cable in first before starting the Gemini up, do your usual sequence then plug the guide cable into the GPUSB.

[1ponders] (Paul) · #29 14-06-2008, 01:11 PM

There is a HUGE amount of backlash in the dec that I haven't been able to get out. The worm block is hard up against the housing and there is still a good 8-10 sec of backlash at 2x sidereal. There is however very little backlash in RA and the calibration didn't get past the RA stage. I checked that the camera was oriented the correct way as well.

[1ponders] (Paul) · #30 14-06-2008, 01:16 PM

I'll give that a go John, though it might be a few weeks away. The observatory will be booked out for the next month and I have to take the mount off the pier and replace it with a different mount.

allan gould · #31 15-06-2008, 09:53 PM

Paul
Whoa back there as you may be doing some damage to the Gemini system. Since this unit has the RJ ports then you will DEFINATELY need an optocoupler or the SBig box to connect to this unit. Irrespective of age - its the old unit that needs an optocoupler. To test out if the system is ok then put online the TVGuider into the autoguider port. The TVGuider has a builtin optocoupler and so NO damage will ensue.
I assume it will work with the TVGuider if thats the case then an optocoupler is needed.

skeltz (Rob) · #32 15-06-2008, 11:19 PM

Paul it would be a good idea if you haven,t already to download the manual from the losmandy site .
It,s a good manual to keep around and handy.
cheers

[1ponders] (Paul) · #33 16-06-2008, 07:11 AM

Good idea Allan, I'll do that.

Rob I have the manual, but at times it's double dutch to me. I'm getting there but sometimes its like trying to infuse water into dry concrete

Gerald Sargent · #34 16-06-2008, 10:23 AM

Dear Paul,
Is this the backlash you spoke to me about on the phone ? Can you feel it by rocking the CW shaft ? If so then it cannot be solved with software, you have to modify the end of worm shaft block, that furtherest from the Motors. If you unscrew this block and send it down to me I will drill a hole
in the end and cement a thick piece of aluminium onto the far end, this I will thread and put a screw with a locking nut into it and supply a small ball bearing to fit between the end oif worm shaft and the end of the screw,
this can then be used to take up the end play and reduce the backlast to software managable proportions, putting the balck back on is a bit of a tedious trial and error business as you have to check most carefully for worm binding or risk burning out a motor, this must be done with the motor removed and turning th worm by hand. GERALD.

[1ponders] (Paul) · #35 16-06-2008, 10:32 AM

Hi Gerald, thanks for the offer. I'll put it to the Observatory Committee and see what they say. Most being non-astronomers though I think they will baulk at the idea of what would be to them "drilling into the mount". I'll work on them though

As for this issue though, the problem includes the RA axis and there is very little backlash in that. There didn't seem to be any instuctions getting through to the autoguider. I'm going to try Allans suggestion and put the TV Guider on it and see how that goes first. If that works then I know the problem isn't with the worm, if it doesn't work then I'll have to look more closely at your suggestions.

cheers

allan gould · #36 16-06-2008, 01:30 PM

Paul
The TVGuider worked brilliantly with the gemini and was idiot proof. Hope it pans out for you.
Allan

netwolf · #37 16-06-2008, 02:02 PM

Paul, could you try setting the Gemini backlash correction to Zero?
I read that in one of the other threads for a LXD75 Autostar setup.

[1ponders] (Paul) · #38 16-06-2008, 02:20 PM

I'll give anything ago Fahim. I'll try the TV Guider first to make sure that the autoguider port is actually working and then it's experiment time

Unfortunately it will have to wait for a month now as the mount is being replaced for 4 weeks with a different mount and scope.

[1ponders] (Paul) · #39 26-06-2008, 12:55 PM

UPDATE:

The G11 guides like a treat using the TV Guider, so it appears there isn't anything wrong with the Gemini. Plugged it in, turned it on, selected a star and away it went, np. Guiding FL was approx 1400mm.

allan gould · #40 26-06-2008, 01:43 PM

Quote:

Originally Posted by [1ponders]

UPDATE:

The G11 guides like a treat using the TV Guider, so it appears there isn't anything wrong with the Gemini. Plugged it in, turned it on, selected a star and away it went, np. Guiding FL was approx 1400mm.

Paul
Then you need an optocoupler for this mount as suggested. If necessary I do have an SBig relay box which serves the same purpose.
Can't beat the TVGuider eh Paul!!!!?
Allan