G11 with gemini need help

[Striker (Tony)]

Reasonably bad pec means taking in consideration that I am measuring Pec at 2800mm focal length with a toucam so i will expect some Pec plus seeing will have to added to the equation....but still not good enoug....lol

Yeah I tried on Orion and the tarantula...both very ordinery.

Should there be any movement regarding End play paul....I think their both tight.

[[1ponders] (Paul)]

No you don't want to have any movement,within reason. It doesn't want to be so tight as to restrict worm rotation.

This is sometimes part of the problem when trying to use autoguiding to correct pe. When you're autoguider tries to make an adjustment or the error in pe "reverses" then instead of making an adjustment by the worm moving the gear, the gear acts as a pivot point and the worm moves backwards/forwards in its blocks. From the autoguiders frame of reference it has made an adjustment and nothing happened, so it has to make another adjustment. However depending on what is happening with your pe at that particular moment it might infact double the adjustment needed or still not be enough so the mount continues to drift or jumps too far, which requires another adjustment. Which again might not be the adjustment needed because the worm may move b/f again. But it might be too late by that time anyway, you have trails starting to appear in your image from the first mis-autoguidement . Either way over correcting or undercorrecting you still end up with trails and your autoguider spends most of the night fighting the endplay and not actually guiding. Does that make sense???

[[1ponders] (Paul)]

Originally Posted by [1ponders]

Btw Tony what do you mean by "reasonably bad pec" How do you measure it?

It's pretty important you know how many arcseconds per pixel you are imaging at. Looking at the K3 graph isn't much use if you don't know that. If you look at the graph and it is swinging 5 pixels above and below the line if your resolution is 0.25 arcsec then the total swing is 5+5 = 10 pixels = 2.5 arcsec. Now while not perfect as far as pec is concerned it something your autoguider should have no problems dealing with. I've heard that many people are very happy if they only have a 5 arcsec pe. Me I'd be ecstatic.

But if your resolution is 2 arcsec then your pe will be 20 arcsec. So its important to know your resolution so you can work out your pe in arcsec to make a value judgement on the ability of your mount. Looking at the graph on its own really doesn't give you much info except that your mount isn't tracking perfectly. How imperfectly you don't know.

BTW have you set your telescope type/ F/ratio, ToUcam pixel size and chip size in K3?

[Striker (Tony)]

Um...I dont use K3....lol

I use Guidedog.

Tested again tonight...no different....I even tried tightning the worms as much as physicaly possibly...besides the odd motor stall the pec was identical to when the worm was physicaly loose not even pushed up against the main gear.

I give up...all I know is the EQ6 has less pec then this mount.....yes the problem may be me...I accept that but it's all fairly basic to adjust once you get in there.

The amount of hours I have spent trying to get this mount just reasonable for imaging is rediculaous.....It's like having a dragcar where you spend most of your time under the bonnet instead of driving...

I think it's time to call a pro.. EDDIE

[JohnG (John)]

Well Tony, you got me, everything I have told you to do worked fine on my mount and I have never had an ounce of trouble. I would not have tightened the worms that tight, you have to have a slight amount of clearance, the only thing left is the known bug in Gemini Level 3. I have pulled my mount apart probably 4 times now over the past 4 years, relubed, worm adjustments etc, no drama, very bizzare.

JohnG

[Striker (Tony)]

When did you say your coming up to Brisbane to give my mount a service John....lol

I am going to test it tonight if weight is an issue.....taking the guidescope off.

Thanks again for your help John & Paul.

[[1ponders] (Paul)]

Tony when you check the pe of your EQ6 what scope are you using and when doing the Losmandy what scope are you using?

[Striker (Tony)]

both with the C11......I have not checked the PE on the EQ6 since I had it in my Observatory.....checking the PE on the EQ6 is not needed now considering I am imaging at 600mm...you wont even see it.

I just remember the star stayed in the same spot most of the time instead of jumping from side to side as it is doing with the G11 atm.

[JohnG (John)]

Tony
With the C-11, the mirror hasn't started to flop a bit more has it.

JohnG

[Striker (Tony)]

No John...I dont think any mirror flop would cause the image to go both ways like PE.

I think my C11 has very little mirror flop....I always use the SCT focus knob to focus and the image still stays central....and thats with a JMI electric focuser installed....I rarely use the JMI.

I have a few more option to play with tonight...let you know how I go.

[Merlin66 (Ken)]

With or without the guidescope, set the counterweight to give an out of balance condition so that the telescope would tend to "fall" to the East of the axis if the locks were not tightened, check the PE in this condition. Sounds like the gears/worm are OK but still may have a slight mis-match which could cause the perceived error. I'd also push the scope east then west and see if the PE reflects the "back pressure" Could be you just need some "pre-load" on the worms.
My 2cents worth.
NB haven't found this problem on a GM8 clone.

[Striker (Tony)]

Thanks Merlin,

Thats the plan tonight....I have always made sure the weights is heavier on the east side but when I say heavier it is a very minimal difference...not enough I am hoping...I have always being so wrapped in getting perfect balance with the G11...maybe it was too good and thats working against me.

[Striker (Tony)]

Ok...we are now heading in the right direction.

All I did was apply more weight to the eastern side as some have already mentioned including the Yahoo group.....I think I had the mount to well balanced from the start....The RA motor did stall on 2 occasions so I slowed down the slew speed and slightly adjusted the weight again...I may have a gone a little to far on the first attempt as the motor was getting a little warm.

I will still getting some PE but less then before...so I tried guiding through the C11 at FL2800 and all went well with some adjustments of figures in Guidedog but had no problem guiding for 10 minutes.

So I am happier then I was last night so thats a good thing.

Atleast this has given me an opportunity to get to know my mount.

Thanks guys...I am still not out of the woods until I do a test image but heading the right way.

Thanks.

[JohnG (John)]

Great news Tony, sounds like you just need to loosen the worm a tad and you may have it nailed, good work, your an expert now. lol

JohnG