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Ring Nebula help.


PhoenixRising
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Hi guys,

I tried to get three minute subs last night on my CG5-GT, 200P, guidescope and Synguider, but I'm still getting streaks. I drift Aligned, Polar Aligned, balanced and all the usual stuff.

Do you think that the 200P with a guidescope is too much for this mount or could it be something else?

5x2min subs.

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mmm, my 1st reaction would be - during the daytime, load the mount as if your just starting an image session, tighten everything, make sure there's no play.

Im wondering could you just mount your guidescope on the mount & take a few shots through it, just to see if you can replicate the same problem...

Nadeem.

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You are not getting classic trailing there. That looks like backlash because you have two images superimposed, more or less, not one with consitent smearing. Since one of the images is brighter than the other the mount is spending more time in that position than the other. So I suspect the mount is oscillating from one side of the play in the gears to the other. Now there is trailing as well but I'll come back to that.

The usual antedote is to run out of balance, with the west side heavy so the gears are always pushing. Also run camera end heavy for the same reason.

Now the trailing is at 90 degrees (ish) to a line drawn between the two images, so doesn't that suggest backlash in one axis and trailing in the other? While it might be reasonable to assume that errros in one axis should not feed back into the other, the reality (in my experience at least) is that they do. So nail that backlash first.

Another possibility is mirror flop. This too could be a kind of backlash between two locations for the mirror.

Olly

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I think Olly is on the money here. Can you fit an eyepiece and move the scope N-S and E-W at about 12x sidereal? If you see largish jerks in the eyepiece that is probably backlash being taken up. Get rid of backlash by balancing properly, don't be tempted to fiddle with the mount.

Dennis

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Nice one guys, it is backlash and my balancing has been mirror side not camera side. Plus, the two 5kg counter weights mean that I can't balance fully as my gears too heavy. So that's it really. Just dropped it at RVO to give it the once over before it sells and just picked up the spanking new neq6 pro. I now survive on toast for a few months!

Anyone got any setup tips for the new mount, is pec correction with an illuminated eyepiece necessary etcetc?

Thanks guys, this is a tough learning curve :D

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Good decision.

I don't use PEC when autoguiding. No need for two sets of commands. However, there are folks who do so I'd sound out the forum.

Toast can be very nice. Anchovies marinated in garlic, olive oil and parsley. Hmmmm.....

olly

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PEC and autoguiding........

There's a very interesting article concerning it with the EQmod documentation, which basically goes along the lines of, "it depends how you guide". If you are pulse guiding through EQmod, then adding a PEC cycle can be complimentary, but bear in mind you will have to re run a PE recording cycle every time you setup if the mount isn't on a pier. If you are guiding through the ST4 port then PEC wasn't recommended, but I cant remember why. Probably worth reading the article as I am very hazy on the details :):D

As it goes, I dont bother with PEC, I use an off axis guider which deals with the slight error very nicely.

Cheers

Tim

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Thanks Tim,

I'm using one of the new Synguiders but I'll have to see how they get on the next clear night we have. Hmm, could be a while then. It's a good piece of kit but the Firmware's at 1.0 and I have to keep resetting it everytime I use it to get it to "wake up", we'll se what a firmware update does.

So with good balancing slightly favouring the Camera side, Polar and Drift Alignment, my autoguiders input should be enough to get a decent pic, well, an aligned right? Is there anything I might have missed or don't know about apart from that? ie Backlash settings in the hand controller, any recommended settings etc etc.

Edited by PhoenixRising
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