Imaging problems with an EQ3 mount

[Grandad]

I have a 6 month old EQ3 synscan mount, with steel legs replacing the normal aluminium, and I use it for guided imaging. At first I thought the number of subs showing star trails (on 4 minute exposures) was down to my inexperience but I soon began to suspect the mount.

For example, in my last serious session of 20 x 4 minute light frames, 8 had to be discarded.

So I set up a small test; suspecting that I was overloading the mount, I reverted to unguided exposures using just my WO megrez 72mm and 314L camera.

The mount is on a concrete base and was well balanced on both axis, carefully polar aligned and the air was still.

I took 60 x 1 minute exposures (well within the capability of the mount). Of the 60 exposures 16 showed some trailing but there was no pattern to the errors. Sometimes I would get 5or6 good shots followed by 1 or 2 bad ones. Sometimes just 3or4 good ones followed by some bad ones.

The overall drift in 1 hour was around 7 - 10 arcminutes.

Is this the level of accuracy I can expect with this mount?

Would a major stripdown and polishing the wheels and cogs likely help?

Could I get a much better imaging experience if I swap to an HEQ5?

Any suggestions would be much appreciated.

John

[Merlin66]

What set-up are you using for "guiding" - you don't mention and I'm thinking you are only tracking with the mount.....

[Grandad]

I guide using a mintron camera through a sw 102mm refractor. I have guided successfully for up to 8 minutes but the guiding has never been consistent. I don't normallym try for more than 4 minutes.

John

[Merlin66]

So normally you'd have the SW102 guiding and the WO72 imaging?

Seems a lot to ask of an EQ3.....

A HEQ5 I'd think would be a much better platform for the gear you have.

You're also comparing the guided with unguided images with completely different loading....but you know that.

[Grandad]

I know that I am asking a lot of the mount. In fact I bought the mount and WO for visual use but was so fascinated by the excellent images on this site that I decided to have a go myself, starting with my dslr and now with the atik 314L.

I did the unguided test to see how the mount performed under minimum weight and it still shows some inconsistancy.

John

[jgs001]

John, my HEQ5 is consistent up to about 3 minutes unguidded, but even then I can lose the odd frame. It might be worth a look at a finder guider setup, there's a fair few people on here using them, and that will dramatically reduce the weight.

[GrantEb]

If you have a spare Finder lying around, why don't you make a finder guider, to reduce the load on the mount?

Just a thought.

[Merlin66]

The tracking (unguided) accuracy of the EQ3 is, as you're finding, somewhat limited.

You've managed to put together a great collection of scopes and cameras; maybe this is now the time to upgrade the mount to get the best out of them??

[GrantEb]

I'm too slow again. haha

[Grandad]

I did in fact make a guide scope out of a 50mm finder but I was not impressed with the guide accuracy. Using the SW102mm made a dramatic difference but the inconsistencies bug me.

I think Merlin is right... I need an HEQ5.

[jgs001]

In that case, then yes, I agree, go for the HEQ5.

[Grandad]

Just a thought.

If I bought a syntrak instead of a synscan HEQ5 would I be able to control the mount via my laptop through the syntrak controller?

[GrantEb]

You will need to get an EQDIR module for the laptop to drive the mount.

There is a cheaper option of this using a FTDI module USB/serial converter.

[jgs001]

John, I bought a SynTrek version and the ftdi module to connect the PC to it. Works a treat.

[Ender Of Days]

Ive an old EQ3 that runs on flat plastic discs rather than bearings,

I had to fully strip the mount to remove a lot of grease that was stopping the mount moving (with the locks undone it still wouldn't move without being pushed) now it moves really easy,

Although one of the motors actually pushes itself off the cog when powered up it tracks a lot better,

It can only be a good thing to strip it down can't it ?,

I wish Id have gone for an EQ5

JJ..