More eratic tracking - any ideas

[Thalestris24]

Hi

Yeah, I think a service would be in order. If it's the same as the heq5, it's a simple matter to just unscrew the cover and inspect the motor gears. My heq5 has issues and needs servicing too. The last time I used the white lithium grease but when I looked after using the mount for a while I noticed it had moved away from the gear teeth and accumulated behind the gears... I don't know if that's really a problem but I bought some Archoil WS2 (tungsten disulphide) spray though I've yet to try it. Not sure if that's any easier for you obtain? I got mine mail order (Amazon). However, in any case, you'd have to at least wipe away whatever is already there. My feeling is that any slight imbalance of an ST80 on an NEQ6 would hardly notice (I'm sure someone will say different!). I have an ST80 with 1100d on my AVX. It's fairly well balanced with the focuser section over the puck. In order to achieve focus (without the diagonal) you need to make up the missing length with an extension tube. I currently have a 40mm one on mine. In fact, that just made me think that could be the source of your problems! If you have the focus tube racked right out it probably won't be rigid. You can probably tell what movement you have just by giving it a little side to side push. If it doesn't seem rigid, that could well be the cause of your troubles! There is an Astronomyshed video on YouTube about tweaking the ST80 - worth a look: https://www.youtube.com/watch?v=Ylb7xnc_03U

Hope that helps

Louise

[dph1nm]

A 40D on a 400mm scope has about 3" pixels I think. Typical periodic error on a EQ6 is say 30" peak-to-peak (some may be better), so in 3 minutes (~1/3 worm cycle) you are looking at 10-20" (3-6 pixels)  of error, depending where you are in the cycle, if you are imaging at zero dec. So that might be consistent with the first image ...

NigelM

[coenie777]

Thanks Louise, I will investigate that possible tube flexure. But still, the amount of movement the mount make in 2 min of exposure, can that small nudge of a movement around the RA axis actually translate into such jerky images?

NigelM, if an average NEQ6 has 30" p2p error, will auto guiding smooth this out or is the only solution reducing the error with tuning or PEC?

[Thalestris24]

Thanks Louise, I will investigate that possible tube flexure. But still, the amount of movement the mount make in 2 min of exposure, can that small nudge of a movement around the RA axis actually translate into such jerky images?

NigelM, if an average NEQ6 has 30" p2p error, will auto guiding smooth this out or is the only solution reducing the error with tuning or PEC?

Hi

It's surprising how even very small movements can mess up your image - it's generally referred to as 'flex'. It can be quite difficult to track down the source of such problems. With the 40mm extension tube I have about 2cm of focus tube showing. Don't forget to tighten the focus lock also. You want everything in your imaging train to be as rigid as possible.

Louise

[lensman57]

Thanks for all the responses so far. Really appreciate it.

The mount was bought second hand. The owner claimed he had it for 18 months which would have put it at around 2012'ish. I then discovered that the local agent in SA who sell these did not get any new stock for at least the last two to three years. So my copy could be a pre 2011 sample with all the issues that I have read about.

Overall the majority of solutions seem to hint at opening up and servicing. I am dreading that since I have never under taken any opening up of something working with grease and bearings etc. I have the Astro baby guide printed out in colour and need to still source white lithium grease locally which seem to be an issue. Any suggestions on an alternative grease that will not corrode the bearings and gears?

I am almost 100% sure that nothing bumped against the mount on that jumped shot. Balancing as some have mentioned in that light scope is very easy. I leave only one weight on the bar and move it all the way up to the mount stop to have it balanced. One thing that I did not do was balance the DEC axis when the camera were in focus. I balanced it with the focusing tube retracted (as for visual viewing) and had to rack it out quite a bit to get focus on the DSLR. So maybe that could have put the DEC axis a bit off balance.

Check the integrity of the DEC gearing. You may have to adjust the backlash and the mesh tension. What you have shown is indicative a jumping DEC gear. The problem is more evident in certain scope orientations.It maybe worth your while servicing the RA and the DEC gears together and the clutch mechanism as the mount is quite a few years old. There are tutorials on the web about this.

A.G

[coenie777]

I braved the clouds last night and got a two hour window for some setting up and tweaking. Did the AT PA thing again to less than 1' and then 2 star align on handset followed by PA on handset and another 2 star alignment. I checked all fittings for flexure and made sure all cables were loose and not dragging etc. I then did the PEC training once on the handset.

Then I shot this 2 min shot and almost fell of the chair:

I immediately followed it with a 3 min shot which proved to be a bit over ambitious but which might not be too bad for 3 min unguided?

I then slewed to another part of the sky and saw a drop in accuracy but never the less shot 20 usable frames of the Tarantula nebula around 30 degrees above my most light polluted area of the sky:

I will start my reading up and sourcing of parts as I guess my mount will make good use of a tune up.

Thanks for all the advise up to this point. Will chat soon again on some other challenge I will no doubt run into.

Coenie

[dph1nm]

NigelM, if an average NEQ6 has 30" p2p error, will auto guiding smooth this out or is the only solution reducing the error with tuning or PEC?

You would hope that autoguiding would eliminate most of this, depending on how smooth the periodic error is. PEC is a sort of poor-man's autoguiding, as far as I can tell. Never got sensible results out of it on my HEQ5, but maybe that is just my mount.

NigelM