Guiding and the meridian... problem, I think!

[StargeezerTim]

I was imaging last night and tried to stack 44 subs in DSS today. It only stacked 30 and when I checked it seemed that the quality of the guiding deteriorated badly at one point and the final subs showed no stars on DSS columns and were omitted from the stack. It looks likes the change happened when the scope went through the meridian, e.g. the arm with the weight on went above the horizontal and the scope started leaning with the bottom towards the mount (would have hit it eventually, it has before!).

Is this normal and is there a way of ameliorating the effects on guiding and tracking?

Thanks, as usual for your expert consideration of my problems! Tim. 

[Freddie]

I can go well beyond the meridian without any issues. A flip would obviously get the scope into a better position.

[Uranium235]

The EQ5/CG5 will only do about 30min past the meridian before things go wrong, you need to flip it.

[StargeezerTim]

The EQ5/CG5 will only do about 30min past the meridian before things go wrong, you need to flip it.

How do I do that? Do I have to start again, star alignment, etc, etc, or is there a way to'flip and keep the current position, tracking and everything... 

[Freddie]

Once you have gone past the meridian, just reselect the target on the handset and go to it. If you are guiding using PHD, there is a selection in there you can make to indicate you have done a flip and the guiding will still work fine.

[StargeezerTim]

Once you have gone past the meridian, just reselect the target on the handset and go to it. If you are guiding using PHD, there is a selection in there you can make to indicate you have done a flip and the guiding will still work fine.

That sounds easy, must get the leads out of the way and safe!

[DaveS]

I often see the guide graph go wonky as the scope gets close to the meridian then settle down again when I get past it, though I've not lost a sub due to it yet. Usually it's no more than about 5-10 min either side. I can usually image for up to an hour past the meridian depending on dec.

[Uranium235]

Just remember that once you flip, everything will be rotated by 180deg - so take a moment to re-frame properly. Use prominent stars as markers is you can.

[MattJenko]

I found my HEQ5 started to wobble when imaging around the meridian, unless pointing really low. Because the balance of the scope is even(ish), or even east heavy, the scope and weights are free to wobble between the gear cogs and it causes the image to oscillate. I have recently installed the Rowan belt mod, and my last meridian flip worked fine, which looks to have helped immensely.

[adamsp123]

Hi Tim,

I have a method that a bit before the meridian flip I will find an object on stellarium that has gone a bit PAST meridian but is of similar DEC. I slew to it (ie meridian flip) then check it has appeared in the field of view if this is OK I then recalibrate the guiding.

By now my target is past meridian so I can slew to it. I check the field of view again and if happy I can guide immediately. 

Pete