Mount levelling and goto accuracy

[cuivenion]

Hi, I've read in various threads that an eq mount does not need to be level in order to polar align.

Does the mount need to be level in order to get accurate gotos? Or is it ok once polar aligned?

My method of polar alignment is using Sharpcap, which uses plate solving. I'm using a Vixen GP.

 

[Peter Drew]

No harm in levelling the mount but it's not necessary. The adjustments on the mount take care of polar alignment. The GOTO is referenced to the polar axis.

[cuivenion]

Awesome that speeds things up a bit.

[spillage]

I have always made sure my mount is level. I may be wasting my time in doing this but it only takes minutes and it means that I start in the knowledge that this box has been ticked.

I just think that if I do have an issue because of this then I would need to strip back and redo everything. I am sure this would take allot longer to sort than just getting it level in the first place.

[Cornelius Varley]

34 minutes ago, spillage said:

I have always made sure my mount is level. I may be wasting my time in doing this but it only takes minutes and it means that I start in the knowledge that this box has been ticked.

I just think that if I do have an issue because of this then I would need to strip back and redo everything. I am sure this would take allot longer to sort than just getting it level in the first place.

That is the only reason to level an eq mount. Whether the mount is level or not doesn't affect polar alignment or goto accuracy.

[Freddie]

Leveling an EQ mount is a waste of time as any issue can only ever trace back to the fact that PA is out NOT that the mount isn't level.

[rotatux]

What about getting a rough altitude start setting each time you set up (at the same latitude) ?

(just a question -- I'm not using SharpCap and have no idea how much time it would save alone)

[Stub Mandrel]

42 minutes ago, rotatux said:

What about getting a rough altitude start setting each time you set up (at the same latitude) ?

(just a question -- I'm not using SharpCap and have no idea how much time it would save alone)

Absolutely, leaving the mount set to your local latitude, roughly pointing it at polaris and having it roughly level all make polar alignment easier. But as long as you CAN see polaris, taht's enough to start polar aligning.

Think of it this way, anywhere between about 30 degrees north and the north pole, you can polar align a standard EQ mount (nearer the equator the scope may foul the tripod). You can also PA the scope at any time of year. That's a 120-degree range in ALT settings and a 360 degree range in AZ settings and the equivalent of the mount being wildly 'unlevel'.

 

[spillage]

But if the mount is level then this should make polar adjustments easier (left,right,up,down) and also increase accuracy when using goto alignment.

Not in this one for the long haul...I do not mind spending 5 mins with my torpedo level checking n/s e/w.

I guess its just part of my routine that I have always done. What do they say about old dogs?

[Ibbo!]

it does not make a jot of difference if the mount is not level as long as the polar axis is aligned with the north(or south) celestial pole.

 

 

In fact my high end mount tripod cannot be adjusted.

 

[Davey-T]

26 minutes ago, Ibbo! said:

it does not make a jot of difference if the mount is not level as long as the polar axis is aligned with the north(or south) celestial pole.

 

 

In fact my high end mount tripod cannot be adjusted.

 

Just a small caveat, some "unguided" mounts that rely on modelling the sky work better if they start out level.

Dave

[Ibbo!]

1 minute ago, Davey-T said:

Just a small caveat, some "unguided" mounts that rely on modelling the sky work better if they start out level.

Dave

Not with an eq mount.

It is dependant on the polar axis pointing at the pole.

 

fork mounts are a diferent ball game all together.

[Davey-T]

4 minutes ago, Ibbo! said:

Not with an eq mount.

It is dependant on the polar axis pointing at the pole.

 

fork mounts are a diferent ball game all together.

They are EQ mounts "just unguided" and rely on assuming having a level start as a reference point.

Dave

[Ibbo!]

We will agree to disagree then.

[StevieDvd]

24 minutes ago, Davey-T said:

They are EQ mounts "just unguided" and rely on assuming having a level start as a reference point.

Dave

Presumably like a Celestron Evolution with starsense on a wedge -  so need to be level-ish :-)

[Davey-T]

2 minutes ago, StevieDvd said:

Presumably like a Celestron Evolution with starsense on a wedge -  so need to be level-ish :-)

I've always found it helps to have wedges level in an east west direction, north / south doesn't matter as it's adjusted out with the alt / latitude setting.

Dave

[spillage]

Im I right in thinking that your are supposed to spell mount level as Marmite...

So do some dont in the end its a personal choice.

[Ibbo!]

It helps if the fork arms and bearings are level.

The old Meade LX200 fork mount thats in the loft has arms of differing length and even then I think its more down to the poor wedge it was on moving around under different balace settings.

 

The 8" SCT that was in it performs much better at pointing on the GPDX,EQ6 or the NJP and can even be used for imaging now

But it performed quite well in alt az if the alignment stars were well spaced.

[kirkster501]

The mount absolutely does NOT need to be level - although it looks better if it is.  As long as the axis is pointed to the NCP it does not matter a monkey's if it is level.

[Zakalwe]

1 hour ago, kirkster501 said:

The mount absolutely does NOT need to be level - although it looks better if it is.  As long as the axis is pointed to the NCP it does not matter a monkey's if it is level.

Absolutely this.

 

What is it level to, anyway? If you stand on the equator and level your mount then the mount base will be at right-angles to a mount that sits on one of the poles. The universe, and where it's stars are located, don't care a jot where the tripod legs are pointing. only that the RA axis is pointing at the Celestial pole matters.

[Stub Mandrel]

2 hours ago, Davey-T said:

Just a small caveat, some "unguided" mounts that rely on modelling the sky work better if they start out level.

Dave

Do they work better at certain latitudes or times of year then?

[Filroden]

I always thought that if the mount was not level then any adjustment you made to either alt or az during PA would introduce a small change to the opposite axis. So if not perfectly level you would have to iterate adjustments between alt and az to gradually hone in on your PA. If the mount is level, the alt and az axis are truly independent so a single adjustment to each could be possible. 

[Davey-T]

36 minutes ago, Stub Mandrel said:

Do they work better at certain latitudes or times of year then?

Oo look what you get starting level and one quick adjust 

Dave

 

 

[Stub Mandrel]

2 hours ago, Filroden said:

I always thought that if the mount was not level then any adjustment you made to either alt or az during PA would introduce a small change to the opposite axis. So if not perfectly level you would have to iterate adjustments between alt and az to gradually hone in on your PA. If the mount is level, the alt and az axis are truly independent so a single adjustment to each could be possible. 

It shouldn't. Imagine the mount leaning at 45 degrees to one side. Adjust Alt until it's aligned with a line through the pole at 45 degrees, then swing Az until spot on. A computer will do that in two moves.

Ok, it MAY be harder to do it by eye as you want the cross hairs of the polarscope vertical/horizontal which may not align with the alt/amovements, but in practice I just jiggle or adjust my tripod until I can see polaris through the polarscope then i's half a minute to get it to the right point on the dial. The hardest bit IS getting that graticule properly aligned without any clear reference - MUCH more important and I may fit a small level to help with this.

[cuivenion]

Well gotos and tracking seemed to work fine last night. I just quickly made sure the mount was roughly level . I made one adjustment to one tripod leg. Next stop guiding! Thanks for the replies everyone.