Wixey Guage Problems- Need Help

[Doc]

Last night I tried out my Wixey angle guage for the first time.

Levelled the Scope and checked level with a spirit level when it was level I zeroed the wixey.

Located jupiter in the west and centred it in my eyepiece. According to Cartes du Ciel it should be Altitude of 13 degree 7 min and I was shocked the wixey was spot on.

I then centred Altair at 44 degree 57 min again spot on. I thought Wow.

I then moved the scope to the M31 in the east, laptop said 49 degree 25 minutes and for some reason the wixey was 10 degrees out. it said 59 degrees.

Dropped down to Alpha Andromeda supposed to be at 46 degree 31 mins and agian it was 8 degrees out.

Strange I thought...

So moved back to Jupiter and have a guess the wixey was only .3 degrees out and jupiter was in fov.

Tried a few more times throughtout the night and looking South/ South West seem very good, but looking east/ South east was way off.

Any ideas guys and have wixey users suffered the same problems.

[kniclander]

I had similar problems and eventually gave up the Wixey cos it was more hassle than it was worth having to constantly check the alt of a body without a pda (but now I have an eeepc so I could 8) ) but I digress - I think the problem is that you can have the ota "level" but if the ground on which the scope stands is not level, when you turn it around west to east the error creeps in - I'm not certain and I am extremely cr*p at visualising these things but that was my conclusion.

dan

[Doc]

I had similar problems and eventually gave up the Wixey cos it was more hassle than it was worth having to constantly check the alt of a body without a pda (but now I have an eeepc so I could 8) ) but I digress - I think the problem is that you can have the ota "level" but if the ground on which the scope stands is not level, when you turn it around west to east the error creeps in - I'm not certain and I am extremely cr*p at visualising these things but that was my conclusion.

dan

I came to a similar conclusion Dan.

Maybe make some sort off leveling contraption that you can adjust to keep scope dead level.

[Kaptain Klevtsov]

Were the positions printed off before hand or "live"? I know its obvious but things move constantly up in the east, down in the west but move horizontally (well almost) to the due south.

Other than that I would say that the scope's optical axis doesn't match the tube where you put the Wixey?

Kaptain Klevtsov

[Doc]

Were the positions printed off before hand or "live"? I know its obvious but things move constantly up in the east, down in the west but move horizontally (well almost) to the due south.

Other than that I would say that the scope's optical axis doesn't match the tube where you put the Wixey?

Kaptain Klevtsov

KK I took the reading straight from the laptop. I made sure the page was refreshed as well. So really only a matter of seconds.

What do you mean the scope's optical axis doesn't match the tube where you put the Wixey? Would this explain why the WEST is accurate and the EAST is wrong.

[Astronut]

You say you

Levelled the Scope and checked level with a spirit level when it was level I zeroed the wixey.

Does this mean you laid the tube horizontal with the spirit level on the tube before zeroing the wixey?

I can understand you'd need to do this before zeroing the gauge but what about the mount? If that's on uneven ground and not level then there's your problem.

re. optical axis possibly at an angle to the tube geometric axis:

If the 'scope is well collimated, the optical axis won't be at a significant angle to the tube's geometric axis. It might be at a slight angle but I wouldn't have thought it would be enough of an angle to cause an error of ten or even eight degrees.

Use the spirit level on the mount base first and check that's reasonably level before you put the spirit level on the horizontal tube to zero the wixey.

[Astronut]

I've been thinking about what I suggested and the more I think about it the more convinced I'm wrong.

It shouldn't matter about the mount being level. It's the angle of the tube to the horizon that's being measured by the wixey which should correspond to the altitude of whatever you're aiming at. If the mount's not level that shouldn't affect it. At least that's what I'm thinking now - sorry, I'm stumped :oops:

[Doc]

Cheers Astronut I'm stumped as well.

I'm putting this idea on the back burner anyway as I'm finding I don't really need to know my altitude.

With this scope and a Telrad I'm finding most of my objects anyway. The 16" of aperture really helps locate things.

[themos]

I haven't encountered this problem but I want to ask you this: Do you keep the Wixey aligned with the optical tube so that the read-out plane is parallel to the optical axis?

[Doc]

I haven't encountered this problem but I want to ask you this: Do you keep the Wixey aligned with the optical tube so that the read-out plane is parallel to the optical axis?

Not sure what you mean.

It's positioned about 8 inches above my focuser

[themos]

The Wixey has a read out panel with LCD crystals. The LCD crystals are on a plane. That plane must always be a) vertical and pass through the optical axis of your telescope. In other words, you must put the Wixey on the "ridge" of your tube and rotate it so that the read out is at right angles to the long axis of the telescope.

[Astronut]

Have a look at the picture in this link.

http://www.nightskies.net/scopetest/accessories/wixey/wixey.html

It must be mounted so the readout is facing you (you at the focuser) and the base is parallel to and in line with the tube's longitudinal axis which (if collimated) corresponds to the optical axis.

Note the report mentions that the board levelling is not important as I suspected.

[themos]

the board levelling is not important

It won't affect the reading, but when you're searching for an object, it pays to have the base horizontal because then the apparent "azimuth" sweep (turn the scope left-right) will correspond to a true azimuth sweep. I hope I'm addressing a relevant point!

[rusirius]

Hmm, I purchased a Wixey along with the 300P Flextube because it sounded like a good idea but although I've used the scope a few times now, I haven't got around to unpacking the Wixey yet. In the meantime, I purchased a used Telrad and had the opportunity to try it for the first time a couple of nights ago. Once I got my bearings from the map, I just pointed the scope to the corresponding area of the sky using the Telrad and then used the optical finder to home in. The three targetting circles made using the Telrad very easy so I'm not sure whether I need the Wixey anymore.

[themos]

Ok, see how quickly you can find the Blue Snowball without a Wixey.

[Doc]

Thanks Themos for your explanation.

Astronut my set up is identical to the photo in your link.

It's just strange it's ok when pointing West and way out when pointing East.

Only thing that springs to mind is my patio is that Indian sandstone and it's at slightly different heights, only by millimeters. But the base is so solid that there is no movement back and forth at all and the spirit level reads perfectly level. could it be by rotating the cradle west to east is putting a little flex on the base board even though it does not show to the eye.

Russirus I personally wouldn't bother. I use a telrad and I'm finding it pretty essy to locate the brighter messiers and NGC's. I even found the snowball without one.

[rusirius]

Funnily enough I tried that the other night and spent some time on it but I couldn't find it. I had the right general area of the sky (very close to zenith) but I just couln'd see it either in the finder or the 16mm Nag T2. I did find Bodes Nebulae, M2 and M15 with relative ease though and Uranus with just a bit more effort. I'm not knocking the Wixey. If it really can yhelp me find the Blue Snowball then I might even give it a try!

[Astronut]

As themos points out, if the board isn't level, then sweeping in azimuth and keeping the tube altitude fixed will cause the tube altitude angle to increase or decrease but the wixey's readout will change correspondingly as you do this forcing you to move the tube up or down to compensate.

I don't see how the board not being level would cause such a big error in locating objects from one side of the sky to the other. It's only a simple device for measuring inclination from the horizontal and if the object you're looking for is at 50 degrees, then the tube pointing upwards 50 degrees (regardless of the board being level) as indicated by the Wixey should get the 'scope pointing at the object as you sweep in azimuth. It's a mystery :?

[themos]

I remember a mini-marathon I did last autumn and it did help me go through about 10 objects in an hour. I wouldn't try to locate faint things without it but maybe that's my LP skies and dodgy eyesight.

[rusirius]

Then maybe its not the Wixey, but as stange as it seems it might be Cartes Du Ciel? If the time was out in the program or the computer, for example by not taking into account BST, then wouldn't objects still be OK more or less close to the meridian, but gradually get further out as you move significantly round to the east and west?

[Doc]

Then maybe its not the Wixey, but as stange as it seems it might be Cartes Du Ciel? If the time was out in the program or the computer, for example by not taking into account BST, then wouldn't objects still be OK more or less close to the meridian, but gradually get further out as you move significantly round to the east and west?

Interesting I'll check now

[themos]

Then maybe its not the Wixey, but as stange as it seems it might be Cartes Du Ciel? If the time was out in the program or the computer, for example by not taking into account BST, then wouldn't objects still be OK more or less close to the meridian, but gradually get further out as you move significantly round to the east and west?

I do think you're correct! Altitude-wise, an hour makes hardly a difference near the meridian...

[Doc]

Well a quick check on Cartes du Ciel and I found this.

In UTC (Same as GMT) is set to zero. So no BST

Arctures in Bootes is in the West it is at 14 degrees 48 min

M31 in the east is at 48 degrees 32min

In GMT plus 1 hour so BST

Acturus in Bootes is 20 degrees 53 min

M31 is 39 degrees 47 min

So my error figures in the East of 10 degrees look good

West error was none so not sure about that.

cartes du ciel was set to no British summer time So GMT only

[rusirius]

Of course you'll need to change it back in a weeks time...

[Astronut]

Mystery solved

re. your west error:

As has been pointed out, a difference of an hour would make a much bigger difference in altitude for objects east or west but near the meridian (north or south azimuth) the difference in altitude wouldn't be nearly as much.

The objects you listed as in the west (Jupiter and Altair) are closer to the meridian (south) than west - actually at this time and based on when Jupiter is about 10 degrees above the horizon during darkness they would both have roughly the same azimuth (approx 200 degrees) which puts them in the SSW ie. quite a bit closer to south than west. That could explain the angle discrepancy when viewing the objects you listed around Andromeda in the east.