Alignment query

[Fypunky]

I have been fortunate since obtaining my AZ goto to had clear skies but I have noted a odd occurrence after I have aligned it. 

Using the hand control if say I choose Jupiter it will skew to it but Jupiter will not be in the centre but bottom left this happens with every target?  I received my cable today to connect to stellarium so I have just been out to play and weirdly the target is now centre when using stellarium to skew to the target! 

Am I missing something when aligning the mount? 

[carastro]

That's pretty good I would say, don't expect 100% accuracy as your initial alignment could be fractionally off with an AZ scope.  at least it is in the field of view.

Carole 

 

[Fypunky]

11 hours ago, carastro said:

That's pretty good I would say, don't expect 100% accuracy as your initial alignment could be fractionally off with an AZ scope.  at least it is in the field of view.

Carole 

 

Many thanks, I can't remember ever that being mentioned in any forums regarding the mounts but having said that it has massively increased my enjoyment of viewing and wouldn't be without it!

There is an option to increase pointing accuracy but if I am getting the target in the FOV I guess its not worth the extra effort?

[Shibby]

If you're getting things centred with Stellarium (and EQMOD direct?), but not with the handset, then I would suggest that perhaps some of your hand-controller settings are wrong. Double-check the time/timezone and latitude to make sure they are correct. For example, does the hand controller expect UTC (currently GMT -1)?

[Fypunky]

2 hours ago, Shibby said:

If you're getting things centred with Stellarium (and EQMOD direct?), but not with the handset, then I would suggest that perhaps some of your hand-controller settings are wrong. Double-check the time/timezone and latitude to make sure they are correct. For example, does the hand controller expect UTC (currently GMT -1)?

The hand controller is the Skywatcher Synscan AZ goto, all the settings I have used are taken from an app SynscanInit (android) which I am lead to believe puts it all in the correct format, I did wonder if this wa causing the slight difference between Stellarium and the HC!

 

Edit: Thank you Shibby, you got me thinking and I have just tried a couple of online Long/ Lat pointers and they are all consistent where as SynscanInit is different to them, I will update the HC tonight and if we have a break in the clouds will try and see if this makes the difference.

[Fypunky]

Ok frustration now setting in!!!

Re-input longitude and latitude using itouchmaps as per you tube viddy which gave a different reading to syncscanInit but still on the second alignment star it was about 4degrees below the star, tried different stars but still the same, once aligned sent the scope to jupiter and there it was bottom left still???

Is it normal to be off when aligning the second star?

When aligning I use a 15mm to centre then use a 6mm out of focus to get it dead centre.

Hoping tomorrow will be clear for a play as it is forcast murky from Thursday onwards.

[JOC]

Just a thought, but are you using the same EP as you used for the calibration?

[jambouk]

Several thing here.

The latitude and longitude are only used by the mount during the star alignment process to help tell the mount where you are on the earth so it can also use the time and date to predict what is liekly in the sky above you at that time. Omnce you have done the start alignment it doesn't care what the lat and long are as you have matched what you can see in the night sky with a sky map inside the handset. So even being several degrees out with lat and long makes no difference, it just means the first star might be off a bit when it slews to it during the star alignment process.

You don't say what scope you are using. If it has a long(er) focal length (say >1000mm) then your field of view will be pretty narrow and this will challenge even the tightest of star alignments and GOTO accuracy. If you can see the target in the FoV your GOTO accuracy is pretty good in my opinion, even if the target is not bang in the centre.You are using kit which cost £200-300 I suspect and it is pretty accurately locating stuff many thousands of light years away... I think that is quite impressive

The pointing accuracy improvement is worth doing. It is easy to do - once you've used GOTO to find a target, centre the target in the middle of the FoV, then following the instructions on how to improve the pointing accuracy witht eh handset (it is a few clciks). The pointing accuracy can be done once in each of the 88 constellations; if you do it twice in teh same constellation, it wipes the previous attempt and uses the latest one. You could spend 5 minutes just tightening up your pointing accuracy in one area of the sky by picking a bright star from each of a few constellations. It just depends how much time and interest you have in this verses the benefits it will give you.

James

 

[jambouk]

And as suggested above, the better you do your star alignment, the better the GOTO accuracy will be. It is common for the first two stars to be initially some way off whenthe mount slews to them. The key is to centre them as well as possible (this is where a reticle eye piece helps) and use the highest power eye picee to do this; you might need to find the star with a low power eye piece, centre the star, then swap to a high power eye piece and centre again and then accept the position. Always end with an up and right arrow move to make sure the gears and worm mesh in the same way each time.

James

 

[Fypunky]

Many thanks for taking the time to reply, The scope is Celestron Astromaster 130eq, I use a 15mm EP to centre then switch to a 6mm and take it out of focus to centre before locking on.

Please don't get me wrong, I am really impressed by this mount, having to spend ages looking for something and not finding it with the original mount was a lot 1000x's more frustrating,  now it is there for both my daughter and I to enjoy, it is just this tiny little thing that is in my head nagging away lol. 

My logic on this is/was it had to be something to do with the 2nd star alignment, as when it skews to the star it is always low, so we adjust to centre which lets say in effect takes it higher than it first thought, so when we swing to the target, the target is now in effect higher than it is by the same amount as we adjusted it in alignment process hence why it is low in the EP!

Again many thanks for taking the time to reply, hopefully some rain is on its way and I can get to bed at a normal time for much needed sleep.

 

[jambouk]

Make sure the kit is as well balanced as possible.

Make sure the power supply is as reliable as possible.

Make sure you mesh the gears in the same way each time you end a manoeuvre.

Make sure the altitude axis especially is not too sloppy  (there is a nut under where the telescope dovetail sits, nip it up so there is no obvious play in the altitude axis of the mount head, but just check the motors can turn the axis easily – literally nip it, don’t over tighten it or you’ll burn the motor out).

If you think you have found a solution (ie not centring the second star) then try an alignment that way and see how it compares.

Most of all, continue to enjoy it all and explore and get the kids involved.

James

 

[Fypunky]

Again many thanks James for your valuable input.

[Fypunky]

Bump: (last one)

Well you will be pleased to know I finally managed some sleep last night!

Spent a half hour playing, my logic did not work?? However I have figured a method out that does work every time and puts the target in the centre every time with both the HC and Stellarium.

The method is I align the first star as per manual in the EP then send it to the 2nd star, however as always it goes low, I then tweak so it is at 1 O clock just above the centre ring of the Telrad, see photo.

I tried this several times with different alignment stars and it worked everytime!

So again many thanks peeps for replying.