Star alignment whats going wrong?

[Eri]

Hey guys, 

I have no idea what is going wrong recently but wondering if someone could give some pointers.  I can polar align fine but when i go to do a 2 star alignment  I align against Altair and then either Caph or Capella as these are the only stars that I can use in my back garden, it aligns and when i slew back and forth between the two it aligns perfect but monday night when I tried to focus on Deneb the star was almost out of view i tried for over an hour but it just refused to align and centre properly on anything but capella or altair, if you have stellarium locate M74 galaxy then search for HD 9928, this is how far out the scope ended up. I know this becuase I took a test image and uploaded to astrometry.

 

I have followed astronomysheds alignment guides then use the synscan set to align and last year and the last 2 months its been fine but the last 2 weeks attempts have been out by this much each time....... whats going wrong??

[Skywatcher 200]

Hi Eri,

just a thought, have you taken into account the change of the clocks, i made that mistake !

[spaceman_spiff]

Thats an error of about 2.5 degrees in declination - pretty substantial. I would be interested in the suggestions as well. My mount also has some error in the goto but luckily objects do appear somewhere in the FoV. 

The issues I can think of are:

- Clocks when back recently (as Skywatcher 200 said), did you factor that in? (although I would have thought the error would be in RA only)

- Cone error, you could do a 3-star alignment to test it

- Backlash error - this can occur if the final movement to centre a star are not consistent. I finish with DEC+ and RA+.

Dan

[des anderson]

I don`t know if  this will help as I use an A.V.X mount. Try a factory reset, this usually puts everything back to how it should be. 

Des

[Owmuchonomy]

A two star align in Synscan is designed to be used with stars on the same side of the meridian.  The Stars you have chosen Altair and Capella don't fulfil that criteria. If you are using stars on both sides of the meridian then you should perform a three star alignment and thus account for your cone error.

[Eri]

hey guys,

yeah i have set to +00 and say no to daylight savings and the scope slews to close to the first target star then i just align and slew to the next. i don't think i have the option of a 3 star alignment as i have a narrow band of sky I can access it's always worked before with altair and caph until the last 2 weeks

its weird because the 2 alignment stars always centre but the other targets are always out so i'd have thought that would rule out backlash

[nigelg]

Just to check your settings there is an Anroid app called SynScaninit. This will give you the information in the correct format.

 

[ronin]

Power or data are the normal items, however power usually means the scope ambles around a bit drunkenly.

So data: Where in South England? Is the longitude correct - think is it West and -ve or East and +ve.  Just easy to be West and enter the vcalue as + -- does assume it expects +/-. Come to think of it read the Longitude when the mount/handset powers up. It might display something incorrect. Synscans have been known to change values that the user has entered.

2 star alignment is a bit "suspect" in a way. The first star is simply a start point, you then slew to another - in a way is that 0ne star alignment or two star alignment. The first offers nothing concerning the errors and corrections that the scope needs to compensate for. On a Meade the 2 star alignment uses a virtual star (Level and North) as the start point then it slews to 2 additional stars to determine the corrections required. In effect making use of "3" stars.

For 3 star alignment you should be able to use Deneb and Capella then use also throw in Alpharatz in Pegasus. It is the corner one that is shared between Pegasus and Andromeda so easy to identify/find.

Is there not a polar alignment option on the mount where Polaris is used as the start position, then pick 2 other stars. Actually Polaris is usually not a great starto use but use that as the first of 3 with the 2 you presently use. The scope should determine some of the corrections it needs to apply going from Polaris to whatever is next.

May still be a good idea the reset the whole thing and reenter the data, goto's seem to have a habit of ending up with something wrong somehow.

[michael8554]

Hi Eri

What happens if you Sync on Deneb after aligning on Altair and Capella?

Can you then go back and accurately GoTo Altair and Capella?

Job done probably.

It would be nice to know the source of your error, but it isn't worth spending forever on it.

Most objects can be accurately found by Synch-ing on a known nearby star before GoTo-ing the object, and it sounds like you have astrometry to fine tune.

Michael

[Eri]

Hi michael,

not sure what you mean by sync on deneb after aligning on altair and cap and i do need to know the source of the error because currently I cant accurately image anything

[ronin]

2 hours ago, Eri said:

Hi michael,

not sure what you mean by sync on deneb after aligning on altair and cap and i do need to know the source of the error because currently I cant accurately image anything

On "some" and I suspect there is one on the Synscan you can goto to a star centre it then "Sync". It in efect tells the mount exactly where it is pointed. At the RA+Dec of the selected star.

On Meade it is called "Sync" and you centre the star, then press and hold Enter for 2 or 3 seconds. On release it asks if you "Sync on ABCDE ?". You say Yes and that is the sync done. I suppose the idea is that all trhe little errors for position are thrown and it starts again at a set popsition.

The problem is that Skywatcher do not appear to have it as clearly specified as Meade does. Or/And they have a different name that is not so obvious. There is a fair chance that doing the same as MEade does the same and Skywatcher have not published the information. They do follow similar features. I would say hold Enter down for 2-3 seconds and see what happens, but someone may have written the self-destruct to use that key.

One other aspect of Skywatcher is that they had V3 of the software and added to that, now they have V4 and have added to that, the manuals are somewhat behind.

[DAVE AMENDALL]

I had exactly the same problem and fixed things by re setting the mount in the home position (Astronomy Shed) and re aligning polaris using the polar scope (Astronomy Shed). I took a lot of trouble with polar alignment to ensure it was spot on. Synscan was left untouched. I now locate and centre DSOs in a C8 at F6.6 without the use of a finder. I only use one star alignment. Pemanent set up on  a pier Skywatcher EQ6 Mount Celestron C8 at F6.6, Hope this helps..... Dave