Mistery of Celestron GoTo

[vincex256]

Hi guys, anyone that have like me  Celestron 127 SLT MAK, can explain why yesterday night i have see that strange with my mount ?

I have do 3 star allignment like i do normally, then i see some of the object suggested from sky tour that is visible on my position (180°, West - Suth West - Nord West) and that appear on my 25 or 32 eyepiece, some star appear on 5mm other object like ring nebula appear on 32mm. Ok i have a doubt on my mount but this is another story.

Well, late in the night after 1.5/2 hours of observation i have do experiment, i start Celestron Portal app on my phone and i have try to insert RA and DEC coordinates to my scope to find object near Altair, well with surprise nothig appear on my eyepiece. Uhmm..  i have try to search the object with SAO Number and surprise some object appear ... .

Ok i think Vincenzo try another experiment,  try to center Altair... whell if i set AR and DEC suggest from APP, star don't appear, but if i search star with mount keyboard  Altair appear. 

Then i have do another experiment .. see what AR and DEC appear on keyboard when GoTo find Altair, well i have se that AR is the same but Dec is 0.50 different from phone App Celestron Portal, DEC on app is 8.55, DEC on GoTo is 9.0...... suggestion ? My mount is broken ?

Yes i have to say that Celestron USA have say me that Alt/AZ mount of my scope is not very good when try to center object near the zenith but i have to go crazy..... 

Thanks to all who help me.

[ronin]

For Altair RA you do not have a problem. the RA is 8^o 52' which is 8.87^o

You are reading the 52' as decimal not as minutes.

Suspect thai is simply a bit of a limitation of the display.

So the RA values are very similar on the app and the mount.

A 5mm eyepiece on a Mak is very very narrow and the general accuracy of the goto is I suspect not good enough to expect an object to be in view with the 5mm. I would not have suggested using an eyepiece less then 12mm on the scope  So over 2x the field of view.

Reading the post I suspect that the confusion is between decimal values and degrees and minutes.

It may be that the scope uses one format the app uses the other. If so then you will need to convert the values yourself or check if the app display can be changed.

[vincex256]

Ok verify

[NotSoSuperNova]

Hi Vince,

I would keep the magnification very low while slewing to objects, 25mm+. This will reduce any small errors in alignment and help you see the object if it's not directly centred. After that you could work your way through the magnification up to high powered eye pieces and you should be fine. A zero magnification finder like a Telrad or RDF would also be useful here.