Setup - Goto - Just not going well

[johnb]

Hi

I have a Skywatcher Explorer 250 OT, Skywatcher EQ6 Pro SynScan

and seem to struggle with setup and then goto. So tonight i really took my time. Put up the mount and ensured it was pointing north and 51 deg. Then finished it off by ensureing Polaris was indeed in the crosshairs through the polar scope. I then mounted the scope and entered the Goto setup routine, my FOV is quite narrow so i chose 1 star aglinment and selected Deneb, the scope slewed to thr right direction and only needed minor adjustments to get it centred.

So then using Goto i selected polaris and it was spot on,back to Deneb spot on, then I selected M45 it slewed to area of sky but was nowere near, several inches away, selected Deneb and it was spot on. Im not sure were im going wrong ? I did start over and try a 3 star aglin and wanted to used Deneb (no issue) and Polaris and Capella, Polaris and Capella were not on the list ?

Pointers appreciated.

Regards

John B

[Starjumper]

Hi John,

I have the HEQ5 Pro and I have to put Polaris in the little bubble for polar aligning and not on the cross as that is NCP.

Do you not have the little bubble on the outer circle.??

John

[DannyL]

I had irritating trouble with my goto. So I jumped on it. Didnt help the 'going to' one little bit, but the sense of revenge for all the irritations was wonderfull !

[Mike_F]

Hi

Then finished it off by ensureing Polaris was indeed in the crosshairs through the polar scope.

That might be your problem right there. If the reticule pattern in your polar scope is the same as mine in my EQ5 - that's not the way to do it.

The centre of the cross-hairs represent where the North Celestial Pole is, not where Polaris is. Around the cross-hairs should be a large circle, with a smaller circle embedded in the circumference. You need to put Polaris in the smaller circle, not in the centre of the cross-hairs.

Astro-baby has an excellent tutorial on polar alignment with these mounts here:

Astro Babys HEQ5 Polar Alignment

Hope that helps, do let us know how you get on.

Mike.

[James]

One star alignment isn't a particularly accurate form of goto alignment and goto's may miss objects a long way across the sky from the star you aligned to quite considerably.

Don't worry too much about the polar alignment yet; as long as Polaris is visible within the circle in the polarscope you'll be fairly close. Once you're happy with the goto setup you can sort the polar alignment out next time (and it's as Starjumper says ).

When you do a three star align the Synscan routine prefers you to start with a star roughly due south (although that's not compulsory) but depending on the first star picked you'll get a reduced number of stars to pick next time, for example if your first star is Deneb the handset will give you a list of stars on the same side of the sky (i.e. to the west) to pick a second star from. What you need to do is pick another star on the list that you can identify (a planisphere helps enormously here) and use that as the second star then the handset will ask for a third star and this time it'll give you a list of stars to the other side of the sky.

James

[Astro_Baby]

Dont use Polaris as an alignment star - there are good reasons for that - none of which I am able to explain fully but its something to do with the fact it doesnt have much movement.

I cant recall exactly the reasons but GoTo systms dont like it as an alignment star for the same reasons you cant use it as a starting position to use setting circles.

That may well be part of your problem.

[James]

With Polaris it's possible to be out by only a little bit but that to translate to many hours of RA - it's a bit like being at the north pole - all the lines of longitude converge and if you step a few feet away from the pole in the direction of London you'll be on longitude zero, just one pace to the left or right and you'll change longitude dramatically.

James

[alfingido]

If your mount isnt exactly level, then a one star alignment wont be very good as the computer wont be able to map the sky accurately. Doing a 3 star alignment will tell the handset whether you are level and make the correct adjustments for you, making goto much more accurate.

Also, the size of ep will make a difference. With accurate 3 star alignment, each new goto should put the object in the FOV of a 25mm ep. A higher power ep may be less accurate.

Perserverance usually works. That and making sure you have the correct time ( and time format, eg mm/dd/yyyy) location and a level site.

Good luck

Allan

[yesyes]

Yes, I also think that it's a matter of date/time and/or your location coordinates being wrong. The goto knows where polaris is (near it's "zero" points) and Deneb because you aligned on it. But if the time/date and/or location are off, it will not find other objects accurately because they will be at different points in the sky at different dates.times and from different locations.

Also, I agree that aligning on Polaris is useless. That's because whatever the position of the RA axis is, as long as the Dec axis is in the direction of Polaris, it will be in the FoV on an equatorial mount. When you look at Polaris through your scope, move the RA axis of the scope. You'll notice that Polaris will hardly move in the FoV because it's so close to the North Celestial Pole.

[arad85]

A one star align doesn't give you a very good translation of the sky. This will be worse as the thing you want to point at (M45) is a long way from the line you have aligned on (Polaris-Deneb). Always multi-star align and if you want good pointing accuracy, try and make sure the stars are far apart and preferably include your desired target (assuming it is only one) within the triangle formed by them.

[SteveP]

John

Unfortunately, you've introduced two potential inaccuracies into your alignment method which a 1 star alignment will not be able to adjust for.

Firstly, setting your mount using the degree scale is, let's be polite, problematic. For example, my own mount scale on an EQ6 is out by about 3 degrees. That's not untypical

Secondly, as others have already said, Polaris should not be in the crosshairs but rather in the direction indicated by the layout on the polarscope ... and so long as that has been properly aligned previously.

Moving to the positive, having Polaris somewhere in the eyepiece is a good starting point. It shows that you're pointing somewhere close to NCP. But don't use it for further alignment purposes. Don't worry too much about having your mount perfectly level. The alignment process will compensate for any inaccuracies

Having done that, check all the data you've input to handset, particularly the date and the time. Now do a 3 star alignment. Either use the stars which are being suggested to you by the handset or Exit from those and select ones from the handset's catalogue which are more suitable for your viewing. Get a good spread of these across your intended viewing area

HTH and good luck:D

Steve