Polar alignment and goto issues

[DancingStar (Tony)]

Hi everyone, I’m having problems with finding things.
I have an HEQ5Pro, with a William Optics FLT98 refractor plus a 50mm f4 finderscope [which is correctly aligned with the scope axis].
But no matter how careful I think I’m being when levelling and polar aligning the mount, then doing 2- or 3-star alignment with the software, then correcting the “Mel”/”Maz” numbers to as small as possible, target stars almost never appear in the telescope eyepiece first-time; I thus need to use the finderscope to try to find, then centre the target star, but my judgement of when the star is in the centre of the finderscope eyepiece seems to be rarely correct - I put it in the centre of the finderscope eyepiece then look in the main scope eyepiece but the star is not there. So I need to use the hand controller to move it around, but there seems to be no easily predictable direction-of-movement based on the direction buttons on the Synscan. It just wastes so much of my time.
Can anyone suggest what I might be doing wrong?
Thanks
Tony

[Nikolas (Nik)]

LAt and long in the correct orientation?

[sharptrack2 (Kevin)]

Hi Tony,

A couple of ideas that pop out at me...

first, have you actually aligned the finder scope to the view or just have it pointing straight up along the scope? Finders will be slightly offset in their view from the straight line through the centre of the scope. One of the easiest ways to check this is to setup in the day, find a target 1-2 km away and using a long focal length EP (>20mm), centre the target in the telescope view, then check your finder scope view. I suspect you'll find it is not pointed at the target. There will be 2 or 3 adjustment screws for the finder scope, adjust these slowly until you get the target in the centre. Then using a shorter focal length EP (10-15mm) refine the adjustment until you can move the scope using the finder scope and the target be in the view every time. Be aware that each time you take the finder scope off it may require adjustment when you put it back on.

Proper polar alignment is needed for the GOTO to align well. It doesn't have to be perfect but closer is better. A compass and inclinometer is needed. Google polar alignment southern hemisphere for 100's of Youtube videos.

The next thing to check is the cone error of your telescope. If the telescope is not accurately aligned with the polar axis of the mount, it can cause the GOTO to align improperly and targets will not appear in the view when you slew to them. Especially if you go from one target in the west to a target in the opposite side of the sky.

Check your finder scope first and go from there.

Good luck!

[DancingStar (Tony)]

Hi ,thanks very much for the replies. However, I am still not clear because different answers use different terminology which does not sound consistent.
So I’ll try to state clearly what I need to clarify: Is the following procedure correct, and if not, what is the correct order:
1 level tripod and point it south correcting for magnetic declination
2 set the latitude
3 do drift alignment [This is what some people are calling ‘polar alignment’. This involves, finding stars, noting the drift, then adjusting the azimuth and altitude bolts manually, not using the Synscan hand controller]
4 do the GOTO setup using 2- or 3-star alignment
I should not do the next Synscan software procedure to further fine-tune the GOTO alignment because that also involves using the adjustment bolts – which would spoil the previous adjustments.
Am I right in thinking that this should be enough? – good polar alignment will help good GOTO alignment. [I’ll leave cone error corrections until I am sure that the procedure I’ve mentioned here is definitely the correct one to follow.
Thanks
Tony

[sharptrack2 (Kevin)]

Hi Tony,

The process you follow looks OK to me, its fundamentally what I do, the only exception is I do continue on after a 2 star alignemnt and make the minor adjustments to bring the error as close to zero as I can. Drift alignment is only as good s how well you can differentiate the 2 path lines. Errors can still be there.

I too still have issues with the telescope not slewing to the target accurately but it is almost always in the FoV of a long EP (>15mm). I attribute it to stacked up errors during setup and aligning. I don't think it is ever possible to get the setup perfect every single time if you constantly have to tear down and setup. I envy the guys with piers and observatories.

You'll find that because most of the imaging people use guiding, polar alignment accuracy is not as important. It's only when you are doing visual that it becomes critical. However, most visual observers probably aren't too fussed as it is easy to make adjustments as you go, and use star hopping to get around the sky. I do understand your frustration with the GOTO function and it should work if everything else is perfect.

I also just thought of another contributor, the mounts mechanical movement will have play in it. So even if you get the PA perfect, the 2 star alignment might add errors if you don't finish the alignment of the star with and "up" and "right" movement. This keeps the gears meshed in the forward RA motion. One of the best mods you can do is replace the gears with belts (http://www.rowanastronomy.com/produc...tm#heq5beltkit.)

Hoping this all helps a bit...

[MattT]

Having owned the HEQ5 and NEQ6 the only thing I can add is what are your alignment stars?

For visual I always did Canopus and Achanear...spelt wrong cause I can't remember what the spelling is and this iPad continues to correct....

Never had trouble with GOTO's with those two stars.

Never did three star alignment....seemed like a waste of viewing time.

If all fails get SkySafari and Skywire or SkyFi and use an iPad/computer to show where you are, which is what I do with my present home made mount.

Matt

Edit: you need a successful alignment on the suns an handset to use SkySafari.

[DancingStar (Tony)]

Thanks guys for all your kind advice I'm getting my new EQ6-R mount this week or next, so I'll try to put the advice into practice.
Thanks again; I appreciate it.
cheers
Tony