Alignmaster ALT and AZ problem

[Amaranthus (Barry)]

I had a go tonight at using 'Alignmaster' software to polar align my new AZ-EQ6 mount. But I had some strange behaviour.

I started with my mount level and approximately polar aligned (done via my iPhone's clinometer and compass). [The polar scope is not useful in my current location - Sigma Octantis is blocked by an unfortunately positioned tree!).

What worked:
I started my Synscan handset up, entered all the correct site coordinates, skipped the handset alignment, and switched to PC Direct mode.

I then kicked off Alignmaster, made sure my EQASCOM was working/communicating okay, and set about targeting/centreing two stars chosen from Alignmaster's list. This went fine -- using the GOTO button in Alignmaster, they were duly placed within the field of view of my finder RDS, and so centreing in the 12mm reticle eyepiece was no problem.

What didn't work:
Alignmaster then reported that I was about -1.5 degrees out in AZ and 55 minutes out in ALT. It then prompted me me to begin the polar alignment procedure. It slewed away from the target star, and told me to adjust my ALT to re-centre it in the reticle. This is where things went badly. You see, just adjusting my altitude winch would not centre the star. I had to adjust both ALT and AZ knobs to get it centred. The same deal when I tried to align the AZ. It slewed away from the target star again, but just adjusting AZ was not sufficient to get the target re-centred.

I tried repeating this on 5 or 6 different pairs of stars. By doing the dual ALT and AZ adjustment each time, I was, iteratively able to get the error down to about 10-15 min. But I always had to do the dual ALT-AZ adjustments.

So what has gone wrong? I would have thought the ALT alignment would have only slewed the scope in the ALT direction, and converse with the AZ.

There is only one possibility I can think of at present. Alignmaster asks for my time zone, which is +9.5 (Adelaide) but it won't accept this entry and reverts to +10. Would this 30 minute time error cause the above problem??

Has anyone encountered this before, or knows of a 'fix'? It otherwise seems like pretty useful software, if I can figure this out!

[Amaranthus (Barry)]

So I played around with the Alignmaster settings, and found that if I entered 9.5 in the "Time" box, it did indeed change the LMST by 30 min! (and now reads the correct UT, whereas before it was 30 min off after reading from my system clock). And, happily, the program holds this new LMST when I go to the alignment stars.

If I quit the program, it resets Time Zone to 10, unfortunately, but that just means I need to remember to set it each time I start the program.

I strongly suspect this 30 min time offset error to LMST/UT was my problem. But I won't be able to verify this until the next clear night!

It'd still be good to hear from others that may have run into this issue.

[Astroman (Andrew Wall)]

I had the same problem, so I unticked the box on the first page that says "Correct axis separately" This way you can move both Alt and Az axis together, enabling you to centre the star.

[Steffen]

I don't know Alignmaster, but FWIW the analogous SynScan feature also slews away then asks you to bring the star back, first in Alt, and during the second step, in Az.

However, unless your mount is perfectly level, neither adjustment will perfectly re-centre the star. The SynScan manual is clear about that. You're only to touch one set of controls during either step and bring the star as close as you can to the centre. In fact, during the Az adjustment step, you're supposed to bring the star as close as possible to where it ended up after the Alt adjustment, not the centre.

Regarding time zones, I always use 0 and enter the UTC time.

Cheers
Steffen.

[Amaranthus (Barry)]

Steffen, that's interesting. I looked through my Synscan manual but couldn't find that function. It only seems to describe the standard 1-star, 2-star or 3-star alignments for correcting the mounts internal sky model (to calculate Mel and Maz values), using the HC direction keys. It doesn't mention about moving the mount knobs (that I could find!)

Thanks Andrew, I will give that a go if I'm still hitting problems.

[Steffen]

The polar alignment function (found in the alignment menu) was added to SynScan as of version 3.35. It briefly appeared in an earlier beta IIRC, was pulled out again and is finally here to stay in 3.35.

Cheers
Steffen.

[Amaranthus (Barry)]

Terrific, I just updated the firmware last night, so I'll check it out. It sounds like basically an inbuilt version of Alignmaster. Thanks a lot Steffen.

[Amaranthus (Barry)]

So I found the updated Synscan manual for v3.35:
http://ca.skywatcher.com/upfiles/en_...1367276646.pdf

The new polar align procedure is described in section 11.3

This is excellent. The way they've set it up, to work in synergy with the 2- or 3-star alignment, and then iterating on a star, is logical and easier (and likely more reliable) than the Alignmaster method (although similar). They claim an accuracy if 1 arcminute after a few iterations.

Clear skies here in Adelaide, so I'll get to try it out tonight. I'll report back on how I went.

[Amaranthus (Barry)]

Alight, I tried the new Synscan 3.35 routine for Polar Alignment last night. I didn't have any real success, alas. After a few iterations (PE + 2-star alignment, redoing each time), I wasn't getting any closer to my target offsets. I'm not sure what went wrong -- mount was dead level.

So I eventually gave up on that and went back to Alignmaster, this time giving it the correct UT by setting my timezone to +9.5. I had reasonably good success with it this time - I got the AZ axis quite close, but with ALT it seemed to iterate around a +/- offset of about 30', which was frustrating. I couldn't get it any better.

So as a third step I spent a few hour re-familiarizing myself with drift alignment. I reckon I got this bang on -- no noticeable drift in over 5 min that I could detect. However, I decided there and then that I really need to teach myself the CCD drift method - a task for next time.

One advantage I have is that I have a semi-permanent mount position. I have to take the mount inside every day, but I have a hard paved pad that I set up on in my backyard, and have marked the mount position exactly on that. I trust this will shorten my future alignment routines!

So, all in all, mixed success with Alignmaster. I got it working, but was not happy with its accuracy for AP purposes.