HEQ5 Polar Alignment problems with Synscan V.3.35

[VPAstro (Andrew and Cam)]

Hi all,
Hoping someone can advise on some issues we are having with polar alignment here in Melbourne using the synscan V3.35 polar alignment function on an HEQ5 mount.
On moonless nights, we (my son and I)are able to locate Octans in the polar scope and align it that way. This is how we use to do it before I added the HEQ5 upgrade kit to our standard mount. Before the upgrade we were doing 90 second exposures and very happy with our results. Since the upgrade, and using the PA function, it seems our setup is getting worse each time and are only able to get 30 second subs before trails appear. We spent about 4 hours last night trying to get our alignment spot on, but were not successful. After aligning the polar scope and doing a 3 star alignment, noting the error in MEL and MAZ, we then complete the PA function, which at this stage only requires minor adjustment to the ALT and AZ. We use live view on our DSLR with the small grid on, so we are able to centre the selected star pretty accurately. We then complete another 3 star alignment, after which the reported error is greater than the first time. We do another PA which requires far greater adjustments to center the star. After completing another 3 star alignment and PA, we are way off. It seems to get worse after each PA adjustment, and the alt adjustment has moved up the scale from approx 38 to over 40.

Here is our process for setup.
1. Level the tripod and point N leg towards south, using 3 indicators/painted marks which we had previously placed on the ground to aid in polar alignment.
2. Mount the head, ensuring that the locating stumps is centered so that we have enough movement in the adjusting screws. The alt adjustment of the head is already set at approximatly our latitude
3. Attach the weights, OTA and balance.
4. Use polar scope to align with Octans
5. Turn on the power and go through the process of setting up the hand controller. I have a garmin GPS attached to the scope so I can accurately enter our observing location and the correct time, down to the second.
6. Complete a 3 star alignment using DSLR with live view and small grid on to accurately centre the selected stars.
7. Star the polar alignment function and make the neccessary adjustments to the alt and az.
8. Complete another 3 star alignemt. A larger error is now reported for MEL and MAZ.
9. Complete another polar alignment and correct the errors and another 3 star alignment.

After complete the final 3 star alignment, the GOTO function works great and is able to place our selected object in the field of view on the camera, but the tracking is very poor. I am just wondering if anyone may know where we are going wrong.
Many thanks
Andrew & Campbell

[glend (Glen)]

What happens if you do the alignment with an eye piece?
Try with an eyepiece and get back to us. What king of scope is it?

Some focusers can flex with a DSLR on them, or if the lock is not tight on the tube, hence asking about doing it with an EP.

BTW, you don't need to use the polar scope if your using the polar alignment subroutine inV3.35, and really a two -star alignment is probably fine.

I don't put my camera on the scope until after it is aligned, and then setup and focus on a bright star near my target.

Good luck

[raymo]

I'd like to add some comments, as well as reinforce some of Glend's.
PA function in 3.35 makes polar scope redundant.
Don't do PA align with the camera; any slightest movement of the
camera/focuser will upset everything.
Synscan has a LOT of functions. Download the Synscan user's manual
from the Skywatcher website. The PA routine is explained on page 35.
Print it out and have it with you at the scope until you are familiar with the routine.
Don't bother with a 3 star alignment, it has a separate purpose. 2 star
is all you need. If your mount is always put in the same place on a hard surface, levelling really only needs to be done once. It will be good enough for your present needs; so you don't need to remove the mount from the tripod every time. You will find the final slight adjustments a
bit fiddly; If you get both axes down to around 10-20 arc seconds, you will get around 100-120 secs exposures with a scope of 1000mm
focal length. A little tip. The error figures shown on the hand
controller are not the error, they are the adjustments you must make
to remove the error.
raymo

[VPAstro (Andrew and Cam)]

Hi Guys,
Thanks for your responses guys. We have been tackling this issue for a while now. The scope is a 10 inch f4.7 Newt with electronic focuser. We have tried it with a 17mm EP in the past, but will try it again soon. We are wondering why every time we do the PA routine it seems as though the adjustments are moving us further and further away from the SCP, if that makes sense? Could this be that we are using the alignment through the polar scope first and then compensating with the synscan, or does the starting point accuracy not necessarily matter?
Thanks again,
Andrew & Campbell

[andyc (Andy)]

I must admit to having the same issues as Andrew just now, using a very similar setup (with a 750mm Newtonian), I find my initial rough alignment is pretty good, but going through the fine alignment process with Synscan leads to exactly the same symptoms as Andrew describes, worse and worse alignment each time. Last night I gave up on the fine alignment and just used a simple initial polar alignment (with a Mel/Maz of <1/4 deg), then let the autoguider do the work. Had a decent result on a couple of 5min test exposures, but I'm missing out on getting the fine alignment right. And feels like something I'm doing...

I'd like to get the alignment better, not yet sure how best to do it!

[glend (Glen)]

Please look at page 35 of the Synscan V 3.35 manual, specifically step number 10 under 11.3 Polar ALignment without Polar Scope (this is the Polar Alignment Sub-routine). Under Step 10, it advises that after completing a correction for error using the routine that you must "Go back to the Alignment menu and execute another 2 -star alignment and then check the reported error again - at which point you can decide whether you do another correction using the sub-routine.

If you do not re-align after the first use of the sub-routine you may get into this ever worsing result as you do multiple alignment sub-routines. I believe that the Polar ALignment subroutine uses the initial alignment figures in memory each time it is executed. You basically build the error each time it is used if you do not do a new alignment before checking it again.

[Camelopardalis (Dunk)]

After my star alignment and polar alignment, I park the scope, power off to clear the computer memory, power it on again and select option 2 (don't resume from park) and go through the star alignment and polar alignment routines again. I've had mixed success with it, but sometimes it only takes a couple of iterations to get under 1 arc minute error in each and that's about where I stop. Some nights it takes many more iterations to get there. I'm only using a short focal length (340mm) refractor but that has allowed me to get 5 minute subs. If I stick my C8 on board, I'm lucky to get 1 minute subs. I use an EQ6 but the software is the same.

Like glen says, I believe it is the replacing of the alignment stars - or clearing the memory in my case - that helps hone in to the right place. Also, a few times it has sent me all over the shop at which point I've powered it all off and sat with a pair of binoculars

One other thing...make sure you are using the same stars for your star alignment and polar alignment correction with every iteration. I thought that , in theory, if I was close to good polar alignment it shouldn't matter, but since I've been enforcing that I seem to be finding it faster.

I'm also keen to learn how to get better results without resorting to autoguiding. Personally I find the altitude adjustment on the mount very difficult to operate.

[raymo]

I've never suffered from the ever worsening error that you describe. After doing the first two star align, and then making an adjustment, you must do another one[using the same two stars], make another adjustment, and so on. If you are making adjustments in the correct direction it is
impossible for the error to increase, unless you make a huge adjustment , and come out the other side, so you end up with an error in the opposite direction. Are you all adjusting the right way? If it says Mel + 10" you should raise the elevation by that amount. If it says Maz +10" turn the mount clockwise that amount.[clockwise looking down onto the mount].
As I said in my previous post, it doesn't show the error, it shows the
adjustment required to remedy the error. The biggest pain is having to slightly slacken the mounting securing bolt to make each adjustment.
If you don't do that, you risk bending the adjusting screws. When doing
the last couple of adjustments I pop my illuminated reticle EP in, so I
know I'm centring the star accurately.
raymo

[raymo]

Regarding your difficulty with the alt adjustment Dunk. It is very difficult
to make it easier to adjust with a mass produced budget level imaging mount like yours and mine. Because of the weight you are lifting you would need a thrust bearing and a geared down drive in order to make
very small adjustments easy.
Why do you switch it off and go through the routine twice? As soon as I get the error down to figures I'm happy with, I just go into the object list, and I'm on my way.
raymo

[Camelopardalis (Dunk)]

Ah OK tx raymo, glad it's not just my fat fingers with the alt adjustment, sadly a G11 or similar will have to wait a while to be fair, I've had a lot of fun imaging what I have so far, it's just some nights can be frustrating getting decent sub lengths I can be happy with.

With the alignment cycle, the least I've ever done it is 3x...so that's power on, star alignment, polar alignment, park, power off, then again, and again, then one last star alignment and be happy. Sometimes, I've spent several hours going through it over and over again. I think with practice it is getting easier to achieve, obviously the azimuth is much easier to nail than the altitude...

[glend (Glen)]

I believe the imaging payload capacity of a HEQ5 is 11kg, for visual its 15kg. I'd be very surprised if a 10" f/4.7 newt weighed as little at 11kg complete with finder, DSLR etc. I know a 10" GSO imaging newt weighs 15kg for the OTA (accordng to Luke at Andrews). My NEQ6 handles my 8" imaging newt and camera just fine but I wouldn't put a 10" production newt on it - which is why I am building a lightweight 10" imaging newt. Andrew do you know how much your newt/camera weighs?

[VPAstro (Andrew and Cam)]

Hi guys, thanks for all your responses. We've read the manual and thought we had an ok grasp on the process, however; we will try out some of the things suggested here that we probably haven't been doing. I'm not particularly sure of the exact weight of the scope but I have no doubts that it is probably a bit too heavy for the mount. That being said, we have managed almost 90 second subs on previous attempts whilst polar alligning through the polar scope. It would be nice to try and nail this process though to increase our reliability with this.

Thanks again for all the help guys.
Andrew and Campbell

[andyc (Andy)]

Glen and Raymo, that sounds pretty promising - I'll try doing the re-aligning after the correction procedure. That may well be the step I was missing, so (hopefully) thanks!

[raymo]

HEQ5 visual is officially 13.7kg. My 10" OTA is 14.6kg + finder 0.2kg
+ DSLR 0.5kg + electric focuser approx. 0.2kg =15.5. way over max for
HEQ5; approx. 40% overloaded for imaging, and 15% for visual.
NEQ6 handles that load easily.
raymo

[raymo]

The penny just dropped Dunk; you are apparently powering off and parking between each 2 star alignment. Why? Once you power up you
you don't need to power off again until the end of your imaging/ viewing
session. You just keep doing 2 star alignments with an adjustment between each one, until you are happy with it, and then just press object list button, and you're in business.
raymo

[Camelopardalis (Dunk)]

OK tx raymo will try that the next time I get the chance, seems like it might save me some time through the course of setting up which is always welcomed!

As for the polar scope...I've not taken the cap off mine since I've been in Australia, just doesn't seem as easy without a nice mag 2 star there

[raymo]

I second that.
raymo