SW Star Adventurer Pro not tracking properly

[Xay]

Hello everyone,

First post here. I recently got the Skywatcher Star Adventurer Pro pack and I've spent the last few weekends trying to use it for photography with a 55-250 mm lens and my DSLR (Canon EOS 80D). I watched lots of tutorials on how to properly set up the tracker and do the polar alignment and I also read the manual. Still, I am getting star traces in my photos instead of pointy stars and I don't know if I'm doing something wrong or if there's a problem with my SA. These are the steps I am following:

1) Set tripod and equatorial wedge up facing north. Set latitude and level. (I have a relatively heavy Manfrotto tripod)
2) Install tracker body on the wedge and camera directly on the declination bracket/fine tuning mounting assembly. Use the counterweight and extension arm to level.
3) Polar alignment. First, I place the reticle correctly (0 up and 6 down) using the graduated cirlces, as explained in the manual. Then, I use the Polar Scope align pro app and the screws on the equatorial wedge to place Polaris on the reticle as accurately as possible. 4) Frame target and check that Polaris is still where it's supposed to be. I check the difference in RA between my initial set up and the current one to calculate the RA rotation and I input this number into the Polar Scope align pro app to see where Polaris should be on the rotated reticle. It's normally still in the right place, but sometimes it does move a little (less than half a fraction of a division in the reticle).
5) Start taking photos.

The pic has some examples from last night. There was a full Moon, so I am certain the only star I was seeing through the polar scope was Polaris. There was no wind whatsoever.
Throughout the session, Polaris did not move from where it was supposed to be (I checked regularly). Something that I find really intriguing is that I seem to be getting almost equally long traces every time (!!!), regardless of how long my exposure times are, up until 3 mins or so. This makes me think the problem is in my camera, but I have tried using mirrow lockup and the self-timer and I still get these traces (I always use an external intervalometer/controller to shoot, I don't touch the camera). I use rechargeable 1.2V batteries, could this be the problem? (I've heard they're not recommended if you have heavy equipment). The other thing I've thought of is that my 55-250 lens does not have its own mount/base, so there's a fair amount of weight off the declination bracket.

Any ideas on what may be wrong here will be greatly appreciated!

 

[Davey-T]

Hi Xay and welcome to SGL, long exposures with long lenses are a bit beyond your average SWSA, mine is pretty good and can only manage a couple  of minutes using a 300mm lens.

Having said that as with any mass produced mount there are always going to be lemons so the first thing to do is check that the screws holding the head to the wedge are tight, the bit with Skywatcher written on it and the four screws holding the dovetail clamp.

If all is well there you can do a tracking time test indoors by mounting some sort of laser pointer in the dovetail, aiming it at the wall and marking a starting point and running it for a sidereal day 4min's shorter than 24 hours, it should end up pointing in pretty much the same spot as it started from, any more than a few millimeters out (usually running slow) will cause elongated stars.

It is quite possible to take longer exposures with long lenses if you invest in a guiding setup.

Dave

Edited November 1, 2020 by Davey-T

[Xay]

Hi Dave,

I know very long exposures with long lenses are not possible with the SA, but I am getting traces with 10 second long exposures!!! I expected to be able to get at least a minute or two with the 250mm lens. 
It seems all the screws are tight, so I'll try the tracking test with my laser pointer.

Thanks!

Edited November 2, 2020 by Xay

[Tomatobro]

I find that good polar alignment is essential and use Sharpcap's polar alignment tool to achieve this.

[Chefgage]

A few points and I am sorry if this sounds patronising (that is not how it's meant to sound).

How tight is the clutch ring?, if this is really tight when imaging it can effect the tracking.

Daft one, but is the button set to North (assuming you are in the northern hemisphere).

Another daft one, is the rotary button set to the star setting (in the dark I have momentarily set this wrong).

[Davey-T]

Here's a test I did on my original Star Adventurer with a similar problem to yours.

Two images 30 seconds apart combined as GIF clearly showing wrong tracking speed, had it exchanged for another one which has performed well.

Dave

[Xay]

Thank you everyone for the suggestions.

I couldn't run any tests yesterday, but I will try today.
Chefgage, don't worry, I understand you're trying to help and you need to rule out all possibilities. The clutch ring is sometimes quite tight, so that could be a problem. I'll try loosening it up a little. The button is set to North indeed and the tracker is set to star setting.
Dave, did you just choose one of the other speeds in the dial or did you change the tracking velocity in a more complicated way? I haven't tried comparing a sequence of photos to check whether the tracking speed is wrong, but I can easily do that next time.

What do you think about the rechargeable batteries? Could they be a problem?

 

[Chefgage]

1 hour ago, Xay said:

 

What do you think about the rechargeable batteries? Could they be a problem?

 

I use rechargeables in mine. They are the 2000mAh version. Seems to work ok for me.

[Xay]

39 minutes ago, Chefgage said:

I use rechargeables in mine. They are the 2000mAh version. Seems to work ok for me.

 

Mine are 2800 mAh

[michael8554]

The rechargeable cell capacity is largely irrelevant, it's the fact that they're 1.2V compared to 1.5V for "ordinary" cells.

But if the same number of rechargeables is more volts than the mount's minimum, you're good to go.

Michael

[Xay]

I finally had time to do the indoor test that Dave suggested. I set everything up on Tuesday night and let it run for 24 hours minus 4 minutes. I put a sheet of graph paper on the wall, approximately 15-20 cm in front of the camera, so I could compare the grid between the first and the last photo and measure how big the difference was. 

I took 7 photos in the last minute, and the video below shows the grid from the first photo, in gray, and the grid in each of these photos, with the original colors. It seems the maximum difference with the first photo is less than 1 mm, but it also looks like it reverses the rotation direction halfway???? I'm 100% sure the photos are in the right order. I'll do some more indoor tests (weather has been bad lately) to investigate a bit more this rotation reversal problem.

What do you think?

[Davey-T]

One of the time lapse settings does 360 degrees then reverses I think, can't remember which, have a read of the manual.

Dave

[michael8554]

Doesn't your video give a very good demonstration of Periodic Error ?

Michael

[shropshire lad]

Probably a daft question but have you turned off IS on the camera, I lost a whole nights images while working on my tripod a while back because the camera hunts for movement even when there isn't one, images looked ok on rear screen but totally useless.

 

 

Edited November 14, 2020 by shropshire lad
wrong word used

[Tomatobro]

 If I have understood the video correctly the tracking error over 23 hours and 56 mins is tiny.

[Xay]

Hi everyone,

Thanks a lot for all the replies. I've had a couple of good nights and could do a few more tests. I took a few series of photos both at 55mm and 250mm and made short time lapses to check how good the tracking is. Unfortunately, it looks very bad, the frames move A LOT in these short series, and not even in the same direction the whole time. I thought I was doing everything correctly, but at this point I'm not sure if it's me or there's a problem with my SWSA. Any comments on these videos would be greatly appreciated.

I did turn off the IS on the camera and used non-reachargeable batteries this time, just to test if they were the problem.

Video 1 - Pleiades - 250 mm, 12 photos total, each one has 1 min exposure time and ISO 800. I cropped the photos to a small area around the center.

Edited November 21, 2020 by Xay

[Xay]

Video 2 - Andromeda - 250 mm, 10 photos. 45 seconds exposure time, ISO 2000. Cropped to a small area near the center of the photo.

Edited November 21, 2020 by Xay

[Xay]

Video 3 - Auriga - 55mm, 21 photos. 130 s exposure time each, ISO 400.

[Jamgood]

My first question to you would be have you calibrated/collimated your polar scope reticule? They are notoriously out of alignment from the factory. If no, I would do that first. It's not hard to do, just take your time with it.

This looks like a pretty good page for info on set up, etc. 

The Ultimate User Guide To The SkyWatcher Star Adventurer PRO

Edited November 21, 2020 by Jamgood

[Davey-T]

Do the star trails get longer with longer exposures ? they don't appear to in your videos

Dave

Edited November 21, 2020 by Davey-T

[Xay]

1 minute ago, Davey-T said:

Do the star trails get longer with longer exposures ?

Dave

A little, but not much! If you look at the photo I uncluded in my first post, you can see how they vary with exposure time.

[Xay]

35 minutes ago, Jamgood said:

My first question to you would be have you calibrated/collimated your polar scope reticule? They are notoriously out of alignment from the factory. If no, I would do that first. It's not hard to do, just take your time with it.

This looks like a pretty good page for info on set up, etc. 

The Ultimate User Guide To The SkyWatcher Star Adventurer PRO

I haven't tried calibrating/colimating it yet! I was trying everything I could before trying that, also because I just bought it and it's still within the guarantee/warranty period.

[Davey-T]

 Calibrating the Polar scope which can be fiddly and it's possible for the reticle to fall backwards and then when you tighten a grub screw it can fall inside so you have to take it apart to reassemble it

Instead after Polar Aligning you can check every 20 minutes or so to see if Polaris is following the circle in the polar scope and if not adjust it back doing this a few times  should get it close enough.

Set it up as you would for imaging then holding the weight move it from side to side and up and down to check there is no movement except for the clutch slipping.

Dave

 

 

[Jamgood]

1 hour ago, Xay said:

I haven't tried calibrating/colimating it yet! I was trying everything I could before trying that, also because I just bought it and it's still within the guarantee/warranty period.

There's an easy way to check if it is out. Get Polaris aligned and rotate the scope 180°. (6 down to 6 up) If Polaris is still on the line, you're fine. If it's off the line, you need to fix it. 

You can do that in the day time with a distant TV aeriel or something. Just have to be very careful and take your time. 

Check YouTube for tutorials, etc. You should only have to do it once as long as the mount doesn't take a serious knock.

Edited November 21, 2020 by Jamgood

[Thorney]

Don’t know if this could be the issue but my Star Adventurer didn’t track properly then it wouldn’t turn off so I sent the unit back and it turned out to be a faulty motherboard. All is sorted now and it works a treat.