Guiding/Tracking issues

[CraigD1986]

I’m currently imaging M42 with my Sky-Watcher 72ED and ASI533MC Pro and noticed that the target was moving across the frame pretty quickly. Upon inspection, the ST4 cable was a little loose in both the star adventurer and ASI120MM guide camera I’m using. My exposures are only 20 seconds so it’s not causing major issues but it’s as though the star adventurer isn’t tracking at all, regardless of any corrections sent from ASIAir Plus guiding. There is a lot of “Settling” going on as the guide camera keeps loosing stars.

Has anyone experienced this before? Is there a way to secure the cable to stop it slipping again?

I’ll have to see if the images will still stack with such a lot of movement but fingers crossed.

[StuartJPP]

When you say the cables are loose do you mean the connectors can move slightly when seated?

RJ connectors are spring loaded and do move within their sockets slightly, especially in the in/out direction.

As long as there is a positive click and the little locking tab is engaged they should be fine.

You could have a faulty cable or one connector failure in either part.

To test in daylight you can use PHD to issue manual guide corrections and listen if the motor noise changes

 

[michael8554]

From what I've read here on SGL, you have to be in the correct Star Adventurer mode, or RA tracking will be OFF.

Don't have that mount, so can't advise on what the setting is.

Michael

[CraigD1986]

Thanks for the replies.

I'm just stacking the images now so am hoping for the best but M42 has moved right the way across the frame one the course of 109 frames, which seems odd.

 

@StuartJPP The cables clip in but have about 5mm of travel at each end. I'm pretty sure the Starr adventurer is working as it should actually as the constellation of Orion had moved quote a way across the sky during the imaging session so if the tracker wasn't working at all, it would be pointing noticeably the wrong way by the end.

@michael8554 I was guiding in RA mode only as, you are correct, the star adventurer can't track along the declination axis.

Come to think of it, I was dithering via the ASIAir Plus so the target should move a little but surely it should just be a couple of pixels and therefore not noticable.

[michael8554]

I didn't mention Dec guiding at all.

I suggested the mount might not have been tracking in RA.

Without seeing, say, the first and last Light, it's hard to say why there was drifting.

Michael

[CraigD1986]

@michael8554 My apologies, I think I misunderstood you. This is still very new to me so I'm still getting my head around it. Attached are the first and last light frames. I'm starting to wonder if something was loose somewhere and the telescope slipped or something but the shift is gradual across the 109 frames.

Light_M42_20.0s_Bin1_0001_1.fit Light_M42_20.0s_Bin1_0040_1.fit

[michael8554]

Thanks Craig, jpegs would have done 😆

RA was tracking, this is just cumulative drift from Polar Alignment error.

Were the star shapes good enough to stack ?

Then carry on as usual, maybe improve the PA, or reframe as necessary during the session.

Michael

[CraigD1986]

Thanks for your help, that makes me feel a bit better about it. I did use the ASIAir’s plate solving polar alignment tool so I assumed I couldn’t be too far off but I’ll try and get it more accurate next time. That said, I find that with the star adventurer, I can plate solve during polar alignment, change nothing at all, plate solve again and get a different result.

The image did stack but M42 was right at the left edge of the frame so not really ideal. Still though, it’s good practice.

[Elp]

Just to confirm whilst you're PA the sidereal switch is not active is it? Are you sure everything is also clamped down tight, tripod hasn't been moved etc.

[CraigD1986]

@Elp yes, when polar aligning, the switch is in the celestial tracking position. Is this not right? I did try first with the switch off but the ASIAir then wouldn’t pick up the mount so I couldn’t guide and had to start again.

[Elp]

If you're polar aligning you shouldn't be tracking as what you're aligning to (Polaris) is essentially not moving (or moving extremely slowly). 

Maybe someone else can help with the asiair sensing the SA issue?

[CraigD1986]

@Elp thanks for clarifying. I’m sure the sensing issue was a blip so I’ll make sure the tracker is off next time (Friday night looks clear this week where I am)

[Elp]

If you're not using the polar scope (I don't particularly like them), for a very rough polar alignment you can use a compass which has an east west declination scale on it to orient your tripod+SA to the pole, then use a digital inclinometer to set the angle. I've found this works fairly well in getting to the ballpark, the asiair PA routine however is the way to go eventually.

[michael8554]

5 hours ago, CraigD1986 said:

The image did stack but M42 was right at the left edge of the frame so not really ideal. Still though, it’s good practice.

Maybe only stack the lights that have acceptable framing ?

Michael

[900SL]

With a tracker you should PA with the tracker switched off (using AAP)

If you have the original SWSA wedge check it is not loose or wobbles in any direction. Mine needed shimming, very poorly made tolerance wise. Sold it be and bought a Fornax LT2 in the end.

Do you polar align with the scope and camera already in place? You should, otherwise PA will move off.

Dithering on a tracker can fail to settle if the Dec drift exceeds the limits. I think this can be disabled on the AAP but check. 

 

 

 

[CraigD1986]

6 hours ago, 900SL said:

With a tracker you should PA with the tracker switched off (using AAP)

If you have the original SWSA wedge check it is not loose or wobbles in any direction. Mine needed shimming, very poorly made tolerance wise. Sold it be and bought a Fornax LT2 in the end.

Do you polar align with the scope and camera already in place? You should, otherwise PA will move off.

Dithering on a tracker can fail to settle if the Dec drift exceeds the limits. I think this can be disabled on the AAP but check. 

 

 

 

Here is my process for coal alignment:

Set up and level the tripod (as low as possible to avoid any wind). Us the skywatcher SA console app (polar clock utility) to see where Polaris should be on the scale in the scope and look through the scope to align manually. I do this with the scope off the mount as I can't get the little red LED thing in with the scope on and balanced.

Mount and balance the scope, turn on ASIAir, go to PA and start the process there.

I was doing this with the star adventurer turned on but I now know this needs to be off. I'm using the original wedge, which is pretty flimsy but I've got to work with what I have. I know FLO have the William Optics Wedge, which is supposed to be a big improvement but the point of me buying a SA was to get started without spending £1k+ on a good mount. It would defeat the object to start spending more money on the SA as I'll eventually upgrade to a HEQ5 or 6 I think.

I started dithering when I was having problems with noise from a DSLR but now that I have the ASI533MC Pro, which is far better with noise, I might try turning dithering off then.

Attached are a couple of images of my setup (Ignoring the bad cable management - some new cable braiding arrived today so I'm going to tidy it up this evening). As the setup is probably pushing it in terms of weight, this is the position the scope needs to be in to be balanced but I can't quite see through the polar alignment scope on the SA with it all in this position. On this note, when the scope is in this position, it is balanced, but the minute I turn the scope from this position, balance is way off. Is that right?

[Elp]

Your PA routine should be carried out with all the equipment mounted as the alignment will change once you put weight on top of it, especially with the SA wedge I've found from experience using it.

Looking at your setup which is nice, have you checked the total weight of it also?

Once everything is mounted it is also critical your setup is balanced in both declination and RA, I usually loosen up the Dec and balance that first, then the RA, and then recheck the Dec. Check this with the focus reasonably racked out toward the focus position as that will affect the centre of balance.

[Elp]

With the SA I also found using a 40cm or longer threaded bar helped with the RA balance as I could place the weight further down the bar without adding more weight to the setup via adding in more counterweights.

[CraigD1986]

1 hour ago, Elp said:

Your PA routine should be carried out with all the equipment mounted as the alignment will change once you put weight on top of it, especially with the SA wedge I've found from experience using it.

Looking at your setup which is nice, have you checked the total weight of it also?

Once everything is mounted it is also critical your setup is balanced in both declination and RA, I usually loosen up the Dec and balance that first, then the RA, and then recheck the Dec. Check this with the focus reasonably racked out toward the focus position as that will affect the centre of balance.

Thanks for clarifying. I didn't know this but it makes perfect sense when I think about it. Seems obvious now. My new procedure will be to align via the polar scope on the SA to get in the right ballpark, then mount the scope, then PA in ASIAir.

I daren't weigh it to be honest as I'm in fear of convincing myself that I absolutely need a new mount, which my wallet won't like one bit. Will have a look tonight though. I know the 72ED and SA is a popular setup so fingers crossed I can make it work.

So in terms of balance, everything I've read and watched explains how to balance the scope but loosening the main clutch, etc. This is really easy but now that I think of it, this is balanced in right ascension only (Correct me if I'm wrong). No tutorials seems to go beyond this so I haven't been balancing in declination at all and I know for a fact it's way off as when I rotate the setup using this clutch, the balance is thrown. So on that basis, Do I need to locate my target before balancing? Or is it: locate target, polar align, then balance, then shoot?

[Elp]

Balance, polar align, guide, frame, focus, shoot

Edited February 2, 2022 by Elp

[Elp]

If your declination isn't supposed to be moving whilst imaging I think you can leave that as it is but it's always good practice to balance it all so that factor has been eliminated if you have any issues, it will also relieve any mechanical stresses.

I would weigh the setup, you might find it may be on the limit.

In this hobby it's always tempting to upgrade, personally I would try to get the best out of what you have first. I was in the same position but got frustrated trying to find targets so for not much difference in cost I got an azgti and sold the SA as I didn't have much more use for it. If you're interested in what I've done via the azgti feel free to look at my "beginner" images on Flickr (doimg).

See what you can achieve first, it's always rewarding when you get somewhere with it, and many people have done great things with the SA.

 

 

Edited February 2, 2022 by Elp

[CraigD1986]

Just had a little look at the scales and I’m at 3.4kg (max load for SA Pro is 5kg) so I should be okay for now. The SA is a great piece of kit and I’m sure I’m not getting the best out of it yet so am happy to keep learning and improving with it.

Your Flickr page looks great and it very inspiring. Many thanks for your help with this, I’ve learned a lot today already. My scope is back heavy due to the camera so I’m going to move the guide scope forward and mount it on top and then maybe look at a longer bar from Sky Watcher

 

[Elp]

Thanks.

This 18cm bar worked for me when I had to shift it all forward, other options are available

https://www.firstlightoptics.com/dovetails-saddles-clamps/astro-essentials-dovetail-bars.html

[CraigD1986]

As tonight was cloudy, I spent the evening re-arranging a little. The guide scope is now on top to try and push a little weight forward and I’ve cleaned up the cables. All ready for the next clear night. I’ll try and get a longer bar here before then though as the scope is still back heavy so could do with better balance.

[Elp]

Looks far tidier than my setup that's for sure. I know you've rejigged it for weight distribution which is good, is the new position of the guidescope bracket however mounted onto one screw point? If so that could cause the alignment of the guidescope to rotate in relation to the main scope pointing direction, it needs to be mounted to two points minimum or keep it on the dovetail as it was previously.