Lakeside focusing.. Help

[souls33k3r]

So last night marks the first night in my imaging history i get to play with the level 99 magic which goes by the name "Lakeside focuser". First impression, it's a bloody fantastic thing. Hardly had to step out other than setting up the kit.

So, i followed some brilliant advice by our very own @RayD and his YouTube channel videos on how to attach it and set up (Video 1, Video 2, Video 3 & Video 4). I highly recommend his videos if you're setting up for the first time. Made the whole process a breeze (This advertisement is brought to by "Simplied Astro" where astronomy is made simple ... i get 10% commission ?)

Now i am using Lakeside without the control box but am using it with Pegasus Ultimate Box and SGP is my main acquisition software.

Now the first thing i did was to find the step sizes after i've set it all up. My steps count came to 25. My initial HFR value was at 1.39 and i tried so hard to get it below that but i couldn't (not sure if it was the seeing or what but would appreciate some input on this)

 The second thing what happened was my V-curves were not really V, the focus started off with an S-curve to begin with and then settled on this. Appreciate some input with how to improve this.

The last V-curve was this

Also i got this warning message, not sure what this means and if there is something i need to do to fix this.

 

Thank you in advance.

[RayD]

19 minutes ago, souls33k3r said:

This advertisement is provided to by "Simplied Astro" where astronomy is made simple ... i get 10% commission

Lol keep that up mate you can have 30%!!!! ?

Glad you finally got to make the journey to the dark side of auto-focus, you'll never look back 

My initial thoughts would be backlash compensation.  You will need it enabled on the Star71, and it is pretty easy to work out.  I think on mine I ended up with about 20 steps or so.  Where the beginning of the curve goes a bit skewiffy, this is what I would expect to see backlash to do.

Hopefully others will have ideas too, but the bottom and return side seem good, so backlash is my best guess.

EDIT:  The backlash compensation is set up and enabled in SGP, not the UPB.

[symmetal]

Yes, as Ray says, it's the backlash compensation. The first couple of focus steps (right side of V graph) are near horizontal so the first focuser steps are just taking up the backlash and not moving the focuser. This also explains why your final message of the HFR tolerance being out, as not actually clearing the backlash when it does its final check means it hasn't settled at the optimum focus setting.

The backlash amount entered isn't important as long as it's greater than your actual backlash. Just increase in steps of 10 or so until your first focus line on your graph is a similar slope to the next one and produces a nice symmetrical V graph.

On the SGP backlash compensation setting, set it to 'IN' so that the focuser is pulling the focuser up against gravity for its final movement and the teeth are fully engaged.

[symmetal]

With regards to HFR I'm not sure what method SGP chooses for the final reading, whether it's an 'average' for the whole frame or 'weighted' towards the best focus area. With my FLT98 and Atik One I manage an HFR of about 0.8 and the ZS61 and ASI1600 I get about 1.1 HFR.

When my FF spacing was out or had slight tilt the HFR reading was higher so check if your corner stars are a similar size to your centre stars.

[souls33k3r]

5 hours ago, RayD said:

Lol keep that up mate you can have 30%!!!! ?

Glad you finally got to make the journey to the dark side of auto-focus, you'll never look back 

My initial thoughts would be backlash compensation.  You will need it enabled on the Star71, and it is pretty easy to work out.  I think on mine I ended up with about 20 steps or so.  Where the beginning of the curve goes a bit skewiffy, this is what I would expect to see backlash to do.

Hopefully others will have ideas too, but the bottom and return side seem good, so backlash is my best guess.

EDIT:  The backlash compensation is set up and enabled in SGP, not the UPB.

30% ? It’s a deal. I’ll soon be a millionaire... let me work that one out ... ok somethings not right here, it says at this rate and even with a 30% commission I’ll be a millionaire when hair grows on my teeth ?

Cheers mate, I’ll enter the backlash values in SGP. Thank you for clearing that up, otherwise I was about to put that value in UPB as the GUI does have that option under the “Focus” tab.

5 hours ago, symmetal said:

Yes, as Ray says, it's the backlash compensation. The first couple of focus steps (right side of V graph) are near horizontal so the first focuser steps are just taking up the backlash and not moving the focuser. This also explains why your final message of the HFR tolerance being out, as not actually clearing the backlash when it does its final check means it hasn't settled at the optimum focus setting.

The backlash amount entered isn't important as long as it's greater than your actual backlash. Just increase in steps of 10 or so until your first focus line on your graph is a similar slope to the next one and produces a nice symmetrical V graph.

On the SGP backlash compensation setting, set it to 'IN' so that the focuser is pulling the focuser up against gravity for its final movement and the teeth are fully engaged.

Cheers mate, very well explained. Makes so much sense.

4 hours ago, symmetal said:

With regards to HFR I'm not sure what method SGP chooses for the final reading, whether it's an 'average' for the whole frame or 'weighted' towards the best focus area. With my FLT98 and Atik One I manage an HFR of about 0.8 and the ZS61 and ASI1600 I get about 1.1 HFR.

When my FF spacing was out or had slight tilt the HFR reading was higher so check if your corner stars are a similar size to your centre stars.

My scope which is a WO star 71 is a quad and the stars are round in each corner too ... Totally stumped as to why I couldn’t get these values any lower.

[RayD]

9 minutes ago, souls33k3r said:

Thank you for clearing that up, otherwise I was about to put that value in UPB as the GUI does have that option under the “Focus” tab.

You can set them there as well mate for if you run the focuser outside SGP, but SGP settings will be used for the auto-focus routine.  Should be spot on tonight if you're able to get out.

 

[souls33k3r]

16 minutes ago, RayD said:

You can set them there as well mate for if you run the focuser outside SGP, but SGP settings will be used for the auto-focus routine.  Should be spot on tonight if you're able to get out.

Sweet as mate. Unfortunately i can't do tonight because last nights session took a real toll on me and i slept silly o'clock in the morning and only woke up mid day and then slept again in the evening for 2 more hours .. the forecast is indeed a clear one  but this soul needs his beauty sleep ?

I'll re-watch your videos once again now that i have played around with the focuser so will be able to relate a lot of things. I hope i don't dream of backlash

[RayD]

1 minute ago, souls33k3r said:

Sweet as mate. Unfortunately i can't do tonight because last nights session took a real toll on me and i slept silly o'clock in the morning and only woke up mid day and then slept again in the evening for 2 more hours .. the forecast is indeed a clear one  but this soul needs his beauty sleep ?

I'll re-watch your videos once again now that i have played around with the focuser so will be able to relate a lot of things. I hope i don't dream of backlash

Don't blame you mate, 2 nights in a row is tough going.  

As @symmetal says, the actual figure isn't important, it just needs to be more than your actual backlash.  You can go out to 40 or 50 steps to make sure you have it covered, and then tickle it downwards at a later stage.  

[souls33k3r]

5 minutes ago, RayD said:

Don't blame you mate, 2 nights in a row is tough going.  

As @symmetal says, the actual figure isn't important, it just needs to be more than your actual backlash.  You can go out to 40 or 50 steps to make sure you have it covered, and then tickle it downwards at a later stage.  

Sounds like a solid plan mate. Hopefully some time during the week i will just get out there and dedicate a few hours to this.

With regards to the HFR, i assume that the initial HFR was just to calculate the steps size but is it really important to get that number to right to the maximum low as i can or was 1.39 a good enough to calculate the 3 - 5x of the value? And also i assume that the focuser will try to get the HFR number as low as it possibly can?

[RayD]

8 minutes ago, souls33k3r said:

Sounds like a solid plan mate. Hopefully some time during the week i will just get out there and dedicate a few hours to this.

With regards to the HFR, i assume that the initial HFR was just to calculate the steps size but is it really important to get that number to right to the maximum low as i can or was 1.39 a good enough to calculate the 3 - 5x of the value? And also i assume that the focuser will try to get the HFR number as low as it possibly can?

You got it spot on mate.  Just get is as low as you can, but it doesn't need to be spot on.  You can just run the routine a couple of times and it will use the first figure as the start for the next run.  Seeing also makes quite a difference to the HFR reading, so don't bust a gut as SGP will account for this in its expected figure, and flag it if it drops outside this, as with your image above.

Once you have the backlash sorted it will sort itself and be good.

[souls33k3r]

4 minutes ago, RayD said:

You got it spot on mate.  Just get is as low as you can, but it doesn't need to be spot on.  You can just run the routine a couple of times and it will use the first figure as the start for the next run.  Seeing also makes quite a difference to the HFR reading, so don't bust a gut as SGP will account for this in its expected figure, and flag it if it drops outside this, as with your image above.

Once you have the backlash sorted it will sort itself and be good.

Awesome, cheers for that mate. Makes perfect sense.

A legend that is RayD, always super helpful and too kind. Don't be like souls33k3r, be like RayD

Cheers @symmetal & @RayD for your help me understanding this valuable information

[symmetal]

1 hour ago, souls33k3r said:

My scope which is a WO star 71 is a quad and the stars are round in each corner too ... Totally stumped as to why I couldn’t get these values any lower.

Oops! Didn't register what your scope was. It's possible the seeing wasn't too good or there was some thin cloud about as the graphs you posted are a little rough looking (ignoring the backlash at the start). I get graphs like that when the sky isn't perfectly clear and some thin cloud drifts by while focusing. When conditions are good the U graph is a perfect shape.

I also bin 2x2 while autofocusing with an exposure of 3 seconds for L, longer for colours and Ha. If you autofocus at 1x1 you need longer exposures so tracking or guiding errors during focusing could show as an increase in HFR.

[souls33k3r]

32 minutes ago, symmetal said:

Oops! Didn't register what your scope was. It's possible the seeing wasn't too good or there was some thin cloud about as the graphs you posted are a little rough looking (ignoring the backlash at the start). I get graphs like that when the sky isn't perfectly clear and some thin cloud drifts by while focusing. When conditions are good the U graph is a perfect shape.

I also bin 2x2 while autofocusing with an exposure of 3 seconds for L, longer for colours and Ha. If you autofocus at 1x1 you need longer exposures so tracking or guiding errors during focusing could show as an increase in HFR.

You know what mate, you could be very well right there about the seeing because I did thought that the it wasn’t particularly good seeing judging by the guiding too. But this is now another thing to remember when doing auto focusing.

I am certainly binning 2x2 . All my broadband filters are autofocusing using 6s subs and Narrowband with 10s subs.

[symmetal]

Also the HFR reading will be worse at lower altitudes due to atmospheric disturbance. The figures I gave for mine were at around 60-70 degrees alt I think. 

[souls33k3r]

Ok, that's very handy to remember in any situation. My target for the night was close enough to 80 degrees.

Ok I've changed the backlash compensation value to 50 which I'm hoping it will be high enough. 

What type of V curve should I expect if the value is higher or lower than the backlash and at what stage should I start making the tweaks to these numbers? 

[RayD]

34 minutes ago, souls33k3r said:

Ok, that's very handy to remember in any situation. My target for the night was close enough to 80 degrees.

Ok I've changed the backlash compensation value to 50 which I'm hoping it will be high enough. 

What type of V curve should I expect if the value is higher or lower than the backlash and at what stage should I start making the tweaks to these numbers? 

If the value is too low you will see that little dogleg at the beginning of the inward part of your curve.  If it is higher it won't make a difference so long as you are not right at the end of the draw tube travel so run the risk of collaring out.

The Lakeside isn't hugely high resolution, and is fitted on the high speed shaft of your Star71, so 50 should be a good starting point, but you can go out to whatever you want (60, 80, 100, it doesn't really matter and can be fine tuned later).  Make sure you have the function enabled so SGP knows to use it (tick box).  

You can test it in the day by just using the goto position function, setting a point further out, and making sure it goes past by the amount set, then drives back in.  I put a cable tie around the focuser knob so the end sticks right out, and is easy to see the wheel movement then.  Obviously make sure the draw tube moves, not just the focus knob, other wise you're not taking up the backlash.

[souls33k3r]

9 hours ago, RayD said:

If the value is too low you will see that little dogleg at the beginning of the inward part of your curve.  If it is higher it won't make a difference so long as you are not right at the end of the draw tube travel so run the risk of collaring out.

The Lakeside isn't hugely high resolution, and is fitted on the high speed shaft of your Star71, so 50 should be a good starting point, but you can go out to whatever you want (60, 80, 100, it doesn't really matter and can be fine tuned later).  Make sure you have the function enabled so SGP knows to use it (tick box).  

You can test it in the day by just using the goto position function, setting a point further out, and making sure it goes past by the amount set, then drives back in.  I put a cable tie around the focuser knob so the end sticks right out, and is easy to see the wheel movement then.  Obviously make sure the draw tube moves, not just the focus knob, other wise you're not taking up the backlash.

Sorry for the uber late reply mate. Been on here all day but didn't get a chance to reply.

Much appreciated for this tip. Will definitely give it a go hopefully some point during the week and will let you know mate.

[RayD]

Just now, souls33k3r said:

Sorry for the uber late reply mate. Been on here all day but didn't get a chance to reply.

Much appreciated for this tip. Will definitely give it a go hopefully some point during the week and will let you know mate.

That's alright matey, no apology necessary at all.  You'll get there in the end, and it's a one time only thing, so once it's done it's done 

[swag72]

1 hour ago, RayD said:

That's alright matey, no apology necessary at all.  You'll get there in the end, and it's a one time only thing, so once it's done it's done 

Unless you end up with a loosening grub screw on  the coupler and it all goes wrong ..... can you see where I'm going with this?...... ? that and a few other things and I am officially cheesed off ?

[RayD]

43 minutes ago, swag72 said:

Unless you end up with a loosening grub screw on  the coupler and it all goes wrong ..... can you see where I'm going with this?...... ? that and a few other things and I am officially cheesed off ?

Yep, I see where you are going.......if it can go wrong, it will..........and for you!!

[souls33k3r]

57 minutes ago, swag72 said:

Unless you end up with a loosening grub screw on  the coupler and it all goes wrong ..... can you see where I'm going with this?...... ? that and a few other things and I am officially cheesed off ?

In which case I’m glad you replied because that’s one thing I’ll most definitely make sure it isn’t from time to time  Was the loosening of the grub screws the result of you tinkering or just happened with over time?

[swag72]

Just happened over time..... I never fiddle ?

[souls33k3r]

37 minutes ago, swag72 said:

Just happened over time..... I never fiddle ?

Somehow an astro imager not fiddling with their gear doesn’t seem to quite fit but I’ll believe you ?

[swag72]

7 minutes ago, souls33k3r said:

Somehow an astro imager not fiddling with their gear doesn’t seem to quite fit but I’ll believe you ?

Seriously when I have everything working I don't touch anything!! 

[RayD]

13 minutes ago, swag72 said:

Seriously when I have everything working

And there lies the challenge ?