Lakeside focusing.. Help

[Davey-T]

Don't get obsessed with minutia Ahmed, that way madness lies 

Dave

[souls33k3r]

1 hour ago, symmetal said:

The HFR for your autofocus was done with an exposure of a few seconds. Your actual images had exposures that were a lot longer so tracking errors throughout the exposure of just an arcsecond or so will accumulate and make the final star image larger. Also the longer image exposure will make the stars 'bloat' more than an exposure of a few seconds. I assume SGP doesn't use excessively clipped stars in the HFR reading.  After autofocusing I just check the images for reasonably tight round stars and don't look at the HFR value.

If you wish take an imaging run with the same exposure as your autofocus and see if the HFR values are then very similar.

Alan

Ah cheers. Makes perfect sense.

I can most certainly try taking an image with the same exp as AF but ideally i would like my focus to be better with the AF as opposed to it being super out.

What can i do to make it better?

@RayD, ti do apologize but tagging you in this as well mate just in case if you have any ideas too  

Ta

[souls33k3r]

1 hour ago, Davey-T said:

Don't get obsessed with minutia Ahmed, that way madness lies 

Dave

hahahaha I'm a mad cat, i have an OCD for little things. I guess that's what happens when you are friends with a perfectionist *cough* @angryowl *cough*

[RayD]

23 minutes ago, souls33k3r said:

@RayD, ti do apologize but tagging you in this as well mate just in case if you have any ideas too  

No worries mate.  I reckon @symmetal is spot on.  Your HFR value will change with the exposure length if this results in the star size changing from your AF exposure length.  The point is, at AF exposure length the stars are in focus, and this is evidenced by the HFR value at that length.  If you now expose at longer length the HFR value may change, but whatever it is, it is still the best focus.

You should just trust the system, it works well, and nothing better to see if you are in focus than just looking at the stars in your images.  You will see if focus is out.

[souls33k3r]

1 hour ago, RayD said:

No worries mate.  I reckon @symmetal is spot on.  Your HFR value will change with the exposure length if this results in the star size changing from your AF exposure length.  The point is, at AF exposure length the stars are in focus, and this is evidenced by the HFR value at that length.  If you now expose at longer length the HFR value may change, but whatever it is, it is still the best focus.

You should just trust the system, it works well, and nothing better to see if you are in focus than just looking at the stars in your images.  You will see if focus is out.

Ah cheers mate, very well explained and between yourself and @symmetal this whole thing totally makes sense. It's just that i was getting a bit paranoid about this and thought that maybe the HFR was supposed to stay around the the AF point but now it does indeed make sense completely.

Can't thank you both enough for explaining it brilliantly to a noob like me

[souls33k3r]

So last night while i was tackling the weirdness in my star shapes in the bottom half of the image, i took some time to re-check my steps sizes. After carefully calculating everything again i had to change my steps from 25 to 35 but this came up with a bit higher value of my best focus HFR value. 

Initially with the 25 steps, i was at 0.8, now with 35 steps i was at 1.22. I tried with both L and OIII filters but it did not make any difference. My mean readout was quite high 2000 for the OIII so not sure if it was high clouds or what. Any tips to get the HFR values while focusing better?

Also, started to tinker with the focusing exposure settings, i changed my NB filters from 10s to 15s thinking that this might give me some better values but it didn't. How do you find the best exposures for filters when focusing?

[souls33k3r]

I tried every possible thing i could think of but still unable to get my HFR numbers any better than 1.20HFR. What can i do?

Also as some of you might know my scope is going back in for repairs so will be taking off the Lakeside focuser. Do i need to re-do the steps size counts or when the scope returns i just put it back and image away?

[RayD]

11 hours ago, souls33k3r said:

I tried every possible thing i could think of but still unable to get my HFR numbers any better than 1.20HFR. What can i do?

Also as some of you might know my scope is going back in for repairs so will be taking off the Lakeside focuser. Do i need to re-do the steps size counts or when the scope returns i just put it back and image away?

Wait until it comes back and have another go.  If there were issues with your star shapes then this could affect the HFR reading.  As noted before, you're getting a bit hung up on the number; this will change with seeing etc. so don't see it as the do all and end all.  I get a variety of HFR readings depending on the imaging conditions, but focus is always as good as it is going to be on that particular night.

No need to redo the step size, just put it all back on and away you go 

[souls33k3r]

1 hour ago, RayD said:

Wait until it comes back and have another go.  If there were issues with your star shapes then this could affect the HFR reading.  As noted before, you're getting a bit hung up on the number; this will change with seeing etc. so don't see it as the do all and end all.  I get a variety of HFR readings depending on the imaging conditions, but focus is always as good as it is going to be on that particular night.

No need to redo the step size, just put it all back on and away you go 

You're absolutely right mate, I guess I am getting a bit too hung up on the numbers. I shall indeed wait for the scope to come back and test

Ah cool, I'll do just that mate. Cheers for the quick response

[RayD]

2 minutes ago, souls33k3r said:

You're absolutely right mate, I guess I am getting a bit too hung up on the numbers. I shall indeed wait for the scope to come back and test

Ah cool, I'll do just that mate. Cheers for the quick response

No worries mate.  Don't forget you will need to do a new calibration though (zero point) 

[souls33k3r]

17 minutes ago, RayD said:

No worries mate.  Don't forget you will need to do a new calibration though (zero point) 

Ah cheers mate. 

I don't suppose UPB has a calibration routine? 

Just manual in and out position is what I did previously

[RayD]

1 minute ago, souls33k3r said:

Ah cheers mate. 

I don't suppose UPB has a calibration routine? 

Just manual in and out position is what I did previously

Unfortunately not mate.  Just setting 0 and then your outermost travel point exactly as you did before as this will have moved.

[souls33k3r]

6 minutes ago, RayD said:

Unfortunately not mate.  Just setting 0 and then your outermost travel point exactly as you did before as this will have moved.

I personally think its much simpler calibrating it manually. You don't have to sit down and keep the button pushed. 

[RayD]

6 minutes ago, souls33k3r said:

I personally think its much simpler calibrating it manually. You don't have to sit down and keep the button pushed. 

It's an easy routine mate and, unless you're taking it off as you have, is pretty much a one time only event on an R&P focuser.

I still love my UPB even though it was one of the first ones.  it never misses a beat.

[souls33k3r]

2 hours ago, RayD said:

It's an easy routine mate and, unless you're taking it off as you have, is pretty much a one time only event on an R&P focuser.

I still love my UPB even though it was one of the first ones.  it never misses a beat.

Totally agree mate, UPB makes life so much easier. One interface to handle most of the stuff. 

Now that my little guy is going back to ES Reid, the big brother will come out. Back to square one for cable management... Well to think of a better way to place the UPB that is