WO Star 71 and Autofocus

Well the good news is that I think I was finally able to get my WO and the Nstep working together on a consistent basis. My autofocus routine is up and running. I also did not figure out offsets but so far I am not needing because my Astrodons are all parfocal. I know what you mean about the Hyperstar, I've had it for almost 2 years and almost never used it. It's always so frustrating and I'm still figuring out colimation I ended up giving up and putting the WO back in the observatory, I know I won't be going outside in the winter to switch filters so I'll probably play with the Hyperstar next summer. If you buy the Nstep for the WO and want me to share the settings, let me know!

Take care

Found out why it was so slow. You have to press the "settings" button and set the steps in there as well as on the main autofocus tab.

Odd. I get crazy error messages from the Rigel nStep driver saying it doesn't have access unless I am administrator. But, it is probably because windows is stupid, not the driver. I will have to ask Rigel about this.

Once I figured out the step problem the V curve looked really good. Even focusing through narrowband filters was no problem.

Good idea. I am about to set up an entirely new computer for astrophotography, so I will rerun the instructions there and see how it goes.

My intention isn't the highjack this thread, but I have a star71-II and will be using it and my qhy10 in SGP.im new to SGP and was wondering if anyone would mind giving or linking me to some manual focus advice (I don't have a bahlitov mask) but I'm very familiar will live view focus in BYEOS.

Tyler Jackson Welch:
My intention isn't the highjack this thread, but I have a star71-II and will be using it and my qhy10 in SGP.im new to SGP and was wondering if anyone would mind giving or linking me to some manual focus advice (I don't have a bahlitov mask) but I'm very familiar will live view focus in BYEOS.

Tyler

My advice regarding manual focus is to buy a Bahtinov mask.

When I manually focus with a mask, I use a program called Bahtinov grabber.  I'm not sure where you can get this program now though, because the chap who wrote it has (I believe) passed away.  But this program gives you 'numbers' that can guide you towards good focus.  When I first set up my autofocus routines in SGP, I will check them using the Bahtinov mask and those numbers.  SGP gets a good result, but I can get slightly better numbers using the Bahtinov mask and grabber approach.  Of course I don't actually know how accurate the mask plus grabber is versus the SGP autofocus routine.

I see no reason why you couldn't use HFR - I have seen people using FWMH values on a single star.  The downside of a mask, of course, is that you would need to slew off target to find a star bright enough that the mask would work.  But SGP's plate solve and centre routine makes this a simple task.  I have autofocus on both my imaging scopes.  When I didn't have it on one, I would slew to a nearby bright star, use a Bahtinov and then 'Centre' back on my target.  It didn't take very long - indeed since you start from being close to focus you probably need less steps than the autofocus routine uses.  Sometimes it didn't need adjusting at all, and in those cases it was probably quicker doing it manually than using autofocus.

Don't get me wrong - autofocus is great.  But running a 9 step autofocus routine using 25 second exposures (because of a 3nm Ha filter), only to find that there is no significant change to the focus position at the end of the routine is a little bit galling.

Samara:

Steve Milne:
Don't get me wrong - autofocus is great. But running a 9 step autofocus routine using 25 second exposures (because of a 3nm Ha filter), only to find that there is no significant change to the focus position at the end of the routine is a little bit galling.

I agree with you to a point. When the temperature drops it is a good idea to spend those precious minutes running autofocus, it's better than losing a 30 min exposure. This time of the year for example I am noticing a huge temperature drop from when I start imaging to end of night, I'm talking about starting at around 20 Celsius and close the dome at 3 Celsius. Can you imagine a night of imaging without re-focusing with those temperature changes? No thank you

Samara - if you re-read my whole post you will see that I was not suggesting that at all.  When I was manually focussing I checked it every hour and every filter change.  Sometimes when I checked it, it didn't need to be adjusted.  On those occasions it was probably a quicker process than running the autofocus routine would have been.

Regards

Don't think so.  The chap I saw doing it this way was using (I think) Nebulosity.  I don't know if you could use one of the single HFR values that SGP gives you.

Steve Milne:

Samara:

Steve Milne:
Don't get me wrong - autofocus is great. But running a 9 step autofocus routine using 25 second exposures (because of a 3nm Ha filter), only to find that there is no significant change to the focus position at the end of the routine is a little bit galling.

I agree with you to a point. When the temperature drops it is a good idea to spend those precious minutes running autofocus, it's better than losing a 30 min exposure. This time of the year for example I am noticing a huge temperature drop from when I start imaging to end of night, I'm talking about starting at around 20 Celsius and close the dome at 3 Celsius. Can you imagine a night of imaging without re-focusing with those temperature changes? No thank you

Samara - if you re-read my whole post you will see that I was not suggesting that at all.  When I was manually focussing I checked it every hour and every filter change.  Sometimes when I checked it, it didn't need to be adjusted.  On those occasions it was probably a quicker process than running the autofocus routine would have been.

Regards

Steve,

I understood your post, ues sometimes it is a waste of time to re-focus. Yes, manually checking is very effective but that's what I like about automation, I really like my sleep. If the temperature is stable I can just autofocus on filter change or by temperatuee change. It is not the best thing next to sliced bread like plate solving is but at least to me, it made a huge difference on my images.

Tyler Jackson Welch:
It sounds like you guys have had a lot more images one with your star71s than myself. I got used to my SCT and how much focus would change with temperature, I'm curious to know what you guys are seeing as far as when its generally worth refocusing?On my SCT the temp could move 5 degreesF and my focus literally didn't need to be touched. What ha w u guys seen with this refractor?

I find it very variable.  I have it set so that I autofocus every hour irrespective of temperature change.  Sometimes there is a significant change of position, sometimes not.  All that is measured is temperature at the telescope, and temperatures elsewhere in the atmosphere may be all over the place.  I also refocus between filters.  Some folks use filter offsets - I'm not confident that I have mine calculated accurately enough yet.  With LRGB it is not much of an issue (5s exposures and 9 steps).  With NB, I use 25 sec exposures (I use 3nm filters).  It takes longer, but there's not much point having a 20 minute exposure that is not in focus.  Everything is binned 2x2 for autofocussing.

The key is getting the step size correct.  The SGP manual is very good on this - just follow that.  Also, pay attention to backlash, by which I mean set a number in there.  I use 100 on my WO71, but it depends on your focusser I guess.

Hope that helps.