What to keep in mind when buying an EAF?

[Shimonu]

I'll most likely be ordering an electronic auto focuser in the upcoming weeks and I wanted to check if there's anything I should check or keep in mind. I'll be using it with my WO Z73 and possibly a newtonian in the future.

I was recommended to get one with a hand controller but I'm not sure I understand why, would that be to get the focus roughly right? I would like to make sure I know how it's used, I photograph in the field so I might have to do some setting up each night. But I'm hoping I can pretty much leave it alone as I carry my scope as a package. Before using it I understand you have to set up how much backlash it has. I was considering getting one without a temperature probe as I already have one on my pocket powerbox but I'm not sure if it will be able to use it in Ekos. Could I just refocus every 10-15 minutes or would that add a lot of time to my session?

Thanks!

[newbie alert]

Not so sure that you need to focus that frequently unless the temp drops are extreme,  especially with a 73mm frac

Think the purpose of the HC is so you can use it without a laptop, so you can focus with a mask

The ZWO eaf looks like a decent bit of kit, many use them and as with any electronic focuser step size and backlash are the only 2 things to work out

 

[scotty38]

With the ZWO you cannot focus manually without the hand control so it’s also an option provided if it’s used visually too. Also worth noting, I use Nina, but the ZWO gives a temperature reading even without the probe attached but obviously just the ambient rather than anywhere specific. 

[Shimonu]

1 hour ago, scotty38 said:

With the ZWO you cannot focus manually without the hand control so it’s also an option provided if it’s used visually too. Also worth noting, I use Nina, but the ZWO gives a temperature reading even without the probe attached but obviously just the ambient rather than anywhere specific. 

You mean there's no driver support for manual focus, so if you don't get the hand controller you have to rely on the automatic focus and already being somewhat focused? It won't be possible to do any manual in/out focus in any software? But surely it has to since you figure out the backlash by manually focusing in and out, right?

I saw that Ekos can perform refocusing based on the HFR and the amount it has changed, so temperature shouldn't be an issue.

[scotty38]

13 hours ago, Shimonu said:

You mean there's no driver support for manual focus, so if you don't get the hand controller you have to rely on the automatic focus and already being somewhat focused? It won't be possible to do any manual in/out focus in any software? But surely it has to since you figure out the backlash by manually focusing in and out, right?

I saw that Ekos can perform refocusing based on the HFR and the amount it has changed, so temperature shouldn't be an issue.

Yes you can focus "manually" or otherwise using software, what I meant was you are unable to turn the focus knob manually unless you use the controller. You could, of course, undo the allen bolts so the spindle is free but then you lose your zero position and would have to set that up again.

I use the ambient temp setting to refocus if the temp changes by say 5 degrees so it works just fine if you want to use it like that without the probe, it's just not measuring a really specific point that's all.

[david_taurus83]

Unless your using or planning to use an ASIAir, there are other options for autofocusers. Have you considered the DeepSkyDad unit? 

[Shimonu]

1 hour ago, david_taurus83 said:

Unless your using or planning to use an ASIAir, there are other options for autofocusers. Have you considered the DeepSkyDad unit? 

I had never heard about it but it seems like a well used and good focuser. Certainly cheaper than the ZWO. Great tip, thanks!

[powerlord]

So, I use the ZWO job. I do have a hand controller I got cheap from a SGL member. I wouldn't buy one new - it's basically 3 buttons and you can make one yourself.

However don't - I don't use mine at all now. I should say I find no use for the zero position thing - so if you do, this won't apply.

get yourself some knurled m4s. and use those to hold the focuser on the shaft (I also use 2 knulred m4s to secure the focuser to the bracket which allows me to swap the EAF between 4 different telescopes in a few minutes with no tools).

ebay 'knurled bolts' and you'll find em. about 10mm long for most shafts, 12mm for my C8.

With the knurled bolts, you can easily in darkness, loosen them, adjust by hand to get initial focus, then tighten up. then let it do it's AF thing. It's also great if you are swapping image train during session. e.g. adding a barlow, changing camera, using an eyepiece, etc.

works a treat. I use the asiair and have mine set usually to then just refocus on filter change (which tends to be about every hour).

 

[Shimonu]

On 24/08/2021 at 14:22, powerlord said:

So, I use the ZWO job. I do have a hand controller I got cheap from a SGL member. I wouldn't buy one new - it's basically 3 buttons and you can make one yourself.

However don't - I don't use mine at all now. I should say I find no use for the zero position thing - so if you do, this won't apply.

get yourself some knurled m4s. and use those to hold the focuser on the shaft (I also use 2 knulred m4s to secure the focuser to the bracket which allows me to swap the EAF between 4 different telescopes in a few minutes with no tools).

ebay 'knurled bolts' and you'll find em. about 10mm long for most shafts, 12mm for my C8.

With the knurled bolts, you can easily in darkness, loosen them, adjust by hand to get initial focus, then tighten up. then let it do it's AF thing. It's also great if you are swapping image train during session. e.g. adding a barlow, changing camera, using an eyepiece, etc.

works a treat. I use the asiair and have mine set usually to then just refocus on filter change (which tends to be about every hour).

 

Since I'm always going away to shoot I'll have prepared the equipment beforehand. So hopefully I won't be swapping anything during a session. But I'm interested in getting a something like 200/800 newtonian in the future and I want to make sure it won't give me any surprises.

[powerlord]

well, mine configured to fit my DSLR lenses, my SW 72ED, Celestron C8 and SW 200P. SO I think you'd be fine with ZWO.

stu