FocusMax or @Focus 2

[gregbradley]

I have everything working now in the Sky X so CCDSoft may soon be a thing of the past. The latest daily builds of the Sky X must have updated for various other manufacturers so FLI and Starlight Express now all seem to work whereas before they didn't.

I am about to start using a FLI Atlas focuser. Its all working pretty much straight away which is practically a first.

I see the Sky X has @focus2 as an auto focuser. I mainly read about Focus Max as being the standard for autofocusing.

What's your advice? If FocusMax plays well with Sky X then I suppose its not a problem and I would use it. It does cost US$150 now (AUD$200). So I would like to know its significantly better than @focus 2 or is it the same?

Greg.

[Paul Haese]

I have been using Focusmax for about 2.7 years now. Very easy to use but you need to be very aware of setting the parameters right for an Atlas. Your step count will need to be about 100 or else it will not make focus convergence in 45 minutes. Make sure you use 3 additional readings too as a setting. Especially for long focal length focusing.

To use focusmax with SkyX I think you need the latest version which is a buy instead of being free. $150 US though is nothing compared to your investment Greg. ;)

I have not used @focus in SkyX but I hear it works ok and not read any really bad comments. SkyX is getting quite mature now and so most things ought to work.

Weird how drivers for STXL and plugins are still not really fully completed for the SkyX though. For example the filter wheel drivers are not even the same and work one week and not the next. Just my experience though.

Hence why I am not using my cameras in SkyX for capture or focus.

For automation I don't know how @focus works and maybe someone who is using for automation can comment here.

Focusing every hour is a must for sharp images and part of why my images always look sharp. Don't use temperature compensation, it's too unreliable in my opinion and the opinion of others who are better imagers than me.

[gregbradley]

Some great tips there Paul. Thanks.

I think I'll go with FocusMax. I have the full version trial and I'll get it going.

So do you slew to an appropriate focus star every hour then have the original image reacquired? One advantage of @focus2 and the Sky X is that is automated. Can you automate that with FocusMax or does it require additional software like CCDcommander?

Good tip about the temperature compensation. It might also be the rate of expansion/contraction may not linear with temperature changes.

The RHA has a small critical focus zone and F3.8 is going to mean spot on focus is vital.

The goo news for me is the FLI Atlas is working with my setup without too much of a bother which is great. It is working in CCDsoft but it requires the Sky X to be running at the same time (which it does anyway as I use Sky X to run my mount).

Sky X also has filter offsets for different focus settings for each filter plus it has dithering for the autoguider. So some nice features there. Also you can program as many filters as you want in an imaging run. For some reason CCDSoft was crippled to only do a max of 5.

Greg.

[RickS]

FocusMax has an AcquireStar coimmand that slews to the nearest star with a magnitude in the appropriate range, focuses, and returns. It works nicely with ACP. I'd presume it works with the Bisque stuff too, but I'm not sure.

Cheers,
Rick.

[Paul Haese]

How my system works is that every hour or after every sub if you like (the time is up to me to set in the command programme) the command programme (in this case CCD autopilot) stops all operations and hands over to the focus programme. It takes an image of where it is and plate solves. Then it heads to the meridian (I set it to do that and you can focus within the same field if you like but it is not as good as straight up) to focus on a 4-6 mag star. After it finds focus convergence it will return slew to the same position, do a plate solve to get back in almost the same place and then hands back the reigns to the command programme which will then further plate solve to get the system back to within the tolerance you are after. I have said in my systems I want 15 arc seconds and it does this in 2-3 slews. It all takes about 5 minutes to complete the operation. So you don't lose much time.

Now you can use focusmax on its own to simply go and focus after you have clicked on one of the buttons and it will do that. That means you need to go out now and again to make that happen. Ok if you like that sort of thing, but for me I am done with that. So a command programme is what I am recommending too.

Maxim has dithering and CCDAP does filter offsets if you like. I don't use offsets as focus looks good across the board on both sets of my filters. So I just use my Lum filter to focus with and get into the imaging. I could be more thorough and get CCDAP to do and offset measurement but it is not apparent that this needs to happen. My images seem to confirm that.

Maxim and CCDAP both allow for as many filters as you want. I reckon you ought to get into some semi automation so you can have the system doing focus for you and doing the imaging without having to go out and do that yourself. Roof operation is another matter and might involves some phone calls. That can be a bit tricky to get that working well.

[gregbradley]

Thanks Rick.




Thanks for the detailed response Paul. I intend to implement that.

Greg.