Auto focusing options

[gregbradley]

I want to implement a good auto focusing routine into my imaging.
Focus Max and perhaps others requires a particular brightness star and slews to that star then does the focus routine.
I would prefer a system that does not move and focuses based on multiple stars in the current view.

What software does that?

Greg.

[Dennis]

Hi Greg

I am not a heavy, every-night user, but I use @Focus3 in The Sky X Pro and have found it to be stable and reliable once you set up the parameters correctly (a one-off process with F Ratio, Focuser step size, Camera Pixel size).

From the SB website:
"Introduction
@Focus3 is a new focusing technique now available in TheSkyX Professional and TheSky LTI. @Focus3 is contrast based as opposed to using a single star’s half flux diameter or full width half maximum. While you can still quickly focus using a single non-saturated star, you can now also focus on a field of stars (some of which can be saturated), the entire frame, a galaxy, nebula, or even a planet such as Jupiter or Saturn, or the Moon or Sun (with proper filters for solar imaging). You can even focus on terrestrial targets. Because of this, it is now more practical than ever to remain on a target during an imaging sequence and refocus without having to slew off to a focus star; other than the meridian flip, you can now stay on target and refocus in situ as desired."

I have only used it on single stars so far, so cannot comment on the other modes of operation.

Cheers

Dennis

[PRejto]

Another vote for @F3 in TheSkyX! It is easy and works quite well...no need to slew away.

Also, you can set focus offsets in TSX and always focus in L for narrow band.

Peter

[Atmos]

I believe Voyager does full FOV focusing. I know SGP does. I believe CCDAP will if you set it up correctly.

[Wilsil]

I am using NINA and it has the autofocus onthe area where you are pointing at.

[ronson]

Adding to above - ASIAIR does this on the condition you use their EAF.

[AdamJL]

Yep, NINA and the AA+ do it. I usually just leave it pointing at the pole once I've polar aligned and then do an AF run (sometimes in reverse if I'm using the main camera to polar align instead of the PoleMaster).

But AF is then part of the sequence in NINA and the AA+ so it does another one when it's platesolved and ready to shoot.

[Andy01]

+1 Voyager, has both Localfield (ie: full frame on your chosen target) and Robostar (slew to single known star) options. 100% reliable, truly effective. Blows my mind every time. :)

[Ryderscope]

I will throw my hat into the ring for the auto focus routine in SGP Pro. Evaluates the entire frame by measuring the HFR of all the stars.

[Wilsil]

So basically what we are all saying, every capturing application does the autofocus.
Even APT, nobody did mention that one yet.

[gregbradley]

Wow, so many choices these days. It used to be FocusMax or nothing!

I use Sky X but it offers @focus2 unless you go to subscription payments which are too much just for an autofocuser that is available with all these other programs.

I'll try out Voyager, NINA and SGP Pro and see how I go. Perhaps even ASI Air Pro and an EAF on my refractors.

Thanks for all the replies.

Greg.

[The_bluester]

Another vote for Voyager, which as Andy says, gives you the choice between "localfield" focusing which uses most of the field of view and "Robostar" which slews to a focus star and uses that star only. It is actually a simplification of localfield to say that it uses the full field though the developer keeps the full details under his hat. It apparently evaluates the FOV and uses a "doughnut" area, weighting the stars in the corners and misshapen stars less in the results than well shaped stars in the chosen area.

The typical advice is to use localfield if you have a setup with significant curvature and/or are chasing a target taking up most of the field of view, or Robostar if you have a good flat field or are imaging a small object in the FOV.

The big advantage to Robostar is focus runs for NB filters, the exposure times are usually around 1 second versus maybe 10-15 secs for Localfield focus. For NB it is faster in my experience to slew and plate solve and focus on a single brighter star then slew and plate solve back, than to do the localfield routine. You can also set it up to do a Robostar run if you are using Localfield and the focus fails due to dim stars etc.

The only word of warning I would have for Voyager is that it has a notably different workflow and set of assumptions to most other imaging software and it can take a little time to wrap your head around. Don't go into it expecting SGP or NINA in different clothes and give it time to get used to the workflow if you have come from the likes of SGP or NINA.

[AdamJL]

ha, exactly. Some will have some extra bells and whistles (like NINA with the plugin to do faster AF and also analyse your tilt/back focus issues after the AF run), but every capture software will do the basics.

[PRejto]

Greg,

I think your comment about TheSkyX and needing to be on a paid subscription is a bit misleading. If you have not updated for years, well, yes, it costs $100 but whatever new features you get are then yours forever. You don't need to pay every year once you update. CCDAutopilot is a bit like this and so is Voyager, etc.

If you are only looking for autofocus and not a full automation suite going the TSX route might just be the easiest option. Going full automation takes a lot of fussing around and learning if focusing is all you really need.

By the way, Focus Max now offers local focusing (i.e., not slewing away) as well. I've not used FM for years but I bet the routine is quite good.

Peter

[gregbradley]

Thanks for clarifying SB subscription system. I'll check that out as I already use Sky X so no learning curve which is appealing. If it's not required to be ongoing to retain the new functions then that would be acceptable.

Greg.

[Ryderscope]

Hi Greg. I noticed a mention of the ZWO EAF. I recently installed the EAF on my new Askar 300 OTA and have been giving it a run with SGP PRO. The installation, set up and configuration worked fine and the auto focus results are great. The only thing I found was that I did have to add some backlash compensation to achieve a nice U shaped focus curve. Not a problem though as once I added this in it worked fine.

[gregbradley]

Thanks Rodney.

I plan to get one once I have built my new observatory.

Greg.

[Startrek]

I don’t know if I’m the only one but I’ve never needed Auto focusing
I check my subs ( stars ) at the start of a day 2 to 4 hour session and near the end and rarely get any noticeable changes ( using your eyes to review ) software may possibly show drift optically/ mathematically but my eyes don’t see it , even zoomed way in
I must say since I’ve had my 10” Carbon fibre newt ( focal length 1280mm ) collimation holds really well and focus is really stable, rock solid
Obviously atmospheric conditions can decline at various degrees during the night which can cause Star bloat but refocusing won’t totally negate that issue. The atmosphere is always the winner. If atmospheric Star bloat is that bad I just shut down.

Cheers
Martin

[gregbradley]

Focus requirements of my various scopes do vary.

My refractors need to be refocused once they cooldown but tend to stay in focus once cooled down.

My AP Honders is the same but does not shift focus much after the initial cooldown. I use temperature compensation to match the focus shift and it helps but is not as precise as it could be.

My CDK is carbon fibre and is very stable focuswise once the primary mirror matches the ambient by around .5C. So much so that the next night focus often is the same.

So for me its more of a getting a bit more precision now there are several autofocusing softwares now.

Greg.

[Dilsh]

I have justed started to use the 925edgeHD having only used refractors. With the Melbourne nights starting hot and ending cold I find that the focus point changes as the night goes on. NINA has an options to run a AF routine if there is a percentage HFR change between subs. I find this works well.

If you are shooting narrowband, the other consideration is whether different filters have different focal points. My Antlia filters are pretty much par focal so that is not a big problem for me. NINA has a program to calculate these differences automatically and have filter offsets but it is not a huge job to do it manually.

The other issue is a slipping focal mechanism. My ED80 with all the gear on the back was terrible. For this reason I used to focus once and leave it. The 925 focuser moves the primary and the imaging train is not attached to it. I find this much better.

My 5 cents.

Cheers,

Dilshan

[The_bluester]

Regards changing focus over the night, my old C925 (Not an Edge model) used to shift focus spectacularly as it cooled and needed regular focus runs. I used to run two sequences, one for the start of the night where the temperature of the scope was dropping rapidly, where I did focus runs very often (After a hot day, just from the heat in the garage it would go from sharp to doughnuts in less than half an hour, so I would do focus runs every 15 minutes) and the second sequence had the focus runs further apart. I lost a fair bit of imaging time as a result but I got more sharp subs than before so it was a win overall.

I can see a difference over the night even with my carbon fibre newt (I am fussy) so I have Voyager configured to do a focus run every 2 degrees temp change or every hour for both my current scopes. 5 minutes every hour to ensure all subs are as sharp as they can be is a trade off I am happy with.

[JohnH]

Yup - AstroArt 8 does Full Frame autofocus as well...has many options and is scriptable...