Using FF Focus in sequence

[Rudi]

I am extremely happy with the new Full Frame Focus feature and have been using it with great success.
I have been running several sessions with L, R, G, B, O-III and Ha with great success, where Astroart has been FF autofocusing automatically for each filter.

However, I recently added a S-II filter to my filterwheel, and it has a relatively large afocal distance compared with the other filters:

Code: Select all

Filter	Pos	Relative
L	3609	  0
R	3605	  4
G	3606	  3
B	3602	  7
Ha	3616	 -7
S-II	3291	318
O-III	3614	 -5

When changing from e.g. Ha in focus to S-II, the stars are so much out of focus, that they are doughnut shaped. This confuses Astroart, which can not make a FF AF.

Is there any way to let Astroart know the relative focus positions in order to aid the FF AF?

[Iver]

Hi Rudi, you could configure the sequencer with a line like the one in the image between your Ha and S-II sequence.

[Rudi]

Hi Iver,

So you mean inserting a "dummy" line, with a short exposure, simply to move the focuser, and after that, the S-II with FF AF?
I guess that would be a good solution.

It would be even better, if yet another column was added, for a pre FF AF focuser relative offset move.

Something like this:

[fabdev]

The "dummy" line would work (plus another one to return to 3600), but maybe the problem can be solved also setting a step/positions combination which cover both 3600 and 3300.

For example, if currently the Step is 50 and Positions are 7, then from 3600 the range covered is 3450-3750. Increasing the Positions to 13-15 would solve. If they are too much (autofocus will take an extra minute), it could be investigated if the Step can be increased instead, without loosing precision, for example Step 70 and 11 Positions.
Fabio.

[Iver]

Rudi, if you look at the sequencer menu tab there is an option to create a similar script. You should be able to modify it with a couple lines to correct for that offset.

[Rudi]

Thanks Iver, I totally forgotten about that feature.

If I do that, then I only need to inject the two lines below.
I will try this out next time I’m in the observatory.

.
.
.
Sequence("H", 4, 240, 1, 99999)
Sequence("O", 4, 240, 1, 99999)
Focuser.GotoRelative(-313)
Sequence("S", 4, 240, 1, 99999)
Focuser.GotoRelative(313)
.
.
.

[Rudi]

I tried the script last night, it didn't work, but that was my mistake. I had made an error, when noting the filters focus offsets.

Last night I got it correct.
Test focus positions:
H-a focus position 2753
OIII focus position 3084
SII focus position 3087

Offsets relative to H-alpha:
H-a relative pos 0
OIII relative pos +331
SII relative pos +334

It's the Baader H-alpha that is ca 330 steps off compared with the ZWO O-III and Baader S-II.

However, in stead of scripting, I personally prefer to use the GUI and this worked:


For each filter, I make a very short "dummy" dark image, which also moves the focuser to the approximate focus position.
Besides clouds came tumbling in arround midnight, the above worked perfect.

However, this produces a bunch of *_dark.fits files that needs to be deleted afterwards.
It would be extremely helpfull, with a feature like the one I sketched above in this post:
viewtopic.php?f=3&t=533#p2104

[Iver]

Hi Rudi, maybe Fabio could just allow the check box next to the focus section to only enable the focus portion of the sequencer line.

[Rudi]

Hi Iver. That would also work. I think that Fabio will think of something for next version.

[fabdev]

OK, I will send you a modified version later this month. Meanwhile you could take the dummy dark frames in binning 2x2 or 3x3 so that they will be smaller and sorting the folder by filesize it will be quick to find and delete them.

[Rudi]

I've tested the new functionality in SP6a, and it works like a charm.
Thanks a lot Fabio ...