FM V5 and Multistar

[Howard Maron]

I have heard very little from those who have configured V.5 or their experience with multistar focus I finally got around to switching to V5 a couple of days ago. Unfortunately the seeing here in the California desert has been disastrous ...lots of high and low winds throughout the day/night But I hope to report my experimenting. With the moon right now this is a good time to goof around. I was surprised to see that there are far many more changes with V.5 than just the multistar capability. It's actually a rather substantial upgrade. Focusmax in its previous versions has been very solid for me even with vastly different imaging configurations so I haven't felt a strong need to change. But it will be nice if multistar affords some benefits. I am not sure what to expect. The main advantage appears to be the ability to focus at the current target position with Acquirestar only kicking in if focus fails on target. (and that backup is a selectable option) Yet, I have never felt using Acquirestar and slewing to the zenith to be an issue or a disadvantage. In fact it seems logical and advantageous. I hope to soon find out. Whether multistar provides improvement in the overall quality of the focus or in reliability remains to be seen. I will be pleasantly surprised if it does. I know people using multistar focus with other software proclaim it is excellent.
Anyway I was just interested in hearing what others have found.

EDIT: Focusmax tip. They make this very clear but is worth repeating. If you run V.5 the first time you must "run as administrator" only once. If you go back to V.4 you must run it as administrator just once also. You can't go back and forth between the versions without doing this or you'll get an error message. Also remember to change your path to the correct version in your Startupobs.js if you're running that file...easy to forget.

[Dick Berg]

Hi Howard,

It's been a while since you posted your note, so I thought I'd give you a few of my impressions. You may know that I was a beta-tester for this version 5 of FocusMax, so I've been using it for fourteen months or so. There is a lot more to this version, to be sure, and it requires careful attention to the configuration and preferences. though in all respects it will also work like FocusMax 4 when it is set up in its preferences to the behave that way. As you see, you can have both versions installed and switch between them by using the "run as administrator" trick. With two system configurations, one could be set up like version 4, though I'm sure the intent was for two configurations to support two difference camera/telescope/focuser systems. I have myself all but forgotten about version 4.

What I like best about the new version is the MultiStar focus determination. There are two main advantages.

-- slew to the target and it focuses without moving away from the target. This is specially advantageous for me and my twenty-year-old Meade fork mount and my small FOV camera, because it avoids slewing away to a second or third sky location. Fewer slews means more stable (and quicker) image positioning for me.
-- statistically better focus determination, with multiple stars involved and several choices of how many images to capture at each stage of the process.

Because of my small FOV camera, one disadvantage is that longer focus image exposure times are necessary in the fainter fields I typically observe, so the total focusing time is often somewhat longer than what would have occurred using FocusMax 4.

I've also implemented FocusMax's temperature compensation for the first time. This is great. My OTA temperature expansion is very well characterized at -111 steps per degree C. With a total focus range of 7000 steps, this covers a temperature range of about 55 degrees C. This is adequate for my climate location. This capability is also in FocusMax 4, but I never thought to figure it out and use it. What a time saver - I focus at the beginning of the night and can run all night.

I'm now installing new LRGB filters along with an older H-alpha filter. This will require redoing the filter offsets. I believe Bob's FocusOffsets.vbs script will run without modifications and use FocusMax's MultiStar capabiliity to focus. I'm waiting for better weather to try this. I'll need new flats for calibration, too.

[Howard Maron]

So timely! I just did my annual NW "portable" setup. I used FM4 deliberately because it was "old shoe". So, I obviously was feeling awkward, still, about FM5. Your email could not have come at a better time. I will settle in and reinvestigate.

Also on your temp comp comments: On some scopes I have seen such spectacular temperature adherence yet, like you, I never formally activate it. Obviously it is so telescope dependent. But on some of my scopes I see such tight and reproducible temperature dependence I should use that enthusiastically. It sure would be nice to focus once and forget it! On the other hand, the cumulative time "wasted" doing periodic focusing is in actuality so small in toto for a night's work.
One thing that I would like to see (I think) is this. Even if temp comp is not activated, when the feature "Return to Start Position" is enabled it would be nice to have it return to the "compensated start position" rather than the true start position. It just makes sense. It seems like a great idea for those of us who don't want to abandon periodic focus but wants temperature to be taken into consideration. Make sense?