Sequence Generator Pro vs Maxim for focusing

[John K]

Hi guys,

Just getting into mono DS imaging with my 12.5" f/5 scope and new 174mm mono cooled camera. Have been imaging for many years mono planetary and OSC Deep sky, but now the mono imaging (and focusing!) games begin!

One of the issues I have with my truss tube break down for transport which means that the rotating upper cage gets removed and re-attached every time I do my imaging - so there is possible some focus / collimation shift does occur - thus a focusing profile may have to be redone (aka. FocuMax) every time.

Just wondering what experiences others have had with SGP in terms of their claimed live and continuous focusing feature vs Maxim Pro 5 and FocusMax?

Ideally looking to automate my capturers: goal is that once I get in the field and polar align and frame my shot, to then capture my LRGB images over the space of the night with intermediate focus checks using the software based on changes in temperature, filters and object elevation etc.

Any advice that can be offered appreciated.

Clear skies,

John K.

[troypiggo]

I've used Maxim/Focusmax and now SGP. I love SGP and no issues with its autofocusing routine, but... I mostly image with a refractor. Hopefully peter_4059 sees this and chimes in. I know he was having issues with SGP's autofocus with his Newt/MakNewt, apparently because the central obstruction causes donuts when stars out of focus, and SGP's autofocus routine uses half flux measures and gets confused. I'm pretty sure FocusMax doesn't suffer the same problem with its autofocus routine. The SGP developers are aware of it and are apparently working on a solution.

[RickS]

FocusMax works fine with obstructed scopes. I would think it would also be fine to use the same profile after removing and reattaching the upper cage. FM doesn't depend on the absolute focus position, only the rate at which focus changes as the focuser moves in and out. That shouldn't vary significantly with minor mechanical variations.

Cheers,
Rick.

[RobF]

Pretty much a given Maxim and FM will do what you want. GUI not the most intuitive place to operate out of, but once you're familiar with it will do the job.

SGP much newer kid on the block and lots less money. More modern interface, but still some quirks in profiles and sequence construction. Getting focus steps and star recognition optimised for your rig is a bit of work, but I've found it a very reliable solution for attended and semi-automated runs. I'm using a mid FL refractor similar to Troy too. No Newt or other experience on SGP. Free for a month - why not give it a try. Very pro-active forum community. Plenty of options for focus on time/no. of frames/filter change etc.

[John K]

Thanks for all the info guys, appreciate it.

I think I will stick with MaximDL to get started and progress from there. Have been reading all the on-line tutorials about FocusMax and will have a go tonight with generating some VCurves.

Just 2 more questions:

1. How good is FocusMax and Maxim DL in focusing on faint stars? I notice that the proper procedure is to slew to a 4-6 magnitude star, focus, and then slew back to the object being imaged. I do not have the ability to SLEW with my mount and will need to rely on the stars within the filed I am imaging.

2. In the space of an evening of LRGB imaging (say 3-5 hours), I was hoping to refocus every during every filter change and every 30 minutes or so within each filter. I don't see MaximDL being able to do that I unless I write a specific script for this in the AUTOSAVE SCRIPT column area. No sure how to do this! Alternatively, I can simply set up the LRGB imaging runs with 30 minute and filter change slots, and simply press FOCUS on FOCUSMAX manually to check focus and then continue to the next slot. Does this sound correct?

Clear skies,

John K.

[peter_4059]

John,

I've managed to get SGP working ok with my SN10 by adjusting the step size and number of steps so I avoid donut stars. It works well if it remains close to focus but not so well if I'm far enough away such that donut stars are generated during the focus run. I like being able to focus without slewing to a specific star.

Peter

[vlazg]

John, does it matter if the rgb is not perfectly focused, just so that luminance is?
George

[Atmos]

It is more important that the luminance is perfectly focused but you do still want the RGB in focus for proper colour and to stop getting colour fringes from there being a big difference in stellar sizes (FWHM).

[RobF]

To get that degree of automation with Maxim, probably need to read up on automation products like CCDAutopilot, CCDCommander, or the Royals Royce - ACP.

[DavidTrap]

I have definitely found focusing more reliable slewing to a mag 4-5 star with focusmax

DT

[John K]

Thanks for all the comments gents,

Got FocusMax and MaximDL working last night and now have myself 4 nice VCurves and able to autofocus. After running VCurves, FocusMax took no more than 15-20 seconds to find the lowest FWHM value and achieve focus on several stars I chose. One of the things I like about it is that is changes the exposure with the camera automatically to get the necessary data it needs.

However, I could not get focusing or VCurves working under the Observatory Focus module of MaximDL - it was all done through FocusMax. For those that use MaximDL this is the area I am taking about:http://www.cyanogen.com/help/maximdl/Focuser_Tab.htm

BUT, as FocusMax works, I am happy. All I will simply do is do my imaging run in LRGB and simply pause and re-focus with FocusMax every 30 minutes. I don't think it's too disruptive. The only thing that I will be limited by is the filed of stars visible in my imaging field.



Thanks Rob but I am not that keen on going to that level yet!



Will be imaging from a dark sky site so lets see what happens - worse case is that I will simply hunt for a brighter star near where I am imaging. Good thing is that ASI174mm is very sensitive.



Thanks Peter - will download and trial.



George - as other have said - critical to focus between channels and also for me as the object rises/sets and temperature changes.

[RobF]

Having put auto-focus in the "too hard" bin for years after buying a scope with decent focus/step control, now couldn't do without it - nothing worse than a not quite focused image.

Hope it lifts your image quality and satisfaction :thumbsup: