Mesu/Sitech, Maxim and pulse guiding

[MartinB]

I currently use guider relays with Maxim but pulse guiding does seem a more logical way to guide and also loses a cable.  Is anyone pulse guiding a Sitech controlled Mesu using Maxim?  If so, could the give me an idiots guide.  Should I use the "telescope" or ascom direct option?

[derrickf]

Hi Martin,

I use "Telescope" to guide with Maxim and my Mesu 200 / Sitech.

My setup is a 12" RC with Atik383, guiding is with a Lodestar2 through an OAG. It works well and my guiding RMS is around 0.25 arcseconds.

HTH

Derrick

[steppenwolf]

Martin, like Derrick, I use the 'Telescope' setting as well for Pulse Guiding. I run MaxIm DL v5.24. On my most recent autoguiding run my RMS value was 0.2255164 arcseconds, on this occasion, using a separate guide telescope during a testing session. I capture 3 second guide exposures as this value works well with the Mesu.

[MartinB]

Brilliant, thanks Derrick and Steve.  Anything else I need to know, any settings to tweak in Sitech?

[steppenwolf]

None that I recall, Martin but setting the aggressiveness in MaxIm DL is always worth experimenting with.

Sent from my iPhone from somewhere dark .....

[derrickf]

Brilliant, thanks Derrick and Steve.  Anything else I need to know, any settings to tweak in Sitech?

You need to switch off declination compensation in Maxim but you probably know this already if you are currently guiding through camera relays with Maxim.

Derrick

[MartinB]

Thanks Derrick, yes I do that with camera relays, I understand it ends up being double corrected if you don't.

[derrickf]

I'm pretty sure it does - I neglected to change this setting in Maxim when I first commissioned the Mesu200 and guiding was erratic.

Derrick

[steppenwolf]

You need to switch off declination compensation in Maxim but you probably know this already if you are currently guiding through camera relays with Maxim.

I have this set to 'enabled' in MaxIm DL as my understanding is that for Pulse Guiding it should be used? This from the SiTech Manual:-

Since Sitechexe does “equal area panning and guiding”, do not use the option in your autoguider program to correct for scope declination if you are using relay guiding or a direct guider input from your camera (like from an SBIG cable connection) or you get twice the proper correction! However, if you are using “ascom guiding” (i.e. your autoguider is connected via ascom, this is not true, so for ASCOM guiding, it’s best to do the declination correction from within your autoguider program.

I haven't tried without and more often than not I re-calibrate at the start of a session anyway so perhaps the SiTech software and manual are at odds with one another on this point?

[derrickf]

Hmm that's interesting - I'll have a play next clear night but I clearly remember issues when I left dec compensation enabled in Maxim - I don't recall what imaging train you are using but my pixel scale at the guider is 0.6 arcseconds per pixel.

I re-calibrate once a year or so - whether I need to or not :grin:

Derrick

[steppenwolf]

I re-calibrate once a year or so - whether I need to or not :grin:

That's where I shall be once the testing is done!

I don't recall what imaging train you are using but my pixel scale at the guider is 0.6 arcseconds per pixel.

We're operating at very different pixel scales which is why talking in terms of arcseconds per pixel is far more meaningful that just 'pixels' - for the purposes of testing the whole automation thing, I am using a small telescope as my guide 'scope so my pixel scale is 7.5 arcseconds/pixel.

[derrickf]

We're operating at very different pixel scales which is why talking in terms of arcseconds per pixel is far more meaningful that just 'pixels' - for the purposes of testing the whole automation thing, I am using a small telescope as my guide 'scope so my pixel scale is 7.5 arcseconds/pixel.

At this scale I'm surprised you see much guider activity at all (assuming you have minimal drift due to polar misalignment); if Maxim's centroid evaluation is accurate to about 1/15th of the guider pixel scale you shouldn't really be detecting / reacting to any movement less than about 0.5 arcseconds.

Regards

Derrick

[steppenwolf]

I have no doubt you are right, Derrick, as I said earlier, this is just a test rig - I was using it to resolve the issue of the guiding sense not working correctly after an automated meridian flip under CCD Commander control, sadly, I am not actually imaging for real at the moment, just testing systems!