Mesu 200 PA

[Mcrogers1]

Hello,

I hijacked a post from this thread: 

 

How Olly and I did it.

-Setup Mesu, make sure it's level

-Look through finder and put polaris at 2/3 off center

-Guide without dec corrections for 5 minutes in East, adlust altitude, recheck ...

-Guide without dec corrections for 5 minutes close to meridian adjust Azimuth, recheck ...

We take 30 minute subs since then without any rotation ...

I've done this 2 times and it never took more than 20 minutes in total (actually last time I spent less then 10 minutes, must have been lucky with the finder scope), easiest mount to polar align ... and that with 50 KG of total weight.

The adjustment screws are just stellar.

/Yves

How are you guiding without dec corrections? Is this under algorithms in PHD2? I know you use the Argo Navis controller and the SiTech has a freeze declination function.

I'm trying to PA the Mesu and haven't had much luck with the Polemaster. I had the routine with the Polemaster spot on with it's PA procedure and it was off by 7 arcminutes in PHD2's drift alignment. I'm going to use your procedure without the Dec corrections to see if I can get better results. I did get a better alignment with the drift align in PHD2 and the guiding assistant didn't recommend any PA corrections but my guide graph was horrible.

Thanks.

Mike

 

 Like this

[kirkster501]

Do you need the MESU Polarscope to PA with Polemaster or can you just use the Polemaster camera on its own?

When I get my MESU I am going to try Alignmaster

http://www.alignmaster.de/

 

[Mcrogers1]

You use only the Polemaster. You have to get the adapter for the Mesu. I got mine from Opt being in the USA but MA sells one.

http://www.modernastronomy.com/shop/accessories/adapters/polemaster-adapter-for-mesu-200-mount/

[ollypenrice]

On 21/12/2016 at 11:14, Mcrogers1 said:

Hello,

I hijacked a post from this thread: 

 

How are you guiding without dec corrections? Is this under algorithms in PHD2? I know you use the Argo Navis controller and the SiTech has a freeze declination function.

I'm trying to PA the Mesu and haven't had much luck with the Polemaster. I had the routine with the Polemaster spot on with it's PA procedure and it was off by 7 arcminutes in PHD2's drift alignment. I'm going to use your procedure without the Dec corrections to see if I can get better results. I did get a better alignment with the drift align in PHD2 and the guiding assistant didn't recommend any PA corrections but my guide graph was horrible.

Thanks.

Mike

 

 Like this

•  

My recollection of doing this with Yves is that we simply tracked  without guiding and watched the drift. These are the notes I use when re-doing a drift alignment.

Cameras set orthogonal to RA and Dec.

Choose southern star at meridian/celestial equator intersection. (+/- half hour, +/-  5 degrees)

Determine west. (Stars drift west without motor running.) Determine N using light peeping over the N side of the objective.

Run motors and ignore any E-W drifting.

Star drifts SOUTH, move mount WEST.

Star drifts NORTH, move mount EAST.

Choose Eastern Star at 20 degree elevation.

Star drifts SOUTH, RAISE the mount.

Star drifts NORTH, LOWER the mount.

Repeat.

I hope that's not too cryptic!

Olly

 

[Mcrogers1]

Thanks Olly I'll do that when I'm able.

[Zakalwe]

17 hours ago, ollypenrice said:

My recollection of doing this with Yves is that we simply tracked  without guiding and watched the drift. These are the notes I use when re-doing a drift alignment.

Cameras set orthogonal to RA and Dec.

Choose southern star at meridian/celestial equator intersection. (+/- half hour, +/-  5 degrees)

Determine west. (Stars drift west without motor running.) Determine N using light peeping over the N side of the objective.

Run motors and ignore any E-W drifting.

Star drifts SOUTH, move mount WEST.

Star drifts NORTH, move mount EAST.

Choose Eastern Star at 20 degree elevation.

Star drifts SOUTH, RAISE the mount.

Star drifts NORTH, LOWER the mount.

Repeat.

I hope that's not too cryptic!

Olly

 

That's basically drift aligning, isn't it, except that you have the tracking enabled. The only issue that I could see with this is that your mount needs to be tracking at the correct Sidereal rate. My Mesu's tracking rate drifted over 12 months to where it wasn't tracking at sidereal. That would throw a spanner in the works if you tried the above, wouldn't it? 

 

[ollypenrice]

1 hour ago, Zakalwe said:

That's basically drift aligning, isn't it, except that you have the tracking enabled. The only issue that I could see with this is that your mount needs to be tracking at the correct Sidereal rate. My Mesu's tracking rate drifted over 12 months to where it wasn't tracking at sidereal. That would throw a spanner in the works if you tried the above, wouldn't it? 

 

It is indeed drift alignment in its classic form, I'd have said. I guess that it's predicated upon reasonable sidereal tracking, yes. It doesn't need to be perfect, though, since periodic error can be ignored.

Odd that your tracking rate changed. Do you know what caused it?

Olly

[Zakalwe]

2 hours ago, ollypenrice said:

It is indeed drift alignment in its classic form, I'd have said. I guess that it's predicated upon reasonable sidereal tracking, yes. It doesn't need to be perfect, though, since periodic error can be ignored.

Odd that your tracking rate changed. Do you know what caused it?

Olly

Nope...Ive being trying to diagnose it's issues for a while now. Ive got it tracking correctly now and have a custom firmware installed to try and diagnose some other problems.

[Mcrogers1]

I don't know what I'm doing I have to admit. I must be the most incompetent polar aligner to ever live. I ran guiding assistant for over 5 minutes and I had an average PA error of .7 arc min but the graph was horrible. I guess I'll do another iteration when the weather clears (I've been at this for 5 hours and its 0330 time to turn in.) I don't if the ScpLat in SiTechExe has any influence on this but mine shows 90 and I'm at 35N. I have ServoConfi and SiTechExe lat parameters set right (never mind on the ScpLat. I guess that's for equatorial). 

 

Merry Christmas and Happy Holidays to all!

[vdb]

Bit late, now a days in PHD2 I just use the drift alignment tool, it will tell you where to slew, it then starts guiding and will show you how much off you are ...

I typically first try to figure out which direction I need to make corrections for the error to get smaller and then iterate till the error is acceptable ...

Beter explanation found here;

https://sites.google.com/site/openphdguiding/phd2-drift-alignment

 

/Yves

[Mcrogers1]

I did a drift align in PHD2 and had under 1 arc min error in alt and az positions that it has you slew the scope to but the guide graph was really bad. I'm going to let it drift for 15 minutes next time once I have a low enough error.

Stars at the edge were elongated after a 5 min guided image. I would think if your polar alignment is stating you're under 1 arc min then your graph should be good and a 5 minute exposure should be easy. I'm really new at this and don't know enough to be an effective troubleshooter. Could seeing or roundness of your stars cause this type of problem. I thought if your total RMS was under 1 then you are good.

I'll get it dialed in eventually when the weather cooperates. I know I'm doing something wrong because this mount is a solid performer.

I use the bookmark method for drift aligning: http://www.cloudynights.com/topic/472874-drift-alignment-with-phd2-the-bookmark-technique/?hl=+phd +drift +bookmark.

I know with the scopes on the Mesu the altitude adjustment is hard. The azimuth I have to be off of where I need the adjustment to be so when I tighten the tommy nut it is correct. I like the adjusment on this mount a lot better than the CGEM.  

[Mcrogers1]

I'm waiting on an email from Lucas. I do have my RA/Dec set to polite mode and a supervisory threshold of 10.

The mount starts moving at a high rate constantly during guiding now once every 30 minutes and I have to shutdown and restart to get it back to tracking at a sidereal rate. 

[Zakalwe]

Have you seen this thread? Similar problem?

 

 

 

[Mcrogers1]

I've been following that thread.

Going to try resyncing the clock in the offset tracking window. I have an atomic clock set to sync my computer on an hourly basis now.

Lucas needs me to try tracking without guiding to see what happens. Hopefully the weather clears to do some testing.  Maybe the new SiTech coming out will help sort things out.

Comparing my guide log to Sara's I did notice that I have backlash compensation enabled. I turned that off just now. Maybe it will help.

[Mcrogers1]

Just an update with the latest problem. The dec axis will only move a bit in one direction then starts moving back the other way with me holding the same key. Then all of a sudden it will work.

I keep getting below horizon limit in SiTech.exe but don't use a horizon file and the scope is pointed at the coordinates for azimuth drift aligning in PHD2. I searched for "horizon limit" in the SiTech user manual and those two words together aren't in there.

The tracking keeps stopping and I can't restart it without cycling power to the mount. Pressing start in SiTech does nothing. 

[Zakalwe]

Unless you have changed the configuration,  the way to start tracking is to issue an  Offset Init.

Have you got a copy of Steve Richards excellent excellent starter excellent starter guide?

[Zakalwe]

tmp_9980-_MESU 200 Mount Quick Guide to Installation1209843937.pdf

[Mcrogers1]

I can get it tracking with an offset init but then it stops tracking and I can't use the start button to get tracking back. I have to restart it after that. 

I used Steve Richards guide thanks.

[gnomus]

I doubt if you'll be able to get your polar alignment much better than 0.7.  It is odd that you start tracking only for it to stop again.  My mount will only stop tracking if it hits its meridian limit (set in Sitech).  I use SGP for imaging and always get this to do a flip before the meridian limit is reached.

 

[gnomus]

I just looked at your PHD screenshot.  The main window (the one that shows the stars) did not llok correct.  The 'star' that has the box around it looks ver cigar-shaped to me, as do the few other points of light visible.  Are you certain that your guide camera is focussed and orthogonal?  Also what were the sky conditions like when you shot this?  

[Davey-T]

I get seagull and banana shaped guidestars with my OAG but it doesn't seem to bother PHD.

Dave

[swag72]

2 minutes ago, Davey-T said:

I get seagull and banana shaped guidestars with my OAG but it doesn't seem to bother PHD.

Dave

I'm with Dave on this..... I rarely have round stars in my OAG and PHD seems pretty happy with the situation...... now if only the same could be said of this blasted Mesu.....  

[gnomus]

Fair enough.  I am struggling to see how a 0.7 arcminute polar alignment could give that graph.  

I don't really understand the interaction between the skymodel that you build and guiding.  Could that be a factor?

[steppenwolf]

I always used to have seagull shaped stars in my OAG guide star images but to my amusement, the stupendously flat field of my Esprit 150ED means that my OAG stars are now perfectly formed despite being (as the name implies) off axis! However, I can confirm that distorted guide stars are not an issue anyway.

[Jonk]

I had 'snowflake' shaped stars in a finder guider the other day. I don't know why, but it didn't appear to affect the guiding that I could see.