What are facts?

[RogerTheDodger]

It's about +/- 15 on my HEQ5

[Erwin Kats]

I think only a guidelog is not enough.

I can not even post one because i can work without guiding.

But also bad seeeing will be translated to the guidelog, focus etc.

Here in the west coast of holland seeeing is terrible, but to compare guide logs you should post 2 mounts with the same guiding setup next to each other for a better conclusion i think.

I think more mesu 2 mount owners will appear on the www and maybe we get a great review from the mount like Rob did.

[Darth Takahashi]

So you want a graph, here is one ...

Telescope Reviews: MESU- mount #2

Yves.

Your data; numbers not an image!!!

With the numbers I can calculated are the relavent stats... with an image I can do nothing at all.

[Erwin Kats]

Your data; numbers not an image!!!

With the numbers I can calculated are the relavent stats... with an image I can do nothing at all.

Not fully support that opinion.

With a single raw picture just from the ccd, without processing you can always measure the roundness of stars, wich is pretty important at the end .

But for that its great to know the guiding stats to see if its impressive

[Darth Takahashi]

I think only a guidelog is not enough.

I can not even post one because i can work without guiding.

But also bad seeeing will be translated to the guidelog, focus etc.

Here in the west coast of holland seeeing is terrible, but to compare guide logs you should post 2 mounts with the same guiding setup next to each other for a better conclusion i think.

I think more mesu 2 mount owners will appear on the www and maybe we get a great review from the mount like Rob did.

Agreed but Yves is up at Olly's place in the south of France, apart from the wind they must have significantly better seeing than us poor souls stuck at sea level or even below it in Holland, right?

[Erwin Kats]

Agreed but Yves is up at Olly's place in the south of France, apart from the wind they must have significantly better seeing than us poor souls stuck at sea level or even below it in Holland, right?

Hahaha indeed .

I did not know yves was still in les granges !

We will see what the results will be soon i hope

[ollypenrice]

I think we may have different hobbies, Neil! In my hobby everything comes down to the beauty of of the universe and whether or not I've captured any of it. One of the first applications of maths to physical reality came in the analysis of the musical scale. Do you need to know that to play the violin?

Johnny never learned to read or write so well

but he could play his guitar like he was ringin' a bell.

If I knew how to do a screen grab on Yves' Mac I'd post a graph - with Yves' permission. But I've all on to do anything except stare at it in frustrated incomprehension at the moment... However, what second light told me is that imaging with this setup is just like ringin' a bell, I kid you not.

Olly

[Tim]

Olly, you are not alone with not understanding PHD. I just set the appropriate bit for the focal length (OAG of course) and that is that. However the output from PHD goes to EQMOD in my obsy, and I DO understand what the peaks and troughs are patterns are with the guide graph in there, simply because the team have provided a great reference document with pictures of what means what, and what needs adjusting to make it right. The sliders in EQMod are dynamic and moving them has an instant effect on the graph. VERY intuitive.

I can live with a bit of up and down, its wild swings and abnormal spikes that are the problem. Also, the smoothness tends to vary depending where in the sky the scope is pointed, ie, if the target is nearer the NCP the guiding graph tends to be smoother.

At longer focal lengths you tend to start pushing the limit of the seeing anyway, but with a nicely tuned system there is no reason not to have subs 2, 3 or 4 hours long at 2400mm focal length with perfectly round stars. The edges will be more diffuse than with a shorter instrument, but even wild swings in the guiding tend to have less of an impact on the final image because of the higher focal ratio, the momentary bad position of the stars dont register enough photons to spoil the picture.

Cheers

Tim

[Erwin Kats]

I think we may have different hobbies, Neil! In my hobby everything comes down to the beauty of of the universe and whether or not I've captured any of it. One of the first applications of maths to physical reality came in the analysis of the musical scale. Do you need to know that to play the violin?

Johnny never learned to read or write so well

but he could play his guitar like he was ringin' a bell.

If I knew how to do a screen grab on Yves' Mac I'd post a graph - with Yves' permission. But I've all on to do anything except stare at it in frustrated incomprehension at the moment... However, what second light told me is that imaging with this setup is just like ringin' a bell, I kid you not.

Olly

Hey Olly,

We all have the same pasion i think

I think Neil is very interested in more information and "facts" due his interest in a new mount for a permanent setup.

For me the mesu mount would not be filling the spaces of emptyness because i want to controll it all with the sky x and other software. (automated would be wonderfull in the future )

[Darth Takahashi]

I think we may have different hobbies, Neil! In my hobby everything comes down to the beauty of of the universe and whether or not I've captured any of it. One of the first applications of maths to physical reality came in the analysis of the musical scale. Do you need to know that to play the violin?

Johnny never learned to read or write so well

but he could play his guitar like he was ringin' a bell.

Olly

I guess your referring to Pythagoras, right and while Johnny can play he will never appreciate the beauty of the harmonic scale and why music works.

Somewhere on the MAC there is a TEXT file where all the guiding data is logged. It will be coma delimited and can be imported into Excel.

With permission of course, thats the file we need. Try using "Spotlight" to look for txt files created on the imaging date?

We have the same hobby and there is also much beauty in the natural statistics of the universe which created the ramdon distribution of Ionised gases that we love to image, such as B33, the dark dust sitting in fornt of the ionised hydrogen that appears to look like a horses head, your first light.

[malc-c]

Interesting thread. I for one must confess to getting hung up on getting the perfect graph in PHD. I think the problem is that when you see a post from someone with the same equipment which contains a flat line, there is that competitive streak in people that want to go one better... or the disappointment when the graph is all over the place and the session ends in tears

I guess at the end of the day, provided the image is pleasing on the eye, sharp focused and stars are not like sausages then that's what counts. In the good old days when the normal way of guiding was to use an off axis guider and either manually make the adjustments or pressed the + and - keys on the key pad... making allowances for the rate of discharge in the D cell batteries ! - I wonder if you plotted those manual corrections how hilly the graph would of been...

[rfdesigner]

Interesting thread. I for one must confess to getting hung up on getting the perfect graph in PHD. I think the problem is that when you see a post from someone with the same equipment which contains a flat line, there is that competitive streak in people that want to go one better...

that's one problem I will never have (see my kit)

oh and I get RMS errors of around 0.6 with a lodestar at 1500mmfl at the moment with no PEC.. got PEC working (I think) over the weekend.. yet to star test it.

[Jessun]

Newbie's reflection: Is this a cut throat guide graph competition or just a delightful non-cancer-curing hobby producing nice looking images that inspire us all to learn more about what is actually found in that image.

In my view end result counts - no it wins hands down. And the kit you chaps have got running down there is simply annoyingly interesting.

But a graph that looks out of sync with expectations should raise the question 'hm that's odd...why is this then'. I belive you already cracked that one though. That mistral down there often tosses my 75 tonne aircraft around like a rag doll, so no wonder it can upset a dustbin on a stick aiming at arc second precision!

I wish you best of luck!

[vdb]

You can control mesu mount with The Sky X, it will do it's magic via the Argo Navis control, one problem solved.

:-)

[AWR]

It seems to me that this may indicate an advantage to the idea of a friction drive.

It is possible to write a control funtion for anything if you know its transfer function. But if a conventional mount has any backlash (or any play at all between the gears) then its transfer function will be variable.

A flat guiding graph (all things being equal - FL for example) indicates that the mount would be good at unguided imaging?

A Pennine graph (let's have some home-grown hyperbole) which results in a clean image indicates that the mount may not image well unguided - but that it takes guiding well!

Obviously, this is difficult to measure from an image. As people have mentioned, random errors produce round stars. I guess you would have to measure the size of the star image (everything else being the same etc..).

Personally, I would be inclined to trust Olly's eyes. I can tell if a note is out of key quicker by listening to it, than I can by recording it and measuring its frequency.

Andrew

[harry page]

Hi

I have done this long focal stuff and different to those little refractors it is

I presume that you are using a oag which means you are guiding at sub arc second scales and at this scale that guide star will bounce around all over the place due to seeing , drive errors etc.

As long as you can guide well below 2 arc sec you will have round stars as the seeing does not normally get much better than this.

Any body can have a flat guide graph below 1 m in focal length

Peace

Harry

[vdb]

Oh the rms errors went up with the focal length, 0.10 to 0.15 at 400 mm and .8-.9 at 2 400 ...

I'm back so it's all Olly, I cannot speak in his voice, but knowing him he is more interested in gathering image data then trying to gather guide data ... he would only do the later if subs are bellow his standard/expectations. (and I can't blame him)

Yves.

[harry page]

Hi

at 2400mm Fl a 9 mu pixel covers .76 x .76 arc sec or 0.577 arc sec square

At 400mm a 9 mu pixel covers 4.61 x 4.61 arc sec or 21.25 arc sec square.

This means at 400mm a point source has over 36 times the area to wander around than at 2400mm before a error is seen so in fact your guiding error is worse at 400mm than 2400mm

The real problem is only going to be if you want arc sec resolution , then a AO will required I think:evil6:

Harry

[ollypenrice]

Newbie's reflection: Is this a cut throat guide graph competition or just a delightful non-cancer-curing hobby producing nice looking images that inspire us all to learn more about what is actually found in that image.

In my view end result counts - no it wins hands down. And the kit you chaps have got running down there is simply annoyingly interesting.

But a graph that looks out of sync with expectations should raise the question 'hm that's odd...why is this then'. I belive you already cracked that one though. That mistral down there often tosses my 75 tonne aircraft around like a rag doll, so no wonder it can upset a dustbin on a stick aiming at arc second precision!

I wish you best of luck!

If 75 tonne aircraft get tossed around I don't want to hear about it. I've been in one of those!!!

So Johnny B Goode could play his guitar like he was ringin' a bell but he couldn't understand the beauty of the musical scale? Erm... I don't think I buy that...

Olly

[Darth Takahashi]

I have given up Olly; play around with the metaphors all you like but until I see some credible independent info on this mount its quality remains unknown and that is a FACT.

Good luck with your round stars that are probably oblate spheroids ;-)

Diffractions a wonderful thing, it can hide all sorts of issues...

[ollypenrice]

Neil, stepping back a bit there are three players in the ring.

1 The image.

2 The guide graph.

3 My understanding of the guide graph.

My problem is very simple; my understandng of the guide graph (doubtless a defective understanding) would lead me to predict a failed image. But the image is patently not a failure. So we have two facts, a bad guide graph and a good image. Maybe it isn't really a bad guide graph, maybe I'm simply not reading it correctly. Now are we goiing to say 'maybe it's not realy a good image? Frankly, that would be silly, though it might not be as good as it could be.

I'd like to do some autoguiding in AstroArt, my regular programme, because what with the the new setup, the Mac and the unfamiliar PHD my head is spinning. I need to compare like with like, ie my past experience with the present.

It seems that finding the graph at odds with the results is very common amongst people moving into long FL OAG guiding for the first time. I only just discovered this.

So all we know about the Mesu 2 at the moment is that it can obtain tight stars at a FL of 2.4 metres over half hour subs in a high wind during full moon. Once it's working properly I'll get a guide trace on here.

Olly

[Darth Takahashi]

Olly, OK I understand.

My interest in this or these types of systems is that there should THEORETICALLY be less random error. Since you only need to machine two cylindrical surfaces which are then forced together by friction to drive the mount; a lot simpler than a worm and gear.

Random error cannot be corrected but systematic error can be, such as PE because its reproducible and represents a bias in the drive system.

The image is the outcome and the guiding data is the journey; how you got there? Which is the most interesting part, at least to me with these friction driven mounts.

I can already achieve +/-3 arcseconds with my G42+ without taking any special precautions, some people use "PEMpro" to better model their PE to achieve < 1.5 arcseonds PE error etc... But if these mounts are to be seen as the future! Then I think you maybe able to understand that I want to see more evidence that just pictures?

I'm sceptical, that much is clear but I'm open to be convinced? Perhaps hoping to be convinced would be a better way of putting it!

I gather this will be a permanent setup?

[Sp@ce_d]

If I knew how to do a screen grab on Yves' Mac I'd post a graph -

Olly

I'm slightly late but FYI Olly

There's an app on the Mac called "Grab"

you can search using Spotlight.. (CMD & Spacebar ) opens search at top right of screen.

HTH

[vdb]

Thanks Harry for that calculation, I did the simplistic divide by focal length which is wrong ...

I found a formula that calculates the airy disc, and that is about 23.5 depending on color and taking a seeing of 2 arcsec!? So yes a 2 second integration time should average that out a bit but still, that is almost 3 units in Y on PHD graph ...

Think we should adjust some parameters so the mount will not chase this (we should get a green filter before guide cam ... I think)

Y

[martin_h]

I treat the guiding graph as a record of what the mount is doing to keep the stars round, Ok sometimes its looks like a broken hacksaw blade but that just means the mount is working harder to achieve the end results. If the guide star is percieved to be moving in one direction and the guiding program moves the mount in response to maintain it, as long as its doing it at the same time and speed.....who cares(within reason)!