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  #21  
Old 16-09-2015, 10:14 PM
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Atmos (Colin)
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Originally Posted by bugeater View Post
I use the PHD2 drift align tool exclusively as well and have found it pretty easy to use. I do take a bit longer than others here to get aligned though. I find the charts will follow a trend for a while and then change direction, so you aren't entirely sure whether you've got it spot on or not. Not sure why this happens. Wind perhaps?
As someone very new to this game feel free to ignore me but it sounds like potentially something on your worm gear? If you're getting a sudden change then it has to be something sudden and pretty nasty causing it I would imagine.
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  #22  
Old 17-09-2015, 05:53 AM
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Originally Posted by bugeater View Post
I use the PHD2 drift align tool exclusively as well and have found it pretty easy to use. I do take a bit longer than others here to get aligned though. I find the charts will follow a trend for a while and then change direction, so you aren't entirely sure whether you've got it spot on or not. Not sure why this happens. Wind perhaps?
Depending on how much backlash etc in your system, early on the trend line can change direction a bit. The more time you give it, the more data it has to settle down and get more accurate. 30secs might be enough. If doing longer narrowband exposures you might leave it 2mins.
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  #23  
Old 17-09-2015, 07:53 AM
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Its the same with a high end mount perhaps not as much shifting. Any mount has PE. It tends to look like a sine wave when smoothed right down with wiggles within the sine wave.

So a system that works on a trend line could at first show part of the curve up or down of the PE and it would be a false reading.

Only after its been averaged for a while would that become more accurate.

Pempro works the same with a trend line being formed on the basis of the plotted guide errors. The instructions for that clearly state it may need to run for a little while to determine an accurate trend line. However its pretty clear if you are a long way off. To get it so the trendline is level (the goal) it has to be very close to correct PA.

I haven't used PHD2 PA but I see the trendlines available in the guide error graphs. It may even be faster than Pempro if it shows both RA and Dec trendlines at the same time if that is possible without slewing to different parts of the sky.

Greg.
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  #24  
Old 17-09-2015, 09:30 AM
bugeater (Marty)
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Originally Posted by Atmos View Post
As someone very new to this game feel free to ignore me but it sounds like potentially something on your worm gear? If you're getting a sudden change then it has to be something sudden and pretty nasty causing it I would imagine.
That was my initial theory, but it's the drift in dec you are watching, not the RA. So PE shouldn't matter. At least that's what I was told and it makes sense.

Quote:
Originally Posted by troypiggo View Post
Depending on how much backlash etc in your system, early on the trend line can change direction a bit. The more time you give it, the more data it has to settle down and get more accurate. 30secs might be enough. If doing longer narrowband exposures you might leave it 2mins.
I have done some work on reducing the backlash, but haven't seen much change really. But yes, if you leave it longer, you should average out any non-polar alignment errors. I often leave it for many minutes before tweaking it (I'll go inside and watch TV or something).
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  #25  
Old 17-09-2015, 03:19 PM
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Have you installed the Daily build update for TSX?
Software bugs are probably why tsx slewed so much.
I had a night where I have a myt, freshly installed tsx, had all sorts of issues. would not even home properly, something that cannot go wrong.
after 2 hrs, installed the daily update, "everything" worked from then on. couldn't believe it.
unless you've already done this, then ignore.

I've been using tsx with a paramount myt and find the PA routine extremely accurate. more than sufficient for 40min subs with 2 secs guiding on a 1m scope.

I make sure the first slew to a star has the star in the fov.
then a 24 point run, difference here is that it tells me how many ticks to turn each knob. after 3 x 24 point runs I don't need to adjust it any more according to it. and I clear the model every time I do a run.
This has worked for me in a field setup every time.

good luck.

Cheers
Alistair
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  #26  
Old 18-09-2015, 10:35 AM
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I use a "lowly" GPD2 mount, fitted with a Synscan GOTO system. If I do multiple iterative 2 star alignments, manually moving alt and az in between with the knobs using the reported alignment errors as a guide (NOT using the useless Synscan Polar Realignment feature), I can get the mount down to 30 sec or less out in both axes - depends how lazy I feel on the night. I usually aim for sub-10sec out maximum.

I then autoguide, and find, if I did a good iterative alignment, that I will get a guide correction every 7 to 8 minutes, the remainder of the time it just tracks. 30 minute subs no issue.

That is using either PHD2 or MaxIM (preferring PHD2 at the moment) for guiding, MaxIM for image acquisition and just the bog standard Synscan handset as "the brain".

Never once tried controlling via ASCOM, though it is all there if I want to.
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  #27  
Old 18-09-2015, 11:56 AM
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Quote:
Originally Posted by LewisM View Post
I use a "lowly" GPD2 mount, fitted with a Synscan GOTO system. If I do multiple iterative 2 star alignments, manually moving alt and az in between with the knobs using the reported alignment errors as a guide (NOT using the useless Synscan Polar Realignment feature), I can get the mount down to 30 sec or less out in both axes - depends how lazy I feel on the night. I usually aim for sub-10sec out maximum.

I then autoguide, and find, if I did a good iterative alignment, that I will get a guide correction every 7 to 8 minutes, the remainder of the time it just tracks. 30 minute subs no issue.

That is using either PHD2 or MaxIM (preferring PHD2 at the moment) for guiding, MaxIM for image acquisition and just the bog standard Synscan handset as "the brain".

Never once tried controlling via ASCOM, though it is all there if I want to.
The gpd2 has a worm period of 10 minutes, having the guider issue one correction every 7 minutes would be unwise unless the periodic error of the mount was considerably better than the local seeing. Even if the mount was performing at 5 arc seconds peak to peak which would be outstanding it should be issuing more corrections than that.
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  #28  
Old 18-09-2015, 12:17 PM
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I dunno Peter - that's all MaxIM seems to do - it continually checks, but the movements readouts are saying 0.00 in both axes, except once every 7 to 8 minutes when I see it make a small correction.

PHD2 keeps the centroid continually within 0.5, usually MUCH less (0.25 or less). RMS is VERY small with this mount.

I dunno the settings - it just works! I let PHD2 decide what, and I use default in MaxIm.

I have had this mount completely apart - polished worms and spurs, regreased, fiddled with meshing for hours. it just plain works right, with stuff all effort. I had to tear it down again maybe 3 months ago after NIL use for 4 months, as the first time out I found slackness in Dec and RA - hence the remesh etc.

I will try to make a graph tonight IF the weather holds - the dec and RA traces are essentially flat, on the smallest measurement scale.
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  #29  
Old 18-09-2015, 12:19 PM
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Might be guiding on a hot pixel.
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  #30  
Old 18-09-2015, 01:38 PM
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Octane (Humayun)
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Lewis,

What are your min/max move settings in MaxIm DL? That will explain why you are only guiding once every few minutes.

H
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  #31  
Old 18-09-2015, 02:01 PM
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Quote:
Originally Posted by LewisM View Post
I use a "lowly" GPD2 mount, fitted with a Synscan GOTO system. If I do multiple iterative 2 star alignments, manually moving alt and az in between with the knobs using the reported alignment errors as a guide (NOT using the useless Synscan Polar Realignment feature), I can get the mount down to 30 sec or less out in both axes - depends how lazy I feel on the night. I usually aim for sub-10sec out maximum.

I then autoguide, and find, if I did a good iterative alignment, that I will get a guide correction every 7 to 8 minutes, the remainder of the time it just tracks. 30 minute subs no issue.

That is using either PHD2 or MaxIM (preferring PHD2 at the moment) for guiding, MaxIM for image acquisition and just the bog standard Synscan handset as "the brain".

Never once tried controlling via ASCOM, though it is all there if I want to.
Could it be that your guide camera is set to 7min subs?
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  #32  
Old 18-09-2015, 03:57 PM
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Probably a hot pixel, and the tracking is so faultless it don't matter none

H, I will look it up later when on the astro comp, but I have been using PHD2 instead lately - bloody good stuff, SO much better than PHD1.x!

There is something about this GPD2 - it's been sold twice, and I bought it back each time (just ask JRC He's since bought the LAST one out of Germany ) when I found other more expensive mounts didn't come CLOSE to this one - I originally bought it from Kunama, who bought it new, and he can attest too to how darned good this one is. Just incredible really, and light enough to be portable (seeing I have about a 2 hour window on most targets, transportability is paramount to me)

Anyway, the GPD2 is good only up to an FSQ-106 maximum - I doubt Colin's 130 would be any good on it, let alone any RC over say 8". It's pretty much a refractor mount, or light Newt/Cat (R200SS / VC200L)
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  #33  
Old 18-09-2015, 04:37 PM
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Sounds pretty amazing. Your mods must have enhanced it. I have heard GPD2 is an accurate mount though. Although mostly zero errors I find hard to believe(do you use auto darks?). No errors does sound like your settings are unusual or a hot pixel which of course does not move is being used. But if you get round stars 30 minutes who can argue? That is a stunning result no matter how high end your gear is.

AP1600 has the best tracking of PMX, PME, Tak NJP, MI250, Vixen Sphinx and I get minor corrections every 10 seconds with perhaps no correction on half the errors.

I often get about .9 to 1 arc second PE which is the best I have seen. PMX was about 1.5-1.8, not sure what NJP was as no graph but probably 3 to 6, MI250 was probably about 6, PME is about 1.5. Sphinx was about 30!

PHD2 guide assistant will make recommendations for min/max move and length of guide exposures plus give a rough idea of how accurate your polar alignment is.

I am imaging at 1159mm and 40 to 43kgs of weight. The PME is carrying around 80kgs.

Usual seeing is around 2.5 to 3.5 arc secs judging by the guide camera guide star which again is rough, as focus is not as perfect on the guide camera (done by hand) compared to the scope. I have seen a few guide stars at 1.6 arc secs but not for long. A bad night must be 5 arc secs seeing. Not too common.

Greg.
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  #34  
Old 18-09-2015, 04:54 PM
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Greg,

Yes, I do use autodarks. I was tongue in cheek re hot pixel - I always make sure it is not.

I just don't have many issues at all any more - it just works, and I am happy with that. I had even been leaving it out covered (sprayed down with Ballistol once every 2 weeks to be safe).

I was even discussing with H how long this one will go - watching the PHD2 status bar, it is "silent" most of the time. The last image I made (http://www.pbase.com/lewism/image/160890603) I watched for the entire 2 hours (OK, I let the focus shift with temp change - my fault - and yes, there is some bottom right tilt in the system) - the guiding was flawless and it issued a minor correction once every 4.5mins (seeing was unusual and fluctuating - thanks for living near a river and ocean!). The centroid graph was scaled to 0.5, and it stayed below 0.25 the entire 2 hrs. The auto settings just seem to work!

I am a complete gumby with the software - I don't even pretend to know what everything does.
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  #35  
Old 18-09-2015, 05:25 PM
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Well you are lucky and I would not take that for granted as normal or usual. Its not.

By the way I can see you need to adjust your camera for tilt. The top right is nice and sharp but the top left the stars are quite a bit larger.

The bottom 2 corners are showing coma so there is significant tilt going on.

First step is to work out where those corners of the image are on your camera.

I used a dim torch and did a focus exposure. I lit up the top half and watched where that appeared on the computer image. In my case the top and bottom of the image was inverted. Then I did the same left and right. Again for my scope left and right were inverted compared to the computer image.

So now you know what corner of the camera corresponds to which corner of the image. Now you can start packing it out.

Then you focus say the bottom right of that image until its sharper. Note does the focus have to go in or out. That tells you how to pack it out. If it has to go in then you need to pack out the other side.. If it has to go out you pack out that side. Keep taking test focus images until you get all 4 corners the same and top and bottom stars, left and right sides show sharp tight star images.

I have found sometimes misshapen stars are easy to mistake as guiding errors when its non squareness of the camera. A lot of systems have some tilt and lesser model CCD cameras may not have well levelled sensors.

Greg.
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  #36  
Old 03-10-2015, 01:06 PM
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Hi, just wanted to pass on some info. What you describe with the APA routine with T-point and TSX is exactly what I encountered when using a Mach -1. When I checked polar alignment with PHD after performing an APA, I found that the alignment was way way off. I investigated further comparing the recommendations in the T-point Polar alignment report with the actual fiducial star movement and noticed that the star was displaced in the wrong direction. I have posted to the Bisque site and worked with them over the last few days. This is a bug in the software. It will be corrected in the next daily build. I tested a preliminary new build tonight for Bisque and I can confirm that the bug is fixed.
Cheers
Carlos
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  #37  
Old 03-10-2015, 01:21 PM
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Quote:
Originally Posted by cdavmd View Post
Hi, just wanted to pass on some info. What you describe with the APA routine with T-point and TSX is exactly what I encountered when using a Mach -1. When I checked polar alignment with PHD after performing an APA, I found that the alignment was way way off. I investigated further comparing the recommendations in the T-point Polar alignment report with the actual fiducial star movement and noticed that the star was displaced in the wrong direction. I have posted to the Bisque site and worked with them over the last few days. This is a bug in the software. It will be corrected in the next daily build. I tested a preliminary new build tonight for Bisque and I can confirm that the bug is fixed.
Cheers
Carlos
Thanks Carlos

I presume you mean the Altitude recommendation
it tells you that the polar axis needs to be lowered and the next line says raise it.

good to know it's fixed.
I'm very happy with my 3 x 24 point T point routine. gets me close to 10arc sec and good for 60 min subs at 1m

cheers
Alistair
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  #38  
Old 03-10-2015, 01:54 PM
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Quote:
Originally Posted by cdavmd View Post
Hi, just wanted to pass on some info. What you describe with the APA routine with T-point and TSX is exactly what I encountered when using a Mach -1. When I checked polar alignment with PHD after performing an APA, I found that the alignment was way way off. I investigated further comparing the recommendations in the T-point Polar alignment report with the actual fiducial star movement and noticed that the star was displaced in the wrong direction. I have posted to the Bisque site and worked with them over the last few days. This is a bug in the software. It will be corrected in the next daily build. I tested a preliminary new build tonight for Bisque and I can confirm that the bug is fixed.
Cheers
Carlos
That's good to know, I'll have to actually go and get the daily build stuff setup.
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  #39  
Old 04-10-2015, 03:17 AM
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A new daily build was released last night. If you haven't already fetched it, please do so now.
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  #40  
Old 04-10-2015, 08:09 AM
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I thought that was fixed a few months ago. The polar alignment report was advising incorrectly the opposite corrections needed for altitude adjustment than it should, ie. raise when it should be lower.

That was fixed 2 months ago. So is this a specific bug for a Mach 1 mount or general? I have not noticed any bug using APA routine since that bug fix around 2 months or more ago.

Greg.
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