Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Hello all.
I should appreciate your help with the problem shown in the attached pictures.
Both curves have been recorded with PHD Guiding, QHY5 mono and FS-60C. The resolution of the camera/guiding tube is 3.02 arcsec/pixel. So, the approximate 0.8 pixel spikes that show the guiding curve will ruin every picture.
I have posted only one unguided and one guided cycle, but the problem occurs in every attemp to guide. The spikes affect both RA and DEC, but independently, and are not periodic. Some cycles show up to 20 of them, while others will have only 5.
I changed from PHD Guiding to GuideMaster and the spikes repeated.
I really cannot think of the probable cause.
Thank you very much for hour help
Pedro
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Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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lineman_16735
3.14159265
Reged: 12/04/04
Posts: 1496
Loc: At home
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Your Dec should not have any spikes for sure if it was unguided. This leads me to think your data is bad or your seeing was terrible. Another thing is you are undersampling a bit too much for accurate PE measurement, try a barlow. I've noticed your unguided RA graph looks very good. The few spikes in the unguided graph could be a lot of things ie, seeing, unbalanced. I think you need to look at your guide parameters and get your arc seconds a pixel down to around 2 at least.
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Chris
Meade 2080 ALT/AZ Goto Autostar 494
"quidquid Latine dictum sit altum videtur"
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Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Thanks, Chris.
These are only two examples within may be a dozen o sessions with different guiding paramenters and declinations on different days.
I already thought of increasing the FL of the guiding tube and used the TSA-102 (816 mm) with similar results.
Not being an expert, what impresses me most is that 0.8 pixels equal to 2.41 arseconds with my guiding setting, and the seeing never seemed that bad. I think I can balance the scope and guiding camera well, i.e., I don't know how to do it better (may be putting some more weight on the eastern side of the mount while guiding?). Besides, the same guiding setting, parameters and balancing get far better results with my Losmandy G11 (and that's no fair, is it?
Regarding the guiding parameters, I keep aggressiveness to 90 out of 100, because looking at the guided curve, after the ascending limb of the spike, the guiding software returns the star to the baseline or very near to it without overshooting. And use 3x3 noise reduction in PHD guiding.
But I forgot to mention a fact (excuse me): the RA has a little play when mooving the counterwaught shaft sideways by hand. Could it be that?
With Guidemaster, identical results.
What makes me think I surely need help.
Thank you very much again.
Pedro
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Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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lineman_16735
3.14159265
Reged: 12/04/04
Posts: 1496
Loc: At home
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A little backlash in RA should not be a problem as long as the RA axis is balanced a little east heavy. Are you using The Sky for goto control? If so have you changed the RA and Dec correction speeds in The Sky? When I had my NJP I noticed so strange guiding a few times and each time it was quickly fixed by changing theses settings in The Sky 6.
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Chris
Meade 2080 ALT/AZ Goto Autostar 494
"quidquid Latine dictum sit altum videtur"
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tim53
sage
Reged: 12/17/04
Posts: 290
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Also make sure you select the slowest guide rate with the buttons on the hand paddle. I got jumps like that while trying to guide with the setting the mount turns on with. The combination of button pushes needed to slow the guide rate down is in the manual somewhere, which I don't have with me at work! 
-Tim.
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"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Thanks, Tim.
Which is the slowest guide rate? It seems that by default the guide rate is set to 90. You mean to lower this speed? To what number?
Pedro.
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Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Thanks, Chris.
Yes, I'm using TheSky 6 for goto. I use the last Chuck Faranda's Takahashi driver and set the guiding rate to 90. You mean this?
Pedro
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Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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tim53
sage
Reged: 12/17/04
Posts: 290
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I don't think the guide rate that you select with the buttons on the hand paddle is displayed anywhere, but it might be in the manual. There were 5 or 6 different values, IIRC, and if you keep hitting the buttons you'll cycle back through the different values. If you watch a star with a reticle (either in a camera window or one of those actual reticles in an eyepiece that we used to use in the olden days) as you try the different speeds, you'll see when you go from the slowest back to the fastest.
I don't know about TheSky6, but in other programs I've tried changing the speed in software, it's had no effect at all on the mount. But maybe I've been doing it wrong!
-Tim.
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"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"
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lineman_16735
3.14159265
Reged: 12/04/04
Posts: 1496
Loc: At home
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I usually set the guiderate to 50 in The Sky. What Tim has said could have an effect as well. I never messed with setting the guide rate in the hand controller but, it is mentioned in the manual.
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Chris
Meade 2080 ALT/AZ Goto Autostar 494
"quidquid Latine dictum sit altum videtur"
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Dan G
scholastic sledgehammer
Reged: 06/27/06
Posts: 979
Loc: Minisink, NY, USA
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I too use 50 on my Tak mounts. Also look at your minimum move time. I use maxim and am not familiar with PDH. If this value is too low then the mount will move too aggressively and chase seeing or PE. Too high and the mount may move in a jerky fashion.
Dan in NY
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TV 76, Vixen VC200L, TV NP-127is
EM-200, NJP
ST-2000xm and ST-402
Tranquility Base Observatory aka "The Shed" by non-tranquil members of the house
www.nyskies.com Still a work in progress!
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Rusty
Postmaster
Reged: 08/06/03
Posts: 15893
Loc: Brooker, FL
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Yeah, and sometimes one has to experiment; seeing conditions can make one pull his hair out (my current excuse for having little  )
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N11GPS Fastar
TOA-130S
MK66 Std
Vintage C5
Megrez II 80mm ED Triplet APO
SolarMax 40
NJP Temma II
Sirius EQ-G
ST8XE/CFW-8 (LRGBHa)/AO-7/DF-2/STV/ST237a/350D (Unmodded)/Mallincam Color Hyper Plus/DSI III Color
Two not-spoiled Golden Retrievers - Maggie and Casey
Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering. - Arthur C. Clarke
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Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Thanks all.
Some weeks ago I decided to scanner the EM-400 manual, but something got in the way and I didn't scanner it and I don't know where it is now.
Dan, I have used 1.5 seconds and shorter. Do you think this is OK?
I will try your suggestions one at a time and repeat mesaurements as soon as weather permits. We are having an unusual rainy/cloudy summer in Spain.
Thanks again.
Pedro
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Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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TxStars
sage
Reged: 10/01/05
Posts: 390
Loc: Lost In Space
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"But I forgot to mention a fact (excuse me): the RA has a little play when mooving the counterwaught shaft sideways by hand. Could it be that?"
The RA and Dec should have no play in them. This is not acceptable and should be sent in for repair. Any play can produce guiding errors.
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http://txstars.org
Tak FC-50
Tak FCT-65
Tak FC-100
"SCUZZO" 300/1.1
Camera Nikon F2 / Mamiya press 6x7 ,6x9 yay Film
Lenses Yes Many - lol
Mount - GoTo by hand and eye
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lineman_16735
3.14159265
Reged: 12/04/04
Posts: 1496
Loc: At home
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A little play in RA is no big deal. Since you never reverse direction in RA there is no backlash to speak of. Just be sure your east heavy and all is fine. Adjusting the worm backlash is simple to do in the NJP, sending it back is costly.
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Chris
Meade 2080 ALT/AZ Goto Autostar 494
"quidquid Latine dictum sit altum videtur"
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Dan G
scholastic sledgehammer
Reged: 06/27/06
Posts: 979
Loc: Minisink, NY, USA
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Pedro -
In Maxim I have minimum move time of around 0.07 secs and max move time of 0.4 secs for X and Y. I typically use 5 second guide exposures and have overall guiding in the +/-0.2 pixel range. Hope this helps. Let us know if you hve more questions.
Dan in NY
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TV 76, Vixen VC200L, TV NP-127is
EM-200, NJP
ST-2000xm and ST-402
Tranquility Base Observatory aka "The Shed" by non-tranquil members of the house
www.nyskies.com Still a work in progress!
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Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Thank you.
I don't feel like sending the mount back at the moment.
In the Uncensored Tak Forum, I've been told to check for voltage fluctuations in my power unit. I will try this also.
I'll keep you informed of the "spikes" business.
Thank you again.
Pedro
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Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Hi all.
As I seem to have lost the manual, I cannot change the guiding rate from it. ¿Would any of you be so king as to send me a scanned picture of the page of the manual or a text explanation of the procedure?
So, yesterday I used a different power unit with voltage digital display (12v the whole session) and the spikes didn't get better.
To compleetly discard a voltage fluctuation problem outside the mount, I will test (buying a tester before) the power cable of the EM-400.
Thank you for your help.
Pedro
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Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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Dan G
scholastic sledgehammer
Reged: 06/27/06
Posts: 979
Loc: Minisink, NY, USA
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Pedro -
Here is a link to the manual on the Texas Nautical website. They are the US distributor.
Are you using battery power or AC??
Again I am not sure how PHD works but 1 sec minimum move time seems very long. Consider this - the PHD will not issue a move command to the mount unless the error to fix requires 1 sec of movement. This is a long time on a Tak mount and why I think you are seeing spikes. Join the PHD yahoo group and ask for others experiences with any quality mount.
Dan in NY
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TV 76, Vixen VC200L, TV NP-127is
EM-200, NJP
ST-2000xm and ST-402
Tranquility Base Observatory aka "The Shed" by non-tranquil members of the house
www.nyskies.com Still a work in progress!
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Garcres
member
Reged: 04/10/08
Posts: 17
Loc: Spain
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Thank you, Dan, for the link.
I use an AC.
It seems I dind't understand quite well the time issue. PHD does not have the option of a maximum and minimum time of correction. I was referring to the time without PHD checking where the star is.
Last week I bought a second hand ST-4ME to use it as an autoguider and I'm learning its functioning. All the same, I will join the PHD group.
Thank you again.
Pedro
--------------------
Takahashi FS-C 60; TSA-102S; Mewlon 250.
Losmandy G11 Gemini 4
Modified Canon 5D; QYH8; QHY5
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Dan G
scholastic sledgehammer
Reged: 06/27/06
Posts: 979
Loc: Minisink, NY, USA
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Pedro -
OK now I understand what your time measurement is. In this case you should extend the length of the guide exposure to 4 or 5 seconds. Using short exposures on a good mount will just have you chasing seeing.
For instance - my old CGE had PE of +/-15 (the newer mounts are much better now). I needed 1 or 1.5 sec exposures to capture decent images. Then I moved to the EM-200 and kept the same exposure times - I saw no better results than the CGE and was very frustrated. Finally someone told me to lengthen the time and the results were much improved. Hope this works for you.
Dan in NY
--------------------
TV 76, Vixen VC200L, TV NP-127is
EM-200, NJP
ST-2000xm and ST-402
Tranquility Base Observatory aka "The Shed" by non-tranquil members of the house
www.nyskies.com Still a work in progress!
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