PHD Guiding issues...Please help!

[Mattjohnson1978]

Hi.

I am using PHD to guide my NEQ6 mount and have noticed a recurring issue. I have been trying to imaging the galaxies in Ursa Major and seem to have trouble getting it to guide correctly. It goes through the calibration stage (eventually) and says that it is guiding but it is quickly obvious that it isn't and eventually loses the guide star. When I set the target to something lower on the horizon (I am south facing), it calibrates and guides fine. Although I am using 5 minute subs, I get no trailing and nice round stars. Does anyone have any ideas?

When I said (eventually), that is because I have to set the exposure time to 5 or 10 minutes just to get the star to move enough and reach the magic number of 25 which is set. Is there a way of reducing the 25 so that calibration can be acheived at a quicker rate or is it really a "magic" number?

Many thanks in advance,

Matt

[Mattjohnson1978]

Just found a whole section on this problem on the stark labs website.......seems complicated!

[Freddie]

When you say "set the exposure time to 5 or 10 mins" where are you setting this? To change the calibration steps, you need to click the brain icon and set the time duration in there and it would be usual to be millisecs not mins!! I think you may be misunderstanding how PHD operates. Have a read of the guide you have found and post again if you have any more questions.

[Mattjohnson1978]

Hi Freddie....that was for trying to calibrate it. I was finding that the star wasn't moving enough which I was putting down to being nearer the pole. By increasing the time was the only way I could get the star to move enough to get through calibration, as it turned out it never guided properly anyway. I normally use between 1 and 3 seconds but this is the first time I have pointed my guider anywhere near that part of the sky and was getting frustrated as to why it wasn't working correctly when it does lower in the sky. I have just been reading some docs on the stark labs page and it goes into detail as to why guiding nearer the pole may induce problems but it doesn't seem to be sinking in too well. Have you had any problems guiding targets around that area? Could I be suffering because of what must be a very short focal length of the Orion Miniguider scope?

Matt

[Freddie]

Hi Matt, not really understanding what you are adjusting from your description. It sounds like you are adjusting the guide cam exposure setting which has nothing to do with calibration. Maybe if you give a bit more detail on exactly how you are setting up and exactly what you are adjusting it would help.

[lensman57]

Hi.

I am using PHD to guide my NEQ6 mount and have noticed a recurring issue. I have been trying to imaging the galaxies in Ursa Major and seem to have trouble getting it to guide correctly. It goes through the calibration stage (eventually) and says that it is guiding but it is quickly obvious that it isn't and eventually loses the guide star. When I set the target to something lower on the horizon (I am south facing), it calibrates and guides fine. Although I am using 5 minute subs, I get no trailing and nice round stars. Does anyone have any ideas?

When I said (eventually), that is because I have to set the exposure time to 5 or 10 minutes just to get the star to move enough and reach the magic number of 25 which is set. Is there a way of reducing the 25 so that calibration can be acheived at a quicker rate or is it really a "magic" number?

Many thanks in advance,

Matt

Hi,

I suffered the same last night trying in vain for M51, I had very good Polar alignment, PHD calibrated, guide satr was good but star trails in the shots. The clouds rolled in anyway and I packed up. Blessing I guess. I'd be interested in this thread and the conclusions.

A.G

[Mattjohnson1978]

Thanks for your reply again Freddie. You were right in saying that I never understood properly how the guiding system worked and you were right. I feel more educated now after reading some online support and what I was doing was in fact incorrect but I will try and explain my logic! What I was findng was that when pointing the scope high in the night sky, towards Ursa Major, PHD kept coming up with the "star did not move enough" error. What I noticed was that if I changed the exposure setting to 5 or 10, then it detected more movement thus allowing the calibration to complete although it never guided correctly and always lost the star quickly. The logic that made sense to me was that if at 1 second, it detected say 1 pixel movent per step, at 5 seconds the star moved say 3 or 4 pixels per step allowing the calibration to reach its target number which is 25 on my set up. I know now that I should have been increasing the calibration step in the settings window. In saying that, looking at my settings, it is already on 1000ms. The system guides perfectly well when point south, east or west (which is the orientation of my garden) and Polaris sits just above the roof of my house which is good for alignment but up till the other night, I hadn't tried imaging in that direction with my guidescope and was confused to why it wasn't working. Looking at the literature, apparently guiding near the pole can cause problems due to the lack of star movement and gave some very scientific explaination as to why but I was wondering if you had any issues calibrating when pointed up at that part of the sky.

It seems like A.G. is having a similar problem, which is kinda comforting to think it isn't just me getting it wrong lol (sorry A.G.). I am using the Orion mini guide package which is effectively a 9x50 finder scope so as the calibration step seems to be linked to focal length, could the fact it is so small be having a bearing on the problem?

I hope that mad some kind of sense.

[Mattjohnson1978]

Hi,

I suffered the same last night trying in vain for M51, I had very good Polar alignment, PHD calibrated, guide satr was good but star trails in the shots. The clouds rolled in anyway and I packed up. Blessing I guess. I'd be interested in this thread and the conclusions.

A.G

Hi A.G.

I am interested in what equipment you are using for guiding. I am using the Orion Starshoot camera and mini guide scope.

Matt

[Freddie]

Hi, when up near the pole, if you adjust the calibration step time to get calibration in ~10 steps you should find that guiding should be ok. This assumes you have a good PA so the guiding isn't having to do too much. You need to recalibrate each time you move to a different part of the sky and this may also require an adjustemt to the calibration step time. Hope it all works out for you.

[Ewan]

I understand exactly what you mean Matt, the stars that are lower in the sky will move a lot quicker allowing PHD to detect star movenemnt quicker as well, i think what you are saying or asking is on the main PHD display window you have the exposure setting from 0.05 to 10 seconds, when guiding lower in the sky PHD should be able to detect movement at a quicker exposure ie 1.5 - 2.5 secs, maybe nearer Polaris 5 seconds may enable PHD to pick up the smaller movement of the stars easier.

For my setup the focal length of the finder guider is only 225mm @ f3.75 so i have found a calibration step of between 1800 - 2200 is best, now someone may disagree with me on the above exposure times but yes it does make sense to me & i am hoping i understood your quertey correctly.

Looks like it may be clear tonight as well

[Ewan]

Hi matt, i am out at the moment imaging M81 guider doing 10 minute subs but moon means ill stick with 5 mins, i Polar Aligned twice then slewed to M81 not far from Polaris, set Phd to 3.5 secs exposures on the main screen and the graph below shows the result.I finished Polar Aligning on Capella which was fairly low by the way.Drop me a pm if you need any more help.

[Mattjohnson1978]

Thanks Freddie and Ewan.

I got it in my head that 1000ms was the maximum. I must have mis-read. Just checked the spec of my miniguidescope and it has a smaller focal length than yours so 1000ms is way way of the mark. Gives me hope!

Thanks a lot guys, will let you know the outcome.

Matt

[Ewan]

Matt i have my calibration steps at 2000 for my 225mm focal lengh.

[Freddie]

The other thing to check is what guide rate you have set in your mount. You will have something like 0.5, 0.75 and 1. My default is 0.5 and that works well enough so I leave it at that to save having to change it each time. Suggested rates are between 0.5 and 1.

[lensman57]

Hi A.G.

I am interested in what equipment you are using for guiding. I am using the Orion Starshoot camera and mini guide scope.

Matt

Hi,

I am using an opticstar PL 131M through a 50 mm guidescope, the mount is EQ5 SynScan pro and is connected through GPUSB, the camera is very sensitive and I think the guidescope is about F3.4. The problem with me is a: I am impatient and b: like a lot of people living up north we don't often get clear skies so as newbie I need more experience to sort out my problems. I also think that havinga mount and scope-camera set up permanently could help a lot, this is not possible with my mobile set up. The next thing I want to do is use PHD for accurate polar alignment but again I'd need clear sky for about a half hour, and that is asking a bit too much.

Regards,

A.G

[Mattjohnson1978]

This is why I love this site...thanks a lot guys!

Without counting my chickens before they hatch too much, it does sound that is what I've been doing wrong. Can't wait to try it out!

And I feel your pain A.G. The weather in general has been pretty hopeless these last few months. Those long dark winter nights disappeared without notice over a blanket of cloud. Here's hoping for a clearer spring!

[Mattjohnson1978]

A.G. have you checked your Calibration Step rate on your setup? Because of the work shift pattern I'm on this week, I doubt I'll get a chance now till next weekend. I'm hoping your rate is set too low like mine and by increasing it to 2000+ will solve the issue. It does sound you have the exactly same symptoms as me. Would love to know how you get on if the weather gods are kind to you.

[Ewan]

Hi Matt, here is a copy of my settings it may / may not help you.

I can't comment on Freddies 'guide rates' as i think that is something specific to the mount you have, the only rates i have on mine are Sidereal, Lunar, Solar etc.

Last Settings 25-04 copy.doc

[Freddie]

Hi, if you have a look through your handset menu you will find tracking rate (siderial, lunar etc) but should also find guide rates. These are different things so it's worth having a look for the guide rate part of the menu.

[Mattjohnson1978]

Ok, this is the first time I've had my kit out since posting this thread and can confirm I am guiding beautifully. Changed the settings to 2000ms and it has solved my problem. I am currently taking 10 minute subs of M51.

Thank you all for your help!

Many thanks

Matt

[Ewan]

Nice one Matt let us know how it went for you.

[Mattjohnson1978]

Thanks Ewan.

Just to report back, I had beautifully pin point stars on 10 min subs, however, I have now become a victim of the thermal noise saga! Warm evenings plus long exposures unfortunately peppered my subs like acne on a teenagers face! I am still very new to this and know I need to find the right balance of exposure/ISO but I am eager to get very nice images so I am now investigating noise reduction by either cooling my DSLR (The condensation issue worries me about this) or by making the expensive step up to a cooled CCD. I'm getting there...!!

[kirkster501]

I read this thread with interest. I also have seen this issue of mount not moving enough when pointed to high in the sky. Shall try the fix myself!