Struggeling with unstable DEC

[Jannis]

I'm struggeling with my guiding, and looking at the PHD graph, it appears my DEC isn't staying stable, and i can't figure out how to correct it. 

I've attempted most settings in PHD, but it appears this issue might not be best to solve in a software, but on the mount mechanically?

Anyone else having this problem with the HEQ5?

Using QHY5L-IIM and the finderscope. Finderscope is fastend with extra screws to prevent the original spring loaded system to cause problems.

Balance is also good, but slightly off to givr the mount something to push against.

[Thalestris24]

Hi

I wish my guide graph was so good! The fluctuations in both axes might just be caused by the atmosphere - you can confirm this by monitoring the star profile and seeing changes in the star appearance that correspond to guide corrections. Also, you could try running the DEC guiding in one direction instead of Auto. You could also try increasing the Min Motion. It's also always worth running the Guiding Assistant from the Tools menu. What are your stars like in your images? They are the acid test!

Louise

Edit: Of course, fluctuations in DEC may be caused by backlash - the guiding assistant will measure that for you. Flexure is another possibility.

Also, there is a Dev5 PHD2 version available: http://openphdguiding.org/development-snapshots/

[StuartJPP]

My graph looks very similar. I need to investigate it a bit more as my stars are not perfectly round but they aren't too bad so I have spent the time outside imaging rather than tinkering. I am convinced that there is some underlying issue with QHY5L-II and similar cameras with PHD2...might not be but I need to investigate further.

Have a read of this thread...

http://stargazerslounge.com/topic/245567-phd2-this-might-explain-why-my-guiding-graph-isnt-flat/

[Thalestris24]

My graph looks very similar. I need to investigate it a bit more as my stars are not perfectly round but they aren't too bad so I have spent the time outside imaging rather than tinkering. I am convinced that there is some underlying issue with QHY5L-II and similar cameras with PHD2...might not be but I need to investigate further.

Have a read of this thread...

http://stargazerslounge.com/topic/245567-phd2-this-might-explain-why-my-guiding-graph-isnt-flat/

Hmm... Interesting, though it might be something to do with PHD2s  image processing rather than the camera itself. It bothers me a bit that I never seem to get the crosshair in the star profile in the centre of the guide star - it's always to one side. At the same time my guide stars behave more like amoebae - even with 4 or 5 sec exposures...

Louise

[Jannis]

My stars are random with 2 min exposures. Stars in some frames are perfect, while in other frames they are twice as wide as tall.

Oddly this is also the case if i disable DEC guiding.

As a siede note i left the 742 ir pass filter in place on the guide cam.

Also i capture with APT. This communicates with PHD as far as i know. Not sure how APT affects PHD though?

[StuartJPP]

Hmm... Interesting, though it might be something to do with PHD2s  image processing rather than the camera itself. It bothers me a bit that I never seem to get the crosshair in the star profile in the centre of the guide star - it's always to one side. At the same time my guide stars behave more like amoebae - even with 4 or 5 sec exposures...

Louise

Yep, I agree, I think the other thread mentions this, I haven't' focussed on this issue for a while but must try to get to the bottom of it....I know what you mean about the crosshairs not being right on the star but always offset a little...

[Thalestris24]

My stars are random with 2 min exposures. Stars in some frames are perfect, while in other frames they are twice as wide as tall.

Oddly this is also the case if i disable DEC guiding.

As a siede note i left the 742 ir pass filter in place on the guide cam.

Also i capture with APT. This communicates with PHD as far as i know. Not sure how APT affects PHD though?

I think it's just what the guide camera/scope see through the atmosphere. The imaging system will see the same but integrate over the much longer exposure. Guiding, though, will likely be affected. I use APT too but only affects things via dithering if you are using that (advisable for dslr imaging). 742nm IR filter? Why? I think IR filters have some strange effects on guide stars...

Louise

[Thalestris24]

Yep, I agree, I think the other thread mentions this, I haven't' focussed on this issue for a while but must try to get to the bottom of it....I know what you mean about the crosshairs not being right on the star but always offset a little...

I keep meaning to try out MetaGuide but never seem to get around to it!

[Jannis]

742nm IR filter? Why? I think IR filters have some strange effects on guide stars...

Louise

i just left it in place after looking for ir targets. It have an effect on stars indeed, but shouldnt affect PHDs ability to calculate the stars center?

I thought it might be seeing/turbulense as well, but its the same regardless if i use 1 or 5 sec exposures for guiding. Thought that long exposure would more or less solve seeing issued?

[Thalestris24]

i just left it in place after looking for ir targets. It have an effect on stars indeed, but shouldnt affect PHDs ability to calculate the stars center?

I thought it might be seeing/turbulense as well, but its the same regardless if i use 1 or 5 sec exposures for guiding. Thought that long exposure would more or less solve seeing issued?

Well I have problems even with 5-6 sec exposures You may get better guiding at 742nm - if you try it without, you'll find out!

Louise