PHD Settings for QHY5 on OAG with MN190

[Gina]

As the title says, I'm now using PHD with the QHY5 guide camera on an OAG with my MN190. I was previously using the QHY5 on an ST80 for guiding and I think I got the settings for that - using an ED80 for imaging. Now with my current setup I'm having problems. I realise, of course that the star field is much narrower and less bright and that I may need a more sensitive guide camera. But I'd like to know if I could improve things by changing settings. Calibrating on a star acquired with the "Auto-select star" feature is working fine, once I get a star or two in the PHD frame, but then it often won't guide in Dec - the red line on the graph just descends off the bottom. Sometime it has guided but the guiding shows about twice the variation that I had with the ST80. I've attached screenshots of the PHD graph and Settings and wonder if anyone can help, please.

[lukebl]

Not sure about the dec drifting off, but I think your jagged graph is simply a product of guiding at a longer focal length and not necessarily a problem. I may be wrong, but minor movement in the guide star will be accentuated at the higher magnification, but won't necessarily affect the image quality. I use an OAG at 1200mm fl, and my graph is similar to yours although the stars in the resultant images are round.

[Gina]

Yes, I guess my guiding is alright when it's working as I'm getting nice round stars with 5 minute subs. I think the Dec graph line slinking off to the bottom may indicate poor PA as I've read that Dec guiding shouldn't be necessary if PA is good. I can see the logic of that - the earth rotates about the polar axis and if the mount axis is parallel to this only RA correction is needed. I shall do a PA tonight and try out the AstroTortilla PA feature, unless the clouds come back or mist comes in. I checked my mount this afternoon and found the central bolt had come loose so I tightened it up again finger tight - can't be too tight as that would prevent azimuth adjustmant. Now azimuth adjustment is stiff but not too tight.

[Merlin66]

Gina,

I was using the PHD "vanilla" defaults when using the QHY5 guide and a beamsplitter on the C9.25 at f10.

No issues, no drama - it just locked the target star onto the 25 micron slit for at least 10min subs. (NEQ6pro/CdC/AP2)

Never even bothered looking at the graphs - the results spoke for themselves.......

[Tim]

Gina, only just seen this, will get in touch or reply properly after a few hours sleep!

[Tim]

You should be able to calm that graph right down, but do your utmost to totally nail polar alignment first. Check it on a part cloudy night by letting the mount run. You should be able to keep a star pretty much centred in an ep or camera for a few hours. Give the guiding as little as possible to do!

When that is right I can give you better settings for PhD, but need a new graph from the realigned mount :-)

[RAC]

I just use PHD to help me PA. I do a calibration then just run a very wide min motion so phd doesn't do anything but watch the star and tell me what the drift is. Do this looking straight up and then to the east or west like you would with normal dfift alignment and you can get it way closer than any visual way of doing it and its way faster. I should look at doning mine again as the last time i did this was about a year ago.

[Gina]

Gina,

I was using the PHD "vanilla" defaults when using the QHY5 guide and a beamsplitter on the C9.25 at f10.

No issues, no drama - it just locked the target star onto the 25 micron slit for at least 10min subs. (NEQ6pro/CdC/AP2)

Never even bothered looking at the graphs - the results spoke for themselves.......

Thank you I'll have to check what the defaults are.

[Freddie]

Hi Gina, I found a similar thing to you having moved from st80 to OAG on my MN190, guiding not looking as good on the graph as it did. I however think this is just down to the scales not being the same on the graph from the original setup to the new one. Mine isn't as bad as yours (stays easily within half a division of the centre line) but has definitely changed slightly. Your red DEC line moving off is an indication (as said) of PA being slightly off. A change in RA and Hist may improve things. Defaults are 100 and 10 and with a OSC up at .5 the suggestion from PHD is to reduce RA and increase Hist. Mine (with Lodestar) are 85 and 10. Also check you are still getting a decent number of steps when calibrating as again this may have changed with your new setup. I use 3 sec exposures, have min motion at 0.1, and max dec at 150 all in an attempt to stop PHD making guiding adjustments when they aren't actually needed. Hope that helps.

[Gina]

You should be able to calm that graph right down, but do your utmost to totally nail polar alignment first. Check it on a part cloudy night by letting the mount run. You should be able to keep a star pretty much centred in an ep or camera for a few hours. Give the guiding as little as possible to do!

When that is right I can give you better settings for PhD, but need a new graph from the realigned mount :-)

Thank you Tim I did a PA last night and got it much closer. I checked the mount adapter yesterday afternoon and found it was loose - the central bolt had come loose. So I took the mount and adapter off and tightened the bolt finger tight again - just enough to hold while allowing PA azimuth adjustment. This was then stiff but not tight. Then put everything back ready for PA at night. Used the electric winch for mount and scope - very handy

[Gina]

I just use PHD to help me PA. I do a calibration then just run a very wide min motion so phd doesn't do anything but watch the star and tell me what the drift is. Do this looking straight up and then to the east or west like you would with normal dfift alignment and you can get it way closer than any visual way of doing it and its way faster. I should look at doning mine again as the last time i did this was about a year ago.

Thank you - I'll try that tonight if we see any stars

[Gina]

Hi Gina, I found a similar thing to you having moved from st80 to OAG on my MN190, guiding not looking as good on the graph as it did. I however think this is just down to the scales not being the same on the graph from the original setup to the new one. Mine isn't as bad as yours (stays easily within half a division of the centre line) but has definitely changed slightly. Your red DEC line moving off is an indication (as said) of PA being slightly off. A change in RA and Hist may improve things. Defaults are 100 and 10 and with a OSC up at .5 the suggestion from PHD is to reduce RA and increase Hist. Mine (with Lodestar) are 85 and 10. Also check you are still getting a decent number of steps when calibrating as again this may have changed with your new setup. I use 3 sec exposures, have min motion at 0.1, and max dec at 150 all in an attempt to stop PHD making guiding adjustments when they aren't actually needed. Hope that helps.

Thank you Freddie - should be a great help Yes, I agree the graph is expectedly worse, going fromm 400mm to 1000mm FL. Before altering any settings or PA, about twice as bad as expected. Thanks for you settings values

[Gina]

It was clear last night so I had another go at improving my PA, this time using AstroTortillato see how good the PA rioutine was in that. I have to say it makes it remarkably easy and quick.

Point the scope east (or west) using CdC or whatever, set the capture program running and getting a few stars, then run the PA menu item in AT and click "Measure altitude error". I'm using the file menu option to choose a capture file so select file and AT will solve it. AT/PA then slews a bit and asks for the new capture file which it solves. It then calculates and displays the result. You can then adjust the altitude bolts accordingly and try again. Once satisfied with altitude the same procedure is used for azimuth but with the scope pointing a bit west of south.

Initially the errors were just under half a degree too high in altitude and 11 mins west in azimuth. After tweaking I got the altitude error down to just under 1 arcminute too low and the azimuth to just under 2 arcseconds east. I'll try the advice of running PHD without guiding next time the stars are visible and see what happens, though I think I know . I tried imaging late last night but guiding was still bad with the Dec going off the top this time. I did eventually manage to find a star that would guide though not very well - evidently PA is still not good enough.

Here is a screenshot of my results after a bit of tweaking the mount. I thought this was good enough but evidently not. I would think the altitude is the main culprit being the furthest out.

[Gina]

I think I need to don my mathematician's hat and see if I can work out some geometry

[Freddie]

CCD to Align Your Scope.pdf

Give this a go. Works very well.

[martin_h]

Seeing as you have PHD and a QHY5 you could try drift aligning with them using this method ........

Also if you want the default settings in PHD, open the brain icon and hover your mouse over the individual settings windows, the defaults will show in a hints window.

[russellhq]

Gina, I use this program to analyse my PHD logs, it's very good and gives a lot of useful info:

http://countingoldphotons.com/phdlab-intro/

[Gina]

Thank you chaps Yes, that's how I did it before - (drift method) but it was some time ago now though I don't see how it could have changed it was well out when checked with the AT/PA method.

[Gina]

Gina, I use this program to analyse my PHD logs, it's very good and gives a lot of useful info:

http://countingoldph...m/phdlab-intro/

Thank you Russell - looks very interesting, I'll check it out

[Tim]

If you drift align properly Gina , then your alignment cant be wrong. Programs will get you close, but tweak it on an actual star over a few hours. I use PhD to do this too :-)

[Gina]

If you drift align properly Gina , then your alignment cant be wrong. Programs will get you close, but tweak it on an actual star over a few hours. I use PhD to do this too :-)

Thank you Tim I'll have another go at that. There's a possibility of some gaps in the clouds tonight so I might get something done.

[Gina]

Too cloudy last night to do PA

[jezhughes]

Hey Gina

Have you tried 'Align master'? I don't use it that much (use PHD) but its great for a quick drift correction. Takes about 5 mins, but you need EQ MOD up.

J

[Gina]

Hey Gina

Have you tried 'Align master'? I don't use it that much (use PHD) but its great for a quick drift correction. Takes about 5 mins, but you need EQ MOD up.

J

No, I don't think so - thanks for your suggestion

[jezhughes]

No, I don't think so - thanks for your suggestion

Its worth a bash, i've compared it against PHD drift align a few times and every time i've used align master before hand my drift alignment has come out almost spot on. Other's opinion may differ