PHD2 options

[Stub Mandrel]

34 minutes ago, newbie alert said:

Not sure on that myself..those rms figures suggest excellent guiding so id of thought wouldn't have elongated stars 

No DEC guide pulses and the big give away is that DEC mode is showing 'OFF'. ?

 

[Stub Mandrel]

34 minutes ago, newbie alert said:

Not sure on that myself..those rms figures suggest excellent guiding so id of thought wouldn't have elongated stars 

No DEC guide pulses and the big give away is that DEC mode is showing 'OFF'. ?

 

[Anthonyexmouth]

32 minutes ago, david_taurus83 said:

I tried Sharpcap first but I got different results when I checked either side of the mount. So I had to try drift aligning. It then became clear I had mechanical backlash problems and the rubbish weather we had in Spring kept cutting short my drift align sessions so I caved and bought the Polemaster. But in the QHY documentation it states to rotate the mount using the handset. When I tried Sharpcap I was loosening the clutches to rotate the mount. I often wondered if this was the mistake I was making. Do you use the handset with Sharpcap?

i use the eqmod controls to rotate. wonder whats making PHD and sharpcap PA so different on my setup. 

[spillage]

Sorry I do not want to hijack the thread but would like to thank @Thalestris24 for her comments on my phd target. I have now been out to the mount and added an adjustable weight on the back of my scope so hopefully tonight I can make some small adjustments and improve my tracking.

[Thalestris24]

5 minutes ago, spillage said:

Sorry I do not want to hijack the thread but would like to thank @Thalestris24 for her comments on my phd target. I have now been out to the mount and added an adjustable weight on the back of my scope so hopefully tonight I can make some small adjustments and improve my tracking.

Just my own experience - hope that improves things!

Louise

[newbie alert]

26 minutes ago, Stub Mandrel said:

No DEC guide pulses and the big give away is that DEC mode is showing 'OFF'. ?

 

There's no corrections on either axis even thou corrections box is ticked..

As a separate issue,I've seen  the line at the top on a few people's guide graphs and don't know what it's for..any ideas?

[Stub Mandrel]

16 minutes ago, newbie alert said:

There's no corrections on either axis even thou corrections box is ticked..

As a separate issue,I've seen  the line at the top on a few people's guide graphs and don't know what it's for..any ideas?

You can see the little blue RA pulses on the graph.

From memory the top line is related to guide star quality.

[spillage]

The white line shows you how good the seeing is for the guide star. I posted the screen shot from last night just to show the op that overtime you learn (I am still learning) how to tweak your mount to get the best out of it. It was between .45" and .36" over the 45 minutes I got last night. I have spent ages tuning the mount the best I can following astro_babies guide on hypertuning and have stripped the mount several times. I am still not happy with the RA movement and backlash but have come to understand this is just how it is and to get on with it.

Some nights it just decides not to play nice and I am lucky if rms keeps below 1". Last night it played nice. I would not bother posting a screen shot that was incorrect or there to deceive anyone.

I am only 45 minutes away form the op and if at any point he wanted to come over then he is more than welcome.

[newbie alert]

2 hours ago, Stub Mandrel said:

No DEC guide pulses and the big give away is that DEC mode is showing 'OFF'. ?

 

Sorry so there is..i didn't zoom in enough and used to seeing bigger corrections than those..

 

[AstroAndy]

Hi

 

Here is what I would do

PA as on the nose as possible, mount level by doing) drift alignment, calib. steps abt. 3000, first az (meridian), then longitude, then az again, then longitude again  (because as you move in one direction, a little error will be created in the other, iterative drift align will reduce this)

Set Agressiveness between 70-99 (if too much, considering other factors, such as the min. motion, you'll get zig zag patterns (correction on both sides, due to "overshooting of the star position of the center line), if too little, the lines (RA and dec., ie, the star position, won't catch up w/ the center line), min mo., 0.15. Dec. Agressiveness should be at 100, exposure, 3 or 3.5 (short exposures and little Min. mo. make you "chase the seeing". Aggresiveness (or minimum motion) can be changed by small values (say 10 for RA, maybe .5, or less, for min. mo.) when watching the graph to see how things are going

Why these values? From the sig, I see a 9x50 guider (180mm focal length, cam? don't know pixel size, abt. 5. something, maybe).

Looking at your graph, it's not that bad, if you look at the rms for RA and dec. separately, you get the answer for your trailing (if the values differ abt. 2-3 times, trailing happens, if the values are too big, bloated stars happen, RA osc., as Louise said, should be around 0.5).

This assumes flex has been looked at, and other conditions (strong winds, etc).

Andy

[newbie alert]

1 hour ago, spillage said:

The white line shows you how good the seeing is for the guide star. 

Some nights it just decides not to play nice and I am lucky if rms keeps below 1". Last night it played nice. I would not bother posting a screen shot that was incorrect or there to deceive anyone.

 

Firstly,can you turn on/off the guide star line in tools or somewhere?

I'm not saying that you're trying to deceive anyone..so please don't take it that I am..we all learn from each other..from our own mistakes usually.. 

For me personally I try also to keep under 1 min RMS if I can  it some nights conditions just won't allow it..wind..seeing etc.. if you're having eggy stars to me it suggest drift in 1 axis..do you think it's because of the backlash in RA? With a belt mod and RA driving the mount id think that's unlikely but as I've never had rms figures that low and I'm not using a mount that's belt driven..

[Anthonyexmouth]

Well. this is interesting , or maybe it isn't. trying to polar align and drift align with phd2 is a nightmare, all over the place. but turned guiding off, PA with sharpcap and took this 10 min sub of M101 

thoughts? why is PHD such a problem for me

 

[Anthonyexmouth]

3 hours ago, AstroAndy said:

Hi

 

Here is what I would do

PA as on the nose as possible, mount level by doing) drift alignment, calib. steps abt. 3000, first az (meridian), then longitude, then az again, then longitude again  (because as you move in one direction, a little error will be created in the other, iterative drift align will reduce this)

Set Agressiveness between 70-99 (if too much, considering other factors, such as the min. motion, you'll get zig zag patterns (correction on both sides, due to "overshooting of the star position of the center line), if too little, the lines (RA and dec., ie, the star position, won't catch up w/ the center line), min mo., 0.15. Dec. Agressiveness should be at 100, exposure, 3 or 3.5 (short exposures and little Min. mo. make you "chase the seeing". Aggresiveness (or minimum motion) can be changed by small values (say 10 for RA, maybe .5, or less, for min. mo.) when watching the graph to see how things are going

Why these values? From the sig, I see a 9x50 guider (180mm focal length, cam? don't know pixel size, abt. 5. something, maybe).

Looking at your graph, it's not that bad, if you look at the rms for RA and dec. separately, you get the answer for your trailing (if the values differ abt. 2-3 times, trailing happens, if the values are too big, bloated stars happen, RA osc., as Louise said, should be around 0.5).

This assumes flex has been looked at, and other conditions (strong winds, etc).

Andy

i'll read through this properly in the morning. when i try and drift align it waves all over the place, the tiniest turn on the know can send it miles in one direction according to the PA error. can sway from 5-100 . oh, cam is an ASI120 mono

[newbie alert]

Once you have phd up and running it won't be such a chore..what you're trying to do is make it work with your setup ..backlash etc..

Looks like you have decent PA with sharpcap..run with that and maybe go back to drift aligning at a later date....you will get decent results with what you have there....as regards to adjustments..tiny tiny micro not even turns are needed at the latter stages....do some guiding with what you have there...good luck

[Thalestris24]

Hi

The calibration needs to be good. You also need to be fairly close with the PA to start with to use the drift align tool. However, there is a polar drift align tool which will get you close. I've never used it but have seen the tutorial vid. You do only need very small adjustments once you are close. There's a bit of a knack to it... Also, if you have any flex or inbalance, that can muck things up.

Louise

[david_taurus83]

I setup with the Polemaster tonight and after I ran the Sharpcap polar align with the Polemaster camera on the polar scope axis. Sharpcap initially said I was 1 minute out, which is typical of what PHD usually says. So I adjusted via Sharpcap down to excellent. PHD rms is around 0.55"... Got a funny calibration report but guiding is going good so far. Gathering 10 min Ha subs on the Veil

[Stub Mandrel]

8 hours ago, Anthonyexmouth said:

why is PHD such a problem for me 

I wouldn't worry.

Last night I set up and decided to try the new PPEC, but realised I had an old version. I decided to try different guide algorithms lowpass 1 for RA and lowpass 2 for DEC.

I ran the guiding assistant then got sub-arc-second guiding for about 15 minutes, but after 'dobbing' for a bit I came back to seethe DEC line was just a huge zig-zag. Some though and I realised it had hugely overestimated the backlash and reducing the figure by about 50% brought things back to normal. It was then OK for a while, but then the same zig-zag  thing started as the algorithm had auto-increased the values again.

I changed DEC to lowpass 1 as that seemed to be working for RA, I had to have a bit of a fiddle to tune it, but reducing minimum move made quite a difference. I was then getting guiding at about 0.6" RMS which is as good as I've ever had.

I'd love to say that's the end of the story, but at some point the mount seems to have simply stopped tracking in RA while DEC gradually drifted downwards. luckily I caught this when it had only ruined 1 or 2 subs. It was easy to slew back on target and from there on everything was dandy.

 

Lessons learned: (1) experiment with different guide algorithms and (2) don't always trust the 'brain' button!

[Anthonyexmouth]

i guess my initial problem is understanding why sharpcap and PHD are so out of sync when it comes to polar alignment. 

[newbie alert]

57 minutes ago, Anthonyexmouth said:

i guess my initial problem is understanding why sharpcap and PHD are so out of sync when it comes to polar alignment. 

I find on my own experience that polemaster,sharpcap and drift align in phd2 are all different 

[Thalestris24]

Drift aligning is the gold standard - with or without PHD2 tools! Nevertheless, at shortish focal lengths you should be able to get unguided subs of several mins in length before egginess sets in. Running unguided is a good way of showing up any fundamental problems. When guiding, make use of the star profile tool and snr figure to make sure you're using a decent guide star. 

It's a dark art - nobody ever said it was easy!

Louise

[Anthonyexmouth]

 

9 minutes ago, Thalestris24 said:

Drift aligning is the gold standard - with or without PHD2 tools! Nevertheless, at shortish focal lengths you should be able to get unguided subs of several mins in length before egginess sets in. Running unguided is a good way of showing up any fundamental problems. When guiding, make use of the star profile tool and snr figure to make sure you're using a decent guide star. 

It's a dark art - nobody ever said it was easy!

Louise

what would you say about the 10min sub of M101 i posted last night. that was unguided. are there any clues in the trails to suggest anything other than polar alignment slighly off? here is the guided one taken just before i tried unguided. no changes to the mount were made between these shots. just switched off PHD

[Stub Mandrel]

16 minutes ago, Anthonyexmouth said:

what would you say about the 10min sub of M101 i posted last night. that was unguided. are there any clues in the trails to suggest anything other than polar alignment slighly off?

As far as I can tell north is more or less up in this image, as the trails are not horizontal there has to be some PA error.

In a perfectly aligned mount there is no DEC error. Angled trails are the give-away for PA error.

If it was pure PA error the trails would be completely even, so there's clearly either periodic error or something else making RA movement irregular as well.

In guided subs you often see stars stretched or distorted vertically caused by sticky, unbalanced DEC or too much DEC backlash.

[Thalestris24]

The guided one above is showing the effects of some kind of movement - vibration, wind,snagging? I don't know what you have your tripod on? Keep well away from the mount/scope when you are exposing. Also, the guiding doesn't seem to be working!

The 10min unguided sub looks very good (much better than I'd have expected!) albeit with some problems, and suggests your PA must have been good. If you have guidescope flex that will mess things up when guiding. Make sure your guidescope is solid. If you'd have asked me which one was guided I'd have said, at a glance, the 10 min one was guided and the most recent one above was not! The above one shows a lot of drift - can't tell if it's in RA or DEC.

Louise

[Anthonyexmouth]

6 minutes ago, Thalestris24 said:

The one above is showing the effects of some kind of movement - vibration, wind,snagging? I don't know what you have your tripod on? Keep well away from the mount/scope when you are exposing.

The 10min unguided sub looks very good (much better than I'd have expected!) and suggests your PA must have been good. If you have guidescope flex that will mess things up when guiding. Make sure your guidescope is solid. If you'd have asked me which one was guided I'd have said the 10 min one was guided and the one above was not! The above one shows a lot of drift - can't tell if it's in RA or DEC.

Louise

wouldn't the wind,vibration,snagging have shown up in the unguided one too? guided one was immediately before the unguided one. would it be worth putting my guide cam on my ed80 and just see how well it guides? see if its the cam/guidescope combo

[Thalestris24]

5 minutes ago, Anthonyexmouth said:

wouldn't the wind,vibration,snagging have shown up in the unguided one too? guided one was immediately before the unguided one. would it be worth putting my guide cam on my ed80 and just see how well it guides? see if its the cam/guidescope combo

Yes, that's true! Do you have the guide log of the guided one? The image suggests you have significant differential flex or some other fundamental guiding problem... What was the guide star profile like? The guide scope needs to be solid relative to the imaging scope. You're trying to guide to within arc seconds - 1/3600 th of a degree, so even tiny relative movements will cause problems. That's why I suggested ditching the finder shoe before.

Louise