First night with Guidescope and PHD - Guiding Results

[cpartsenidis]

Hello everyone,

Tonight was my first night with my new guidescope and guide camera. I thought it would be a bit too much to try and photograph something, and instead dedicate the night to play around with the new setup.

I'm using PHD Guiding, with a QHY5 Mono camera mounted on a Skywatcher 50mm guide scope. The QHY5 is guiding my CGEM mount.

The initial trial went pretty good, but as the night progressed, the results got worse. I consider my alignment to be OK as the objects selected came almost in the center of my crosshair eyepiece used for alignment.

I also performed a 2 star alignment with 4 calibration stars.

After around 2,5 hours playing around, I got the follow results from PHD (attached picture), which was certainly not acceptable and I'd like your input as to what might have gone wrong.

If anyone can share their setup or recommendations, it would be much appreciated.

Keep in mind that I have never performed any PEC on my mount, nor do I know how exactly it should be done at this point of time

Many thanks,

[swag72]

I use a QHY5 and a SW 9x50 finderscope for guiding. I am not good at trying to diagnose problems with guiding, but your settings look rather different to mine and these get me a nice flat graph (Using an HEQ5) - I'll post them so you can see whether a tweak of the settings will help.

[RogerTheDodger]

Was the calibration done in a different declination to where you were imaging?

[cpartsenidis]

Thanks for your replies guys!

Swag, I'll definitely try out your settings and see if they make any difference.

Roger, I setup the equipment at my home for the first time and started to do the guiding to see how it works. I actually didn't worry about imaging as I wanted to first figure out the tweaks on PHD Guide.

Hope that answers your question

Any other suggestion from those experienced imagers out there ?

[Digz]

Was the calibration done in a different declination to where you were imaging?

I think what Roger is getting at did you move the scope after calibration of PHD to another part of the sky before starting to guide?

A few simple checks - was anything snagged? RA and DEC axis locked off - clutch may have slipped?

There might have been some high level clouds whic obscured the guide star, also you might be chasing the seeing at 1.5s, try upping this to 2s, along with Swag's settings.

HTH

[Davey-T]

Took me a while playing with settings to get PHD working OK.

You need to calibrate in the area of sky where your imaging.

Also join stark-labs-astronomy-software yahoo group for lots of advice

Davey-T

[cpartsenidis]

Lee,

I initially setup it up to guide a star, then moved the scope to another part of the sky and then again back to the original star

Apart from this though, I performed a calibration everytime. I would exit PHD and start it up again so it can perform the calibration.

I did change a few of the values found in the advanced menu, but I'm not sure if that could explain the massive zig-zags I managed to produce

I can however guarantee that the scope was not bumped or moved from its initial setup.

One thing that I was really struggling with was the focusing of the guiding camera - After reading and testing, I think I got it right

[Digz]

Ok that's knocked that on the head then, Technic looks sound.

I never tinkered with the advanced settings until recently when my guiding went haywire. I changed some of the values, but can't find any screen shots of what I used. I would strongly suggest trying the settings above.

Focussing can be a real pain. One thing I found out recently is that being slightly de-focussed can actually help PHD, as the guide star becomes bloated an easier to lock onto I guess.

[cpartsenidis]

Lee,

Thanks for your input. Defocusing the guide scope might help, however from what I've read, it wouldn't help PHD 'catch' minor errors, so the actual guiding might not come out to be that precise I guess?

I'm going to try the values suggested and post my results. I just have to wait for the dam weather to sort itself out as its been cloudy all week!

Thanks,

[Davey-T]

You don't need to exit PHD to recalibrate just click on the brain and tick the force calibration

box

Davey-T

[Starflyer]

The Dec line is drifting off quite quickly, if you can try and get your polar alignment closer that will certainly help.

Increasing the Max Dec duration (ms) setting to around 750 / 1000 will help keep it in check but you should try and get your polar alignment better

[Farooq]

Yesterday I replaced my latitude bolts and although the setting on the mount is as it was previously. On my PHD graph the Red Dec line starts gradually going downwards and off the graph over a period of time. The RA is virtually level.

Any pointers on what that could be. I cannot do visual polar alignment, and I only have views of the sky between NE to SE and from 25degs up to 55degs.

[Shibby]

How did you perform the polar alignment? Poor alignment will show up primarily as a drift in the DEC axis, as you are experiencing.

As has been mentioned, increasing the DEC rate (this in a setting in the ASCOM panel, not PHD) will help you recover more quickly, preventing it from drifting off the scale, but ideally you should tackle the source of the problem.

cpartsenidis, you didn't by chance cross the meridian while guiding did you?

[Starflyer]

Yesterday I replaced my latitude bolts and although the setting on the mount is as it was previously. On my PHD graph the Red Dec line starts gradually going downwards and off the graph over a period of time. The RA is virtually level.

Any pointers on what that could be. I cannot do visual polar alignment, and I only have views of the sky between NE to SE and from 25degs up to 55degs.

This thread will tell you how to use PHD to perform a fairly quick, fairly painless drift alignment. Use google to find other info on drift aligning, it's the only way you can do it if you can't see polaris or don't have a polar scope.

For any sort of long exposure imaging you need reasonably accurate polar alignment. This isn't something you can guess, it just won't work. Guiding can only combat a certain amount of polar alignment error, and with longer exposures you'll start to see field rotation even if it appears to be guiding correctly.

Oh, and don't worry about PEC it isn't the problem, if you can sort the basics out it'll all fall into place

[Uranium235]

Firstly, nail your polar alignment. Do your alignment and calib stars, then use the software PA routine to polar align. After that, update your initial two alignment stars as they will have moved a little bit (depending on how far your PA was off), do the same for your calib stars if you want a spot-on goto.

Next (very important), use these settings:

RA Agressiveness: Usually between 60 and 90

RA Hysteresis: 30

Max RA Duration: 200

Min Motion: 0.05 (the important bit)

Calibration step: 2500 or 3000

Dec guide mode: open to whatever the conditions dictate - default = Auto

Max Dec duration: 285

Leave the other settings at default, set your loop time to between 1.5 to 3 seconds (depending on sky conditions) you will never fail to pick up a star.

You know its working right when you get a graph like the one attached, and that was with a finderguider on a CG5 which is of a much lower spec than your mount (same Nexstar system though).

[Farooq]

Thanks, I tried your suggested settings. I am now finding that my Dec is almost flat,however my RA is oscillating below the centre line. What could that be due to ?. Also where is the max RA duration setting ?

[Uranium235]

Thanks, I tried your suggested settings. I am now finding that my Dec is almost flat,however my RA is oscillating below the centre line. What could that be due to ?. Also where is the max RA duration setting ?

Just increase your max RA duration + aggression until it starts to respond. Different mount = slightly different settings, so just play around a bit.

Make sure you have the latest version of PHD, your settings screen should look something like this:

[Uranium235]

The latest 1.13 version can be downloaded from stark labs here:

http://www.stark-labs.com/downloads_files/Setup_PHDGuiding.zip

Well worth updating

[Shibby]

Personally I wouldn't dare because for the moment it "aint broke"! (My guide graph brought a tear to my eye the other night - RMS 0.07)

[Uranium235]

Absolutely, if its working - dont mess with it!

Its all about finding out about whats right for your mount by trial and error, once youve cracked it for your setup - you can use those settings for eternity (assuming you dont change your guidescope!).

It took me at least 6 months to start getting to grips with PHD and the foibles of my mount, I remember many long nights sitting in the shed screaming at a PHD graph thats wandering off into the stratosphere

The only thing that sends my PHD into a hissy fit is backlash, which is all down to the mount, not the software.

[cpartsenidis]

Hello everyone,

I managed to successfully perform my first proper PHD Guide last night!! Following the advice provided from this thread, I performed a 2-Star Alignment and then moved to the Polar-Alignment routine (for the first time) and the results of PHD were (I believe) well within acceptable limits.

I also tried to take a few snapshots using my Canon400D, but discovered that nebulosity requires a special "long-exposure" adapter in order to take shots greater than 30 seconds - which is a real bummer. I wasn't aware there was such as limitation with this camera.

Can someone else confirm this? Is it really necessary to purchase the D2USB device to connect the camera with the PC for long exposures?

I also have a wireless remote control kit that can be programmed to instruct the camera to take images for as long as I want, so I'm thinking of using this with nebulosity, rather than forking out more money for the adapter.

Any suggestions are welcomed.

Thanks again

Chris.

[swag72]

For longer exposures, you can use EOSUtilities that came with the camera and connect the camera to the PC. EOSUtilities will fire up once it recognises the camera and from there you can select bulb setting and control the length of exposures as well as the number.

As I recall, the bulb setting is in the Manual mode and you scroll through, past the 30s exposure and there it is. I used EOSUtilities to control my camera for ages. The other alternatives are APT and BackyardEOS whcih you have to buy, but you can get them on a trial period. I *think* they support the 400D.