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PHD - not enought movement


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Good luck Malcolm lets hope all the hard work pays off :(

Regards

Kevin

Hi Kevin,

Well, it's cleared up enough by 8.30pm to allow me to polar align using EQMOD, which was the goal for this evening (also suffering with a blinding headache so bed is calling ;) ). Anyway, just for a laugh, just to see if I could get calibration I tried PHD. Even though I've not drift aligned I was amazed just how close to the centre line the DEC trace was (RA was a different thing altogether, zig-zaging across the centre line... ) - at least it shows promise

I'm amazed that given how many of us newbies suffer with getting true alignment, even with permanent setups, how the guys do this in the field.

Weather forecast isn't looking good for the next few days, so it maybe some time before I get chance to continue with setting up the scope. Also at the moment with the moon so bright finding stars in the East at this time of night to drift align is a bit challenging :)

Right, couple of paracetamols and off to bed before this turns into a full blown migraine ... shame really as it's very rear we get three clear nights on the trot... :p

Edited by malc-c
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Following on from resetting the mount etc the other day, and doing a polar align a couple of nights ago, I've taken advantage of the clearing skies to do some DARV drift alignment and some further tests with PHD.

Without going into too much waffling, here are the traces I'm getting and a the result - a single 5 min exposure @800 ISO -the only processing is cropping to 1024 x 768 to suit forum regs

some slight ovaling of the stars, but it's a lot better than I was getting.

I've also attached my settings - comments welcome

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That looks pretty good to me... broadly similar to what I get.

I went out in that high wind the other night and my graph was all over the place and still the stars were OK.

You seem to have nailed it?

Ant

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Cheers Ant...

I think I've discovered one possible cause for the RA to be more erratic than the DEC. I noticed that the mount was making a regular deep "clunk" as if something was rubbing or catching... It seemed to be around the area where the RA setting circle is... I'm not that keen on removing the covers etc, but will try and investigate further...

Give the LP and other factors where I'm based, I can live with 4 - 5 min subs like that above, but it would be nice if I could tune it just that bit more

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If I forget to properly balance the scope I have noticed a clunk/click - which I've assumed is the clutch slipping.

What happens if you go for longer? I would think that with what you've posted you could go on for a lot longer?

If your polar alignment is off you may get field rotation - but the guiding should work.

Ant

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Reading another thread debating the use of short or long counterweight bars, I'm wondering if that has anything to do with it. I spent a lot of time on Friday balancing the mount in all axis (good old astronomy shed videos helped a bundle). However there must be different forces on the drive for different scope positions.... ?

I'll take a look at the clutches... it might of been that it was slipping a tad or I had over-tightened ?

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Have you tried increasing/decreasing your frame rate on your guide camera? You may be chasing the seeing, adding a second or 2 generally helps and remember seeing changes all the time and you may have to tweak this setting over a imaging period :)

Your DEC looks pretty much spot on and I would switch off auto and select north or south depending which way you have slight drift, this will stop over correction or bounce.

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Malcolm. Choose the exposure length according to the brightness of the star that you've picked. The latest PHD tells you when the star is saturated so you can reduce exposure time. I typically start at 2.5 seconds and change accordingly.

Also I've found that changing the calibration step has a greater effect on the smoothness of the graph and guiding than the other settings. Try a higher step (say 1000) and when the graph is smoothish play with the other settings. With my NEQ6 set to a RA guide rate of x0.2 I am using a cal.step of 1200 and my graph is pretty much flat.

Hope this helps :)

Mark

Edited by mark7331
Forgot some details. :)
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Mark,

I've just tried your suggestions and here is the trace. Just running off some 5min subs of M31 and all is looking good (apart from all the airccraft coming into Luton Airport and lighting up the sky !)

post-23388-133877665613_thumb.jpg

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Malcolm that looks better. Your graph looks good and stable. Getting good five minute subs is a major achievement. :glasses2:

I've been really trying to push PHD and now I'm getting an almost flat line on the graph but to be fair I only have clouds to contend with not an airport! :rolleyes:

I think with a bit of tweaking you could get your RMS down a little (and maybe longer subs if you need them). My OSC is usually about 0.30 and RMS 0.11 although I had it down to 0.06 yesterday. Since you have the same guide scope/camera as me I wondered if these settings would work as well for you? I am now able to reliably get 15 minute subs depending on the seeing.

My current settings (which have lasted three sessions now) are:-

EQMOD guide rate of x0.20

Guide exposures of 2.5 seconds.

CalStep 1500,

RA Agr 80,

RA hyst 12,

MinMo 0.15,

MaxDec 110.

EW calibration happens in 22 steps and NS in 10 steps.

I hope this is useful info. It'd be nice to be able to build up a picture of some useful groups of settings.

Regards

Mark

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Mark, thanks again for the input. I'll have to try your settings another night as the clouds have now rolled in and I'm calling it a night. Just before I closed down I was running an 8min sub on M45 just to see what the results are... but that will wait until morning to process the image...

Sounds like you too are getting the results.. 15min subs - WOW !

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Keep posting, this thread has been quite helpful for myself as well.

Thanks for the encouragement, and I'm glad it's been of use to you and hopefully others. It's been a steep learning curve, but thanks to forum members I think I've finally got to a point where I can guide for the limits of my camera and location.

Here is the end result. This was taken from the last image I took of M45, its a single exposure, and I ended the exposure after 482 seconds (just over 8 minutes) as the clouds strated to cover that part of the sky. I've set the camera to dump both RAW and JPEG images, and this image is the JPEG copy. The only "processing" I've done to this image is to resize it to comply with the 1024 limit of the forum, and to copy a section at 100% so you can see the star in more detail. - Also the image on my PC doesn't have that green tinge that seems to happen when JPEGs are uploaded to the forum

I'm happy enough with this result, and whilst the tracks in the graph are not as flat as other PHD users, I feel they are good enough for quality of skies I get from my back garden

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Looks brilliant. Really nice round stars - even the small ones. :glasses2:

I'm happy enough with this result, and whilst the tracks in the graph are not as flat as other PHD users, I feel they are good enough for quality of skies I get from my back garden

You know I think the graph can be misleading. That's why I always take a sub to actually see what's happening. Who cares if you have a lumpy graph when you can take 8+ minute subs like this. :rolleyes:

I think you've cracked it! Nice one.

Mark

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George, thanks for the tip. I was typically running at 1s - might try 2 or 3 next time

Malc I think this has been your main problem, 2 seconds and upwards is generally the norm for UK seeing and obviously the nearer the horizon the worse the seeing.

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Well strange how things change from one night to the next. last night I tried tweaking the PHD settings and it all went astray... plauged by dew, and flat batteries in the camera.

Tonight, EQMod has found each object without being miles off target, even with high humidity my DIY card dew shield seems to be working, and PHD has given me my smoothest trace yet - and I've not changed anything !!

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I was just about to post myself on exactly the same subject with exactly the same issues. I have an LX-90 8" ACF with the new 'Audiostar' handbox. I did wonder if this was the problem, but it does connect and works fine with the Meade software. Piggybacked to this I have an ST80 with a QHY5!!

The calibration stage (PHD) did not come up with any errors, but the guiding stage never seemed to guide. The guide stars (because I tried different brightness and sizes) would just gently drift down the screen with no change in rate between guiding or not and within a few moments the buzzer would sound.

I tried numerous combinations of settings, bit none seem to make any difference, or if they did it was only for a brief time. The only setting I don't remember changing is the minimum motion.

I am using the Meade with Autostar 1 Ascom driver. Can anyone confirm this is the right one? It was my impression that it is, but then I did wonder what is an Autostar 2? Is there any other Guiding software worth trying, bearing in mind this is not an EQ mount or similar - it is a Meade Alt-Az on an equatorial wedge accurately polar aligned with WCS.

Any further help or suggestions will be greatly appreciated, in the meantime I shall persevere.

Yours aye - David

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