Jump to content

stargazine_ep46_banner.thumb.jpg.34e6cdd5a0856b006a0b47c6373eb9b1.jpg

PHD - not enought movement


Recommended Posts

I'm already grey and now frantically pulling my hair out...

Whilst it's not ideal for imaging DSO's with an almost full moon around, I'm trying to use this rare clear night to test the equipment and try to get to grips with guiding. So far I've only managed to get PHD guiding once in the three sessions I've used it. Tonight it keeps erroring with a message that the star didn't move enough.

I've tried various exposures, different stars (now more in focus than before) and still no joy !!

Any ideas ?

Link to post
Share on other sites
  • Replies 72
  • Created
  • Last Reply

Top Posters In This Topic

Not changed anything other than the exposure times (0.5, 1, 2 sec) and the gain slider

the mount is shown drift over a 3 min exposure so the star should be moving around ?

When it says star is not moving enough, thats an error from the calibration step. PHD calibrates (look at the status bar) then starts to guide.

PHD needs to move the mount around to see how far the star goes when it blips the mount.

If it can't calibrate, it can't work out how to correct star drift as such it won't guide.

Look in the settings for aggression and increase it a bit. Then watch what happens when you press guide. Follow the status bar to follow the calibration steps.

Edited by Stephen
Link to post
Share on other sites

Thanks for the suggestions. Yes sorry should of stated it's fails when calibrating.

Pete, following your post I closed CdC and then re-tried... it's got further than it did before... it's now guiding... although it now keeps loosing the guide star... ruddy clouds have rolled in :) - nothing I can do about that !!

Seems CDC must of conflicted with the connection to the scope and blocked PHD - although PHD was showing as connected to scope ?? - strange

Thanks guys

Link to post
Share on other sites

Hi Malcolm,

This is a common issue that is talked about pretty much every week. Go to the search bar above and type in PHD Guiding and you will get numerous threads. The threads featuring AndyUK were the most useful to me. You may have to make some changes in PHDs Brain icon (aggressivness and min motion being the big ones). Have a look and good luck.

Link to post
Share on other sites
This could happen as Pete says if you have a poor connection. It would also happen if you choose a hot pixel instead of a star.

If your guide scope has a short focal length less than 500mm then you need to increase the calibration step length upto something like 2000ms

Thanks for the suggestions. The guide scope is an ST80, with a QYH5, so I'll give that a go.

Would that improve the graph I'm getting

post-23388-133877659854_thumb.jpg

Link to post
Share on other sites

I thinknthat the calibration step reply would solve the not moving star problem assuming this isn't a hot pixel.

About the graph - it's one or more of: polar alignment, balance, flex. In this order.

Cheers,

Harel :)

Link to post
Share on other sites
I thinknthat the calibration step reply would solve the not moving star problem assuming this isn't a hot pixel.

About the graph - it's one or more of: polar alignment, balance, flex. In this order.

Cheers,

Harel :)

Thanks. I polar aligned using the DARV method with a digital camera, Whilst I had no problem with the scope pointing south at zero dec, I have cr@p east and west horizons, which might go some way to explaining that. balance, well the scope is quite loaded, but appears balanced in all directions, but will look at this more carefully. I assume by flex you mean general movement, and even though the scope is in an obsy, it's quite gusty outside, and I have the south wall dropped down...

Uhmmm more to do !

Link to post
Share on other sites

Well as I wasn't getting far with the guiding I took the 200P off the mount and gave my newley acquired Celestron 127 MAK its 1st light (well with me at least :) ) - Looks a bit lost on the HEQ5, and had the weight right up tight to try and balance the thing, but managed to get some nice video of Jupiter. Using a Celestron X-Cel 8mm and 2x barlow the detail was amazing... although the air wasn't steady....

Once I stopped playing I spent some time re-aligning the polar axis. The previous owner of the HEQ5 had done a good job of colimating the polar scope as when the RA was rotated through 180 degrees Polaris remained under the cross-hairs.. Used EQMOD to rotate the mount to the HA for Polaris and placed it bang central in the circle and then locked everything off. I then re-ballanced the OTA and was just about to start the cone angle adjustment so the OTA is true to the RA axis when the clouds rolled in :(

Oh well time for bed and look forward to continuing with the setting up another time. I'm not going to give up (just yet !) with this guiding lark.... but the learning curve is very painful :)

Link to post
Share on other sites

I've had the same error with PHD, changing the Calibration step to a higher value sorted mine out. Short fl guider high value, longer fl guider smaller value. For my ST-80 I us 500, for my 9x50 finder I use 1500 - both with the same QHY5 cam.

Link to post
Share on other sites
I've had the same error with PHD, changing the Calibration step to a higher value sorted mine out. Short fl guider high value, longer fl guider smaller value. For my ST-80 I us 500, for my 9x50 finder I use 1500 - both with the same QHY5 cam.

Could you post up a screen capture of your settings for an ST80. Before I dismantled the 200p I played about with some settings, but obviously they were the wrong ones as nothing was improved

Link to post
Share on other sites

I also think that it is the calibration step number that is the issue.

I have had this error a few times and adjusting the setting fixed it!

Please see attached the screen grab - hope this helps.

Cheers

Ant

Link to post
Share on other sites

Hi Malcolm - As mentioned in one of the above threads, I had this problem with not enough movement recently - The two settings I was advised to amend from default were min motion (pixels) and calibration (ms). I use a finderguider (210mm FL) with a Lodestar and the min motion setting was 0.05 (due to the smaller FL), but I was given a calculation for min motion:

Arc seconds/pixel = (206.3 * ccd pixel size) / focal length.

The QHY5 has 5.2um pixels and the ST 80 has a focal length of 400mm so:-(206.3 * 5.2) / 400 = 2.68 Arc seconds/pixel. We want pixels per Arc second so flip it: 1/4.28 = 0.37 pixels/arcsecond, but as PHD wants sub-pixel movements, divide that number by half a pixel: 0.37 / 2 = 0.18 (ish)

Re: calibration, this is a setting I was advised needs to be set so that it gives about 10-16 steps in each direction. With my finderguider last time out I used 3500ms with some success (although that gave me 18 steps - I probably should have gone to 4000ms), but with the greater FL I'm sure you could reduce that by quite a bit (as mentioned above) - Here's my last PHD settings:

PHDSettings20110828.jpg

(Just for completeness, the guiding exposure setting I then used was 2.5s... Hope that helps?)

Link to post
Share on other sites

ROTATE your GUIDE CAMERA 45 DEGREES and try again! Yep, it's that simple!

It happens sometime to me, depending where in the sky I launch my guide star calibration. I've never played with the default PHD settings, my guide scope is F/11, and SSAG.

When it happens, then I loosen the guide camera, rotate the guide camera, and I'm back in business.

Give it a try!

:)

Link to post
Share on other sites

Well DugDog it aint !!

I've spent the past hour and a half trying to get this to work, following suggestions from above but the graphs are worse than before. In my last ditch attempt I've increased the calibration stops to 4000, and tried different pixel sizez from 1 (as shown in the attached image) to 0.05.

Polar alignment checked - you can spin the mount round and polaris follows the circle in the rectical - I've tried the scope pointing in the home position and towards m101 (vain attempt to capture the super nova). Balance is spot on too

I can see why there are a lot of threads about giving up imaging... I've just started and find it so frustrating wasting time for PHD to calibrate only to find that it makes little difference....

Oh and the zig zag is when I stopped guiding and tried a different setting and then started guiding again. It starts off close to the middle line and then diverges !

post-23388-133877660966_thumb.jpg

post-23388-133877660969_thumb.jpg

Edited by malc-c
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.