Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

joecoyle

PEC and guiding with PHD2

Recommended Posts

Hi

The longest frames i seem to be able to capture using my Atik 414ex and PHD2 are about 2 minutes. Any longer than that and i start to get egg shaped stars. PHD is making corrections, but i can't understand why i can't get to subs of at least 5 minutes. I'm not sure if its a limitation of the scope (6SE, with f/6.3 FR), limitation of the guide camera (orion magnificent mini, 50mm scope), poor polar alignment or poor worm gear. 

Would PEC training help improve my sub length? Or is it settings in PHD to experiment with? I look at the logs, but it's all just numbers to me. I can provide logs if that would help?

Any suggestions appreciated.

Thanks

Joe

Share this post


Link to post
Share on other sites

Its probably the mount as its an alt/az (you will be getting field rotation after a few min), so PEC training wont help. On an decent EQ mount you can quite easily crack off a 20min guided sub without ever going near PEC training.

Share this post


Link to post
Share on other sites

I should have said my OTA is on an AVX mount :) Is that a decent mount for a 20 minute sub? 

Share this post


Link to post
Share on other sites

Post a screen capture of your PhD guiding screen, you can also down load PhD log analyser.load into it your last guide log and post a screen shot of that.

Ray

Share this post


Link to post
Share on other sites

Hi,

I was on exact the same boat as you are now. 

PHD - should only correct when it sees it need to correct so if the mount is tracing correctly there should not be an issue with subs length.

My issue was simply resolved by:

polar alignment - as best as possible

PEC file  and make sure use set gain to anything other than 0 - I used PEMPro v2 and it produced excellent PEC file

Your guide scope should be ok for telescope up to 1500mm fl

If you eliminate poor polar alignment AND poor worm gear ( good PEC) your subs should be close to perfect even with long exposure times.

 

Kris

 

Share this post


Link to post
Share on other sites

Ahhh so its the AVX!  If im not mistaken, thats a jazzed up version of the old CG5-GT (my first mount).

Well, in theory you should be able to do 10min subs on a regular basis. But with mine, I settled for 7.5min as a compromise in order to get a better hit rate. So there are a number of things you can look at:

1) Polar alignment

2) Any flex between the OTA and guidescope

3) Velcro up all your cables (to remove strain from the cameras)

4) PHD settings - minimum motion should be quite small (ie: the amount a star should move before a guide command is triggered)

5) Check the mount for slop in either axis (most likely in DEC), a small tweak of the worm may help there.... but be careful with it, its easy to overdo it.

6) Try to guide in one direction only (in DEC), either north or south - depending on what way it likes to drift. That will help take out a lot of the backlash.

 

Its all little things that can add up, but check everything!

Share this post


Link to post
Share on other sites

So in terms of Polar alignment then... What is the best way to get that as good as possible? Currently, this is my routine:

1. Point roughly north.
2. Use polar align scope... rotate RA until Cassiopeia is correct orientation. Then adjust bolts to get Polaris in the little circle.
3. Do a quick one star align to get the Handset to generate a model.
4. Use SGPro to plate solve the target then sync the mount to those coordinates.

I used to run the All Star Polar Align routine on the handset but it didn't improve things massively (still 2 minute subs, the Polar Align error said 000 but i don't believe it). And now with plate solving, i supposedly don't need to?

 

Thanks

Joe

Share this post


Link to post
Share on other sites

Hi Joe

You could use the PHD2 drift align tool. You are imaging at quite a long focal length which makes things more challenging. Make sure you are well balanced too. Also run PHD2 with guiding OFF (can use the PHD2 guiding tool). That will indicate how much you might be drifting. Plus what Rob said :)

Louise

Share this post


Link to post
Share on other sites

Doesn't look like it's making many RA corrections, do you know which way it's drifting ?

May be over / under correcting in Dec

Dave

Edited by Davey-T

Share this post


Link to post
Share on other sites

Take a pic 'of something that has an obvious way up / round so you can see if your stars are going eggy in RA or Dec.

I think PHD2 has some sort of assistant that runs with guiding off and indicates drift that needs correcting.

Dave

Edited by Davey-T

Share this post


Link to post
Share on other sites

Here are my PHD settings.... Ive only changed the calibration step... used the calculate button for that.

Louise - My imaging program (SGPRO) says "waiting for Autoguider to settle" before beginning the next exposure. So I'm guessing it is waiting. It has (distance 0.5, 0.4, 0.3) next to it. It starts the exposure when it gets to 0.3. 

Cheers

Joe

 

56c48dc773806_phdsettings1.PNG.8cf3d0ebb56c48dcae2fce_phdsettings2.PNG.e7399206c

Share this post


Link to post
Share on other sites

Your guide log shows a very slow reaction to corrections, I would suggest looking at you guiding rate and if possible choose a rate between 0.5x & 1.0!

Ray 

Share this post


Link to post
Share on other sites

Actually, just re-looking at the guide log....it appears to say that your rates differ slightly.0.8x & 1.0x so the rates should be fine...but...the log shows all correction on one side for a time then on the other side for a time when ideally it should be a little more balanced, in addition ..you appear to have some backlash in Dec, and that's taking time to correct. Which led me to suggest upping the guide rate

turn the aggressiveness down a bit ..perhaps 70. But do make sure your alignment is good, use PhD your polar scope alignment is unlikely to be close enough really and that would require higher rates and more aggressiveness to correct the lager excursions.

Ray

Share this post


Link to post
Share on other sites

So, can I use PHD to align ? I'll reduce the aggressiveness to 70 and see what it changes. Can i fix the backlash in dec?

Share this post


Link to post
Share on other sites

Sorry joe, I use Eqmod it's easy in there but I don't know what you use, perhaps someone familiar with you set up can assist but at a 1st guess, look in the hand paddle set up.

run the guiding assistant and enable backlash correction it may help with the Dec issue.

Ray

Edited by libraryman

Share this post


Link to post
Share on other sites
13 minutes ago, joecoyle said:

So, can I use PHD to align ? I'll reduce the aggressiveness to 70 and see what it changes. Can i fix the backlash in dec?

Yes, you can use the PHD2 drift align tool providing you can point south to adjust az and east or west to adjust allt.

Share this post


Link to post
Share on other sites

O.k I would suggest raising them a little ...perhaps 0.7 x (70%). or perhaps 0.1x and test....lower aggressiveness can be used then.

Ray

ps..plate solving has nothing to do with polar alignment and does not guarentee it.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By AstroRuz
      Hello all,
      So I routinely have issues with guiding. Last night, I was getting some solid sub exposures of 5 minutes on the Flaming Star Nebula. When it got to about 15-20minutes of the meridian, I began getting trails on my stars. Then after the flip, I was still getting trails despite PHD reporting all's well.  I moved over to the Horsehead Nebula and tried 5 minutes there, and it behaved itself. Then I tested it on the Jellyfish Nebula and it also behaved (just about - minor trails). But it just did not want to dig it with the Flaming Star Nebula, which was practically near the zenith (about 2:30am 30/11/19).
      I tried recalibrating PHD (I use Pulseguide so the scope knew where it was). I then also recalibrated PHD at Alnitak so it was near the celestial equator (as the PHD best practices recommend). I even checked my Polar Alignment (done with a Polemaster), which was fine. I couldn't find anything wrong. 
      The guide scope was slightly off alignment with the main OTA, but that wasn't making any differences before the Meridian. 
       
      I did find the helical focuser of the Starwave 50mm guide scope I was using to have some movement in it again when I manipulated the guide camera. So that's something I need to look into. But before I start throwing money at this issue, I see the terms "flexure" and "differential flexure" coming up. Can anyone shed light on what this means please?
      I tried manipulating the OTA in its tube rings, that didn't yield any movement either. The piggyback scope is secure, the g/scope is secure in its rings as well, there's no movement in the OTA focus rack and the cameras are secure in their tubes. 
      I do have my guide rings quite far back on the body of the telescope to assist with fitting the guide scope piggyback. 
      Video of g/scope play: 
       

      Flaming Star Nebula. 5 minute sub, post Meridian Flip, about 2:50am (30/11/19). Note the plate solve compass in the top left. Drift appears to be in S/W direction.

      Position of tube rings (they're now at the focus end).
      I think I am leaning towards needing to move my tube rings (once I remember to get the tools from work). 
       
       
      Equipment:
      (brand new) Skywatcher EQ6-R Pro, SW Evostar Pro 80ED, Altair 0.8x R/F, Canon 600D, Altair Starwave 50mm Guide Scope, Altair AR130 Mono Guide Cam. 
       
       
    • By John Lawley
      Hi - I've not posted here before as only just launched into this hobby, although I've always been massively interested in astronomy.
      I had first light on my rig last night, which is:
      Esprit 100, HEQ 5 Pro, ZWO EAF, ZWO mini filter wheel, skywatcher 50ED guidscope with ASI120, ZWO1600mm Pro, Lynx dew controller w 2 astro zap tapes
      A big endeavour to get that lot working from zero experience, but I love a challenge and have really enjoyed the computer side (I'm a grade A nerd)...
       
      So - what went well... I got the guide scope in focus (was stressing about this), and also the main scope. Even more awesomely, the autofocus routine in SGP is working perfectly Filter wheel also working perfectly and I'm getting lovely smooth pics from the main camera (I've already done the flats and darks while I was waiting for clouds to clear). Final good thing (well, good-ish), is that I got the platesolving working eventually, and was able to get the scope to align from Park to the Soul Nebula and centre fine. For some reason the "number of attempts" in my SGP profile hadn't applied, so it was giving up after 1 go, but I got it working in the end.
       
      So the bad...
      I couldn't take any data because every time it finished the platesolving and started PHD2, PHD2 would start the calibration process and then halfway through, the sidereel tracking on the EQMOD panel would turn off. Obviously, that would lead to a "lost the star" error. Is there some reason why sidereel tracking would turn off like that? I'm generally a bit confused as to whether I should be controlling the telescope from SGP (i.e. unpark) or using the park and unpark + tracking button on the EQMOD panel. Both PHD 2 and SGP are setup to use EQMOD ASCOM HEQ5/6?
      So at the moment I can't do anything, because there's no way of guiding without it turning tracking off
       
      Also I was cold. Very Very Cold.
    • By Nikolas74
      From AST Optics selling my mini guiding system that i used for my Redcat51 , i have used it also with my Esprit 100 and had excellent guiding results.
      There is a nice review here if someone wants to read :
      https://www.cloudynights.com/topic/575047-ast-mini-guide-kit-any-comments/
      Lens:    f=100mm F3.5 CCTV objective - made in Japan
      Adjustment:    by ballhead - with reliable clamping
      Dovetail:    compatible with most finder shoes
      True field of view:    2.9° x 3.8°
      Maximum guidable focal length:    1000 mm
      Focusing:    via lens cell
      Connection to camera:    C-Mount
      Lens filter thread:    M30.5mm P=0.5
      Weight:    79 grams
      Length of the objective:    44 mm
       
      PRICE : £100 (selling the mount and the CCTV lens not the camera)
      Paypal accepted buyer pays the fees
      I will cover the postage expenses
      Thank you,
      Nikolas




    • By BUDA
      Hi All!

      I have guiding problem with the following guider setup: 9x50 finder + ZWO ASI 120mm mini + PHD2.
      The imaging scope is a 6' newtonian + canon dslr on a HEQ5, driven by a laptop via diy EQDIR cable.
      When the mount is set up and running correctly, polar aligned and all... I connect the guider camera
      and mount with phd2. All nice and easy, I run a calibration, then it starts to guide. All seems ok.

      Then I am starting to take pictures. The first seems OK, then the second have the star trails...
      I check phd2 and there is a message: the camera (ASI) did not take a picture for "xy" seconds so it is disconnected.
      Grrr.... I reconnect try to set up a longer period for "xy" in the settings as mentioned in the message.
      And all the same again and again. Whatever I add for connection timeout for the camera, it just reaches that
      and disconnect the camera.
      PHD + philips toucam has worked for me flowlessly. I changed to PHD2 because I gave myself a birthday present,
      the little ZWO camera. (and PHD did not recognize it)
      Do you have any idea what can be the problem? I will contact PHD2 help also, but maybe somebody had already
      the same problem and figured out how to overcome. I am almost sure I make some dumb mistake in the PHD2
      software settings, however I tried to change only what was needed.
    • By Tom Shinal
      Can Nebulosity and Ph.D operate simultaneously and share a single camera. Running Win 10.
       
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.