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HEQ5 Guiding Performance


Robny
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Hi All

I have an HEQ5 with the ROWAN Belt mod and on average my guiding RMS error total settles around the 1.20 to 1.40 mark and I was just curious if that is within 'ballpark'of where it should be?  I always aim to get an excellent PA using Shatpcap with Dec and Ra error into single figures.

My stars look pretty round and I have no complaints looking at my images to my inexperienced eyes anyway.

Is there still more I can get out of it or should I just leave it be?

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I've just checked on a pic that I took of my graph after polar aligning.  Belt modded Heq5 pro pier mounted RMS error was 0.43 so I think yes there may well be more to get out of it. Sorry its a really poor pic had to use my phone to take the picture off my face book page then send it to myself and save it.

trace.jpg

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@Xiga is another member using a belt modded HEQ5 and definitely gets lower RMS than that, the norm being 0.8 as far as I can recall.

I think anything below 0.5 is exceptionally unusual, and I wouldn’t say you should be expected that.

It will also depend on the local conditions too. My belt modded EQ6 gets below 1.0 RMS. A couple of nights ago my DEC was 0.39 but the RA was 0.76.  It’s on the limit for weight thought but still I’m content with those figures as I image at 2.13”/px. 

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17 hours ago, Robny said:

Hi All

I have an HEQ5 with the ROWAN Belt mod and on average my guiding RMS error total settles around the 1.20 to 1.40 mark and I was just curious if that is within 'ballpark'of where it should be?  I always aim to get an excellent PA using Shatpcap with Dec and Ra error into single figures.

My stars look pretty round and I have no complaints looking at my images to my inexperienced eyes anyway.

Is there still more I can get out of it or should I just leave it be?

Hi Robny 

1.2 to 1.4 is definitive on the high side for this mount, even without the belt mod. Can you give us some more info of your setup? What scope are you using? And what's your image scale? The fact you say your stars are ok tells me your image scale is probably a bit on the low side, but better guiding is always a desirable goal so I would hazard a guess that you need to look at balance and Phd2 settings. 

8 hours ago, paraman said:

I've just checked on a pic that I took of my graph after polar aligning.  Belt modded Heq5 pro pier mounted RMS error was 0.43 so I think yes there may well be more to get out of it. Sorry its a really poor pic had to use my phone to take the picture off my face book page then send it to myself and save it.

trace.jpg

Paraman that's an RMS of 0.57 arc secs (not 0.43) but that's still seriously good! I've no idea how much weight you're carrying, but the pier will no doubt be a big help here too. 

Pretty sweet though!

3 hours ago, tooth_dr said:

@Xiga is another member using a belt modded HEQ5 and definitely gets lower RMS than that, the norm being 0.8 as far as I can recall.

I think anything below 0.5 is exceptionally unusual, and I wouldn’t say you should be expected that.

It will also depend on the local conditions too. My belt modded EQ6 gets below 1.0 RMS. A couple of nights ago my DEC was 0.39 but the RA was 0.76.  It’s on the limit for weight thought but still I’m content with those figures as I image at 2.13”/px. 

Adam's right. On a bad night, I would expect to get 0.9-1.0", on a typical night 0.7-0.9", and on an exceptional night 0.6-0.7". I once got ~0.5" for about an hour one night, but I've never matched that since. It definitely depends on multiple factors,  sky conditions and location (my mount definitely prefers having the scope on the East side for example). 

Just so you know, I image with an 80ED and a finder-guider on my Heq5-Pro, so not much weight at all. The mount is nearly 7 yrs old now, and has had a motherboard replacement (by me) so is no spring chicken lol. 

@Robny can you give us more details on how you balance? Do you do Meridian flips? And do you rebalance afterwards? Also, what are your Phd2 settings? 

Ps - I'm not as active on the forums these days as I'd like to be, but I'll do my best to help you out with getting your settings optimised. 

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7 hours ago, Xiga said:

1.2 to 1.4 is definitive on the high side for this mount, even without the belt mod. Can you give us some more info of your setup? What scope are you using? And what's your image scale? The fact you say your stars are ok tells me your image scale is probably a bit on the low side, but better guiding is always a desirable goal so I would hazard a guess that you need to look at balance and Phd2 settings. 

Thanks for the feedback everyone, definitely something to work on it seems...so, a little more info:

HEQ5 PRO with Rowan Belt Mod

William Optics GT71 Imaging scope with Altair Astro 183m Protec imaging camera

AA 60mm Guide scope  with GPcam 130mono guide camera guiding through ST4 

I generally try to balance East heavy (slightly) - but I do generally find balance difficult to achieve.  Also, when I unlock my clutches it seems the axis don't move as free as they should, so that maybe affecting my ability to get balance nailed?  My guiding RMS generally starts out around 0.7 then gradually makes its way up to 1.2 - 1.5 through the night and settles there.  I do go through meridian flips and infact rite before the imaging run began it did do a meridian flip but I never re-balance after.

I have attached my guide log if that is any use? Also a single sub from that guiding session.

Many Thanks

Rob

PHD2_GuideLog_2019-10-16_201636.txt L_2019-10-16_21-50-03_Bin1x1_240s__-15C.fit

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15 hours ago, Xiga said:

 

 

Paraman that's an RMS of 0.57 arc secs (not 0.43) but that's still seriously good! I've no idea how much weight you're carrying, but the pier will no doubt be a big help here too. 

Pretty sweet though!

Yep your'e right, brain fade mode. I dont know what the weight is but its carrying megrez 90,  atik 314L+, Starlight express 7 way filter wheel, Sharpstar autofocusser, and its power supply,   finder guider with Qhy5 camera and a powered usb hub.  The scope was pointing to the wnw as it was the first time that I had ever been able to image in that direction.

 

 

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A few things you could try.

Your star HFD is 5 pixels, you could try focusing to get nearer to 3 to 4 pixels on the Star Profile in PHD2.

I don't know if Guide Assistant has suggested the settings you have ?

3.5 secs exposure isn't giving PHD2 a chance to grab the 2 arcsec excusions you have in RA and Dec, so try 2 secs.

RA min move is effectively at just over 1 arcsec according to PHD2 Log Viewer, so if you want sub 1 arcsec guiding try lowering, that will grab those 2 arcsec excursions before they get over 1 arcsec in size.

Same for Dec, min move is 1.5 arcsecs, so those 2 arcsec excursions aren't being grabbed before they get too big.

Michael

Edited by michael8554
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9 hours ago, michael8554 said:

A few things you could try.

Your star HFD is 5 pixels, you could try focusing to get nearer to 3 to 4 pixels on the Star Profile in PHD2.

I don't know if Guide Assistant has suggested the settings you have ?

3.5 secs exposure isn't giving PHD2 a chance to grab the 2 arcsec excusions you have in RA and Dec, so try 2 secs.

RA min move is effectively at just over 1 arcsec according to PHD2 Log Viewer, so if you want sub 1 arcsec guiding try lowering, that will grab those 2 arcsec excursions before they get over 1 arcsec in size.

Same for Dec, min move is 1.5 arcsecs, so those 2 arcsec excursions aren't being grabbed before they get too big.

Michael

That's really great feedback thanks!!

I've adjusted what setting I can to your recommendation and will check focus next time I go out...when ever that will be.  You lost me on the reasoning why but I appreciate you telling me and will just follow your reccomend changes :)

I'm always a little lost in PHD2 settings and never really adjusted anything...I've got it working and ran the wizard thingie a couple of times but that's about it.

Thanks again

Rob

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3 hours ago, newbie alert said:

Few things to try first before adjusting anything...

Are you pretty well balanced?

 How are you polar aligning?

Where did you calibrate?

Did you run the guiding assistant 

I'm balanced as good as I can get it, I'm polar aligning with Sharpcap Pro until I achieve excellent and I have run guiding assistant a couple of times...not sure what you mean by "Where did you calibrate?"

Rob

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2 hours ago, Robny said:

"Where did you calibrate?"

I forgot to mention that because you're using ST4 connection, PHD2 doesn't get RA and Dec position information back from the mount, which it uses to alter the RA guiding to suit the Dec position.

The ST4 connection is fine as long as you recalibrate on every target. Using a Cal from low Dec will be too aggressive for higher Dec, and vice-versa.

If you tell me which part of my post you didn't understand I will re-explain.

Michael

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On 18/10/2019 at 08:20, Robny said:

Hi All

I have an HEQ5 with the ROWAN Belt mod and on average my guiding RMS error total settles around the 1.20 to 1.40 mark and I was just curious if that is within 'ballpark'of where it should be?  I always aim to get an excellent PA using Shatpcap with Dec and Ra error into single figures.

My stars look pretty round and I have no complaints looking at my images to my inexperienced eyes anyway.

Is there still more I can get out of it or should I just leave it be?

I get about 0.8 on a regular basis if its higher then its down to poor seeing / wind. On the very best nights it can hit 0.6 for periods.

Edited by Adam J
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3 hours ago, Robny said:

I'm balanced as good as I can get it, I'm polar aligning with Sharpcap Pro until I achieve excellent and I have run guiding assistant a couple of times...not sure what you mean by "Where did you calibrate?"

Rob

Sorry I missed that you was using a st4, so calibrate on every target..

Have you tried the drift tool?  I also use sharpcap if I've either not got much time or the clouds are looming and there's only a couple of hours to collect data.. but, if you have enough time it's worth doing..can get those rms figures down a fair bit further, every little helps as they say

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