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Would you be happy with 0.35 - 0.50 RMS in PHD2?

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#1 ChiTownXring

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Posted 12 June 2021 - 09:48 PM

I am running my EQ6R-Pro and hop between 0.35 and 0.50 RMS in PHD2 and I am happy with that even though I haven't run a calibration or the guiding assistant in PHD2 for over a month for fear of not getting better results but more so in fear of getting worse results.. With out a Field Flattener I think the stars in the center of my images look good but then again I am new to the hobby and have a lot to learn about this subject.. But would like to of course get the best out of my mount.

So have any one of you experienced running at my numbers then tweaked them for better results just by running a calibration or the guide assistant? 


Edited by ChiTownXring, 13 June 2021 - 07:15 PM.


#2 sbharrat

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Posted 12 June 2021 - 09:56 PM

I am running my EQ6R-Pro and hop between 0.5 and 3.5 RMS in PHD2 and I am happy with that even though I haven't run a calibration or the guiding assistant in PHD2 for fear of not getting better results but more so in fear of getting worse results.. With out a Field Flattener I think the stars in the center of my images look good but then again I am new to the hobby and have a lot to learn about this subject.. But would like to of course get the best out of my mount.

So have any one of you experienced running at my numbers then tweaked them for better results just by running a calibration or the guide assistant? 

Don't have a direct answer to your question since I generally do run the guiding assistance and the calibration, maybe not as regularly as I should but certainly several times since I started guiding in Feb 2021. 

 

But are you happy with the 3.5? I know my image scale is about 2" so I have been trying to debug when it goes over that. I know that the real goal is round stars, not good guiding in of itself. But being a newbie, I have no idea what is "round enough" so I also do try to watch the guiding RMS. 



#3 Phishin_phool

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Posted 12 June 2021 - 10:46 PM

So I have an Eq6-R pro and here is something that has made a huge impact on my guiding- adding a third weight. I added another weight which has allowed me to move the weight up further on the shaft of the EQ6-R Pro. This has reduced the momentum arm and made guiding so much better I went from around 0.5-0.6 when using 2 weights towards the end of my shaft to less than .3 on most nights after adding the third weight and moving them all up as high as they would go - giving me perfect balance without that long distance from the weight requiring much less force and reducing momentum of the weight. I shot the Eastern Veil Nebula last night with around .26 avg RMS on my guiding.


Edited by Phishin_phool, 12 June 2021 - 11:09 PM.

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#4 ChiTownXring

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Posted 12 June 2021 - 11:05 PM

So I have an Eq6-R pro and here is something that has made a huge impact on my guiding- adding a third weight. I added another weight which has allowed me to move the weight up further on the shaft of the EQ6-R Pro. THis has reduced the momentum arm and made guiding so much better I went from around 0.5-0.6 when using 2 weights towards the end of my shaft to less than .3 on most nights after adding the third weight and moving them all up as high as they would go - giving me perfect balance without that long distance from the weight requiring much less force and reducing momentum of the weight. I shout the Eastern Veil Nebula last night with around .26 avg RMS on my guiding.

Seems like a quick and cheap thing to try.. How heavy was the third weight?



#5 Phishin_phool

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Posted 12 June 2021 - 11:09 PM

I ordered the same as what came with the scope IIRC they are 5KG. Since then I have added a second mount (MEADE LX85) and the weights which are lighter also work on the EQ6-R pro.



#6 bobzeq25

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Posted 12 June 2021 - 11:09 PM

I am running my EQ6R-Pro and hop between 0.5 and 3.5 RMS in PHD2 and I am happy with that even though I haven't run a calibration or the guiding assistant in PHD2 for fear of not getting better results but more so in fear of getting worse results.. With out a Field Flattener I think the stars in the center of my images look good but then again I am new to the hobby and have a lot to learn about this subject.. But would like to of course get the best out of my mount.

So have any one of you experienced running at my numbers then tweaked them for better results just by running a calibration or the guide assistant? 

 

Don't fall into the trap of striving to improve guiding numbers.  If you like your stars, that's all that counts.  The only reason for the numbers is to diagnose any issues you have with your stars.  They are _not_ goals in themselves.  I repeat...  <smile>

 

Happiness is an emotion best reserved for your stars.


Edited by bobzeq25, 12 June 2021 - 11:12 PM.

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#7 Phishin_phool

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Posted 12 June 2021 - 11:15 PM

Fine numbers.

 

But don't fall into the trap of striving to improve guiding numbers.  If you like your stars, that's all that counts.  The only reason for the numbers is to diagnose any issues you have with your stars.  They are _not_ goals in themselves.  I repeat..

Great Point, the reason I ordered my additional weight is I also have/added a dual saddle allowing me to run 2 scopes on the same mount when I want (OSC on one and SHO on the other). I needed that weight for when they were both there. During a discussion with another imager on FB he pointed out what is easy to recognize - moving weight further up the shaft reduces the momentum arm and makes guiding easier so I tried it and results are noticeable in my imaging. I don't care about the numbers but the quality of my stars due to guiding (streaks no more) has definitely improved. Image improvement has been a blend of a number of improvements as experience sets in.


Edited by Phishin_phool, 12 June 2021 - 11:32 PM.


#8 rgsalinger

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Posted 12 June 2021 - 11:21 PM

First of all are you measuring the guiding in pixels or arc seconds? If arc seconds then I would say with that mount it's impossible to do any better. You're "at the seeing". If it's pixels then the next question is what your image scale is. I agree that if the stars are good then the guiding is good.

 

I do not agree that you can state that the stars cant' be improved unless you do measure them. If you don't then it's purely subjective. You'll never know if improvement is possible, if you just eyeball them. 

 

Rgrds-Ross


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#9 Birddogoby

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Posted 13 June 2021 - 02:52 AM

Ross - be careful about what you say are impossibilities.smile.gif  I have an EQ6R- Pro and consistently achieve .3-5 RMS with my Tak 120 onboard.  My numbers were running .4-8 until I changed my initial balancing setup.



#10 michael8554

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Posted 13 June 2021 - 04:16 AM

"I am happy with that even though I haven't run a calibration or the guiding assistant in PHD2"

 

You must have run the PHD2 Calibration at some point in the past, because PHD2 won't start guiding if it doesn't have a Calibration.

 

You could theoretically run PHD2 for ever with that old Cal, so long as the guidescope/guidecam is always mounted in the same orientation with respect to RA and Dec.

 

Total guide error is often quoted.

 

If the RA and Dec errors are similar then that's good guiding, but if your 0.5 is a combination of RA  = 0.4  and Dec = 0.1 you may have problems......


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#11 ChrisWhite

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Posted 13 June 2021 - 06:07 AM


 

If the RA and Dec errors are similar then that's good guiding, but if your 0.5 is a combination of RA  = 0.4  and Dec = 0.1 you may have problems......

Think about this for a minute, as it is important.  If one axis contains the majority of your total RMS error, it may lead to high eccentricity depending on what your image scale is.  The question is not are you happy with your numbers, but are you happy with your stars.  Are they round (low eccentricity) and tight (low FWHM).  If not, you have room for improvement. 

 

If you stars are both tight and round, and you are guiding at 0.3 to 0.5 Total RMS in arcseconds... you are unlikely to improve upon this further.  I'd be satisfied with those results with pretty much any scope. 


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#12 Phishin_phool

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Posted 13 June 2021 - 09:01 AM

"I am happy with that even though I haven't run a calibration or the guiding assistant in PHD2"

 

You must have run the PHD2 Calibration at some point in the past, because PHD2 won't start guiding if it doesn't have a Calibration.

 

You could theoretically run PHD2 for ever with that old Cal, so long as the guidescope/guidecam is always mounted in the same orientation with respect to RA and Dec.

 

Total guide error is often quoted.

 

If the RA and Dec errors are similar then that's good guiding, but if your 0.5 is a combination of RA  = 0.4  and Dec = 0.1 you may have problems......

I am not so sure about that when I started out I didn't know a calibration was needed (did not RTFM) and did my first target without - the lines were dotted yellow instead of green but I believe it did run although with a very high RMS.



#13 michael8554

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Posted 13 June 2021 - 09:58 AM

I really don't understand why you are guiding without even the most basic understanding of PHD2, how do you expect to improve ?

 

https://openphdguidi..._User_Guide.pdf



#14 Phishin_phool

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Posted 13 June 2021 - 10:13 AM

That was a year ago when I didn't know anything and tried to learn it all in a day or 2. SInce then I have read and understand phd2 and the latest multi-star guiding. I calibrate my guiding before every session now.


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#15 kel123

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Posted 13 June 2021 - 10:41 AM

Don't fall into the trap of striving to improve guiding numbers. If you like your stars, that's all that counts. The only reason for the numbers is to diagnose any issues you have with your stars. They are _not_ goals in themselves. I repeat... <smile>

Happiness is an emotion best reserved for your stars.


Bob, guiding seems to have become a hobby by itself for some people . An acquaintance "confessed" to me that he has gone out several nights without capturing any data but only guiding and trying to see what to do to improve on 0.5" rms. Yet, his set up is around 1.52"/pixel. It is just crazy.
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#16 rgsalinger

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Posted 13 June 2021 - 11:18 AM

"hop between 0.5 and 3.5 RMS in PHD2" was what the OP posted. I misread this as .5 and .35. Having said that, ".3-5" is really not an improvement, is it? So, I think that I'll stick to my guns and say that I'd love to see a guiding log and a system picture of EQ6R guiding at less than .5 and .35 over even a full turn of the worm. Then, I'll eat another of my hats and ask for help with my guiding and/or location. 

 

I'll just amplify my original points. If you like what you are getting then be happy. However, if you want to know if you can do better by tweaking parameters then you need to be measuring. It's hard to imagine not getting oblong stars if the (DEC, RA?) are varying that much. 

 

All that I can say is that my two systems guide at between .3 and .5 arc seconds RMS all night long. I don't particularly look at the guide graph but it's up on one of my screens at all times. So, from time to time I give it a peek and that's what I see. It's more dependent on weather and altitude than anything else. I don't know if those points can be generalized but they seem reasonable to me because my portable system behaves the same way and that goes to different places. YMMV.

 

Rgrds-Ross


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#17 ChrisWhite

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Posted 13 June 2021 - 12:19 PM

"hop between 0.5 and 3.5 RMS in PHD2" was what the OP posted. I misread this as .5 and .35. Having said that, ".3-5" is really not an improvement, is it? So, I think that I'll stick to my guns and say that I'd love to see a guiding log and a system picture of EQ6R guiding at less than .5 and .35 over even a full turn of the worm. Then, I'll eat another of my hats and ask for help with my guiding and/or location.

I'll just amplify my original points. If you like what you are getting then be happy. However, if you want to know if you can do better by tweaking parameters then you need to be measuring. It's hard to imagine not getting oblong stars if the (DEC, RA?) are varying that much.

All that I can say is that my two systems guide at between .3 and .5 arc seconds RMS all night long. I don't particularly look at the guide graph but it's up on one of my screens at all times. So, from time to time I give it a peek and that's what I see. It's more dependent on weather and altitude than anything else. I don't know if those points can be generalized but they seem reasonable to me because my portable system behaves the same way and that goes to different places. YMMV.

Rgrds-Ross

Ross, may I borrow a hat?

I also misread this and 0.5 and 0.35"/px. The real number of 3.5"/px is not very good. The OP wpuld do well do carefully polar align, calibrate and the refine settings starting out with guiding assistant suggestions.

EDIT- Ross it doesn't look like we misread. Check the title of this thread. Now I don't know what's going on. The OP needs to clarify.

Edited by ChrisWhite, 13 June 2021 - 12:27 PM.

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#18 rgsalinger

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Posted 13 June 2021 - 12:45 PM

Until the dude comes back with a clarification about pixels versus arc seconds and posts a sub to look at, his question could mean pretty much anything.

 

Rgrds-Ross



#19 kel123

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Posted 13 June 2021 - 01:01 PM

Yeah. There are discrepancies between what the OP wrote on the title and what was written on the post. The title says 0.35" - 0.50" and post says 0.5- 3.5". The difference is so significant. The OP needs to clarify this.
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#20 sbharrat

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Posted 13 June 2021 - 05:42 PM

Think about this for a minute, as it is important.  If one axis contains the majority of your total RMS error, it may lead to high eccentricity depending on what your image scale is.  The question is not are you happy with your numbers, but are you happy with your stars.  Are they round (low eccentricity) and tight (low FWHM).  If not, you have room for improvement. 

 

If you stars are both tight and round, and you are guiding at 0.3 to 0.5 Total RMS in arcseconds... you are unlikely to improve upon this further.  I'd be satisfied with those results with pretty much any scope. 

So this seems to be quantitative parameters I am looking for in terms of deciding "are my stars good enough"... My setup is a 480mm FL triplet scope, just under 2"/px image scale (3.76 um pixels), on a Orion Sirius (HEQ5 equiv) mount. Bortle 8, NJ if relevant. 

 

What should I be looking for in terms of eccentricity and FWHM, let's say on a night of average seeing on cleardarksky? 



#21 ChrisWhite

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Posted 13 June 2021 - 05:49 PM

So this seems to be quantitative parameters I am looking for in terms of deciding "are my stars good enough"... My setup is a 480mm FL triplet scope, just under 2"/px image scale (3.76 um pixels), on a Orion Sirius (HEQ5 equiv) mount. Bortle 8, NJ if relevant.

What should I be looking for in terms of eccentricity and FWHM, let's say on a night of average seeing on cleardarksky?

First of all, you mentioned that you didn't calibrate phd. If not, you are not guiding.

For eccentricity any value below 0.5 will look round to the human eye. For fwhm, just a guess off the cuff you'd be looking for around 3 with precise focus.

Edited by ChrisWhite, 13 June 2021 - 05:50 PM.


#22 ChiTownXring

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Posted 13 June 2021 - 07:11 PM

My deepest apologizes on the initial post with the confusing numbers I just corrected them so things match.. I have run the assistant and a calibration but not in about a month or more as I didn't want to mess with what I think is a good thing RMS wise. Here is a picture of what I have been typically seeing when I am guiding in the last month.

Phd2


#23 Jared

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Posted 13 June 2021 - 07:32 PM

You are using an off axis guider, yes? Not a separate guide scope? That would explain the astigmatic shape to your guide stars. 

 

Assuming you are, 0.3" - 0.5" RMS guide error is very low. That is essentially what I get with my AP1100GTO AE mount (which I usually use unguided, but I still use PHD occasionally to make sure my pointing model is working well). Well, 0.3"-0.4" with the 1100, but that's substantially the same as you are getting. That SHOULD yield good stars in your sub exposures. That's the goal, after all, not the guiding results themselves. If your eccentricity is under 0.5 as measured by PixInsight and your exposures have FWHM under, say, 3" near the center of the field, you are likely doing fine. That's assuming decent but not exceptional seeing, objects above 45*, and that you are using your 100mm refractor. Obviously, sky conditions, focus, focus drift, etc. can have a profound affect on FWHM in your final image, but I'd say that once you are under 0.5" in guide error with an OAG, it is extremely unlikely that tracking/guiding is the limiting factor in your image resolution. 


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#24 ChiTownXring

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Posted 13 June 2021 - 07:51 PM

You are using an off axis guider, yes? Not a separate guide scope? That would explain the astigmatic shape to your guide stars. 

 

Assuming you are, 0.3" - 0.5" RMS guide error is very low. That is essentially what I get with my AP1100GTO AE mount (which I usually use unguided, but I still use PHD occasionally to make sure my pointing model is working well). Well, 0.3"-0.4" with the 1100, but that's substantially the same as you are getting. That SHOULD yield good stars in your sub exposures. That's the goal, after all, not the guiding results themselves. If your eccentricity is under 0.5 as measured by PixInsight and your exposures have FWHM under, say, 3" near the center of the field, you are likely doing fine. That's assuming decent but not exceptional seeing, objects above 45*, and that you are using your 100mm refractor. Obviously, sky conditions, focus, focus drift, etc. can have a profound affect on FWHM in your final image, but I'd say that once you are under 0.5" in guide error with an OAG, it is extremely unlikely that tracking/guiding is the limiting factor in your image resolution. 

Yes I am using the COAG with the ASI120MM and I have also contemplated if I should mess with trying to get round stars in the Phd2's star profile but have left it alone again for fear of making things worse and not better.. I am going to take your advise and leave things as is until I find a reason to change things..



#25 KTAZ

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Posted 13 June 2021 - 08:08 PM

I'm going to try and close this topic. OP, you have guiding numbers which are absolutely fantastic. You would be foolish to try anything to improve them. You appear to have a high quality sample of this mount. Enjoy it. Many folks that have a mount that falls closer to the median quality would kill for those numbers.

 

I assume your payload is less than 15lbs. Many of us are running upwards of 30lbs on our rigs and see something in the range of .50 to .75 and get nice stars.

 

OAG's will usually have elongated stars, but PHD2 knows how to deal with that. Just make your focus tight, that is all you have to do.

 

As others have said; chasing a good RMS is not the goal, chasing good images is.




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