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iExos100 Peak Performance #iexos-100

@Huangdi
 

Ever since I managed to get past the issues of my mount, it has done nothing but amaze me. While my results have been great so far, I'm wondering whether or not there is room for improvement.
My rig is currently imaging and I'm wondering how well the other iExos100 users are guiding it. My RMS has settled at 1.02" (hopefully sub 1" soon) and I got it loaded up with roughly 4kg of imaging gear. 
Has anyone been able to consistently get an RMS below 1"? If so, I'd love to know how you managed to get every last bit of performance out of it.

Cheers, 

Julian

 

Julian,
 
But you already have round stars, right?  :-)    Never mind - I do understand RMS fever !
 
I looked through your previous posts, and it sounds like you have power train adjustments figured out.
Are your tripod legs down at their lowest setting?
 
If you've got the power train managed, and the mount/tripod are physically stable, balance is ok, and conditions permit (wind, seeing, etc.), then what you might look at is guiding resolution. 
 
I was trying to get below 1.0" with my (EXOS2) setup, and Jerry suggested that I go to a guide scope FL between 250 and 300mm.  I changed out my (easy to use) 50/200mm guide scope for a (not quite as easy to use) 60/280mm, and it really did help me.  Kept the same guide camera, but it will change too, one of these days.
 
Lots of convenient tools for playing with options on the Astronomy Tools site - here's one:  https://astronomy.tools/calculators/guidescope_suitability    
 
- Bob
--
Mounts: ES PMC-8 EXOS2
Scopes: SV 102EDT, ZWO 60/280 Guide
Cameras:  Nikon D5300, Altair GPCAM2-IMX224C
Software: ASCOM, CdC, AstroTortilla, BYN Pro, Sharpcap, PHD2
Computer:  Thinkpad x230, Win7Pro/64

@Huangdi
 
Edited

Hey Bob,

yeah my stars are fine and my setup is well adjusted as far as I know. I'm merely interested whether or not/how I can further improve my guiding :p

Wes Mcdonald
 

Julian

If you are at 1.1 I doubt you need better.  At least you are danged near great.  What is your average seeing?  What is the arc second scale per pixel of your imaging rig?  Comes to a point where you just can't do any better images.

I also wonder what the waveform of your residual tracking error is....the RMS has different relationships to the peak error depending upon the wayeform.  

In the end, if you can't see the residual in the image it is unimportant.  Right?

It's amazing though to me that you consistently get 1.1.  wish I did.  At my pixel scale and average seeing I would be as good as it gets.

Wes



--
Wes, Southport NC
PMC-8, ES ED 127, 10" LX200GPS, Astro-Tech 8" Newt, ETX-90
Polemaster, Orion ST-80 and SAG
Electrical Engineer, Retired

@Huangdi
 
Edited

Hey Wes,

like I said, I'm merely trying to figure out whether or not I can push it further. But you are right when saying that it depends on the camera/scope and seeing.

I live in a rather rural area, my skies are something between Bortle 3 and 4. Last night avg seeing was pretty good, I had a FWHM of around 1". I'm using an ASI 120mm mini with a 8x50 162mm scope, giving me a pixel scale of 4,77 "/px.

Another reason why my guiding seemed very good last night was my PA, don't ask me how (considering the limited Azimuth adjustment possibilities on the iExos100), but I managed to get the PAE well below half an ArcMin.

asanmax@...
 

Hello everyone.
Like everyone, I had to go through the initial learning curve with the new mount.
I've been imaging only from my backyard in the middle of the city, that's Bortle 7.
The Polaris is not visible for me, so I do a rough polar alignment all the time, no plate solving or drifting, just eyeballing.
I use a 40mm f/3 guider with a modified dash cam, don't ask me why, I'm just a DIY person.
I've been able to constantly get the RMS around 1" or just below 1". This sure enough gives me the pin point stars even at 500mm, I even tried imaging through my Celestron C5 with focal length of 1250mm with somewhat acceptable results.
I'm afraid that the mount is simply not capable of doing better than 1" RMS because it is not a high end mount and the worm gear pair is not manufactured with the same precision as the more expensive models.
I guess RMS of 1" is enough, at least I haven't seen anyone achieving better results.

@Huangdi
 

On Thu, Sep 5, 2019 at 10:49 AM, <asanmax@...> wrote:
Hello everyone.
Like everyone, I had to go through the initial learning curve with the new mount.
I've been imaging only from my backyard in the middle of the city, that's Bortle 7.
The Polaris is not visible for me, so I do a rough polar alignment all the time, no plate solving or drifting, just eyeballing.
I use a 40mm f/3 guider with a modified dash cam, don't ask me why, I'm just a DIY person.
I've been able to constantly get the RMS around 1" or just below 1". This sure enough gives me the pin point stars even at 500mm, I even tried imaging through my Celestron C5 with focal length of 1250mm with somewhat acceptable results.
I'm afraid that the mount is simply not capable of doing better than 1" RMS because it is not a high end mount and the worm gear pair is not manufactured with the same precision as the more expensive models.
I guess RMS of 1" is enough, at least I haven't seen anyone achieving better results.

 That's certainly impressive. Would it be too much to ask for a view of your PhD algorithm settings? I'm always interested in those.

Just to make sure, you're talking about the iExos100, not the Exos 2, right?

asanmax@...
 
Edited

I for sure use iExos-100. I never made any changes to the default settings in PHD2, just did the initial gear setup, pixel size, guider focal length etc.
So no changes at all.
I noticed that the RMS has not changes since I've gone from the 200mm guider (Takumar lens 200mm f/40) to the 40mm f/3.
The latter is actually so light that I was able to attach it to the hot shoe mount of my DSLR.

Sean
 

About a week ago I was at a dark sky site and doing an all niter. I specifically remember a period where I was imaging M81-M82 and was pleased to see my RMS was at around 1. When I saw this post I decided to take a look over all what I was doing these nights. I used PHD log viewer and saw that the logs were showing my average RMS was above 2. By any chance would BYN's dithering affect the RMS average? I had assumed not, but guess trying to find an explanation. 

I typically have used the Orion .8 reducer, but another night I went without. Both nights I was doing 3 minute at ISO 800, and zoomed in the stars were solidly round. The only issue was without the reducer I did see some trailing at the edges, but center objects were solid. I have not gone above 3 minutes, but hope soon to see what 5 minute guided with the iexos-100 will provide. At the moment the most important issue for me is to figure out the whole balancing issue (my balancing needs a lot of work). 


--
Mounts: iEXOS-100
Scopes: ES ED80
Cameras:  Nikon D5300, Sony A6000
Msc: ZWO 60mm guide, ZWO ASI290MM, ZWO ASIAIR
Software: Backyard Nikon

@Huangdi
 

Hey Sean, 

were you looking at the individual RMS of your DEC/RA axis or at the total RMS when you checked it while imaging? 
The individual ones are usually much lower than the total one, but added up they give you the total result. 

Yeah, balancing has been a struggle for me as well because I didn't find a way to mount my guide scope on the camera lens. Having them mounted next to each other turned out to be a huge issue, due to the weight distribution. Can't wait to get my refractor :D

asanmax@...
 

Hi Sean,

I noticed that dithering actually affects the overall RMS results. It doesn't mean though that the tracking get worse, PHD2 just shows the total RMS including the dithering periods that actually make the graph look worse.

As to the trailing at the edges, I seem to have had this issue either when the polar axis was not perfectly aligned or when I was guiding on a star far from the object.

Sean
 

Huangdi,

At the time I was only focusing on the total RMS. 

asanmax,
As for the trailing at the edges, I believe this is due to not using a field flattener correct? I think overall I need to do more work in PHD2 learning, as of yet I really am just picking the brightest object and guiding off that. In other words no tweaking or advanced setup so far. I did read earlier thread on settings for the Pulse guiding rate, I will check on the results hopefully someday if we ever have a clear night.





--
Mounts: iEXOS-100
Scopes: ES ED80
Cameras:  Nikon D5300, Sony A6000
Msc: ZWO 60mm guide, ZWO ASI120MM, ZWO ASIAIR
Software: Backyard Nikon

asanmax@...
 

Sean,

I thought you were talking about star trainling at the edges, that is most likely due to field rotation because of poor polar alignment.
If you see the start uniformally blurry with sometimes coma like spots toward outside, that is most likely caused by not very flat focal pane.