Is your telescope guiding good enough?

Answering the question "what is good guiding" as simply as possible. As the size of your telescope increases, and your sky quality improves, the impact of your guiding becomes more obvious. So what kind of guiding do you need to achieve so you're not losing too much detail?
Find out your limiting error rates using this calculator: www.astrowithroro.com/guiding
Find out more: www.astrowithroro.com
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Timestamps:
0:00 Intro
1:07 Cheat sheet
3:58 Uneven error rates
5:32 Guiding calculator

[@AstroWithRoRo]

As always, any errors or updates will be pinned to this comment as they are found.

[@VisionCommunications]

Another great video! Good guiding is round stars. Good guiding is also not sharing guiding information with people on Facebook! LOL!

[@deepskytrekkin9600]

Thanks for the video. I am looking for a tutorial that explains how change (tweak) the RA and DEC to match (or at least get them as close as possible on a given night/conditions.

[@zyban99]

Good to see you back. More videos pleeeeease

[@suzannebeers6238]

Great video....looking forward to trying out your tools. Thank you very much!!

[@rtpman1953]

Thanks, RorRo for the very informative video. I'll be using your guiding/OTA calculator to better check my results when imaging.

[@handwrittenjello]

Thank you for the video. I would love to hear a video on sampling. And more corgis!

[@gregerianne3880]

Great video and terrific tools, Rohan! Thanks so much for these. Yes, I'd be very interested in a video about sampling, especially since your videos are so clear and helpful.

[@gregerianne3880]

@@anata5127 Sorry, this is a little cryptic. Is what 'it'? I'm not understanding what you mean.

[@AstroWithRoRo]

@anata5127 I have no idea what you're talking about. I would have rather linked to original content than have to make it myself as it would have been much easier. If you can stop spreading lies and incorrect facts that would be appreciated.

[@gregerianne3880]

@@anata5127 Ah, I see what you're getting at. Well, I liken these hard-working KZbin creators to professors teaching a class. Unless you're in an advanced graduate-level course, the professor isn't going to give you his/her original research, in fact, it is going to be a rehash of second-hand information found in a textbook (or other channels). But the real question is, which of those professors' styles really resonate with you and helps you understand what you wouldn't be able to understand otherwise. So, for ME, this video is one of those that explains things to a non-engineer (me) in terms that are easy to understand and provides tools for me to explore that help me adapt the information to my own situation. Although you may have advanced knowledge, e.g., in engineering or mathematics or both, and prefer to learn in a different way (from primary sources), not all of us are at that level and depend on people like Rohan and channels like this to provide information in an understandable way. Hope that gives you a clue about why I think this is a great video and the tools were terrific -- for ME.

[@igoreq4495]

Very interested in a video about sampling, already sybscribed a while ago, so just waiting now :)

[@AlexN-Astro]

It doesn't matter if you have incredible (sub arc second) seeing and a 300mm aperture, if you've got 4.6 micron pixels and your 300mm telescope happens to be F/2. The theoretical maximum of the optical system is only relevant if you're oversampled and there is any chance of actually capturing that theoretical maximum. If your telescope has a theoretical maximum of 0.3", and you happen to be in 0.5" seeing on top of a mountain, but your complete imaging system has a 2.2~2.5"/pixel resolution, amount of improvement to your guiding is going to get you anything better than your imaging systems actual resolving limit which is a function of pixel size and focal length. When building an imaging system, it's important for people to consider their best and average local seeing conditions of where they are going to be imaging, as well as their skill level, and pair the right camera and optics to take advantage of those conditions without creating complications that they may not have the skill, knowledge or hardware to resolve...

[@bobbeanbags]

This was excellent. I’d love to see a video on setting guiding aggression numbers to achieve the best guiding.

[@AstroWithRoRo]

@anata5127 not sure why you continue to watch all my video's if I'm such an amateur who won't take you anywhere. If you're not enjoying the channel you're welcome to find these answers elsewhere :)

[@bobbeanbags]

Roro … love your videos and have learned a ton! Thank you for making your channel one of the best on the internet for astrophotographers

[@AstroWithRoRo]

@bobbeanbags thanks for your kind words!

[@Astrophotography_love]

Thank you

[@AstroWithRoRo]

You're welcome

[@NunoAg]

And what are the values if I have RA axis only?

[@jesuspineiro1622]

There is another factor that you are not taking into account: the resolution of one step in arc second. In most mounts this value ranges from 0.24 to 0.14"/step. Therefore it is impossible to have a guide less than these values (no RMS error) On an EQ6, the mount itself introduces an error of 0.14" of arc due to the stepping. Regards

[@jesuspineiro1622]

In your calculator you should take into account the relationship between the tolerable error in the guider scaled to the main scope with its camera and the optical train. An error of 0.5" RMS in a 50 x 200mm guider with a 2.9um pixel, can mean a real error of 2.5" in an 8" telescope and 1600mm focal length, with a 3.76 um pixel.

[@alexalmeida8627]

Great video! I was always wandering whether my guiding was fine. I have a Redcat 51 with aperture of 51mm. I have great seeing, Bottle 3, high elevation and my RMS range from 0.8'' and 1.3"". Interesting fact is that my stars are always round (before post processing), even in a particular night which my RMS was around 2"

[@AstroWithRoRo]

So long as your error rates are similar in each axis your stars should continue to look round. The FWHM of stars will increase on nights your guiding errors increase and this can mean smaller details are lost, but at the scale of a Redcat51 the impact shouldn't be too great. :)

[@ryanwood1911]

Video about sampling, please!

[@ryanwood1911]

Also, how can you tell how good your seeing is? Can you tell with a PHD2 Guide Assistant run?

[@AstroWithRoRo]

You can find it in weather forecasts like those from meteoblue or by using a sky quality meter.

[@nikanj]

Great video Rowan. I tried your calculato and it seems about right, when I have greater than 0.69" is when I start to see elongation/issues in my subs. How can I tell if my system is diffraction limited?

[@AstroWithRoRo]

Usually the telescope will mention if it's diffraction limited optically, and most moderate to high and telescopes should be. If that's the case then you just need to make sure your camera's sampling is correctly matched to see all the detail your telescope can capture. Hope that helps!

[@Astrophotography_love]

Can we write guide camera scope aperture and focal or main scope ? At your website

[@AstroWithRoRo]

Write the imaging scope's aperture & focal length, not guide scope.

[@MikeMcCann-xz6jn]

side request: using PHD2 comet guiding feature

[@MethiasZa]

One question i've had on seeing is how do you know what your seeing is at the location on that day?

[@AstroWithRoRo]

Best way is either with a weather forecast like meteoblue or using a sky quality monitor.

[@MethiasZa]

@@AstroWithRoRo Thanks, I then seem to be in the lucky position of having somewhere between very good seeing to exception seeing on most nights (generally its around 0.8 on Meteoblue seeing chart which means I really need to work harder on my guiding setup (i'm between 0.5" and 0.8" RMS). Would you be able to do a PHD2 Guiding tips and tricks to improving your guiding?

[@michaelbibby8636]

Is your calculator assuming that both your guide scope and telescope have the same focal length and the guide camera has the same pixel size as the imaging camera?

[@AstroWithRoRo]

The calculator only needs your imaging scope & camera information. Your guide scope & pixel size doesn’t really matter for this calculation.

[@michaelbibby8636]

@@AstroWithRoRo But it should, is my point: if your guidescope is, say, one tenth of the focal length of your telescope, then its errors are multiplied by a factor of 10 in your imaging camera (assuming the same size pixels of guide camera and imagiang camera), is that right?

[@AstroWithRoRo]

Ahh, I see what you're asking. The calculation is done in arcseconds, so as long as your phd2 is set to show error in arcsec (and is setup correctly with guide cam focal length & guice camera pixel size) then it will work all that out for you. The error in phd2 via arcsec can be directly correlated to the pixel resolution of your imaging scope. If your imaging scope & guide scope are far out of whack (eg 100mm fl guide scope on 2000mm fl imaging scope) then you can definitely have issues with guide accuracy, but generally phd2 is pretty good at guiding, even sub 1-pixel of your guide camera.

[@michaelbibby8636]

I see, thanks for clearing up my confusion.

[@michaeltonge1971]

"Keep total guide errors under: 1.18"". Per second? Per Hour? Per fortnight?

[@poruatokin]

You're not understanding. Arc seconds is the angular error. Total guiding is calculated over an imaging session. There is no time factor.

[@poruatokin]

One huge elephant in the room that you fail to address, or explain badly As the seeing deteriorates, there is no way to achieve better guiding. If you try then you're just going to be chasing the seeing. Bad seeing = bad guiding.