Off-Axis Guiding (OAG) for Astrophotography

Off-Axis Guiding using the Lumicon Easy Guider
In this video I attempt to use an off-axis guider (OAG) on the iOptron SkyGuider Pro.
Full Post: astrobackyard.com/off-axis-gu...
The weather conditions were less than ideal for a true test of this system, but I share everything I learned about using an OAG.
The William Optics RedCat 51 makes another appearance, with the ZWO ASI294MC Pro camera and ASI 290mm Mini for guiding.
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[@AstroBackyard]

My favorite comment from the premiere "This video was a POG" had to look it up. Ouch! Lol. Sorry for the lackluster reveal guys but I think there is some good information for anyone looking into Off-axis guiding and what to expect. Thanks for watching guys

[@paulruemmele]

AstroBackyard don’t sweat the haters.

[@cruikshank]

Yes a POG: Positively Outstanding Guru you are for us wanting to learn & improve our Astrophotography. Even for a mere novice such as myself. Like Rush you Rock from The Great White North.

[@AstroBackyard]

@@cruikshank Thanks Dave 😊

[@wesleydonnelly2141]

Trevor your vids are the best on here for info and inspiration! Please ignore the haters who just jealous of your success with the channel/website. No matter how nice we are, there will always be haters! We just smile some more! haha they hate that! Wes, Liverpool, UK

[@vertex3243]

pog is a good thing lol

[@BKBees]

I appreciate that you willingly admit when you're just learning something or when you did something wrong. I appreciate everything about this channel but that aspect really makes these videos likable and I feel I can relate. So thank you.

[@jayballauer8353]

Differential Flexure is movement in the system caused by a weak connection between guide scope and imaging scope. It's not an error between the axes, but rather movement between them. It's not exclusive to guide scope setups either. It can also happen when the visual back is poorly constructed, putting flexure between the OAG camera and the main imager. This is why we use threaded connections. What you state as differential flexure, a constant misalignment of the axes of the main scope and the guide scope, would actually induce field rotation in an image. This can be modelled out in T-Point, as can "cone" error, which would be the error between imaging scope and the top of the saddle (when the scope isn't pointing in the direction that the mount thinks it is). A couple of points about differential flexure. It's never an issue at short to medium focal lengths if you are using typical Losmandy (and other) types of mounting rails. To see it, you'd need to be imaging upwards of 3000mm or more. Second, using an OAG, especially with HEAVY cameras is more likely to cause flexure problems than with a guide scope solution. So, I wouldn't call it an "advantage." Good job on the videos, Trevor. They are enjoyable and well done.

[@shawnewaltonify]

Trevor, thank-you for showing us that you can get professional results within the restrictions of city light. ALso, thank-you for your commitment to showing us the capabilities of the skyguider pro mount. In my opinion, astronomy done as recreation means you do not have to take time and money away from your other activities. For this reason, the skyguider pro is the smart choice for many parents teaching their kids. You are promoting astronomy to a new and dedicated generation! You are a natural at this.

[@stephennield29]

Trevor, you don't have a garage; you have the best Mancave ever! Great video as always Sir!

[@Codyyyyyyyyyy]

Man, your shed looks like such an awesome place to chill lol. I for one appreciate these videos where you try stuff out "live" for us.

[@jimmyfleming3257]

great video Trevor. That's great your garage is coming together.

[@paulruemmele]

This is giving me the confidence to try OAG with my 10” SCT. Totally different setup I know, but I thought if I had issues it would be very difficult to figure out why. This shows clearly what I need to check for when starting out. Now if I could only get some clear skies!

[@patrickmckay403]

Greatly enjoyed the video! I have been trying to guide with the SGP for months but lack experience with PHD2. I missed that button too! I went outside last night right after watching this video and was pulling guided shots of the Leo Triplet of 5 minutes before I had to shit it down for the night. Many thanks for the inspiration.

[@trewhoffman4517]

the new lighting looks great!

[@Afterburner]

Been missing seeing you on there Trevor - glad to see a video come out. I just bought at ZWO ASI294MC Pro and am getting my rig all set to go. Waiting on my Sky-Watcher EQ6-R Pro to arrive. I was going to go with the EQ5 version but what swayed me was the extra carrying capacity and the polar finder being a much better arrangement. Keep the videos coming and THANK YOU for such a great web site with all the tutorials. Definitely studying things there a LOT! -- Clear Skies -- Jon

[@Cessna172SNavIII]

I also plan on getting that mount for my big reflector. I’m still using the mount that came with it, and it can barely carry my 17 pound newt

[@Dennis-tf2cs]

I've used on OAG with my 10" SCT for many years and have always had excellent results, no need for a guide scope ever. Never had an issue finding a star to use for with the OAG either.

[@Jerry-tw7sb]

Spent 100’s of hours bent over a Classic C8 with an OAG, hype red 2415 film, and a Pentax K1000. In winter. Good times.

[@dgodiex]

Man, you're putting together a little arsenal!

[@caracolr1]

Hi Trevor nice video, congratz. About the autoguide and phd2 on the star adventurer when doing autoguiding we need to change some configuration in phd2 setup not only turn off the dec, i dont know if the mounts works the same way but its allways good to check. ;)

[@celestromel]

Perfect timing, Trevor! I’m just setting up an OAG with the ASI290MM on my 8in R-C in time for the South Pacific Star Party in New South Wales, Aust in two weeks’ time. I’m also intending to use ASIAir control for the first time. I’m hoping you may have time to fit the OAG to one of your longer FL scopes and control with ASIAir. I’d LOVE to know the results in time fir the Star Party. Big thanks.Mel

[@hybridram8129]

“Got the TV, the Xbox, got Skyrim in there” Sounds like paradise…

[@frankm81m82]

Off access guider are harder to use at long focal length due to the small field of view and hence fewer guide stars to choose from, especially away from the milkway where star field are very sparse.

[@jmthier]

i definitely didnt think of the DEC setting. as a new user to PHD2 and guiding - i dont really know what i'm doing. so just next/next/finish and hoping things worked. one night, it did say calibration successful (with the iOptron SGP) and said i was then guiding for maybe 20 minutes before clouds rolled in. and the two other times i've tried "calibration failed". now i know to check this setting!!

[@claudio-nature-photography7669]

thanks for the video .... next week I will make an attempt with an OAG on a Mak ... do deepsky with a f11 is madness ... but if you do not experiment in life you do not have fun😎😎

[@shivercanada]

I just got my ZWO OAG with ASI290MM mini from ontariotelescopes today! still need parts to connect it with my DSLR and SCT but can’t wait!

[@boetschge]

My main Setup is a Megrez 72 at F6 with a Canon EOS M6 modified on a Skywatcher AZEQ 5 and Guiding it with the Lacerta Mgen II using a OAG from TS and its a lot of FUN !!! OAG has its difficulties especial using Filters...but my workaround is using Clip in Filters,so the OAG is not limited by the Filter. Great Video,but I whish you would get more deeply into the Subject! Best Whishes and keep on filming,Marc

[@rickylovenuts7466]

Yay I think we shall get a video about cherry springs star party in may

[@muddyexport5639]

Good job. Keep ‘me coming.

[@billyt7225]

Perfect man cave Trevor! 😃

[@JRizzo-li2dr]

I always off axis guide with my scopes with focal lengths over 1000mm. It's a pain to get started, but once its dialed in you cant beat it.

[@wesleypronovost7011]

Yay a new video!! Love your work, Trevor! you inspired me to get into astrophotography and I hope to take images like yours someday!

[@AstroBackyard]

That's very kind of you to say Wesley - I have no doubt you will surpass my image quality!

[@wesleypronovost7011]

@@AstroBackyard Thanks Trevor but I'm pretty sure the night sky is just better in Canada than here in the US LOL

[@natemandoo]

OAG through short focal length is some Junior Varsity stuff. Break out the 1000+ focal lengths and you REALLY gotta have your stuff ironed out. Best thing to help with those longer focal lengths are focal reducers. You can put a focal reducer on your guide camera (more spacing challenges) and it will be VERY helpful. I put a 0.5X focal reducer on my guide camera and I could resolve stars, AND the secondary mirror assembly and edges of the scope.... on a 1600mm focal length 8" R/C scope.

[@dasimcoes]

Trevor, thanks for the informative video. This will be awesome portable system once the bugs are worked out. I didn't see the cem60 mount. Do you still have it ?

[@scoot4081]

Beer fridge + classic rock = real man

[@haibeth5421]

Thanks for doing a video on trying to guide the Sky Guider Pro with ASIAIR. I have an ASIAIR on order and I’m hoping that it would work with the Sky Guider Pro too so I can have a portable rig like your for traveling in my van. Could you share what ZWO had you modified to make the ASIAIR work with the Sky Guider Pro? Thanks.

[@chettdavidson1812]

Thank you for everything you do for astrophotography. I am working with a 115mm apo refractor. What would you suggest would be most accurate auto guide for this scope? Thanks in advance...

[@tolgagumusayak]

Hi Trevor, finding guide stars with an OAG is only problematic when using very long focal length scopes or using very cheap insensitive cameras. I recommend Starlight Xpress Lodestar as a guide camera. You should not have any issues finding a guide star with any telescope I see you use on your channel.

[@deckardbr]

Hi Trevor - thanks for the video. I have the exact setup you tested - you mentioned some challenges with focus that you solved. What did you do? I cannot get both cameras to focus at the same time using the various spacers combinations. Thanks in advance

[@ibustanut]

lol i thought i was one among just a few people to use the app at 0:51, then i see you using it lol! i highly recommend using Dark Sky map (android, dont know if its on iphone) to see where the light pollution is highest to lowest. Great video as always!

[@JC130676]

You're not the only one, it's a really nice service from FLO . I just wish it'd let me set the home location instead of defaulting to Exeter.

[@edfredian8825]

Read your article and watched them video. Both very informative. One question, though. What is the wiring sequence using phd2 and the Starguider Pro. Camera->laptop/phd2->Skyguider ST4 port?

[@blueobject]

Hey Trever, awesome videos, hope I meet you some time maybe Cherry Springs... Hey qq - what is the ideal gain and offset for the 290mm? What did you find worked well? thanks! Marty

[@stuparker776]

Hi Trevor Great vid thanks.I have been guiding with the redcat and skyguider pro for a few months using the ZWO mini guider.I seem to get good results, the question I have is if you use a off axis guider and filter with the redcat design and where the filter goes wouldn't it be harder to find a guide star as the light coming from the scope goes through the filter and then the off axis guider?It seemed that you found no issues here. I would of thought it would of been really hard to find a guide star using a Ha 3nm filter for example. That's where the little guide scope works really well?? Thanks form New Zealand Cheers Stu

[@daz.78]

Great video buddy,I want a garage like that telescopes,beer and xbox I could live in there.😂😂

[@JeffHorne]

How do you find dithering in RA only? Is it as good? ...and do you dither after every image?

[@mabdinur85]

I might be wrong but differential flexure might be a more pronounced problem with truss based Newtonian or RC's. OAG on that small aperture might make exposure compensation required like you said ... which means more noise. I wonder a better trade-off might be to do one long exposure (ie. 30 min) instead of several sub's.

[@kacerhomebeerbrewing]

Nice Trev, cheers!

[@philbivins7133]

Just subbed to your channel. It's very informative, the things you have covered are the things I need to know about. I'm new to this hobby and recently purchased a Celestron SCT 8in. I also purchased a Celestron focuser. What I'm really having issues with is purchasing a good guide/ finder scope. I purchased an Orion 50mm scope with the ZWO ASI 120mm b&w guide camera. I learned from another KZbinr this Orion will not be enough based on the FL of the Celestron. So I purchased an f/6.3 focal reducer. Based on all this stuff and this setup, what do you recommend for a good guide/finder scope? Any and all help is greatly appreciated. Thank you

[@51rwyatt]

Now I'm thinking of using OAG on Redcat mounted on C8 to have Redcat do double-duty as a guide scope.

[@DawgcityClev]

Problem with OAG is that it won't work well with every set-up. It still may be hard to find guide stars on some rigs.

[@2badger2]

Great video! Have you used the OAG with your Optolong eXtreme filter yet? How did it work? Thanks

[@BSVGenius]

nice work! Are you planning on doing more membership vids etc?

[@wanderingquestions7501]

Will a car fit in the garage anymore?

[@Nico.75]

Hi Trever! Did you have the chance to compare the ASI290mm Mini vs. the ASI174mm Mini regarding OAG guiding using the Redcat as main scope? Thanx so much for all your videos and great images! Cheers from Zurich!

[@finnr3472]

Do you think it's ok to pack 4kg on an equatorial mount, that can handle a maximum weight of 6kg? Normally you should only put 3kg on this mount for astrophotography but does this one kilogram make a difference?

[@jalenab2374]

Love your videos!!! What app do you use for the clear sky chart?????😄

[@neverfox]

Thanks for the OAG discussion but I'm actually more curious about the ASI294MC Pro with the RedCat 51. Doesn't the pixel size of that camera with the short focal length of the RedCat lead to significant under-sampling? Maybe that's okay for wide-field images like the ones you tend to go after?

[@kisho2679]

How would you use an OAG with a 2800mm tubus in general, just for solar system or also for deepsky?

[@novoscapellc6102]

Would you say the 290mm mini is more precise than the 120mm mini ? By how much ? The 290mm mini has more pixels but is also slower. Thanks

[@DFPiper]

Which mount do you select in PHD2 connection box? I don't see the SkyGuider and can't find any SkyGuider drivers even on the iOptron website :(

[@hurdpcs2802]

Trevor, Is it worth going to an OAG on my edge HD 8 when I also use a Hyperstar that I can't use an OAG on. I would have to leave my guidescope on for the Hyperstar and put an OAG adapter and probably a second camera on so I don't have to fiddle with setting up the camera each time I switch from my Hyperstar to the long focal length.

[@paulbenoit249]

Seems like ASI is just about to release an OAG with a helical focuser built in, .....should make things much easier to get the right focus for both cameras (guiding+imaging).

[@paultadrick8801]

Please let us know if you get the SkyGuider guiding working through the ASIAir. That would be a sweet setup.

[@msenin]

@Trevor @AstroBackyard Did you solve your ST4 connection problem with ASIAir? I'd like to build a similar setup with ASI294MC Pro as main cam and ASI120MM as a guide cam on OAG and use AISAir because I prefer to use iPhone and iPad over a laptop. But I don't want to drop $$$$$ on it before I know this set up will work. If your ST4 connection doesn't work then I can't use ASI120MM as a guide camera :(

[@jimm5593]

Thanks for another great video that features highly portable, more affordable equipment, such as many of us use. My AP so far has been done mostly with an AT72 ED scope on a Star Adventurer mount. As I watched I kept asking myself, when will he mention the fact that he has no DEC drive? Glad you brought it up. Great image from a portable, affordable rig. Thanks and God bless.

[@simonresch9677]

have you talked with astro-vault because he released at the same day a video about oag

[@JohnS916]

Very nice video Trevor. Fun to watch your personal experiences trying a new toy out for the first time. You make it look a lot easier than what I'm used to. One of the biggest issues in general with these devices or any addition to the imaging train is correct spacing. Much of it is a mystery and very confusing, at least for me. Fortunately, the easiest setup is the one I currently use and is virtually plug and play, DSLR imaging using a focal reducer or field flattener. The correct spacing is 55mm and I achieve this without having to do any additions or subtractions. I simply connected the field flattener to a T Ring, connected it to the camera and then insert the end of the field flattener into the focuser tube. The 2" light pollution filter is screwed into the field flattener and you are done. However, where things get confusing (to me) is when you upgrade to other imaging devices like a CCD mono setup, field flattener or reducer, filter wheel and whatever else that might be required including the use of an OAG. The key apparently is that 55mm figure and to achieve that requires some addition or subtraction of imaging train spacing by using or removing spacers. Maybe 55mm isn't the absolute benchmark to use, maybe there are options? I realize as well it helps to have accessories that are on the thin side rather than having thicker ones. Off the top, I can't visualize getting the correct spacing when you add additional devices described above, but I realize imagers do it all the time. One of the problems here is how the process is explained to novices such as myself. What would be ideal is to detail what devices are included in your imaging train (including widths) with someone responding to how to connect them in order to reach the correct spacing requirement.

[@Dennis-tf2cs]

Do you have the prism measurements on this OAG?

[@randydonnelly5897]

I tried using an OAG on my Nexstar 8SE with the Celestron OAG and Lodestar X2 but experienced nothing but problems with it. Parafocal issues aside, finding a suitable guide star at such a long focal length is a pita. Another con using the Celestron OAG is that it doesn’t have a way to attach a 2” filter anywhere along the image train...no filter drawer or way to thread one on. Ended up using a traditional guide scope mounted atop my main optical tube: Meade Adventure 80mm. Of course, now I have weight issues. Damned if you do, damned if you don’t.

[@subhodeepmondal7937]

Plz make a video on off axis guider with celestron edge hd 11 with 2800mm focal length

[@deancamp4914]

I'm looking at the ZWO OAG - and it's about the price of most guide scopes - and saves on weight. Are people getting superior results with OAG vs guide cameras? Also, have seen comments that the helical micro focuser is a good add-on, so you're able to get precise and easy focus with the OAG?

[@nicklloyd9165]

Dig the bird feeder shoutout... especially brown creeper.

[@alanhat26]

Love it awesome 😍

[@youdiedlol7718]

I bought an oag and never got it in focus :(

[@GTGeorgeW]

Hey Trevor... About this audio;) Which mic are you using?

[@MrJonathan0691]

Question (not a real english speaker so I may misunderstood what you said) : OAG needs to divide the light flux, right ? To guide it to 2 differents cameras. So you will collect less light on your 2 cameras ? So it will need longer poses and still need a more sensitive guiding camera? I might be all wrong but I need to ask ! Maybe there still are much more benefits to use this technic. Thanks for your videos

[@claudioarchi]

Hi Trevor. As always great video and very clear explanation. I was wondering how do you power all your gear. I meant what type of converter you have to feed 110v to 12 v as many AP gear requires. Thanks and clear skies

[@wrnchhead76]

I'm not Trevor (lol) but I was in the local Goodwill store and found 2 5 amp (!) power supplies for $1 each!

[@bofblog]

Great informative video Trevor, only thing I've heard against OAG is when shootings narrow band such as Ha with lack of light coming through and harder for the cam to pick up a star to guide on

[@paulruemmele]

Les Houghton I’m wondering if shooting with a EOS DSLR, can I use my narrowband EOS clip filters to only filter the imaging camera and avoid filtering my guide cam

[@bofblog]

@@paulruemmele Yes that's the best way with no filter on the guide scope and just on the camera or an alternative if you use an Off Axis Guider such as Trevor is put the OAG before the filter wheel or filter draw and it will guide on the light before filtering

[@bofblog]

@@paulruemmele Hi .. that's the best way , no filter on the guide scope and only before it gets to the sensor, same applies to a CMOS or CCD camera..if like Trevor use the OAG in the video you can put the OAG in front of the Filter wheel or filter draw so it guides on the light before it gets filtered

[@UNDERST0RY]

Is there any reason data from the astrophotography camera cannot also be used to guide the scope. I mean, this tech is from the '80s when a 4K computer was a big deal. These days our cheap cell phones have far more computer power than was used to send the Apollos to the moon. Surely we can just route data from the primary camera into tracking software?

[@joshuadtaft]

Your timing is impeccable. I literally just started researching on OAG not more than a day or two ago, lol. Now if my SGP would get here already so I can start tracking. It's timing is not very impeccable 😂

[@charleswa]

This will be interesting. I'm curious to see how it goes and wondering if the same idea could be extended to a DSLR/telescope setup with a Sky Guider Pro.

[@wesleypronovost7011]

Of Axis guiding works with a DSLR, I almost used off axis but had a guide scope on hand so just went with the traditional method.

[@charleswa]

@@wesleypronovost7011 I haven't spent the money either way yet for a scope or OAG...

[@Yanthungbemo]

Is there a way to guide without any additional accessories? Guiding with just the data coming in directly from the main camera.

[@M-Mir]

No

[@capturethephotons2078]

Beer skyrim and classic rock 🆒️ Clear skies ✨

[@astronomylivestream]

Yes!

[@TheLuxentertainment]

How exactly do you need to connect Skyguider + Autoguider to the PC? (Cables, Slots)

[@TheLuxentertainment]

If anyone else has the same question I think I found the answer. It should be Guide Camera USB to Laptop USB and Guide Camera ST4 to Skyguider ST4 and then in PHD using "on camera" setting for the mount.

[@JamesLee-pf2dz]

I thought the flexure occurs when the guidescope and the imagescope are not tied up tightly so that there is a play between them and the guiding error the guidescope sees is different from what the imagescope sees... but I guess I am wrong...

[@makers_lab]

James Lee you are correct. The guider and OTA don’t need to be on the same axis, though I try to get mine close as I use the guide cam as well as main cam when aligning as my focal length is long.

[@jturie]

OK, I get the beer fridge and the stereo. What are those tires doing in your garage?

[@WaWfan64]

probably a set of winter or summer tires

[@michaellovell4390]

Do you find you are undersampling with the Redcat51 ?

[@AstroBackyard]

With the setup in this vid - I am at an image scale of 3.81 which some would considered to be way oversampled. Honestly, I'll need to take some images on a better night of a bigger target to really see if it's a factor to consider. The RedCat is fantastic with my DSLR's!

[@OddSoxChris]

OK, this may be a noob question but why not just use the primary imaging camera for both imaging and guiding? I always only see people use two cameras. Would that be such a bad idea? It feels like a logical thing to do.

[@makers_lab]

It’s because you need long exposure for imaging and short for guiding, e.g. 1 second on the guide cam vs 3 mins+ on imaging.

[@eyesoftexasskywatch]

The app at the beginning of the video, which was it? If you don't mind me asking.

[@johngiromini5745]

At 0:51, believe that is Clear Outside. It's available for both Android and iOS

[@sjondemolphotography]

for sure clear outside! use it myself

[@eyesoftexasskywatch]

Clear Outside - Thanks all! I will give it a try. I have been using Astrospheric so far. It's ok. Like to have options!

[@lst141]

That’s a clear Night?, it’s full of clouds!. Definitely the beer frige is a important Astro accessory.

[@meghjoshi7031]

Guiding with an iOptron Skyguider Pro? Count me in!

[@cryptojihadi265]

So why wouldn't everyone use this method? Is there a downside to it I'm not realizing? Ok heard about the aperture limitations. I'd assume a 130 mm f7 or above would be no problem.

[@jeheehan7234]

대한민국의 서울에서 기다리는 중.... I'm waiting "Lumicon Easy Guider" .....historical item in astrophotography. It's from film astrophoto

[@strelnikoff7]

Declination motor? I have an AVX and I got the same message... but now I wonder - it should be obvious though - does AVX has dec motor? It should ... two axis are rotating.

[@paulruemmele]

strelnikoff7 it does, I have the same mount. Got this error one night and upon inspection saw that I totally forgot to plug in the dec motor cable. 🤦‍♂️

[@strelnikoff7]

Paul Ruemmele Ah the joy of confused and worried face in the night, just before the intervalometer is depressed “Have I connected everything?” Its not even funny 😃 well, we will have some clear nights soon, I’ll try again...

[@seanmolony-redstickastro238]

Needs a redstickastro flag!!! I need to look at your ASI294 images. I just got one for myself along with the new Triad Filter from OPT. I'm hoping to be able to shoot OSC in my LP Skies with that filter. By the way using two tie wraps enables me to connect my Polemaster to my Sky Guider Pro. Peace Sean

[@darrenwarne9005]

Join the ASIAIR fb group for help with settings!

[@bluebirdkim4134]

May I ask you a question? So, I have a Skymemo S (Star adventure) and I'll have Asiair So Could I connect these two? Let me know if you know.

[@MikeD606]

Now I'm confused ... Just today I was watching your video "I'm seeing RED" (released one month before) and you were doing unguided 4-min subs with a DSLR, and now you're doing guided 3-min subs with a cooled astro-camera? 🤔 I thought you were going to go for something crazy like 10 minutes, or at least try! 😃

[@davepastern]

all I have to say is: Fus ro dah!

[@XPFTP]

wouldnt be to hard to make that garage a roll off.. haahahha

[@SKYST0RY]

None of us have ever had a dummy moment like forgetting some random option in PHD2. You should be ashamed! JK. Happens to everyone. I know this is an old vid but as a fan of OAGs, I was glad to see it.

[@kostasastro]

Once you go OAG you can't go back

[@hdagent8080]

Cut the tree down. Build a telescope with the wood.

[@darbycrash55]

Skyrim!