18 replies to this topic

[jaimac]

Someone is selling a 2015 AVX for $350. Is this a good deal? How do I test if the mount is working properly? As per the seller, he was able to take 4+ mins long duration pictures using Starshoot autoguider.

 

I am very much interested in the Goto capability and some astrophotography. My current mount is a CG4.

 

[Oyaji]

My advice:  run, don't walk, away from this deal if you want to do astrophotography.  Even a brand-new AVX is a chancy proposition for that use.  

[KJR]

As one who owns an AVX mount that is now about 1 year old I would probably recommend a used HEQ5 if your budget will allow. Easy to work on and upgrade to a belt system or replace bearings.

 

I use a C8 SCT with Celestron OAG with an ASI174mm mini guide camera with my main camera a ASI071MC Pro. I use an ASIAir Plus 256 and a Mele miniPC with NINA. PHD2 always complains about DEC backlash and very rarely do I get a nice right angled orthogonal graph of the RA and DEC when I calibrate. Guding assistant can't measure the DEC backlash to be able to compensate for the backlash. I've opened up the RA and DEC worms, cleaned them, lube and then set them with no visible or tactile movement. Many say to balance East heavy. ASIAir guiding calibration doesnt' seem to complain but doesn't offer the details like PHD2. 

 

I use the predictive PEC algorithm in PHD2 with using NINA and I guess under ASIAir it defaults to hysteresis algorithm. Sometimes with the ASAir guiding I'm at 0.8 or beter and with PH2 I rarely get an overall RMS error much below 1", but individually RA and DEC will be under 1". But the guiding is not consistent. An axis with be running under 1" and then suddenly take off. I guess the backlash might be responsible or maybe stiction. My RA axis is smoother than my DEC. My DEC is sticky and it's difficult to balance. 

 

I get by with it but I'm actively looking for a replacement that will suit my C8 SCT. However, I manage to get 2, 3 and 5 minute exposures that seem to look pretty good. One good night of guiding and was able to take a 10 minute exposure just to see if it could be done. You just have to work hard with the AVX to get the guiding good enough for astrophotography. Maybe if you are using a small focal length scope it won't be as hard to use and will guide better compared to my C8 at 1442mm. 

 

The reason I'm recommend the HEQ5 is because you can replace gears to the worm with belts and it's easy to remove the old bearings and install better ones. With a belt system all you theoretically have to worry about is adjusting the worm. The AVX will not allow a belt upgrade and the DEC axis doesn't have a full set of bearings.

 

The best part of the AVX mount is its tripod.

 

See if the seller has posted any images from using the AVX. 

 

KJR.

[TelescopeGreg]

What sort of scope the current owner use, and how was it mounted?  What sort of scope do you intend to put on the AVX? 

 

That makes a huge difference.  I do 4+ minute subs with my AVX, supporting a large (130mm f/7) scope, but it took me a long time and a lot of tweaking to get it to work halfway reliably.  A shorter / lighter scope, say the proverbial 80mm f/6, would be a lot less stressful.  I'd also get a proper guide scope, something in the 50-60mm f/4 class, and a good guide camera.  Don't believe anything you read on the Celestron website regarding their product capabilities without finding independent corroborating evidence.

[jaimac]

My advice:  run, don't walk, away from this deal if you want to do astrophotography.  Even a brand-new AVX is a chancy proposition for that use.  

I was hoping it will be better than CG-4 in all ways for the price. Go for better mount if I end up doing lot of astrophotography.

[jaimac]

As one who owns an AVX mount that is now about 1 year old I would probably recommend a used HEQ5 if your budget will allow. Easy to work on and upgrade to a belt system or replace bearings.

 

I use a C8 SCT with Celestron OAG with an ASI174mm mini guide camera with my main camera a ASI071MC Pro. I use an ASIAir Plus 256 and a Mele miniPC with NINA. PHD2 always complains about DEC backlash and very rarely do I get a nice right angled orthogonal graph of the RA and DEC when I calibrate. Guding assistant can't measure the DEC backlash to be able to compensate for the backlash. I've opened up the RA and DEC worms, cleaned them, lube and then set them with no visible or tactile movement. Many say to balance East heavy. ASIAir guiding calibration doesnt' seem to complain but doesn't offer the details like PHD2. 

 

I use the predictive PEC algorithm in PHD2 with using NINA and I guess under ASIAir it defaults to hysteresis algorithm. Sometimes with the ASAir guiding I'm at 0.8 or beter and with PH2 I rarely get an overall RMS error much below 1", but individually RA and DEC will be under 1". But the guiding is not consistent. An axis with be running under 1" and then suddenly take off. I guess the backlash might be responsible or maybe stiction. My RA axis is smoother than my DEC. My DEC is sticky and it's difficult to balance. 

 

I get by with it but I'm actively looking for a replacement that will suit my C8 SCT. However, I manage to get 2, 3 and 5 minute exposures that seem to look pretty good. One good night of guiding and was able to take a 10 minute exposure just to see if it could be done. You just have to work hard with the AVX to get the guiding good enough for astrophotography. Maybe if you are using a small focal length scope it won't be as hard to use and will guide better compared to my C8 at 1442mm. 

 

The reason I'm recommend the HEQ5 is because you can replace gears to the worm with belts and it's easy to remove the old bearings and install better ones. With a belt system all you theoretically have to worry about is adjusting the worm. The AVX will not allow a belt upgrade and the DEC axis doesn't have a full set of bearings.

 

The best part of the AVX mount is its tripod.

 

See if the seller has posted any images from using the AVX. 

 

KJR.

The picture posted by the owner looks good. He was using a Newtonian. I have 108mm refractor with 600mm focal length. I doubt, I will get a longer focal length scope any time soon. 

[TelescopeGreg]

The picture posted by the owner looks good. He was using a Newtonian. I have 108mm refractor with 600mm focal length. I doubt, I will get a longer focal length scope any time soon. 

Ok, add in a guide scope and cameras and you're going to be pushing the AVX.  Not impossibly so, but it's not going to "just work".  It will teach you things you never knew needed to be learned.  You may even learn to swear in foreign languages.  But if you stick with it, very likely you will get it to work.

 

Good deals on used AVX mounts aren't all that uncommon, so what I would do first is to first see what you can do with the CG4 that you already own.  Get some images under your belt, and learn from them.  Every image you take is a record of all the good and bad things that occurred while the shutter was open.  Study them.  Ask questions.  When the time comes for a better mount, you'll be much better able to assess what you really need.  As a long shot, you may even be happy enough with what you have that you can spend the money on something else (camera upgrades, filters, auto focuser, etc.).  No end of opportunities there.  My own upgrade journey was turned upside down when I upgraded from an 8" Newtonian to a 5" refractor, spending the money on the scope that was earmarked for a new mount.  Surprisingly (though not so in hindsight), the lower inertia profile of the refractor system made my AVX much happier, enough so that the next upgrade was for the camera and not the mount.  I still have the AVX...

 

Also, how well do you know the night sky?  How well do you want to learn it?  I'm continually amazed at the folks with a nice Dob who can find all kinds of stuff in the sky.  One "risk" that I realized when buying my AVX was that the GoTo capability meant I would probably never learn how to navigate the sky on my own.  So true was that.  I bought my AVX back in 2017, and 7 years later the number of deep sky targets that I can locate without it can probably be counted on one hand. 

[mikemarotta]

As one who owns an AVX mount that is now about 1 year old I would probably recommend a used HEQ5 if your budget will allow. Easy to work on and upgrade to a belt system or replace bearings.

I bought my AVX in November 2021. I googled the HEQ5 and found the Sky-Watcher website. The two mounts seem about the same to me. I can grant that perhaps the Sky-Watcher was tested to closer specifications but I have no way to know that objectively. My hobby is observational astronomy not automobile mechanics, so I am not likely to replace belts and bears. The thing either works or it does not.

 

Ok, add in a guide scope and cameras and you're going to be pushing the AVX. 

The AVX carries an Astro-Tech 115 mm apochromatic triplet. Weight is 13 lbs. I am strictly visual.

 

The signature of the original poster shows two telescopes that will be served well on this mount.

William Optics Megrez 72FD Refractor
iOptron Versa 108mm Refractor

 

My caveats center on any used instrument. If you cannot fix it, then buy it new from the manufacturer or licensed reseller. I bought my used gear from Explore Scientific because they sell it factory reconditioned with a new warranty.

 

Clear Skies,

Mike M.

Edited by mikemarotta, 25 July 2024 - 12:16 PM.

[KJR]

I managed to get 40 images of the Crescent Nebula a couple of nights ago with my C8, Starizona focal reducer, Celstron OAG and ASI071MC. Guiding started out acceptable, RMS was just below 1" but out of the blue the DEC goes crazy and despite lots of pulses it doesn't come down then finally reacts. It caused the DEC RMS to go from 0.60 to almost 3", then it settle down and was running under 0.5". Looking at that frame I have double and misformed stars. I'll have to throw it out. Sometimes, in guiding the DEC won't show that behavior, I guess it depends on the target location.  Maybe because the OTA was pointing almost straight up towards Cignus. 

 

I've never used the GoTo except maybe once. I realized using the telescope visually would be boring for me. Luckily, I didn't spend a lot of money on eyepieces. I suppose if you just wanted to do EAA and take short exposures under 30 seconds the AVX would be fine.

 

I dived into photography almost off the bat buying an ASIAir. I found several issues using that device with the AVX mount so moved to a miniPC and NINA. The AVX worked fine with CPWI under NINA. Slewing and centering works fine with the AVX as long as plate solving is working correctly. But guiding is the the make or break feature for astrophotography in my opinion

 

My OTA and image train weight is about 19lbs which is 10lbs under the AVX weight rating.

 

KJR

[TelescopeGreg]

The AVX carries an Astro-Tech 115 mm apochromatic triplet. Weight is 13 lbs. I am strictly visual.

Visual, sure.  Mine came with an 8" f/5 beast of a Newtonian scope.  FAR heavier, larger, longer, etc., and it was fine for visual work.  But the OP said they wanted to get into imaging; THAT'S where the difficulty is.

 

Oversimplifying a bit, when you're imaging you need to keep the scope aimed at a spot on the sky to within the size of a pixel or so, for as long as the shutter is open (typically 10's of seconds to minutes).  That span of the sky depends on the size of your sensor's pixels and the focal length of the scope, but it's on the order of an arc-second.  (Math:  206 * pixel size in microns / focal length in mm.)  The AVX cannot do this by itself, and will struggle even with an autoguider.  The gearing and bearings just aren't designed for that sort of use; it's a visual mount. 

 

The autoguiding challenge is not simply one of telescope weight.  Weight is used as a proxy for moment of inertia, but it's a poor one because it does not consider the physical size and mass distribution of the scope.  Inertia goes by the mass times the square of the distance to the pivot.  When you square something it gets really big really fast.  A Newtonian scope with a heavy camera + focuser on one end and a heavy mirror on the other is about as worse-case as you can get.   Imagine trying to spin a set of barbells length-wise and you get the idea.  A refractor is a bit better because the focuser has a significant horizontal length component, meaning a lot of it is closer (less distance squared) to the Dec axis, compared to the Newt.  Much better still for Dec would be an SCT scope which has a folded optical path, but they tend to have very long focal lengths (1-2 meters) which narrows that required accuracy considerably.  They're often rather tall (8+ inches), making for a more difficult job on the RA axis. 

 

On a good night, my own setup can keep the Dec orientation to well under an arc-second, but the RA side is about 1.5 arc-seconds or so.  Binned 2x2, the pixel scale of the optical system is 1.7 arc-seconds, so generally I'm good, but again it's taken a good bit of system tuning to get that sort of result.  Getting any better will require digging into the mount's gearing.  Assuming a typical 3.7 micron pixel size, the OP's pixel scale would be about 1.2 arc-seconds, and the scope is both shorter and lower in height.  That all helps (some of it squared), but as I said it will still require some zen-like focus on finding a best setup.

[jaimac]

I got to look at the AVX. Couldn't run it to see how it functions as the power cable was missing. The hand controller is dated and doesn't have the usb connector nor does it use latitude and longitude for aligning. The seller did find the power cable, so I will test the mount over the weekend. 

 

Assuming the mount is working alright, will the dated hand controller work correctly? Should I get the newer hand controller and the wifi dongle? At this time if I can get a goto visual, I will be quite happy. When I want to do real astrophotography, I will upgrade the mount. 

 

I am tired of crouching and searching and a goto will really help. 

[Skywatchr]

I got to look at the AVX. Couldn't run it to see how it functions as the power cable was missing. The hand controller is dated and doesn't have the usb connector nor does it use latitude and longitude for aligning. The seller did find the power cable, so I will test the mount over the weekend. 

 

Assuming the mount is working alright, will the dated hand controller work correctly? Should I get the newer hand controller and the wifi dongle? At this time if I can get a goto visual, I will be quite happy. When I want to do real astrophotography, I will upgrade the mount. 

 

I am tired of crouching and searching and a goto will really help. 

That handbox can be firmware updated the same as the newer ones with the USB port instead of the Serial port so that is no big deal. I have both for my AVX and they function the same when updated. Of course I also have the USB to Serial adapter cable.  If you want WiFi, sure thing get the dongle.  As long as the mount wasn't abused, nor "beat to death", it will work just fine for a reasonably long time considering it's age, and likely no appreciable maintenance was done.  The price is very reasonable too.  Heck, the tripod alone is worth the price of admission any day of the week.  

If you were mechanically inclined, I would disassemble the mount, thoroughly clean it getting all the thick damping grease off, put the "bearing mod" in it, re-lube it with SuperLube w/Teflon synthetic grease, reassemble and set the gearing clearances, and enjoy it into the future.

I did the above with my brand new AVX (after testing it first) so I know it will last, and last, and last...  The AVX, when properly "tuned up" mechanically, is a workhorse of a mount for it's weight class. For $350 (I am a mechanic), I would not hesitate for a split second.

[jfaldo]

I'm going to be the odd man out here I suppose. I have that vintage of AVX (2013ish) and it's been a great mount. There's nothing really bad I can say about it. I used to put my 8" SCT on it with all the imaging gear and it performed fine considering it was above it's recommended payload. Now that I have my Losmandy mount I have my 80mm ES triplet on it with a 50mm guide scope ASI air, ASI 174 guide camera, ASI 224 main camera. I use a usb adapter to connect to the phone plug on the bottom of the mount and everything plays fine together. That mount in those days was less than $900 so I would say $350 is a little high. If everything worked I would throw an offer out $100 less and negotiate from there.

[mikemarotta]

I got to look at the AVX. Couldn't run it to see how it functions as the power cable was missing. The hand controller is dated and doesn't have the usb connector nor does it use latitude and longitude for aligning. The seller did find the power cable, so I will test the mount over the weekend. 

 

Assuming the mount is working alright, will the dated hand controller work correctly? Should I get the newer hand controller and the wifi dongle? At this time if I can get a goto visual, I will be quite happy. When I want to do real astrophotography, I will upgrade the mount. 

 

I am tired of crouching and searching and a goto will really help. 

My opinion after reading this through once more is that you will not be happy with the purchase because you are buying someone else's problems. I understand that a new Celestron AVX is available from Astronomics here for under $1000. (Celestron has this on sale from several sources. The sale prices are all close.) You are looking at saving money with a used mount for $350. However.... so far,the seller had to go find the power cord. So, it was not really sales-ready. What else is not included that the seller forgot?  And more to the point now, you need a new hand controller and a wifi dongle. That is an additional cost and perhaps a technical challenge with different versions.

 

If you can afford $500 now ($350 plus extras), will you have $1000 on hand by the end of the year? Talk to Astronomics about lay-away.

 

Ultimately, you can forego the purchse entirely. It is better to regret the purchase you did not make than to regret the one you did.

 

Best Regards,

Mike M,

[Skywatchr]

My opinion after reading this through once more is that you will not be happy with the purchase because you are buying someone else's problems.

That's a mighty bold statement to be tossing out there when you know absolutely zero about it.
 

[MikeS11]

My advice:  run, don't walk, away from this deal if you want to do astrophotography.  Even a brand-new AVX is a chancy proposition for that use.  

Probably the worst advice on the forum, I don't get the hate for the AVX, I've had my AVX with my C8 for a long time and the amount of misguiding information on here is completely unwarranted. 

 

As long as you have the mount properly polar aligned, keep the weight under 20lbs, even with a 2032 focal length tube, its going to be an excellent mount for astrophotography @ 5+m exposures.

[KJR]

Probably the worst advice on the forum, I don't get the hate for the AVX, I've had my AVX with my C8 for a long time and the amount of misguiding information on here is completely unwarranted. 

 

As long as you have the mount properly polar aligned, keep the weight under 20lbs, even with a 2032 focal length tube, its going to be an excellent mount for astrophotography @ 5+m exposures.

It would be helpful to post your guide settings and maybe a PHD2 graph.

 

I've been able to obtain 5 minute exposures and once I even tried a 10 minute exposure.

https://www.cloudyni...inute-exposure/

 

The problem I have is the consistency with guiding. One night it's pretty good, below 1" RMS average for both axes, the next night its much worse.

 

My C8 SCT with image train is about 19lbs.

 

A few nights ago I shot a new target for me, NGC6888, Crescent Nebula. Here are screen shots of my PHD2 calibration and a snapshot of a guide graph.

 

I imaged for 2 hours at 180 sec exposure, 90 gain, 60 offset using NINA. I use a Starizona focal reducer. I only have an Antlia Quad Band Light Pollution filter. The final image was processed in Siril 1.2.1 (MacOS) and background extraction and noise reductionis performed by GraXpert. I had to throw out 10 frames due to the DEC spikes. My AVX seems to have these crazy DEC spikes, I think, depending on the Alt/Az position. This target is very high in the sky almost straight up. Other targets lower seem to do better guiding in my experience.

 

I use the Predictive PEC algrithm in PHD2. I have an ASIAir. I may try imaging this target with the ASIAir to see if I see spikes like this.

 

I have attempted to adjust the DEC and RA worm gears to remove play.

 

KJR

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[Oyaji]

Probably the worst advice on the forum, I don't get the hate for the AVX, I've had my AVX with my C8 for a long time and the amount of misguiding information on here is completely unwarranted. 

 

As long as you have the mount properly polar aligned, keep the weight under 20lbs, even with a 2032 focal length tube, its going to be an excellent mount for astrophotography @ 5+m exposures.

It isn't hate at all; it's playing the odds.  

 

But how many posts over the years In CN have cautioned AP newbies to spend a few hundred more on the tried and true HEQ5 rather than the AVX?  Maybe 50, and maybe 100?  Could there be a reason for that?  Other than "hatred?"

[jaimac]

Thank you everyone for your inputs. I ended up buying the AVX. Will keep an eye for a better mount once I hit the limitation of the AVX.