Celestron's AVX default accuracy.

[Olsin]

I was wondering if anyone has an idea on Celestrons AVX mounts default accuracy.
For example.
If the assumption that the base was 100% level, mount well aligned with a well calibrated polar scope and all handset parameters correctly entered = true, how accurate should the first selected star in a 2 star alignment be?

I'm having all sorts of problems with my own mount although i'm sure they are all of my own doing.
I couldn't get the 2 + 3 star alignment plus ASPA to work for me (though that maybe because i simply don't fully understand the procedure). Then i read a few posts where someone said that he don't bother with ASPA. He accurately polar aligns the mount first, then does a 2 + 4 star alignment and end of story. So i've been trying that route myself.
I didn't get a polar scope with the mount so i initially tried winging it by simply aligning Polaris through the hole where the PS should be and tried to get it as close as possible by eye. Wasn't satisfactory though.
I then got a polar scope and discovered i couldn't use it because of the chunky latitude bolt restricting access to the eyepiece. Quick drive (that shouldn't really have been necessary) to the DIY sorted that out ready for the promised nights clearish skies. Unfortunately i knocked the finderscope out of alignment when it was dark and wasted much of the clear skies on trying to realign the finderscope on a star although i couldn't really do it as my 8" sct doesn't allow anything in the sky to stand still. I had to wing it as best i could although it caused a lot bother. Before i could finish messing about clouds came in.
I've now discovered that the polar scope also needs aligning to the mount so that's the next job.
So, does anyone with an AVX mount know of their default accuracy when all parameters = true?
 

[mikeyj1]

wow, your not having a great start!

finderscope and polarscope can both be aligned during the daylight hours, much easier.. (sorry if i am telling you things you already know here..)

• Basic setup: Level tripod, mount and balance scope, polar align, (make sure you know the orientation of the polestar to the reticle).
• Start with scope at home position (facing north, 'weights down') - at least i have to do that with my AZ-EQ6.  take time to get that right on the first setup, and put the setting circles to zero ready for next time.
• Set Timesite info including Lat/Long/Time/Date for your location (I struggle with this on Celestron controller, as it doesnt always show you the lat/long on setup)
• Two star alignment should be ok for pointing accuracy, but a three star alignment gets rid of 'Cone Error' (long axis of scope not matching RA axis) and make them in different quadrants of sky for better accuracy.  Use a 10mm eyepiece for more accurate centering, with a reticule if you have it.
• Check the handset for PA error when finished, needs to be less than 1 degree in both axis.

i have seen mixed reports on the AVX, but it should still be better than my old CG5, which was pretty good!  In the end you should get the GOTO to show you objects in a 20mm EP

cheers

Mike

[Olsin]

No no Mike, i never take offence to people trying to help me, especially when i recognise my newbie status..

I actually use the live view on my DSLR to center on stars. Only the brightest stars are visible on my display so that cuts out distractions. I also get a correct up/down L/R picture which makes using the keypad on the handset much more intuitive i feel. I turn the grid on which gives me an intersecting line smack in the middle of the display. I can then zoom in and get the star exactly in the middle. The camera is attached prime focus and it all feels solid so i assume the middle of the live view screen is just as good as the middle of an EP.
As there's quite a bit of movement when zoomed in i usually try an ambush method where i line the star up and wait for it to cross the cross hairs, at which moment i immediately press align on the handset.

Ok...checking the handset for PA error. Hmm, i haven't come across that yet. Thanks for the heads up.   
Yes, i too have read reports of people getting on very well with the AVX mount. I've also read reports of people having nothing but trouble with them. It's hard to judge in all accounts, whether it's because of intermittent quality from the producer, inherent instability with the mount or just inexperience from the user. I think a lot of it maybe inexperience as i'm certain that's the roots to my own problems. I'm hoping so.

Saturday tomorrow with the clear skies from the afternoon onwards (apparently!) So i'll calibrate the polar scope tomorrow and take another crack at getting a good mount alignment and tracking...Cheers

[The-MathMog]

I own a AVX mount too, and I would be one of those people for whom it works very well. My first advice, and most simple/obvious one, is to make sure that you input all the correct informations. Check map charts for your latitude/longitude, make sure the clock and date is accurate (be aware of the date format that is Month/Day/Year), what timezone you're in (I believe london is 0, but check the chart in the supplied manual if uncertain) and lastly that daylight-savings time is enabled as it is right now. Most of the times I've had issues,  has been where one of these was entered incorrectly/mistakenly.

I also use ASPA (actually twice for better accuracy) and it has given me great results. I don't have a polar scope, but I still look through the polar axis. I just make sure that I can see polaris through it, which is rough enough for me. Then I go through the star-alignment, doing a 2-star align and then adding 4 calibration stars. I then slew to a star close to the meridian, at this time it is often "Regulus", and then select Polar Align. First it slews to the target, you center it with the hand-control and press align. You prompt it to start the polar alignment procedure, it slews back to the target but this time most likely misses. This time when you center it, you DON'T use the hand-control, but use the Azimuth and Latitude bolts to adjust the mount, because the mount slewed to the position where the star SHOULD be, if you were polar aligned (of star aligned accurately). When star is centered press align, finito. Then I normally turn of the mount, and do everything again. This has given me unguided subs of over 180 secs.

But just to clarify, does the alignments simply fail when you try, or is the GOTO severely inaccurate? When I've properly polar-aligned + star-aligned and synced to a star near my target, I can get it dead-on with the goto, on my 130slt OTA, using a 2.25x barlow, so it is like 1500mm focal length.

Also to your first points, if my first rough polar-alignment was actually good and I've put in very accurate information (I tend to go into clock-options on my computer and sync the time with some government server, just before inputting time, and then putting it in at second precision), the slew to the first alignment star is then well inside either my 32mm or 25mm, so fairly accurate I'd say under good conditions.

[Olsin]

Thanks MathMog. Yes, i'm sure i've entered all the time/date/location/daylight information in the correct format. The only thing that caused any head scratching was my timezone. I've never thought of the western European continent as anything other than GMT+1, so +1 was entered. It took until the next session attempt to realise Denmark, at this time is UTC+2.
Due to one problem or another, i haven't actually been through the whole alignment yet. I've just noticed that the additional calibration stars don't usually end up close to the scopes FOV by the time i've got to adding let's say, the 2nd additional calibration star ... i'm sure though the problems are all my own and not the mount. I guess i just wanted to hear someone tell me, that the mount can achieve good things.  
However, now that i've acquired a polar scope, i'm going to use today to calibrate it to the mount and hopefully run through the whole alignment procedure tonight.
 
I don't quite understand why you do the whole routine 2 times. It was my impression that the mount dumps all info apart from location, when you turned it off. How does it use the 1st alignment to improve the 2nd?.

[Gazabone]

Hi, I'm one of the unfortunates that bought an AVX and hate it with a passion (it's now languishing in the attic because I can't quite bring myself to putting it out for rubbish collection). Cutting a very long story short, I now think that it's very fussy on power supply; I was using a Baadar mains adapter and it would never maintain the correct declination but the one occasion I ran it from a power tank, it seemed to behave itself. 

Once you've done all the checks other posters have suggested it my be worth trying this;

in daylight, turn off the tracking and point a scope to a stationary object and make a note of the alt/az coordinates. 

With the handset, slew the scope in both axis, if possible 180 degrees and then slew back and centre your original target again and note the alt/az coordinates again. 

They should be near enough the same as you started with. If not, do the exercise a few more times to identify a consistent error. 

If this does show an error, try running from a different power supply and see if it changes. 

I'd be very interested if you do this to hear how you get on. I think I've fried the motherboard on my AVX and might consider getting it repaired. 

Good luck and happy viewing. 

[Olsin]

Thanks Gazabone ... You know, i have read a few other places that some avx users also have reached the same conclusion with regards to power supply. This has made me doubt my own source.
I don't have a power tank and use a 12v ac adapter rated at 3A. From the moment i clicked on "buy" i've been wondering if i should have paid the extra for a 5A rated power supply.
If i can't get good tracking despite all other parameters being good then a power supply will probably be the next buy. I just don't like using any type of rechargeable battery when i have a perfectly well functioning mains outlet not more than 3 meters from where i stand my scope. Besides, from experience in other interests i know that rechargeable power tanks only have a certain shelf life before they start to drop off.

Still, your test sounds worth a try. As mentioned, i don't have another power supply but i will do the test today just to see how my mount preforms with the power supply i use. Thanks for your input.

[newbie alert]

My Avx is awesome,I don't own a polar scope but get reasonable results without one..heres how I do it..right or wrongly it works for me..

I setup the mount dead level and not on a soft area.. I setup with the eyepiece tray in place to spread and lock the legs out as much as poss..i lookup on stellarium where Polaris is in relation to the ncp  and from experience in my finder it's about 1cm gap from the cross hairs..i use a illuminated 12mm ep to Centre the stars on the star alignment and Polaris won't be in the fov.. Once I'm happy and the date/time is entered I start the star alignment,knowing the first star won't be too far away but won't be near the cross hairs in the finder..center and align on all stars and calibration stars until I get align success.. .at the moment I'm using Capella to align the mount so I slew onto capella and the press the align button..scroll through until you can select polar align and the scroll again  until you can select align mount then follow the instructions on the handset..i can get good enough alignment to do 2 mins it a 8sct and 3 with a 80ed.. not too sure if this is the ASAP but it's great.

Sharpcap is great for PA as it's free..but you will need to use a laptop..

[PeterCPC]

I use an AVX and am very pleased with it. I use Polemaster now but I was getting good results using ASPA. I am attaching my reminder for getting a good PA with ASPA - hope it helps.

Peter

Telescope Set Up Checklist.odt

[The-MathMog]

5 hours ago, Olsin said:

I don't quite understand why you do the whole routine 2 times. It was my impression that the mount dumps all info apart from location, when you turned it off. How does it use the 1st alignment to improve the 2nd?.

Well I am glad I could provide some insight.

The reason I do it twice is not for the star alignment, but for improving the polar alignment. When you adjust the polar alignment after the first ASPA, the correction also includes the potential errors in the star align. So by doing it all again, you will most likely futher improve the polar alignment, given that you do the star-aligning very accurately, in my case using a 6mm eyepiece + 2.25x barlow

A proper power-supply might very well be something you should try out! From the manual it states that it requires "12V DC 3.5A" so if you provide it with 3A as you mentioned that might very well be the issue! My power-adapter is a 5A. And I see you're also from Denmark, so I'll share the one I bought. https://www.avxperten.dk/stroemforsyning-med-fast-stik/12v-stroemforsyning-fast-stik-5-amp.asp 

[Olsin]

Thanks Peter. I've printed your checklist and i'll try that routine if my attempt at PA first with PS then 2+4 star alignment doesn't pan out. Decent of you supply the link.

And thank you to MathMog. I was looking at a 5ah power supply on Teleskop Ekspress. That stands at approx 500kr, yours at only 150kr. Not only did you explain why doubling up the routine improves accuracy, you also saved me 350kr. Tak for det du..

@newbie alert ... And yet another routine. Crikey, i didn't realise there was so many ways of achieving good results. Thanks a lot for your input.

[The-MathMog]

57 minutes ago, Olsin said:

And thank you to MathMog. I was looking at a 5ah power supply on Teleskop Ekspress. That stands at approx 500kr, yours at only 150kr. Not only did you explain why doubling up the routine improves accuracy, you also saved me 350kr. Tak for det du..

You're very welcome! Might as well help a fellow astronomer and dane! When buying powersupplies just always check for the power that the equipment requires and then find a power-supply that delivers MORE than that if possible. Especially for hobbies like ours when we're outside, the power it delivers can actually drop below its stated amp, so if you had a 3.5A it could at times still not provide enough power as the cold would make it perform worse than expected.
Also to note, the one I linked is not specifically designed for outdoor use, so try at best to keep it dry/under some protection. Not sure how crucial it is, but better be safe. What I did was that I got a "frying plastic bag" that you put chickens in into the oven, and wrapped it around the AC-adapter, to keep it away from moisture. I didn't chose a regular plastic bag for the freezer as they aren't to be exposed to more than like 60 degrees celsius, and I was not sure how hot it could/would get

[PeterCPC]

12 hours ago, Olsin said:

Thanks Peter. I've printed your checklist and i'll try that routine if my attempt at PA first with PS then 2+4 star alignment doesn't pan out. Decent of you supply the link.

No problem. I hope that you find it useful. I used to get a very accurate PA using this routine and it took about 20 mins. Polemaster takes about 5 mins.

Peter

[Olsin]

So here's the results of the nights attempts.
I started out using the daylight to align the polar scope to the mount (a time consuming frustrating exercise) and was happy with the end result. The cross-hairs didn't move a nano when moved back and forth through 180 degrees.
As soon as i could spy Polaris i used the polar align iPhone app to find it's position in relation to the NCP and adjusted the mount until it was absolutely spot on.
Then i started the 2 star alignment, first on Capella and then on Regulus. The 2nd calibration star was surprisingly close to the scopes FOV. The remaining 2 (4 in all) calibration stars were all within the FOV after the scope slewed to them. Brilliant!
ASAP was done on Arcturus and my align success showed 00,00,32 on one axis (i didn't jot that down!) and 00,01,01 on the other, so about a half arc minute difference between the 2 axis's.
I know i should have powered down and redone the setup but i was eager just to see what this kind of accuracy could produce. I selected M51 on the handset and slewed to it. I see nothing on my camera monitor so i took a 30 sec/iso 800 sub and was impressed by the result. It was probably the best picture i have produced to date (i still had to crank up the exposure in PS to see any detail though). M51 just slightly right of center. I then tried a 60 sec sub but this showed terrible star trails. Back to 45 sec and a slight improvement on the 30 with only very small star trails.
Instead of redoing the setup i ended up swapping the camera for an EP and spent the next few hours just looking around although both tracking and goto quickly became unreliable. I'm assuming this was because i didn't redo the alignment.
Another thing i noticed was that i could be zeroed in on a star. The star would move around within the FOV and then stop, remain static for 15-30 seconds (sometime much longer though) and then start moving about again.
I put the camera back on (i can see bright stars on the monitor) so that i better could see the movement pattern but there wasn't really any. The stars just kind of wiggled around with varying speed without favouring any particular direction. Then the star seemed to settle down and it'd be quite motionless within the FOV.

I selected goto Jupiter and it didn't end up in the FOV. I could see it in my finderscope so it wasn't totally misplaced. I slewed to it and watched as it slowly drifted of the screen. I used the handset to re-center it and this time it started to move away but stopped and then stayed reasonably still for maybe 10 minutes until i slewed away to Vega!
I would have thought an inaccuracy in precision would be consistent. I don't understand how the mount can intermittently produce good results while showing obvious precision errors?
Could it simply be a combination of small alignment error + low fluctuating power supply or is it systematic to mount error?
Would it also be normal to assume that even an initially well aligned polar/star unguided setup would lose precision with time?

Clear skies again tonight, so i'll of course be trying it all again. This time i will do the routine 2 times and make a proper note of mount error.
I finished on Vega last night. After just looking at and around it through an EP, i put my DSLR back on and took a quick 20 sec sub.
I know you guys can see a ton of problems with this picture and i'm sure i will to one day ... but for now, this is probably the best astro pic i've produced to date.

 

@MathMog .. Actually i'm english. I just live here

@Peter .. I've seen quite a few video's on YouTube demonstrating and explaining the polemaster. No doubt i to will go that way too sooner or later. It definitely looks like a good bit of kit.

 

 

[PeterCPC]

Have you checked the balance? If it is unbalanced it will gently drift.

Peter

[Filroden]

I think you're seeing a couple of things:

• Accuracy of goto is impacted by any adjustment to the mount so you really need to do a new 2 star alignment after completing your final polar adjustment.
• Accuracy of tracking sounds like a power issue. The fact it holds position for a good length of time and then act variably suggests this is just power. Poor balance will affect power as the mount has more to drive.

[newbie alert]

Sounds very much like a power issue...balance is important..but you should get 60 sec subs no problem on a avx..what scope are you using?

My avx only starting playing around when my power tank was coming to the end ..once I sorted that it was fine..

[The-MathMog]

Well until you get a stronger power-supply you will still encounter these issues, as I am pretty much certain this is the main root of your issue. If you provide 3A to a 3.5A rated mount, then it is literally not getting enough power to track properly, and this sounds consistent with what you've observed, with the star being tracked properly for a few minutes, then moving around inconsistently.

Also, if you check the "Polar Alignment accuracy" in the handset after having done the ASPA, then that number is not accurate at all, because your handset can't know what the alignment is AFTER you've done the correction. If you did everything 100% after the book, then the alignment should be 0.0% off, which the mount think you did, but more than likely it is not. Only way to know what it actually is, is as mentioned, either looking at the PA accuracy BEFORE doing the ASPA or turning of the mount and star aligning again. That way the mount can give an actual estimate of how good your PA is

Another question, do you know how big your field of view is with your camera. Not that I think this is the problem, but if you have a very small field of view, then periodic errors will also begin to show more noticeably, as they did when I barlowed my DSLR. Then doing a PEC training routine fixed that problem. But that was ofc only an issue in one axis.

[Olsin]

I've ordered the new power supply but i was out again last night anyway even though i expected to have problems ... which i of course, did.

I don't know if this is power related but i've noticed (actually noticed it the 1st time i used the handset) that the scrolling text is incredibly hard to read. The static text is plain enough but as soon as it starts scrolling across the screen, the text seems to blend together. I often don't know if it's telling me to press enter or align. There's also some kind of warning message when choosing a star to polar align on but i've never really been able to read it. Does anyone else experience hard to read scrolling text on the handset?

Another strange thing is that my mount can't remember it's home position. It was by default set at the index position but i accidentally pressed "set" instead of "goto"  the 1st night i was using it. If i now set the home position to the index position and select "set" it only remembers while the mount is powered up. I've tried returning to factory settings but it doesn't associate the index position as home position by default anymore. I updated the firmware about 2 weeks ago.

@Peter ... I'm still having trouble with the ASPA procedure. Small discrepancies that make it slightly confusing..

Polar Alignment

1. Slew to bright star high and near meridian.(not overhead) ... Check
2. Press Align – Polar Align – Align Mount. ... It's here i see some kind of warning scrolling across the screen but i cant' really understand what it says
3. Scope will slew away and back. ... it only does that after i've pressed Enter in response to the scrolling message
4. Centre star in finder – Enter – centre star in EP. Scope will sync. ... I understand this as you mean center star in the finder scope using the handset controls and then press enter and then center it in the EP again using the handset controls and again press enter?  
5. Enter – Use Lat and AZ bolts to centre star – Enter  ... but the star is already centered in the EP from the previous steps?

Updating Star Alignment

1. Press Align – Undo sync – Enter
2. Slew to one of the original alignment stars.
3. Press Align – alignment stars – select star.
4. Centre star – Enter- Align.
5. Repeat for other Alignment star.
6. Slew to bright star on opposite side of Meridian.
7. Press Align – Calib stars – Enter.
8. Centre star – Enter – Align.
9. Press Back – Align – Polar Align – Display Align. (this will show your actual PA error)

EDIT: ... Yes, sorry. I have a 8" sct. The standard 25mm EP i got with the scope Has a tighter FOV than my camera use in prime focus with the telescope. I use the camera for aligning because it gives correct orientated pictures and only allows the brightest stars to be seen on live view cutting out distractions. It also allows me to zoom in with a grid pattern on screen to get dead accurate middle of the screen precision.

[newbie alert]

1. Press Align – Polar Align – Align Mount. ... It's here i see some kind of warning scrolling across the screen but i cant' really understand what it says.

If you have a warning it's telling you not to choose a star in the zenith,poles or western horizon..choose another star..

what star did you use?

after the entering in finder and ep it should realign on the star where it should be and then you use the bolts to Centre in the ep .

[The-MathMog]

30 minutes ago, Olsin said:

I've ordered the new power supply but i was out again last night anyway even though i expected to have problems ... 

I don't think that the mount can actually remember its home position after turning it off/on. That is why it asks you to set it to the index? Not 100% sure though.

As far as I remember, the warning is actually just the mount telling you, that adjusting the polar alignment, will ruin your star alignment?

Before you do the Latitude and Azimuth adjustment, the mount should have slewed to the star one last time, but most likely missing, as it is slewing to where the star should be, and then asking you to adjust the mount. Maybe you are pressing enter twice sometimes? When syncing the star, you first press "enter" after centering it in the finder, and then press "Align" when centering it in the EP. Then press enter again to start the polar aligning, it slews to the star (the position it should be in), you adjust the Lat/Azi bolts centering it, and then press align. I made that mistake with my previous mount, that I pressed Enter or Align twice at both screens, and thought it had already went on to the next screen. It can of course be hard to read with a screen that blurs, which my old Nexstar SLT mount also did (Maybe a power issue, but I never checked). Try changing the text scrolling settings or the brightness and see if any of it helps.

[Olsin]

Yes thanks MathMog. I think that is exactly the problem i had. I've tried running through the manual and this checklist as well as another technique where you select identify and enter on the handset and then press undo before it slews to the star. There is no undo on my handset so i assumed "back" was the same although pressing back while it was slewing to the star done nothing, it carried on slewing.
So yes, there seems to be small discrepancies in the various descriptions that cause confusion ... especially when you don't really know what you are doing.
There is a more than a good chance i incorrectly pressed enter when i should have pressed align or vice versa. Enter and Align are both 5 letter words and hard for me to tell the difference when mixed and blended with other words that scroll across the screen in soft shades of red.

Still, between you and Peter i think i now know just what i have to do. Now i just need the new power supply (hopefully tomorrow) and clear skies to try it out.

@newbie alert. I was going to PA on Regulus but could see some kind of flashing warning but couldn't read what it said. So i chickened out and pressed back and manually slewed to Arcturus instead. I got the flashing warning again and again hit back. So i manually slewed to Denebola and got the same warning again...I kept thinking i had done something wrong so i'd power down and power up again and restart right from scratch.
So yes...going to have to look in the settings and see how i can change that scrolling flashing text.

[PeterCPC]

" There is no undo on my handset so i assumed "back" was the same although pressing back while it was slewing to the star done nothing, it carried on slewing. " Undo comes up as an option in the text window when you carry out the procedure - cannot understand why you are not seeing it.

 

Peter

[The-MathMog]

7 hours ago, PeterCPC said:

" There is no undo on my handset so i assumed "back" was the same although pressing back while it was slewing to the star done nothing, it carried on slewing. " Undo comes up as an option in the text window when you carry out the procedure - cannot understand why you are not seeing it.

As he mentioned, his scrolling text screen is blurring, making it hard to read, probably due to power or settings. My old SLT mount did this too, and it can be really hard to read anything when it does that

[iapa]

If it helps, in the menu under handset is an option to change  the scrolling speed.

i found legibility was depended on scroll rate, display brightness and ambient llight.