Drift aligment error

[alexV]

Hi everyone

I have noticed that when I do drift aligment with Bakyard EOS the star does not go up or down. It actually goes up for a min then down

I thought if there was something bend then it would take same amount of time to go up and down

Takes about a min to go one way the a bit longer to go the other

I have EQ5 with go to

Any help would be great
I will post a print screen later on tonight
Thank you

http://i179.photobucket.com/albums/w297/csiro/drift_error_zpsd9d1021b.jpg

[alexV]

Both the same for altitude and azimuth

[RobF]

Maybe re-read that Alex and see if its exactly what you meant to say?

[Geoff45]

Backlash?

[alistairsam]

Hi Alex,

I haven't tried drift aligning with BEOS although I have it, that sine wave is very strange.
can you tell us where you were pointing. did you have tracking at sidereal on?
Were you guiding?
There usually aren't many bright stars near Dec0 and the Meridian, so its good to use the guide camera in the main scope and plot the drift using phd with guiding disabled.

just to clarify, you need to point at dec 0, meridian for the azimuth correction and E or W at around 25deg max altitude for the Altitude correction.

Cheers
Alistair

[alexV]

Geoff before you mentioned about backlash i was never heard about it.
I had a look in my seeings and it all was set to zero.

I will do research about backlash on the net and see what its all about

Thank you

[alexV]

Alistar i was pointing north and managed to find a dim star to do drift alignment, not sure how many degrees but i know thats where i was told to point.

Same for azimuth it was about 30 degrees

I was not guiding but
Here the settings i had on Synscan: tracking was set to side rale autoguing to 1x

I was also told to try PEC training which i tried tonight and it did not work, but iam not sure if every thing i did was 100% correct although i did follow the manual.

Thank you

[alistairsam]

when you say autoguiding to 1x, did you mean sidereal rate at 1x?
did you have a guide camera and the st4 cable connected?
the idea is that you can keep tracking at sidereal rate, but not use auto guiding to monitor drift.
also remember, you must only look at drift in Dec and not RA. ignore all RA errors for both the meridian star and the East/West star.

Also, don't look at PEC just yet. try and practise drift alignment and get your polar alignment as close as possible. that will make a huge difference with imaging, and with goto's. guiding becomes so much easier.
so a good polar alignment is like a pre requisite.
Alistair

[alexV]

Yes Sidereal was set to 1x

Guide camera was not connected to ST4 because i thought guide camera is of no use to me until my drift alignment is good enough.

My main concern that how can i do drift if star goes up and down.
That's why i was told to do PEC training to see if that will eliminate the problem.

Why do you think i should not do PEC training?

Thank you

[alexV]

Geoff it say in a Synscan manual that default baclash is set to 10' 00" (10 arcmin. and arcsec.).

I have to double check bu i think mine was set all to zero.

How does baclash effects drift alignment.

[alexV]

Geoff why do you think its a baclash?

http://www.celestron.com/c3/support3/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=1664

[alistairsam]

were you doing a pec train during that drift alignment?

[alexV]

Before drift aligment

[alistairsam]

If possible, I'd suggest trying again and posting a screenshot.
pls also mention the steps you took.
I don't think PEC applies here because you're looking for drift in Dec, whereas PEC applies primarily to RA tracking errors, and while tracking, Dec isn't used unless you're guiding.
so creating a pec curve won't help with drift aligning, but it will help with guiding. But they usually have to complement each other, I'm not sure if using PEC with ST4 guiding is a good idea because the move commands could cause unpredictable behaviour, unless this is documented in the manual.
issue is this, the guiding software looks at movement and sends correction pulses via the st4 port when it see's drift. but if a PEC curve is loaded in the hand controller or in software, that correct could be over compensated.

so usually, when a curve is loaded via EQASCOM and pulse guiding is used, it knows what the combined result would be before sending the correction command. so they work well.

i'm not familiar with the hand controller PEC, but I'd suggest fixing one issue at a time.

so try using the guide camera in the main scope and using phd. disable guide outputs and turn on sidereal tracking and watch the dec drift in the phd graph.

Cheers

[Steffen]

I can't imagine a mechanical problem with the mount that would cause a star to drift up and down in Dec in the space of a few minutes and with the mount pointing East. To rule it out you could use a reticle eyepiece and watch a star drift, with the mount running stand-alone, just tracking in RA.

If it drifts properly there you know the problem has something to do with the way your electronics are hooked up, or with what the software is doing.

Cheers
Steffen.

[RobF]

Certainly a strange one, and would be good to know what happens visually. I'm not familiar with Backyard EOS - is that what you normally use to guide in? Is there any other software that you could use to verify drift. Is there definitely no tracking at all turned on? (another reason to use a different program possibly).

Drift aligning with a camera is a great way to got aligned once you have it sorted, so worth persevering (not that helps much right now :))

[alexV]

I have suspecion that it is a ByEOS that playing up like was mentioned here before.

I use to do drift with my Orion auto guider camera connected to my main telescope. Dont remember if i had the same problem or not.

Hope fully next week end if weather permits i will do drift with reticle eyepiece.
If ill menage to get that drift right ill switch back to BYEOS and see if it will show any errors.

If thats not going to work ill document all my steps and post them here.

Is it possible that this Active USB 2.0 Extension Cable Repeater causing that problem. I bought it for my DSLR because original USB cable was to short.

http://www.ebay.com.au/itm/New-16FT-5M-Active-USB-2-0-Extension-Cable-Repeater-For-Laptop-PC-Computer-E0Xc-/160991269592?pt=AU_CablesConnectors&hash=item257bd3d2d8&_uhb=1

Thank you

[RobF]

I don't think it'd be the repeated Alex - I use 2 all the time with no issues.
Drift aligning by eye can take a long time as you get closer to alignment. Do you have any other software the camera will talk to?

[alexV]

PHD that came with my Orion Auto guider.

[RobF]

Perhaps try Phd with guiding off? I use Maxim but someone here will be able to help with phd. Fundamentally just letting star drift with no tracking and monitoring rate of drift off the graph. Would be interesting to see if you still get the up and down (it doesn't make sense though unless something is moving your mount/OTA during the drift run)

[alexV]

Ill let you know as soon as weather will permit
Thank you

[alexV]

went to MPAS observing site.
here are steps i took before drift alignment.

1. Tripod N pointed to true South.
2. Level the tripod.
3. Level the mount with telescope and view finder on
4. Synscan On
5.Skipped through setup (day, daylight saving, time etc)
6. Went in to Setup mode of Synscan an set tracking to Sidereal rate
7. Still in Setup mode of Synscan AutoGuide set to 1X
Synscan only allows to set to speed 1X, 0.5x, 0.75x,
0.25X and 0.125X for sidereal

I did drift alignment with reticle eyepiece and is very difficult to say if star goes up and down.
Next i took my orion autoguider connected it straight to my scope and computer. I used PHD with bulls eye.

I still get the same problem. Takes about 5 min to slowly go up and then down.

:(

Any help would be great.

[Steffen]

Please note that I'm not really sure what your setup looks like (being a visual guy I'm spared the joys of auto guiding), but to me it sounds very much like you're guiding the drift away while trying to measure it. Hence the sine curve.

Wouldn't the auto guider, umm, auto guide as soon as it's plugged into the mount's auto guider port? Can't you see the drift in PHD without connecting the auto guider to the mount?

Cheers
Steffen.

[alexV]

its not connected to auto guider port only to laptop through USB

[RobF]

This is unlikely, but you'd see this if you had turned off tracking in RA rather than DEC Alex - effectively the sine wave reflecting your periodic error. Only other thought I have for now. What sort of mount is it? EQ6 worm period is about 8mins.

[alexV]

eq5

[pluto]

Not really sure about your issue but I would recommend drift aligning with PHD. I use the guide at the bottom of this page: http://www.njstargazer.org/PolarAlignment.asp

I have an EQ5 and the dy graph line can be a bit choppy if everything isn't balanced just right.

However if you're just learning to drift align it might be a better idea to get a cheap illuminated reticule eyepiece and do it 'the old fashioned way' for a while as it can be pretty tricky and you don't want to be dealing with camera and software as well as any quirks with the mount.

[naskies]

Alex, the funny looking S shaped squiggle looks to me like a combination of (1) drift due to polar misalignment, and (2) periodic error of the mount and/or backlash.

First of all, have you calibrated the BYE reticle with the RA/DEC axes of your mount? The fact that they're perfectly vertical/horizontal on screen suggests to me that you haven't (though I could be wrong). Basically, what you need to do is:

1. use the arrows on your hand controller to centre the star on screen
2. use the RA buttons, e.g. East, to move the star to the edge of the screen
3. rotate the reticle in BYE so that the star is inside one of the reticle line pairs - remember that this is the RA axis
4. move the star back to centre using the opposite RA button, e.g. West

Now you're ready to drift align. You'll notice the star wobble back and forth along the RA axis due to periodic error - you can ignore this. You only need to pay attention to star drift away from the RA axis (i.e. towards north or south).


Btw - if you have computer control of your mount, it's worth looking into software-assisted polar alignment methods such as AlignMaster or PoleAlignMax. It's much faster and can handle *huge* initial misalignments. The latest Synscan firmware also has this feature built in.

[SteveInNZ]

I don't see any units anywhere. How can you tell that it's "huge" ? Nor do I see any indication of RA and Dec axis. If we knew the period and the amplitude in arcsec then we could offer more meaningful suggestions.
That could well be a normal plot showing the periodic error of the worm.
You say that it's not connected to the ST4 guideport. Just to check - Is the mount connected to the laptop and running EQMOD or anything or is the only connection from the laptop to the guidecamera ?

[alexV]

It's not connected to ST4 port and no eqmod

[SteveInNZ]

Looking at your screen capture, is that the elapsed time (565 seconds) on the right side ? If so, you have a single sine cycle with a period of about 10 minutes. The EQ5 has 144:1 worm, giving a period of 10 minutes.
I would say that the star is drifting in Dec towards about 4 o'clock. You also have periodic error from the worm that makes the mount speed up and slow down in a direction that is right angles to the Dec, giving you the sine shape.

This is quite normal for mount that is tracking but not being guided. That is what guiding and/or PEC fixes.
I get a similar track for a Super Polaris mount with the height of the sine wave being about +/- 15 arcsec.

Depending on the numbers, you could be very well polar aligned or you could have horrendous periodic error.

My preference for drift alignment is EQAlign which I use with a webcam but it should work with your guide camera. I like it because I can use it with a non-goto mount but it's also very good at helping you through the process.

[alexV]

Iam a bit confused with what should I do

[RobF]

I'm a great believer in having 2 or 3 polar alignment techniques up your sleeve Alex. Would suggest:

1. Figure out how to drift align in software with tracking RA but none in DEC (Phd would allow this I believe - I use Maxim normally)
2. Have a go with the demo of alignmaster as others have suggested.

Personally I found drift aligning with a reticle far harder than a webcam - you have to wait quite a while to get a definitive signal. What Dave says is important too. You either have to rotate you cam to get its axis aligned with your RA/Dec axes OR do an alignment in software (like PhD) before drifting so the software already "knows" which directors are RA and Dec.

If its all getting too hard next best plan might be to find a kindred IIS spirit near your location.....:)

[alexV]

ok thank you all for your help.
So from what i understood is that i need to learn fine tuning, is that right?
i also updated my SynScan it has a polar alignment now.

next time ill go ill do rough polar as usual, then ill try SynScan polar alignment i also got full copy of align-master.
I just glad to hear it is not mechanical issue.

Alex

[naskies]

It would probably be easiest to pick a method (e.g. drift aligning with BYE, or using AlignMaster) and have a go - we can help you with any troubles you might have :thumbsup:

As for the drift aligning with BYE... you need to centre the star and rotate the reticle like I described earlier - otherwise it won't work at all!

By the way, it is really really helpful to ensure that your mount is both (1) horizontally level, and (2) set up on firm ground that won't sink. Don't trust the bubble level on the mount (99.9% of them are incorrect from the factory) - you can use a bubble level or even a smart phone with a built-in inclinometer on top of the tripod plate. I find that setting up on grass or dirt causes no end of grief (one leg will inevitably gradually sink in), so I have a few Besser bricks half-buried into the dirt to keep things solid.

[pmrid]

Alex, since Rob has mentioned PHD, I might just throw in this - to drift align with PHD, you have to remember that after you have calibrated it, you then go to the Brain and Disable Guide Output before restarting the guiding. I mention it because it is often the obvious thing that I overlook.

Peter

[alexV]

Thank you Peter
Ill keep that in mind

Alex

[alexV]

Thank you

[alexV]

Update.

Can i just by saying that current update from Synscan is great.
I did polar alignment just under a min. It was supper easy.

With just polar alignment i have managed to get 1min and 40sec unguided.

But i think i still have the same problem. Because out of lets say 5 shots, 1 has drift.

Thank you

[RobF]

What scope (and weight) do you have on the EQ5 Alex? They can be a challenge to get tracking well.

[naskies]

Good work! You can repeat the polar alignment routine a couple of times to increase the alignment accuracy. The Skywatcher EQ5/EQ6 mounts are not very accurate on their own, so you'll almost certainly need to use autoguiding to not get trailing with long exposures.

[alexV]

Saxon 100 ed
Finder scope
Canon 60d

[RobF]

I suspect you're seeing a lot of periodic error in RA and backlash in Dec Alex (people have described this earlier on). The EQ5 is a lot lighter in construction than the HEQ5 or EQ6 - only uses teflon bearings from memory. It can definitely do astrophotography, but you'll be working harder to keep it working within limits. Typically that means shorter guidescope/camera exposures (1 sec) and a lot more corrections issued versus an expensive (non-chinese) mount. Even HEQ5s and EQ6s take a lot of work to behave well as Dave says.

I get the impression you're trying to work it unguided, which is probably going to be tough for exposures over 30-60 secs?

[alexV]

So which mount will give me less headaches?

[Jon]

Alex, if you are getting over a minute unguided with decent results with an EQ5 you are doing well. The next step up is autoguiding. Something like the Orion mini auto-guider package should let you get much longer subs with your setup.

[alexV]

i have Orion Awesome auto-guider package.

Can you recommend any material for setting it up?

[alexV]

Went for another session yesterday and i am glad to say that everything went perfect.

Manage to get 10 min exposures guided.

Did not had to do any drift alignment at all.

All i did was rough polar alignment, 2 star alignment and Synscan Polar alignment.

Thank you everyone for your help and hope this post will make someones life easier.


This image is 530sec not stacked but photoshoped

http://i179.photobucket.com/albums/w297/csiro/Astrophotography/AstroP/LIGHT_300s_800iso_4ms_zpsaed046e3.p ng (http://s179.photobucket.com/user/csiro/media/Astrophotography/AstroP/LIGHT_300s_800iso_4ms_zpsaed046e3.p ng.html)

[Jon]

Well done Alex. That's pretty good guiding! Stack 10 of those in Deep Sky Stacker and you'll have a really nice Eagle image.

[alexV]

Thank you Jon

i have tried to stack about 5 but some reason DeepSkyStaker did not like my long exposure shots.

Is it better to have lots of short exposure shots something like under a minute or fewer but longer exposure shots ?
Thank you