Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Terrible RA drifting with a Celestron AVX

  • Please log in to reply
58 replies to this topic

#26 overnight

overnight

    Vanguard

  • *****
  • Posts: 2211
  • Joined: 10 Jan 2017
  • Loc: San Diego, CA

Posted 18 June 2017 - 01:20 PM

Polar alignment is only one part of the equation. In equatorial mounted scopes, when  operating unguided,  balance also plays a part, as one circle of RA/DEC  will often produce stability and another will produce drift, even with a "well balanced" system...

Yeah, but I'm pretty sure balancing isn't the problem due to what the OP said.

 

Of course it could be a bunch of factors, highly likely in fact.


Edited by overnight, 18 June 2017 - 01:21 PM.


#27 xiando

xiando

    Fly Me to the Moon

  • *****
  • Posts: 6388
  • Joined: 27 May 2015
  • Loc: Cloudy NEOhio

Posted 18 June 2017 - 01:34 PM

I tend to agree but I will still note that with even a well balanced system, especially for asymmetric OTA assemblies like newts are often equipped, there are sweet spots and unsweet spots along the RA/DEC curves


  • overnight likes this

#28 overnight

overnight

    Vanguard

  • *****
  • Posts: 2211
  • Joined: 10 Jan 2017
  • Loc: San Diego, CA

Posted 18 June 2017 - 01:36 PM

Best way to balance with a Newt is to point the focuser down when its in home position. It reduces the number of inconsistencies due to the fact that Newts are asymmetrical.


Edited by overnight, 18 June 2017 - 01:44 PM.


#29 xiando

xiando

    Fly Me to the Moon

  • *****
  • Posts: 6388
  • Joined: 27 May 2015
  • Loc: Cloudy NEOhio

Posted 18 June 2017 - 01:39 PM

they are no longer symmetric once a finder and or guidescope is attached. My focuser sits about 30 degrees off vertical  to offset the guidescope as well as I can. And when I ran unguided, my max exposure time depended on where I was pointing, even when I meticulously balanced and rebalanced.. (that was with a finder instead of guidescope)

 

PS. even if you have a symmetric assembly, (no guidescope and or finder attached to the side) the pointing position would change the center of balance due the the optical train sticking out of the focuser. Perhaps you're thinking of a newt attached to an alt-az.


Edited by xiando, 18 June 2017 - 01:43 PM.


#30 overnight

overnight

    Vanguard

  • *****
  • Posts: 2211
  • Joined: 10 Jan 2017
  • Loc: San Diego, CA

Posted 18 June 2017 - 01:44 PM

I forgot to put the "a" in front of symmetric lol.gif

 

No, I completely agree all Newts are asymmetric due to their design.


Edited by overnight, 18 June 2017 - 01:44 PM.

  • xiando likes this

#31 Genryuu111

Genryuu111

    Explorer 1

  • -----
  • topic starter
  • Posts: 54
  • Joined: 14 Jun 2017

Posted 19 June 2017 - 12:57 AM

It's all I've been doing whenever I could for the past month, spending whole nights (from 11 to 4) trying to fine tune everything, while at first I still needed to understand how it worked, now I'm quite sure I got it, since I manage to have stars not to drift in Dec for more than five minutes..
From my understanding, Ra drift is not correlated to good alignment, is it?

A few days ago l tried using ASPA but as I suspected the results were really disappointing.
I tried taking 30 seconds subs, half of them had trails, and comparing all pictures, the stars were moving sometimes left and sometimes right (with the camera oriented, left-right with Ra movement.

About balance, as l read online, it's basically impossible to properly balance on the AVX because of its stiffness.
But anyway I tried many degrees of balance and east heavy balance, but that didn't solve the problem.

Just to be sure, I'll recap my drift alignment routine, there are some parts that are not optimal, I don't think that's the issue, but please point out if I'm doing something very wrong..

-I align the camera left and right with the hand controller Ra, left-right movement.
-I point to a bright star as much close to equator-meridian intersection (from my house I can't get very close).
-If the star drifts up, I turn the azimuth knobs to have the star move to the left, and vice versa. Ignore left-right drift, and go on until the star doesnt go up-down for five minutes.
-Find a star in the east as close to the horizon as possible (with buildings in front of me, I can't go lower than 20ish degrees.
-Ignore left-right drift, if the star goes up turn the Alt knob so the star goes down, and vice versa. Again, until it doesn't move for five minutes.

Is this all right?

#32 overnight

overnight

    Vanguard

  • *****
  • Posts: 2211
  • Joined: 10 Jan 2017
  • Loc: San Diego, CA

Posted 19 June 2017 - 09:15 AM

If it interests you, some AVX users have rebuilt their AVX using WAY better cheaper common sense bearings, WAY better grease, and one person said they got 15 minute *guided* subs. That can translate to 2 minutes to you on your AVX.

 

I'm doing this one right now on mine.

 

https://www.cloudyni...on-avx-rebuild/


  • zakry3323 likes this

#33 Genryuu111

Genryuu111

    Explorer 1

  • -----
  • topic starter
  • Posts: 54
  • Joined: 14 Jun 2017

Posted 19 June 2017 - 09:29 AM

Thank you overnight, I already saw that post, but it honestly sounds something I would screw up..

I already took the risk by messing with the gears, but a complete rebuild like that sounds really scary.

But honestly at this point I might think about it. The problem will be finding the bearing and proper tools here in Japan, since it's not my country, and even if I speak the language decently there is still a barrier when it comes to things I don't usually deal with :p



#34 overnight

overnight

    Vanguard

  • *****
  • Posts: 2211
  • Joined: 10 Jan 2017
  • Loc: San Diego, CA

Posted 19 June 2017 - 10:25 AM

Besides fine-tuning your methods, and rebuliding the AVX, the only alternative really is to get a guiding setup.

 

There is another one too, which is to upgrade your mount. I know its expensive and difficult, but last resorts....

I badly want to get a better mount...



#35 Genryuu111

Genryuu111

    Explorer 1

  • -----
  • topic starter
  • Posts: 54
  • Joined: 14 Jun 2017

Posted 19 June 2017 - 04:02 PM

I just bought the mount, so I'm not going to upgrade it :p

I'll try to fix it and adding a guiding setup, we'll see :)


  • xiando likes this

#36 xiando

xiando

    Fly Me to the Moon

  • *****
  • Posts: 6388
  • Joined: 27 May 2015
  • Loc: Cloudy NEOhio

Posted 19 June 2017 - 04:30 PM

Just get that guider and start using it. FWIW, My astro-buddy, who uses an AVX pretty successfully, doesn't guide in DEC due to issues, what I believe is probably due to the stiction associated with the DEC axis sleeve-bearing from previous knowledge about the performance limits of sleeve bearings and due to correlated posts made at CN about the axis and challenges it presents.

 

He's guiding at a little over 1 arc sec RMS.


Edited by xiando, 19 June 2017 - 04:31 PM.


#37 Genryuu111

Genryuu111

    Explorer 1

  • -----
  • topic starter
  • Posts: 54
  • Joined: 14 Jun 2017

Posted 08 July 2017 - 10:05 AM

In the end I god the autoguiding stuff, and I didn't have a single decent night since then...ALWAYS cloudy!

 

Just for two times I managed to at least test everything inbetween clouds, and while I can say that "it works" (as in, the camera works, I can see stars, I can guide on stars), everything is too erratic to do decent tests, and then take actual pictures.



#38 Achernar

Achernar

    Voyager 1

  • *****
  • Posts: 11328
  • Joined: 25 Feb 2006
  • Loc: Mobile, Alabama, USA

Posted 09 July 2017 - 11:35 AM

Drift in right ascension could be caused by the fact the drive has three tracking rates, sidereal, lunar and solar. I found out firsthand when imaging the moon that using the lunar rate is necessary. If you want to image planets and deep sky objects, set the rate to sidereal. The others are for tracking the moon and Sun respectively. If that doesn't help, are you sure you're balancing the telescope correctly? As for the coma in the picture of M-27, that is mostly misaligned optics, with some coma inherit to the parabolic mirror. A coma corrector will get rid of coma from the parabolic curvature of the primary mirror, but it can't fix misaligned, improperly mounted or defective optics. The uneven appearance of the stars shows collimation is the main culprit.

 

By the way, use the polar alignment scope if you have one, after calibrating it first. Or simply sight in on Polaris through the polar axis. Get a good GOTO alignment and use three or four calibration stars around the other side of the sky from the two you used to align the mount. Then push the align button after you are done and check the polar alignment to see how close you are to the North Celestial Pole. Then use the All Star Polar Alignment feature on a star that is not close to the horizon, the pole or overhead and align the mount using the altitude and azimuth adjustments on the mount. Power down the mount then repeat the GOTO alignment, then check the polar alignment again. I've got my AVX within two arc-minutes of the NCP, and found that there was virtually no drift discernible over the course of a few minutes. I've then left the telescope to track for 15 minutes and returned to find the star has just moved off the reticle. The ASPA feature really does work.

 

Your Jupiter and Saturn photos turned out quite nicely, better in fact than what I've been able to do so far with a 60 dollar video eyepiece.

 

Taras


Edited by Achernar, 09 July 2017 - 12:08 PM.


#39 Genryuu111

Genryuu111

    Explorer 1

  • -----
  • topic starter
  • Posts: 54
  • Joined: 14 Jun 2017

Posted 09 July 2017 - 01:19 PM

Thanks Achernar
My tracking rate has always been the right one, and about coma, yeah, I didn't collimate before taking those pictures.

 

I cannot polar allign on polaris because I can't see it from where I live. And in general, I'm very limited with the portion of sky I can use.

Some day I will try to get out and use it just outside my place, the problem is I don't want to be a bother to neighbors so I always avoided it for now.

 

As for planets, it's such an easier task to take "decent" pictures of them compared to DSOs (in my opinion).

Once seeing is good and you're properly focused, that's it.

It's a bit tricky with postprocessing, but you can still come back to the original files and modify them differently if you don't like the results.

My pics were taken with a modified PS3 eye camera, costed me 8 dollars, plus something for the tools I used. So I was really pleased with the pictures I could take with such a low investment :p



#40 overnight

overnight

    Vanguard

  • *****
  • Posts: 2211
  • Joined: 10 Jan 2017
  • Loc: San Diego, CA

Posted 17 July 2017 - 02:20 PM

If you can't polar align, you have to take your images elsewhere where you can see Polaris.



#41 rmollise

rmollise

    ISS

  • *****
  • Posts: 22874
  • Joined: 06 Jul 2007

Posted 17 July 2017 - 02:35 PM

You don't need Polaris to do a polar alignment with the VX.


  • dfisherows likes this

#42 overnight

overnight

    Vanguard

  • *****
  • Posts: 2211
  • Joined: 10 Jan 2017
  • Loc: San Diego, CA

Posted 17 July 2017 - 03:06 PM

You don't need Polaris to do a polar alignment with the VX.

For AP it is.



#43 mclewis1

mclewis1

    Thread Killer

  • *****
  • Posts: 19039
  • Joined: 25 Feb 2006
  • Loc: New Brunswick, Canada

Posted 17 July 2017 - 05:49 PM

 

You don't need Polaris to do a polar alignment with the VX.

For AP it is.

Oh no you don't. Even for AP you can do either or both the ASPA (all star polar alignment) which will get you close and then a drift alignment to fine tune your polar alignment if are imaging at longer focal lengths (which requires greater accuracy). Neither of these requires access to Polaris (or the southern polar region).



#44 rmollise

rmollise

    ISS

  • *****
  • Posts: 22874
  • Joined: 06 Jul 2007

Posted 18 July 2017 - 11:32 AM

 

You don't need Polaris to do a polar alignment with the VX.

For AP it is.

 

 

Nope. Not at all. The AllStar Polar Alignment built into the hand control will yield a noticeably better polar alignment than the polar scope could. wink.gif

 

Do you actually own this mount?


Edited by rmollise, 18 July 2017 - 11:33 AM.

  • barbarosa likes this

#45 Genryuu111

Genryuu111

    Explorer 1

  • -----
  • topic starter
  • Posts: 54
  • Joined: 14 Jun 2017

Posted 18 September 2017 - 01:04 PM

Hello everyone.

 

Summer in Japan is extremely humid, and there were basically just a few clear nights in total.

 

I fiddeled a lot with the mount, and got my guiding system, but long story short, it's not solving my problem at all.

I'll attach a few graphs I took one night in PHD2, with some adjustments in settings between each. Can anyone guide me to something I can do to fix this mess?

Or, are my hardware problems so bad that I should simply give up on this mount?

Please keep in mind I'm a complete novice..

 

Both Dec and Ra are not ideal, but Ra is really terrible.

 

I'm not looking for something extremely flat, I live in a very light pollutted area, so there's a limit to what I can picture anyway.

But I'd like at least to be able to do something like 2 minutes subs, and with how things are right now, I get trails after 30 seconds, guiding..

 

In case I should move this part of my problem somewhere else in the forum, please let me know.

 

Thanks.

Attached Thumbnails

  • phd2 1.png
  • phd2 2.png
  • phd2 3.png
  • phd2 4.png


#46 Whuppy

Whuppy

    Viking 1

  • *****
  • Posts: 928
  • Joined: 20 Aug 2013
  • Loc: Ortonville, MI

Posted 18 September 2017 - 01:50 PM

Okay, a few things...what are you using to guide with, OAG or guide scope?

Make absolutely certain that you input the correct focal length and pixel size for your setup (very, very important).

Next time out...
Reset PHD and start over with default settings. Go to the brain tab> guiding and click both the Ra and Dec reset buttons.

Do this on a good clear night, you don't want anything clouding your results.. pun intended­čść. Read all the phd help documents you can (do that first). Pick a good star that gives a nice peak and do your calibration...you did a calibration first right? Once you get a good calibration and it starts guiding go to tools and start the "guide" assistant. Now just walk away and let it drift for at least 10 minutes or one worm period.

Yes, the graphs you posted are pretty nasty looking, but that's about all that can be taken from them. I usually guided my AVX with 1 or 2 second exposures.

Edited by Whuppy, 18 September 2017 - 01:53 PM.


#47 Darrenlh

Darrenlh

    Vostok 1

  • -----
  • Posts: 183
  • Joined: 08 Sep 2010
  • Loc: Alberta, Canada

Posted 18 September 2017 - 09:45 PM

Try increasing the MX RA setting to 2000+ and reduce RA aggression to 85 and see what result that gives. 



#48 JamesTX

JamesTX

    Vostok 1

  • -----
  • Posts: 137
  • Joined: 27 Aug 2017
  • Loc: Texas

Posted 19 September 2017 - 01:17 AM

Are you using the same test target through out this troubleshooting process?

Where is your test target?

 

As mentioned earlier in this thread, some have had problems tracking objects that are above 70┬░.  I have noticed this with my setup (same avx with 6" reflector).

 

If you have not tried a different object, try something else, preferably something between 30-70┬░.

 

The only other thing I can think of is that maybe something is not right with your drift alignment.  I used drift alignment with my first mount, a cg4 with the clock drive.  Sometimes I could get some odd results where I thought I was good based on the star I was using to drift, and then got trails when I moved to the object I wanted to image. 



#49 Genryuu111

Genryuu111

    Explorer 1

  • -----
  • topic starter
  • Posts: 54
  • Joined: 14 Jun 2017

Posted 19 September 2017 - 08:59 AM

Thanks everyone for your inputs.

 

@Whuppy

I'm using this scope

https://www.amazon.c...r/dp/B00PUXC50U

 

with this camera

https://www.amazon.c...a/dp/B01C5W2KIK

 

They are both rebrandings for the asian market.

I had PHD detect the pixel size (it's set on 7.5, and on amazon it says 3.75 x 3.75...is it ok?), and set 240mm as focal length.

I already reset the whole thing (both mount and PHD) many times, but I'll give it a new try.

 

@Darrenlh

Thanks, after resetting everything, I'll try with those settings.

 

@garandthumb

I honestly don't remember, but I think those 4 graphs were from different stars in the same area of the sky.

I never go too high in the sky because right now I'm using it on my balcony, and there's the roof.

Drift alignment may be one of the issues, but since I started trying to take DSO pictures, even before guiding, I've always had this crappy RA drift, very evident, compared to DEC.

 

 

One more question I'd like to ask, with this camera I have to use ASCOM toupcam driver, and ToupST4 (ASCOM). Which is fine, but the problem is that like this (as far as I understand), it's treated as ST4 and not ASCOM, and for example, when I use the drift allignment function, I will get the dotted circle instead of the normal one (which means it's less precise). If I use any other ASCOM named thing under "mount" it will either not work properly, or not work at all (giving me constant errors).

The setup is: USB port connecting the PC to the camera, and phone-like cable connecting the camera to the mount (auto guide port).

If impossible it can't be helped, but is there anything I can do about it?

 

Thank you again.



#50 fgraus

fgraus

    Vostok 1

  • *****
  • Posts: 164
  • Joined: 12 Feb 2013
  • Loc: Kansas, usa

Posted 19 September 2017 - 01:54 PM

 

 

 

One more question I'd like to ask, with this camera I have to use ASCOM toupcam driver, and ToupST4 (ASCOM). Which is fine, but the problem is that like this (as far as I understand), it's treated as ST4 and not ASCOM, and for example, when I use the drift allignment function, I will get the dotted circle instead of the normal one (which means it's less precise). If I use any other ASCOM named thing under "mount" it will either not work properly, or not work at all (giving me constant errors).

The setup is: USB port connecting the PC to the camera, and phone-like cable connecting the camera to the mount (auto guide port).

If impossible it can't be helped, but is there anything I can do about it?

 

Thank you again.

I'm just starting to learn PHD but I think the instructions said that if you connect the camera to the ST4 port on the mount (guide) that when you connect PHD to the mount in the pull down menu you should select "on-camera".




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics