#1  
Old 13-05-2014, 06:03 PM
SimmoW's Avatar
SimmoW (SIMON)
Farting Nebulae

SimmoW is offline
 
Join Date: Jan 2014
Location: Tamleugh, Victoria, Australia
Posts: 1,383
NEQ-6 alignment/guiding

Hi, last night I got cocky and tried imaging with my 200mm Canon lens and camera, mounted on the NEQ-6.

I'd read some handy tips about polar aligning with a mobile phone, so used a compass app to help me align the tripod to true south. The mount causes a bit of interference with the compass, so I just stood directly behind the rear tripod leg and aimed the tripod carefully in alignment to where the compass was pointing. Far more accurate than I'd previously done with a 50mm lens and getting 1 min okay subs.

I aligned the altitude using another phone app, firstly levelling the tripod (on grass, i know that's bad but that's all I got right now), then using the phone to fine tune the azimuth. Freaking phone has a curved back, so it's pretty hard to get dead right, I know.

I even managed to do a 3 star alignment, and the mount slewed to objects very well.

BUT with the 200mm lens, any exposures over 15 secs revealed quite large star trails. With 30 secs it was ridiculous and the object was visibly moving in each subsequent image.

What's going on? Am I asking too much of the mount with the 200mm lens? Is the camera too light, are there speed settings I might need to adjust? Do I really need to be within 1 second angle accuracy? Not sure what to do from now, other than keep working on drift alignment/further tweaking of alignment accuracy.

I need to take the scope inside every night, so I'm afraid I can't have a permanent setup. I did set up a compass guide, crude! Just lined up a pot to the point of the house pointing south, so I can line the tripod up within reasonable limits. The Azimuth alignment, I figure, should be permanent, using those adjusting knobs.

Any help appreciated.

Simon
Reply With Quote
  #2  
Old 13-05-2014, 06:28 PM
Meru's Avatar
Meru (Michael)
More stars please!

Meru is offline
 
Join Date: Jan 2012
Location: Vic
Posts: 560
Hey Simon,

Using your phone for any sort of alignment will give you extremely poor alignment, and that's at best! The 3 star method will account for errors and slewing accuracy can still be fairly good even if you are polar aligned poorly. I know this because I used to try to image without any knowledge on proper polar alignment and wonder what was going on! Use your phone or a compass to point it roughly south but thats about as far as it will help. And the NEQ6 can handle loads quite comfortably over 10kgs, so your 200mm lens will be just fine.

Most important, above all else, is to understand what polar alignment is, why it is needed, and why does moving your scope in this direction or adjusting it in that direction make it better or worse. Once you get the theory down pat, polar alignment is extremely easy

Have a look on youtube and google polar alignment, I personally found the best way is to use the CCD drift method if you doing astrophotography. If you google this you will find plenty of instructions. I can get to a few minutes unguided at 200mm using the method and doesnt take more than 15 minutes to get there. Handy tip - your altitude angle of the mount is equal to your latitude (so for melbournians thats about 37 degrees) and once set never needs to be adjusted again, unless you drive north or south for a few hundred kms! Your azimuth (left-right) however does change every night simply because you can never point your mount in exactly the same direction again and again. I also used to set up every night and not leave it out so once I got my mount aligned really well, I marked the position of the legs on the ground and glued washers . Then every night I could just move the mount out, let the legs fall inside the washer and bang all done!
Reply With Quote
  #3  
Old 13-05-2014, 08:52 PM
SimmoW's Avatar
SimmoW (SIMON)
Farting Nebulae

SimmoW is offline
 
Join Date: Jan 2014
Location: Tamleugh, Victoria, Australia
Posts: 1,383
Thanks Meru, nice clear explanation, I'll give it a go.
Reply With Quote
  #4  
Old 13-05-2014, 09:43 PM
Steffen's Avatar
Steffen
Ebotec Alpeht Sicamb

Steffen is offline
 
Join Date: Feb 2010
Location: Toongabbie, NSW
Posts: 1,965
EQ mounts require two types of alignment.

The first one (1-, 2- or 3-star alignment) tells the mount which way it is oriented in space. After successfully completing this kind of alignment the mount will be able to GOTO objects.

The second kind is polar alignment, it means making the mount's RA axis parallel to the Earth's axis of rotation. This is required for tracking (following objects as the move across the sky).

Polar alignment is not required for a successful 2- or 3-star alignment. The mount will be able to GOTO objects regardless. However, it will not be able to keep objects in the field of view for extended periods of time.

It is only that way because of a design choice made my the manufacturer. After 2- or 3-star alignment the mount knows the polar alignment error and could automatically compensate for it. This would require using both the RA and Dec motors for tracking. Mounts like the NEQ6 (and many other EQ mounts) only track using the RA motor, hence the requirement for polar alignment.

Interestingly, Alt-Az mounts like the AZ-EQ6 are perfectly capable of tracking using both RA and Dec motors. This will cause field rotation of course, and would therefore be unsuitable for most imaging purposes. However, Synta have no HEQ5Pro or NEQ6 caliber Alt-Az mounts in their line-up that would suit visual astronomers. The AZ-EQ6 is more expensive than the NEQ6, which is why a lot of visual observers put up with the quirks of EQ mounts.

Cheers
Steffen.
Reply With Quote
  #5  
Old 14-05-2014, 09:14 AM
batema's Avatar
batema (Mark)
Registered User

batema is offline
 
Join Date: Jul 2006
Location: Sunshine Coast
Posts: 1,827
Hi Simon,

I use an EQ6Pro (older model to yours). I always start by polar aligning my scope. I use a program called K3CCD tools. After making sure that my imaging scope,guiding scope and view finder are all aligned and the scope is balanced I focus on a star using my computer to view the star and after that I rebalance.

Then I point the scope straight up to near the meridian and using K3CCD tools drift align tool I use the round knobs to rotate the mount either left or right until the star does not drift in this direction using K3CCD. Then I go toa star about 30 degrees above the eastern horizon and repeat the drift alignment tool until it doesnot drift in this direction. Then I am polar aligned and this usually takes me about 10 minutes. Then I do a three star alignment and then I am set to go to objects and they barely move. While imaging I use PHD guiding. I believe that K3CCD won't work on windows 8 but I use mine on my windows 7. A mate uses PHD2 on his windows 8 machine as it is new and free and has a drift alignment tool in it that looks very easy.

Have fun

Mark
Reply With Quote
  #6  
Old 14-05-2014, 03:45 PM
SimmoW's Avatar
SimmoW (SIMON)
Farting Nebulae

SimmoW is offline
 
Join Date: Jan 2014
Location: Tamleugh, Victoria, Australia
Posts: 1,383
Thanks chaps, it all clears it up for me more and gives plenty of ideas to try, will do some experimenting tonight, weather permitting!
Reply With Quote
  #7  
Old 14-05-2014, 08:40 PM
alistairsam's Avatar
alistairsam
Registered User

alistairsam is offline
 
Join Date: Nov 2009
Location: Box Hill North, Vic
Posts: 1,837
Hi

What version of software so you have on your hand controller?
If its 3.2 and higher ( I think), it comes with a polar alignment routine which works similar to alignmaster.
Give that a shot if you can.

Otherwise you could do drift alignment with your dslr but it'll be rough which is sufficient for 200mm.

slew to the meridian/equator, do a 10sec exposure at the highest iso and use the ra control to move in ra west for 5secs then stop tracking. At the end of the exposure You should get a v.
That shows you the start of the star and the gap in the v is the drift in dec which is whay you want to remove.

Adjust the azimuth till repeats of this gives you a line instead of the v.
Its a bit hard with the dlsr and its display but doable.
Same thing applies to altitude with an east/west star.

The washer idea is very good and helps heaps.

Cheers
Alistair
Reply With Quote
  #8  
Old 15-05-2014, 08:26 AM
acarleton's Avatar
acarleton (Aidan)
Registered User

acarleton is offline
 
Join Date: Dec 2013
Location: Sydney
Posts: 141
I have a similar issue in that i have to bring my scope and mount in every night and it can be annoying doing a polar alignment each night, especially when you only want to do a short session. what i have done is performed a good drift alignment and then place a V shape duct tape mark on the tiles. this way i can bring my mount out and align perfectly the tripod with my previous markings and go from there. this has been very successful and has saved me from a lot of set up time
Reply With Quote
  #9  
Old 15-05-2014, 10:35 AM
traveller's Avatar
traveller (Bo)
Not enough time and money

traveller is offline
 
Join Date: Aug 2011
Location: Melbourne
Posts: 2,133
Don't forget you can do a solar noon procedure before you set up the scope to improve the initial alignment before polar alignment.
Bo
Reply With Quote
  #10  
Old 15-05-2014, 05:44 PM
SimmoW's Avatar
SimmoW (SIMON)
Farting Nebulae

SimmoW is offline
 
Join Date: Jan 2014
Location: Tamleugh, Victoria, Australia
Posts: 1,383
Hey thanks, more good ideas. I definitely need to set up some tape, great suggestion.

Last night I did my first serious polar alignment, using the DARV method. Carefully double-checked my compass heading too, that was way off last time.

Doing the drift exposure resulted in a damn straight line, a real fluke. So I was able to image at 30 secs and one minute, in moonlit skies, at least I got reasonably round stars, so thanks everyone!
Attached Thumbnails
Click for full-size image (tarant1.jpg)
201.5 KB49 views
Reply With Quote
  #11  
Old 16-05-2014, 08:19 AM
rrussell1962
Registered User

rrussell1962 is offline
 
Join Date: May 2014
Location: Brisbane
Posts: 493
I've previously used golf tees as position markers in the lawn for tripod feet after I was totally happy with the alignment.

rrussell1962.
Reply With Quote
  #12  
Old 16-05-2014, 04:18 PM
acarleton's Avatar
acarleton (Aidan)
Registered User

acarleton is offline
 
Join Date: Dec 2013
Location: Sydney
Posts: 141
looking at that image, you might want to check your focus, it looks like some of the brighter stars are doughnut shaped
Reply With Quote
  #13  
Old 16-05-2014, 06:05 PM
gbeal
Registered User

gbeal is offline
 
Join Date: Oct 2004
Location: New Zealand
Posts: 4,345
I use a rolling pier, and have threes S/S washers glued to the asphalt, I drift aligned to find the correct positions.

Since you're on grass perhaps sink three bricks or small paving tiles into and flush with the grass, them glue some washers.

All you're looking for is repeatability, align it once and mark for the washers.
Gary
Reply With Quote
  #14  
Old 19-05-2014, 05:12 PM
Andy01's Avatar
Andy01 (Andy)
My God it's full of stars

Andy01 is offline
 
Join Date: Mar 2012
Location: Melbourne
Posts: 3,253
Hi Simmo,
+1 from me on the washers, bricks embedded in the grass, and purchase a proper compass and inclinometer.
Also +1 on the solar noon method for finding true south.
I use the PHD method of drift alignment. Very painless.
Cheers
Andy
Reply With Quote
  #15  
Old 19-05-2014, 06:53 PM
The_bluester's Avatar
The_bluester (Paul)
Registered User

The_bluester is offline
 
Join Date: Feb 2011
Location: Kilmore, Australia
Posts: 3,342
We will hopefully have a fenced off area to play in by the June new moon Andy too. We can set up something more permanent for you by way of alignment marks, then a pier!
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:43 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement