#1  
Old 27-09-2019, 07:27 PM
Mickoid (Michael)
We learn every day

Mickoid is offline
 
Join Date: Feb 2016
Location: Melbourne, Australia
Posts: 752
Balancing Act

I've just started autoguiding using Phd2 and have been trying to overcome some teething problems. Auto guiding using the 550mm Esprit 100 is not a concern but last night I did a test using the 1000mm 8 inch Newtonian. Balancing the Newtonian with a heavy DSLR hanging off the side has always given me grief, concluding that it will never balance correctly in every position.

My solution has been to just balance it as best I can in the position it will be guiding my target object. I've realised from last night's test this is the way to go with autoguiding as well. I had the scope balanced to shoot objects high above and a little to the north last night. This is the position where most of my clear sky sits in the front yard. Here I did two 4 min subs of NGC 253 and both were close to perfect but for 47 Tuc I had to throw four out of six 4 min subs away. Obviously the mount was struggling to maintain accurate guiding due to it being out of balance, as the object was in the south.

An important lesson on making sure your rig is balanced as best as possible for Phd2 to have a chance to guide accurately, especially at 1000mm focal length. This is one area where refractors have the advantage over reflectors, the camera sits at the end of the OTA.

These two shots at 8mins and 15mins integration are definitely not ones to hang on the wall but I'm glad I've proven that I can autoguide using this set up. It should come in handy for the warmer months when longer exposures will allow me to use lower ISO values to reduce noise.
Attached Thumbnails
Click for full-size image (8minNgc253.jpg)
207.1 KB61 views
Click for full-size image (15min47Tuc.jpg)
193.5 KB45 views
Reply With Quote
  #2  
Old 27-09-2019, 07:43 PM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,696
Michael
What mount is your 8” newt sitting on ?
My 8” f5 1000mmFL sits on an EQ6-R with my DSLR and I can guide under 1 arc sec with PHD2 and capture 5 minute plus exposures
Here’s my balancing procedure -

Ensure telescope is set in the “Home Position” before you balance
Also ensure all equipment and cabling is installed on your telescope and mount ready to observe or image

Start with balancing Dec axis first
Dec Balancing
1/ Release the Dec clutch and rotate the telescope so it is horizontal and parallel to the ground, then carefully see which way it tilts.Telescope should sit level if balanced
2/ Adjust if necessary by locking the Dec clutch, loosen the tube rings and slide the telescope forward or backward as required and retighten tube rings.
3/Check Dec balance again by releasing Dec clutch and rotate telescope to the horizontal position to check if it sits level.
4/ Repeat adjustments until telescope is freely sitting level then return to home position and lock Dec clutch
5/Release the RA clutch and rotate the mount so that the counterbalance shaft is level and parallel to the ground then lock the RA clutch
6/ Unlock the Dec clutch and rotate the telescope so it is level and parallel to the ground then lock the Dec clutch. If you viewed from above you would see the letter “T” formed by the mount and telescope
7/ Now unlock the Dec clutch while holding the telescope and see if it tilts to one side or the other.Lock the Dec clutch and loosen the tube rings and slide the telescope forward or backward as required then retighten tube rings
8/ Repeat adjustments until the telescope is freely sitting level and parallel to the ground and then retighten Dec clutch. Dec is now balanced in horizontal position.
9/ Now release the Dec clutch and rotate the telescope in the vertical position whilst holding it. If it falls one way or the other you must balance in the vertical position by locking the Dec clutch , loosening the tube rings and rotating the telescope clockwise or counterclockwise , tightening the tube rings and then unlocking the Dec clutch until it remains stationary in the vertical position
10/ Repeat adjustments until the telescope sits freely in the vertical position then rotate the telescope to the horizontal position level or parallel to ground. The telescope should now be balanced in Dec at both horizontal and vertical position
Leave the telescope locked in the horizontal position ready for RA balancing

RA Balancing
1/ Unlock the RA clutch whilst holding the telescope to see if the telescope falls down or lifts up
Move the counter balance weights up or down the shaft as required to ensure the telescope is balanced level parallel to the ground. Adjust as required and lock the RA clutch
2/ Now you need to make the telescope slightly “East Heavy” by moving the counterweights down the shaft a bit so the balancing is slightly in favour of the counterweights. Lock the RA clutch
3/ The telescope should now be balanced in Dec and RA so unlock the RA and Dec and return the telescope to the home position and lock both clutches

I found this procedure on Astronomyshed.com

I balance slightly “East Heavy” too
Reply With Quote
  #3  
Old 27-09-2019, 08:32 PM
Mickoid (Michael)
We learn every day

Mickoid is offline
 
Join Date: Feb 2016
Location: Melbourne, Australia
Posts: 752
Thanks for the quick reply Martin. I've got the 8inch Newt on a HEQ5 pro so with the DSLR camera and mini guide scope with the ZWO guide camera on, it's a little heavy. I have added some extra counter weights as well.

I'll give the balancing procedure a go, though I don't understand when it says to loosen the tube rings to slide the OTA forward or backward to sit level in step 2 AND 7. Surely moving it in step 7 will change the balance adjusted in step 2. It will probably make sense as I go through each step. It's hard to visualise what's actually happening by reading the instructions.

Maybe your heavier duty EQ6 mount is more forgiving in dealing with balance problems than the HEQ5, that would explain your ability to acquire such accurate guiding.
Reply With Quote
  #4  
Old 27-09-2019, 09:24 PM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,696
Michael
My HEQ5 has a 6” f6 newt on it for AP and I’m up at 67% payload
For long exposure AP “in theory” you should be no more than 60 to 65% of the maximum payload capacity of your mount
You are certainly overloaded on the HEQ5 for DSO long exposure AP with an 8” on board
All you can do is balance your mount as precisely as you can and image on good seeing nights with no wind around
Good luck with the balancing procedure
Cheers
Reply With Quote
  #5  
Old 27-09-2019, 10:08 PM
doppler's Avatar
doppler (Rick)
Registered User

doppler is offline
 
Join Date: Nov 2012
Location: Mackay
Posts: 1,547
I find that my scope balances and guides better if the finder and focuser /camera are pointing down. I've also put bits of tape on the tube and dovetail to mark the balance points so I don't have to spend time balancing each time I set up.

Rick
Attached Thumbnails
Click for full-size image (pier.jpg)
180.2 KB29 views
Reply With Quote
  #6  
Old 28-09-2019, 06:12 AM
Startrek (Martin)
Registered User

Startrek is offline
 
Join Date: Dec 2017
Location: Sydney
Posts: 1,696
I’ve also tried balancing with the DSLR pointing down and pointing up at 45deg and found no major difference in guiding performance as the scope is orientated at various positions through a nights imaging particularly past the meridian ( centre of mass )
One of the most important part of balancing is step 9 in my procedure as it defines the balancing of the position of your DSLR , focuser and guide scope
But as Rick said try it with the DSLR underneath
My OTA has texta marks too
Cheers
Reply With Quote
  #7  
Old 28-09-2019, 07:18 AM
doppler's Avatar
doppler (Rick)
Registered User

doppler is offline
 
Join Date: Nov 2012
Location: Mackay
Posts: 1,547
Back in the days when they put large scopes on eq mounts, many were fitted with counter balance systems to fine tune dec balance. I have heard of people using magnets for a similar effect.
Rick
Attached Thumbnails
Click for full-size image (875933-1.jpg)
130.6 KB19 views
Reply With Quote
  #8  
Old 30-09-2019, 05:34 PM
LostInSp_ce's Avatar
LostInSp_ce
Unregistered User

LostInSp_ce is offline
 
Join Date: Mar 2017
Posts: 451
Mick, Orion make a magnetic counter weight. It's only 1 pound which is a good thing if you're close to your mount's load capacity.
http://www.sirius-optics.com.au/astr...terweight.html
Reply With Quote
  #9  
Old 30-09-2019, 07:32 PM
Mickoid (Michael)
We learn every day

Mickoid is offline
 
Join Date: Feb 2016
Location: Melbourne, Australia
Posts: 752
Those magnets would solve a lot of my problems and you don't need to loosen and retighten any screws, clamps or tube rings to move them to the best position. Thanks for pointing that out to me LostInSp_ce, I may look into buying one.
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 08:10 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Advertisement
Star Adventurer
Advertisement
Astromechanics
Advertisement
Lunatico Astronomical
Advertisement
Celestron RASA
Advertisement
EQ8-R
Advertisement
Bintel
Advertisement
Testar
Advertisement
Astronomy and Electronics Centre
Advertisement