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Old 29-08-2019, 01:30 PM
Startrek (Martin)
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East Heavy , Guiding and Meridian Flip

I just re arranged the guide scope on my 6Ē f6 newt from its offset location in the little shoe bracket to the central axis location on the OTA using a losmandy bar mounted on the tube rings
This so I can have my finder scope and guide scope mounted on the OTA together.Previously I would remove the finder and replace it with the guide scope once framed up ready for imaging ( a bit of a pain in the butt )
Obviously I had to rebalance the mount with the added payload, which I did but both counterweights were pushed to the end of the rod with no spare space.
I balanced RA and Dec as best as I could
Last night in Sydney there was a window of 3 hours to Image so to test the new guide scope position I decided to capture M16 .Ē, Iíve only captured this object from my dark site south coast NSW
Guiding was troublesome at first so I re calibrated due to the new location of the guide scope and it improved a little ( counterweight east , OTA west )
After a meridian flip guiding improved dramatically ( counterweight pointing west , OTA east )
My question is firstly explain balancing the mount ďEast HeavyĒin relation to the position of the counterweights and OTA
I totally understand the ďconceptĒ of East Heavy where the imbalance of a small amount of weight against the drive system tightens up the gearing and reduces the slop and therefore inefficiency and error in tracking
Iíve watched so many clips and read so much and no one explains or details what happens after a meridian flip in regard to East Heavy
In my case last night, my mount was evenly balanced and guiding improved dramatically on the other side of the meridian later into the night
Conditions last night were stable and seeing was average most of the night from starting imaging at 8.00pm until the cloud rolled in around 11.00pm and obviously my guiding went totally off the rails after that so I shut down and captured my darks

Could some of you experienced folk explain East Heavy ( especially after a meridian flip) and possibly why my guiding improved so much after the meridian
NB : M16 moved from around 70 to 55 degrees Altitude throughout the capture so still nice and high

Thanks in advance
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Old 29-08-2019, 02:29 PM
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The_bluester (Paul)
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East heavy as a concept I find a little troublesome unless you are willing to manually flip and rebalance as your target passes the meridian. I understand that it means the worm stays in mesh at all times and on the same face but for automated imaging it is a bit of an issue unless you are willing and able to limit yourself to a max of about three hours per target per night to keep the meridian and maybe 45 degrees before it.

Rather than being "east" heavy, I have normally just been counterweight heavy and by enough to be sure that it will overcome any friction in the mount when the scope is on the west, pointed east so the worm stays under some tension at all times.

Basically I am set up so that the scope is imbalanced by enough that the mount stays meshed on the "lee" side of the worm when it is pointed west and the counterweight is going down, but not so imbalanced that tracking is unduly effected when it is pointed east and lifting the counterweight heavy configuration.

I figure if they can rip USB ports out of cameras and do damage when they crash into the leg of the tripod they can probably stand a couple of hundred grams of imbalance.
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Old 29-08-2019, 03:01 PM
Startrek (Martin)
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Paul
Thanks for your comments
I suppose in principle East Heavy is a good practice to adopt but Iím not going to stop an Image session and rebalance on the other side west Heavy . Time is too precious on clear nights to muck around in the dark rebalancing again
Do you agree ?

Any ideas why my guiding improved from 1.60 to 1.80 arc sec on the east side to 1.20 to 1.40 arc sec on the west side ( and both sides I was dithering ) literally 10 to 15 minutes apart !!
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Old 29-08-2019, 03:31 PM
Startrek (Martin)
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Thanks Glen
Iíve been imaging with both 6Ē and 8Ē newts for 2 years , 5 minute subs and perfect round stars with both DSLR and finder at 45 degrees opposite on topside of the OTA ? I seen both set ups ( magazines , YouTube, astronomy books , you name it ) on top at 45 deg opposite and also directly below along the axis of the OTA like you advised
Mine has been working ok , maybe Iím lucky ??
My DSLR is narrow field so itís useless as a finder, once Iím aligned to the first star with the finder , Iím off and running with EQMOD and Stellarium via my DSLR
I also sometimes do DSO and Planetary imaging on the same night so the finder is a must for me
Everyone has there own system of find and capture , and having both finder and guide scope on board works well for me
Thanks for your input
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Old 29-08-2019, 05:16 PM
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ChrisV (Chris)
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Maybe where the guidescope was positioned before balanced the weight of the imaging train/camera better?

But that doesn't answer your question about before and after the meridian flip
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Old 29-08-2019, 09:11 PM
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Quote:
I suppose in principle East Heavy is a good practice to adopt but Iím not going to stop an Image session and rebalance on the other side west Heavy . Time is too precious on clear nights to muck around in the dark rebalancing again
No need to rebalance. You can mark the spot where the counterweight balances the usual gear perfectly and then you shift it slightly one way before the meridian flip and the other way after the meridian flip.
It will take less than a minute to do but unfortunately it still requires manual attention.
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Old 30-08-2019, 10:22 PM
RyanJones
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I personally donít let my mount flip. If Iím starting east of meridian I force no flip on the hand controller and start my imaging with the weights pointing up in the air. I can generally get about 6 hrs in in one session which is enough for me.
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Old 31-08-2019, 07:06 AM
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multiweb (Marc)
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Depending on your mount backlash you might not have a choice and rebalancing is usually done by unwinding one counterweight once up or down. There are other things that conspire against perfect balance. Offset telrad or finder, filter wheel, side by side setup, so balance is never perfect and changes as your mount moves closer or away from the meridian.
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