Re: Orthogonality question

DFisch

Jimmy, best explanation of OE I have ever seen or heard, great post!

On Fri, Nov 1, 2019 at 00:26 jimmyjujames <jimmy_an@...> wrote:
If OE is short for orthogonality error.

An Orthogonality error (OE) is only east-west when pointing at zenith.
OE is always in line with the counter-weight shaft.
When pointing at NCP with counter-weight shaft pointing down, OE is north-south.

What is an orthogonality error (OE)?

With the counter-weights down and scope pointing at NCP.
An orthogonality error will cause the viewing point to be above or below NCP.

To the left or right of NCP is not an error.
You can move Dec to remove any left or right offset.

Rotating RA will move the viewing point around NCP forming a circle around NCP.
Diameter of the circle is 2 times (2x) your orthogonality error.

If you move the counter-weight shaft to west side and horizontal/level with ground, the scope's
viewing point will be either east or west of NCP by (1x) your orthogonality error.
If you move scope from NCP to zenith to Dec=0 to SCP, your scope's viewing point will be east or
west of meridian by your 1x orthogonality error everywhere along that path.

If you do a meridian flip at NCP, you will miss NCP by 1x on the other side of NCP.
1x on one side of NCP, meridian flip and 1x off on other side = 2x orthogonality error when
flipping from east to west side.

You will have to shim the front or rear ring to bring your viewing point back to NCP.

future meridian flips should result in star in FOV on both sides.

If not then you may have flexure and/or worm needs re-meshing and/or
something is loose and needs tightening.

As always, I may be wrong again.
Jimmy

Re: Orthogonality question

jimmyjujames

If OE is short for orthogonality error.

An Orthogonality error (OE) is only east-west when pointing at zenith or along meridian.
OE is always in line with the counter-weight shaft.
When pointing at NCP with counter-weight shaft pointing down, OE is north-south.

What is an orthogonality error (OE)?

With the counter-weights down and scope pointing at NCP.
An orthogonality error will cause the scope's viewing point to be above or below NCP.

To the left or right of NCP is not an error.
You can move Dec to remove any left or right offset.

Rotating RA from east side to west side will move the scope's
viewing point around NCP tracing out half of a circle around NCP.
Scope will hit the pier before the other half of circle completes.

Diameter of the circle is 2 times (2x) your orthogonality error.

If you move the counter-weight shaft to west side and horizontal/level with ground, the scope's
viewing point will be either east or west of NCP by (1x) your orthogonality error.

If you move the counter-weight shaft to east side and horizontal/level with ground,
you will miss NCP by 1x on the other side of NCP.

1x on one side of NCP, meridian flip and 1x off on other side = 2x orthogonality error when
flipping from east to west side.

If you move scope from NCP to zenith to Dec=0 to SCP, your scope's viewing point will be east or
west of meridian by your 1x orthogonality error everywhere along that path.

You will have to shim the front or rear ring to bring your viewing point back to NCP.

future meridian flips should result in star in FOV on both sides.

If not then you may have flexure and/or worm needs re-meshing and/or
something is loose and needs tightening.

As always, I may be wrong again.
Jimmy

Help with getting mount (AP 1100GTO) to flip in Voyager

Tony Benjamin <tonybenjamin@...>

Hi,

While I have been using Voyager successfully for a bit now (thanks Bill :)) I still have not been successful in getting the mount to flip automatically when reaching the meridian. Can anyone see what may need changing in the settings I have to get the mount to flip successfully at the meridian?

Thanks

Tony

Orthogonality question

Suresh Mohan

I know this question was discussed by Roland several years back but I seek the answer . Why does OE always show up on the east west axis
Thanks
Dr Suresh

Re: Polemaster adapter for AP-1600 w/o absolute encoders

Dale Hooper

Paige from Astro-Physics gave me the part number for the AP-1600 dec sight hole cover, in case anyone else is interested in trying Tony's idea of drilling and tapping a spare.  The part number is:  M16148. The charge is \$24, and shipping is \$7.50.

Clear skies,
Dale.

Re: What good are the encoders on the Mach2?

Roland Christen

The encoders cannot anticipate wind but can react to it after the fact. So you will have excursions but the axis being affected will recover much faster when the encoders are on. The best strategy is to set your mount low to the ground without extending the tripod legs. Large telescope tubes catch more wind then skinny ones. Same with short scopes versus long ones.

Rolando

-----Original Message-----
From: Rich Sornborger via Groups.Io <sornborger@...>
To: main <main@ap-gto.groups.io>
Sent: Thu, Oct 31, 2019 7:47 am
Subject: Re: [ap-gto] What good are the encoders on the Mach2?

I have a question regarding encoders and wind.  Do encoders make a vast improvement in gusty wind conditions?

Re: What good are the encoders on the Mach2?

Rich Sornborger

I have a question regarding encoders and wind.  Do encoders make a vast improvement in gusty wind conditions?

Re: Pointing for all night tracking

Michael Hambrick <mike.hambrick@...>

Hi Claude

Do you have a Keypad controller ? If so you might be able to use the directional buttons to manually slew to the RA and Dec coordinates of the object keeping the weights pointed up. Then once you find it you could start guiding. I am sure that Roland or Ray can offer some better suggestions.

Best Regards

Michael Hambrick
ARLANXEO
TSR Global Manufacturing Support
PO Box 2000
Orange, TX 77631-2000
Phone: +1 (409) 882-2799
email: mike.hambrick@...

Re: Pointing for all night tracking

Geof Lewis

Hi Claude,
I achieve this by setting a meridian delay in the APV2 driver, usually no more than 2 hours, but the other night I set a +3 hour delay, which actually advances the meridian flip point east of the true meridian, so that continuous tracking through the meridian is achieved, starting with CWs up.
Good luck,

Geof

On 31 Oct 2019, at 04:34, Isphotoman via Groups.Io <Isphotoman@...> wrote:

Hello, I have the AE1100 and am just learning how to use it. I would like to know what I need to do to slew the mount my scope is pointing to the east on an object and with the weights up? Not sure how to ask this question clearly. The problem is if I use my planetarium software to slew to an object that is rising in the east the mount slews so the weights are down, that means when the object crosses the meridian I would have to do pier flip. What I think I can do with this mount is slew to the object but have the weights pointing up, then image all night long without having to do a pier flip, The problem I have is I don't know how to point to the object so the weights would be up, if I slew to the object with the planetarium program it wants to keep the weights down. Am I off the mark trying to do this and should I just settle for a meridian flip?

Thanks
Claude

Re: Polemaster adapter for AP-1600 w/o absolute encoders

Dale Hooper

Oops...I hadn't noticed that you were the author of the videos.  Thanks so much for making them, they are very helpful to us in the A-P community!

Clear skies,
Dale.

Pointing for all night tracking

Claude Benoit

Hello, I have the AE1100 and am just learning how to use it. I would like to know what I need to do to slew the mount my scope is pointing to the east on an object and with the weights up? Not sure how to ask this question clearly. The problem is if I use my planetarium software to slew to an object that is rising in the east the mount slews so the weights are down, that means when the object crosses the meridian I would have to do pier flip. What I think I can do with this mount is slew to the object but have the weights pointing up, then image all night long without having to do a pier flip, The problem I have is I don't know how to point to the object so the weights would be up, if I slew to the object with the planetarium program it wants to keep the weights down. Am I off the mark trying to do this and should I just settle for a meridian flip?

Thanks
Claude

What good are the encoders on the Mach2?

Roland Christen

Hi Astronuts,

I have seen this question asked on other groups by people who wonder whether it is worthwhile to have encoders on a mount and what it will buy you in terms of performance.

To answer the question about the utility of a high resolution encoder, I have prepared some tests to show how they enhance the performance of high res imaging on our new Mach2 mount (same applies to our larger encoder mounts). I will be showing these tests and more at the Advanced Imaging Conference in 2 weeks, but thought it might be useful to post a preview here.

Of course everyone wants round stars, but a lot of the time people forget that there is also such a thing as high resolution. I have seen plenty of images that show round stars taken on mounts that are less than adequate. The stars are round but a lot of time they are rather big, even the faint ones, which means either the focal length was short, the optics were not sharp, the seeing was atrocious or the focus was off, OR the mount was bobbling back and forth in both axes. Now, if you have a great optic and great seeing, you might want to have a mount that tracks or guides close to perfection. In imaging the mount is the most important item.

Below I have two graphs. The first one show one worm cycle (about 400 seconds) of the Mach2 with the encoders turned off. It is running with a microstep-servo and belt drive (34 tooth pulley) which people seem to think is the hot setup these days. The periodic error of the worm shows up at around 7 arc seconds. What's also shown are the considerable errors caused by the toothed belt and the inherent error of a microstep motor (about 5% for each full step). These short term errors are typically 2 - 3 times larger than what you get with our DC servo motor/spur gearbox combination, so in my opinion going just with a belt drive does not enhance performance, but it does make the mount very quiet while slewing. These errors are very common in micro-stepper belt-drive mounts that are now a dime a dozen.

The first graph shows the main periodic error, and a combination of belt and microstepper ripple of around 2 arc seconds on top of the 7 arc sec PE. About 1/2 way thru the run I gave the scope a couple of good raps with my knuckles to see how fast it would settle back. The mount is heavily loaded with almost 70lb of scope and 90 lb of counterweight. Even without the encoders operating the RA axis settled quickly to resume tracking.It lost about 2 arc seconds of position, which of course would have to be made up by a guider loop.

The second graph shows the performance with the encoders turned on. Same rap on the scope shows much faster response and lower settling time. The tracking error has dropped to below 1/4 arc second P-P with almost negligible RMS value. During the test I trimmed the tracking rate by 0.4% and then back down. The mount is controllable to any rate and drives very smoothly regardless if it's sidereal, King or custom rate, which makes it highly useful for unguided imaging using a tracking model (APPM or similar). Toward the end I sent the mount West and then back East in 0.5 arc second steps to show the response you can expect during autoguiding. If the guider sends a 1/4, 1/2, or 1 arc sec move command the mount will move by that amount, no more, no less, and with no dramatics (no overshoots, no oscillations, no retrograde motions, etc). This is what you want your mount to do. Have a look:

Re: Polemaster adapter for AP-1600 w/o absolute encoders

Harley Davidson

Thanks Dale...a very easy project and you don't need to be "exact" with the placement of the tapped hole. Those are my videos by the way.

tony

On 10/30/2019 11:16 AM, Dale Hooper wrote:
Hi Tony,

Thanks so much for the info.  I think I will do like the author of the video and get another dec sight hole cover and drill that.  I'm a bit surprised that QHY hasn't released an adapter for the A-P 1600.

Thanks and clear skies,
Dale.

sydney77@...

When I was having intermittent issues with my keypad, George suggested removing the back cover and checking the contacts on the large ribbon cable.  Sure enough, the cable was loose but the contacts were still shiny clean.  After pressing it back in everything was fine.

Ted Mickle

I removed the back and reseated the major connections; the “5" button worked intermittently thereafter.

When sent back to AP, no overt problem could be found.

A few months later the “5” button went totally inoperative — it was returned to AP, who in turn sent it back to the manufacturer for definitive repair at no charge.

Ted

On Oct 30, 2019, at 01:14, Suresh Mohan <drsureshmohan@...> wrote:

To me this has happened twice ( now I remember ) . I think somewhere in the files section there are instructions to open the key pad and clean the pins , that should fix It  but it didn’t work for me . The first time I sent to AP as it did not solve the problem , they found the cable faulty at the point it enters the HC . The second time it happened I simply replaced the cable and it became fine .
Suresh

On 30-Oct-2019, at 5:58 AM, Kent10 <kent.moore@...> wrote:

﻿Thanks again, Don.  I'll follow your advice and clean everything up.  I live in Arizona so very dry here.

Re: Polemaster adapter for AP-1600 w/o absolute encoders

Cheng-Yang Tan

PoleMaster doesn't need to be on the DEC sight hole. I do this way for both my Mach1GTO and AP1100:

cytan

On Wednesday, October 30, 2019, 10:16:14 AM CDT, Dale Hooper <dchooper5@...> wrote:

Hi Tony,

Thanks so much for the info.  I think I will do like the author of the video and get another dec sight hole cover and drill that.  I'm a bit surprised that QHY hasn't released an adapter for the A-P 1600.

Thanks and clear skies,
Dale.

Re: Polemaster adapter for AP-1600 w/o absolute encoders

Dale Hooper

Hi Tony,

Thanks so much for the info.  I think I will do like the author of the video and get another dec sight hole cover and drill that.  I'm a bit surprised that QHY hasn't released an adapter for the A-P 1600.

Thanks and clear skies,
Dale.

Re: Brand new used Ap1600, initial startup

J. Belden

Thank you Roland, I will give George a call this morning to get some ideas.  I did check the keypad connector for pushed back pins and made sure the pins were clean.

Joe

Re: Polemaster adapter for AP-1600 w/o absolute encoders

Harley Davidson

Dale

The 1600 mount's cap for the polar scope has a much larger diameter than the AP-900 adapter for the polemaster so it won't work. It works fine for the 1100 as seen here:  https://www.youtube.com/watch?v=piFWxBcJOJ8

For the 1600 this would work fine:  https://www.youtube.com/watch?v=550pZhBKeRw&t=18s

In fact you could just eliminate the "mending plate" and mount it directly on top of the polar cap for the 1600 after drilling and tapping for the 1/4"-20 hole.

tony

On 10/30/2019 1:21 AM, Dale Hooper wrote:
Hi Everyone,

I tried a keyword search of polemaster and 1600 and I was surprised that I couldn't see a direct answer to this question - so I thought I would ask it.

I have an AP-1600 GTO without absolute encoders.  I'd like to know if I can use the AP-900 adapter for the Polemaster or if there is some other adapter I should be looking for?  There is *lots* of space around the polar sight hole - so it seems like this should work - if the threaded hole is the same size.

Clear skies,
Dale.