My iOptron 'little gem' GEM28 Report

[SteveNickolls]

GEM Guiding (continued)

The recent clear but cold nights in the UK have allowed more imaging to be done with the GEM28 and I have been able to check if altering the PHD2 algorithm to 'PEC' improved the RMS values. 

Previous session details-

First guiding run 14.12.22-

Second run same night-

Changing to the PHD2 algorithm doesn't seem to have altered the heights of the errors so I will be reverting back to the 'Hysterisis' setting in PHD2.

Cheers,
Steve

[SteveNickolls]

January 2023 Update-Guiding, GPS and Images.

January has been a very good month for DSO imaging this year in the UK and I was able to obtain a fair amount of consistent data on how the GEM28 mount performed when guiding. My DSO imaging equipment has a modest focal length comprising a Samyang 135 lens (used at f/2) + Astronomik 12nm Ha filter + ASI533MM-Pro but I have been happy with the images produced.

	Session 1 RMS	Session 2 RMS	Session 3 RMS	Session 4 RMS
RA	0.72" (0.11px)	0.73" (0.11px)	0.74" (0.11px)	0.86” (0.13 px)
DEC	0.52" (0.08px)	0.53" (0.08px)	0.63" (0.10px)	0.50” (0.08 px)
Total	0.88" (0.14px)	0.89" (0.14px)	0.97" (0,15px)	0.99” (0.15 px)
PA Error	1.0'	0.2’	1.5’	0.1’

I ran two instances of Guiding Assistant, one reproduced below.

I also received an iOptron GPS unit for Christmas and was able to connect the device  and use it during the imaging sessions. The unit worked fine straight out of the box and makes set up time a little less, no longer do I need to set the hand controller time each session.

One outcome of having several consecutive clear nights was developing a set up procedure that was robust. I was able to set up in the afternoon, leaving the equipment powered on with only polar alignment being required each evening outdoors.

Images stacked in DSS and processed using StarTools, all taken at f/2 in Bortle 6 location-

Nebulae and Open clusters in Auriga (Flaming Star Nebula (IC 405 Caldwell 31, Sharpless 229), Tadpole Nebula IC 410) Spider Nebula (IC 417)and Fly Nebulae (NGC 1901) and open clusters NGC 1907  and M38. Total of x388 ninety second light frames (9.7 hours)+ master dark + master flat frame. 

A friend produced this ghostly starless image for me using Star Net ++-

California Nebula in Perseus, x165 ninety second light frames (4.1 hours) +master dark frame + master flat frame-

Cheers,
Steve

[The Admiral]

18 minutes ago, SteveNickolls said:

A friend produced this ghostly starless image for me using Star Net ++-

It certainly gives the nebula a more solid appearance, though I do tend to like structures anchored by stars, but not too many of 'em!

Nice captures Steve.

Ian

[SteveNickolls]

Thanks for the +1 Ian over the images. The top image of Auriga had the stars dimmed using StarTools and adjusted to 50% using the LAYER module to reduce the distraction of the many stars in the region. This is the original image before separating the stars for treatment.

I only have a 12nm Ha filter right now but my intention is to purchase a 12nm OIII filter later this year then add OIII data to these images as weather allows.

Thanks once again for your comments.

Cheers,

Steve

Edited January 24, 2023 by SteveNickolls

[Doc817]

Thanks Steve for providing the guiding details.  Great insight.

[SteveNickolls]

On 25/01/2023 at 08:51, Doc817 said:

Thanks Steve for providing the guiding details.  Great insight.

Hi, I'm pleased it is of help. I'm still very much learning about guiding and given the short focal length I use don't anticipate issues and certainly the mount is providing round stars which is the real purpose for guiding not to get lower and lower RMS values. The standard guiding values 'out of the box' with PHD2 seem as good as any others. I realise that there will be a need to adjust the looping duration depending on an individual night's seeing conditions.

I'd be pleased to hear the guiding results from other GEM28 owners as that will help in turn more people deciding on this mount.

Cheers,

Steve

[Elp]

I was imaging at 1000mm focal length the other night so was using an OAG, the star field however was awful as the stars kept wobbling so I had to settle on 2s exposure for the guidecam as anything longer or shorter would give problematic guiding, it was so bad the guidestars kept getting lost constantly. RMS average seemed to go all over the place from 1-4, and it showed in some of my subs. When seeing was more settled it was typical around 1.5-2 RMS and the subs were fine. Part of the issue maybe my setup was back heavy and the mount is difficult to get perfectly balanced, didn't have any more dovetail to clamp onto though so used it as is.

Imaging C/2022 E3 ZTF a few days ago at 300mm FL, I left the autoguiding and just used the gem28 sidereal rate set at 0.9x in my asiair, this worked very well, from first sub to last for an hour the star field hardly moved, if at all.

Edited February 6, 2023 by Elp

[SteveNickolls]

Thanks Elp for this information glad you were able to get some data when the seeing was more settled. Well done imaging the comet too. 👍 I have found the mount isn't the easiest to balance but more in the z axis. I wonder if that's why the iguider is located on the opposite side to where the iPort  (GPS) is found to help with balance? I only have the GPS unit and have Velcroed it onto the housing above the iPolar to help balance things better.

Sometime I will use my RedCat and 500mm FL StarTravel on the GEM28 and see what guiding performance I get. 

Cheers,
Steve

[Elp]

I was wondering why there's a threaded hole on the side of the saddle clamp, I once put my guidescope onto it. It's for a z balance counterweight I presume as declination balance is usually more troublesome than ra.

[Elp]

Wondering if anyone else is using a gem28 or ioptron equivalent with asiair firmware 10.47. I regularly get an issue. I always start after power on by sending the mount to home position, if I've set it up right pointing the scope at polaris the mount shouldn't move and it doesn't. Focus routine, PA, sending to intended targets etc... Then an unusual thing has started happening. After creating an imaging plan, start, then scope slews to target, images, trys to plate solve, adjustment... But then the adjustment is wrong, it moves slightly, then next iteration (second or third) the mount starts going somewhere completely wrong. If I look at the real-time ra and Dec coordinates whilst it's doing this I've noticed the Dec keeps flashing to near where it's supposed to be going to then back to near 90 degrees (ie home position) all whilst moving incorrectly. I did this indoors out of line of sight the other night, and knew something was going wrong as the intended Ra coordinate seemed way off what it should have been, looked out the window and the scope was pointing down (think the dovetail had stopped against a tripod leg, hopefully nothings damaged inside the mount, haven't used it since). Stopped it when I saw it, then couldn't send to home as the Dec wanted to move in the direction of the tripod leg, so declutched both Ra and Dec slightly moved the scope, reclutched and sent to home, now it was somewhere different. It's happened a few times, it changes its home position by itself to something like west 90 degrees (OTA is 90 degrees to the left of the mount pointing at polaris). Has this got something to do with the asiair being out of sync with the hand controller or something?

Edited June 19, 2023 by Elp

[SteveNickolls]

Hi Elp, sorry to learn of the problem you are having. Unfortunately I don't use an ASiair to control imaging but hopefully someone on SGL will be able to assist. I have heard of some ASiair users having odd problems with recent software.

Yesterday I was getting my firmware and iOptron software updated to use this coming season and a couple of matters strike me. Have you replaced the button type battery in the hand controller as it discharges very quickly? You could say it was a 'feature' of the hand controller but best to call as it is-a bane. Before I replaced the battery I noticed date and time were incorrect and the offset for time zone completely wrong both on the hand controller and in iComander 9. There is a relatively recent firmware update too- CEM26/GEM28 Firmware Package including 8409 hand controller (v230305) which adds a new version for the hand controller and DEC. I've yet to try the updated mount outsdie due to the time of year.

I will be very interested in what the solution to the problem you are having is.

Cheers,
Steve

[Elp]

One of the suspected issues was the hand controller, it's the only other thing which can interfere other than the asiair software, so I'll probably change the battery. But, it had also happend on my azgti late last year so...

Edited June 19, 2023 by Elp

[Ratlet]

I've had a couple issues with the mount deciding it needed to point at the core of the earth.

Have you tried resetting the zero position on the ioptron handset whilst having the mount setup and all pointing to north?  That fixed it for me.

[SteveNickolls]

As regards the zero position every session after polar aligning I set the new zero position in iCommander. As I use the main camera and Samyang lens with a fov around 5 degrees this is ideal to use with SharpCap Pro and removes any cone error I was previously getting after polar aligning with the iPolar.

Cheers,

Steve

[SteveNickolls]

2 hours ago, Ratlet said:

I've had a couple issues with the mount deciding it needed to point at the core of the earth.

Can I enquire the version of the GEM28 software in use when you had these slew issues? It's good however to know that restting the zero position worked regardless of the hand controller firmware version.

Cheers,

Steve

[Ratlet]

1 hour ago, SteveNickolls said:

Can I enquire the version of the GEM28 software in use when you had these slew issues? It's good however to know that restting the zero position worked regardless of the hand controller firmware version.

Cheers,

Steve

I'll have a check once I get home.  I've not updated my software in ages so it's possibly an older version.  It's definitely a version 8 from about 9 months ago.

From memory the initial problem in february happened when I was using a side by side mount so the saddle was zero 90° from normal, something happened ( I can't remember what) and it wouldn't slew to target and went to random parts of the sky and I abandoned the session.  When I next used it about 4 months after that I used my 130pds so saddle orientate normally.  I didn't zero the mount at the start and when I tried to slew to target the power cable to my camera snagged on the mount and nearly pulled tight.  It's why I recently go 90° plugs for my power cables as it will pull out if pulled tight.

Edit: I'm also going to stick a "zero home position before use" sticker on the mount!

Edited June 19, 2023 by Ratlet

[The Admiral]

16 hours ago, Elp said:

Wondering if anyone else is using a gem28 or ioptron equivalent with asiair firmware 10.47.

I thought that you had reverted to the earlier version?

Looking on the ZWO discussion forum I see folk are still complaining of problems with the latest firmware. Could this not be the issue here?

16 hours ago, Elp said:

if I've set it up right pointing the scope at polaris the mount shouldn't move and it doesn't.

When I do a goto to home, even if I am already in that position, the mount (AM5) will move a bit and then return to the home position. Or am I missing something here?

Ian

[SteveNickolls]

8 hours ago, Ratlet said:

Edit: I'm also going to stick a "zero home position before use" sticker on the mount!

That's excellent advice. I've highlighted the same advice in my set up list, just got to follow the list now!

There's been a numer of updates to iCommander over the last several months that may help with using the GEM28, I like the "Bug fixes: Lots of minor bug fixes"-

 

2023-02-07 9.06 Bug fixes: iOptron Commander will fail to connect to iOptron devices when running under Windows 11 and "Terminal settings" has been chosen to "Windows Terminal". ASCOM driver for electric focuser now registered to the correct type.

2023-01-13 9.04 Bug fixes: In rare cases, iOptron Commander may failed to connect to mounts.

2022-12-23 9.03 Bug fixes: Sometimes the altitude and azimuth may refresh incorrectly. For some mount model, the hand controller model may display incorrectly.

2022-12-12 9.02 Major update! New features: Added support for a batch of new mount models (HEM, HAE, HAZ series). Now display distance of Solar System objects. Now attempt to connect to all available COM ports after program launched. Improvements: Performance optimizations. No console windows will be displayed when connecting. List of COM port will be refreshed when in "Port Settings". Local apparent sidereal time and star coordinates will be refreshed more frequently. Buttons will auto scale when moving window between screens with different DPI. Bug fixes: Lots of minor bug fixes.

Cheers,
Steve

[Elp]

2 hours ago, The Admiral said:

I thought that you had reverted to the earlier version?

Looking on the ZWO discussion forum I see folk are still complaining of problems with the latest firmware. Could this not be the issue here?

When I do a goto to home, even if I am already in that position, the mount (AM5) will move a bit and then return to the home position. Or am I missing something here?

Ian

I did revert to a previous version (10.40 on the mini is the earliest you can roll back to as it's the factory version). It's still happening. If it continues to happen might have to go back to using the pro.

Sending to home with either my azgti or gem they usually makes a slight sound like they're about to move, may move a tiny tiny fraction, the gem doesn't really move at all due to the clutches only allowing engagement at certain rotational points so it's really locked into home position if it's already physically set at that.

Edited June 20, 2023 by Elp

[SteveNickolls]

The time of the year and the poor weather in the UK have both conspired to limit adding new posts on this thread, however in the background I have been steadily working towards imaging in the coming season using the GEM28 mount.

GEM28 Update July 2023

This coming season I’m intending to use the GEM28 set up to principally obtain OIII data for several nebulae and add this to the Ha data obtained last season. In preparation a number of new items have been added to the imaging rig-

An Astronomik Max FR OIII 12nm filter. The work of Brian Mantooth has demonstrated that the Samyang 135mm lens at f/2 is best served by a 12nm filter rather than a 6nm one. Reference- https://www.youtube.com/@BrentMantooth

A Hyperpod ring system with ZWO EAF holder. I had intended buying an Astrodymium ring kit but recent shortages mean an alternative supplier had to be sourced.

ZWO EAF. I would have preferred to use a Pegasus EAF but presently the company do not make an adapter to secure the EAF on the Samyang lens.

William Optics 290mm Vixen dovetail plate. This provides more space to attach the Pegasus Power Box Micro unit in line with the main weighty items on the dovetail.

To help balance in the ‘z’ axis I have added an Omegon tri-finder accessory.

This has added to the overall mass of the set up, and I needed to replace a smaller 2kg counterbalance weight with the standard 4.5kg iOptron weight originally supplied with the mount. The imaging rig however remains portable if heavier.

I am going to experiment using the USB 2.0 hub on the main ASI533MM-Pro camera to see if it will operate while taking the USB cables from the EAF and guide camera. Presently the guide scope is connected to the StarTech USB 2.0 hub directly by its own cable but the cable is long and could in this way be shortened to just 0.2m in length. The present arrangement is shown below.

If the weather becomes kind and we get some clear nights soon I hope to be able to try out the new arrangements showing what the GEM28 can do and will report back on progress.

Regards,
Steve

 

 

 

 

iOptron cable USB/RJ11

USB cable

 

 

 

 

 

Edited July 29, 2023 by SteveNickolls

[Ratlet]

I had issues in the past trying to run my guide camera through my Altair 533 camera.  Hopefully it'll work in your case, maybe better internals on the zwo, but it frequently lost connection for me.  You'll know quick enough either way.

[SteveNickolls]

Thanks Ratlet, I've done a test indoors with the EAF conected to the main camera and will see if additionally connecting the guide camera (ASI 120MM-mini) works under the stars. A friend has sucessfuky run his guide camera, a 224 through his ASI 533MC-PRO along a single USB cable and which has prompted me to just try.

Cheers,

Steve

Edited July 29, 2023 by SteveNickolls

[Ratlet]

31 minutes ago, SteveNickolls said:

Thanks Ratlet, I've done a test indoors with the EAF conected to the main camera and will see if additionally connecting the guide camera (ASI 120MM-mini) works under the stars. A friend has sucessfuky run his guide camera, a 224 through his ASI 533MC-PRO along a single USB cable and which has prompted me to just try.

Cheers,

Steve

Hmmmm, I might have to try again.  A couple of my cables are pretty cheap and old.  That might be the issue.

Never thought of testing indoors though.  That's a good shout.

[SteveNickolls]

I think better cables are always a good idea and trying not to make and break connections to save on wear and looseness of ports. Do let us know how any re-testing goes on. 👍

Cheers,

Steve

[SteveNickolls]

Well last night we had clear skies over Nottingham so I was able to get outside and trial the ZWO EAF and whether the EAF and guide camera could share the USB 2.0 hub on the main camera (ASI533 MM-Pro) and connect to the StarTech USB over Ethernet hub. The good news is the EAF worked fine using the Hyperpod ring system controlled using Sharpcap Pro and I was able to have the EAF connected alongside the guide camera while imaging with the main camera. I had received two new shorter USB 2.0 cables in the post to connect up the EAF and guide camera to the main camera hub. This is now the control and power arrangements on the GEM 28 mount-

Cheers,
Steve