My iOptron 'little gem' GEM28 Report

[Ratlet]

Just now, Elp said:

It's the reason I tend to use my azgti more as it's quicker and easier to transport and setup. Maybe a harmonic drive is the way to go but the prices are high in comparison.

For mounting flexibility especially with a DSLR/multi lens setup I've found buying a few cheese plates helps a lot when you're chopping and changing setups. The small guidescope I put on the side of the gem28 saddle is attached via a small narrow cheese plate.

I hear ya.  The az-gti was my first choice, but the gem28 came up for a really good price and I figured it would present some alternative paths.  All my stuff has to be lugged up and down the stairs to get setup so weight was always going to be a factor.  I think at the moment I'm in a good place weight wise, but not by much.

I think someone else on here said much the same when I put everything together about the cheese plates. Makes the setup and even transportation easier for the lenses.

[SteveNickolls]

September 2022 Update

Well the new imaging season has started here in the UK and August proved a good month for being able to get out under the stars with the GEM28. I have begun trying out different procedures for using the iPolar but feel it’s still early days to be definitive on the best method for using the iPolar and particularly whether better polar alignment arises after clearing the camera rotation each session or not. Currently I am using the following procedure with the GEM 28 set up on the imaging pad.

• The tripod is placed on pre-made marks to help point the iPolar quite closely to the NCP each evening and the iPolar is connected up to my laptop. The mount is in its Zero Position, that is with counterweights pointing straight down. The two hex bolts holding the mount head to the tripod are slightly loosened.
• The laptop is started up and I connect to the iPolar.
• I press the ‘Connect’ button then the ‘Settings’ button. After a 20 second countdown I am allowed to take a new dark frame for the current session which I do. I them take off the cap to the iPolar.
• I have not been clearing the camera centre values between sessions but want to see if a better imaging session results when a new camera centre of rotation involving moving the iPolar to a second position to plate solve.
• The on screen instructions will advise if any changes are required to increase or reduce the number of star positions shown on the screen. I have found in my Bortle 6 skies that 250 ms to 500 ms is ok to provide a sufficient number of stars for the software to plate solve by.
• I have found that once the plate solve has been made that both the camera centre and NCP positions are shown on screen and I do not need to rotate the counterweights to a second position.
• I adjust the position of the camera centre using the mount’s Az and Alt adjustment knobs until I get a perfect match up of the camera centre and NCP.
• The two hex bolts are nipped up and I check there has been no movement in the match up.
• The iPolar software is disconnected, the mount is switched on and the correct time checked on the hand controller against an online atomic clock.
• The laptop is moved indoors and set up to control the imaging session.

Dithering without Guiding

SharpCap Pro provides a capability to send pulse guiding commands to the GEM28 which randomly dithers between captures as required by the user. This worked very well when I was using 30 and 60 second sub-exposures and improved the quality of the stacked images. I have begun to see what increasing the sub-exposure duration brings in terms of the final image and found I needed to begin guiding to ensure round stars at 90 seconds exposure.

Beginning Guiding

My imaging set up is a Samyang 135mm lens imaging at f/2 with a 12nm Astronomik filter and ASI533MM-Pro astro-camera so this does not put much strain on the mount nor guiding. I have successfully guided before using a Celestron CG-5 and Star Adventurer mount, employing PHD2 and the Eagle OS respectively.

I have found that the GEM28 returns a very good calibration result and have been happy with the images produced from 90 seconds sub-frames.

Below an image taken of the area incorporating IC1396 in Cepheus taken with the GEM28 using a mix of 30 and 60 seconds sub exposures totalling 2 hours 18.5 minutes with master dark and flat frames and Moon present in the sky.

And the region around NGC 7822 in Cepheus, just x65 ninety second sub frames with master dark and flat frame-

New iCommander software v8

Recently iOptron have released an updated version of their iCommander software which can be used to control the GEM28 and other mounts. The latest version brings changes and a new look to iCommander. For now I have held off updating the software as I want to concentrate getting to grips with v7.

New iCommander Lite Apps 

iOptron have just released Apps to wirelessly control a range of their mounts (this includes the GEM28). The Apps, for iOS and Android can be downloaded free from the respective App Stores. The Apps are timed around the launch of the iOptron Sky Hunter range of lightweight mounts. An 11 page leaflt is available from the iOptron site detailing how the App works with the the Sky Hunter mounts. The instructions should still be useful when  employing with the GEM28 and other mounts. THE APP DOES NOT ALLOW REMOTE CONTROL OF THE iPOLAR DEVICE. I have again contacted iOptron Support over any plans to create such an App which would use a USB cable between the control device (Android) and the iPolar.

(Added 15.9.2022) Here is the pdf with the iOptron Commander Lite Application notes (11 pages)-

iOptronCommanderLiteAppNote.pdf

Edited September 15, 2022 by SteveNickolls
Added download file

[Ratlet]

Fantastic to see you back posting for the GEM28 @SteveNickolls.  I've had mine out a couple times now since getting the basic setup going.  I've got enough now I think to write up a quick guide for users of NINA with it (It's pretty straightforward).

I've recently updated to the Version 8 of the iCommander software.  On the previous version I found that sometimes the mount would not communicate with the iCommander software however I've had no issues with the new version.

With any luck they will release an app to allow ipolar use with the phone.  It would seem sensible since the sky hunter comes with one.  Having a look online the app looks very bare bones unfortunately.

[SteveNickolls]

Hi Ratlet thanks for posting. Yes it's been a little time since I've posted anything really waiting for somthing to give feed back on or anything else related to the mount.  I will enjoy reading your NINA guide. 👍 Very pleased you have been able now to have your mount operational.

I'm pleased you have got on fine with iCommander 8, I will migrate over to it but have lots going on at home at the moment. How have you found the new iCommander interface?

Yes when I last contacted iOptron support I got what I took to be a positive response regarding the iPolar App and didn't expect it to be part of any App to control the Sky Hunter and other mounts. Still I've contacted iOptron again today so will see if they have any plans to provide an iPolar App. 

Cheers,
Steve

Edited September 5, 2022 by SteveNickolls

[SteveNickolls]

I've had a reply from iOptron Support today to a query over the possibility of an App in the future for the iPolar device. As I've mentioned before I would like to see a simple solution for my mount such as an App running on a tablet and controlling the iPolar through a USB OTG type of arrangement. I have had a ASI120MM-S, ASI120 MM mini and ASI178MC running at different times from ASI Studio on my tablet so thought some such arrangement would work. The response I've received  states, "iPolar supports Windows and MacOS currently. We may add a Raspberry Pi adapter/APP to support Android/iPhone wirelessly. There is no option for USB connection for Android devices."

I am not adverse to needing to employ an adapter to perform the necessary control of the iPolar using a tablet and will have to start saving up for it.

Cheers,
Steve

[Elp]

Thought I'd put my feedback here regarding ipolar as I hadn't used it previously.

Downloaded and installed the software from ioptrons website, installed fine but when I started the program it said MS .net 3.5 SP1 was not installed. So I installed the latest version of .net v4.8.1 and it still didn't work. So I installed v3.5 SP1 too, then the program worked fine.

Camera was connected though I note my up axis requires rotation of the camera 90 Deg clockwise for it to work as per alt az 3d space.

Tried it at night, fairly straightforward, if you don't see any stars make sure the front cap on the mount is removed and change the exposure to something like 250ms, dark images are taken upon startup (keep cap on polar scope end) or you can instruct the program to take them at a touch of a button, and program offers instructions on the LHS of the window as to what it's doing and what to do next, starfield appears quickly afterward. I input my longitude and latitude manually as the mount wasn't on at the time then moved it up in altitude until it plate solved then asked me to rotate the mount in RA, I then powered it on to do the rotation. You have to confirm the position once done. A maroon circle appears as what it thinks should be the pole then if it's not on camera FOV a red arrow appears on the edge of the screen denoting which way you should move the mount. Once the pole star is in view it appears as a red cross and you simply adjust altitude and azimuth of the mount until the maroon circle overlays the red cross. When you're very close the two shapes magnify so you can make fine adjustments, once it's on they'll change colour to green.

Simple process and easy to use.

I don't however see me using it personally as I use an Asiair which is much quicker to PA in, and it also doesn't require a computer to be with me. But ipolar certainly is one of the better PA routines I've used.

Edited September 11, 2022 by Elp

[Ratlet]

1 hour ago, Elp said:

Thought I'd put my feedback here regarding ipolar as I hadn't used it previously.

Downloaded and installed the software from ioptrons website, installed fine but when I started the program it said MS .net 3.5 SP1 was not installed. So I installed the latest version of .net v4.8.1 and it still didn't work. So I installed v3.5 SP1 too, then the program worked fine.

Camera was connected though I note my up axis requires rotation of the camera 90 Deg clockwise for it to work as per alt az 3d space.

Tried it at night, fairly straightforward, if you don't see any stars make sure the front cap on the mount is removed and change the exposure to something like 250ms, dark images are taken upon startup (keep cap on polar scope end) or you can instruct the program to take them at a touch of a button, and program offers instructions on the LHS of the window as to what it's doing and what to do next, starfield appears quickly afterward. I input my longitude and latitude manually as the mount wasn't on at the time then moved it up in altitude until it plate solved then asked me to rotate the mount in RA, I then powered it on to do the rotation. You have to confirm the position once done. A maroon circle appears as what it thinks should be the pole then if it's not on camera FOV a red arrow appears on the edge of the screen denoting which way you should move the mount. Once the pole star is in view it appears as a red cross and you simply adjust altitude and azimuth of the mount until the maroon circle overlays the red cross. When you're very close the two shapes magnify so you can make fine adjustments, once it's on they'll change colour to green.

Simple process and easy to use.

I don't however see me using it personally as I use an Asiair which is much quicker to PA in, and it also doesn't require a computer to be with me. But ipolar certainly is one of the better PA routines I've used.

Yeah the ipolar is pretty easy to use.  I use a nuc to control everything and remote desktop onto that.  Never thought about just using remote desktop from my phone to do polar alignment.  That's going to save me a bit of hassle lol

[SteveNickolls]

On 11/09/2022 at 14:28, Ratlet said:

I use a nuc to control everything and remote desktop onto that.  Never thought about just using remote desktop from my phone to do polar alignme

Hi, thanks for this Ratlet. Could you describe using your mobile to help with polar aligning?

Cheers,

Steve

[Ratlet]

10 minutes ago, SteveNickolls said:

Hi, thanks for this Ratlet. Could you describe using your mobile to help with polar aligning?

Cheers,

Steve

So at the moment I use an Intel nuc setup by the mount to control everything on my rig.  I control this remotely from a laptop in my shed.  Previously I would take the laptop out so I could see the Ipolar app running on the nuc.  Now I'll just quickly log on from my phone using the remote desktop client app to do the polar alignment.  Really you just need to be able to see the guidelines and click on a couple of buttons.

I was going to give it a try tonight (full moon isn't an issue since I'm still very much getting things to work stage), but my work have changed my shift so I have to start at 0400 tomorrow.  Hopefully there will be some clear skies in 2 weeks.

Edited September 12, 2022 by Ratlet

[SteveNickolls]

Thanks for that Ratlet much appreciated. Yes clear skies would be much appreciated right now.

Cheers,

Steve

[SteveNickolls]

October 2022 Update

iPolar, goodbye to all that

 

Anyone reading through this thread will have noticed I have found the iPolar to be a weak point on the GEM28 mount for more than one reason and last night in an unplanned break in the clouds I was finally able to try out an alternative polar alignment available to me, that of using SharpCap Pro (SCPro) software.

As a backdrop the iOptron support site page contains suggestions from a number of equipment users going back to pre-Covid times to develop a means to control the iPolar using a tablet/mobile for Android users and which despite periodic promises has not materialised. More recently from my own contact with support I understand a pure software App solution cannot be created but will necessitate a seperate device to allow its wireless control.

As documented in preceeding entries I have encountered trouble getting my iPolar to consistently and reliably give a sound basis for imaging. This has not been helped by the change in software versions with earlier versions (while being more laborious in terms of the number of times the payload had to be moved) giving better results albeit on my previous CG-5 mount. I find the iPolar manual to be badly written and failing at important points such that the right process is left to the user to figure out. I have tried to fathom a way of using the iPolar with the latest software that works for me but despite advice, numerous attempts and the problems created by the UK weather this priority sadly still remains undone.

I had also identified what I believed was a ‘cone error’ problem with the GEM28 whenever using the iPolar to polar align, typically the optics were pointing around 14 arc minutes away from the NCP after polar alignment. I had tried shims to correct the difference in pointing angle but never removed this entirely. I was also conscious of the ability to not quite have the DEC head switch accurately positioned when locked if one was not careful and which could add to any misalignment.

Therefore, yesterday evening, I took the chance of setting up the GEM28 mount regardless of the local weather forecast since the sky was clear and in a matter of an hour was able to reproduce using SCPro’s polar aligning tool the kind of control and accuracy I wanted from the iPolar and a little more. I found the SCPro software worked flawlessly with my imaging combination of Samyang 135 mm lens and ASI533MM-Pro camera and was quickly able to produce an ‘excellent’ rated polar alignment. The SCPro software has a number of plusses lacking in the iPolar software-

• You can see at a glance if your rig is decently initially centred pointing at the NCP. The software having a number of concentric circles centred on the NCP this gives immediate feedback if the GEM28 DEC head is slightly out of position in its 'Zero Position'.
• The software informs the user of the closeness in alignment in numerical terms not the camera centre and NCP coinciding and turning green as with the iPolar.
• You have more leeway in controlling the camera gain and exposure times used to polar align with.
• Using the main optics you overcome the effects of cone error. 

I'm sure other iPolar users will have different and better experiences with their iPolar devices  is really expected and which I respect. If they can document their solution step by step please feel fit to add into the thread if you wish.

Thanks,
Steve

 

Edited October 11, 2022 by SteveNickolls

[Ratlet]

I'm still trucking along with the Gem28 also.

With respect to the ipolar specifically:

• I've not had any issues with the iPolar.  However, I am using it in a setup where I have the laptop close to the mount. 
• Typically I load up the mount with everything, ensuring it is all balanced and then I just run the software, load in the last darkframe and begin polar alignment. 
• The ipolar software has been manually configured with the latitude/longitude.  I have not and do not determine the camera centre.
• The software then displays a red dot and red cross.  I adjust the alt/az until the dot and cross are matched and they both turn green.  When I get close I tighten the 2 bolts that hold the mount to the tripod and the azimuth tension until snug.  Once green I 'nip them up'.  This seems to minimise the alignment getting thrown during this step.
• I have a clear view to the NCP.  I have the ipolar connected through the USB hub on my Hypercam 533c.  I have had no issues during polar alignment this way.  The software is a bit odd in that it appears to just be an .exe file that you run.

When I am next out with the scope I will polar align with the ipolar and then compare to nina's 3 point polar alignment.  I've not seen any major issues with guiding, but I've not looked particularly hard.  I have been imaging at 650mm and 200mm focal length with the 533c.  I will say that after polar aligning NINA usually needs 2 or 3 goes to centre itself exactly on a target with platesolving which may or may not be due to the polar alignment being out.  I will check what nina thinks of the alignment by ipolar next time I get the rig out.

More generally:

• I've found the connection from my intel NUC to the mount has improved substantially since the version 8 of the icommander software was released.  Previously getting the commander software to recognise that hte mount was connected was problematic requiring the mount to be restarted and disconnected several times.  Since upgrading the icommander softwre to V8 I have had no issues.
• I have been using the 12V DC output (which the manual only refers to as powering the polar scope if the illuminated polar scope is used) to power my Hypercam 533c.  I've had no issues powering it through this connection.  I am powering the mount with a 5A power adapter and the Hypercam came supplied with a 3A power adapter.  Typically I run the hypercam at -5C.
• I couldn't say for certain, but I strongly suspect that when you connect the mount to nina, or possibly turn the mount on it assumes the default position is park.  I have been using it with a side by side mount and when I park the scope in nina it returned the mount to the position from the start of the session even though the declination was 90 degrees from 'normal'.

 

[SteveNickolls]

Thanks Ratlet for all of this, very informative and helpful. I do like that you have found the mount's 12v output runs your astro-camera, that's really good to know as it will save at least one power wire at the tripods legs. I use the ASI533MM-PRO, snd also operate at minus 5 degrees C.

I have to pop out soon but will do a longer post this afternoon to all you have posted. Thanks for this it will a great help to many. I'm glad your processes work fine too.

Cheers,

Steve

Edited October 12, 2022 by SteveNickolls

[SteveNickolls]

Hi Ratlet, I'm now on the main pc where it's better to type replies than the tablet. 😁

My iPolar routine mirrors your own though I was getting to question whether the camera centre value ought to be removed each session to let iPolar populate it's new value. Do you find you need to rotate the payload to position 2 or that the iPolar software instantaneously it seems does a second plate solve (in what is position 1)? I have tried covering the iPolar before moving to position 2 then taking off the dust cap to let the software do a second plate solve in position 2.  I have to place my mount outside each seesion but have marks on the imaging pad which give a close positioning to the NCP. When I used Sharpcap Pros polar alignment tool a few nights ago this showed initially the gear to be pointing around 5 arc minutes off the NCP so the original alignment just using the marks on the concrete were doing their job.

I would be pleased to hear how the iPolar compares in operation to using NINA.

I'm pleased to hear you have found iCommnder v8 an improvement for you. I still use v7 as I can be lazy and if everythnig is working ok in v7... In the future when I get a new main pc for the house I will migrate over to the latest version. In v7 I always use the same USB port on my laptop to control all USB peripherals using the StarTech USB over Ethernet device to avoid any issue with phantom USB ports.

As mentioned before it's really good news that the GEM's 12V output port will power your 533C. Just need to buy a cable now to duplicate this. 👍

I've found that one needs to take care when securing the GEM28's RA and DEC clutches in place as you can easily slightly miss the 'right' positions and so the mount is not properly in its normal Zero Position. You more have to feel the connection is correct than any visual clue, especially in the dark.

My next step is to use my tablet to control the SharpCap Pro polar alignment process and leave the laptop connected up indoors to later control the mount and imaging. A friend introduced me to some software called 'spacedesk'

https://www.spacedesk.net/

which permits the tablet to be used as a pc monitor. I'm going to set up an external wi-fi extender so I can get network coverage from the imaging location. Ultimately it will mean I wont have to replace the laptop in the future and shift control to a new more powerful main pc. I find the USB over Ethernet solution very convenient in the colder months being able to control the mount and camera from the living room, a bit more social than standing freezing outdoors or alone in the kitchen.

Hope you get some clear, dark skies.

Cheers,
Steve

Edited October 12, 2022 by SteveNickolls

[Ratlet]

22 minutes ago, SteveNickolls said:

Hi Ratlet, I'm now on the main pc where it's better to type replies than the tablet. 😁

My iPolar routine mirrors your own though I was getting to question whether the camera centre value ought to be removed each session to let iPolar populate it's new value. Do you find you need to rotate the payload to position 2 or that the iPolar software instantaneously it seems does a second plate solve (in what is position 1)? I have tried covering the iPolar before moving to position 2 then taking off the dust cap to let the software do a second plate solve in position 2.  I have to place my mount outside each seesion but have marks on the imaging pad which give a close positioning to the NCP. When I used Sharpcap Pros polar alignment tool a few nights ago this showed initially the gear to be pointing around 5 arc minutes off the NCP so the original alignment just using the marks on the concrete were doing their job.

I would be pleased to hear how the iPolar compares in operation to using NINA.

I'm pleased to hear you have found iCommnder v8 an improvement for you. I still use v7 as I can be lazy and if everythnig is working ok in v7... In the future when I get a new main pc for the house I will migrate over to the latest version. In v7 I always use the same USB port on my laptop to control all USB peripherals using the StarTech USB over Ethernet device to avoid any issue with phantom USB ports.

As mentioned before it's really good news that the GEM's 12V output port will power your 533C. Just need to buy a cable now to duplicate this. 👍

I've found that one needs to take care when securing the GEM28's RA and DEC clutches in place as you can easily slightly miss the 'right' positions and so the mount is not properly in its normal Zero Position. You more have to feel the connection is correct than any visual clue, especially in the dark.

My next step is to use my tablet to control the SharpCap Pro polar alignment process and leave the laptop connected up indoors to later control the mount and imaging. A friend introduced me to some software called 'spacedesk'

https://www.spacedesk.net/

which permits the tablet to be used as a pc monitor. I'm going to set up an external wi-fi extender so I can get network coverage from the imaging location. Ultimately it will mean I wont have to replace the laptop in the future and shift control to a new more powerful main pc. I find the USB over Ethernet solution very convenient in the colder months being able to control the mount and camera from the living room, a bit more social than standing freezing outdoors or alone in the kitchen.

Hope you get some clear, dark skies.

Cheers,
Steve

I'm going to be honest, I never read the manual for the iPolar so I'm beginning to think I might have been doing it wrong!  I just turn it on and load the last dark frame.  I've never done anything with positions or rotating the payload.  I just get the mount loaded and balanced, turn on ipolar and wait for it to give me the dot and cross and then align them.  Once they go green I close the software and carry on.  I think I might have a read of the manual as I can see how it could in fact not be aligned properly.  I'll need to wait 2 weeks till I can get a chance to compare NINA Vs Ipolar.

If you are powering the camera from the mount just make sure to check the polarity of the connections.  I believe the mount is centre positive.

[Elp]

Same here, it's straightforward. The mount does have to rotate though to figure out polar alignment. It takes a first image via the camera which should be the home position of the setup (position 1), once it's confirmed the mount needs to rotate in RA a certain number of degrees (position 2), this way the software can determine mathematically how far off pole the mount it. The asiair works the same, phd2 also works the same.

[SteveNickolls]

Hi folks, last night we had a clear night for imaging so thought I would report how the GEM28 performed etc.

Polar alignment using SCPro's polar alignment tool went fine and I had these logs out of PHD2 concerning the calibration and subsequent guiding. The values will be of interest to others with similar set up's.

Equipment on GEM28 were Samyang 135mm lens at f/2 with ASI533MM-Pro astro-camera with Astronomik 12nm Ha filter. Guide scope ZWO mini guider and ASI120MM-Mini camera.

I was able to take 140x ninety second exposures using SCPro's Live Stacking and this is a 'rush' from the session showing the area around Sadr in Cygnus-

Samyang 135 mm lens at f/2, ASI533MM-Pro camera with 12nm Astronomik Ha filter. 140 x ninety second exposures plus master dark and flat frame stacked in DSS and processed in StarTools.

Cheers,
Steve

Edited October 18, 2022 by SteveNickolls

[Elp]

An excellent result, a region I am yet to image. I was also out with the gem28 and C6, seeing seemed a bit iffy to me, guiding between 0.4-1.2 typical.

[SteveNickolls]

Hi, and thanks for the +1 Elp I do appreciate it. I hope your results with your C6 turn out well, incidentally can the C6 use a Fastar?

The Sadr region is a rich area to choose to image and good for making mosaics if that's what you like doing. I've just processed the RAW data from last night and stacked in DSS and processed using StarTools.

Good luck with your processing.

Cheers,
Steve

[Ratlet]

Indredible images 

[Elp]

On 18/10/2022 at 20:01, SteveNickolls said:

can the C6 use a Fastar?

Oh yes...

 

[SteveNickolls]

19 hours ago, Elp said:

Oh yes...

Thanks very much for this I will enjoy reading the thread. 👍

Don't know if you have watched any of these astro-videos, the author has made a number of videos on the subject of filters and fast optics which I found most useful with my set up on the GEM28. 

https://www.youtube.com/c/BrentMantooth

Cheers,
Steve

[SteveNickolls]

Year Review-GEM28

It hardly seems possible but the end of October has come around meaning a whole year has passed since I took delivery of my iOptron GEM28mount-where does the time go in this hobby?

The past year has provided just 22 occasions when DSO imaging was possible for me, not nearly as many as I would have liked but that’s what circumstances and the great British weather have allowed. I do however feel able to write a review of the mount its abilities and foibles.

While a lot of research went into choosing the GEM28 (it is likely the last mount I will own) its purchase was an instinctive one. I had been keeping a watching brief on stock levels at FLO and steadily saving up the ££’s required so that when a delivery became available in late October 2021 I immediately hit the buy button for the bundle comprising mount, 1.75” Lite-Roc tripod, iPolar and storage box. The price was then £1,282.95 (it's now risen to £1,620 an increase of 26%).

My first unboxing reactions were of a well built, small, solid mount literally only physically marred as I have previously mentioned by the condition of two tripod legs showing cosmetic scuffing. I have found the RA and DEC axes were very smooth in motion meaning no more ‘East heavy’ loading needed from now on as with my previous CG-5 mount. The mount has proven really quiet in operation, no more coffee grinder moments capable of waking up neighbours at night. The mount arived with a glossy set up short manual but I downloaded the comprehensive manual for the mount from the iOptron website.

The biggest advance that the mount has brought to the table was providing up to date technology being ASCOM compliant and ideal for control on a Windows computer.

The mount and tripod provide a relatively lightweight set up and with my wide field gear the whole package can be carried out to the imaging location as one unit saving greatly on the setting up/taking down time spent each session. Being overall lightweight the imaging equipment can be left attached to the mount between nights including many cables.

Over the year the mount has proven a sound, robust vehicle to use with SharpCap Pro (Imaging)/ASTAP (plate solving)/PHD2  (Guiding)/Stellarium (Slewing/Go-To). iCommander v7 (Slewing/Go-To and ‘Zero Position’).

I have found the mount can be controlled fine using a variety of options-

·         Go2Nova hand controller.

·         USB to hand controller and pc.

·         Wi-fi control from pc to the inbuilt iStarFi in the Go2Nova 8409  hand controller. Decent range but just not enough for my location.

·         And my current preferred method-USB over Ethernet for long distance control from the comfort of the living room.

The main weakness of the mount really comes with the pre-installed iPolar, a problem that was unexpected having used another iPolar in the past on my CG-5 mount without issue. I consider the problem was down to a faulty iPolar unit and/or a USB cable that didn’t meet standard.  To help users the iPolar manual should be rewritten with emphasis explaining the important steps in the process, and presently users are left to discover their own solutions. My final solution was to employ the polar alignment tool in SharpCap Pro instead. I must say that my supplier FLO were very prompt in replacing the faulty Polar/Cable and deserve another mention. As an aside I have found that the iPolar camera is detected by SharpCap Pro. However I have not (yet) tried using the camera for this purpose in SharpCap Pro. My initial thoughts are that the field of view of the iPolar camera is too wide for SharpCap Pro to properly use.

Set Up. In the past year after polar alignment I have quickly gone from using a nightly set up involving using the hand controller and three star alignment to control involving USB over Ethernet and employing the plate solving ability (ASTAP) with SharpCap Pro to slew to a nightly imaging target, sync and commence imaging. This has greatly reduced the time getting ready to image and mount control and imaging can all be done from inside the house, a more pleasant and social arrangement not to mention being much warmer in the winter.

I have found the Light Roc 1.75” tripod very stable in use and have sometime pondered whether the more lightweight carbon fibre tripod weighing just 2.29kg and costing £298 extra (the 1.75” Lite Roc tripod weighs in at 7.5kg) could be worth considering in the future to decrease overall weight by another 5kg.

Polar alignment tip. One aspect of polar alignment requiring care is the re-tightening of the two hex bolts for adjusting polar alignment. I now initially start with the payload at 90 degrees and return the payload to the ‘Zero Position’ when completing polar alignment in SharpCap Pro. This way I know I have maintained the best polar alignment while carefully re-tightning the hex blts when back in the ‘Zero Position’ for the session.

Cone error. I found that my iteration of the mount presented some cone error after using the iPolar method which could be reduced with the use of a thin shim (around 0.7 mm thick). However I now polar align using the main optics/camera which eliminates the need for a shim.

Balancing. I have found exact balancing requires the patience of a saint and resolved this by adding a small weight (short M4 threaded rod and nuts) at the top of the payload offset to the left of the guide scope mounting. This small weight (13g) acting around 290mm from the centre of mount rotation offsets the tendency for the mount to move regardless of orientation. I understand that the internals of the mount along with other models is not exactly bilaterally balanced. iOptron sell ‘z’-co-ordinate balance weights for other models.

Firmware upgrade successful. I updated the firmware on the hand controller successfully following the iOptron guidance. Something I would never dare try on my older CG-5 mount.

Software. Advice on what planetarium software will/won’t work with the mount would have been appreciated when first setting up I was however able to get Stellarium working straight way. I have found iCommander 7 and Stellarium interchangeable for slewing and robust and at some future time will migrate over to iCommander 8, probably when we get a new main pc.

I am intending getting a GPS module basically to save having to manually check and adjust local time with the hand controller, bit of a luxury really.

Would I repurchase the GEM28 again? Yes indeed. Knowing what I do now I would forgo the iPolar unit and save some money. The mount has brought so much capability to imaging (ASCOM compatibility) to help with the hobby.

I hope this review helps others when deciding over the GEM28. I hope if you do plump for the mount that you enjoy what it brings to the hobby.

Cheers,
Steve

[SteveNickolls]

Late November Update

November here in the UK has been a pretty poor month for imaging and I’d like to think others using the GEM28 have had better conditions and more opportunities to actually get out imaging under clear skies. I was however able to image the North American Nebula and Pelican Nebula area on the very clear night of the 13^th capturing around 3.5 hours before the targets dropped too far into the western sky. The equipment all worked fine. The image below is composed from stacked 180 second light frames plus master dark and flat frame stacked in DSS and processed using StarTools. Equipment GEM28 mount, ASI533MM-Pro and 12nm Astronomik Ha filter. The GEM28 performed well all night guiding without any problem  and PHD2 reported the following data from the session.

I do intend in the future to use the 'PEC' setting in PHD2 as advised by Cuiv in one of his videos.

The result of the night's imaging-

Since then I have added a Pegasus Pocket Power Box Micro unit to the imaging set up in an attempt to remove power cables and weight of power adapters from the tripod legs. The new unit powers the GEM28, main imaging camera, two dew heater straps and eventually will also power the StarTech remote hub which requires a 5V/2A input.

I have been able to locate the Pegasus unit at the back end of the dovetail holding the imaging gear and the environmental senor which automatically regulates power to the dew straps is locate at the front of the dovetail. Velcro provides the means to hold everything in place.

After setting up which outlets I wanted to provide power on start up and updating the firmware of the Pegasus Utility Platform everything is working fine. I remain wary until I have used the set up more of trusting the variable output port to provide 5V for the StarTech hub but so far in testing the Pegasus unit has properly booted up each time. Pegasus Astro have a very responsive Tech Support even advising me over updating firmware on a Sunday-very good service indeed that goes well beyond the norm. 👍

This photo shows the amount of cables, power adapters and dew heater controller wiring I have been able to remove by using the Pegasus unit on the GEM28.

The Pegasus unit can be used  in a stand alone mode or connected to a computer which provides immediate viewing of power outputs and graphs.

For anyone else in a similar position requiring better power control over long distances the Pegasus unit is well worth considering. It is the 'baby' of their stable with other more able units providing both USB and power solutions.

Cheers,
Steve

[SteveNickolls]

GEM28 Guiding Examined

I didn't know until watching a Cuiv recent video concerning PHD2 guiding that the periodicity of small errors in the manufacture of a mount's worm and cogs could be determined and improved through changing a setting in PHD2.

Yesterday I took up the tip to use an option within PHD2 Log viewer to have the frequency of the errors from my GEM28 analysed, this is what I found. I find it fascinating that the workings of the mount can be viewed in this way and improvement applied. The worm in the GEM28 is 600 seconds duration and the analysis of my last auto-guiding sesion in November yeilded several components-

The main values occur each cycle of the worm at times of-

6 seconds of  0.1" 

21.35 seconds of 0.2"

99.9 seconds of 0.1"

112.6 seconds of 0.25"

150.4 seconds of 0.17"

161.3 seconds of 0.45"

198.8 seconds of 0.2"

601.3 seconds of 0.1"

In future I will alter the guide setting in PHD2 from hysterisis to PEC which according to Cuiv will train the mount each session to anticipate periodic error rather than react to events, hopefully reducing both the levels of each error and a smoother guiding session. Will post the results of future guiding examination to perhaps help others with the GEM28.

Cheers,
Steve

Edited November 30, 2022 by SteveNickolls