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The diagram in my message may not have been clear about what is going on. Maybe this will help.

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This is the situation when I power up Gemini-2 after being off for several days.

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When I tell it to park CWD, this is what happens:

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After doing a cold start (usually requiring a power cycle as well), it fixes the problem. If I tell it to park at my Home location (due west ), it reports the correct location now.??

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Leaving Gemini-2 unpowered for one day, the problem doesn't happen. If I leave it unpowered for several days, that is when it starts up (after a Warm Restart) with the wrong location reported.? As I mentioned in my previous message, maybe the firmware update fixed something. I'm leaving it off for a few days right now to see what happens when I restart it next.

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On Wed, Apr 9, 2025 at 05:23 AM, Paul Kanevsky wrote:

Are these helpful in overcoming periodic error and for reducing the need for autoguiding on these mounts?

Well you asked things which I have not tested lately but long time ago and do not remember. I would need to test it again but honestly ?for what? The price of the mounts compared to other encoder equippedones is good.

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The tracking is very good I would say even so I do autoguide with maybe 1-2 second exposure time and inbetween a pause of 4-5 seconds.

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The big problem is the SDE error ( Sub-Divisional error) but this comes from bad programming.

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BTW I have number 1 and 2 from the production start and they had a lot of bugs which I reported during 2 years and iOptron gave me the nickname " Mr. Bug #1".

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I was the one who reported the most quantity of Bugs but then they left me standing in the rain with my rest problems, but OK, I can use them and SDE error comes up mainly over 1500mm focal length at high resolutions. At lower focal length you do not see it.

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I assume iOptron has solved this problem in the last 7 years. I got mine in April 2018. Mechanically those mounts are very good. Balancing is a piece of cake.

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I can track the Sun over 4 hours and it moves a negligible amount in RA. Of course the Sun moves in DEC all the year feom South to North and backwards.

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Here is the Sun tracking with the eclipse of 2024 at my place. I had Ha and White light scope on the same mount. I did not correct during the whole eclipse.

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Rainer

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Do you mean the check boxes on the hand controller to reverse movement direction?? I use those all the time, but they don't result in Gemini reporting coordinates on the opposite side of the sky from where the mount is pointing.

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FYI, I updated to the latest firmware recently.? After I did that, I had this problem happen once more, but then the next time I checked it didn't happen. My next chance at clear skies will be Friday when I'll check again. I'm hoping the firmware update may have fixed whatever was wrong.

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Thanks,

-Joe

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Check your Gemini 2 settings for reverse RA and DEC movement.?

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hi guys,

It looks like the a new battery fixed.?

Clear Skies,

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Paul

On Tue, Apr 8, 2025 at 05:47 PM, Rainer wrote:

Some more images, but the configuration has changed now. On the mount in the back is a Mewlon 250S 1st generation which I modified to ASCOM focuser using a slim 22mm? ? Faulhaber stepper motor with ZWO EAF electronics.

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On the mount on the front the two Solar setup were replaced by the ASKAR 103APO.

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I also attached an image of the encoder disc on the worm wheel. This is not from a CEM 120EC2 but from a CEM 60EC.

On Tue, Apr 8, 2025 at 02:49 PM, Rainer wrote:

On Tue, Apr 8, 2025 at 03:21 PM, Paul Kanevsky wrote:

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Very nice! But I think you need more weight on that mount to get it to full capacity ;)

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The mount with TOA and ASKAR has 42.6kg of counterweight

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I agree, the Askar optics seem to be pretty good,? overall people are getting good results.? This little Askar is an FRA500 is sharp at its native 500mm f/5.6 and a wonder at f/3.9.? Okay so it's no match for the modern Takahashi FC-100DF with a CAA and? FC-35 reducer but it was $1,200 used vs $4,500.? Askar is a good deal IMHO.? ??

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The most counterweight I had on the G11G counterweight shaft was 41kg.? In this photo I only had 37kg as the other 9.5kg weight was in use and I had to use the 5kg and move them down the shaft more.? It works fine but I think this is pushing it with 34kg + in a Losmandy Side-By-Side saddle mount.??

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For the last few years I've been using the ASIAIR and have not had any issues guiding with the same old piggybacked Stellarvue F050 50mm f/4 guidescope in the matching non-adjustable clamshell I've used for the last maybe 7-8 years.? It worked great with PHD2 and people claimed it wouldn't because I needed adjustable rings and I was doing about a zillion other things wrong which were absolutely incorrect.? The one thing I know is true and has remained true since way back when I first started using PHD2 is that the relationship between the imaging scope's image scale and the guide scope's image scale is critical.? That ratio has changed over the years as PHD2 has improved tremendously with the addition of multi-star guiding, CMOS cameras taking over and the CMOS sensor photosites somehow managing get more sensitive with lower noise and somehow also getting even smaller, it's a win win IME.??

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All of these things have been making it easier to get better autoguiding with modern CMOS cameras.? Back in the olden days, some OGs like to fondly imagine them as the "golden days" of CCD cameras, people all struggled to try and maintain a 1:1 or 1:2 ratio between the imaging camera and guide camera.? This of course was absurd and only increased the likelihood of differential flexure due to all that extra mass and weight hanging off the main scope, obviously this was bad for guiding and everyone thought OAG was the way to go.? It still is bad for auto guiding, lower mass is more easily corrected and makes your back hurt less the next day if you are a portable imager with a larger optic and OAG use while much better still a PITA and more expensive.? Anyway as time as moved forward and autoguiding hardware and software has improved the ideal ratio has moved too.?

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I think the ideal ratio is now up to around 1:3 with good results and acceptable results on a good mount and heavy tripod (don't discount what a heavy tripod can add) out to 1:5 or so, once you get past around there stuff starts to get less reliable and at least my mount starts to behave less than ideally.? I know this because in my driveway I have tested the idea using that same old Stellarvue F050mm f4 (210mm measured fl) with a new ASI678MM screwed on the back of the helical focuser clamped rigidly to the top dovetail of an LX200 8" f/10 ACF (2,000mm) and LX200 10" f/6.3 EMC (1,600mm) SCTs with good results.? I have not managed to Barlow the ASI678MM yet but I expect it will return better results at 1:2.5.? Testing shows that the 1:1-1:2 ratio works extremely well with my very typical focal length refractors which range from 350mm to 802mm focal length refractors.? ? ? ? ? ? ? ? ?

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Anyway that's where I'm at at the moment.? Obviously, as per usual YMMV.??

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Thanks Gents

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I have a G2 tallboy on the way...ARM is hot.?? So needs new ARM and i'll try the new bootloader.?? I'll report back....shouldn't be to long

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cheers

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Brendan

On Tue, Apr 8, 2025 at 03:21 PM, Paul Kanevsky wrote:

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Very nice! But I think you need more weight on that mount to get it to full capacity ;)

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The mount with TOA and ASKAR has 42.6kg of counterweight

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Some more images, but the configuration has changed now. On the mount in the back is a Mewlon 250S 1st generation which I modified to ASCOM focuser using a slim 22mm? ? Faulhaber stepper motor with ZWO EAF electronics.

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On the mount on the front the two Solar setup were replaced by the ASKAR 103APO.

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I also attached an image of the encoder disc on the worm wheel. This is not from a CEM 120EC2 but from a CEM 60EC.

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Rainer

On Tue, Apr 8, 2025 at 05:11 PM, Rainer wrote:

Those are iOptron CEM 120EC2

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On top a TOA 130 and ASKAR 103APO. BTW the chinese ASKAR telescopes are quality wise very very good. Takahashi is getting big competition. BTW I have a total of 5 Takahashi all bought in the years 2005 to 2010. Nowadays Takahashi is not worth. When I bought them there was no real good quality but nowadays chinese are showing what they are capable off.

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:-)

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Rainer

Those are iOptron CEM 120EC2

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On top a TOA 130 and ASKAR 103APO. BTW the chinese ASKAR telescopes are quality wise very very good. Takahashi is getting big competition. BTW I have a total of 5 Takahashi all bought in the years 2005 to 2010. Nowadays Takahashi is not worth. When I bought them there was no real good quality but nowadays chinese are showing what they are capable off.

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:-)

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Rainer

On Tue, Apr 8, 2025 at 04:26 PM, Rainer wrote:

stepper motors and encoder discs (big glass discs glued on the worm gear) on the RA and DEC axis

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Any photos? I'm curious to see what it looks like!

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Hi,

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Now that I am here I have a curiosity question. Those who knew from the times before 2018 back to >2008 when I still had my Losmandy G11-RS, know that I like to tinker, and improve?? (maybe make things worse :-0 ), everything I have.

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I have two mounts, big mounts with 52kg capacity(counterweights not included), with stepper motors and encoder discs (big glass discs glued on the worm gear) on the RA and DEC axis Worm gear with 360 teeth and 216mm ?.

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According to the producer the resolution of the encoder is 0.035" (arcseconds).

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Is it possible to use Gemini 2 with Stepper motors and the encoder discs?

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Rainer

NHSA Observatory

Mexico (in order to not create confusion)?? :-)

Hi,

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There are two ways of guiding.

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Piggyback guide scope and Off Axis Guider.

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Depending of your setup up eg. camera and other accessories like maybe Filter wheel and optical accessory be it a reducer, flattenner or extender optic.

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OAG guiding is the best as as you avoid flexing differences between guide scope and Imaging scope.

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When you decide for Piggyback guiding then the ratio between the guide scope and the Imaging scope should not be more then 1:2 and really max. 1:2.5 maybe but really not more then 1:3.?

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I do guide 560mm with a 420mm piggyback and 3200mm with OAG. In both cases I do use guide cameras with an IMX249 sensor.

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when OAG guiding a G11-RS mount i achieved round stars troublefree with my Mewlon 250S at 3200mm focal length on 10 minute exposure on my favourite Galaxies which are the ARP's.

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I would say F.X. Flinn's results is the exception to the rule. I do not know what imaging focal length he has.

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IMHO Rainer

Hi Jeremy,

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I wanted to jump in and mention a couple things as a new (actually born again) hobbyist. ?I did basic visual stuff for many years with a Celestron CPC1100. ?Recently retired (for sure this time) I decided to re engage and invest in an equatorial mount. ?After lots of reading I decided to go with a Losmandy G11G and talked with Tanya. ?I was so excited to find a company that is clearly very proud of their products, work, and customers. ?What a great experience it has been for me so far. ?The quality and craftsmanship is unbelievable. ?And USA built to boot….

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Now the boxes show up and it’s time to get this all set up. ?Listened to all the videos and got lots of stuff done but still always more questions. ?It’s only been a month or so for me but I’ve come a long way from where I started. ?Chip Louie has helped me with tons of questions and given great advice.

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I had the exact same question as yours and will investing in a guiding scope and camera soon. ?I hope you continue posting so we can all learn together.

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Thanks to Losmandy, this forum, and especially Chip for helping me get out of the gate. ?I’m sure this is only the beginning, but I look forward to learning this new hobby.

On Mon, Apr 7, 2025 at 02:31 PM, Paul Kanevsky wrote:

Hi Folks,

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René, as usual, has been busy with Gemini improvements. The new Bootloader is an update to the original one that was created when 2GB SD cards were all that was available :)

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The new bootloader isn't required if your Gemini is working fine. You can skip it if you don't care about the benefits listed below, or if you feel uncomfortable performing the update.

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The update process itself is about as complicated as the L6 upgrade to the new servo firmware, and requires:

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1. A 20 pin ULINK2 emulator/programmer -- about $30 from Amazon
2. Keil ULink-2 software (runs on Windows)
3. MB_BL_2024.uvproj bootloader project file

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Detailed Instructions can be found here:

/g/Gemini-II/files/Latest%20Firmware%20Files/Bootloader%20Update%20Instructions%20-%20April%202025/Gemini%20Bootloader%20Installation%20Instructions%20-%20Apr%202025.pdf

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The new bootloader is based on a modern version of Keil middleware and helps with the following:

• Faster boot-up time for Gemini
• Better compatibility with different types and larger size SD cards
• Resolves the issue with the dreaded M:Curr_Gem.bin file for those who have experienced it

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Be careful if you decide to update your Gemini. Follow instructions!

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Regards,

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? ? -Paul

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My favorite little birdy told me about this a couple weeks ago.? I think it is worth doing if you are one of the impatient people or like me (okay so I'm impatient) just want to keep up to date on code revisions.? I'm a sucker for the latest and greatest LOL.?

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On Tue, Apr 8, 2025 at 06:41 AM, Jeremy Benson wrote:

Thanks to everyone who responded to my question about autoguiders.

It seems I’m so new to the whole thing I didn’t even know the right questions to ask.? I’ll do a little more research on exactly what I want to do and come back with my specs and a better idea of what I’m looking for.

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Thanks!

Jeremy Benson

Keeper of Keys and Labs

NIU Department of Physics

NASA Solar System Ambassador

La Tourette 202A

815.753.1953

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Hi Jeremy,

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It's not that complicated.? The way the autoguiding apps work like the free standing PHD2 guiding or an integrated system like ASIAIR etc. require certain conditions to be met in order to work well.? We know you are working with a Losmandy G11G and Gemini 2 controller which is great but in order to help determine your best options for autoguiding we need to know what your imaging optic(s) and camera(s) used to image with.? Many of us have and use more than one imaging setup to cover more of the sky at the desired scale. Give us the main telescope and imaging camera and I'll walk you through the process to determine what your best options are and why.? Come on, this is how our little community gets it done.??

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