Re: Guiding without Gemini
I'm a recovering attorney, Jim (19 years without lawyering), not an EE. My dad left Pratt after 2 years of ME and returned to the farm, so some of that rubbed off.?
I recommend Losmandy products quite frequently, based on their quality and support. However, I've never been a great fan of the Gemini systems, if only on the basis of cost. A system that adds a grand or more to a mount when?the competition asks half or less for theirs leads to folk opting for a lot of bad mounts and buggy systems.
I have always championed used equipment for anyone getting into the hobby. First, if one buys intelligently they can usually bail out without too great a financial?loss. Buy new and you are always going to lose at least 25% of your outlay. Second, the stuff that is more durable is going to be pretty well known after the free field testing by early adopters.
Used Losmandy equipment usually commands a premium on the used market. I've never purchased an unused Losmandy mount. Nor one with an original Gemini. A recent purchase was a "mature" G11 head with the 492 system for $900, a fairly typical price. I sold the system parts for $175. So now I have a $725 G11 with no drive. Should I shop for a Gemini 1? Drop $2K on a new Gemini? Or should I just spend $150 on an OnStep goto controller and the system's drive components?
You raise the issue of support. I doubt I can email Losmandy and get the almost instant support that I can get from the OnStep community or even the chief programmers? Does the Gemini firmware?get constant testing and frequent upgrades??
I'd estimate there are about a thousand OnStep systems in use. I have shipped about 500 in the last 18 months and Paypal tells me my shipments?are up 24% from last year and order value is up 49%. This is in spite of my decision to drop my biggest seller due to what I felt was its limited features and ability to handle future upgrades as similarly priced options.
An additional argument for non-proprietary systems is that they restore functionality to? deceased equipment with proprietary systems. Think ASCG-5GTs. This out of production goto mount that sold for $700, as much as a used 492 GM-80, has a fairly high failure rate. A motor control board, if one can be found is about $200. It also has experienced troubled servo encoders, bad power panels and electrical connectors. With OnStep it can be put back to work with a few more features for less than $100. Just saves me a few more trips to the scrap yard.
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Re: Guiding without Gemini
Liam....you got these good answers...a summary:
Is Gemini required for auto-guiding or for dithering? ? ? No.? There are several alternatives ?Or can those functions be accomplished well with a laptop connected to a GM8S or G11S without Gemini? ? ? Yes.??
?Any suggestions on the major pro¡¯s and con¡¯s with operating without Gemini? ? ? Gemini offers proven compatibility with Losmandy mounts ? ? Gemini (G-2 upgrade kit is like $1100-$1400? has motors and cables and a Gemini-2 unit)? is more costly than some alternatives, but proven mechanical and software operation. You are paying for that engineering work done for you in advance.? ? ? The Losmandy 492 digital drive unit is like $400 and each stepper motor for that is like $150, but you can find the entire kit used for a low price when someone decides to upgrade to another system.? This can't do GoTo by itself but can track well and autiguide with an ST4 cable. ? ? Henk has explained his successful implementation of an OnStep stepper motor control system.? This is also inexpensive maybe less than the 492.? But it requires some work to fit it.? ?This can do Go-to and computer control.? You save money by doing this adaptation work ...and Henk and others who've solved it can help ease that effort.? Some folk told me they tried and gave up their effort, but many did do it and could advise you.? ? ? ?? ?It looks like Gemini comes with different motors, right? Does that make a difference?
The Gemini operates using "servo" motors.? These are DC motors, that get no current, or get a reversing current supply (from the Gemini) to hold their position.? The gemini knows the rotation position of the motor from an optical encoder installed inside the back of the motor housing.? That has 256 marks, so the gemini knows the motor rotation to that level of precision.? That motor output is further divided by a gearbox that has 25:1 ratio...so the motor angle is divided by 25.? The worm is turned by the gearbox and the worm connects with a large diameter gear with either 180 (GM8), or 360 (G11) or 270 (G11T or Titan) teeth.? This gives the system sub arcsec control of the mount pointing.??
Other motor systems use stepper motors that use separate windings inside the motor to pull it's rotor to any fixed position.? There are now amazing methods to "microstrip" the rotation.? (Does the OnStep stepper motor also need a gearbox?? I'm not sure).? The older 492 stepper motors have an ovoid gearbox built in with the motor.? I don't know if the 492 microstep or not, but they work smoothly for tracking or autoguiding.? They can be autoguided...the 492 needs an simple ST4 cable.??
The Gemini can use an ST4 cable or skip that and pulse guide with ASCOM computer commands sent via it's serial port.? Both methods work well.? The ST4 cable is small and light...but getting rid of another cable may save a snag or bad cable connection in the dark some night.? OnStep is computer controlled too and can probably use ASCOM commands for pulseguiding.??
Decisions decisions!??
Have fun, Michael
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Liam,
The majority of Losmandy owners, at least those on this forum, seem to have the Gemini control system. That being the case, there are many who can advise you with mount operation, guiding, and trouble shooting. Also the Gemini will accept upload of PEC curves from PEMPro, to further smooth guiding performance. Once you get into astrophotography, the price of the Gemini unit is not that much of the whole expense, compared with scopes, cameras, filters, auto focusers, etc.
For guiding, ST4 seems like it is becoming less used, with direct mount control over USB or Ethernet supposedly more responsive. If you have the expertise to use some of the less expensive control units that is fine too. But you may not have the same level of tech support from the forum or the manufacturer. Just my opinion, others may advise differently.
Best Regards,
John
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Re: PREVIEW Part 3 of Practical Periodic Error Correction
I¡¯ll try in a week or so, all packed up now ¨C and cloudy. ? Thanks ? ? ?
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From: [email protected] <[email protected]> On Behalf Of Ray Gralak
Sent: Sunday, 28 February 2021 2:52 PM
To: [email protected]
Subject: Re: [Losmandy_users_io] PREVIEW Part 3 of Practical Periodic Error Correction? Hi Richard, ? Have you tried creating a Pec curve with the 0.2x rate in PEMPro? Then set the guide rate to 0.2x. I think drift you are seeing should be reduced. ? -Ray ? ? Hi Brian ? YES ¨C was having trouble with drift when PEC ON and then with the Gemini Drift Compensation tool in PEMPro. Basically could not get it to ¡°converge¡±. ? Hence interested in Part 4 and hoping you got past the drift issue, you must have as I understand you use PEMPro PEC with your Losmandy mounts. ? Ray said I have some strange frequency that he hadn¡¯t seen before. He was going to look at it some more, ¡¡¡. ? ? I will try again in a week or so when the skies allow. Do it all again on a single night and see what happens. Send Ray the logs etc. ? Cheers ? ? Those were not released videos.? There is eventually going to be a full series, but we are working with Ray right now to fine tune PEMPro for Gemini, so we are likely going to re-do this from the start Richard I think i saw some comments from you in the PEMPro forum? ? These are the three ; ?
? ? ? ? ? Where did this come from (so I can see all the parts)?? ? Derek ? ? Hi All
Is there a Part 4 somewhere ?
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Re: PREVIEW Part 3 of Practical Periodic Error Correction
Hi Richard, ? Have you tried creating a Pec curve with the 0.2x rate in PEMPro? Then set the guide rate to 0.2x. I think drift you are seeing should be reduced. ? -Ray ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Richard Triglavcanin
Sent: Saturday, February 27, 2021 10:40 PM
To: [email protected]
Subject: Re: [Losmandy_users_io] PREVIEW Part 3 of Practical Periodic Error Correction? Hi Brian ? YES ¨C was having trouble with drift when PEC ON and then with the Gemini Drift Compensation tool in PEMPro. Basically could not get it to ¡°converge¡±. ? Hence interested in Part 4 and hoping you got past the drift issue, you must have as I understand you use PEMPro PEC with your Losmandy mounts. ? Ray said I have some strange frequency that he hadn¡¯t seen before. He was going to look at it some more, ¡¡¡. ? ? I will try again in a week or so when the skies allow. Do it all again on a single night and see what happens. Send Ray the logs etc. ? Cheers ? ? Those were not released videos.? There is eventually going to be a full series, but we are working with Ray right now to fine tune PEMPro for Gemini, so we are likely going to re-do this from the start Richard I think i saw some comments from you in the PEMPro forum? ? These are the three ; ?
?
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? ? ? Where did this come from (so I can see all the parts)?? ? Derek ? ? Hi All
Is there a Part 4 somewhere ?
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Re: PREVIEW Part 3 of Practical Periodic Error Correction
Hi Brian ? YES ¨C was having trouble with drift when PEC ON and then with the Gemini Drift Compensation tool in PEMPro. Basically could not get it to ¡°converge¡±. ? Hence interested in Part 4 and hoping you got past the drift issue, you must have as I understand you use PEMPro PEC with your Losmandy mounts. ? Ray said I have some strange frequency that he hadn¡¯t seen before. He was going to look at it some more, ¡¡¡. ? ? I will try again in a week or so when the skies allow. Do it all again on a single night and see what happens. Send Ray the logs etc. ? Cheers ?
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From: [email protected] <[email protected]> On Behalf Of Brian Valente
Sent: Sunday, 28 February 2021 1:20 PM
To: [email protected]
Subject: Re: [Losmandy_users_io] PREVIEW Part 3 of Practical Periodic Error Correction? Those were not released videos.? There is eventually going to be a full series, but we are working with Ray right now to fine tune PEMPro for Gemini, so we are likely going to re-do this from the start Richard I think i saw some comments from you in the PEMPro forum? ? These are the three ; ?
? ? ? ? ? Where did this come from (so I can see all the parts)?? ? Derek ? ? Hi All
Is there a Part 4 somewhere ?
--
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Re: Typical Guided Performance of GM8G, GM811G, and G11
I¡¯ve been imaging M42 and NGC2264 and find the GM811G isn¡¯t very good past 30 seconds, its not about tracking its like the image is on a bumpy road with stars moving left/right/up/down like too much coffee. ?Since I am just hunting for new objects in the sky I am NOT using guide software (PHD2) but everything is level and balanced. ?I thought the Nikon DSLR was bad but its really this GM811. ?Serious imaging will require Guide software which is easy to setup and gives good results. ? ? ? ?AT115 reflector and Nikon DSLR bare bones tonight.
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Re: Guiding without Gemini
Liam,
The majority of Losmandy owners, at least those on this forum, seem to have the Gemini control system. That being the case, there are many who can advise you with mount operation, guiding, and trouble shooting. Also the Gemini will accept upload of PEC curves from PEMPro, to further smooth guiding performance. Once you get into astrophotography, the price of the Gemini unit is not that much of the whole expense, compared with scopes, cameras, filters, auto focusers, etc.
For guiding, ST4 seems like it is becoming less used, with direct mount control over USB or Ethernet supposedly more responsive. If you have the expertise to use some of the less expensive control units that is fine too. But you may not have the same level of tech support from the forum or the manufacturer. Just my opinion, others may advise differently.
Best Regards,
John
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Re: PREVIEW Part 3 of Practical Periodic Error Correction
I can't find Part 1 or 2 either.
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Re: PREVIEW Part 3 of Practical Periodic Error Correction
Those were not released videos.?
There is eventually going to be a full series, but we are working with Ray right now to fine tune PEMPro for Gemini, so we are likely going to re-do this from the start
Richard I think i saw some comments from you in the PEMPro forum?
These are the three ; ?
?
?
? ? ? Where did this come from (so I can see all the parts)?? ? Derek ? ? Hi All
Is there a Part 4 somewhere ?
-- Brian?
Brian Valente portfolio
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Re: Guiding without Gemini
I replaced the 492 system of my G11S with a DIY OnStep controller.? It is a lot of work but it's fun to do, it works very well and is a whole lot cheaper.? Mine is controlled be Ekos on a Pi but OnStep also has an Ascom driver for use on Windows.
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Re: G11T vs AstroPhysics - opinions wanted
On Fri, Feb 26, 2021 at 01:15 PM, <altuttle@...> wrote:
Thanks a ton for these latest replies!!!
Yes, I do know the added costs.... (my spreadsheet is a scary thing to look at).? ?It's the same story with all the next tier mfgrs I've looked at (AP, Paramount, 10micron, & Planewave), in some cases even having to rebuild/modify the observatory.? I can convince myself (& the CFO) that the cost is justified.....? but I have doubts that I really need to go that far.
Chip, your comment really hits home.? I'm looking for a relatively high capacity, strong mount that tracks very smooth.? I have several scopes (mostly mid-tier) and I change them often to suit the season/targets.? As such balance and position often changes a bit, so parking position for easy restart and pointing models are mostly irrelevant for me.? The level of controller I have with the Gemini 1 (or even with my Celestron) is more than adequate.? My problem is drivetrain errors that impact good guiding, mainly backlash and PE (not the averaged PEC, but the higher frequency errors/roughness).? ?I don't know if its really necessary to spend 2 or 3 times the price to get those improvements in the gear train, or would much of that cost be for things like optical encoders and fancier controllers?
I'll think seriously about getting a G11G as a tryout so to speak before going all-in on a Mach2, particularly if the wait for it gets pushed out further.? The G11G may be just the ticket.
Thanks again,
al
Al, If you can truly afford an AP Mach2 the $3,500 cost of a G11G fill-in mount will be trivial and who knows, you may decide you like your results. It is very hard to see the differences between these mounts unless you are working at a supremely high level of imaging craftsmanship. In that place you know that you are oversampling for a reason and have the sky conditions to take advantage of it. Additionally simply by putting a building around a G11G you will instantly improve your PE over the long haul by eliminating the biggest issue any high payload portable mount has, payload windage. This can push the G11G into the high priced spread territory in terms of performance. Will the G11G give you 100% of the same performance as the AP Mach2? Of course not, not in absolute terms but 99% - maybe. At that point the question is are you that level of imager?? My next question is what level of automation does your observatory have? As in can it open the roof and if it has a slit can it track automatically? If you plan to image from the house in the winter I would buy the AP mount. They have a more robust control system especially the Mach2 with encoders. Put a IR video camera in the observatory and you can probably recover remotely. If you don't plan to do this then I'm still in favor of buying a new G11G while you wait and like I said, who knows you may become a convert.? ? Just saying. ?? -- Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Re: G11T vs AstroPhysics - opinions wanted
On Fri, Feb 26, 2021 at 11:39 AM, Arun Hegde wrote:
That is unquestionably true. AP prices are for mount only. You will need counterweights, a counterweight bar, a dovetail to mount your telescope, a flat surface adapter and knobs to mount them on something like a Losmandy tripod all of which add to the price of the mount. Mine came with the counterweights and bar, but I had to purchase the other stuff, along with the V2 chip for the upgrade from the old Q firmware. All that adds up. And I still kept by GM811G because it is a really nice mount and more portable than the Mach 1. Plus the LHD tripod works with both mounts, so that's a win!
I'm well aware of this, I guess I was not clear when I said $10K and add accessories. It should have read $10K plus at about 50% for items Losmandy owners consider standard but AP considers accessories and assuming a fixed non-AP pier.? For what an AP Mach2 costs - well equipped - for a variety pack of scopes you can buy a several Losmandy G11G moutns sans FHD saving nearly $700 per mount and build a roomy observatory to house them and never have to swap optics allowing for perfect polar, orthgonal alignment and balance for each optical tube design. There are many many images of very high quality produced on Losmandy mounts every year and that number will go up as the newer mounts get out there to serious imagers. Additionally having multiple mounts allows capturing multiple objects at once or a single object with differnt cameras and optics. Or imaging on two mounts while visually observing on the third, so many options whith multiple mounts none of which are possible with just a single mount as nice as it is.? ? ? -- Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Re: PREVIEW Part 3 of Practical Periodic Error Correction
Hi All
Is there a Part 4 somewhere ?
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Re: Guiding without Gemini
I use my digital drive G11 for astrophotography and guide via the ST4 cable. I use the setting circles to find objects. It is much easier nowadays since the camera chips are big enough to get a wide field of view if you have a scope with a focal length of 500-800 mm so you can usually find the object you want to image and the centre it using the hand controller.?
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Re: Guiding without Gemini
If you have the older 'non Gemini I or II' models you can auto-guide and dither.? You will need an ST4 cable.
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Re: Guiding without Gemini
Liam?,
You can auto guide and dither using the non Gemini, but you need to use an ST4 type cable.
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Is Gemini required for auto-guiding or for dithering? Or can those functions be accomplished well with a laptop connected to a GM8S or G11S without Gemini? Any suggestions on the major pro¡¯s and con¡¯s with operating without Gemini? It looks like Gemini comes with different motors, right? Does that make a difference?
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Is Gemini required for auto-guiding or for dithering? Or can those functions be accomplished well with a laptop connected to a GM8S or G11S without Gemini? Any suggestions on the major pro¡¯s and con¡¯s with operating without Gemini? It looks like Gemini comes with different motors, right? Does that make a difference?
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Re: Typical Guided Performance of GM8G, GM811G, and G11
Thanks again for all the helpful information! I see the benefit of going straight to the G11 instead of the G8, especially because I would probably want to upgrade to a G11 eventually. I¡¯ll just have to patiently save a little longer for it and practice with my current setup in the meantime.
I ran into the the DSLR back focus problem on my Newtonian with my DSLR. I ended up modifying the Focuser to achieve focus. Of course, I think my new dedicated astronomy camera will be able to achieve prime focus without the adapter (and without torquing the tube as much as the heavy DSLR).
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Michael Herman
Bill P.
Chip Louie