Requesting experienced opinions on the Mach2GTO with 2 axis encoders - Forums

Topic starter

Jan 11, 2022

Hi All,

I am considering the Astrophysics Mach2GTO with the absolute encoders for a pier mount within an observatory (design TBD). I want to use this to run a survey rig, with a 12 inch imaging Newtonian that will move between multiple targets each session. Possibly back and forth between targets during the night. I am not intending the subs to be particularly long, though I cannot state what they will be since the scope is still on backorder. The hope is that I can get the scope to reliably slew many times during any one session and that this setup can do so reliably. If really reliable, I would be able to skip plate solves each slew and save a lot of time. Also, I hope the subs are short enough that I could save time by not guiding. The use I describe would be for photometry and not aesthetic imaging. On the other hand, from time to time, I will want to switch cameras and do some deep sky imaging for fun.

So now that you know what the setup is, my questions to anyone using this mount is the following: 1. Is this mount necessary for these purposes? Please suggest others if you have experience. 2. Related question: Are the absolute encoders necessary to do the job? I am understanding that if set up accurately on the pier, the precision of the mount and accuracy of pointing should save time with each slew (especially if plate solving and guiding become unnecessary). 3. Should I assume that mount and included software would be sufficient to drive such a system fully with the typical sequencing software in use today? I have used SGP in the past and NINA currently. 4. Any concerns with the following? The mount has a listed weight capacity of 75lbs, this is a fairly large OTA (F4). It is carbon fiber and I expect the total weight to be well under 55 lbs. It seems to fall well within the AP size(diameter-length)/weight chart. I am hoping that the observatory will prevent most wind issues. 5. Not a question, but I am aware that if I go in this direction, I am likely to be waiting for some time before one becomes available. But I know that I have time to plan at this point and I am looking forward a good number of months to get the location, observatory set up, etc., etc. If the feedback I get is positive, I will be more aggressive at getting the mount (or alternative) in the pipeline.

Thanks in advance!
Alan

Engaging

fred.germain2812

Jan 11, 2022

Hello alan
I’m using Mach 2 for more than a year now with a c11 edge hd and an AP starfire130gtx Absolute encoders give you the ability to track without guiding even with long time exposure. I’ve done 600´´´´´´ ´ Exposures with FWHM eccentricity less than 0.01.
Pointing model with about 260 points takes a bit more than an hour with APPM and APPC PRO, it is very quick . With absolute encoders the mount never gets lost especially with a permanent pier .
Y hope this will help you
fred

Alan Brunelle

Topic starter

Jan 11, 2022

Thanks Fred!

This is very helpful, thank you!

I have heard of shorter pointing models that can be used that take less time. Am I correct in thinking that with a fixed mount on a pier, that a much shorter model can be run prior to starting a night?

Best,
Alan

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fred.germain2812

Jan 11, 2022

Yes of course you can easily run a much shorter model every night . It will take a couple of minutes.
I use a shorter model with 40 points when moving outside the city , It takes about 12´

best
Fred

Miguel Morales

Jan 11, 2022

I understand that the current wait time for a Mach2 mount is about 2 years.

Well Written

Marcelof

Jan 11, 2022

Hello,

If your Mach 2 is going to be permanently fixed to an pier just do a complete modeling, with several points. It will take about 1 hour, but that model will serve for at least 6 months or more, that is until the environmental conditions change significantly (winter/summer).

Note that for the modeling to work properly you need some device to monitor the environmental conditions (temperature, humidity and pressure). Pegasus Astro and MBox have devices for this.

Helpful Concise

Wei-Hao Wang

Jan 12, 2022

Hi,

I would worry that a 12" Newtonian is pushing the limit of Mach2. I put a 12" RC on it and it works well, but the tube is short. For a longer tube and a heavy camera (if you have one), the length can be an issue.

I picked Mach2 because I am doing mobile imaging. If you have a fixed observatory, a 1100 would be much more suitable, I think. Even without encoders, a 1100 should do the tasks you mentioned just fine (but you need to ask others to confirm this). And it seems you can get a 1100 faster.

Cheers,
Wei-Hao

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Luca Marinelli

Jan 12, 2022

I use both a AP Mach2 and an AP 1100 (without encoders) in my observatory. I choose to guide because it is easy and I only have one telescope on each mount. The Mach2 is a great mount and one that I have used without breaking a sweat with a TS ONTC 10in f4 Newtonian. 12in Newtonian is not a log bigger but as you know it's the square of the diameter that matters. If I knew that I am going to use a big tube like that, I would agree with Wei Hao that you may be better off with the AP 1100. If the mount is observatory mounted, the slightly higher weight of the 1100 is not going to be a major concern.

The AP1100 is available both with and without absolute encoders. For visual use, the encoders on the Mach2 are a bit more convenient because they follow the position of the mount even with the clutches disengaged. For imaging and/or remote use, there is no difference because you don't disengage the clutches during a session. Modeling via APPC/APPM provides both tracking and pointing correction, so with a good model you should be able to skip plate solving (assuming the telescope does not have significant mirror shift as is the case in some SCTs, for example). Unguided imaging is a big easier with mounts with absolute encoders but ultimately it depends on the image scale. The periodic error on the AP1100 without encoders can be knocked down to sub-arc sec levels with PEM Pro, so often it is buried in the seeing. Absolute encoders completely eliminate periodic error and Dec backlash.

Luca

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Alan Brunelle

Topic starter

Jan 12, 2022

Wei-Hao and Luca,

Your comments are very welcome and valuable to me. I do welcome other options as well. Many good points to consider. And I will certainly consider options for mounts as well. In particular, the point of being a permanently mounted rig, makes an alternative better and more viable choice. I will look into the AP1100 and I have already started to research the Planewave L-350 with wedge as another option.

Thanks!

Respectful Supportive

Alan Brunelle

Topic starter

Jan 12, 2022

If your Mach 2 is going to be permanently fixed to an pier just do a complete modeling, with several points. It will take about 1 hour, but that model will serve for at least 6 months or more, that is until the environmental conditions change significantly (winter/summer).

Note that for the modeling to work properly you need some device to monitor the environmental conditions (temperature, humidity and pressure). Pegasus Astro and MBox have devices for this.

Very good point Marcelof! In fact last night I think I had a dream that given the extreme precision of these mounts, that the whole thing could get screwed up because of geological movements! Not quite a nightmare, but... But, yes, certainly the conditions will impact this setup. My scope is not a super long focal length, just 1200mm, but the camera sensor is small, so effectively it acts as if it is. It would not take much to move completely off frame. If I needed to plate solve, but could minimize that action to a few set actions based on conditions, that would be fine.

Alan Brunelle

Topic starter

Jan 12, 2022

Miguel Morales:
I understand that the current wait time for a Mach2 mount is about 2 years.

Maybe a bit depressing! I was awaiting more comments here before giving AP a call. I did hit the button for alerts, but I have heard that the best way to get these answers are to call, and that they are very helpful. I don't mind a bit of a wait, since I can use my current mount to spend time with the new scope and get the system worked out and my approach and methodology. But 2 years is a long time at my age! I will call them and let people here know what I get for an answer.

Thanks Miguel!
Alan

John Hayes

Frequent contributor

Jan 12, 2022

I own three mounts: a Mach2, an AP1600 with encoders, and a L500. I agree with Wei-Hao that the Mach 2 may be a bit on the edge for a 12" Newtonian. It is a very stout mount and I like the design with respect to the encoders. If you bump it against the clutches, it won't get lost–unlike the 1100 or 1600 with encoders. I think that something like the 1100 would be better suited to a 12" Newtonian.

- John

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Shannon Foye

Jan 13, 2022

John Hayes:
If you bump it against the clutches, it won't get lost--unlike the 1100 or 1600 with encoders.

John - Can you elaborate on the difference between the Mach2 and the 1100/1600 (both w/encoders) regarding the mounts getting lost from bumping the clutches?

Thanks,
Shannon

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John Hayes

Frequent contributor

Jan 13, 2022

Shannon Foye:
John Hayes:
If you bump it against the clutches, it won't get lost--unlike the 1100 or 1600 with encoders.

John - Can you elaborate on the difference between the Mach2 and the 1100/1600 (both w/encoders) regarding the mounts getting lost from bumping the clutches?

Thanks,
Shannon

Shannon,
Both the AP1100 and the AP1600 have the encoder attached to the main spur gear for each axis. This corrects for PE errors and allows the mount to know where it is at all times--so long as neither axis is moved against the gear clutches. As soon as you loosen the clutch and manually move the scope, it is lost. The reason for this design is that the encoders were added as an afterthought to a design that already existed and it's ultimately not the best way to do things.

AP started with a clean sheet of paper with the Mach2 design and they did it right. The encoders in that mount are attached to each axis so that they act like digital setting circles independent of the drive system. You can loosen the clutches and swing the scope around the sky and the mount always "knows" where it is pointed. BTW, this is also how the L-series mounts from Planewave work. I don't own one but I believe that the 10 micron mounts also work this way. Someone else will have to say how the SB (Software Bisque) mounts work--I just don't know.

The AP1100 and AP1600 mounts are VERY good, but unless you really need it for unguided operation, I probably would not recommend the encoder option for either of those particular mounts. I'll also add that although unguided operation can work, it's not always as easy as it sounds--even with encoders.

John

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Shannon Foye

Jan 13, 2022

Thanks John

Tim McCollum

Jan 13, 2022

Take a look at the 10 Micron GM2000HPS, it might meet your needs.
I just received mine after being on order for 4 months.
Europe stops working in August each year so that added to the lead time as well as being shipped during the holidays.
I ordered thru Tolga Astro.
Tim

Jared Willson

Jan 13, 2022

To image unguided for more than about 60s with a 1,200mm focal length requires absolute encoders and a good pointing model. To image unguided for more than 30s at that same focal length requires a good pointing model (that will correct tracking rates for polar alignment errors, atmospheric refraction, flexure, etc.) but NOT the absolute encoders. To slew to an object and have it be consistently within a couple arc minutes without a plate solve also requires a good pointing model, but not absolute encoders (though they do help a bit).

The Mach 2 always comes with absolute encoders. The 1100GTO is available with or without absolute encoders. I would recommend APCC Pro (software for pointing model) be purchased with either.

If this is for an observatory, I would get an 1100 rather than a Mach 2 given your telescope’s size. The portability means nothing for an observatory instrument, so go with the higher capacity and better availability. If your sub exposures (you mentioned photometry) are going to be 30s or less you could skip the absolute encoders on the 1100–at least as long as it’s not a huge deal to drive to the observatory (or have someone there to support you if things get messed up). If the observatory will be unmanned and is more than a few hours away, I would recommend the encoder version for the “homing” function—the mount can’t get lost in space short of an actual collision, and you should be able to avoid collisions even with counterweight up positions with the horizon and meridian limits built into APCC. Even without the encoders, needing to go to the observatory will be rare, but stuff does go wrong sometimes with software, and a blind plate solve won’t work if your scope is pointed at the concrete.

I can’t speak to the 10 Micron products as I have never owned any. Worth considering, though, if the wait time for AP is too long. The wait time on the 1100 is likely much shorter than on the Mach 2. It has been out longer and appeals to fewer people as it’s an observatory class mount rather than a portable one. Less demand. The price difference between the two is not all that big. The 1100 without encoders is 5e least expensive, then the Mach 2, then the 1100 with encoders.

Just for reference, I own and have used for years the Mach 1, the AP900, and the AP1100 with encoders. I don’t happen to own a Mach 2 since I prefer either the portability of the Mach 1 or the capacity of the 1100.

Helpful

Alan Brunelle

Topic starter

Jan 13, 2022

Thanks Jared! Very helpful.

I would hope to have at least a small residence at the observatory site. However, there may be times that I will be much farther away.

CS,
Alan

Ruediger

Jan 13, 2022 · Edited: Jan 14, 2022

Hi Alan,

10M is a good advice. I shoot at 2563mm unguided with no issue (GM 2000 HPS II). This is one among many strengths of these mounts e.g. they are perfect for remote operation. If you look for quality they are the very top notch.

CS
Rüdiger

Concise Supportive

Mike S

Jan 16, 2022 · Edited: Jan 16, 2022

Wei-Hao Wang:
Hi,

I would worry that a 12" Newtonian is pushing the limit of Mach2. I put a 12" RC on it and it works well, but the tube is short. For a longer tube and a heavy camera (if you have one), the length can be an issue.

I picked Mach2 because I am doing mobile imaging. If you have a fixed observatory, a 1100 would be much more suitable, I think. Even without encoders, a 1100 should do the tasks you mentioned just fine (but you need to ask others to confirm this). And it seems you can get a 1100 faster.

Cheers,
Wei-Hao

I apologize if this is hijacking the thread... I am on the waiting list for the Mach2 which I would use for mobile imaging. Is there any value in spending the extra $$ for the encoders since this mount will not be fixed to a pier?

Thanks,
Mike

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Ruediger

Jan 16, 2022

Hi Mike,

there is an advantage. Tracking is more precise since you compensate some errors e.g. PE. If you do PEC on mounts without encoders it is an estimated extrapolation. If you have encoder you precisely measure the error at any time and you can compensate it in real time.

Also there is the advantage you can open the clutches and you are still aligned.

There is a quite similar discussion on CN. There are many value information given for everyone who is evaluating the value of such high end mounts.

https://www.cloudynights.com/topic/798092-why-buy-a-10-micron-mount/

CS
Rüdiger

Helpful Concise

Wei-Hao Wang

Jan 16, 2022 · Edited: Jan 17, 2022

I do mobile imaging with Mach2GTO for exactly a year now. I think the absolute encoders do add values to it.

First, I always guide. So in terms of suppressing PE, I don't find the encoders that useful. I guide the PE off anyway.

One advantage that the high-resolution encoders add is rapid and accurate response, particularly the elimination of Dec backlash and Dec stickiness. My experience with my previous mount has been increasingly painful over the years, because of Dec backlash and stickiness. I had to watch the PHD2 graph all the time in case Dec guiding causes troubles. This is not an issue at all on Mach2. It does exactly what the guider tells it to do, in real time. I don't need to watch it any more. Just let it start guiding, and I can take rest and come back in an hour or two. Totally hands-off, very easy.

Another advantage is getting rid of the finder scope, even at a focal length of 2400mm. As long as the the tripod is reasonably leveled and the mount is polar-aligned, Mach2 knows where it is pointing at as soon as it powers up. This can save some time especially when using narrow-band filters. Even when doing broad-band imaging, this is quite convenient.

Some people said that the encoders also help to real-time compensate the vibration caused by wind. I don't feel that. Perhaps I never encounter a wind that's not too strong for this to work.

For the two advantages I mentioned above, is it worth the cost? That I can't answer for you. I can only say that I like it a lot.

Hope this helps.

Cheers,
Wei-Hao

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Marcelof

Jan 16, 2022

Mike S:
I apologize if this is hijacking the thread... I am on the waiting list for the Mach2 which I would use for mobile imaging. Is there any value in spending the extra $$ for the encoders since this mount will not be fixed to a pier?

Thanks,
Mike

You do not have that option. Encoders are an integral part of the Mach 2, there is no Mach 2 without encoders.

For an AP mount without encoders you would have to look for a used Mach 1 or one of the larger ones like the AP1100 (but for the price, it would not really be worth it).

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Mike S

Jan 16, 2022

Wei-Hao Wang:
I do mobile imaging with Mach2GTO for exactly a year now. I think the absolute encoders do add values to it.

First, I always guide. So in terms of suppressing PE, I don't find the encoders that useful. I guide the PE off anyway.

One advantage that the high-resolution encoders add is rapid and accurate response, particularly the elimination of Dec backlash and Dec stickiness. My experience with my previous mount has been increasingly painful over the years, because of Dec backlash and stickiness. I had to watch the PHD2 graph all the time in case Dec guiding causes troubles. This is not an issue at all on Mach2. It does exactly what the guider tells it to do, in real time. I don't need to watch it any more. Just let it start guiding, and I can take rest and come back in an hour or two. Totally hands-off, very easy.

Another advantage is getting rid of the finder scope, even at a focal length of 2400mm. As long as the the tripod is reasonably leveled and the mount is polar-aligned, Mach2 knows where it is pointing at as soon as the it powers up. This can safe some time especially when using narrow-band filters. Even when doing broad-band imaging, this is quite convenient.

Some people said that the encoders also help to real-time compensate the vibration caused by wind. I don't feel that. Perhaps I never encounter a wind that's not too strong for this to work.

For the two advantages I mentioned above, is it worth the cost? That I can't answer for you. I can only say that I like it a lot.

Hope this helps.

Cheers,
Wei-Hao

Thank you - very helpful. At the end of the day, the cost of the encoders compared to the overall cost - makes sense to purchase.
mike

Mike S

Jan 16, 2022

Mike S:
I apologize if this is hijacking the thread... I am on the waiting list for the Mach2 which I would use for mobile imaging. Is there any value in spending the extra $$ for the encoders since this mount will not be fixed to a pier?

Thanks,
Mike

You do not have that option. Encoders are an integral part of the Mach 2, there is no Mach 2 without encoders.

For an AP mount without encoders you would have to look for a used Mach 1 or one of the larger ones like the AP1100 (but for the price, it would not really be worth it).

I did not realize that - I thought they were an option. Thanks for clarifying.
mike