Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

10 Micron mounts and guiding

  • This topic is locked This topic is locked
35 replies to this topic

#1 JeremyFXDWG

JeremyFXDWG

    Lift Off

  • -----
  • topic starter
  • Posts: 9
  • Joined: 17 Oct 2018

Posted 24 September 2020 - 09:42 PM

I am considering a 10 Micron mount with the main reasoning to do unguided imaging. I was reading another thread where folks were using PHD2 and still doing guiding with the mount. It seemed that results were better guided than unguided. If guiding is still required to get optimal results I am reconsidering the expense of the mount. 
 

I was just wondering what current 10 Micron users are doing and if guiding is improving your imaging?

 

Thanks,

JP


 

#2 Kevin Thurman

Kevin Thurman

    Mariner 2

  • -----
  • Posts: 264
  • Joined: 12 Jul 2020

Posted 24 September 2020 - 10:59 PM

Seems silly to me to spend so much money just to avoid guiding. Is there any reason specifically you can't/won't guide? Even the most expensive mounts benefit from it. All of the best images I've seen ever, even with people that have $100k+ personal observatories, use guiding. From what I hear you can get away without guiding on those 10micron mounts, but if it worked so well, you'd expect more of the top guys would be doing that, no?


 

#3 xthestreams

xthestreams

    Explorer 1

  • -----
  • Posts: 66
  • Joined: 18 Feb 2020
  • Loc: Melbourne, Australia

Posted 25 September 2020 - 03:37 AM

I have to admit I’m attracted to the idea of fewer elements in the image train, hassles finding a guide star, Locking  a hot pixel etc. not to mention saving $2000 in ONAGs and guide cams.

 

In other news, check out the Planewave mounts at iTelescope, they run unguided at massive FLs with old school CCDs - so it is happening daily. Whether it’s any good, another story, curious to get some real world feedback on whether well implemented encoders means a new way or working or if it’s all hype. 


 

#4 SimonIRE

SimonIRE

    Viking 1

  • -----
  • Posts: 720
  • Joined: 16 Dec 2018
  • Loc: South East England

Posted 25 September 2020 - 06:08 AM

I am going to repost what I said in another thread...

 

This line of questioning is very similar to threads you have posted previously.

What I am about to say is my opinion only. Also, because I am becoming interested in using my observatory for science, I am currently evaluating my equipments performance precisely.

The first thing to say is that in order to talk about unguided imaging, you need some objective standard to measure mount performance. You can't simply say "if the stars look good to you then why does it matter". That level of subjectivity just doesn't cut it if your goal is make fair comparisons. Don't get me wrong - there is the whole debate about how "perfect" do you need. That is a valid debate. But it is not valid if you want to make fine judgement claims about one mount over another mount.

 

This leads me to my second point. There are many people here (and on Stargazers Lounge) that claim unguided imaging performances of 20 minutes or more at moderate focal lengths. If you ask them what their threshold for acceptability is, they often say 'my stars look round from corner to corner". I am a Scientist and I work in Computational Imaging Analysis and my job is to analyse images. I can assure you that many of these unguided images have elongated stars. No question. But the imager says they are perfect. This leads people to think that unguided imaging is a reality for long exposures and then get frustrated when they can't replicate this. One person on SGL recently claimed 30 minute unguided imaging with an NEQ6 with an Esprit 120 - this preternatural performance from a mass produced mount is not helpful to anyone who is having difficulty with their mounts tracking.

 

I now have two 10 Micron Mounts. A 2000 and a 3000. To measure performance I look at star eccentricity. There are other ways to do it and other metrics but this is the one I have found useful. I ran experiment after experiment doing unguided imaging up to 30 minutes on targets all over the sky. First at 1200mm FL (LZOS 152) and then at 530mm (FSQ106). The results weren't that good. Subs were inconsistent - sometimes ecc was 0.47-0.50 but often there would be 0.6's and the occasional 0.7. To get consistent results at either focal length, I had to drop to somewhere between 7 and 10 mins. Even then, the occasional sub was thrown out.

 

This year I have used a MX+ and AP 1100 and an ASA DDM85. Only the ASA outperformed my 10 Micron by a fraction and it wasn't on the same night and was at a different location so the comparison isn't even valid.

So I tried guiding. I quickly read the manual, set exposures to 10 seconds. I kept dual tracking (encoder guiding) on. Now I can easily image up to 1 hour and keep my star eccentricity below 0.45 ON ALL SUBS, even under mediocre conditions.

 

So the point I am making is

 

1. Treat claims of unguided imaging cautiously. I have yet to see consistent round stars (as measured objectively - not with eyeballs) on long exposure (>10 min) unguided imaging even at reasonable focal lengths (i.e 500mm or more). You will say...but wait! Here is an example. Yes - you may have a couple of examples (I have many), but can you reproduce this night after night? That matters, a lot. You don't want the lottery of checking your images in the morning. You want to know that on all but the most infrequent night, mount performance has not negatively impacted your subs. There may be other reasons - clouds etc, but it won't be the mount.

 

2. The benefit of a premium mount is not that you can do unguided imaging. It's that the mount will guide so well and with ease. Guiding essentially locks everything down so its consistent. My system is automated now so guiding just gets activated and off it goes. I don't intervene at all. When I started guiding I was fiddling with everything and changing stuff. Once I just let it do its thing, it did. Attached is my guiding graph from last night - this is very average behaviour from my mount under nonideal conditions. It does this night after night after night. I have seen the RMS to drop below 0.3 arcseconds for sustained periods of time when the night is still.

 

So to make the point in a different way - 

 

- If you are the sort of person* who requires that your stars are objectively round by a reasonable measure (in PI, eccentricities of 0.42 or less are considered by some to be visually indistinguishable from perfectly round), then the arguments above may apply. In other words, if you knew that if the sub length and focal length were shorter, your unguided images would improve, then the arguments above may apply. 

 

I have used an example of most of the premium brand mounts this year including a direct drive mount and none could consistently perform, unguided for more than about 15 minutes at focal lengths over about 800mm. 

 

With trivial guiding that requires no supervision and involves no "fear" in the morning that things might have gone wrong, I can image for all practical purposes indefinitely (certainly more than 3600s) and maintain star eccentricities below 0.5. If I want to run 10 min subs unguided, I can with similar results. That is what you are paying for with a 10 Micron mount. 

 

- If you are the sort of person* who is happy to look at your images and understand that actually, the stars aren't round but you don't notice, then the arguments above probably don't apply and I think you may be better served saving your money. 

 

I hope this helps - I have analysed and analysed during lockdown on various mounts and under different conditions and these are the conclusions I have come to. Many people grossly over blow their unguided imaging performance and I think that this makes decisions difficult for people who are hovering over that "guided vs unguided rabbit hole" as they pull the trigger on a new high end mount. 

 

*Both these viewpoints are equally valid. What is not valid is to make claims about mount performance for the purpose of comparing two mounts using a metric that is not fit for purpose. "To my eyes, the stars are round from corner to corner" is perfectly fine if it satisfies you, but in a mount shoot out, it isn't good enough. 


Edited by SimonIRE, 25 September 2020 - 06:13 AM.

 

#5 SimonIRE

SimonIRE

    Viking 1

  • -----
  • Posts: 720
  • Joined: 16 Dec 2018
  • Loc: South East England

Posted 25 September 2020 - 06:26 AM

I have to admit I’m attracted to the idea of fewer elements in the image train, hassles finding a guide star, Locking  a hot pixel etc. not to mention saving $2000 in ONAGs and guide cams.

 

In other news, check out the Planewave mounts at iTelescope, they run unguided at massive FLs with old school CCDs - so it is happening daily. Whether it’s any good, another story, curious to get some real world feedback on whether well implemented encoders means a new way or working or if it’s all hype. 

 

I just went through this site - I could be wrong, but I couldn't see many PW mounts or information showing very long FL instruments being used without guiding. I also don't see any raw data to look at. 

 

I am not saying you are wrong, because I may have overlooked something on the site, but pending a mistake by me, this is the kind of thing that is misleading. 

 

A few weeks ago I used an ASA DDM85 Premium. This is as good a mount as you can buy as an amateur. Using a 1000mm focal length refractor, I was able to get objectively round stars up to about 20 minutes. Using a 4000 mm focal length astrograph, stars were very very subtly elongated at 15 minutes. Now don't get me wrong - this is incredible performance. Really incredible performance. I know people with Skywatcher mounts who are happy with 120s unguided using a 500mm scope. 

 

But I think some people dive into the premium mount market thinking they will routinely "image unguided". Obviously it depends on a lot of factors, but I wouldn't count on it being reliable. Expectations should be managed. I know this very well because I discovered this myself...

 

With a premium mount, you are buying consistency. 


 

#6 xthestreams

xthestreams

    Explorer 1

  • -----
  • Posts: 66
  • Joined: 18 Feb 2020
  • Loc: Melbourne, Australia

Posted 25 September 2020 - 08:19 AM

Challenge away! In god we trust, everyone else bring data! 
 

WRT iTelescope, I am a member but struggle to get imaging time on these specific highly sought after mounts but there are three or four at Siding Springs. https://support.itel...9-telescope-32 

 

I was thinking about reaching out to their chief scientist to get their perspective on this, because agree, the claims for unguided seem too good to be true - hence I keep hesitating and investing time into my ME (0.7 on a BAD) night at 2400mm even with an ASI1600 leaves me pretty happy, but ugh the guiding hassles if when you flip a star ain’t there and I’m asleep... lots of lost data those nights.

 

 

I just went through this site - I could be wrong, but I couldn't see many PW mounts or information showing very long FL instruments being used without guiding. I also don't see any raw data to look at. 

 

I am not saying you are wrong, because I may have overlooked something on the site, but pending a mistake by me, this is the kind of thing that is misleading. 

 

A few weeks ago I used an ASA DDM85 Premium. This is as good a mount as you can buy as an amateur. Using a 1000mm focal length refractor, I was able to get objectively round stars up to about 20 minutes. Using a 4000 mm focal length astrograph, stars were very very subtly elongated at 15 minutes. Now don't get me wrong - this is incredible performance. Really incredible performance. I know people with Skywatcher mounts who are happy with 120s unguided using a 500mm scope. 

 

But I think some people dive into the premium mount market thinking they will routinely "image unguided". Obviously it depends on a lot of factors, but I wouldn't count on it being reliable. Expectations should be managed. I know this very well because I discovered this myself...

 

With a premium mount, you are buying consistency. 


 

#7 xthestreams

xthestreams

    Explorer 1

  • -----
  • Posts: 66
  • Joined: 18 Feb 2020
  • Loc: Melbourne, Australia

Posted 25 September 2020 - 08:20 AM

Oh and AMAZING post. Thanks for sharing. 

I just went through this site - I could be wrong, but I couldn't see many PW mounts or information showing very long FL instruments being used without guiding. I also don't see any raw data to look at. 

 

I am not saying you are wrong, because I may have overlooked something on the site, but pending a mistake by me, this is the kind of thing that is misleading. 

 

A few weeks ago I used an ASA DDM85 Premium. This is as good a mount as you can buy as an amateur. Using a 1000mm focal length refractor, I was able to get objectively round stars up to about 20 minutes. Using a 4000 mm focal length astrograph, stars were very very subtly elongated at 15 minutes. Now don't get me wrong - this is incredible performance. Really incredible performance. I know people with Skywatcher mounts who are happy with 120s unguided using a 500mm scope. 

 

But I think some people dive into the premium mount market thinking they will routinely "image unguided". Obviously it depends on a lot of factors, but I wouldn't count on it being reliable. Expectations should be managed. I know this very well because I discovered this myself...

 

With a premium mount, you are buying consistency. 


 

#8 RazvanUnderStars

RazvanUnderStars

    Viking 1

  • *****
  • Posts: 862
  • Joined: 15 Jul 2014
  • Loc: Toronto, Canada

Posted 25 September 2020 - 10:56 AM

One factor to consider is how long the exposures need to be. Modern CMOS cameras with back-illuminated sensors have high sensitivity and very low read noise so very long exposures, like for CCD cameras, are not needed and if the unguided performance allows for, say, 10-minute exposure then this can work very well. I think that especially with a mobile setup, I'd be wary of using 1-hour exposures in case something goes wrong during it.
 

#9 SimonIRE

SimonIRE

    Viking 1

  • -----
  • Posts: 720
  • Joined: 16 Dec 2018
  • Loc: South East England

Posted 25 September 2020 - 11:02 AM

One factor to consider is how long the exposures need to be. Modern CMOS cameras with back-illuminated sensors have high sensitivity and very low read noise so very long exposures, like for CCD cameras, are not needed and if the unguided performance allows for, say, 10-minute exposure then this can work very well. I think that especially with a mobile setup, I'd be wary of using 1-hour exposures in case something goes wrong during it.

 

Of course, and I doubt anyone would suggest 1 hour subs is a good idea. I mentioned that interval because I tested this out to see what the mounts extremes might be. 


 

#10 psandelle

psandelle

    Soyuz

  • *****
  • Posts: 3,516
  • Joined: 18 Jun 2008
  • Loc: Los Angeles

Posted 25 September 2020 - 11:36 AM

I am considering a 10 Micron mount with the main reasoning to do unguided imaging. I was reading another thread where folks were using PHD2 and still doing guiding with the mount. It seemed that results were better guided than unguided. If guiding is still required to get optimal results I am reconsidering the expense of the mount. 
 

I was just wondering what current 10 Micron users are doing and if guiding is improving your imaging?

 

Thanks,

JP

I'm strictly mobile, and unguided is the best for me. I'm fine guiding (do it on other mounts), but with a rigid wide-field rig (anything from an 80mm f4.4 refractor, to an OS RH200 at f2.4), it's a dream. Totally set-and-forget, and tight stars for the sub length I'm using (I've pushed to 30 minutes just for fun, but keep it to 10-minutes and under because I don't need anything more). Totally fun mount to use; my favorite of all the ones I've used.

 

Paul


 

#11 JeremyFXDWG

JeremyFXDWG

    Lift Off

  • -----
  • topic starter
  • Posts: 9
  • Joined: 17 Oct 2018

Posted 25 September 2020 - 08:03 PM

Thanks for all the feedback and Simon that post was very helpful and it’s great to hear someone with firsthand knowledge.

 

 I will be using a TEC180 in the mount and it has a moderate focal length of 1260mm. It sounds like unguided subs in the 10-15 min range are possible but may still benefit from guiding. If I am going to guide part of me reverts back to an AP1100 without encoders. 
 

I guess it’s a good decision to have. 


 

#12 ahelms

ahelms

    Vostok 1

  • *****
  • Posts: 133
  • Joined: 22 Mar 2015
  • Loc: Chandler, AZ

Posted 26 September 2020 - 01:16 AM

I have a GM1000 with an ODK12 on it (2000mm focal length). It's equipped with a QHY163M CMOS camera and exposures are 120s for broadband and 300s for narrowband both at 120 gain (unity) and 70 offset. I primarily image without guiding though sometimes I do, not sure why I guess I just feel like it...I dont really have a good answer for that one. I have the QHY OAG with a QHY5III178. I get excellent performance unguided -- eccentricity is almost always below < 0.45 with the rare excursion but that is to be expected when exposures are 5 minutes or less. I agree with everything SimonIRE posted. If you NEED long exposures (10+ min) guiding will always help you and make things more consistent. If you only use CMOS and have short exposures then guiding will still help you stay consistent, but you wont have to rely on it much. 

 

One thing I have realized is unguided helped me a lot with imaging the helix nebula recently. At my latitude the highest it gets is 36 degrees elevation. It is so low in the sky that guiding is very inconsistent because of scintillation. Imaging it unguided proved to be very reliable. My final stacked images had an eccentricity of 0.18! 

 

IMO, unguided imaging is a strong nice to have. It certainly isn't a requirement, but man it sure is nice when you only use CMOS cameras and it "just works".


 

#13 barnold84

barnold84

    Vostok 1

  • -----
  • Posts: 133
  • Joined: 15 Aug 2020
  • Loc: Germany

Posted 26 September 2020 - 03:05 AM

Of course, and I doubt anyone would suggest 1 hour subs is a good idea. I mentioned that interval because I tested this out to see what the mounts extremes might be. 

Hi,

 

This thread triggers some questions or thoughts in me. I don't want to lay out a lot of background how I came to these questions so let's get to them directly:

How was it done with the (large) telescopes say 80 years ago? As far as I see and understand it, you HAD to expose for hours in order to collect the amount of light to see details of faint objects. Even though people build huge high-end research grade telescopes, I hardly can imagine that one could bring the mechanics to the precision that one would need or like to have the perfect imaging?

What I've seen in old films is that during exposure, the astronomer looked through the OTA in parallel. Although it's not explained by the narrator, I assume he's doing manual guiding?

 

Maybe somebody knows about this.

 

Björn


 

#14 vdb

vdb

    Surveyor 1

  • -----
  • Posts: 1,571
  • Joined: 08 Dec 2009

Posted 26 September 2020 - 03:25 AM

For me it’s simple take the same mount with expensive encoders and without, the cheaper without encoders will always win because of guiding, always ... on the conditions both systems are mounted and setup in a professional way, meaning both have low to no flex, no moving mirrors etc and that you mounted your guiding infrastructure in a professional manner, if any of those play a role the high end eronder mounts have an even harder time to equal a guided image ...

I admit I was also in the camp of high res encoder no guiding mounts, but it really does not make sense from an investment / quality point of view. But if you can afford and would like to have bragging rights that you can take unguided 15 minute subs at moderate focal length, why not ...

 

/Yves

PS Finding a guide star is not really an issue with a premium mount as you can have guide subs that are long enough and today with the super sensitive cams I still have to come across a target where I was not able to find a guide star.


 

#15 SimonIRE

SimonIRE

    Viking 1

  • -----
  • Posts: 720
  • Joined: 16 Dec 2018
  • Loc: South East England

Posted 26 September 2020 - 04:32 AM

For me it’s simple take the same mount with expensive encoders and without, the cheaper without encoders will always win because of guiding, always ... on the conditions both systems are mounted and setup in a professional way, meaning both have low to no flex, no moving mirrors etc and that you mounted your guiding infrastructure in a professional manner, if any of those play a role the high end eronder mounts have an even harder time to equal a guided image ...

I admit I was also in the camp of high res encoder no guiding mounts, but it really does not make sense from an investment / quality point of view. But if you can afford and would like to have bragging rights that you can take unguided 15 minute subs at moderate focal length, why not ...

 

/Yves

PS Finding a guide star is not really an issue with a premium mount as you can have guide subs that are long enough and today with the super sensitive cams I still have to come across a target where I was not able to find a guide star.

 

This is only part of the story and discounts other benefits you get with a high quality mount (aside from "bragging rights" - if you have that kind of mindset). 

 

A premium mount with encoders will do moderate length unguided imaging without all the hassle of guiding - if you think guiding is easy for everyone, regardless of their mount, then do a search on threads relating to PHD2 to see all the issues faced by regular folk using non-premium equipment. 

 

This thread sums it up pretty well (and this CN member is trying very hard to improve and maximise his set up)

 

https://www.cloudyni...-i-delete-phd2/

 

If you decide to guide with your premium mount, you are more likely to get rock steady results, night on night, month on month, year on year than you will with a mass produced mount. 

 

You may say - "my mass produced mount performs consistently night after night" - Yes. And I am sure you also have perfect stars from "corner to corner" without guiding wink.gif - but the point you are missing is the consistency in manufacturing (and performance) from one premium mount to the next.

 

In other words, across a population of astrophotographers, premium mount performance will always outperform mass produced mount performance. People don't seem to get this - its the difference between a cohort statement and an individual statement. If you are about to buy a new mount and you want to be sure you will get a good sample, it's the former that matters. 

 

When you say

 

"For me it’s simple take the same mount with expensive encoders and without, the cheaper without encoders will always win because of guiding, always ... on the conditions both systems are mounted and setup in a professional way, meaning both have low to no flex, no moving mirrors etc and that you mounted your guiding infrastructure in a professional manner, if any of those play a role the high end eronder mounts have an even harder time to equal a guided image"

 

you have left out one of the most important conditions - performance over many many sessions (not just one single night). 

 

Finally, does the premium mount performance warrant x2 or x3 the price? Is the performance x2 or x3? Of course not, but in all manufacturing, as you approach bleeding edge performance, you pay through the nose disproportionately. 


Edited by SimonIRE, 26 September 2020 - 04:36 AM.

 

#16 RazvanUnderStars

RazvanUnderStars

    Viking 1

  • *****
  • Posts: 862
  • Joined: 15 Jul 2014
  • Loc: Toronto, Canada

Posted 26 September 2020 - 05:53 AM

Manual guiding indeed. An astronomer would stay for hours in a "cage" up the telescope (some telescopes had the focus plane up there), looking through an eyepiece with a reticle put on a star and would use manual controls to keep the star centered. A rather hard job, as it was done in the cold and no bathroom breaks. There is a wonderful book, recently published, about what working in an observatory was/is like, see https://thelaststargazers.com/. But don't want to go more off topic. 

 

This thread triggers some questions or thoughts in me. I don't want to lay out a lot of background how I came to these questions so let's get to them directly:

How was it done with the (large) telescopes say 80 years ago? As far as I see and understand it, you HAD to expose for hours in order to collect the amount of light to see details of faint objects. Even though people build huge high-end research grade telescopes, I hardly can imagine that one could bring the mechanics to the precision that one would need or like to have the perfect imaging?

What I've seen in old films is that during exposure, the astronomer looked through the OTA in parallel. Although it's not explained by the narrator, I assume he's doing manual guiding?

 


 

#17 vdb

vdb

    Surveyor 1

  • -----
  • Posts: 1,571
  • Joined: 08 Dec 2009

Posted 26 September 2020 - 06:53 AM

This is only part of the story and discounts other benefits you get with a high quality mount (aside from "bragging rights" - if you have that kind of mindset). 

 

A premium mount with encoders will do moderate length unguided imaging without all the hassle of guiding - if you think guiding is easy for everyone, regardless of their mount, then do a search on threads relating to PHD2 to see all the issues faced by regular folk using non-premium equipment. 

 

This thread sums it up pretty well (and this CN member is trying very hard to improve and maximise his set up)

 

https://www.cloudyni...-i-delete-phd2/

 

If you decide to guide with your premium mount, you are more likely to get rock steady results, night on night, month on month, year on year than you will with a mass produced mount. 

 

You may say - "my mass produced mount performs consistently night after night" - Yes. And I am sure you also have perfect stars from "corner to corner" without guiding wink.gif - but the point you are missing is the consistency in manufacturing (and performance) from one premium mount to the next.

 

In other words, across a population of astrophotographers, premium mount performance will always outperform mass produced mount performance. People don't seem to get this - its the difference between a cohort statement and an individual statement. If you are about to buy a new mount and you want to be sure you will get a good sample, it's the former that matters. 

 

When you say

 

"For me it’s simple take the same mount with expensive encoders and without, the cheaper without encoders will always win because of guiding, always ... on the conditions both systems are mounted and setup in a professional way, meaning both have low to no flex, no moving mirrors etc and that you mounted your guiding infrastructure in a professional manner, if any of those play a role the high end eronder mounts have an even harder time to equal a guided image"

 

you have left out one of the most important conditions - performance over many many sessions (not just one single night). 

 

Finally, does the premium mount performance warrant x2 or x3 the price? Is the performance x2 or x3? Of course not, but in all manufacturing, as you approach bleeding edge performance, you pay through the nose disproportionately. 

You clearly skipped the part where I said Premium for BOTH encoder and none encoder based ... 

 

I REPEAT both being premium, you just wasted a lot of money on encoders to have less quality subs with encoder based unguided images ...

And most, and I dare say all PHDx guiding problems are none premium mounts or people who do not understand that you need to guide close to (OAG) or in FOV with a guiding setup that is rigid, which in itself is not that expensive to acquire ...

 

/Yves

 

 

/Yves


 

#18 SimonIRE

SimonIRE

    Viking 1

  • -----
  • Posts: 720
  • Joined: 16 Dec 2018
  • Loc: South East England

Posted 26 September 2020 - 07:58 AM

You clearly skipped the part where I said Premium for BOTH encoder and none encoder based ... 

 

I REPEAT both being premium, you just wasted a lot of money on encoders to have less quality subs with encoder based unguided images ...

And most, and I dare say all PHDx guiding problems are none premium mounts or people who do not understand that you need to guide close to (OAG) or in FOV with a guiding setup that is rigid, which in itself is not that expensive to acquire ...

 

/Yves

 

 

/Yves

 

I assume then by "none" you actually mean "non". 

 

Not all mounts come with an option for encoders; the point you are making is predicated on you having the option to add on encoders before purchase. 

 

Also, you are missing the second point I made (again), not comparing like with like and concluding that encoders are irrelevant. You are assuming an encoder-based mount won't guide better than the same mount without encoders if you choose to guide.  


Edited by SimonIRE, 26 September 2020 - 08:02 AM.

 

#19 vdb

vdb

    Surveyor 1

  • -----
  • Posts: 1,571
  • Joined: 08 Dec 2009

Posted 26 September 2020 - 10:53 AM

I assume then by "none" you actually mean "non". 

 

Not all mounts come with an option for encoders; the point you are making is predicated on you having the option to add on encoders before purchase. 

 

Also, you are missing the second point I made (again), not comparing like with like and concluding that encoders are irrelevant. You are assuming an encoder-based mount won't guide better than the same mount without encoders if you choose to guide.  

I’m not missing the point on encoders making the mount better or worse in regards to being guided,, so I’m not missing that point, I just do not have an opinion on that as I have seen it also go in the negative way, but it’s really complex and can only be concluded if one can do the test with 2 of the same mounts with and without encoders and even that would only tell us if it is valid for that specific mount it would not tell us if that would be the case for every encoder no encoder based solution. (One of the reasons 10Micron started with encoders was that they had a mechanical issue with DEC stictation and getting all mounts behave correctly when guiding, they will never admit that though ;-))

 

By premium it’s clear that not all have the option to add an encoders ... but hey that does not change my view (a cheap friction drive mount guided will probably be better as the error is so slow I can take 5 minute subs without guiding), so in that respect I’m not saying it should be the same premium mount, it could be a 10Micron with encoders and a PM without for that matter ... 

 

If you want to do medium focal length based imaging on a fixed setup, and you can afford it why not. It just will not delver better images than guided on the contrary, especially at pixel scales below 0.5.

And for a fixed setup, maybe, but for mobile it makes even less sense, making a model time after time (yeah I know in theory you should not, you could sync back the previous and tweak it, but in reality you need to), I’m already at least 30 minutes into imaging before my neighbour can even think about it’s first sub ... but than again, he could be up and running within 10 minutes and I’m still struggling to find that extra USB cable for the guide camera that I misplaced, I’m so de organised, it’s a wonder I can even get my mobile setup to work. 

 

Maybe I’ll buy one day one just for the fun of it, but I will not be expecting better images, on the contrary. I would buy it as I’m a technology nerd and I admire the skills and thinking that went into a solution like encoder / model based controlled mount.

 

And yeah I have had 10 years of guiding success, my remote has imaged with wide field separate guide scope FSQ based all the way up to OAG and 14 inch reflector I never had an issue with guiding, not once. Till recently when I took it for granted that fixing my guide scope on one of 2 rings was enough, it clearly wasn’t ... that was being to complacent ...

 

So if you have any study/test of a guided versus encoder based analysis, I would love to see that, maybe I’m just to convinced that I’m to blind to see that encoder based mounts are better in taking better quality subs.

 

/Yves


 

#20 Whichwayisnorth

Whichwayisnorth

    Gemini

  • *****
  • Posts: 3,174
  • Joined: 04 Jul 2011
  • Loc: Southern California

Posted 26 September 2020 - 10:55 AM

Everything has to be very very stable and the image scale needs to be below your seeing problems and you can do about 10 minutes unguided with the 1000HPS at about 1000mm focal length.

 

I would not try it with an SCT for example nor a lot of refractors even.  There can be no flex in any component from the ground up.


 

#21 Arcamigo

Arcamigo

    Mariner 2

  • -----
  • Posts: 212
  • Joined: 31 May 2020
  • Loc: Gaston, Oregon, United States

Posted 26 September 2020 - 02:33 PM

This is a good discussion, as I've been on the fence for over a year on whether to invest in a high end mount with encoders or autoguide. Autoguiding seems like an obvious choice if you have an observatory, since it's only an extension of the manual guiding process that it replaced. In this environment, one can work out all the configuration and setup problems once, with occasional periodic maintenance.

 

But if you setup and tear down your equipment every night, all the extra hardware, software, and time can be a deterrent for some, including me. I have read so many threads on this forum regarding so many issues with just about everything that comes after the telescope. A recent one that sticks in my mind was from a member who lost a night of imaging because Windows 10 did an update in the middle of his session.

 

It certainly would be much easier if the mount had sufficient accuracy to do 10 minute subs without all the extra hardware, software, and time required to get it to work each night, and after reading the posts above, it seems like these mounts can do that. I wonder if encoders will one day find their way down into less expensive mounts.


 

#22 endlessky

endlessky

    Viking 1

  • -----
  • Posts: 556
  • Joined: 24 May 2020
  • Loc: Padova, Italy

Posted 26 September 2020 - 02:47 PM

- If you are the sort of person* who requires that your stars are objectively round by a reasonable measure (in PI, eccentricities of 0.42 or less are considered by some to be visually indistinguishable from perfectly round), then the arguments above may apply. In other words, if you knew that if the sub length and focal length were shorter, your unguided images would improve, then the arguments above may apply.

Very interesting post (I didn't quote it all, but I am referring to it as a whole) and some very valid points.

 

I never looked at it this way, since I am still way too far from - and early into the astrophotography game to - consider buying a "premium" mount. I used to think that after spending so much, these mounts would be pretty much "plug and play".

 

Now I know that the actual point of having a mount like this, beside carrying more load, is to have less troubles with guiding.

 

But what about those that build a sky model with hundreds if not thousands of points and then are supposed to correct for atmospheric distortions and pretty much "guide themselves"? Of course, these would have to be meant for a permanent setup (I doubt anybody would do a point model that big if they were tearing down equipment and setting it up each session). Do these still need guiding?

 

And, regarding the quoted statement: if 0.42 is considered indistinguishable from perfectly round, what is the value of eccentricity for perfectly round, just out of curiosity? (Just to have a measure on how close or how far away I am from it. I, too, am a perfectionist and I prefer having a measured number rather than eyeballing things).


 

#23 psandelle

psandelle

    Soyuz

  • *****
  • Posts: 3,516
  • Joined: 18 Jun 2008
  • Loc: Los Angeles

Posted 26 September 2020 - 03:19 PM

I understand money is money (and don't buy anything you can't afford), but I never understood getting a premium mount without encoders (if you're going to get a premium mount anyway). That way, not only do you have a choice between guided and unguided (and there are certain circumstances where unguided will give superior results, not to mention less equipment; one less thing to not work), but if you do guide, you still get to all-sky model/path model (including all the real-time refraction data), and your pulses can be every 10 seconds or so, and just slight nudges. Really easy-peasy and gentle. Anyway, I've tried almost all the premium mounts (and, back to that one post: I even hand-guided manually as a kid...NO THANKS!), and I just wouldn't get a premium mount without encoders and a method of modelling (be it Protrack, APCC, Model Creator, etc.), for the choice of options alone.

 

Paul


Edited by psandelle, 26 September 2020 - 04:42 PM.

 

#24 vdb

vdb

    Surveyor 1

  • -----
  • Posts: 1,571
  • Joined: 08 Dec 2009

Posted 26 September 2020 - 05:51 PM

It depends on what you define as a premium mount, I have friction drives that pure mechanically, are as good or even better then the premium mounts that cost up to 2x and more without encoders (so I consider my mounts premium, I know they don’t have the aura of PM, AP, 10Micron ...), (I can do even unguided imaging without encoders and modelling, 3 to 5 minutes, which is enough in my LP zone not at my dark site) But guiding is easy with a mount that has zero backlash can be setup mobile and be used with moderate wind, friction is very stif and no backlash. Polar alignment does not need to be good, just a polar scope, I timed it last time, from putting the tripod at my imaging spot, to imaging I was up after 15 minutes ... no models to initiate and guiding will take care of the polar mis alignment, especially if you guide in the image (OAG you image narrow field so rotation is no issue)

So good luck with your models and encoders, I never had a need for them and especially with mirrors good luck on modelling that none 100% repeatable flex.  

Did I mention I have a fiction drive in operation for over 7 years without any, I mean any maintenance, and that with at least 100 nights of operation per year. No opening up and cleaning, which I wonder is probably with some of these more complex mount a delicate operation, let alone if the mount is remote, thanks to corona I will not see my setup for about 2 years.

 

So if someone has an analysis of having better subs with encoders, I would love to see that, as mentioned, will I ever buy one, probably but not for the better performance, but the little geek in me ... and when I see proof it is better I would do it sooner rather than later, but I still have not seen a qualified comparison.

 

Ideally a friction drive with high res encoders, the G53F has low res encoders, and the pulsar can use those, but no advanced model. The only Europe based mount I know of is 10Micron so I guess that would probably be my number 2 pick, if I where living in the US I would go for PM or AP ... because service is important, access to service for such delicate systems is a must.

 

/Yves


 

#25 psandelle

psandelle

    Soyuz

  • *****
  • Posts: 3,516
  • Joined: 18 Jun 2008
  • Loc: Los Angeles

Posted 26 September 2020 - 06:21 PM

It depends on what you define as a premium mount, I have friction drives that pure mechanically, are as good or even better then the premium mounts that cost up to 2x and more without encoders (so I consider my mounts premium, I know they don’t have the aura of PM, AP, 10Micron ...), (I can do even unguided imaging without encoders and modelling, 3 to 5 minutes, which is enough in my LP zone not at my dark site) But guiding is

Ideally a friction drive with high res encoders, the G53F has low res encoders, and the pulsar can use those, but no advanced model. The only Europe based mount I know of is 10Micron so I guess that would probably be my number 2 pick, if I where living in the US I would go for PM or AP ... because service is important, access to service for such delicate systems is a must.

 

 

Just a couple things: don’t forget about ASA mounts, direct drive, high end absolute encoders. Also, not sure why you say “delicate systems?” I know 10Microns are anything but with no service required for at least 10 years, and AP’s have been used professionally in rigorous environments (as well as 10Microns and ASAs). So, unsure why you say “delicate.”

 

Paul


 


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics