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Gemini GTD E.Fric new mount or?

astrophotography equipment mount
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#51 Speppino

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Posted 08 May 2020 - 10:10 AM

This is part 2 of the same review...........

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#52 Speppino

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Posted 08 May 2020 - 10:11 AM

and finally part 3 with probably the most important part of the review........

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#53 ajaymandke

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Posted 09 May 2020 - 09:50 AM

The mount looks really interesting. Based on couple of reviews in this thread it seems to deliver on specs and can stand upto elements. No lubrication, no tweaking is great.

I have couple of questions and pardon my ignorance about friction drive mechanism:

 

1) Since the drive is very sensitive to imbalance, is there a software based utility to assist in balancing?

2) Also if the power is lost to the mount, is there a risk of OTA collision or are there any clutches to prevent it.

 

Thanks,

Ajay


Edited by ajaymandke, 09 May 2020 - 09:56 AM.


#54 GeminiGTD-Italy

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Posted 09 May 2020 - 10:06 AM

The mount looks really interesting. Based on couple of reviews in this thread it seems to deliver on specs and can stand upto elements. No lubrication, no tweaking is great.

I have couple of questions and pardon my ignorance about friction drive mechanism:

 

1) Since the drive is very sensitive to imbalance, is there a software based utility to assist in balancing?

2) Also if the power is lost to the mount, is there a risk of OTA collision or are there any clutches to prevent it.

 

Thanks,

Ajay

Hi, 

the mount has a clutch system that can fully disengage the drive, making balancing possible, as precise as it can be.

 

When the clutch is engaged, there is substantial resistance of the axes due to the permanent magnet of the stepper motors. This refers to the case when the motors are not powered. It is not like a direct drive mount that has close to zero torque without power.

 

András


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#55 ajaymandke

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Posted 09 May 2020 - 10:13 AM

Hi, 

the mount has a clutch system that can fully disengage the drive, making balancing possible, as precise as it can be.

 

When the clutch is engaged, there is substantial resistance of the axes due to the permanent magnet of the stepper motors. This refers to the case when the motors are not powered. It is not like a direct drive mount that has close to zero torque without power.

 

András

Thank you András,



#56 Gregory

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Posted 10 May 2020 - 12:22 PM

Hello all,

 

I am wondering -- why not use the Pulsar2 controller from the mount

manufacturer?  Is the OnStep controller superior in some way(s)?

 

Gregory



#57 GeminiGTD-Italy

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Posted 10 May 2020 - 12:32 PM

Hello all,

 

I am wondering -- why not use the Pulsar2 controller from the mount

manufacturer?  Is the OnStep controller superior in some way(s)?

 

Gregory

If you do not mind paying 1k EUR more for a few deg/sec higher slweing...why not. Pulsar2 misses sky modeling and the consequent tracking speed correction, although it allows applying corrections as continous offset in both RA and DEC, but someone (an interface) must calculate and send/update these values to Pulsar2.

András



#58 Speppino

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Posted 10 May 2020 - 01:18 PM

Onstep is just cheaper and open source. Not sure it is better then the Pulsar, it does not look like it either. But it does the job on budget and it does it good for now.
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#59 gotak

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Posted 10 May 2020 - 01:31 PM

And if you can code, you can make the changes or fixes you need yourself.
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#60 greg_gorr77

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Posted 14 May 2020 - 05:15 PM

Nico/Seppino,

Any more pics ?

#61 greg_gorr77

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Posted 25 May 2020 - 11:21 AM

Anyway, it looks like the guys are busy ….
I will make sure that I will give you more details about the mount as soon when I get it.
For now, I ve managed to order new counterweights SS309 - 2x 10kg, 1x 5kg, 1 x 3kg.Also, after talking with Berlebach (Marion A++++++),
we've come up with an ideal adaptor for the mount and their tripod Planet,

I have 18volt 3AMP wall charger - as advice from Gemini,
I have few quotes coming for Peli cases...and the last,
I am researching the Gemini recommendation for the controller - OneStep,
also Pulsar 2 as it is more than capable enough to work with it...

#62 nico974

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Posted 26 May 2020 - 06:16 AM

Hi,

 

sorry, no more pics for the moment. The weather here is really bad and I'm gone be father in few days, so I think I won't have lots of time for it after lol.gif 
Nice greg, sure you will love it !
Hope that you will have better skies than me those times ...

 

nico

 



#63 lillo78d

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Posted 26 May 2020 - 10:24 AM

Hi, I contacted insten.eu, and I purchased the control unit plus the bluetooth system, for a couple of days, and I communicated it to them via two emails Vankarem77@gmail.com and through another email that they gave on the site insten .eu @ and then I don't remember, but they don't give any answer, it turns out that they don't contact, and they don't communicate to the e-mails?, because if the payment with paypal was collected,'m sorry for my English , I'm Italiangrin.gif



#64 Speppino

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Posted 26 May 2020 - 10:34 AM

Hi, I contacted insten.eu, and I purchased the control unit plus the bluetooth system, for a couple of days, and I communicated it to them via two emails Vankarem77@gmail.com and through another email that they gave on the site insten .eu @ and then I don't remember, but they don't give any answer, it turns out that they don't contact, and they don't communicate to the e-mails?, because if the payment with paypal was collected,'m sorry for my English , I'm Italiangrin.gif



#65 Speppino

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Posted 26 May 2020 - 10:36 AM

Hi Lillo78D,
Indeed instein is very slow to answer and sometimes he might seem not responsive at all. But you will eventually get it.
Good luck.

#66 greg_gorr77

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Posted 26 May 2020 - 12:30 PM

Hi Lillo78D,
Indeed instein is very slow to answer and sometimes he might seem not responsive at all. But you will eventually get it.
Good luck.

That is not a good news, specially that this new mount needs total/full support and customer service from the controller manufacture... Hopefully this is only temporary...

Edited by greg_gorr77, 27 May 2020 - 02:34 AM.


#67 greg_gorr77

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Posted 26 May 2020 - 12:37 PM

...I'm gone be father in few days,  
 
nico


What's the name? - is it going to be : 111 from Messier Catalogue?smile.gif)))
Congrats smile.gif))

Edited by greg_gorr77, 27 May 2020 - 01:36 AM.


#68 greg_gorr77

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Posted 27 May 2020 - 05:40 PM

...so after very busy day I got several replies - all positive - regarding the OnStep. Current pandemic didn't help and there is significant staff shortage.
All will be back in line very soon.

#69 Bovski

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Posted 02 July 2020 - 05:28 PM

I'm gone be father in few days, so I think I won't have lots of time for it after

 

So do you think you are going to be getting lot's of sleep?


Edited by Bovski, 02 July 2020 - 05:33 PM.


#70 yonafunu

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Posted 07 July 2020 - 04:49 PM

Hi all

 

I’m looking for a new mount after having sold my old but venerable G42 mount from 2010.
I had some strong issue with my pulsar controller (first version) in the south hemisphere. The pulsar goto  doesn’t allow a goto directly to the object without passing through the north (which is a big problem when you have a long optic train with a lot of cables). So my experience with my Gemini mount Is mixed between the very good mechanical quality of their mounts and my bad experience on the electronical side. I had some great photos with my G42 after all theses years after all… a small amount of theses are here : https://www.astrobin.../users/jdurand/

 

I’m allergic to Chinese mounts. Not because of the quality which is starting to get better and better. 

But I prefer now to favour European or American stuff. Maybe it’s dumb but I’ve made the choice to support European/American company over Asian ones. It’s kind of difficult nowadays but when I can, I do.

 

So even if ioptron & co make good mount I want to avoid to buy from them. If I can’t (for budget reason or whatever), I will then.

I’ve seen this new mount from gemini. One point I like is the electronic part. I used to build teenastro and onstep controller. I have one without mount, so I can save some money. I like also the design.

I’ve read the Valerio’s review (thank you ! Very useful).
I know well Nicolas (nico974), a good friend of mine living on the same island before I move out.  (Btw He IS a father now :) I think he is to busy now to spend some time here, but all seems to be good for him. Congrats again Nico !)

 

So why all theses paragraphs. I’m still uncertain about my future mount. The Nico974’s cons afraid me a little, especially the balance part. I will used a fsq106 on it, but I will also used a CDK (260mm) on it. Is there somebody here have used the E.Fric mount with long focal length (> 1300mm) ? Some issue to revealed ?
Is there some general PE graph to show ?

 

I wish to find a mount for my next 15years :)
So if you have any tips to give me, or another mount to advise me in a relative mid-budget (around 4000 euros), I’ll take it :)

 

Clear skies to all !


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#71 Speppino

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Posted 08 July 2020 - 12:03 AM

In my review there is a mention of mounting a C11 on it. The plate solve calculated focal length was about 2940mm and I was able to get 3 min unguided subs with no issues. I am sure I could go longer than that if flexure was not an issue, but the C11 is not forgiving in terms of flexure and on a 5 min subs I can see stars elongation always in the same direction. I confirmed the flexure by doing the same test while guiding with a small 200mm guide scope. The guiding was perfect still, but the 5 min subs show the exact same elongation as the unguided subs. Unfortunately I could not use and OAG because I am not able to see any stars in it with the C11 or when I am lucky to find one, the guide star shape has a very ugly shape that cannot be guided.

I am 100% confident that with your cdk260 you will not have any issue with flexure and you could go unguided for more than 3 min. if you use OAG, then your guide star shape will still be usable and you might go for way longer exposures.

 

Hope this helps,

 

Clear skies......



#72 yonafunu

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Posted 09 July 2020 - 12:37 PM

In my review there is a mention of mounting a C11 on it. The plate solve calculated focal length was about 2940mm and I was able to get 3 min unguided subs with no issues. I am sure I could go longer than that if flexure was not an issue, but the C11 is not forgiving in terms of flexure and on a 5 min subs I can see stars elongation always in the same direction. I confirmed the flexure by doing the same test while guiding with a small 200mm guide scope. The guiding was perfect still, but the 5 min subs show the exact same elongation as the unguided subs. Unfortunately I could not use and OAG because I am not able to see any stars in it with the C11 or when I am lucky to find one, the guide star shape has a very ugly shape that cannot be guided.

I am 100% confident that with your cdk260 you will not have any issue with flexure and you could go unguided for more than 3 min. if you use OAG, then your guide star shape will still be usable and you might go for way longer exposures.

 

Hope this helps,

 

Clear skies......

Thanks for the reply, it helps of course :) 

Something i don't understand is "A pure friction drive has no PE. The tracking precision is under 1" for unlimited time." written in the FAQ on the website. Someone can explain me how a pure friction drive doesn't give any PE? and what is the main reason in comparison with a normal german mount (ie EQ6 or another)?

 

After a lot of comparison, there is still 4/5 possible mounts in my mind. In order of preference : 

 

- An used mach1 (a good friend of mine has one and always be delight of it)

- A E.Fric mount, i have lived with a G42 for almost 10 years, i know the serious of built of the gemini mounts. So i'm trying to convince myself to take another one from Gemini even if there is not a lot of reviews for this mount, which is a kind of brake for me.

- An used AP900 CP3 (or CP4 but too expensive)

- An G11 (not a big fan, i had an old G11 before...it was a solid one but the PE was...meeh.)

- An Ioptron CEM70 (as a last choice)

 

Maybe the most logical thing is to take the cheapest of the list, don't know. It's not that simple to choose in this range of price, there is a kind of gap between the "common" mounts , ie EQ6, Celestron etc and the high end range of mount (10micron, AP, Paramount...) 



#73 EFT

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Posted 09 July 2020 - 02:33 PM

The most logical thing is not to just buy the cheapest.  That is a decision you will very likely regret, particularly since you already see the differences.  The most logical thing is to make the harder decision as to what mount will suit your needs now and potentially for some time in the future (you've already had a mount for 10 years and that is a lot) within the price range you can afford.  That may be the cheapest or the most expensive mount.  This is your most important investment in the hobby at this point (and for quite a while down the road hopefully) and you do largely get what you pay for.  Getting this wrong very simply means a waste of money probably sooner rather than later.  I wouldn't hesitate on the AP choices.  I don't have enough information to judge the E.Fric (hate the name) but you have had good experience with a Gemini mount already and that is important.  If you have the money, I wouldn't bother with other two.

 

A friction drive mount has the potential to have very little, if any, backlash.  As long as a friction drive mount does not have gears at all (e.g., in a servo motor gearbox), then technically it can have no backlash.  Backlash is the mechanical interaction between gears, belts, pulleys, etc.  The E. Fric uses stepper motors so there should be no backlash.  That doesn't necessarily mean there is perfect tracking or other issues that might mimic backlash.  Slippage, for whatever reason, would appear as something resembling backlash.  Stepper motors without encoders are dumb motors that can skip due to defects or misadjustment of the mount and will appear as error that is otherwise unaccounted for without a feedback encoder system.  What might be called PE can exist depending on how far the rollers are off from round or if something gets in and damages the surfaces in some manner (e.g., silicon found in most sand and dust is harder than steel and will cause eventual wear).


Edited by EFT, 09 July 2020 - 04:54 PM.


#74 GeminiGTD-Italy

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Posted 09 July 2020 - 03:33 PM

The most logical thing is not to just buy the cheapest.  That is a decision you will very likely regret, particularly since you already see the differences.  The most logical thing is to make the harder decision as to what mount will suit your needs now and potentially for some time in the future (you've already had a mount for 10 years and that is a lot) within the price range you can afford.  That may be the cheapest or the most expensive mount.  This is your most important investment in the hobby at this point (and for quite a while down the road hopefully) and you do largely get what you pay for.  Getting this wrong very simply means a waste of money probably sooner rather than later.  I wouldn't hesitate on the AP choices.  I don't have enough information to judge the E.Fric (hate the name) but you have had good experience with a Gemini mount already and that is important.  If you have the money, I wouldn't bother with other two.

 

A friction drive mount has the potential to have very little, if any, backlash.  As long as a friction drive mount does not gears at all (e.g., in a servo motor gearbox), then technically it can have no backlash.  Backlash is the mechanical interaction between gears, belts, pulleys, etc.  The E. Fric uses stepper motors so there should be no backlash.  That doesn't necessarily mean there is perfect tracking or other issues that might mimic backlash.  Slippage, for whatever reason, would appear as something resembling backlash.  Stepper motors without encoders are dumb motors that can skip due to defects or misadjustment of the mount and will appear as error that is otherwise unaccounted for without a feedback encoder system.  What might be called PE can exist depending on how far the rollers are off from round or if something gets in and damages the surfaces in some manner (e.g., silicon found in most sand and dust is harder than steel and will cause eventual wear).

I feel the need to correct a few things before they get burned in too deep to be overwritten. What I share is not only my oppinion but rather an engineering fact and it is completely independent of who the manufacturer of the actual product is.

1) decent quality 200 and 400 step steppers have step angle tolerances that will not show up as an error with a gearing of 300 or more.

2) steppers do not skip steps if the device they must move is designed correctly, respecting the torque specifications of the motor. This is why we use them in many fields of engineering. Does your printer have encoder feedback? NO, Does it print correctly? YES

3) A friction drive as  used in an astronomical application has NO SLIP, (in observable quantity).

 

I realize that on the web everyone is a professor but using telescopes for a lifetime and earning a Master's Degree in mechanical engineering are two different things. In other words, if I need medical advice I ask my doctor and not his assistant.

Andras


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#75 vdb

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Posted 12 July 2020 - 02:55 PM

This mount is an engineering marvel, I had no chance to bring it outside yet, maybe in the coming week(s) ... But all I can say is I do not want anything else than friction drive’s, they run for years and years without mechanical wear / issues and have very low and slow PE. Guiding is very easy and not always needed.

 

I was a Mesu fan, but the build quality and responsiveness of Andras made me go for the G53F and now for the E.Fric, which is designed that for people with electronic skills and I guess even mechanical skills is a dream come true ...

 

/Yves


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