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EQ Mount with GOTO for a camera setup for DSO imaging

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#1 driven13

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Posted 30 June 2020 - 02:24 AM

Hello all.

 

I have read many articles and help questions on different retail sites but have not been able to find a definitive answer/guide to my situation.

 

I am trying to figure out a relatively affordable (~$600-$700) mounting solution for doing some DSO imaging using my full-frame as well as crop-framed Canon cameras using 400mm lens (max). So I would need tracking that would require an Equitorial mount.

 

I am a bit of a noob to all this so I may be making this more complex than it needs to be.

 

I believe the Skywatcher AZ-GTI is the solution to this as it will work as an Equatorial mount.  This can be connected to SynScan and also to SkySafari App and it becomes a GOTO mount.  I think.  Is this indeed true and is this all I would need for my purposes as described above...??

 

My confusion stems from the fact that folks keep talking about installing a wedge to the setup above.  Is that really necessary when the Skywatcher AZ-GTI has been set to the Equatorial mode...??

 

If it is indeed necessary to get a wedge, I was looking at either the iOptron SkyGuider Pro Camera Mount with iPolar or the Sky-Watcher Star Adventurer Equatorial Wedge Base...???  Or are these totally different things altogether...??  Or do I need both...?? (Sorry, total confusion here.)

 

The only other consideration that I would need to keep in mind is the ease of use for Polar alignment.  I have heard folks like the Polar alignment that the AZ-GTI/SynScan/SkySafari setup provides.  I have also heard folks rave about the iOptron's iPolar mentioned above.  (Once again, I am confused about why I would need both of these pieces.) Given my absolute ignorance about all this, this has to be really foolproof for me.

 

Well, I am hoping that some of you very knowledgeable and experienced folks can clear this very muddled mind.

 

Thank you tons in advance.


Edited by driven13, 30 June 2020 - 02:28 AM.


#2 Hesiod

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Posted 30 June 2020 - 02:47 AM

The mount has to be aligned to Polar axis, so either get the wedge or a very good geared head (tilting the tripod could be doable but potentially risky).
Once mechanically aligned you may set the software to work in eq mode.

Anyway, I would prefer a mount with a counterweight system were using a 400mm Canon prime.
As for the polar alignment, there are many options: if do not plan to bring a PC, a mount with a Polarscope is really handy.
Take also note that at 400mm you need a rather smooth tracking or the autoguiding equipment for good results (or a beefier mount if have the f/2.8 lens)

#3 sg6

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Posted 30 June 2020 - 04:22 AM

The Az GTi is or started as an Alt/Az mount. Initial software didn't have the Eq option in it. By the next release Skywatcher had added it, and I suggest after some "pressure".

 

A few reports seem to imply that Skywatcher somewhat regret the addition of Eq. Basically people now expect a good accurate equitorial mount and rather simply that is not what the mount is, or was.

 

On the retailers sites here they play "safe" and reproduce the Skywatcher blurb, oddly none mention the Eq operation of the mount. Skywatcher are not keen to push it and once I read they said it is not an equitorial or AP mount. The FLO sites states:

"Sky-Watcher's AZ-GTi Wi-Fi Alt-Azimuth mount features a built-in WiFi module, enabling it to to be controlled wirelessly via your Smartphone or Tablet using Sky-Watcher's free SynScan App for iOS or Android."

Note the Alt-Azimuth mount bit, and nothing about Eq.

 

At best you can approximately polar align the mount. There is no polar scope or even similar to perform alignment with on the Az GTi - I have one and believe me there is no "polar alignment" other then point some imaginary line at/towards Polaris. So never expect the often talked of results seen around. Usually when I read that someone expects 120 sec exposures it is because they have read it on Youtube and not/never actually managed it themselves. The other is they manage it once in 6 months, then that is quoted as if the norm.

 

The mount is nice and for light weight and portability very good. Negative is you need power - power for the mount and power for the tablet/phone. And if you have a phone the phone stays with the mount. Don't put phone in pocket and wander off for a few minutes. You lose connection and have to start again.

 

I was happy with a small Alt/Az mount and I use it only as an Alt/Az mount. The "Az" bit in the description sort of indicates the purpose.

 

My arguement is ultimately if you want/need an Eq mount rather obviously buy an Eq mount. Don't buy an Alt/Az mount then add a wedge and try to "construct" an Eq mount from 2 pieces that correct for the lack of Eq ability.

 

My belief is that if Skywatcher could remove the Eq feature they put in, it was basically just rotate by one moter, they would but at any firmware upgrade people would find they have lost a feature.

 

So you can set/select Eq mode. Do not expect Eq mount accuracy. I often see people wanting/expecting 90-120 sec exposures from one that is unguided, and cannot be accurately polar aligned.

 

Unsure of the use of counter weights. On the original concept, Alt/Az, there were none, you just had scope on one side. So in this case I would expect that the counter weight are contributing to the 5Kg max weight. Meaning add a 2Kg weight and you max camera+ is now 3Kg.

 

Sorry to sound negative but just be aware of the limitations. If you can decently accurately polar align the system and are within weight and balance tolerance and if you accept say 40 second exposures then you may well find it all manages what you want and in a small package. But you will need to put in the work.

 

What usually happens is: people add the full max scope weight (or more), then a 2Kg weight, then approximately set the wedge to their latitude and then point the sort of imaginary center line toward Polaris and try 120 second exposures. And it all goes wrong.



#4 driven13

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Posted 30 June 2020 - 01:56 PM

@Hesiod  Appreciate the pointers and they seem to be the general consensus among the community.

 

@sg6 Thank you for the detailed post about the AZ-GTI.  I guess we now know how you really feel....:p

 

But, I think you have convinced me to look away from this mount.

 

I am not looking at super long exposures; maybe something in the 90secs-120secs range for now.  If this can be achieved via an Alt-Azimuthal mount, then that may be the way to go for now.

 

So, any thoughts on the other options that I had mentioned in my OP...??  In a nutshell, looking for a mount that has GOTO feature and relatively easy to setup and run for a novice like me and not having to pay $1000-plus for it.  I think alt-azi mount is the way to go for now, don't you think....??  (Combined weight of camera and lens to not exceed 5-6lbs.)

 

Maybe even one of those mounts from Celestron/Orion/Meade that has the GOTO feature built in to their mounts and it's all more-or-less "press a button"...??

 

Thanks again.



#5 Hesiod

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Posted 01 July 2020 - 12:35 AM

No, alt/az is not the easiest way to go if want to take deep sky pictures (will have issue with "field rotation"); besides, the "push a button and the mount will do all the rest" is for the most a myth...

There are small and inexpensive "goto" equatorial mount such as Skywatcher eq3 and iOptron SmartEqPro which would serve you better than any altazimuthal mount; another option, albeit potentially more pricey, is to get a "star tracker".

The best is probably the Fornax Lighttracker (unless are willing to purchase straight from Japan) but even a lesser unit can fill the bill depending on your equipment: as I said earlier, to handle a 400L f/2.8 you need a substantial device and the Fornax would be your best bet



#6 Waldemar

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Posted 01 July 2020 - 12:46 AM

Why not simply choose for this one: https://www.firstlig...o-synscan.html    SkyWatcher HEQ5 Pro go-to
Within your budget, equatorial, simple, go-to, many made so well established, perfectly serves your goal....

 

edit: not to forget: you will be set for a couple of years to come


Edited by Waldemar, 01 July 2020 - 12:49 AM.


#7 OldManSky

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Posted 01 July 2020 - 01:01 PM

I would suggest the iOptron CEM25P mount.  Costs less than the HEQ5 Pro, has better tracking performance (guaranteed +- 10" PE -- there's no guaranteed spec on the HEQ5 Pro), is really easy to use, and weighs a lot less though it has nearly the same load capacity.  I liked mine very much.


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#8 driven13

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Posted 02 July 2020 - 12:12 AM

Thank you all again for all the valuable advice.

 

The Fornax and the iOptron CEM25P mount does seem like something that I would use for my purposes, even though they are different beasts.

 

Celestron's SkySense seems like a wonderful tool for alignment, as it is all done via the camera and no manual polar alignment required.

 

Food for thought, for sure.



#9 Hesiod

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Posted 02 July 2020 - 12:23 AM

The Celestron Starsense does nothing about polar alignment: its purpose is only to automate the goto initialization procedure, id est the process through which the mount learn to match its own "map" with the real sky.
In truth, at 400mm, the easiest and fastest way to align the mount to the pole is to use a polarscope; if really want an electronic help, either can exploit the guiding equipment (this is the option I like more) or get a dedicated accessory (QHY Polemaster or iOptron iPolar)
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#10 driven13

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Posted 02 July 2020 - 07:00 PM

@Hesiod  Indeed so.  I have looked at so many different kinds of instruments and mounts that they are all blending into one.

 

The Fornax with the Polemaster is the way to go.  But the total cost of this would be US1,200...!!!  I guess all of this becomes a money pit sooner or later.

 

Thanks for all your suggestions and patience.




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