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Best camera solution for an azimuthal mount with goto

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#1 Paulo Marcos

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Posted 03 December 2019 - 06:47 PM

I have a Maksutov 127 GoTo SynScan Skywatcher with azimuthal mount and would like to know what could be the best camera solution for deep sky photography. Something that could take some nice photos not spending much money. What DSLR or ZWO camera should I use. What parameters should I care about regarding this telescope and mount.

#2 kathyastro

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Posted 03 December 2019 - 07:03 PM

Welcome.

 

You are going to have a very hard time shooting DSOs with that scope and an alt-az mount.  At f/12, the scope will require exposures more than twice as long as an f/8 scope, and 9 times as long as an f/4 scope.  And yet, the mount is going to limit you to 30-second exposures.

 

I am not saying it can't be done, or that you shouldn't try.  Just be prepared that it will be difficult, and you may not be pleased with the results.

 

You will need a very sensitive camera.


Edited by kathyastro, 03 December 2019 - 07:03 PM.


#3 zxx

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Posted 04 December 2019 - 12:05 AM

Planet imaging with the ZWO would be the way to go.



#4 Paulo Marcos

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Posted 05 December 2019 - 08:36 PM

Thanks for your help. Could you please be more technical on this? I am new on this and I am trying to get all possible information to make the best decision. Yes, I agree that a ZWO camera with asiair would be a fantastic solution in terms of usability but what would be thet best option for my telescope as there are so many cameras? Some will be too much for this and others will be bad. What calculations should I consider regarding sensor size, sensitivity, shooting times according to the camera and my telescope. It has a go-to that will follow the targets. Why Viking1 was talking about 30s due to mount limitations?



#5 zxx

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Posted 05 December 2019 - 08:55 PM

Thanks for your help. Could you please be more technical on this? I am new on this and I am trying to get all possible information to make the best decision. Yes, I agree that a ZWO camera with asiair would be a fantastic solution in terms of usability but what would be thet best option for my telescope as there are so many cameras? Some will be too much for this and others will be bad. What calculations should I consider regarding sensor size, sensitivity, shooting times according to the camera and my telescope. It has a go-to that will follow the targets. Why Viking1 was talking about 30s due to mount limitations?

What's your budget ? It's difficult to image DSOs with your mount and long FL scope. But a decent scope for planet imaging. Planet imaging is done with video, the ZWOASI120MC is about the cheapest one , Sells for around $150


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#6 zxx

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Posted 05 December 2019 - 09:08 PM

What's your budget ? It's difficult to image DSOs with your mount and long FL scope. But a decent scope for planet imaging. Planet imaging is done with video, the ZWOASI120MC is about the cheapest one , Sells for around $150

You need an EQ mount for long exposure AP. Example, I need 5 min exposures with my 6RC scope at ISO 800 at F9.

 You would need to go maybe 10 min exposures at F12 to get the same data.    After say 30s or so your mount will show field rotation not being an GEM


Edited by zxx, 05 December 2019 - 10:03 PM.

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#7 kathyastro

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Posted 06 December 2019 - 07:19 AM

Why Viking1 was talking about 30s due to mount limitations?

The rotation axis of an alt-az mount is not parallel to the Earth's axis, about which the sky rotates.  So when it is tracking the sky, the field of view seems to rotate.  The amount of rotation varies depending on where in the sky you are pointing, but in general, 30 seconds is all you can get out of an exposure before the rotation begins to show in the exposure. 

 

The only way to avoid the rotation is to use an equatorial mount, in which the rotation axis is parallel to the Earth's axis.  (You can also get a rotator for the camera, but that's more complexity than you want.)


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#8 Paulo Marcos

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Posted 06 December 2019 - 02:48 PM

You need an EQ mount for long exposure AP. Example, I need 5 min exposures with my 6RC scope at ISO 800 at F9.
You would need to go maybe 10 min exposures at F12 to get the same data. After say 30s or so your mount will show field rotation not being an GEM



#9 Paulo Marcos

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Posted 06 December 2019 - 02:55 PM

That means that I will need a sensor that will do the job in 30s. With ZWO type of cameras I can choose accordingly and I will get also more sensitivity to red-h light and less noise if cooled. The difficulty is to find the best choice at the best price. What is the impact mentioned before of the FL of the telescope on this?

#10 kathyastro

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Posted 06 December 2019 - 03:11 PM

What is the impact mentioned before of the FL of the telescope on this?

Focal length will determine the image scale.  That is an artistic decision that is up to you.

 

However, focal ratio is something to be concerned about with a Mak.  Exposure time varies with the square of the focal ratio, all else being equal.  So an f/12 scope will require (12 / 4) ^2 = 9x the exposure of an f/4 scope.  So what you can get in 30 seconds is what a fast scope can get in 3.3 seconds.

 

I know people who have successfully used Maks on alt-az mounts for DSO photography.  But you have to plan with those limitations in mind.  So where I might take a total of 1 hour of exposures with my f/4 Newt, you would want 9 hours of exposures.  That is about 1000 frames at 30 seconds each.



#11 descott12

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Posted 06 December 2019 - 03:34 PM

I think what you should get from this is that photographing DSO's at f12 with an alt-az mount is really not something you can do.  You may want to consider doing some EAA (check out that forum) as the restraints are much lower than for traditional AP and you can get some surprisingly good shots (see the attached example)

 

However, your scope and alt-az mount would work well for planetary photography which is done typically at f20 or even f30 and the exposures are very short (10's of milliseconds) and captured as a video file. For that, the ASI224MC is considered a great choice.

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Edited by descott12, 06 December 2019 - 03:35 PM.


#12 zxx

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Posted 06 December 2019 - 03:36 PM

That means that I will need a sensor that will do the job in 30s. With ZWO type of cameras I can choose accordingly and I will get also more sensitivity to red-h light and less noise if cooled. The difficulty is to find the best choice at the best price. What is the impact mentioned before of the FL of the telescope on this?

Mounting the scope on a GEM or buying or making a wedge would be more practical IMO then buying a cooled camera.

Though starting out learning AP at F12 ,even with a GEM can be challenging 




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