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Orion SkyQuest XT8g suitable for EAA?

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#1 Pcbessa

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Posted 30 January 2019 - 07:50 AM

Hello,

 

I am thinking about buying an Orion XT8 with GoTo system.

 

I know people have done simple EAA on Alt Az mounts with telescopes like the Skywatcher 200P Dobsodian or the Celestron SE8, which have GoTo tracking. The key is doing multiple stacking of exposures limited to 10 seconds.

 

This way one would be able to image several deep sky objects like nebula and galaxies. Though the limitation is rotation of field which limits exposure and a mount not suited for perfect EAA or AP.

 

Are there anyone here doing EAA or AP with this telescope, or a similar one?

I assume the tracking allows to keep the object on the field for a sufficient time for short exposures.

 

One concern is that the weight of the sensor may cause small movements and the tube to move slightly down during imaging.

 

Finally, because I am a true beginner! Can I do stacking of pics taken on different days or do I need to do them all at same time? Do I need to upload each frame to the computer right away during observation or can I do it later from the comfort of home?

 

My idea is buying the XT8g, a focal reducer (not sure if its possible for focusing), a simple EAA sensor (or even in the mid term a simple camera), and start the hobby, of which I have no experience whatsoever/

 

I owned a 60mm refractor for 15 years, so my intentions is mainly visual of DSOs, by going for a much larger aperture (the 8" satisfies my cravings) and introducing myself to EAA by ocasionally imaging some nebula and galaxies. I await advice!

 



#2 jgraham

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Posted 30 January 2019 - 08:57 AM

I would highly recommend taking a peek in the EAA forum (way down towards the bottom) and see what folks are using. Like imaging, smaller tends to be better, but this scope might work when paired with the right camera and you can work within the parameter space that it gives you.

Have fun!

#3 OleCuss

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Posted 30 January 2019 - 09:23 AM

Robrj has done some really good work with a 12" Dobsonian with tracking and the IMX294 camera.  That is more challenging than with the 8" Dobsonian  (because of the longer focal length) so you should be able to do pretty well with the 8".

 

Nothing beats a system optimized for imaging of specific targets but that doesn't mean you can't do pretty well with a non-optimal system even though it might prove more challenging.



#4 Pcbessa

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Posted 30 January 2019 - 04:54 PM

Thanks for your feedback!

 

Does putting a sensor on the Orion XT8g Dobsonian tips the balance of the optical tube, defeating the purpose of imaging?

I also heard stories of putting a 2" 38mm eyepiece on it, tipping the balance of the tube.

 

Anyone knows of this?



#5 OleCuss

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Posted 30 January 2019 - 05:13 PM

Thanks for your feedback!

 

Does putting a sensor on the Orion XT8g Dobsonian tips the balance of the optical tube, defeating the purpose of imaging?

I also heard stories of putting a 2" 38mm eyepiece on it, tipping the balance of the tube.

 

Anyone knows of this?

Well, that likely depends.

 

Some of the astronomical cameras (especially un-cooled CMOS) are fairly lightweight.  They'll not be too much of a problem.  A bit heavier and there might be more of an issue.

 

But you can get some magnets and put them on your OTA near the mirror cell and effectively do some counterbalancing.

 

You may, however, really not need to mess with counterbalancing.  The need for counterbalancing is greatest when you are aiming near the horizon.  But near the horizon is also where our worst imaging occurs so you really don't want to do imaging there anyway.

 

BTW, Orion now sells magnetic Dobsonian counterweights.  They look to be very convenient.


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#6 Pcbessa

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Posted 30 January 2019 - 10:05 PM

One reason also that concerns me is that the XT8g has a noisy GoTo. (The intelliscope PushTo version is silent, but has no autotracking, hence EAA is mostly out of question). I do not want to wake up or scare any neighbors. Otherwise I may consider also buying a Celestron SE6, which has a silent GoTo (but would require a focal reducer for EAA).

 

Regarding the computer system of the XT8g, once you locate an object with GoTo, can I then proceed immediately start autotracking with it and after a while go to another object with Goto and so on, or do I have to align north every time in between? I can't understand how it works.



#7 numchuck

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Posted 31 January 2019 - 12:19 AM

Orion's GoTo Dobsonians are great (I own a XX12g myself) . Simply turn it on and tell it time and location ; and "show" it the postions of 2 stars ; and then it will find and track as many objects as you want , all night long . Get a CMOS camera and download a program called SharpCap . This setup will let you take frames of very short exposure (just a few seconds) and then combine them in SharpCap's live-stacking utility . You will be amazed . Your mount will not track perfectly ; but when your image drifts away from the center , just pause the program and re-center , and resume with live-stacking . Because of the way a Dobsonian mount tracks , you may , in addition to re-centering , also have to periodically rotate the camera in the focuser to keep the image oriented as it was when you started ; but the program will do most of the work for you . Here is a link to show you what to do .

 

https://www.highpoin...ts-dave-barrett


Edited by numchuck, 31 January 2019 - 12:28 AM.


#8 OleCuss

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Posted 31 January 2019 - 05:28 AM

One reason also that concerns me is that the XT8g has a noisy GoTo. (The intelliscope PushTo version is silent, but has no autotracking, hence EAA is mostly out of question). I do not want to wake up or scare any neighbors. Otherwise I may consider also buying a Celestron SE6, which has a silent GoTo (but would require a focal reducer for EAA).

 

Regarding the computer system of the XT8g, once you locate an object with GoTo, can I then proceed immediately start autotracking with it and after a while go to another object with Goto and so on, or do I have to align north every time in between? I can't understand how it works.

numchuck mostly nailed it down for you.  What's more, once you have aligned your GoTo system you can actually manually move your OTA without destroying the alignment (although it may degrade the alignment a bit).

 

I, too, have the XX12g.  I don't find it to be particularly noisy.  I'd be surprised if a well-functioning XT8g GoTo were much noisier.  If I had one which was quite noisy I'd be calling Orion to ask them if they know of a fix for that.

 

A suggestion if I may, however?  If today I were planning to buy something like the XT8g I'd very likely get the Sky-Watcher unit instead (they're both Synta products).  While I like the look of a black OTA, in the dark I'd prefer to have a white OTA (and the cool-down can be better as well).  The re-sale on the Sky-Watcher should be better since the second owner may not be able to get service from Orion - at all.  The upshot is that I'd probably be getting the Sky-Watcher.



#9 Stelios

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Posted 31 January 2019 - 02:01 PM

Moving to EAA forum for a better fit.



#10 RazvanUnderStars

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Posted 12 February 2019 - 09:37 PM

I've used an XT10g a few times. It works well with only one downside which will depend on your location: wind-induced vibrations. The top of a dob, now even heavier with the camera, is at a distance from the mounting point.

 

If there is even a slight breeze (10-15km/h), many of the frames (remember, exposure times are in seconds/dozens of seconds) will be blurry and unusable. Stacking will fail, so you will have to wait a lot longer to get usable frames. If it's a breezy evening, you may find that most frames are unusable. 

 

If you have a sheltered location, it will likely be fine. If not, you'll probably curse that nice breeze. In my case, I tried a few times and since I don't have a dome, I gave up using the dob for EAA.




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