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EAA with a Dob.....Really?

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#1 JTNX01DC

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Posted 27 January 2021 - 06:12 PM

I've got a 12" Skywatcher dob and intend to get an equatorial platform for automatic tracking. Mostly interested in DSOs, not so much moon & planets. It seems that cameras need alot of backfocus? My collapsable dob can be set for binoviewers, should that handle the backfocus concern? I also had a look at available cameras, there's billions and billions. I would appreciate any advice on filtering my choices down to between  3 and 5 options. Budget is not my primary concern, but $10k isn't happening :-)


Edited by JTNX01DC, 27 January 2021 - 06:47 PM.


#2 Borodog

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Posted 27 January 2021 - 06:14 PM

I presume you mean an EQ platform, not a wedge. If you really mean a wedge, good luck with that!

 

What is your focal length?



#3 Maritime

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Posted 27 January 2021 - 06:32 PM

DOB?  We don need no stinking DOB!  


Edited by Maritime, 27 January 2021 - 06:33 PM.

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#4 JTNX01DC

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Posted 27 January 2021 - 06:48 PM

1500mm, F5. 


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#5 Rickster

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Posted 27 January 2021 - 06:48 PM

It can be done.  Hold on.  I will look up the links for you.



#6 Borodog

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Posted 27 January 2021 - 06:55 PM

1500mm, F5. 

Can definitely be done. Your issues will be stability and polar alignment of your EQ platform. You want a large sensor with large pixels that will allow a large FOV, soak up light faster at F/5, and be more forgiving of vibration and alignment.

 

FWIW I just posted a thread in Mounts about using SharpCap to better polar align my EQ platform for my Dob (10"). I will report back on how that goes.


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#7 JTNX01DC

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Posted 27 January 2021 - 07:18 PM

Here's a camera w/ big pixels & image area. Am I in the right neighborhood?

https://agenaastro.c...ra-qhy294c.html


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#8 Borodog

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Posted 27 January 2021 - 07:24 PM

I am too much of a novice to provide useful advice on individual cameras, but that is one I am looking at as well for my 1200mm F/4.8 Dob & my 2000mm F/10 C8.



#9 Borodog

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Posted 27 January 2021 - 07:26 PM

The one that has been recommended to me a lot is the 533MC, for what it's worth.



#10 ButterFly

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Posted 27 January 2021 - 07:30 PM

It seems that cameras need alot of backfocus?

Not necessarily.  Many of the larger chip astro cameras have chips very close to the body edge.  I can use my ASI183MC as a two inch eyepiece in a Paracorr.  It has a setting somewhere around B.  Anything set up for visual will focus with this camera.  The distance from the chip to the body is usually published for astro cameras.  For DSLRs, look up the flange focal distance of the model to see how far inside the body the chip is.
 



#11 Rickster

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Posted 27 January 2021 - 07:30 PM

Here is the link:  https://www.cloudyni...g/?hl=dobsonian

 

Since money isn't an obstacle, I would recommend getting a camera with a relatively large sensor.  A small sensor means a small field of view which makes finding objects a pain.  An ASI294 or 533 should do it.  You wont need a cooled version, but you may as well get one.  And although most newbies start out with a color cam (because, yeah, they want to see color), a mono cam is more sensitive and easier to use.

 

 f4.9/1500mm fl (right?) needs precise tracking.   So tracking is going to be your main problem.  You can make your life much easier by reducing sub exposure times (increase optical "speed).  Think a few seconds.  That means a focal reducer.  Unfortunately focal reducers are a bit of a crap shoot.  The answer may be to contact this guy https://www.cloudyni...etup/?p=9298498  He runs a 12" Newt with a high quality ($) focal reducer/coma corrector (ASA) that does an excellent job.  If he doesn't respond to a PM here on CN, he is a regular on the French forum http://www.astronomi...c.php?f=22&t=83

He is fluent in english, so language won't be a problem.  Tell him I sent you.  smile.gif

 

Well, that should be enough to get you started on the right track.  Any more questions?


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#12 JTNX01DC

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Posted 27 January 2021 - 07:39 PM

Awesome, Thanks to all. Joe



#13 fromEarth

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Posted 28 January 2021 - 12:08 AM

It's doable. My setup is SW 12" manual dob + EQ platform + Nexus-II digital setting circle.

Also check these links:

https://www.cloudyni...b/?fromsearch=1

https://www.cloudyni...to-dob-for-eaa/


Edited by fromEarth, 28 January 2021 - 12:22 AM.

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#14 alphatripleplus

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Posted 28 January 2021 - 10:28 AM

Good luck, and let us know how it works out for you.



#15 Borodog

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Posted 28 January 2021 - 12:35 PM

It's doable. My setup is SW 12" manual dob + EQ platform + Nexus-II digital setting circle.

Also check these links:

https://www.cloudyni...b/?fromsearch=1

https://www.cloudyni...to-dob-for-eaa/

Does the Nexus II support 2 & 3 point alignment? How does it know about the EQ platform?


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#16 fromEarth

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Posted 28 January 2021 - 09:43 PM

Does the Nexus II support 2 & 3 point alignment? How does it know about the EQ platform?

I use my SkySafari 5 Pro with the Nexus-II DSC. After 2- or multi-star alignment on SkySafati, you can track your dob (on EQ-platform) under SkySafari's "EQ-platform mode" --- just tracking. Nexus-II and SkySafari do not have any control over my single-axis EQ platform.

 

A good 0.5x focal reducer and/or a big-sensor camera are strongly recommended. 

 

fromEarth


Edited by fromEarth, 28 January 2021 - 09:55 PM.


#17 Borodog

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Posted 29 January 2021 - 09:50 AM

I have not found a good 0.5X reducer that works well with my 10" Dob. Do you have a recommendation for one?



#18 fromEarth

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Posted 29 January 2021 - 10:44 AM

I have not found a good 0.5X reducer that works well with my 10" Dob. Do you have a recommendation for one?

 

My current 1.25'' 0.5x focal reducer is a HighPoint version (a gift from a CN member). It works well with my SW12'' and IMX224 camera.

 

https://www.highpoin...al-reducer-1-25

 

I think GSO, Apertura, HighPoint, and TPO's 0.5x focal reducers are all the same. 

 

I once had a bit cheaper (~ $15) no-brand focal reducer before, but found lots of optical aberrations.

 

fromEarth


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#19 Borodog

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Posted 30 January 2021 - 08:32 AM

Thank you kindly. I think I will pick one of those up. Has to be better than the SVBONY 0.5X, which is probably the same as your no-brand reducer and is terrible.



#20 fromEarth

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Posted 30 January 2021 - 08:49 AM

Thank you kindly. I think I will pick one of those up. Has to be better than the SVBONY 0.5X, which is probably the same as your no-brand reducer and is terrible.

 

You may want to read these threads on 0.5x focal reducers:

 

https://www.cloudyni...ucers-any-good/

 

https://www.cloudyni...focal-reducers/

 

https://www.cloudyni...ducer-asi224mc/

 

fromEarth



#21 JTNX01DC

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Posted 08 February 2021 - 09:06 PM

Tks for all the info, advice and support!  Just ordered a ZWO 294 camera and a ridiculously fast computer, $900 each. Don't tell my wife, lol. Hopefully looking at spirals w/in the weeksmile.gif .



#22 Rickster

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Posted 08 February 2021 - 09:37 PM

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