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Question about motors for mount

astrophotography accessories beginner
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#1 F22Tech

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Posted 19 December 2018 - 12:02 AM

Hello everyone, I have a question.

 

I just purchased a DSLR (Canon T6) and a Single Axis RA motor for my telescope (made for this telescope).

Right now I'm waiting on my T-Ring and T-Adapter to get in the mail so I can do Eye Piece shots.

 

Well my Celestron Astromaster 4.5 has a mounting screw on the top for a DSLR Camera.

So I mount my camera to it, turn the single axis RA motor on and begin to take some exposure shots.

 

The problem is - either the motor isn't fast enough, or it's too slow. There's always star trailing.

Is the motor only made for (eye pieces light gathering)? The reason I ask - is because I'd think the light in the eye piece is more focused, so the speed is directly made for that, or should it not matter so long as it's rotating?

 

(P.S. - yes my scope is polar aligned as well)....

 

The other thing is - I can't seem to find a load balance on what weight the motor can handle anywhere so I'm just not sure if my camera is adding too much weight on it.

 

Do you happen to know if what I'm trying to do with work?

I mean I don't expect to be able to do 1 hour exposures without issues, but I'm just doing normal exposures E.G. - 30 seconds and no matter the speed I set it on - trailing.

 

I mean I can understand if the motor is made for the eye piece light, but isn't that sort of relative? The speed of the Earth rotating should be the same even with a camera on top of the telescope.

 

I also do understand there are dedicated tools for this, but I'm trying to use what I already have, just not sure if I'm fighting a battle that can't be won by using my DSLR on top of my telescope to capture longer exposures.

 

Sorry everyone, I'm just trying to figure this out. So I wrote as much as I could in the initial post to elaborate on things.



#2 bobzeq25

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Posted 19 December 2018 - 12:23 AM

I hate to be the bearer of bad tidings, but this is exactly what I'd expect with that equipment.  The mount is just not good enough for photography.  Too flimsy.  Putting the scope on itself burdens it too much.

 

It's just not intuitive _how_ good the mount has to be.  The pixels are tiny, about .005mm.  Start moving things around by less than 1/1000 of an inch, you've moved them enough to trail the image.

 

Path forward.  I recommend this book.  It starts with using just a tripod for a camera and lens, and goes from there.  Basically piggybacking on the scope is part of the problem.

 

http://www.astropix....bgda/index.html



#3 F22Tech

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Posted 19 December 2018 - 01:31 AM

I hate to be the bearer of bad tidings, but this is exactly what I'd expect with that equipment.  The mount is just not good enough for photography.  Too flimsy.  Putting the scope on itself burdens it too much.

 

It's just not intuitive _how_ good the mount has to be.  The pixels are tiny, about .005mm.  Start moving things around by less than 1/1000 of an inch, you've moved them enough to trail the image.

 

Path forward.  I recommend this book.  It starts with using just a tripod for a camera and lens, and goes from there.  Basically piggybacking on the scope is part of the problem.

 

http://www.astropix....bgda/index.html

I appreciate the insight, I figured it was something like that so I just wanted to make sure. I appreciate the advice. I'll check the book out.



#4 sg6

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Posted 19 December 2018 - 01:31 AM

Mount is not capable of the weight you have on it. Just because there are some potential mounting holes does not mean the weight can be handled. You have added about 1.25Kg maybe 1.5Kg to a mount bearly able to handle the scope.

 

The motor is again not up to the job. People want a motor so they have made one, just not a good one. The purpose of the motor will be to make visual a little less of a problem, objects may remain in view for say 2 minutes rather then drift out in 30 seconds. A reasonable idea but it is certainly not up to AP.

 

Looking at the mount it cannot be polar aligned - I assume that it is the one shown on the Celestron site. There appears no option for a polar scope and so no way to perform the required alignment.

 

Scope reads as a "Bird Jones" design. 1000mm focal length and 457mm optical tube. It has a spherical mirror and a barlow lens built in to the focuser. Not well implimented and in some ways questionable as a mirror and simpler focuser would deliver better.

 

Really the mount is the item that people should purchase, it is easy to replace the scope, not so easy to do the same with the mount, Get a good mount, drop a cheap achro on it to get going, replace scope with a bit bigger achro, move on to an ED or whatever. The stable item is/was the decent mount purchased initially.

 

For AP the mount size required will be around EQ5, EQM-35 in Skywatcher, the iOprton 25 (CEM/ZEQ or whatever) better still the "30". Not sure of the ES mounts. But they need a polar scope and the load capacity needs to be sort of double the weight of the intended scope. And scope includes DSLR. So a 4Kg scope with a 1Kg DSLR is 5Kg so a mount capable of 10Kg is the area to be looking at. And that allows for a little expansion, not a lot but some.

 

Say this as people get a 4Kg scope add a 1Kg DSLR and a 10Kg mount, then the required attachments T-ring and nosepiece and/or flattener are forgotten, as are the tube rings, as is the guide scope, the base to the guide scope and the camera for the guide scope. OTA weight does not include finder and in some instances does not include the focuser.

 

For any form of AP at present your best option I can think of is remove the scope and mount the DSLR direct to the mount. You cannot sensibly image and view as every time you look the whole setup shakes. And getting a series of images to stack will be at least 20 minutes duration, closer to 30 I suggest.

 

AP starts at around $1000-$1200 as a minimum and that is for a fairly basic setup: $600 mount, $400 scope, T-ring, Nosepiece, Flattener better, Intervalometer, Memory cards.


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#5 Sky Muse

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Posted 19 December 2018 - 03:33 AM

The Celestron "AstroMaster" 114mm f/4 kit includes an EQ-1 mount which is the smallest of the series.  Equatorials are preferred for imaging with a camera.  You do have the option of attaching just the camera to the mount, setting the telescope aside.  If you have the 9V-battery motor-drive attached, like this one...

 

3a.jpg

 

...then you can adjust the speed here...

 

3c.jpg

 

I have an "AstroMaster kit, too, and with the same EQ-1(CG-2) mount...

 

kit4.jpg


Edited by Sky Muse, 19 December 2018 - 03:40 AM.


#6 Ian Robinson

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Posted 19 December 2018 - 04:30 AM

Look … it should be OK for very wide field imaging of the Milky Way, constellations etc, even bright comets (when they are around), just loose the telescope that came with it, invest in light weight camera with interchangeable lenses , you'll get nice images if polar aligned properly and keep the subs (exposures) under 5 minutes (or 2 minutes in light polluted spots) and you restrict yourself to lenses shorter than 100mm.



#7 F22Tech

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Posted 20 December 2018 - 02:51 AM

Thanks everyone, I'll head to the hardware store tomorrow and make me a little wooden dovetail bracket thing for my camera.

I have a Canon EOS Rebel T6.



#8 JohnnyBGood

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Posted 20 December 2018 - 09:17 AM

I have issues like that with my old ETX-90 RA sometimes. Its little motor is just not up to the task of handling the camera's weight if the batteries aren't super fresh, even for the basic 30 second exposure photos I can manage with my wife's camera. One question I have is your polar alignment: are you aligned on Polaris or the true north celestial pole? It does make a slight difference. If I recall correctly, your scope has a red dot finder, which makes that sort of alignment difficult. You might be able to come up with a way to use the "drift method" with your current setup, especially if you can view something bright on your cameras view screen and zoom in a bunch. Otherwise, with an inexpensive (<$10) conventional finderscope you can try Dr. Clay's Kochab Clock method. Takes less than 2 minutes. That's what I use and it usually gets me close enough for satisfactory (to me) 30 second exposure prime focus images. My apologies if you already know that, but I was aligning directly on Polaris for a long time before I learned the error of my ways.



#9 bobzeq25

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Posted 20 December 2018 - 10:41 AM

Thanks everyone, I'll head to the hardware store tomorrow and make me a little wooden dovetail bracket thing for my camera.

I have a Canon EOS Rebel T6.

Not wood.  1/1000 of an inch, and all that.

 

Would this work?

 

https://www.telescop...ASABEgJ3UPD_BwE



#10 DrDoug

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Posted 24 December 2018 - 10:19 AM

I have successfully taken shots with a canon T6 attached to my astromaster 130EQand 2x Barlow. Alligning without a built-in play scope was almost impossible, though. It also took at least an hour of fiddling with the motor speed until I didn't get star trails on something like 45 second exposures. It was a great way to learn. I'm now using a small achromat on a somewhat sturdier mount with a polar scope built in and am getting much better results.


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