Imaging Question...

[JohnSadlerAstro]

Hi Guys,

I know that this is ridiculous, but NOWHERE can I find the answer to my question... Basically, the problem is this, I want my first DSO image (apart for focusing, test expos, etc.) to be of the Andromeda Galaxy, M31. At the moment, the Galaxy is overhead, which is good for light pollution. However, when I try to point the scope toward it, the bottom of my telescope tube hits the wire that plugs into my tracking motor. There's no way I'm going to be able to shift the scope up in the tube rings enough without smashing something or everything  , so I wondered whether if when I piggyback a DSLR and lens on the scope I could point the camera a right angles to the telescope tube, and then move the scope so the cam points at the right place? Would that wreck the tracking accuracy, being that the mount won't be pointing at the same RA/DEC as the object I want to track? It doesn't matter too much if I can't piggyback like this, as I've made an adapter to attach the cam directly to the mount, but it will mean that I won't be able to correct any tracking errors by watching the object through the scope. I hope that all makes sense.....

John

[Leveye]

You could have a custom tripod pier extension built. That will raise everything and it will clear the connections. Balance is very important so you don't want to just push everything forward in the rings.

[Pompey Monkey]

If you are not guiding, it doesn't matter if your DSLR is pointing in the same direction as the telescope or not.

If you intend to guide, then this advice is invalid.

It would also help people answer the question better if you include details of your set-up in your signature.

[StuartJPP]

Hi John,

As long as the mount is polar aligned and tracking properly and everything is mounted solidly, it doesn't matter where the camera+lens is pointing in relation to the OTA as long as you frame M31 correctly.

It may become an issue if you taking long exposures but in your case I doubt you will be doing that so it shouldn't be an issue.

[Scott]

if you don't intend taking the pic through a scope, I'd be inclined to remove it. when I use camera only on an eq mount, I've got a ballmount mounted on a small dovetail.

You could have a custom tripod pier extension built. That will raise everything and it will clear the connections. Balance is very important so you don't want to just push everything forward in the rings.

Surely the motors are above the extention tube? 

[wimvb]

I agree with Scott. If you don't image through the scope, leave it off. Put the camera directly on the mount.

I use this method with my EQ3-2 GOTO and still use star-alignment. First polar alignment, then star-alignment using the camera as scope. This works fine for most of my scope-less imaging. I make sure that the camera is properly aligned with the mount, This way I keep my GOTO capability.

The camera won't collide with the tripod and meridian flips aren't as critical.

[Pompey Monkey]

The OP's question relates to a camera pointing in a different direction to the telescope and how the (unguided?) tracing accuracy is affected.

Does no-one actually read the posts?

[StuartJPP]

The OP's question relates to a camera pointing in a different direction to the telescope and how the (unguided?) tracing accuracy is affected.

Does no-one actually read the posts?

The OP also says that he has an adapter that can be used without the scope...do people actually read the whole posts?

Hi Guys,

I know that this is ridiculous, but NOWHERE can I find the answer to my question... Basically, the problem is this, I want my first DSO image (apart for focusing, test expos, etc.) to be of the Andromeda Galaxy, M31. At the moment, the Galaxy is overhead, which is good for light pollution. However, when I try to point the scope toward it, the bottom of my telescope tube hits the wire that plugs into my tracking motor. There's no way I'm going to be able to shift the scope up in the tube rings enough without smashing something or everything  , so I wondered whether if when I piggyback a DSLR and lens on the scope I could point the camera a right angles to the telescope tube, and then move the scope so the cam points at the right place? Would that wreck the tracking accuracy, being that the mount won't be pointing at the same RA/DEC as the object I want to track? It doesn't matter too much if I can't piggyback like this, as I've made an adapter to attach the cam directly to the mount, but it will mean that I won't be able to correct any tracking errors by watching the object through the scope. I hope that all makes sense.....

John

[JohnSadlerAstro]

Hi guys,

Thanks for the advice and suggestions!

John

[D4N]

Have you tried flipping the RA axis or does that still cause a collision with the mount?

You can just wait an hour for it to move otherwise.

/Dan

Sent from my iPad using Tapatalk

[cjdawson]

Just a thought experiment but might be relevent....

1. Considering that the mount is an EQ mount.

2. Assuming that the mount is correctly Polar aligned

3. Setup the scope so that the telescope is pointing to a star near the celestial equator.

Here's my thoughts.

The objects track across the sky at the same speed.  It's the rotation of the earth that provides the motion.  All objects rotate around the celestial pole at the same rate (~One revolution per day - sidereal time). The object closer to the celestial equator appears to be moving faster.   Therefore the object will show up tracking errors better than an object near the pole.  With that in mind, the camera will image fewer tracking errors due to pointing closer to the celestial pole, or at least the error will not appear as dramatic.

Using a guidescope on the object closer to the celestial equator, the scope will get feedback to minimise tracking errors.  These corrections will limit the amount of error by being able to make smaller corrections more frequently due to the faster apparent motion of the object further from the pole. This means that the imaging scope should capture a sharper image as the tracking errors will appear smaller in the image.

Summary...

Provided that the object that you are imaging is between the celestial pole and the telescopes pointing direction, surely the tracking could actually be enhanced by pointing the guidescope at a star which is closer to the Celestial Equator.