Camera orientation

[ngwillym]

Up until now, I've done planetary, solar & lunar work and dabbled in DSO stuff.

I now want to take the DSO stuff more seriously and am aiming/trying to do both monochrome & LRGB with my ASI 1600MM-Cool. I've also realised thatit might be necessary to collect subs over more than one evening - due to weather and the amount of integration time needed.

Question:- how do you keep the camera at the same orientation over multiple nights? Do you:-

i) leave the camera attached to the scope? - my scope is in an obsy with dehumidifier etc, but the thought of leaving that expnesive bit of kit outside all the time worries me or,

ii) put registration marks on the camera and scope and let the stacking software worry about slight differences in alignment?

iii) something else - all advice welcome.

Thanks

Neil

[Tim]

It's a good question Neil

Personally I leave my cameras attached and in the obsy. I figure they will do worse if I take them inside after running at -20° for hours.

If I have to remove them, putting them back is no problem, I have an adjustable M42 or M50 ring that can be set to any position on the filter wheel, so the camera always screws back on in place.

Before I had these I used arrows cut from insulation tape, one on the camera, one on the scope.

However, most times, and for most targets, I find that a square alignment to the mounts axis works very well indeed, and makes it easy when framing a target as the view either moves up or down, left or right. Also this way, the camera always goes back in the same place, give or take a few pixels, which as you say, the registration process takes care of.

Tim

[ollypenrice]

Square to RA and Dec for me. To get it there, take a sub of about 5 secs while slowly slewing. This will create trails. The angle of the trail is the angle of the camera to RA or Dec. Rotate till the trails align with the chip in either landscape or portrait format.

My kit is never taken apart so I only do this to go from landscape to portrait on occasion.

Olly

[ngwillym]

Thanks guys - I'd completely ignored the slewing method - doh!.

I also always try for alignment with RA & Dec- registration marks on camera & scope, but in future if I've got a forecast of several clearish nights -I'll leave it all attached

[Gerry Casa Christiana]

18 hours ago, ollypenrice said:

Square to RA and Dec for me. To get it there, take a sub of about 5 secs while slowly slewing. This will create trails. The angle of the trail is the angle of the camera to RA or Dec. Rotate till the trails align with the chip in either landscape or portrait format.

My kit is never taken apart so I only do this to go from landscape to portrait on occasion.

Olly

Olly does it make a difference to guiding if the camera orientation is slightly off square to RA or DEC? An interesting thought can I ask what the benefits are apart from knowing where to put the camera. 

Thanks

 

[spillage]

I leave my 1600 attached in a wooden framed cover that I remove when imaging. I always use platesolving to put me back to a previous target. Only the orientation of the guide scope may effect guiding, having the imaging camera as Ollie has describe make things easier to rectify any issue.

This has also helped me as I move some gear around the other day and have guiding issue..forgot I have move my guide scope so can check this when I get home.

[mikey2000]

I just leave the camera undisturbed, attached to the scope.  easy enough with my smallish 150PDS - i don't need to remove the camera to help lift the rig back into the garage.

 

If i remove the camera from the scope, I just use my MK1 eyeball to judge if I put it back into the scop nice and squarely.  I have a reflector so a nice square installation gives diffraction spike lined up with the photo edges.  

 

From night to night, plate solving does the job.  Any minor misalignments get cropped off.   As I can't get my coma corrector 100% truly aligned,  I tend to crop the edges off anyway so this is no great loss.

 

As an aside, I have a similar camera to the OP (1600MM-Cool Pro version with built in DDR buffer).  I've persuaded to give up on LRGB and move on to just RGB with synthetic L.  I can see how this might work but I keep getting clouded out.  Initial results are promising!  (Soon to be uploaded/posted)

[ollypenrice]

On 3/21/2018 at 17:35, Gerry Casa Christiana said:

Olly does it make a difference to guiding if the camera orientation is slightly off square to RA or DEC? An interesting thought can I ask what the benefits are apart from knowing where to put the camera. 

Thanks

 

No, it has no effect at all on guiding precision. It just makes it ten times easier and quicker to add new data at some later time.

Olly

[ollypenrice]

21 hours ago, mikey2000 said:

I just leave the camera undisturbed, attached to the scope.  easy enough with my smallish 150PDS - i don't need to remove the camera to help lift the rig back into the garage.

 

If i remove the camera from the scope, I just use my MK1 eyeball to judge if I put it back into the scop nice and squarely.  I have a reflector so a nice square installation gives diffraction spike lined up with the photo edges.  

 

From night to night, plate solving does the job.  Any minor misalignments get cropped off.   As I can't get my coma corrector 100% truly aligned,  I tend to crop the edges off anyway so this is no great loss.

 

As an aside, I have a similar camera to the OP (1600MM-Cool Pro version with built in DDR buffer).  I've persuaded to give up on LRGB and move on to just RGB with synthetic L.  I can see how this might work but I keep getting clouded out.  Initial results are promising!  (Soon to be uploaded/posted)

The alignment of the camera has no effect on the orientation of the diff spikes on the sky. You could (but you wouldn't!) rotate the camera between each sub and the diff spikes would retain the same orientation on the sky because they are created by the spider vanes. To rotate the diff spikes you would need to rotate the spider vanes - ie the telescope in its rings. The camera angle has nothing to do with this.

I'm not sure what you mean by aligning your coma corrector. It's round...? Because a quick slew to ensure that you are aligned along RA and Dec using the method I mentioned earlier is so easy I really do think it's worth doing so that you don't lose field of view in adding later data.

Olly

[tooth_dr]

Probably a spacing issue @ollypenrice as opposed to a rotational issue 

[mikey2000]

Yep, that's what I meant - a spacing issue. (with my coma corrector).   It seems to be very very sensitive to the last fraction of a mm.    I think my focus tube might be a little tilted too as it's worse in one side/corner than the other.  That's for a different topic.

 

Olly - the geometry of camera orientation vs star spikes etc is definitely a bit mind bending!   I think I follow what you mean now.  I'll have a go the RA/DEC alignment method for camera vs slewing.  Does this always end up with the camera in the exact same rotation in the focus tube?  I'm in the habit of re-using master flat files so I'd prefer not to have to keep re-building the master flat for different camera orientation.