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markarian's chain framing frustration


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Hi everyone. Galaxy expert needed.

I used a dslr which I synscan centred on m84, m86 beneath. I can see m84 and m86 in the finder. I now see m84 was a bad choice. I tried trial and error nudging and taking 10 second exposures. I tried relating what I saw through the finder to what was seen in the camera, the latter only stars. Impossible. 3 hours later, I gave up. Anyway, there's a smaller galaxy , 4438 just out of shot below m86. So, 1. I turn the camera 90º. 2. I centre on 4438 so that m84 is top right.  Question: am I heading in the right direction for the chain? Or WHY. Cheers and TIA

m86.jpg

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Without knowing the focal length you shot this with its difficult to determine your FOV, however what you need to do is put M86 into the centre of your field, then move it to the right a bit. That should get you most of the chain. You also need to rotate your camera by 90o.

Here is what you get with a dslr and a 650mm FL newt:

 

M86.jpg

The galaxy in the centre of your image is M84.

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Here's where you are, courtesy of Registar.

I always think it best to have a camera orientated along RA and Dec, either in portrait or landscape, unless there is a good reason not to do so. It makes life easier in many ways. It is easy to do so. Just take a short exposure while slewing slowly. The camera angle is shown by the angle of the star trails.

Olly

markarian combined.jpg

Edited by ollypenrice
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Thanks, that's very neat. I take your point about camera alignment. Presumably then, I'd be nudging left-right-up-down relative to the camera frame rather than nudging and hoping? Is there an easy way to orient the camera in ra-dec, say in the home position?

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Yep, just twist the camera so the bottom of it is parallel to the focuser knobs (for portrait), or exactly 90o either way for landscape. Either way its best done indoors before you take the scope out, otherwise its tricky to get it right in the dark. And once its done - leave it in place so subsequent sessions dont suffer from camera rotation (ie: losing FOV to stacking artefacts) - and it means you can use the same flats on all your data.

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I've just this minute ordered some mini 2 way self adhesive bubble levels intended for caravans and camping cars. I'm going to get my cameras perfectly orientated either in landscape or portrait using the star trail method, then set the counterweight arm and OTAs to horizontal and stick them on the backs of the CCDs. I use a dual scope fast imaging rig and this should allow me to switch between landscape and portrait on both very quickly and fairly accurately.

I'll report back on how well this works.

Olly

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For my 450D, I've lightly counter-drilled one of the marks made by the microfocuser clamp screws on the 2" nosepiece.

One for each orientation.

Even in the dark you can feel when the screw has popped into the depression.

May not be precisely lined up with RA, but it's a very repeatable setup.

Michael

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On 3/29/2016 at 09:02, ollypenrice said:

I've just this minute ordered some mini 2 way self adhesive bubble levels intended for caravans and camping cars. I'm going to get my cameras perfectly orientated either in landscape or portrait using the star trail method, then set the counterweight arm and OTAs to horizontal and stick them on the backs of the CCDs. I use a dual scope fast imaging rig and this should allow me to switch between landscape and portrait on both very quickly and fairly accurately.

I'll report back on how well this works.

Olly

Or you could draw some fine lines on white tape ;) 

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On 29/03/2016 at 09:02, ollypenrice said:

I've just this minute ordered some mini 2 way self adhesive bubble levels intended for caravans and camping cars. I'm going to get my cameras perfectly orientated either in landscape or portrait using the star trail method, then set the counterweight arm and OTAs to horizontal and stick them on the backs of the CCDs. I use a dual scope fast imaging rig and this should allow me to switch between landscape and portrait on both very quickly and fairly accurately.

I'll report back on how well this works.

Olly

Not wishing to teach you to suck eggs, Olly, I'd check that the bubble levels are accurate. On mine I've found that the indication differs depending on its orientation, i.e. level one way, but not when rotated! Also, the sticky pad underneath is a foam.

Ian

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51 minutes ago, Pompey Monkey said:

Or you could draw some fine lines on white tape ;) 

But then what would I do? Hold a normal bubble level next to them? I can do this by holding a normal level against the Atik sitcker which is aligned with the chip but it's a fiddle and only fairly accurate. I'm hoping this will be easier, and won't require me to find my bubble level each time. I mean, I'm a bloke. I can never find anything!!

Marking the FW against the draw tube won't work because you sometimes take the camera off it and it won't necessarily go back in the same orientation.

8 minutes ago, The Admiral said:

Not wishing to teach you to suck eggs, Olly, I'd check that the bubble levels are accurate. On mine I've found that the indication differs depending on its orientation, i.e. level one way, but not when rotated! Also, the sticky pad underneath is a foam.

Ian

Sure, I'm not expecting perfection, just a hand to get close. If the target needs perfect alignment (because it nearly fills the chips) then I'll refine it the usual way. If one or both of these cheapo levels is not at right angles to the other then either the idea won't work or I'll get to remember how far off centre a particular bubble needs to be, and in which direction. I might even write it down on a piece of paper and lose it...

It does occur to me that a classic engineering track rod could be used between cameras to oblige them to rotate together but you'd need to pull out all the cables for it to work. An idea too far, perhaps! 

Olly

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Phew, that takes some following! My camera is still where it was. So I'm not far off if I rotate 90º to where I am and centre on 4438? This is where I get another spatial headache. Instinct tells me I should rotate 90º clockwise. But does it matter? I've 2 batteries and no mains. That gives me about an hour of trial and error. An 8Gb card gives me about 100 shots, although I suppose I wouldn't RAW for trial and error. Just thinking out loud...

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Yessss! Thanks to everyone for the sanity check. I did get a bubble level but only used it to make the RA weight bar horizontal. The biggest clue was in the camera orientation. Gonna see if I can get more detail tonight. Any tips on exposures would be great. This is 8 x 30s in dss with a blur layer subtracted.

IMG_20160402_182606324.jpg

markarians-32bit.jpg

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On 02/04/2016 at 20:16, Uranium235 said:

Looks bang-on now. Leave it there!

As for exposure times, as long as you can manage really (or as long as the camera can handle without getting too much thermal noise... 5-10min each should do it).

OK. It's been cloudless all day [1]. So, just one final check: if I leave the camera there, it's going to be that orientation all night?

TIA

[1] Precictions about what will happen 10 seconds into the first exposure anyone?

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Hi and thanks for the reply. Are you saying that the orientetion changes? Say I start at 23:00 and take 3 snaps. Then it's cloudy. I leave the mount running until 23:45 when it's clear again. Is the chain still in the same orientation? TIA.

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6 minutes ago, alacant said:

Hi and thanks for the reply. Are you saying that the orientetion changes? Say I start at 23:00 and take 3 snaps. Then it's cloudy. I leave the mount running until 23:45 when it's clear again. Is the chain still in the same orientation? TIA.

Hi

If your camera (sensor) is oriented along RA/DEC the framing won't change over time. You can check for yourself in Stellarium if you set up the framing tool with your scope and sensor data.

Louise

Edited by Thalestris24
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Blimey. all I do is similar to Louise. I fire up sky safari, use the camera chip orientation tool, match that to my camera/scope orientation. Use GoTo to hit the centre of the chip image I had on sky safari and then use EOS utilities live view to check and adjust it a bit.

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2 hours ago, Thalestris24 said:

Hi

If your camera (sensor) is oriented along RA/DEC the framing won't change over time. You can check for yourself in Stellarium if you set up the framing tool with your scope and sensor data.

Louise

I think you're overcomplicating things louise :) . Regardless of orientation on an eq, providing its not altered it stays the same

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5 hours ago, Thalestris24 said:

Hi

If your camera (sensor) is oriented along RA/DEC the framing won't change over time. You can check for yourself in Stellarium if you set up the framing tool with your scope and sensor data.

Louise

Ah, OK. So if it's not oriented RA-DEC it is gonna change. That's a good reference. Slowly getting there...

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2 hours ago, Scott said:

I think you're overcomplicating things louise :) . Regardless of orientation on an eq, providing its not altered it stays the same

Ahhgghh! I didn't see this. In one post we have orientation dependence, but now we don't.

Sorry to be a pain. Could I go back to my clouds example? Say I take 3 exposures at 23:00. Then it clouds over. I leave everything as it is; tracking and camera orientation. The sky clears at midnight. I continue with exposure number 4. Question, is snap 4 the same orientation as snap 3?

TIA

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8 hours ago, alacant said:

Ahhgghh! I didn't see this. In one post we have orientation dependence, but now we don't.

Sorry to be a pain. Could I go back to my clouds example? Say I take 3 exposures at 23:00. Then it clouds over. I leave everything as it is; tracking and camera orientation. The sky clears at midnight. I continue with exposure number 4. Question, is snap 4 the same orientation as snap 3?

TIA

@alacant

Tia,  

Yes, the orientation will be the same. as Dave has pointed out, there may be slight rotation due to polar alighnment being off a little but this would also apply to a camera aligned to the RA/DEC.

As you can see, I've deliberately rotated the camera alignment in my planetarium software by 40and taken two pics 10 hrs apart and there is no rotation at all. Ihope this explains it for you.
As others have said, working with a camera aligned RA/DEC is so much easier when it comes to adjusting the camera and especially when you get to doing mosaics :D

 

align 2.PNGalign1.PNG

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13 hours ago, alacant said:

Ahhgghh! I didn't see this. In one post we have orientation dependence, but now we don't.

Sorry to be a pain. Could I go back to my clouds example? Say I take 3 exposures at 23:00. Then it clouds over. I leave everything as it is; tracking and camera orientation. The sky clears at midnight. I continue with exposure number 4. Question, is snap 4 the same orientation as snap 3?

TIA

Hi

Sorry for the confusion! My bad - have a rotten cold at the moment :( But, as I said, you can see for yourself in Stellarium :)

Louise 

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