Mosaics and how to work out where to put the next pane

[swag72]

Normally my camera is orientated at NSEW and so if I end up doing a mosaic I use the excellent programme EQMOSAIC and with a mouse click I am at my next pane with a specified overlap - No problem.

My question with mosaics relates to when the camera is no longer orientated as NSEW for framing purposes say. In this case, EQMOSAIC continues to move my image in the NSEW direction, which does not correspond at all to where I *want* it to go! Try as I might for over an hour last night I couldn't work out how to continue my mosaic, and so in a huff I reorientated the camera and will ditch the previous nights data and start the mosaic again.

How do you do it? I certainly couldn't manage it!

[Psychobilly]

I used to stick with RA or Dec orientation unless a skewed target would fit in a single frame... M31, NAN & Pelican etc... I made up a set of 360 degree scales in CorelDraw that I could then scale to wrap around any diameter part in the optical train...

It will be interesting to find out if EQMosaic can do it... I will have a look what SB's TheSky can do it has a mosaic function it I used to use that to generate RA/Dec cords for the centres of each pane

Peter...

[ollypenrice]

I don't have EQ mosaic (though it sounds nice!) so here's what I'd suggest when not orthogonal.

Model the mosaic in a planetarium. I use SkyMap Pro but there are lots. Set the model camera angle you need.

Note the centre point of each panel and write down the RA and Dec of each.

For the first image be sure that the camera angle on the scope matches the model.

Slew to the RA and Dec co-ordinates of the appropriate panel.

For greater accuracy I'd recentre the GoTo on a nearby star before the slew.

Olly

PS I have gone so far as to use a spirit level with an angle finder to set the camera to the right angle first in the daytime. Level the counterweight bar first then use the level and angle finder together to set the camera.

[swag72]

Thanks Peter for that. Glad that I'm not the only one who likes to keep it all orthogonal!

Cheers Olly - That's a little bit of re-reading and working out, but I shall persevere with it. Looks like my framing was still off last night and I've probably made my mosaic 2 panes larger than I had originally hoped for.

[opticalpath]

What Olly said .... work out in advance with a planetarium program (I use CdC) displaying the angled camera FOV box and surrounding area for each pane in turn. I take a screen-grab of each page as I go and save these as a series of reference images that I can use later to refine the positioning for each pane, comparing them to short-exposure binned trial frames of each pane. (Drop the ref. images into PS layers and inspect to confirm you have suitable object coverage and overlaps.) After that at capture time, I usually just eyeball it, taking trial exposures of each frame, noting star positions near the edge of the FOVs and comparing to the ref. images as a guide to correct positioning.

If it's a big/ more complex mosaic, RA and Dec of the centre of each frame can be read off the planetarium program and used to get you close with GOTO as Olly described. If your GOTO allows you to define user objects, you could even set up the frame-centre positions in advance as user objects called Pane1, Pane2 etc. then GOTO those in turn. But I'd still take short binned test exposures and compare them to the ref. images to make sure I'm close to plan before the imaging run.

Adrian

[swag72]

I really am going to have to change my system. I'm more of a 'oh dear, this target doesn't fit in one frame' sort of girl and my planning beyond what I am going to image next is zero. When a target's too big I go to EQMOSAIC and just make it happen, with no thought to framing and what I am ultimately aiming for, beyond trying to make something fill a frame or two.

[Psychobilly]

Now I am home I was able to check it out...

SB's TheSky6 allows you to specify the Number of Rows, Columns, Percentage Overlap, Offset Angle and Centre of Mosaic RA and Dec , and FOV based on the Sensor and Scope and then generates the mosaic with Centre Points for each frame.

Peter...

[Gina]

I have a list of DSOs with their sizes and which scope or lens focal length would be best for a single image coverage. So far I have only done single images though I did have a go at mosaics some time back with the DSLRs.

Here's the list for the 314L+ - now I'll need to do one for the 460EX

[ollypenrice]

I really am going to have to change my system. I'm more of a 'oh dear, this target doesn't fit in one frame' sort of girl and my planning beyond what I am going to image next is zero. When a target's too big I go to EQMOSAIC and just make it happen, with no thought to framing and what I am ultimately aiming for, beyond trying to make something fill a frame or two.

Then don't get involved with O'Donoghue, who doesn't consider something a mosaic till it has thirty panels... How did I get involved with this mania??? Get me outta here!

Olly

[swag72]

That sounds interesting Peter - Scurries off to have a look!!

I've got something similar Gina, so I know what should fit in one frame, but there's a couple of things that I want to do that are a little on the larger size!!

Thanks for the tip Olly!!! I think I'll be safe from Tom's mosaics, they are great to look at though.

[Psychobilly]

If you want anything worked out let me kniw...

Sent from my GT-I9100 using Tapatalk 4 Beta

[swag72]

If you want anything worked out let me know...

Thanks Peter

[Catanonia]

Sara,

Looks like you found my PI video on how to do these mosiacs. It isn't very clear, but I am glad the video worked for you.

Cat