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Diffration spikes on multi night images?


ollypenrice
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I don't image with a Newt but have a question; if you have to come back to an image after having taken out your camera, surely you are going to have to reorientate it with incredible precision in order not to get the second set of spikes slightly rotated with regard to the first? A slight rotation in a spikeless image is neither here nor there. Registar 'just does it.' And since you will need to collimate a Newt each night then you will have to take out the camera. How do folks get on in practice?

Product idea; a little clamp that goes round the EP holder with a notch on it. This can be set at any rotation on the holder. Then you have the male equivalent around the camera or F/W so you can duplicate the orientation each time.

Olly

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I can see the problem occuring in a setup that you have to dismantle every night Olly, but not in a permanant setup as I can't see why you'd have to collimate it every night.

I must say that diffraction spikes are what puts me off a newt or RC for that very reason....images done over several seasons would be very hard to do due to misalignment of the spikes.

Edited by RobH
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Not a clue Olly, but that adapter sounds like a great idea. I've probably found another way around it, I've now taken to leaving my SLR fitting in the scope, I've done it up tighter than I can undo it by hand (twas deliberate, it worked too :icon_eek:), so it's easier just to treat the scope as a large Telephoto lens, but it means the camera is always in the same orientation to the scope. As long as I shoot the same target over a sequence of nights and don't need to adjust the camera angles, it'll work nicely. Not that I have spikes with my frac anyway :D

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It's not a problem unless you rotate the OTA in relation to the mount. The diff spikes will always be in the same direction in relation to the stars no matter how you rotate the CCD.

when the stars are alined by software so will the diff spikes. As long as you dont move the OTA in the tube rings the diff spikes will always line up.

Mike.

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Mike is spot on any rotation of the spikes, due to a rotation of the CCD, will be exactly the same for the stars so as long as the software correctly aligns the stars it will align the spikes as well.

From another post I know Olly does not like diffraction spikes but I find they add an ascetic quality to star field images in particular. So I went for the Epsilon 180 rather than an FSQ.

Andrew

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Ah, of course, it is not rotating the tube tha matters! Thanks Mike. Doh.

FSQ or Epsilon was seriously a tough choice, Andrew. One thing was combining spikes with non-spikes images but another was the critical chip distance issue for visiting cameras.

Olly

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