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So after much faffing around, I think I've almost eliminated the eggy stars issue. When I zoom REALLY close, I can see they're not pinpoint like they should be, so a few more tweaks required but it's usable I think. (I think the issue was for some reason SGPro had my Latitude as being 53 degree's SOUTH. My PA was also quite far out for some reason but I'm going to tweak that again).


So here we have NGC6888. Ha captured on NYE last year and OIII captured last night (10/9/15). Ha is 3 hours and OIII is 5.5 hours. The OIII is very faint so I might need more data there I think? 


Capture details:


WO Star 71

Linear Fast Reverse

Astrodon 3nm Ha and 5nm OIII

QSI583WSG

Lodestar X2

SGPro

PHD2

Pixinsight for processing


First time I've really tried doing a bi channel combination with a synthetic green channel so comments and criticism are welcome.


Thanks for looking.


Phil


21128400200_9885313783_b.jpgNGC6888 by Phil Wright, on Flickr

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Excellent capture - glad you managed to iron out the majority of your eggy stars! I wonder how you managed to set the latitude to South  :smiley: ?

I do see eggy stars in the bottom right hand corner. Maybe it's the camera sensor alignment rather than PA? Maybe CCD Inspector can help?

Regards

John

Edited by strutsinaction
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John,

I'm fairly certain it has something to do with the guiding/alignment as if it was sensor tilt it'd show up in a 30 second sub as much as a 30min sub and the longer the sub the more pronounced the "eggyness" is. I have just done another integration of all the separate subs from last night without aligning them to see what the motion is and it's the same as before just not as pronounced. I must have my PA wrong but drift alignment and AlignMaster are telling me I'm pretty much bang on. Really confused!

post-37511-0-48870000-1441977814_thumb.j

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That looks like a pretty classic polar alignment error. The field appears to rotate around the guide star (presumably you're using an off-axis guider, which is located just "above" this image?) because the guider forces the telescope to stay pointing exactly on the guide star, and therefore forces the scope to wander around to keep it in the right place. 

How "pretty much bang on" are you with the polar alignment?  The fact the trails are not the same all across the image is probably telling you how far off, and in which direction, the polar alignment is -- but I'm afraid I'm not quite clever enough to work that out from scratch!! :-\  Given they change substantially over the field, it's probably on the order of the field size; within a degree I guess??

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Hi Fraser, I'm thinking polar alignment too and, having thought about it, I think I know where my mistake has been made. I was using align master to check my pa but I was also using sgp to image the star. When I wasn't bang on I probably should've manually slewed to centre the star but I was using plate solving with pinpoint instead. I think that was a mistake.

I'll try again next clear night and manually slew to see because when I used plate solving it was telling me I didn't need to make any corrections when obviously I do!

Sent from my SM-G925F using Tapatalk

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'Eggy stars' (?!)  Yeah right ;)

What a stunning image. I had a crack at this  a while back when I first got my TS 65mm quad but alas, got nowhere near the depth of this (although I did only manage about 2hrs worth).

It's crying out for a mosaic to include the other nebulosity creeping in from bottom right !!

:)

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Thank you.

This image is part of what I'm hoping will pan out to be a rather large 30+ pane mosaic of the whole Cygnus area. Going to take a while I think, but I don't think the stars are going anywhere :)

Sent from my SM-G925F using Tapatalk

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