Uranium235

Then its a process of elimination. If your CC isnt crooked, then your next step is to look at secondary rotation or tilt. But before you try that, just pop your DSLR on with the CC to see if the problem persists (ie: dodgy stars on one side of the field, getting increasingly worse). If it goes away, then it cant be the telescope.

What I mean by using a torch is shining it on one side of the pushfit connection, while looking at the other to see if any light makes it through (around the edges):

From looking at your images its most likely one of three things. Firstly, your corrector is skew-iff, Secondly (depending on angle you have your camera attached) you may have secondary rotation, or the secondary tilt is wrong. My camera is mounted so the bottom edge of the camera is in line with the dovetail bar (not in-line with the focuser lock). That way, if I see any coma on the left or right sides - I know its rotation. A way to check if the corrector + camera is mounted crooked is to first secure is, with one hand grab the dovetail bar and hold the telescope vertically (ie: move it around like it would on a mount). Then, get a bright torch and hold it behind one side of the pushfit connection - now look from the other side... where the corrector meets the 2" pushfit adaptor, do you see any gaps where the light is getting through? (it should be flush... no gaps). If you have a gap, then its time for that third screw, if you have a friend with a bench drill and M4 tap its only a little job - shouldnt take long.

There are any number of causes regarding tilted fields. #1 of these is collimation, collimation and collimation. Yes, I know thats three times - but thats how important it is when trying to get good corners on a larger than average chip #2 Have you upgraded your 2" pushfit adaptor to 3 screws? If you havent, then the coma corrector will be sitting crooked in the drawtube. #3 Are all your adaptors fitting flushly together? #4 If you have done/checked all of the above, then you need to square your focuser (mine was a long way out). You need to get to the point where you dont need to use the tilt adaptor (or only very minor adjustments), but having an image to look at would make things easier for us to work out. If you can reduce it to a minimal level - you can further eliminate it by focusing in the bad part of the field, that helps balance it out a bit better. To help you visualise whats going on, Ive put together this diagram so you can see whats happening in regard to your coma/field correction: (slightly exaggerated for illustration) The red line is what your camera sees, point A is within the tolerance of correction and focus but if you have a tilted field the other side (or one corner) - point B of your image will be either above or below the two white lines. Above the tolerance gives radial distortion, and below giving coma. If the corrector is skew-iff, then your depth of tolerance will be too (ie: the red line might be straight, but the white lines would be the ones that are tilted). I just need to add, that the faster the f ratio - the shallower that tolerance becomes. The best way to get points A and B within that tolerance is by adjustment of the secondary mirror and ensuring everything is fairly stiff so it doesnt sag the focuser. Adjusting camera side (after the corrector) is ok, but if you think about it - the more you adjust, the further out of collimation your telescope going to get (because you collimated it without the imaging train in place).

It aint too bad, I can have it up and running in 20min since the 130 is kept in a fairly cool place. In fact, during the Summer months its more of a "warm up" rather than a cool down.

I used Sony Video Vegas to put it together, the footage was timestretched to speed it up, then the photos, trasitions, pan/zoom fx and text put in as separate tracks. If you've ever used Sony Acid, its very much along the same lines. Jim: Yep, I have wooden stairs to contend with - a real hazard during the winter.... ive almost come a cropper a few times on those, so I have a bag of salt for when it gets a bit icy.

A quick 2014-2015 showcase for the 130pds: Enjoy!

And the funny thing is... a lot of that is what I arrived at independantly last night! It took quite a while to go around with the clone brush and remove the star remnants manually, especially as it was over a four pane mosaic! The only thing I did wrong was to paste the starless version on top of the other, rather than the other way round as you have just described (I'll give it a go later on)... cheers for the tip! To clean up some of the smaller remnants in the outer areas I laid on a really heavy dose of selective NR and dropped the background levels a bit.... still experimental, but its something to do while I wait for the clouds to go away Martin: If you want to have a bash at it, the star removal tool (Ps action) is here: http://astroanarchy.blogspot.co.uk/2008/11/star-removal-ps-action.html

Just messing about with a starless version of my current project (hope to finish the Ha on Thursday): PS: Its quite hard to kill the stars from a newt!

Just a little something thats in the oven.... Only 1 hour per pane at the moment, and still a fair way to go before its up to scratch:

Oh, so youve already got an M48-T2? On further reading, the spacing requirement of the GSO is quite different to any other CC... 75mm if im not mistaken. Meaning that you need to make up about 30mm of spacing, which is roughly one T-Ring, and a 18-20mm spacer (adjustable would be better). The Altair CC is just a rebranded GSO, and they have a set of setup instructions here: http://www.altairastro.com/altair-astro-photo-visual-coma-corrector-and-field-flattener-for-newtonian-reflectors.html Apologies for any confusion, as you wont be needing the adaptor I quoted earlier.

If its the dslr in you sig that you are using, you need the M48-Canon bayonet adaptor - thats all you need to achieve the right spacing. Something like this: http://www.firstlightoptics.com/adapters/skywatcher-dslr-m48-ring-adapter.html

The promised clear sky has arrived, just topping up the Crescent.... a stack of 16 should be good enough if the Moon doesnt wreck it. Im pointing straight up, so there' s a possiblilty I could get away with it.

Looking alright Jim, be on standby from wed onwards - we might me in for some clear stuff!

Pokey pokey! Keepin' the flag flying for the 130: On a side note, its quite interesting what you get when you type "130pds" into Google and click the images tab a lot more astro images than there used to be!

You should boogie on down to SGL XI then, even though there are darker places - the view would make your eyes pop out on a good night!

Only around the zenith, it presents itself as a misty patch/streak. On nights like those I know my data will be good, in fact it was so good last night I havent used any flats for the Tulip (naughty me!). No such luck tonight, its looking a little soupy as the jetstream is bang over us at the mo. So ive decided not to set up as that would only serve to damage the image.

Started this one last night, just one hour per pane (x2) - and by the looks of it, still a way to go yet in order to get the noise down. A victory for fiddling too, as my corner stars are more than OK now