glowingturnip

oh, I'd hate to hold myself out as an expert in collimation - took me a lot of trial and error to get my 2ndry into the right position, and probably not by approved means ! But here goes, and ppl more knowledgeable than me please chime in. As you know, there are four things that have to be right - the distance along the axis of the scope where the 2ndry is so it's properly pointing through the focusser, the rotation of the 2ndry so it's square to the focusser, then 2ndry mirror tilt and primary tilt. To get the first bit, the position along the scope axis, you will need to be able to see both the left and right hand edge of the mirror or clips (as you look at it through the cheshire) and they should be equally spaced from the edge as they appear in your cheshire. If you can't see the whole of the mirror or all of the clips, maybe you do need the short cheshire. To adjust, slacken off all three of the little screws and then adjust with the big screw in the middle - being very careful not to unscrew it all the way, else the 2ndry will fall out, and being very careful not to touch the glass or let things flop about ! The three surrounding screws push against the mirror base plate and the centre screw pulls it, so if your 2ndry needs to go further inside the tube you would loosen the centre screw, and vice versa. Unfortunately while you're doing this, the 2ndry is obviously completely out of collimation, so even when you think it's right, once you've re-tightened the 3 screws and adjusted the tilt back, you can find you're way off still, or even worse ! A little trick though, you can kind of 'hold' the secondary in collimation while the three screws are loose - hold the base of the mirror (without touching the glass and without bending anything) then as you're looking through the cheshire, tilt the mirror by hand till the crosshairs on the cheshire line up with the spider veins, that's a rough collimation, and while you've got it lined up like that, then check the left and right hand edges of the primary, readjust, look again, etc. Then you need to adjust the rotation of the 2ndry in the tube so that it's square to the focusser. Looking through the cheshire, the mirror should appear round, not oval, and the mirror edges, or clips, should be same distance from top and bottom and the same distance as the left and right ones are. When the three screws are slack, the secondary is free to be rotated around the centre screw. You don't need to adjust the centre screw any more, since you've got the distance right, but now you will be slackening the 3 screws, rotating the mirror by tiny amounts, checking in the cheshire while holding it in collimation again, retightening the 3 screws, finding you've disturbed the rotation whilst tightening them, starting again, repeat, repeat. These two steps are definitely the hardest part, but once done once, it'll hardly ever need doing again. As I said, it took me a whole afternoon, and I started over several times. The two mirror tilts probably need doing every time, and are much quicker with a laser than by eye - it does need to be a properly collimated laser though, and it sounds like you've got a dud one. The Hotech ones are good. Just reading that back, it sounds like a nightmare doesn't it ! and we've not even mentioned coma correction yet. It takes a real masochist to use a fast Newtonian I reckon, mind you, I love mine.

I use a long one with my 200PDS - with the secondary properly positioned I can *just* about see all of the mirror through it, at which point I'd say I'm good. Just putting the cheshire, or even a laser into a focusser that has the two tightening knobs isn't even going to help either, you really need one of those compression collar style focussers to make sure the collimation tool is square in the tube. It's a pain - my 200PDS was well out of collimation when it came new, but it was in Spain, maybe came from handling during shipping. Took me a whole afternoon to get the 2ndry right with the Cheshire, but with that done, it's now just a 5 minute job with the laser, then pop the cheshire in afterwards for a quick pat on the back at how nicely lined up it looks

2018 was my first foray into narrowband imaging - lots more to come hopefully. A fairly light year for me, an unpleasant dose of real life back in September got in the way. Equipment as per sig.

awful lot better than my first ! Careful, it's a slippery slope towards a black hole in your bank account.

very nice ! get a proper feel of the depth of it, the dust in front of the background stars

I've just been delving into narrowband processing for the first time too - if you're using Pixinsight, have a look at this tutorial - really nice way to do it and no magenta halos - http://www.arciereceleste.it/articoli/translations/75-narrowband-color-composition-eng

love it, really like the colours. I'd echo the comments on the flame though, looks curiously flat and yellow compared to the rest of the image

Late to the party with this thread. I got my CCD camera in July 2017 and had my first dabbles with Ha only and HaLRGB. Equipment as per sig. Eagle in Ha, want to add OIII Iris, LRGB Heart of the Heart, Ha Helix, HaLRGB (want to add OIII to this one) and my last ever modded DSLR pic: Happy imaging in 2018 all !

blimey, i'm being quoted from over two and a half years ago ! :-)

apols, I posted the last comment without having seen this last page of the thread and ensuing argument - you'll have Olly saying DSLR's are the wrong camera too soon (kidding ! )

Colour calibration should always do a good job, and i don't think it removes any colour - in this image, use the structure detection turned on so that it picks up all the stars, and play around with the background levels so that the white reference mask it outputs contains only stars and the background reference mask contains only background. (ie no noise is included in either in error) Then the Curves Transformation tool can do a lot to enhance colour - open it up, put the real time on, and then you'll see there are a number of tabs on it - 'R, G, B, RGB/K, etc etc' select the last one called 'S' and that's saturation, drag up the middle of the curve a bit which will raise saturation in the weak saturated areas. You might want to pull the top of the curve back down again if things start getting a bit too garish. You can also go into the 'a' and 'b' tabs and put in a gentle s-shape curve in each to separate out the colours a bit more. You would probably want to do this using a mask for the bright areas only, so you don't saturate background noise. You can kill any excess green with SNCR

oo - here's mine, a year of getting used to my modded 1100d and my new AZEQ6GT: (not deep-sky, but does this count ?) (think I could probably nudge the saturation a bit more on this one)

sshh, I didn't like to mention that ;-)

I've not actually used eqmod really yet, may have to look into it in more detail if I can't resolve my problems another way

90 minutes ! yikes, tl;dw ;-) thanks very much for the pointers though, I will certainly try them all and report back. I should be getting some more scope time in a couple of weeks, so let's see

cheers mate

are you using EQMOD, or an Ascom driver ? If a driver, do you know which one ?

yes, I noticed that, but then I think that's because it's not crossing the axis at all, but is always trying to pull back towards it, so not oscillating around the axis. I need to do some more experimenting - at the moment, I'm thinking that connecting ST4 should see me right. Pompey, how are you connecting your pc to scope, if u don't mind me asking ?

@Robin - yes, you're right, more experimentation needed (I just wanted to carry on imaging at the time, since I was getting decent enough data anyway). I'll certainly see what the guide trace looks like with the guiding output turned off, I hadn't tried that but v good idea. I haven't visually noticed any drifting when unguided. Was also going to give it a go with ST4. I need to reduce the calibration step size to 400 from 800 actually (I changed it from x0.5 guide speed to x1.0 guide speed but forgot to change the calibration steps, so this calibration finished in about 5 steps each in W and E. I definitely could see the guidestar moving in all four directions when it was calibrating though and in equal-ish amounts, returning back to where it started. It's got me thinking though - my previous run had been with a guide speed set on the mount of 0.5x which gave me a strange calibration - the moves in W were very small and it took about 50 of those but the moves back E were much bigger so it completely overshot. The N and S moves were normal. The resulting guide graph looked the same. Once I changed to 1x guide speed though, it calibrated normally as I said, so I assumed that had fixed it. However, it's got me wondering if the same kind of thing is still happening in the background when it's guiding, if the pulseguides in one direction are making the mount move in a much smaller amount than in the other direction meaning it has to play permanent catch-up. Maybe that Celestron ASCOM driver isn't up to the new mount, and I should look at ST4... @Zakalwe - nah, it's not that. The Dec guiding is ok. The polar align wasn't perfect but not far off, so I was seeing a small drift being corrected for by the dec guiding in the North direction, but a spike every time it crossed the axes and tried to correct back South, so i turned the South off in this occasion. Maybe I should look at the other dec algorithms though rather than just turn one direction off, especially when using dither could leave the guidestar on the wrong side. After all, this mount should I guess be backlash-free with its belt drives (?). The problem is with the RA though.

I had the first few proper sessions with my new AZ EQ6 GT Skywatcher mount last weekend and was getting this guiding graph: The Dec graph looks ok, but the RA graph is weird - it is below the axis and all the adjustments in RA seem to be in the same direction. If I stopped guiding, selected a new star and started guiding again, then the RA graph would immediately drop that inch or so again and carry on below the axis. The grouping in the little bullseye scatter graph looks nice, and the resultant stars look decent enough, but what worries me most is that if PHD is always adjusting RA in the same direction to stay on target then that implies to me that the new mount is not tracking at exactly sidereal rate and that PHD is having to do the heavy lifting to keep it on target. If that is the case, I suppose I could train the PPEC when I've got a better PA and use the Sidereal+PEC to stay on target better and then guide from that, but that seems beside the point if I really do have an expensive mount that doesn't track properly. So it's an AZEQ6GT, PA wasn't perfect, was out by about (1',10'), connected via ASCOM through the Synscan handset and RS232/USB converter, Celestron ASCOM Driver 5.0.23, QHY5liic as guide camera, 36 degrees latitude and -13 declination. PHD calibration was uneventful and nicely orthogonal, the star was almost back to where it started. Has anyone seen anything like this before, and have any ideas ? Really hoping I don't have a duff mount... Cheers,

there's this book too - http://www.amazon.co.uk/Observing-Handbook-Catalogue-Deep-Sky-Objects/dp/0521256658/ref=sr_1_2?ie=UTF8&qid=1432798460&sr=8-2&keywords=deep+sky+object+catalogue#reader_0521256658 gives an 'impossibly' detailed and comprehensive list of DSO's. The sections on the big targets, where it breaks them down into individual NGC's by type is pretty interesting, for example if looking at one of your own andromeda pics you can identify individual star-forming regions, clusters etc

very nice image, lovely colours, well done mate

I can see the same dark spot in my newt in daytime, Louise, but doesn't seem to appear at night. It's also linked to the foacl length of the eyepiece, short focal length higher magn eyepieces don't show it