frugal Posted January 6, 2015 Share Posted January 6, 2015 Where I live, I have a hill ridge running all along my Southern aspect. As a result Ihave not been able to see Lovejoy at all. However it has now risen sufficiently high in the sky that I can have a crack at it. As I have never imaged a comet before, and as I may only have a single chance at it given the awful weather we have been having, I want to maximise my chances.My kit is a AZ-EQ6 mount, with an ED80-DS pro scope. For imaging I have a stock Canon 60D with the Skywatcher 0.85 ff/fr. For guiding I have a Lodestar X2 on an ST80.My questions are:1 - should I guide on the comet, or the stars nearby?2 - What sort of expose lengths should I be going for? I can acheive 600s at ISO400 given my light conditions. The images on the forum seem to range from 15s to 300s with a wide range in between.3 - should I aim to take a stack of images guiding on the comet and then a separate set guided on the backgroud and try to proces them separately and then combine them, or should I just stick to the comet? Link to comment Share on other sites More sharing options...
chris_suffolk Posted January 7, 2015 Share Posted January 7, 2015 Seen a few pics with stacks of 5 images of 30 secs., not necessarily guided, just tracking on the mount - they look quite acceptable to me Link to comment Share on other sites More sharing options...
Skipper Billy Posted January 7, 2015 Share Posted January 7, 2015 If you are using DSS it has a comet stacking mode - you can either stack for the stars, stack for the comet or both (takes a while depending upon the power of your computer). Link to comment Share on other sites More sharing options...
laser_jock99 Posted January 8, 2015 Share Posted January 8, 2015 I've never tried- but theorrtically you could guide on the comet itself. It would be a more useful thing to do if you were planing very long exposures. Link to comment Share on other sites More sharing options...
Uranium235 Posted January 8, 2015 Share Posted January 8, 2015 Your choice, you can go about it two ways - just guide on the comet and have star trails (I think it gives a sense of movement), or first take some subs guiding on the stars - then switch to guiding on the comet so you can get the tail.When it comes to processing you have to make one "stars only" image, then one "comet only" image. Merge the two in Ps as layers and there ya go! Example here:http://www.weatherandsky.com/blog/2013/5/comet-processing-for-non-trailing-stars-and-comet Link to comment Share on other sites More sharing options...
Astrosurf Posted January 9, 2015 Share Posted January 9, 2015 This is a great thread. I've only done a few comets and have forgotten what I did!That's a good link, Rob.Alexxx Link to comment Share on other sites More sharing options...
happy-kat Posted January 9, 2015 Share Posted January 9, 2015 I left it to DSS to sort out my images you get to pick how you want the comet managed there are 3 ways.You first on each image, after registering, mark where the comet is and save repeat for all lights. Then on stacking there is a comet tab (tab only shows if you marked and saved the positions). Link to comment Share on other sites More sharing options...
frugal Posted January 9, 2015 Author Share Posted January 9, 2015 Your choice, you can go about it two ways - just guide on the comet and have star trails (I think it gives a sense of movement), or first take some subs guiding on the stars - then switch to guiding on the comet so you can get the tail.Thanks for the link.When imaging the comet is it a case of "take as long a shot as you can to get the tail, and ignore any star trailing"? Or is there an effective limit for exposure length? Link to comment Share on other sites More sharing options...
Uranium235 Posted January 9, 2015 Share Posted January 9, 2015 frugal, on 09 Jan 2015 - 4:01 PM, said:Thanks for the link.When imaging the comet is it a case of "take as long a shot as you can to get the tail, and ignore any star trailing"? Or is there an effective limit for exposure length?I found there to be a limit of 3min on a CCD @ f4.4 when guiding on the comet (for the tail), otherwise it started to get a bit bloated. You might be able to go for longer on a DSLR, but thats only because of its reduced sensitivity when compared to a CCD.Depends on how desparate you are for the tail. Its there, but its a tough one to capture.The trailing will vanish once youve stacked using sigma clipping, but ensure you have enough subs for it to work (16 as a minimum with DSS). Link to comment Share on other sites More sharing options...
frugal Posted January 10, 2015 Author Share Posted January 10, 2015 The promised broken cloud has turned into "not muchcloud at all", so the scope went out at dark. I had intended to image the comet first and then the background, but after a bit of a mistake I realised that the nice bright comet I was guiding on was not actually the comet. Turns out that I the mounting for my main scope had a bit of slop in it and it was not perfectly aligned with the guide scope. However after some jury rigging it seems to be good enough for the night. I managed to get about 10 subs of the actual comet and 5 of the background before it started to dip below the horizon.I will have to wait until tommorow until I can process the images to see if they are really any good.The other good thing was that my wife and daughter were able to come out and we were all able to see the comet in the binos. My wife and I even managed to spot it very faintly with the naked eye. Link to comment Share on other sites More sharing options...
Carina Lass Posted January 10, 2015 Share Posted January 10, 2015 Lovejoy Q2 is now visible without glass here in SE Queensland (A couple of miles from where Terry (Lovejoy lives) he didn't attend the Club meeting last night so we had a look without him ( he's a member here) .Recommended exposures are about 20-30 seconds with a standard 50mm lens (no tracking) on a tripod which shows the green comet well without too much star trail.On a rig, two minutes will give you a decent colour without too much trailing and allow you to stretch the stack to show a long trail.The trail is now getting interesting as it is getting blown about a bit by solar wind. Dust is now also visible at right angles to the tail if you have clear skies when you take pics.Presently if you go to Aldebaran track East to the next bright star and then South and West a little, you can pick it up easily with binoculars. Looks like a fuzzy ball with a tinge of green - it is bigger than M79 so easy to spot. Link to comment Share on other sites More sharing options...
frugal Posted January 11, 2015 Author Share Posted January 11, 2015 Carina, thanks for that, unfortunately I did not have clear enough skies to see any dust off at 90 degrees. In fact there is quite a lot of halo around the comet head, and I am not sure how much is the comet, and how much is my skies I ended up with 10x300s of the comet. It is too late to process them properly, so I just threw the whole lot into PixInsight and quickly stretched the result to see what might be there.The alignment is obviously out as the head of the comet is a line rather than a point. I also think that the orange and black bars on the right hand side are next doors tree branches as Lovejoy dipped below the treeline I will have to try again when I have a decent amount to time to do so.However I can see some tail which I am really pleased with. Link to comment Share on other sites More sharing options...
Astrosurf Posted January 12, 2015 Share Posted January 12, 2015 That's a lovely shot! Link to comment Share on other sites More sharing options...
Uranium235 Posted January 12, 2015 Share Posted January 12, 2015 Youve got the tail - which is more than what most of us got! I was going to have another stab last night, but it was one of those night where the sky is playing games with you. Looks clear - start puting the gear out, goes cloudy - put it away, then goes clear again.... and so on and so forth!Oh, if you guided on the comet then there is no need to align the images, just stack them without registraton/alignment and it should sort the comet shape out. Link to comment Share on other sites More sharing options...
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