I'd hate to say it, but imaging at F/8 through a Ha filter, you really may want to consider 20 minute subs... The area below the curtain is still pretty dim in your shot, and there is lots of detail to be had down there...
On a brighter note, the detail you've captured in the horse head and in the curtain, including the streamers, looks very - very nice! Looks like you've got that guiding and collimation under control! Was this guided with the OAG or with the ED 80?
Good going mate.. More exposure required, but a fantastic start!
Alex, the actual stacked image was quite a lot brighter but also a little too noisey for my liking. I did a little curves work just to hide the noise a little.
The trouble with longer subs is that something can go wrong and you lose that sub. I could do longer subs in my luminance layer though and that would brighten up the eventual image.
The guiding was conducted through my TSA102 which is now riding on top of the RC via a set of Parrallax Rings.
Marc, yeah probably is a little over sharpened. I did not do much too it though.
In many ways, this image is very close to the one that won the Royal Observatory Greenwich's Astro Photo of the year for 2009 (with one obvious difference being this is in Ha and it was colour). But the interesting thing it deminstrates is the significant enhancement in contrast and hence in detail that Ha seems to make possible. The winning image was praised for its "delicate wispy detail around the horse's head and mane". Having compared the two in that limited respect, it seems to me that Paul's image is even more subtly detailed and executed. Makes me want to have a play with narrowbanding.
Peter.
Yes that's pretty good Paul, a little dark perhaps but that was your intenton by the sounds of it and besides, it is a no brainer to alter if you want.
The repro is brilliant mate.. A little noise is readily acceptable in my opinion, especially if it allows more fine detail in an image...
Great work indeed.
I think you really need to spend more time refining and using the OAG built into your QSI583. The chances of something going wrong in 20 minute subs are minute providing that your guiding is tight and well controlled... I've shot nothing but 20 minute exposures for the last few months worth of imaging and not lost a single sub... Granted, im working with 1/5th the focal length, but I'm also working with a mount thats 1/10th as capable as yours...
Alex, yeah that is true. My guiding is getting pretty tight now and I should give this a try. Working with the OAG is a little more difficult because the stars are so much dimmer and a little harder to find too.
The horsey is very dim and could do with the 20 minute subs mentioned here.
I hate to say it but the star shapes are a little elongated and the circular diffraction pattern around the brighter stars is not symmetrical. I'm not sure what this means as I'm no optical expert, but it must be affecting the star shape off centre.
I thought that the OAG in your system is in front of the filters? Why are the stars dim? Being where it is there should be plenty to pick from. I have the advantage of being able to change the orientation of the guider to the main chip, but I try not to change it too much as that means I have to recalibrate it.
Nice detail though. I'll have to wait another month or so until Orion rises out of Melbourne's murk.
Stuart, there is elongation only on the upper right and lower left of the image at full size. The off center ringing is odd as I have not had this before myself. Finding the sweet spot has been a pain in the butt, but I have had it before with the 40D which has a bigger sensor and I will find it again. My adapter for the flattener is due to arrive from the States next week. This will mean I can sort collimation and have a truely flat field. I might have tightened up the collimation screws a little too much too. Still quite happy with the detail of the head despite some "small" issues.
Yes the OAG is in front of the filters but it is still quite dim with regard to stars. Sometimes I can use the OAG and sometimes I cannot; it just depends on the field.
Yes the OAG is in front of the filters but it is still quite dim with regard to stars. Sometimes I can use the OAG and sometimes I cannot; it just depends on the field.
The f-ratio of your optics has very little effect on the intensity of point sources. For diffuse objects, then the image is spread over more pixels for longer FL, and unless you have a huge mirror, then that generally relates back to f-ratio. I'm not going to start another "f-ratio myth" argument, but most of this doesn't hold for point sources, where it is the size of the Airy disk which matters.
Sometimes I struggle to find a decent guide star, but I'm usually looking for sub 1 second guide exposures to run the AOL. If I were doing normal guiding then I'd be going out to 2-3, maybe even 5-6 seconds, anything faster than that and you'll end up "chasing the seeing".
You're on a G11 aren't you? If so then get the Ovision worm, run PEC training (I used pempro, not necessary, but worth every cent, getting cheaper as the $A goes up). Then you'll easily be able to guide at up to 10 second guide exposures.
You really have to use OAG at the focal length we're imaging at, even the slightest flexure stuffs things up completely.
Stuart I am using an EM400. However, I am sure I don't have flexure. However there is something going on with the way I have the camera squared to optical path. Possibly even that final touch of collimation.
In the images below you can see that center top left and bottom right are all circular but top right and bottom left are definitely elongated. Well at least that is what I am thinking. Can you see what I am talking about? Personally I reckon it needs to go just a little to the right with the collimation.
