I had a lot of fun last night while I stayed up to watch Felix jump from his balloon. Primarily sitting on the balcony taking happy snaps of Orion whilst nervously biting my nails in anticipation of the highest ever sky dive and was not dissapointed on either front!!!
Settings used:
Canon 60d
50sec exposures
640iso_31min_40frames
Sky Watcher ED80 Pro Gold Edition
Sky Watcher HEQ5
Orion Star Shoot Guider on a 50mm Scope
Backyard EOS Software 'Camera Control'
Comments and suggestions welcomed
ps: Is the fuzzy around the star what you refer to as coma?
Last edited by ourkind; 15-10-2012 at 03:34 PM.
Reason: damn grammer I speak english good not ...
Increase your exposures You are guiding, so drop the guider frame refresh to below 1 second - I usually use 0.2s or 0.5s if doing deep stuff. I have used 0.05s, but I had to turn my sound off cause even a bee's johnson out of pixel alignment, and it beeps at you BEAUTIFUL guiding, but the sound is annoying, especially when listening to music during subs I still cannot believe how well these guide.
Thanks for your suggestions Lewis I am definatley looking at increasing my exposures but also at taking a shorter exposure to avoid the burnout in the trapezium. This site has been suggested to me as to the method used to combine 2 different expsosures http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM
Sorry for my ignorence but can you tell me what difference it makes to imaging when you lower the refresh rate i.e. make it quicker from say 1.5 to 0.02? I've noticed this setting and you are right, I had mine at 2.00 I think. Everytime it beeps I panic and try and realign the tracking
Lewis is mistaken, you do not need fast refresh rates to guide well. Infact it can be detrimental. I would leave it at 2 seconds. The reason being is that anything under 2 seconds will "chase the seeing" meaning your mount will make corrections that are not due to the star moving but are due to atmospheric refraction. With a 2 or 3 second guide exposure you average out the seeing and a better position of the guide star can be computed. The guide star that you will guide on will also have a higher signal to noise ratio, which is better for guiding.
Infact the guiding on your image looks ok, the odd stars in the corner look like field curvature, are you using a flattener?
Peter, I found the other day that if I did a 5 min exposure using a 2 second refresh, I got star trails (small, but noticeable). If I dropped the refresh to 0.2s, a 5 min sub showed no star trails. So, I just suggested this based on the experience at the time. I found the mount hunted no more than usual, and definitely no aggressive corrections as it seems to sometimes do at 2 sec exposure.
So, not sure where to go with that then. You are probably correct.
Great Pic dude., I tend to agree with Peter here though. If the seeing is bad I would extend my PHD exposures to 3.5 or even 4 secs, if clear skies and good seeing I would use 2 sec-2.5 secs. Extend the exposure increases the likelihood of gathering in that centroid for guiding.
Carlos- I have the 60Da, which is the same camera but for the "astro mod" so more sensitive to the Ha red stuff.
Even without that the deal is really longer exposure time/ maximise the signal to noise etc- which to put it nicely- more frames / longer frames/ try and get colder frames etc.
I enclose a small section of the same - M42- this between terrible clouds last week but is 7 frames of 400 secs at ISO 800.
Carlos , you are doing well.
Graham
NB I think the halo around the stars looks like poor seeing /thin clouds or water vapour in the upper atmosphere, your stars look good, but the refraction from the atmosphere has bloated them. I talk from experience living in Tassie where the clouds are frequently ruining good nights.
Last edited by graham.hobart; 17-10-2012 at 07:04 PM.
Reason: added stuff
Infact the guiding on your image looks ok, the odd stars in the corner look like field curvature, are you using a flattener?
Thanks Peter, I appreciate your comments and I will be taking them on board. I do not have a flattner yet, I will research it and get one soon. Any suggestions welcome.
Quote:
Originally Posted by graham.hobart
NB I think the halo around the stars looks like poor seeing /thin clouds or water vapour in the upper atmosphere ...
Thanks Graham, aha I was wondering why I got purple while others like yourself got red. So its the mod and the fact that your seeing the HA. Cool I think the wife would kill me if I removed the UV filter off our one and only dearly loved camera Your photograph is very nice too
Have you thought about underexposing the trapezium? The link I posted above seems to be a good guide at manipulating our images to bring out detail in bright areas.
Cheers for answering my last question, there was a thin line of cloud/mist that night plus Orion was rising above Sydney City from my perspective.
Thanks guys for all your comments you've all been very helpfull!!
Not to beat a horse, but I did a SINGLE 10 minute exposure on Eta Carinae last night, with the Starshot set to refresh every 0.5s. Did not beep once all night. Even did a 20 minute sub as a test - NO star trailing, perfect images (except light pollution orange cast).
Here is a 100% unprocessed shot of Eta Carinae, using unmodded Canon 5DMkII, single 10 minute sub. Only cropped to show a target area.
Your results may vary, as it seems it does with others, but I am happy getting 10 and 20 minute single subs without any noticeable trailing or oblongaton/elongation.
ten and twenty min subs with no star trailing would indicate very good PA with good guiding to limit field rotation.
What I would bear in mind how ever is you may have to increase your Starshoot exposure time if the seeing isn't too good, to allow the better acquisition of guide star.
That's just what I do (or did when I used PHD) when it's a bit murky/ poor seeing.
fantastic. Looking at this and comparing it to mine, i really can see your stars are way better and the overall image is a lot better.
Good work
Thanks Steve, I just took a look at yours and I think it's very good too, especially as you didn't have the luxury of guiding. Because I'm a beginner and still learning I don't know the exact reason why our images differs so, you have a lot of data, my guess is our cameras followed by the exposure times and ISO's used. Post editing can make s big difference too.
I noticed another user the other day posted his final image and a sub side by side which allowed us to compare subs and final images really well. I will do the same from now on.
Sorry for the slightly off-topic discussion, but I thought it might be useful...
Quote:
Originally Posted by LewisM
Peter, I found the other day that if I did a 5 min exposure using a 2 second refresh, I got star trails (small, but noticeable). If I dropped the refresh to 0.2s, a 5 min sub showed no star trails.
If you get star trails with 2 second guide captures at relatively short focal lengths (900 mm on your ED100), then I suspect one of three common issues:
1. Polar alignment isn't accurate enough. Have look in the extreme corners of your 5/10 min images. Are the stars equally round as in the corners? Poor PA with good guiding will give you elongated corner stars (field rotation) while the centre area will still look great. Another way is to do a "difference" mask with the first and last sub from a session (e.g. 2 hours apart) and see whether the corner stars have rotated.
2. Mount is unbalanced. If the mount is unbalanced, you can end up with lots of oscillations every time it moves. Very short guide exposures would try to fix the oscillations. This may work great for wide fields (< 1000 mm) but isn't effective with longer focal lengths. Many people find that balancing the EQ6 so that it's slightly east-heavy reduces slop-related oscillations.
3. Mount needs tuning. The gears on your mount might not be moving very smoothly. My first EQ6 (bought new) was terrible in this regard - I could actually see it periodically getting "caught" on the PHD guiding graph (and hear it on the mount too). My second EQ6 - hyper-tuned by another IIS member - is much, much better and runs far more quietly than my first one did.
I've attached a couple of examples taken last weekend with my Canon 5DmkII attached to a GSO RC8 (1600 mm focal length, ~0.8 arc sec/pixel). The first is an unguided 60 second framing exposure at ISO 25600 (H2) - notice round stars with slight elongation due to periodic error of the mount. The second is a 360 sec light frame taken at ISO 3200 and guided with an Orion 50 mm mini guide scope (only 162 mm focal length) with 2 sec exposures - round stars
I still cannot believe how well these guide.
Your photograph is very nice too 
