Very interesting and impressive! True, that one picture was a bit longer but some of the other ones were not as long. I guess that's the benefit of a 10" over a 4". -----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of David Rankin Sent: Wednesday, October 21, 2009 10:13 PM To: Utah Astronomy Subject: Re: [Utah-astronomy] Cluster of galaxies in Aries Craig, I guess that is a simple way to put it...but When you say "regular" scope, mount, and camera...its a bit more involved than that (I do guide) I had originally started out with a rip off CG5 I had upgraded with good motors that could track. It could not come close to handling the weight I wanted tho. So I upgraded to the Orion Atlas, EG-G with the EQMOD. This is an interface with the mount directly to the laptop for full control of the mount and pulse guide which is very nice. The Stock Atlas has some issues tho. I have taken the entire mount apart, fine tuned all of the adjustments and re-greased it with a Teflon based grease that does not suffer separation and works well under a large temperature range. I also replaced the worm bearings with high quality ceramic ones. The atlas is a power horse to start with...and with the upgrades its a bit more than regular ;) I am running a setup that is over 40lbs on it right now and still getting good auto guides up to 5 minutes. I will eventually upgrade to something bigger in the future tho. The scope is very nice as well. As you know when you go from 8 - 10 inches ect. The light gathering increases as a function of the area of the primary. The Orion 10" F4.7 OTA is a sweet scope. It has some very fast optics, and with the Baader Multi Purpose Coma Corrector, you will get sweet looking stars across the entire camera sensor. The OTA is 500$ and the MPCC is 145$. So I would not say it is a "high end" setup, but 10 inches at F4.7 is sweet resolution and fast photon capture. One major issue was the vixen style dovetail, had to upgrade all of that to the much wider Losmandy style to prevent flexing under all the weight. There is a picture of my setup in action here under (equipment) http://www.rankinstudio.com/astro The camera is another story as well. I have shot with the Canon Rebel XTi, and now the XSi. The first two issues you have with using a DSLR for astro is noise at high ISO (sensitivity) and the fact that they put an IR CUT filter in front of the sensor. I have modified my camera to shoot Infrared light, and image stacking takes care of the SNR (Signal to noise ratio). The nice thing about DSLR's is the noise is random, and the light signal (light coming off the object your trying to shoot) is not random. So if you take 12 exposures of one object, and average them out, you reduce the noise signal vastly while preserving the light from the object your shooting. You also have to do dark frame subtraction to remove false pixels that fire when they are not supposed to be, and bias frames to remove the readout signal. It sounds a bit complicated, but its really not that bad. Most of the software for doing these things is free (deep sky stacker, Iris). The XSi is a sweet camera with the 12.2 million pixels it sports, and it gives you a lot of headroom to play with the photos, and crop them down at still very high resolutions. As far as exposure times. I have spent up to 4 hours on one object, and less than 1 hour on others. The cluster in the subject here is 21 light frames at 270 seconds each. Doesn't sound like much, but that is 1.5 hours of exposure. The image stacking ect is explained in much more detail here. http://deepskystacker.free.fr/english/theory.htm That is what really opened up my eyes to the possibilities. Also check out the DSLR imaging forum on cloudy nights. You can see whats possible on setups that are less than 3000$. The final thing is the post processing. This takes some time to learn and it can be a bit challenging. Photoshop is the ticket tho. So many people are making actions and plug-ins that help with the processing pipeline and cut a lot of time out, also giving some killer results. My favorite so far is Gradient X Terminator. If anyone on this forum is getting into imaging with DSLR's and has any questions, I would be more than glad to help out. It's really an addiction for me and I am learning new stuff every day. Cheers, David Rankin Craig Smith wrote:
So you're taking all these pictures with a "regular" scope on a "regular" mount with a "regular" camera and no guiding? Just a relatively few stacked frames of relatively short exposures?
-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of David Rankin Sent: Saturday, October 17, 2009 10:10 PM To: Utah Astronomy Subject: [Utah-astronomy] Cluster of galaxies in Aries
This took a lot of exposure and some careful processing :)
I couldnt find a lot of info on these galaxies, I did discover that NGC 678 is 120 + MLY away.
Enjoy!
http://www.slas.us/gallery2/main.php?g2_itemId=2590&g2_imageViewsIndex =1
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