Anyone doign DSO AP with their SCT?
Posted 26 December 2012 - 12:19 PM
I am looking for a more "powerful" imaging scope to complement the ED80 so I can get better image scale on stuff liek individual galaxies, globulars etc.
I hear some say the F10 ratio of the SCT is a no-go for AP. Anyone here think otherwise?
How do you guide etc?
I am very tempted to get a C9.25 OTA.....
Thanks for your thoughts and ideas.
Posted 26 December 2012 - 01:32 PM
Posted 26 December 2012 - 01:45 PM
Posted 26 December 2012 - 03:55 PM
My CPC1100 is for keeps as my visual rig.
Posted 26 December 2012 - 04:58 PM
I don't think it is bad advice to suggest a small refractor and a good quality GEM for anyone approaching AP as a hobby. The lighter, smaller and faster scope will provide very good images to a beginner within a few outings. Finding a mount that can carry an SCT for imaging requires some "reading into" of manufacturers weight ratings. Many newcomers don't understand that and that is why the importance of a quality mount cannot be understated.
As well, imaging at f10 will require longer exposures than many newcomers can adequately achieve. Before I got a guiding setup, I maxed out at 30-45s exposures. At the time I was happy with my images, but looking back they were terrible. It took me 2 years before I fully understood drift alignment and got what I'd call respectable images. But looking back, some of my beginning images taken with the WO66 and guiding through the SCT were also respectable.
It is for that reason, I always suggest a small refractor and discourage SCTs for beginning imaging. Now, all of that said, I believe SCT's are excellent imaging scopes. If you understand all of the variables, they have a strong place in a imagers lineup.
So.. if you are decided on an SCT, I'd consider the Edge series. You will have perfect stars to the edge, unlike the C9.25. They also have mirror locks which overcomes one of the SCT biggest problems, mirror flop. If you can't spend the money, go with the 8" Edge. From a practical standpoint, the slight difference in resolution would be negligible and most often beyond seeing. As well, according to rumor the 8" Edge focal reducer is coming out in January and the 9.25 is some time off. I struggled between the 8, 9.25 and 11 but am happy with my choice.
Posted 26 December 2012 - 06:29 PM
Posted 26 December 2012 - 06:32 PM
Posted 26 December 2012 - 06:55 PM
It is all about the mount (the mount, the mount) and the seeing at 2800mm. On my rig that gets me 0.51 arcsec/pix. Its more managable with a reducer, but not still no cakewalk. Rod just made the point I was going to make - For planetary's it is a weapon of choice when the conditions dictate. I've spent enough hair pulling sessions to know not go there unless the seeing is exceptional, and then only with a self-guiding camera (and then you need luck getting a guide star at F10). The other downside that I have with a C11 (metal tube) is it's ability (or lack there of) to hold focus when the the ambient temp is droping at any kind of rate (refocus needed every 2F-3F degrees of change).
Posted 26 December 2012 - 07:04 PM
f/10 is not where you want to start with imaging but if you are like me, after a while, f/10 and longer focal lengths are where you will want to end up. The widefield stuff is fun at first and then it becomes...well...boring . How many widefield M42s can one stand! It's the closeups of galaxies, planetaries, and globs that are seldom seen that are most fun (to me). Of course, YMMV!...John
Posted 26 December 2012 - 10:17 PM
Posted 27 December 2012 - 12:51 AM
Thanks for the thoughts. I would not be using my CPC, I'd be buying another C9.25 OTA to go onto my NEQ6 mount.
My CPC1100 is for keeps as my visual rig.
We have very similar thoughts here. My CPC1100 is my 'grab and go' visual scope for star parties and outreach. It's a scope I plan to keep for a while, too.
I'm currently piecing together an imaging setup using an 8" EdgeHD as my primary scope with an AT66ED refractor as the guide scope/wide field imaging scope. I choose 8" because it will ride a little better on the CGEM mount and because the focal length will not be so difficult to guide. An 8" with an Optec f/6.2 focal reducer will have a focal length of about 1240mm. That's a fairly nice place to be.
With a focal length less than 1500mm, guiding with a guide scope is more practical. At very long focal lengths, guiding with an off-axis guider becomes more important. I have not been successful in using an OAG, so I'm staying away from focal lengths greater than 1500mm.
Posted 27 December 2012 - 06:31 AM
The widefield stuff is fun at first and then it becomes...well...boring . How many widefield M42s can one stand! It's the closeups of galaxies, planetaries, and globs that are seldom seen that are most fun (to me). Of course, YMMV!...John
That is more my feeling also. With shorter focal length you can "take a picture" of something, but with longer focal length you can "reveal detail within" something. I would recommend a small refractor and guidescope for someone getting started, but for people who want to take it further, high res. work has its own rewards. I don't think it requires a high end mount, and instead results tend to be limited by technique, software, and low expectations. Results with my relatively humble setup (c11 on cge or cge-pro) are on the metaguide site. I do recommend OAG at long focal length, but the recent FlexRX result may change that.
There is also a downside to wide field work, which is that gradients can be a nuisance, which puts processing demands on a new imager. It's less of an issue with a narrow field.
I think f/10 and long focal length are less of a win for faint objects that don't have much detail - such as the cocoon nebula. But for objects with detail such as galaxies and complex Ha regions, high res has benefit. Instead of wide field images of nebulosity in our own galaxy, you can aim for detail in the Ha regions of other galaxies.
Just measure your fwhm's in arc-seconds, and methodically work on your setup and technique to determine what is limiting it and how it can be reduced. Experiment, and don't just follow anecdotal advice.
Posted 27 December 2012 - 11:45 AM
Posted 27 December 2012 - 12:19 PM
As mentioned above there are some targets like planetary nebula that really do need F10 or C11 like field length to pull details out of.
Personally I think you need both a short focal length refractor for the wide field shots and a long focal length scope so you can get the details. That's why I'm going to mount a AT72 or 65 on top of my CPC.
One other thing you might consider is getting either a Orion or Astro-Tech imagine Newtonian or a Astro-Tech Ritchey Chretien on a CGEM. These are the other scopes I considered before buying the CPC and wedge. I did consider the Edge but the lack of a focal reducer option kept me a way. Depending on your budget and timeline you might also want to consider a Meade once we get some more clarity on their financial situation, although in general I think you overpay for the same scope with them.
Besides looking at others photos I think Carte De Ciel is great for seeing what you can image and at what resolution with a given setup.
Posted 27 December 2012 - 02:43 PM
I image with a CPC1100 on a Milburn wedge at f6, using an SXVR-H694. I guide with a Flea3 on an OAG (Taurus Tracker III). Take a look at the galaxies and planetary nebulae on my website (linked below), and you'll get an idea what you can achieve with this setup. And my recent images (which I'll post as soon as I can dig out from under a mountain of Jupiter data) are better than those. I finally got an absolute focuser in early summer, and I'm now much more aware of precise focus. In good seeing, I now routinely get stars with an HFR of 1.5 arcsecs in 5-10 minute exposures. (And Frank may scold me for being satisfied with only that! )
If you've already learned the ropes with your ED80, I think you can make the leap to long FL imaging without too much trouble.
Posted 27 December 2012 - 05:48 PM
Posted 27 December 2012 - 06:46 PM
All the best,
Posted 28 December 2012 - 09:33 AM
Posted 30 December 2012 - 07:50 PM
Posted 17 October 2013 - 03:25 PM
Posted 17 October 2013 - 09:08 PM
M42 at F6.3 October 16,2013. C-14 CGE Pro, SBIG ST4200XCM color camera. 30 2 minute exposures stacked and corrected with one flat frame and 30 dark frames.
Posted 18 October 2013 - 11:59 AM