couple of questions regarding CCD imaging
Here is my first question. How do you achieve focus with a CCD camera since there is no live focus mode? Does the software let you know when you are in focus? How does the guide chip on the SBIG dual chip cameras or 237 chip work when finding a guide star? Is this easier than having a separate guidescope and autoguider? I want to know what I'm getting into before I dive into CCD imaging? Debbie
Hi Debbie, You do see the image on the screen -- it is live. Your computer screen shows exactly what the camera sees and can update it quickly. If you use a bright star the focus can have an exposure can be about as fast as the camera is capable of taking, say 1/1000 of a second, and it refreshes immediately. Best wishes, Joe ________________________________ From: Debbie <astrodeb@beyondbb.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 11:19 AM Subject: [Utah-astronomy] couple of questions regarding CCD imaging Here is my first question. How do you achieve focus with a CCD camera since there is no live focus mode? Does the software let you know when you are in focus? How does the guide chip on the SBIG dual chip cameras or 237 chip work when finding a guide star? Is this easier than having a separate guidescope and autoguider? I want to know what I'm getting into before I dive into CCD imaging? Debbie _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
so if I wanted to image M22 I would focus on Antares then go to M22? Thanks, Debbie On Tue, May 31, 2011 at 11:24 AM, Joe Bauman <josephmbauman@yahoo.com>wrote:
Hi Debbie, You do see the image on the screen -- it is live. Your computer screen shows exactly what the camera sees and can update it quickly. If you use a bright star the focus can have an exposure can be about as fast as the camera is capable of taking, say 1/1000 of a second, and it refreshes immediately. Best wishes, Joe
________________________________ From: Debbie <astrodeb@beyondbb.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 11:19 AM Subject: [Utah-astronomy] couple of questions regarding CCD imaging
Here is my first question. How do you achieve focus with a CCD camera since there is no live focus mode? Does the software let you know when you are in focus?
How does the guide chip on the SBIG dual chip cameras or 237 chip work when finding a guide star? Is this easier than having a separate guidescope and autoguider?
I want to know what I'm getting into before I dive into CCD imaging?
Debbie _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
There are focusing aides like knife edge focusers.
so if I wanted to image M22 I would focus on Antares then go to M22?
Thanks,
Debbie
On Tue, May 31, 2011 at 11:24 AM, Joe Bauman <josephmbauman@yahoo.com>wrote:
Hi Debbie, You do see the image on the screen -- it is live. Your computer screen shows exactly what the camera sees and can update it quickly. If you use a bright star the focus can have an exposure can be about as fast as the camera is capable of taking, say 1/1000 of a second, and it refreshes immediately. Best wishes, Joe
________________________________ From: Debbie <astrodeb@beyondbb.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 11:19 AM Subject: [Utah-astronomy] couple of questions regarding CCD imaging
Here is my first question. How do you achieve focus with a CCD camera since there is no live focus mode? Does the software let you know when you are in focus?
How does the guide chip on the SBIG dual chip cameras or 237 chip work when finding a guide star? Is this easier than having a separate guidescope and autoguider?
I want to know what I'm getting into before I dive into CCD imaging?
Debbie _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
You can focus on much dimmer stars too -- in fact, Antares might be so bright it overwhelms the chip even at the fastest speed. Often any star in the field will do, just not as fast to focus. (When you want to get ridiculous about it you can do what I did this recently -- I purchased a RoboFocus device for $475 that, combined with the FocusMax freeware, is supposed to automate it.) Until now I've been using masks I cut out of cardboard to help with focusing. Best wishs, Joe ________________________________ From: "erikhansen@thebluezone.net" <erikhansen@thebluezone.net> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 12:20 PM Subject: Re: [Utah-astronomy] couple of questions regarding CCD imaging
There are focusing aides like knife edge focusers.
so if I wanted to image M22 I would focus on Antares then go to M22?
Thanks,
Debbie
On Tue, May 31, 2011 at 11:24 AM, Joe Bauman <josephmbauman@yahoo.com>wrote:
Hi Debbie, You do see the image on the screen -- it is live. Your computer screen shows exactly what the camera sees and can update it quickly. If you use a bright star the focus can have an exposure can be about as fast as the camera is capable of taking, say 1/1000 of a second, and it refreshes immediately. Best wishes, Joe
________________________________ From: Debbie <astrodeb@beyondbb.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 11:19 AM Subject: [Utah-astronomy] couple of questions regarding CCD imaging
Here is my first question. How do you achieve focus with a CCD camera since there is no live focus mode? Does the software let you know when you are in focus?
How does the guide chip on the SBIG dual chip cameras or 237 chip work when finding a guide star? Is this easier than having a separate guidescope and autoguider?
I want to know what I'm getting into before I dive into CCD imaging?
Debbie _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
PS, When you're focused on one star, if the telescope doesn't slew too much going to your target, you're focused for that too. -- Joe ________________________________ From: Joe Bauman <josephmbauman@yahoo.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 12:41 PM Subject: Re: [Utah-astronomy] couple of questions regarding CCD imaging You can focus on much dimmer stars too -- in fact, Antares might be so bright it overwhelms the chip even at the fastest speed. Often any star in the field will do, just not as fast to focus. (When you want to get ridiculous about it you can do what I did this recently -- I purchased a RoboFocus device for $475 that, combined with the FocusMax freeware, is supposed to automate it.) Until now I've been using masks I cut out of cardboard to help with focusing. Best wishs, Joe ________________________________ From: "erikhansen@thebluezone.net" <erikhansen@thebluezone.net> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 12:20 PM Subject: Re: [Utah-astronomy] couple of questions regarding CCD imaging
There are focusing aides like knife edge focusers.
so if I wanted to image M22 I would focus on Antares then go to M22?
Thanks,
Debbie
On Tue, May 31, 2011 at 11:24 AM, Joe Bauman <josephmbauman@yahoo.com>wrote:
Hi Debbie, You do see the image on the screen -- it is live. Your computer screen shows exactly what the camera sees and can update it quickly. If you use a bright star the focus can have an exposure can be about as fast as the camera is capable of taking, say 1/1000 of a second, and it refreshes immediately. Best wishes, Joe
________________________________ From: Debbie <astrodeb@beyondbb.com> To: Utah Astronomy <utah-astronomy@mailman.xmission.com> Sent: Tuesday, May 31, 2011 11:19 AM Subject: [Utah-astronomy] couple of questions regarding CCD imaging
Here is my first question. How do you achieve focus with a CCD camera since there is no live focus mode? Does the software let you know when you are in focus?
How does the guide chip on the SBIG dual chip cameras or 237 chip work when finding a guide star? Is this easier than having a separate guidescope and autoguider?
I want to know what I'm getting into before I dive into CCD imaging?
Debbie _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
_______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php
Hi Debbie, On 31 May 2011, at 11:19, Debbie wrote:
Here is my first question. How do you achieve focus with a CCD camera since there is no live focus mode?
One of the first things I discovered when I ventured into CCD imaging is that focusing can be a real pain. But as with most things, given some practice it gets easier. I typically start by getting close to focus by taking full frame images binned 3x3 (3x3 so they download and display faster). Then once I'm close I subframe (i.e. draw a box around) a small group of stars so only that tiny portion of the frame is imaged and downloaded and then switch to 1x1 binning. Those tiny images come down very quickly and 1x1 is the highest resolution. Then it's a matter of taking an image and adjusting the focus, taking an image and adjusting the focus, taking an image and adjusting the focus and so on. Not real time but pretty close. I should add that in the end the amount of focus adjust becomes very small so it helps to have a focuser that can make tiny corrections. With my ancient (circa 1984) C-14 the tiny focus knob was just too small to make tiny corrections. So I replaced the knob with an old 100mm diameter metal gear I had laying around. Using that I can make very tiny and precise moves. And I find it's usually best to make those corrections by moving the knob anti-clockwise. That way your fine adjustments are always made with the mirror being pushed up against gravity. I was able to do pretty good work with that but a while back I added an external electric focus which makes even more accurate adjustments. Oh, and unless you are using a carbon-fibre tube changes in ambient temperature will also change the focus. I keep a digital thermometer next to my desk that shows outside temperature. With my metal tube I've found that just a 1 degree C temperature change can change the focus enough to be detectable. 2 degrees and it is very noticeable.
Does the software let you know when you are in focus?
Depends on the software. I can't speak to others but CCDSoft can display a graphical representation and with an electric focus can even do the focusing for you. But it's not perfect and it seems to take a long time sometimes, especially if the seeing is changing. So being the impatient person I am I usually don't use the auto-focus feature.
How does the guide chip on the SBIG dual chip cameras or 237 chip work when finding a guide star? Is this easier than having a separate guidescope and autoguider?
That will depend on the field you are shooting. I have not used a separate guide scope in years. Rather I just use the guide chip in my imager and it looks thought the main OTA. The trick is finding a guide star and there isn't always a guide star available. So sometimes I have to compromise and shoot several shorter exposures and use software to add them together.
I want to know what I'm getting into before I dive into CCD imaging?
Honestly, there is a reason there are so few serious astroimaging folks out there. The learning curve (curse?) can be pretty steep and the costs (in money and sanity) are not small. And it can be very frustrating to spend hours on an image only too see a better one in the next issue of Sky & Telescope. :) Speaking thereof, how you seen how many *hours* of exposure time goes into some of the S&T iamge?! Which is why I'm a fan of taking data rather than "pretty pictures". Images for data can be (usually are) less than appealing to the eye but still produce top notch scientific results. It REALLY helps to have a mentor with whom you can visit and who can show you how to do things right. Good luck, patrick
participants (4)
-
Debbie -
erikhansen＠thebluezone.net -
Joe Bauman -
Patrick Wiggins