Some imaging advice with CCD cameras

[euphony]

Hi all,

I recently purchased a Mintron 12V6HC-EX camera and have been using it with my CPC1100 with an f6.3 focal reducer.

I have taken numerous streams of images live to show my wife through the television and also have been recording them using Virtual dub.

I have got to the point now that I am used to what I am doing, where the initial novelty and wow factor has worn off and I'm starting to analyse exactly what I am getting and have found that overall I am quite disappointed with the results achieved. I have everything focused as well as I possibly can and am still finding that the picture quality isn't very good. Most the stars just appear pixellated, and not round.

I wondered if this was something I was doing wrong, or whether it was just the quality of the camera. I have set the camera and capturing software up as advised and processed the images afterwards using tutorials found all over the web, but am not getting the clarity of images I see other people are capable of

I get the same quality image whether I'm viewing through my laptop or through the television. The skies near me aren't perfect, but visually on a good night I can see galaxies up to mag 12 with my naked eye (just!).

I wondered if it was the particular capturing software I was using, and if so, if someone had any better recommendations? I tried using Gstar capture, but I couldn't fathom out how to record with it. No matter what I did, it just wouldn't let me!

Any thoughts?

As a demonstration, I have attached two stacked and processed images of M57.

'Version 2' had a bit of processing after stacking, and 'Version 3' had a little more processing in photoshop.

This particular example is the best I have managed. I have captured M13, M27, M92 and M31, but none are particularly great to my eyes (M31 is just a fuzzy elongated ball where you can't make out any structure).

Any help or advice would be greatly appreciated

Chris

Oh, and I have been recording a stream of 5-6 minutes and then stacking them in batches using Deep Sky stacker (as it doesn't like me trying to load in 5000+ images at once!). I've been adding roughly the same amount of dark files. I haven't done any bias or flats, as that part bewildered me, so perhaps that could be the issue?

version 2 better.tif

version 3 better.tif

[dmahon]

Is that a video camera? If so - good for planets, solar and lunar (stacked with Registax or similar), bad for DSOs (you need a smaller number of long [300+ second] exposures).

[euphony]

It's a CCD camera (Basically a CCTV camera), which reading all the reviews etc suggested it was good for DSO's as it is so sensitive (after all I can see mag 13 galaxies with it viewed through a live stream). It can only take exposures up to 2.5 seconds though and continually refreshes the image on screen. When I record the live stream as an AVI file I can then export the movie as single frames that number in the thousands. It's these that I have stacked which according to all the instructions and reviews I have read should work well, but something isn't quite right still and I can't put my finger on what it is

[swag72]

For DSO's you benefit hugely from long exposures. You say that you can only take 2.5s exposures, although thousands of them. As a CSO imager, I use 300s subs for colour images (that is a mono camers with LRGB filters) and for narrowband imaging 20-30 minutes. If you want to capture more detail and go deep, you need longer exposures.

[dmahon]

Looks like its good for viewing DSOs live, as it stacks images internally for 2.5s, to give a video feed of what you can see through an eyepiece. Unfortunately, through an eyepiece, everything looks a bit pants compared to what you can see with long exposure photography.

You can get good images of bright objects (the sun (with appropriate filter), moon and planets) with stacked sub second (video) images. ForDSOsyou often need many hours, even days, worth of stacked long(5-30 minute) exposure photos.

[euphony]

Many thanks for your helpful replies

It was initially only bought for live viewing, so that my wife can see what i see without her having to sit out in the cold on a winters night! The fact I was told you could image with it was just a secondary thing really.

But the more I thought about it, the more I wanted to get into it. I know when using DSLR's etc you needed really long exposure times, but I was led to believe that my mono CCD camera could handle it (maybe not quite in as much detail) by using the stacked shorter exposed images.

@Swag72: What CCD cameras would you recommend? I notice you have Atik 314L+ mono / Atik 16HR OSC in your sig. How do you find these?

Chris

[swag72]

The Atik 314L+ is an excellent camera, and the Sony chip that it uses is very low noise and sensitive as well. As it's a mono camera I need to use filters with it to make a colour image. The 16HR OSC is a good camera I am sure, it too has the same Sony chip, but I've only used it once as I prefer mono!! If you want to seriously consider DSO AP, then you need a camera capable of long exposures. I take it that your mount is a good one and that you are able to guide with it, as you'll need guiding running as well.

Regarding a camera for AP, there's quite a few chip sizes out there, so you would benefit from using CCDCalc (free download) to put in your telescope and different camera's as you'll get very different field of views with the different chips.

[euphony]

Many thanks for the helpful advice

Yes, i can guide with Celestron no problem and it tracks very accurately. I notice the Atik 314L has the ability to take very long exposures, so that looks like a good bet for that. I just need to save up for 2 years now!

Thanks again,

Chris

[Shibby]

Yes, i can guide with Celestron no problem and it tracks very accurately.

Hi Chris,

Forgive me if I'm making some incorrect assumptions here but there is a big difference between accurate tracking for visual use and the sort of sub-pixel accurate guiding required for long-exposure astrophotography. To achieve long exposures, most use an equatorial mount, guide camera and guidescope or off-axis guider. My assumption is that you have the standard Alt-Az mount that comes with the CPC1100; exposure length is inherently limited due to field rotation. Take a look around the imaging forums for guides on... guiding.

[euphony]

Hi Shibby,

Yes, I've got an equatorial mount (That also cost me a fortune!), not sure if the celestron one I bought is the best though having read some reviews, but until I use it fully I guess I won't know! Having spent so much on that too, I really want to start getting some use out of it!

Thanks for double checking that anyway, as I never mentioned that, so could have scuppered me if I didn't have one!

Chris