From: milton Aupperle <milton@outcastsoft.com>

Date: December 27, 2010 9:39:54 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Narrowband Imaging with Flea2

Hi Jim;

On 27-Dec-10, at 6:44 AM, jimchung2338 wrote:

I finally got a chance to try out my second experiment last night because it was finally clear (that makes three clear nights since midNovember).

I placed my Flea2 inside an old 8" Celestron Schmidt Camera with a Baader Ha filter and also jumped the terminals for long exposure.  That resulted in a disappointing maximum exposure of only 40s!

If your limited to a maximum of 40 seconds, then you did not check mark (and close the camera control window) the :

"Allow extended PGR cameras  exposure times"

checkbox in Preferences section. You have to set the jumper pins and check that item. Since Camera Preferences are saved into a file  for each camera used, (by serial number)  this will need to be set for each camera that is used.

I'm hoping to turn the Schmidt camera at f/1.5 into an astro outreach/star party scope that can do DSO narrowband imaging from within the city within say 2 minutes.

http://dl.dropbox.com/u/4852049/m42flea20x40.jpg

M42 is a fairly bright Ha target so the 40s subs look like the stacked image just noisier.

What gain settings di you use? Remember my "mantra" High Gain = High Noise.

The focal plane of a Schmidt camera is curved hence the star aberrations starting to show on the margins of the image.    I attempted the Horsehead Nebula but the small pixels of my Flea2 even binned 2x2 could not clearly show it with only a 40s exposure.    I had much better success with my Starlight Express Lodestar guider ccd  and exposure control is also much easier.  But both these ccds are really small and do not take advantage of the Schmidt camera's ability to deliver a large flat coma free image.  So my next step is to dissect this slightly broken Canon 10D camera with its APS sized sensor and create a remote CCD sensor head to place inside the Schmidt.  Unfortunately I'm getting slightly off topic with this forum!

Different CCD's have different sensitivities for narrow band light, especially hAlpha.

Is you DSLR camera modded or normal with respect to the IR filter? The unmodded ones with IR Filter will basically filter out hAlpha light completely.

I think your expecting too much for your exposure time. Your only capturing a very small amount of the visible spectrum. Search "Halpha M42" with Yahoo and I get a tonne of images, where people were using up to 900 second exposures with narrow band 7 nm HAlpha filter and F2 to F4.5 systems for M42 with a variety of cameras.

HTH..

Milton Aupperle