[sac-forum] Re: CCD imaging guidance needed

Thank you kindly for sharing your insights Jeff.

Bob

Jeff Hopkins wrote:

Hello Bob,

The DSI is a great camera for the price.
M13 is usually an easy object, but M31 is harder than it looks. Be sure to take darks and auto subtract them. The AutoStar Software is very god for the imaging and processing. You can also try stacking images. For deep sky objects set the Quality and # to zero and 1 and stack a dozen or so to start. A key for the stacking is to draw a box around a star to guide the stacking. This allows the software to precisely stack the images. If you use an Alt/Az mount, draw a second box and it will de rote the images. 

Experiment and ask questions.
As for the focal reducers I use a F/6.3 and F/3.3. I have no experience with the 1.25" reducers. Best just experiment. While I am a Mac person I bought a refurbished Dell to use for the imaging. For $500 you can get a very nice system from TigerDirect and not worry about taking your Mac out into the elements. 

Jeff



At 14:02 -0700 10/12/2007, Bob Christ wrote:

Hi all, need some astrophotographer guru guidance ŠŠ
Tim Jones and I fired-up a Meade DSI single-shot color camera last night - basically our first hands-on experience with astrophotography. The results were both good and bad. The good; we can effectively place objects on the chip. The bad: well, the images (Albireo, M13, M31) could stand improvement to put it kindly. The seeing wasn't good, but I'll pass on blaming it.
Longer term we plan to image with an f4'ish refractor, but last night we used a C9.25" SCT, not an ideal imaging platform at f10: 

C 9.25" at 2350 mm focal length, alt/az mounted
DSI color camera: pixels = 9.6 microns W by 7.5 microns H
Nebulosity software (Mac w/USB 2.0)
Astro-Physics 2" adapter attached to the SCT threads
2" to 1.25" converter inserted into AP adapter
DSI camera inserted into converter
~ 20 exposures taken of each object - limited to 20 seconds max each exposure
The question: A 1.25' filter format 0.5x focal reducer manufactured by GSO ($35 shipped) looks viable to use. Does this approach make sense to implement on the SCT/DSI combination? Would an extension tube (25 mm offered) help further reduce the focal length (sub f5)?
We could use the original 1.25' visual back to move the camera even further forward if that is recommended. If yes, again, would the 25 mm extension be of value? Seems not, but the answer may be counter-intuitive.
I don't want to go the Meade f3.3 reducer/field flattener + variable T-adapter route ($150) because most of the imaging will be done through the RFT.
Feedback regarding the 1.25" .5x focal reducer strategy is most welcomed. 

Thanks.

Bob

--
Bob Christ
Executive Vice President
TOLIS Group, Inc.
bchrist@xxxxxxxxxxxxxx
Ph: 480.505.0488 x228
Fax: 480.505.0492
www.tolisgroup.com
The Data Backup & Recovery Experts

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