To Wedge or not to Wedge, is that the question?

[psychobabbler]

Dear All

I am keen to get into imaging of deep sky stuff and was hell bent upon a new WO refractor, HEQ5 ans something like an Atik CCD camera. But dogfish reminds me that i could save a considerable fortune by sticking a good quality wedge on the CPC 1100 i have, and still have more than enough pennies for the Atik. Besides me missing out on a more portable set-up, can anyone think of any other disadvantages of sticking with the wedge option, or is it the way to go. I'm in two minds myself.

I also need a bit of advice how i might deal with periodic error on the CPC and how i would go about autoguiding if i went for the Atik.

Thanks for any thoughts

Psychobabbler

[SteveL]

If you are serious about imaging, then a wedge is essential. Field rotation will bite you when you take subs of longer than about 20-25 seconds.

This is 30 x 20 second subs, made into a movie. Quite disturbing how much the sky rotates in such a short timeframe. When I tried the same shots at 25 seconds, I got field rotation quite noticably

http://zorlac.peonic.net/images/m13-altaz-rotation.gif

I have just moved my NS8GPS to a wedge, and if/when the bl**dy clouds ever go away and I can get some practise in with polar alignment, I`ll be using an Off Axis Guider with my DSI (or LPI) to guide my scope. I`ll also be using the OAG/DSI to train the PEC on my scope a few times and then averaging the runs out with the Celestron PECTool.

Sure, using a wedge takes a bit longer to set up. I plan to stay AltAz for purely visual sessions, but use the wedge if I plan to do any imaging at all. Its not any less portable, just takes a while to get the alignment sorted out first.

[GordonCopestake]

You might find that a HEQ5 is as expensive as a decent wedge. You wouldn't be able to use your SCT on it but you could use your WO refractor. The EQ mount takes all the trouble out of imaging with an Alt Az fork mount.