M51, ten minute exposure

A Tequila Sunrise in Antalya will loosen me up enough to let you into the secret world... - and Fiona will have one too

Totally agree with you on the DSI route for your OTA. Unless you got your hands on a 3.3 reducer, you'd have to do a mosaic of M51 to fit it all in! A nice big fat Kodak chip though... Or if you have the dosh, a Marconi back illuminated CCD <drool>

I don't thing the DSI v DSLR stands up very well on the side of the DSI. But, a DSLR versus a large format SBIG, Finger Lakes or Alta... Now that's a different story... For another Tequila

Bottoms up!

Dave

Dave(s)

Totally agree with your DSI/DSLR/SBIG analysis. Big chips also give you the advantage of cropping out the bits you dont like:) On the other hand vignetting isnt such a problem with smaller chips since even at low f ratios the FOV is generally fully illuminated.

Dave L: Couple of things. Dont forget the chip on the ST4 is really tiny, Jed will tell you that it can be a real b*&^ to get a guide star on chip, even with a guidescope. I'm sure you will master it with practice.

Also noticed on your unpocessed image the 'glow' on the top and bottom of the right hand side is also visible on mine but the one of the left isn't I wonder why they'd be different?

Dont forget the chip on the ST4 is really tiny, Jed will tell you that it can be a real b*&^ to get a guide star on chip, even with a guidescope. I'm sure you will master it with practice.

What you have to learn is how close the star has to be to be on the chip and where the focus point of the ST-4 is.

I now have a parfocal eyepiece and with a reticle eyepiece for alignment I get the star on the chip every time.

Like most things in astrophoto, having a procedure to follow is half the battle!

Later,

Jed

The main thing determining ccd (using this term to mean all chip based sensors) sensativity is the QE (quantum efficancy).

One of the main culprits for low QE is CFA colour arrays. That is why an increasing number of people are using a mono imager to capture Luminance data and the a CFA imager to capture the RGB data.

Some people even use differing sized imageres and scale the frames.

Later,

Jed.

Dave G,
you're dead right the st-4 chip makes the toucam chip like like a roof slate, its really tiny, but thats why I got the parafocal flipmirror, otherwise I reckon I'd end up bouncing it off the wall. :lol:
As far as I can see, ALL 300Ds had this thermal noise in 2 places on the right and also the lower left, I dont know why yours would be different, unless it has a newer rev of internal hardware?

Jed, I also think a monochrome camera is the way to go, then get a filter wheel to go with it, the st-10 xme has a very high quantum efficiency, somewhere in the high 80s if I remember rightly, there is also a lower QE version of this camera, somewhere in the 60s.
I't'll be a long wait though before I take the plunge on the camera.

As for chip size, vignetting is something that can be fixed, I think doing many images to make up a mosaic would drive me around the bend.