Quote:
Originally Posted by strongmanmike
Yeh..? Not sure I completely agree. While I certainly wouldn't give one back should I be handed one  these long FL scopes can't fit in the bigger objects so a time starved imager on a realistic budget is often looking for the holy grail compromise, so 1200mm FL with as much apperture as practicable and in average levels of seeing experienced in Oz, can be pretty much the sweet spot for most IMO  .
150mm FL 1100mm FL
12" FL 1120mm
12" FL 1120mm
152mm FL1300mm
152mm FL1300mm |
Wow Mike, that is an impressive set of images. Thanks for posting them. regards ray
Quote:
Originally Posted by clive milne
Hi Ray,
I'm in the process of doing pretty much the same thing.
The (equipment) selection process I have employed goes basically like this:
The equatorial mount I have at present has excellent drives but doesn't
have the payload capacity that I would like. A C14 is the largest aperture
telescope I could reasonably use. The short moment arm of schmidt cassegrain
OTA's means that they transfer less mechanical energy to the mount during
wind gusts and from the effects of stresses induced by cables. I subsequently
managed to pick up a C14 off
astromart for a pretty good price.
I have since ordered a 0.77x reducer corrector made by Phillip Keller which
has a plate scale of 14 microns per arc second on the C14.
A moonlight focuser with stepper motor was purchased second hand through
the IIS classifieds, and as it turned out required a 20 minute drive to pick up.
Just 2 inches to the left of my keyboard as I type this is the sharpsky digital
focusser controller kit I am assembling for the project.
The CCD camera I will be using is an ST10. The choice was pretty simple
in as much as I already own it, and even to this day the Kodak KAF-3200 is
still arguably the best front illuminated CCD out there. It has a similar QE to
the Sony 694 albeit more weighted towards the red end of the spectrum,
but 4 times the well depth. It also has very low noise. The one aspect of
the KAF-3200 that has seen it fall out of favour is that it simply doesn't have
the area coverage of the scientifically inferior 16803 (etc) chips. If you are
only interested in galaxies, field coverage isn't nearly as important as the
signal to noise ratio and overall quantum efficiency.
Putting it all together, I realised that AO would be desirable at 3m of focal
length but impracticable with the back focal length available (97mm) using SBIG equipment.
ST10+CFW8+A08 needs more back focus than 97mm and will rarely be usable
with colour filters.
ST10 + Orion Nautilus CFW + Orion steady star AO with built in off axis guider
and field rotator adds up to pretty much bang on the money.
~c
|
Thanks for the info Clive - you are using a similar set of priorities in the design, with an emphasis on high QE and optimised sensitivity/scale. What sort of seeing do you expect? It's the main design input parameter and all I have been able to do is guess what it might be here - maybe I will get some better idea after I get the system going. I regularly watch planets jumping around and distorting by many arc sec when doing planetary imaging, so it's not likely to be very good much of the time.
the 3200 was way ahead of its time - you are lucky to have one.
I also have one of Dave's focusers, what a nice bit of work it is - it just worked as advertised from day 1 - I haven't calibrated the temp compensation yet, but even that seems to be perfectly functional.
Thought about AO, but it was a pretty short thought with an f4 system The RCC1 would make it a bit easier, but still just beyond the realm of the doable.
Really looking forward to seeing how your system performs.
and thanks very much for Dave's email. I now have a copy, so you can take it off the post if you wish.
Regards ray