Altair RC250 TT

[ChrisLX200]

Interesting that I posted in this thread earlier :-) I did investigate the Altair 12" RC but unfortunately the image circle it produces is only around 40mm, far too small to cover the sensor of my new 16803 camera. So in the end I ordered an Orion Optics ODK12 f/6.8 which offers an image circle of 52mm - just about big enough! I still have a long wait for it be made though...

ChrisH

[DrRobin]

Hi Graham,

Many thanks for the quick response and nice annotated photo.  Nice to know that others have been thinking about a focal reducer, which I guess is going to reduce the back focus a little.  All I need to do now is carefully measure the obs again to make sure it is going to fit.

I am intending to keep my C11 until after testing an RC250, so I can always try my Moonlite and if it doesn't fit sell it with the scope and look to buy another.  I am sure it will fit, I might need to get another adapter ring, but that will be a whole heap less than a new motorised Moonlite.

Chris, I stated by looking at a new 35mm mono ccd to match my C11, but then I have to buy a genuine Celestron 0.7x FR (major expense) and decided it was a lower cost route to stick with the camera I have and go for a scope with a lower focal length.  The C11 Edge are great, long focal length (good for planets) and a flat field, but F10 is really too long for most DSOs.  I bought a Lepus 0.62x FR, which brings it back to a reasonable focal length, but the Lepus only has a 24mm imaging circle so won't support a larger chip camera than I already have.  Plus an RC250 is a good deal less money than a SX35, Atik 11000, etc and almost a kings ransom on your 16803 camera.

BTW I fancied a 6303 chip camera until I read about the problems with the chip.

[ChrisLX200]

Hi Graham,

Many thanks for the quick response and nice annotated photo.  Nice to know that others have been thinking about a focal reducer, which I guess is going to reduce the back focus a little.  All I need to do now is carefully measure the obs again to make sure it is going to fit.

I am intending to keep my C11 until after testing an RC250, so I can always try my Moonlite and if it doesn't fit sell it with the scope and look to buy another.  I am sure it will fit, I might need to get another adapter ring, but that will be a whole heap less than a new motorised Moonlite.

Chris, I stated by looking at a new 35mm mono ccd to match my C11, but then I have to buy a genuine Celestron 0.7x FR (major expense) and decided it was a lower cost route to stick with the camera I have and go for a scope with a lower focal length.  The C11 Edge are great, long focal length (good for planets) and a flat field, but F10 is really too long for most DSOs.  I bought a Lepus 0.62x FR, which brings it back to a reasonable focal length, but the Lepus only has a 24mm imaging circle so won't support a larger chip camera than I already have.  Plus an RC250 is a good deal less money than a SX35, Atik 11000, etc and almost a kings ransom on your 16803 camera.

BTW I fancied a 6303 chip camera until I read about the problems with the chip.

Yes I think the 6303 is a NAB sensor, very high QE but an utter PITA for our purposes having to deal with blooming ( :-) ) spikes.... I'm just unboxing my new camera as I type, polystyrene peanuts everywhere  :-)

ChrisH

[DrRobin]

Don't drop it Chris, I think I might hear the 'oh ....' from here.

Having had a look around at ccd sensors it seems the astro market is full of cameras based on fairly old chip designs, the exceptions are the 16803s and other very large chips which seem a bit more modern.  Even the KAI 11002 seems to be fairly old now, so perhaps I am better off sticking with my KAF-8300 and waiting until something significantly better comes along before making the investment?

Robin

[ChrisLX200]

Don't drop it Chris, I think I might hear the 'oh ....' from here.

Having had a look around at ccd sensors it seems the astro market is full of cameras based on fairly old chip designs, the exceptions are the 16803s and other very large chips which seem a bit more modern.  Even the KAI 11002 seems to be fairly old now, so perhaps I am better off sticking with my KAF-8300 and waiting until something significantly better comes along before making the investment?

Robin

Yes the 11002 is a bit weak for NB imaging, the 16803 is a bit better but still nowhere near the QE of Sony sensors (for example). I'm not sure where the new generation of large sensors is going to come from, CMOS probably. I wouldn't swap out the 8300 unless you definitely need the larger size sensor. There are some new QHY cameras listed on their website with 8300-size sensors but they're a bit of an unkown at the moment.

ChrisH

[DrRobin]

Yes the 11002 is a bit weak for NB imaging, the 16803 is a bit better but still nowhere near the QE of Sony sensors (for example). I'm not sure where the new generation of large sensors is going to come from, CMOS probably. I wouldn't swap out the 8300 unless you definitely need the larger size sensor. There are some new QHY cameras listed on their website with 8300-size sensors but they're a bit of an unkown at the moment.

ChrisH

Chris,

Quite so.  My C11 + 0.63 FR and KAF8300 gives 35.1' x 26.3' (arc minutes) and a useful 1.26"/pixel with 2x2 binning.  A 11002 at F/10 only gives 44.5' x 29.7' with 1.32"/pixel with 2x2 binning, so not a lot more FoV.  This improves if I buy a 0.7x FR to 64.8' x 43.2' with 0.96"/pixel with no binning, but the 0.7x FR with 44mm imaging circle are £650.

Whereas an RC250 @ F8 with my KAF8300 gives 30.9' x 23.2' and using a 0.67x FR gives 46.2' x 34.6', so about the same as my C11 with the 11002, but for a lot less money.  The FRs I have seen can go up to 34mm imaging circle (depending on reduction ratio) so a camera mid way between a KAF8300 and a KAI 11002 would be ideal, especially if it had good QE and anti-blooming. 

Sounds like a winning camera to me, SX, Atik, etc take note.

Robin