Increasing ODK 16 FOV

[eatabean]

Does anyone have a clear answer as to whether I can use a focal reducer on a 16 inch ODK? We are using a Starlight Express SX694. I wrote to Orion Optics, but their answer was rather vague... something like "we have not found any that work to our satisfaction..." not exactly those words, but not a satisfactory answer, in my opinion. I have been told to change cameras, to one with a larger element, but unless the problem is reaching focus then I see no other reasons it will not work. Any help?

Thanks!

Jim in Sweden

[ChrisLX200]

Can't give you an answer I'm afraid but I was wondering the same thing about my 12" ODK. I have a 2" AP reducer I can try at some point. The corrected field on my OTA is quoted as being 52mm diameter so for my main camera a reducer won't be needed (16803 sensor) but for a smaller sensor it could potentially be very useful. I suspect the only way you'll find out is to experiment - OO won't offer a recommendation if it increases the spot size significantly even though you may find you could live with that.

ChrisH

[eatabean]

I suspect there would be some coma, and that may make their scope look worse. But the fov of our setup is just so dang small! Let me know how that works out for you.

[ollypenrice]

The suggestion that you go for a bigger chip isn't daft! In bin 1 you're imaging at 0.34 arcsecs per pixel and even in bin 2 you're at an optimistic 0.69. Does your seeing support that? Failing that you go to bin 3 at a potentially attractive 1"P/P but by now you're down to a 2 meg final image size. In a nutshell it has to be the wrong camera for the  scope.

You paid a lot of money on the ODK16 to have a very large corrected circle and with this camera you're using only a fraction of it. I used a full frame 18 meg Kodak in an ODK14 for a couple of years. This worked in Bin 1 at 0.66"P/P. The idea was to bin colour 2x2 but the SX camera in question wouldn't bin properly so we lost that opportunity. If you went for, say, an Atik 11000 or the big Moravian such as Chris has you'd be at about the same resolution as we were with the 14 inch. That works. The deciding factor between the giant chip and the fullframe might be the filter prices. The difference is huge.

Some examples from the 14 inch and the 18 meg Kodak:

 

My instinct on focal reducers would be to say 'no.'  The scope is already susceptible to internal reflections and adding glass at the back would, in my view, be asking for trouble every time you went near a bright star. Like OO, I have no means of knowing - but that's my instinct.

Olly