Images of DSOs with Maks

[Analysis Paralysis]

Hi, anyone with some good examples of DSO images they have taken using a mak? I would regard this as a real challenge given the high F ratio. 

Thanks

Mark

[fireballxl5]

I've imaged at 2700mm focal length using an Orion Optics OMC300 (12" Mak-Cass) and SX H16 mono camera. Here are some from a few years back.

These were taken between 2008-12 and so I'm hoping that my processing skills have improved in the meantime...

HTH, Andy

[Analysis Paralysis]

55 minutes ago, fireballxl5 said:

I've imaged at 2700mm focal length using an Orion Optics OMC300 (12" Mak-Cass) and SX H16 mono camera. Here are some from a few years back.

These were taken between 2008-12 and so I'm hoping that my processing skills have improved in the meantime...

HTH, Andy

Thanks for these wonderful images. I calculate F/9 focal ratio, is that correct? 

I'm wondering about F/15 in a 7 inch. Would you think the same results could be obtained in this case?

Thanks

Mark

[ollypenrice]

I've rather done 'the F ratio myth' to death on here but it's good to see images which confirm that it is, in the right circumstances, a myth. The 'right circumstances' are essentially simple: will the object fit on the chip at the given focal length? If it will, the number of object photons arriving on the chip depends on aperture. F ratio has, quite literally, nothing to do with that. (This is simple and entirely beyond debate. If anyone wants to tell us that you get more photons from the ring nebula in a camera lens than you do from a 14 inch SCT then I can only invite them to try!) Any 'wiggle room' in the argument comes from the need to put enough light onto each pixel to get a good enough S/N ratio in the exposure time possible.

Andy's images, and particularly his outstandingly good M51, invite explanation by those convinced that F ratio alone is the dominant factor.

So, to answer the OP's original concern, choose objects which fit on the chip and a mount, camera, autoguiding system and location which allow you to expose for long enough and the F ratio won't have much to say on the matter!

Olly

[Analysis Paralysis]

1 hour ago, ollypenrice said:

I've rather done 'the F ratio myth' to death on here but it's good to see images which confirm that it is, in the right circumstances, a myth. The 'right circumstances' are essentially simple: will the object fit on the chip at the given focal length? If it will, the number of object photons arriving on the chip depends on aperture. F ratio has, quite literally, nothing to do with that. (This is simple and entirely beyond debate. If anyone wants to tell us that you get more photons from the ring nebula in a camera lens than you do from a 14 inch SCT then I can only invite them to try!) Any 'wiggle room' in the argument comes from the need to put enough light onto each pixel to get a good enough S/N ratio in the exposure time possible.

Andy's images, and particularly his outstandingly good M51, invite explanation by those convinced that F ratio alone is the dominant factor.

So, to answer the OP's original concern, choose objects which fit on the chip and a mount, camera, autoguiding system and location which allow you to expose for long enough and the F ratio won't have much to say on the matter!

Olly

Thanks Olly. My very basic understanding from what I've read, is that a lower f ratio makes it easier to get the correctly exposed image more quickly. The longer exposure times needed in the higher f ratio make guiding more critical and hence harder to achieve high quality. But not impossible in the hands of someone with the knowledge and right kit. Is that correct or nearly correct? 

[fireballxl5]

1 hour ago, ollypenrice said:

Andy's images, and particularly his outstandingly good M51, invite explanation by those convinced that F ratio alone is the dominant factor.

Sorry, I've just got to quote this from a true master of the dark arts - thanks for the compliment 

PS, yes these are at f9 (300mm aperture, prime focus).

Regards, Andy

[Analysis Paralysis]

25 minutes ago, fireballxl5 said:

Sorry, I've just got to quote this from a true master of the dark arts - thanks for the compliment 

PS, yes these are at f9 (300mm aperture, prime focus).

Regards, Andy

I think that an F15 mak dso challenge would be interesting, although the kind of people who own F15 Maks may,in general,  prefer planetary imaging over dso. I did see a 180 mm F15 mak image of the trapezium and interestingly, due to underexposure - by accident- all 6 stars in trap were visible as well as some delicate nebulous structure. It was quite different to the normal lower f ratio images that tend to over expose the trap.