Fuji S2 Pro DSLR with Celestron 80ED refractor (1 Viewer)

Playing some more with lens combinations. After a number of tests with different configurations, I find that stacking the Kiron 2X teleconverter with a GSO 2X barlow gives me the overall best results. The images from this combination are even slightly better than I can get from the GSO 2X barlow alone. I still don't know how to explain this, even though I have seen people in other forums getting similar results when stacking teleconverters. This configuration gives me a working focal length of 2400mm and factoring in the 1.5x crop factor for the Fuji S2 Pro, that's 3600mm and still getting good detail (although I'm down to around 1/180 sec shutter speed at 400 ISO). I think this is going to be my working combo for those distant raptors.

Rick

bluedubius said:

Playing some more with lens combinations. After a number of tests with different configurations, I find that stacking the Kiron 2X teleconverter with a GSO 2X barlow gives me the overall best results. The images from this combination are even slightly better than I can get from the GSO 2X barlow alone. I still don't know how to explain this, even though I have seen people in other forums getting similar results when stacking teleconverters. This configuration gives me a working focal length of 2400mm and factoring in the 1.5x crop factor for the Fuji S2 Pro, that's 3600mm and still getting good detail (although I'm down to around 1/180 sec shutter speed at 400 ISO). I think this is going to be my working combo for those distant raptors.

Rick

Click to expand...

Rick,

If you are shooting for distance, I don't understand why you don't go Prime Focus. It would allow you to get rid of the 40mm Maxview which is which is not renowned for its sharpness and you would still get your 3600mm, using a lot less glass:
600 x 2 x 2 x 1.5 = 3600

I have tried to use a Canon 2x TC in front of the 2x barlow and results were not very exciting. Using a Canon 1.4x TC and the 2x barlow was much better. However, it may be different with the Kiron TC.

I was just experimenting with the lens on the camera. I agree 100% that I am getting better images at prime focus, with or without the teleconverters. I really was expecting a lower quality image when stacking the barlow and 2x converter, but to my eye at least the stacked image is better. Will eventually acquire and try a 1.4x for the increase in light over the 2x. I've got a post in to Paul (or anyone else) to explain how he got the glass lens element out of the GSO barlow. I'll try that next and see what happens.

bluedubius said:

I was just experimenting with the lens on the camera. I agree 100% that I am getting better images at prime focus, with or without the teleconverters. I really was expecting a lower quality image when stacking the barlow and 2x converter, but to my eye at least the stacked image is better. Will eventually acquire and try a 1.4x for the increase in light over the 2x. I've got a post in to Paul (or anyone else) to explain how he got the glass lens element out of the GSO barlow. I'll try that next and see what happens.

Click to expand...

Have you tried taking quite a few pictures with that setup to confirm that you are getting better results or just a few ? With manual focus, results vary a lot when shooting at long distances because it is not easy to focus accurately. Also, the smallest movement shows up big time at those magnifications.

I've been using the scope at prime focus both with and without the converters and barlow for several months. Last week I took 200 shots of one perched Cooper's Hawk. Most of the time the shots taken with the 2x barlow or 2x converter (or stacked) have been sharper than those I take without. One possibility may be that I seem to be able to focus more accurately with the larger bird image. Here is a sample of a photo of the Cooper's Hawk with the barlow and converter stacked.

Rick

What I tend to do is go for the least amount of magnification possible and just crop the image in close if I want the bird bigger in the photo. This probably applies more to modern dslr's of 12 million or more pixels which allows for plenty of cropping.

Here's an example of a bird at approx 50m (165 feet). Photo was taken with just the scope at 600mm and to make focusing really easy I used Live View and magnified the bird to 10X. 2nd photo is 100% crop but to make a pleasing photo you would only really need to crop about 50%.

Out to 100m I can get away with just using the 1.4X Kenko Pro teleconverter and at the most I'll combine it with the 2X GSO but the success rate generally goes down as the magnification goes up. Cropped photos using less magnification are as good as the ones where I've used maybe double the magnification.

Paul.

Had a bit of time this morning after a couple of snow days to play with the equipment again. This was a quick shot stacking the 2X Kiron teleconverter and the 2X GSO barlow. Pretty good detail for a 3600mm fl equivalent.

Rick

Good stuff Rick.

Your photo shows a few black specks which is dirt on the sensor. Stacking the teleconverters and barlows increases the f number so high that any dirt on the sensor will easily show up. It's not such a problem on modern dslr's with auto dust removal but it's something I noticed a lot with my old Pentax dslr whenever I stacked up the magnification.

Paul.