Creating a F2 refrator using a f3.3 FR.

[MGTechDVP (Mariusz)]

Hello,

Has anyone tried adding a f3.3 focal reducer to a f6.3 refractor for long exposure photography.

The reason I want to do that is basically to get a wider field of view on my refractor for big nebulas such as the horsehead nebula. The 8SE at 2032mm is still narrow even when using the f6.3 FR, the f3.3 on the DSLR has too much vignetting. So I thought an f3.3 on a 500mm refrator and the DMK41 can will give a faster scope (in theory) and a wider field of view.
Unless my numbers are out, that would yield the scope to be about f2.

I modded my CCD nosepiece to get the chip close enough to the FR to achieve focus at infinity. On landscape tests it seems to be OK, but I'm waiting for the skies to clear up on a night when I'm not working the next morning.

Thanks in advance for any responses.

Mariusz

[dannat (Daniel)]

Surplus shed in US are selling a 6" f1.9 plane camera at the moment,

[gregbradley]

The really small camera chip will have the effect of creating a narrow field of view which will negate a lot of the wider field of view.

Greg.

[MGTechDVP (Mariusz)]

Thank you for the responses gents,

I simulated the field of view on Starry Night Pro 6 and it is a considerable amount wider... but how it operates in the real world.. particularly long exposure astro photography, will be revealed when I get a chance to experiment.

If successful, i'll post my results, might help a few people in wider/faster astrophotography.

Mariusz

[LightningNZ (Cam)]

I suspect you'll end up with field curvature and a bunch of other nasties but will be keen to see your results. I know John Wall has successfully imaged with an F/3 Hypochromat and a narrow-band filter (over at the CN) so it can work.