Experiments with focal reducer and a fast Newtonian

[riklaunim]

I've got a no-brand 1,25" 0.5 focal reducer:

To use it with 150/750 f/5 Newtonian and DMK21. To get backfocus needed and not to strong reduction I've also bought shorter nosepiece for DMK:

And low profile eyepiece holder:

TEST IMAGES

DMK21 + reducer at M10 (lol coma!):

Without a reducer M5 looks like this

And for fun and big coma - DSI III Pro + reducer at M10 - no coma corrector used.

"Saturn" test shots:

- no reducer, f/5

- reducer on, about 30 mm distance from the CCD

- reducer on + locking ring - about 33 mm distance from the CCD

Using reducer calculator for Atik 0,5 reducer at 33mm I should get f/2.94 According to my initial calculations I've got ~2,25 at 33 mm distance.

Comparison: http://i42.tinypic.com/2zhmrut.png

Comparison 2: http://i40.tinypic.com/11j6dye.png - f/5 image resized and placed on the reduced image.

2 sec exposures, 100 frames for the reduced version, few frames for the not-reduced (clouds)

Photoshoping the third reduced image and looking at Stellarium with stars up to ~16mag I've got this:

Coma is noticable (no Coma Corrector used), and the increase in magnitudo range captured also (Saturn is killing it a bit, but still it's nice). At f/5 2 sec stack got hyperion at no-moon + lot of frames.

VISUAL USE:

- 12mm NLV: Moon slightly bigger than in 25mm without reducer

- 25mm Super: some vignetting, stronger stars.