Stellarvue SFF7-2 Flattener

[citivolus]

Stellarvue has a relatively new flattener out, designed with a 2" focuser in mind. It is optimised for f/7, with a claim that it will work from f/6 to f/8.

It is stated as a non-reducing flattener, with a 1x result.

Pricing is $265 US at all the vendors I could find it at, not including a t-ring. This puts it a fair amount cheaper than the Borg DG-L, and the same price as the Televue 0.8x.

Has anyone given this flattener a try? I suspect it would be a good match for the Megrez 90. Stellarvue claims that it has good corner performance, in part due to its non-reducing design.

Regards,
Eric

[Kal]

Here are a couple of pics using a SV105 and an STL11K. Note that the SFF7-2 is designed to flatten the field for APS sized chips.

http://www.starscapeimaging.com/M48_Feb09.html
http://www.starscapeimaging.com/M44_Feb09.html

[MrB]

I was looking at this flattener when trying to decide between it, the $150 AstroTech one and a WO FF4.
Have ordered the FF4, but might look at getting one or both of the others at a (much) later date for comparison.

[citivolus]

Is M48 a full frame? If so, it would seem to do quite a good job at the APS-C size, given that the curvature is outside of that area.

[citivolus]

Are you getting the new, 0.8x version of the FF4? If so, I'll be curious to see your results.

Regards,
Eric

[MrB]

Yeah the v3, should be here soon, though it will be a while before I can do any testing... need a mount.

[glasseyes]

Jerry Lodriguss has written a review of the SFF7-2 flattener when used on the Stellarvue SV70ED scope. He compares the performance with an Astro-Tech 2" (AT2FF) flattener and the "William Optics 0.8x combined field flattener / telecompressor", which could be the WO flattener 2 (or perhaps an earlier model?)
Jerry's review is here
http://www.astropix.com/HTML/I_ASTROP/EQ_TESTS/SV70ED.HTM

There is also some relevant discussion here
http://www.cloudynights.com/ubbthreads/showthreaded.php/Cat/0/Number/3329297/page/0/view/collapsed/sb/5/o/all

[citivolus]

Given the processing date embedded in the nebula shot near the end, which was in May, it would have to be either the WO Flat 2 or 3 to be 0.8x.

The Stellarvue definitely out performed the others tested for that focal ratio.

[glasseyes]

Hmm . . . quite possible Eric, but I also found this model which is a ZS66SD APO Reducer/Flattener.
http://www.pulsar-optical.co.uk/prod/generalaccessories/williamoptics/zs66sdaporeducer/flatener.html

See also here http://www.frontieroptics.com.au/Focal%20reducers.html

Perhaps this is the one that Jerry tested on the Stellarvue SV70ED scope?

[glasseyes]

I bought a Stellarvue SFF7-2 flattener and tried it on my WO Megrez 90 with the Nikon D90 DSLR.
I have added a crop from the extreme top left region of the frame, which is where I notice the problem the most. The images were taken a week or two apart so there is a little bit of rotation present.

The SFF7-2 seems to do a pretty good job straight out of the box with no extra spacers fitted, didn't quite flatten everything right to the extreme corners of the image, but a very good result for the money. :thumbsup:

[citivolus]

Not bad, and clearly better than the results with the WO Flat 3.

Thanks John!

[MrB]

Better than the Flat4 too, can't even get focus :(