Crop or flatten?

[LewisM]

Anyone found an effective flattener for the GSO 8" RC's?

Or simpler/more cost effective to crop the image?

Also, anyone tried the new focal reducer GSO made for these?

[rmuhlack]

The 4000 chip is smaller than APS-C - you might not need a flattener. From Paul's thread it seems like he only needs a flattener for the corners of his images and he is using a full frame sensor (an SBIG 11000).

[LewisM]

Seems we might get a crack at testing it all tonight. Technically it's not mine (YET), as I bought it on behalf of a mate with the proviso I showed him how to use it etc (bad choice of teacher...).

I have made him an offer with something else he might like instead... :D

[DJT]

Hi Lewis, I picked up a ts flattener spruiked as working well with the RC8. Got the adapters made up for the moonlite and the STL

Chucked it on and indeed flat to the edges but reflections and the introduced hotspot was quite something. Have set it aside for now and am happy to crop till I figure out what to do with the flattener. The RC8 with my chip means I just crop 20% which is fine for what I want to image.

Will look at maybe flocking for the flattener and adapters at some point but no rush. With hindsight, the extra glass is just another point of failure at the moment and I can get away without it

[LewisM]

Thanks David.

First thing we did was matt-down the focuser/drawtube spacers with some ultra-flat black paint. These looked suspiciously shiny, despite the grooving/mini baffles.

The intention is almost solely galactic imagery with this one, so definitely not wanting a reducer, but after the test tonight, will decide if it needs any sort of field flattener. The CCDInspector result Lars provided showed around 30% curvature, though almost all of it at the periphery of the mirror. The central area looks nice, and it certainly is beautifully collimated (survived the road trip very well, thanks to Lars supreme packaging). Lars had tried a Tak flattener in it, to minimal effect.

The 4000 chip gives me a little hope for being outside the curve, as Richard suggests. I know my sadly departed ST8XE would have had no issue, with that tiny chip :D

[ReaPerMan]

Hi Lewis, I had success with the Astrotec 2" FF. This worked on my QHY10.

[Paul Haese]

Tak flattener 35 works well with that scope. Produces a flat field to the edges of an APS size sensor.