7Cyg

[MikeWilson]

I aimed for 52Cyg and got 7 and a ton of stars instead.

I thought it rather nice and a good test of field flatness.

Lots and lots of stars. (Testing field flatness) by MikeWPhotos, on Flickr

10 x 10 minute subs in RGB (using a CLS filter during a waning gibbous moon).

Curvature: 17.4%

Total Tilt: 7%

^ Is this acceptable for the TRF-2008? With some practice heavily tightening the compression ring (three screws hold it tightly), I've managed to get the modal flatness to be pretty flat. It's just the right edge now that concerns me a bit.

Clear skies, everyone!

Mike

[blackparticle]

That looks pretty good for a larger chip camera and more than acceptable to me.

It's possibly something that could be rectified in the processing using an image deformation plug-in anyway if it's really apparent on some images. Personally I'd go for putting the centre of the object slightly down and to the left and cropping the right hand side out, using that area to account for the overall RA drift of the mount as the session goes on.

What software did you use to get the curvature readout btw?

[perfrej]

That looks decent, but I agree that the right side is a bit worrisome.

We should have a loooong dedicated thread on field flatness using only CCD Inspector. For those who don't want to fork up the money for it, well, they can participate for a month or so on trial license. It is a fantastic piece of software!

There is so much to gain from a discussion like that. Acceptable values, the importance of flatness versus the importance of even illumination versus focus versus collimation etc.

I, for one, am going to try to get my scopes really straight with CCD Inspector. I have a Feathertouch on its way from Ian King and will start by collimating that properly and see what that brings.

/per