The Double Cluster in Perseus, Tuesday 19th October

[The Thing]

Meade LX90 8", Baader Alan GeeII flattener reducer, Canon 350Da, Astronomik CLS-CCD clip filter, Lakeside automatic focuser.
Guided with finder/guidescope and QHY5 using PHD.
FoV approx 2x1 degrees (Maxim).

18(of 20)x240s processed in Deep Sky Stacker, 20 flats, 20 darks, 20 bias. This image is 1/4 size, and I don't know what the jets are bottom right!

Unfortunately I messed up the darks - they were only 4 sec not 4 mins. Hence the amp glow hasn't been removed. Something to redo when it's only 1 degree C.

[RobertM]

That looks really good Duncan, once you have proper darks you should be able to pull out many more stars.  It still looks like you have some abberation in the corners; on the other hand an APS chip must be pushing the optical limits of that flattener so maybe that's to be expected.

Whats that streak going through that star in the bottom right - looks mighty peculiar !

Robert

[The Thing]

Thanks Robert. The corners are always going to be off with this setup.

The artefact is due to a  water mark under the ccd glass caused by frost melting. Or I've imaged an event of some importance!

[Tony G]

I don't know what the jets are bottom right.

Could it possibly be a meteor?

Great image Dunc

Tony G

[Mac]

Something to redo when it's only 1 degree C.

Take the darks in a fridge?

Nice image, will look much better when you add the darks.

That is a strange streak, could be a meteor as Tony said, however as it must be in all of them
otherwise it would have disappeared during the stacking, its probably as you said, a bit of frost
causing dare i say it, diffraction spikes.

Mac.

[MarkS]

Duncan,

That's a great image - nicely focused and well collimated (since the corner aberrations are symmetric).  These aberrations are expected from an SCT.

Something has gone wrong with the overall colour - it looks overall brown with very little star colour.  I think this is probably something that DSS has done.

I would say the jet is a diffraction spike - something was obstructing the lightpath.  A rubber band or something?

BTW there's only one corrector I know of that will nicely correct an SCT over the size of a DSLR CCD.  It is this one:
http://www.teleskop-express.de/shop/product_info.php/language/en/info/p3291_Image-Corrector---0-8x-Focal-Reducer-for-Schmidt-Cassegrains.html

Mark

[Fay]

Well done Duncan, perhaps you have caught something of great importance... 

[Rocket Pooch]

Duncan, thats the most focused and flat images I think you have done, it looks really nice, also just say you caught a meteor.


Chris

[Fay]

I agree, the best, nice round stars, waiting for the next one now

[mickw]

Nice one Duncan

[The Thing]

Thanks everyone.

The mystery spike coincides with a drying mark on the underside of the glass over the CCD i.e. inaccessible unless I dismantle the camera again. It's easily visible on the flats. The bright star is right on one of the lines. Weird effect though.