Barlow problems

[GrantR]

Really hoping someone can help me with this one. I'm mainly into planetary and lunar imaging so I recently sold my SPC900NC and bought a DFK 21AU04.AS to use with my Celestron NexStar 5se. After a few false starts I can now get a reasonable image from it but Jupiter is still very small. The 5se is only 1250mm and the resulting image is too small to get much detail. I can push it slightly with extension tubes but if I try any sort of barlow the results are dire, fuzzy images, no detail, onion skinning etc. Same results with my cheap Celestron 2x and my Revelation 2.5x. I never had this problem with my SPC900 and Skywatcher 200P but the wee SCT really doesn't seem to like the extra magnification. Any thoughts? It's not all down to conditions either, we had some great seeing last night and got a decent Jupiter but again, total nonsense with the 2.5x barlow. It's doing my head in!

[JamesF]

To be brutally honest, I probably wouldn't have exchanged the SPC900 for that DFK21AU04. The sensor in the SPC900 is probably the better of the two.

However, there's no reason I can see that the 5SE shouldn't be capable of a good image of Jupiter in the general case. My Mak has a slightly smaller central obstruction and a touch more focal length, but they're in the same kind of ballpark and I'm usually imaging at around f/35. Without the option to go back to the SPC900 and see how it behaved in the scope, I'm not sure what to suggest.

James

[Rockrae78]

What EP are you using with the Barlow?

[JamesF]

What happens if you push the gain up more? Does that help at all?

James

[GrantR]

Hi James, doesn't seem to help much at all. Even with the gain up I still get the onion skin effect, too high and it burns out even the strongest of the bands on the planet. From what I've seen, the DFK is way better then the SPC900 and it's performance on lunar is brilliant but this barlow on Jupiter thing is doing my head in. I'm now wondering if it's a focus issue? Seems very hard to get focus with the barlow.