I think I need an APO

[Kaptain Klevtsov]

Gordon has very kindly lent me his neodymium Baader filter for comparison purposes and I aimed it through the clouds using the big Frac. and the D50.

Is a crop of one of the subs. As you can see the colour fringing is quite pronounced so I either use it with narrow band filters in future or trade up to a more expensive APO. Or is there another way round this?

Captain Chaos

BTW it's pin sharp on the moon and planets, almost like the Mak. so don't think I'm saying that achros are carp.

[FLO]

I am not sure I understand the post CC. A neodymium is a LPR filter, it isn't designed to prevent false colour. What effect are you after?

[Kaptain Klevtsov]

Steve, I was just moaning really.

I'm not suggesting that the filter would APOise the 'scope, rather that my image illustrates the point that it isn't an APO. The colour fringing is something that I need to get rid of before I can get good images. The 'scope does that, so I might need to get rid of the 'scope, or use a CCD with coloured filters and refocus each colour individually.

I have a Baader fringe killer which does what it says, but the neodymium one is a 2" to test the vignetting effect (or lack thereof) when compared to the 1.25" version.

Vignetting wise it cures it completely, which tells me that for the DSLR I need to go to 2" everything to get even illumination.

I posted it as I was surprised how bad the fringing is and it gets worse if I try to boost the nebulosity (this is M45 BTW) for obvious reasons.

Next step is to stick it in the 8" Newt., but the clouds got in the way big time.

Captain Chaos

[FLO]

Ah, I see.

I often use the same achro refractor as yours and consider it to be one of the better corrected models.

So 'yes' you need an APO 8)

[Kaptain Klevtsov]

I want to see how the filter and camera setup does on the Newt. then have a scratch of my head over this. So much to spend and so little cash!

Captain Chaos

[FLO]

Good idea - Newtonians have no false colour.

[GordonCopestake]

Mike is selling an ED120 for £650 which is a bargain. On the cheaper side you could get an ED80 for £200 and on an EQ6 you have a fantastic imaging platform. You would probably get close to the cost of an ED80 if you sold the 120 f/8.3 achro

[GordonCopestake]

http://www.astrobuysell.com/uk/propview.php?view=9907

[Ambermile]

Ooo yes, that's a nice one. I had it for a while in the spring.

arthur

[iancandler]

A cheap alternative worth trying is a WO vr-1 minus violet filter, it wont give you APO but it knock's colour fringing on the head far more effectively than the baader fringe killer in my opinion, they also do it in a 2" version should you prefer it ( I do lol) you could use both that and the LPR together

[Ambermile]

The WO VR-1 is pretty much tuned to the WO and clones objectives Ian, I'd not reccomend it for a Synta tbh.

Arthur