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Rossete Neb and Horsehead/Flame neb Taken with WO GT81


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Just thought I would post a couple of images taken with the new WO 81GT.

The focuser seems easily hold my Atik 460EX/filter Wheel/OAG.

Still having a few problems with the reducer-CCD distance but I'm very close now to

the optimum value. Both images were taken using a 0.8X focal teducer.

1. NGC 2244 (Rosette Neb) 5X8mins Ha and 5X8mins OIII - synthesised green channel.

White stars - no time for RGB.

2. Horsehead and flame Neb 10 X 5mins Ha filter.

Quick processing to get some results quickly.

John

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The corners look fairly good to me, have you tried focusing with the 2/3rds focus technique? That might be the thing that helps it towards a flatter field. What have you found the FR > CCD distance to be? And how have you measured it (digitally?).

Looking forward to getting my hands on one of those GT81 scopes sometime next year, but I need to see if there are any potential pitfalls to overcome first.

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The corners look fairly good to me, have you tried focusing with the 2/3rds focus technique? That might be the thing that helps it towards a flatter field. What have you found the FR > CCD distance to be? And how have you measured it (digitally?).

 

Looking forward to getting my hands on one of those GT81 scopes sometime next year, but I need to see if there are any potential pitfalls to overcome first.

Hi,

I have been focusing on a star about half way between the centre of the image and the corner.

Not sure what the 2/3 rds technique is.

The reducer to CCD distance was about 53/54mm a bit less than the 55/57mm that WO suggest.(digital calipers)

The reducer does not cover a DSLR chip completely.( its not bad but stars in all corners are elongated slightly)

John

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2/3rds is exactly like what youre doing, but not halfway - a bit further out ;)

Thanks for the info, Hmmm.. 53mm, thats cutting it closer for me (but not impossible). The sales blurb said "covers APS sensors", but you've just stated otherwise - so it puts into doubt whether it will give me perfect stars in the corners of a 383L+ (which is what im after) - hopefully you can get it perfect before long :)

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2/3rds is exactly like what youre doing, but not halfway - a bit further out ;)

 

Thanks for the info, Hmmm.. 53mm, thats cutting it closer for me (but not impossible). The sales blurb said "covers APS sensors", but you've just stated otherwise - so it puts into doubt whether it will give me perfect stars in the corners of a 383L+ (which is what im after) - hopefully you can get it perfect before long :)

I think the 383L would be OK as it is that bit smaller than a DSLR sensor.

13.5 X 18.2 mm for 383L and 14.8 X 22.2 mm for DSLR

John

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