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Uranium235

Veil nebula test with a tweaked 200pds

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Finally! Some clear skies (yay!) :)

Ive been doing a bit of fettling to get this 200pds up to scratch and sort out the awful starfield I was getting in the first couple of sessions. So what I did was to strengthen the inside of the OTA with some plating, so I could attach the Baader diamond steeltrack extra-tight without deforming the tube. Also Ive invested in a Baader clicklock to replace the standard compression ring (which I hated with a passion).

Both tweaks seem to have done the job, apart from one very slight distortion towards one corner - which Im now going to put down to the CCD camera becuase its always been there (same corner) regardless of the telescope ive used (frac and newt). So I think I will ship it off to Vince @ Atik to get it cleaned and sorted out.

One other thing that bothers me is a very slight internal reflection that I only seem to get with reflectors in OIII - its almost like a reflection bouncing off the filter onto the secondary and back again. A bit of post calibration DBE sorted it out but I want to be at the stage where I dont need to do that. I might get a UV/IR blocking filter and insert that at various points in the optical train to see if it has any effect.

Anyway, it was just a testing session to see if I'd fixed the immediate problems -  its just over an hour in each channel, so ive not exactly battered the target into submission :)

 

10x450 Ha + OIII (2x2 bin)  2.2" p/p

200pds, Atik 383L+, NEQ6

 

Thanks for looking! :)

28059832113_246d549679_h.jpg

 

200pds at work.jpg

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Very nice, fits in the frame well, great colour, love the rustyred, always rewards the veil.

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Fantastic Rob!

The detail and presentation of this image is superb. It shows the brighter streaks (grey/blue in image) in the 3rd split of the broom that I see visually which is very rewarding to see presented.

This is an incredible image.

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looking nice that is Rob looks like your hard work payed off :thumbright:

 

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1 hour ago, toxic said:

looking nice that is Rob looks like your hard work payed off :thumbright:

 

Cheers Chris! Im still trying to get my head around this reflection problem though. Its present in in raw frames, and in the flats - im trying to figure out exactly which surface is giving me the problem. It doesnt occur in Ha, only OIII.

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You really do manage to get the best out of these Skywatcher Newtonians, Rob - Beautiful image...! :)

 

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What a great image superb 

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Right!! Ive completed my investigations into the OIII problem and here is what I found.

1) Remove the coma corrector - problem goes away (not a viable option)

2) Increase spacing beween FW and camera - problem persists

3) Increase spacing between FW and corrector - problem reduces, but doesnt go away entirely

4) Remove FW and mount the filter scopeside of the corrector - problem goes away

 

So on the basis of that, I will opt for #4 when using the 200pds until further notice. Not great, but the only saving grace is that the clicklock makes it really easy to whip the imaging train off/on to change filters (until I find a workaround). I'll just have to plan my sessions a little better in future.

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Another awesome pic Rob ! You really do get the very best out of every scope you have .

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Very nice.  I'm WIP same target.  Did you get most of this night before last?  Conditions were exceptional up the hills and I got 90 mins ultra-sharp OIII.  Veil reveals any errors in focus and / or haze.

 

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6 minutes ago, physicus said:

Very nice.  I'm WIP same target.  Did you get most of this night before last?  Conditions were exceptional up the hills and I got 90 mins ultra-sharp OIII.  Veil reveals any errors in focus and / or haze.

 

This was from last Saturday night mate :) quite right in that the OIII came through quite sharp, in fact it was so good it unbalanced the Ha a bit so I need to top that up in order to match it.

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On 7/31/2016 at 20:47, Uranium235 said:

Cheers Chris! Im still trying to get my head around this reflection problem though. Its present in in raw frames, and in the flats - im trying to figure out exactly which surface is giving me the problem. It doesnt occur in Ha, only OIII.

are you on about the halo's around the stars in OIII i put that down to my 36mm unmounted OIII filter (baader 8.5nm)

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9 minutes ago, toxic said:

are you on about the halo's around the stars in OIII i put that down to my 36mm unmounted OIII filter (baader 8.5nm)

 

Nah, its not a star problem - its a background level problem. Here, I'll post a flat - you will see a large bright circle taking up most of the frame (its pretty obvious):

MasterFlat_ISO0.jpg

Its present in the raw OIII subs too (to a lesser degree), it turns out that its a reflection of the OIII filter onto the first surface of the MPCC. I dont get this issue with a refractor (ie: the Star71)

The closer the corrector was to the filter, the smaller it was - and vice versa... up to a point where the spacing required to get rid of it was way over the usual 59.5mm (was something like  68mm). When I switched the filter to the front of the corrector, it completely vanished.

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oh hmm what size filter is it rob is it 1.25 mounted or 36 unmounted cos it looks a little like vignetting sorry if i am stating the obvious and you all ready covered that.

 

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3 hours ago, toxic said:

oh hmm what size filter is it rob is it 1.25 mounted or 36 unmounted cos it looks a little like vignetting sorry if i am stating the obvious and you all ready covered that.

 

Its 2", but its definitely not vignetting.

Ive been toying with a way to mount the filter very close to the camera, but it might require me buidling a custom adaptor. I did consider a 2" filter drawer but I reckon I could get it closer with the right bits. That would leave about 32 mm between the filter and the corrrector - maybe a large enough distance to eliminate the reflections.

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