Veil nebula test with a tweaked 200pds

[Uranium235]

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!

 

[Mick J]

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

[jetstream]

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.

[toxic]

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

 

[Uranium235]

1 hour ago, toxic said:

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

 

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.

[AndyUK]

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

 

[andyo]

What a great image superb 

[laudropb]

Very nice image.

[Mrbloke]

lovely, nice work

[Uranium235]

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.

[Nicho]

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

[peter shah]

Lovely detail with tight stars

[physicus]

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.

 

[Uranium235]

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.

[toxic]

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)

[Uranium235]

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):

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.

[toxic]

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.

 

[Uranium235]

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.