Djorgovski 2, Barnard 86 and NGC 6520 (Dead Man’s Chest star cluster)

[Dennis]

Last night (Wed 6th Aug) I was hunting for the galactic globular cluster known as Djorgovski 2 (ESO456-SC38). After the ‘scope had slewed there and a 30 sec test image was downloaded I noticed Barnard 86 and NGC 6520 (Dead Man’s Chest star cluster) in the same field - 3 objects for the price of 1. Lucky me.:)

There was an almost full Moon chasing the GC, on top of the Brisbane light pollution.

Tak Mewlon 210, Tak x0.8 RF, ASI1600MM Pro camera.

L:60, R:30, G:30, B:30 mins, all sub-exposures 30 secs at Gain 75 and Offset 10 (per The Sky X Pro Camera Control).

I’ve included a 1280x960 full field view (down sampled from 4650x3520) and higher res crops of Barnard 86/NGC 6520 and Djorg 2.

Cheers

Dennis

[multiweb]

That's an awesome close up Dennis. A field I definitely want to try to image too. :thumbsup::thumbsup::thumbsup:

[multiweb]

Had another look on the big screen this morning. That's the Mewlon 210 but did you use a reducer? What's your image scale, FL and FOV size in arc minutes? Trying to work out the field to expect with the CN-212. :thumbsup:

[Dennis]

Hi Marc

The Mewlon 210 is F11.5 (2415mm FL) and the Tak x0.8 Reducer/Flattener should take it down to 1932mm at F9.2.

However, I have just started playing around with NINA and a plate solve gave me a FL of 2080mm which would be around F9.9. The Sky X Pro Image Link gave me a FOV of 29x22 arc min at a scale of 0.38 arcsec/pixel.

This discrepancy is probably the result of having the focuser racked out (main mirror moved) further than the Tak ideal specs so I could insert a motorised focuser and a filter wheel.

Your CN212 as F12 should be an ideal combo for this object.

Cheers

Dennis

EDIT: just added a full res crop of the B86 region to show the view at 2080mm, F9.9, 0.38 arcsec/pixels with 60 mins Lum and 30 mins R:G:B with the ASI1600mm.

[multiweb]

Good stuff Dennis. Thanks for all the info. :thumbsup:

On the paper the CN-212 at F12.4 gives me 2630mm FL and an image scale with the QHY9 of 0.42 with a field of 23.4'x17.4'. Because like you I'm further at the back those figures will probably be on the low side.

I have a reducer to bring it to F9.9 but that's another element that takes backfocus.

That's a really good shot up close. Still not many gaps between stars even at that FL.

[Dennis]

Thanks Marc, I appreciate your comments.:)

The processing phase was a bit of a baptism by fire in using PixInsight, as I found that CCDStack really struggled with the ASI1600MM files (I had previously been using the ATIK 414 EX which it handles much more responsively).

I found a “Batch Pre-processing” Script in PI and just chucked in my Bias, Dark, Flat and Light Frames and punched the “go” button and all seemed to work well.:)

I used to blink through all my LRGB frames manually in CCDStack to catch and manually reject any funny ones that should be excluded, so I will have to figure out how to achieve the same in PI, as I may have included some duds in the big bucket of frames I poured into PI, without any prior checking.

These large chips certainly stress the PC during the processing phase, thank goodness for apps like PI.

Cheers

Dennis

[multiweb]

If you have the CCDIS plugin you can rank your subs with it. I find the high precision star alignment in CCDStack struggles when stars cover a lot of pixels at longer FL. When that's the case I use Prometheus which is part pf MBJ's Goodlook suite.

You can rate subs in PI. There is a script for this under SCRIPT>Batch Processing>Sub Frame Selector. Not sure about blinking but I'd say they have a tool to do this as well.

[Zubenel]

Drop dead gorgeous region!I viewed this area originally through my ATM 10" B86 the Ink spot has to be the best Barnard .. but then there is the Snake.... Ahh too many haha.:lol: Came away from an astrofest with
this image burnt into my retinia . Then Ron put me onto Djorgovski 2 and sure enough it was there for the taking. I should give AP a crack on "Zamar":question:

[Dennis]

Thanks for the comments and feedback Marc and Wes, I appreciate it.:)

@Marc - I have just discovered a very useful function in Images Plus (I have V 6.5) that allows you to blink files.:)

It's under "Image Set Operations" then "Blink Files". Works extremely well.:thumbsup:

Cheers

Dennis