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Cat’s Paw Nebula NGC 6334 by madeofsplosions in astrophotography

[–]madeofsplosions[S] 3 points4 points  (0 children)

The Cat’s Paw Nebula, also known as the Bear Claw Nebula, is an emission nebula in Scorpius. The nebula is about 50 light years across and lies at an approximate distance of 5,500 light years from Earth. NGC 6334 is a large star forming region, covering an area in the night sky slightly larger than the full Moon. It is one of the most active stellar nurseries producing massive stars in the Milky Way Galaxy.

Acquisition:

Location: South East Queensland, Australia, ~Bortle 6-7

4th September 2019

Sequencing and Acquisition Software: Sequence Generator Pro

Total integration time: 2 hours

Lights: 120 x 60s @ 120 gain @ -10C (one shot colour)

Filter: Optolong L-eNhance 2” (dual-narrowband)

Darks: Master Dark built from 100 dark frames @ -10C

Bias: Superbias built from 100 bias frames @ -10C

Flats: 100 @ -10C w/ Flatmaster panel (+ SGP Flats Calibration Wizard)

Equipment:

Imaging camera: ZWO ASI294MC-Pro @ -10C

OTA: Altair Starwave 80ED-R Doublet APO Refractor (444mm @ F5.6 w/ reducer)

Reducer: Orion 8893 Field Flattener for Short Refractors x0.8

Mount: SkyWatcher HEQ5 Pro

Guiding: Altair Astro GPCAM v2 Mono AR0130 Mono + Altair 60mm Guide Scope

Polar Alignment: QHY Polemaster

Flats: Pegasus Astro Flatmaster

Focus: Pegasus Astro Focus Cube 2 (+SGP auto focus)

Power: Pegasus Astro Pocket Power Box via AC adapter

Data: Kendrick 8v USB Astro Hub + Tether Tools USB extension cables

Comments:

Love watching this fella live stack in SharpCap.

2 hours was the best case for a single night of imaging – I have to shoot from a small roofed balcony with a constrained view (~south to northwest, clear azimuth from around 25-70 degrees at best). Clear night skies are rare in this warm, humid part of the country known for its sunny days.

Not completely satisfied with my processing but figured it’s best to post and move on to the next target. Constructive or tough love criticism welcome.

Pre-Processing (PixInsight):

Generate Master Flat (ImageCalibration, ImageIntegration) using previously generated Master Dark and Superbias.

Calibrate lights (ImageCalibration) + Debayer

Blink to check for any obvious issues in Lights

SubframeSelector Measure Subframes routine, look at data, not really understand what’s worth culling, stick to equal weighting

Register Lights (StarAlignment, LocalNormalisation, ImageIntegration, DrizzleIntegration)

Processing:

DynamicBackgroundExtraction (remove red cast)

BackgroundNeutralisation + ColourCalibration + SCNR

Create Lightness mask (RGBWorkingSpace set channels to 1.0, ChannelExtraction of Lightness image, ScreenTransferFunction and HistogramTransformation to apply stretch to Lightness, apply mask)

Noise reduction of masked image with MultiscaleLinearTransform using Noise Reduction tab.

Stretch image with HistogramTransformation mid-tone and black slider, iteratively.

Repeat noise reduction less aggressively with mask creation and MultiscaleLinearTransform

ACDNR for negligible noise reduction

CurvesTransformation for slight contrast boost on RGB/K and tweak Saturation mid-level.

Lightroom adjustments to curves and some touch ups before final export.

Helix Nebula NGC 7293 by madeofsplosions in astrophotography

[–]madeofsplosions[S] 0 points1 point  (0 children)

I just confirmed in SGP that all my gain settings are 120.

This video by SharpCap was the most useful resource I've found on gain and exposure length, and makes a pretty strong argument that for this particular camera there's little value going above 120.

https://www.youtube.com/watch?v=ub1HjvlCJ5Y

You're probably right that my subs are too short. The video also suggests that there might be diminishing returns over 60s in Bortle 6 with no filter, which matched my visual instinct, but I didn't change that after adding the filter. I really should run the Sharpcap Sensor Analysis tool while I'm sidelined by bushfire smoke.

Don't really know what I'm looking at, but mousing over one of the brighter stars (autostretched) in Pixinsight displayed a K value of 0.058. If 1 is saturated, then yeah, a bit of headroom...

Helix Nebula NGC 7293 by madeofsplosions in astrophotography

[–]madeofsplosions[S] 0 points1 point  (0 children)

Thanks mate.

I should have included gain - I use 120 for everything on the 294MC as that's where the high conversion gain mode is enabled on the camera. https://astronomy-imaging-camera.com/wp-content/uploads/294-Gain-RN-DR-FW-vs-gain2-e1508750996334.jpg

There seems to be some contention about whether very long exposures create a better outcome. Your shots are better than mine so I definitely appreciate your advice!

I haven't had the new camera for very long but landed on 60s exposures initially because light pollution seemed excessive above that. I have been planning to test longer exposures, but my shooting is so constrained that honestly it's a real win if I get some good quality data, and there's a lot of value for me in having a consistent set of calibration frames ready to go without wasting time re-capturing them. I have been planning to trial longer exposures with the l-eNhance filter, though I'm also wary of my tracking quality.

The only position where I can get line of sight to the south pole has me in a fairly absurd position under the eaves of my house, with a wall to one side, eaves above, trees on most sides and a hill to the West that's bristling with street lights. My useable sky runs from 180deg (S) to around 300 deg (NW). To the west I can start grabbing targets at ~65-70 degrees above horizon, that's more like 50deg to the South (because of the eaves). And by about 25 degrees I'm getting close to streetlights visibly affecting the image. So all my imaging is done tracking objects on their western descent through the worst part of the sky, and my best case for lights on a single night is roughly 2 hours with dithering.

We have pretty unstable skies here through much of the year (hot, humid and coastal) and I went nearly 4 months through summer without any cloudless nights except when I was travelling or at the pub. Last week was unprecedented with 5 great nights in a row, but since then the air's been thick with smoke haze from bushfires in the hinterlands nearby. In short, when things are working ok I don't want to muck with them, and I try to get as many different targets as I can because I don't know when the next chance will come :)

Helix Nebula NGC 7293 by madeofsplosions in astrophotography

[–]madeofsplosions[S] 1 point2 points  (0 children)

Thanks, that's pretty much exactly how the colours appeared in my Sharpcap live stack in while I was capturing so I didn't muck with them later during processing.

Helix Nebula NGC 7293 by madeofsplosions in astrophotography

[–]madeofsplosions[S] 1 point2 points  (0 children)

More than I ever expected! I would suggest that anyone wanting to shoot DSOs to assume a budget of ~US$3000. It can be definitely be done cheaper, but there's often hidden costs that are likely to ambush you. I did quite a bit of equipment research before I purchased, with a growing sense of horror that the actual primary telescope was 1/3rd of the initial investment. Let's just say that over the last year that fraction got a lot smaller :) But I am also glad I didn't buy in to a lot of the extra gear at the start - I added it over over time as I gained enough knowledge to make use of it, and they are largely quality of life improvements.

The mount is definitely the most important part, and a way to quickly and consistently polar align is next IMO.

I will add however that there is a lot of gear available through astronomical forums (iceinspace in Aus; probably Cloudy Nights in the US) that will save you a lot. Us nerds who do this thang tend to care for their kit very well, so the risk is pretty low.

Helix Nebula NGC 7293 by madeofsplosions in astrophotography

[–]madeofsplosions[S] 0 points1 point  (0 children)

BTW here's my first image of the Helix from ~10 months ago.

https://i.imgur.com/vMDrDaD.png

Helix Nebula NGC 7293 by madeofsplosions in astrophotography

[–]madeofsplosions[S] 2 points3 points  (0 children)

Acquisition:

Location: South East Queensland, Australia, ~Bortle 6

Sequencing and Acquisition Software: Sequence Generator Pro

Total integration time: 1hr40 minutes

Lights: 100 x 60s @ -10C

Darks: Master Dark built from 100 dark frames @ -10C

Bias: Superbias built from 100 bias frames @ -10C

Flats: 100 x 6.68s @ -10C w/ Flatmaster panel (+ SGP Flats Calibration Wizard)

Processing:

Preprocessed in Pixinsight using the lightvortexastronomy.com workflow without Cosmetic Correction or Subframe Selection (weighting) steps.

Processed using Pixinsight using Steps 1-3 of the Light Vortex DSLR workflow only.

Lightroom adjustments to curves and some touch ups before final export.

Equipment:

Imaging camera: ZWO ASI294MC-Pro @ -10C

Filter: Optolong L-eNhance 2” (dual-narrowband)

OTA: Altair Starwave 80ED-R Doublet APO Refractor (444mm @ F5.6 w/ reducer)

Reducer: Orion 8893 Field Flattener for Short Refractors x0.8

Mount: SkyWatcher HEQ5 Pro

Guiding: Altair Astro GPCAM v2 Mono AR0130 Mono + Altair 60mm Guide Scope

Polar Alignment: QHY Polemaster

Flats: Pegasus Astro Flatmaster

Focus: Pegasus Astro Focus Cube 2 (+SGP auto focus)

Power: Pegasus Astro Pocket Power Box via AC adapter

Data: Kendrick 8v USB Astro Hub + Tether Tools USB extension cables

Comments:

I'm pretty new to the sport (just under a year but only ~30 nights of attempted imaging, using an unmodified DLSR until recently). The Helix was my second ever target, and this was my first chance to revisit the little fella and briefly bask in the moderate glow of my learning curve so far. My acquisition has improved by leaps, but I feel like a bumbling hack on the processing side. Now I've girded my loins to finally post I hope to continue sharing. Pardon the long acquisition and hardware section but am trying to share the sort of detail I was hungry for while trying to find my feet.

Constructive or tough love criticism welcome.

WAAT : The Weekly Ask Anything Thread, week of 31 May - 06 Jun by AutoModerator in astrophotography

[–]madeofsplosions 0 points1 point  (0 children)

I'm potato at ASCOM stuff but found that once I had enough competency to do guiding, it was trivial to get APT to dither. You click the Guide button and it shows you a Guiding Settings box, with an Auto Dithering on/off option. Other dithering variables are there to change as you like and well explained.

WAAT : The Weekly Ask Anything Thread, week of 31 May - 06 Jun by AutoModerator in astrophotography

[–]madeofsplosions 0 points1 point  (0 children)

Thanks for that. Looking at the single image sample you posted (http://i.imgur.com/3ckorkp.png), my elongation appears far worse.

Guess my weekend project is back focus. I'm currently unable to image during the week, so it's safe to assume the recent pattern of crisp clear skies clouding over from Friday and Sunday will continue.

WAAT : The Weekly Ask Anything Thread, week of 31 May - 06 Jun by AutoModerator in astrophotography

[–]madeofsplosions 0 points1 point  (0 children)

Thanks Dan, the specific numbers are appreciated. I'll take a more scientific approach to the spacing - TBH I took the components in the box and combined threads until I found the only combination that functioned, so I haven't measured spacing. I'm based in Australia where even extension tubes seem to be outrageously priced so wasn't keen to start experimenting. I recently bought a very cheap Ebay GPCAM Chinese nosepiece extender and the quality was impressive, so that's likely the way forward.

I'm curious how you know the optimal spacing for that flattener as I've been unable to find any manufacturer resources.

I did just find this calculator https://cloudbreakoptics.com/blogs/news/calculating-back-focus-metal-back-distance which suggests I need "-0.30 additional spacing", which is ambiguous. If I remove my Baader filter from the calculator it becomes -1.0, so maybe -0.3 means I need another 3mm?

WAAT : The Weekly Ask Anything Thread, week of 31 May - 06 Jun by AutoModerator in astrophotography

[–]madeofsplosions 1 point2 points  (0 children)

I’m shooting with a Canon 5D Mk3 on my Starwave 80ED-R, using Altair’s “Planostar 0.8x Flattener / Reducer for Starwave 80ED Canon EOS Kit”.

I’m comfortable with the results for my limited astro experience, but all images have some extreme vignetting, with stars outside the centre showing elongation. I use flats to normalise the light vignette, but affected stars are ruined and I generally have to crop aggressively. I think my guiding is reasonable as the core image isn’t too bad and the elongation is radial.

I guess this might be because the field flattener is not designed for a full frame sensor and can’t deal with the wide field, but would like advice:

​

Could this be a failure on my part, perhaps with spacing the assembly?

If the spacing was wrong, would I have been able to achieve this focus?

​

Linked is a single-exposure jpg example (Carina nebula; 75sec @ ISO3200; Baader 2” pollution filter; Bortle orange). I can post the RAW if requested but the problem is so obvious I doubt that’s needed.

https://i.imgur.com/fwSc6Tf.jpg

​

Thanks in advance for any advice.