Pickerings Triangle in HST

[ChrisLX200]

Finished this tonight, despite poor seeing conditions for the SII data. Image is a total of  5x 20min HA and OIII, and 7x 20min SII. My usual hardware, NP127is refractor, Atik 490EX (@ 1x1 binning), Losmandy G11, and TV Pronto + Lodestar for guiding. Processing done in StarTools, PI and Ps.

ChrisH

[ollypenrice]

That's strong and clean. Good stuff.

Olly

[Ant]

I agree that's very nice Nice and crispy, focus looks bang on!

I'll have to go off and find out where it is and how big it is

Ant

[ChrisLX200]

Many thnaks

I agree that's very nice Nice and crispy, focus looks bang on!

I'll have to go off and find out where it is and how big it is

Ant

Just out of interest... I looked at my records and the scope was re-focused 11 times (using autofocus) during the total exposure for that image (17 subs in total).

ChrisH

[Ant]

Is the re-focus an automatic process at the end of each sub? Or a manual thing?

Ant

[ChrisLX200]

Is the re-focus an automatic process at the end of each sub? Or a manual thing?

Ant

It re-focuses automatically on each filter change and also each 1degC temperature change.

ChrisH

[Ant]

That's interesting cheers Chris, i understand the refocus on filter change. I wasn't expecting a refocus every 1 degree drop in temp though.

I assume that the software waits till the end of a sub before refocusing lol.

[ChrisLX200]

That's interesting cheers Chris, i understand the refocus on filter change. I wasn't expecting a refocus every 1 degree drop in temp though.

I assume that the software waits till the end of a sub before refocusing lol.

Yes it does There is also an option to adjust focus dynamically as temperature changes but for that you need good calibration of its effects - something I don't have. I know it's approximately 200 steps per degree (175,000 steps total focuser travel) but I don't think it is linear so it gets complicated. I'll just stay with the 1degC change I think.

ChrisH

[Ant]

How do you allow for Flats?

I was always under the impression that for Flats you shouldn't adjust the camera orientation or focus from the Lights?

Or is the amount of focus change so slight that for flats it doesn't really matter.

Sorry I realize we are getting a little off topic (this will be my last question honest!)

Ant

[ChrisLX200]

How do you allow for Flats?

I was always under the impression that for Flats you shouldn't adjust the camera orientation or focus from the Lights?

Or is the amount of focus change so slight that for flats it doesn't really matter.

Sorry I realize we are getting a little off topic (this will be my last question honest!)

Ant

I think as you say, the amount of change is small and there are no sharply defined artifacts on the flats - just gradients - so it makes no real difference.

If anone is interested I have put the raw FITs files in an archive (with just Master calibration files, too big with all the raw calibration files) and uploaded to my new DropBox folder. The total size of the RAR file is 228Mb. So if you want to play at image processing you can download them. You might well do a better job than me...

https://www.dropbox.com/s/bywlph2domxchgc/Pickerings%20Triangle.rar

ChrisH

[Stargazer33]

Now that is gorgeous!

[swag72]

I like that Chris - Very nice indeed

[ChrisLX200]

thanks Bryan

ChrisH

[ChrisLX200]

I like that Chris - Very nice indeed

Thaks Sara

ChrisH

[PhotoGav]

Lovely image Chris. I particularly like the stars given no RGB data. Very interesting about re-focusing through the acquisition. How minute were the focus changes, do you know? I have so far only focused at the beginning of a session, with my latest setup the filters seem very par-focal... Perhaps this explains my unsharp images!!!

Also, well done on the raw data thread. I will add some DSLR data to it soon, though server space starts to become an issue as the files are laaaarge!

[ChrisLX200]

Lovely image Chris. I particularly like the stars given no RGB data. Very interesting about re-focusing through the acquisition. How minute were the focus changes, do you know? I have so far only focused at the beginning of a session, with my latest setup the filters seem very par-focal... Perhaps this explains my unsharp images!!!

Also, well done on the raw data thread. I will add some DSLR data to it soon, though server space starts to become an issue as the files are laaaarge!

Thanks Gav, a (very) rough calculation suggests there is a 0.117mm (117uM) change for each 1degC temperature change (that is, 200 steps per degree, and 175,000 steps for a total focus range of 102mm).

The critical focus range (green light wavelength 510) where the focused image of the star lies within the airy disk (with my pixel size and f/ratio) is 67uM.

I guess based on that fact I should be re-focusing for every 0.5degC rather than 1degC to stay within critical focus, but that would get tedious!

ChrisH

[wuthton]

Just out of interest, which Startools processes do you find useful?

[ChrisLX200]

Just out of interest, which Startools processes do you find useful?

I've tried all of them to see what they do and all are useful in some types of image. Routinely I use (in this order):

Autodevelop - to see everything in the image

Crop - remove stacking artifacts

Develop - from scratch again to remove the autodevelop, may require several stages.

StarMask - create this now and save it as an image, then invert it

Wipe - if there are any gradients. It will also remove faint nebula if you're not careful.

Deconvolve - Carefully! to reveal fine detail without messing the stars up (usually 2pxl, 12 iterations, 6pxl mask fuzz)

Contrast - is not always useful, you can lose the background

Sharpen - again, needs to be used judiciously as it increases contrast.

HDR - many options here, Optimise and Tame Highlights are most useful

Life - the Isolate function can be very useful to lift certain objects out of dense starry backgrounds.

De-Noise - Stop tracking and de-noise. Last step before saving the image.

If a colour image then use the colour tool to balance.

LRGB tool does more than LRGB, you can create bi-colour and narrow-band images.

Layer is also useful for removing noise in combination with specific masks

Heal will remove the stars for you if you want to work on nebulae alone

Repair can be used to correct poor star shape (although not good if you want to stack with other channels afterwards)

Flux is useful for modulating the deconvolution effects

Filter for colour images means you can manipulate features in certain colours etc.

Well I'm not going to write an advert for StarTools or a user manual! There is a lot more to it than at first appears and you need to read the StarTools manual (http://www.startools.org/download/StarTools%20Manual%20V1_3_5%20Unofficial.pdf) to get a better idea. I'll use StarTools by default unless I hit a problem it cannot deal with - then I move to PixInsight because it is certainly more flexible and has more options (at the expense of being far more hardwork to use IMHO). You can make a complete mess of an image with PixInsight if you don't know what you are doing with it (and generally I don't )

ChrisH

[NOMH]

Great image and a difficult target to get looking right using all three NB filters.

What automation program do you use? Does it slew to another target star or does it use a star in the FOV?

Thanks,

JB

[wuthton]

I've tried all of them to see what they do and all are useful in some types of image. Routinely I use (in this order):

Autodevelop - to see everything in the image

Crop - remove stacking artifacts

Develop - from scratch again to remove the autodevelop, may require several stages.

StarMask - create this now and save it as an image, then invert it

Wipe - if there are any gradients. It will also remove faint nebula if you're not careful.

Deconvolve - Carefully! to reveal fine detail without messing the stars up (usually 2pxl, 12 iterations, 6pxl mask fuzz)

Contrast - is not always useful, you can lose the background

Sharpen - again, needs to be used judiciously as it increases contrast.

HDR - many options here, Optimise and Tame Highlights are most useful

Life - the Isolate function can be very useful to lift certain objects out of dense starry backgrounds.

De-Noise - Stop tracking and de-noise. Last step before saving the image.

If a colour image then use the colour tool to balance.

LRGB tool does more than LRGB, you can create bi-colour and narrow-band images.

Layer is also useful for removing noise in combination with specific masks

Heal will remove the stars for you if you want to work on nebulae alone

Repair can be used to correct poor star shape (although not good if you want to stack with other channels afterwards)

Flux is useful for modulating the deconvolution effects

Filter for colour images means you can manipulate features in certain colours etc.

Well I'm not going to write an advert for StarTools or a user manual! There is a lot more to it than at first appears and you need to read the StarTools manual (http://www.startools.org/download/StarTools%20Manual%20V1_3_5%20Unofficial.pdf) to get a better idea. I'll use StarTools by default unless I hit a problem it cannot deal with - then I move to PixInsight because it is certainly more flexible and has more options (at the expense of being far more hardwork to use IMHO). You can make a complete mess of an image with PixInsight if you don't know what you are doing with it (and generally I don't )

ChrisH

Thank you for that, a much more comprehensive reply than I was expecting.

I'm off to give startools another go, I always seem to end up with images that look over-processed.... fake.

[MartinB]

Wonderful detail and colour.  Excellent!

[sharkmelley]

An excellent result - very nicely processed.

Mark