Bleeping autoguider

[LewisM]

Annoying scattered cloud tonight - moving fast and frequent enough to make the autoguider have fits. So, in the end, only ONE 5 minute sub of M42 was worth keeping.

I had Canon long exposure noise reduction on, but also ran it through DSS with flats and darks (master files of same ISO I had).

Turned out O.....K..... needs a LOT more data.

Not too shabby for a 5" apo refractor taken from inner suburbia with more streetlights than needed (seriously, 5 streetlights for a quiet suburban area???)

GOOD quality png: http://img21.imageshack.us/img21/1320/m424nov12.png

So-so jpeg:

[LewisM]

PS: that was taken PRIOR to moon rise of course.

[Forgey]

Very nice Lewis. I'd be happy with that.

[Larryp]

Yes, very nice, Lewis!:thumbsup:

[LewisM]

Thanks. I am not happy with it, though had to show SOMETHING besides my latest supernova picture for the night.

My focus was a little soft for starters. Then my over-compensating for light pollution (did NOT use the filter for a change - decided to try fixing it in PS, which was only partially successful - some stars look somewhat golden/brownish tint)

Last night was just a bummer. From the guider refusing to even guide on Tarantula until JUST before moonrise (and even then, some non-circular stars), to the cloud, to eventually the moon. I knew I was right to stop at 11pm.

Ah well, it was first true test of the new refractor, and whilst I think it still needs some tweaking, it' getting there. I flocked the lens shade yesterday, which made a MAJOR difference. I think it needs flocking from the objective to the first baffle, so will likely do that today. Northgroups black paint is not exactly matt.

[cometcatcher]

Good shot Lewis. Maybe a little black point clipping in the processing but otherwise the new refractor is working fine. When you sell it in 2 days time I want first offer. :P

[LewisM]

Hmmmmmmmmmmm. Tempting, seeing I was offered something I have always wanted.

Buying another Vixen today too :) ;)

[rmuhlack]

Stars look a little bloated to me. As you have identified it could be guiding, could be focus - but if it was me I'd look into that. Perhaps get a bahtinov mask if you don't have one.

Also don't know why you're using the in-camera noise reduction (which if I'm not mistaken basically takes an in-camera dark and subtracts it from the previous light frame). That's what dark subtraction in DSS (or whatever software you're using) is for. Not to mention that taking in camera darks after every light frame effectively halves your available imaging time. For me I'd much rather gather twice as many light frames

Why not just build up a 'library' of dark frames on an evening when you're not doing any imaging, note the ambient temps, and then use the appropriate dark frames or dark masters when it comes to processing? If the reason is hot pixels left after dark subtraction in DSS, you can get rid of those easily with the cosmetic correction feature.

[LewisM]

I use in-camera noise reduction 'cause I dislike what DSS spits out. Just me I guess.

It was a focus issue, as I verified in my shots of the Tarantula Nebula from last night too. Thought it was spot on, but alas, not quite! I think I "bumped" the electric focuser button once when shifting between PHD and my camera controller - fat fingers on a laptop touchpad.

I do have alibrary of darks and flats, as I said: "I had Canon long exposure noise reduction on, but also ran it through DSS with flats and darks (master files of same ISO I had)." Iwill typically tweak a RAW in PS first, then throw it into DSS for some final pixel treatment.

I think that StarTools also bloated the stars a bit.

All in all, like I said, the shot is a DRAWN OUT O...K..not good, but not BAD either. 1 shot on a funny night, and I HAD to show SOMETHING for the time expended! :)

[pluto]

Any reason you didn't use the filter Lewis?
I just bought an Astronomik CLS 2" on the weekend but I haven't used it yet. Of course Sydney is still under its nightime blanket of clouds, as it has been for the last few weeks... :(

[LewisM]

Simply forgot!

Had to put Miss 4 to bed by myself last night (wife was studying for uni). Rushed to get out before my favourite alignment stars weren't too darned high (I use Achernar primarily, then Markab and usually Peacock), and then was trying to do it all before the clouds really started to roll over.

All in all, just a rushed night. Did at least get the supernova image I wanted... keeping a record of it as and when I can.

[cometcatcher]

If possible, the Orion nebula + running man is best taken without any filter. Perhaps a very gentle LP filter for M42 itself. There's such a wide range of nebula types in this area that LP filters tend to clip some of them. It would be different if it was only Ha nebula, but running man is mostly blue reflection nebula so the CLS and most LP filters will clip it to some degree.

[rmuhlack]

so i assume the dark and flat libraries were collected with in-camera noise reduction enabled as well? Otherwise if you're not subtracting like from like you're introducing noise rather than removing it. And what about dark flats and bias/offset frames?

I refer back to my earlier comment that for me i'd rather spend my precious available imaging time collecting as many light frames as possible to maximise my SNR and pool of usable subs, and collect new dark frames either before/after the imaging session or at another time altogether (when the moon is up, when its cloudy etc).

If you don't like the dark subtraction DSS is giving you perhaps you need to try some different dark frame integration settings, or acquire more dark frames for your masters, or perhaps try different software? For example I started earlier this year with DSS, but have recently moved to PixInsight and the difference it has made to my images is remarkable.

[rmuhlack]

Another thing to possibly look at is your guiding settings. I assume you're using PHD? Adjusting the exposure time to your guide star and the conditions as well as optimising the RA aggressiveness/hysteresis and min pixel motion to your equipment (something i'm still working on) will also affect tracking performance.

[LewisM]

I am using Pixinsight now... yeah, the difference is EXTREME!

The dark, flats and Bias files are 20 frames EACH per master. A small catalogue of temperature variance - my usual nights are about 24°, so that is what I mainly use.

No, noise reduction in camera is OFF for the D,F and B files :) I ain't that silly :)

Because of my dislike in general of DSS previously, I turned NR ON. Now I am using pIxinsight, I find LESS need for this, but still do it out of habit I guess. Still learning Pixinsight fully.