Thoughts on which imaging rigs to concentrate on

[Gina]

Right - imaging rig back on mount and ready to go except that I'll have to check focus.  Probably re-do the flats too.  I reckon to re-do flats after moving the rig off the mount and back on.

[Gina]

15 minutes ago, Filroden said:

Indeed. I think my sky is drowning out the faint Ha so I either need to get many hours or think about investing in some narrowband filters. 

If you have light pollution you need narrowband filters.  They don't have to be the very best and most expensive - I've seen lots of good results with Baader filters.  No idea how good the ZWO filters are - don't even know what they do.  I'll stick with what I've got unless I hear of anyone doing better ones at little cost  

One good thing about the ASI1600MM-cool is that you can use 1.25" filters without worrying about vignetting (particularly with the filters close to the camera as with the ZWO filter wheel).

If you want a suggestion I would recommend trying the Baader 7nm Ha filter - cheap and cheerful   Good for a start if you're short of cash.  I know Baader 1.25" filters fit the ZWO filter wheel - I use their LRGB filters.

Edited November 30, 2016 by Gina

[Filroden]

Thankfully I'm short of sense, not cash so if I do it would be the Astrodon. Starting with Ha to do HaLRGB and then onto OIII and SII. 

But I still have more to do before that. I really want to automate focusing. 

[Gina]

Ah yes.  I too would like to automate focussing and that is something I plan to do but in the meantime my remote manual focussing works pretty well with my own DIY remote focuser.  The control software was developed for a triple imaging rig which I've pretty much given up on so the focuser selector is redundant.  I haven't bothered to alter the control software as the current version works well enough.

Here is a screenshot of the observatory laptop via TeamViewer showing the tree on a far hill that I use to set focus up roughly ready for night-time use.  It's about a mile away and I find this gives a good starting point.  SharpCap is set at 200% and rig slewed such that the top of the tree is central in the FOV.  My "Triple Remote Focussing System" window can be seen in front of the SharpCap window and as can be seen the focus hasn't changed much(Focus Count of 1).

[Gina]

1 hour ago, Filroden said:

Thankfully I'm short of sense, not cash so if I do it would be the Astrodon. Starting with Ha to do HaLRGB and then onto OIII and SII.

In that case I would recommend going straight for the 3nm Ha filter rather than trying to save some funds by going for 5nm first like I did.  The difference is significant and seems far greater than you would expect from changing from 5 to 3.  At least I didn't buy the 5nm OIII

Ha definitely brings out the most nebulosity as hydrogen is more prevalent than oxygen or sulphur (I'm stuck in the mud and refuse to use the "f" version ).  Adding OIII give you a colour rendition and works quite well for most DSOs.  SII is far less useful and most DSOs seem to have very little SII - still worth buying the 3nm version though so that the stars match up.  Where available the SII brings out extra detail and more colours if you use the Hubble palette.

[Gina]

Dark now and the stars are out.  Checked focus and the difference from the tree was just one count.  Seeing causes variation around 2 or 3 counts so it's a matter of watching and adjusting focus for the overall tightest pixel pattern at 400% zoom in SharpCap.  At that zoom individual pixels are visible.  Next to sort out a target.  NAN is currently at the zenith but I've done that except in SI where I couldn't see any image.  Might just try that again.

[Gina]

Trying SII on the NAN but nothing to see with 120s = 2m subs so I'm trying 240s = 4m and see if anything shows

[Filroden]

Good luck. It's cloudy here so I at least get to look at some of last night's data. Just finishing the RGB integrations for the Flaming Star. I see a little more detail, but not much more.

[Gina]

Maybe something starting to show but I don't want to go to much more than 4-5m or I'll start to get oval stars.  Instead I've increased gain from 500 to the maximum of 600 and see if anything shows then.

[Filroden]

It will be interesting to see what a difference that makes though to be fair, if it's that faint it may require integrating before it becomes visible. Maybe try a run of 5 and do a quick star align and integration?

[Gina]

Gain of 600 brings in a bit more of the image but I think I prefer the 500 version so I've gone back to that.  Here's a screenshot of both gains, auto-stretched.  Might try g600 with 120s.

[Filroden]

I can see everything in the 500 that's in the 600. once integrated and stretched I think they would be comparable except I prefer the stars in the 500.

[Gina]

Here's a comparison of 2m and 4m with gain of 600.  The 2m one has better stars.

[Gina]

One advantage of higher gain is that the read noise is reduced.  Sounds counter-intuitive I know but that's what the ZWO graph says.  Of course thermal noise increase but so does the signal.  This seems to be saying the using maximum gain is beneficial on weak targets.  Takes a while to get one's head round these new CMOS sensors

Edited November 30, 2016 by Gina

[Filroden]

Yes, and using the shorter subs and many more of them allows the noise to be reduced through integration.

[Gina]

Collected 30 2m SII subs g600 -30C NAN and decided to see if IC1396 had any SII nebulosity.  Can't see anything with same settings as NAN so trying 4m subs.

Edited November 30, 2016 by Gina

[Gina]

Still nothing even auto-stretched in PI.  Moving on then...  Heart & Soul next...

[Gina]

H+S SII 4m g600 -30C is showing some image when auto-stretched in PI

[Gina]

May give this capture a 1hr run as for the NAN and then see where my other targets have got to.

[Gina]

Found Simeis 147 but it's very very faint.  This is 120s g600 -30C auto-stretched.  Used you navigation instructions, Ken

[Filroden]

That's going to be a great target. It might be faint but you can clearly see it's there.

[Gina]

Here's a single 2m g600 Ha sub post processed in Photoshop.  No calibration just Photoshopped with levels, curves and "Enhance DSO and Reduce Stars" in Noel's Actions.

[Allinthehead]

That looks worthwhile.

[Gina]

Here's an interim result - 23 2m Ha subs g600 -30C pre-processed in BPP with slightly wrong calibration files - I need to capture bias and dark frames for a gain of 600 (nearest ATM is with gain of 550).  Then saved as TIFF and post processed in Photoshop with curves, slightly cropped and saved in PNG format for upload.

[Allinthehead]

Looks promising. What's that blob lower left of target?