Thoughts on which imaging rigs to concentrate on

[Gina]

Here's the result.  Screenshot of auto-stretched image in PI plus post processed in GIMP to adjust the histogram to show the image better.  This is the full frame and I think is showing slight vignetting which isn't corrected by the flat.

[Gina]

Cygnus Loop OIII light frames selected in Blink and something like half rejected just choosing the really good ones.  Selected the best frame for reference and now running BPP on 148 60s g440 -30C lights.

[Gina]

Here's the result - screenshot of image auto-stretched PI.  Different vignetting this time.  I think I may know why - the dew shield is just push on and might have been "skew-whiff".  Fortunately the image will be well cropped so the vignetting will be removed.

 

[ChrisLX200]

I don't know if you've read this thread Gina: http://www.astrobin.com/forum/c/group-forums/zwo-asi1600mm/gain-and-offset-settings-for-long-exposure/

Jon Rista is a good guy who knows what he's doing so his comments particularly may be helpful.

ChrisH

[Gina]

That thread is about long exposures so not really relevant - most I use is 2m.  Thanks all the same   Mind you, the advice is to use short exposures.

Edited November 24, 2016 by Gina

[ChrisLX200]

3 minutes ago, Gina said:

That thread is about long exposures so not really relevant - most I use is 2m.  Thanks all the same

Well it was his use use of the offset parameter in shorter (90-120s) I thought interesting...

Anyway, here are the gain settings I use, with a 150mm aperture at f/4:
Optimal SNR: Gain 75/Offset 15, 480-600s
Balanced SNR/Resolution: Gain 139/Offset 30, 210s
High Detail/Resolution: Gain 200/Offset 60, 90s

ChrisH

[Gina]

Yes, I hadn't read that far down but now I have and it's interesting   I think I might do more experimenting with even higher gain - the higher the gain the lower the read noise.  I might take it to the very limit of 600 that's 60dB and see what happens.  But I think this might be best just for fainter DSOs.  I've been getting pretty good results with the gain and exposures I've been using.  In fact I reduced the gain for the bright DSOs in Cygnus.

[Gina]

This gives me an idea.  I've been using the default gain of 210 for the ASI178MM for night-time yet the sensor is from the same "stable" as the 1600 so will no doubt have similar properties.  I could put the gain up to more like I'm using on the 1600.  I'll try that tonight.

[Gina]

Now for the North American Nebula and friends.  100 Ha light frames checked in Blink and passed - all very good.  Chose one for reference and all now being processed in BPP with the new calibration masters.

[Gina]

The OIII light frames show very little image and I think I may have to capture another set.  I would also like to try SII lights.  If I'm going to it will have to be soon as the NAN is fast disappearing in the west.

I have 105 OIII NAN lights which I'm putting through BPP in the hope of getting something.

[Gina]

Auto-stretched NAN results 100 Ha and 105 OIII.

[Gina]

Been through this thread and listed the capture events

2016-10-05 M31
2016-10-06 Flats & more M31 50s g139
2016-10-09 M31 Ha
2016-10-10 Continued & Cygnus Loop
2016-10-13 NAN
2016-10-15 NAN
2016-10-17 Heart & Soul
2016-10-18 Heart & Soul  More NAN
2016-10-20 Flats  More NAN
2016-10-26 Heart & Soul
2016-10-31 Heart & Soul
2016-11-01 Flats
2016-11-02 Cygnus Loop + Heart & Soul
2016-11-03 Heart & Soul
2016-11-04 Heart & Soul
2016-11-07 Cygnus Loop OIII

Here's the current list of focal lengths and fields of view :-

1.     28mm f3.5 lens --- 2103m x 1322m  35° x 22°
2.     45mm f2.8 lens --- 1309m x 1005m   22° x 17°
3.     55mm f1.8 lens ----- 1071m x 823m   18° x 14°
4.     135mm f2.5 lens ----- 433m x 335m   7.2° x 5.6°
5.     200mm f4 lens ------- 295m x 226m   4.9° x 3.8°
6.     400mm f5 scope ----- 147m x 113m   2.5° x 1.9°
7.     1.0m f5.3 scope --------- 59m x 45m  1.0° x 0.75°  Oversampled at 1x1 binning

[Gina]

Clear sky   Looked at NAN as I wanted more data but it's gone below the roof of the observatory so I'm imaging the Heart and Soul instead.  Here's a single Ha sub 60s g500 -30C stretched a bit in GIMP.

Edited November 24, 2016 by Gina

[Gina]

 Been looking through data from earlier and it seems I have oodles of H&S OIII subs so I'll go over to SII when I've finished the 100 Ha I have set up.  I don't seem to have any SII subs.

[Gina]

Been running the SII subs through Blink discarding heaps but there are some that could integrate into something useful   Scanning through the stretched images you can see the clouds blowing through the images and untick the clouded out images.  I've gone though the set several times moving image files to my Junk folder.  The first run tailed the set for dawn onwards then discarding for clouds.  I've ended up with 75 possible images to process further out of the original nearly 300.  So the night may well have provided useful data from the gaps between clouds - the advantage of short exposures

[Gina]

Just finished collecting darks and biases to match the SII subs of the Heart and Soul from last night and with the sky clear have swapped the lens cap for dew shield and opened the observatory roof ready for more imaging.

[Gina]

Capturing the Heart and Soul in SII but the data is very sparse - almost invisible in unprocessed subs but I've dragged a bit out in GIMP using curves and "despeckle" several times over

[Gina]

Gave up on H&S SII and decided to have a go at IC 443, Jelly Fish Nebula, in Ha.  Here is a single Ha sub of 60s g500 -30C histogram stretched in GIMP.  The Monkey Head Nebula is also in the frame

[Gina]

Processing tonight's H&S SII subs - total 80 passed the Blink test - in BPP.

[Gina]

Neither last night's nor tonight's H&S SII masters look any good   I think the combination of Ha and OIII will be as far as I will be able to go - I can't see the SII adding anything useful.  I might try combining all the subs and feeding them through BPP.

[Gina]

Sky has deteriorated now   I'll capture more IC 443 data next clear night.  Meanwhile, I've fed just 45 files selected in Blink through BPP and done a bit of post processing in GIMP.  Here's the result - full frame and cropped the the Jelly Fish.

[happy-kat]

Yey the jelly fish :-) all these interesting shapes just hanging up there. Will you be adding more data to it?

[Gina]

Yes indeed, I certainly will - soon as I get the chance   I like to get at least 100 of these short subs.  I was quite pleased how much I got with just 45m total imaging time

[Filroden]

1 minute ago, Gina said:

Yes indeed, I certainly will - soon as I get the chance   I like to get at least 100 of these short subs.  I was quite pleased how much I got with just 45m total imaging time

That's what I'm loving with this camera. You can get something you're happy with in a reasonable time. That doesn't stop you adding to it, but at least you see something good quite early

[Gina]

Yes indeed   Also, this was calibrated with the wrong darks and I'm taking matching darks right now.  This was captured with a gain of 501 and the darks were 439 (nearest APT will go to 500 and 440).  I'll process again once I get the new darks and see what difference there is.  6dB gain difference I would expect to make a difference but we'll see.  Looks like next clear night will be Monday.  Meanwhile, I have lots of unprocessed data to work on for other DSOs.