wimvb

That’s an impressive Loch Ness Olly.

2 hours ago, DaveS said:

I made a Synthetic Luminance from the entire data set just calibrated with a Master Dark then used it for a Synthetic LRGB. I was able to apply a touch of Unsharp Mask at the end of the processing but not sure if it's made a great deal of difference.

I did the same. Combined the R, G and B masters in image integration without pixel rejection. I may have darker skies, since I could see the faint parts of the galaxy in the superstretched synthetic L after 7.5 hours of imaging time.

Very nice already. Adding L will bring out the faint arms/shells of ngc 7550.

3 hours ago, WolfieGlos said:

Lovely image Wim, really like NGC7549 in there.

Thanks, Chris. It is one of kind. If it were any closer it would probably be a very popular target.

1 hour ago, Elp said:

Are you referring to the residual pattern which is left on the image after calibration (it's shown in the link above)? I've never really managed to get rid of it on my uncooled OSC and I normally use gain 200 with this camera. Reading about it I believe it had something to do with bias not being removed from flats correctly at lower gains, as the sensor works differently. A lot of people don't see the issue, you generally won't if you don't push the data hard, after a background extraction in Siril the issue is amplified further.

 

I've only used 0 gain for all my imaging, and flat fielding hasn't really been a problem for me. What I see here is first and foremost a subtle banding and noise at high signal, both of which shouldn't be there. What my tests also show is that this anomaly disappears for gain 139 and higher.

20 minutes ago, DaveS said:

And you've also got HCG 93 down in the bottom left, my next target with the ODK 12 / SX 694 combination

yes. It will be interesting to see your result. Good luck.

Much has been written about the sometimes odd behaviour of the sensor inside the ASI294MM, the IMX492.

To get the best dynamic range (highest full well depth), I have so far only used it at its lowest gain. On the other hand, I've always wanted to take advantage of the lower read noise at high conversion gain. Before just adopting a new setting, I've done some homework and read up on this as well as doing my own very unscientific testing.

Robin Glover (SharpCap) has commented on this sensor on various occasions, for example here:

https://forums.sharpcap.co.uk/viewtopic.php?t=5561&sid=0bc6040e8c7a98eb6cba4f0ae1215f51

I decided to test the behaviour of the sensor regarding saturation and found disturbing results.

I set the temperature to 2 degrees C, offset to 5, bin 2, and used 5 and 20 seconds exposures with my flat panel at its lowest setting. At both exposure times, the sensor was saturated (20 s made sure of that)

First a few images, one with low conversion gain (119) and one with high conversion gain (121)

The same stretch was applied to both images

The hcg image shows noise and some banding (maybe difficult to see in the jpeg).

Next I measured the minimum pixel value of overexposed frames versus gain. Here's what I found

The graph shows the lowest pixel value in a frame for 5 and 20 seconds exposures, vs camera gain setting. Gain 120 is where the high conversion gain kicks in.

This is a disturbing behaviour because it means that not all pixels are saturated at gain just above the high conversion gain threshold.

At gain 139 and above, the sensor behaves as it should, but between the switch to hcg (120) and 138, the sensor is not well behaved.

This behaviour is documented in the IMX492 spec sheet.

Tonight will be a clear night, although wiindy, and I'll try to do some test exposures at 0 gain and 139 gain, just to compare lcg mode with hgc mode.

1 hour ago, ONIKKINEN said:

Maybe a little bit of IFN/dust too?

Yes, but still very faint. Flat fielding needs to be perfect to show it (which it wasn't).

This is a not so often imaged area of the autumn sky. The constellation Pegasus contains a large amount of small galaxies, which by themselves aren't much to look at. But in a widefield image (if an image at 1,000 mm focal lengthcan be called that) the wide variety in galaxy shapes, sizes and distances becomes quite impressive.

Annotated version:

Image details:

7.5 hours of RGB data (no luminance), captured with the SkyWatcher MN190 and ASI294MM camera during two nights in early October.

Relative humidity during both nights was 93% or higher, and the moon was more than 50%, so not the best of conditions.

2 hours ago, GalaxyGael said:

And a good idea to go with that SW base plate so your focuser position is unchanged for this type of scope.

Good luck with it this season

That was my main requirement. Thanks.

2 hours ago, GalaxyGael said:

My mn56 corrected circle doesn't quite do aps c with the tiny secondary

Do you need aps-c? I used the ASI174MM-Cool for a few years. Great little camera for dso, apart from the horrible amp glow. But if zwo ever release a cooled version of the ASI482 with 5.8 um pixels, I will be seriously tempted to get one.

I think that asian focusers have improved so much over the last few years that Starlight Instruments and the likes must be hard pressed to keep up. And with so much going on at that company, I wouldn't be surprised if they go out of business.

2 hours ago, GalaxyGael said:

Handsome image.

Which focuser did you use to replace the stock one? 

Thanks, Colm. I originally planned to treat myself to a FeatherTouch focuser, but Astroshop kept pushing the delivery date forward. After one year, several mails, and reading about all the troubles Starlight Instruments was (still is?) going through, I did a bit more homework, and found that the Omegon Steeltrail Crayford focuser should match the MN190 base plate. I ordered that model and had money left to add a Pegasus AstromFocuscube, plus a Pegasus Astro powerbox advance. I'm happy with the replacement. It has much better stability than the original SkyWatcher low profile focuser with its wobbly built in extension tube.

Very nice. I agree with @tooth_dr regarding the green. Try scnr with its default settings. Once you've subdued the green, the other colours will come through much better. In histogram or curves, you can also target just the blue colour. Subtle adjustments can shift the colour balance.

On 01/10/2023 at 16:30, WolfieGlos said:

That’s a great final image, love the star colours and faint fuzzies too.

Thanks, Chris. Yes there are quite a few fuzzies in the background. For some reason, no more than a handful are mentioned in Simbad/Vizier. This is uncharted territory in a way.

On 01/10/2023 at 17:37, tomato said:

Great colour and detail on the galaxies. I’m not a fan of images where the IFN takes precedence over the galaxies, but it is nicely balanced on your image.

Thanks. Detail on the galaxies could have been better in my opinioin. Warm autumn nights aren't the best for shooting galaxies. I agree with you aobut the ifn; it should be a whisper, not a shout.

51 minutes ago, Rodd said:

Wow--that MN190 is awesome.  Truly an amazing image.  I am not familiar with these and I need to look into them

Thank you, Rodd. After replacing the stock focuser and re-collimation, the scope is ready for another season.

No longer a work in progress. https://stargazerslounge.com/topic/414033-ngc-7640-and-ugc-12588-in-hargb-wip/ 

It turned out that shooting flats with the camera at -10 degrees and 96 % humidity isn't much of a hit. I had ice forming on the sensor which ruined the calibration. I shot new flats, now at +2 C to avoid freezing, and reprocessed the data from scratch.

The light frames weren't affected by the ice, either because I collected the data under better conditions, or simply because of the dithering and registration which reduced the effect.

This is what I got from the data. I think reprocessing the original data payed off.

Ngc 7640 is a barred spiral galaxy in the constellation of Andromeda. It is at a distance of 25 - 30 Mly and has a size of about 90,000 light years.

Ugc 12588 is a spiral galaxy at about the same distance. Its size is only about 18,000 light years

Both galaxies show signs of star formation, which is why I collected H-alpha data.

• 3 x 2 hours RGB
• 5 hours L
• 5 hours Ha

As always, I used my trusted MN190 and ZWO ASI294MM camera

Processed in PixInsight

2 hours ago, Stu said:

I shouldn’t worry if I were you…… 😉

 

My office is always a mess, not the desk necessarily but I have scope kit all over the floor most of the time 😬

A manager at a research facility where I worked ages ago had a variation of this message on his door: a clean desk is a sure sign of a sick mind.

If I recall correctly, his boss had a much cleaner desk. Probably because that person received more high profile visitors.

Very nice. According to Simbad, the yellowish structure to the right is a "bubble", and the left one is a Hii region, an emission nebula, with several stars and young stellar objects.

1 hour ago, bomberbaz said:

weight wise it's heavier than what I am considering but thanks for the pointer

Image quality-wise it can compete with telescopes that are in an entirely different price range. But I agree with you on the weight. I wouldn’t want to lift it every imaging night. If you can have it on a permanent site, I would absolutely recommend it. Otoh, the MN190 probably isn’t heavier than a 150mm APO. 😁

The luminance data had several issues in the background, but I figured out a way to apply it to the galaxies alone. I just uploaded the not-so-wip version in my original post

LHaRGB, roughly 16 hours integration time

8 hours ago, Mandy D said:

Very nice! The 190 MN looks like a superb piece of kit.

Thanks. It is, although I still have to do a tiny collimation tweak. The secondary wasn't properly centered under the focuser. Last spring I replaced the stock focuser with an Omegon low profile focuser and at the same time adjusted the secondary. On close inspection it looks like I should move the secondary a tiny bit more.

7 hours ago, tomato said:

Yes, the detail and colour are excellent, and the background is spot on. Any AI processing on this one?

Thanks. The xT suite of course. BxT for deconvolution. In my opinion, it would be possible to get similar results with "conventional" deconvolution, but BxT is just easier and allows sharpening of details that have a lower snr. StarxT is tricky on galaxy images because it tends to remove galaxy details and background galaxies as well. Here I used it with a mask to protect the main galaxies. Together with BxT it does a better job of keeping foreground stars under control than Morphological Transformation.

Edit: scroll down for the LHaRGB version

*************************************************************

Astro season started with a cloud cover, but recently we've enjoyed a few gaps. There's still a lot of moisture in the air, but thanks to the Pegasus Power Box Advance and a dew band, I haven't had any condensation on my telescope.

Ngc 7640 is a barred spiral in the constellation Andromeda. The galaxy is slightly smaller than the Millky Way and about 24 Mly distant. As many other galaxies, the ones in this image are very seldom imaged with H-alpha filter. In my experience, if a galaxy shows blue "knots", that is an indication of star formation, and those young stars were at one time born from Hydrogen clouds. I decided therefore, to collect H-alpha and not just RGB.

This image consists of 78 4 minute exposures (about 5 hours) with a H-alpha filter, and 3 x 24 5 minute exposures with RGB filters, for a total of more than 11 hours of data. As usual, imaged with my SW 190MN and ASI294MM camera. I've also collected luminance data, but I didn't like the quality and haven't used it. Maybe I will collect new L when the weather allows.

Both galaxies have small H-alpha inclusions, and to my knowledge, this is the first amateur image to show these.

close up

****** New version with L ******

and close up

12 hours ago, gorann said:

 

Thanks a lot guys! @wimvb just pointed out that the Coat Hanger asterism is at the bottom of the image (upside down since I turned the image to get Nessie's head upwards)

The Coathanger is always upside down, so the image orientation is as it should, and Nessie won't get a headache. The image solver on Astrobin also shows that the image orientation is as it should. On AB, the dot on the red rectangle in the sky plot indicates the upper left corner of the image

https://www.astrobin.com/lak9k2/#sky-plot

Diffraction spikes is one of the reasons I bought the MN190. I'm so relieved to no longer being bothered by them. Instead of flocking, you could try black matte paint.

My guess is that it's the low number of subs that prevented adequate pixel rejection. As the OP wrote, the purpose of the test was to evaluate settings, not to create a final image. The settings look ok to me.

11 hours ago, iwols said:

approx 20 mins just need to know my camera is collecting data ok

I wonder if I got the same data as anyone else? i find that there are a lot of "hot pixels" in the masters that are difficult to remove with cosmetic correction in PI. This is probably due to there being only 6 or7 subs in each stack, too few for proper pixel rejection. The exposure time seems ok, as no stars are over exposed.

Here's a crop of the Sii master, showing the bad pixels