The core of NGC 7023, the Iris Nebula

[Menno555]

This crop is the core of NGC 7023, the Iris Nebula. The FOV is around 10' x 6' (arc minutes). In total 5:15 hours of integration time.

I did have some data left from 2021. Due to my own fault, I lost a lot of data of 2021 and earlier, but these Lights survived. But no calibration files
Had another session 2 weeks ago and did combine the two datasets.
Stacked it all without calibration files, resulting in a very clean image but with almost no contrast and a lot of vignetting. That's the main reason for the crop: almost no vignetting there.
Luckily I almost never have any dust donuts, so that was an extra.

The result is a detailed view of the core. But there is almost no reference material of NGC 7023 with this small FOV, so I left the colour as it is.
The only small FOV that I found, was made by Hubble. Couldn't use that for color reference because it also contains Near IR data. But could use it for detail reference. This animated GIF shows my data and that of Hubble.
It's the orange nebula part above and right from the central star.

iris-me-hubble.gif (58.29 KiB) Viewed 8290 times

On purpose (and also because it was somewhat difficult with processing) not a lot of contrast.
To counter the blow-out of the central star somewhat, I did capture the 2023 session with 180sec instead of 300sec of the 2021 session.
This helped a lot with processing

Menno

Iris-core2.jpg (424.32 KiB) Viewed 8290 times

Bortle 6/7
Meade LX200 8" f/10 ACF OTA
Ioptron CEM25EC mount (no guiding)
Baader IR/UV Cut filter
Zwo ASI071MC Pro camera

Captured with SharpCap Pro @ -10 Celsius / White balance R50 B50
2021: 39 x 300 sec / Gain 0 / Offset 4
2023: 40 x 180 sec / Gain 0 / Offset 4
No calibration files

Stacked with SiriL and Sirilic

Processed in Photoshop
Photoshop: Curves (a few times with the arcsinh30 preset) and Levels, StarXterminator, Camera Raw Filter (blacks, contrast, color saturation, clarity, curves), NoiseXterminator with details on 70.

[john_robertson1953]

Hi Menno,

Very beautiful photo!

How in the world are you able to shoot 3 & 5 minute subs without guiding?

Great coloring but you didn’t use any kind of narrow band filter?

Was that shot at f/7?

Again, very nice work,

John

[Menno555]

Hi Menno,

Very beautiful photo!

Thanks John!

How in the world are you able to shoot 3 & 5 minute subs without guiding?

I do everything I do with tracking only. For now the maximum I can capture is 10 minute captures. Main reason for this is because I really am at the edge of what my mount can have on payload of the mount for it to track precisely.
To get to this, I firstly do very precise PA (polar alignment). For this I use a Ioptron Ipolar camera and its software. Then (if needed) I adjust the PA on the fly during capturing: I use the "bullseye overlay" of SharpCap on 1 star on which I zoom in around 400%. If that moves in the DEC direction during a capture, I know I have to adjust the PA.
Secondly, I use the User Defined Tracking feature of the mount. I can very precise alter that value. That's a bit tricky because it's a set speed there with normal tracking, the speed is auto adjusted when going higher or lower. This means that 3 or 4 times in an hour, I have to adjust the tracking.
And here again I make use of the bullseye overlay on a star at 400% zoom. When I see the star starting to move in RA, I adjust the tracking value of the mount. So in a way it's a kind of "manual guiding", with the difference being that auto guiding and adjusting is happening all the time, while I only can see and adjust it after a capture.
Third: the combination of the short length telescope and the center balanced build of the mount seems to work very good. And the mount also has a optical encoder on RA, so the movement is smooth and precise.
Fourth: I experimented a lot to get it to this. Experimenting with the things I have is something I enjoy a lot

Great coloring but you didn’t use any kind of narrow band filter?

No, only the IR/UV Cut filter. NGC 7023 is a reflection nebula, so it's all in the broadband range. I did try it with narrowband in the past (because, why not?) but that just gives non to nothing because it's not an emission nebula.

Was that shot at f/7?

No, this is at f/10. The 2021 data was at exactly f/10 (2032mm) but I'm now at f/10,3 (2100mm): I did set my camera a bit further away from the scope to reduce vignetting: I get get focused stars now also in the corners.

Again, very nice work,

John

Again, thanks

Menno

[john_robertson1953]

Wouldn’t it be a lot easier if u added an OAG and used PHD2 for auto guiding?

Thanks for your responses,

John

[Menno555]

I am at the limit of the payload weight of what the mount can do for astrophotography, john.
Adding an OAG and camera would just add too much weight.
Also, I am at f/10, meaning (as I understand it?) that the guidestar is difficult to find/use. A lot of times there are simply no real bright stars in my f/10 FOV.

Plus I have one (big) advantage with tracking over guiding: guiding is done in pulses, giving very tiny changes in the mount's position during capturing.
With the tracking only (especially with the optical encoder), I have a mount movement which is "smoother", there are no corrections during capturing.
Somebody experienced (I'm only busy with this set-up for 3 years now) over at Cloudynights once did check the FWHM of some of my light files and was surprised and impressed about the roundness of my stars. He said that in roughly the same FOV, with guiding the stars were not as round.

But bottom line: for me it's fun this way. It's a rather active way of capturing, I have to keep an eye out for multiple things. It's a mix of old school and modern and I figured out a way which both works fine and is fun

Menno

[timh]

Hi Menno, that came out pretty well. You are right about the lack of good images to compare the image of the core with - I had a go at the same object last year. So now I can use yours as a comparator at least. Comfortingly the two images are very similar - right down to the detail of the cloud around the new-born star. Tim

[Menno555]

Thanks Tim
I could share my data with you and you can make a collaboration version? I mean, there is not much around in this FOV.
If interested, PM me and we'll work something out

Menno

[john_robertson1953]

Hi Menno,

Your photos inspired me to take a shot at Iris.

Thank you,

John

SCT HD Edge8, F/7, asi2600mc, asi174MM guiding, shot over 3 recent nights: total 5 hrs 42 min, 3 minute exposures , processed w/ Pixinsight.

[Menno555]

Nice capture John.
The Iris is always challenging I find due to the fact of different circumstances: bright center with blue around it and the faint clouds around it with their whole own color challenge

Menno