NGG5146 the 'Cocoon'

[centroid]

Started off last night, under a beautifully clear sky, hoping to get a least 2 hours on the Cocoon Nebula.

Unfortunately, after 70 mins, the cloud moved in, and that was it for the night .

Still, the 7x10 min subs produced a reasonable image, albeit a bit 'noisy', so not too bad after all, and at least better than no image at all.

12" LX200R at f/7 and 7x10 min subs with the SXVF-H9C. Guiding with the ED80 and Lodestar camera. Processed with AA4.

Dave

[MikeD]

Very nice result Dave, lovely colour and detail in there.

Mike.

[centroid]

Would have liked it, with a lot less noise Mike. I feel that my H9C is a lot less sensitive than it should be.

70 mins (7x10 min) through a 12" scope at f/7, should have produced a much less noisy image than that, IMO.

Trouble is, I've nothing to make a direct comparison with, in order to prove it.

Dave

[barkis]

Looks fine to me Dave. Very aacceptaple indeed. I know noise when I see it, and this doesn't look that bad to me.

Of course you probably see it what I dont.

Do you think the extra time would have cleaned it to your satisfaction?

Ron.

[centroid]

Do you think the extra time would have cleaned it to your satisfaction?

Ron.

Difficult to say, without actually being able to try it Ron.

I do know, from when I converted my MX7C to Mono, and had to set the 'anti-blooming' gate to the correct level, that if this was set too 'hard', then the sensitivity of the camera would degrade. It was as matter of getting the balance right, between no 'blooming' on bright stars, and retaining full sensitivity.

This info came directly from Terry Platt, who supplied the mono 'chip', and advised me what needed to be done.

I'm wondering if when this H9C was set up at the factory, if the 'anti-blooming gate' may have been set too 'hard', and hence knocked the camera's senitivity back.

I sent a 15 min sub of the Crescent Neb, to Terry Platt a couple of days or so ago, to ask his opinion. As yet I've not had a reply, so I guess Terry must be on holiday, as he normally replies very quickly.

I could have a 'tweak' of the 'anti-blooming gate' setting, but I think I'll wait until I hear from Terry.

Looking back at some old MX7C images, taken with the 10" LX, seems to re-enforce my 'gut feeling' that this H9C is a bit lacking in sensitivity.

Dave

[steppenwolf]

Hi Dave,

This object is not that easy to capture as it is not that bright photographically and although your overall exposure time is reasonably high, your sub count is low because each one was 10 minutes in duration. A 'smoother' result would have been achieved with more subs of less exposure but it is a fine balance to get right. I like your image though, there is plenty of detail and colour.

Are there any other images that you have taken that lead you to believe that the sensitivity is down?

[steppenwolf]

Ooops our posts coincided so you have partly answered my question. For a totally different reason, I had to calibrate my ABG on the M25C but got the effect I wanted.

I have nothing to compare my own H9C with (aprat from the M25C) but have never felt that it was not sensitive enough and looking back at an image of the Cocoon taken last year, I note that I used additional 'smoothing' processing on it because of the 'noise', as below:-

[centroid]

Hi Steve

I agree with what you are saying Steve, but the 12" scope is quite a 'light-bucket', and I seemed to do better with the old MX7C and the 10" LX.

I did 15 min subs on the Crescent the other night, and there was so little nebula captured in each one, it really wasn't worth 'stacking'. It was one of these subs that I sent to Terry. They were taken with the ED80, as I just can't fit these size object into the 12" LX, even at f/7.

I looked at what detail you captured of the Veil with the ED80/M25C, this object being of similar mag to the Crescent and Cocoon etc, and you captured a wealth of detail, without mega exposure times.

Dave

[centroid]

What was setup and exp time for that one Steve?

Dave

[Paxo]

Looks good for the exposure time given Dave, at least with this astroimaging lark you have a pretty good chance of adding to it again, and again. Should be a stunning image with more subs.

Steve.

[centroid]

I think I just need to satisfy my own mind Steve (Paxo), that this H9C is 'par for the course' or a bit lacking in the sensitivity department.

Perhaps I should buy another H9C, just so that I can compare the two.

Dave

[steppenwolf]

This is a horrible situation for you to be in, Dave, as doubting the equipment is no pleasure at all - I know, I have been there recently with the M25C. If there are any tests that you would like me to run here with my H9C, don't hesitate to ask me and if I can assist, I will.

What was setup and exp time for that one Steve?

The details that I logged for this image were:- SXVF-H9C on 10" Reflector (F4.72), EQ6 SkyScan Mount. 14 subs 400 secs. each, guided, SD Mask stacked in Maxim DL, processed in NeatImage and PS4. Average seeing, reasonable transparency. 07/07/07

The following image is my original just converted from FITS (in 8 bit :shock: ) before I attacked the stars for roundness ( I had some star trailing that night) and it shows the noise just as it came out - I hope this helps. Oh, the shame, my image laid bare ....

[centroid]

That seems to endorse my thinking Steve, that the sensitivity of my H9C is down on what it should be.

Your subs 400 secs, and 14 of them. My subs 700 secs, albeit only 7 of them.

Yours at around f/5, mine at f/7.

Your aperture 10", my 12".

So if you offset my extra 2" of aperture, against your faster f ratio, then my exposure time being something approaching double yours, then as a whole, it probably balances out.

All 'wet finger in the air' I know, but I still think it indicates that my camera's sensitivity is below spec.

Having a good selection of electronic test gear, if could get hold of the necessary information on circuit levels, I could carry out some tests.

Dave

[barkis]

Dave,

I'm not sure If I am going to be talking rubbish here but, Is the camera you use capable of guiding using half of the sensors pixels. That obviously would need an increase in the exposure time.

I know you have the Lodestar guidehead, and that would indicate that my question is on the stupid side. I have seen in Maxim, a feature called dual chip which can be switched on or off.

I think you probably know what I'm suggesting here, so in the liklihood I am up the creek on this,

just ignore it. I know the MX 916 I have can use the imaging sensor for guiding, but I bought a sxv guidhead, so I don't have to double the exposure time.

Ron. :oops:

[centroid]

Hi Ron

The SX Star 2000 system, allowed the sharing of the CCD for guiding and imaging, which does of course double the time taken to acquire an image.

Before I used a separate guide scope and camera, I used Star 2000 with the MX7C.

I could be wrong, but I don't think this system works with the 285 CCD, as used in the H9/H9C.

The 'dual chip' feature that you describe, is something that SBig used in there cameras, and is just as the name suggests, two 'chips', in the same camera. One for imaging and one for guiding.

I currently out in the obs, having yet another late night, and acquiring some more subs of the Cocoon, to add them to what I already have.

Assuming that I can get another hours worth, it will be interesting to see if this 'smoothes' the image a bit.

Dave

[centroid]

Incidently, nobody 'spotted' my deliberate mistake!!

The Cocoon Nebula is actually IC5146 and not NGC5146

Dave

[RichieJarvis]

Beautiful image there Dave - you've caught it beautifully - it could definately do with more subs to reduce the noise. Terry was very responsive in the week, so he's been around.

I have an SXV-H9 here - but no LX200 anymore. I didn't know that was up there - will have to give it a try!

Cheers,

Richie