M20

[Jeffkop]

Boy this run of clear nights is gonna be the death of me, but if there is ONE thing Ive learned in this game ... Never let a clear nite go by !!!! It could be a month before the next one.

Rite, heres my effort at the Triffid Nebula last night. It is is comprised of:

LRGB all binned 1x1 20x2 minute subs so each channel is 40mins of data.

Shame I cant get the deep colours some get ... Seems I have to accept that I cant get enough data because of the obstacles ... So this is my lot, unless there is a software trick someones holdin out on.

All will change when I build my observatory towards the end of the year .. I HOPE.

Thanks for looking

Jeff

[g__day]

Very nice - I did M20 last night - haven't really processed it yet - I was trialling my new Hutech IDAS light pollution filter - did 20 minute shots on a Canon 400D fine without blowing out the core. So without darks, flats or bias and only slight levels, curves and Gaussian Blur on a C9.25 I got a single shot as such - Wish I had your detail - I take it that's the ST2000XM in action?

[Jeffkop]

Yep thats with the SBIG camera Matthew. Still trying to find a good 2nd scope to throw up on the G11 to image with the 40D. At those times either in conjunction with or singlely I will guide with the SBIG on the prime scope.

Jeff

[g__day]

Jeff,

One other thing that impresses me with your shot - the size of the core (how do you do that?).

Why is it the core of M20 is much bigger on your shot than mine? I can easily understand your shot being much sharper and having better colour (a TAK super apo -> S-BIG should beat a SCT -> DSLR hands down) - so that doesn't surprise me. But your image scale does and I am trying to understand why.

The TSA102s is I think an F8, 816 mm focal length tube. My SCT has a focal reducer in the off axis guider bringing my focal ratio down to imaging at 1,500 mm.

Your S-BIG has a 7.4 * 7.4 micron pixel size and close to 2 million pixels. The Canon 400D is a 10MP 5.7µm vs 6.4µm (3888 x 2592 pixel) chip
(so not wildly smaller pixels, but given my sky quality I might be better with 2*2 binning?


But what simple factor makes the core of M20 bigger in your shot than mine - have you a lens in the imaging training or what simple thing have I overlooked?

[iceman]

Good effort, Jeff.
Some nice detail but i'm not sure about the processing - did you use shadows/highlights?
Some of the faint areas appear to be too stretched and ends up grainy. Also, what's happened in the top right corner?

[Jeffkop]

Hi Mike

Thanks for the input. To answer your questions, I dont play with shadows/highlights .. well not intentionally. I have to adjust the histogram after colour combining because you cant see anything .. well not much until i do. And really, this image has not had very much of anything done to it.

Maybe I should send someone some of the FITS files straight from the camera, see how the experts can make a diamond studded purse from a pigs ear ;)

OK the top RH corner .. every image, and there is 76 of them, there is a dark lane up there ... well an area of significantly less stars then anywhere else. Thats the only way i can explain it. Anyway .. all the images have it.

Thanks again
Jeff

[Jeffkop]

Hey Matthew

OK all the information you have is correct for my telescope and camera ... I dont have anything in the optic train other than the scope, a hollow TAK adapter tube and the camera. Thats it mate ... I do have a TAK Focal Reducer but it wasnt used in that shot and if it was then it would make the whole picture smaller not bigger. So Matthew, I cant answer the question, but thanks again for your input.

Jeff

[jase]

You sure its not ice Jeff? Its also present in the bottom two corners. Time for a recharge of the desiccant I suspect.

[Jeffkop]

Well like I keep on saying .. you learn something everyday in this game.

Could be ice, I have only just started imaging at -25c the last couple of nights Jase, but to tell you the truth, I didnt have any idea about ice. Whats desiccant recharge .. and how do i do that ???

I think this may be a strong possibiltiy. I was only wondering last night how the camera didnt end up with ice in it at that temperature.

OK I have looked in the camera manual about the desiccant. IT says that it may require servicing in a yearly. I have only had this camera for 4months MAX from new and I guess Ive used it maybe 20 times in that time, so I dont know. Anyway, I will keep an eye out Jase, the procedure for servicing it isnt complicated, just remove a container and put it in the oven for 4 hrs. Bit like anzac biscuits :lol:

Thanks for the info

Jeff

[Jeffkop]

OK all .. I have probably confirmed that it is ice, well I guess Im hoping. Earlier yesterday evening I was imaging M20 and I had to do a meridian flip. After that the image changed orientation but low and behold those marks in the image are in exactly the same places, so it is definitely something to do with the camera. I saw it last night and just thort it was a dark lane in the stars or something .. didnt investigate it any further.

Just checked the night before image of M8 .. No such problem .. so it seems that last night was the beginning of it.

Jeff

[Bassnut]

Excellent Jeff, seems pretty deep, a lot more stars than I get :P.

Desicant usually lasts a year or so before recharge on an SBIG, but then you are at -25deg. Did you wait 30mins or so before imaging?, you should anyway to allow optics to stablise.

[Alchemy]

be nice with a few more minutes of exposure to fill out the lighter blue nebulosity....... as for processing tricks yep theres a few which can do wonders. but at the moment its just getting the quality data first.