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Xiga

Sombrero Galaxy (M104) - Breaking all the Rules!

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We had some clear skies last Saturday night, and rather than do another widefield galaxy shot with the 80ED, i thought i'd try something a bit nuts, lol. 

I've always loved the Sombrero Galaxy, but i don't really have the gear to image it properly. The 80ED just doesn't have the aperture or (more to the point) FL to do it justice. So i made a last minute decision to try and use the C8 (which hasn't even been out of it's case in over 2 years, basically since i took up DSO imaging). I know all too well that the C8 is not really for imaging with, so i've never bothered to even buy a T adapter to attach the D5300 to the scope, so in desperation i thought, why not use the SW x0.85 FF/FR from the 80ED! ? (seeing as it does at least have a 2" barrel that i could just insert into the crayford). Plus it would allow me to use my 2" IDAS-D1 filter. 

The next problem was balance, as the scope was waaay too heavy in Dec, camera-side. So i quickly scavenged around and found an old box of metal bits and bobs and taped it to the front of the dovetail. It wasn't perfectly balanced, but it was close.

20190331_050141.thumb.jpg.a5da2fe0a8855a72b2a7b87ca904d2bb.jpg

 

Now, what about guiding? Well the only thing i have is the finder-guider i use on the 80ED so i fired that on. It has an old original QHY5 on it, with pretty big pixels by today's standards (5.2um). The pixel scale of the finder-guider is 6.09", and when i plate-solved a frame with the D5300 through the SW FF/FR, SGP was telling me that my imaging scale was 0.38" (ridiculous, i know), and which meant the FL was about 2,117! So that's an imaging-to-guiding ratio of just 16:1 ?. Oh yes, the scope has never been collimated either in the 5 or so years i've owned it, and i didn't have the time or inclination to start now. 

I was surprised how easy it was to find focus (the crayford made a big difference) and the plate-solving all worked as expected. I did accidentally leave the Bahtinov mask on (twice!) which cost me just 1 frame thankfully. The first time i left it on during plate-solving (which was why the first few pre-flip frames were a bit off-centre. This was annoying, as it meant i had to crop the image more than i could have in PP. In fact, i was surprised at how relatively flat the field looked when i calibrated the frames. 

Guiding was, as expected, not great (to put it mildly). My belt-modded HEQ5-Pro usually manages 0.6-0.9" on most nights, but on this occasion it started out at 1.25" but by the end of the session it had degraded to around 1.8". I kept dithering to a minimum (every 3 or 4 frames just) to not stress the guiding too much. I did lose 2 frames due to a big deflection in RA which caused the images to streak, but the rest were keepers (albeit with big stars). The FWHM in SGP was between about 8.1 and 9.5 for most frames. I've no idea what the norm would be for a C8 under proper guiding conditions, i'd be interested to hear if anyone knows?

So in the end i got 23 x 300s at ISO 200 (so just shy of 2 hrs) before it disappeared behind the neighbour's house. APP was used for stacking, gradient reduction, and star colour calibration. Everything else was done in PS. 

PP was a struggle, as the data is obviously noisy, and there's nowhere near enough of it. I had to take a sledge-hammer to it in places (it ain't pretty under the hood believe me!) but in the end i'm pleased that i was just about able to tease enough out of it to get something that is worth keeping. I was honestly not expecting anything productive to come from the experiment, so it was a nice bonus. 

And now that silly season is over, i can say that i have nothing but admiration for all the guys out there imaging at these long FL's. It's a lot harder than imaging at 522mm let me tell you! 

It won't be winning any awards but here's how it came out (note, it's been reduced down to 25% as well, as there's nothing more to see any closer than that!). 

1079171437_M104v1(27).thumb.jpg.f9db4a58c6a519c7dfbaf7463b42feb1.jpg

 

and just for reference, this is what a single raw, uncropped calibrated (stretched) sub looked like:

m104_300sec_ISO200_filter0__frame8-cal-St.thumb.jpg.fc49884914654471ad838651c610ce37.jpg

 

Thanks for looking! 

Edited by Xiga
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23 minutes ago, tooth_dr said:

Simply astonishing Ciaran, I love it. 

Thanks Adam. It was a fun experiment, but i'm not entirely convinced i'd go back for a 2nd bite of the cherry. Maybe if i knew i could get twice as much data on something. But then, the need to baby-sit it and constantly re-focus would be too much of a pain. Plus i'm pretty sure my blood-pressure was mimicking the guide graph peak for peak ?

But you never know.

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You can keep breaking those rules. Great result.

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Great story and also a rather successful one. A C8 on an HEQ8 is obviously quite a balancing act. I think you could do the final image more justice in processing. The core looks blown out but not so in the single sub, so with a bit more careful stretching you should be able to bring out a more dynamic and colourful core and have an even better result of that nights adventure.

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Great post, and a fine result, sometimes rules are made to be broken.?

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4 hours ago, wimvb said:

You can keep breaking those rules. Great result.

 

3 hours ago, gorann said:

Great story and also a rather successful one. A C8 on an HEQ8 is obviously quite a balancing act. I think you could do the final image more justice in processing. The core looks blown out but not so in the single sub, so with a bit more careful stretching you should be able to bring out a more dynamic and colourful core and have an even better result of that nights adventure.

Thanks Wim and Goran.

Goran, if you look at the histogram for the image you will see that no part of it is actually blown (not the galaxy core nor even a single star core). I do know what you mean though. It does look like it's been blown. This was actually deliberate. I did have a more subdued version, but it just didn't have the impact i was looking for, so i decided to stretch the brightness to the absolute limit and just live with the extra noise. 

But now that i look at it again, i think you're right. It is a bit too bright. I don't want to tame it too much though. Hmm ok. Here's a more subdued version. 

Pretty sure this is the final version now: 

 

1889304159_M104v2(27).thumb.jpg.7b624a401507a4c890c3882a99e99a85.jpg

Edited by Xiga
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27 minutes ago, tooth_dr said:

1st of the two. 

Yep me too. I accidentally deleted the other one, lol, so i just amended the post with the final version.

1 minute ago, carastro said:

Excellent result.

Carole 

Thanks Carole.

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Hah that is pretty cool, and the result is very good. I am a little surprised actually how well it turned out considering you went all McGyver with that reducer/flattener from the ED80. ?

Props!

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2 minutes ago, jjosefsen said:

Hah that is pretty cool, and the result is very good. I am a little surprised actually how well it turned out considering you went all McGyver with that reducer/flattener from the ED80. ?

Props!

Thanks @jjosefsen  ?

The seed of the idea came from this old thread. I read it a couple of years back, but thought nothing of it at the time, as using the C8 for DSO work has never really been on my radar:

 

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Under the circumstances I think that's a pretty impressive result.

James

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21 minutes ago, JamesF said:

Under the circumstances I think that's a pretty impressive result.

James

Thanks James

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One of those captivating targets that everyone wants to get. Great job and good to see your creativity pay off.

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I'd say you have done it some justice, nice result for the extra reach indeed...enjoyed the tale told as well ? 

Edited by SIDO

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5 hours ago, Allinthehead said:

One of those captivating targets that everyone wants to get. Great job and good to see your creativity pay off.

Thanks Richard. You're right, for me it's definitely one of the iconic targets up there. You don't see many images of it on the forums though, and now I know why! lol. If I ever get a cooled CMOS, I might try it again with very high gain and very short subs, to help with the tracking and seeing. But the mount is the main problem I fear (and with no MESU's on the horizon any time soon I'm pretty much stuck with HEQ5 for now!).

5 hours ago, SIDO said:

I'd say you have done it some justice, nice result for the extra reach indeed...enjoyed the tale told as well ? 

Thanks SIDO!

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That's a really nice image.  M104 is always too low for me - sheds, trees etc.  Nevertheless, despite the low angle and high FL, this a a very good job with plenty of star colour.  Well done!

Chris

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Great result! If you don't try you'll never know...

Tape is under rated in astrophotography... :icon_mrgreen:

Olly

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Very impressive result Ciaran and great write up - perseverance and 'rule' breaking can indeed pay dividends ?.

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3 hours ago, cfpendock said:

That's a really nice image.  M104 is always too low for me - sheds, trees etc.  Nevertheless, despite the low angle and high FL, this a a very good job with plenty of star colour.  Well done!

Chris

Thanks Chris! At ISO 200 the FWC of the D5300 is aittle over 16k, so pretty good for a DSLR. It really helps with star colour, and at 5 mins per sub nothing was clipped. 

3 hours ago, ollypenrice said:

Great result! If you don't try you'll never know...

Tape is under rated in astrophotography... :icon_mrgreen:

Olly

Cheers Olly. 

If you look closely you'll see more tape on the LHS of the mount too. After I did the belt mod there was a small gap left in the housing, so for peace of mind I did the only thing I could, and slap some duct tape on there ?

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4 hours ago, Barry-Wilson said:

Very impressive result Ciaran and great write up - perseverance and 'rule' breaking can indeed pay dividends ?.

Thanks Barry ?

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