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Hello from Italy

FaDG

By FaDG
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FaDG

FaDG

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Hi all,

I'm new to this forum but not to Astronomy. I started around 2005 with a 70/700 Bresser SkyLux (Lidlscope) with the idea that even if I didn't like it, so what? the bet was less than 100€.

And now, several years (and scopes, and mounts...) later, I'm still enjoying it and trying to use any decent night to image the wonders above. And for me this means Deep Sky: Did I mention that I live in Rome? And I mean in the centre of Rome... Not among the darkest sites in the world, and that's where it starts to get tough! 

Yet,  years spent trying to image faint fuzzies from here have been a (frustrating but) rewarding experience, and they taught me that you can achieve fair results even from the centre of a big city (except on galaxies, these are really hopeless!) using Light Pollution filters and short exposures at low ISO on a modded DSLR, but that it's sooo much easier to get incredibly better results from the countryside. This led me to completely rethink my setup, adding to my HEQ5 mounted SW 150/750 Newton a 72ED APO refractor on a Star Adventurer with a couple of Prime lenses for my Canon, and eagerly waiting for that one-two nights a month of new moon and clear sky to drive 100 km and pick up some photons. Anyway, long nights spent testing and optimising the setup in dress rehearsals from home really help in reducing the "Oh no" factor when you're under a dark sky and something just doesn't work as planned.

So, long story short, being quite technically oriented I try to avoid solving problems just by throwing money at them, and like to spend my time finding solutions, although the hard truth is that there is a direct proportionality between the money spent and the results achieved (or at least the ease in achieving them)... not going to invest tens of thousands in this hobby, but you can't get away with some tens of €. And this leads to a fully different type of headache, no? I'm pretty sure that the time I spend fiddling with my equipment is largely exceeding the amount of time spent imaging: and this is where SGL enters into play! I have learnt so much lurching and reading the great info in your posts, that in the end I decided to join and possibly contribute, in hope that something that has been learnt the hard way could come in handy to people experiencing the same issues.

So, thanks for all the help you gave to me, I'm not going to stop the learning process, but trying to give you back something on my side!

Clear skies,

Fabio

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FaDG

FaDG

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Hello and thanks for the welcome!

@ Sunshine: Well, I have overcome several difficulties, and I've learnt that it's easier to find roundabouts to some others! Which mainly means testing the whole setup at home learning to rejoice for a "decent" image, driving out of town every once in a while to get a better one, albeit enduring the cold (or insect attacks if it's not cold!), tiredness, uncomfortable positions, lack of power outlets etc.

But if I have to tell the story in a few images, here you are.

The first pic is also The first M42 that I found satisfying, taken from the centre of Rome in an excellent night - and excellent is when 8 stars in Orion are visible to the naked eye! – Of course from such an extreme environment you need to use filters, and I chose the IDAS v4 because it is almost narrowband in the Halpha (20 nm). Its bandpass in the blue/green is somewhat larger (60nm, I think) and this leads to a cyan cast which is quite annoying and hard to remove. At the time I used a CG5 (non GT, with self-built controller) and an ED80: great little scope that I can’t decide to sell as it really has textbook optics. Man, was I happy when I first saw this result!

20190130_094821.jpg

Yet I don’t use the ED80 too much nowadays… because from town APERTURE RULES! As a matter of fact, before buying the ED80 there has been a long tradeoff: rather a small frac or a mid-sized Newt? Years after (too many years, in hindsight) I got to use a friend’s SW 150/750: he wasn’t satisfied but being a beginner couldn’t tell why. When I first looked at it I knew exactly why! It had pinched optics, strongly uncollimated primary and secondary, the focuser was squinted, the drawtube entered the lightpath causing any sort of reflections. He had bought it new and only used three or four times. I just told him to give it away for cheap highlighting the defects… but then started to put my hands (and tools, including a hacksaw!) on it and was astonished by the optical quality after solving the issues. In the end I got for small money a really top class Newt and he bought a Mak. This shows that sometimes excellent elements can be ruined by a terrible assembly and QC. So, the Second pic is M42 again, with the Newt and IDAS, this time.

20190130_094829.jpg

One of the reasons for the ED80 choice over the Reflector had been the capability to deliver pinpoint stars. Yes, that’s THEORY, but in practice, with 2.5 to 3 arcsec seeing stars get bloated anyway, and thus the Newt stars aren’t actually any worse than the ED80 ones, but you get a low more light to work on!

Just to give you an idea of what an excellent 6” newt can deliver even from Rome, I also attach a Jupiter imaged through it with a 2x barlow and a Mono ASI120 + RGB filters. As I wrote, I’m all for deep sky, but on steady nights with loads of very short exposures planets are definitely doable from the centre of Rome. Sure, you can get better with wider apertures, longer focal lengths and from outside town… but that wasn’t the point, no?

20190130_094850.jpg

 

Now to the roundabout: I’ve always had a soft spot for small APOs, and finally I purchased an FPL53 72ED f5.5 with 0.8x reducer/flattener (thus 320mm focal length f4.4) for my Star Adventurer. This time it took me three months to get it right and optimize the flattener backfocus (wasn’t a dedicated one), which is – I suspect –why the guy owning it sold it cheap. The last pic is again M42, but this time from outside Rome, where I can use 300” exposures @ISO800. The amount of information that a small APO can catch under clear skies is impressive, and I’m not that motivated to continue shooting from home, except for the fact that here I just need to open a window, while driving 100km takes some planning (also: the next day you’re probably not so proficient at work when you have imaged until 2 in the night and then driven back, just to stand up at 6:30… but please don’t tell my boss). Yet I use every opportunity from home to ensure that the setup is top notch when I go out.

Trying to get out the dust lanes, processing in the red is a bit overdone by Star Tools, that I don’t like too much as it tends a bit to decide on its own… I could reprocessit but it isn’t worth it: next time I’ll shoot WITHOUT IDAS filter, because LPS filtered images are rich in Red and Blue, but totally lack other colours. So, hang on for a new pic sooner or later.

20190130_094843.jpg

 

In summary, I’m not saying anything new, but I have learnt it the hard way: you can achieve decent results from a very light polluted sky, by

using as good a mount as you can (in my case a HEQ5, limited by a slipped disk) and  autoguider,

going for as much aperture you can without undermounting the scope,

using aggressive filters (narrowband would be better, but then it’s like astro CCDs and a completely different cost point) and

taking loads of shorter exposure frames: this is limited by the sky brightness – too long and you lose dynamics, too short and you don’t get deep enough.

On excellent nights I can push 240” @ 400 ISO with the Newt @ f5, and the histogram is around 40%-50%. What’s too deeply drowned in the background just won’t come out of noise, and you have to push processing to discriminate the faint signal from background noise. Flats and darks are critical here. Also, this doesn’t work on every target: emission nebulas are OK, but my experience is that Light Pollution takes a heavy toll on OIII. And wideband is just a no-no, so forget galaxies: even the bright ones are really disappointing.

Long post, open for discussion and suggestions (although the welcome section is possibly not the right place): what’s your view on the subject?

CS,

Fabio

 

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