The Eagle Nebula

[tim.stephens]

Hi everyone,

Thought it is about time I should share one of my images here for constructive critique. I've been watching from the sidelines for a while and appreciate the feedback given to novices as it is generall very instructive and helpful

I'm an Aussie currently living in NZ under very mildly light polluted skies - a real step up from central suburban Brisbane. Unfortunately the weather has been quite variable during the winter and is just starting to become more predictable and fine during the evening. I purchased a telescope back in August for a birthday and I've been hooked on astrophotography and astronomy in general since.

Here is my nth attempt at 'a nebula'. I have others but this is probably the only one worth sharing just yet. Focus was the best thus far and now appreciating how much it can shift during an imaging session. I check/refocus every 2 subs as the night cools rapidly, less so after. Made a Bahtinov mask from a very helpful mask generator website which has been invaluable.

Might be good to share details of my equipment as I don't think very many people are shooting with a Fuji as far as I can tell...

The photo was about 50 minutes of total exposure on an unmodified Fuji XPro1. The camera is a little unusual as it eschews the bayer filter and is moderately sensitive to the red/far red spectrum. I'm unable to find a spectral response diagram for the xtrans sensor to prove this but I can expose with normal shutter times and handheld using a Hoya IR-pass filter. My Nikon d5000 required a substantial increase in exposure to see anything useful with the IR filter in place and I needed a tripod. I can only assume the Xtrans filter is less active in that spectral region... which makes it suitable for astrophotography unmodified apparently!

Equipment:
Skywatcher 120mm (500mm focal length) achromat. Loads of CA which is surprisingly reduced with the Astronomik UHC-E filter I use for most of the nebula photos. More CA is removed with the very easy to use Lightroom CA removal tool
Standard HEQ5 Pro
ZWO guidescope (280mm). Purchased a slightly longer than normal FL mini guidescope so I can hopefully use it with a longer FL telescope in the near future... pending budget control officer (wife) approval.
QHY 5l-II guide camera. Fantastic little camera and very sensitive. Unlike many, had zero issues with drivers or setting it up to guide with PHD2 and Metaguide. I modified a MS lifecam but it was not sensitive enough to use for guiding purposes.

And that's about it really... probably need a field flattener at some point but honestly, don't want to spend too much more on this scope and would rather find something a little better quality and longer FL in the near future. The aim is to improve my technique first and then perhaps spend more money where needed once I've pushed my gear to the limit.

First time I've used astrobin:
http://astrob.in/219574/0/

Yes, you are more than welcome to zoom right in and pixel peep. :-)

Photo details:
ISO800
10 minute subs x 5
2 darks
2 flats - I don't think these have corrected the vignette....
uncropped
Stacked in DSS.
PHD2
No noise reduction
Touch of sharpening
Tone curve balanced in Lightroom

Post processing is something I'm only just beginning to experiment with!!

Thanks!

Tim

[Atmos]

You've done well getting rid of the halos! I don't think my personal PS processing skills go that far haha

It is looking pretty good, nicely captured.

As per the camera, some cameras have a better Hydrogen Alpha pass than others or just have sensors that are more sensitive to that wavelength.

[tim.stephens]

Thanks Colin but honestly, skill has nothing to do with it... Lightroom is almost idiot proof now :-)

I think if I were to improve on imaging at the moment, reducing the vignette with (better) flats and improving my star shape with a flattener would be top of the list. I've got my eye on one of the GSO RC8's in the near future perhaps. While I might be increasing my FL for these tiny objects and reducing the CA, I'm worried the added hassle of collimation may not outweigh the benefits. Don't have a lot of money to spend on a high quality refractor so I have to compromise somewhere unfortunately.

[Atmos]

One good flat should remove the vignette but will begin to introduce more noise into your images, so it is better to take more. I typically take 25, some do more, others do less. Shiraz says as many flats as there are lights as a rule of thumb.

A flattener will help kill all of that curvature, amazing the difference that it can make.

A few months back I was considering the GSO RC8 and decided against it for the very reason that you mentioned, the collimation AND I wanted to keep away from those diffraction spikes :) Ended up going with a 130mm refractor while I am JUST starting to get used to after 1-2 months. The GSO RC8 does have a focal length of ~1600mm, if you wanted to go down a cheaper path you could go with a 8-10" Newtonian Astrograph, they come in either F/4 or F/5 typically, far easier to collimate than the RC8 I believe. If you get a newtonian you'll need a coma reducer, Baader do a really good one for ~$300 I believe.

[tim.stephens]

Thanks Colin, I'll experiment with flats tonight after work. Might make an artificial (extreme) one first to see the effect in DSS. I made several under a cloudy sky the other day but clearly not suitable.

Honestly I don't mind the diffraction spikes but know what you mean. Yes I had a similar idea. Plenty of fast moderate FL newtonians around for very reasonable prices. I think I underspent on my tripod unfortunately as many will push me past the weight limit. Should have bought a NEQ6 for the added weight capacity!!

Tim