NGC 1491

[Nicola Hannah Butterfield]

I spent a lot of time imagining this on a non modified Canon 40D to end up with just 3hrs 20min of data at 400 ISO, at first i was a little disappointed but knowing it is really suited to the 40D and the moon being present, I did a search on the net, and whilst yes it isn't great, it does I think compared with some images of similar quality from much better scopes and imaging techniques if I am reading the information correctly.

 

Hopefully this is aloud

https://www.utopia-photography.ch/universe/i/01/p23.html

https://www.flickr.com/photos/97939735@N04/37903269415

 

[Elp]

I think it's a nice effort. Have you considered using an Optolong L-extreme, works very well on emission targets. Not sure how much effect your internal IR filter will have though, works well with my modified Canon.

Edited November 6, 2022 by Elp

[Nicola Hannah Butterfield]

52 minutes ago, Elp said:

I think it's a nice effort. Have you considered using an Optolong L-extreme, works very well on emission targets. Not sure how much effect your internal IR filter will have though, works well with my modified Canon.

Thanks. I need to invest in a coma corrector first and possibly a manual rotator and possibly a better/low profile focuser, a lot of the standard SW one pokes into the tube, though the stars I seem to be getting of late don't seem to have been affected too much.

One thing I have noticed, is there is a lot more gas a dust, I have been until I got the new light panel, been thinking it as imaging flaws, and whilst there may be an element of that still. I also need to work on image processing a little more and even though my stars are better you can still see the coma in the diffraction spikes. I also need to analyse my subs a little better, for example in this case I have 110 subs, would it be better to choose the 55 top SNR ones, is there an SNR number above which you don't use for certain images for certain objects.  I do live in a bortle 6 thanks Wakefield council, for bringing it down 1 notch, so LP is always going to be difficult.

I would love to get filters etc but being on ESA this hobby was never going to be easy, so step at a time, it takes me time to save, but the core needs to be right first, no point spending on things if your basic image isn't right, I do think after the light panel investment I am moving in the right direction.

I also need to look more at images of objects I might image and look to see if there are clouds of dust ect, I might want to get rid of on the pp side.

I will never win any awards on this side of imaging things as a whole, but it is interesting sometimes to see I CAN match superior scopes in light gathering, 2nd image specifically, light diffraction on the first much superior to mine, my highlight detail is better.

All that said, it is all subjective as we all see things differently, even in what is deemed correct.

[Elp]

If it helps, I had a 130pds and the coma corrector I chose to buy was the gso one as I believe it is the only one which worked which didn't require shortening the focus tube. This may help you not needing a low profile focuser. All I needed in addition was a 20mm spacer for the backspacing to get focus with my 224mc.

Tbh I didn't think it made that much difference really, if you're gonna crop your images certainly can do without.

Regarding subs, if you load them all in Deep Sky Stacker and run the registration (without stacking), it'll analyse and grade each sub and provide some statistics including a score. You can then go over the subs which are out of the average and eliminate them. It's also a good way of quickly going through a set and getting rid of ones which may have clouds in them. Then typically I just stack with a 10 percent rejection and kappa sigma clipping at 2, 5.

Sometimes if there's stacking artifacts I'll try Siril, Siril is also magic for pre preparing a stacked image prior to post process, just do a crop first to remove any mismatch of images at the edges, dynamic background extraction which will remove any gradients, green noise reduction, banding reduction (good for DSLRs), then one asinh stretch and a few histogram stretches. Then the saved image will be in a better position for finishing in PS or GIMP.

[Malpi12]

4 hours ago, Elp said:

It's also a good way of quickly going through a set and getting rid of ones which may have clouds in them.

Ah! good idea, I must remember that ! Previously I roughly pick, then do somewhere between 90% and 50% depending on condx 

 

[Nicola Hannah Butterfield]

@ElpThanks for the input.

If you look at the diffraction spikes I think that is showing some of the coma effect as those on the right left to the left and those on the left tend to the right, the actual coma on the stars isn't so bad, but then it is an crop sensor, that of my 6d is full frame and is much more noticeable, and this image is cropped a little.

I believe the Baarder MPCC3 also a doesn't change the focal distance and would I believe just replace the 2" nose piece which has an M48 EOS. I say this as on occasions I do shoot larger objects like M43 and M31 I can't quite get them especally M31 in the full frame, but you have to work with what you have.

 

Again, you can see the coma effect of the diffraction spikes. That was shat on the 6D with the 200P as was this

You can see the coma on that one.

 

[Elp]

They're nice images. Are you sure you have your backspacing as best as you can get it, it looks more like the sensor is a bit too close more than coma. Coma patterns from my experience flare out more making the stars triangular or seagull shaped.

[Nicola Hannah Butterfield]

On 08/11/2022 at 09:55, Elp said:

They're nice images. Are you sure you have your backspacing as best as you can get it, it looks more like the sensor is a bit too close more than coma. Coma patterns from my experience flare out more making the stars triangular or seagull shaped.

If you look at this, which is a single 120s exposure 400ISO on a Canon 40D of M44, especially the edges you will see the coma, the previous 2 images I shot on the 6D, the centre stars whilst not perfect are not bad, to say I am only a week back into this after nearly 6 or 7 months out.  The stars start to stretch and the further you go, the worse they get. This is simply a jpg conversion of the raw, nothing done.