At least I tried - NGC 7090 - galaxy

[jsmoraes]

to try isn't to get :sadeyes:

GSO 305 mm - Canon T3 - ISO 400 - 13 x 4 min ( 52 min) - OAG - Skyglow filter - Coma Corrector

Not like http://christianready.com/2012/09/17/hubbles-view-of-an-edge-on-starburst-galaxy/ngc7090_croppe/

[cometcatcher]

That's alright, it just needs a few more hours Jorge. :)

[wayne anderson]

Give it a few more hours and it should be much better.

[jsmoraes]

:question: , I reckon MANY more hours ! This galaxy is very faint and small. Perhaps only with a clear and black sky, distant from any light polution.

This target is out of my possibiliies (site and equipments). I can capture it, as I did, but I don't believe that I can bring some internal details.

Well, no matter, it was done ! :)

An wygiwyc ! (what you get is what you can) :rofl:

[Camelopardalis]

Wow that is faint mate, good effort :thumbsup:

As it is faint, why choose ISO400? Bumping up to ISO1600 would surely increase the SNR?

[cometcatcher]

Why not make a multiple night effort to get the hours up? For the really faint stuff, I need 4 - 6 nights of subs to get enough data.

[tlgerdes]

But it will increase the noise, and possibly end up worse.

[jsmoraes]

yes, it is possible. I don't like it very much because of the difference of visibility of each night and centralization in the FOV. It demands much processing effort.

I thing that maybe I haven't camera to get good image of this galaxy. I have good resolution: 0.8 arc seconds, but when I call the faint information, the stars become more fat, and I presume all the other thin details.

Perhaps a CCD with similar resolution, instead of CMOS, will capture the faint details with more sharpness.


Not only noise issue. I have problem with light pollution as sky glow. With 1600 the time of exposition must be small.
With small (7.3' x 1.2') and faint objects the sky glow is the worse occurence. It merges with the object.
I think that with much more low ISO subs I wil get better result than high ISO.

Its magnitude is about 11 - 13, but with galaxy this is relative. Galaxy isn't nebula. The interior details are very small and with very little difference of magnitude.

[cometcatcher]

Well, not that much effort really. I just copy one image, paste it on the other (which creates another layer), use the opacity slider to blend and the move and rotate tools to register. Easy.

[Camelopardalis]

Ah thanks Jorge, good to know :thumbsup: sky glow is indeed a curse!

[jsmoraes]

I stack with DSS, I don't know about any ressources do move and rotate in it. The best way is to adjust the position before start the capture. I can let the camera intalled to don't need adjustment of rotation, but perhaps some adjust of RA or DEC will be needed.

When I tried this mode of capture - multiple night - I hadn't possibility to let all ready between the days. And the more difficult to adjust was rotation.

You called my attention: why do you (me) don't try again, since you (me) have the ease of stationary equipment ? Will you (me) be traumatized with past experience ?
Yes, at that time I lost almost 1 hour by adjusting the position. But, now, it isn't the case ! I will do ! :thumbsup:

[Camelopardalis]

What I do is to refer to a sub from the previous session...I use a copy on my phone/tablet...and attempt to match the rotation of the camera with what I did before. Sounds clumsy, perhaps, but I took a second batch of subs of M42 this past weekend and after stacking the two sets of subs I found I needed to crop the scene by a total of 200 pixels in each dimension. Not perfect, but I can live with it :D

With an obsy I'm sure it'd be more easily reproducible. As for the weather...it can change enough in one night that it may or may not be a bad thing! I found in my two sets of subs (taken 2 months apart), that the fwhm for the subs are distributed about the same.

I'm still learning of course, refining my technique, enjoying my 1100D :thumbsup:

[jsmoraes]

There is another issue with rotation of camera. At least with my focuser the camera can stay with different inclination. What this cause ? Distortion of field.

I had problem with it. When the left side of the photos where well aligned, the right side isn't. And vice-versa. Normally at the periphery.

Stacking all photos in DSS or merging multiple results from stacking different groups of photos, the result was the same: I needed crop the image to eliminate the side with misalignment.

As I said, today I have the telescope and camera assembled full time. This and those prior problems are off. I must return to try multiple nights and ... why not ? ... mosaics, again ! :)

[Camelopardalis]

Ahhhh mosaics...sounds awesome :thumbsup: