Trouble getting anything useful

[Pipshag]

Hi! I've been loving StarTools for about 6 months and gotten some nice pictures with stacks of shorter exposures out of it but I'm still feeling like a newbie when it comes to the whole astrophoto process. I recently modded my 1100D and took out the IV-cut filter and realized that I could probably go for longer exposures than 45-60 seconds.

So a few days ago I shot the Leo Triplet with my 102mm refractor and I simply can't get anything useful out of the stack. I can see the data there, but when I try to wipe the picture I can't get a clean image useful enough to continue processing. I've also tried different stacking techniques (about every possible combination) but I seem to get a lot of noise. The 1100D has a lot of weird processing to the RAW-files and I'm not sure as to how I should be pre-processing for 1100D to get the most out of my data.

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Tech specs:

- I live in a city with about 100K and I'm sadly facing the city when shooting. No direct light is hitting the scope though.
- Startravel 102mm f4.9 refractor, dew tube is not flocked
- Off-Axis Guider for guiding w/ PHD2
- Dithering is king, so of course I do it
- Shooting w/ Canon 1100D IR-cut removed
- No filters

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Stacking specs:
- As I wrote, I tried every possible combination of (11 useful) Lights, (11) Flats, (200) Bias, (11) Darks, (11) Dark Flats. They all suck with vertical noise, weird vignetting.
- Stacking with Nebulosity.
- My flats seemed to have been a bit off and it's not 100% perfectly aligned. Shot them right after, but inside the apartment.
- Lights are ISO 400 and 300sec.
- There's negative blooming on the brightest star.
- I also shot some shorter exposures to layer in the blown out segments.

I've put up a stack of 11x300s lights and another one with . I'm reaching out to you to help me improve my captures with my 1100D and maybe even help me process and show me a log of how to combat my specific problems! Shorter exposures but more of them? Higher ISO to combat read noise and light pollution?

Stack: 11x300s Lights only
Stack: 11x300s Lights and Flats
StacK: 11x300s Lights, Flats, Bias and Darks

[Rowland]

This should help with your preprocessing. DSLRs benefit from different processing to 16bit CCD, which is pretty much the default.

http://forum.startools.org/viewtopic.ph ... =721#p2952

Removing the ir cut filter without replacing it with an astronomical filter or clip-in UV/IR filter (Astronomik) will result in focus problems using refracting optics.

Having a look at your stacks - no promises!

EDIT: Can you post a sub and confirm whether or not you were using a replacement astronomical filter, of any sort?

[Pipshag]

Removing the ir cut filter without replacing it with an astronomical filter or clip-in UV/IR filter (Astronomik) will result in focus problems using refracting optics.

Thanks a lot for looking at the stacks. I thought that not replacing the LPF#2 on a 1100D would still allow me to get a decent clip using the first filter but that I would loose any autofocus using regular lenses - because of the refractive properties from the filter that's not there. But if it's correct then I'll be sure to add in a UV/IR filter!

[Rowland]

I was referring to wavelengths particularly at the red end of the spectrum not focusing properly, rather than autofocus. I remove both filters and use a clip-in and still have auto-focus (1000D). The first filter is also antialiasing and tends to soften the image. Looking at the the stacks, I am guessing clipped data due to the method of preprocessing and unwanted wavelengths and noise due to the very wide spectrum with the ircut filter removed - possibly.