S Migol's photostream  

One of my oldest sets of data that I have had kicking around on the server waiting until I had the knowledge to do something about it. This is from one evening in September 2009 when I got a couple of sets of lights on M31.

Taken with my standard setup of the SV4 on the GM8 with an unmodified Pentax K10D camera. Guiding was with the SV70ED and SSAG with PHD. This was likely taken at Henry Coe SP.

I didn't really know what I was doing at the time and so I changed framing a few times through the session. There were a lot of tracking errors, but luckily, I kept doing the lights. In the end, there was enough that I was able to get a decent intersection and have some smoothness.

Over time, I've learned how to match the temperature of my lights with darks and the last beta version of DSS seems to do a pretty decent job of scaling darks - especially when the darks are already at the same temperature as the lights. I know it seems strange - why scale when the darks are the same - but I think it helps with the fact that the dark noise in this camera appears to be non-linear - especially with regards to the amp glow.

I'm still left with a strong color gradient across the field, but now I've learned a lot about how to remove this gradient by a heavy hand in PI.

Because of the framing issues, I've had to cut off a lot of the data. You can see one bad frame edge along the lower left. There are many more on the full size version.

Here's the stacking information:
Lights: 3 frames (ISO: 800) - total exposure: 24 mn 6 s | Darks: 7 frames (ISO : 800) exposure: 8 mn 3 s
Lights: 1 frames (ISO: 800) - total exposure: 8 mn 2 | Darks: 8 frames (ISO : 800) exposure: 8 mn 3 s
Lights: 1 frames (ISO: 800) - total exposure: 10 mn 3 s | Darks: 1 frames (ISO : 800) exposure: 10 mn 6 s
Lights: 5 frames (ISO: 400) - total exposure: 1 hr 15 mn 20 s | Darks: 2 frames (ISO : 400) exposure: 15 mn 7 s
Lights: 1 frames (ISO: 800) - total exposure: 8 mn 2 s | Darks: 5 frames (ISO : 800) exposure: 8 mn 3 s

The grouping was because of ISO and temperature ranges.

I did the final framing and crop with saturation, sharpness, and a last noise reduction for the web in LR.

An old set of data that I've brought back for a revisit. This is based only on a small number of lights, captured back in September 2010. This was done with an unmodified Pentax K10D camera, which for this target is not a problem given the colors available.

Again, taken with my standard setup of the Stellarvue SV4, flattener, K10D. Baader Moon and Skyglow filter used. Guided with the Stellarvue SV70ED and SSAG with PHD.

Stacked with DSS using dark optimization because I didn't have darks at the right temperature.
Lights: 5 frames (ISO: 400) - total exposure: 50 mn 10 s
Darks: 3 frames (ISO : 400) exposure: 10 mn 4 s

Extensive work in PI with DBE to flatten out the amp glow. I'm really getting a handle on the tool and what I can do. This was a pretty good image to play with because it's mostly stars with little nebulosity. There's a lot of noise waiting just below the basic histogram because of the low number of lights available.

My second oldest glass. This is my first screwmount lens. I picked this up at Keeble and Schucat about a month ago. With the Pentax M42/K Mount adapters, it works just fine on my K10D camera. Focus is smooth. Because it has a manual aperture, I can meter with it just fine.

It's hard to see in this shot because the room I took this picture in is yellowish, there is a yellow cast to the coatings. This is not one of the radioactive lenses, instead, this yellow cast is a natural reflection of the coatings. The light through this lens is balanced a little on the blue side. Nothing that some PP can't fix.

I'm looking forward to taking this lens out under the stars and putting it on a film camera for some portraits.

I've had this lens for a little while, purchased used. I like the rendition it has as well as the small size. When I want to go light, I'll bring this lens on a stripped down body. It's almost old-school in the size and simplicity.

I've taken a lot of recent lessons learned and applied them to this data set. The original lights were captured on the night of Aug 24, 2011. At the time, I tried working with them and could only get some burned out images out of them. Over time, I learned about getting temperature matched darks for my DSLR and then about working with groups in DSS. With all this effort, I've been able to bring this shot to life.

There are still problems with flawed flats, but there's not much I can do about them since I didn't take flats that evening. I still had not learned the lesson to do that every night. Also, you can barely see some amp glow along the top of the frame. This may be something that I could remove with some better darks or by doing the stacking in PI.

Color balance was reset when I stacked, as I did not have the white balance set properly for the filter at the time I did the shots. I'm not sure if I like the burgundy look of the nebula. I did tweak the balance a bit in LR but at this point it's all aesthetics.

Used a full-spectrum modified Pentax K10D camera with a Stellarvue SV4 scope. Guiding with PHD by Orion SSAG on the Stellarvue SV70ED all on Losmandy GM8 mount. SV flattener used with Baader Moon and Skyglow filter.

3 frames (ISO: 200) - total exposure: 15 mn 0 s with 4 darks
2 frames (ISO: 200) - total exposure: 20 mn 4 s with 2 darks
4 frames (ISO: 200) - total exposure: 40 mn 8 s with 4 darks

Grouping like this was done to keep the lights and darks temperature matched. Stacking was done in DSS.

Processing done in PI. Mostly masked stretch, histogram stretch, sharpening, deringing, noise reduction, black structure enhance. Brought the image into LR to do spot fixes and a final stretch, sharpen, and denoise for the web.