First AP attempt with an astro camera (gone wrong?)

Björn Hoffmann:
I cannot open your final light, but the single frame looks as if you slightly missed focus. 60sec seems a liitle too short for me. I usually go for at least 3 minutes with my 533mc pro.

I used a bahtinov mask and the “cross” was exactly in the middle. I did 60secs just to be safe, I am using a star tracker with guiding, don’t want to exaggerate .

Is there a better way to focus than a bahtinov mask? Maybe a fwhm value on the sharpcap focus aid?

Master light is xisf, it can be viewed in PI.

Hi Dimitris,

the master light looks slighly out of focus. Did you re-focus during the night? When temperature drops, the focus will change.

Using FWHM value (V curve) for focusing usually produce more consistent results (because it excludes human error). The focusing step in Sharpcap must be selected to produce a curve. The out-of-focus FWHM values on the left and right of the curve should be about 3 times large then at the good focus point.

I do not know your imaging setup, so I can't be sure. But it looks like the backfocus distance might be slightly off. See the stars in the upper left and lower right corners. They looks like small comets with tails pointing to the center of the image.

Best regards,
Vitali

Focus was not an issue with my DSLR and since I “see” the x pattern with my bahtinov mask on, doesn’t it mean that my back focus is ok? At least for my first light frame…At least my first capture is focused ,right?

Any good electronic focused for my redcat out there? Since manual focusing will not get me far I guess…

The titled camera parameter what effect does it have on my image? 

Thanks for the replies

Björn Hoffmann:
The redcat telescope is a petzval optic. There is no correct Backfocus with those optics because all elements move at the same time.

So what do you recommend? Getting an auto focuser? Any suggestions?

Focus was not an issue with my DSLR and since I “see” the x pattern with my bahtinov mask on, doesn’t it mean that my back focus is ok? At least for my first light frame…At least my first capture is focused ,right?

Any good electronic focused for my redcat out there? Since manual focusing will not get me far I guess…

The titled camera parameter what effect does it have on my image? 

Thanks for the replies

Seeing the X doesn't mean it is in focus. As the focal length gets shorter and shorter even the best of the Bahtinovs out there can't help. As a rule I stop using the Bahtinov for focal length shorter than 400mm. You really need to see that the star is in focus or relay on autofocusing and computers. The tilting is for the out-of-focus first light frame but yes it would affect how the final image is rendered, to which degree depends on how much actual tilt is there in focus.

Honestly I believe this is very good as a first light image - I don't dare to share mine ...

Yes, sharpness is not 100% if we pixel peep and maybe the filter creates a bit of halo around the stars - Optolong filters seem to have a reputation to do that. But I don't see a huge problem that would bother me too much. At the moment more equipment like a focuser will just increase the complexity of your gear. What was the RMS value of your guiding? If you use a tracker maybe just the lack of DEC guiding introduced a very slight fuzziness. As Björn pointed out, light polution and bad seeing may be another explanation. There may be a lot of factors and reasons for the not perfect stars. If you nailed focusing with the Bathinov mask I don't believe the "issue" is due to your focusing process. AP is a marathon and not a sprint, so just observe the behaviour of your gear over more than one session and then draw your conclusions. In your case I would use Bathinov mask again next time and then compare with FWHM method how close you nailed it. The FWHM value will also tell you something about your seeing conditions.

Is this the fits image that results in this published image: Rosette Nebula ( Dimitris ) - AstroBin ?
If so, I would worry more about the processing. To me it appears like you overdid boosting the red channel and pushing the black point and in my eyes you somehow lost a lot of the subtlety of the nebula that is in your data but not in your final image. Compare for example with this IOTD: Rosette Nebula ( Salvopa ) - AstroBin
If this is all intended and your artistic expression it's all fine and then just forget about my comment.

Have fun with your equipment and clear skies
Wolfgang

Honestly I believe this is very good as a first light image - I don't dare to share mine ...

Yes, sharpness is not 100% if we pixel peep and maybe the filter creates a bit of halo around the stars - Optolong filters seem to have a reputation to do that. But I don't see a huge problem that would bother me too much. At the moment more equipment like a focuser will just increase the complexity of your gear. What was the RMS value of your guiding? If you use a tracker maybe just the lack of DEC guiding introduced a very slight fuzziness. As Björn pointed out, light polution and bad seeing may be another explanation. There may be a lot of factors and reasons for the not perfect stars. If you nailed focusing with the Bathinov mask I don't believe the "issue" is due to your focusing process. AP is a marathon and not a sprint, so just observe the behaviour of your gear over more than one session and then draw your conclusions. In your case I would use Bathinov mask again next time and then compare with FWHM method how close you nailed it. The FWHM value will also tell you something about your seeing conditions.

Is this the fits image that results in this published image: Rosette Nebula ( Dimitris ) - AstroBin ?
If so, I would worry more about the processing. To me it appears like you overdid boosting the red channel and pushing the black point and in my eyes you somehow lost a lot of the subtlety of the nebula that is in your data but not in your final image. Compare for example with this IOTD: Rosette Nebula ( Salvopa ) - AstroBin
If this is all intended and your artistic expression it's all fine and then just forget about my comment.

Have fun with your equipment and clear skies
Wolfgang

Just did and autostretch on STF and some curves/saturation I didn’t boost the red channel separately…I will reprocess it though to try other alternatives!

Honestly I believe this is very good as a first light image - I don't dare to share mine ...

Yes, sharpness is not 100% if we pixel peep and maybe the filter creates a bit of halo around the stars - Optolong filters seem to have a reputation to do that. But I don't see a huge problem that would bother me too much. At the moment more equipment like a focuser will just increase the complexity of your gear. What was the RMS value of your guiding? If you use a tracker maybe just the lack of DEC guiding introduced a very slight fuzziness. As Björn pointed out, light polution and bad seeing may be another explanation. There may be a lot of factors and reasons for the not perfect stars. If you nailed focusing with the Bathinov mask I don't believe the "issue" is due to your focusing process. AP is a marathon and not a sprint, so just observe the behaviour of your gear over more than one session and then draw your conclusions. In your case I would use Bathinov mask again next time and then compare with FWHM method how close you nailed it. The FWHM value will also tell you something about your seeing conditions.

Is this the fits image that results in this published image: Rosette Nebula ( Dimitris ) - AstroBin ?
If so, I would worry more about the processing. To me it appears like you overdid boosting the red channel and pushing the black point and in my eyes you somehow lost a lot of the subtlety of the nebula that is in your data but not in your final image. Compare for example with this IOTD: Rosette Nebula ( Salvopa ) - AstroBin
If this is all intended and your artistic expression it's all fine and then just forget about my comment.

Have fun with your equipment and clear skies
Wolfgang

Had another go based on the IOTD Rosette you referred and altered saturation/contrast/star reduction/crop size. What do you think?

Still the lack of sharpness is still there...Wish I knew the info you guys gave me,I would not have to "waste" 2 clean nights of time.

Honestly I believe this is very good as a first light image - I don't dare to share mine ...

Yes, sharpness is not 100% if we pixel peep and maybe the filter creates a bit of halo around the stars - Optolong filters seem to have a reputation to do that. But I don't see a huge problem that would bother me too much. At the moment more equipment like a focuser will just increase the complexity of your gear. What was the RMS value of your guiding? If you use a tracker maybe just the lack of DEC guiding introduced a very slight fuzziness. As Björn pointed out, light polution and bad seeing may be another explanation. There may be a lot of factors and reasons for the not perfect stars. If you nailed focusing with the Bathinov mask I don't believe the "issue" is due to your focusing process. AP is a marathon and not a sprint, so just observe the behaviour of your gear over more than one session and then draw your conclusions. In your case I would use Bathinov mask again next time and then compare with FWHM method how close you nailed it. The FWHM value will also tell you something about your seeing conditions.

Is this the fits image that results in this published image: Rosette Nebula ( Dimitris ) - AstroBin ?
If so, I would worry more about the processing. To me it appears like you overdid boosting the red channel and pushing the black point and in my eyes you somehow lost a lot of the subtlety of the nebula that is in your data but not in your final image. Compare for example with this IOTD: Rosette Nebula ( Salvopa ) - AstroBin
If this is all intended and your artistic expression it's all fine and then just forget about my comment.

Have fun with your equipment and clear skies
Wolfgang

Had another go based on the IOTD Rosette you referred and altered saturation/contrast/star reduction/crop size. What do you think?

Still the lack of sharpness is still there...Wish I knew the info you guys gave me,I would not have to "waste" 2 clean nights of time.

It's not a waste of time, it's called learning and improving and will pay back in future images.

Your second version looks better to my eyes. However, when I do a quick and dirty process run with your data in Pixinsight I get more nebulosity in the outskirts of Rosette Nebula:



I use the "Generalized Hyperbolic Stretch" Script by Dave Payne and Mike How to improve your astro images ... - AstroBin
It allows more control than the STF, of course it's a bit more complex but the youtube video you find linked in the thread  provides a good start.
Not sure if this is the reason, there may be others depending on your processing steps. It seems to me you're cutting this off somewhere in your process.

Disclaimer: This image serves only to show the additional nebulosity I get out of this data. I don't consider this a final polished image.

Clear skies
Wolfgang

I am not sure if this is nebulosity, or just residual gradients. Furthermore, despite the usage of an LP filter and the lack of focus, there should be some blue stars in the image. Most of the bright stars in the center of the Rosette should be blue.

Andy Wray:
I had another go at your master light.  I did the following:

* Used chanelextraction to extract RGB channels
* Used background neutralisation on each channel
* Used linear fit to try and get colours right
* Combined the channels to a new RGB image
* Stretched the image using histogram stretch to a medium stretch
* Extracted a star mask using Starnet V2
* Used curve stretch and sinh stretch on the starless image
* Dabbled with deconvolution on the star mask to tame your stars and "pseudo-refocus" them
* Used opixelmath to combine the starless image with 80% of the star mask

...

Way better than my humble quick and dirty attempt. I would not have posted my image if I had seen yours which was posted around the same time. Brilliant image and thank you for pointing out your processing steps. 

Clear skies
Wolfgang