Image artefact what is it?

[alcol620]

Hi folks

Had a couple of quick sessions with the SSA with a Canon 550d mounted on it. Tried a 50 mm fixed lens and a 18/55 mm zoom lens. First problem is dew, not too much dampness required before the lens fogs up, in the process of making up a small dew heater to go over the lens. The wide field images I obtained using 120 sec iso 800 settings give reasons for optimism once I get a bit more practice.

My reason for posting was to get views on the partly processed image shown. I assume the artefact on the two bright stars (deneb and vega) are caused by reflections in the lens somewhere? The 50mm lens images are fine, the image shown is from the 18mm/55mm lens.

Would anybody like to comment? Also is there a Pixinsight technique to remove the artefact?

[Thalestris24]

Hi

I've no experience of using short focal length lenses but you might be able to lose the artefacts by taking at least 15 (preferably more) subs and stacking using the DSS Kappa-Sigma algorithm. You may need to increase the DSS median filter setting too. Just wondering if there are any filters in the light path that could be causing the problem?

Louise

[alcol620]

Hi Louise

Thanks for your input. I'm using Pixinsight so not sure what to do with DSS, haven't used it for some time and I'm really looking for a Pixinsight solution. Will re-image with the same settings and see if it repeats. I'm simply using a Canon 550d with the 18/55 zoom on it. Mounted on a Skywatcher Star Adventurer. A recent secondhand buy, so that I can easily take out to dark sites and possibly on holiday.

Best regards

Alec

[Thalestris24]

1 hour ago, alcol620 said:

Hi Louise

Thanks for your input. I'm using Pixinsight so not sure what to do with DSS, haven't used it for some time and I'm really looking for a Pixinsight solution. Will re-image with the same settings and see if it repeats. I'm simply using a Canon 550d with the 18/55 zoom on it. Mounted on a Skywatcher Star Adventurer. A recent secondhand buy, so that I can easily take out to dark sites and possibly on holiday.

Best regards

Alec

Hi Alec

I have PI too though haven't really put it to good use yet. I know you can stack with it but not sure if it gives options for stacking algoriths. You could always stack in dss anyway.

Louise

[alcol620]

Hi Louise

You won't be sorry you got PI, it is super, although it is a steep learning curve and never ending in terms of its possibilities (although I haven't found anything to get rid of the artefacts!! Kayron at  http://www.lightvortexastronomy.com/tutorials.html has some great tutorials and without them I would never have had any idea how to make use of PI.

Take care

alec

[Thalestris24]

1 minute ago, alcol620 said:

Hi Louise

You won't be sorry you got PI, it is super, although it is a steep learning curve and never ending in terms of its possibilities (although I haven't found anything to get rid of the artefacts!! Kayron at  http://www.lightvortexastronomy.com/tutorials.html has some great tutorials and without them I would never have had any idea how to make use of PI.

Take care

alec

I've had it for over a year!

[alcol620]

Use it you won't regret it. If someone as old as me can get the hang of it, then anyone can. It takes time. Practice makes perfect.

Regards

Alec

[Thalestris24]

I just haven't acquired any images that I've felt desrved PI treatment. I've only been doing mono imaging recently - either just luminance or Ha and have only needed to do simple processing. I'll be doing colour again - next time the skies are clear and the moon stays out of the way!

[alcol620]

PI is fine for mono images, good place to start