ASI224-MC in Halpha ...

sweiller

Low and hazy Winter Sun ... well, enough for a test :)

http://spaceweathergallery.com/indiv_upload.php?upload_id=121623&PHPSESSID=g2eub9oc3ilb2n9s44soqd1q37

See full size pictures and infos at http://sweiller.free.fr/

firstc8

Cool stuff. Can this technique be used for DSOs?

sweiller

Hum... ?

Which technique ?

firstc8

sweiller wrote:
Hum... ?

Which technique ?

One shot color camera + narrowband filter to bring out nebulosity.

riklaunim

You can but it's not the most effective way to do it. Note that Sun is very bright so it's totally different imaging than DS imaging.

sweiller

Hi,

I will test Orion nebula asap with this camera and could try filters.

I guess it will be at least as good as with the 120MC

See my post there

http://zwoug.org/viewtopic.php?f=21&t=2243

firstc8

sweiller wrote:
Hi,

I will test Orion nebula asap with this camera and could try filters.

I guess it will be at least as good as with the 120MC

See my post there

http://zwoug.org/viewtopic.php?f=21&t=2243

Should be easier than 120mc since the 224 is more sensitive to red/IR I think, with lower noise which will help in long exposure for Ha narrowband.

I do suggest try M1. It is more easily enhenced by Ha band. Although a longer FL scope with narrow FOV is a benefit for M1.

firstc8

sweiller wrote:
Hi,

I will test Orion nebula asap with this camera and could try filters.

I guess it will be at least as good as with the 120MC

See my post there

http://zwoug.org/viewtopic.php?f=21&t=2243

On the ZWO Facebook page a recent Orion image done by 224mc with narrowband filters shows great details of nebulosity, but I noticed the stars suffered a great deal, even no filter exposure used as the L channel could not show stars in their more natural state.

This does not happen with a mono camera. I am curious if this has do do with the fact the 224 is after all a color camera?

riklaunim

https://www.facebook.com/photo.php?fbid=1520027881630869&set=a.1379520349014957.1073741827.100008710147631&type=3&theater - this is a very correct image and there is nothing wrong with the stars.

firstc8

Believe me I am in no way criticizing that image by 224. The level of detail shown of the nebulosity is impressive. As such it appears the stars were not brought out to match the intensity. I wonder if that was intentional, or a limitation of a color cam with filters, vs. a mono cam with filters.

To better visualize where my question came from, I will borrow a image on starimagelab.com, cropped both images for comparison:

riklaunim

It's not easy to get color stars - with whatever camera you use. Even on that second image only star halos have color. Stretching of the stacked frame to get the nebulosity out usually stretches star signals so high they end up white. Some photos end with color stars - via additional processing in for example Photoshop where stars are colourized based on the original data.

firstc8

riklaunim wrote:
It's not easy to get color stars - with whatever camera you use. Even on that second image only star halos have color. Stretching of the stacked frame to get the nebulosity out usually stretches star signals so high they end up white. Some photos end with color stars - via additional processing in for example Photoshop where stars are colourized based on the original data.

Even just white stars will help. The nebulosity is visible because of the stars, either reflecting the star light, or the gases excited by the star charges. So a brilliantly bright and detailed and large nebulosity body without stars looks unnatural. The nebulosity body itself does not emit light.

riklaunim

Emission nebulae do emit and their emission lines are covered by narrowband filters. Reflection nebulae just reflect starlight. Even with narrowband filters you will have nice stars - but in most cases you end up with white, not color stars.

firstc8

riklaunim wrote:
Emission nebulae do emit and their emission lines are covered by narrowband filters. Reflection nebulae just reflect starlight. Even with narrowband filters you will have nice stars - but in most cases you end up with white, not color stars.

An emission nebula is lighted by ionized gases, but gases are ionized by nearby hot stars. Why I said they either reflect star light, or are "excited by star charges"-not the best way to describe it of course. Either way a rich colored nabulosity field without stars would be unnatural.