First shots with EOS Astronomik CLS filter

[Bhm2344]

Hi Guys, whilst on holiday last week I brought an Astronomik CLS filter from 365 Astronomy. The other night I had a quick go under cloudy sky with a full moon. I could just make out Vega, so I thought I would have a go just to see what the filter could do. I attached my EOS 350D and Sigma 70-300 to my 4SE and took this shot. Now I just have to figure out how to take out the blue, and take more photos. I have noticed that some of the stars have star trails in, and I have a few blown pixels too

[Astrosurf]

I've also been having problems with halos (usually red) around stars and some blue hue, so only use it when absolutely necessary. I hope someone's on soon to help as I need it too!

Alexxx

[swag72]

Getting rid of the blue is a fairly easy process.

Open up the picture in photoshop and click CTRL-L, this will bring up the levels box. You will probably see 2 peaks in the histogram. Look at each channel individually, so click on the RGB tab in the levels box and then select each individual channel. You want to align them, so that when you look at it in RGB they peak and start at the same place. Move the left hand slider and that will move the histogram of each channel.

Hope that helps - It will level out your blue.

[Bhm2344]

Thank you, I'll have to go dig out a copy of photoshop

[Bhm2344]

I got a trial of Photoshop CC and tried as you said, but I got a bit confused, and I couldn't get a good result So I looked around and someone else mentioned "IMAGE > ADJUSTMENTS > Match COLOR > Neutralise" and I got a better result and very quickly. This is down to me not knowing how to use Photoshop or other picture editing software. Thanks for the assist, I just need to play with Photoshop now

[Pete Presland]

I have noticed that some of the stars have star trails in, and I have a few blown pixels too

the hot pixels would be easily solved with a dark frame. a couple of questions - was the image saved as a RAW file? also for the trailing, how long was the exposure?

[Davey-T]

I've also been having problems with halos (usually red) around stars and some blue hue, so only use it when absolutely necessary. I hope someone's on soon to help as I need it too!

Alexxx

Me too, got red haloes round bright stars with Astronomik CLS filter , I can remove them individually in PS easily enough, but time consuming, anyone know how to select them all and fix in one go ?

Dave

[Bhm2344]

the hot pixels would be easily solved with a dark frame. a couple of questions - was the image saved as a RAW file? also for the trailing, how long was the exposure?

Thank you for that, I think it would have been around 30sec, I brought the celestron piggyback mount and the camera is mounted to the side, so I'm guessing the weight is playing around with my tracking. Going to have to play with the mount to get the best ballance. Not used RAW much, as I use jpeg as the camera is used for day to day use

[Bhm2344]

Me too, got red haloes round bright stars with Astronomik CLS filter , I can remove them individually in PS easily enough, but time consuming, anyone know how to select them all and fix in one go ?

Dave

just out of interest what white balance and iso are you using?

[Davey-T]

just out of interest what white balance and iso are you using?

ISO 400 & 800 auto WB as I've only just started mucking about with it.

Dave

[Bhm2344]

ISO 400 & 800 auto WB as I've only just started mucking about with it.

Dave

I use ISO 800 and AWB too, last night I tried tungsten lights but the cloud rolled in I'll play around a bit more to see if I can help.

Phill

[Pete Presland]

Thank you for that, I think it would have been around 30sec, I brought the celestron piggyback mount and the camera is mounted to the side, so I'm guessing the weight is playing around with my tracking. Going to have to play with the mount to get the best ballance. Not used RAW much, as I use jpeg as the camera is used for day to day use

RAW files would be much better, pretty much unprocessed, uncompressed and much more information contained in the file. ISO 800 is fine but i would also experiment with higher, especially if your tracking is limiting your exposure length.

[Bhm2344]

Thank you, I had a go last night. I spent part of the day building a better place to mount the 4SE and had a go at imaging last night. I took this shot as my last one of the night of NGC 7000. It is a single 5 min shot, unguided using my EOS 350D with no live view so I had to guess how much the stars were in focus. The lens is a sigma 70-300mm at f4.5 and ISO 800 using raw. I edited in photoshop to remove the blue from the CLS filter. I'm happy with it, I know I can stack images etc but I just wanted to see what the mount old camera and a long exposure could do. Kinda push the limits and see type of thing

[Pyrofer]

So. I decided to put this filter to the test as I just received mine

I have to say, from reviews I expected a lot. I was dubious as to how much it could do, but wow. After seeing a comparison shot in these forums I went and ordered it.

Now for context, I live in central London. I mean RIGHT in the center. I can't think of a worse place to try taking photos of stars. It is possibly the most light polluted part of the whole of England. I did a 10 image stack with 4 dark frames. I twiddled the levels a little bit and came up with this.

To be honest, I am astounded. To get this good an image from inside the source of almost all the LP ! I can only recommend the Astronomik CLS filter highly. Judge the image for yourself.

[jgs001]

The CLS is very good, and I've not had any issues with it, in terms of halos etc. The blue colour is, well, there... but very easily dealt with. Let DSS do it. Don't bother with custom white balances on the camera etc. When you go to stack the image, first in the RAW?FITS settings, uncheck the white balance boxes...

Then in the lights stacking tab, set RGB Channels background Calbration

DSS will then sort out the colour imbalance caused by the CLS filter.

As for the red halos, that sounds more like CA induced by the lens optics. I had exactly the same problem with my EF 50mm f/1.4 at f/3.5. Red rings around most of the stars. Defo CA from the lens, as the CLS has been used with both scopes and other lenses without causing it. A couple of options.. try stopping the lens down more, or use the CA reduction tools (I used Apertures CA removal) to reduce it.

[wxsatuser]

Thank you, I had a go last night. I spent part of the day building a better place to mount the 4SE and had a go at imaging last night. I took this shot as my last one of the night of NGC 7000. It is a single 5 min shot, unguided using my EOS 350D with no live view so I had to guess how much the stars were in focus. The lens is a sigma 70-300mm at f4.5 and ISO 800 using raw. I edited in photoshop to remove the blue from the CLS filter. I'm happy with it, I know I can stack images etc but I just wanted to see what the mount old camera and a long exposure could do. Kinda push the limits and see type of thing

Bit more processing and there is a nice North American Nebula in there.

[Bhm2344]

Bit more processing and there is a nice North American Nebula in there.

Thank you, I'm getting used to using photo editing software at the moment and camera/mount settings