8 replies to this topic

[Alnitak2009]

Hi all,

 

I setup my Canon 60D h-alpha modded camera with a uv-ir cut filter. I set the ISO to 1600 and shoot about 10-1minute exposures from Bortle 4-5 skies. Object about 25 degrees above the southern horizon.

 

My target was the Blue horsehead nebula in Scorpius. After using Siril and DSS the nebula was not visible in a the stacked image. I had to stretch it greatly to see anything.

 

I was hoping to see something before applying the stretch. I could not expose longer than 1 minute as the histogram on the camera was about 25 percent. Maybe I can try 2 minutes and the histogram would be about 40-50 percent.

 

I might have to use a specialized light pollution filter.

 

Any advice would be appreciated. I know total exposure time was only 10 minutes but that imaging session was just for testing purposes to see if imaging this area was worth it for me.

 

Thanks 

Don

Edited by Alnitak2009, 29 May 2025 - 07:34 AM.

[Tapio]

10 minutes is way too short. Even 10 times that might be too short.

Even when you don't mention your optics, and how fast it is.

 

Light pollution filters are mostly obsolete now. Just compensate with longer total exposure, and processing.

Edited by Tapio, 28 May 2025 - 08:50 AM.

[Overtime]

Some people sometimes call me captain obvious but I wonder if an EQ mount might help for long exposures and a something for tracking? Just guessing I no very little on the subject I am just hoping to help. 

[matt_astro_tx]

Like Tapio said, 10 minutes likely yields nothing on this target. Go for several hours. And, you’ll see nothing but maybe a few stars before you stretch an image. If you’ve done it right.

[Alnitak2009]

I used a 80mm Meade Series 5000 apo refractor with a Televue .8x reducer/flattener. I think this is f/4.8

 

I am not particularly pleased with the overall flatness of the fov with this setup. The stars are flared in the corners and sides. When I stretch the image the center area is much brighter than the perimeter. Not sure if the spacing is incorrect with this combination or perhaps the Televue is optimized with their telescope line.

 

I am highly considering a Askar PHQ 65mm with reducer. Heard great things about these scopes providing very flat fov and nice round stars to the corners.

 

Any way I will have to take longer exposures and about 3hrs or more to go get something decent.

 

The imaging scope and camera were atop a Meade LX200 16" and mount. The tracking is very good as we had implimented PemPro application.

Edited by Alnitak2009, 28 May 2025 - 01:31 PM.

[Tapio]

Are you using flats?
Those are essential for reducing vignetting and take care of dust motes.

[Alnitak2009]

Are you using flats?
Those are essential for reducing vignetting and take care of dust motes.

No I didn't. I will when doing the full blown imaging. 
 

[17.5Dob]

Ten minutes exposure isn't enough exposure for any target, let alone a faint reflection nebula. I would want at least 10 hours at the bare minimum in your skies.

[erictheastrojunkie]

In terms of results, not surprising at all given the 10 minute integration, honestly surprised you saw anything at all. In terms of the image quality, the scope doesn't have great reviews and from what I've read you have to work on dialing in your backfocus quite a bit with that setup. Plus you are piggy backing the setup on top of a 16" LX200 (I'm guess with fork alt-az mount)? Of course you're going to have star trailing, that's not surprising assuming it was on the stock alt-az fork mount. I'd be surprised if you can get 20 second subs with that setup before star trailing occurs. 

 

Tough target from light polluted skies with a not ideal setup is just going to result in outcomes like this.