ASI585MC – 15 March 2024

[Fir Chlis]

First clear night for about 10 days, so I was itching to get going. I’d hoped to do some exposure/gain testing, but the sky was still a bit bright (sky background 11.6), with some remains of twilight and a near quarter-moon, so I went straight onto observing. I’d put together a list of good objects gathered from threads on here and Cloudy Nights.

I made a flat before sunset and made a dark before live stacking each object.

I wanted to keep trying the SharpCap Brain and, for the first time since I tried it, it came up with a recommended gain that wasn’t 300, so I tried gain 0 with 60s exposures on the Bubble Nebula for 10 mins. The result wasn’t that good, but it did confirm that my set-up seems capable of 60s exposures with no (to my eye) evidence of star trails.

 

 

I followed this with NGC3718 and, now it was darker (sky background around 2.5 -  it’s usually around 1.3), the Brain returned to gain 300, and an 8s exposure for 10 min. I’m really pleased with the small objects in this, and this morning I loaded it into SharpCap to annotate it. I’d downloaded all the catalogs I could find in the Cloudy Night posting “SharpCap and Deep Sky Image Annotation”, and this is what it came up with. I’m very happy to see that I’m picking up some objects at magnitudes of 18.5 or so, and even one at 19.2.

 

 

Next target was NGC4631, the Whale Galaxy, again (to me) a really nice image. This was (Brain) gain 300, 4s, 10min.

 

 

Now I tried to do my exposure/gain test at gain 300 on M51, but only managed to get runs at 4s (10min) and 8s (8min) before clouds rolled in. The 8s run does seem to confirm the benefit of a longer exposure time. This is my first image of this object and for me it was a Wow! moment when I saw the detail emerge. Tonight was the first night I’ve watched closely the frames stacking, and seen the noise gradually diminish.

 

 

It was getting late now so I went for one final target M97, Owl Nebula, which I’ve only ever seen before as a tiny white fuzzy blob. This was gain 300 at 15s for 10min. A bit fuzzy, so one to revisit another night, but I like the colour.

 

 

Geoff

 

Edited March 16 by Fir Chlis

[Martin Meredith]

Looks like a great session! When the moon is up I tend to favour open clusters as they're less affected, but in galaxy season the temptation can be strong...

The Owl general comes out fuzzy for me so perhaps the nature of the beast for EAA timescales? I always enjoy seeing the blue central star.

M51 is always a wow moment for me regardless of how often I've seen it. I see that in your first image you're getting a good representation of the 'horns' (as I call them) or trailers running to the right of NGC 5195, and evidence of the streamer heading off diagonally towards the lower left.

[Fir Chlis]

@Martin Meredith Thank you. I've only had the camera out 6-7 times since I got it at the end of January, so it's still a novelty, but I hope that the thrill of seeing what I see doesn't go away. My rig is similar - an 8" F/5 Newt on an EQ mount, but a wee bit North of you.

I hadn't appreciated the detail on M51, but I'll have another look - last night I kept all the raw frames so I could try out a bit of post processing.

[PeterC65]

Some nice images there, especially the second one of M51.

I was surprised by how much more I could see with longer frame exposures, even with the same total exposure time. I find the longer frame exposures a bit less "close to real time" and my mount is in AZ mode so I'm limited to no more than 15s, but that's generally the frame exposure that I use now.

I haven't used the brain function for a while but will give it another go as it seems to have been suggesting settings for you to use that still make sense for EAA.

 

[Fir Chlis]

2 hours ago, PeterC65 said:

 

I haven't used the brain function for a while but will give it another go as it seems to have been suggesting settings for you to use that still make sense for EAA.

 

I'm setting the min/max exposures to 1s/60s, and the maximum exposure time to 10m when I run the Brain and choosing Max Dynamic Range, and then rounding up the proposed exposure time to the next highest of 1s, 2s, 4s, 8s, 15s, 30s, 45s, 60s. This way I can keep a standard set of darks, rather than having to make a new dark for, say, 6.2s. I still want to finish my own exposure/gain testing to see how good are the Brain recommendations.