Datalord

29 minutes ago, gorann said:

My RASA 8 is ready for some serious Ha collection success (or failure🥴)

You will be amazed. I only had a single quick run one evening with the filter (you have the fast narrowband filters from Baader, right?) and this is the completely unprocessed stack from 42 minutes of 3 min subs:

Lovely data! You image seemed green to me, so I took it and added PixInsights SCNR to remove the green tones. Nothing else.

38 minutes ago, wimvb said:

I have been entertaining myself with the data that Göran provided earlier in this thread.

I love this version. Very well done!

17 minutes ago, gorann said:

Hmm. This is SGL, that sounds like a Cloudy Nights comment.

I wouldn't know, I don't frequent that site.

2 hours ago, Rodd said:

Yes--when one of those images gets a top pick or image of the day it drives me crazy.

So much this. Show me how you have battled an uncooled DSLR on a newt with 5s subs in postprocessing and I will be impressed. Using Hubble just warrants a big middle finger in my book.

1 hour ago, ollypenrice said:

When you have wide, there is only one way to go and that's wider...

Still a considerable boatload cheaper than my desire to deep. Really deep!

I have had some of the same thoughts, but I think there is something to be said for the story about the image. For example, on one of my Abell cluster images I took the time to write out a lot about the various galaxies and it got a ton of comments. On others I have merely dumped in the image and the integration time and they just receive some likes. Latest we have seen Gorann explore the fun of a RASA8 and we have all been very active with that. Other images get comments if you ask for opinions or help with something related to the processing. I also use SGL as an inspiration for targets I want to do myself.

Astrobin on the other hand is a pile of peacock rubbish I only use for image storage and nice clean calculation of integration time. I can't stand the "hey I processed Hubble and Liverpool data and to everyone's surprised this clean, beautiful data gave me a glorious image" that receives 8 bazillion likes.

4 minutes ago, vlaiv said:

Now we can compare different combinations of gear like 200mm at 1"/px to 80mm at 2"/px.

200mm at 1"/px is just 200mm per 1px per arc second so 200 (or 200 x 1 = 200)

80mm at 2"/px is 80mm per 0.5 px per arc second is 160mm per 1px per arc second so 160 (or 80 x 2 = 160).

First system is 200 and second is 160 - first is faster by 1.25 in SNR (200/160) for given time (in light dominant regime) or 1.25^2 = 1.5625 in signal strength / photons per pixel.

Yeah, this is a perfect example of how we should compare "speed". I wish I had had this clarity in the beginning. I took the long way around to the large mirrors I have now.

17 minutes ago, gorann said:

The way I calculated this was simply to compare the 8" RASA with 400 mm FL with a commonly used wide field scope like a 400 mm f/5 Apo, so with 80 mm aperture (like an Esprit 80). Both should of course have the same camera to be comparable. In that case the RASA will have (200 x 200)/(80x80) = 6.25 times more light collecting capacity, so 6 hours will correspond to 37.5 hours with the smaller scope.

Right, the aperture. I was more reacting to the use of f/ in the argument somewhere. I've seen it a hundred times and while it's a derivative of the real reason, it can completely skew the point, especially for anyone new to the hobby.

22 hours ago, gorann said:

With regard to capturing photons, 6 hours at f/2 should equal 70 hours at f/7, if I got it right. Someone may correct me like @ollypenrice or @vlaiv......

It was too tempting to let this one go unanswered. I think I have gotten myself into the mode of "f value has no meaning on photons". I have an 11" RASA f/2 and a 12" RC f/8, 620mm and 2400mm. The number of photons are purely a matter of aperture. The number of photons per pixel is a matter of the camera and the aperture and is ultimately the only factor that makes sense. A 1m mirror with a camera that has a resolution of 0.52"per pixel collects more photons per pixel than my 12" with a resolution of 0.52"per pixel. Notice how they will have the same resolution and if the cameras have the same number of pixels, they will have the same image.

Contrary, if your RASA8 has a camera with 0.3"per pixel vs a 71mm refractor rig with a 2.5"per pixel camera, you're not saving all that time. You will have a much higher resolution, but SNR won't be improved 12 times. However, make both have 2.5"per pixel and yours will have a 12 times higher SNR.

3 minutes ago, gorann said:

What is the difference between V1 and V2 of the RASA11? I assume it has to do with the holding/focusing of the primary. I think the RASA 8 came last so it was maybe V2 from the start.

Yeah, V2 has "New Ultra-Stable Focus System (USFS)" which is pretty much just a better primary hold. I don't know what the 8 has, but I assume it is already better in that regard.

5 minutes ago, gorann said:

except for the tilt issues

yeah. Unfortunately I have the V1, so I suspect it has something to do with the main mirror in mine. 😞

Nope, no collimation problems ever. I have some issues with star shapes in 3 corners, which I also strongly suspect is down to tilt. Focus otherwise stays through the night with the Celestron motor focuser installed.

10 minutes ago, gorann said:

I do not understand the gain-scale for the QHY in your graphs and how that translates to ASI gains

Me neither. I put my trust into a short article made by the chief engineer at QHY which basically boils down to: Try it out with your own gear and light pollution, tune the settings. I tried 2800 with 10s and 30s subs, but the result simply isn't as good as low gain with 180s subs.

12 minutes ago, gorann said:

but last night Sadr was in the frame so I had to go down to 1 min

Yeah, a mag 2 star will do Bad Things to any image with the RASA. I can't remember my gain settings without powering up the rig, but I seem to recall 100 as well.

If I read your chart right, you have a full well capacity of 18000 at gain 100? That seems low. I'm trading FWC for noise with my settings because of the light pollution and the photon buckets we have.

Here's the QHY247C charts.

1 minute ago, gorann said:

Great image - must be nice to have forgotten data😉

Thanks! Definitely a luxury problem...

33 minutes ago, gorann said:

And at f/2 the exposures have to be short - have maily gone for 60 s

You may want to have a look at the version I posted this morning from the RASA11. I ended up using 3 min exposures in a pretty light polluted area without blowing out the stars. I think the extra time gives me more colour data, if I'm comparing our images. I only boosted saturation in mine, I didn't alter hue. 

I forgot I had taken this set of images on the night of July 22nd and found them last night. Processed them with DeepSkyStacker, PI and PS.

51 subs of 3 minutes with the RASA11, 10Micron GM2000HPS and QHY247C camera. 

50 minutes ago, gorann said:

Realized that the image sharpness could benefit from some deconvoluton and more distant dust could also be brought out:

I like it. Well done!

I was looking for good RGB targets for the New Moon and trained in on NGC7549 in CdC. I liked the little cluster and started collecting data and processed it. Turns out there is very little info readily available on the interwebs about these distant galaxies.

It is a galaxy cluster and they are interacting. About 250 million light years away, the star of the show is NGC 7549, which is also the largest at 200kly in diameter. NGC 7558 is the outlier and isn't interacting with the other galaxies as it is almost 500 million light years away. All of them are hovering on the 14th to 15th magnitude.

7 hours ago, gorann said:

Thanks for the suggestions Olly. Did another red adjustment and saturated the blue stars - it did help. I must have stared too long at this data to see clear!

It's a vast improvement!

I think perhaps I would try extracting L on this one, sharpen and contrast it hard and blend that back in. There's something too flat in all the redness that just doesn't sit well with me.

Full disclosure, this is an NaN I did some years back and I had the same problem and I cringe every time I look at it. Perhaps it's just me. It's a refractor image, but with a one-shot color camera.

Hmm, this one seems a bit saturated to me. How was the processing of this one?

Very close indeed! What scope/camera is this?

6 hours ago, gorann said:

Still quite happy with how deep I could go with less than 3 hours of data and I found a bit more details in the core.

 

Beautiful. My RASA is getting very little showtime because I'm too lazy to fight the light pollution, but you are really giving me the urge to spin it up.

The RASA really is a remarkable scope. Very well done! And congratulations!