gorann

Fortunately Olly I have only been into this wide-field imaging for about a week so I think it will take a while before I run out of tragets and go into making mosaics. Right now I am more thinking about using my Esprits to sharpen up parts of what I get from the RASA when the moon is gone and nights get longer.

The RASA8 is at least a cheap lunch compared to the other "astrographs" on the current menue😊

Here I just turned on the BBQ for Saturday night dinner - so there is a time difference. You said "Perhaps when I have grown and matured I will once again begin posting". So it struck me that I have no idea of your age Rodd. I am 61 so a bit over-matured but I try not to think about it.

Astrobin and SGL complemet each other in my view. Like you I also use Astrobin as an album to see what I have done. Cannot easily do that on my harddrive. But it has a limited capacity for discussing. Maybe in the future you should post everything on Astrobin, and then turn to SGL if you have something specific to discuss. But on the other hand it is not a big effort to also post your images on SGL - takes 2 minutes. You may then also alert specific people by using the @ function. I live in Sweden and have never attended a UK star party and I get the feeling that many people on SGL knows each other quite well and are good friends and show this by always commenting on their friends images. We are not in that group (yet?) but that is how it is and it does not annoy me.

Filling in after Mark, actually Rodd your image has right now 80 views here. Maybe you should be happy that you do not have 80 comments - then you would have not time for processing😉

Yes, that second one is excellent Rodd! I noticed that the images of mine that get most comments on SGL are often those that people feel need some adjustments. If there are no comments, and only some likes, I just assume that there is nothing to comment on. Like my recent post of LDN1228 that Vlaiv suggested was too red and should really have been grey. Not everyone agreed about the colours of dark nebulosity and soon there were three pages of discussions. In your case the time difference may also play in, if you post images when Europeans are not home in front of the computer. I, for example, had not seen your post until now. Astrobin is excellent but as you have noticed one soon runs out of discussion space there since the text each time is moved to the right. So, maybe if you want to post something that really merits a long discussion you should still do it also on SGL.

First you got me worried, so thanks for that last line Vlaiv!

Unfortunately that is still not really true. My ASI2600MC has 3.76 µm pixels, which is in the lower end of what is out there, so with the 400 mm FL of the RASA8 I am undersampling at 1.94 "/pixel. On the positive side is that I do not have to feel too bad when I cannot get the guiding of my NEQ6 to fall below 1" RMS. With my 14 " Meade that would be totally useless and fortuantely it is on another mount. The other good thing is that smaller pixels on an APS-C chip would give astronomical file sizes. They are already 50 Mb coming off the camera and increase to 300 Mb after debayering in PI. So Debayering, aligning and calibrating takes half a day.

Hi Olly for me it was kind of obvious that it had to be the same camera and FL to make sense, so maybe I should avoided the dreaded f-word and initially have talked about comparing 200 mm aperture with 80 mm at the same FL to be more pedagogic. In any case the fact is that my RASA8 captures >6 times more photons per hour than my 3" refractor with the same camera. But it makes a lousy travel-scope in comparison😉

Good to hear and now Vlaiv has analyzed my raw data and calibrated according to the star colours, and then he actually finds that the dark nebulosity in LDN1228 shall be reddish brown and not gray.

The file I sent you was only debayered, aligned and integrated, all in PI, so there should probably not be any colour adjustment done (but who knows what magic PI is doing?)

There is a built in UV/IR filter is the ASI2600 (as I remeber) so maybe it has an effect on what the IMX571 sees?

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.

Thanks Vlaiv, Then the dark nebulosity in my image is rather close to what it should look like when watched from Earth. Regarding flats so have I never had any good experience with those with colour cameras. Seem to mess up the color balance. There are long threads obout doing OSC flats and how the channels should be separated and calibrated first. I decided it is not for me as long as there are no or few dust bunnies in the system, Vignetting can be fixed in processing.

Thanks Olly, but what are you looking at, in daytime on a bar stol?

Vlaiv, here is the stacked file of my data. I would be pleased if you could use it to detmine the true colour of the nebula. 20200826-27 LDN1228 3days.tif

If most stars as you say Vlaiv are yellow and very few blue, then would we not expect a lot of nebulosity lit up by these to be brownish? You also say that very few are blue and that fits with the fact that there are very few blue reflection nebulas out there, and the few there are often end up on our astrophotos.

Well, between us and the sun and universe is our atmosphere and it scatters blue light away from us so we get more of the red. Is it then not analogous that the nebula dust is between us and the stars behind it and that is scatters away the blue from us and lets through the red?

Lovely image Maurice! I can see some almost squid like objects in there. I notice the reddish tone in the dark nebulosity. I have it in LDN1228 that I recently posted and @vlaiv is trying to convince us that dark nebulosity should be grey and the red is an effect of scattering in our atmosphere. I am still to be convinced about that.

Yes, is it not possible that the nebula is scattering light just like our atmosphere so that it scatters the blue light in the direction of the stars behind it so that mainly red light gets through in our direction? @vlaiv Looking close at the nebula to the right in my LDN1228 image (the most reddish one) there is a clear red glowing spot in it. Maybe there is some strong Ha object in there that lits it up with red light. I also see it in other images of LDN1228, like this one:

And then there is NB imaging where everything is allowed😉. I have to admit I belong to the group (possibly the majority) that go for a colour balance that look pleasing and believable. After all, we completely distort the relative brightness of the image when we start stretching it, so maybe we could also defend a rather relaxed relation to the colours, unless that is the goal of the imager.

So then, what is the correct rendention Vlaiv? According to your suggestion LDN1228 will be brown when seen from earth, and that is from where we are looking at it and take pictures of it....

So upon suggestions I have turned down the red saturation a bit, so here is a new version. I agree that it may look better. Maybe I am just a sucker for red😉. I finally also gave the darker parts a bit of NR.

Found this IOTD by Maurice Toet. Looks like he also picked up brownsh-red in LDN1228. But maybe I had my red saturation turned up a bit too much. I thought it looked nice. https://www.astrobin.com/full/z4sajo/0/

No, no color calibration done.