Mr Thingy

Really happy with my ASI 183MM. Super bit of kit.

I managed to use some processing tools to tone down the bloat. It's still visible but definitely reduced.

Using Ha as luminance didn't work out well i  the end as it obscured some features (I guess those not emitting in Ha!), particularly in the nebula to the left, so I tried using the red and green data to make a luminance layer, as between them they seemed to contain all the structure. I think it worked OK.

I'm very happy with the image, though it looks much nicer on my computer versus here on my phone. I might actually get this printed! 

Thanks to @AstroRuz for the youtube video on reducing star size. I applied to the blue channel to get the bloat down.

-Thingy-

7 hours ago, The Lazy Astronomer said:

That's a very pleasing image. ☺ Not exactly a shortage of nebulosity in there either!

If you reprocess, see if you can get the OIII teal-ish colour in the core. Can't for the life of me bring it out in my image, but I'm assured it definitely should be there!!

Thanks! I think the luminance layer is too dominant at the moment and I need to boost the colours. Just got to figure out how to do that. 

Here's my first crack at processing the image - or any RGB image for that matter!

I'm going to redo it now I have a better handle on what I'm doing - I made a few errors aling the way.

Pretty sure I can bring more nebulosity out. Colours don't seem quite right either.

48 minutes ago, DuncanC said:

Other posibility is the filters aren't par-focal. Did you check focus between filters? Could it be a simply focus issue due tot he colour change?

After seeing that the R and G filters were parfocal I skipped refocusing with the blue but when I saw the first exposure, with the bloaty stars, I stopped and ran the autofocus routine. 

With the help of this discussion, I think it could be a combination of scope and filter (can't rule out user error in my case though!)

@alacant

Just starting to process but in the meantime I compared the relative star sizes between each filter.

Not much separating the Ha, R & G, but the blue is clearly much more bloated.

4 hours ago, alacant said:

For such a cheap telescope, we thought the detail was good. Stars rubbish!

@Mr Thingy are your stars worse? Could you post an example? We don't know what to expect from the 72ed.

Cheers

 

I plan to process the images shortly and will share here once done.

Many thanks for taking the trouble to explain in so much depth @vlaiv. It helps immensely to understand the source of the problem.

4 hours ago, The Lazy Astronomer said:

I suppose there is another slightlyslightly more expensive option: buy a Takahashi!!! 😅

A Tak is way too good for my limited skills. It would be like giving a chimpanzee a boeing 747 to fly 😂

4 minutes ago, The Lazy Astronomer said:

 The other alternative, although more expensive, is to look for a new set of RGB filters which cut at around the 400 - 420nm range in the blue channel. 

Astronomik ones seem to meet that criteria:

https://www.firstlightoptics.com/rgb-filters-filter-sets/astronomik-deep-sky-rgb-filters.html

2 minutes ago, The Lazy Astronomer said:

 The other alternative, although more expensive, is to look for a new set of RGB filters which cut at around the 400 - 420nm range in the blue channel. 

Yes, I was wondering about that. I bought some basic ZWO ones but maybe need to throw more money at them.

I was just having a sneaky peak on FLO but then the wife came in... quick! Hide page.

3 minutes ago, scotty38 said:

Looks pretty good to me that does but I appreciate it's the RGB you're speaking about....

Thanks!

The stars look pretty tight in Ha but appreciable less through the blue filter.

I will compare properly later when I process the images.

10 minutes ago, Simon Pepper said:

This looks pretty awesome to me! What scope and camera do you use? Thanks

Thanks! I have a SkyWatcher 72ED 'scope, 0.8 reducer/flattener and a ZWO ASI GT (Mono) camera.

1 minute ago, The Lazy Astronomer said:

I had the same problem a while back too - the stars in both blue and luminance channels were bloated compared to red and green. 

After a bit of research, l came to the conclusion the problem was unfocused UV passing through the filters.

Bought an Astronomik L3 filter and problem solved!

Thanks a lot. I will have to check that out, though I will need to consider where in the image train I can add a filter. 

6 minutes ago, Simon Pepper said:

Hi Thingy,

I noticed the same issue yesterday on the same target, but think this is pretty normal especially on starts like Alnitak! I dont use Gimp, so cant comment. I use PS which has a plug in where you can reduce bright blue halos.

Thanks 

I need to see if the same exists in GIMP.

Thanks

5 minutes ago, scotty38 said:

Probably completely different setups and experience but I captured some Orion data last night (image posted in a couple of other threads so won't do so again) but how do yours compare?

I only ask as I did nothing fancy whatsoever mainly because I have no idea how to do anything fancy....

😂 Sounds like my approach too. Nothing fancy but I also like images with minimal processing, though I do want to learn how to reduce bloat.

I only have my image for Ha so far but hopefully will process the R,G&B data this evening. This is about 1 hour of data in Ha.

I finally managed to get some RGB data on Orion last night, to add to my Ha data. Watching the images come in I noticed that the stars in the blue images were significantly bloated versus R&G.

I've not processed these yet but what could be the reason for this? My scope is a SW 72ED, and I thought that doublets focused red and blue well. Focus was OK. Maybe a filter issue or just a normal phenomenon?

Is there a neat way to reduce these in processing? I use Gimp and normally just basic processing.

I will upload images later, once I've solved a current IT issue!

Thanks for looking.

-Thingy-

Due to only short periods without clouds in my last 2 sessions I did only a basic polar alignment using the polar scope, and didn't use the PA routines in NINA to fine tune. I wanted to see how much of the slack could be taken up by guiding and maximise imaging time.

I was getting values ~ +/- 1 arc second on both axes. The images showed no obvious distortion of the stars, though I have only a short FL scope (420 w/ 0.8 reducer), which must be pretty forgiving.

What is a reasonable tracking error? I assume it gets narrower the higher the focal length.

I also assume that the proof of the pudding is in the eating, but I wanted to know if there id any conventional wisdom on this.

-Thingy-

I think I've found the issue and it's nothing to do with my imaging train, thankfully.

I had a brainwave last night when transferring data from my laptop to desktop via a memory stick. I checked the offending images again on both machines and, you've guessed it, they are only present after transferring. 

New memory stick arrives today.

I'm relieved that this doesn't seem to be a camera fault.

-Thingy-

6 hours ago, Clarkey said:

I wonder if it is linked to when the guide camera is being 'pinged' by the software during the data download. If it was plugged in it would still be active through the USB. What data capture software do you use and does it auto connect to all the devices?

I use NINA. I connect devices manually through that.

6 minutes ago, michael8554 said:

Try taking some Darks indoors with just the camera connected.

Michael

Good idea.

I wondered if this was a known and common occurrence with an easy fix, but I think I need to start the laborious process of eliminating variables.

Taking darks with just the camera would be a decent place to start.

Thanks for looking and your guidance. I will try tonight.

Sky looks clear too 🤞 so I may even grab some new data for M42 whilst I'm at it.

Wonderful image! Despite the headaches you experienced during the session, you must be happy with the result!

+1 for plate solving.

24 minutes ago, wxsatuser said:

I would think it is not the sensor if it varies in location.

may be someone has seen this before

Yes, I was thinking the same.

I was wondering about some kind of interference but not sure from where or what.

My EAF is powered and driven via the hub on this camera, but that would not have been active during these images.

I also connect my guide camera through the hub but in the previous session tgat wasn't even active either.

Just now, wxsatuser said:

how does it look on the whole frame?

Thanks for looking. Here's a dark frame with the line across. You may need to zoom to see it - it's roughly 1/5 of the way up from the bottom.

On 15/02/2021 at 19:57, Basementboy said:

How important is the focuser? I'm not quite sure how much to pay attention to this factor

A focuser with dual speed/fine focus is nice to have and eliminates some of the challenge finding the perfect focus, but it's not the be-all and end-all. My grab and go scope has a basic focuser and works fine. Not as nice as my scopes with dual speed focusers but not an encumbrance really.

I'd be tempted to spend that money on the scope itself or the mount and upgrade later if you find yourself wanting to. There are always DIY options to improve fine focusing anyway, like increasing the focus wheel diameter.