Shibby

I was having some trouble with my flats (hardly an uncommon thing) so decided to play around with them in photoshop. What I found was that I had to nudge them precisely 2 pixels "up" and "left" in order that they be aligned with my light frames. Now they're perfect.

Has anyone else experienced this issue?? The lights were captured with Artemis and the flats with NINA, but they're both the same resolution so I can't understand how that's happened?

Use curves to drop the background level, otherwise you can cause clipping. Can't do it perfectly with a jpeg, but it could be tweaked closer to something like this:

10 minutes ago, geordie85 said:

What sort of filter issue could cause this?

I really don't know - it's always incredibly difficult to figure these things out. But there could be some sort of reflected, stray light, that at some point has passed (possibly backwards) through a filter causing the dark circle. That stray light could easily come from the light panel if it was at night.

Just a follow up - I think this must have been down to a timezone thing. Even though, the mount time seemed to match up as far as I could tell, re-synching from PC seems to have solved the issue (before the clocks changed, this was). Or that could be a coincidence! 🤷‍♂️

You've got some very good signal there. I would just drop the background level a bit and also fix the magenta cast of the galaxy.

Truly superb detail! What kit are you using?

Yep, you just need to fix the colour balance and also watch out for the background during processing - it appears to be clipped.

Really not bad at all if you ask me - the galaxies are coming though nicely with some decent detail and very good colour. I guess you just need to keep going if you want to reduce the noise further.

To me, the star shapes look like (small) guiding errors, though perhaps not if you really do get the same with short exposures. I would test with a very short exposure just to be sure.

The larger circles don't really look like dust bunnies to me - they might be something related to the filters... The flats don't look quite right. Is it possible that light is leaking in somewhere? Were the flats taken in daytime? Do you have the imaging train covered up?

Wait - what?? I've always trusted my Bahtinov mask but now I'm gonna have to try without. Is there an easy way to manually focus in NINA with HFR?

5 seems like it could be about right for FWHM in pixels. However, under 2" seems far too small to me, so maybe it's their own measure of some sort? 

What date was the image captured? There's something suspect about the way the initial trajectory lines up with the other trails. I wonder if you've captured a starlink launch, the last of which was on the 19th March. I'm not sure what happens to the second stage after deployment though, whether it has another burn or not.

Fascinating. And a lovely mosaic! Congratulations!

Perhaps I should have a try for a close-up of that bright** looking region of it to the East? I imagine it would require some long exposures at F/5, though...

**Relatively speaking; not bright at all!

Looks like you could have a really nice image here - I just wanted to say that I believe the noise reduction applied to the galaxy is too aggressive and has given it a sort of poster-like appearance, losing the detail. I'd be interested to see it with some more selective use of NR, with less applied to the galaxy itself?

Recently, I've found that when I try to slew to a target near the meridian, my mount is flipping when it shouldn't (i.e. to the wrong side). For example, if my pier-side is West, pointing East and I try to slew to a target that's East of the meridian but within a few degrees of it, the mount tries to flip. My mount is a Mach1GTO and I'm using ASCOM.

This is a recent problem - I don't think I've changed any settings, but I'm not sure where to look - any ideas?

I was comparing two sets of M33 luminance captures taken on different dates and noticed a huge difference in detail.

It got me wondering whether the first set was on a night of exceptional seeing or whether it was more likely down to my equipment e.g. focus or guiding. Unfortunately I don't have the guide logs but I'm fairly certain the total RMS was in the typical range of 0.5-0.6" on both nights. So I guess my question is, should I always be expecting the level of detail achieved in the first set or is that an exception to the rule?

Here are some crops. Both are at 100%, which is 0.94 arcsec/pixel. No processing other than a linear stretch.

The first was taken on the night of 13/01. DeepSkyStacker reports an FWHM of around 3.8 pixels:

The second was taken on the night of 27/01. FWHM around 4.8". This seems like a fairly typical level of detail for me - but should it be? (Note there is bit less noise because there were more subs)

Are you really in the UK??? 😆

Crikey, you were brave to return to it! A lovely image, great detail and colour.

I started randomly looking for a target the other night and selected a circumpolar galaxy identified as NGC2460, which has a few others nearby. I can't seem to find any reference to it elsewhere on the forum.

I think there is a hint of tidal stream between NGC2460 and the nearby IC 2209 but I can't be sure as I couldn't seem to really get that deep with ~5hours integration in my light-polluted skies.

• 30x600s Luminance
• 5x3x300s RGB
• 190MN + Atik 460ex

Thanks for looking

Great work. I also started on this recently - decided to go for the Ha and Oiii for a single panel. Seems like an awful long way to go doesn't it? Especially since it's already passed the meridian by dark.

Different, if not differential. Thanks for sharing!

The jagged appearance could be caused by noise and/or seeing. In both cases, you can improve the situation by increasing the exposure time and enabling multi-star guiding if you're not using it already?? Other than that, I also deliberately like to keep the graph scale large 🤣

Thanks all. Its given me plenty of food for thought!
 

On 20/02/2022 at 21:00, tomato said:

I have combined RGB from a OSC CMOS with L from a CCD with reasonable success

What setup do you have @tomato? Are you using a side-by-side rig currently?

4 hours ago, ollypenrice said:

With the low noise of modern cameras I don't know how import dither is, in any case. I don't miss it. 

I also don't dither yet, despite it being highly recommended by many. Perhaps my guiding isn't accurate enough to make it a necessity? (Although I do typically have an RMS ~0.5"). I often combine data from multiple sessions so I suppose that makes a difference.
 

4 hours ago, ollypenrice said:

The signal, however, will be far weaker in the unbinned small-scope data

Indeed - the smaller aperture is going to mean I wouldn't get away with shorter exposures for RGB as I do now. The overall benefits seem to be diminishing the more I explore the idea.

If my spare camera was a large-sensor OSC I might instead consider using it to capture some "context" images to show alongside the close-ups. Or just to have the option of wide/narrow field on the night.

I would say it's an aeroplane, as you can see the lights blinking from one wing to the other.

Very nice! Interesting region, nicely framed and well presented

It's hot pixel streaks caused by field rotation. Doesn't matter how good the guiding is, if the polar alignment isn't perfect (or the guide star isn't close to your target) you will end up with some field rotation in the corners. The reason they're still present is down to the stacking method - sigma rejection will get rid of them if you have enough subs. Alternatively, you could calibrate with darks or use the cosmetic options in DSS.