Fegato

Hadn't noticed there was an ASI585MC Pro. The ASI585MC is probably mostly used for moon and planetary work, but the cooling turns it into a deep sky camera. It's newer technology than the ASI294MC Pro - so lower read noise, no amp glow (easier to calibrate etc.) in particular. But the ASI294MC Pro has the bigger sensor - and it's a good camera, I still use one with my 8 Edge HD.

As Elp mentions - pixel size is an important factor.  Resolution, or potential resolution, is measured by arc seconds per pixel - this is (pixel size / telescope focal length) x 206.265. 

So with your ZS 73 you get:

ASI294MC Pro - 2.22 arc secs per pixel

ASI585MC Pro - 1.39 arc secs per pixel

So the 585 "can" give you better resolution. But this then depends on how good the seeing is. In the UK you might find that a lot of the time you can't get 1.39" seeing, so the advantage might be somewhat limited.

I don't think either camera is "better" for this set up - often the case in this game! One gives you more resolution, might work better for small targets in particular, and can double as a planetary camera. One still has a good resolution and will provide a larger FOV for larger nebulae, mosaics etc.

I think pixel size is an important parameter here - are you assuming pixel size is identical?  So if e.g. you "upgrade" from an ASI2600 to ASI6200 on the same scope - in my book, the overlapping (APS C size) image area will surely be identical?  As for the extra bits around the edge of the frame on the full frame sensor - well it depends on how well your scope / setup can cope with the extra size. You might suffer from vignetting, or greater issues with stars if you have any tilt or other problems with the precision of your image train.

The planets are very small and you're trying to pick up much greater detail/resolution than you'd expect to with DSO work. In poor seeing you see them wobble about all over the place. On the other hand they are very bright - so obviously exposures are very short, you shoot video and use "lucky imaging" to pick the best frames. I found I just had to use a pretty small % of the frames when seeing was poor, and my results were mediocre.

But really, I haven't put nearly enough effort in to it. I'm sure if you persevere with it, some nights you'll get good seeing or periods of it, and you can definitely get good results in the UK, as you'll see by others work.

I'm no expert either, although I have shot the moon and planets. I have an older ZWO ASI290MC with 2.9um pixels which did an OK job. I think my problems were normally related to seeing...  having the perfect set up for planetary is all very well, but if the seeing is crap, then it's hard to get any sort of result! My F/10 wasn't quite enough either, and my barlow was too powerful (made it F/22.5).

I think a rule of thumb is to aim for a focal ratio of 5x your pixel size. So with the 2.9 - about F/15. So your F/13 sounds pretty good. 

I think the 585 is more expensive because the sensor size is  larger? That might be good for moon work, but won't give you anything on the planets. That's the problem with having one set up for lunar and planetary, the size difference is massive (unless you just want to do ultra close-ups of the moon). I've tended to use my larger sensor ASI294MC Pro for moon pics and compromised on resolution. 

Must admit, I like the look of that 2um pixel camera - might work well with my 8 Edge HD at F/10. But then again, that seeing....

47 minutes ago, Anne S said:

That's a lovely image. I must add the object to my imaging list.

Anne

thanks Anne!

17 hours ago, tomato said:

Great image! With regard to your lens group now turning, this happened to me and I was advised not to disturb the corrector plate housing, but instead remove the primary mirror cell and put my hand up the tube to hold the secondary assembly so it could be tightened back up. This was all carried out successfully.

Having said that, I note you have a RASA11 as opposed to my RASA8, so it could be a question of if your arms are long enough to reach up inside the tube.

Thanks!  Yes it's a pretty long tube, I'll have to do some measuring up!

That was amazing. Huge band glowing over my head from horizon to horizon, mostly North East - South West, but could clearly see it due South as well. Stunning!

I live near Carmarthen, great shop - and I enjoy walking past that wooden Newtonian! 

Here's my other effort from Friday - centred on LBN552 in Cepheus, with larger areas of dust to left and right categorised as LBN550 and 555.  The dark area far left is LDN1228. There's a bit of star forming brightness in this dark area and some more towards the centre. This area is sometimes called fighting dragons I think, and there's certainly a lot going on. I'm normally quite good at getting the composition right, but missed a bit with this one, and  the right hand side is cropped a bit to try and balance things.

It was nice to have a few hours imaging with no cloud or rain to worry about, and with my equipment behaving as it should. My camera had been playing up with failed exposures, and I managed to track this down to a faulty power cable - all good now - these cooled cameras need their power for imaging as well as cooling and dew control. I've also been having awful guiding recently, and have both tweaked my RA aggressiveness and loaded a PEC curve from Pempro, which seems to have sorted things out quite nicely (early days, fingers crossed). Having smugly sorted all that out, I didn't spot that the camera dew heater wasn't on - lost quite a lot of the comet subs due to that!

I'm just left with one more painful issue now - I've managed to get my RASA lens group turning when changing the filter in a previous session (for some reason the filters are really hard to get in and out of my filter drawer), so now I can't get my imaging train off. As I don't tear down every time anyway, I'm just ignoring this for now. As far as I can see, the only way to sort it is to take the whole corrector and lens group off and I'm not looking forward to that.

Anyway - acquisition details for this one: RASA 11 v2 on iOptron CEM120, ZWO ASI2400MC Pro, 164 x 30s (82 minutes)

7 hours ago, WolfieGlos said:

That's a superb result, really nice image!

I'd dread to think of the processing involved to get the comet into that background.

Thanks!

I guess the final solution wasn't too bad - it just took a while to get to it! (and I really should write it down, bound to forget).  Once I worked out how to use it properly, the CometAlign process in Pixinsight did a very good job at producing an image with no comet in it (just a tiny bit of a background hole next to the comet head to correct).  But the aligned comet image was a right mess, even after removing all the stars from every frame before running it. I literally painted a mask around the comet master (heavily convoluted)  and removed everything except the comet, set the empty background to median level, and then added it to the comet-less image. 

Have to say that the ability to quickly and efficiently remove stars at various points to check or correct the odd blemish was critical. Not sure how I'd have achieved anything much without the ability to do that.

A clear night last Saturday - from dusk till dawn, a first this year for me, albeit dusk and dawn a bit closer together than they have been!

I've got limitations to low altitude targets to the north, but can just about get down to 30 degrees in the NE, and can get at the northern part of Cygnus now. I spotted this comet passing through, so thought I'd have a go at it against a busy background. This is only my second comet attempt, and the other one was over a year ago and simpler (just a dark background). So... processing this was a pita, I had to CometAlign the comet and essentially remove all the background, star align removing the comet, and then get the two back together again. Took a lot of fiddling around to get things to work as I wanted, and I have to own up to some CloneStamp usage (just for mask creation and some background correcting - I didn't "draw" the comet, I promise!).  

The comet isn't spectacular, and I couldn't find any colour (was hoping for a nice bright green head!), but it adds something different to this rather red scene. Mostly LBN and LDN categorised nebulae here, but Simeis 57 (aka Propeller Nebula) is down at bottom left.

RASA 11 v2 on CEM120, ASI2400MC Pro, 91 x 30s

Yes I agree - moon is miles worse at a dark site.  I live in a Bortle 3 area - and I can walk home from the pub without a torch in "complete darkness" down little country lanes when the moon is big. It's so bright it casts massive shadows!

So - I much prefer imaging in June with no moon than other times of year with any sort of bright moon. I would normally aim to use about 2.5 hours of nautical twilight - circa  midnight to 2.30. 

As an example - just using ASTAP to measure, it tells me a sub from 9 June 2023 at 01:04 in the morning, altitude 56 degrees, gives an SQM of 21.09 (Bortle 4.5 - rural/suburban).  Best I get is around 21.8.

NGC 4725 is a barred spiral galaxy in Coma Berenices. It is over 100,000 light years across and lies at a distance of 41 million light years. Just above it in this frame is NGC 4747, another spiral galaxy. And another one, NGC 4712, sits below (this is small but looks quite a pretty one for a higher resolution set up). Nearby lies Longmore Tritton 5, a planetary nebula 2609 light years distant. With awful weather this winter, getting the data for this was painful, requiring multiple sessions and a lot of throwing away of subs. I don't shoot many galaxies, so the processing doesn't really come naturally, and getting the balance between the galaxy and PN, plus adding in Ha and OIII were added complexities. My motivation levels haven't been great this year, with weather and equipment issues giving me grief, so it took me a good few weeks to have a go at this data. This attempt doesn't feel quite right, but I'm not going to do any more at the moment, so here it is!

RASA 11 v2 on CEM120, ASi2400MC Pro, 28 x 30" and 60 x 60", plus enhanced narrowband from 80 x 120" and 12 x 180" with NBZ dual narrowband filter.

Just add them all in and don't take them out again. They just stay there. I have darks for two cameras in there. WBPP just recognises which one to use for which lights (probably using the sensor size). I'm sure it will work with multiple bias too.

4 hours ago, Vic L S said:

I actually use PixInsight, and WBPP to integrate my files, I should have mentioned that in my post. 

Just in case you're not using them, note that WBPP has Grouping Keywords as well. These are really useful.

So - I also organise different sessions into sub-directories (flats and lights, or a flat master if I'm re-using). I name them either Session 1, Session 2...  or Panel 1, Panel 2....  and I have them set up to calibrate separately, and then Session is set up to integrate to a single master, and Panel to separate masters. You just use the Grouping Keywords table to the right hand side.

re: Darks - I have all my dark masters permanently loaded into WBPP. It just picks the right exposure, so I never even have to think about them.

I use flats, darks and bias. The darks and bias are only updated very occasionally, so these remain the same anyway.

With flats, it depends on your situation to some extent.  I don't have an observatory, but I don't build and tear down every time, I have the rig on wheels and wheel it outside a short distance. I also don't normally rotate my camera. So if I'm happy that nothing has changed in my image train, I will re-use flats. Any fiddling with anything, or an extended time period, and I'll shoot new flats.

If you need to take new flats for your second session (& flat darks if using), then yes - calibrate separately, and then integrate the two sets together after calibration.

9 minutes ago, david_taurus83 said:

Back here in Gulf Stream Alley, the donut method is as good as I'm ever likely to get it.

yes indeed. I often find even the doughnut is so wobbly it's hard to make out the shape very well!

PS nice M106 despite your issues!

I have an 8 Edge HD, but only use it with an OSC (ASI294MC Pro), and not at all recently as my RASA 11 tends to take preference. I'm not sure I can help much really, but thought I'd give you one response at least!

What I will say is that I'm surprised to see that much vignetting with a smallish sensor. What's your image train and what size filters?  I don't get anything like that with the 294 and 2" filters. And I'm afraid I don't know why you'd get such a bright central area with Lum. What method are you using for the flats?

As for collimation, I have the original screws not Bob's knobs. I find it holds reasonably well, and don't often bother to reset. But I think this is partly because I find the whole process a bit of a struggle - seeing always seems to be appalling when I attempt to work on collimation! Anyway - I wonder if your star shapes might relate to backspacing, as there's a bit of pointing into the middle going on? Maybe try pushing the sensor away a little and see if that helps?

1 hour ago, ollypenrice said:

An absolute cracker of an image! The blend was certainly the right way to go - which I would say because I do that all the time. 

Hat's off for the Ha. The received wisdom is that there isn't any and the received wisdom is clearly wrong. You have the deep satisfaction of having brought something new to a familiar target.

As for the rest, stars, background, dust, nebulosity - flawless. Take a bow!

Olly

thanks Olly, that's very kind - it was certainly one that took a lot of time and a certain amount of care! As for the Ha - well, I largely got the idea from this image, which has tons of integration and has found a bit more than I did, but to my mind is perhaps just a bit over-done in the processing / stretching

https://www.aapod2.com/blog/m45-pleiades-in-hoorgb

Yeah I've had similar feelings...  think the depressing weather is definitely part of it. And my clear 4 hours or so forecast for tomorrow evening has changed to part cloud, so I'm not holding my breath.

OK, so I just averaged the two images together (half and half as we say in Wales)...  and like this one better!

I've seen one or two images that pulled out some faint HII areas around M45, so I thought I'd have a go. This three panel mosaic was planned back in November, but well, you know what the weather's been like....  Before Christmas I gave up on any chance of getting the Ha with my equipment, and booked some time in Spain with Roboscopes on their Tak 130 Epsilon, which has a similar FOV and alignment to my set up. This seemed to encourage poor weather in Extremedura, and in the end I had to call a halt on the Ha gathering on my final panel a few days ago as M45 was fast disappearing below the Horizon in astro-darkness. So excuses first - I'd have liked more data in both RGB and Ha, but, well, beggars can't be choosers.

The HII areas are so faint that bringing them out was very tricky, and I hope that what I've got bears some relationship to reality. Anyway, having spent all that time and money, I had to get something in there! This is the first time I've combined data from two separate setups - at least that went smoothly. 

As for M45, I played around with HDR and masking to try and contain its blousiness...  but in the end, I think the blousier version is the one I prefer. The best of my HDR versions certainly accentuates some of the detail in there, but just looks a bit flat to my eye. But then again, I keep changing my mind as they are so different.  I'll attach them both anyway - always interested in any feedback!  Apart from that, the wide field of view was aiming to pick up all the surrounding dusty areas as well as the Ha. I've tried to bring these out, but also tried to keep the end result reasonably subtle.

It took nearly 5 months, but I sort of got there in the end!

RASA 11 v2 on CEM120, ZWO ASI2400MC Pro, 326 x 30s across 3 panels

Tak 130 Epsilon on Paramount MX+, ZWO ASI2600MC Pro, Baader Ha 7nm filter, 189 x 240s across 3 panels (but only 80 providing anything useful!)

I like it. Not sure there's much more detail to be found than that. Amazing just to contemplate all those galaxies...

11 hours ago, Anne S said:

I'm in Carmarthenshire too, managed 2 images last autumn and 2 at 2 Kelling starparties. Just as well we spent 6 weeks in Portugal with 9 images.

Though I've probably jinxed it now, bought a new 80mm triplet. It'll probably rain until Xmas!

Nice image there. I hope you've fixed your issues. I dread to think what my equipment will do when it's clear again. We have washed the observatory in between the rain though!

Hi Anne - 6 weeks in Portugal sounds good! Having said that, in desperation I ordered some data from Roboscopes in Extremedura in December, and the weather there seems to have been pretty poor since then. 15 hours worth, and the last 3 hours are still outstanding with the target fast disappearing for the season!

Robin