Lee_P

I've had a crack at reprocessing some data, trying to get a sharper result and more blue into the image -- often tricky with an L-eXtreme filter.

It is sharper, but also quite noisy  I got the blue in, though!

More info, including the original attempt, here: https://urbanastrophotography.com/index.php/2021/07/29/the-pelican-nebula/

* June & July 2021 (reprocessed November 2021)
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Software: PixInsight, Topaz DeNoise AI, Lightroom
* Control: ASIAIR PRO
* 780 x 120 seconds

Total integration time: 26 hours

That's good going for a short integration time! And good on you for maxing out your current equipment before upgrading. I second every suggestion made by powerlord, and would add in spend a bit of time making sure your focus is as good as it can be.

11 hours ago, mackiedlm said:

That is really superb. I'd been thinking of trying this target but all th images I found of it were rather flat and uninteresting. This has just pushed it back to the top of my list.

Thanks, I'd be interested to see your final image once you've tackled it

I've been using the Askar FRA400 for nearly a year now, and have written an updated review here: https://urbanastrophotography.com/index.php/2021/11/03/review-askar-fra400-f-5-6-quintuplet-apo-astrograph/

(I still think it's great 👍)

2 hours ago, Jerry Barnes said:

Signal to noise calculations using https://snrcalc.vercel.app/home 

That's a potentially very useful site! I just tried it, but found the surface brightness section a bit tricky to fill in. Cartes du Ciel doesn't seem to have the surface brightness for most of the targets I'm interested in. Have you found any workarounds?

Regarding your question, you can get by with short subs with the 2600MC. Guiding is useful though, least of all because it allows you to dither, which is more-or-less essential. So I'd say that if you can reliably get subs of a couple of minutes using your EQM35 with guidescope, then why upgrade? 

3 hours ago, raadoo said:

I have the same FRA400 and am in awe of what you’re doing with it! I definitely went on a bit of an Urban Astrophotography binge on your website just absolutely gawking at your work. Top shelf, altoghether!

Thanks, this made my day 😎  More Urban Astrophotography content is on the way, including a one year with the FRA400 review!

The new CMOS sensors are excellent. As Olly says, the ASI2600MC in particular is ace, especially combined with a dual-band filter like the Optolong L-eXtreme. Lots of examples on my website here. newbie alert does raise a good point though,  that you need a lot of harddrive space. Fortunately that's not too expensive these days.

10 hours ago, vlaiv said:

There is some increase in resolution for DSO imaging - but not as much as for planetary imaging.

For planetary / lucky type imaging, resolution grows linearly with aperture diameter.

For DSO / long exposure things are not quite so straight forward. Aperture combines with seeing and mount performance to produce final FWHM. This is for diffraction limited optics. Once you start adding reducers / flatteners / coma correctors and examine FWHM over larger field - things get even worse, as scopes tend not be diffraction limited in those cases.

As far as speed is concerned - that really depends.

I would put it like this - larger aperture scope has potential to be part of faster setup. We can define speed of setup by simple metric of "aperture at resolution". Resolution is determined by focal length and pixel size.

Speed grows with aperture size, and falls with increase in resolution - 200mm at 2"/px is faster than 100mm at 2"/px, and 100mm at 2"/px is faster than 100mm at 1"/px.

If you change both parameters - aperture and resolution - then you have to take their squares in order to compare them - so something like aperture^2 * sampling rate ^2.

Comparing 200mm at 1"/px vs 100mm at 2"/px would then give you 200^2 * 1^2 = 40000 versus 100^2 * 2^2 = 40000

So 200mm aperture at 1"/px is as fast as 100mm at 2"/px.

There is another very important aspect of speed - that favors big scopes.

Big scopes tend to illuminate big sensors - and that is advantage.

Say you compare 8" F/8 scope and ASI1600 to 16" F/8 scope and ASI6200. They will produce same FOV, can be binned to the same resolution and at same resolution 16" will clearly win as it has x4 aperture surface.

Thing is - you can't illuminate ASI6200 with 8" F/8 RC - at least not natively without flattener. And even with flattener - it is really question of how good corner stars will be at such large sensor.

 

Thanks vlaiv, that’s helpful. Broadly speaking then, is it accurate to say that a larger aperture:

* Helps a lot to increase resolution for planetary imaging;
* Helps to increase resolution (i.e. sharpness and ability to separate close objects) for DSOs, but seeing and mount performance are also big factors;
* Makes a faster system (i.e. lower focal ratio) possible;
* Is important to get good quality all the way to the edges of a large sensor.

46 minutes ago, Stu said:

You will likely have to specify if it’s the focal length or focal ratio which are remaining the same as the aperture increases in order to get valid answers.

Ok, good point. Let's say the focal length stays the same. The focal ratio will be lower for the larger aperture telescope, given that focal ratio = focal length / aperture, right? Makes sense, bigger aperture means you're collecting more light. But then if you have the smaller telescope, you could just aim for a longer total integration time to then match the bigger telescope. So what are the other benefits? Increased resolution, i.e. being able to separate closer objects? 

Ever find that as you gain knowledge, you start to question your understanding of more fundamental topics? I'm getting that right now. I wonder if someone would be so kind as to answer this question: assume you've got two telescopes that have very similar specifications, but one has a larger aperture than the other. The bigger one has more light-gathering ability; but what does that actually translate to in real terms for astrophotography? Shorter total integration time needed to get the same signal-to-noise ratio as its smaller counterpart? Sharper images? Something else?

Thanks in advance!

Fantastic, no wonder you're happy! 😆

As part of my quest to push the limits of what a small refractor and OSC camera can achieve from a light-polluted city centre, I present my latest experiment: NGC 7822.

More info on my website here, but if you're just interested in the capture details:

* NGC7822 / NGC 7822
* October 2021
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Control: ASIAIR Plus, ZWO EAF
* Software: PixInsight, Lightroom, Topaz DeNoise AI
* 600 x 120 seconds
------------------------------------------------------------
Total integration time: 20 hours
------------------------------------------------------------
By Lee Pullen

7 hours ago, oymd said:

I did stress on QUALITY in the example I gave above. By quality cameras, I meant a high end top quality camera, like a 6200MM or 2600MM. 

Then it's...
OSC: 1 for sale
Mono: 0 for sale

I'm not disagreeing with you -- rather, I actually think you're right -- but we have to be careful when using assumptions to draw conclusions as then we tend to reinforce our pre-existing notions. I don't think we can draw any solid conclusions just from the used market sales (especially not just the very brief research I did 🤣) without more information. If we guess that almost all those selling an older CCD or 1600MM are upgrading to a newer Mono, then of course we'll stack the deck full of Mono users.

For what it's worth, I sold my 1600MM and bought an OSC

17 minutes ago, vlaiv said:

That was my first thought, but that can be easily checked.

Can you filter by type - like CCD / CMOS? Or maybe check models being offered manually (I know it is a bit of work, but in the interest of science? ).

I've just done this, but speedily -- so my data won't be completely accurate! It's just for fun though...

OSC: 11 for sale
Older Mono (CCD): 18 for sale
Modern Mono (CMOS): 10 for sale.

4 hours ago, oymd said:

My take on this is from a completely different angle.

Usually the USED market is a good indicator of where the current state of astrophotography is at. 

You rarely, if ever, see a quality MONO camera come on the used market.

On the other hand, you will definitely see, every once in a while, a quality OSC come on the market. It is usually sold by an imager who wants to take the leap and up their imaging quality by a notch or two.

Please do not take my analysis in a negative way regarding OSC. I myself have just ONE camera, the 294MC Pro, which is obviously OSC. 

I have been pondering upgrading to the 2600MC Pro, but what is actually holding me back is the theory that if I want to go up a level in imaging, I should save a bit more and go all out for the much more expensive setup of the mono 2600MM with filters and wheel.

I quite like that way of looking at things: using the used market as an indicator. So out of interest I just went to UK Astronomy Buy & Sell, and filtered by the category "CCD equipment" (which seems to encompass CMOS too). I then tallied the OSC and Mono cameras for sale, just quickly: not counting guide cameras, and only cameras over £500 (as an indicator of quality). I gave up after the first two pages, but the results... drumroll...

OSC: 11 for sale
Mono: 28 for sale

I was surprised by that. Obviously my method has a lot of holes in it, but it's still an interesting result. A lot of the Mono cameras seemed to be older CCD, so I think that perhaps the owners are selling up and maybe jumping to Mono CMOS? 

Rarely does a day go by when vlaiv doesn't blow my mind 🤯 🤣

Both great images! If I had to choose, I'd go for the first one. It just looks a bit crisper. 

8 hours ago, Adam J said:

The physics of mono Vs OSC has not changed. Both have gotten better equally. It's just OSC has now improved to the point when people are willing to settle for the results, nothing wrong with that I may get one on that basis at some point. But if I want to get the very best image I can it's going to be using a mono camera. 

I think it's more specifically that the development of dual and tri-band filters have increased the versatility of OSC cameras, rather than OSC sensors simply getting better in quality in-step with their Mono equivalents.

6 hours ago, 69boss302 said:

Thank you, That is great information. Do you have a good filter recommendation for dual band? I see a ton of them out there.

bob

Optolong L-eXtreme is great.

Wonderful image, bravo!

30 minutes ago, George Gearless said:

Ok, so I've checked up on the recommended stacking settings for ST and tried to do a re-run. Pretty big difference, I have to say. How to attain the pitch black bacground of space, still eludes me. I did try and crop, vigerously, to try and get the wipe function to work, and you were absolutely correct. Once I cropped out a significant amount of the picture, the wipe function did not mess things up as bad as previously. But still, I haven't quite gotten the hang of the function and need to work more on it. I'm convinced that this is key to getting the proper light. Incidently, I gave the glas plate in front of the camera a quick dust-off with a photography equipment brush, and it's all gone now. Was starting to bug the heck out of me.

I'm perfectly aware that I still have a long way to go. But because of the help I've recieved here, the journey doesn't seem so long and daunting as it might otherwise have. So thankyou to everyone for the help and very helpful advice. 

While I don't consider this picture the 'final, end all, be all' result because there's still so much to learn, I'm sure you'd agree that a prettier picture of the Andromeda galaxy has never been taken  .

 

 

This is great! Fantastic progress. One more tip for the road: don't aim for pitch blackness. Space isn't actually completely black. It should be a little bit lighter. If you make your background black then you'll be missing detail.

1 hour ago, Sp@ce_d said:

I’m not so sure how it performs under heavy light pollution

FYI these are all 2600MC under Bortle 8 skies. Broadband with no filter, narrowband with L-eXtreme.

I used to have a 1600MM with filters, but sold it and bought a 2600MC -- very happy I did, it's a great camera. I've made a whole website about OSC imaging, and you may find this article about OSC vs Mono to be useful.

5 hours ago, George Gearless said:

 

I have gotten simillar results as yours with Startools, although I spent much longer time than you to achieve it. I am however content with your result because it confirms that I'm not doing something fundamentaly wrong in my processing in Startools. 

Although I cannot entirely discount that the image is slightly out of focus, I think it more likely that I've messed something up in settings of DSS. I use an EAF and feel confident that Ekos' focusing module has done its job . Thinking back, I did change some settings when I stacked my second target (IC405) and they don't seem to have the same saturn-like rings on them. I think it was the settings involving cleaning cold/hot pixels? Easily found out. I'll just do a restack and see whats what.

Here's IC405 from that same night, same focus, but 15x5min subs. Fiarly round stars I'd say. But I have a suspicion that I changed the hot/cold picxel repair in DSS for this stack:

 

 

As for the dustbunny and sattelite trail, those have obvious solutions that I was just to lazy to do anything about for the purpose of the 'dark background' issue I was struggling with. Remove the bunny physicallly, and identify and leave out the satelite pic in the next stack. And yes, I too can see the dark square box that seems to frame the center of this picture. No idea how that came about. But let's leave that for another thread :).

Thankyou so much for your helpful feedback. From this short thread I've learned more than I could study my way to in days. Also thankyou for taking the time to have a crack at it. Even if it was only for 5 mins.

 

George

 

 

That image looks out of focus to me as well. Maybe get some more opinions on that though? I'd expect an EAF to nail it.

Satellite trails should be automatically removed if you use a particular stacking algorithm -- I think it's Sigma Kappa, but I'm not 100% on that. That would mean you could keep individual images with satellite trails in your stack.

I don't use StarTools, but had a crack at your image using PixInsight and Lightroom. Literally five minutes of work, so I was quite blunt in my editing. Just wanted to get an idea of what can be pulled out.

There's a fair amount of data in there, especially considering it's a short integration.

A few things to note:

* I think that your focus is slightly off. I'd expect it to all be a bit sharper. This might be a limitation of the telescope optics, but my first guess is focus.
* You've got some satellite trails in there. They should be removed during stacking, so maybe check your settings.
* The dust bunny was annoying! Normally that would be an easy fix -- remove all the stars using Starnet, then clone out the dust spot in the starless image -- but Starnet didn't work, I think because your image is slightly out of focus. So I just cloned it out. Not sure how you'd handle this in StarTools but I'm sure there will be a good way.
* Many of your stars have this strange pattern. Not sure what's causing it. Perhaps some kind of internal reflection? Others can diagnose better than I

Overall I'd say that your data acquisition was a good attempt, and I think you'll be producing some really good images in the near future!