2600MC or 533mm pro, hear me out

[900SL]

I've been yo-yo-ing between these for weeks.

Here's the logic. I have a 533MC pro. I have 2" dual narrowband filters. I live in a B5 location and it's usually cloudy, so imaging nights are few. I could upgrade to the 2600MC Pro and enjoy the extended FOV and use my old filters. The 533MC Pro gets repurposed as a lunar / galaxy camera.

For similar cost, I could get a 533MM Pro and SHO filters. I could run both 533's (OSC and mono) side by side.I have a GT71 and 1 x flattener, and a TS 90 and 0.8 reducer/flattener. I like the idea of this set up, but it may be too complex for my pea brain.

Help a brother out here

 

[Elp]

I'd go mono, it's far more flexible as you can image whatever bandpass you want, and you'll be surprised by the clarity difference. I started the opposite with mono (183) and the latest acquisition is the 533MC to supplement the mono with OSC data, but the mono takes priority with any project.

Edited November 5, 2023 by Elp

[Clarkey]

I would have to agree. I started with mono and moved to OSC as well. Not only does mono allow full narrowband imaging, but undoubtedly gives better results. You also have the benefit of weighting the channels as you see fit. Personally, I find mono processing easier too. Obviously if you ever get a RASA things might be different......

[900SL]

Thanks for the feedback. I'm leaning towards the 533MM, likely with Antlia 4.5mm Edge SHO filters. I find the OSC to be a bit mushy/noisy at times, and I prefer clarity

Now I've just got to figure out how to control two cameras with different exposure durations whilst dithering

[Clarkey]

31 minutes ago, 900SL said:

Now I've just got to figure out how to control two cameras with different exposure durations whilst dithering

This is the bit that stopped me using the dual rig. I now have two separate rigs imaging simultaneously - sometimes on the same target. I use NINA and PHD2 and there was no way of dithering 'intelligently'. As far as I could work out you needed to dither every frame of one rig which I felt wasted too much time. 

[Elp]

1 hour ago, 900SL said:

mushy/noisy

Any setup will produce noise, this is one of the first things I quickly learned and NR is needed on the final image regardless if you want a smooth result. More total imaging time helps reduce this a little.

I suspect what you're referring to is colour noise, imaging with a refractor shouldn't be "mushy", refractor data is normally sharp so it may be that you're imaging during bad transparency, but colour noise can have the effect of an image not looking as clean as you'd like (this can also happen on daytime images or in low light). A mono will look cleaner but once you RGB combine them you'll see the noise again, but it's a bit less and the fact you're using all pixels on the sensor per band will mean a very slight clarity boost, it's quite noticeable on very small targets/details.

As @Clarkey has mentioned it's usually easier to setup two separate rigs rather than two on one mount, you also have the flexibility of imaging two different targets if you want. The main issue on one mount will be getting both scopes aligned to the same FOV, it's not a case of mounting them parallel (if you imagine looking through one eye at a time and notice the FOV shift), the same thing happens with two scopes, due to the focal length you'll find one may not even frame the target at all whilst the other has it centred. It's not just a pan adjustment (I've tried it with my dual SY135 rig) but there are saddles which allow pan/roll and maybe tilt adjustment (I don't think you need the tilt from my initial tests), they're not cheap though. It's usually easier to have one setup with a wider FOV if you want to do two on one.

Controlling two on one mount also has the acquisition issue, I normally use two asiairs, one doing everything, the second only controlling image capture with lens 2. It does mean lens 2 looses a few subs but I found if you stick to 30/60/120s you don't really loose too much at all during say a 3 hour run.

Edited November 6, 2023 by Elp

[Clarkey]

I have the JTD dual saddle from FLO, which costs £300. I could (and should) have bought a second hand mount, such as another HEQ5 instead. I could have picked one up for £500.

[tooth_dr]

Just throwing in my view - I run a mono and a OSC IMX571 cameras on the same rig.

Both cameras in their own right produce great images.  The OSC produces great images but needs exposure time.  I often think I’d prefer two monos but I’d miss not having the OSC.

I run identical scopes, reducers and sensors so alignment is critical as the FOV is identical.  This was not difficult using the JTD saddle, but helped by having a rotatable focuser too.  I just centred the fixed scope on a bright star using the crosshairs in SGPro and adjusted the saddle on the other scope until it was aligned. Plate solving confirmed angles etc.  Took a good hour but that’s a one-off.

I used to synchronise my dithering using APT.  This was important with 30 minute subs, not to lose one. Now with 2 minute subs I don’t bother synchronising dithering and only dither every 15th sub.  I only lose a small % of my subs this way.

I run all off a run of the mill mini PC with a few GB ram.  One scope does the platesolving, guiding, controls the meridian flip etc.  The other scope just keeps taking images all night.

 

10 hours ago, Elp said:

The main issue on one mount will be getting both scopes aligned to the same FOV, it's not a case of mounting them parallel (if you imagine looking through one eye at a time and notice the FOV shift), the same thing happens with two scopes, due to the focal length you'll find one may not even frame the target at all whilst the other has it centred

I don’t believe this is correct.  The scopes will, for all intent and purposes, be completely parallel. This is due to huge distances involved to our targets - look up the ‘parallax method’ - astronomers use the orbit of the earth around the sun to create a large enough distance between their two scope to observe a minute shift in the image.

 

 

[900SL]

Thanks  @Elp @Clarkey, much appreciated. I  don't think I can justify a second mount at the moment. I've just moved house and there's a bit of work to be done (and money to be spent) so i'm limited to the camera and filters (I'm also looking at getting an Altair Wave 115mm f7 FPL-53, so the budget for the next couple of years is spent).

I'll likely keep it simple to start, shoot mono for DSO and have the OSC set up with a barlow and spacers ready for lunar

[Clarkey]

5 minutes ago, 900SL said:

I'm also looking at getting an Altair Wave 115mm f7 FPL-53

You could save some money and buy the Starwave 115mm. Yes, it is FPL-51, but the correction is excellent. I purchased one recently and I have been really impressed. I did wonder whether the FPL-51 would be an issue, but I am glad I saved my pennies. The £400 you saved could buy the new (second hand) mount😀

[Elp]

11 minutes ago, tooth_dr said:

The scopes will, for all intent and purposes, be completely parallel

I tried this as I initially thought the same. The dovetail I mounted the lens rings onto have perpendicular slots so there's very little chance of any misalignment between the two lens rings. Imaging tests showed lens 1 centred on target, lens 2 was to one side with the target just about visible in one corner. My second iteration was to add a pan head to lens 2, this also missed the target with any sort of adjustment. My latest addition without trial is adding a tilt head but utilising it for roll adjustment instead.

I'm only doing this at 135mm focal length but with two identical cameras.

Haven't really had the time to mess with it from earlier this year though due to inconsistent weather.

Edited November 6, 2023 by Elp

[tooth_dr]

2 minutes ago, Elp said:

I tried this as I initially thought the same. The dovetail I mounted the lens rings onto have perpendicular slots so there's very little chance of any misalignment between the two lens rings. Imaging tests showed lens 1 centred on target, lens 2 was to one side with the target just about visible in one corner. My second iteration was to add a pan head to lens 2, this also missed the target with any sort of adjustment. My latest addition without trial is adding a tilt head but utilising it for roll adjustment instead.

I'm only doing this at 135mm focal length but with two identical cameras.

Haven't really had the time to mess with it from earlier this year though due to inconsistent weather.

This will be down to errors in your mounting equipment, but the light rays are (basically) parallel.  This is why you need an adjustment saddle. You need the light rays parallel, and this may not coincide with your mass produced equipment mounting points.

[900SL]

I can mount both scopes side by side with an adjustable Vixen L bracket for alignment. I haven't pointed this skyward yet..

[Richard_]

On 06/11/2023 at 07:38, 900SL said:

Thanks for the feedback. I'm leaning towards the 533MM, likely with Antlia 4.5mm Edge SHO filters. I find the OSC to be a bit mushy/noisy at times, and I prefer clarity

Now I've just got to figure out how to control two cameras with different exposure durations whilst dithering

If you're happy with the FOV of the ASI533 then if go for the mono option. I was fortunate enough to upgrade from my ASI533MC to QHY268M (QHY version of ASI2600MM) and there was a dramatic improvement in image quality. Processing images were much easier and there is nowhere near as much colour noise mottling like I used to see in OSC. 

As an FYI, I have the Antlia LRGB and 4.5nm edge SHO filters. You can head to my astrobin website in my signature to see some example images from the aforementioned cameras. Please note that I alternate between two telescopes and I haven't exactly imaged the same object with a change in camera (ie like a before and after). So it won't be an apples-to-apples comparison by all means, but at least you can get a feel for example images with these filters and a similar mono sensor. 

Edited November 19, 2023 by Richard_

[900SL]

Thanks Richard. The concensus is go mono, and Flo are running a ZWO promotion at the moment, so I'm shopping 

 

[Richard_]

1 hour ago, 900SL said:

Thanks Richard. The concensus is go mono, and Flo are running a ZWO promotion at the moment, so I'm shopping 

 

Sounds like a good time to buy then! Hope you find what you're looking for 🙂

[Ibbo!]

If you go NINA there is a plug in that controls 2 cameras on one mount and handles the dithering/guiding  as well.

 

It is done by magic I think but does work.

[900SL]

Side by side, around 12 kg. 533MM Pro incoming

[ollypenrice]

On 05/11/2023 at 23:36, Clarkey said:

I would have to agree. I started with mono and moved to OSC as well. Not only does mono allow full narrowband imaging, but undoubtedly gives better results. You also have the benefit of weighting the channels as you see fit. Personally, I find mono processing easier too. Obviously if you ever get a RASA things might be different......

Exactly. I have been a long term advocate of mono for speed and flexibility. I'm not persuaded that there is much gain in resolution, the debayering algorithms being as good as they are. I am now blissfully happy imaging with two OSC CMOS cameras but both rigs are F2.  It they weren't, I'd be missing my mono. I work from a seriously dark site, too, and with lots of clear nights - so a clear, moonlit night is not exasperating!

Olly

[tomato]

I have operated two mounts simultaneously and a big dual rig, in terms of least hassle I prefer the dual rig. Sure, getting the FOVs aligned is a hassle but only needs to be done once. The second scope just dumbly takes images, no need to worry about finding the target or guiding. 

[Elp]

On 06/11/2023 at 19:57, tooth_dr said:

why you need an adjustment saddle.

Think I've managed to sort this so I can set it up every time, doesn't take long.

[900SL]

Quick first light with the 533MM pro that arrived from FLO. Edge 4.5nm filters, a single 5 min Ha sub. Only 25 degrees altitude and quite windy so FWHM wasn't great, but the signal is blowing my socks off

 

[Richard_]

10 minutes ago, 900SL said:

Quick first light with the 533MM pro that arrived from FLO. Edge 4.5nm filters, a single 5 min Ha sub. Only 25 degrees altitude and quite windy so FWHM wasn't great, but the signal is blowing my socks off

 

Congratulations and welcome to the club! That's a great looking first sub, I'm sure you won't forget it. After 18 months of mono imaging, I'm still excited/shocked when that first H-alpha sub comes out on a new target

[900SL]

2 minutes ago, Richard_ said:

Congratulations and welcome to the club! That's a great looking first sub, I'm sure you won't forget it. After 18 months of mono imaging, I'm still excited/shocked when that first H-alpha sub comes out on a new target

Thanks Rich. I jumped around to check it out, single subs on Rosette, Jellyfish, Orion, Tadpole. The Oiii on Altinak at 6 minutes didn't look bad either, no obvious halos. Happy chap here

[Richard_]

So pleased for you, I'm sure it was worth the wait! Glad to hear that the OIII filter creates decent results from Alnitak. I haven't imaged the Horsehead nebula yet but it's comforting to know that when I do get around to it, the Antlia EDGE filters will be up to the task!