Yep I know, which camera......

[scotty38]

Hi all,

I’ve decided to jump in the deep end and have a go at imaging. I’ve never done it before but have years and years of photography background so, at least, that side of it is fine for what it’s worth.

The scope will, hopefully, be a WO GT81 with its 0.8 flattener/reducer and I already have an AZ-EQ6 mount and iPolar. My “plan” is to use a ZWO OAG and probably a ZWO 120mm for that bit.

The next bit is the question and I think I’m veering towards OSC as there’s enough to learn already without adding mono too so what camera would you be recommending please? I’ve looked at the ZWO 178, 183 and 294 uncooled along with 183, 533 and 294 cooled and compared FOV etc on astronomy tools until I’m blue in the face and will be looking to image DSOs primarily. 
 

Any thoughts on where I should concentrate or anything that I’m missing please, do I even need to bother with cooling at this point in the game for example?

Im intending using my Sony A7III at times too so if I need really wide I can play with that....

 

Many thanks in advance. 

[Adreneline]

11 minutes ago, scotty38 said:

do I even need to bother with cooling

I think you would regret it in the long run if you choose not to go with a cooled camera, especially for long exposure DSO imaging.

I also think the new CMOS OSC cameras are game changers compared with the CCD models that were around when I started down the AP track four/five years ago. If you search on this forum or the likes of Astrobin you will find many amazing images taken with the ZWO 533.

Good luck!

Adrian

[ollypenrice]

An OAG is potentially a complicated choice for guiding a small refractor. I guide a large refractor perfectly happily with a guidescope. Still, either will work.

Going for OSC now makes more sense since CMOS came along. With CCD I'd still recommend mono, myself. The dual band filters bring more versatitility to CMOS CCDs.

In choosing a camera your concerns should be 1) how much FOV would you like and be prepared to pay for, along with whether the corrected and fully illuminated field of the scope will cover it. The diagonal of the chip must be no greater than the diameter of the image circle. 2) Pixel scale. There's a calculator here. http://www.12dstring.me.uk/fovcalc.php  With a modern CMOS camera and an 81mm scope I'd have thought almost any camera would give a decent sampling rate. The range 1.5 to 3.0 will give nice results, best towards the mid point, perhaps.

At least half the imaging process is done after capture, possibly more. So you'll need a stacking/calibrating software and a post processing software. Stacking can be done in free DSS but it's very slow and with lots of short-sub/high pixel count CMOS subs it might take forever. I use AstroArt, which is excellent and also has a good gradient removal tool, something which you will need.

Maybe you already have Photoshop? It's still a wonderful tool for AP. Gradient Xterminator is a good gradient plug-in if you do. AstroPixelProcessor is making friends and Pixinsight is powerful but wantonly obscure, to me at least. I do use it but find it a stressful environment.

Have fun!

Olly

[scotty38]

Thanks both, I have to admit the 533 cooled was my favourite and you’ve done nothing to convince me otherwise 😃

I’ve been having a play with a few of the tools, PixInsight included, but have made no decision yet, given the myriad options. I have ON1 Raw, Affinity Photo, Luminar and that may be it for software I’ve paid for, oh and Sharpcap Pro but will take your comments onboard and check out the gradient tools.

thanks again.....

 

Edit - l just checked and the Xterminator plug-in is supported in Affinity Photo.......

Edited January 31, 2021 by scotty38

[DaveS]

Definitely go with cooled. AstroArt 7 will handle everything from capture through stacking and calibration to post processing, and isn't eye-wateringly expensive either. Affinity Photo is brilliant for final polishing, and the latest GIMP should also be considered.

[Skipper Billy]

If you dont go for a cooled camera you aren't gaining much over a DSLR which I guess you may already have if you are into photography??

I cant comment on the latest colour CMOS cameras as I haven't got one ! I see great images from them though.

The rest of your planned kit sounds like a match made in heaven - personally I would avoid the added complexity (as per Olly) of an OAG and go with a converted finder scope.

Welcome to the Asylum 😉 

 

 

 

[scotty38]

Thanks both.

It’s  the second time OAG has been mentioned and I have no real axe to grind either way, so happy to use a guide scope, but I am interested why it’s not recommended, what’s involved in the extra complexity?

 

[Skipper Billy]

A guide scope is more than adequate for up to about 1200mm focal length - above that OAG comes into its own as it helps eliminate differential flexure.

The OAG can be very fiddly to set up - whereas the separate scope is a piece of cake. You will have enough to fiddle with at the start! 😉 

 

[scotty38]

Thanks, separate scope it is then....

[vlaiv]

Uncooled camera do offer a bit over DSLR type cameras.

If we examine DSLR stats, like in this website:

https://www.photonstophotos.net/Charts/Sensor_Characteristics.htm

we'll find that most cameras have QE that is in 50-60% range. They have anti alias filter and aggressive UV/IR cut filters that people often end up modding.

They are much heavier than equivalent astro model.

Astro cameras have sensors that have QE in 80% range - no or very efficient UV/IR cut filter and are lightweight without all the bells and whistles of DSLR cameras.

Price is major disadvantage, as you can get mirrorless type camera now for 1/2 - 1/3 of price of uncooled astro camera.

Having said that - go with ASI294mc - pro. Cooling is not as important as ability to have set point temperature. That enables you to properly calibrate your data.

ASI294 simply has best price / area ratio of the cameras mentioned. And sensor size is speed.

[The Lazy Astronomer]

Don't discount mono straight off the bat.

Sure, it's a little more complicated/fiddly than OSC, and yes, it can be annoying if your imaging session gets cut short before you've been able to capture all the colour channels, but there'll always be another night to get the rest of the data (plate solving helps massively with this).

I believe I'm right in saying this, although happy to be corrected if not, but I think mono + lrgb filters is technically faster than OSC for a given quality of image, all other things being equal. It also gives you the option of branching out into narrowband, so you can still image on full moon nights.

[Skipper Billy]

1 hour ago, The Lazy Astronomer said:

I believe I'm right in saying this, although happy to be corrected if not, but I think mono + lrgb filters is technically faster than OSC for a given quality of image, all other things being equal. It also gives you the option of branching out into narrowband, so you can still image on full moon nights.

Its not just 'technically' faster - it is demonstrably faster by at least 50%  - but I can understand that the extra complexity (and cost) of a filter wheel, filters etc may be off-putting - but on the upside the processing on mono images is easier.

[The Lazy Astronomer]

1 hour ago, Skipper Billy said:

Its not just 'technically' faster - it is demonstrably faster by at least 50%  - but I can understand that the extra complexity (and cost) of a filter wheel, filters etc may be off-putting - but on the upside the processing on mono images is easier.

Wow, ok, I thought it was a bit faster, didn't realise it was quite that significant. Mono all the way then!

[scotty38]

Thanks, all useful information, great stuff. You'll have me on to mono in no time at all 😃

[rickwayne]

Welcome!

Maybe I'm just masochistic, but I figure if a ten-thumbed goof like me can manage something, it can't be THAT hard. I am, in fact, running an OAG on a short refractor, and while it did take a bit of sorting out, it's lighter, simpler to balance, and less bother overall than when I used a guidescope. Once I figured out where to put the pickoff stalk (hint: on the long side of the sensor) and how deep I could push it without vignetting, I have had pretty much zero issues. Focusing is one issue people struggle with, unless your setup allows a helical focuser you have to slide the camera up and down on its stalk and then pin it with its fixing bolt. But once it's set, you don't have to touch it again. What you're doing is adjusting the light-path length to the guide camera so it's the same as that to the imaging camera, so that when  you focus the latter, the former is  sharp  too.

The field of view and f-ratio are usually smaller and slower, respectively, so some folk have  trouble finding guide stars. Never really been a problem  for my 386mm f/5.5 refractor.

Likewise mono and filters. The luminance filter is a royal road to good detail with overall shorter integration time, and the option of doing full-performance narrowband is HUGE for me. You can do narrowband with a tri-pass filter on a one-shot color camera, but it's much less efficient. Processing is also pretty easy. Admittedly I cheat and use Astro Pixel  Processor.

Edited February 1, 2021 by rickwayne

[scotty38]

Thanks again all....

Well scope is now sorted plus the ZWO guide scope and 120 mini so that's that question dealt with.

The only "issue" is that my preferred 533 is not available. I can get the 183 or 294 (both cooled) so do I stretch to the 294 or buy, say a 385/178/462 that is available too and then get the 533 a a later date and off load the other one?

[vlaiv]

10 hours ago, Skipper Billy said:

Its not just 'technically' faster - it is demonstrably faster by at least 50%

I'm not sure that difference is that significant. Could you walk us thru the reasoning behind 50% figure?

[Shimonu]

42 minutes ago, vlaiv said:

I'm not sure that difference is that significant. Could you walk us thru the reasoning behind 50% figure?

Would also like to know the reasoning. This 50% figure really made me question my plan to get a cooled OSC.

[Skipper Billy]

45 minutes ago, Shimonu said:

1 hour ago, vlaiv said:

I'm not sure that difference is that significant. Could you walk us thru the reasoning behind 50% figure?

Would also like to know the reasoning. This 50% figure really made me question my plan to get a cooled OSC.

I cant remember the details but @ollypenrice wrote a very convincing article some time ago that explained the 'how and why' - I will see if I can find it. I remember being very convinced by the powerful arguments made for mono over OSC.

[Seelive]

1 minute ago, Skipper Billy said:

I cant remember the details but @ollypenrice wrote a very convincing article some time ago that explained the 'how and why' - I will see if I can find it. I remember being very convinced by the powerful arguments made for mono over OSC.

I hope you can, I'm sure it would make interesting reading.

[DaveS]

2 hours ago, scotty38 said:

Thanks again all....

Well scope is now sorted plus the ZWO guide scope and 120 mini so that's that question dealt with.

The only "issue" is that my preferred 533 is not available. I can get the 183 or 294 (both cooled) so do I stretch to the 294 or buy, say a 385/178/462 that is available too and then get the 533 a a later date and off load the other one?

I think if you can stretch to it then the 294 is the way to go, I wouldn't mess around with stop-gap cameras as you will end up losing money, when you sell them.

[Messy Hair 101]

I'm a firm believer in buying once (after having bought astro gear, realised it wasn't up to my expectations, sold it and bought the more expensive option anyway!) I would definitely go Pro straight off the bat. FLO recommended the 183 for my ED80 which pairs really well, although some of the shots I've seen with the 294 are amazing and make me wonder if I should have gone with that. I also shoot mono and, although I'm no pro, it hasn't been hard to pick up and get reasonable results but there is a lot more headroom to go further with mono and filters. So for example I can shoot narrowband on a full moon and still get OK data (for me anyway). Of course you need to factor in the cost of filters and a wheel which isn't to be sniffed at.

I'm pleased with my 183mm but I feel like half the great pictures I see online are with a 294mc so who knows? I don't want to be responsible for restarting the mono vs. OSC debate! 

[The Lazy Astronomer]

2 hours ago, scotty38 said:

Thanks again all....

Well scope is now sorted plus the ZWO guide scope and 120 mini so that's that question dealt with.

The only "issue" is that my preferred 533 is not available. I can get the 183 or 294 (both cooled) so do I stretch to the 294 or buy, say a 385/178/462 that is available too and then get the 533 a a later date and off load the other one?

The 385/178/462 have small sensors and are really more suited to lunar and planetary work. 

The 294 has a larger sensor than the 183, so is better value for the sensor size, plus the mono version of the 294 allows you to shoot in "unlocked" mode, so you can shoot with very small pixels (2.31um) if you so desired (~90mb image files though!).

Another slightly cheaper option than the 294MM is the 1600 - same sensor size, but but a little older, and with lower QE. Also microlens issue on very bright stars, but is a very popular camera. 

[ollypenrice]

My argument over mono versus OSC versus time goes like this: Lum = R+G+B per pixel, simultaneously. You cannot shoot this with an OSC camera, you can only shoot R or G or B per pixel. Now the OSC filters don't have hard cutoffs so this is slightly overstating the case since the green OSC filter, in particular, overlaps into R and B.  Still, the total photon count per unit time is very considerably higher in L than in RGB or OSC.  Sticking to the simplified version where colour collects 1/3 luminance we can make this comparison in 'luminance units:'

1st hour:  mono in R, 1/3.  OSC 1/3

2nd hour: mono in G ,1/3.  OSC 1/3

3rd hour: mono in B, 1/3.   OSC 1/3

4th hour: mono in L, 3/3.     OSC 1/3

Add this up and mono scores 6/3 while OSC only scores 4/3.  While shooting equal amounts of LRGB makes processing easier, it would be perfectly possible to add another hour's lum in mono, taking us to 9/3 while OSC only advances in a further hour to  5/3. And so on...  Some targets can be shot with a hugely extended luminance run, some cannot. Faint stuff like tidal tails, IFN etc can have way more luminance than RGB bot colourful targets do need a higher percentage rgb.  On top of this you can, with CCD, gain further time by binning colour 2x2. Binning with CMOS is something I haven't tried and don't fully understand.

And then, should you want to do pure NB, you will certainly want mono.

But  I don't argue in favour of mono CCD over OSC just on the basis of the arguments above but on experience of both and, the fainter the object, the more the real world advantage of mono became evident. On M42 there was nothing in it. On galaxies the OSC was rather lame.

2nd but: I've been really impressed by CMOS OSC data I've processed and also by dual band filtration of OSC. How does this work in the moon? Not a clue. Perhaps Goran could advise? So I would personally consider an OSC CMOS whereas I would not consider an OSC CCD.

Complexity?  On all our rigs I focus in L and let RGB look after itself. Non parfocality doesn't come, in our cases, from the filters but from the optics and it isn't worth worrying about. With OSC you cannot refocus between colours anyway. You can in mono but personally I usually don't. Nor do I shoot separate flats, except very exceptionally. Luminance flats work for all filters almost invariably. What you can usefully do in mono is shoot lum and blue with the object at its highest.

Olly

[scotty38]

I ordered the 294...... Please don't tell my wife