Stuf1978

14 minutes ago, wimvb said:

With a square sensor you don’t need to rotate your camera, you just crop to the aspect ratio you want. Much easier, in my opinion.

That may be true, but you also have less space to play with especially for bigger targets

48 minutes ago, Adam J said:

I see better images from the 533 than the 294 people talk about the images being easier to process. That's why I would go for it not because of sampling vlaiv is correct lenses are not likely to be diffraction limited. The only other consideration is FOV and that depends on what you want to image. 

Double quoted, see below  

55 minutes ago, vlaiv said:

With cooled cameras amp glow is really not an issue.

Both cameras that I use have amp glow in one form or another. Here is for example very stretched dark frame from ASI178mcc (used for above test of Samyang lens - but not with native 2.4µm pixel size but rather in super pixel debayer mode):

And I get very decent results with this camera - have look at what I recently took with above mentioned Samyang lens:

You'll see that image is still a bit blurry / not as sharp as it could be - that is mostly because of the fact that I used lens at F/2 (wanted to do decent image in just one hour from strong light pollution - I probably should have gone for two hours and F/2.8 instead) and that even with 4.8um pixel size - image is over sampled.

Thanks, yeah it's a non issue with the correct calibration frames

48 minutes ago, Adam J said:

I see better images from the 533 than the 294 people talk about the images being easier to process. That's why I would go for it not because of sampling vlaiv is correct lenses are not likely to be diffraction limited. The only other consideration is FOV and that depends on what you want to image. 

Yeah I've seen some very nice images taken with the 533 but that can also be said for the 294. I'm just not keen on that square sensor, you've got way more framing options with a rectangular sensor and the 294 fits in with what I want to image much better. In what way are the 533 images easier to process?

14 minutes ago, TerryMcK said:

I have no complaints with my ZWO ASI183MC and ASI183MM with the apertures/focal lengths I use. I too don't like the square format of the 533 despite its promise of zero amp glow.

One thing to bear in mind with the 183 is the amp glow but it can be calibrated out completely. Also keep the gain down to default 111 or even 53 and it is more than sensitive enough. The 183's from ZWO also have AR coatings on the aperture windows so you don't get any internal reflections.

Thanks that's good to know, the 183 FOV looks a little tight for my liking which would mean I'd have to resort to mosaics for larger targets. I've also read about amp glow on the 294MC Pro, but good calibration frames make it a bit of a non-issue. 

I think in a money no object world I'd have a range of cameras to cover all eventualities 😆

9 minutes ago, vlaiv said:

First things first - don't worry about under sampling.

Two reasons for that - first is that under sampling is not a bad thing in itself. It is just a working resolution and lower working resolution just means wider field of view (over sampling is a bad thing as you loose SNR and gain nothing in return).

Second thing - you are worrying about under sampling with camera lens. You should not. Camera lens are not diffraction limited and star image that they are producing is much larger than aperture would suggest.

To prove my point, here is measurement of Samyang 85mm F/1.4 lens that I did with artificial star:

No filter at F/1.4 - Red: 2.66, Green: 2.48, Blue: 2.30
No filter at F/2.0 - Red: 3.82, Green: 2.28, Blue: 2.42
No filter at F/2.8 - Red: 2.53, Green: 2.36, Blue: 2.31
No filter at F/4.0 - Red: 2.24, Green: 2.27, Blue: 2.29

Values that you see are FWHM of different channels expressed in pixels and pixel size is 4.8µm.

Best of these values are around 2.3px or if we convert that into microns - 11.04µm. FWHM of 11.04µm requires pixel size of 6.9µm to be properly sampled.

In the case of this lens, and probably most of other lenses (don't think that other lens are much better than this one - this is pretty good/sharp lens) - it is neither seeing nor tracking that produces blur, it is lens itself. They are far, far from diffraction limited optics.

Btw, this is what star looks like at F/1.4

And this is what it looks like at F/2.8 (and above sampling with pixel size of 4.8µm):

While slightly over sampled (yes indeed even at F/2.8, 4.8µm pixel size is over sampling rather than under sampling), this star looks rather nice. Going further to F/4 will not make much of a difference:

Bottom line - don't worry about under sampling, if you are happy with FOV for your intended targets at focal lengths that you work with - go for ASI294. It has best size/£ ratio and it is very decent performing camera.

Wow!! Thank you, that's great information  

It confirms my suspicion that I was procrastinating over nothing and that the ASI 294MC Pro is going to be a massive improvement over my 450D. 

Hi All,

Apologies for the long post and I’m sure this has probably been covered numerous times but I’m trying to get it clear in my head (I'm still relatively new to this so it’s taking me a while to get my head around it).

I’m looking to upgrade my dslr (450D mod) to a cooled astro cam in the next few months. I’m currently imaging with a SW ED72 with OVL flattener (so 420mm FL) and a range of Canon EF lenses ranging  from 24mm up to 300mm focal length. These are all used on a SW HEQ5 Pro running EQMOD and APT so image capture will remain the same. I’ll probably be going down the OSC route as I like the simplicity of it, and it isn’t such a massive change from what I’m currently doing. I’m already using a ZWO ASI120MM Mini for guiding so was looking at sticking with ZWO for compatibility reasons  as I like the idea of being able to connect the guide camera to the main imaging camera to simplify cable management (not sure this could be done if I used a different brand of camera?). At some point I also want to add a couple more OTA’s to my collection for more focal length (e.g. SW ED80) and more widefield (e.g. Redcat) in order to be less reliant on camera lenses.

I was just going to order the ZWO ASI294MC Pro and be done with it as the field of view isn’t too dissimilar to my current dslr which I like. However, I then got reading about under sampling/oversampling and this got me concerned over image quality at short focal lengths. So, I started looking at other options (183 and 533 MC Pro).

As far as I can see these will still under sample at short focal lengths but are likely to fair better than the 294MC Pro. However, I don’t like the square sensor on the 533MC Pro and the FOV is too narrow for my liking on the 183MC Pro. I’ve tabulated all my options and simulated the FOV and keep coming back to the 294MC Pro. I guess what I’m asking is how much impact will under sampling on the 294 have on widefield image quality (24-200mm). It should fare fine if I add the scopes outlined above to my collection. Part of me thinks I’m just overthinking this as all options will fare better than my current camera and I’m fairly happy with the images it can produce.

So, if anyone else has had this predicament please let me know what you decided on 😊

Thanks,

Stu

Stunning image 😍

I'd stay away from the ED80 on a star adventurer as personally I think its's way too much for that mount, the WO is a much better match imo. Have you also considered the ED72? I used this on a SA for while and with guiding I could get 5 minute exposures no problem, however without guiding I struggled to get anything over 60 seconds consistently 

12 hours ago, Adreneline said:

This is an amazing result for a Bortle 8 location and the more you look the more you see in the image.

On my MacBook there is a distinct albeit mild green cast so I applied SCNR in PI - I think Hasta La Vista Green does the same thing in PS (Windows only).

Hope you don't mind me sharing the result:

Adrian

Thanks for the compliment Adrian, appreciated  

Yes I can see the slight green cast now you have pointed it out. Thank you for having a little play with the image and removing the cast, there's a definite improvement   I think it's always worthwhile sitting on an image for a little while once you think you are done with the processing as I find there are always slight improvements you can make.

1 hour ago, mackiedlm said:

I think thats really good. I like the colours and the trunk and other features are showing well. For me though the stars feel just a little too sharp and particularly near the centre.

 

But its a nice image with good atmosphere.

Thank you, I appreciate the feedback. I can see what you mean. I think one of the issues is that this lens shows some slight coma even when stopped down so you really need to sharpen up the stars in post to clear it up a bit 😃

Looks great to me 😎

Stunning work 😃

Taken over the last three nights while dodging cloud and sorting out dithering issues. Stars are a little funky as focus on the sigma lens is really difficult to nail down. 

Skywatcher HEQ5 Pro
Canon 450Da
Sigma 150mm F2.8 macro at F4
Optolong L-eNhance 
SW 50mm Guidescope
ZWOASI120MM guide camera 
Pegasus pocket power box
EQMOD/APT/PHD2
46x5minute light frames with calibration 
Stacked in DSS processed in Ps
Bortle 8 garden 

Critique welcome 🙏 

Have a look at the Sharpstar EDPH II, it's cheaper than the redcat too 👍

16 minutes ago, david_taurus83 said:

When it dithers does it recenter on the star before the next exposture starts?

I'm not 100% sure to be honest so I'd have to check the next time I run it. The graph definitely hasn't settled when the next exposure starts. However, this doesn't seem to be effecting image quality as far as I can see. 

20 minutes ago, david_taurus83 said:

How much are you dithering? If the mount has backlash it can take a while for PHD to recentre on the guide star. The Dec axis is usually the worst for this.

The dithering distance is set to 5 within APT which as far as I can gather equates to 5 guide camera pixels as the dither scale is set to 1 within PHD2. 

I've just stripped and regreased the dec axis as it was running a bit stiff however I encountered this issue both before and after the strip down. For what it's worth the dec axis is running more smoothly but nowhere near as freely as the RA axis. There is no play at all in the dec axis so there should be minimal backlash. 

Hi All,

Lately I have been having issues with dithering timing out. I'm using:

HEQ5 Pro via EQMOD

Canon 450Da 

SW ED72 or a range of lenses

SW 50mm guidescope with ZWO ASI 120mm mini

Image capture in APT with guiding via PHD2.

I haven't changed anything in my setup or any settings within APT or PHD2. The last few sessions dithering would start but then timeout and APT would continue with the next exposure. I'm dithering after every exposure and the timeout is effecting maybe 80-90% of the individual subs. Looking at PHD2 the dithering is taking place but not sure why it's timing out. 

This is frustrating as hell considering I haven't changed anything.  Has anyone else experienced this?

Thanks

Stu

I'm also looking at the same camera as an upgrade to my dslr and as has already been said the amp glow is a non issue with calibration frames. I also don't like the idea of a square sensor as seen on some other cameras. 

47 minutes ago, mackiedlm said:

In App yes. I don't know if you can split channels in DSS. But in PS  I'm not sure what the best way would be. I'd probably do a first stretch to see what I had, crop, then pull the individual channel data at that point. But I've not done it so...?

Thanks, that's something to start from. Can always download the trial version of APP and see how I get on. 👍

17 minutes ago, mackiedlm said:

Read to the bottom because you can do it without PI.

So initial splitting of the channels was in APP using the "extract Ha and Oiii" algorithms. Further processing was indeed in PI following this 

 BUT.. I'm pretty sure you could do it in Photoshop if you know your way around it. Copy out the R & B channels, work them separately using levels and curves. For recombine if you have carbonis actions that would work but if you are good with PS I expect you'd do it manually. Watch the video, and I'm sure you will be able to translate it to your own application.

 

Good luck and do post your result.

Thanks I'll take a look, I have the photoshop action set as well so I'll have a play around. Is the splitting of the channels done on the linear data? 

Looks great

I have a similar set up (ED72/Canon 450Da/L-eNhance), how did you split the channels and assign the colours? Don't say in Pixinsight...................... it was in Pixinsight wasn't it? 😂

Outstanding, love it

29 minutes ago, Rustang said:

Ive been on it all day and got no where!! lol

Lol, fingers crossed you get something out of it 😃

I also had a shot at M31 last night but haven't had a chance to look at the data yet. I can tell you that every time I've tried it in the past I've given up as I find it a really difficult target to process and my images just look terrible 😂

1 hour ago, m.tweedy said:

I am just up the road from you and it will be marginal if its any better than Bortle 8. Well done on a great image

Thanks, yeah it's marginal at best. I'm on the outskirts of Sunderland South so I'm generally shooting away from most of the light pollution from the city centre which I suspect helps slightly. 

9 minutes ago, scitmon said:

7 min subs in Bortle 8 with a DSLR!? no filters used?  I would have thought you would get massive over-saturation at that length?

Oops missed the Optolong L eNhance filter 😄

Additionally I'm taking the Bortle 8 from Clear Outside although I have a suspicion my sky is slightly better than that