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Newbie Camera Question (For Evolution 8 SCT Scope)

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#1 georgec02


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Posted 11 June 2021 - 11:11 AM

Hi all,


Thinking about venturing into some casual imaging with my telescope, a Celestron Evolution 8 SCT.  I've been doing research here and other sites online, but a bit overwhelmed, and thought I'd turn to folks with actual experience.  I wanted to keep it as simple as possible, and prefer to keep it on the entry-level side (realizing you do get what you pay for).  This would more be from a hobbiest / occaisional imaging perspective.  Not a full-on dive into imaging.


This is what I think I understand:

  • I know my scope is best for visual, and not ideal as an imaging scope 
  • The mount is nice and solid, and while it has goto/tracking, there will still be some drift vs an equatorial mount.
  • One of the main issues is a narrow FOV given its 2032 focal length
  • Narrow FOV doesn't sound like it's an issue for planetary imaging, but would be (as would the setup) if I wanted to do any DSO?

Cameras:  I've been looking at the ZWO cameras, and using astronomy tools, calculated the FOV (table and FOV shot attached).  I'd prefer to stick to the entry level side, and upgrade later if I end up imaging more frequently.

  • Looking at the entry level options:  120MC-S ($150) vs. 224MC ($250) it looks like all the specs are similar except for the sensor used (ONS vs Sony), which gets you more resolution.
  • As you move up to the next level of options, looks like you're getting a bigger field of view : ASI462MC ($300), ASI178MC ($350), ASI385MC ($350) 

Other stuff:

  • Focul Reducer:  It looks like a focul reducer would helpful?  Is there an advantage to something like the Celestron reducer made for SCTs vs a much cheaper GSO reducer?
  • Software:  (on a macbook). Is the stock ZWO software easiest or would something like firecapture be the way to go?
  • Filters:  I live in a city.  If I want to try to take images in my neighborhood, should I be looking for a light polution filter?


Thanks again for all the help in advance.


Screen Shot 2021 06 11 At 8.17.33 AM
FOV Screenshot for ZWOs



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#2 RedLionNJ



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Posted 11 June 2021 - 12:27 PM

Focal reducer - No, quite the opposite, in fact.  You'll want to extend your effective focal length so Jupiter takes up a couple hundred pixels on your camera.  With the ASI462MC, for example, the 2.9 micron pixels will lend themselves very nicely to a 1.5x barlow on the (nominal) f/10 scope.  The resulting small field is never an issue. It's ok for the target to move around a little on the chip during a three-minute capture.


Light pollution isn't much of an issue for Jupiter, Saturn or Mars.  You need an IR-cut filter for most one-shot color cams, as the sensors are typically sensitive well into the IR range (across more than just the red photosites).


I would also recommend an ADC (atmospheric dispersion corrector) for high-resolution work. This counters the spectral dispersion incurred by light's path through the prism-like atmosphere.


The generally-used applications were all developed for Windows (but some can be made to run on other platforms) and are free:


FireCapture for data acquisition

AutoStakkert for quality assessment, alignment and stacking

Registax for mild sharpening

WInjupos for combining the results of more than one capture (to increase SNR)



Welcome - and enjoy!

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#3 Tulloch



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Posted 11 June 2021 - 05:35 PM

The Evolution is a great system for imaging the planets - I started with the Evo 6", then upgraded to the 9.25", and am very happy with my images.


As Grant (aka RedLion) says, forget about the focal reducer, and go straight for the barlows. Choose a barlow that matches your camera, you are aiming for a focal ratio around 5x the pixel size of the camera. There are two options I would recommend, both require an IR cut filter:


Excellent: ASI224MC with a 2x Barlow (my setup)

Excellent+: ASI462MC with a 1.5x Barlow. 1.5x barlows are not common, Siebert Optics comes highly recommended.


These are the best consumer colour cameras out there for planetary imaging, no need to upgrade later.


Also, watch these tutorial videos, they are excellent (although Steve's recommendation for which camera to use is out of date, choose the 224 or 462 instead).


Edited by Tulloch, 11 June 2021 - 05:40 PM.

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#4 georgec02


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Posted Yesterday, 09:00 PM

Thanks for the pointers on the imaging options. I’ll take a look at the link too.

#5 georgec02


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Posted Yesterday, 09:46 PM

So... optimal focal ratio from the website mentions about 5-7X pixel size.  I think I'll probably go with the ASI224MC, as it's a little less expensive, and I already have a 2X barlow.

  • ZWO ASI224MC = 3.75 microns
  • Target focal ration should be 5X-7X pixel size = 18.75 - 26.25
  • Evolution 8 SCT has a focal ratio of F/10.  So as mentioned 2X barlow gets me in the range with a 20X focal ratio

Now, to order the camera and get up in the middle of the night to try it out.


Thanks again all.

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#6 descott12



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Posted Yesterday, 10:00 PM

As a newb, I think there is also something to consider that took me awhile to appreciate. While the optimal FL for an SCT and the 224 is usually around f20 with a 2x barlow, your seeing conditions have to be good enough to support it.  I have found, in my neck of the woods, that I can rarely use a  barlow and I usually get my best data at f10 even though f20 would be theoretically ideal. So you may need to experiment. I would guess that I can only use my barlow less than 20% of the time.

Edited by descott12, Yesterday, 10:02 PM.

#7 jesco_t


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Posted Today, 01:46 AM

Hi George.

When I started I found it easier to not use the Barlow initially. Everything is *a lot* easier without Barlow. The FOV is larger which makes finding the planet easier, focusing (the hardest part in planetary) is easier and the framerate is much higher.

The 5-7x rule is an excellent one and the Barlow is required for best image size and quality. But even without you can still do very nice images. Additionally, the magnification of most Barlows depends on the distance between it and the sensor. I can tune my 2x Barlow from 1.8x - 2.4x just by adding around 30mm of distance between it and the sensor.

I’ll second the advise about the ADC. I use it below 40 degrees. ZWO offers a good one for decent money.


#8 Tulloch



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Posted Today, 02:34 AM

FYI, I used to find putting the planet on the camera sensor difficult with my 9.25" SCT, 2.5x PowerMate and ASI224MC, until I got a better finder scope. The one I use now is a GSO 8x50 RACI, they are pretty cheap but made a huge difference to me to getting the planet on target. Once you've aligned (I usually just choose the 3 bright stars alignment method with a 30mm EP), align the finder with the main OTA as best you can and you don't have to worry again.



One tip is that the focus point for the camera is significantly different to the eyepiece - with the 2x barlow fitted it can be as much as 20 full turns of the focus knob. These days, I don't align on focused stars - I normally use the out of focus donuts through the EP (as the focus is correct for the camera), that way I don't have to hunt around searching for a dim, out of focus donut on the screen once I've connected the camera.


The Evo isn't the most stable mount either, so I invested in some pipe insulation foam and one of my wife's long hairclips attached to the focus knob. It really works well, have a look here for details.



Hope this helps.

#9 Ittaku


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Posted Today, 03:33 AM

You are far better off with two cameras if you want to do planetary and DSOs. They're totally different disciplines and require different features in the cameras. The closest to a great colour planetary camera that is also wide field enough for DSOs is the 183MC, but you'll need a completely different imaging train with lots of reduction to make the most of it with DSOs since its pixels are small. The 224 is the bargain darling of planetary though, and you can't go wrong with it.

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