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Best scope to match with Asi 533?

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#1 adamsdp

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Posted 18 October 2020 - 01:23 PM

I am fairly new to eaa and looking for advice as to which scope/focal reducer combination would be the best fit for general purpose eaa with the asi 533 camera.  I will be using an Celestron evolution mount with the setup and have come up with the following ideas-

 

1 -  c6/hyperstar - fast but not the best match with the pixel size of the asi533 - undersampling 2.59"/pixel

2 -  c6/starizona night owl - not as fast but better match with pixel size - 1.29"/pixel

3 -  c8/starizona night owl - another good match with pixel size - 0.97"/pixel

4  - c8/6.3 reducer - slight oversampling - 0.62"/pixed

5  - c8 edge/0.7 reducer - slight oversampling - 0.55"/pixel

 

I have a c8 edge with starsense mounted to the ota and was planning to keep it for visual use and have a second scope dedicated for eaa thinking this would be the simplest way to go - I leave each scope with camera and eyepieces attached and switch the ota.  Does anyone have thoughts on the second scope vs trying to just use the c8 edge for visual and eaa?  As I have gotten into this deeper, I realize that either I need to get a second starsense unit for the dedicated eaa scope or do a skyalign and hopefully be able to use the 533 in preview mode to do the alignment.  If it is not practical to use the 533 to do the mount alignment, I am back to swapping out the camera for an eyepiece and makes less sense to have a second scope.

 

Of the choices above, I am leaning towards the c6 or c8 with thestarizona night owl.  I like the lighter weight and smaller size of the c6 on the evolution mount and am under the impression that aperture isn't as big of a factor in eaa than in visual.  There isn't a huge difference in cost for used c8 though so maybe should go that router for the greater aperture?

 

If anyone has other suggestions, they will be greatly appreciated!



#2 chilldaddy

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Posted 19 October 2020 - 09:41 PM

Hi Dave,

 

A couple of thoughts.  I use a C8 on a wedge mounted Evolution with the 533 and it's a great combination.  Whether at F/10 or F/6.3, it's a very capable setup. 

 

You can easily use the 533 as a live view for alignment so that is not a problem. 

 

To be real honest with you, after seeing far more detail, color, and bright objects instead of faint fuzzies with EAA, you might find visual less appealing.  I don't even touch eyepieces anymore because I can see so much more with a camera. 

 

If you still want two scopes, then go for a C8 and Night Owl.  More aperture always helps but it isn't as big of an issue since live stacking adds more photons too.  The Night Owl is a great choice, but they are hard to come by.  You might grab an F/6.3 focal reducer as they are more readily available  The hyperstar is fantastic for a wide FOV and F/2 speed but it certainly comes at a price of around $1000.  So the best reducer may be the one you can get!

 

 

Good luck!

 

Greg


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#3 alphatripleplus

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Posted 19 October 2020 - 11:09 PM

I would not worry too much about oversampling, as I believe you should be able to do a 2x2 software  bin of the ASI533 if you feel you are oversampled.

 

You will also probably end up undersampling when you have a short focal length instrument for widefield use, given currently available pixel sizes. It can't really be avoided. 


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#4 GazingOli

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Posted 20 October 2020 - 01:05 AM

what about vignetting?

 

I got an ASI294 and vignetting is an issue with the C8 f/6.3. Trying to find out if the ASI533 would be vignetting, too, I figured out the situation by showing the relative sensor dimensions in one of my last night attempts with the ASI294:

 

SensordimensionsASI224ASI533ASI294.jpg

(Attempt to observe the Pacman Nebula)

 

So the question is: is it about realistic and do you need flats when using an ASI533 with a C8 f/6.3 or f/10?

 

CS.Oli


Edited by GazingOli, 20 October 2020 - 01:27 PM.


#5 jprideaux

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Posted 20 October 2020 - 08:47 AM

A couple things to note.

 

1.  You MIGHT get more mount clearance with the C6/NightOwl vs the C8/NightOwl with the Evolution mount when not using a wedge.  Hopefully someone with the NightOwl and both the C6 and the C8 can confirm that.

 

2.  The last I checked, Starizona has not released yet the NightOwl for the Edge (but it is "coming soon").  


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#6 DSO_Viewer

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Posted 20 October 2020 - 11:42 AM

what about vignetting?

 

I got an ASI294 and vignetting is an issue with the C8 f/6.3. Trying to find out if the ASI533 would be vignetting, too, I figured out the situation by showing the relative sensor dimensions in one of my last night attempts with the ASI294:

 

attachicon.gifSensordimensionsASI224ASI533ASI294.jpg

 

So the question is: is it about realistic and do you need flats when using an ASI533 with a C8 f/6.3 or f/10?

 

CS.Oli

You can clearly see the severe vignetting even when using the 533 with your setup at f/6.3 and flats would eliminate the glow to establish a uniform darker background. Using f/10 would probably not require flats (for vignetting) unless you have many dust spots.

 

Steve


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#7 adamsdp

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Posted 20 October 2020 - 12:08 PM

Thanks for all the replies and I spoke with Dean at Starizona and he relayed that they expect the night owl for the edge in the first quarter of 2021.  I am not in any hurry so that is another option.  Making it tough to decide is that I don't have a good feel for how important aperture and f/ratio are for eaa.  I was reading old posts and someone posted two photos of the orion nebula with a c11/hyperstar and and 80mm refractor operating at around f/5 or 6 and they both used 15 second subs and they images were suprisingly similar.  Makes me lean towards going with the c6/night owl as it would be easy to handle and a good match for the 533 pixel size.



#8 cmooney91

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Posted 20 October 2020 - 12:57 PM

Scope speed is raw speed.

 

An F4 and an F8 scope can produce the same quality image, but the F4 scope can do it in 1/4 the time.

 

I am a fan of fast newts + coma correctors. 

 

Since you already have the C8 EVO it makes sense to start off using that reduced. 

 

But, If you are considering getting a new OTA for specifically for EAA, a 6" F4 newt +CC might also clear the EVO mount. 

 

Here is a flat from my 8" F4 and ASI294

gallery_280529_10874_10805.jpg

 

The darkest corner is ~75%, and easily cleaned up with flats. The smaller 533 would be more evenly illuminated   (a slightly bigger secondary would improve it too)

 

 

 

 


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#9 adamsdp

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Posted 20 October 2020 - 01:42 PM

Good to know that using the live view of the 533 to align is possible.  I have heard the night owls are back ordered so will keep that in mind.  The comment about aperture not being as big a deal in eaa as it is in visual tips my thoughts towards the c6.  I too have thought that maybe the c6 will give more clearance on the evolution mount and hopefully someone will post about that.  I will keep in mind the binning as a way to deal with oversampling.  Thanks for mentioning about the fast newtownian and will take a look at them.



#10 mic1970

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Posted 20 October 2020 - 01:53 PM

Check Bintel's calculator.  Put in the specs for different camera's, scopes, reducers, binning, and barlows to find good matches.  

 

 

https://www.bintel.c...?v=322b26af01d5


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#11 adamsdp

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Posted 21 October 2020 - 04:10 PM

Check Bintel's calculator.  Put in the specs for different camera's, scopes, reducers, binning, and barlows to find good matches.  

 

 

https://www.bintel.c...?v=322b26af01d5

Thanks for the link and very helpful!

 




#12 BinoGuy

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Posted 21 October 2020 - 06:07 PM

You don't mention if this is a static mount or if you need/want to move around the yard or go to dark sky sites.  I'm getting very nice images with my little WO 73 and the same ASI 533.  As @Chilldaddy mentioned above, live stacking is a game changer and I no longer crave more aperture.  Sure, at some point I'll get my 6'' frac going with the camera but for now I'm happy to gain the advantage of portability.  If that's a need for you then consider the smaller scopes you listed.  All should give a good result with that camera.

 

 

Clear skies, BG   {°¿°}



#13 adamsdp

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Posted 22 October 2020 - 02:18 PM

I don't nned to maove the scope around much.  I bet your WO 73/asi 533 is a very nice setup.  Still thinking a c6/night owl willl be a nice match to the asi533 and a good general purpose focal length.



#14 roelb

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Posted 24 October 2020 - 06:48 PM

I apply ROI in SharpCap to avoid vignetting with the Evolution 8.


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#15 DSO_Viewer

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Posted Yesterday, 11:54 AM

I apply ROI in SharpCap to avoid vignetting with the Evolution 8.

I paid good money for the real-estate (FOV) and always try to get the best corrected coverage (correct spacing for reducers, flats, comma correctors etc.) as possible without taking the easy way out by chopping off the sensor.

 

Steve


Edited by DSO_Viewer, Yesterday, 11:56 AM.


#16 roelb

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Posted Yesterday, 07:31 PM

I paid good money for the real-estate (FOV) and always try to get the best corrected coverage (correct spacing for reducers, flats, comma correctors etc.) as possible without taking the easy way out by chopping off the sensor.

 

Steve

Fair enough.


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#17 alphatripleplus

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Posted Yesterday, 09:00 PM

The nice thing about these larger sensor cameras (which I do not own) is that you have the flexibility, depending on the size of the target, to use as much of the real-estate as you need to frame the target as you wish. You may be able to use the one scope to frame both large and small objects (within reason).

 

For small faint fuzzies, where the galaxy detail you are interested in may cover only a few arcminutes, you can happily choose a small ROI and just zoom and crop the centre of the field, while a large emission nebula may take most of the sensor real-estate at the same focal length.

 

With a small sensor camera, you have to think more about focal length of the scope when trying to figure out if large targets will fit into the field of view. 




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