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Second camera for small DSOs and planets?

Planet DSO EAA
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#1 vladm

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Posted 30 November 2022 - 01:47 PM

It was three great years (after retirement) to enjoy practical astronomy using CN forums as a primary source of great accumulated knowledge and useful practical advises.  Based on them, I bult very reliable and simple EAA C8Edge-based rig using Baader T-2 pieces including short-pass diagonal to accommodate bulky QHY 294 MC for unrestricted zenith area viewing with Evolution mount. I am happy (well, almost) for my set-up for most DSO and Lunar observations.
One problem I want to address:
Even while ROI in Sharpcap supposed to be king, it is not always convenient to use with wide view camera, especially small FOV DSOs (like m57) and also Planets.    Also, planets are totally different animals requiring different optics and cameras (smaller sensor and higher fps).
I need your opinion about having second narrower view camera to compliment DHY 294 for use on small DSO and planets.  Please note that my goal is NOT any kind of AP (DSO or planetary), but electronic observation aide (views for me are more important for me than pictures).
I have played with zoom eyepiece/Barlow combination to find out that reducer can be easily overpowered by Barlow without visible negative effect.  I mean, that 2.9 um pixel camera required F15 scope (1.5X Barlow on native F10) for planetary, but 2X Barlow can be used on existing train (F7 with reducer installed) with similar results (again, I am not competing with Hubble).  For DCO Barlow can be unscrewed.
I see many CN members listed several cameras; while some may be upgrade leftovers, but some look very recent.  What is your experience of having more than one camera for EAA?

Recently I looked at ZWO ASI 585 and 678 cameras.  The second looks more planetary, while 585 (or QHY analog III 585) looks quite attractive.  What do you think and any other suggestions?
Thank you very much for you input!

Sincerely,
Vlad
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Celestron C8 Edge /Evo (StarSense , Sky Link GPS, Celestron focuser); Edge 0.7X reducer; Baader T-2 Stardiagonal (Zeiss) prizm with BBHS; Baader T2 clicklock adaptor. Eyepiece: Baader Zoom Mark IV (8-24 mm) / -Barlow 2.25X. Filters: Optolong L-Enhance, Baader Sky &Moonglow Neodymium filter, Ice Moon variable polarizing filter.  Camera: QHY 294MC-PRO.  Astrozap heated dew shield. Software: CPWI, Sharpcap 4 pro/ ASTAP on AZW Beelink Core-i5 PC, under Win11pro (on scope site), connected (remote desktop via WiFi / range extender) to home PC.



#2 bips3453

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Posted 30 November 2022 - 02:59 PM

I would first try the bin 2 mode on the 294 camera. Use the ROI at f/6.3 for smaller DSOs and f/10, f/15, and f/20 for the planets without the reducer.



#3 Mark Lovik

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Posted 03 December 2022 - 07:54 PM

Vlad

 

Your 294 camera should have a 0.77" pixel scale for your SCT if it reduced to F/6.3.  This is just about perfect sampling for your scope aperture and typical seeing.  I can jump down to about a 0.7" image scale (different camera and focal length) but tend to look at small objects with a 0.9" image scale with the same sized scope.  I get full resolution even when I get better than average seeing - and it's optimized to view these small objects quickly.

 

This comment is for EAA on DSO's in the sky -- not for lucky imaging for the moon and planets.  For planets you get higher resolution by high speed imaging (freeze the sky) and finding small windows of good seeing.  Here you want a fast camera with a fine pixel scale.

So - for planets you may want a dedicated planetary camera ... this is not EAA.

 

For EAA you really don't want to view objects with finer (smaller) pixel scale.  You are already at the sweet spot and will start to oversample your objects if you pick a smaller pixel camera -- need significantly more time to view an object for no real improvement.   The wider field of view makes most everything easier (polar alignment, plate solving) for EAA.  The only problem is the image is tiny in the full field of the camera - just remember it's looking as good as it's going to get.  You just need to zoom to view the teenie object to see it with all the details collected from your rig.

 

I have the same issue for many of my objects, ROI, zoom (during live stacking), and cropping an image to show others are the obvious tricks of the trade.  AND ROI is really easy in SharpCap - just make sure to take darks and flats using the same ROI settings.  Also be careful with really tight ROI ... it can mess up your plate solving.  My trick - open the fov for finding and centering the image -- ROI for final image collection.


Edited by Mark Lovik, 03 December 2022 - 08:15 PM.

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#4 vladm

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Posted 13 December 2022 - 01:25 PM

Thank you very much for your answers! I appreciate them.

Actually, 0.63 is not a world constant in Edge world, where it goes to 0.7 making 0.67"/pixel size, which is (astronomy tools clc.) 0n the edge of acceptable for OK seing.  I live in B6 zone; that's why I want to look at planets; however you are right that  EAA for DSOs and planets imaging are totally different animals. 

Again,

thank you for your help,

Vlad 



#5 cnbilbo

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Posted 16 December 2022 - 10:23 AM

Thank you very much for your answers! I appreciate them.

Actually, 0.63 is not a world constant in Edge world, where it goes to 0.7 making 0.67"/pixel size, which is (astronomy tools clc.) 0n the edge of acceptable for OK seing.  I live in B6 zone; that's why I want to look at planets; however you are right that  EAA for DSOs and planets imaging are totally different animals. 

Again,

thank you for your help,

Vlad 

Hi Vlad

 

I had to move to EAA for observing myself this year, Didn't have much choice.   Is your QHY camera a 294M or 294C. ( MM / MC is used by ZWO) If its the mono version I would probably stay with It

 

I have a very similar set of kit, bit with the addition of an EQ Mount. With 2.4um pixels on my IMX 183 mono  I can bin the output to suit all of my scopes. If I want to go small & fast I just use a smaller frame sze (ROI)

 

Steve




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