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Evo 8 HD: 2" barlow or 1.25" barlow for planets photography?

astrophotography beginner Celestron CMOS planet
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#1 iamkrish

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Posted 29 September 2020 - 10:14 PM

I just bought a Celestron Nexstar Evo 8 HD scope with Starsense. Apart from whatever came with the scope, bought a Baader 8-24 zoom lens as well. I have only this much as of now.

 

I want to try some planetary photos. As Mars opposition is coming soon, thought of buying additional accessories required for this.

 

I think need the following things:

1. Camera - thinking of asi224mc

2. Barlow - I am not sure whether I should a 2 inch one or 1.25 inch one. Would 2" one would fit onto the visual back?

3. Filters - Not sure which one(s) I need to capture Mars, Saturn and Jupiter.

4. Filters - Also not sure whether I should buy 2" or 1.25".

5. Spacers: Do I need any spacing rings?

 

I am hoping these are the minimum things required, at least for now. Appreciate expert's comments.

 

PS: I am planning to buy a 2" diagonal some time later. I could not still decide on which one I should buy. Baader's Clicklock seems to be good, but as I understand it would mess-up the back-focus on my scope.

 

Thanks,

Krish



#2 audioengr

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Posted 29 September 2020 - 11:07 PM

For planetary, you are at high magnification to get decent planet sizes, so the light path is narrow.  There is no advantage to 2" Barlow in this case.  Save some money and get the 1.25".  I have both 2X and 3X in 1.25" just for this purpose.  If you use a Focal Extender instead of the Barlow, the back-focus is affected less.

 

The Baader 2" Clicklock diagonal is a good choice.  You can remove the Clicklock and thread it directly onto the rear cell, using a Baader LRING locking nut to secure it in the optimum position, eliminating the rear-cell adapter with locking ring.  Then you re-install the Clicklock clamp.  It is shorter optical path than the 1.25" diagonal.


Edited by audioengr, 29 September 2020 - 11:13 PM.


#3 Kevin Thurman

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Posted 29 September 2020 - 11:14 PM

No filters needed for basic color imaging of the (bright) planets. RGB filters are needed for mono cameras (not what you are getting) or for specific cases like the methane band or IR longpasses (don't worry about that for now) which is not necessary or useful for a true-color image. Some even consider using such filters to be practically sacrilege, but who cares we're just making pretty pictures!

I don't think you need to bother with a 2" barlow because if you're using a camera with a small sensor like that you don't need a wider image circle. I could be wrong there. Seems better to use the money you'd have to spend on a 2" instead on a better quality 1.25".

You may need spacers but if you do the camera should come with some. I don't need any with a barlow personally but it may change for your scope.



#4 donel

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Posted 29 September 2020 - 11:31 PM

Try a UV-IR cut filter.



#5 sanbai

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Posted 29 September 2020 - 11:54 PM

The backficus is mainly an issue for imaging. For visual, don't worry about. I don't and this is the consensus here. Btw; any 2" diagonal will bring backficus further that the "optimal". The alternative for 2" eyepieces is detect insertion in the visual back, but that's just too expensive (a medical bill) and certainly pain in your neck.


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