ASI174MM Vs ASI178MM

[nicoscy]

Question to those who perhaps tried both for solar imaging: Any real perceived benefit to using the 174 over the 178 (excluding FOV) for solar imaging?

Background:

I am quite happy with my Lunt LS60 and ASI178MM, which gives me a full disk.

I use a SW SolarQuest mount, so I can image at peace with no drift, and therefore the FOV does not come into question as I have sufficient clearance with the ASI178MM

 

What would (if any) be the benefit of switching to the 174? Inquiring minds that want to be educated want to know!

[inFINNity Deck]

Hi Nicos,

if your ASI178MM works well I doubt if there is an advantage switching over to the ASI174MM. I use a 174 with my Lunt LS80THA, which gives a full disc. With a 4x PowerMate I get nice close-ups of the prominences. I know from a Dutch amateur that the 178MM can give interlacing problems when used with a H-alpha scope, while the 174MM always performs well.

An example of what may happen (this is his data that I processed):

Nigella Bryant on this forum has no issues at all with the ASI178MM:

The main advantage of the 178MM over the 174MM is the pixel size and image resolution (6.4Mpx vs. 2.35Mpx). ZWO does recommend the 174MM for solar imaging:

Quote

Sun & Moon imaging

Our ASI174MM/MC with a resolution 2.3 Mega Pixels is the best solution for serious astronomers who want to capture the Sun or Moon in all its beauty.

So I would stick to the ASI178 if it works well for you.

Nicolàs

[nicoscy]

Nicolàs,

Thanks for the feedback!  I don't see any artifacts in mine if I am not mistaken.

The 178MM works great for me, but there is of course a part of me that wonders what possible improvement I could have. Ignoring my deficiencies in post processing, I am happy with the 178, but wonder about the 174...

Attached are all single stack images with my 60mm. Same image, different processing. Gives an idea of what the camera does (let's ignore lack of skills in post processing). So, could I get more to work with, with the 174?

 

 

[inFINNity Deck]

Hi Nicos,

these images are better than what I achieve with the 174MM, even though I am using a 80mm scope. This is a full -disc image of the 174MM:

And this with a 4x Barlow:

Nicolàs

 

[Lowjiber]

I've never tried the 178, but bought a 174 when I started using a Quark.  It performs very well with the Q.

Clear Skies

[Davey-T]

I use 178 with the LS60 as pixel size is a better match.

Dave

[nicoscy]

Hmmm, from what I gather, the pixel size of the 178 is a better match for the smaller focal length of the LS60, correct?
 

And basically, since there is no issue with the FOV for full disks and I don’t have any issue with banding or whatever, I should shut up, go out (once the temps drop - we had 46.2 degrees Celsius 2 days ago) and do more imaging!

[inFINNity Deck]

2 hours ago, nicoscy said:

Hmmm, from what I gather, the pixel size of the 178 is a better match for the smaller focal length of the LS60, correct?

The focal ratio should be more than 3 x pixel size (for a monochrome camera). The ASI178 has a pixel size of 2.4 microns, so the focal length of the scope should be at least f/7.2. A lower focal ratio results in undersampling, a higher in oversampling. It is better to over- than to undersample, the only downside of oversampling is that the exposure times go up. The 60mm Lunt has a focal ratio of f/8.33, so that is just fine it is slightly oversampled. The ASI174 has a pixel size of 5.86 microns, so the focal ratio should be at least f/17.58. My 80mm Lunt is f/7, so capturing the full disc without a Barlow results in severe undersampling. I therefore image details with a 4x Barlow (my other Barlow is 2x, I do not yet have a third), making the scope f/28. As light is in abundance I do not mind oversampling this much.

Maybe I should get myself a 178MM, it is an almost perfect for the 80mm Lunt.

Nicolàs

 

[nicoscy]

I am all for saving money - and then spending it on other astronomical purchases!

I'll lay this to rest and hopefully the heat will subside soon and I can get back into regular Ha imaging schedule!

Thanks much!