Faster scope for imaging

[Tim star]

I am looking to upgrade from my SW Equinox 80 which has been a great little scope for AP combined with an Atik 460 mono with Atik filter wheel. EQ6 mount.  With our weather and not unlimited time for imaging I am hoping to get better results with a faster scope, but can't afford thousands for a fast refractor such as Takahashi.

I have been looking at the SW MN 190 and the ofputtingly named ES comet hunter. 

Firstly is the advice that this would be an upgrade in terms of brighter images or should I be looking elsewhere? I looked at the SW quattro but read horror stories about collimation. Secondly I have an autofocus setup with the ED80 using a Moonlite focusser and Lakeside motor which works well with SGP. I have advice from FLO that they can supply equipment to adapt the SW MN 190 in this way but does anyone know if autofocus can be retrofitted to the comet hunter?

I would like to focus from the warm room of my obsy or even indoors if I can get TeamViewer to link

Any advice welcome, thanks

 

 

 

[Zakalwe]

Any fast reflector is going to need careful collimation. And the cheaper ones will make it more difficult to achieve and retain a critical collimation. And a fast refractor is going to be expensive.

You cannae change the laws of physics.

 

[ronin]

I thought that the ES Comet Hunter was a visual OTA more then an imaging one and so would half expect that the field is not suited to imaging as in too curved and a presence of coma. Thought really is if it is then could you actually correct the scope to be suited to imaging.

Tne MN's are intended for imaging but seem little used, there is little mention of them, which leads to the question: Why?

Is there not a reducer+flattener for the 80mm?

[alacant]

1 hour ago, Tim star said:

I looked at the SW quattro but read horror stories about collimation

So did I and was put off by the horror stories too. I got the ES pn208, f3.9 [1]. It makes you wonder what all the fuss is about. It's collimated just like any other Newtonian. You'll notice immediately how dim the refractor is by comparison. HTH.

[1] Issues with MkI versions -secondary spider and main springs- have been corrected in the MkIII, although I'd recommend a longer, wider dovetail

[tony210]

Hi - I would broadly agree with above - collimating fast reflectors will be a lifetime mission also

3 hours ago, Zakalwe said:

You cannae change the laws of physics.

Captain-sorry

[triton1]

There's a special offer on a mn190 at FLO at the moment.

[ollypenrice]

The faster it is the harder it is. Anecdotes about 'my fast astrograph being perfectly straightforward' are fine, and will crop up everywhere without being in any way false, but will they predict your experience? Who knows? You simply need to be aware of the risk that you might struggle to get your fast system to work to your satisfaction.

One thing is dead certain: if an exceptionally fast and reliable system at 'x' focal length existed it would have an enormous following and dominate the deep sky imaging boards. Do you see any evidence for the existence of such a system? I don't. I think the DS boards represent a predictable cross section of the compromises inherent in deep sky imaging.

Olly

[Tim star]

Many thanks for the advice. Makes sense, you don't get something for nothing. I think I am going to go for the Quattro CF 10 inch on discount at FLO and just learn the dark art of collimation. Something to do on cloudy nights anyway, and there are plenty of those!

Tim  

[ollypenrice]

3 hours ago, Tim star said:

Many thanks for the advice. Makes sense, you don't get something for nothing. I think I am going to go for the Quattro CF 10 inch on discount at FLO and just learn the dark art of collimation. Something to do on cloudy nights anyway, and there are plenty of those!

Tim  

If you're up for it, do it!

Olly

[alacant]

18 hours ago, Tim star said:

I am going to go for the Quattro CF 10

That's the spirit...

[pete_l]

Be aware that with a faster optic the "sky fog" limit will be reached much quicker, too. That could be the limit to your imaging time / depth - how quickly your CCD fills up its little quantum wells with photons from the local light pollution!

Shorter focal ratios give you wider fields, but the targets are smaller and brighter in equal measure and you get more non-target taking up a larger proportion of your image. You can mimic the effect of a smaller FR by either adding a focal reducer / corrector, which you probably already have on your refractor, or since you are using a mono-CCD, by binning the pixels.

It all depends what you consider a "better" image to be.

[alacant]

4 hours ago, pete_l said:

Shorter focal ratios give you wider fields, but the targets are smaller and brighter in equal measure

I think the f4 Quattro will provide the OP with larger images of targets than his f5.

[ollypenrice]

Ths size of the projected image is governed only by the focal length.

Olly

[johnrt]

Have you considered the field of view the Quatro will give you in comparison to the ED80. I assume the ED80 is with a reducer flattener? If so then you are at somewhere like 400mm focal length, and the quatro is 800mm, double that of the ED80.

I would have a serious play around with this http://www.12dstring.me.uk/fovcalc.php and compare the 2 fov's before you commit.

Your imaging resolution will also be halved, which means your tracking will be under twice as much strain to get those round stars.

If you have never collimated a scope before, you're certainly diving in at the deep end with a "cheap" f/4 Newt, but I wish you the best of luck, you might need it!

[ollypenrice]

Singlin posted a detailed and very informative thread about his journey with a Quattro a couple of years or so ago. I'd certainly look that up. (It was a long journey.)

Olly