Skywatcher Quatro for visual ? (as well as AP)

[Astro-Geek]

I've read quite a few threads on here and elsewhere on the Internet where people have asked the same question.

There seems to be a consensus that extension tubes will enable enough focus range for eyepieces, that the additional light path blockage of the larger secondary mirror will reduce the contrast slightly, and they need Coma correctors even for eyepieces to get acceptable sharpness over the whole field for visual.

They've started to appeal to me for a number of reasons.

1. I like using Binoviewers, and if I could achieve focus with its hollow nosepiece rather than its 1.8 barlow, that would be a big plus for me.  My 200PDS doesn't have enough in-focus for that, despite also being shorter for prime focus with cameras.(maybe the tube shortening is to a lesser extent with those than Quatros ?)
2. They have physically shorter OTA tubes, so I may be able to use quite a large aperture one on my EQ6 Pro without it becoming too unwieldy. Ideally, I would prefer a 300, then I could dispense with my wheeled Skywatcher 300p goto Dob, giving me more room in my Skyshed Pod. There are many opinions on forums that a 12 inch is too much payload for an EQ6, especially for AP, but if it was a Quatro, maybe the much shorter tube would make it more stable, even though it's about the same weight ( 21kg) ?

A 250 Quatro is much lighter, around 14kg, and hardly any longer than my 200PDS, but I do like my 300 Dob's light gathering power and max magnification when conditions permit.

Apologies for yet another of my long rambling posts, but I guess I'm interested in hearing from anyone that uses a large Quatro as their main scope for visual as well as AP, and also anyone that uses a 250 or 300 Netwonian on an EQ6 Pro.....  🤓

 

[Northernlight]

AstroGeek,

There are a few things you need to consider:-

1) As you have already mentioned - The large secondary will really reduce contrast for Visual. I think the Quattro 12" has a secondary nearly a 100mm so you're looking at a 33% obstruction by aperture.

2) For Focuser will need to be changed for Astro Imagining - So plan for another couple hundred euros for a replacement focuser like the Baader steel Track

3) As you mentioned at F4 you will definitely need a Coma corrector, so another few hundred euro's.  - F5 you might be able to get away without a coma corrector

4) I was looking at the Quattro 12" - but i've read mixed reports about the stability of the mirror cells - you might need to upgrade the springs on the primary cells with stiffer ones.

For your mount i would really consider the lower a lighter 10" Newt -  or maybe a lighter 12" carbon tube mount.

 

I am in the same Dilemma - but i'm looking to get a 12" F4 Carbon Tube with a smaller secondary  so it's just enough to fully illuminate my Kaf8330 sensor  - i need to check with the Vendor i think a smaller 70mm secondary will improve contrast both for imaging and for visual.

Rich. 

 

[Astro-Geek]

Thanks for the detailed reply Rich.

Yes, the bigger secondary mirror making visual less contrasty is my main concern, as it can't be remedied by add-ons.

 

[rl]

I've tried both AG12 and CT12 Newtonians (both 12" F/4 carbon fibre) on a AZ-EQ6 mount and both were too much weight even with an extra counterweight. And that's before adding the filter wheel, camera et cetera. Scopes this size really deserve something in the EQ8 class. 

Given really good mirrors in the first place, I've not found the large secondary obstruction to be much of a showstopper but there will be a slight loss of contrast. It's never going to be the ultimate planetery scope but the large aperture makes up for a lot if the atmosphere plays ball. 

And yes, on lower magnifications for certain, coma will be an issue without a corrector. As will off-axis aberrations in budget eyepieces..

 

[Northernlight]

So would you not consider an F5 scope - Still fast for imaging, but easier to collimate, focus, Less coma and better contrast for both Imaging & Visual.

Only real downsides are that Tube lengths on F5 scopes tend to be longer and your imaging subs would also be longer.

*** Important **  - One other really big aspect to make sure you don't overlook is your ccd sampling rate - make sure you dont under-sample or over-sample too much.

My advice would be to get a 10" for your mount as you would struggle with a 12" and you would be constantly battling with it during imaging. On your EQ6 the slightest bit of wind will have a massive impact on imaging, hell a cricket farting too close to the mount would probably throw it off lol - For big newts, you need a bigger mount like the EQ8.

 

Edited May 2, 2020 by Northernlight

[Astro-Geek]

The helpful replies to this post have confirmed my previous research  ( sigh... 🤓)  I'll probably stay with my 12 inch goto Dob and use the EQ6 with my other scopes, as before.

I'll have to get round the field rotation with either an EQ platform or maybe in the software.

Thanks for the replies.

 

[Northernlight]

Field rotation east to sort in software but can lead to large % crop. You could buy a feield rotator. 

[Astro-Geek]

"A field rotator",    mmmm...    I hadn't thought of that.   👍

[Peter Drew]

The saying "horses for courses" springs to mind.      🙂

[Northernlight]

My saying is "buy whichever one is cheaper" 🙂   but that doesn't always work as i'm also conflicted with the saying "Buy cheap buy twice"...........Doooohhhhhh