quattro f4

[darknight]

already have a 200p, but was thinking as smaller tube length and faster optics for dso.

what are your thoughts on them compared to say an "normal" ed 80.

I know they are both really different and the Quattro needs regular collimation, but in the end I hope to mount in a small obsy so not from house to garden every night.

my main wonder is yes the f4 will gather more light and need less exposure time, but will the 80 gather the same images ...in the end with longer exposure,

and so actually with the longer exposures do the same job with less hassle?

thanks for your input 

[xtreemchaos]

your 200p with  CC fitted in the train is a f4.5 "I think" so image size thay wont be a lot different, but I have hear quite a bit of good stuff about the Q range but never tried one myself, the price puts me off a bit, as for the ED80 ,amazing little scopes, thay take a lot of beating, you would have to pry mine from my cold dead hands  charl.

[darknight]

lol, yea I did think that maybe looking at a Quattro was not a lot different than using the 200p, was only looking at one as theres one going cheap, but was it worth another 200, as I hear the 250 is the better scope, think its one of those oooo scope going cheap must buy lol

[gazza]

Hi,

I have an 8" Quattro, and have had issues with it - though these are now fixed.

In the past I have posted that I had no issues with collimation. I was wrong. My scope is permanently mounted and I had collimated it in place and spent a long period imaging in just one section of sky. This was fine, until I moved to a different section of sky. Suddenly I was unable to get a decent flat field (using the Skywatcher f4 coma corrector / Kaf8300 sensor). I was always getting tilt someplace or another, not consistently. I tried collimating in place, but simply tightening rings was enough to throw things out. I spent several months trying to fix all this. Note that I have a full set of Catseye and Glatter tools. I have 30 years experience (including making half a dozen of my own mirrors), so I know how to collimate. Every time moved the scope, I got crap images. I progressively had to make a number of changes:

I at first suspected the primary mirror collimation springs, so first step was to fit much stronger ones. This did not help, so I fitted extra springs inside the stronger springs - so it had 2 springs per collimation screw. Still no improvement.

Perhaps the focuser was flexing or moving? I adjusted the life out of the focuser, made it much smoother and stiffer, no flex I could detect. Result, no improvement.

Ok, lets see if the secondary spider flexes - yes it does! slewing over he sky showed the Glatter laser (mounted in a Parallizer) was moving up to 3mm !! This was easily enough to throw out collimation every time the scope moved. I SHOULD HAVE CHECKED THIS FIRST!!!

How to fix this? I had a cast Vixen spider (bought as a spare years ago). This was not the correct diameter, being for a tube slightly smaller, so it was put on a lathe and after a tiny skim it was able to fit inside the Skywatcher carbon tube. Was able to position it and fit it using the existing holes in the Skywatcher.

After this, collimation was trivial, as nothing moved. Suddenly I had perfect stars everywhere, no matter where I pointed the scope, Collimation is now very stable, I check every couple of weeks, may need a tiny tweak using a Tublug to adjust the primary. Have never had to touch secondary collimation again.

Would I buy this scope again? NO. It is sold at a premium price but is not built like a premium scope. I would either buy a cheaper GSO f4 and modify it, or pay more and buy a Vixen R200ss.

If anyone is interested I will put a photo up of the Vixen spider fitted to the scope.

cheers

Gary

PS, but man is F4 nice to image with - gobbles photons FAST!!!!

[AKB]

5 hours ago, gazza said:

If anyone is interested I will put a photo up of the Vixen spider fitted to the scope.

Yup.  Certainly up to have a look at that.  

I'm enjoying my Quattro, because, as you say, ...

5 hours ago, gazza said:

  man is F4 nice to image with - gobbles photons FAST!!!!

...however, for my sins (or perhaps in advance of them) I'm also trying F2.3 with a Hyperstar on a C9.25.  This may be a step too far?

[gazza]

pics attached

cheers

Gary

[AKB]

Thanks for the pics.  This didn't change the secondary distance?  Or did you have to make some adjustment in the holder?

 

[gazza]

11 minutes ago, AKB said:

Thanks for the pics.  This didn't change the secondary distance?  Or did you have to make some adjustment in the holder?

 

You'll see that the spider is fitted by the screw holes that are for the white plastic end ring (yes it is plastic, not cast aluminium). Fitting it here meant that the secondary mirror could be centred in the focuser without any other changes. The only other mod was that I had to turn an aluminium ring to fit over the secondary holder to make it wider. This was because the adjustment screws for the Vixen spider are much wider apart than they are in the standard Skywatcher spider.  F

From memory the extra ring was about 2 inches in diameter, and had a bore that allowed epoxying it to the mirror holder. The extra distance between the screws allows for much finer collimation adjustment.

cheers

Gary

[AKB]

37 minutes ago, gazza said:

The extra distance between the screws allows for much finer collimation adjustment.

That's a good point.  Thanks!

[darknight]

Wow, all that hassle would do me in, credit to you for doing it all

[ollypenrice]

So when is fast not fast? When it takes you a year to make it work. In my view the step from F5 to F4 makes a quantum change in difficulty which may never repay itself. (It may, but it may not.) Personally I'd be far more tempted by the more tolerant F5 Newt. I've hosted some very expensive 'fast corrected Newts' and have ended up wondering what was corrected about them since they didn't work in the time available.

What's wrong with F5? It's fast, it's tolerant. And don't forget, it's aperture which finds the photons. 8 inch F5, 8 inch F4, you get exactly the same number of object photons from small objects in each. Be sure to read up on the F ratio myth before worshipping F4.

Olly

[AKB]

1 hour ago, ollypenrice said:

it's aperture which finds the photons.

So it is, but it's focal length which gives the FOV, so you need both when you don't have 300 days of clear skies.  Surely?

 

[ollypenrice]

10 hours ago, AKB said:

So it is, but it's focal length which gives the FOV, so you need both when you don't have 300 days of clear skies.  Surely?

 

Focal length certainly affects FOV and resolution but the change in FL between F5 and F4 is rarely going to be a game changer in terms of framing, I'd have thought. Most of the time you'd be able to use either FL to frame targets within the general range of angular size for the instrument.

Olly

[gazza]

1 hour ago, ollypenrice said:

Focal length certainly affects FOV and resolution but the change in FL between F5 and F4 is rarely going to be a game changer in terms of framing, I'd have thought. Most of the time you'd be able to use either FL to frame targets within the general range of angular size for the instrument.

Olly

I have to agree Olly - if I had known the hassle I was going to have with this scope, I would have stuck with an F5 newt. Unfortunately when you have limited funds you can't always swap quickly when you have made a bad purchase. I had to fix what I had :-)

I'm very happy with it now, but it has been a frustrating journey.

cheers

Gary

[Chris]

I've had plenty of f/5's and a couple of f/4's (the second f/4 was just to check that they are indeed very hard work!). The f/5's just work and are fast, the f/4 are erm? a challenge not suited to everyone...yes that's a nice way of putting it