Another new scope

[mickw]

With Astrofest 2 days away I'm thinking of another scope for imaging with CCD or DSLR.
Skywatcher ED80 seems to be the weapon of choice for quite a few, but I've been leaning towards slightly larger aperture while keeping to roughly 600 fl.
I'm being tempted by :
Burgess Optical 91 600mm f6.6 - TMB triplet
http://www.scsastro.co.uk/it120001.htm
WO Megrez 90 621mm f6.9 - Doublet
http://www.iankingimaging.com/show_products.php?category=64&offset=10
New mount is on the cards - perhaps a new Meade    OK, very likely HEQ5 Pro

Comments/Warnings/Alternatives ?
Thanks
Mick

[Ian]

I would recommend giving the money to me.

As far as which scope, I don't think there's too much to choose between the two. What's the prices like?

[RobertM]

You're probably better off putting all the money into a better mount.  But as an alternative scope there is the new Skywatcher Equinox 80 which uses the better quality FPL53 glass. You could then buy everyone at the next society meeting a round of drinks and still have some left over

[mickw]

Ian
Burgess 91 - £649 including finder, rings+dovetail and Paragon 40 ep - diagonal £75
Megrez 90 - £749 including case and diagonal - only has L bracket for fixing, no rings etc.
Burgess "seems" better value especially as triplet 

Robert
Will also be getting mount    Looked at the Equinox, looks good but got this thing about 90s at the moment

[RobertM]

It's this 'size matters' thing - you've been watching too many adverts ...

Even a 60mm scope can give really good results, just look at what people achieve wth the Tak FS60 or ZS66 !  Bear in mind that in a larger scope you're going to get a narrower field of view for the same f/l and if you want a fast objective then it will take expensive glass and a good optical design.  A bigger scope also means less portability.

What about a second hand kit, sometimes a bargain comes up.

[mickw]

I know what you mean but I was going to go for an 80 anyway and as the fl of the 90s are as near as dammit the same, I figured what the hell, physicaly there's not that much difference.
I don't think (hope) the narrower fov will be an issue - still can't get my head round why that is though

[Ian]

the field of view is related to the focal length not the focal ratio. If the 80 and the 90 have the same focal length, that is the 90 has a lower focal ratio, the field of view will be the same but exposure times will be lower.

However, once you get guiding, you can image for minutes at a time, so the next question is, is it worth spending quite a bit of cash just to reduce your exposure times. You could invest the same money in focal reducers, filters or indeed, dare I say it, beer.

Bear in mind that for visual, aperture is king...

So, any clearer?

[JohnP]

Download this - its free & great for calculating FOV for CCD & telescope combo. Also gives you colour pictures of DSO's etc. There are additional ones you can download as well.

http://www.newastro.com/newastro/downloads/ccdCalcFree.htm


Cheers,  John

[mickw]

Thanks for all the input guys.
As It will also be used for a bit of visual, a 90 it is - probably 

Mick

[MarkS]

Thanks John for that prog - it's a nice find.

[Mike]

Oh great! Another month of cloudy skies !   

[mickw]

Don't panic Mike - I ordered it, but it's not in my mit yet.
Due warning and apologies will be issued at the appropriate time