Need some help picking a Coma Corrector!

[nebulosity.]

G’day,

I’m building an 8 inch F5 truss imaging newt and would like your opinion on a coma corrector for it.

I have looked around and it seems I have these options:

GSO type CC (http://agenaastro.com/gso-2-coma-corrector.html). (increases focal length by 10%)

SkyWatcher type CC (http://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html). (reduces focal length by 10%)

Baader MPCC. (http://agenaastro.com/baader-2-multi-purpose-coma-corrector-newtonian-telescopes.html)

Baader ROWE. (http://www.optcorp.com/ba-rcc-i-rowe-coma-corrector.html)

The GSO corrector looks like it is sold under a few names, notably Bintel (http://www.bintel.com.au/Astrophotography/Reducers--Correctors--Flatteners/Bintel-Coma-Corrector-2-/1136/productview.aspx) and Altar astro (http://www.altairastro.com/product.php?productid=16363&cat=291&page=1). I like this as it is cheap and reviews say it does an alright job, don’t like the 10% increased focal length.

While the SkyWhatcher type looks like it has a rebranded version by Teleskop express (http://www.teleskop-express.de/shop/product_info.php/info/p3822_TS-Optics-2--Newtonian-Telescope-Coma-Corrector-from-f-4.html). Have read some great reviews (http://stargazerslounge.com/topic/58587-the-new-skywatcher-f5-coma-corrector-review/) of this, it’s up beside or better than the MPCC! (probably the older style MPCC) I really like the idea of a reduced focal ratio. ( bring my scope down to 4.5)

Everyone knows about the Baader MPCC, I’m just not hugely keen on the price.

The Baader ROWE is quite nice, especially as it has 91.5mm (I think?) distance between the corrector and sensor, enough for filter wheel or OAG (http://www.teleskop-express.de/shop/product_info.php/language/en/info/p3317_Baader-RCC-Newton-Coma-Corrector---triplet-lens---long-distance.html). The only problem here is that, if you want an OAG, I think you need the special ROWE one that isn’t really cheap.


So what do you reckon? What will float my boat for the best price in your opinion? If there is any other affordable coma correctors that I haven’t mentioned, I would like to hear about them.

I should say, in the foreseeable future I will be imaging with APS size DSLR’s if that is any consideration.

Looking on the Teleskop express website they have a SkyWatcher style CC a built in OAG! (http://www.teleskop-express.de/shop/product_info.php?products_id=4101#e bericht) This would be great if it wasn’t so expensive.

Thanks for any help,

Cheers
Jo

[tlgerdes]

There was a Mk2 Baader MPCC in the forsale ads 2 days ago for $110 if I remember correctly. At F5 it would have been perfect for you.

[AG Hybrid]

Don't get the GSO. There is no tuneable top. Its difficult to use. Alternatively... get the GSO and muck around with spacers and what not.

[Shiraz]

the Rowe is very good if you are looking for the highest possible resolution and want to fit in extra gear, but there will be some vignetting at APSc. You don't need any special OAG, provided you get the spacing right - I used an elcheapo for a while with good results. Downside is that it may not just fit in - the RCC1 is quite long and the focal plane also needs to be 91.5mm out from it's back surface, so the scope may need mods to move the mirror up and you may need a bigger secondary. I guess that if you are making the scope yourself, that is no big deal.

MPCC just fits in and has the right spacing for a DSLR, which is a big advantage. Downside is that with a DSLR and MPCC, you will not be able to use OAG. Try getting a used MPCC, they don't wear out. Not sure how much different the mk3 is, but at f5, the older ones should work fine anyway.

[nebulosity.]

Thank you very much for you suggestions Trevor, Adrian and Ray.

I have done some measurements and I think the Rowe will stick into the light path :sad eyes: so we can't have that.

Will give some more attention to the SkyWhatcher CC.

Cheers
Jo