Coma Correctors GSO(Revelation) vs Skywatcher units

[Darkmatter]

The Revelation unit is similar to several others as discussed here

http://stargazerslounge.com/topic/222477-revalation-coma-corrector/

I would be interested to learn if other have compared this to the Skywatcher Coma Corrector?

I am considering one of these for use with a 16" F5 Newtonian.

The Skywatcher I gather is optimised for F5 scopes so in theory would be the best match.

The unit will be used for visual use only at Medium to medium/high powers 150 - 400x range

Thanks

Simon

[estwing]

wouldn't think that you'd be seeing a lot of coma at F5?

[cs1cjc]

A coma corrector desinged for, say F/4, will work perfectly well at f/5.  All newtonians have the same shaped mirrror, a parabelloid.  A f/5 is simply a stopped down f/4 or even f/3!

Thhe GSO com corrector works well visually for me at f/4.5 with the right (approximate) spacing.  I have no experience of the SkyWatcher product(s).

I hope this helps.

[Darkmatter]

Coma will matter or figure in the application I will be using this scope for.

Though an F5 would not normally be used for Double star work as coma would affect the observations made the coma free field of an F5 scope is surprisingly small around ~ 1.4mm aprox in my 16" F5 scopes or around 2.3 arcminutes!!

looking at various Coma correctors available the skywatcher seems best optimised for an F5 system, however

Reading this link

http://stargazerslounge.com/topic/158529-astro-techaltair-astrogso-coma-corrector-and-user-guide/

Got me thinking, should I look for a used TV Paracor 1 as I will be using several types of EP and don't want to mess around with spacers.

The learning continues.

[Darkmatter]

A coma corrector desinged for, say F/4, will work perfectly well at f/5.  All newtonians have the same shaped mirrror, a parabelloid.  A f/5 is simply a stopped down f/4 or even f/3!

Thhe GSO com corrector works well visually for me at f/4.5 with the right (approximate) spacing.  I have no experience of the SkyWatcher product(s).

I hope this helps.

Thanks for the advice, I am still learning about the spacing requirements my eyepieces will need mainly quality Japan and Zeiss Orthos a few Konigs and some Clave units

[russ.will]

I had the GSO CC in an F4.9 SW Dob. Got it spaced for roughly the middle of my EP range, it was remarkably unfussy with those EPs that fell toward the ends and delivered pin points stars to the edge, as long as the EPs did! An under hyped and very effective tool IMHO.

Russell

[alan potts]

I have a TeleVue Mk 1 Paracorr at the side of the computer, now all I need is the other parcel of my new F4.3 scope to find it's way from England. I don't know why or how but the top box, base and secondary mirror has been to more countries this last 10 days than I have in the last 10 years, this is it's second time in the UK in 4 days, I wonder if it is collecting AirMiles.

It started out in Holland and is now further away for the second time in a week.

Back on track which is more than you can say for the scope, the Mk 1 TV Paracorr looks a very nice piece of kit and can be picked up for around 140-160 pounds, the new Mk2 is over 400 quid so very worth while waiting for a S/H one.

Alan

[ghostdance]

Am I correct in thinking that the TV Type 1 Paracorr is the only corrector available (s/h) for 1.25"? I've not come across any others, they seem to be all 2"....

[alan potts]

Ghostdance,

The only thing I see that make the TV Paracorr useable for 1.25 inch eyepieces is the converter to the size, I have not had it along side any of my others but it looks much the same as any other 2-1.25 fitting.

Alan.

[ghostdance]

Thanks Alan

For some reason I was thinking converters were for 1.25 to 2" - not the other way round. 

A Paracorr (with converter) then...dammit, wallet overheard & just jumped a train...

[russ.will]

I'd save yourself the money, buy the GSO/Altair CC and spend the difference on a 13-14mm 100deg EP for general DSOs. That really will produce some wow moments.

Another point worth noting is that nearly all CCs have a mild Barlow effect, increasing the focal length of your scope. The tunable ES HR Coma Corrector is very mild at +6% (and getting some good reviews), the GSO at +10% with the TV PC at +15%. Now TV claim this Barlow effect is to push focus further out, to account for the fact that the CC takes up some of you in-focus. However, if you replace the top of the SW focuser with a 2" compression ring and do away with the blessed extension tubes, this is practically a non-issue for all of them.

However, you're still left with the Barlow effect itself and +15% *may* just push your shortest EPs into magnifications that are unusable. Of course, it may also push some EPs into previously un-occupied and useful magnifications, so it's worth sitting down and running the figures.

Finally. As you're apparently using narrow FOV EPs at high magnifications, both of which seriously negate coma, are you sure it's worth it at all?

Russell