does bigger aperture mean more magnification

[scarp15]

I use a Baader coma corrector for my 28mm 68˚ ES, it wouldn't be the end of the world without it to be honest but for objects like open clusters it really does tidy it up. From 28mm I go up to a 17.3mm Delos and you can see a little bit of coma but its nothing really but this is on a f/4.5, at f/4 my gut feeling is that a coma corrector will be worth the investment but once again Shane is probably the best person to give you the best answer.

 

If you do go ahead and purchase this scope, it might be worth trying it first with your e.p's. Mine is referred to as F4.6 on the Zygo report. If this is the standard VX14 it will probably be the same (F4.5 or F4.6). Mike's comments above are valid in that (at the very least in terms of cost) a baader coma corrector for a low power eyepiece might suffice. If your eyepiece's are well corrected, then as you step up magnification, coma, even at 82 degrees, might not be too consciously noticeable (along the edges) at F4.5.

You could however, go with a paracorr later on, if on the contrary, coma is felt to be after all a distraction.

[Moonshane]

would it be feasible to put the baader cc on the end of a 2" extension tube and then use a bit like a paracorr?

[Mike73]

would it be feasible to put the baader cc on the end of a 2" extension tube and then use a bit like a paracorr?

No, you need to set the correct spacing from the CC to the field stop on the EP which is +/- 55mm, you wouldn't be able to get this if you screwed it into an extension tube so the best way to use the Baader MPCCIII is just to leave it attached to the EP.

This does mean that if you have two low power EP's that need correcting you will need two MPCCIII's but this would cost the same as a new Paracorr 2! 

The beauty of the MPCC is that unlike the Paracorr it doesn't effect anything in the optical train so you don't lose any TFoV and you don't need any additional back focus, its also very light so it won't change the balance point of the scope. 

For me at least the Baader MPCCIII was the perfect solution for coma as I only have one EP that needs correcting, it only shows 1.07" TFoV and I didn't want to lose any of that by using a Paracorr.

[faulksy]

so after everything else, you(me) buy a reasonable fast ota so you get lovely wide fields, but you get coma which we all no and then you buy a 400 quid paracorr to correct this which we all no, but then you loose field of view, didnt no that. i thought the paracorr just corrected coma but didnt alter anything else

[John]

so after everything else, you(me) buy a reasonable fast ota so you get lovely wide fields, but you get coma which we all no and then you buy a 400 quid paracorr to correct this which we all no, but then you loose field of view, didnt no that. i thought the paracorr just corrected coma but didnt alter anything else

It's all compromises isn't it ?. You could go for a slower scope with little or no visible coma, easier to collimate, but loose a bit of the ultimate FoV and need a ladder to get to the eyepiece in 16" plus apertures. I guess it's a case of deciding which compromises are the most acceptable to you ?

[faulksy]

very true john nothing is easy, i think this 14" 00 is ideal easy to transport and great optics, well reading on what you and shane see, cheers john

[Mike73]

I can't think of many objects which have left me thinking I wish I had more FoV, for me the extra light grasp and resolution is far more important.

[scarp15]

No, you need to set the correct spacing from the CC to the field stop on the EP which is +/- 55mm, you wouldn't be able to get this if you screwed it into an extension tube so the best way to use the Baader MPCCIII is just to leave it attached to the EP.

 

This does mean that if you have two low power EP's that need correcting you will need two MPCCIII's but this would cost the same as a new Paracorr 2! 

 

The beauty of the MPCC is that unlike the Paracorr it doesn't effect anything in the optical train so you don't lose any TFoV and you don't need any additional back focus, its also very light so it won't change the balance point of the scope. 

 

For me at least the Baader MPCCIII was the perfect solution for coma as I only have one EP that needs correcting, it only shows 1.07" TFoV and I didn't want to lose any of that by using a Paracorr.

Certainly an interesting feature, to retain the focal ratio / focal length and therefore not increase magnification of the eyepiece / narrow the TFoV - which may be a little compromising at low power. There is information on the web, a table for particular eyepieces and the spacers required (I sourced this via USA dealer on ebay). I think that you also reduce 10mm of backfocus - so a 2" extension tube may require to be changed for a 1.5"? There seems to be two versions at retail, the one with the spacer kit is applicable.

[estwing]

I'm just and I mean just getting the double cluster in mine with the 21E ...its a wonderful view,but I do sometimes hanker a look with a 31 Nag just to tempt me! its almost too much mag for some targets at 90x..the 31mm gives me 61x

[faulksy]

I'm just and I mean just getting the double cluster in mine with the 21E ...its a wonderful view,but I do sometimes hanker a look with a 31 Nag just to tempt me! its almost too much mag for some targets at 90x..the 31mm gives me 61x

thats good calv, that must be lovely site, i can get most of it with my 40mm aero but thats around 1.2 tfov

[John]

I'm just and I mean just getting the double cluster in mine with the 21E ...its a wonderful view,but I do sometimes hanker a look with a 31 Nag just to tempt me! its almost too much mag for some targets at 90x..the 31mm gives me 61x

I've got both the 21E and the 31 Nagler now and, based on last nights comparison, I'll be keeping both. The N31 showed noticeably more sky, eg: with my 4" F/6.5 refractor the E & W portions of the Veil nebula were bumping up against the field stop of the 21E whereas the 31N showed clear starry sky framing the whole object, which made observing it more enjoyable to me. 

[estwing]

that's right John some objects "need" framing to really..finish off the whole spectacle? I found this more with m52 and m56...

[Joves]

I found comparing my 21 Ethos and 31 Nagler quite an unusual experience. Seeing more of the sky in a narrower AFOV in the 31 Nagler and less of the sky with a wider AFOV in the 21 Ethos kind of scrambled my brain a little

Both awesome eyepieces, that's for sure. I would never part with either of them!

[swamp thing]

so after everything else, you(me) buy a reasonable fast ota so you get lovely wide fields, but you get coma which we all no and then you buy a 400 quid paracorr to correct this which we all no, but then you loose field of view, didnt no that. i thought the paracorr just corrected coma but didnt alter anything else

Your going to find wide field and large aperture aren't two things that sit well together, and thank goodness for that. You buy bigger aperture for larger image scale and resolution, not wide fields.

For wide fields and big faint fuzzies use a small scope, that's what they do. For resolution and small faint fuzzies buy a big scope, that's what they do.

[faulksy]

Your going to find wide field and large aperture aren't two things that sit well together, and thank goodness for that. You buy bigger aperture for larger image scale and resolution, not wide fields.

For wide fields and big faint fuzzies use a small scope, that's what they do. For resolution and small faint fuzzies buy a big scope, that's what they do.

probably worded it wrong, i was looking for a reflector with a shorter focal length around 1600 so i could gain over mt sct,with my sct and 40mm i get 1.15 tfov with the reflector/dob i get 1.7 tfov ok i havnt took in to account exit pupil as it was just rough calculations but this did make me smile :grin: but as you say light buckets are to make things less dim

[Moonshane]

it's all about compromise. I can think of very few common visual objects only that need more than 1 degree of field.  double cluster, veil, NAN, M44, M31, M45. there are a few more obscure ones but the vast majority would fit in the field of even your SCT.  I rarely wish I had a wider field either.

[Mike73]

I think choosing the right magnification for an object comes down to personal preference and more often than not with DSO's if you up the mag you'll see so much more than just using one EP to make the object fit in the entire FoV.

With a 26mm Nag x73 (1.1TFoV) M42 easily fitted in the FoV but I needed a UHC for the best view but when I increased the mag with a 17.3mm Delos x109 it didn't fit in the FoV but showed so much more detail and I didn't need a filter!

Its a bit of a ropey sketch but if you squint and you use your imagination a bit you may get an idea of how it looked! 

[John]

I think choosing the right magnification for an object comes down to personal preference and more often than not with DSO's if you up the mag you'll see so much more than just using one EP to make the object fit in the entire FoV.

With a 26mm Nag x73 (1.1TFoV) M42 easily fitted in the FoV but I needed a UHC for the best view but when I increased the mag with a 17.3mm Delos x109 it didn't fit in the FoV but showed so much more detail and I didn't need a filter!

Its a bit of a ropey sketch but if you squint and you use your imagination a bit you may get an idea of how it looked! 

Thats where a 20 / 21mm 100 degree eyepiece comes in - you can get the whole object in and have the magnification to bring out the detail / contrast.

Lovely sketch I think - not ropey at all 

I always feel that M42 "sprawls" across the FoV and your sketch brings that out perfectly.

[AlexB67]

That's a cracking sketch Mike.  I had a marvellous view of this thursday morning around 3 AM, with a UHC and without, either way,  so much ... stuffff   I need to get my 10 inch under a darker sky for that object,   but even from my garden it was spectacular on that occasion,  the timing of Orion is not ideal though to be taking trips out a that time. 

I just found this to see what it might look like in a 22 inch Dob

http://www.asod.info/?p=8444

 

[mert]

That's a cracking sketch Mike.  I had a marvellous view of this thursday morning around 3 AM, with a UHC and without, either way,  so much ... stuffff   I need to get my 10 inch under a darker sky for that object,   but even from my garden it was spectacular on that occasion,  the timing of Orion is not ideal though to be taking trips out a that time. 

I just found this to see what it might look like in a 22 inch Dob

http://www.asod.info/?p=8444

 

That is what it looks like through a 22" dobsonian, I had a good look at it two days ago and the detail is stunning.

[AlexB67]

That is what it looks like through a 22" dobsonian, I had a good look at it two days ago and the detail is stunning.

I stand corrected, delete the might. I guess I should be buying one in the future if I ever do win that lottery one day  :0)

[John]

I had a look through a 20" David Lukehurst dob at an SGL star party a few years back. The views of M51 and M13 were simply astounding 

WIth M51 the spiral structure was fully defined with knots and loads of other structure in the spiral arms. The whole galaxy and it's satellite seemed to fill the field of view from side to side. Totally magnificent  

The only problem was, for a while at least , that my own scope from my own back yard seemed rather underwhelming 

[mert]

I stand corrected, delete the might. I guess I should be buying one in the future if I ever do win that lottery one day  :0)

I'd go for a 24" or bigger  

[mert]

I had a look through a 20" David Lukehurst dob at an SGL star party a few years back. The views of M51 and M13 were simply astounding 

WIth M51 the spiral structure was fully defined with knots and loads of other structure in the spiral arms. The whole galaxy and it's satellite seemed to fill the field of view from side to side. Totally magnificent  

The only problem was, for a while at least , that my own scope from my own back yard seemed rather underwhelming 

 M13 is incredible, I'll need to look at M51 when the skies clear, before I got my dob I had a look a M57 through a 16" from a fairly light polluted driveway, it was a big jump over my SCT  I knew then I had to buy Big Blue, recently I was offered a very generous price for it but I know it would be difficult to replace it a reasonable price, especially with Big Blue having Argo Navis & Servocat. I'll never sell it now, unless a bigger scope comes along.

[AlexB67]

I'd go for a 24" or bigger

 

This

http://telescopes.net/store/09162-50-inch-monster-dobsonian-telescope.html

 

One day I'll turn up at a star party and do my Dundee impression

 

http://www.youtube.com/watch?v=W09ghiWskUk]http://www.youtube.com/watch?v=W09ghiWskUk

 

substitute knife with Dob. :0)