Baader MPCC coma corrector spacing???

[SkyHiker]

There is a known defect with some of the Baader MPCC IIIs where the lens was put in in the wrong direction. It happened to me, then also to another member in Australia whose problem was fixed once she turned it around.

It may actually be 2 lenses. I don't want to take mine apart now but the outer lens has its convex side outward (away from the camera), the inner lens has its convex side facing inward (towards the camera). AFAICT.

I'm going to have to double check mine today. As evidently something is wrong.

Oops Tom I misstated the second part. The inner lens has its concave side pointing inward. Hope it's not too late.

[yobbo89]

Rob since I will have an F/4 12" Newt and I have a Baader MPCC Mk III, I see you have one too but you are using your Skywatcher aplanatic CC? Should I start looking for something else, what is your experience with the Baader?

https://www.asztrofoto.hu/tudastar/koma ... -resz.html , translate the page to english if needed .

i havn't touch my mpcc in some time,it sits in the parts bin haha ...

it corrects perfectly on a f4.5 scope, but at f4 i'm afraid you'll dislike it ..

I'm happy with my skywatcher aplanatic for single framing, but it sometimes can be a pain for mosaics , it dosn't correct full frame ,only up to aps-c size , it can be as fiddlely as tom is expereancing with his badder on his scope , it needs a fair amount of time to get the distance correct and tilt correction if needed .scope collimation throws the corners out a fair bit ..

unfortunately i don't have enough space to fit in my tilt ring, this would allow me to eliminate my tilt error more easily ,at the moment i have to rely on tilting the focuser and collimation which isn't ideal, it should be done at the camera chip end.90mm back focus rowe

but havn't realy had any major problems with it , it's been in my scope most of the year ,havn't adjusted it maybe 18+ months ,once the distance is set then the rest of the errors are from tilt and collimation ..

i will move on to another corrector when and if i get a full frame mono camera .. not any time soon though, the prices !

i think kathy runs a televue, it's the beez kneez ,

i hope tom gets some good results on his badder rowe cc , might be something to look at .

[UlteriorModem]

Oops Tom I misstated the second part. The inner lens has its concave side pointing inward. Hope it's not too late.

Actually found an image in the webs that shows the 'proper' orientation.

BCC 1 by Tom Whit, on Flickr

BCC 2 by Tom Whit, on Flickr

I actually havent gotten to it yet

I will post on the Rowe CC when it arrives. In browsing for info on it evidently some folks claimed they had to move their mirrors to change the focal point in order to get it to work. Also it is apparently finicky to alignment / collimation. But that's just interwebs hearsay. I will see for myself.

[yobbo89]

do you have a tilt ring tom ?

[UlteriorModem]

do you have a tilt ring tom ?

The ASI 017mc pro has tilt adjustment built into it.

But honestly I have no idea on how to tell which way it needs to be moved.

[UlteriorModem]

Well I took the MPCC apart and it was assembled correctly. So back to square 1.

[yobbo89]

It seems zwo placed the adjustment screws in a smart place, they have one screw on the width axis of the chip, this will be the axis that would be affected a little more.

[UlteriorModem]

Yea but I need to get this coma thing sorted out before I start fussing with tilt.

I'm going to check both mirrors to make sure they are not pinched.

[UlteriorModem]

Got around to going through last nights data. Here is the results.

NGC7696 3 by Tom Whit, on Flickr

As you can see the Coma is still there pretty much across the entire field. Worse in the corners of course.

Just double checked both of the mirror cells. They seem okay.

[SkyHiker]

Rob since I will have an F/4 12" Newt and I have a Baader MPCC Mk III, I see you have one too but you are using your Skywatcher aplanatic CC? Should I start looking for something else, what is your experience with the Baader?

https://www.asztrofoto.hu/tudastar/koma ... -resz.html , translate the page to english if needed .

i havn't touch my mpcc in some time,it sits in the parts bin haha ...

it corrects perfectly on a f4.5 scope, but at f4 i'm afraid you'll dislike it ..

I'm happy with my skywatcher aplanatic for single framing, but it sometimes can be a pain for mosaics , it dosn't correct full frame ,only up to aps-c size , it can be as fiddlely as tom is expereancing with his badder on his scope , it needs a fair amount of time to get the distance correct and tilt correction if needed .scope collimation throws the corners out a fair bit ..

unfortunately i don't have enough space to fit in my tilt ring, this would allow me to eliminate my tilt error more easily ,at the moment i have to rely on tilting the focuser and collimation which isn't ideal, it should be done at the camera chip end.90mm back focus rowe

but havn't realy had any major problems with it , it's been in my scope most of the year ,havn't adjusted it maybe 18+ months ,once the distance is set then the rest of the errors are from tilt and collimation ..

i will move on to another corrector when and if i get a full frame mono camera .. not any time soon though, the prices !

i think kathy runs a televue, it's the beez kneez ,

i hope tom gets some good results on his badder rowe cc , might be something to look at .

Thanks Rob. I found some more useful links,

https://www.cloudynights.com/topic/5966 ... 0+paracorr


Kathy's superb images are one main reason for me to get the Newt. I don't think I will be happy with a mediocre result so I think I'll be ordering a Paracorr 2. Thanks for the advice!

[UlteriorModem]

Hrm maybe I will see if I am happy with the one I ordered. If not I will return it and get a paracorr.

[SkyHiker]

My Paracorr arrived today. Now, where is that scope??

[UlteriorModem]

My Paracorr arrived today. Now, where is that scope??

Barely ahead of the clouds!

[SkyHiker]

My Paracorr arrived today. Now, where is that scope??

Barely ahead of the clouds!

Say what? The clouds are here already! No deed goes unpunished.

[yobbo89]

Is the televue 2.5"?

[SkyHiker]

Is the televue 2.5"?

No 2", I did not know there was a 2.5". If I got the wrong thing let me know, you can almost buy an 8" Dob for the price. I intend to keep using my DSLR for now so 2" should be good. It's a long tube so I hope the vignetting is not too bad.

[UlteriorModem]

Just checked and the Rowe CC is supposed to arrive today. So at least another week of clouds!

Dunno why I never received a ship notice. Had to go to the website and check for myself.

Anyhow stay tuned for a initial impression. Especially on the mechanics and insertion depth.

[UlteriorModem]

Bah the shipping tracking was borked. Probably put it on the wrong truck or something.

Tomorrow it says now.

[UlteriorModem]

Okay as promised.. the RCC-I arrived yesterday. Got around to getting some images of it today.

20201108_122354 by Tom Whit, on Flickr

Here is sort of an exploded view. From left to right is the RCC-I, 2 x 20mm for 40mm worth of spacers, the OAG, a filter, a 5mm spacer, and finally the camera. The MPCC is shown below for reference. Pretty big size difference.


20201108_122501 by Tom Whit, on Flickr

A view of the RCC-I to show its 'insertion depth' 70mm! Almost as long as my draw tube. I do not know about focus point because of course it was cloudy last night, and tonight, and... well you know how it is. Might need a 2" spacer. Problem with the spacer is the RCC-I will not fully insert into the spacer because they have shoulders on them.


20201108_122621 by Tom Whit, on Flickr

Here is the current configuration. There is a little parallax error in the image the length to the camera body is 150mm.

From the stop ring to the image plane is 92.5mm. 1.0mm long from 'ideal' spacing of 91.5. I will try it as is next time I can see some stars. Might have to grind back 1mm off one of the 20mm spacers.

[UlteriorModem]

Well I kind of knew that the new CC would bring some cloudy weather.

But a Tropical Storm?! Good grief! It's freakin November!